Field-effect transistor phase shifter

Abstract

This application relates to a method and apparatus for implementing a radar array, the radar array including a gate bias source for providing a first variable voltage, a back gate well control unit for providing a second variable voltage, and a field-effect transistor having a drain, a source, a gate, and a back gate well control unit, the field-effect transistor being further configured to couple an AC radar signal between its drain and source, and to adjust the phase of the AC radar in response to the first variable voltage applied to the gate and the second variable voltage applied to the back gate well control unit.

Description

Technical Field

[0001] This disclosure generally relates to radar sensor systems. More specifically, some aspects of this disclosure relate to systems, methods, and apparatus for achieving low-loss phase shifts in FET-based on-chip radar by adjusting the effective capacitance of the drain-body and / or source-body via the back-gate node of the FET. Background Technology

[0002] Currently, some vehicles use radar systems. For example, some vehicles utilize radar systems to detect other vehicles, pedestrians, or other objects on the road. Radar systems can be used in this way, for example, to implement automatic braking systems, adaptive cruise control, and avoidance features, as well as other vehicle features. Some vehicle radar systems, such as multiple-input multiple-output (MIMO) radar systems, have multiple transmitters and receivers configured in phased arrays or electronically scanned arrays. Phased array radar systems can manipulate the radar in different directions by adjusting the individual phase of each transmitted signal without physically moving the antenna. While radar systems are generally useful for this type of vehicle feature, existing radar systems may have certain limitations in some situations.

[0003] Vehicle-mounted radar systems require high performance, low maintenance, and low cost to be suitable for implementation in civilian vehicles. To achieve these goals, multiple phased array radars, each with a specific operating angle range, can be used on the vehicle. Currently, integrated circuit (IC)-based radar systems are being developed to reduce the complexity of these vehicle-based radar systems and improve their durability. Most IC-based radars perform phase shifting by switching capacitor banks on / off or by selecting different real-time delay lines. Field-effect transistors (FETs) or microelectromechanical systems (MEMS) switches are used as general-purpose switching devices. In the case of MEMS switches, the large size can be a problem for compact IC circuit design and high-voltage-based drives, and the relatively slow switching speed limits its general application. Therefore, phase shifters using FET switches are generally suitable for small IC circuit applications. However, the switching speed limitations of FETs and poor isolation at high frequencies (beyond millimeter waves) cause high insertion loss problems and a maximum application frequency limitation. FET-based switches also generate nonlinear harmonics at high power. Therefore, as power demands increase, the size of the FETs must also increase, leading to problems related to increased matching networks and switch isolation. Phase shifters based on capacitor bank switching are also susceptible to capacitor process variations and are not suitable for fine-tuning phase shift resolution. The aim is to overcome these issues and provide a low-loss, high-resolution tuned phase shifter for applications in the RF or millimeter-wave range.

[0004] The information disclosed in this background section is merely intended to enhance the understanding of the background of the invention, and therefore may contain information that does not constitute prior art known to those skilled in the art in this country. Summary of the Invention

[0005] This document discloses various solid-state electromagnetic sensing systems and related control logics for supplying vehicle sensor systems, methods for manufacturing such systems, methods for operating such systems, and motor vehicles equipped with onboard sensors and control systems. By way of example and not limitation, a car with an onboard array radar transmitter and receiver and a corresponding control system is presented.

[0006] According to one aspect of this disclosure, a radar array includes: a gate bias source for providing a first variable voltage, a back gate bias source for providing a second variable voltage, and a field-effect transistor having a drain, a source, a gate, and a back gate well control portion, the field-effect transistor being further configured to couple an AC radar signal between its drain and its source, and to adjust the phase of the AC radar signal in response to the first variable voltage applied to the gate and the second variable voltage applied to the back gate well control portion.

