Technical Field
[0001] The invention relates to a phased array antenna comprising several antenna elements,
a signal feed network from or to which a signal is transmitted to or from the several
antenna elements, and for each antenna element a corresponding phase shifting device,
whereby the phase of each signal that is transmitted from the signal feed network
to the respective antenna element or that is transmitted from the respective antenna
element to the signal feed network is modified by the corresponding phase shifting
device in order to adjust the superposition of each signal according to the preferred
direction of radiation of the phased array antenna, and whereby for each phase shifting
device a bias voltage is applied via two bias voltage electrode lines that are connected
to a bias voltage driver.
Background of the invention
[0002] For many applications a phased array antenna offers many advantages with respect
to the reception and emission of information signals that are wirelessly transmitted
between a transmitter and a receiver. By using a phased array antenna, the dominant
direction of the information signal transmission or information signal reception of
the phased array antenna can be varied over a wide angular range in order to increase
the signal strength that is emitted to or received from a given direction.
[0003] Already existing phased array antennas comprise a large number of antenna elements
that are usually arranged on a flat level or on a substrate layer in a regular or
matrix pattern. Each antenna element is connected to a signal feed network. If the
phased array antenna is used for signal emission the signal feed network creates and
distributes respective antenna signals that are transferred to the respective antenna
elements and result in emission of an information signal that is the result of a superposition
of all single antenna signals. If the phased array antenna is used for signal reception
the respective antenna signals that are received by the corresponding antenna element
are transferred to the signal feed network and the received information signal is
composed from a superposition of all single antenna signals. Between the signal feed
network and the antenna elements there is for each antenna element a dedicated tunable
phase shifting device which allows for adding a tunable phase shift to the signal
that runs along the phase shifting device. By adding an individual phase shift to
the antenna signals that are emitted or received, the superposition of antenna signals
can be controlled in order to provide for a dominant direction of the information
signal transmission or information signal reception of the phased array antenna.
[0004] The tunable bias voltage that defines the phase shift which is generated by a respective
phase shifting device is usually applied by a bias voltage driver. It is possible
to operate the phase shifting devices with a dedicated bias voltage driver for each
phase shifting device. However, connecting each phase shifting device with a suitable
bias voltage driver requires costs and efforts for manufacturing and operating the
phased array antenna.
[0005] Accordingly, there is a need for a phased array antenna that allows for easy and
cost-saving manufacturing and that also allows for easy operation of the corresponding
phase shifting devices resulting in a wide range of a respective phase shift of the
antenna signal.
Summary of the invention
[0006] The present invention relates to a phased array antenna as described above, characterized
in that the bias voltage driver comprises several output channel terminal pairs with
two output channel terminals whereby the bias voltage driver is able to apply a tunable
output channel voltage difference to the terminal pair, and in that the two bias voltage
electrode lines of each phase shifting device are connected to a respective terminal
pair.
[0007] According to an advantageous aspect of the invention the bias voltage driver has
a common voltage output channel terminal and a number of odd output channel terminals
and just as many even output channel terminals, whereby the bias voltage driver is
able to operate in a manner that the polarity of a voltage difference between any
odd output channel terminal and the common voltage output channel terminal is opposite
to the polarity of a voltage difference between any even output channel terminal and
the common voltage output channel terminal, and whereby each terminal pair comprises
an odd output channel terminal and an even output channel terminal.
[0008] According to an embodiment of the invention each odd output channel terminal is arranged
adjacent to a corresponding even output channel terminal, whereby an odd output channel
terminal and the adjacent even output channel terminal form the terminal pair. It
is considered a yet further advantage of the invention to allow for using multi output
channel drivers that have been developed and that are currently used in a different
field of application. Suitable drivers can be multi-channel digital to analog converters
that are implemented as integrated circuits and are widely used for many different
applications and voltage ranges.
[0009] There are so called source driver ICs available that are dedicated to controlling
and operating liquid crystal displays (LCDs) with a large number of pixels for which
an individual bias voltage must be applied with great precision and short response
times. Even though within display applications each channel is connected to a corresponding
pixel and dedicated to control said pixel, is it possible and advantageous to respectively
combine two channels into terminal pairs and to connect a phase shifting device to
such a terminal pair, i.e. to connect a single phase shifting device to two output
channels of such a source driver, i.e. preferably to one even channel and one odd
channel. Such specialized source driver ICs are usually used for operating LCD panels
with dot inversion, whereby the operation control of the source driver IC is adapted
to operate each output channel by quickly switching between voltage values of opposite
polarity with respect to a fixed common voltage. For instance, specialized source
driver ICs for use in display applications have been developed that provide a positive
voltage value to a first output channel terminal and a negative voltage value to a
second output channel terminal that is in close proximity or adjacent to the first
output channel terminal, whereby the positive or negative voltage is produced as voltage
difference to a common voltage which is usually in the middle of the voltage range
of the source driver IC. The first output channel terminal can be an odd output channel
terminal and the second output channel terminal can be an adjacent even output channel
terminal. Apart from the opposite polarity, the voltage value of the first output
channel terminal can be identical or different to the voltage value of the second
output channel. With a preset timing, polarity of paired output channels changes e.g.
