Technical Field
[0001] The invention relates to a radio frequency phase shifting device with a transmission
line comprising a first electrode and a second electrode that are spaced at a distance
to each other, and which are suitable and used for propagation of a radio frequency
electromagnetic signal along the first electrode and the second electrode with a phase
difference of 180° between the respective electromagnetic signals, wherein a tunable
dielectric material affects a phase shift of the electromagnetic signal that is propagated
along the transmission line.
Background of the invention
[0002] Phase shifting devices can be used to modify the relative displacement between two
corresponding features like peaks or zero crossings of an electromagnetic wave or
signal without changing the frequency of the electromagnetic wave or signal. When
two or more electromagnetic signals of the same frequency are superimposed, the result
depends on the phase difference between the respective electromagnetic signals. The
electromagnetic signals can be reinforced or weakened. Furthermore, by superimposing
two or more electromagnetic waves that are radiated by respective antennas, the phase
difference between the radiated electromagnetic waves will determine a direction of
a reinforced superposition of the electromagnetic waves, resulting in a preferred
direction of irradiation originating from the respective antennas.
[0003] In order to intensify the reception or emission of electromagnetic irradiation from
a given direction, a phased array antenna comprises several antenna elements that
are distributed next to each other. The phase difference of electromagnetic signals
received or emitted by the respective antennas is predetermined in such a manner that
the superposition of the respective signals is maximized for a given direction, resulting
in enhanced signal sensitivity or signal emission for said direction.
[0004] There are known prior art phase shifting devices that create a pre-set phase difference
between the incoming and outgoing signal. A phased array antenna that is equipped
with such constant phase shifting devices can be designed to maximize the signal sensitivity
or signal emission for a given single direction.
[0005] Furthermore, phase shifting devices with a tunable phase difference are known and
described e.g. in
EP 2 761 693 A1 or
EP 2 956 986 B1. These phase shifting devices include a linear transmission line comprising a first
electrode and a second electrode that are spaced at a distance to each other, wherein
a tunable dielectric material is arranged between the first electrode and the second
electrode. The phase difference created by a tunable phase shifting device can be
tuned, i.e. it can be operated to produce different phase differences whereby the
respective phase difference can be modified and controlled by a control setting applied
to the tunable dielectric material which affects the phase of the signal along the
linear transmission line. A phased array antenna with several antennas that are interconnected
with such tunable phase shifting devices can be operated in such a manner as to change
the direction of enhanced signal sensitivity or signal emission in accordance to the
requirements at a given time.
[0006] Therefore, one of the key components which are necessary to build phased array antennas
with adaptive beam forming is a tunable phase shifting device, meaning a device which
dynamically can adjust the phase or the delay of a radiofrequency signal. Usually,
there is at least one phase shifting device for each radiating element of the array
antenna. Each phase shifter device in turn is fed by a feed network. Due to the usually
required large number of radiating elements, an at least equally large number of phase
shifting devices must be integrated within a limited area in such a phase array antenna.
[0007] Accordingly, there is a need for a phase shifting device that allows for easy manufacturing,
requires little space and provides for a large phase difference between the input
signal and the output signal. Easy manufacturing is possible if techniques can be
used to fabricate a large number of electrodes at high density on an area of e.g.
0.5 m
2 which is a typical surface area for phased array antennas operating at frequencies
of e.g. 20 GHz. The necessary fabrication techniques are in principle known from Liquid
Crystal Display (LCD) manufacturing but are usually not applied to building phased
array antennas. In order to employ the fabrication techniques of LCD manufacturing
suitable tunable phase shifter topologies have to be found which can be both electrically
and also mechanically be integrated in a phased array antenna system.
[0008] Accordingly, there is a need for a phase shifting device that allows for easy manufacturing,
requires little space and provides for a large phase difference between the input
signal and the output signal.
