Antenna array with square wave signal steering

Abstract

An antenna array is electronically controlled by controlling the speed of transmission of RF signals in the feed lines of each radiator in the array. The speed of transmission is controlled using phase shifters that include a variable dielectric constant (VDC) material that causes the speed of transmission to vary. A control signal applied to the VDC material generates the required phase shift. The control signal is calculated in real time for each phase shifter for each control period to enable the main beam to track a target such as a satellite. The control signals are square wave signals and each control signal has a duty cycle or frequency that is specifically calculated to generate the required phase shift.

Description

[0001] Related applications

[0002] This disclosure relates to and claims priority to U.S. Provisional Application No. 62 / 713,986, filed August 2, 2018, the disclosure of which is incorporated herein by reference in its entirety. Background Technology

[0003] 1. Field

[0004] This disclosure generally relates to the field of liquid crystal-based antennas, and more specifically, to the control of the orientation of liquid crystal and / or any and variable dielectric / phase material domains for RF antennas.

[0005] 2. Related Technologies

[0006] Liquid crystals can be used in a variety of applications. One characteristic of liquid crystals is that external disturbances can cause significant changes in the macroscopic properties of the liquid crystal system. These changes in macroscopic properties can be used in optical and electrical systems, to name just two examples. Both electric and magnetic fields can be used to induce these changes. For specific applications, the amplitude of the field and the velocity of molecular alignment are important properties. The amplitude of the field applied to a liquid crystal and / or other variable dielectric materials will change its physical orientation and / or macroscopic level as waves pass through it or propagate in either TEM, TE, or TM mode, and the presence of the material will subsequently result in a visible or felt difference in the speed of light, which is directly related to the material's effective dielectric constant. In the case of liquid crystals, this effective dielectric constant is directly related to the mechanical tilting of molecules under the influence of an induced electric or magnetic field.

[0007] In liquid crystal devices, special surface treatments can be used to force the specific orientation of dipole molecules, thereby orienting the director through mechanical and / or chemical influences (e.g., mechanical friction, alignment materials, etc.). The ability of the director to orient itself along an external field is caused by the electrical properties of the molecules. In this respect, the director refers to a dimensionless unit vector n, which represents the direction of the preferred orientation of the molecule near any point. When one end of the molecule has a net positive charge and the other end has a net negative charge, a permanent electric dipole is generated. When an external electric field is applied to the liquid crystal, the dipole molecules tend to orient themselves along the direction of the field because they are formed as dipoles.

[0008] In a general system, the molecules are aligned in one direction in the relaxed state (i.e., no external field is applied). When a change is needed, an appropriate electric and / or equivalent magnetic field is applied, which causes the molecules to rotate by an amount related to the strength / magnitude of the applied field. When this effect is no longer needed, the field is removed and the molecules return to their relaxed state. These two actions can be viewed as an electrical reaction and a chemical reaction: when the field is applied, an electrical reaction occurs to rotate the molecules, while when the field is removed, a chemical reaction returns the molecules to their relaxed state. However, the electrical reaction occurs much faster than the chemical reaction. Thus, the timing operation is asymmetric - "turning on" is much faster than "turning off" that a controllable antenna needs to address.

[0009] Dual-frequency liquid crystals (DFLCs) are a type of liquid crystal (LC) mixture whose dielectric constant can be switched by frequency, not just by voltage. In these mixtures, the dielectric constant ε∥ depends largely on the frequency, and typically, the frequency range is kHz to MHz, while the dielectric constant ε⊥ depends on frequencies up to the MHz range; ε∥ is the dielectric constant along the long axis of the molecule, while ε⊥ is the dielectric constant perpendicular to the long axis of the molecule. The arithmetic difference between ε∥ and ε⊥ is the dielectric anisotropy Δε. For DFLCs, Δε is positive at low frequencies and negative at high frequencies, so for DFLCs one applies electric fields of the same amplitude but different frequencies to rotate the molecules from horizontal to vertical and then from vertical to horizontal, respectively, and thus the response time no longer depends on the relaxed state and / or chemical processes, but on the applied field, and it is possible to shorten this response time accordingly.

