System and method for emulating echo signals from an emulated target with reduced interference - Patents.com

Abstract

To provide emulation of targets for radar testing.SOLUTION: A system and a method are provided for emulating echo signals using test equipment, including an antenna 108 and an I / Q mixer 203, in response to a radar signal transmitted by a radar under test 105. The method includes receiving the radar signal from the radar under test 105, where a reflection component of the radar signal is reflected from at least the antenna; mixing the received radar signal as a local oscillator (LO) signal with I and Q signals at the I / Q mixer 203 to output a mixing product as a radio frequency (RF) signal, where a leakage component of the LO signal leaks through the I / Q mixer 203; substantially canceling the reflection component of the radar signal using the leakage component of the LO signal; and transmitting the RF signal as the emulated echo signal to the radar under test 105.SELECTED DRAWING: Figure 2

Description

[Background technology]

[0001] Advanced driver-assistance systems (ADAS) and autonomous driving systems for vehicles rely on detection and ranging systems that use detection and ranging electromagnetic signals, including, for example, millimeter-wave radar signals. Radar signals are used to warn of forward and rear collisions, to implement, for example, adaptive cruise control and autonomous parking, and ultimately, to perform autonomous driving on streets and highways. ADAS are promising because of their low cost and ability to operate at night or in severe weather conditions (e.g., fog, rain, snow, dust).

[0002] Conventional automotive radar systems typically have multiple transmitters and receivers on a vehicle. Actual driving environments in which radar systems may be deployed can vary widely, and many such driving environments can be complex. For example, real driving environments include numerous objects, and some of the objects encountered in real driving environments have complex reflection, diffraction, and multi-reflection characteristics that affect the echo signals that respond to radar signals. Incorrect detection and / or interpretation of echo signals can directly result in false alarms or inappropriate responses being triggered, or warnings or responses that should be triggered not being triggered, which can ultimately lead to a collision.

[0003] Target emulation for radar testing is desirable because operating vehicle radar in real driving environments can be dangerous, inefficient, expensive, and difficult to control. For example, road testing can be problematic and costly. Only a few locations worldwide allow so-called unmanned road testing. Even then, these locations typically require a human in the driver's seat as an emergency driver in case the ADAS fails. Much of the early data is particularly questionable because safe drivers actively control the steering wheel.

[0004] Typically, conventional radar target emulators attempt to emulate the physics of a problem. For example, a conventional radar target emulator may receive a radar signal transmitted from a radar under test, delay the radar signal by an amount corresponding to the propagation delay due to the range to the emulated target, scale the amplitude of the radar signal to account for the range and the radar cross section (RCS) of the target, and then retransmit the scaled and delayed signal to the radar under test, thereby emulating the transmission of the radar signal from the radar under test to the target and the reflection of the corresponding echo signal.

[0005] Some conventional emulator systems use single-sideband (SSB) modulation and frequency-shifted signal reflections (retransmissions) to test, for example, frequency-modulated continuous wave (FMCW) radars. Such emulator systems may include a transmit-receive probe antenna connected to a microwave circulator with an SSB mixer and variable attenuator in the feedback path. Conventional emulator systems generate return signals from the emulated radar target (emulated echo signals) and unwanted signals sometimes referred to as "ghost targets." Ghost targets result from extraneous radio frequency (RF) signals, such as harmonics or intermodulation products, local oscillator feedthrough, and / or reflections of the radar signal from the emulator system hardware, such as the probe antenna, microwave circulator, and / or other downstream components.

[0006] The illustrative embodiments are best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that the various features are not necessarily drawn to scale. In fact, dimensions may be arbitrarily increased or decreased for clarity of discussion. Wherever applicable and practical, like reference numerals refer to like elements. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a simplified block diagram illustrating a system for emulating an echo signal with reduced interference, according to a representative embodiment. [Figure 2] FIG. 1 is a simplified block diagram illustrating a re-illuminator device of an echo signal emulation system that emulates an echo signal with reduced interference, according to a representative embodiment. [Figure 3]FIG. 10 is a simplified block diagram illustrating a re-illuminator of an echo signal emulation system for emulating echo signals with reduced interference, according to another representative embodiment. [Figure 4] FIG. 1 is a simplified flow diagram illustrating a method for emulating an echo signal with reduced interference, according to a representative embodiment. [Figure 5] FIG. 1 is a simplified flow diagram illustrating a method for calibrating a system that emulates an echo signal with reduced interference, according to a representative embodiment. [Figure 6A] 10 is a graph illustrating the effect of calibrating a frequency offset transceiver at one frequency on leakage components and USB, according to a representative embodiment. [Figure 6B] 10 is a graph illustrating the effect of calibrating a frequency offset transceiver at multiple frequencies on leakage components and USB, according to a representative embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the following detailed description, for purposes of explanation and not limitation, exemplary embodiments disclosing specific details are described to provide a thorough understanding of an embodiment according to the present teachings. Descriptions of known systems, devices, materials, methods of operation, and methods of manufacture may be omitted to avoid obscuring the description of the exemplary embodiments. Nevertheless, systems, devices, materials, and methods within the understanding of those skilled in the art are within the scope of the present teachings and may be used in accordance with the exemplary embodiments. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Defined terms have meanings commonly understood and accepted in the technical field of the present teachings, in addition to the scientific and technical meaning of the defined term.

[0009] Although terms such as first, second, and third may be used herein to describe various elements or components, it should be understood that these elements or components should not be limited by these terms. These terms are used only to distinguish one element or component from another. Thus, a first element or component discussed below could be referred to as a second element or component without departing from the teachings of the present disclosure.

[0010] The terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting. As used in this specification and the appended claims, the singular terms "a," "an," and "the" are intended to include both the singular and the plural unless the context clearly dictates otherwise. Furthermore, the terms "comprises" and / or similar terms, when used herein, specify the presence of the stated feature, element, and / or component, but do not exclude the presence or addition of one or more other features, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0011] Unless otherwise stated, when an element or component is said to be "connected," "coupled," or "adjacent" to another element or component, it is understood that the element or component can be directly connected or coupled to the other element or component, or there may be intervening elements or components. That is, these and similar terms include instances where one or more intervening elements or components may be used to connect the two elements or components. However, when an element or component is said to be "directly connected" to another element or component, this only includes instances where the two elements or components are connected to each other without any intervening or intervening elements or components.

