Millimeter-wave radar antenna for drone interception

Abstract

A system for drone radar includes an antenna array having an arc configuration, where a set of transmit antennas and a set of receive antennas are arranged in an arc along the arc configuration.

Description

[Background technology]

[0001] Drones are common and can carry payloads such as cameras and improvised explosive devices that could be misused. Detecting and determining that drones are a threat can be difficult, and intercepting them when determined to be a problem can be even more difficult. [Brief description of the drawings]

[0002] Various embodiments of the invention are disclosed in the following detailed description and the accompanying drawings.

[0003] [Figure 1A] FIG. 1 is a block diagram illustrating an embodiment of a counter-drone.

[0004] [Figure 1B] FIG. 1 is a block diagram illustrating an embodiment of a radar system.

[0005] [Figure 2A] FIG. 2 is a block diagram illustrating one embodiment of an antenna array.

[0006] [Figure 2B] FIG. 1 illustrates an embodiment of waveforms related to parameters.

[0007] [Figure 2C] FIG. 2 is a block diagram illustrating one embodiment of a rotated set of antenna arcs.

[0008] [Figure 3A] FIG. 2 is a block diagram illustrating one embodiment of an antenna array.

[0009] [Figure 3B] FIG. 2 is a block diagram illustrating one embodiment of an antenna array.

[0010] [Figure 4A] FIG. 2 is a block diagram illustrating one embodiment of an antenna array circuit board.

[0011] [Figure 4B] FIG. 1 is a block diagram illustrating one embodiment of a drone radar system.

[0012] [Figure 4C] FIG. 1 is a block diagram illustrating one embodiment of a drone radar system architecture.

[0013] [Diagram 5] 1 is a block diagram illustrating one embodiment of an antenna array calibration system.

[0014] [Figure 6] 4 is a flow chart illustrating one embodiment of a method for calibrating an antenna array.

[0015] [Figure 7] 1 is a flow chart illustrating one embodiment of a method for providing a drone radar. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention may be embodied in various forms, including as a process, an apparatus, a system, a composition of matter, a computer program product embodied on a computer-readable storage medium, and / or a processor configured to execute instructions stored in and / or provided by a memory coupled to the processor. These embodiments or any other form the present invention may take may be referred to herein as techniques. In general, the order of steps of a disclosed process may be altered within the scope of the present invention. Unless otherwise noted, components such as a processor or memory described as configured to perform a task may be implemented as general components temporarily configured to perform the task at a given time, or as specific components manufactured to perform the task. As used herein, the term "processor" refers to one or more devices, circuits, and / or processing cores configured to process data, such as computer program instructions.

[0017] A detailed description of one or more embodiments of the present invention will now be given with reference to the drawings illustrating the principles of the present invention. The present invention will be described in connection with such embodiments, but is not limited to any of them. The scope of the present invention is limited only by the claims, and the present invention includes many alternatives, modifications, and equivalents. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. These details are for the purpose of example, and the present invention may be practiced according to the claims without some or all of these specific details. For simplicity, technical matters well known in the art related to the present invention have not been described in detail so as not to unnecessarily obscure the present invention.

[0018] A system for drone radar is disclosed. The system includes an antenna array. The antenna array includes an arc configuration. A set of transmit antennas and a set of receive antennas are disposed in an arc along the arc configuration.

[0019] A system for calibrating a radar is disclosed. The system includes an antenna array and a processor. The antenna array includes an arc configuration. The processor is configured to calibrate the drone radar. The calibration includes having transmitters of the antenna array transmit toward a single target, measuring signals at each receiver in each arc configuration of the antenna array to determine a phase offset of each receiver paired with the transmitter, and determining a calibration of the transmitter-receiver pairs relative to the antenna array.

[0020] The drone radar system is small enough to be mounted on an unmanned aerial vehicle (UAV) (e.g., a counter-drone) and can detect targets with a low radar cross section (RCS) (e.g., an RCS of -20 dBsm). For example, the system has a field of view (FOV) (e.g., 60 degrees by 60 degrees) sufficient to provide tracking and acquisition of an incoming threat drone from the edge of its specified detection range (e.g., 100 meters) all the way to the target while the counter-drone is pitching and rolling during the pursuit.

[0021] In various embodiments, the configurations are narrower or wider depending on the system requirements: in various embodiments, the radar sensing system has a wider FOV and is fixed, a narrower FOV (e.g., less than 60 degrees by 60 degrees) and is gimbaled and mechanically steered, a narrower FOV (e.g., less than 60 degrees by 60 degrees) and is electronically steered (e.g., using an active electronically scanned array), or has any other suitable configuration.