[0010] Fast-response DFLCs have been used in adaptive optical systems to correct atmospheric aberrations and in optical phased arrays for beam steering. Liquid crystal-based phased arrays require little base power, even for large apertures. Unlike mechanical systems, liquid crystal devices are generally insensitive to acceleration, and their cost decreases rapidly with volume production.

[0011] For more information on DFLCs, the reader is referred to "Liquid Crystal Materials and Liquid Crystal Displays," Martin Schadt, Annual Review of Materials Science 1997; and "High Performance Dual Frequency Liquid Crystal Compounds and Mixture for Operation at Elevated Temperatures," Haiqing Xianyu et al., Liquid Crystals, 2010.

[0012] Recently, the Applicant has proposed the use of liquid crystals to control the characteristics and operation of non-optical devices. Examples can be found in U.S. Patents 7,466,269 and 7,884,766 and publication No. 2018-0062238. In such devices, in order to change the dielectric constant of the liquid crystal layer, the orientation of the director is controlled, thereby changing the operating characteristics of the electrical device. However, as the inventors have discovered, contrary to conventional technology, the asymmetric operation of the liquid crystal is undesirable for such applications. The inventors have determined that when controlling the operation of an electrical device, it is desirable to make the "off' process as fast as the "on" process.

[0013] In addition, when using an array of non-DFLC antennas, each radiator in the array will need a different voltage applied to change the dielectric constant of that radiator. Such a system would require many voltage suppliers, each providing a different voltage level, and a controller to apply the different voltages to different radiators, greatly increasing the complexity and cost of the system.

[0014] Furthermore, prior art disclosures relating to DFLCs use two different frequencies, one to "turn on" the LC and the other to "turn off" the LC. The inventors have determined that utilizing such a standard dual frequency arrangement is insufficient to form and control a scanning array.

[0015] Accordingly, there is a need in the art to improve the control of the director in liquid crystals operating in antennas. SUMMARY

[0016] The following summary of the disclosure is included in order to provide a basic understanding of some aspects and features of the present application. This summary is not an extensive overview of the application and as such it is not intended to specifically identify key or critical elements of the application or to delineate the scope of the application. Its sole purpose is to present some concepts of the application in a simplified form as a prelude to the more detailed description that is presented below.

[0017] The disclosed embodiments provide improved control over the orientation of liquid crystal domains. The disclosed embodiments utilize multi-frequency control over a variable dielectric constant (VDC) material to control the contribution of each radiator in the array, providing an electronically scanned antenna array. Using the arrangement of the disclosed embodiments, each radiator in the array receives a different activation signal with different characteristics than the signals of the other radiators. Furthermore, each signal for each radiator can change over time as the platform of the antenna moves or the platform of the target moves.

[0018] In the disclosed embodiments, a single voltage source is provided and used to generate multiple signals, each signal for each radiator in the array. A pulse width modulator (PWM) generates the multiple signals such that each signal has a different duty cycle, thus essentially applying different power levels to the delay line of the radiators. In other embodiments, the duty cycle remains constant, but each signal has a different frequency. In these embodiments, the pulse width modulator generates multiple frequencies, which in this disclosure can mean that the number of frequencies generated in each cycle can equal the number of radiators in the antenna. It is certain that "multiple frequencies" refers to more than two frequencies, as is typically used in optical devices to generate on and off signals.

[0019] In the disclosed embodiments, the antenna array includes a two-dimensional array of radiators, each having a delay line that meanders through a VDC, the dielectric constant of which is controlled by a pulse width modulated signal. Multiple electrodes are provided to deliver individual control PWM signals to each VDC to cause the domain to be quickly placed in the desired state, thus controlling the direction of the main beam of the antenna.

[0020] In a general aspect, the disclosed embodiments use voltage-dependent differences in dielectric anisotropy in tunable phased array antenna applications. In such embodiments, multiple duty cycle square waves are applied to orient the LC director of different phase shifters, which results in a given dielectric constant. Changes in the dielectric constant cause changes in the phase of signals propagating in the phase shifters. Multiple duty cycles can refer to a number of duty cycles equal to the number of phase shifters in the array.

