VEHICULAR ANTENNA DEVICE

Abstract

 A vehicular antenna device includes a first antenna, a second antenna, a first feeding unit, a second feeding unit, and a combiner unit. The first antenna is operable in a first frequency band. The second antenna is operable in a second frequency band different from the first frequency band. The first feeding unit is connected to the first antenna. The second feeding unit is connected to the second antenna. The combiner unit combines a signal from the first feeding unit and a signal from the second feeding unit.

Description

[0001] This application is based on Japanese patent application NO. 2020-12765, filed on Jan. 29, 2020, the content of which is incorporated hereinto by reference.

BACKGROUND

TECHNICAL FIELD

[0002] The present invention relates to a vehicular antenna device.

RELATED ART

[0003] In recent years, for example, as disclosed in Japanese Unexamined Patent Publication No. 2015-142379, various vehicular antenna devices have been developed. The vehicular antenna device according to an example disclosed in Japanese Unexamined Patent Publication No. 2015-142379 includes an antenna formed by a winding connected to a common connector, and is operated in multiple bands such as an Amplitude Modulation/Frequency Modulation (AM/FM) radio band, a Long Term Evolution (LTE) band, a Digital audio Broadcast (DAB) band, and the like. The vehicular antenna device according to another example disclosed in Japanese Unexamined Patent Publication No. 2015-142379 includes a telematics antenna.

SUMMARY

[0004] In recent years, increase of sensitivity of the vehicular antenna device over a wide frequency band is required in a frequency band for various purposes such as the LTE band. However, when the antenna is formed by the winding connected to the common connector, for example, as in the vehicular antenna device according to the example of Japanese Unexamined Patent Publication No. 2015-142379, a signal in a high frequency band is affected by various factors (for example, harmonics of a signal in a low frequency band), and thus the increase of the sensitivity of the vehicular antenna device over a wide band may be difficult. On the other hand, for example, a telematics antenna may be used as in the vehicular antenna device according to another example of Japanese Unexamined Patent Publication No. 2015-142379. However, even if a shape of the telematics antenna is optimized so that the telematics antenna operates well in a specific frequency band, this shape may not be an optimum shape for another frequency band. In this case, even if the telematics antenna operates well in the specific frequency band, the telematics antenna may not operate well in another frequency band.

[0005] An example of an object of the present invention is to increase sensitivity of a vehicular antenna device over a wide frequency band. Other objects of the present invention will become apparent from the description of the present specification.

[0006] One aspect of the present invention is a vehicular antenna device. The vehicular antenna device includes a first antenna operable in a first frequency band, a second antenna operable in a second frequency band different from the first frequency band, a first feeding unit connected to the first antenna, a second feeding unit connected to the second antenna, and a combiner unit combining a signal from the first feeding unit and a signal from the second feeding unit.

[0007] According to the aspect of the present invention, it is possible to increase the sensitivity of the vehicular antenna device over the wide frequency band.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The above and other objects, advantages and features of the present invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a perspective view of a vehicular antenna device according to an embodiment.

Fig. 2 is a left side view of the vehicular antenna device shown in Fig. 1.

Fig. 3 is a top view of the vehicular antenna device shown in Fig. 1.

Fig. 4 is a bottom view of a first substrate.

Fig. 5 is a circuit diagram showing a configuration of the first substrate shown in Fig. 4.

Fig. 6 is a diagram showing a first modification example of Fig. 5.

Fig. 7 is a diagram showing a second modification example of Fig. 5.

Fig. 8 is a diagram showing a third modification example of Fig. 5.

Fig. 9 is a graph showing an example of a relationship between a length of a second Micro Strip Line (second MSL) between a first filter circuit and a combiner unit, and a combined loss in a combiner unit for a 2690 MHz signal of a second antenna in the same circuit configuration as a circuit configuration shown in Fig. 5.

Fig. 10 is a left side view of a vehicular antenna device according to a first comparative embodiment.

Fig. 11 is a left side view of a vehicular antenna device according to second comparative embodiment.

Fig. 12 is a graph showing a frequency characteristic of sensitivity in a low frequency band of LTE in each of a first antenna and a second antenna of the vehicular antenna device according to the embodiment, a multi-resonant antenna of the vehicular antenna device according to the first comparative embodiment, and a telematics antenna of the vehicular antenna device according to the second comparative embodiment.

Fig. 13 is a graph showing a frequency characteristic of sensitivity in a high frequency band of LTE in each of the first antenna and the second antenna of the vehicular antenna device according to the embodiment, the multi-resonant antenna of the vehicular antenna device according to the first comparative embodiment, and the telematics antenna of the vehicular antenna device according to the second comparative embodiment.

Fig. 14 is a left side view of the vehicular antenna device according to the first modification example.

Fig. 15 is a top view of the vehicular antenna device shown in Fig. 14.

Fig. 16 is a left side view of the vehicular antenna device according to the second modification example.

Fig. 17 is a top view of the vehicular antenna device shown in Fig. 16.

Fig. 18 is a left side view of a vehicular antenna device according to a third modification example.

DETAILED DESCRIPTION

[0009] The invention will be now described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purposes.

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals are attached to the same components throughout all the drawings, and the description thereof will not be repeated.

[0011] In the present specification, ordinal numbers, such as "first", "second", and "third", are attached only for distinguishing components to which the same names are attached unless specifically limited, and do not mean particular features (for example, an order or a degree of importance) of the components.

[0012] Fig. 1 is a perspective view of a vehicular antenna device 10 according to an embodiment. Fig. 2 is a left side view of the vehicular antenna device 10 shown in Fig. 1. Fig. 3 is a top view of the vehicular antenna device 10 shown in Fig. 1.

[0013] In addition to Figs. 1 to 3, in Figs. 4, 10, 11 and 14 to 18, which will be described later, a first direction X, a second direction Y, and a third direction Z are as follows. In each drawing, an arrow indicating the first direction X, the second direction Y, or the third direction Z means that a direction toward a side indicated by the arrow is a positive direction of the direction indicated by the arrow. Further, a white circle with a black dot indicating the second direction Y or the third direction Z means that a direction from a back to a front of a paper surface to which the white circle is attached is the positive direction of a direction indicated by the white circle. On the other hand, a white circle with an X indicating the third direction Z means that a direction from a front to a back of a paper surface to which the white circle is attached is the positive direction of a direction indicated by the white circle.

[0014] The first direction X is a front and rear direction of the vehicular antenna device 10. A positive direction of the first direction X is a front direction of the vehicular antenna device 10. A negative direction of the first direction X, that is, an opposite direction of the positive direction of the first direction X is a rear direction of the vehicular antenna device 10. The second direction Y is a left and right direction of the vehicular antenna device 10. The second direction Y intersects the first direction X, and is specifically orthogonal to the first direction X. A positive direction of the second direction Y is a left direction of the vehicular antenna device 10 when viewed from a rear side of the vehicular antenna device 10. A negative direction of the second direction Y, that is, an opposite direction of the positive direction of the second direction Y is a right direction of the vehicular antenna device 10 when viewed from the rear side of the vehicular antenna device 10. The third direction Z is a vertical direction of the vehicular antenna device 10. The third direction Z intersects both the first direction X and the second direction Y, and is specifically orthogonal to both the first direction X and the second direction Y. A positive direction of the third direction Z is an upward direction of the vehicular antenna device 10. A negative direction of the third direction Z, that is, an opposite direction of the positive direction of the third direction Z is a downward direction of the vehicular antenna device 10. In the specification of the present application, the first direction X may represent the front and rear direction of the vehicular antenna device 10, the second direction Y may represent the left and right direction of the vehicular antenna device 10, and the third direction Z may represent a height direction of the vehicular antenna device 10.