[0022] Narrower FOV configurations to achieve greater range come at the cost of more complex search algorithms in flight that compromise avoidance tracking, or require gimbals that require greater pointing accuracy, controllability at high speeds, reliability, and the burden of additional complexity.

[0023] The system exhibits higher angular accuracy and greater range than existing radar systems that can be mounted on counter-drones. In some embodiments, the system has high enough angular resolution to discriminate between multiple threat drones in the presence of multiple counter-drones. In some embodiments, the radar is utilized for target imaging, as the resolution is sufficient to create an image of detection.

[0024] In some embodiments, the system for drone radar comprises a millimeter wavelength radar. In some embodiments, the system for drone radar comprises a phased array radar (e.g., a multiple-input multiple-output (MIMO) radar).

[0025] Due to space constraints within a counter-drone, the radio frequency (RF) generation / detection, interface, and signal processing circuit boards of the system for the drone radar have a modular hardware architecture to provide design flexibility. In some embodiments, the first modular circuit board includes an antenna array and an analog radar processor (e.g., an RF antenna circuit board with integrated waveguide and RF processing). In some embodiments, the first modular circuit board integrates millimeter wavelength RF and signal processing within a complementary metal oxide semiconductor (CMOS) process. In some embodiments, the second modular circuit board includes a field programmable gate array (FPGA) interlink board. In various embodiments, application specific integrated circuits (ASICs) are used for one or more of the FPGAs on the FPGA interlink board. For example, utilizing an ASIC instead of an FPGA reduces power and / or saves circuit board space. In some embodiments, the third modular circuit board includes a digital radar processor board (e.g., a MIMO processing board).

[0026] The antenna array comprises a set of transmit antennas and a set of receive antennas arranged in one or more arc configurations. The antenna arc configuration describes a non-uniform configuration for arranging transmitters and receivers to provide higher drone radar system resolution than typical uniform array configurations used in synthetic aperture radar (SAR). The disclosed non-uniform arc configuration enhances resolution by suppressing grating side lobe interference compared to standard arrays (e.g., linear transmitter and / or receiver arrays). The shape or shapes of the arc configuration are selected to achieve design specifications for wide FOV and high elevation and azimuth resolution compared to commercially available radar systems suitable for counter-drone applications.

[0027] 1A is a block diagram illustrating one embodiment of a counter-drone. In the illustrated example, the counter-drone 100 is in or on a drone station (not shown) and receives counter-drone commands via a communication network. The battery 102 receives charging current via a drone pad interface 104 (e.g., the drone pad interface 104 comprises a hardwire connection or an electromagnetic inductive coupling with the drone station).

[0028] In some embodiments, the counter-drone 100 is part of a counter-drone system that includes a network linking one or more sensor systems (e.g., in-station, in-tower, in-drone, in-drone station, vehicle-mounted, person-worn sensor systems) with one or more counter-drone stations to monitor and protect a geofenced area against incoming threat drones. The sensor systems cooperate with the network to provide raw and / or derived sensor information to aid in determining which counter-drones to launch and / or direct (e.g., if already in flight) in response to incoming threat drones, based on available desired counter-drone characteristics (e.g., battery level, payload, etc.), and taking into account interception probability.

[0029] In one example where the counter-drone 100 is deployed to intercept a threat drone, the radar system 106 provides raw data and / or derived sensor information (e.g., radar imagery) to the drone processor 108 (e.g., to aid in determining an interception flight path). In some embodiments, the radar system 106 provides the raw data and / or derived sensor information to the counter-drone system via the drone processor 108 over a communications network (e.g., to communicate the position, altitude, velocity, acceleration, and / or trajectory of the threat drone).

[0030] The drone processor 108 then transmits the intercept flight path information to a flight controller 110, which activates and controls a counter-drone motor 114 via a speed controller 112 to achieve takeoff. The flight controller 110 includes a processor, gyros, accelerometers, altitude sensors (e.g., barometers), current sensors, proportional-integral-derivative (PID) controllers (e.g., for maintaining stability of the counter-drone 100 during flight), as well as other standard and customary components that enable the flight controller 110 to navigate and maintain a course suitable for intercepting the threat drone.