[0021] In general aspects, the disclosed embodiments use the frequency dependent differences in dielectric anisotropy in tunable phased array antenna applications. These embodiments implement dual frequency liquid crystal (DFLC) material as part of the phase shifter element with a layered or sandwiched structure. In this tunable phase shifter, square waves with multiple frequencies are applied to orient the LC director of different phase shifters, which results in a given dielectric constant, and more importantly, by responding to two fields with different frequencies, the mechanism allows the dual frequency molecules to rotate in two opposite directions, which allows the molecules to have the same t rise and t fall , and also allows. The change in dielectric constant causes a phase change in the signal propagating in the phase shifter. The result is a much faster response time, especially for the decay side which is usually slower when the LC molecules are slow to relax. Therefore, the combined switching time (T rise +T decay / fall ) will be much faster than a phase shifter built with conventional LC. As a result, the new invented DFLC phase shifter antenna with pulse width modulation will meet the beam steering speed required for satellite communication antennas.

[0022] In the disclosed embodiments, a fast switching nematic liquid crystal (LC) phase shifter is provided based on the DFLC effect. The switching of the DFLC phase shifter corresponding to each delay line of the antenna array is controlled individually by applying a frequency controlled fixed voltage square wave voltage signal to the electrodes of the DFLC phase shifter. In some embodiments, both electrodes of the DFLC phase shifter are driven by a frequency controlled fixed voltage square wave voltage, so the natural self-relaxation time of the liquid crystal molecules no longer affects the switching time.

[0023] According to one embodiment, the dual frequency LC is used with one arrangement for parallel spin and another arrangement for perpendicular spin. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present application and, together with the description, serve to explain and illustrate the principles of the application. The drawings are intended to illustrate major features of the exemplary embodiments in a diagrammatic and not a precise manner. The drawings are not intended to depict every feature of actual embodiments nor relative dimensions of the depicted elements and are not drawn to scale.

[0025] One or more embodiments of the application are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements and in which:

[0026] Figure 1An antenna array is shown according to one embodiment with a controller for individually controlling each radiator to scan the main beam, which can be done in many different variations and can be designed with multiple layers and / or a single subsequent structure;

[0027] Figure 2 is a simplified schematic of pulse width modulation control according to one embodiment.

[0028] Figure 3 is a graph showing square wave signals with different duty cycles.

[0029] Figure 4 is a graph showing square wave signals with different frequencies.

[0030] Figure 5 is a schematic of a system for controlling the phase shifters of an array according to one embodiment.

[0031] Figure 6 is a schematic of a system for controlling the phase shifters of an array according to another embodiment.

[0032] Figure 7 is a schematic of a system for controlling the phase shifters of an array according to another embodiment. DETAILED DESCRIPTION

[0033] Embodiments of antennas and controls of the present invention will now be described with reference to the accompanying drawings. Different embodiments or combinations thereof can be used for different applications or to obtain different benefits. Depending on the results sought, different features disclosed herein can be utilized in part or in whole, alone or in combination with other features, to balance advantages with requirements and constraints. Thus, certain benefits can be emphasized with reference to different embodiments, but these benefits are not limited to the disclosed embodiments. That is, features disclosed herein are not limited to the embodiments in which they are described, but can be "mixed and matched" and incorporated into other embodiments.

[0034] As with all RF antennas, reception and transmission in the class of antennas and devices introduced here are symmetric, equivalent, falling into passive antennas, while active antennas, including nonlinear devices, are not equivalent, making the description for one equally applicable to the other. In this description, it can be easier to explain transmission, but reception will be the same, only in the opposite direction. Also, in the disclosed embodiments, it is assumed that the disclosed antennas are mounted to a platform, and their main beams are aimed at another antenna, referred to here as a target. The target's antenna is also mounted on a platform, and either or both platforms can be moving. For example, the antennas can be mounted on a vehicle such as an airplane, ship, car, etc., and the target can be mounted on a satellite. The symmetry concept applies here as well, as the antennas can be antennas mounted on a satellite, and the target can be mounted on a vehicle.

