[0001] The present invention relates generally to an antenna for a vehicular glass, and
more particularly to such a vehicular glass antenna capable of securing a sufficient
reception sensitivity without being limited by the position of a power supplying section
of the vehicle.
[0002] Japanese Patent Application Laid-open Publication (
JP-A) No. 2002-299932 describes a nongrounding type balanced antenna for a vehicle to be provided on a
side window glass and that can obtain an excellent receiving gain and an excellent
directivity for receiving AM/FM radio broadcast and TV broadcast etc. The antenna
therefore comprises a first and second element each of which having at least one horizontal
filament. The horizontal filaments extend from first and second feeding points connecting
the first and second filaments to an internal conductor and an external conductor
in a coaxial cable respectively.
[0003] Japanese Patent Application Laid-open Publication (
JP-A) No. 2002-064317 discloses a glass antenna for an automobile suitable to receive TV broadcast. The
antenna includes a first antenna extending from a first feed point, which is located
close to one corner of the side glass, and a second antenna extending from a second
feed point located close to the first feed point. The second antenna element thereby
forms a trapezoidal loop inside the first antenna.
[0004] Japanese Patent Application Laid-open Publication (
JP-A) No. 2011-193381 shows a planar antenna (antenna for a vehicular glass) designed for the reception
of vertically polarized radio waves, especially terrestrial DAB (digital audio broadcasting)
waves. The planar antenna disclosed in
JP 2011-193381A includes a core wire-side element (core wire-side antenna element) and a ground-side
element (ground-side antenna element). The ground-side element extends from a ground-side
power supplying section in a horizontal direction and is disposed in proximity to
an upper edge or a lower edge of a window opening of the vehicle body over the entire
length of the ground-side element. The core wire-side element includes a first element
extending in a vertical direction from a core wire-side power supplying section located
in proximity to the ground-side power supplying section. The first element of the
core wire-side element extends in a direction separating away from the upper or lower
edge of the window opening along which the ground-side element is disposed in proximity
thereto.
[0005] Since the ground-side element extends in the horizontal direction in such a manner
as to be in proximity to the upper edge or the lower edge of the window opening over
the entire length thereof, the planar antenna shown in
JP 2011-193381 can only be installed in a vehicle having a power supplying position located in proximity
to the upper edge or the lower edge of the window opening. In other words, the planar
antenna shown in
JP 2011-193381 cannot be installed in such a vehicle which has a power supplying position located
in proximity to a left edge or a right edge of the window opening.
[0006] Japanese Patent Application Laid-open Publication (
JP-A) No. 2011-160236 shows a glass antenna (antenna for a vehicular glass) capable of receiving vertically
polarized radio waves, especially DAB waves. As re-illustrated here in Fig. 1, the
glass antenna 100 disclosed in
JP 2011-160236A includes a first L-shaped element 101 formed by a first element section 103 extending
from a core wire-side power supplying section 107 and a second element section 104
extending from a terminal end of the first element section 103, and a second L-shaped
element 102 formed by a first element section 105 extending from a ground-side power
supplying section 108 and a second element section 106 extending from a terminal end
of the first element section 105. The core wire-side power supplying section 107 and
the ground-side power supplying section 108 are disposed in proximity to a left edge
109a of a window opening 109 of the vehicle body. The glass antenna 100 shown in
JP 2011-160236A can thus be installed in a vehicle having a power supplying position located in proximity
to the left edge 109a of the window opening 109 of the vehicle body.
[0007] According to
JP 2011-160236A, the second element section 106 of the second L-shaped element 102 is adjusted to
have a conductor length of more than 150 mm, preferably 200 mm or more in order to
improve the antenna gain (reception sensitivity). For the purpose of improving the
antenna gain, the glass antenna 100 is required to be installed in such a vehicle
which has a ground-side power supplying position located in proximity to the left
edge 109a of the window opening 109 and separated from a lower edge 109b of the window
opening 109 by at least more than 150 mm. In other words, when the glass antenna 100
disclosed in
JP 2011-160236A is installed in a vehicle having a ground-side power supplying position located in
proximity to the left edge 109a of the window opening 109 and separated by less than
150 mm from the lower edge 109b of the window opening 109, a sufficient antenna gain
cannot be obtained.
[0008] The present inventors have acknowledged that depending on the position of a power
supplying section of a vehicle, the vehicular glass antennas shown in
JP 2011-193381A and
JP 2011-160236A become impossible to install in the vehicle; and even when they can be installed
in the vehicle, a sufficient antenna gain cannot be obtained. More specifically, the
present inventors have recognized that there is room for improvement in the shape
and configuration of a core wire-side element and/or a ground-side element of a vehicular
glass antenna when the antenna is installed in either a vehicle having a power supplying
position located at a left lower corner portion or a right lower corner portion of
a window opening of the vehicle body, or a vehicle with a window opening having a
small size in a vertical direction (e.g., less than 200 mm).
[0009] It is therefore an object of the present invention to provide a vehicular glass antenna
which is capable of securing a sufficient reception sensitivity without being limited
by the position of a power supplying section of the vehicle.
[0010] This object is solved by the subject-matter of claim 1.
[0011] According to the present invention, there is provided an antenna for a vehicular
glass, comprising: a core wire-side power supplying section; a core wire-side antenna
element electrically connected to the core wire-side power supplying section; a ground-side
power supplying section; and a ground-side antenna element electrically connected
to the ground-side power supplying section, wherein the core wire-side antenna element
includes: a core wire-side first element extending from the core-side power supplying
section as a starting point along an edge of a window opening of a vehicle body in
such a manner as to keep a first predetermined distance relative to a part of the
edge of the window opening closest to the core wire-side first element; and a core
wire-side second element extending from the core wire-side first element in a substantially
vertical direction at a position separated by more than a prescribed distance from
each of left and right edges of the window opening, and wherein the ground-side antenna
element has a portion extending from the ground-side power supplying section as a
starting point along the core wire-side first element in such a manner as to keep
a second predetermined distance relative to the core wire-side first element, wherein
the first predetermined distance is less than 40 mm.