[0015] The vehicular antenna device 10 includes a base 100, a first substrate 200, a first antenna 310, a second antenna 320, a second substrate 400, a Global Navigation Satellite System (GNSS) antenna 510, and an LTE antenna 520. An upper surface of the base 100, the first substrate 200, the second antenna 320, the second substrate 400, the GNSS antenna 510, and the LTE antenna 520 are covered by a not-shown case, and the first antenna 310 is exposed from the case except for a lower end of the first antenna 310 and a vicinity of the lower end of the first antenna 310.

[0016] The vehicular antenna device 10 is attached to a roof of a not-shown vehicle. Specifically, the base 100 is disposed on an upper surface side of the roof of the vehicle. Details described in the present embodiment for the vehicular antenna device 10 may also be applied to an antenna device attached to an object different from the roof of the vehicle.

[0017] A length of the base 100 in the front and rear direction of the vehicular antenna device 10 is longer than a length of the base 100 in the left and right direction of the vehicular antenna device 10. Further, the base 100 has a thickness in a direction parallel to the height direction of the vehicular antenna device 10.

[0018] The first substrate 200 is disposed above or on the upper surface of the base 100. The first substrate 200 is, for example, a Printed Circuit Board (PCB). The first substrate 200 has a thickness in a direction parallel to the height direction of the vehicular antenna device 10.

[0019] The first antenna 310 and the second antenna 320 are disposed on the upper surface side of the first substrate 200. The first antenna 310 and the second antenna 320 are disposed in a predetermined direction, specifically, in the front and rear direction of the vehicular antenna device 10. More specifically, the first antenna 310 is located in the rear of the second antenna 320, and the second antenna 320 is located in front of the first antenna 310. However, disposition of the first antenna 310 and the second antenna 320 is not limited to the disposition according to the present embodiment. For example, the first antenna 310 may be located in front of the second antenna 320.

[0020] The lower end of the first antenna 310 is connected to a first feeding unit 210 of the first substrate 200. A lower end of the second antenna 320 is connected to a second feeding unit 220 of the first substrate 200. The first feeding unit 210 and the second feeding unit 220 are physically spaced apart from each other. In this case, as compared with a case where the feeding unit of the first antenna 310 is common to the feeding unit of the second antenna 320, it is possible to secure isolation between the first antenna 310 and the second antenna 320, and it is possible to reduce interference between a signal transmitted and/or received by the first antenna 310 and a signal transmitted and/or received by the second antenna 320. Therefore, it is possible to increase sensitivity of the first antenna 310 and the second antenna 320 of the vehicular antenna device 10 over a wide frequency band. That the antenna transmits and/or receives the signal means that the antenna performs at least one of transmission and reception of the signal.

[0021] The first antenna 310 is operable in multiple bands including a predetermined first frequency band. Specifically, the first antenna 310 is operable in three frequency bands, that is, a low frequency band of an LTE band, a DAB band, and an AM/FM radio band. Further, the first antenna 310 functions as a telephone (TEL) main antenna in the low frequency band of the LTE band. In the present embodiment, the first frequency band is the low frequency band of the LTE band, and includes, for example, at least a part of 699 MHz to 960 MHz. However, the first frequency band may be a band different from the low frequency band of the LTE band. Further, the first antenna 310 may be operate only in the first frequency band without operating in the DAB band and the AM/FM radio band.

[0022] The first antenna 310 has a rod shape extending in one direction. In the present embodiment, the first antenna 310 is tilted from the front direction of the vehicular antenna device 10 toward the rear direction of the vehicular antenna device 10. The first antenna 310 includes a winding (not shown) that spirally extends along an extending direction of the first antenna 310, and an antenna cover 312 that covers the winding and extends along the extending direction of the first antenna 310. In this case, the first antenna 310 is operable in the multiple bands depending on an aspect of the winding, such as the number of windings, a winding pitch, a winding diameter, a shape, or the like. For example, a part of the first antenna 310 that operates in the three frequency bands has a common winding. In this case, the shorter the length of the winding in the extending direction of the first antenna 310 is, the shorter the corresponding frequency band is. Therefore, for example, when the length of the winding from a lower end of the winding is set to winding lengths A, B, and C, the winding functions as an antenna that operates in the low frequency band of the LTE band at the winding length A, functions as an antenna that operates in the DAB band at the winding length B, and functions as an antenna that operates in the AM/FM radio band at the winding length C. In this case, the winding length A is shorter than the winding length B, and the winding length B is shorter than the winding length C. In this way, when a configuration in which the first antenna 310 shares the winding is provided, it is possible to effectively utilize components, and it is possible to effectively utilize a disposition space of the first antenna 310. A compact winding configuration may be provided in such a way that a part of the winding length A of the winding does not wind a support such as a core wire, and adjacent winding parts of the winding are adhered to each other. By doing so, it is possible to prevent the part of the winding length A of the winding from being broken. Further, when a wire diameter of the part of the winding length A of the winding is increased, it is possible to provide a spring property that returns to an original shape even when being bent by an external force. In addition, since the winding diameter is thick (large), conductor resistance is small, and thus an operating gain can be improved in the low frequency band of the LTE band and a wide bandwidth can be acquired.

[0023] The second antenna 320 is operable in a predetermined second frequency band. The second frequency band is different from the first frequency band. In the present embodiment, the second frequency band is a high frequency band of the LTE band, and includes, for example, at least a part of 1710 MHz to 2690 MHz. That is, the second frequency band is a higher frequency band than the first frequency band. Further, the second antenna 320 functions as the TEL main antenna in the high frequency band of the LTE band. However, the second frequency band may be a frequency band different from the high frequency band of the LTE band. Further, the second frequency band may be a frequency band lower than the first frequency band.

[0024] The second antenna 320 includes a first conductor plate unit 322 and a second conductor plate unit 324. The first conductor plate unit 322 is disposed on the upper surface of the first substrate 200. The first conductor plate unit 322 is connected to the second feeding unit 220. Further, the first conductor plate unit 322 has a thickness in a direction parallel to the second direction Y and a width in a direction parallel to the first direction X. The second conductor plate unit 324 extends from an upper end of the first conductor plate unit 322 in a direction orthogonal to the third direction Z, specifically, in the positive direction of the second direction Y. More specifically, when viewed from the front of the vehicular antenna device 10, the second conductor plate unit 324 extends from the upper end of the first conductor plate unit 322 toward a right side of the first conductor plate unit 322. Further, the second conductor plate unit 324 has a thickness in the direction parallel to the height direction of the vehicular antenna device 10. According to the present embodiment, as compared with, for example, a case where the second conductor plate unit 324 does not extend in the direction intersecting an extending direction of the first conductor plate unit 322 and simply extends in the same direction as the extending direction of the first conductor plate unit 322, it is possible to reduce the height of the second antenna 320 in the height direction of the vehicular antenna device 10.

[0025] In the present embodiment, the first conductor plate unit 322 and the second conductor plate unit 324 are formed by bending a conductor plate, such as sheet metal, between a part that becomes the first conductor plate unit 322 and a part that becomes the second conductor plate unit 324. However, the first conductor plate unit 322 and the second conductor plate unit 324 may be formed by another method of, for example, joining, for example, welding the conductor plate, such as the sheet metal, which becomes the first conductor plate unit 322, and the conductor plate, such as the sheet metal, which becomes the second conductor plate unit 324 to each other.