[0031] FIG. 1B is a block diagram illustrating an embodiment of a radar system. In some embodiments, the radar system 120 of FIG. 1B is used to implement the radar system 106 of FIG. 1A. In the illustrated example, the radar system 120 includes an antenna array 122, an analog radar processor 124, a digital radar processor 126, and a memory 128. The analog radar processor 124 receives mm-wave signals (e.g., radar frequencies between 30-300 GHz) from the antenna array 122 and downmixes the mm-wave signals to generate intermediate frequency (IF) inputs (e.g., frequencies in the range of 250 KHz to 5 MHz [check required]) to the digital radar processor 126. For example, mm-wave signals are transmitted by the antenna array 122, reflected from a target of interest, and received by the antenna array 122 to downmix and generate an IF input to the digital radar processor 126. The analog radar processor 124 digitizes the IF signals (e.g., using an analog-to-digital converter). Digital radar processor 126 calculates the amplitude and phase of the IF signal and determines the elevation and azimuth angles of a target of interest (e.g., an incoming threat drone) and the range to the target of interest. Memory 128 stores raw sensor data and / or derived sensor information (e.g., from digital radar processor 126), or any other suitable information to facilitate operation of radar system 120.

[0032] FIG. 2A is a block diagram illustrating an embodiment of an antenna array. In some embodiments, the antenna array 200 of FIG. 2A is used to implement the antenna array 122 of FIG. 1B. In the illustrated example, the antenna array 200 comprises a pair of antenna arc configurations of one type (e.g., antenna arc 202A and antenna arc 202B) and a pair of antenna arc configurations of another type (e.g., antenna arc 204A and antenna arc 204B). In some embodiments, the antenna array 200 includes multiple arc configurations. Each type of antenna arc configuration describes a non-uniform configuration for arranging the transmitters and receivers that comprise the antenna array 200. In contrast, the transmitters and receivers of standard virtual antenna arrays used in synthetic aperture radar (SAR) (e.g., inexpensive SAR systems available in counter drones) are typically arranged in a uniform configuration (e.g., linear).

[0033] The number of virtual channel elements in a SAR system is the product of the number of transmitters and the number of receivers used to form the array. For example, an antenna array with 12 transmitters and 16 receivers provides 192 virtual channel elements. The advantage of the large number of virtual channel elements used in SAR is that it produces a narrow beamwidth (i.e., provides higher resolution than non-SAR systems). Further resolution improvement is achieved using a non-uniform configuration.

[0034] The non-uniform arc configuration of FIG. 2A increases resolution by suppressing grating sidelobe interference. The narrow beamwidth of the SAR comes at the cost of grating sidelobes (i.e., secondary intensity peaks away from the beam center). The secondary intensity peaks are strong enough to create ambiguity in determining the location of the target (e.g., confusing the location of the beam center with the location of the secondary intensity peak). In the disclosed drone radar system, the arc configuration shown in FIG. 2A provides higher system resolution compared to uniform array configurations (e.g., providing 3-4 degree resolution compared to 5-7 degree resolution of other configurations) as a result of suppressing the grating sidelobe intensity.

[0035] In some embodiments, the azimuth and elevation resolutions are less than 6 degrees to resolve targets according to system requirements. In some embodiments, the azimuth and elevation resolutions are less than 4 degrees full width at half maximum (FWHM) to resolve targets according to system requirements. In some embodiments, the azimuth and elevation resolutions are as high as 18 degrees, depending on system requirements to separate multiple potential targets. In some embodiments, the azimuth resolution of the antenna array and the elevation resolution of the antenna array are within + / - 50% of each other. In some embodiments, the azimuth resolution of the antenna array and the elevation resolution of the antenna array are approximately equal (e.g., within + / - 1%, 5%, 10% of each other). In some embodiments, the angular accuracy is less than 1.5 degrees measured at a signal-to-noise ratio (SNR) of 10 dB. In some embodiments, the range resolution is less than 0.2 meters at a range of 70 meters for targets with an RCS of -10 dBsm. In some embodiments, the system achieves a range of 120 m with a resolution of 0.1 m for an RCS of -20 dBsm.

[0036] In various embodiments, system performance characteristics can vary depending on various software-defined parameters. These parameters can vary range, range resolution, Doppler, Doppler resolution, reflected power / SNR, and various waveform and beam characteristics. Developing a waveform (also known as a chirp configuration) for an application involves complex tradeoffs across various parameters to achieve sufficient coverage of the use case (e.g., to be able to detect a very small target traveling at X speed at Y range (distance) with Z other targets in the ocular field of view).

[0037] FIG. 2B is a diagram illustrating one embodiment of a waveform associated with a parameter. In some embodiments, the waveform is a radar waveform of a radar system (e.g., radar system 106 of FIG. 1). In the illustrated example, frequency is represented along the y-axis and time is represented along the x-axis, with multiple waveform chirp ramps of a frame displayed in waveform 240. Waveform 240 includes chirp ramps C 1 , C 2 , C 3 , C 4 , , C N-1 , C N The chirp ramp C of frame period 244 separated by interframe time 242 from 1 , C 2 , C 3 , C 4 , , C N-1 , C N Equipped with.