[0012] With this arrangement, the core wire-side first element and the ground-side first
element are allowed to be arranged in proximity to the vehicle body serving as a grounding
potential, thereby reducing their influences on performance of the antenna. As a result,
the core wire-side second element is allowed to be disposed at a prescribed distance
to each of the left and right edges of the window opening without being limited by
the position of the core wire-side power supplying section, wherein the prescribed
distance is set to be a value sufficient to reduce the influence of the vehicle body
upon the core wire-side second element. With the first predetermined distance being
less than 40 mm the core wire-side antenna element and the ground-side antenna element
can only give little influence to performance of the vehicular glass antenna, a further
improvement in the reception sensitivity is possible.
[0013] The starting point of the core wire-side second element can be provided at an upper
part of the window opening without being limited by the position of the core wire-side
power supplying section. This arrangement will ensure that a length of the core wire-side
second element, which is suited for frequency bands of vertically polarized radio
waves to be received by the vehicular glass antenna, can be secured. A sufficient
reception sensitivity can thus be obtained without being limited by the power supplying
position of the vehicle.
[0014] Some vehicle is unable to provide a power supplying position located in an upper
part or a lower part of the window opening due to the presence of another device such
as an air-bag device. Even in an application to such vehicle, the vehicular glass
antenna can also secure a sufficient reception sensitivity because it is able to secure
the same level of reception sensitivity without being limited by the power supplying
position of the vehicle.
[0015] Preferably, the prescribed distance by which the core wire-side second element is
separated from each of the left and right edges of the window opening is more than
50 mm. With this arrangement, the influence of the vehicle body upon the core wire-side
second element can be reduced, and the reception sensitivity is increased correspondingly.
[0016] It is preferable that the core wire-side second element has a length more than 140
mm. In the case where the vertically polarized radio waves to be received by the vehicular
glass antenna include radio waves of BAND III DAB frequencies, the core wire-side
second element can secure a sufficient length long enough to improve the reception
sensitivity.
[0017] Preferably, the second predetermined distance is in a range of from 5 to 20 mm. With
this arrangement, because the core wire-side antenna element and the ground-side antenna
element are arranged in proximity to the vehicle body serving as a grounding potential,
the influence of the core wire-side antenna element and the ground-side antenna element
exerted upon performance of the antenna can be reduced, which will lead to a further
improvement in the reception sensitivity.
[0018] It is preferable that the core wire-side antenna element and the ground-side antenna
element at least partially include a looped shape. The loop-shaped part of the wire-side
antenna element and the ground-side antenna element has the same effect as a thickened
part of the antenna element and hence is effective to improve the reception sensitivity.
Furthermore, the antenna element having a looped shape is inconspicuous as compared
to an antenna element having an enlarged line width or diameter and, hence, the antenna
reception sensitivity and the appearance of the entire vehicle can be compatibly achieved.
[0019] The vehicular glass antenna may further include a glass provided with the core wire-side
power supplying section, the core wire-side antenna element, the ground-side power
supplying section, and the ground-side antenna element. The core wire-side antenna
element and the ground-side antenna element are formed, for example, by screen-printing
on a surface of the glass to thereby complete a vehicular glass antenna.
Fig. 1 is a view diagrammatically showing a basic structure of an antenna for vehicular
glasses according to the present invention;
Fig. 2 is a view diagrammatically showing a structure of an antenna for vehicular
glasses according to a first embodiment of the present invention;
Fig. 3 is a view diagrammatically showing a structure of an antenna for vehicular
glasses according to a second embodiment of the present invention;
Fig. 4 is a graph showing a performance evaluation of the vehicular glass antennas
according to the first and second embodiments;
Figs. 5(A) and 5(B) are views diagrammatically showing vehicular glass antennas according
to further embodiments of the present invention;
Figs. 6(A) and 6(B) are views diagrammatically showing vehicular glass antennas according
to still further embodiments of the present invention; and
Fig. 7 is a view diagrammatically showing the structure of a vehicular glass antenna
according to the prior art.
[0020] Certain preferred structural embodiments of the present invention will be described
in greater details below, by way of example only, with reference to the accompanying
sheets of drawings.
1. Basic Structure
[0021] Fig. 1 shows a glass 10 having power supplying sections, antenna elements, etc. formed
thereon, which constitutes a structural example of a vehicular glass antenna 10 according
to the present invention. The vehicular glass antenna 10 shown in Fig. 1 is configured
to receive digital audio broadcasting (DAB) waves as an example of vertical polarization
radio waves.
[0022] As shown in Fig. 1, the vehicular glass antenna 10 includes a core wire-side power
supplying section 20, a core wire-side antenna element 30 electrically connected to
the core wire-side power supplying section 20, a ground-side power supplying section
40, and a ground-side antenna element 50 electrically connected to the ground-side
power supplying section 40. In the illustrated example, the vehicular glass antenna
10 is arranged in a vehicle body 1 such that a combination of the core wire-side power
supplying section 20 and the core wire-side antenna element 30 and a combination of
the ground-side power supplying section 40 and the ground-side antenna element 50
are located inside a window opening 5 of the vehicle body 1. In Fig. 1, the shape
of the vehicle body 1 is omitted from illustration.