[0026] As described above, the second antenna 320 includes a first portion connected to the second feeding unit 220 and a second portion connected to the first portion at an angle. In the present embodiment, the first portion and the second portion of the second antenna 320 correspond to the first conductor plate unit 322 and the second conductor plate unit 324, respectively. According to the second antenna 320 having the shape, it is possible to configure, for example, a low-profile antenna equal to or smaller than 40 mm even while securing a desired frequency band. Further, since a part of the second antenna 320 that overlaps the first antenna 310 in a height direction is reduced, it is possible to secure spatial isolation between the first antenna 310 and the second antenna 320. Depending on a connection location (bending position) between the first conductor plate unit 322 and the second conductor plate unit 324, the sensitivity of the second antenna 320, and the spatial isolation between the first antenna 310 and the second antenna 320 can be adjusted.

[0027] The shape of the second antenna 320 is not limited to the shape according to the present embodiment. For example, although the direction in which the first conductor plate unit 322 extends is set to the positive direction in the third direction Z, a configuration may be provided in which the first conductor plate unit 322 is inclined to extend to a side of the second direction Y. Further, the extending direction of the first conductor plate unit 322 and the extending direction of the second conductor plate unit 324 may not be orthogonal and may be oblique. Further, when viewed from the front of the vehicular antenna device 10, the second conductor plate unit 324 may be extended toward the right side of the first conductor plate unit 322 from the upper end of the first conductor plate unit 322, that is, a side different from the negative direction of the second direction Y, such as the left side of the first conductor plate unit 322, in other words, the positive direction of the second direction Y. Further, the second antenna 320 may not have a part corresponding to the second conductor plate unit 324. For example, the second antenna 320 may include only a conductor plate, such as a single sheet metal, having a thickness in a direction orthogonal to the height direction of the vehicular antenna device 10, for example, in the left and right direction of the vehicular antenna device 10. Further, although the surface of the first conductor plate unit 322 of the second antenna 320 is disposed to face the second direction Y, the present invention is not limited thereto, and the surface of the first conductor plate unit 322 may be disposed to face the first direction X.

[0028] Further, the second antenna 320 may be configured by a pattern provided on the substrate instead of the conductor plates such as the first conductor plate unit 322 and the second conductor plate unit 324. In this case, for example, a substrate, on which the pattern configuring the second antenna 320 is formed, is disposed on the upper surface of the first substrate 200.

[0029] In the present embodiment, the first antenna 310 can correspond to the low frequency band of LTE. Therefore, it is not necessary to design the second antenna 320 in consideration of the low frequency band of LTE. Therefore, as compared with the case where the second antenna 320 also corresponds to the low frequency band of LTE, a degree of freedom in designing the second antenna 320 is improved. In particular, in the present embodiment, as compared with the case where the second antenna 320 also corresponds to the low frequency band of LTE, it is possible to expand a frequency band, to which the second antenna 320 can correspond, toward the high frequency band by adjusting the size and height of the second antenna 320.

[0030] In the present embodiment, the second antenna 320 can correspond to the high frequency band of LTE. Therefore, it is not necessary to design the first antenna 310 in consideration of the high frequency band of LTE. Therefore, as compared with the case where the first antenna 310 also corresponds to the high frequency band of LTE, a degree of freedom in designing the first antenna 310 is improved. In particular, in the present embodiment, as compared with the case where the first antenna 310 also corresponds to the low frequency band of LTE, it is possible to expand the frequency band, to which the first antenna 310 can correspond, toward the low frequency band by adjusting the aspect of the above-described winding of the first antenna 310. Further, when the first antenna 310 corresponds to the high frequency band of LTE, it is necessary to consider an influence that the signal of the high frequency band of LTE receives from the harmonics of the signal of the frequency band lower than the high frequency band of LTE. On the other hand, in the present embodiment, it is not necessary to consider the influence when designing the first antenna 310.

[0031] The second substrate 400 is disposed above or on the upper surface of the base 100. The second substrate 400 is, for example, a PCB. The second substrate 400 has a thickness in the direction parallel to the height direction of the vehicular antenna device 10. The second substrate 400 is located in front of the first substrate 200. In the present embodiment, the first substrate 200 and the second substrate 400 are respective substrates spaced apart from each other. However, the first substrate 200 and the second substrate 400 may not be spaced apart from each other, and may be connected to each other. When the first substrate 200 and the second substrate 400 are connected to each other, the first antenna 310, the second antenna 320, the GNSS antenna 510, and the LTE antenna 520 are disposed on the substrate, such as the PCB, in which a part corresponding to the first substrate 200 and a part corresponding to the second substrate 400 are integrated. When the first antenna 310, the second antenna 320, the GNSS antenna 510, and the LTE antenna 520 are disposed on one substrate, the electrical property of each antenna is more stable. Further, in this case, a signal of each antenna may be output through one integrated connector configured with multiple poles. When the signal of each antenna is output through one integrated connector, it is possible to reduce the number of soldered cables and to realize easiness of attachment and detachment.

[0032] The GNSS antenna 510 and the LTE antenna 520 are disposed on an upper surface side of the second substrate 400. The GNSS antenna 510 and the LTE antenna 520 are disposed in a predetermined direction, specifically, in the front and rear direction of the vehicular antenna device 10. More specifically, the GNSS antenna 510 is located in the rear of the LTE antenna 520, and the LTE antenna 520 is located in front of the GNSS antenna 510. However, the disposition of the GNSS antenna 510 and the LTE antenna 520 is not limited to the disposition according to the present embodiment.

[0033] The GNSS antenna 510 is, for example, a Global Positioning System (GPS) antenna. The GNSS antenna 510 is connected to a feeding unit provided on the second substrate 400. In the present embodiment, the GNSS antenna 510 is a patch antenna. Specifically, when viewed from an upper side of the vehicular antenna device 10, the GNSS antenna 510 has a quadrangular (for example, rectangular or square) shape. However, the shape of the GNSS antenna 510 is not limited to the example, and may be, for example, a circular shape. Further, the GNSS antenna 510 may be an antenna having a structure different from the patch antenna such as an antenna having a helical structure.

[0034] The LTE antenna 520 functions as, for example, a TEL sub-antenna. The LTE antenna 520 is connected to the feeding unit provided on the second substrate 400. The LTE antenna 520 includes a third conductor plate unit 522 and a fourth conductor plate unit 524. The third conductor plate unit 522 is disposed on the upper surface of the second substrate 400. Further, the third conductor plate unit 522 has a thickness in a direction parallel to the first direction X and a width in a direction parallel to the second direction Y. The fourth conductor plate unit 524 extends obliquely downward from the upper end of the third conductor plate unit 522 toward the front of the vehicular antenna device 10. According to the present embodiment, as compared with a case where, for example, the fourth conductor plate unit 524 does not extend in the direction intersecting an extending direction of the third conductor plate unit 522 and simply extends in the same direction as the extending direction of the third conductor plate unit 522, it is possible to reduce a height of the LTE antenna 520 in the height direction of the vehicular antenna device 10. As a result, it is possible to configure the design of the case as a gentle streamline, and thus an antenna disposition space can be effective. Further, according to the present embodiment, as compared with a case where the fourth conductor plate unit 524 extends from the upper end of the third conductor plate unit 522 toward the side where the GNSS antenna 510 is located, that is, toward the rear of the vehicular antenna device 10, it is possible to secure the spatial isolation between the GNSS antenna 510 and the fourth conductor plate unit 524. Further, as compared with the case where the fourth conductor plate unit 524 is present above (in the positive direction of the third direction Z of) the GNSS antenna 510, it is possible to suppress interference with the GNSS antenna 510 while securing a desired frequency band. However, a shape of the LTE antenna 520 is not limited to the shape according to the present embodiment.

