CN112558024A

CN112558024A - Radar array phase shifter verification

Info

Publication number: CN112558024A
Application number: CN202010863422.7A
Authority: CN
Inventors: T·海勒; O·卡茨; D·埃拉德; B·沙因曼
Original assignee: Semiconductor Components Industries LLC
Current assignee: Adikay LLC
Priority date: 2019-09-10
Filing date: 2020-08-25
Publication date: 2021-03-26

Abstract

The invention provides a radar array phase shifter verification. An improved circuit configuration is disclosed for calibrating and/or verifying the operation of phase shifters in a phased array radar system. In an exemplary embodiment, a method comprises: (i) programming a set of phase shifters to convert the radio frequency signal to a set of channel signals; (ii) while coupling the set of channel signals to the set of antenna feeds, separating a monitor signal from each channel signal; and (iii) measuring the relative phase between each pair of monitoring signals while employing the pair of monitoring signals associated with the adjacent channels.

Description

Radar array phase shifter verification

Technical Field

The present disclosure relates generally to self-test techniques for phased antenna array radar systems, and more particularly to verifying the function of phase shifters in such systems.

Background

In an effort to seek safer and more convenient transportation options, many automobile manufacturers are developing autonomous vehicles that require a large number of various sensors. In the sensing technology envisaged, there is a multiple input multiple output radar system for monitoring the distance between the car and any vehicle or obstacle along the route of travel. Such systems may employ beam steering techniques to improve their measurement range and resolution.

On the transmit side, beam steering is typically performed using a phased array (i.e., by supplying transmit signals with different phase shifts to each of a plurality of antennas), with the beam direction being determined by the difference between the phase shifts. When the phase difference is changed to steer the beam, the desired signal amplitude remains the same. Device mismatch, even due to temperature and aging, can lead to beam pattern distortion and even sidelobe formation. Such effects may shift the viewing direction of the obstacle, or produce a null that completely "hides" the obstacle. Thus, automotive radar safety standards or mere engineering design caution may dictate that some mechanism be included to calibrate and/or verify proper operation of the phase shifter. Existing mechanisms for this purpose may unduly compromise the cost or reliability of automotive radar systems.

Disclosure of Invention

The above-mentioned problems may be at least partially solved by an improved circuit configuration for calibrating and/or verifying the operation of phase shifters in a phased array radar system.

According to an aspect of the present application, there is provided a method characterized by comprising: programming a set of phase shifters to convert the radio frequency signal to a set of channel signals; while coupling the set of channel signals to a set of antenna feeds, separating a monitor signal from each channel signal; and measuring the relative phase between each pair of monitoring signals while employing the pair of monitoring signals associated with the adjacent channels.

In one embodiment, the method is characterized by further comprising: obtaining sequential relative phase measurements over a range of phase settings of phase shifters associated with even channels while maintaining the phase settings of phase shifters associated with odd channels; obtaining sequential relative phase measurements over a range of phase settings of phase shifters associated with odd channels while maintaining the phase settings of phase shifters associated with even channels; and providing an error notification if the difference between sequential relative phase measurements fails to match a predetermined step size.

In one embodiment, the method is characterized by comprising determining a phase setting offset for each pair based on the relative phase measurements, wherein said determining comprises measuring the relative phase over a range of phase setting differences for adjacent channels.

In one embodiment, the method is characterized in that said measuring comprises: combining each pair of monitoring signals to form a combined signal; and measuring the power of each combined signal.

In one embodiment, the method is characterized by comprising: disabling the adjustable gain amplifiers associated with the odd channels while measuring the power of each combined signal; disabling the adjustable gain amplifiers associated with the even channels while measuring the power of each combined signal; and adjusting the gain of the adjustable gain amplifier based on the power measurements to equalize the power of each channel signal in the set of channel signals.

According to another aspect, there is provided a radar system characterized by: a signal generator, the signal generator providing a radio frequency signal; a set of programmable phase shifters, the set of programmable phase shifters converting the radio frequency signal to a set of channel signals; a set of couplers coupling the set of channel signals to a set of antenna feeds, the couplers in the set providing monitoring signals; one or more power combiners, each power combiner combining a pair of monitor signals to produce a combined signal; one or more power detectors, each power detector converting a respective combined signal to a power level signal; and a controller that uses at least one of the power level signals to determine a relative phase between at least one pair of channel signals in the set of channel signals.