[0012] The present disclosure is therefore intended to achieve one or more of the advantages, as specifically mentioned below, through one or more of its various aspects, embodiments, and / or specific features or subcomponents. For purposes of explanation and not limitation, exemplary embodiments disclosing specific details are described to provide a thorough understanding of one embodiment in accordance with the present teachings. However, other embodiments that depart from the specific details disclosed herein but are not inconsistent with the present disclosure may still be within the scope of the appended claims. Furthermore, descriptions of known devices and methods may be omitted so as not to obscure the description of the exemplary embodiments. Such methods and devices are within the scope of the present disclosure.

[0013] According to various embodiments, a driving emulation system is capable of emulating echo signals from emulated targets in response to radar signal transmissions from a radar under test located on a vehicle under test, such as an automobile or other moving platform. The embodiments minimize interference, such as ghost targets observed at the radar under test, caused by harmonic and intermodulation products, reflections of the radar signal from test hardware, and / or LO leakage (residual radar signal passing through a mixer). Ghost targets from an array of radar reflection-altering devices can similarly be minimized through calibration of the entire emulator system.

[0014] 1 is a simplified block diagram illustrating a system for emulating the echo signal of a radar under test with reduced interference (e.g., ghost target rejection) according to a representative embodiment. As will be understood by those skilled in the art having the benefit of this disclosure, one possible vehicle radar is an automotive radar used in various capacities in current and upcoming automotive applications. However, it is emphasized that the echo signal emulation system described herein is not limited to automotive radar systems, but can be applied to other types of vehicles that can utilize vehicle radar systems, including, for example, trucks, buses, motorcycles, bicycles, mopeds (e.g., scooters), and aircraft.

[0015] 1, an echo signal emulation system 100 is configured to test a radar under test 105, which may be configured to transmit an FMCW radar signal and receive a return signal, including an emulated echo signal that emulates a reflection (echo) of the radar signal from a target in a scene emulation. The radar under test 105 includes one or more radar transmitters and corresponding transmit antennas, and one or more radar receivers and corresponding receive antennas. All or a portion of the system 100 may be contained in a test chamber, such as an anechoic test chamber.

[0016] The system 100 includes a plurality of re-illuminators 106, each of which includes at least one re-illumination antenna 108 and at least one frequency-offset transceiver 110, which may be, for example, a modulated reflection device (MRD). The re-illumination antenna 108 may be, for example, a horn antenna (probe antenna). As discussed in more detail below, each transceiver 110 generally includes receiver circuitry, transmitter circuitry, an in-phase (I)-quadrature (Q) mixer (I / Q mixer), and a signal generator that generates I and Q signals that are input to the I / Q mixer and mixed with a local oscillator (LO) signal. The I / Q mixer can be considered part of both the receiver circuitry and the transmitter circuitry. The received radar signal is input to the I / Q mixer as an LO signal, and I and Q signals from a signal generator are input to the I / Q mixer as intermediate frequency (IF) signals, and the mixing product of the LO and IF signals is output by the I / Q mixer as an RF signal. The RF signal is amplified / attenuated as necessary and transmitted by the transmitter circuit as an emulated echo signal via the re-illuminating antenna 108 to the radar under test 105. Generally, the frequency and amplitude of the RF signal indicate the emulated range and RCS of the emulated target. For example, in the case of an FMCW radar signal using a chirp signal, the lower the RF frequency of the RF signal within the linear ramp of the chirp signal, the closer the emulated target appears to the radar under test 105.

[0017] In an alternative configuration, a signal generator 130 may not be physically included in each of the re-illuminators 106, in which case one signal generator 130 may provide I and Q signals to multiple transceivers 110 without departing from the scope of the present teachings. Each signal generator 130 may be implemented, for example, as a direct digital synthesizer (DDS).

[0018] There may be one reilluminator 106 for each emulated target in the scene emulation. Alternatively, one reilluminator 106 may be used for multiple emulated targets, including one or more scattering targets and / or one or more non-scattering targets. In one embodiment, the reilluminators 106 may be arranged in a 2D array, with each reilluminator 106 representing an element in the 2D array. In this case, the element having a spatial location corresponding to an emulated target will generate an emulated echo signal corresponding to that target.

[0019] The system 100 also includes a computer 140 having a controller 144. The controller 144 described herein may include a combination of a memory 146 that stores instructions and an exemplary processor 148 that executes the stored instructions to implement all or a portion of the processes described herein. A database 120 may store information used for target emulation, including various predetermined scenarios having one or more targets. For example, the database 120 may store desired characteristics of point targets, such as range, RCS, velocity, acceleration, etc., from the radar under test 105. The database 120 may further store information regarding parameters of a particular radar under test 105, such as code, power, field of view, etc. The radar under test 105 may be connected to the computer 140 by various types of wired and / or wireless network connections. The controller 144 is configured to control the operation of the frequency offset transceiver 110 and the signal generator 130 via control signals, indicated by dashed lines.

[0020] Controller 144 can be housed within or linked to a computer or another assembly of one or more computing devices, such as a workstation, a display / monitor, and one or more input devices (e.g., keyboard, joystick, and mouse) in the form of a standalone computing system, a client computer, a desktop, or a tablet in a server system. The term "controller," as understood in the art of this disclosure and as illustratively described in this disclosure, broadly encompasses all structural configurations of application-specific mainboards or application-specific integrated circuits that control the application of various principles as described in this disclosure. The structural configuration of controller 144 can include, but is not limited to, processor(s), computer-usable / computer-readable storage medium(s), operating system, application module(s), peripheral device controller(s), slot(s), and port(s), as discussed below.

[0021] Additionally, while computer 140 and / or controller 144 are shown as networked components, multiple components may be integrated into a single system. For example, computer 140 and / or controller 144 may be integrated with a display (not shown) and / or system 100. On the other hand, the networked components of computer 140 and / or controller 144 may be spatially distributed, such as across different rooms or buildings, in which case the networked components may be connected via a data connection. In yet another embodiment, one or more of the components of computer 140 and / or controller 144 are not connected to other components via a data connection, but instead are manually provided with input and / or output, such as via a memory stick or other form of memory. In yet another embodiment, the functionality described herein, while based on the functionality of elements of computer 140 and / or controller 144, may be performed outside of system 100.