Summary of the invention
[0009] The present invention relates to a radio frequency phase shifting device with a transmission
line with a first electrode and a second electrode, whereby the transmission line
comprises several non-overlapping sections, wherein the first electrode runs at a
distance to the second electrode, and whereby the transmission line comprises several
overlapping sections, wherein an overlapping area of the first electrode is overlapped
by a capacitor electrode area and wherein an overlapping area of the second electrode
is overlapped by a capacitor electrode area in order to provide for a parallel plate
capacitor area within the overlapping section, and whereby a tunable dielectric material
is arranged between the respective capacitor electrode areas and the overlapping area
of the first electrode and the overlapping area of the second electrode that affects
the phase of an radio frequency electromagnetic signal that propagates along the overlapping
section of the transmission line.. The phase of the electromagnetic signal that propagates
along the transmission line will be affected by the parallel plate capacitor areas
that are distributed along the transmission line. The electromagnetic signal is preferably
a radiofrequency signal with a frequency in the range of 20 kHz to 300 GHz. The phase
shifting device is adapted to transmit such a radiofrequency signal and to affect
and modify the phase of this signal.
[0010] From a topological view the transmission line with non-overlapping sections and with
overlapping sections is similar to a periodically loaded differential or balanced
transmission line. The resulting phase shift depends inter alia on the number and
the area of the parallel plate conductor areas that are implemented along the transmission
line.
[0011] Preferably the tunable dielectric material is a liquid crystal material with a high
dependency of the dielectric characteristics on an electric field that is applied
to the liquid crystal material. Suitable liquid crystal materials as well as other
tunable dielectric materials are known in the art and commercially available. The
electric field that is applied to the liquid crystal material superimposes the radio
frequency signal that is propagated along the transmission line, but this does not
significantly interfere with the signal propagation.
[0012] According to an advantageous aspect of the invention the overlapping area of the
first electrode overlaps the overlapping area of the second electrode in order to
provide for one parallel plate capacitor area. Thus, no dedicated and separate capacitor
electrodes are required.
[0013] The first electrode and the second electrode are divided into sections that do not
overlap each other and into sections that overlap each other. The tunable dielectric
material is arranged between the first electrode and the second electrode. The tunable
dielectric material may be arranged as a layer that is confined by glass or other
material. The surface of the layer may extend over both electrodes and cover overlapping
sections and non-overlapping sections of the first electrode and the second electrode.
It is also possible to limit the tunable electric material to separate areas that
only cover the respective capacitor electrode areas between the first electrode and
the second electrode.
[0014] According to an alternative aspect of the invention the first electrode and the second
electrode are arranged side by side, and a capacitor electrode is arranged above or
below the first electrode and the second electrode in such a manner that a first capacitor
electrode area overlaps the overlapping area of the first electrode and that a second
capacitor electrode area overlaps the overlapping area of the second electrode, thus
providing for two parallel plate capacitor areas between the capacitor electrode and
the respective overlapping areas within the overlapping section. The first electrode
and the second electrode may be arranged next to another on the same level of the
phase shifting device. In addition to the first and the second electrode at least
one or a few, but preferably many capacitor electrodes are arranged at another level
below or above or below and above the first and second electrodes. The use of separate
capacitor electrodes allows for complex shapes of the parallel plate capacitor areas
along the transmission line and may simplify the manufacturing of the phase shift
device.
[0015] According to an advantageous embodiment of the invention, the first electrode is
arranged at a first surface of a first substrate layer, in that the second electrode
is arranged at a second surface of a second substrate layer, whereby the first surface
of the first substrate layer faces the second surface of the second substrate layer
and whereby the first surface is arranged at a distance to the second surface. The
first electrode and the second electrode can be manufactured by deposition of electroconductive
material onto a corresponding nonconducting substrate layer. The two substrate layers
can be spaced at a distance to each other, thereby confining an intermediary layer
of the tunable dielectric material. Such a sandwich structure can be manufactured
by easily controllable and reliable methods. The space requirement is approximately
one millimeter for the thickness of the sandwich structure. Manufacture of the sandwich
structure is similar to fabrication of liquid crystal displays and can be integrated
into the respective production methods which then include such phase shifting devices.
The substrate layers can be made of glass or any other material with non-conductive
or sufficiently low conductive characteristics and with sufficient surface smoothness.
[0016] According to an advantageous embodiment of the invention the first surface of the
first substrate layer and the second surface of the second substrate layer confine
the tunable dielectric material. Thus, no further substrate layers are required for
confining the tunable dielectric material, which reduces the size and manufacturing
costs for the phase shifting device.