from positive to negative voltage and from negative to positive voltage with respect
to the same common voltage, whereas for each output channel and thus for each terminal
pair the corresponding voltage value can be individually preset to a voltage value
within the voltage range. Such a specialized source driver IC seems very suitable
for use with a phased array antenna according to the invention. Furthermore, such
specialized source drivers are commercial off-the-shelf products which are available
in large quantities at low cost.
[0010] Whereas in known display control applications each output channel is used to apply
an appropriate voltage difference with respect to a fixed common voltage to a single
pixel or cell of the display, according to the invention each phase shifting device
is connected to two output channels, but not to a fixed common voltage, which allows
for full use of the voltage range of the bias voltage driver irrespective of a fixed
common voltage which is usually preset to a middle value within the range of a source
driver IC. It is therefore advantageous to enlarge the achievable voltage range by
not using the common voltage as a reference voltage that is dedicated and useful to
conventional LCD applications, but to combine output channels with opposite polarity
with respect to the common voltage.By combining such output channels into a terminal
pair the liquid crystal molecules of the corresponding phase shifting device can be
driven completely with higher bias voltage which is very advantageous since liquid
crystal material suitable for phased array antennas usually require higher saturation
voltage than that of a LCD. With display control applications the maximum voltage
difference that is applied to a pixel or cell is the difference between a maximum
voltage value or minimum voltage value of the output channel and the fixed common
voltage, whereas the maximum voltage difference that can be applied to a phase shifting
device is the difference between the maximum voltage value and the minimum voltage
value of an output channel terminal pair, which is irrespective of the fixed common
voltage.
[0011] Since the voltages in one output channel terminal pair with opposite polarities are
allowed to have different magnitudes, a further advantageous aspect of this invention
is that, while the tuning voltage range available for a phase shifter device is doubled,
the absolute voltage resolution remains the same and the resolution with respect to
the full voltage range is doubled compared to the use case of a conventional display
application.
[0012] It is advantageous to combine two adjacent output channel terminals to form the terminal
pair of the bias voltage driver that is connected with a respective phase shifting
device. Due to the close proximity of the two terminals of the terminal pair, the
corresponding bias voltage electrode lines can be arranged to run in close proximity
to each other from the terminal pair of the bias voltage driver to the phase shifting
device. This allows for short bias voltage electrode lines without elaborate arrangements
of electrode lines or complex electrode line patterns. Short bias voltage electrode
lines of identical or at least similar length allow for fast and undisturbed application
of a preset bias voltage to the respective phase shifting devices, thus reducing the
response time for adjusting each phase shifting device and for realigning the phased
array antenna towards a new direction.
[0013] It is also possible to make use of a flat flexible cable that provides for a flexible
connection of the output channel terminal pairs with a rigid flat-pin plug that allows
for easy mounting and connecting with the bias voltage electrode lines of each phase
shifting device. If required or advantageous, a reordering of some of the connection
lines can be included within the flexible section of the flat flexible cable. Thus,
it is possible to provide for a low-cost combination of odd and even output channel
terminals into a terminal pair, whereby the corresponding odd and even output channel
terminals are not adjacent to each other, but at a distance and separated by a number
of other odd and even output channel terminals that are arranged in between.
[0014] According to an advantageous aspect of the invention the two bias voltage electrode
lines that connect the phase shifting device to the terminal pair of the bias voltage
driver are located next to each other in a non-overlapping manner between the terminal
pair and the phase shifting device. Non-overlapping electrode lines are easily manufactured
and help to reduce an undesired interference of the bias voltage that is applied to
the phase shifting device via the bias voltage electrode lines.