[0035] A top view of the antenna is shown in the schematic diagram of Figure 1 , while the inset schematic shows a simplified cross-section of the array at one radiating element. In general, the antenna is a multilayer antenna that includes a radiating patch layer, a true-time delay layer, a ground layer, and a feed layer, whether it is designed for co-axial feed, traveling wave feed, or standing wave field, as will be described in more detail below. In some cases, additional layers are added to provide multiple polarizations, wider bandwidth, etc. The various elements of the antenna can be printed or deposited on an insulating substrate.

[0036] The antenna includes a two-dimensional array of n x m radiating elements, n and m being integers. In the illustration of Figure 1 , the antenna in this particular example includes a 4 x 4 array of radiators 110, although any number of radiators in a variety of geometries and arrangements can be used, and the square arrangement of 4 x 4 elements is chosen as an example only. In this example, each radiator 110 is a conductive patch disposed (e.g., deposited, adhered, or printed) on top of an insulating layer 105, and has a delay feed line 115 coupled to it, either physically or capacitively. Each delay feed line 115 is a conductor that provides an RF signal to its corresponding patch 110. The RF signal can be manipulated, e.g., delayed to change the phase, by controlling a variable dielectric layer positioned below the delay line. By independently controlling all of the delay lines to change the phase of the RF signal in each delay line, the main beam of the array can be pointed in different directions as needed, providing an electronically scanned array.

[0037] In the illustration of Figure 1 , each element is fed from only one delay line. However, each radiating element 110 can be fed by two orthogonal feed lines, e.g., each with a different polarization. The description provided herein applies to both, as well as any similar architectures.

[0038] As shown in the inset, the top dielectric spacer 305 is generally in the form of a dielectric (insulating) plate or sheet and can be made of, for example, glass, PET, etc. The radiating patches 310 are formed on this spacer by, for example, adhering a conductive film, sputtering, printing, etc. At each patch location, a via is formed in the dielectric spacer 305 and filled with a conductive material such as copper to form a contact 325 that is physically and electrically connected to the radiating patch 310. The delay line 315 is formed on the bottom surface of the dielectric spacer 305 (or on the top surface of the overlying adhesive 342) and is physically and electrically connected to the contacts 325 and is immersed in the variable dielectric material 340 that provides the maximum shock / RF phase change, any additional layers separating the delay line from the variable dielectric material would reduce the tunability of the device. That is, in this example, there is a continuous DC electrical connection from the delay line 315 through the contacts 325 to the radiating patches 310. As shown in the inset, the delay line 115 is a curved wire and can take any shape to have sufficient length to generate the required delay to induce the required phase shift in the RF signal, the electrodes to activate the VDC 340 can be part of the delay line and ground or can be designed on a separate layer. Figure 1

[0039] The delay in the delay line 315 is controlled by the VDC layer 340 with VDC material. Although any means for constructing the VDC layer 340 can be suitable for use with embodiments of the antenna, as a brief representation in a specific embodiment, the VDC plate 340 is shown as being bounded between the spacer 305 and the back dielectric 350 (in this example, the VDC material can be a standard liquid crystal or a liquid crystal that reacts to different frequencies for the oriented and relaxed states). An adhesive such as epoxy or glass beads can be used to hold the LC material within the layer 340.

[0040] The effective dielectric constant of the VDC plate 340 can be controlled by applying a DC potential across the VDC plate 340. To this end, electrodes can be formed and connected to a controllable voltage potential or a control line 370 can be connected to the delay line 315 so that the delay line 315 functions as the activating electrode. There are a variety of arrangements to form the electrodes and any conventional arrangement is acceptable as long as multiple frequencies can be applied to control the state of the VDC material. In the arrangement shown in the inset square wave, the square wave controller 120 applies a signal across the delay line and ground plane 355. Each delay line 115 and its associated VDC form part of a phase shifter.

[0041] ​Control line 370 is shown connected to square wave controller 120, which can provide pulse width modulation (PWM) and / or frequency control and / or standard voltage, as will be described in detail below. By changing the signal applied to each pair of control lines from controller 120, the dielectric constant of the VDC material near the corresponding delay line 315 can be changed, thereby altering the RF signal propagating on delay line 315. Changing the controller's output can be accomplished by running software that causes the controller to output appropriate control signals to set the appropriate phase shift on each feed line in real time. Therefore, the performance and characteristics of the antenna can be controlled using software—thus providing a software-controlled antenna.