In one embodiment, the radar system is characterised in that the controller uses the at least one power level signal to determine the phase setting offset for each pair by: measuring the at least one power level signal over a range of phase setting differences for adjacent channels; and identifying a power level maximum or minimum corresponding to the phase setting offset.

In one embodiment, the radar system is characterized by a set of adjustable gain amplifiers that amplify the set of channel signals provided to the set of couplers, wherein the controller is operative to: while measuring the power of each combined signal, disabling the adjustable gain amplifiers associated with odd channels; disabling the adjustable gain amplifiers associated with even channels while measuring the power of each combined signal; and adjusting the gain of the adjustable gain amplifier to equalize the power of each channel signal in the set of channel signals.

According to yet another aspect, there is provided a radar system characterized by: a signal generator, the signal generator providing a radio frequency signal; a set of programmable phase shifters, the set of programmable phase shifters converting the radio frequency signal to a set of channel signals; a set of couplers coupling the set of channel signals to a set of antenna feeds, the couplers in the set providing monitoring signals; and one or more phase detectors, each phase detector determining a relative phase between the monitoring signals of a pair of adjacent channels.

In one embodiment, the radar system is characterized by a controller that: obtaining sequential relative phase measurements over a range of phase settings of phase shifters associated with even channels while maintaining the phase settings of phase shifters associated with odd channels; obtaining sequential relative phase measurements over a range of phase settings of phase shifters associated with odd channels while maintaining the phase settings of phase shifters associated with even channels; and providing an error notification if the difference between sequential relative phase measurements fails to match a predetermined step size.

In one embodiment, the radar system is characterized in that the one or more phase detectors comprise: a pair of phase detectors to determine a first relative phase between a central channel and a first adjacent channel and a second relative phase between the central channel and a second adjacent channel, the controller operative to calculate a difference between the first relative phase and the second relative phase.

Drawings

FIG. 1 is a top view of an exemplary vehicle equipped with sensors.

FIG. 2 is a block diagram of an exemplary driver assistance system.

Fig. 3 is a block diagram of an exemplary radar transceiver chip.

Fig. 4 is a block diagram of an exemplary phase-shifted transmit array.

Fig. 5 is a schematic diagram of an exemplary phase detector.

FIG. 6 is a schematic diagram of an exemplary calibration circuit.

FIG. 7 is a schematic diagram of an exemplary verification circuit.

FIG. 8 is a schematic diagram of another exemplary calibration circuit.

Fig. 9A is a graph of inverting combiner output versus phase.

Fig. 9B is a graph of in-phase combiner output versus phase.

FIG. 10A is a flow diagram of an exemplary verification method.

Fig. 10B is a flow chart of an exemplary calibration method.

Detailed Description

It is to be understood that the following description and drawings are provided for purposes of illustration and not limitation of the present disclosure. Rather, they provide the basis for those skilled in the art to understand all modifications, equivalents, and alternatives falling within the scope of the claims.

Fig. 1 shows an illustrative vehicle 102 equipped with an array of radar antennas including an antenna 104 for short range sensing (e.g., for parking assist), an antenna 106 for medium range sensing (e.g., for monitoring parking & driving and passing events), an antenna 108 for remote sensing (e.g., for adaptive cruise control and collision warning), each of which may be placed behind a front bumper cover. An antenna 110 for short range sensing (e.g., for reverse assistance) and an antenna 112 for medium range sensing (e.g., for rear collision warning) may be placed behind the rear bumper cover. An antenna 114 for short range sensing (e.g., for blind spot monitoring and side obstacle detection) may be placed behind the fender of the vehicle. Each group of antennas may perform multiple-input multiple-output (MIMO) radar sensing. The type, number and configuration of the sensors in the sensor arrangement differ for vehicles with driver assistance and automatic driving functions. Vehicles may employ sensor arrangements to detect and measure distances/directions to objects in various detection zones to enable the vehicle to navigate while avoiding other vehicles and obstacles.