[0023] The core wire-side power supplying section 20 and the ground-side power supplying
section 40 shown in Fig. 1 are configured to be electrically connectable with a transmitting
path such as a coaxial cable (not shown). The coaxial cable is connected to a signal
processing device such as a receiver (not shown) installed in the vehicle in connection
with DAB. The core wire-side power supplying section 20 is connected, for example,
with a central conductor of the coaxial cable. The ground-side power supply section
40 is connected, for example, with an outer conductor of the coaxial cable. The core
wire-side power supplying section 20 and the ground-side power supplying section 40
are provided in the proximity of a power supplying position of the vehicle, which
is a position connectable to the coaxial cable. The power supplying position of the
vehicle is different according to the type, model, etc. of the vehicle so that the
core wire-side power supplying section 20 and the ground-side power supplying section
40 need to be provided in accordance with the power supplying position of the vehicle.
[0024] The core wire-side antenna element 30 and the ground-side antenna element 50 are
made of an electrically conductive material. For example, the core wire-side antenna
element 30 and the ground-side antenna element 50 may be formed by preparing a conductive
paste composed of fine particles of silver, a powder of low melting point glass, etc.
made into a pasty state by an organic solvent, screen-printing the conductive paste
on a surface of the glass 10, and baking the printed conductive paste. Alternatively,
the core wire-side antenna element 30 and the ground-side antenna element 50 may be
formed on a surface of the glass 10 via a sheet (not shown), in which instance the
sheet may be a transparent insulating film sheet fixedly attached to a surface of
the glass located inside the window opening 5, and the core wire-side power supplying
section 20, the core wire-side antenna element 30, the ground-side power supplying
section 40, and the ground-side antenna element 50 may be formed directly on the sheet.
The sheet provided with the core wire-side power supplying section 20, the core wire-side
antenna element 30, the ground-side power supplying section 40, and the ground-side
antenna element 50 also constitutes an antenna for a vehicular glass.
[0025] The core wire-side antenna element 30 includes, at least, a core wire-side first
element 31 and a core wire-side second element 32. The core wire-side first element
31 extends from the core wire-side power supplying section 20 as a starting point
to a terminal end h1. The core wire-side second element 32 extends from the terminal
end h1 of the core wire-side first element 31 as a starting point to a terminal end
h2. The core wire-side antenna element 30 may further include a core wire-side third
element 33 extending from the terminal end h1 of the core wire-side first element
31 as a starting point to a terminal end h3, an a core wire-side fourth element 34
extending from the terminal end h2 of the core wire-side second element 32 as a starting
point to a terminal end h4.
[0026] The ground-side antenna element 50 includes at least a ground-side first element
51. The ground-side first element 51 extends from the ground-side power supplying
section 40 as a starting point to a terminal end g1. The ground-side antenna element
50 may further include a ground-side second element 52 extending from the terminal
end g1 of the ground-side first element 51 as a starting point to a terminal end g2.
[0027] In the example shown in Fig. 1, the core wire-side power supplying section 20 and
the ground-side power supplying section 40 are disposed in proximity to a left edge
5b of the window opening 1 and arranged in vertical juxtaposition with each other.
The core wire-side first element 31 extends along that part of the edge of the window
opening 5 closest to the core wire-side first element 31 in such a manner as to keep
a first predetermined distance relative to the closest edge part of the window opening
5. The first predetermined distance between the core wire-side first element 31 and
the closest edge part of the window opening 5 will be sometimes referred to as "edge
distance". The edge distance measured at a first part of the core wire-side first
element 31 located closest to the left edge 5b of the window opening 5 may be made
equal to or made different from an edge distance measured at a second part of the
core wire-side first element 31 located closest to an upper edge 5a of the window
opening 5. Preferably, the core wire-side first element 31 extends along the closest
edge part of the window opening 5 in such a manner that more than 50% of the entire
length of the core wire-side first element 31 (extending from the core wire-side power
supplying section 20 to the terminal end h1) can keep the first predetermined distance
(edge distance) relative to the closest edge part of the window opening 5. More preferably,
the core wire-side first element 31 extends along the closest edge part of the window
opening 5 in such a manner that more than 70% of the entire length of the core wire-side
first element 31 (extending from the core wire-side power supplying section 20 to
the terminal end h1) can keep the first predetermined distance (edge distance) relative
to the closest edge part of the window opening 5.
[0028] As shown in Fig, 1, in the case where there is a left upper corner edge 5e provided
between the upper edge 5a and the left edge 5b of the window opening 5 of the vehicle
body 1, the core wire-side first element 31 may be arranged to extend without consideration
of the element-to-edge distance between relative to the left upper corner edge 5e.
Alternatively, the core wire-side first element 31 may be arrange to extend along
the left upper corner edge 5e of the window opening 5 in such a manner that the first
predetermined distance (edge distance) is kept between that part of the core wire-side
first element closest to the left upper corner edge 5e and the left upper corner edge
5e. The same shall apply when a corner edge is located at another position.
[0029] In the example shown in Fig. 1, the ground-side first element 51 extends from the
ground-side power supplying section 40 as the starting point to the terminal end g1
along the core wire-side first element 31 in such a manner as to keep a second predetermined
distance relative to the core wire-side first element 31. The second predetermined
distance between the core wire-side first element 31 and the ground-side first element
51 may be sometimes referred to as "first element distance". The first element distance
measured at first parts of the core wire-side first element 31 and the ground-side
first element 51 extending along the left edge 5b of the window opening 5 may be made
equal to or made different from a first element distance measured at second parts
of the core wire-side first element 31 and the ground-side first element 51 extending
along the upper edge 5a of the window opening 5. A first element distance measured
at third parts of the core wire-side first element 31 and the ground-side first element
51 extending along the left upper corner edge 5e of the window opening 5 may be made
equal to the aforesaid two first element distances or alternatively made different
from at least one of the aforesaid two first element distances.