[0042] In transmit mode, the RF signal is applied to the feed patch 360 via connector 365 (e.g., a coaxial cable connector). As shown in the illustration, there is no DC connection between the feed patch 360 and the delay line 315, the purpose of which is to insulate the multiple phase shifters from each other, so that a control line on a single phase shifter will not be short-circuited to other phase shifters, and therefore individual control of each phase shifter will not be allowed. In some embodiments, when we want to control a group of phase shifters and / or want to combine individual non-current couplers in the feed network, contact lines or vias can be used instead of slots. However, in the disclosed embodiments, these layers are designed to provide an RF short circuit between the feed patch 360 and the delay line 315, and this can be modified. This feature is not relevant to the invention but is shown as an example.

[0043] A back conductive ground (or common terminal) 355 is formed on the top surface of the back insulator (or dielectric) 350. The back conductive ground 355 is typically a conductor layer covering the entire area of ​​the antenna array and forms the ground for the RF signal propagating in all delay lines 115. At each RF feed location, a window (DC interruptor) 353 is provided in the back conductive ground 355. The RF signal propagates from the feed patch 360 through the window 353 and is capacitively coupled to the delay line 315. The reverse occurs during reception. Therefore, a DC open circuit and an RF short circuit are formed between the delay line 315 and the feed patch 360.

[0044] In one example, the back insulator 350 is made of It is made of (FR-4 printed circuit board), and the power supply patch 360 can be a conductor formed on Rogers. PTFE (polytetrafluoroethylene) or... (or other low-loss materials to replace Rogers.)

[0045] In the disclosed embodiments, control of the VDC for each delay line is done separately and in real time, i.e., the signal applied to each pair of electrodes is determined separately for each pair of electrodes and can change according to the movement of the platform and / or target in each control cycle. Thus, the control system determines the direction of the main beam and generates a plurality of control signals, where each VDC can receive a signal of different duty cycle or different frequency, which can change over time to steer the main beam.

[0046] The following are some examples of individual real-time control of the delay lines. In one example, two electromagnetic waves with the same amplitude are applied, one to each electrode. The phase offset of one wave relative to the other is changed to move the LC molecules to the desired position. In another example, one electromagnetic wave with a variable shape (duty cycle) but constant amplitude is applied to the electrodes (one electrode is return or ground). The shape of the electromagnetic wave is changed to move the LC molecules to the desired position. In yet another example, two electromagnetic waves are applied to the electrodes, each with a variable shape but constant amplitude. The shape of each wave is changed simultaneously to move the LC molecules to the desired position. In another example, two electromagnetic waves have constant shape and constant amplitude, but the frequency is variable.

[0047] In the disclosed examples, the controller uses a constant voltage electronic switch array to create a pattern on the plurality of dual electrode LC cells. The controller can generate a plurality of signals with different duty cycles or frequencies to generate different delays on each delay line. Depending on the material and the way it responds to the signal.

[0048] Continuing Figure 1 In the example of FIG. 3, the dual electrode LC cell responds to the root mean square voltage applied across the two electrodes 343 and 347. The amplitude of the applied voltage changes the position of the LC inside the cell, thereby controlling the properties of the dielectric. Changing the voltage provides a high degree of control over the position of the LC cell, thereby changing the final obtained delay on the delay line 115 for each radiator 110. However, changing the voltage on each pair of electrodes of a large array separately requires a large number of electronic components in order to create the required voltage level for each cell. Typically, any method that changes the root mean square voltage applied to the cell will control the liquid crystal inside the cell.

[0049] The disclosed examples use a single source to generate multiple signals with different final obtained voltages by implementing pulse width modulation. For example, two positive bias square waves can be applied, one to each electrode, while the phase between the control signals is varied. For example, when the duty cycle of each signal is 50%, if the signals are synchronized (zero degrees offset from each other), the sum of the two signals generates the maximum output power. If the signals with a 50% duty cycle are applied in an out-of-sync manner (180 degrees offset from each other), the result is zero and power. The offset can be set anywhere between zero and 180 degrees to change the state of the liquid crystal cell. For further fine control, the duty cycle of the signals can be set to a value other than 50%.