[0035] In the present embodiment, the third conductor plate unit 522 and the fourth conductor plate unit 524 are formed by bending a conductor plate, such as the sheet metal, between a part that becomes the third conductor plate unit 522 and a part that becomes the fourth conductor plate unit 524. However, the third conductor plate unit 522 and the fourth conductor plate unit 524 may be formed by another method of, for example, joining, for example, welding the conductor plate, such as the sheet metal, which becomes the third conductor plate unit 522, and the conductor plate, such as the sheet metal, which becomes the fourth conductor plate unit 524 to each other.

[0036] Further, in the present embodiment, the extending direction of the fourth conductor plate unit 524 from the upper end of the third conductor plate unit 522 in the LTE antenna 520 is different from the extending direction of the second conductor plate unit 324 from the upper end of the first conductor plate unit 322 in the second antenna 320. In this case, as compared with a case where the extending direction of the second conductor plate unit 324 from the upper end of the first conductor plate unit 322 in the second antenna 320 is the same as the extending direction of the fourth conductor plate unit 524 from the upper end of the third conductor plate unit 522 in the LTE antenna 520, it is possible to reduce interference between radio waves transmitted and/or received by the second antenna 320 and radio waves transmitted and/or received by the LTE antenna 520.

[0037] Further, in the present embodiment, the GNSS antenna 510 is located between the second antenna 320 and the LTE antenna 520. In this case, the second antenna 320 and the LTE antenna 520 can be spaced apart from each other so that the interference between the radio waves transmitted and/or received by the second antenna 320 and the radio waves transmitted and/or received by the LTE antenna 520 is reduced. Further, it is possible to dispose the GNSS antenna 510 in the space formed by spacing the second antenna 320 and the LTE antenna 520 apart from each other. Therefore, it is possible to dispose the second antenna 320, the GNSS antenna 510, and the LTE antenna 520 in a small space so that the second antenna 320 and the LTE antenna 520 operate suitably.

[0038] Fig. 4 is a bottom view of the first substrate 200. Fig. 5 is a circuit diagram showing a configuration of the first substrate 200 shown in Fig. 4.

[0039] The first substrate 200 includes the first feeding unit 210, a first matching circuit 212, a first filter circuit 214, a first microstrip line (first MSL) 216a, a second MSL 216b, the second feeding unit 220, a second matching circuit 222, a second filter circuit 224, a third MSL 226a, a fourth MSL 226b, a combiner unit 250, and an output unit 252. In the example shown in Fig. 4, respective elements shown in Fig. 5 are provided on a lower surface side of the first substrate 200. However, the respective elements shown in Fig. 5 may be provided on the upper surface side of the first substrate 200. Further, some of the elements shown in Fig. 5 may be provided on the lower surface side of the first substrate 200, and some other elements shown in Fig. 5 may be provided on the upper surface side of the first substrate 200. For example, the first feeding unit 210 may be provided on one side of the upper surface and the lower surface of the first substrate 200, and the second feeding unit 220 may be provided on the other side of the upper surface and the lower surface of the first substrate 200. In this case, as compared with the case where the first feeding unit 210 and the second feeding unit 220 are provided on the same surface side of the upper surface and the lower surface of the first substrate 200, it is possible to secure isolation between the first antenna 310 and the second antenna 320, and it is possible to reduce an area for providing the first antenna 310 and the second antenna 320 when viewed from a direction parallel to a thickness direction of the first substrate 200 by disposing the first antenna 310 and the second antenna 320 to be close when viewed from the direction parallel to the thickness direction of the first substrate 200.

[0040] The first feeding unit 210 is connected to the combiner unit 250 through the first matching circuit 212, the first MSL 216a, the first filter circuit 214, and the second MSL 216b in this order. The second feeding unit 220 is connected to the combiner unit 250 through the second matching circuit 222, the third MSL 226a, the second filter circuit 224, and the fourth MSL 226b in this order. In this way, the combiner unit 250 combines a signal sent from the first feeding unit 210 and a signal sent from the second feeding unit 220. Further, the signal combined by the combiner unit 250 is output from the output unit 252.

[0041] The first matching circuit 212 has a filter structure including a capacitor and an inductor. The filter structure is shown as a lumped constant circuit. However, a circuit configuration of the first matching circuit 212 is not limited to the circuit configuration according to the present embodiment, and may be, for example, a distributed constant circuit.

[0042] In the present embodiment, the first filter circuit 214 includes a one-stage LC parallel circuit. The LC parallel circuit includes an inductor and a capacitor connected in parallel. Further, the LC parallel circuit is shown as the lumped constant circuit. However, the present invention is not limited thereto, and, for example, a distributed constant circuit may be provided. The first filter circuit 214 may include a plurality of stages of LC parallel circuits connected in series. That is, the first filter circuit 214 may have at least one stage of the LC parallel circuit. The first filter circuit 214 passes a signal in the first frequency band and blocks a signal in the second frequency band. For example, in the circuit of Fig. 5, when a length of the second MSL 216b is 0 mm, the first filter circuit 214 becomes an open circuit having impedance as high as 17 times a characteristic impedance for 2690 MHz of the second frequency band. Therefore, in the circuit of Fig. 5, the first filter circuit 214 can reflect the signal with 2690 MHz of the second frequency band as the best point. Further, in an electrical path, the first filter circuit 214 is located between the first feeding unit 210 and the combiner unit 250. The "electrical path" means that, for example, the first filter circuit 214 is provided on a wiring that connects the first feeding unit 210 and the combiner unit 250 on a circuit diagram of the first substrate 200 as in the circuit diagram shown in Fig. 5, and means that the first filter circuit 214 may not be physically located between the first feeding unit 210 and the combiner unit 250. As compared with the case where the first filter circuit 214 is not provided, when the first filter circuit 214 is provided, it is possible to reduce the amount of signals in the second frequency band that enter the first feeding unit 210 through the combiner unit 250 from the second feeding unit 220. That is, the first filter circuit 214 can separate the first feeding unit 210 from the second feeding unit 220 for the signal in the second frequency band.

[0043] The second MSL 216b is a transmission line between the first filter circuit 214 and the combiner unit 250. As will be described later with reference to Fig. 9, it is preferable that the physical length of the second MSL 216b is short. That is, it is preferable that the first filter circuit 214 is directly connected to the combiner unit 250. Details of the meaning that the first filter circuit 214 is directly connected to the combiner unit 250 will be described later.

[0044] The second matching circuit 222 has the filter structure including the capacitor and the inductor. The filter structure is shown as a lumped constant circuit. However, a circuit configuration of the second matching circuit 222 is not limited to a circuit configuration according to the present embodiment, and may be, for example, the distributed constant circuit.