[0030] The starting point h1 of the core wire-side second element 32 is located at a position
separated from each of the left edge 5b and a right edge 5d by a prescribed distance
or more. In other words, the core wire-side first element 31 is extended to a position
separated from each of the left and right edges 5b, 5d of the window opening 5 by
the prescribed distance or more.
[0031] In the example shown in Fig. 1, the terminal end h2 of the core wire-side second
element 32 is located at a position separated in a vertical direction from the starting
point h1 of the core wire-side second element 32 by a third predetermined distance
or more. In other words, the core wire-side second element 32 extends in the substantially
vertical direction from the position h1 (as a starting point separated from each of
the left and right edges 5b, 5d of the window opening 5 by the prescribed distance
or more) to the terminal end h2 separated from the starting point h1 by the third
predetermined distance or more.
[0032] The core wire-side third element 33 extends from the terminal end h1 as a starting
point to the terminal end h3 along a direction in which the core wire-side first element
31 is extending to the terminal end h1. The core wire-side fourth element 34 extends
from the terminal end h2 of the core wire-side second element 32 as a starting point
along a lower edge 5c of the window opening 5 to the terminal end h4 in such a manner
as to keep a fourth predetermined distance relative to the lower edge 5c of the window
opening 5. The fourth predetermined distance between the core wire-side fourth element
34 and the lower edge 5c of the window opening 5 may be equal to the first predetermined
distance (edge distance).
[0033] In the example shown in Fig. 1, the ground-side second element 52 extends from the
terminal end g1 of the ground-side first element 52 as a starting point in a substantially
vertical direction to the terminal end g2. A distance between the ground-side second
element 52 and the core wire-side second element 32 may be equal to the first element
distance between the aforesaid first parts of the core wire-side first element 31
and the ground-side first element 51 extending along the left edge 5b of the window
opening 5. The core wire-side third element 33, the core wire-side fourth element
34, and the ground-side second element 52 will be sometimes referred to as "adjusting
elements". The adjusting elements will be described later on.
[0034] In general, the antenna has a high sensitivity reception radio wave frequency band
which is determined by a total length of antenna elements formed by conductive material.
More specifically, the reception sensitivity is improved when the total length of
the antenna elements is determined such that the respective antenna elements resonate
at approximately an intermediate frequency of a reception radio wave frequency band.
Normally, in order to improve the reception sensitivity, the total length of the antenna
elements is increased as the reception radio wave frequency band becomes low, and
conversely, when the reception radio wave frequency band becomes high, the total length
of the antenna elements is reduced.
[0035] The vehicular glass antenna 10 shown in Fig. 1 is configured such that a reception
radio wave frequency band for the vehicular glass antenna 10 is determined mainly
by a length of the core wire-side second element 32. In other words, the vehicular
glass antenna 10 shown in Fig. 1 is configured such that antenna elements other than
the core wire-side second element 32, and more particularly, the core wire-side first
element 31 and the ground-side first element 51 can only give little or limited influence
on performance of the vehicular glass antenna 10, such as reception sensitivity, frequency
characteristic, etc. Ideally, the vehicular glass antenna 10 is configured such that
the core wire-side first element 31 and the ground-side first element 51 function
as transmission paths and not as antennas.
[0036] To this end, it is preferable for the vehicular glass antenna 10 that the edge distance
(i.e., the first predetermined distance between the core wire-side first element 31
and that part of the edge of the window opening 5 closest to the core wire-side first
element 31) is less than 40 mm. Furthermore, the first element distance (i.e., the
second predetermined distance between the core wire-side first element 31 and the
ground-side first element 51) is preferably in a range of 5 to 20 mm. Specific optimum
values for the edge distance and the first element distance are determined by simulation
or measurement performed in accordance with the size of the vehicular glass antenna
10 and/or the window opening 5 such that the effects of the core wire-side first antenna
31 and the ground-side first antenna 51 upon performance of the vehicular glass antennal
10 become small.
[0037] In order to improve the reception sensitivity, it is preferable that adverse effects
of the vehicle body (such as loss of antenna function of the core wire-side second
element 32), which may occur when the core wire-side second element 32 is disposed
in proximity to the vehicle body as a grounding potential, should be minimized. Preferably,
the starting point h1 and the terminal end h2 of the core wire-side second element
32 are separated from each of the left and right edges 5b, 5d of the window opening
5 by at least 50 mm or more.
[0038] Additionally, since the vehicular glass antenna 10 shown in Fig. 1 is designed for
reception of vertically polarized radio waves such as DAB radio waves, it is preferable
to arrange the vehicular glass antenna 10 in the vehicle body 1 such that the core
wire-side second element 32 extends in a direction substantially perpendicular to
a horizontal plane (i.e., a substantially vertical direction). Furthermore, in the
case where the vertically polarized radio waves to be received by the vehicular glass
antenna 10 shown in Fig. 1 include, for example, those in DAB BAND III (i.e., a frequency
band of 174 MHz to 240 MHz), a length of the core wire-side second element 32 as measured
from the starting point h1 to the terminal end h2 is preferably more than 140 mm.