[0050] By varying the duty cycle of the square wave input to the liquid crystal cell (and antenna), we can change the state of the liquid crystal without changing the amplitude of the applied wave. This allows for a more affordable system design, using digital control circuitry rather than analog signals and devices, since there is no need for voltage step levels. That is, the voltage level is constant, but very fine control can be applied to the cell by controlling the duty cycle and / or phase. Notably, while for optical liquid crystal devices, on and off state control is sufficient, to precisely control the radiators of an antenna array to generate a steerable main beam, fine control of the state of the liquid crystal is required, rather than simple on-off control.

[0051] The liquid crystal response to the applied field operates through a similar fine control of the LC cell by varying the PWM duty cycle, but keeping the voltage constant. The dependence on the energy delivered causes the LC to respond to any PWM duty cycle, enabling more fine beamforming and real-time control. Thus, the disclosed embodiments are able to communicate even if the platform and target are in motion.

[0052] Figure 2is a simplified schematic showing the concept of using a pulse width modulated (PWM) real-time control of the delay lines of an array, which is particularly beneficial for antennas using standard liquid crystal or dual frequency liquid crystal as the VDC material. The control 200 includes a controller 201 that calculates or receives an antenna pointing direction 203. The antenna pointing direction is generated in real time so that the target can be tracked. When the target is a satellite, the pointing direction can be calculated, for example, using the known position of the satellite in the sky, the GPS coordinates of the antenna platform, an accelerometer indicating the physical orientation of the antenna relative to the platform, and a magnetic compass. The known position of the satellite in the sky can be obtained by looking up the satellite coordinates from a satellite look-up table 207, which lists various satellites and their positions in the sky. Using the antenna pointing direction, the appropriate phase shift for each radiator can be calculated so that the main beam is pointed in the direction of the target. The information about the amount of phase shift for each radiator is then converted to PWM for each phase shifter.

[0053] The square wave controller 202 receives a control signal indicating the PWM for each radiator. Based on the control signal, the square wave controller 202 modulates the output of a constant voltage power supply 204 with reference to a clock 206. In one embodiment, the duty cycle of the output of each electrode is calculated in real time independently so that each output has a different duty cycle, the duty cycle being calculated to introduce a phase delay at each radiator to control the direction of the resulting main beam. By introducing the appropriate delay at each radiator, the array of radiators generates a main beam that is aimed at the target. As the platform and / or target move, the duty cycle of each output is changed to ensure that the target is tracked by the main beam.

[0054] Figure 3 is a graph showing examples of different duty cycles for signals that generate different delays. The top-most graph is for a 50% duty cycle, where the signal is a square wave that is at maximum amplitude 50% of the time and off (i.e., zero amplitude) 50% of the time. The middle graph is for a signal with a 75% duty cycle, where the signal is at maximum amplitude 75% of the time and off 25% of the time. The bottom graph shows the inverse of the middle graph, where the square wave signal is at maximum amplitude 25% of the time and off 75% of the time. Of course, the signal can take on any duty cycle, these are just three examples.

[0055] When the VDC material is dual frequency liquid crystal, it is preferred that the frequency of the control signal be controlled with a fixed voltage (i.e., a digital controller) rather than an analog controller (and not the duty cycle). In this way, for each delay line, a specific activation frequency is calculated to generate the precise domain rotation needed for the required phase shift. The frequency is calculated for each delay line at each cycle so that the delay is determined in real time.

[0056] Figure 4An example of three square wave signals is shown, all having a 50% duty cycle, but having different frequencies. Thus, for this system, the controller 201 sends appropriate control signals to the square wave controller 202 to generate different signals having different frequencies, but maintaining the same duty cycle on all signals. It is noted that when the VDC material is a dual frequency material, the square wave controller 202 generates multiple frequencies in order to change the amount of domain alignment for each delay line separately. Also, this simplification is enhanced by using a single power supply 204 having a constant voltage for all signals.