[0007] According to another aspect of this disclosure, a sub-state is provided, wherein a field-effect transistor is formed within a substrate, wherein the field-effect transistor has a drain-body capacitance between the drain and the substrate, and wherein adjusting a first variable voltage and a second variable voltage can modify the drain-body capacitance.

[0008] According to another aspect of this disclosure, the preamplifier is used to adjust the amplitude of the radar signal and couple the radar signal to the source.

[0009] According to another aspect of this disclosure, the amplifier is used to receive radar signals from the drain, adjust the amplitude of the radar signals, and couple the radar signals to the radar antenna.

[0010] According to another aspect of this disclosure, the radar array includes multiple antennas, and each antenna is coupled to one of multiple phase shifters.

[0011] According to another aspect of this disclosure, the radar signal is a millimeter-wave radar signal.

[0012] According to another aspect of this disclosure, an insulating well is formed between a field-effect transistor and a substrate, wherein the insulating well has an insulating well-substrate capacitance that forms part of a drain-substrate capacitance, and a second variable voltage applied at the back gate well control section can change the insulating well-substrate capacitance.

[0013] According to another aspect of this disclosure, the second variable voltage is applied to the back gate well control unit via an RF choke resistor.

[0014] According to another aspect of this disclosure, a method for changing the phase of a radar signal by means of a field-effect transistor formed on a substrate includes: receiving a radar signal at the source of the field-effect transistor, applying a first variable voltage to the gate of the field-effect transistor, applying a second variable voltage to a back gate well control portion, such that the phase of the radar signal is adjusted to a desired phase, and transmitting a radar signal with the desired phase from the drain of the field-effect transistor.

[0015] According to another aspect of this disclosure, changing the second variable voltage alters the drain-body capacitance between the drain and the substrate.

[0016] According to another aspect of this disclosure, the amplitude of the radar signal is adjusted by a preamplifier and the radar signal is coupled to the source.

[0017] According to another aspect of this disclosure, the method includes adjusting the amplitude of a radar signal having a desired phase by an amplifier and coupling the radar signal to a radar antenna.

[0018] According to another aspect of this disclosure, the field-effect transistor is one of a plurality of field-effect transistors, and the plurality of field-effect transistors form part of a radar array.

[0019] According to another aspect of this disclosure, the radar signal is a millimeter-wave radar signal.

[0020] According to another aspect of this disclosure, the field-effect transistor is formed on an insulating well formed within a substrate, and the insulating well has an insulating well-substrate capacitance that forms part of the drain-substrate capacitance, and a second variable voltage applied at the back gate well control portion can change the insulating well-substrate capacitance.

[0021] According to another aspect of this disclosure, the second variable voltage is applied to the back gate well control unit via a switched-on DC bias source.

[0022] According to another aspect of this disclosure, a solid-state radar array includes: a first radar signal channel and a second radar signal channel. The first radar signal channel includes a first antenna, a first amplifier, and a first bandpass filter. The second radar signal channel includes a second antenna, a second amplifier, a second bandpass filter, and a phase shifter. The phase shifter includes a field-effect transistor having a drain, a source, a gate, and a back gate well control portion. The field-effect transistor is configured to couple a first AC radar signal between its drain and source, and to adjust the phase of the first AC radar signal in response to a first variable voltage from a gate bias source applied to the gate and a second variable voltage from a back gate control source applied to the back gate well control portion.

[0023] According to another aspect of this disclosure, the first antenna is configured to receive a second AC radar signal, the second antenna is configured to receive a first AC radar signal, and a phase shifter is configured to adjust the phase of the first AC radar signal to match the phase of the second AC radar signal.

[0024] According to another aspect of this disclosure, the first antenna is configured to transfer a second AC radar signal, the second antenna is configured to transmit a first AC radar signal, and a phase shifter is configured to adjust the phase of the first AC radar signal to change the directivity of the solid-state radar array.

[0025] According to another aspect of this disclosure, the first amplifier, the first bandpass filter, the second amplifier, the second bandpass filter, and the phase shifter are formed as an integrated circuit.