[0045] In the present embodiment, the second filter circuit 224 includes the one-stage LC parallel circuit. The LC parallel circuit includes an inductor and a capacitor connected in parallel. Further, the LC parallel circuit is shown as the lumped constant circuit. However, the present invention is not limited thereto, and, for example, a distributed constant circuit may be provided. The second filter circuit 224 may include a plurality of stages of LC parallel circuits connected in series. That is, the second filter circuit 224 can include at least one stage of LC parallel circuit. The second filter circuit 224 passes the signal in the second frequency band and blocks the signal in the first frequency band. For example, in the circuit of Fig. 5, when a length of the fourth MSL 226b is 0 mm, the second filter circuit 224 becomes the open circuit having impedance as high as 450 times the characteristic impedance for 840 MHz of the first frequency band. Therefore, in the circuit of Fig. 5, the second filter circuit 224 can reflect the signal with 840 MHz of the first frequency band as the best point. Further, in the electrical path, the second filter circuit 224 is located between the second feeding unit 220 and the combiner unit 250. The "electrical path" means that, for example, the second filter circuit 224 is provided on a wiring that connects the second feeding unit 220 and the combiner unit 250 on a circuit diagram of the first substrate 200 as in the circuit diagram shown in Fig. 5, and means that the second filter circuit 224 may not be physically located between the second feeding unit 220 and the combiner unit 250. As compared with the case where the second filter circuit 224 is not provided, when the second filter circuit 224 is provided, it is possible to reduce the amount of signals in the first frequency band that enter the second feeding unit 220 through the combiner unit 250 from the first feeding unit 210. That is, the second filter circuit 224 can separate the second feeding unit 220 from the first feeding unit 210 for the signal in the first frequency band.

[0046]  The fourth MSL 226b is a transmission line between the second filter circuit 224 and the combiner unit 250. Similar to the physical length of the second MSL 216b which will be described later with reference to Fig. 9, it is preferable that a physical length of the fourth MSL 226b is short. That is, it is preferable that the second filter circuit 224 is directly connected to the combiner unit 250. Details of the meaning that the second filter circuit 224 is directly connected to the combiner unit 250 will be described later.

[0047] In the present embodiment, the isolation between the first antenna 310 and the second antenna 320 is realized by the first filter circuit 214 and the second filter circuit 224. Therefore, there is no restriction on an electrical length between the first antenna 310 and the first filter circuit 214 and an electrical length between the second antenna 320 and the second filter circuit 224. Therefore, as compared with a case where the first filter circuit 214 and the second filter circuit 224 are not provided, it is possible to increase a degree of freedom in a layout of the first antenna 310 and the second antenna 320.

[0048] Fig. 6 is a diagram showing a first modification example of Fig. 5. The example shown in Fig. 6 is the same as the example shown in Fig. 5, except for the following points.

[0049] The second feeding unit 220 is directly connected to the combiner unit 250. That is, the first substrate 200 does not include the second matching circuit 222, the second filter circuit 224, the third MSL 226a, and the fourth MSL 226b shown in Fig. 5. In the second feeding unit 220, when the second matching circuit 222 and the second filter circuit 224 are not necessary, such as when the output impedance is the characteristic impedance of the combiner unit 250 without the second matching circuit 222 or when a combined loss is allowed when viewed from the signal in the first frequency band without the second filter circuit 224, the second feeding unit 220 may be directly connected to the combiner unit 250. In this case, it is possible to prevent from narrowing the frequency band of the signal sent from the second antenna 320 to the combiner unit 250 by the second matching circuit 222. Further, it is possible to prevent from causing loss of the signal sent from the second antenna 320 to the combiner unit 250 by the second filter circuit 224.

[0050] As being described with reference to Figs. 5 and 6, the first substrate 200 can include at least one of the first filter circuit 214 and the second filter circuit 224, such as both the first filter circuit 214 and the second filter circuit 224.

[0051] Fig. 7 is a diagram showing a second modification example of Fig. 5. The example shown in Fig. 7 is the same as the example shown in Fig. 5 except for a configuration of the first filter circuit 214 and a configuration of the second filter circuit 224.

[0052] The first filter circuit 214 includes a T-type low-pass filter circuit. The T-type low-pass filter circuit includes two inductors connected in series and a capacitor connected to a part between the two inductors and a ground potential. Further, the T-type low-pass filter circuit is shown as the lumped constant circuit. However, the present invention is not limited thereto, and, for example, a distributed constant circuit may be provided. Also, in the example shown in Fig. 7, the first filter circuit 214 can pass the signal in the first frequency band and block the signal in the second frequency band. Further, as compared with the first filter circuit 214 of Fig. 5, the number of inductors is increased by one. Since the filter has multiple stages, it is possible to widen a frequency band in which a combined loss of the second frequency band can be reduced.

[0053] The second filter circuit 224 has a T-type high-pass filter circuit. The T-type high-pass filter circuit includes two capacitors connected in series and an inductor connected to a part between the two capacitors and the ground potential. Further, the T-type high-pass filter circuit is shown as the lumped constant circuit. However, the present invention is not limited thereto, and, for example, a distributed constant circuit may be provided. Also, in the example shown in Fig. 7, the second filter circuit 224 can pass the signal in the second frequency band and block the signal in the first frequency band. Further, as compared with the second filter circuit 224 of Fig. 5, the number of capacitors is increased by one. Since the filter has multiple stages, it is possible to widen a frequency band in which a combined loss of the first frequency band can be reduced.

[0054] Fig. 8 is a diagram showing a third modification example of Fig. 5. The example shown in Fig. 8 is the same as the example shown in Fig. 5 except for the following points.

[0055] The vehicular antenna device 10 further includes a third antenna 330. The third antenna 330 operates in a third frequency band different from both the first frequency band of the first antenna 310 and the second frequency band of the second antenna 320. The third frequency band may include, for example, a frequency band higher than 2690 MHz such as a 5 GHz band. When the third frequency band includes the 5 GHz band, the third antenna 330 may function as, for example, a Wireless Local Area Network (W-LAN) antenna, a Vehicle-to-everything (V2X) antenna, or a Sub6 for 5G communication.

[0056] The third frequency band may be the same frequency band as the second frequency band. In this case, when the second frequency band and the third frequency band include the high frequency band of LTE, it is possible to transmit and/or receive the signal of the high frequency band of LTE by the two antennas, that is, the second antenna 320 and the third antenna 330. In addition, the signal of the high frequency band of LTE may be transmitted and/or received by two or more antennas.

[0057] The first substrate 200 further includes a third feeding unit 230, a third matching circuit 232, a third filter circuit 234, a fifth MSL 236a, and a sixth MSL 236b. The third feeding unit 230 is connected to the third antenna 330. The third feeding unit 230 is connected to the combiner unit 250 through the third matching circuit 232, the fifth MSL 236a, the third filter circuit 234, and the sixth MSL 236b in this order. In this way, the combiner unit 250 combines a signal sent from the third feeding unit 230 in addition to the signal sent from the first feeding unit 210 and the signal sent from the second feeding unit 220.

[0058] The third feeding unit 230 is physically spaced apart from the first feeding unit 210 and the second feeding unit 220. In this case, as compared with a case where the feeding unit of the third antenna 330 is common to the feeding unit of the first antenna 310 and the feeding unit of the second antenna 320, it is possible to secure isolation between the first antenna 310, the second antenna 320, and the third antenna 330, and it is possible to reduce interference between the signal transmitted and/or received by the first antenna 310, the signal transmitted and/or received by the second antenna 320, and a signal transmitted and/or received by the third antenna 330. Therefore, it is possible to increase the sensitivity of the first antenna 310, the second antenna 320, and the third antenna 330 of the vehicular antenna device 10 over the wide frequency band.

[0059] As being described with reference to Figs. 5 and 8, the combiner unit 250 can combine the signals sent from the plurality of feeding units, such as the first feeding unit 210, the second feeding unit 220, and the third feeding unit 230 which are correspondingly connected to each of the plurality of antennas, such as the first antenna 310, the second antenna 320, and the third antenna 330. In this case, the plurality number of antennas may be, for example, two as shown in Fig. 5, may be three as shown in Fig. 8, or may be four or more. Further, some of the frequency bands of the plurality of antennas may be different from each other or may be the same.