[0017] In another aspect of the invention the first electrode and the second electrode each
comprise a strip-shaped transmission line segment, whereby both transmission line
segments are directed along the transmission line. A strip-shaped transmission line
segment usually has a uniform width. Both transmission line segments can be of linear
shape, i.e. the strip-shaped transmission line segment extends along a straight line,
whereby the respective transmission segments are parallel and at a distance to each
other.
[0018] The strip-shape transmission line segment can also be curved. It is also possible
for the strip-shape transmission segment to comprise linear sections in combination
with corners or curved sections. Furthermore, the strip-shaped transmission segment
may also have a spiral shape or meandering shape. The strip-shape transmission line
segment may also have a zig-zag pattern.
[0019] According to another aspect of the invention, each of the overlapping areas of the
first electrode and/or of the second electrode is laterally protruding from the respective
strip-shaped transmission line segment of the first electrode and/or of the second
electrode. When viewed from above, the combined shape of the first electrode and the
second electrode can be similar to a ladder, wherein the strip-shaped transmission
line segment of the first electrode and of the second electrode are similar to the
first and second ladder beams, and wherein the laterally protruding overlapping areas
are similar to the rungs of the ladder. Each rung of the ladder comprises one overlapping
area that protrudes from the strip-shaped transmission line segment of the first electrode,
and one overlapping area that protrudes from the strip-shaped transmission line segment
of the second electrode. Even though the two respective overlapping areas of the first
and second electrode do overlap, they are spaced apart and separated by the tunable
dielectric material that is between the first electrode and the second electrode,
or at least between the overlapping areas of the first electrode and the second electrode.
[0020] In yet another embodiment of the invention the respective overlapping areas of the
first electrode and the second electrode provide for a rectangular or a quadratic
parallel plate capacitor area. However, the overlapping areas may have any shape and
contour that is advantageous for the desired phase shift or for the design of the
electronic component that includes the phase shifting device.
[0021] In yet another aspect of the invention, subsequent parallel plate capacitor areas
along the transmission line differ in respective distance to each other and/or in
size and/or in shape. Thus, the parallel plate capacitor areas may be of identical
shape and size and may be arranged in a regular pattern along the transmission line.
However, it might be advantageous e.g. for signal propagation or for reduced size
or manufacturing costs to arrange for parallel plate capacitor areas that have a different
shape or size along the transmission line. Also, the distance between two adjacent
parallel plate capacitor areas may vary according to demands related to size or cost
of the phase shifting device, or in order to allow for better signal propagation or
enhanced phase shifting properties of the phase shifting device.
[0022] According to another aspect of the invention, the first and second electrode can
be referenced to one or more ground electrodes located on the outward facing surfaces
of the substrate layers. However, the phase shifting device does not rely on the presence
of a ground electrode. If e.g. for reasons of integrating the sandwich structure with
other layers of a phased array antenna one or more ground electrodes are necessary,
the size and the distance of the strip shaped transmission line segments can be easily
adjusted when compared to a phase shifting device without ground electrodes.
[0023] According to an aspect of the invention, the first electrode and the second electrode
are electrically connected to a bias voltage source. The bias voltage can be a constant
bias voltage or a preferably low frequency voltage with a frequency of up to several
kHz. The bias voltage does not interfere with the signal propagation along the transmission
line of the phase shifting device. The bias voltage that is applied to the first and
second electrode by the bias voltage affects the dielectric characteristics of the
tunable dielectric material that is arranged between the first and the second electrode.
By applying a bias voltage to the first and second electrode and thereby affecting
and changing the dielectric properties of the tunable dielectric material in between
the parallel plate capacitor areas, the phase difference between the input signal
and the output signal of the phase shifting device can be easily and reliably controlled
and modified according to the respective requirements.
[0024] According to an advantageous embodiment of the invention, the first electrode is
connected to a first bias electrode which is connected to the bias voltage source,
and that the second electrode is connected to a second bias electrode which is connected
to the bias voltage source. The width of the bias electrode can be small when compared
to the width of the first electrode and of the second electrode. The width can be
approx. 10 % or less of the width of the first or second electrode. A small width
or cross-section area of the first and second bias electrodes contributes to a high
impedance of the first and second bias electrode resulting in reduced leakage of the
electromagnetic signal from the first and second electrode into the first or second
bias electrode.