[0026] The above-described advantages and other advantages and features of this disclosure will become apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings. Attached Figure Description

[0027] The above and other features and advantages of the invention, as well as the ways in which they are implemented, will become more apparent from the following description in conjunction with the accompanying drawings and embodiments of the invention, and the invention will be better understood.

[0028] Figure 1 The operating environment of a field-effect transistor phase shifter in a radar system according to an exemplary embodiment is shown.

[0029] Figure 2 A block diagram illustrating a field-effect transistor phase shifter in a radar system according to an exemplary embodiment is shown.

[0030] Figure 3a A diagram illustrating a floating back gate bias control section in a phase-shifting field-effect transistor for a phased array radar, according to another exemplary embodiment, is shown.

[0031] Figure 3b A diagram illustrating a back-gate bias control section in a phase-shifting field-effect transistor for a phased array radar, according to another exemplary embodiment, is shown.

[0032] Figure 3c This is a diagram illustrating a switched-on floating back gate bias control section in a field-effect transistor for phase shifting in a phased array radar according to another exemplary embodiment.

[0033] Figure 3d A diagram is shown illustrating a back-gate bias control section with A / C shorted in a field-effect transistor for phase shifting in a phased array radar, according to another exemplary embodiment.

[0034] Figure 4A schematic diagram of an exemplary embodiment of an N-state phase shifter according to another exemplary embodiment is shown.

[0035] Figure 5 A block diagram illustrating another field-effect transistor phase shifter in a radar system according to another exemplary embodiment is shown.

[0036] Figure 6 A flowchart illustrating a method for controlling a field-effect transistor phase shifter in a radar system according to another exemplary embodiment is shown.

[0037] The examples set forth herein illustrate preferred embodiments of the invention, and these examples should not be construed as limiting the scope of the invention in any way. Detailed Implementation

[0038] This document describes embodiments of the present disclosure. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various alternative forms. These figures are not necessarily to scale; some features may be enlarged or reduced to show detail of a particular component. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely representative. Various features illustrated and described with reference to any of the accompanying drawings may be combined with features illustrated in one or more other drawings to produce embodiments not explicitly illustrated or described. The combinations of features shown provide representative embodiments for typical applications. However, various combinations and modifications of features consistent with the teachings of this disclosure are desired for particular applications or implementations.

[0039] Figure 1 The operating environment of a FET phase shifter in a radar system is schematically illustrated. In this exemplary embodiment of the present disclosure, a typical configuration of an analog beamformer 100 for a phased array radar is shown. The exemplary analog beamformer 100 is shown as a radar transmitter, but a similar structure can be used for an analog beamformer of a radar detector. The exemplary analog beamformer 100 may include multiple transmission channels T1, T2, T3…Tn, each employing independent phase and amplitude control.

[0040] Each of the plurality of transmission channels T1, T2, T3…Tn in the exemplary analog beamformer 100 may include an antenna 110, an amplifier 120, a phase shifter 130, an attenuator 140, a preamplifier 150, a mixer 160, a bandpass filter 170, and a digital-to-analog converter 180. The analog beamformer 100 may also include digital circuitry 190, such as a digital signal processor, an equalizer, a digital filter, etc. In this exemplary embodiment, the antenna 110 in each of the plurality of transmission channels T1, T2, T3…Tn is in a fixed position. In a phased array transmitter, by adjusting the phase of each transmitted signal using the phase shifter 130, the attenuator 140, and the preamplifier 150, the radar beam direction is electronically scanned, such that the radiation amplitude is increased in the desired direction and suppressed in the undesired direction.