[0060] Fig. 9 is a graph showing an example of a relationship between the length of the second MSL 216b between the first filter circuit 214 and the combiner unit 250, and a combined loss in the combiner unit 250 for a 2690 MHz signal of the second antenna 320 in the same circuit configuration as the circuit configuration shown in Fig. 5.

[0061] A horizontal axis of the graph shown in Fig. 9 indicates the length of the second MSL 216b between the first filter circuit 214 and the combiner unit 250. The λ shown on the horizontal axis of the graph of Fig. 9 means a wavelength of a signal propagating the second MSL 216b at 2690 MHz. The wavelength λ is a value in consideration of a wavelength shortening rate, and is 62.4 mm. The combined loss on a vertical axis of the graph shown in Fig. 9 means a loss generated due to the interference between the 2690 MHz signal that is sent from the second feeding unit 220 to the combiner unit 250, and the 2690 MHz signal that is sent from the second feeding unit 220 to the combiner unit 250, sent from the combiner unit 250 to the first filter circuit 214 through the second MSL 216b, reflected by the first filter circuit 214, and sent to the combiner unit 250 through the second MSL 216b.

[0062] As shown in Fig. 9, the combined loss is approximately equal to or higher than -2 dB at 0 to 2/16, 6/16 to 10/16 and 14/16 to 18/16 with respect to a ratio of the length of the second MSL 216b to the wavelength λ. On the other hand, the combined loss is locally large at 4/16 and its vicinity, 12/16 and its vicinity, and 20/16 and its vicinity with respect to the ratio of the length of the second MSL 216b to the wavelength λ. A reason for this is as follows. That is, when the ratio of the length of the second MSL 216b to the wavelength λ is 0 and its vicinity or an integral multiple of 1/2 and its vicinity, constructive interference of the signal occurs due to the signal sent from the second feeding unit 220 to the combiner unit 250, and the signal sent from the second feeding unit 220 to the combiner unit 250, sent from the combiner unit 250 to the first filter circuit 214 through the second MSL 216b, reflected by the first filter circuit 214, and sent to the combiner unit 250 through the second MSL 216b. On the other hand, when the ratio of the length of the second MSL 216b to the wavelength λ is an odd multiple of 1/4 or its vicinity, destructive interference of the signal occurs due to the signal sent from the second feeding unit 220 to the combiner unit 250, and the signal sent from the second feeding unit 220 to the combiner unit 250, sent from the combiner unit 250 to the first filter circuit 214 through the second MSL 216b, reflected by the first filter circuit 214, and sent to the combiner unit 250 through the second MSL 216b. Therefore, as shown in Fig. 9, the combined loss differs depending on the length of the second MSL 216b between the first filter circuit 214 and the combiner unit 250.

[0063] In the example shown in Fig. 9, it is preferable that the ratio of the length of the second MSL 216b to the wavelength λ is 0 to 2/16, 6/16 to 10/16 or 14/16 to 18/16. However, when the second frequency band of the second antenna 320 is wide, that is, the wavelength band corresponding to the second frequency band is wide and the length of the second MSL 216b is relatively long, such as when the ratio of the lengths of the second MSL 216b to the wavelength λ in Fig. 9 is larger than 1/8, the loss does not necessarily become low at a frequency different from the frequency in the example shown in Fig. 9 even through the loss is low at the frequency in the example shown in Fig. 9. Therefore, from a viewpoint of reducing the combined loss of the signal of the second frequency band in the combiner unit 250, it is preferable that the length of the second MSL 216b between the first filter circuit 214 and the combiner unit 250, that is, a length of transmission line between the first filter circuit 214 and the combiner unit 250 is equal to or smaller than 1/8 times the wavelength of the signal propagating in the transmission line at the maximum frequency in the second frequency band.

[0064] When the second frequency band of the second antenna 320 is relatively narrow, such as when the wavelength corresponding to the maximum frequency in the second frequency band is equal to or smaller than 3/4 times the wavelength corresponding to the minimum frequency in the second frequency band, the length of the second MSL 216b between the first filter circuit 214 and the combiner unit 250 may be equal to or smaller than 1/8 times the wavelength of the signal propagating the second MSL 216b at the maximum frequency in the second frequency band or may be equal to or larger than (4N - 1)/8 times or equal to or smaller than (4N + 1)/8 times the wavelength of the signal propagating the second MSL 216b at the maximum frequency in the second frequency band (N: an integer equal to or larger than 1).

[0065] The description performed with reference to Fig. 9 is the same for the length of the fourth MSL 226b between the second filter circuit 224 and the combiner unit 250. That is, from the viewpoint of reducing the combined loss of the signal of the first frequency band in the combiner unit 250, it is preferable that the length of the fourth MSL 226b between the second filter circuit 224 and the combiner unit 250 is equal to or smaller than 1/8 times the wavelength of the signal propagating the fourth MSL 226b at the maximum frequency in the first frequency band. Further, when the first frequency band of the first antenna 310 is relatively narrow, such as when the wavelength corresponding to the maximum frequency in the first frequency band is equal to or smaller than 3/4 times the wavelength corresponding to the minimum frequency in the first frequency band, the length of the fourth MSL 226b between the second filter circuit 224 and the combiner unit 250 may be equal to or smaller than 1/8 times the wavelength of the signal propagating the fourth MSL 226b at the maximum frequency in the first frequency band or equal to or larger than (4M - 1)/8 times or equal to or smaller than (4M + 1)/8 times the wavelength of the signal propagating the fourth MSL 226b at the maximum frequency in the first frequency band (M: an integer equal to or larger than 1).

[0066] As described above, that the first filter circuit 214 is directly connected to the combiner unit 250 means that the length of the transmission line between the first filter circuit 214 and the combiner unit 250 is equal to or smaller than λ/8. However, as described above, depending on conditions, that the first filter circuit 214 is directly connected to the combiner unit 250 means that the length of the transmission line between the first filter circuit 214 and the combiner unit 250 is equal to or larger than (4N -1)λ/8 times and is equal to or smaller than (4N + 1)λ/8 times (N: an integer equal to or larger than 1). Here, the wavelength λ is a wavelength of the signal propagating in the transmission line at the maximum frequency of the second frequency band such as 2690 MHz. Further, that the second filter circuit 224 is directly connected to the combiner unit 250 means that the length of the transmission line between the second filter circuit 224 and the combiner unit 250 is equal to or smaller than λ'/8. However, as described above, depending on the conditions, that the second filter circuit 224 is directly connected to the combiner unit 250 means that the length of the transmission line between the second filter circuit 224 and the combiner unit 250 is equal to or larger than (4M - 1)λ'/8 times and is equal to or smaller than (4M + 1) λ'/8 times (M: an integer equal to or larger than 1). Here, the wavelength λ' means a wavelength of the signal propagating in the transmission line at the maximum frequency of the first frequency band such as 960 MHz.

[0067] Fig. 10 is a left side view of a vehicular antenna device 10 according to a first comparative embodiment.

[0068] The vehicular antenna device 10 according to the first comparative embodiment does not have a configuration corresponding to the second feeding unit 220 and the second antenna 320 of the embodiment. Further, the vehicular antenna device 10 according to the first comparative embodiment includes a multi-resonant antenna 910 instead of the first antenna 310 of the embodiment. A winding in the antenna cover 912 of the multi-resonant antenna 910 is adjusted so that the multi-resonant antenna 910 is operable in the low frequency band of the LTE band, the DAB band, and the AM/FM radio band. A lower end of the multi-resonant antenna 910 is connected to the feeding unit.