Fig. 2 shows an Electronic Control Unit (ECU)202 coupled to various radar sensing front ends 204 to 206 as the center of a star topology. Of course, other topologies, including serial, parallel, and hierarchical (tree) topologies, are suitable and contemplated for use in accordance with the principles disclosed herein. The radar front ends each include a Radio Frequency (RF) transceiver coupled to some of the transmit and receive antennas 104-114 to transmit electromagnetic waves, receive reflections and optionally perform processing to determine the spatial relationship of the vehicle to its surroundings. (such processing may alternatively be performed by the ECU 202.) to provide automated parking assist, the ECU 202 may be further connected to a set of actuators, such as a turn signal actuator 208, a steering actuator 210, a brake actuator 212, and a throttle actuator 214. The ECU 202 may be further coupled to a user interactive interface 216 to accept user input and provide a display of various measurements and system status.

Using interfaces, sensors, and actuators, the ECU 202 may provide automated parking, assisted parking, lane change assistance, obstacle and blind spot detection, autonomous driving, and other desired features. In automobiles, various sensor measurements are collected by one or more Electronic Control Units (ECUs), and may be used by the ECUs to determine the state of the automobile. The ECU may also take action on the status and incoming information to actuate various signaling and control transducers to regulate and maintain the operation of the vehicle. The operations provided by the ECU include various driver assistance features including automatic parking, lane tracking, automatic braking, and automatic driving.

To collect the necessary measurements, the ECU may employ a MIMO radar system. Radar systems operate by transmitting electromagnetic waves that travel outward from a transmitting antenna before reflecting back to a receiving antenna. The reflector may be any reasonably reflective object in the path of the transmitted electromagnetic wave. By measuring the travel time of the electromagnetic wave from the transmitting antenna to the reflector and back to the receiving antenna, the radar system can determine the distance to the reflector. If multiple transmit or receive antennas are used, or if multiple measurements are taken at different locations, the radar system can determine the direction of the reflector and thus track the position of the reflector relative to the vehicle. With more complex processing, multiple reflectors can be tracked. At least some radar systems employ array processing to "scan" the directional electromagnetic beam and construct an image of the surroundings of the vehicle. Both pulsed and continuous wave implementations of radar systems can be achieved, but frequency modulated continuous wave radar systems are generally preferred for accuracy.

Fig. 3 shows a block diagram of an illustrative transceiver chip 300 for a radar system. Chip 300 has an antenna feed or termination coupled to an array of transmit antennas 301 and receive antennas 302. The adjustable gain amplifiers 303A to 303D drive the transmission antenna 301 with the amplified signal from the transmitter circuit 304. Circuitry 304 uses a programmable chirp rate and range to generate carrier signals within a programmable frequency band. The signal generator may employ a voltage controlled oscillator with a suitable frequency multiplier. The splitter and phase shifter derive the transmit signals for the multiple transmitters TX-1 to TX-4 to operate simultaneously and further provide a reference "local oscillator" signal to the receiver for down conversion processing. In the illustrated example, the transceiver chip 300 includes 4 transmitters (TX-1 to TX-4), each fixedly coupled to a corresponding transmit antenna 301. In an alternative embodiment, multiple transmit antennas may be selectively coupled to each transmitter.

Chip 300 further includes 4 receivers (RX-1 to RX-4), each selectively coupled to two of receive antennas 302, thereby providing a reconfigurable MIMO system with 8 receive antennas, where four receive antennas may be used simultaneously to collect measurements. The down-converted received signals from the receivers RX-1 to RX-4 are sampled and digitized by four analog-to-digital converters (ADCs) 306A to 306D, and the digitized signals are supplied to a Digital Signal Processor (DSP)308 for filtering and processing or directly to a high bandwidth interface 310 for off-chip processing of the digitized baseband signals. If used, the DSP308 generates image data that may be communicated to the ECU via a high bandwidth interface 310.

The control interface 312 enables the ECU or other host processor to configure the operation of the transceiver chip 300, including the test and calibration peripheral circuitry 314 and the transmit signal generation circuitry 304.