[0039] Thus, the vehicular glass antenna 10 shown in Fig. 1 ensures that the core wire-side
first element 31 and the ground-side first element 51 can be arranged in proximity
to the vehicle body serving as the grounding potential to the extent that they can
give only a small or limited influence on performance of the vehicular glass antenna
10. As a result, the core wire-side second element 32 is allowed to be arranged, without
being subjected to a limitation by the position of the core wire-side power supplying
section 20, in such a manner as to keep an appropriate distance from the left and
right edges 5b, 5d of the window opening 5 which can sufficiently reduce the effect
of the vehicle body 1 on the core wire-side second element 32.
[0040] Furthermore, since the starting point of the core wire-side second element 32 is
disposed at an upper part of the window opening 5 without being limited by the position
of the power supplying sections and particularly the core wire-side power supplying
section 20, it is possible to secure a length of the core wire-side second element
32 which is suited for a frequency band of the vertically polarized radio waves to
be received by the vehicular glass antenna 10. More particularly, when the vertically
polarized radio waves to be received by the vehicular glass antenna 10 include the
DAB BAND III, which is lower than L-BAND (i.e., a frequency band of 1452 MHz to 1492
MHz), the length of the core wire-side second element 32 can be adjusted within a
range more than 140 mm. The vehicular glass antenna 10 shown in Fig. 1 can secure
desired reception sensitivity without being subjected to a limitation by a power supplying
position of the vehicle.
[0041] The core wire-side third element 33, the core wire-side fourth element 34 and the
ground-side second element 52, which are provided as adjusting elements, may be added
singly or in combination. In the vehicular glass antenna 10 shown in Fig. 1, antenna
elements other than the core wire-side second element 32 give little influence to
performance of the vehicular glass antenna 10. It is not to be said that these antenna
elements give no effect on the performance of the vehicular glass antenna 10.
[0042] For instance, it may occur that the vehicular glass antenna 10 cannot secure sufficient
reception sensitivity for radio waves to be received only by adjustment of the length
of the core wire-side second element 32. Under such condition, at least one of the
core wire-side third element 33, the core wire-side fourth element 34 and the ground-side
second element 52 may be added, and through an adjustment of the length of the added
one or more of the antenna elements 33, 34, 52, the vehicular glass antenna 10 can
secure a desired level of reception sensitivity for the radio waves to be received.
As an alternative, at least one of the core wire-side third element 33, the core wire-side
fourth element 34, and the ground-side second element 52 may be added and, through
an adjustment of the length of the added one or more of the antenna elements 33, 34,
52, reception sensitivity can be secured for radio waves in a frequency band (e.g.,
DAB L-BAND) which is different from a frequency band of radio waves to be received
mainly by the core wire-side second element 32.
[0043] In the case where the length of the core wire-side second element 32 has a fixed
value, an adjustment of the lengths of the core wire-side third element 33 and the
core wire-side fourth element 34 is preferably be achieved such that one of the third
and fourth elements 33, 34 is increased and, at the same time, the other of the third
and fourth elements 33, 34 is decreased. Similarly, an adjustment of the lengths of
the core wire-side fourth element 34 and the ground-side second element 52 is preferably
achieved such that one of these elements 34, 52 is increased and, at the same time,
the other of these elements 34, 52 is decreased.
2. First Embodiment
[0044] Fig. 2 shows a first embodiment of the vehicular glass antenna 10. The first embodiment
shown in Fig. 2 is comprised of a vehicular glass antenna 10 which is configured for
installation in a window opening for a rear quarter glass for the purpose of reception
of radio waves of BAND III and L-BAND DAB frequencies. In the vehicular glass antenna
10 according to the first embodiment shown in Fig. 2, these parts which are designated
by reference characters identical to those used in Fig. 1 are the same as or corresponding
to those of the vehicular glass antenna according to the basic structure shown in
Fig. 1. In Fig. 2, those parts provided outside the window opening 5 are omitted from
illustration. Additionally, a shielding film which is identical to the one 15 shown
in Fig. 1 is not shown in Fig. 2.
[0045] The vehicular glass antenna 10 according to the first embodiment shown in Fig. 2
includes a core wire-side power supplying section 20, a core wire-side first element
31, a core wire-side second element 32, a core wire-side third embodiment 33, a core
wire-side fourth element 34, a ground-side power supplying section 40, and a ground-side
first element 51. In the first embodiment, the core wire-side power supplying section
20 and the ground-side power supplying section 40 are arranged in vertical juxtaposition
with each other at a position which is in proximity to a left edge 5b of the window
opening 5 and which is substantially intermediate between an upper edge 5a and a lower
edge 5c of the window opening 5. The first embodiment is therefore directed to such
a vehicular glass antenna 10 which is applicable to a vehicle having a power supplying
position which is located in proximity to the left edge 5b of the window opening 5
and substantially intermediate between the upper edge 5a and the lower edge 5c of
the window opening 5.
[0046] According to the first embodiment, the core wire-side first element 31 includes a
core wire-side first element main wire 31a extending from a left side edge of the
core wire-side power supplying section 20 as a starting point, and a core wire-side
first element subsidiary wire 31b extending from a right side edge of the core wire-side
power supplying section 20 as a starting point. It is to be noted, however, that the
terms "main wire" and "subsidiary wire" are used herein for the purpose of convenience
only and they do not mean that the core wire-side first element main wire 31a is an
essential or indispensable wire while the core wire-side first element subsidiary
wire 31b is a subsidiary or auxiliary wire. This also applies to other antenna elements
as well as to other embodiments. Although in the embodiment shown in Fig. 2, the core
wire-side first element main wire 31a and the core wire-side first element subsidiary
wire 31b are arranged to extend from different positions on the core wire-side power
supplying section 20, it is possible for another embodiment or another antenna element
to arrange the core wire-side first element main wire 31a and the core wire-side first
element subsidiary wire 31b in such a manner as to extend from the same position on
the core wire-side power supplying section 20.