[0038] Waveform 220 shows a close-up view of a chirp ramp. Waveform 220 includes indications of chirp cycle time 222, analog-to-digital converter (ADC) sampling window 224, ADC start 226 from ramp start 228, idle time 230 from ramp end 234 to ramp start 228, transmit start 232 from ramp start 228, and transmitter on 236 where the frequency is ramped with a frequency slope 238 across a sweep bandwidth 239.

[0039] In various embodiments, the basic parameters include effective sweep bandwidth (e.g., 3000 MHz sweep bandwidth 239), initial ramp slope (e.g., 65.97 MHz / μs), ramp slope parameter (e.g., 1366), ramp slope (e.g., 65.95 MHz / μs frequency slope 238), inter-chirp time (e.g., 20.20 μs idle time 230), chirp time (e.g., 45.48 μs), number of samples per chirp (e.g., 223), maximum beat frequency (e.g., 4.4 MHz), minimum sampling frequency (4.89 Msps), total sweep bandwidth (e.g., 3881.04 MHz), carrier frequency (e.g., 77.80 GHz), lambda (e.g., 3.86 mm), minimum idle time (e.g., 7 μs average), and the like. s), the number of Doppler FFT bins (e.g., 32), active frame time (e.g., 4.21 ms), range bin resolution (e.g., 4.36 cm), velocity bin resolution (e.g., 0.47 m / s), radar cube size (216 KB), or any other suitable parameter.

[0040] In some embodiments, other parameters are altered to interface across the radar chip and modulate in a multi-phase configuration, hi some embodiments, the waveforms are customized to the desired system performance characteristics.

[0041] FIG 2C is a block diagram illustrating one embodiment of a rotated set of antenna arcs. In some embodiments, the antenna array 290 of FIG 2C is used to implement the antenna array 122 of FIG 1B. In the illustrated example, antenna arc 292A and antenna arc 292B comprise a pair of antenna arcs of one type, and antenna arc 294A and antenna arc 294B comprise a pair of antenna arcs of another type. The positions of antenna arc 292A and antenna arc 292B are such that, if antenna arc 292A is rotated 180 degrees about center 296, they are positioned such that antenna arc 292A overlaps antenna arc 292B, and similarly antenna arc 292B overlaps antenna arc 292A. The positions of antenna arc 294A and antenna arc 294B are such that when antenna arc 294A is rotated 180 degrees about center 296, antenna arc 294A overlaps antenna arc 294B, and similarly antenna arc 294B overlaps antenna arc 294A. The positions of the antenna arcs of antenna array 290 are rotated about center point 296 to achieve minimum grating side lobe interference. The antennas of the antenna array are positioned to achieve a predetermined FOV and resolution. In some embodiments, the azimuth field of view of the antenna array and the elevation field of view of the antenna array are within + / - 10% of each other. In some embodiments, the system has an elevation FOV of 20 degrees and an azimuth FOV of 60 degrees. In various embodiments, the azimuth field of view and the elevation field of view are about 40, 60, or 80 degrees, or any other suitable field of view angle.

[0042] In some embodiments, the plurality of arc configurations of the antenna array 290 includes a set of similar arc configurations rotated about a center point 296. In some embodiments, the plurality of arc configurations of the antenna array 290 includes pairs of L types of arc configurations, where L is an integer. In some embodiments, a first pair of arc configurations of a first type of the L types of arc configurations of the antenna array 290 is disposed at a rotated position about the center point 296. In some embodiments, a second pair of arc configurations of a second type of the L types of arc configurations of the antenna array 290 is disposed at a rotated position about the center point 296. In some embodiments, the first pair of the first type and the second pair of the second type are disposed rotated 90 degrees from each other.

[0043] FIG. 3A is a block diagram illustrating one embodiment of an antenna array. In the illustrated example, the antenna array of FIG. 3A comprises two types of antenna arcs and two types of antennas (i.e., type A and type B). In the illustrated example, a first type of antenna arc is formed by type A antenna 300 and type B antenna 302, and a second type of antenna arc is formed by type A antenna 304 and type B antenna 306. Type A antenna 308 and type B antenna 310 form a first type of antenna arc rotated 180 degrees around a center point with respect to the antenna arc formed by type A antenna 300 and type B antenna 302. Type A antenna 312 and type B antenna 312 form a second type of antenna arc rotated 180 degrees around a center point with respect to the antenna arc formed by type A antenna 304 and type B antenna 306. In some embodiments, the type A antenna is a transmitting antenna and the type B antenna is a receiving antenna. In some embodiments, the type A antenna is a receiving antenna and the type B antenna is a transmitting antenna. In various embodiments, the set of transmit antennas includes N transmit antennas and the set of receive antennas includes M receive antennas, where M and N are integers (e.g., N is 3 or 4 and / or M is 3 or 4). In some embodiments, N and M are equal integers. In various embodiments, N is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, or any other suitable number. In various embodiments, M is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, or any other suitable number. The antennas of the antenna array are arranged to achieve a predetermined FOV and resolution.