Fig. 4 adds additional detail to illustrate the phased array technique. The transmit signal (for automotive radar, the envisaged frequency range is the W-band (75GHz to 110GHz)) is supplied to four programmable phase shifters 402A to 402D to provide respective phase shifts for the signal of each antenna. Adjustable gain amplifiers 303A to 303D amplify the phase shifted signals to drive the transmit antennas, but just before the drive signals are output from the chip, a set of couplers 404A to 404D split off a small portion of the signal power as monitoring signals that enable calibration circuit 406 to monitor the performance of the transmit circuits.

In at least some embodiments, the calibration circuit monitors the relative amplitude and phase of the drive signals. Fig. 5 is a block diagram of an illustrative phase detector 502 that may be employed at millimeter wave frequencies contemplated herein. Quadrature coupler 504 converts the Local Oscillator (LO) signal into two quadrature signals (signals having the same frequency but 90 degrees out of phase). Quadrature couplers are known in the literature and suitable examples include branch line couplers, blue-based couplers (Lange couplers) and overlay couplers. Splitter 506 splits the RF input into two equal signals. The multiplier mixes each of the quadrature signals with one of the RF signals to generate a baseband voltage. The voltage obtained using the leading quadrature signal may be referred to as the in-phase voltage VI, while the use ofThe voltage obtained by the lagging quadrature signal may be referred to as the quadrature-phase voltage VQ. One or more ADCs 508 may digitize the voltage, and a processor, ASIC, or look-up table 510 may convert the digitized voltage into a detected phase θ by performing an equivalent of an arctan operation on the ratio of VQ to VI_det. The detected phase represents the phase difference between the LO and RF inputs.

Fig. 6 shows an illustrative calibration circuit using a naive approach, where N drive signals are each supplied to a respective RF input of phase detectors 502A-502N, and the LO inputs of the phase detectors receive buffered copies of the LO signals from respective amplifiers 602A-602N. (although they present a large area requirement, amplifiers are usually required to avoid undue loading of the LO signal source.) phase detector (θ)_i) Represents the phase angle difference between the LO and RF inputs (where the offset represents the contribution of the coupler, amplifier, and any routing delay difference):

θ_i,j＝θ_RFi–θ_ref＝θ_PSi,j–θ_LO–θ_offset

wherein theta is_PSi,jIs the jth phase shift setting for the ith phase shifters 402A through 402D, i ranges from 1 to the number of phase shifters, and for each phase shifter, j ranges from 1 to the number of programmable phase shifts. The measured phase shift θ can be determined by comparing adjacent values of j_i,jAnd identifying the difference from the expected step change delta theta_sMatching to verify the operation of each phase shifter:

θ_i,j–θ_i,j+1＝Δθ_s。

the verification can be repeated for each value of j and when j reaches its maximum value (the number of available phase settings) a wrap-around operation will be performed.

Note that it is also desirable to ensure an appropriate inter-channel phase difference. The distribution of the LO signal to all phase detectors may cause problems and the phase shift associated with the amplifier may be temperature dependent. Thus, in conjunction with the step change verification described above, it is desirable to perform inter-channel phase difference verification on one or more values of j and k:

θ_i,j–θ_i+1,k＝(j–k)Δθ_s。

the inter-channel verification may be repeated for each value of i.

Fig. 7 shows an illustrative verification circuit that uses an adjacent channel as a reference LO signal instead of a global LO signal. The 3-

port couplers

404A, 404D at the edges of the array are retained, but the couplers (404B, 404C) inside the array are replaced by 4-

port couplers

704B, 704C to supply the monitoring signals to two (rather than one) phase detectors. In at least some embodiments, the 4-port coupler comprises a directional coupler cascaded with a power splitter, while the 3-port coupler may be implemented as a standard directional coupler.

As previously described, the coupler splits a small portion of the RF signal power and outputs a large portion of the signal to the corresponding transmit antenna. Amplifiers 602A-602C amplify the monitor signals to drive the LO inputs of phase detectors 502A-502C. Each phase detector 502A to 502C compares the phase of the monitor signal from the adjacent channel. (because the channels are compared in pairs, one less phase detector is used in this arrangement than in the arrangement of FIG. 6.)