[0025] In yet another embodiment of the invention the first and second bias electrodes consists
of a material with a lower electrical conductivity that the first and second electrode.
The resulting higher resistance of the bias electrodes prevents the electromagnetic
signal that propagates along the transmission line from leaking from the first and
second electrode into the first or second bias electrode. Preferably the first and
second electrode are made of or comprise a material with a high conductivity of more
than 40 * 10
6 S/m like e.g. gold or copper. The first and second bias electrodes preferably has
a sheet resistance of more than 20 Ohms/square and can be made of or comprise Indium
Tin Oxide (ITO) or Nichrome (NiCr).
[0026] According to another aspect of the invention, the width of the first and second electrode
is between 100 µm and 500 µm, preferably approx. 200 µm. Furthermore, the width of
the overlapping area between the first electrode and the second electrode is between
100 µm and 500 µm, preferably approx. 200 µm. The width of the first and second electrode
should be smaller than Lambda/10, i.e. one-tenth of the characteristic wavelength
of the electromagnetic signal that propagates along the transmission line. The lateral
distance between the first electrode and the second electrode can be less than 50
µm or even less than 25 µm. For most applications the distance is between 10 µm and
200 µm. However, it is also possible to provide for a distance of more than 200 µm.
In general, it is considered advantageous for the distance to be smaller than Lambda/10.
[0027] The invention also relates to a phased array antenna comprising several antenna elements
that are arranged at a surface of a substrate layer, a single entry point at which
a signal is transmitted to or from the several antenna elements, and for each antenna
element a corresponding phase shifting device as described above, whereby the phase
of each signal that is transmitted from the single entry point to the respective antenna
element or that is transmitted from the respective antenna element to the single entry
point is modified in order to adjust the superposition of each signal according to
the preferred direction of radiation of the antenna system.
[0028] In order to reduce the space requirement and to facilitate the manufacturing, the
phased array antenna comprises on top of each other a base layer with an entry point,
a first substrate layer with a first electrode, a tunable layer that comprises the
tunable dielectric material, a second substrate layer with a second electrode and
an antenna layer with a radiating antenna structure. The first and second electrode
can be arranged onto the respective surface of the first and second substrate layer
by any suitable method, e.g. by printing or vapor deposition or by any method used
within the semiconductor industry. The lateral dimension of the phased array antenna
can be some millimeters or up to some centimeters or decimeters. The dimensions are
preferably adapted to the frequency of the electromagnetic signal that is received
or emitted by the respective antennas. The more antennas that are incorporated into
the phased array antenna, the larger the lateral dimensions will be. The individual
antennas are preferably arranged in a regular grid pattern of a rectangular or quadratic
shape. However, it is also possible to arrange the antennas of the phased array antenna
in a circular shape with several concentric circles of individual antennas.
[0029] According to an advantageous embodiment of the invention, the first substrate layer
and the second substrate layer consists of a glass material, and the tunable layer
comprises a liquid crystal material with tunable dielectric properties.
Brief description of the drawings
[0030] The present invention will be more fully understood, and further features will become
apparent, when reference is made to the following detailed description and the accompanying
drawings. The drawings are merely representative and are not intended to limit the
scope of the claims. In fact, those of ordinary skill in the art may appreciate upon
reading the following specification and viewing the present drawings that various
modifications and variations can be made thereto without deviating from the innovative
concepts of the invention. Like parts depicted in the drawings are referred to by
the same reference numerals.