[0044] 3B is a block diagram illustrating one embodiment of an antenna array. In the illustrated example, the antenna array of FIG. 3B comprises a pair of transmit antenna arcs of one type (i.e., a set of transmit antennas 320 and a set of transmit antennas 322 each form an antenna arc of one type) and a pair of receive antenna arcs of another type (i.e., a receive antenna 324 and a receive antenna 326 each form an antenna arc of another type). In various embodiments, the set of transmit antennas includes N transmit antennas and the set of receive antennas includes M receive antennas, where M and N are integers (e.g., N is 3 or 4 and / or M is 3 or 4). In some embodiments, N and M are equal integers. In various embodiments, N is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, or any other suitable number. In various embodiments, M is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, or any other suitable number. The antennas of the antenna array are positioned to achieve a predetermined FOV and resolution.

[0045] FIG. 4A is a block diagram illustrating one embodiment of an antenna array circuit. In some embodiments, the antenna array circuit board 400 of FIG. 4A is used to implement the antenna array 122 and the analog radar processor 124 of FIG. 1B. In the illustrated example, the antenna array circuit board 400 includes an antenna array 402, an analog radar processor 406A, an analog radar processor 406B, an analog radar processor 406C, and an analog radar processor 406D. The analog radar processor 406A, the analog radar processor 406B, the analog radar processor 406C, and the analog radar processor 406D receive mm-wave signals (e.g., radar frequencies between 30-300 GHz) from the antenna array 402 and downmix the mm-wave signals to generate intermediate frequency (IF) signal outputs (e.g., frequencies in the range of 250 KHz to 5 MHz [check required]). For example, mm-wave signals are transmitted by antenna array 402, reflected from targets of interest, and received by antenna array 402 for downmixing to generate an IF signal output. Analog radar processor 406A, analog radar processor 406B, analog radar processor 406C, and analog radar processor 406D digitize the IF signals (e.g., for use as input to a digital radar processor).

[0046] Antenna array 402 includes multiple antennas (e.g., multiple antennas in the form of antenna 404). Antenna 404 comprises multiple antenna pads. In the illustrated example, antenna 404 comprises antenna pad 408A, antenna pad 408B, antenna pad 408C, and antenna pad 408D. In some embodiments, an antenna pad of the multiple antenna pads spans 1 mm by 1 mm or any other suitable dimensions to achieve design specifications for a compact antenna array.

[0047] FIG. 4B is a block diagram illustrating an embodiment of a drone radar system. In some embodiments, the radar system 420 of FIG. 4B corresponds to the radar system 120 of FIG. 1B. In the illustrated example, the radar system 420 includes an antenna array 422, an analog radar processor board 424, an FPGA interlink board 426, and a digital radar processor board 428. Due to space constraints within the counter-drone, the analog radar processor board 424, the FPGA interlink board 426, and the digital radar processor board 428 include a modular hardware architecture to provide design flexibility and a compact form factor. In some embodiments, the analog radar processor board 424 integrates millimeter wavelength RF and signal processors in a CMOS process. In some embodiments, the FPGA interlink board includes an interface (e.g., an Ethernet link or other communication bus connector) to the drone processor. In various embodiments, an application specific integrated circuit (ASIC) is used for one or more of the FPGAs on the FPGA interlink board 426. For example, utilizing an ASIC instead of an FPGA may result in power reduction and / or circuit board space savings. The digital radar processor board 428 includes a processor for performing digital signal processing, including radar signal calibration and amplitude / phase calculations, to determine the range and angle of targets detected using the radar. In some embodiments, radar signal calibration is used to aid in the accuracy of the elevation and azimuth angles determined. Additionally, the radar system 420 transmits and receives signals used to determine the range to a target. In some embodiments, radar signal calibration is used to aid in the accuracy of the determined range to a target.

[0048] FIGURE 4C is a block diagram illustrating one embodiment of a drone radar system architecture. In some embodiments, the drone radar system architecture of FIGURE 4C corresponds to radar system 120 of FIGURE 1B. In the illustrated example, the drone radar system architecture of FIGURE 4C includes a digital radar processor board 440, an FPGA interlink board 442, and an analog radar processor board 444. Board connectors 458 (e.g., 60-pin Samtec QSH type connectors) are used to electrically connect the digital radar processor board 440, the FPGA interlink board 442, and the analog radar processor board 444.