[0041] The exemplary phase shifter 130 is configured using a FET structure to achieve a low-loss, high-resolution tuned phase shifter for RF or millimeter-wave range applications by utilizing the volume capacitance variation of the FET. The FET with volume capacitance variation can also achieve phase amplitude and resolution adjustment by regulating external bias control. Because the exemplary phase shifter 130 is adjusted in response to the FET's volume capacitance, it can generate less nonlinear harmonics than any other transistor-switched phase shifter. In another embodiment of the radar transmitter, the phase shifter 130 is added at the input of this stage before up-conversion at the intermediate frequency (IF), such that the phase shift range is increased proportionally to the RF / IF. In this embodiment, a large phase shift range can be achieved at very high frequencies, such as sub-Terahertz frequencies.

[0042] In one exemplary embodiment, a radar signal is coupled to a phase shifter 130, which includes a transmission line between an input and an output. A FET transistor is mounted in place on the transmission line. The gate of the FET transistor is provided with an appropriate bias voltage. In analog control applications, the back-gate (BG) terminal of the FET transistor is connected to an adjustable DC source. In digital switching control applications, the BG node can be connected to a switching transistor and a ground / bias load to change the impedance of the line by introducing a different load in series with its source. Advantageously, this phase shifter topology has negligible power dissipation, making the sole source of power dissipation the gate / base current.

[0043] Now go to Figure 2This diagram illustrates an exemplary embodiment of a FET 200 with back-gate control for use in a phased-array radar. The exemplary FET 200 includes a source S, a gate G, a drain D, a semiconductor layer 210, an insulating layer 230, a back gate well control 215, a well 220, a substrate 240, a source-well capacitor 255, a drain-well capacitor 250, and a well-to-substrate capacitor 260. By manipulating the back gate of the device, the exemplary FET 200 is used as a phase shifter, which can be manipulated to change the effective drain-to-body capacitance and / or source-to-body capacitance via analog voltage or digital switch control through the back gate well control 215. The effective drain-to-body capacitance is a combination of the drain-well capacitor 250 and the well-to-substrate capacitor 260. The effective source-to-body capacitance is a combination of the source-well capacitor 255 and the well-to-substrate capacitor 260.

[0044] Now go to Figure 3a This diagram illustrates a floating back-gate bias control in a FET used for phase shifting in a phased array radar. In this exemplary embodiment, a variable back-gate bias 315 is applied to the back-gate well control 305 via a resistor 310. The resistor value can be selected such that resistor 310 provides an RF choke resistance. The effective drain-body capacitance can be adjusted by regulating the variable back-gate bias 315. In this configuration, the effective drain-body capacitance is approximately the drain-to-substrate capacitance in series with the well-to-substrate capacitance.

[0045] In another exemplary embodiment, if the resistance of resistor 310 is zero, thereby creating a short circuit between the variable back gate bias 315 and the back gate well control 305, the back gate node is effectively introduced to AC ground. This configuration provides an AC short circuit to the back gate bias control, resulting in an effective AC drain-body capacitance approximately equal to the drain-well capacitance, which can be adjusted by the variable back gate bias 315. In this configuration, the well-substrate capacitance is minimized.

[0046] Now go to Figure 3bThis diagram illustrates a schematic of an on-state back-gate bias control unit in a FET used for phase shifting in a phased array radar. The floating back-gate bias control unit configuration includes a resistor 330 with a resistor, a switch 335, a back-gate well control unit 325, and a variable back-gate bias 340. The back-gate potential can be switched between ground and open circuit by toggling switch 335. This switch 335 can be a transistor (FET or BJT) switch or a MEMS, if desired. When switch 335 is off, the back gate is floating, resulting in an effective drain-body capacitance approximately equal to the drain-well capacitance effectively connected in series with the well-substrate capacitance. When switch 335 is off, resistor 330 can be used to release any accumulated charge on the well. When switch 335 is on, back-gate well control unit 325 is grounded, resulting in an effective drain-body capacitance approximately equal to the drain-well capacitance.