Figure 1 illustrates a schematic top view of a phased array antenna that comprises
64 individual antennas arranged in a quadratic grid pattern,
Figure 2 illustrates a schematic top view of a transmission line of a single phase
shifting device,
Figure 3 illustrates a sectional view of the transmission line as shown in figure
2 taken along the line III-III,
Figure 4 illustrates a sectional view of the transmission line as shown in figure
2 taken along the line IV-IV,
Figure 5 illustrates a topological representation of the transmission line as shown
in figure 2,
Figure 6 illustrates a schematic top view of a transmission line of a single phase
shifting device, whereby strip-shaped transmission line segments of the first and
second electrode are arranged in a zig-zag pattern,
Figure 7 illustrates a schematic top view of a transmission line of a single phase
shifting device, whereby the strip-shaped transmission line segments exhibit a square-wave
meandering pattern,
Figure 8 illustrates a schematic top view of a transmission line of a single phase
shifting device, whereby parallel plate capacitor areas along the transmission line
differ in size and in shape,
Figure 9 illustrates a schematic top view of a transmission line of a single phase
shifting device, whereby the first electrode 5 and the second electrode 6 are overlapped
by several capacitor electrodes,
Figure 10 illustrates a sectional view of the transmission line as shown in figure
9 taken along the line X-X, and
Figure 11 illustrates a sectional view of the transmission line as shown in figure
9 taken along the line XI-XI.
Detailed description of the invention
[0031] A phased array antenna 1 that is shown in figure 1 comprises 64 individual antenna
elements 2 that are arranged in a quadratic grid pattern with 8 x 8 antenna elements
2. In the center there is a single signal feed point 3 that is located on the back
side of the grid pattern. An electromagnetic signal, preferably a radiofrequency signal,
can be introduced into the phased array antenna 1 by the signal feed point 3 and distributed
to all of the respective antenna elements 2. In the same manner an electromagnetic
signal that is received by the individual antenna elements 2 of the phased array antenna
1 can be transmitted to the signal feed point 3 and extracted from the phased array
antenna. All individual antenna elements 2 are connected with the signal feed point
3. The connection comprises a dedicated phase shifting device for each individual
antenna element 2, however, the phase shifting devices are is not shown in figure
1.
[0032] The phase shifting devices can be the electrical connection of the individual antenna
elements 2 to the signal feed point 3. Preferably, for each antenna element 2 the
corresponding phase shifting device is only a part or section of the electrical connection
to the signal feed point 3.
[0033] Figure 2 illustrates a schematic top view of a transmission line 4 of a single phase
shifting device. The transmission line 4 comprises a first electrode 5 and a second
electrode 6, whereby the first electrode 5 is at a different level with respect to
the second electrode 6, thus resulting in a distance between the first electrode 5
and the second electrode 6. In figure 2 the first electrode 5 is on top of the second
electrode 6. In order to better illustrate the lateral distance between the first
electrode 5 and the second electrode 6, the first and second electrode 5, 6 are shown
slightly displaced with respect to each other, and the respective parts of the second
electrode 6 that are below the corresponding parts of the first electrode 5 are shown
with a dashed line.
[0034] Each of the first and second electrode 5, 6 comprises a strip-shaped transmission
line segment 7, 8 that runs along a straight line in the direction of a signal propagation
direction 9. At regular intervals a rectangular overlapping area 10, 11 laterally
protrudes from the respective strip-shaped transmission line segment 7, 8 of the first
electrode 5 and of the second electrode 6. Within an overlapping section 12 of the
transmission line 4, one overlapping area 10 of the first electrode 5 overlaps with
one corresponding overlapping area 11 of the second electrode 6. The two overlapping
areas 10, 11 provide for a parallel plate capacitor area 13 of quadratic shape when
viewed from the top. The overlapping sections 12 of the transmission line 4 alternate
with non-overlapping sections 14 that only comprises the strip-shaped transmission
line segments 7, 8 that are at a distance to each other and that do not overlap like
within the overlapping sections 12 of the transmission line 4.
[0035] The non-overlapping sections 14 do not change much of the phase of the electromagnetic
signal that propagates along the first and second electrode 5, 6 of the transmission
line 4 in the direction of the signal propagation direction 9, as only a small portion
of the electromagnetic field penetrates the tunable layer. However, each of the overlapping
sections 12 affects the phase of the propagating electromagnetic signal resulting
in a significant phase shift of up to 2π or more from a phase shifting device that
can be easily integrated into the phased array antenna 1 of figure 1.