[0057] As can be appreciated from the present disclosure, in the method of controlling an antenna array to track a target, the coordinates in space of the target are obtained. This can be done, for example, by reference to a look-up table that lists the coordinates of a variety of targets such as satellites. Also, the physical orientation of the antenna array is obtained. That is, the antenna array can be, for example, a flat plate on which a plurality of radiating elements are formed. The direction of the orthogonal lines emanating from the middle of the plate corresponds to the boresight, and its direction of pointing can be defined as the physical orientation of the antenna array. In the embodiments disclosed herein, the main beam is tracked by electronic steering rather than mechanical steering. That is, by changing the phase of the signals propagating in the feed of the plurality of radiating elements, the main beam is deviated from the boresight so that the beam can be electronically scanned while maintaining the physical orientation of the antenna unchanged. Of course, when the platform moves, the physical orientation of the antenna does change, so that a corresponding electronic steering is needed to correct for that motion.

[0058] Using the target coordinates, the physical orientation of the antenna, for example, from a compass, the GPS coordinates of the platform, accelerometers, etc., the electronic steering of the main beam is determined. The electronic steering of the main beam is the result of the summation of all the RF signals from the array of radiators, which summation is controlled by the speed at which the RF signals propagate on each delay line, thereby generating a delay, resulting in a phase shift. As described herein, each feed line needs to calculate its individual phase shift in real time for each cycle of the steering control signal. As shown herein, the phase shift is controlled by changing the duty cycle or the frequency of the square wave generated individually for each radiator.

[0059] Figure 5 An example of providing a PWM or frequency control signal to one of the delay lines is shown. The power supply 504 outputs a constant voltage potential that is used to activate all the delay lines. For simplicity, only the detailed information of one output line is shown in Figure 5 but in practice, this line will be divided into a plurality of parallel lines, all carrying the same voltage potential as shown by the ellipse. The voltage potential is adjusted to rotate the liquid crystal of each delay line 540 by an amount that is determined to cause the required delay of the RF signal in that line.

[0060] In this example, two lines are provided for LC rotation (positive line and negative line) in order to achieve fixed amplitude or frequency control and / or pulse width modulation control according to any of the embodiments disclosed herein. In this example, each of the positive and negative lines is connected to a corresponding bipolar junction transistor 522 and 524. The source of the transistors 522 and 524 is connected to the power supply 504 and the gate of the transistors 522 and 524 is connected to the controller 501. By sending an excitation signal to the gate of the transistors 522 and 524, the controller generates a square wave with a variable duty cycle or a variable frequency.

[0061] Figure 6 An antenna array system is shown in which each phase shifter is controlled by only one control line, the other control line being connected to ground or common potential. In Figure 6 In this example, only a 3x3 phase shifter is shown, but the array can have any nxm size. The power supply 604 provides a constant voltage potential that is applied to the source of all transistors 622, one transistor per phase shifter. The drain of each transistor 622 is connected to the corresponding phase shifter 640. The controller 601 sends an activation signal to the gate of each transistor 622, thereby generating a square wave with a varying frequency duty cycle.

[0062] Figure 7 A system for PWM control is shown in which the negative side of the phase shifter receives a constant common voltage (here it is set to +15V) while the positive side receives a PWM signal from zero to +30V. Thus, a square wave from -15V to +15V is used to activate the phase shifter. The setting is controlled using a TIVA microcontroller 702 which incorporates an internal clock system for controlling the PWM signal. The TIVA microcontroller is coupled to a personal computer PC via USB (Universal Serial Bus) for programming and monitoring. On the other hand, the microcontroller 702 is coupled to a CPLD 701 (Complex Programmable Logic Device) via SPI (Serial Peripheral Interface). The output of the CPLD 701 is a plurality of square waves from zero to 3.3V which are individualized for each phase shifter 740 and are calculated for each update period. Each individual output signal of the CPLD 701 is applied to a corresponding transistor 722 which converts the signal to a square wave from zero to 30 volts. This signal is applied to the positive side of the corresponding phase shifter.

[0063] It should be understood that the processes and techniques described herein are not inherently related to any particular apparatus and can be implemented by any

[0064] In addition, to the extent permitted by law, other embodiments of the application will be apparent to those skilled in the art from the foregoing description and practice of the present application. Various aspects and / or components of the described embodiments can be used separately or in any combination. It is intended that the patent description and examples be considered as exemplary only, with the true scope and spirit of the application being indicated by the following claims.