[0047] Now go to Figure 3c This diagram illustrates an on-floating back-gate bias control unit in a FET used for phase shifting in a phased array radar. The on-floating back-gate bias control unit is configured to include a first resistor 360 with a first resistance, a second resistor 370 with a second resistance, a switch 365, a back-gate well control unit 355, and a variable back-gate bias 375. The back-gate potential can be switched between on and floating states of the back-gate bias control unit. When switch 365 is off, the back-gate well control unit 355 is floating, resulting in an effective drain-body capacitance approximately equal to the drain-well capacitance in series with the well substrate capacitance. When switch 365 is off, discharging the first resistor 360 can release any accumulated charge on the well. When switch 365 is on, the back-gate well control unit 355 is connected to the variable back-gate bias 375, and the effective drain-body capacitance is approximately equal to the drain-well capacitance in series with the well substrate capacitance, and can be adjusted by the variable back-gate bias 375.

[0048] Now go to Figure 3d This diagram illustrates a schematic of a floating back-gate bias control unit in a phase-shifting FET used in a phased-array radar. The floating back-gate bias control unit configuration includes a resistor 385 with a resistor, a switch 390, a back-gate well control unit 380, and a variable back-gate bias 395. In this exemplary embodiment, the back-gate potential can be switched between an open-circuit and an AC-short-circuit back-gate bias control unit. When the switch 390 is in the open position, the back gate is floating, and the effective drain-body capacitance is approximately equal to the drain-well capacitance in series with the well-substrate capacitance. The resistor 385 can be used to release any accumulated charge on the back-gate well control unit 380 during switch-off. When the switch 390 is in the closed position, the back-gate well control unit 380 is connected to the variable back-gate bias 395, and the effective AC drain-body capacitance is approximately equal to the drain-well capacitance and can be adjusted by the variable back-gate bias 395.

[0049] Now go to Figure 4This diagram illustrates an exemplary embodiment of an N-state phase shifter. The exemplary phase shifter 400 may include a first impedance matching circuit 420a, a second impedance matching circuit 420b, a variable gate bias 410, and a plurality of phase shift circuits PS1, Ps2…PSn. In this exemplary embodiment, each of the plurality of phase shift circuits PS1, Ps2…PSn includes resistors R1, R2,…Rn, FET devices F1, F2,…Fn, and back gate controls C1, C2,…Cn. In this exemplary embodiment, resistors R1, R2,…Rn are configured as RF choke resistors. By cascading the series-connected FET devices R1, R2,…Rn, an n-state phase shifter can be implemented by manipulating each back gate control. The back gate controls C1, C2,…Cn can be configured as reference... Figure 3a , 3b One of the configurations discussed in the 3C and 3D discussions.

[0050] In an exemplary millimeter-wave system, multiple phase-shifting circuits Ps1, Ps2, ... PSn can each be connected between each section of a microstrip or stripline. The source and drain of each FET device F1, F2, ... Fn can be bundled together. The phase of the propagating wave is then determined in response to the capacitance values ​​of the back-gate control FET devices F1, F2, ... Fn. A first impedance matching circuit 420a and / or a second impedance matching circuit 420b may be optional, depending on the resistance of the transmission line between the phase shifters Ps1, Ps2, ... Psn.

[0051] Now go to Figure 5 The diagram illustrates an exemplary embodiment of a phase shifter 500 for a radar array. The exemplary phase shifter 500 may include a gate bias source 510, a back gate bias source 520, a field-effect transistor 530, a preamplifier 540, and an amplifier 550.

[0052] In this exemplary embodiment, the gate bias source 510 is configured to provide a first variable voltage to the gate of the FET 530. The gate bias voltage provided by the gate bias source 510 is used to provide a conduction path between the drain and source of the FET 530.

[0053] A back-gate bias source 520 is configured to provide a second variable voltage to the back-gate well control section of the FET 530. The second variable voltage is used to adjust the drain-body capacitance between the drain of the FET 530 and the substrate. In an exemplary configuration, the second variable voltage is applied to the back-gate well control section via an RF choke resistor.