[0022] In the illustrated embodiment, computer 140 includes memory 146, controller 144 including processor 148, and user and / or network interfaces (not shown) and a display (not shown). Computer 140 and / or controller 144 may be implemented as a processing unit. In various embodiments, the processing unit may include one or more computer processors (e.g., processor 148), digital signal processors (DSPs), central processing units (CPUs), field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), or combinations thereof, using any combination of hardware, software, firmware, hardwired logic, or any combination thereof. Computer 140, controller 144, and / or processor 148 may each include their own processing memory (e.g., memory 146) that stores computer-readable code (e.g., software, software modules) that enable it to perform various functions described herein. For example, the processing memory may store software instructions / computer-readable code executable by a processing unit (e.g., a computer processor) to perform some or all aspects of the methods described herein, including various steps of the methods described below with reference to Figures 4 and 5. That is, execution of the instructions / computer-readable code generally causes the processing unit of the computer 140 and / or controller 144 to emulate echo signals reflected from an emulated radar target in response to radar signals transmitted by the radar under test 105.

[0023] Memory 146, and any other memory described herein (including database 120), can be various types of random access memory (RAM), read only memory (ROM), and / or other storage media, including flash memory, electrically programmable read-only memory (EPROM), electrically erasable and programmable read only memory (EEPROM), compact disk read only memory (CD-ROM), digital versatile disk (DVD), registers, latches, flip-flops, hard disk, removable disk, tape, floppy disk, Blu-ray disk, or universal serial bus (USB) driver, or any other form of storage media known in the art, which are tangible and non-transitory (e.g., as compared to a transient, propagated signal). The memory may be volatile or non-volatile, secure and / or encrypted, or non-secure and / or unencrypted without departing from the scope of the present teachings. Memory 146 and database 120 may represent one or more memories and databases, as well as multiple memories and databases, including distributed and network-connected memories and databases.

[0024] Generally, in operation, the radar under test 105 emits an RF radar signal (illustratively, a mm-wave signal) that is focused at a respective one of the re-irradiating antennas 108 (beneficially, relatively high-gain antennas) of one of the re-irradiators 106. The re-irradiating antennas 108 may be horn antennas (probe antennas) selected for the wavelength of the signal received from the radar under test 105. The re-irradiating antennas 108 may have variable gain and may be coupled to beam-shaping elements, such as lenses, that adjust the degrees of freedom of the angle of arrival (AoA). Of course, other types of antennas, such as patch antennas or patch antenna arrays, may be incorporated as the re-irradiating antennas 108 without departing from the scope of the present teachings.

[0025] In one embodiment, system 100 can further include a diffractive optical element (DOE) that directs the radar signals toward each of the re-illuminators 106, as described in U.S. Patent Application No. 16 / 867,804, filed May 6, 2020, to Gregory S. Lee, which is incorporated herein by reference in its entirety. The DOE is configured to focus the radar signals at the re-illumination antennas 108. In this embodiment, the emitted radar signals are incident on a first side of the DOE, which diffracts the signals from the radar under test to focus them at a respective one of the re-illumination antennas 108. Thus, the DOE diffracts the incident wave at a particular angle relative to the second side of the DOE, and each diffracted wave is focused onto a respective one of the re-illumination antennas 108. Of course, system 100 can include other means for focusing the radar signals at a respective one of the re-illumination antennas 108 without departing from the scope of the present teachings. In particular, the respective focal points (alternatively, focal points) of each one of the redirecting antennas 108 represent targets that are emulated by the system 100 .

[0026] The radar signal incident on the re-irradiating antennas 108 is provided to a respective one of the frequency-offset transceivers 110. As described more fully herein, based on input from the controller 144, a frequency shift of the incident signal is performed in each of the frequency-offset transceivers 110 to beneficially emulate the target's distance from the radar under test 105, the target's velocity relative to the radar under test 105, or both. In addition, the azimuth angle (the +x direction in the coordinate system of FIG. 1 ) and the elevation angle (the +z direction in the coordinate system of FIG. 1 ) are emulated by the re-irradiating antennas 108. The re-irradiating antennas 108 may be part of an electronically steerable antenna array of the re-irradiator 106. Alternatively, the re-irradiating antennas 108 may be mechanically gimbaled, may move mechanically, or may have a combination of mechanical gimbaling / movement and electronic emulation. Similarly, the re-irradiator 106 may be mechanically moved instead of or in addition to the re-irradiating antennas 108. The re-illuminated signal provided by frequency offset transceiver 110 is incident on radar under test 105. Computer 140 receives the signal from radar under test 105 for further analysis of the accuracy of radar under test 105.

[0027] Typically, radars utilizing FMCW waveforms operate by transmitting an RF radar signal, for example, in the 77 GHz band. The radar signal is modulated so that its instantaneous frequency varies linearly from a first frequency to a second frequency over a predetermined period of time, referred to as a chirp signal. The RF frequency can rise linearly over a predetermined period of time (an up-chirp), where the first frequency (e.g., 77 GHz) is lower than the second frequency (e.g., 78 GHz), or the RF frequency can fall linearly over a predetermined period of time (a down-chirp), where the first frequency (e.g., 78 GHz) is higher than the second frequency (e.g., 77 GHz). This linear ramp in frequency is repeated to form a continuous wave signal transmitted from the radar.

[0028] The transmitted radar signal propagates toward the target at the speed of light, reflects off the target, and returns to the radar as a reflected echo signal, delayed by the round-trip time between the radar and the target. This delay corresponds to the distance between the radar and the target. The echo signal is then mixed with the radar signal currently being transmitted, an operation known as homodyne reception. The resulting IF signal has a frequency equal to the instantaneous difference between the frequency of the received echo signal and the frequency of the radar signal currently being transmitted.

[0029] That is, due to the delay in the received echo signal and the linear slope in frequency of the transmitted radar signal over a given period, there will be a frequency difference between the currently transmitted radar signal (which is changing linearly in frequency) and the received echo signal (which is at the frequency of the originally transmitted radar signal). This frequency difference is therefore proportional to the round-trip delay multiplied by the frequency sweep rate in Hertz per second (Hz / s). For example, because closer targets have less delay than more distant targets, closer emulated targets will result in a smaller frequency difference and therefore a lower IF signal frequency than more distant emulated targets. If the emulated target is a point target, the resulting IF signal will be a single tone at a single frequency. If the emulated target includes multiple targets, the resulting IF signal will have multiple tones with frequencies corresponding to the instantaneous range to each target. In the general case of considering N targets, the radar IF signal will include N tones, each frequency corresponding to the range to the corresponding target, and each amplitude corresponding to the relative received strength of the echo signal from that target. In particular, the received power is a function of the range from the radar to the target and the target's reflectivity per the target's RCS. For a given target RCS, the power is generally a function of 1 / R4 where R is the distance between the radar and the target.