Detected paired phase difference θ₁₂、θ₂₃、θ₃₄Is that

θ_i(i+1),jk＝θ_RF(i+1),k–θ_RFi,j–θ_offset＝θ_PS(i+1),k–θ_PSi,j–θ_offset

As previously described, the difference can be confirmed from the expected step change Δ θ by comparing the measured phase shift of adjacent values of j or k_sMatching to verify the operation of each phase shifter:

θ_i(i+1),jk–θ_{i(i+1),(j+1)k}＝Δθ_s

θ_i(i+1),jk–θ_{i(i+1),j(k+1)}＝Δθ_s

the verification may be repeated for each value of j or each value of k and a wrap-around operation is performed when j or k reaches a maximum value (the number of available phase settings).

For inter-channel phase difference verification, the differences between pairs of differences (representing the phase settings for channels i, i +1, and i +2 as j, k, and l) may be used:

θ_i(i+1),jk–θ_{(i+1)(i+2),kl}＝θ_PSi,j+θ_PS(i+2),l–2θ_PS(i+1),k＝(j+l–2k)Δθ_s。

the inter-channel verification may be repeated for each value of i and the wrap-around operation is performed when i +1 and i +2 exceed the maximum value (number of channels).

Intra-channel phase shift verification requires scanning of the phase shift settings and is therefore preferably performed between regular transmissions and infrequently consistent with maintaining confidence in proper operation of the radar system. It is expected that there may not be enough opportunity to complete a complete scan in the available time between regular transmissions, and if this is the case, the scan may be performed in stages and dispersed over multiple measurement cycles.

In contrast, inter-channel phase shift verification does not require a change in phase shifter settings and therefore can be performed during normal use. If desired, inter-channel authentication may be performed at the same time as each transmission.

Since the measured difference is used to verify the operation of the phase shifter, the phase offset is cancelled and there is no longer a need to determine the offset or calibrate its dependence on lifetime and process or temperature variations.

Although the arrangement of fig. 7 can be verified without the need for explicit calibration, it may still be necessary to calibrate the phase shifters and amplifiers of each channel to ensure accurate beam steering. To this end, fig. 8 shows an illustrative calibration arrangement. Instead of supplying phase detectors as shown in fig. 7, the

couplers

404A, 704B, 704C and 404D of fig. 8 supply signals to the power combiners 802A to 802C. Combiner 802A combines the monitor signals from

couplers

404A and 704B to provide a combined signal. The combiner 802B combines the signals from the couplers 702B and 702C. Combiner 802C combines the signals from

couplers

704C and 404D.

As discussed further below, the combiners 802A-802C may be in-phase power combiners or anti-phase power combiners. The combined signal output from each combiner is coupled to power detectors 804A to 804C. In at least some contemplated embodiments, the power detector rectifies the combined signal using a diode or other non-linear element. The power detector generates a voltage indicative of the power output by the combiner. The output of detector 804A is labeled V12, the output of detector 804B is labeled V23, and the output of detector 804C is labeled V34. These voltages are digitized by the ADCs 806A-806C and provided to microcontroller unit (MCU) logic 808. In other contemplated embodiments, a single ADC is used with a multiplexer to digitize the detector voltage.

As shown in fig. 9A to 9B, the detector output voltage V depends on the relative phase between the combined signals. The graphs each assume that each of the two signals is coupled to the combiner at a power level of-10 dBm and that there is no insertion loss. The inverted combiner output shown in fig. 9A has a minimum at zero degrees and monotonically increases in each direction to a maximum at ± 180 °. The in-phase combiner output shown in fig. 9B has a maximum at zero degrees, monotonically decreasing to a minimum at ± 180 °. Examples of an inverting combiner may include a ring coupler, magic t, branch line coupler, or blue-base coupler. These may also be configured as in-phase couplers or they may be implemented as Wilkinson power converters.

The range of the power detector does not have to be large to correctly detect the phase setting offset at 0. It is only required to be monotonic.