[0049] The digital radar processor board 440 includes a processor 446 (e.g., a digital signal processor (DSP) microprocessor chip), memory 448 (e.g., used by the processor 446 to store raw sensor data and / or derived sensor information, phase offset calibration data, or any other suitable data used in the operation of the drone radar system), a Joint Test Action Group Industrial (JTAG) connector 450 (e.g., used to directly communicate with the processor 446 and / or one or more of the other ICs that make up the drone radar system architecture of FIG. 4C ), and a 32-bit I / O (e.g., for connecting to an external computer). The drone radar system includes a universal serial bus (USB) connector 452 for connecting to a data storage device, data storage 454 (e.g., a fixed data storage device (e.g., hard drive, solid state drive, etc.) or a removable data storage device (e.g., a microSD (Secure Digital Industry Standard) card, etc.), and a power management integrated circuit (IC) 456. The power management IC 456 is used for one or more of the following functions required by the drone radar system specifications: DC-DC conversion, battery charging, power source selection, voltage scaling, power source sequencing, or any other suitable power management function.

[0050] FPGA Interlink board 442 includes four FPGA Interlink ICs (i.e., FPGA Interlink 460, FPGA Interlink 462, FPGA Interlink 464, and FPGA Interlink 466), a controller area network (CAN) connector 464, an Ethernet connector 470, and a power connector 472. The four FPGA Interlink ICs connect and convert signals from each antenna arc of the drone radar system antenna array for use by processor 446. In various embodiments, an ASIC is used for one or more of the four FPGA Interlink ICs on FPGA Interlink board 442. For example, using an ASIC instead of an FPGA can result in power reduction and / or circuit board space savings.

[0051] The CAN connector 464 is used to connect to a controller area network for sending and receiving commands (e.g., returning sensor data, reading contactor status, etc.) and / or communicating with an external computer or end user (e.g., via an Ethernet connector 470). For example, an external computer may be used during antenna array calibration, system debug, or maintenance to offload system event logs or diagnostic files, or any other suitable functionality to assist an end user in calibrating, operating, or maintaining the drone radar system. The power connector 472 is used to connect the drone radar system architecture of FIG. 4C to a power source (e.g., one or more rechargeable batteries, or any other suitable power source that meets the design specifications of the drone radar system (e.g., design specifications for weight, size, battery capacity, etc.).

[0052] The analog radar processor board 440 includes four antenna arc ICs (i.e., antenna arc 474, antenna arc 476, antenna arc 478, and antenna arc 480) and two power management ICs (i.e., power management IC 482 and power management IC 484). Each of the four antenna arc ICs (i.e., corresponding to the four antenna arcs constituting the antenna array of the drone radar system) is used to receive mm-wave signals (e.g., radar frequencies between 30-300 GHz), downmix the mm-wave signals to generate intermediate frequency (IF) signal outputs (e.g., frequencies in the range of 250 KHz to 5 MHz [check required]), and digitize the IF signals for transmission to the processor 446 via the four FPGA interlink ICs of the FPGA interlink board 442. The power management IC 482 and the power management IC 484 are used for one or more of the following functions required by the specifications of the drone radar system: DC-DC conversion, battery charging, power supply selection, voltage scaling, power supply sequencing, or any other suitable power management function.

[0053] FIG. 5 is a block diagram illustrating an embodiment of an antenna array calibration system. In some embodiments, the antenna array calibration system of FIG. 5 is used to calibrate the radar system 120 of FIG. 1B. In some embodiments, the antenna array 500 corresponds to the antenna array 122 of FIG. 1B. In the illustrated example, the antenna array 500 and the target 506 are disposed in an anechoic chamber 512. In some embodiments, the target 506 comprises a corner reflector. For example, the target 506 comprises a single corner reflector consisting of three mutually orthogonal planes that reflect waves back to the source. The antenna array 500 is disposed at the reference point 504 toward a pointing direction 502. For example, the pointing direction 502 points in substantially the same direction as the antenna array 500 points when mounted on a counter drone.

[0054] In some embodiments, the antenna array 500 is mounted to the counter-drone. For example, the antenna array 500 is mounted in a radar system mounted to the counter-drone and disposed within an anechoic chamber 512. In some embodiments, the counter-drone mounted antenna array 500 is disposed at a reference point 504 and oriented in a pointing direction 502 (e.g., a pointing direction pointing to the center of the FOV of the antenna array 500, or any other suitable pointing direction).