[0030] In this situation, exemplary embodiments of the present disclosure utilize a frequency offset provided by the frequency offset transceiver 110 to emulate the range from the radar under test 105 to the emulated target. Using the frequency offset, each emulated target is indicated by an effective frequency shift due to propagation delay. However, rather than delaying the transmission of the echo signal to indicate range, the delay itself is emulated by the frequency offset transceiver 110, which provides an expected frequency shift corresponding to the desired delay for the echo signal. For example, as discussed in more detail below, the radar signal transmitted from the radar under test 105 can be mixed in the frequency offset transceiver 110 with a frequency offset signal using a single-sideband (SSB) mixer. The frequency offset signal has a frequency (or pattern of frequencies) equal to the desired frequency shift that would be present in the echo signal corresponding to the delay (or round-trip difference). In practice, the frequency offset signal is precisely the form of the desired IF signal at the radar under test 105 when it receives the echo signal and mixes it with the currently transmitted radar signal. Therefore, a single emulated target at a first range will result in an IF signal at the radar under test 105 consisting of a single tone having a frequency representing the range to the single target. This can be generated using an SSB mixer in the frequency offset transceiver 110 by using the desired IF signal as a frequency offset signal. Multiple emulated targets will result in an IF signal consisting of multiple tones. Therefore, using this multi-tone IF signal as an offset signal will result in echo signals that emulate multiple emulated targets.

[0031] 2 is a simplified block diagram of the exemplary re-illuminator (and corresponding frequency offset transceiver) of FIG. 1 that emulates an echo signal with reduced reflected and leakage components, according to an exemplary embodiment. Aspects of the re-illuminator described with respect to this exemplary embodiment may be common to all re-illuminators.

[0032] 2, the re-illuminator 106A includes a re-illuminating antenna 108 and a frequency-offset transceiver 110A connected to the re-illuminating antenna 108, as described above. Of course, in practice, there may be more than one frequency-offset transceiver 110 in a system, and therefore more than one re-illuminating antenna 108 (e.g., as illustrated in the exemplary embodiment of FIG. 1). The re-illuminating antenna 108 is configured to receive over-the-air radar signals 201 from the radar under test 105. The frequency-offset transceiver 110A is configured to generate emulated echo signals 220 in response to radar signals indicative of an emulated target, where the emulated echo signals 220 are transmitted by the re-illuminating antenna 108 and received by the radar under test 105. The emulated echo signal 220 indicates the range from the radar under test 105 to the emulated target, for example, based on a scene emulation stored in the database 120. In addition, a reflected component 222 of the radar signal is reflected by the re-illuminating antenna 108 and the frequency-offset transceiver 110A, and a leakage component 224 of the radar signal leaks through the I / Q mixer 203. As used herein, the reflected component 222 refers to the portion of the radar signal that is physically reflected from system hardware, such as the external structure of the re-illuminating antenna 108 and the frequency-offset transceiver 110A, and the portion of the radar signal that is reflected from non-zero reflection coefficients (S 11) The reflected component 222 and leakage component 224 may be received by the radar under test 105, thereby interfering with the emulated echo signal 220, unless the reflected component 222 and leakage component 224 are reduced and / or minimized in accordance with aspects of the present disclosure discussed below.

[0033] In the illustrated embodiment, the frequency offset transceiver 110A includes a circulator 202, an I / Q mixer 203, and a signal generator 130. The circulator 202 enables the frequency offset transceiver 110A to use a single re-irradiating antenna 108 to receive a radar signal 201 from the radar under test 105 and to transmit an emulated echo signal 220 to the radar under test 105. Alternatively, the re-irradiating antenna 108 can be implemented as separate receive and transmit antennas without departing from the scope of the present teachings, in which case the circulator 202 can be omitted.

[0034] The I / Q mixer 203 can be, for example, an SSB mixer with a standard 90-degree phase shift for radar signals, resulting in an output of either the upper sideband (USB) with the lower sideband (LSB) removed, or the LSB with the USB removed. The signal generator 130 can be implemented, for example, using a direct digital synthesizer (DDS) or an FPGA and a digital-to-analog converter (DAC), although other types of controllable signal generators can be incorporated without departing from the scope of the present teachings. The signal generator 130 can be controlled, for example, by the computer 140, to provide I and Q signals of various amplitudes and phases. The signal generator 130 can also be controlled to separately adjust the DC values ​​(DC offsets) of the I and Q signals, as discussed below.

[0035] In the illustrated embodiment, the I / Q mixer 203 includes an LO port, an RF port, and an IF port, where the LO port is configured to receive the radar signal 201 from the re-illuminating antenna 108 as an LO signal, and the IF port is configured to receive the I and Q signals from the signal generator 130. In the illustrated embodiment, the radar signal 201 can be considered an LO signal and input to the LO port because it is amplified and / or limited to drive the I / Q mixer 203 with a large signal. The I / Q mixer 203 mixes the radar signal with the I and Q signals and outputs the mixing product as an RF signal from the RF port, e.g., after amplification and / or attenuation, to ultimately provide the emulated echo signal 220. Notably, the RF signal includes two signals having quadrature phases, corresponding to the I and Q signals, respectively. However, for convenience, the RF signal will be referred to in the singular herein. Although not shown, it is understood that the frequency offset transceiver 110A may further include signal processing components, such as filters, attenuators, and / or amplifiers, to process the radar signal 201 before it is input to the I / Q mixer as an LO signal.

[0036] The signal generator 130 adjusts the amplitude and phase of the I and Q signals input to the I / Q mixer 203 to adjust the amplitude and phase of the output RF signal. For example, the RF signal output by the I / Q mixer 203 may include a desired sideband (DSB) and an undesired sideband (USB), where the DSB is a frequency-shifted version of the LO signal (radar signal 201) that is transmitted to the radar under test 105 as the emulated echo signal 220. In one embodiment, the signal generator 130 adjusts the amplitude and phase of the I and Q signals to minimize the USB of the RF signal.

[0037] Similarly, signal generator 130 adjusts the DC values ​​of the I and Q signals to adjust the amplitude and phase of leakage component 224 of the LO signal. In the illustrated embodiment, the amplitude and phase of leakage component 224 are adjusted to substantially cancel reflected component 222 of radar signal 201. That is, leakage component 224 is the portion of the LO signal (radar signal 201) that passes through I / Q mixer 203 without mixing with the I and Q signals input from signal generator 130. Because leakage component 224 avoids the mixing process, leakage component 224 has the same RF frequency as radar signal 201, and therefore the same RF frequency as reflected component 222.