Let us denote the power combiner input voltage as x₁＝A₁cos (. omega.t) and x₂＝A₂cos (ω t + θ). The reverse phase power combiner outputs a voltage of

And the output voltage of the in-phase combiner is

If one or the other of the phase shifters associated with the inputs of the combiner is changed, the magnitude of y is dependent on its relative phaseThe bit angle theta varies. If A is₁＝A₂Then y is zero or will reach a maximum when the relative phase angle is zero.

A method of using the verification circuit of fig. 7 will now be discussed with reference to fig. 10A. In block 902, a controller (such as DSP 308) systematically changes the settings of the phase shifters 402A-402D to scan the phase of each channel relative to the phase of its neighboring channel feeding one of the phase detectors 502A-502C in fig. 7. This enables the controller to verify that each adjustment of the phase setting produces a change in the phase detector output corresponding to the expected step change. If this verification is not successful, the process will stop and alert the ECU: there is a fault in the radar system. (the controller may send an error code to the ECU, set the measurement to a value indicating an erroneous measurement, and/or set a field in a status register that is periodically read by the ECU.)

Otherwise, in block 904, normal operation begins with the first periodic transmit pulse in the series of periodic transmit pulses. The controller sets the phase shifter to a desired setting to steer the beam from the phased transmit array in a desired direction and generate a pulse. When a pulse is generated, the verification circuitry measures the relative inter-channel phase and calculates the difference between adjacent ones of the relative inter-channel phases in block 906, as previously discussed, to verify that the difference matches the expected difference. If this verification is not successful, the process may stop and alert the ECU: there is a fault in the radar system.

Otherwise, in block 908, the controller collects radar return measurements and repeats blocks 904-908 to collect a series of measurements. The echo measurements are processed according to existing practice to determine the direction and distance of the obstacle relative to the vehicle.

A method of using the calibration circuit of fig. 8 will now be discussed with reference to fig. 10B. In block 910, a controller (such as the DSP 308) measures the output level of each channel. In one contemplated approach, the controller enables only one power amplifier 303A-303D for each adjacent channel. For example,

power amplifiers

303A and 303C may be enabled while

power amplifiers

303B and 303D are disabled. Subsequently,

power amplifiers

303A and 303C may be disabled, while

amplifiers

303B and 303D are enabled. The disabled power amplifier does not provide an output signal.

Although only one power amplifier is enabled for each pair of adjacent channels, the controller measures the output of the power detectors 804A-804C. This process is repeated for another power amplifier enabled for each pair of adjacent channels, thereby providing a power level measurement for each channel to the controller. Then, in block 912, the controller may equalize the power levels by adjusting the power amplifier settings (e.g., increasing the amplifier setting for the channel with the lowest power level and/or decreasing the amplifier setting for the channel with the highest power level). The controller performs a verification step and repeats the operations of

blocks

910 and 912 until the power levels are equal.

Once the power levels have equalized, the controller performs phase calibration beginning at block 914. The controller scans the phase shifter settings while keeping the phase shifter settings on adjacent channels unchanged. When the detected power level reaches a minimum (for an anti-phase combiner) or a maximum (for an in-phase combiner), the controller records the relative phase shifter setting (i.e., the phase setting offset) and designates the phase setting offset as the relative phase angle θ of 0 in block 916 so that the desired phase difference can be obtained by appropriately increasing or decreasing the relative phase shifter setting offset from the phase setting. This process is performed for each pair of adjacent channels and can be verified for all phase shift settings of each phase shifter.

Thereafter, during normal operation represented by blocks 918-922, the controller sets the phase shifter to the desired setting to steer the beam from the phased transmit array in the desired direction and generate the pulse. While the pulses are being generated, the verification circuitry measures the output levels of the power detectors in block 920 and verifies that they match the power output level expected for the desired phase shift (see fig. 9A-9B). if this verification is not successful, the process may stop and alert the ECU: there is a fault in the radar system.

Otherwise, in block 922, the controller collects radar echo measurements and repeats blocks 918-922 to collect a series of measurements. The echo measurements are processed according to existing practice to determine the direction and distance of the obstacle relative to the vehicle.