[0015] According to an advantageous embodiment of the invention, the two output channel
terminals of a terminal pair are arranged at the same level or at the same surface
of a substrate layer, and that one of the two bias voltage electrode lines comprises
a conductive cross-over between two different levels or two different surfaces of
substrate layers resulting in connecting sections of the two bias voltage electrode
lines that run into the corresponding phase shifting device at two different levels
or two different surfaces of substrate layers. For some advantageous embodiments of
the phase shifting device, such a phase shifting device comprises two electrodes or
at least two electrode sections that are arranged at two different levels of the phase
shifting device. Usually, such phase shifting devices comprise electrodes that are
arranged at two different surfaces of a single substrate layer or that are arranged
at two different surfaces of two different substrate layers of the phase shifting
device. According to the advantageous embodiment of the invention, the bias voltage
electrode lines comprise terminal sections that are arranged on the same level for
connecting the bias voltage electrode lines with the bias voltage driver that has
terminal pairs on the same level or on the same surface of a substrate layer. The
bias voltage electrode lines also comprise connecting sections for connecting the
bias voltage electrode lines to the phase shifting devices, but the connecting sections
are at a different level or at a different surface of a substrate layer, namely the
same level or the same surface of a substrate layer on which the corresponding electrode
of the phase shifting device is located. Thus, the cross-over between different levels
or different surfaces of substrate layers can be positioned at a distance to the bias
voltage driver as well as at a distance to the phase shifting device, which allows
for a less complex design and for a reduced space requirement of the bias voltage
electrode lines.
Brief description of the drawings
[0016] 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 with a 4 x 4 matrix
of antenna elements,
Figure 2 illustrates a sectional view of the phased array antenna shown in figure
1 taken along the line II-II,
Figure 3 illustrates a schematic view of a bias voltage driver of the phased array
antenna that is connected to several antenna elements of the phased array antenna
shown in figures 1 and 2 in a direct drive configuration,
Figure 4 illustrates a sectional view of the bias voltage driver and the corresponding
antenna element connected to the bias voltage driver as shown in figure 3 taken along
the line III-III,
Figure 5 illustrates a schematic view of another embodiment of a bias voltage driver
of the phased array antenna that is connected to several antenna elements of the phased
array antenna shown in figures 1 and 2,
Figure 6 illustrates a perspective view of a commercially available LCD source driver
in combination with a flat flexible cable that can be used as bias voltage driver
for the phased array antenna,
Figure 7 illustrates an embodiment where the bias voltage driver is suitable to also
drive source voltages of a TFT matrix, and
Figure 8 illustrates an enlarged view of the region VIII of the embodiment shown in
Figure 7 with an optional addition to this embodiment.
Detailed description of the invention
[0017] Figures 1 and 2 show a schematic top view and a schematic sectional view of an exemplary
phased array antenna 1 with a 4 x 4 matrix pattern of antenna elements 2 that are
arranged on the same level of a flat surface of a substrate layer 3 of the phased
array antenna 1. However, for most applications the phased array antenna 1 comprises
several hundred or several thousand antenna elements 2. Each antenna element 2 is
connected to a signal feed network 4 via respective phase shifting devices 5. In order
to allow for a suitable superposition of antenna signals of all antenna elements 2,
each phase shifting device 5 is controlled by a bias voltage driver that applies individual
bias voltages to the respective phase shifting devices 5. Each phase shifting device
5 generates a predetermined phase shift of the corresponding antenna signal that runs
along the phase shifting device 5 which results in an advantageous superposition of
the several antenna signals that are emitted or received by the antenna elements 2
of the phased array antenna 1. By applying suitable bias voltages to all of the phase
shifting devices the superposition of all antenna signals emitted or received by the
respective antenna elements 2 will result in an advantageous enhancement of a predetermined
direction for emission or reception of the information signal emitted or received
with the phased array antenna 1, thus enhancing the information signal quality and
the signal to noise ratio of the information signal transmission along said direction.
[0018] Each phase shifting device 5 comprises two phase shifting electrodes 6, 7 that are
usually arranged at different surfaces 8, 9 of two different substrate layers 3, 10.
In between the two phase shifting electrodes 6, 7 at different substrate layers 3,
10 a tunable dielectric material 11 like e.g. liquid crystal material is arranged.
For each phase shifting device 5 a dedicated reservoir of the tunable dielectric material
11 is confined by the two substrate layers 3, 10 and separator elements. By applying
a bias voltage to the two phase shifting electrodes 6, 7 the dielectric characteristics
of the tunable dielectric material 11 in between said two phase shifting electrodes
6, 7 is modified and set to a predetermined value, resulting in a corresponding phase
shift that is applied to an antenna signal that is transferred along this phase shifting
device 5. The appropriate bias voltage must be provided by a bias voltage driver that
is not shown in figures 1 and 2, and then applied to each of the phase shifting devices
5.