Claims

1. An antenna array system with square wave steering control, comprising: A radiator array comprising multiple radiating patches; Multiple delay lines, each delay line providing RF coupling to a corresponding one of the radiating patches; Multiple variable dielectric constant (VDC) regions, each VDC region being configured to change the propagation speed in a corresponding one of the delay lines; Multiple control lines, each configured to transmit a control signal to one of the VDC regions; A single constant voltage power supply; A square wave modulator receives a constant voltage signal from a single constant voltage power supply and simultaneously generates multiple individual square wave signals. Each square wave signal is coupled as a control signal to one of the control lines and has an independent pulse width or frequency, such that each of the square wave signals has a different and variable duty cycle or a different and variable frequency.

2. The antenna array system according to claim 1, wherein, The VDC region includes a liquid crystal region, and the square wave modulator outputs an independent duty cycle for each square wave signal in real time.

3. The antenna array system according to claim 1, wherein, The VDC region includes a dual-frequency liquid crystal region, and the square wave modulator outputs an independent frequency for each square wave signal in real time.

4. The antenna array system according to claim 1, wherein, The antenna array system also includes multiple transistors, each of which is coupled to one of the control lines, and each square wave signal is applied to the gate of one of the multiple transistors.

5. The antenna array system according to claim 4, wherein: The constant voltage power supply is a dual voltage power supply that provides a first constant voltage and a second constant voltage; Each VDC region has two control lines, one of which is coupled to the first constant voltage, and the other of which is coupled to the output of the corresponding transistor among the plurality of transistors; Furthermore, the source of each of the plurality of transistors is coupled to the second constant voltage.

6. The antenna array system according to claim 4, wherein, Each VDC region has two control lines, one of which is coupled to the common potential and the other is coupled to the output of the corresponding transistor among the plurality of transistors.

7. The antenna array system according to claim 4, wherein: Each VDC region has two control lines, and each control line is coupled to the output of the corresponding transistor in the plurality of transistors; Furthermore, the source of each of the plurality of transistors is coupled to the constant voltage power supply.

8. The antenna array system according to claim 1, wherein, The antenna array system also includes an accelerometer and a controller. The accelerometer provides the controller with an output signal indicating the relative motion of the antenna array. The controller uses the output signal to calculate the control signal arriving at the square wave modulator.

9. The antenna array system according to claim 8, wherein, The antenna array system also includes a satellite lookup table that lists the positions of various satellites in the sky.

10. A method for controlling the main beam of an antenna array system according to any one of claims 1-9 to track a target, the method comprising: The multiple control lines are coupled to the array antenna, and each control line is coupled to one of the multiple phase shifters of the array antenna; Obtain the coordinates of the target; Obtain the physical orientation of the array antenna; The directional direction of the main beam of the antenna is calculated using the coordinates and the physical orientation. The required phase shift for each feed line of the antenna array is determined by the steering direction; Simultaneously, the plurality of individual square waves are generated, each square wave having parameters according to the phase shift required by its corresponding feed line; The plurality of square waves are applied to the plurality of control lines.

11. The method according to claim 10, wherein, Generating multiple square waves involves calculating the duty cycle of each square wave separately to generate the pulse width modulation required for the phase shift of its respective feeder.

12. The method according to claim 10, wherein, Generating multiple square waves involves calculating the frequency of each square wave separately to generate the phase shift required for its corresponding feed line.

13. The method according to claim 12, wherein, The method also includes keeping the duty cycle of the square wave constant at 50%.

14. The method of claim 10, wherein, Generating multiple square waves involves keeping the amplitude of the square waves constant for all control lines.

15. The method according to claim 10, wherein, Generating multiple square waves involves applying an activation signal to multiple individual transistors.

16. The method of claim 10, wherein, The method further includes coupling the drains of two transistors to each of the phase shifter, and generating multiple square waves including applying an activation signal to the transistors.

17. The method according to claim 10, wherein, The method also includes coupling all phase shifters to a common potential.

18. The method according to claim 17, wherein, The common potential includes the ground potential.

19. The method according to claim 17, wherein, The common potential includes the constant voltage of the dual-voltage power supply.

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