[0038] Both the reflected component 222 and the leakage component 224 are unwanted signals that, if not removed, would be transmitted to the radar under test 105 and cause interference. To prevent this, the amplitude and phase of the leakage component 224 are adjusted using the signal generator 130 so that the leakage component 224 has the same amplitude and opposite phase as the reflected component 222, thereby substantially canceling out the reflected component 222 (and the leakage component 224 itself). By "substantially canceling out," we mean reducing the power of the reflected component 222 and / or the leakage component 224 to a level indistinguishable from the noise floor or "clutter." Removing the reflected component 222 (and the leakage component 224) in this manner prevents the appearance of ghost targets.

[0039] The RF signal output from the I / Q mixer 203 is provided to a variable gain amplifier (VGA) 204, which has a gain control input 205. As alluded to above, the gain control input 205 of the VGA 204 can be controlled by the computer 140. The VGA 204 enables proper emulation of an echo signal 220 at the re-illuminating antenna 108 in response to the radar signal 201 from the radar under test 105. Among other things, the power of the emulated echo signal 220 from the re-illuminating antenna 108 is an indication of the RCS of the emulated target and an indication of the emulated distance between the emulated target and the radar under test 105. Thus, the gain provided by the VGA 204 is selected at the gain control input 205 based on the power of the radar signal incident on the re-illuminating antenna 108 and the desired emulation distance of the emulated target.

[0040] 3 is a simplified block diagram of another exemplary re-illuminator (and corresponding frequency offset transceiver) of FIG. 1 that emulates an echo signal with reduced reflected and leakage components, according to an exemplary embodiment. Aspects of the re-illuminator described with respect to this exemplary embodiment may be common to all re-illuminators described above.

[0041] 3 , the re-illuminator 106B includes a re-illuminating antenna 108 and a frequency-offset transceiver 110B connected to the re-illuminating antenna 108, as described above. The re-illuminating antenna 108 is configured to receive a radar signal 201 wirelessly from the radar under test 105. The frequency-offset transceiver 110B is configured to generate an emulated echo signal 220 in response to the radar signal indicative of an emulated target, where the emulated echo signal 220 is transmitted by the re-illuminating antenna 108 and received by the radar under test 105. In addition, a reflected component 222 is reflected from the test hardware, and a leakage component 224 leaks through the I / Q mixer 203, and the reflected component 222 and the leakage component 224 may interfere with the emulated echo signal 220.

[0042] In the illustrated embodiment, frequency offset transceiver 110B includes circulator 202, I / Q mixer 203, and signal generator 130. I / Q mixer 203 includes an LO port, an RF port, and an IF port, where the LO port receives radar signal 201 from re-illuminating antenna 108 as an LO signal, the IF port receives I and Q signals from signal generator 130 for mixing with the LO signal, and the RF port outputs the mixing product as an RF signal to be used as emulated echo signal 220. Signal generator 130 generates the I and Q signals and is configured to adjust the amplitude and phase of the I and Q signals, for example, under the control of computer 140, to adjust the amplitude and phase of the output RF signal. In the illustrated embodiment, signal generator 130 does not adjust the DC values ​​of the I and Q signals. This is because the amplitude and phase of the leakage component 224 of the LO signal is adjusted using an attenuator circuit, discussed below, to substantially cancel the reflected component 222 .

[0043] In particular, frequency offset transceiver 110B further includes RF splitter 211, RF combiner 212, first attenuator 213, second attenuator 214, and phase shifter 215. RF splitter 211 receives radar signal 201 from re-illuminating antenna 108 via circulator 202 and splits radar signal 201 to provide split components of radar signal 201. The remaining components of radar signal 201 are input as LO signals to I / Q mixer 203 and mixed with the I and Q signals to provide an RF signal. The output of I / Q mixer 203 includes the RF signal and a leakage component 224 at the same RF frequency as radar signal 201. The split components of radar signal 201 are input to a first attenuator 213 to provide a first attenuated signal, and the output of I / Q mixer 203 is input to a second attenuator 214 to provide a second attenuated signal, where the first and second attenuated signals are attenuated to the RF frequency of the radar signal. The first and second attenuated signals are combined by an RF combiner 212 to provide a combined signal including an emulated echo signal 220 and a leakage component 224, and the combined signal is phase shifted by a phase shifter 215.

[0044] The attenuation by the first attenuator 213 and the second attenuator 214 is controlled, for example, by the computer 140, so that the leakage component 224 in the combined signal has the same amplitude as the reflected component 222. The phase shift by the phase shifter 215 is controlled, for example, by the computer 140, so that the leakage component 224 has an opposite phase to the reflected component 222. Thus, the leakage component 224 substantially cancels the reflected component 222. Although not shown, the frequency-offset transceiver 110B shown in FIG. 3 can also include a VGA and gain control input as described above without departing from the scope of the present teachings. Also, although the phase shifter 215 is shown following the RF combiner 212, it is understood that the phase shifter 215 can be located before the RF combiner 212 in either or both of the signal paths including the first attenuator 213 and the second attenuator 214, respectively, without departing from the scope of the present teachings.

[0045] Typically, control of the retransmitted power is used to emulate a consistent RCS, which can be stored, for example, in a lookup in a table in database 120. To that end, for a given range R to an emulated target, the amplitude (strength) of the returned echo signal is proportional to the RCS, as 1 / R 4 It is known that the noise level decreases as σ / σ. Vehicles are typically quoted as being 10 dBsm, where 10 dBsm is the area of ​​measurement, meaning 10 dB per square meter (sm), or in layman's terms, 10 square meters. Many objects are tabulated (vehicles, pedestrians, bicycles, buildings, etc.), and non-tabulated objects can be calculated by ray tracing techniques. The present teachings allow the distance R (known as 1 / R) to a particular object to be calculated. 4 The emphasis is on providing a return echo signal strength to the radar under test 105 that corresponds to the radar attenuation law (and RCS tolerance). According to exemplary embodiments, signal strength (and therefore power) is adjusted by adjusting the strength of the I and Q signals, with weaker I and Q signals providing a relatively weaker emulated echo signal. Notably, in certain exemplary embodiments, the computer 140 pre-calculates a consistent return echo signal to be provided to a single focal point at the radar under test 105, and the controller 144 then adjusts the strength of the I and Q signals to achieve this SSB strength. Alternatively, and advantageously, the gain of the VGA 204 can be adjusted to control the SSB strength of the return echo signal.