[0019] Figures 3 and 4 each illustrate a schematic view and a schematic sectional view of
a part of the phased array antenna 1 with a bias voltage driver 12 of the phased array
antenna 1 that is connected to several phase shifting devices 5 for respective antenna
elements 2 of the phased array antenna 1. In figure 3 the bias voltage driver 12 is
connected in direct drive configuration, i.e. one out channel terminal pair 15 is
connected to exactly one phase shifting device 5. The bias voltage driver 12 is a
commercial off-the-shelf source driver that is common and usually used for operating
LCDs or similar display panels. Making use of a common LCD source driver allows for
a very low-cost manufacture of the phased array antenna. The bias voltage driver 12
may also be a modified off-the-shelf source driver whereby the required modifications
e.g. for pairing output channel terminals can be performed with low cost and reduced
efforts. Each phase shifting device 5 requires an individual bias voltage that is
applied to the phase shifting device 5 and determines the phase shift that is imposed
onto an antenna signal that is transmitted by the corresponding phase shifting device
5.
[0020] The bias voltage driver 12 comprises a number of odd output channel terminals 13
and just as many even output channel terminals 14. Two adjacent output channel terminals
13, 14 of the bias voltage driver 12 form a terminal pair 15 that is indicated by
a dashed border. Each output channel terminal 13, 14 of a terminal pair 15 is conductively
connected to a dedicated phase shifting device 5 by two bias voltage electrode lines
16, 17. The two bias voltage electrode lines 16, 17 run from the terminal pair 15
to the corresponding phase shifting electrodes 6, 7 of the phase shifting device 5.
For each phase shifting device 5 the corresponding two bias voltage electrode lines
16, 17 run next to each other in a non-overlapping manner between the terminal pair
15 and the phase shifting device 5, i.e. the two phase shifting electrodes 6, 7.
[0021] The bias voltage driver 12 is mounted on the same surface 9 of the same substrate
layer 10 as one of the phase shifting electrodes 7 of the phase shifting device 5.
The bias voltage electrode line 17 that connects the phase shifting electrode 7 with
the terminal pair 15 runs along this surface 9 of said substrate layer 10. The other
bias voltage electrode line 16 that connects the phase shifting electrode 6 mounted
on the surface 9 of the substrate layer 3 comprises a conductive cross-over 18 between
the two different surfaces 8, 9 of the corresponding substrate layers 3, 10. Thus,
both bias voltage electrode lines 16, 17 comprise a connecting section 19, 20 that
runs on the same surface 8, 9 of the substrate layer 3, 10 as the corresponding phase
shift electrode 6, 7 to which the respective bias voltage electrode line 16, 17 is
connected.
[0022] Figure 5 illustrates a schematic view of a part of another embodiment of the phased
array antenna 1. The bias voltage driver 12 of the phased array antenna 1 is connected
to several phase shifting devices 5 for respective antenna elements 2 of the phased
array antenna 1. However, contrary to the embodiment shown in figure 3, some terminal
pairs 15 comprise an odd output channel terminal 13 and an even output channel terminal
14 that are separated by to output channel terminals 13, 14 in between. Thus, some
of the terminal pairs 15 are formed by adjacent output channel terminals 13, 14 and
some other terminal pairs 15 are formed by output channel terminals 13, 14 that are
at a distance towards each other. Within the exemplary embodiment shown in figure
5, a suitable arrangement of the bias voltage electrode lines 16, 17 allows for a
connection of the phase shifting devices 5 in a non-overlapping manner.
[0023] In both embodiments illustrated in figures 3 and 5, the bias voltage driver 12 is
a common LCD source driver that is commercially available at low cost. A common voltage
terminal 21 that is used for operating thin film transistor LCDs is not used within
the phased array antenna 1 and is thus not connected to a phase shifting device 5.
[0024] Figure 6 shows a perspective view of a commercially available LCD source driver 22
in combination with a flat flexible cable 23 that can be used as bias voltage driver
12 for the phased array antenna 1. Within the flat flexible cable 23 some conducting
wires may overlap and cross other conducting wires which allows for pairing distant
or remote output channel terminals 13, 14 into a terminal pair 15 if need arises.
However, in Figure 6 a non-overlapping arrangement of the conducting wires is shown.
The conducting wires on or within the flat flexible cable 23 connects the bias voltage
driver 12 with respective rigid flat-pin plugs 24 that allow for easy mounting and
connection with the bias voltage electrode lines that run to the phase shifting devices
5.