[0054] The FET530 is configured as a phase-shifting device having a drain, source, gate, and back-gate well control section. The field-effect transistor is also configured to couple an AC radar signal between the drain and source, and to adjust the phase of the AC radar signal in response to a first variable voltage applied to the gate and a second variable voltage applied to the back-gate well control section. The FET530 can be formed on or within a substrate, such that the FET530 has a drain-body capacitance between the drain and the substrate. Therefore, adjusting the first and second variable voltages modifies the capacitance of the drain-body capacitance. In an exemplary embodiment, the radar signal is a millimeter-wave radar signal, such as a millimeter-wave signal with a frequency of 240 GHz.

[0055] An exemplary radar array may further include a preamplifier 540 and an amplifier 550, wherein the preamplifier 540 is used to adjust the amplitude of the radar signal and couple the radar signal to the source of the FET 530, and the amplifier 550 is used to receive the radar signal from the drain of the FET, adjust the amplitude of the radar signal, and couple the radar signal to a radar antenna. Furthermore, the radar array may be coupled to multiple antennas, and each antenna may be coupled to one of multiple phase shifters.

[0056] In one exemplary application, the FET530 may include an insulator well formed between the FET530 and the substrate. The insulator well may have an insulator well-to-substrate capacitance that forms part of the drain-to-substrate capacitance, and a second variable voltage applied at the back gate well control portion may change the insulator well-to-substrate capacitance.

[0057] In one exemplary embodiment, the exemplary phase shifter 500 may form part of a solid-state radar array including a first radar signal channel and a second radar signal channel. The first radar signal channel includes a first antenna, a first amplifier, and a first bandpass filter, and the second radar signal channel includes a second antenna, a second bandpass filter, and the phase shifter 500. The phase shifter may include a FET 530 having a drain, a source, a gate, and a back gate well control. The FET 530 may then be configured to couple a first AC radar signal between its drain and source, and to adjust the phase of the first AC radar signal in response to a first variable voltage from a gate bias source 510 applied to the gate and a second variable voltage from a back gate bias source 520 applied to the back gate well control. In one exemplary embodiment, the first amplifier, the first bandpass filter, the second bandpass filter, and the phase shifter may be formed as an integrated circuit.

[0058] In a radar receiver configuration, a first antenna can be configured to receive a second AC radar signal, and a second antenna can be configured to receive a first AC radar signal. An exemplary phase shifter 500 can be configured to adjust the phase of the first AC radar signal to match the phase of the second AC radar signal.

[0059] In the transmitter configuration, the first antenna can be configured to divert the second AC radar signal, and the second antenna can be configured to transmit the first AC radar signal. In this case, the phase shifter 500 can be configured to adjust the phase of the first AC radar signal to change the directivity of the solid-state radar array.

[0060] Now go to Figure 6 A flowchart illustrating an exemplary implementation of method 600 is shown, illustrating the use of radar signal phase in a mobile radar array. The method first receives (610) a radar signal at the source of a field-effect transistor. The radar signal can be received from the radar array antenna via an amplifier and other analog signal processing components (e.g., bandpass filters, mixers, etc.). Alternatively, the radar signal can be received from a radar signal processor, and the method is configured to modulate the radar signal before transmission via the radar array antenna. In one exemplary configuration, the amplitude of the radar signal can be adjusted by a preamplifier and by coupling the radar signal to the source.

[0061] The method can then be operated by applying a first variable voltage (620) to the gate of the field-effect transistor. The first variable voltage applied to the gate can have the effect of opening a conduction path between the source and drain, allowing the radar signal to be coupled between the source and drain.

[0062] The method can then be operated by applying a second variable voltage (630) to the back gate well control section, such that the phase of the radar signal is adjusted to a desired phase. In this example, changing the second variable voltage can change the drain-body capacitance between the drain and the substrate on which the field-effect transistor is formed. In one embodiment, the second variable voltage can be applied to the back gate well control section via a switched-on DC bias source.