Note that the embodiment of fig. 8 may require much less silicon area due to the use of a power detector instead of a down-conversion I/Q mixer to convert the RF signal to baseband/DC. Both embodiments avoid routing long lines to the calibration receiver, which may reduce fidelity when the calibration receiver is interleaved with the RF lines carrying the TX signal. The coupled RF signal is immediately converted to DC and is therefore easier to route.

In summary, disclosed method embodiments include: (i) programming a set of phase shifters to convert the radio frequency signal to a set of channel signals; (ii) while coupling the set of channel signals to the set of antenna feeds, separating a monitor signal from each channel signal; and (iii) measuring the relative phase between each pair of monitoring signals while employing the pair of monitoring signals associated with the adjacent channels.

The disclosed radar system embodiments include: a signal generator, the signal generator providing a radio frequency signal; a set of programmable phase shifters, the set of programmable phase shifters converting the radio frequency signal to a set of channel signals; and a set of couplers coupling the set of channel signals to a set of antenna feeds, the couplers in the set providing the monitor signal. The system further comprises: one or more power combiners, each power combiner combining a pair of monitor signals to produce a combined signal; and one or more power detectors, each power detector converting a respective combined signal to a power level signal. The controller uses at least one of the power level signals to determine a relative phase between at least one pair of channel signals in the set of channel signals.

Another disclosed radar system embodiment includes: a signal generator, the signal generator providing a radio frequency signal; a set of programmable phase shifters, the set of programmable phase shifters converting the radio frequency signal to a set of channel signals; and a set of couplers coupling the set of channel signals to a set of antenna feeds, the couplers in the set providing the monitor signal. One or more phase detectors are provided to each determine the relative phase between the monitoring signals of a pair of adjacent channels.

Each of the foregoing embodiments may be used alone or in combination, and may include one or more of the following features in any suitable combination: 1. an error notification is provided if one of the relative phase measurements fails to match a difference in programmed phase shifts of a set of phase shifters. 2. Acquiring sequential relative phase measurements over a range of phase settings of phase shifters associated with even channels while maintaining phase settings of phase shifters associated with odd channels, and acquiring sequential relative phase measurements over a range of phase settings of phase shifters associated with odd channels while maintaining phase settings of phase shifters associated with even channels; 3. an error notification is provided if the difference between sequential relative phase measurements fails to match a predetermined step size. 4. The phase setting offset for each pair is determined based on the relative phase measurements. 5. The determining includes measuring relative phase over a range of phase setting differences for adjacent channels. 6. The measurement comprises the following steps: combining each pair of monitoring signals to form a combined signal; and measuring the power of each combined signal. 7. Disabling the adjustable gain amplifiers associated with the odd channels while measuring the power of each combined signal; disabling the adjustable gain amplifiers associated with the even channels while measuring the power of each combined signal; and adjusting the gain of the adjustable gain amplifier based on the power measurements to equalize the power of each channel signal in the set of channel signals. 8. The controller uses the at least one power level signal to determine the phase setting offset for each pair. 9. The controller determines the phase setting offset by: measuring at least one power level signal over a range of phase setting differences for adjacent channels; and identifying a power level maximum or minimum corresponding to the phase setting offset. 10. One or more of the power combiners is an inverting combiner, and the phase setting offset corresponds to power waterThe minimum value is averaged. 11. The one or more power combiners are in-phase combiners, and the phase setting offset corresponds to a power level maximum. 12. A set of adjustable gain amplifiers that amplify the set of channel signals provided to the set of couplers. 13. The controller adjusts the gain of the adjustable gain amplifier to equalize the power of each channel signal in the set of channel signals prior to determining the relative phase. 14. Prior to equalizing the power, the controller disables the adjustable gain amplifiers associated with the odd channels while measuring the power of each of the combined signals; and disabling the adjustable gain amplifiers associated with the even channels while measuring the power of each combined signal. 15. A controller, the controller: obtaining sequential relative phase measurements over a range of phase settings of phase shifters associated with even channels while maintaining the phase settings of phase shifters associated with odd channels; obtaining sequential relative phase measurements over a range of phase settings of phase shifters associated with odd channels while maintaining the phase settings of phase shifters associated with even channels; and providing an error notification if the difference between sequential relative phase measurements fails to match a predetermined step size. 16. The one or more phase detectors include a pair of phase detectors that determine a first relative phase between a center channel and a first adjacent channel and a second relative phase between the center channel and a second adjacent channel, the system further including a controller that calculates a difference between the first relative phase and the second relative phase. 17. The controller provides an error notification if the difference fails to match the expected difference based on the phase settings of the phase shifters associated with the center lane, the first adjacent lane, and the second adjacent lane. 18. The expected difference is (j + l-2 k) Δ θ_sWhere j, k, and l represent the phase settings of the first adjacent channel, the central channel, and the second adjacent channel, respectively, and Δ θ_sRepresenting a predetermined step change.