[0036] A first bias electrode 15 is connected to the strip-shaped transmission segment 7
of the first electrode 5 and projects in the opposite direction of the overlapping
areas 10 of the first electrode 5. Similarly, a second bias electrode 16 is connected
to the strip-shaped transmission segment 8 of the second electrode 6 and projects
in the opposite direction of the overlapping areas 11 of the second electrode 6. The
first and second bias electrodes 15, 16 are connected to a bias voltage source not
shown in figure 2. The bias voltage source provides for a constant, i.e. DC voltage
or for a low-frequency AC voltage that is applied to the first and second electrode
5, 6 and creates an electric field in the space between the first electrode 5 and
the second electrode 6, thereby superimposing the electromagnetic field of the signal
that propagates along the transmission line 4. The electric field is perpendicular
to the plane of view, i.e. perpendicular to the parallel plate capacitor areas 13
shown in figure 2. Due to the material and the small width of the first and second
bias electrode 15, 16, the impedance of the first and second bias electrode 15, 16
is significantly higher than the impedance of the strip-shaped transmission segments
7, 8 of the first and second electrode 5, 6 which prevents the propagating electromagnetic
signal from leaking from the first and second electrode 5, 6 into the first and second
bias electrode 15, 16 and away from the transmission line 4. By choosing a highly
resistive bias electrode material the impedance of the bias electrodes can be further
increased.
[0037] Figures 3 and 4 illustrate two sectional views of a phase shifting device 17 with
a transmission line 4 as shown in figure 2. Figure 3 is a sectional view of a non-overlapping
section 14 of the transmission line 4, whereas figure 4 is a sectional view of an
overlapping section 12 of the transmission line 4.
[0038] The first electrode 5 is on top of a first substrate layer 18 made of glass material.
The second electrode 6 is on top of a second substrate layer 19 also made of glass
material. The first and second substrate layers 18, 19 are arranged at a distance
to each other with the first electrode 5 facing the second electrode 6. Between the
first and second substrate layer 18, 19 there is a tunable layer 20 that is filled
with a liquid crystal material. The dielectric properties of the liquid crystal material
can be modified by applying different bias voltages to the first and second electrode
5, 6 resulting in electric fields of different magnitude between the first and second
electrode 5, 6. In the overlapping section 12 as shown in figure 3, the overlapping
area 10 of the first electrode 5, the corresponding overlapping area 11 of the second
electrode 6 and the liquid crystal material in between provide for a parallel plate
capacitor with a capacitance that depends on the bias voltage.
[0039] The topological representation of the transmission line 4 as illustrated in figure
5 is that of a periodically loaded differential transmission line with the two electrodes
5, 6 and capacitive loads 21 of the overlapping sections 12 that alternate with the
non-overlapping sections 14.
[0040] Figure 6 illustrates a schematic top view of an alternative embodiment of the transmission
line 4, whereby the strip-shaped transmission line segments 7, 8 of the first and
second electrode 5, 6 are arranged in a zig-zag pattern. This allows for longer non-overlapping
areas 22 of the respective first and second electrodes 5, 6 between the overlapping
sections 12 along the transmission line 4 when compared to a straight-line arrangement
of the transmission line segments 7, 8 as shown in Figure 2.
[0041] Figure 7 illustrates a schematic top view of a transmission line 4 of a single phase
shifting device, whereby the strip-shaped transmission line segments 7, 8 exhibit
a square-wave meandering pattern. The first electrode is separately shown in Figure
7a, the second electrode is separately shown in Figure 7b, and the overlapping arrangement
of both first and second electrode 5, 6 is shown in Figure 7c.
[0042] Figure 8 illustrates a schematic top view of a transmission line of a single phase
shifting device that is similar to the embodiment shown in Figure 2. However, the
parallel plate capacitor areas 13 along the transmission line 4 differ in size and
in shape. Furthermore, the distance between subsequent parallel plate capacitor areas
13 may also vary along the transmission line 4.