[0069] Fig. 11 is a left side view of a vehicular antenna device 10 according to a second comparative embodiment.

[0070] The vehicular antenna device 10 according to the second comparative embodiment includes a telematics antenna 920. A shape of the telematics antenna 920 is optimized so that the telematics antenna 920 operates well in the high frequency band of LTE.

[0071] Fig. 12 is a graph showing a frequency characteristic of sensitivity in the low frequency band of LTE in each of the first antenna 310 and the second antenna 320 of the vehicular antenna device 10 according to the embodiment, the multi-resonant antenna 910 of the vehicular antenna device 10 according to the first comparative embodiment, and the telematics antenna 920 of the vehicular antenna device 10 according to the second comparative embodiment. Fig. 13 is a graph showing a frequency characteristic of the sensitivity in the high frequency band of LTE in each of the first antenna 310 and the second antenna 320 of the vehicular antenna device 10 according to the embodiment, the multi-resonant antenna 910 of the vehicular antenna device 10 according to the first comparative embodiment, and the telematics antenna 920 of the vehicular antenna device 10 according to the second comparative embodiment.

[0072] A vertical axis of each of the graphs of Figs. 12 and 13 shows the sensitivity. A horizontal axis of each of the graphs of Figs. 12 and 13 shows the frequency. In the graph of Fig. 12, an area between two dotted lines indicates the low frequency band of LTE, that is, 699 MHz to 960 MHz. In the graph of Fig. 13, an area between two dotted lines shows the high frequency band of LTE, that is, 1710 MHz to 2690 MHz. Solid lines in each of graphs of Figs. 12 and 13 show the frequency characteristic of the sensitivity of the first antenna 310 and the second antenna 320 of the vehicular antenna device 10 according to the embodiment. A broken line in each of the graphs of Figs. 12 and 13 shows the frequency characteristic of sensitivity of the multi-resonant antenna 910 of the vehicular antenna device 10 according to the first comparative embodiment. A dash-dotted line in each of the graphs of Figs. 12 and 13 shows the frequency characteristic of sensitivity of the telematics antenna 920 of the vehicular antenna device 10 according to the second comparative embodiment.

[0073] In the multi-resonant antenna 910 of the vehicular antenna device 10 according to the first comparative embodiment, the sensitivity is as high as -2 dBi or greater over the entire low frequency band of LTE, as shown in Fig. 12. On the other hand, in the multi-resonant antenna 910 of the vehicular antenna device 10 according to the first comparative embodiment, the sensitivity is reduced to be equal to or lower than approximately -4 dBi at 1900 MHz, 2300 MHz, and 2600 MHz in the high frequency band of LTE, as shown in Fig. 13. This is presumed to be due to influence that the harmonics of the signals of the frequency band lower than the LTE band such as the DAB band and the AM/FM radio band is generated from the winding constituting the multi-resonant antenna 910, that is, the helical antenna. Further, as shown in Fig. 13, the sensitivity of the vehicular antenna device 10 according to the first comparative embodiment is lower than the sensitivity of the vehicular antenna device 10 according to the embodiment at every frequency in the high frequency band of LTE. This is presumed that the multi-resonant antenna 910 causes a loss such as attenuation, and the length of the multi-resonant antenna 910 is not the optimum length for the high frequency band of LTE.

[0074] In the telematics antenna 920 of the vehicular antenna device 10 according to the second comparative embodiment, the sensitivity is as high as -2 dBi or greater in most of the high frequency band of LTE, as shown in Fig. 13. On the other hand, in the telematics antenna 920 of the vehicular antenna device 10 according to the second comparative embodiment, the sensitivity is reduced to be equal to or lower than -6 dBi in the entirety of the low frequency band of LTE, as shown in Fig. 12. The reason for this is as follows. That is, the shape of the telematics antenna 920 is optimized so that the telematics antenna 920 operates well in the high frequency band of LTE. However, the shape of the telematics antenna 920 is not optimal for the low frequency band of LTE. Therefore, the sensitivity of the low frequency band of LTE of the telematics antenna 920 is lower than the sensitivity of the high frequency band of LTE of the telematics antenna 920.

[0075] In the first antenna 310 and the second antenna 320 of the vehicular antenna device 10 according to the embodiment, the sensitivity is as high as -4 dB or greater in both the low frequency band and the high frequency band of LTE, as shown in Figs. 12 and 13.

[0076]  From the results shown in Figs. 12 and 13, when the feeding unit connected to the antenna operable in the low frequency band of LTE and the feeding unit connected to the antenna operable in the high frequency band of LTE are separated from each other, the vehicular antenna device is operable well in both the low frequency band and the high frequency band of LTE. That is, according to the present embodiment, it is possible to increase the sensitivity of the vehicular antenna device 10 over the wide frequency band.

(First Modification Example)

[0077] Fig. 14 is a left side view of a vehicular antenna device 10 according to a first modification example. Fig. 15 is a top view of the vehicular antenna device 10 shown in Fig. 14. The vehicular antenna device 10 according to the first modification example is the same as the vehicular antenna device 10 according to the embodiment except for the following points.

[0078] The first antenna 310 is a monopole antenna with a capacitive loading element. Specifically, the first antenna 310 includes a radiating element 314a and a capacitive loading element 314b. The radiating element 314a has a shape that extends linearly in a predetermined direction, specifically, in a vertical direction of the vehicular antenna device 10. A lower end of the radiating element 314a is connected to the first feeding unit 210. The capacitive loading element 314b is attached to an upper end of the radiating element 314a. In the present modification example, the second antenna 320 includes the first conductor plate unit 322, and does not include, for example, the second conductor plate unit 324 shown in Fig. 1. With the configuration, for example, in a low-profile case equal to or smaller than 70 mm, it is possible to secure isolation between the respective antennas while corresponding to a wide band LTE band.

(Second Modification Example)

[0079] Fig. 16 is a left side view of a vehicular antenna device 10 according to a second modification example. Fig. 17 is a top view of the vehicular antenna device 10 shown in Fig. 16. The vehicular antenna device 10 according to the second modification example is the same as the vehicular antenna device 10 according to the first modification example except for the following points.

[0080] The first antenna 310 is located in front of the second antenna 320, and the second antenna 320 is located in the rear of the first antenna 310. The first antenna 310 is a planar inverted-F antenna (PIFA). Specifically, the first antenna 310 includes a radiation plate 316a, a feeding conductor unit 316b, and a ground conductor unit 316c. The radiation plate 316a is located above the first substrate 200. The radiation plate 316a is connected to the first feeding unit 210 through the feeding conductor unit 316b. Further, the radiation plate 316a is grounded through the ground conductor unit 316c. With the configuration, for example, in a low-profile case equal to or smaller than 40 mm, it is possible to correspond to the LTE band of the wide band and to secure the isolation between the respective antennas while providing the plurality of antennas corresponding to the plurality of frequency bands.

(Third Modification Example)

[0081] Fig. 18 is a left side view of a vehicular antenna device 10 according to a third modification example. The vehicular antenna device 10 according to the third modification example is the same as the vehicular antenna device 10 according to the first modification example except for the following points.

[0082] The first antenna 310 includes an LTE antenna 318a, a trap coil 318b, a helical element 318c, and a capacitive loading element 318d. A lower end of the LTE antenna 318a is connected to the first feeding unit 210 of the first substrate 200. The trap coil 318b is connected to an upper end of the LTE antenna 318a. One end of the helical element 318c is connected to the trap coil 318b. The other end of the helical element 318c is connected to the capacitive loading element 318d. The capacitive loading element 318d is located above the second antenna 320.