Numerous other modifications, equivalents, and alternatives will become apparent to those skilled in the art once the above disclosure is fully appreciated. For example, each of the disclosed circuit arrangements may be used for verification or for calibration or both. It is intended that the following claims be interpreted to embrace all such modifications, equivalents, and alternatives as are appropriate.

Claims

1. A method, characterized in that the method comprises:

programming a set of phase shifters to convert the radio frequency signal to a set of channel signals;

while coupling the set of channel signals to a set of antenna feeds, separating a monitor signal from each channel signal; and

the relative phase between each pair of monitoring signals is measured while employing the pairs of monitoring signals associated with adjacent channels.

2. The method according to claim 1, characterized in that the method further comprises:

obtaining sequential relative phase measurements over a range of phase settings of phase shifters associated with even channels while maintaining the phase settings of phase shifters associated with odd channels;

obtaining sequential relative phase measurements over a range of phase settings of phase shifters associated with odd channels while maintaining the phase settings of phase shifters associated with even channels; and

an error notification is provided if the difference between sequential relative phase measurements fails to match a predetermined step size.

3. The method of any one of claims 1 to 2, comprising determining a phase setting offset for each pair based on the relative phase measurements, wherein the determining comprises measuring the relative phase over a range of phase setting differences for adjacent channels.

4. The method of claim 1, wherein the measuring comprises:

combining each pair of monitoring signals to form a combined signal; and

the power of each combined signal is measured.

5. The method of claim 6, comprising:

disabling the adjustable gain amplifiers associated with the odd channels while measuring the power of each combined signal;

disabling the adjustable gain amplifiers associated with the even channels while measuring the power of each combined signal; and

adjusting a gain of the adjustable gain amplifier based on the power measurements to equalize the power of each channel signal in the set of channel signals.

6. A radar system, characterized in that the radar system comprises:

a signal generator providing a radio frequency signal;

a set of programmable phase shifters that convert the radio frequency signal to a set of channel signals;

a set of couplers coupling the set of channel signals to a set of antenna feeds, the couplers in the set providing monitoring signals;

one or more power combiners, each power combiner combining a pair of monitor signals to produce a combined signal;

one or more power detectors, each power detector converting a respective combined signal to a power level signal; and

a controller that uses at least one of the power level signals to determine a relative phase between at least one pair of channel signals in the set of channel signals.

7. The radar system of claim 6, wherein the controller uses the at least one power level signal to determine the phase setting offset for each pair by:

measuring the at least one power level signal over a range of phase setting differences for adjacent channels; and

identifying a power level maximum or minimum corresponding to the phase setting offset.

8. Radar system according to any one of claims 6 to 7, characterised in that:

a set of adjustable gain amplifiers that amplify the set of channel signals provided to the set of couplers,

wherein the controller is operative to:

adjusting a gain of the adjustable gain amplifier to equalize a power of each channel signal of the set of channel signals.

9. A radar system, characterized by:

a signal generator providing a radio frequency signal;

a set of couplers coupling the set of channel signals to a set of antenna feeds, the couplers in the set providing monitoring signals; and

one or more phase detectors, each phase detector determining a relative phase between the monitoring signals of a pair of adjacent channels.

10. The radar system of claim 9, wherein a controller that:

11. The radar system of claim 10, wherein the one or more phase detectors comprise: a pair of phase detectors to determine a first relative phase between a central channel and a first adjacent channel and a second relative phase between the central channel and a second adjacent channel, the controller operative to calculate a difference between the first relative phase and the second relative phase.