[0043] Figure 9 illustrates a schematic top view of a transmission line of a single phase
shifting device, whereby the first electrode 5 and the second electrode 6 each consists
of a straight-line strip-shaped transmission line segment 7, 8 that are directed along
the direction of the transmission line 4 that equals the signal propagation direction
9. The transmission line segments 7, 8 are overlapped by several rectangular capacitor
electrodes 23 that are directed perpendicular to the signal propagation direction
9. A first capacitor electrode area 24 of each capacitor electrode 23 overlaps with
the corresponding overlapping area 10 of the first electrode 5, and a second capacitor
electrode area 25 of each capacitor electrode 23 overlaps with the corresponding overlapping
area 11 of the second electrode 6. Thus, the first and second capacitor electrode
areas 24, 25 and the corresponding overlapping areas 10, 11 of the first and second
electrode 5, 6 provide for two separate parallel plate capacitor areas 13 within each
overlapping section 12 of the transmission line 4.
[0044] Figures 10 and 11 illustrate two sectional views of a phase shifting device 17 with
a transmission line 4 as shown in figure 9. Figure 10 is a sectional view of a non-overlapping
section 12 of the transmission line 4, whereas figure 11 is a sectional view of an
overlapping section 14 of the transmission line 4. Both first and second electrode
5, 6 are on the same level and on top of a first substrate layer 18 made of glass
material. The rectangular capacitor electrodes 23 are on top of a second substrate
layer 19 also made of glass material. The first and second substrate layers 18, 19
are arranged at a lateral distance to each other with the first and second electrode
5, 6 facing the capacitor electrodes 23. Between the first and second substrate layer
18, 19 there is a tunable layer 20 that is filled with a liquid crystal material.
The dielectric properties of the liquid crystal material can be modified by applying
different bias voltages to the first and second electrode 5, 6 and to the capacitor
electrodes 23, resulting in electric fields of different magnitude between the first
and second electrode 5, 6 and the respective overlapping areas 24, 25 of the capacitor
electrodes 23. In the overlapping section 12 as shown in figure 3, the overlapping
area 10 of the first electrode 5 and the corresponding overlapping area 24 of the
capacitor electrode 23 as well as the overlapping area 11 of the second electrode
6 and the corresponding overlapping area 25 of the capacitor electrode 23 in combination
with the liquid crystal material in between each provide for a parallel plate capacitor
area 13 with a capacitance that depends on the bias voltage. The bias electrode 16
that is connected to all capacitor electrodes 23 is a strip-shaped linear bias electrode
16 that runs parallel to the fist and second electrode 5, 6, but on the same level
as the capacitor electrodes 23 and provides for electrical connection of all the capacitor
electrodes 23 with the bias voltage source that is not shown in the figures.
1. Radio frequency phase shifting device (17) with a transmission line (4) comprising
a first electrode (5) and a second electrode (6) that are spaced at a distance to
each other and which are suitable and used for propagation of a radio frequency electromagnetic
signal along the first electrode (5) and the second electrode (6) with a phase difference
of 180° between the respective electromagnetic signals, wherein a tunable dielectric
material affects a phase shift of the electromagnetic signal that is propagated along
the transmission line (4), characterized in that the transmission line (4) comprises several non-overlapping sections (14), wherein
the first electrode (5) runs at a distance to the second electrode (6), and that the
transmission line (4) comprises several overlapping sections (12), wherein an overlapping
area (10) of the first electrode (5) is overlapped by a capacitor electrode area (11,
24) and wherein an overlapping area (11) of the second electrode (6) is overlapped
by a capacitor electrode area (10, 25) in order to provide for a parallel plate capacitor
area (13) within the overlapping section (12), and whereby a tunable dielectric material
is arranged between the respective capacitor electrode areas (24, 25) and the overlapping
area (10) of the first electrode (5) and the overlapping area (11) of the second electrode
(6) that affects the phase of an radio frequency electromagnetic signal that propagates
along the overlapping section (12) of the transmission line (4).
2. Radio frequency phase shifting device (17) according to claim 1, wherein the overlapping
area (10) of the first electrode (5) overlaps the overlapping area (11) of the second
electrode (6) in order to provide for one parallel plate capacitor area (13).
3. Radio frequency phase shifting device (17), wherein the first electrode (5) and the
second electrode (6) are arranged side by side, and wherein a capacitor electrode
(23) is arranged above or below the first electrode (5) and the second electrode (6)
in such a manner that a first capacitor electrode area (24) overlaps the overlapping
area (10) of the first electrode (5) and that a second capacitor electrode area (25)
overlaps the overlapping area (11) of the second electrode (6), thus providing for
two parallel plate capacitor areas (13) between the capacitor electrode and the respective
overlapping areas (10, 11) within the overlapping section (10).