[0025] Figure 7 shows a schematic view of a part of yet another embodiment of the phased
array antenna 1. This embodiment applies the pairing of odd and even output channel
terminals 13, 14 to terminal pairs 15 not to a direct drive topology as shown in Figure
3 but to a TFT matrix topology that is commonly used for operating TFT displays. The
phase shifting devices 5 are arranged in an array of rows 25 and columns 26. In addition
to the bias voltage driver 12 an additional gate driver IC 27 is required which is
also available off-the-shelf. For each phase shifting device 5 a corresponding Thin-Film-Transistor
(TFT) 28, 29 is provided. Source terminals 30 of all TFTs 28 related to phase shifting
electrodes 6 are connected to odd output channel terminals 13. Likewise, the source
terminals 31 of all TFTs 29 related to phase shifting electrodes 7 are connected to
even output channel terminals 14. Equivalent to regular display applications, short
gate voltage pulses are applied from the gate driver terminals 32 column 26 by column
26 to the gate voltage lines 33 to the gate terminals 34 of the TFTs 28, 29 in order
to control and apply the voltages on all bias voltage electrode lines 16 or 17 to
the drain of TFTs 28 and 29 and thereby to the phase shifting electrodes 6 and 7 of
each phase shifting device 5.
[0026] Figure 8 illustrates an enlarged view of the region VIII of Figure 7. For each phase
shifting device 5 a holding capacitor 35 can be arranged parallel to the respective
phase shifting device 5. The TFTs 28, 29 are activated row by row with a given refresh
rate of the gate driver IC 27. These capacitors 35 may be required for upholding and
supporting the bias voltage if the tunable dielectric material 11 cannot hold the
bias voltage for a long enough, or if the refresh rate of the gate driver IC 27 is
low.
1. Phased array antenna (1) comprising several antenna elements (2), a signal feed entry
(4) 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 (5), whereby
the phase difference of each signal that is transmitted from the signal feed entry
(4) to the respective antenna element (2) or that is transmitted from the respective
antenna element (2) to the signal feed entry (4) is modified by the corresponding
phase shifting device (5) in order to adjust the superposition of each signal according
to the preferred direction of radiation of the phased array antenna (1), and whereby
for each phase shifting device (5) a bias voltage is applied via two bias voltage
electrode lines (16, 17) that are connected to a bias voltage driver (12), characterized in that the bias voltage driver (12) comprises several output channel terminal pairs (15),
whereby each output channel terminal pair (15) comprises two output channel terminals
(13, 14), whereby the bias voltage driver (12) is able to apply a tunable output channel
voltage difference to each terminal pair (15), and in that the two bias voltage electrode lines (16, 17) of each phase shifting device (5) are
connected to a respective terminal pair (15).
2. Phased array antenna (1) according to claim 1, characterized in that the bias voltage driver (12) has a common voltage output channel terminal (21) and
a number of odd output channel terminals (13) and just as many even output channel
terminals (14), whereby the bias voltage driver (15) is able to operate in a manner
that the polarity of a voltage difference between any odd output channel terminal
(13) and the common voltage output channel terminal (21) is opposite to the polarity
of a voltage difference between any even output channel terminal (14) and the common
voltage output channel terminal (21), and whereby each terminal pair (15) comprises
an odd output channel terminal (13) and an even output channel terminal (13) .
3. Phased array antenna (1) according to claim 2, characterized in that each odd output channel terminal (13) is arranged adjacent to a corresponding even
output channel terminal (14), whereby an odd output channel terminal (13) and the
adjacent even output channel terminal (14) form the terminal pair (15).
4. Phased array antenna (1) according to claim 2 or claim 3, characterized in that the bias voltage driver (12) is suitable for use as a source driver for a thin film
transistor matrix.
5. Phased array antenna (1) according to any preceding claim, characterized in that the two bias voltage electrode lines (16, 17) that connect the phase shifting device
(5) to the terminal pair (15) of the bias voltage driver (12) are located next to
each other in a non-overlapping manner between the terminal pair (15) and the phase
shifting device (5).
6. Phased array antenna (1) according to any preceding claim, characterized in that the two output channel terminals (13, 14) of a terminal pair (15) are arranged at
the same level or at the same surface (8, 9) of a substrate layer (3, 10), and that
one of the two bias voltage electrode lines (6) comprises a conductive cross-over
(18) between two different levels or two different surfaces (8, 9) of substrate layers
(3, 10) resulting in connecting sections of the two bias voltage electrode lines (16,
17) that run into the corresponding phase shifting device (5) at two different levels
or two different surfaces (8, 9) of substrate layers (3, 10).