[0046] If the radar under test 105 is an FMCW device, then range / velocity is emulated electronically using a frequency offset transceiver 110. To do so, FMCW radar systems use chirp waveforms, as described above, whereby correlation of the original transmit (Tx) waveform from the radar under test 105 with the received (Rx) echo waveform reveals the target range. For example, ±k swIn an up-chirp / down-chirp system with a chirp rate (measured in Hz / s), a target at a distance d and at zero relative velocity with respect to the host vehicle carrying the radar under test 105 will experience a frequency shift (δf) given by equation (1), where c is the speed of light and the factor of 2 is due to the round-trip propagation of the signal from the radar under test 105. δf=±(2k sw d / c) Equation (1)

[0047] The sign of the shift depends on which part of the waveform (up-chirp vs. down-chirp) is being processed. In contrast, Doppler shift due to relative velocity manifests itself as a "common-mode" frequency shift; for example, a pure upshift across both halves of the waveform indicates that the radar under test is approaching a target. Correlation is performed in the IF / baseband processor of the radar under test, and bandwidths of several MHz are typical.

[0048] Commonly deployed variations of FMCW radar systems use repeated up-chirps or repeated down-chirps, but not both (with dead time in between). Thus, the range to the emulated target is determined as in the previous paragraph, but now without the sign issue. Relative velocity is determined by measuring the phase shift between successive frame IF correlation signals, where frame is a term used in the art to refer to one period of the waveform. In many FMCW radar applications, frame repetition rates are typically from a few kHz to tens of kHz.

[0049] Once amplification / attenuation is achieved in circulator 202, frequency-offset transceivers 110A, 110B provide amplified / attenuated SSB signals that are retransmitted from re-illuminating antenna 108 to radar under test 105. Specifically, reducing the strength of the modulated I and Q drive signals reduces the output tone strength and, therefore, the RCS. In practice, this approach may not achieve more than 15 dB to 20 dB of dynamic range using modulated drive alone. However, VGA 204 compensates for this deficiency to achieve the desired RCS dynamic range, and variable gain of 10 dB to 50 dB can be easily achieved through a combination of variable attenuator and amplifier bias adjustment.

[0050] 4 is a simplified flow diagram illustrating a method for emulating an echo signal from a target with reduced reflected and leaky components using an echo signal emulation system, according to a representative embodiment. The method can be implemented, for example, by the system 100 described above under the control of the computer 140.

[0051] Referring to FIG. 4, in block S411, a radar signal is received from a radar under test through a probe antenna (e.g., re-illuminating antenna 108) at a frequency offset device (e.g., frequency offset transceiver 110). The radar signal may be, for example, an FMCW radar signal. A portion of the radar signal (the reflected component) is reflected from test equipment including the probe antenna and frequency offset device used to emulate an echo signal. As described above, the reflected component may include physical reflections from system hardware and, for example, a reflection coefficient (S 11 ) If no correction is made, the reflected power may be received by the radar under test as interference, which may indicate, for example, a ghost target.

[0052] In block S412, the received radar signal is mixed with the I and Q signals in an I / Q mixer (e.g., I / Q mixer 203) as an LO signal, and the I / Q mixer outputs the mixed product as an RF signal. It is understood that the received radar signal may be processed, for example, filtered, attenuated, and / or amplified, before being input to the I / Q mixer as the LO signal. A portion of the LO signal (leakage component) leaks through the I / Q mixer without being mixed with the I and Q signals. If not corrected, the leakage component may also be received by the radar under test as interference, for example, indicative of a ghost target.

[0053] In block S413, the reflected component of the radar signal (LO signal) is substantially canceled using the leakage component of the LO signal. For example, the DC values ​​of the I and Q signals input to the I / Q mixer can be adjusted to set the amplitude and phase of the leakage component of the LO signal to an equal amplitude and opposite phase of the reflected component of the radar signal. Alternatively, the radar signal can be split using an RF splitter to provide split components of the radar signal, which can be attenuated, before mixing the LO signal with the I and Q signals in the I / Q mixer. The remaining components of the radar signal are mixed in the I / Q mixer as the LO signal, as described in block S412, with the leakage component of the LO signal similarly attenuated. The attenuated split components of the radar signal and the attenuated leakage component of the LO signal are combined using an RF combiner to provide a combined leakage component of the LO signal. At least one of the attenuated split component of the radar signal, the attenuated leakage component of the LO signal, or the combined leakage component of the LO signal is phase shifted using a phase shifter so that the combined leakage component of the LO signal has the same amplitude and opposite phase as the reflected component of the radar signal.

[0054] In block S414, the RF signal is amplified / attenuated as necessary to accurately represent the emulated target and transmitted as an emulated echo signal to the radar under test. The radar under test receives the emulated echo signal without interference that would otherwise be caused by reflected components of the radar signal and / or leakage components of the LO signal. As described above, the radar under test includes at least one homodyne receiver that mixes the received emulated echo signal with the radar signal currently being transmitted from the radar under test to provide a corresponding radar IF signal. The radar IF signal has a frequency indicative of the range to the emulated target and an amplitude indicative of the RCS of the emulated target.

[0055] In block S415, the USB in the RF signal transmitted to the radar under test as the emulated echo signal can be minimized by (optionally) adjusting the amplitude and phase of the I and Q signals input to the I / Q mixer. That is, the RF signal includes a DSB, which is a frequency-shifted version of the LO signal, where the amount of frequency shift corresponds to the range of the emulated target from the radar under test. The RF signal also includes USB, which typically occurs at harmonics of the DSB.

[0056] The method described with reference to FIG. 4 is most effective over a narrow range of radar signal frequencies. Typically, as the frequency of the radar signal (and therefore the LO signal) drifts from the calibrated frequency, the frequency is tracked and the phase, amplitude, and DC level of the I and Q signals are adjusted to maintain cancellation of the reflected components of the radar signal, as described above; otherwise, the cancellation will not be optimal. This is particularly effective when the leakage component of the LO signal is minimized in the center of the frequency range covered by the radar signal. Alternatively, a solution that includes splitting the radar signal, attenuating the split components and the output RF signal, and combining the split components and the RF signal can offer a wider range of applications.

[0057] To avoid calibrating each individual emulated target, especially when there are several such targets emulated by multiple frequency-offset transceivers, and still cancel out reflected components, a group calibration can be performed in situ on the same echo signal emulation system in a test room. Typically, the frequency-offset transceivers are driven at different IF frequencies while the test room is filled with an mm-wave signal from a source probe antenna, provided by a signal generator or vector network analyzer (VNA). That is, each frequency-offset transceiver outputs an RF signal from its I / Q mixer that has a different frequency from the RF signals from the other frequency-offset transceivers, thereby generating different DSB, USB, and harmonic signals. Meanwhile, the LO signal (the mm-wave signal from the source probe antenna) is the same for each, allowing for coordinated adjustment of the leakage components of the LO signal passing through each I / Q mixer.