[0047] The core wire-side first element main wire 31 extends from the left side edge of
the core wire-side power supplying section 20 along the left edge 5b of the window
opening 5 while keeping a predetermined edge distance relative to the left edge 5b
until it approaches the upper edge 5a. After arrival at a position proximate to the
upper edge 5a of the window opening 5, the core wire-side first element main wire
31a is arranged to extend along the upper edge 5a while keeping the predetermined
edge distance relative to the upper edge 5a until it arrives at a terminal end h1.
The core wire-side first element main wire 31a is arranged only in consideration of
the edge distance relative to the left edge 5b and the edge distance relative to the
upper edge 5a without taking into consideration of an edge distance relative to a
left upper corner edge 5e formed between the upper edge 5a and the left edge 5b of
the window opening 5. The core wire-side first element subsidiary wire 31b is arranged
such that at least more than 70% of the entire length of the core wire-side first
element subsidiary wire 31b extends along the core wire-side first element main wire
31a while keeping a predetermined element distance relative to the core wire-side
first element main wire 31a.
[0048] The core wire-side first element 31 as a whole is arranged such that at least more
than 70% of the entire length extending from the core wire-sider power supplying section
20 as a starting point to the terminal point h1 extends along a closest edge part
of the window opening 5 while keeping a predetermined distance (edge distance) relative
to the closest edge part. In the first embodiment, the edge distance between the left
and upper edges 5b, 5a of the window opening 5 and the core wire-side first element
main wire 31a is less than 10 mm. More specifically, in the first embodiment, the
edge distance between the core wire-side first element main wire 31a and the closest
edge part of the window opening 5 is smaller at a first longitudinal part of the core
wire-side first element main wire 31a extending alongside the left edge 5b than at
a second longitudinal part of the core wire-side first element main wire 31a extending
alongside the upper edge 5a.
[0049] The core wire-side first element 31 in the first embodiment has a looped shape as
the core wire-side first element main wire 31a and the core wire-side first element
subsidiary wire 31b are closed by the core wire-side second element 32 which extends
from the terminal end h1 of the core wire-side first element 31 or the core wire-side
first element main wire 31a. The antenna element (e.g., the core wire-side first element
31) having such looped shape is able to achieve a similar effect to that attained
when the length width or diameter of an antenna element is increased. In general,
the resistance value of an antenna element reduces with an increase in the line width
or diameter, which will lead to an improvement of the reception sensitivity of the
vehicular glass antenna 10. The antenna element having a looped shape is inconspicuous
as compared to an antenna element having an enlarged line width or diameter and, hence,
the antenna reception sensitivity and the appearance of the entire vehicle can be
compatibly achieved. In the first embodiment, the element distance between the core
wire-side first element main wire 31a and the core wire-side first element subsidiary
wire 31b is approximately 20 mm. The same shall apply to other antenna elements as
long as they have a looped shape.
[0050] In the first embodiment, the core wire-side second element 32 extends from the terminal
end h1 of the core wire-side first element 31 or the core wire-side first element
main wire 31 as a starting point to a terminal end h2 in a substantially vertical
direction and, more precisely, in parallel to the left edge 5b of the window opening
5. Since a lower edge 5c of the window opening 5 curves upward as it approaches a
right edge 5d, the arrangement of the core wire-side second element 32 in parallel
to the left edge 5b allows the core wire-side second element 32 to have a larger length
than a length obtain when it extends exactly in a vertical direction from the terminal
end h1 of the core wire-side first element 31 or the core wire-side first element
main wire 31a. In the first element, the length of the core wire-side second element
32 is more than 190 mm. The reception sensitivity of the antenna tends to deteriorate
as its orientation deviates from the vertical direction. It is therefore preferable
that the core wire-side second element 32 is arranged to extend in a direction close
to the vertical direction as much as possible. In the first embodiment, the terminal
end h1 of the core wire-side first element 31 or the core wire-side first element
main wire 31a, which is a starting point of the core wire-side second element 32,
and the terminal end h2 of the core wire-side second element 32 are separated by at
least more than 100 mm from each of the left edge 5b and the right edge 5d of the
window opening 5.
[0051] The core wire-side third element 33 in the first embodiment includes a core wire-side
third element main wire 33a extended to a terminal end h3 along a direction in which
the core wire-side first element main wire 31a, and a core wire-side third element
subsidiary wire 33b extended along a direction in which the core wire-side first element
subsidiary wire 31b extends. The core wire-side third element subsidiary wire 33b
is joined with the core wire-side third element main wire 33a at the terminal end
h3. Thus, the core wire-side third element 33 has a looped shape.
[0052] The core wire-side fourth element 34 in the first embodiment extends from the terminal
end h2 of the core wire-side second element 32 as a starting point to a terminal end
h4 along the lower edge 5c of the window opening 5 in such a manner as to keep a predetermined
edge distance relative to the lower edge 5c. The edge distance for the core wire-side
fourth element 34 is equal to the edge distance defined between the upper edge 5a
of the window opening 5 and the core wire-side first element main wire 31a of the
core wire-side first element 31.