[0063] Next, the method is configured to transfer a radar signal with a desired phase from the drain of a field-effect transistor (640) to a subsequent state in the radar signal processing path, such as an amplifier, mixer, etc. In one embodiment, the amplitude of the radar signal with the desired phase can be adjusted by the amplifier, and the radar signal can then be coupled to a radar antenna.

[0064] In one exemplary configuration, the method is configured to change the phase of a radar signal using a field-effect transistor formed on a substrate, wherein the field-effect transistor is formed on an insulating well formed within the substrate. The insulating well may also have an insulating well-substrate capacitance, forming part of the drain-substrate capacitance. Changing a second variable voltage applied to the back-gate well control section can change the insulating well-substrate capacitance, thereby changing the phase response of the field-effect transistor to the radar signal.

[0065] While at least one exemplary embodiment has been given in the foregoing detailed description, it should be understood that numerous variations exist. It should also be understood that the one or more exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of this disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient roadmap for implementing one or more exemplary embodiments. It should be understood that various changes can be made to the function and arrangement of the elements without departing from the scope of this disclosure as set forth in the appended claims and their legal equivalents.

[0066] It should be understood that various changes may be made to the function and arrangement of the elements without departing from the scope of this disclosure as set forth in the appended claims and their legal equivalents.

Claims

1. A radar array, comprising: A gate bias source is configured to provide a first variable voltage; The back-gate bias source is configured to provide a second variable voltage; and A field-effect transistor having a drain, a source, a gate, and a back gate well control section, the field-effect transistor being configured to couple an AC radar signal between the drain and the source, and to adjust the phase of the AC radar signal in response to a first variable voltage applied to the gate and a second variable voltage applied to the back gate well control section. The substrate, wherein a field-effect transistor is formed within the substrate, wherein the field-effect transistor has a drain-body capacitance between the drain and the substrate, and wherein adjusting a first variable voltage and a second variable voltage can modify the drain-body capacitance.

2. The radar array according to claim 1 further includes a preamplifier configured to adjust the amplitude of the AC radar signal and couple the AC radar signal to the source.

3. The radar array of claim 1 further includes an amplifier configured to receive the radar signal from the drain, adjust the amplitude of the radar signal, and couple the radar signal to the radar antenna.

4. The radar array of claim 1, wherein the radar array comprises a plurality of antennas, and wherein each of the plurality of antennas is coupled to one of a plurality of phase shifters.

5. The radar array according to claim 1, wherein the AC radar signal is a millimeter-wave radar signal.

6. The radar array of claim 1 further includes an insulating well formed between the field-effect transistor and the substrate, wherein the insulating well has an insulating well-substrate capacitance forming part of the drain-substrate capacitance, and wherein a second variable voltage applied at the back gate well control portion changes the insulating well-substrate capacitance.

7. The radar array of claim 1, wherein the second variable voltage is applied to the back grid trap control unit via an RF choke resistor.

8. A method for changing the phase of a radar signal using a field-effect transistor formed on a substrate, comprising: The radar signal is received at the source of the field-effect transistor; A first variable voltage is applied to the gate of the field-effect transistor; A second variable voltage is applied to the back grid trap control unit, causing the phase of the radar signal to be adjusted to the desired phase, thereby generating an adjusted radar signal; and Emitting an adjusted radar signal with the desired phase from the drain of a field-effect transistor; in, A field-effect transistor has a drain-body capacitance between the drain and the substrate, and the drain-body capacitance can be modified by adjusting a first variable voltage and a second variable voltage.

9. The method for changing the phase of a radar signal by means of a field-effect transistor formed on a substrate according to claim 8, wherein the second variable voltage is applied to the back gate well control unit via a switched-on DC bias source.

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