[0058] 5 is a simplified flow diagram illustrating a method for calibrating a system for emulating echo signals with reduced interference, according to a representative embodiment. The method can be implemented, for example, by the above-described system 100 under the control of a computer 140, where the system 100 includes a plurality of re-illuminators 106, each of which includes at least one re-illuminator antenna 108 and at least one frequency-offset transceiver 110.

[0059] 5, in block S511, a calibration signal having a mm-wave frequency of the radar signal is received at a plurality of frequency-offset transceivers (frequency-offset transceivers 110) through corresponding probe antennas (e.g., re-illuminator antennas 108) from a signal generator. The calibration signal can fill a test chamber through a source probe antenna connected to the signal generator. A portion of the calibration signal is reflected from the re-illuminators, e.g., each of the antennas, as a reflected component of the calibration signal corresponding to that re-illuminator.

[0060] In block S512, the calibration signal is mixed with the I and Q signals input to the I / Q mixers as LO signals, and the mixing products are output as RF signals. Due to differences in the I and Q signals for different frequency offset transceivers, the RF signals each contain different frequencies, DSBs, USBs, and harmonics. The portion of the LO signal that passes through each I / Q mixer is the corresponding leakage component of the LO signal for that I / Q mixer. The LO signal can have an LO frequency in the center of the chirp frequency range of the FMCW radar signal. For example, the LO frequency can be 76.5 GHz for an FMCW radar signal that chirps between 76.0 GHz and 77.0 GHz. However, other LO frequencies can be selected without departing from the scope of the present teachings.

[0061] In block S513, the DC values ​​of the I and Q signals input to the I / Q mixers are sequentially adjusted to minimize the corresponding leakage components of the LO signal passing through the I / Q mixers, respectively, and to minimize harmonics of the RF signal, such as upper harmonics, that track with the corresponding leakage components of the LO signal. That is, the DC values ​​can be adjusted individually, i.e., for each I / Q mixer, one at a time. For example, the leakage components of the LO signal and the harmonics of the RF signal can be monitored using a VNA or spectrum analyzer while adjusting the DC values ​​of the I and Q signals until their respective minimum values ​​are obtained. In one embodiment, while the DC value of the I / Q mixer in one frequency-offset transceiver is being adjusted, all of the other frequency-offset transceivers are turned off. The DC values ​​of the I and Q signals for the group of frequency-offset transceivers are then set accordingly. Initially minimizing the leakage components of the LO signal is particularly useful when the leakage components dominate the output of the I / Q mixers.

[0062] In block S514, the amplitude and phase of the I and Q signals input to the I / Q mixers are sequentially adjusted to minimize the USB of each RF signal output by the I / Q mixers. That is, the amplitude and phase can be adjusted individually, i.e., one at a time, for each I / Q mixer. For example, the USB of the RF signal can be monitored using a VNA or spectrum analyzer while adjusting the amplitude and phase of the I and Q signals until the minimum USB of each is obtained. The amplitude and phase of the I and Q signals are then set accordingly.

[0063] In block S515, the DC values ​​of the I and Q signals input to the multiple I / Q mixers are simultaneously adjusted to create a cancellation signal from the corresponding leakage components of the LO signals from the I / Q mixers in all of the frequency-offset transceivers. That is, because the re-illuminators and corresponding re-illuminating antennas and frequency-offset transceivers are located at substantially the same range from the radar or source probe antenna under test, they collectively provide a large reflected signal, referred to as the total reflected component of the calibration signal. To substantially cancel the total reflected component, the cancellation signal is created to have an equal amplitude and opposite phase of the total reflected component.

[0064] Once the DC values ​​of the I and Q signals input to the multiple I / Q mixers have been set, along with the amplitude and phase values ​​of the I and Q signals previously set in block S514, the echo signal emulation system can be used to test the radar under test. Testing can be performed, for example, according to the method shown in FIG.

[0065] The calibration described above works particularly well if performed at each frequency of interest for possible radar signals. To do this, the frequency of the chirp is tracked, and the I / Q settings of the DC value, as well as the amplitude and phase, are varied as a function of time across the chirp. This can be labor-intensive. Alternatively, the calibration can be performed only at the center frequency of the chirp's frequency band. While a calibration using only the center frequency may be less complete, it still dynamically reduces the amplitude of unwanted terms, including the leakage component of the LO signal and the USB of the RF signal.

[0066] For comparison purposes, FIG. 6A is a graph showing the effect of calibrating a frequency offset transceiver at one frequency on leakage components and USB in accordance with a representative embodiment, and FIG. 6B is a graph showing the effect of calibrating a frequency offset transceiver at multiple frequencies on leakage components and USB in accordance with a representative embodiment.

[0067] In Figure 6A, calibration was performed using a calibration signal at a single frequency, 76.5 GHz, which is the center frequency of an exemplary FMCW radar signal chirping between 76.0 GHz and 77.0 GHz. Trace 611 shows the DSB of the RF signal, trace 612 shows the leakage component of the LO signal, and trace 613 shows the USB of the RF signal resulting from the calibration. In Figure 6B, calibration was performed using calibration signals at multiple frequencies across the chirp's frequency band, including 76.0 GHz, 76.1 GHz, 76.2 GHz, 76.3 GHz, 76.4 GHz, 76.5 GHz, 76.6 GHz, 76.7 GHz, 76.8 GHz, 76.9 GHz, and 77.0 GHz. Trace 631 shows the DSB of the RF signal, trace 632 shows the leakage component of the LO signal, and trace 633 shows the USB of the RF signal resulting from the calibration.

[0068] A comparison of trace 611 with trace 631 shows that the DSB of the RF signal is constant regardless of the calibration technique. A comparison of trace 612 with trace 632 shows that the leakage component rises approximately 20 dB further (from approximately -70 dBm to approximately -50 dBm) from the center frequency used as the calibration point. This is typically an acceptable difference because the radar signal is at the midpoint of the chirp frequency band most of the time, so there may be some DC reflection only during portions of the chirp. A comparison of trace 613 with trace 633 shows that the USB is effectively nulled out, similar to using a single-frequency calibration.

[0069] While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustrations and descriptions are to be considered illustrative or exemplary and not restrictive, and the invention is not limited to the disclosed embodiments. Those skilled in the art will understand and can make other variations to the disclosed embodiments when practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere recitation of certain measures in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0070] Aspects of the present invention may be embodied as an apparatus, a method, or a computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which may be collectively referred to herein as a "circuit," "module," or "system." Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer-readable medium(s) having computer-executable code embodied therein.