[0053] In the first embodiment, the ground-side antenna element only have a ground-side
first element 51. The ground-side first element 51 extends from the ground-side power
supplying section 40 as a starting point to a terminal end g1 along the core wire-side
first element 31 (more specifically, the core wire-side first element subsidiary wire
31b) while keeping a predetermined first element distance relative to the core wire-side
first element 31 (the core wire-side first element subsidiary wire 31b). The first
element distance in the first embodiment is approximately 10 mm or less. However,
the first element distance is set to be smaller at a part extending along the left
edge 5b of the window opening 5 than at a part extending along the upper edge 5a of
the window opening 5. The ground-side first element 51 in the first embodiment has
a ground-side first element subsidiary wire 51b by which that part of the ground-side
first element 51 extending along the left edge 5b of the window opening 5 is made
to form a looped shape. The remaining part of the ground-side first element 51, which
extends along that part of the core-side first element 31 extending along the upper
edge 5a of the window opening 5, may be made to have a looped shape.
[0054] As thus far described, the vehicular glass antenna 10 according to the first embodiment
can secure a more than 190-mm-length of the core wire-side second element 32 even
though it is installed in the window opening 5 having a relatively small size in a
vertical direction (e.g., less than 200 mm).
3. Second Embodiment
[0055] Fig. 3 shows a second embodiment of the vehicular glass antenna 10. The second embodiment
shown in Fig. 3 is comprised of a vehicular glass antenna 10 configured to be installed
in a window opening 5 for a rear quarter glass in a same manner as the first embodiment
for the purpose of reception of radio waves of BAND III and L-BAND DAB frequencies.
The vehicular glass antenna according to the second embodiment shown in Fig. 3 is
therefore a modified form of the vehicular glass antenna according to the first embodiment.
Following description will be limited to these parts of the vehicular glass antenna
10 of the second embodiment which are different from those described in conjunction
with the first embodiment. As will be discussed under the heading "Performance Evaluation
of First and Second Embodiments", the vehicle glass antenna 10 of the second embodiment
is designed to have a same level of reception sensitivity as the vehicular glass antenna
10 of the first embodiment.
[0056] The vehicular glass antenna 10 of the second embodiment shown in Fig. 3 includes
a core wire-side power supplying section 20, a core wire-side first element 31, a
core wire-side second element 32, a core wire-side third element 33, a core wire-side
fourth element 34, a ground-side power supplying section 40, a ground-side first element
51, and a ground-side second element 52. In the second embodiment, the core wire-side
power supplying section 20 and the ground-side power supplying section 40 are disposed
in vertical juxtaposition at a position located in proximity to a left upper corner
edge 5e of the window opening 5. The vehicular glass antenna 10 of the second embodiment
is therefore is suitable for application in a vehicle having a power supplying position
located in proximity to the left upper corner edge 5e of the window opening 5.
[0057] In the second embodiment, a core wire-side first element main wire 31a and a core
wire-side first element subsidiary wire 31b extend from a same position on the core
wire-side power supplying section 20. The core wire-side first element main wire 31a
extends from the core wire-side power supplying section 20 as a starting point in
such a manner as to first approach an upper edge 5a of the window opening 5 then run
rightward along the upper edge 5a while keeping a predetermined edge distance relative
to the upper edge 5 unit it arrives at a terminal end h1. The edge distance between
the core wire-side first element main wire 31a and the upper edge 5a of the window
opening 5 is equal to the edge distance in the first embodiment, which is defined
between the upper edge 5a of the window opening 5 and a corresponding longitudinal
part of the core wire-side first element main wire 31a.
[0058] In the second embodiment, the terminal end h1 of the core wire-side first element
31 is located more closely to a right edge 5d of the window opening 5 than the terminal
end h1 of the core wire-side first element 31 in the first embodiment. The core wire-side
second element 32 has a length more than 180 mm, which is smaller than the length
of the core wire-side second element 32 in the first embodiment. Furthermore, lengths
of the core wire-side first element 31 and the ground-side first element 51 are set
to be smaller in the second embodiment than in the first embodiment.
[0059] In order to secure a reception sensitivity similar to that in the first embodiment,
lengths of the core wire-side third element 33 and the core wire-side fourth element
34 in the second embodiment are set to be larger than lengths of the core wire-side
third element 33 and the core wire-side fourths elements 33, 34, respectively, in
the first embodiment. Furthermore, in the second embodiment, the ground-side second
element 52 is also provided. Additionally, the entire ground-side first element 51
in the second embodiment has a looped shape. A first element distance defined between
the ground-side first element 51 and the core wire-side first element 31 (more precisely
between the core wire-side first element subsidiary wire 31b and a ground-side first
element main wire 51a) is set to be larger than the first element distance in the
first embodiment which is defined at a part extending along the left edge 5b of the
widow opening 5.
[0060] In the first and second embodiments, a total length of antenna elements is designed
to be substantially equal regardless of whether the total length is obtained when
only main wires of looped portions are taken into consideration, or obtained when
both of the main and subsidiary wires of the looped portions are taken into consideration.
4. Performance Evaluation of First and Second Embodiments
[0061] Fig. 4 is a graph showing reception sensitivities of the vehicular glass antennas
according to the first and second embodiments of the present invention. In the graph
shown in Fig. 4, a horizontal axis represents the frequency (MHz), and a vertical
axis represents the sensitivity (dBd). A range of the frequency shown on the horizontal
axis of the graph of Fig. 4 is from 174 to 240 MHz, which corresponds to a frequency
band assigned to BAND III OAB frequencies.
[0062] In the graph shown in Fig. 4, a solid line 60 represents a frequency characteristic
of the vehicular glass antenna 10 according to the first embodiment, and a broken
line 70 represents a frequency characteristic of the vehicular glass antenna 10 according
to the first embodiment. As is evident from the frequency characteristics, in both
the first and second embodiments, a reception sensitivity exceeding -10.0 dBd is achieved
over the substantially entire frequency range shown in Fig. 4 excepting that the reception
sensitivity in the second embodiment is lowered to be close to -12.0 dBd at a frequency
around 180 MHz. This means that not only in an application to a vehicle having a power
supplying position located in proximity to the left edge 5b of the window opening
5 and intermediate between the upper and lower edges 5a, 5c of the window opening
5, but also in an application to a vehicle having a power supplying position located
in proximity to a left upper corner edge 5e of the window opening 5, the vehicular
glass antennas 10 of the present invention can exhibit a sufficient reception sensitivity.