4. Radio frequency phase shifting device (17) according to claim 2, characterized in that the first electrode (5) is arranged at a first surface of a first substrate layer
(18), in that the second electrode (6) is arranged at a second surface of a second substrate layer
(19), whereby the first surface of the first substrate layer (18) faces the second
surface of the second substrate layer (19) and whereby the first surface is arranged
at a distance to the second surface.
5. Radio frequency phase shifting device (17) according to claim 4, characterized in that the first surface of the first substrate layer (18) and the second surface of the
second substrate layer (19) confine the tunable dielectric material.
6. Radio frequency phase shifting device (17) according to one or more of the preceding
claims, characterized in that the first electrode (5) and the second electrode (6) each comprise a strip-shaped
transmission line segment (7, 8), whereby both transmission line segments (7, 8) are
directed along the transmission line (4).
7. Radio frequency phase shifting device (17) according to claim 6, characterized in that the strip-shaped transmission line segments (7, 8) each comprise alternating non-overlapping
sections (14) and overlapping sections (12) .
8. Radio frequency phase shifting device (17) according to claim 6, characterized in that the strip-shaped transmission segments (7, 8) only comprise non-overlapping sections
(14), and that each of the overlapping areas (10, 11) of the first electrode (5) and/or
of the second electrode (6) is laterally protruding from the respective strip-shaped
transmission segment (7, 8) of the first electrode (5) and/or of the second electrode
(6).
9. Radio frequency phase shifting device (17) according to one or more of the preceding
claims, characterized in that the respective overlapping areas (10, 11) of the first electrode (5) and the second
electrode (6) provide for a rectangular or a quadratic parallel plate capacitor area
(13).
10. Radio frequency phase shifting device (17) according to one or more of the preceding
claims, characterized in that subsequent parallel plate capacitor areas (13) along the transmission line differ
in respective distance to each other and/or in size and/or in shape.
11. Radio frequency phase shifting device (17) according to one or more of the preceding
claims, characterized in that the first electrode (5) and the second electrode (6) are electrically connected to
at least one bias voltage source.
12. Radio frequency phase shifting device (17) according to claim 11, characterized in that the first electrode (5) is connected to a first bias electrode (15) which is connected
to the at least one bias voltage source, and that the second electrode (6) is connected
to a second bias electrode (16) which is connected to the same or a different bias
voltage source.
13. Radio frequency phase shifting device (17) according to one or more of the preceding
claims, characterized in that the width of the first and second bias electrodes (15, 16) is smaller than the width
of the first and second electrode (5, 6).
14. Radio frequency phase shifting device (17) according to one or more of the preceding
claims, characterized in that the width of the first and second electrode (5, 6) is between 100 µm and 500 µm,
preferably approx. 200 µm.
15. Phased array antenna (1) comprising several antenna elements (2) that are arranged
at a surface of a substrate layer (23), a signal feed network from or to which a signal
is transmitted to or from the several antenna elements (2), and for each antenna element
(2) a corresponding phase shifting device (17) according to one or more of the preceding
claims, whereby the phase of each signal that is transmitted from the single signal
feed point (3) to the respective antenna element (2) or that is transmitted from the
respective antenna element (2) to the single signal feed point (3) is modified in
order to adjust the superposition of each signal according to the preferred direction
of radiation of the phased array antenna (1).
16. Phased array antenna (1) according to claim 15, characterized in that the phased array antenna (1) comprises on top of each other a base layer (22), a
first substrate layer (18) with a first electrode (5), a tunable layer (20), a second
substrate layer (19) with a second electrode (6) and an antenna layer (23) with a
radiating antenna structure for each of the antenna elements (2).
17. Phased array antenna (1) according to claim 15 or 16, characterized in that the first substrate layer (18) and the second substrate layer (19) consists of a
glass material, and that the tunable layer (20) comprises a liquid crystal material
with tunable dielectric properties.