[0055] The targets 506 are located at multiple altitudes and azimuth angles relative to the reference point 504. In the illustrated example, the targets 506 are located at altitude 508 and azimuth angle 510. Calibrating the antenna array 500 includes determining the angle of arrival for each transmitter-receiver pair of the antenna array 500 for each of the multiple altitudes and azimuth angles. For example, a transmitter of the antenna array 500 transmits toward the target 506 while a receiver paired with the transmitter measures a reflected signal from the target 506. Analog and digital radar processors associated with a radar system including the antenna array 500 determine a phase offset of the reflected signal for each receiver paired with each transmitter of the antenna array 500 and determine the calibration of the transmitter-receiver pair for the antenna array 500. This process is repeated for multiple altitudes and azimuth angles sufficient to cover the entire FOV of the antenna 500 at a predetermined resolution (e.g., [Adnan, insert a typical number and range of multiple sufficient altitudes and azimuth angles]). A calibration offset is then determined by comparing the radar-measured angle and range to the target with the known angle and range to the target. This calibration offset is determined for each virtual channel (e.g., transmitter-receiver pair) of the radar array.

[0056] Figure 6 is a flow chart illustrating one embodiment of a method for calibrating an antenna array. In some embodiments, the process of Figure 6 is used to implement the antenna array calibration system of Figure 5. In the illustrated example, at step 600, the antenna array is positioned in a pointing direction. For example, the antenna array is positioned in a pointing direction that points in substantially the same direction (e.g., within a degree, within a few degrees, within 5 degrees, etc.) as the antenna array points when attached to the counter drone, a pointing direction that indicates the center of the antenna array's FOV, or any other suitable pointing direction.

[0057] At step 602, an altitude and azimuth angle is selected for a pointing direction. For example, the altitude and azimuth angle is selected from a plurality of altitudes and azimuth angles (e.g., a plurality of altitudes and azimuth angles sufficient to cover the entire FOV of the antenna array at a predetermined resolution).

[0058] At step 604, a target is positioned at a selected altitude and azimuth. For example, the target may have a single corner reflector and be positioned at a selected altitude and azimuth. At step 606, the next transmit antenna of the antenna array is selected. For example, the next transmit antenna of a transmitter-receiver pair of the antenna array is selected.

[0059] At step 608, a calibration signal is transmitted toward the target using a transmitting antenna. For example, a transmitter of an antenna array is caused to transmit the calibration signal toward the target to obtain a reflected signal. At step 610, phase data of the signal reflected from the target is measured at each receiving antenna of the antenna array. For example, an analog radar processor and a digital radar processor associated with a radar system with an antenna array determine a phase offset of the reflected signal measured at each receiving antenna of the antenna array.

[0060] At step 612, a phase offset calibration is determined based at least in part on the phase data. For example, a calibration for a transmitter-receiver pair is determined. At step 614, the phase offset calibration is stored in a memory. For example, the phase offset calibration data is stored in a digital radar processor memory associated with the radar system with the antenna array.

[0061] At step 616, it is determined whether there are more transmit antennas. For example, it is determined whether there are more transmit antennas in the antenna array that require calibration. In response to a determination that there are more transmit antennas, control proceeds to step 606 where the next transmit antenna in the antenna array is selected. In response to a determination that there are no more transmit antennas, processing proceeds to step 618. At step 618, it is determined whether there are more altitudes or more azimuth angles. For example, it is determined whether there are more altitudes or more azimuth angles remaining to complete the calibration of the selected transmitter-receiver pair.

[0062] In response to a determination that there is more altitude or more azimuth angles, control proceeds to step 602 where the next altitude and azimuth angle are selected. In response to a determination that there are no more altitudes or more azimuth angles, control proceeds to step 620. At step 620, the calibration is indicated as complete and processing ends, e.g., the calibration is indicated to a user of the calibration system as complete and processing ends.

[0063] FIG. 7 is a flow chart illustrating one embodiment of a method for providing a drone radar. In some embodiments, the process of FIG. 7 is used to implement the radar system 120 of FIG. 1B. In the illustrated example, at step 700, a digital radar processor is provided. At step 702, a memory coupled to the digital radar processor is provided. At step 704, an analog radar processor is provided, where the analog radar processor provides data to the digital radar processor. At step 706, an antenna array is provided, where the antenna array provides signals to the analog radar processor, the antenna array comprising an arc configuration, a set of transmit antennas and a set of receive antennas arranged in an arc along the arc configuration, and the process ends.