[0063] Furthermore, the frequency characteristics of the first and second embodiments have
substantially the same reception sensitivity over the substantially entire frequency
range shown in Fig. 4 except for a frequency around 180 MHz. This also means that
the vehicular glass antennas 10 of the present invention can possess substantially
the same frequency characteristic regardless of whether the power supplying position
of the vehicle is located in proximity to the left edge 5b of the window opening 5
and intermediate between the upper and lower edges 5a, 5c of the window opening 5,
or located in proximity to the left upper corner edge 5e of the window opening 5.
[0064] Additionally, the vehicular glass antennas 10 according to the first and second embodiments
of the invention are able to secure a sufficient reception sensitivity even when they
are installed in a window opening 5 having a relatively small size in a vertical direction
(e.g., less than 200 mm).
5. Other Embodiments
[0065] The present invention should by no means be limited to the first and second embodiments
described above. Rather, various antenna patterns other than those of the first and
second embodiments can be realized by adjusting the antenna elements in terms of the
length, arrangement, and presence/absence of a looped shape. Needless to say, the
position of the power supplying sections and the pattern of antenna elements can be
reversed left and right or up and down.
[0066] Fig. 5(A) shows a structural example of the vehicular glass antenna in which a core
wire-side antenna element 30 and a ground-side antenna element 50 do not have a looped
shape. In the vehicular glass antenna 10 shown in Fig. 5(A), a core wire-side second
element 32 extends in a substantially vertical direction. In the case where the vehicular
glass antenna 10 can possess a sufficient reception sensitivity for radio waves in
the required frequency bands without providing a looped shape, a fine adjustment of
e.g., the length of antenna elements can be achieved easily as compared to the case
where the vehicular glass antenna does not have a looped shape.
[0067] Fig. 5(B) shows a structural example of the vehicular glass antenna in which only
a core wire-side antenna element 30 has a looped shape, and a core wire-side third
element 33 is not present. The vehicular glass antenna 10 exemplified in Fig. 5(A)
and the vehicular glass antenna 10 exemplified in Fig. 5(B) are designed for use in
the same radio-wave frequency band to be received and possess the same reception sensitivity.
The vehicular glass antenna 10 shown in Fig. 5(B) differs from that of Fig. 5(A) in
that a core wire-side first element 31 has a looped shape provided in place of the
core wire-side third element 33, and an edge distance of the core wire-side first
element 31 and an edge distance of the core wire-side fourth element 34 are set to
be smaller than those shown in Fig. 5(A). Due to the absence of the core wire-side
third element 33, the vehicular glass antenna 10 shown in Fig. 5(B) has a reduced
number of antenna elements to be adjusted in length, which will facilitate fine adjustment
of the vehicular glass antenna.
[0068] Fig. 6(A) shows an example of the vehicular glass antenna 10, which is installed
in a vehicle having a window opening 5 having a curved left upper corner edge 5e between
an upper edge 5a and a left edge 5b. In the example shown in Fig. 6(A), a core wire-side
first element 31 is arranged to extend to a terminal end h1 while an edge distance
relative to the left edge 5b of the window opening 5, an edge distance relative to
the curved left upper corner edge 5e, and an edge distance relative to the upper edge
5a are taken into account. The core wire-side first element 31 has a longitudinal
portion closest to the left upper corner edge 5e of the window opening 5, which extends
along the left upper corner edge 5e in such a manner as to draw a curved line while
keeping the edge distance relative to the left upper corner edge 5e. A ground-side
first element 51 has a longitudinal portion extending along the curved longitudinal
portion of the core wire-side first element 31, the longitudinal portion extending
in such a manner to draw a curved line.
[0069] Fig. 6(B) shows an example of the vehicular glass antenna 10, which is installed
in a vehicle having a window opening 5 having a rounded shape as a whole. A core wire-side
first element 31 extends along an edge of the window opening 5 and a ground-side first
element 51 extends along the core wire-side first element 31, so that in the example
shown in Fig. 6(B), the core wire-side first element 31 and the ground-side first
element 51 extend with roundness. A core wire-side fourth element 34 shown in Fig.
6(B) extends to draw a straight line. However, if a part of the edge of the window
opening 5 closest to the core wire-side fourth element 34 is formed by a curved line,
the core wire-side fourth element 34 may extend in a manner to draw a curved line.
It is preferable however that a core wire-side second element 32 extends to draw a
straight line as it give a great influence to performance of the vehicular glass antenna
10. Preferably, a ground-side second element 52 extending along the core wire-side
second element 32 extends to draw a straight line. Except for the core wire-side second
element 32 and the ground-side second element 52, the antenna elements may be extended
to draw a curved line according to the shape of an edge of the window opening 5 closest
to each of the antenna elements.
[0070] Though not shown in the embodiments discussed above, the core wire-side second element
32 and/or the ground-side second element 52 may have a looped shape. However, since
the length of the core wire-side second element 32 gives a great influence to performance,
such as reception sensitivity, of the antenna, it is assumed that the frequency of
fine adjustments of the length of the core wire-side second element is high. If the
core wire-side second element 32 has a looped shape, a fine length adjustment should
be performed for two wires. To facilitate the fine adjustment, it is preferable that
the core wire-side second element 32 does not have a looped shape.