[0071] While exemplary embodiments are disclosed herein, those skilled in the art will recognize that many variations are possible in accordance with the present teachings and are within the scope of the appended claims. Accordingly, the invention is not to be limited except as within the scope of the appended claims.

Claims

1. 1. A system for emulating an echo signal reflected from an emulated target in response to a radar signal transmitted by a radar under test, comprising: a probe antenna (108) configured to receive the radar signal over the air from the radar under test, wherein at least a reflected component of the radar signal is reflected from the probe antenna; a receiver (110) including an I / Q mixer (203) configured to input the received radar signal as a local oscillator (LO) signal, mix the LO signal with an I signal and a Q signal, and output a radio frequency (RF) signal, wherein a leakage component of the LO signal leaks through the I / Q mixer; a signal generator (130) calibrated to generate the I and Q signals to be mixed with the LO signal in the I / Q mixer; a transmitter (110) configured to transmit the RF signal as the emulated echo signal to the radar under test, the emulated echo signal indicating at least the range to the emulated target; Equipped with the amplitude and phase of the leakage component of the LO signal is set to an equal amplitude and opposite phase of the reflected component of the radar signal, such that the reflected component of the radar signal received by the radar under test is substantially canceled.

2. 2. The system of claim 1, wherein the signal generator is further configured to adjust DC values ​​of the I and Q signals mixed with the LO signal in the I / Q mixer to set the amplitude and the phase of the leakage component of the LO signal to the equal amplitude and opposite phase of the reflected component of the radar signal, so that the reflected component of the radar signal received by the radar under test is substantially canceled.

3. an RF splitter (211) configured to split the radar signal received from the probe antenna to provide split components of the radar signal, the remaining components of the radar signal being input to the I / Q mixer as the LO signal; a first attenuator (213) configured to attenuate the split component of the radar signal to provide a first attenuated signal; a second attenuator (214) configured to attenuate the RF signal to provide a second attenuated signal, the first attenuated signal and the second attenuated signal being attenuated at a frequency of the radar signal; an RF combiner (212) configured to combine the first attenuated signal and the second attenuated signal to provide a combined signal including the RF signal and the leakage component of the LO signal; a phase shifter (215) configured to phase shift at least one of the first attenuated signal, the second attenuated signal, or the combined signal to provide the leakage component with the equal amplitude and opposite phase of the reflected component of the radar signal, such that the reflected component of the radar signal received by the radar under test is substantially canceled; The system of claim 1 further comprising:

4. 10. The system of claim 1, wherein the signal generator comprises a direct digital synthesizer (DDS) and includes a field programmable gate array (FPGA) and a digital-to-analog converter (DAC).

5. 2. The system of claim 1, wherein the RF signal includes a desired sideband (DSB) that is a frequency-shifted version of the LO signal and an undesired sideband (USB), and the signal generator adjusts the amplitude and phase of the I and Q signals to minimize the USB of the RF signal.

6. 1. A method for emulating an echo signal in response to a radar signal transmitted by a radar under test using test equipment including an antenna and an I / Q mixer, comprising: receiving the radar signal from the radar under test, wherein a reflected component of the radar signal is reflected from at least the antenna (S411); Mixing the received radar signal as a local oscillator (LO) signal with an I signal and a Q signal in the I / Q mixer to output a mixed product as a radio frequency (RF) signal, wherein a leakage component of the LO signal leaks through the I / Q mixer (S412); using the leakage component of the LO signal to substantially cancel the reflected component of the radar signal (S413); transmitting the RF signal to the radar under test as the emulated echo signal indicative of range to at least the emulated target (S414); A method comprising:

7. 7. The method of claim 6, wherein substantially canceling the reflected component of the radar signal includes adjusting DC values ​​of the I and Q signals input to the I / Q mixer to set the amplitude and phase of the leakage component of the LO signal to an equal amplitude and opposite phase of the reflected component of the LO signal.

8. Substantially canceling the reflected component of the radar signal comprises: splitting the radar signal using an RF splitter prior to the I / Q mixer to provide split components of the radar signal; attenuating the split components of the radar signal; attenuating the leakage component of the LO signal; combining the attenuated split component of the radar signal and the attenuated leakage component of the LO signal using an RF combiner to provide a combined leakage component of the LO signal; phase-shifting at least one of the attenuated split component of the radar signal, the attenuated leakage component of the LO signal, or the combined leakage signal of the LO signal using a phase shifter, whereby the combined leakage component of the LO signal has an equal amplitude and opposite phase to the reflected component of the radar signal; The method of claim 6, comprising:

9. the RF signal includes a desired sideband (DSB) that is a frequency-shifted version of the LO signal, and an undesired sideband (USB); 7. The method of claim 6, further comprising adjusting the amplitude and phase of the I and Q signals input to the I / Q mixer to minimize the USB of the RF signal transmitted as the emulated echo signal to the radar under test.

10. 1. A method for calibrating a plurality of transceivers to emulate echo signals in response to radar signals transmitted by a radar under test, the plurality of transceivers each comprising an I / Q mixer; receiving a calibration signal at a plurality of antennas, each antenna being connected to a respective one of the plurality of transceivers, and a portion of the calibration signal being reflected from at least each of the plurality of antennas as a reflected component of the calibration signal (S511); mixing the calibration signal as an LO signal with an I signal and a Q signal input to each of a plurality of I / Q mixers to output a respective mixing product as a radio frequency (RF) signal, the RF signals including different RF frequencies, different desired sidebands (DSB), different undesired sidebands (USB), and different harmonics, and a portion of the LO signal passing through each I / Q mixer of the plurality of I / Q mixers as a corresponding leakage component of the LO signal (S512); Sequentially adjusting DC values ​​of the I signal and the Q signal input to the plurality of I / Q mixers to minimize the corresponding leakage components of the LO signal passing through the plurality of I / Q mixers and the harmonics tracking with the corresponding leakage components of the LO signal (S513); Sequentially adjusting the amplitudes and phases of the I and Q signals input to the plurality of I / Q mixers to minimize the USB of each of the RF signals output by the plurality of I / Q mixers (S514); simultaneously adjusting DC values ​​of the I and Q signals input to the plurality of I / Q mixers to create cancellation signals from the corresponding leakage components of the LO signal, the cancellation signals having equal amplitude and opposite phase to the total reflection component of the calibration signal to substantially cancel the total reflection component of the LO signal (S515); A method comprising:

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