[0083] The first antenna 310 in the vehicular antenna device 10 according to the third modification example shares some of the elements constituting the first antenna 310 to form a composite antenna. That is, the first antenna 310 is operable in the low frequency band of the LTE band and the DAB band or the AM/FM radio band. Therefore, for example, in a low-profile case equal to or smaller than 70 mm, it is possible to correspond to the LTE band of the wide band and to secure the isolation between the respective antennas while providing the plurality of antennas corresponding to the plurality of frequency bands.

[0084] Although the embodiments and modification examples of the present invention have been described above with reference to the drawings, these are examples of the present invention, and various configurations other than the above may be adopted.

[0085] According to the present specification, the following aspects are provided.

(First Aspect)

[0086] A first aspect is a vehicular antenna device comprising:

a first antenna operable in a first frequency band;

a second antenna operable in a second frequency band different from the first frequency band;

a first feeding unit connected to the first antenna;

a second feeding unit connected to the second antenna; and

a combiner unit combining a signal from the first feeding unit and a signal from the second feeding unit.

[0087] According to the first aspect, the first feeding unit and the second feeding unit are physically spaced apart from each other. In this case, as compared with a case where the feeding unit of the first antenna is common to the feeding unit of the second antenna, it is possible to secure isolation between the first antenna and the second antenna, and it is possible to reduce interference between a signal transmitted and/or received by the first antenna and a signal transmitted and/or received by the second antenna. Therefore, it is possible to increase sensitivity of the first antenna and the second antenna of the vehicular antenna device over a wide frequency band.

(Second Aspect)

[0088] A second aspect is the vehicular antenna device according to the first aspect further comprising at least one of
a first filter circuit located between the first feeding unit and the combiner unit in an electrical path, the first filter circuit blocking a signal in the second frequency band; and
a second filter circuit located between the second feeding unit and the combiner unit in the electrical path, the second filter circuit blocking a signal in the first frequency band.

[0089] According to the second aspect, as compared with the case where the first filter circuit is not provided, when the first filter circuit is provided, it is possible to reduce the amount of signals in the second frequency band that enter the first feeding unit through the combiner unit from the second feeding unit. That is, the first filter circuit can separate the first feeding unit from the second feeding unit for the signals in the second frequency band. Further, as compared with the case where the second filter circuit is not provided, when the second filter circuit is provided, it is possible to reduce the amount of signals in the first frequency band that enter the second feeding unit through the combiner unit from the first feeding unit.
That is, the second filter circuit can separate the second feeding unit from the first feeding unit for the signals in the first frequency band.

(Third Aspect)

[0090] A third aspect is the vehicular antenna device according to the second aspect, wherein
a length of a transmission line between the first filter circuit and the combiner unit is equal to or smaller than 1/8 times a wavelength of a signal propagating in the transmission line at a maximum frequency in the second frequency band.

[0091] According to the third aspect, the constructive interference of the signals occurs due to a signal sent from the second feeding unit to the combiner unit, and a signal sent from the second feeding unit to the combiner unit, sent from the combiner unit to the first filter circuit, reflected by the first filter circuit, and sent to the combiner unit. Therefore, it is possible to reduce a combined loss of the signal of the second frequency band in the combiner unit.

(Fourth Aspect)

[0092] A fourth aspect is the vehicular antenna device according to the second or third aspect, wherein
a length of a transmission line between the second filter circuit and the combiner unit is equal to or smaller than 1/8 times a wavelength of a signal propagating in the transmission line at a maximum frequency in the first frequency band.

[0093] According to the fourth aspect, it is possible to reduce the combined loss of the signal of the first frequency band in the combiner unit in the same manner as in the third aspect.

(Fifth Aspect)

[0094] A fifth aspect is the vehicular antenna device according to any one of first to fourth aspects, wherein
the first frequency band includes at least a part of 699 MHz to 960 MHz, and
the second frequency band includes at least a part of 1710 MHz to 2690 MHz.

[0095] According to the fifth aspect, it is possible to increase sensitivity of the vehicular antenna device over 699 MHz to 960 MHz and 1710 MHz to 2690 MHz.

(Sixth Aspect)

[0096] A sixth aspect is the vehicular antenna device according to any one of first to fifth aspects further comprising:

a third antenna operable in a third frequency band different from both the first frequency band and the second frequency band; and

a third feeding unit connected to the third antenna,

wherein the combiner unit also combines a signal from the third feeding unit.

[0097] According to the sixth aspect, the third feeding unit is physically spaced apart from the first feeding unit and the second feeding unit. In this case, as compared with a case where the feeding unit of the third antenna is common to the feeding unit of the first antenna and the feeding unit of the second antenna, it is possible to secure isolation between the first antenna, the second antenna, and the third antenna, and it is possible to reduce interference between the signal transmitted and/or received by the first antenna, the signal transmitted and/or received by the second antenna, and a signal transmitted and/or received by the third antenna. Therefore, it is possible to increase the sensitivity of the first antenna, the second antenna, and the third antenna of the vehicular antenna device over the wide frequency band.

(Seventh Aspect)

[0098] A seventh aspect is the vehicular antenna device according to any one of first to sixth aspects, wherein
the second antenna includes a first portion connected to the second feeding unit and a second portion connected to the first portion at an angle.

[0099] According to the seventh aspect, it is possible to configure a low-profile antenna also while securing a desired frequency band. Further, since a part of the second antenna that overlaps the first antenna in a height direction is reduced, it is possible to secure spatial isolation between the first antenna and the second antenna.

[0100] It is apparent that the present invention is not limited to the above embodiment, and may be modified and changed without departing from the scope and spirit of the invention.

Claims

1. A vehicular antenna device comprising:

a first antenna operable in a first frequency band;

a second antenna operable in a second frequency band different from the first frequency band;

a first feeding unit connected to the first antenna;

a second feeding unit connected to the second antenna; and

a combiner unit combining a signal from the first feeding unit and a signal from the second feeding unit.

2. The vehicular antenna device according to claim 1, further comprising at least one of:

a first filter circuit located between the first feeding unit and the combiner unit in an electrical path, the first filter circuit blocking a signal in the second frequency band; and

a second filter circuit located between the second feeding unit and the combiner unit in the electrical path, the second filter circuit blocking a signal in the first frequency band.

3. The vehicular antenna device according to claim 2, wherein
a length of a transmission line between the first filter circuit and the combiner unit is equal to or smaller than 1/8 times a wavelength of a signal propagating in the transmission line at a maximum frequency in the second frequency band.

4. The vehicular antenna device according to claim 2 or 3, wherein
a length of a transmission line between the second filter circuit and the combiner unit is equal to or smaller than 1/8 times a wavelength of a signal propagating in the transmission line at a maximum frequency in the first frequency band.

5. The vehicular antenna device according to any one of claims 1 to 4, wherein

the first frequency band includes at least a part of 699 MHz to 960 MHz, and

the second frequency band includes at least a part of 1710 MHz to 2690 MHz.

6. The vehicular antenna device according to any one of claims 1 to 5, further comprising:

a third antenna operable in a third frequency band different from both the first frequency band and the second frequency band; and

a third feeding unit connected to the third antenna,

wherein the combiner unit also combines a signal from the third feeding unit.

7. The vehicular antenna device according to any one of claims 1 to 6, wherein
the second antenna includes a first portion connected to the second feeding unit and a second portion connected to the first portion at an angle.

Drawing