[0064] Although the above embodiments have been described in some detail for ease of understanding, the invention is not limited to the details provided. There are many alternative ways of implementing the invention. The disclosed embodiments are illustrative and are not intended to be limiting. [Application Example 1] A system for radar, comprising: An antenna array is provided, the antenna array having an arc configuration; A system, wherein a set of transmitting antennas and a set of receiving antennas are arranged in an arc along said arc configuration. [Application Example 2] A system according to Application Example 1, wherein the set of transmitting antennas includes N transmitting antennas, and the set of receiving antennas includes M receiving antennas. [Application Example 3] A system according to Application Example 2, wherein N and M are equal integers. [Application Example 4] The system according to Application Example 2, wherein N is 3 or 4. [Application Example 5] The system according to Application Example 2, wherein M is 3 or 4. [Application Example 6] A system according to Application Example 1, wherein the antenna array has a multiple arc configuration. [Application Example 7] A system according to Application Example 6, wherein the multiple arc configurations include a set of similar arc configurations rotated around a center point. [Application Example 8] A system according to Application Example 6, wherein the plurality of arc configurations include pairs of L types of arc configurations, where L is an integer. [Application Example 9] A system according to Application Example 8, wherein a first pair of a first type of the L types of arc configurations is arranged in a rotated position around a center point. [Application Example 10] A system according to Application Example 9, wherein a second pair of a second type of the L types of arc configurations is arranged in a rotated position around the center point. [Application Example 11] A system according to Application Example 10, wherein the first pair of the first type and the second pair of the second type are arranged rotated 90 degrees relative to each other. [Application Example 12] A system according to Application Example 1, wherein the azimuth resolution of the antenna array and the elevation resolution of the antenna array are within + / - 50% of each other. [Application Example 13] A system according to Application Example 12, wherein the azimuth angle resolution and the elevation angle resolution are less than 6 degrees. [Application Example 14] A system according to Application Example 1, wherein the azimuth field of view of the antenna array and the elevation field of view of the antenna array are within + / - 10% of each other. [Application Example 15] The system described in Application Example 14, wherein the azimuth angle field of view and the elevation angle field of view are approximately 40 degrees, 60 degrees, or 80 degrees. [Application Example 16] The system according to Application Example 1, wherein the antenna array is for radar frequencies between 30 and 300 GHz. [Application Example 17] A system according to Application Example 1, wherein the antenna pads of the antenna array span 1 mm x 1 mm. [Application Example 18] A method for radar, comprising: providing an antenna array; the antenna array having an arc configuration; A method, wherein a set of transmitting antennas and a set of receiving antennas are arranged in an arc along said arc configuration.

Claims

1. 1. A system for a radar, comprising: An antenna array is provided, the antenna array comprises a first arc configuration and a second arc configuration; a set of transmitting antennas and a set of receiving antennas are disposed in an arc along at least one of the first arc configuration and the second arc configuration; The system, wherein at least one of the first arc configuration and the second arc configuration is positioned on a circuit board so as not to overlap a center point of the antenna array.

2. 2. The system of claim 1, wherein the set of transmit antennas includes N transmit antennas and the set of receive antennas includes M receive antennas.

3. 3. The system of claim 2, wherein N and M are equal integers.

4. 3. The system of claim 2, wherein N is 3 or 4.

5. 3. The system of claim 2, wherein M is 3 or 4.

6. 2. The system of claim 1, wherein at least one of the first arc configuration and the second arc configuration comprises a set of similar arc configurations rotated about the center point.

7. 2. The system of claim 1, wherein at least one of the first arc configuration and the second arc configuration includes pairs of L types of arc configurations, where L is an integer.

8. 8. The system of claim 7, wherein a first pair of a first type of the L types of arc configurations are disposed in rotated positions about the center point.

9. 9. The system of claim 8, wherein a second pair of a second type of the L types of arc configurations is disposed in a rotated position about the center point.

10. 10. The system of claim 9, wherein the first pair of the first type and the second pair of the second type are arranged rotated 90 degrees relative to each other.

11. 2. The system of claim 1, wherein the azimuth resolution of the antenna array and the elevation resolution of the antenna array are within + / - 50% of each other.

12. 12. The system of claim 11, wherein the azimuth and elevation resolutions are less than six degrees.

13. 2. The system of claim 1, wherein the azimuth field of view of the antenna array and the elevation field of view of the antenna array are within + / - 10% of each other.

14. 14. The system of claim 13, wherein the azimuth field of view and the elevation field of view are approximately 40 degrees, 60 degrees, or 80 degrees.

15. 10. The system of claim 1, wherein the antenna array is for radar frequencies between 30 and 300 GHz.

16. 10. The system of claim 1, wherein the antenna pads of the antenna array span 1 mm by 1 mm.

17. 1. A method for a radar, comprising: providing an antenna array; the antenna array comprises a first arc configuration and a second arc configuration; a set of transmitting antennas and a set of receiving antennas are disposed in an arc along at least one of the first arc configuration and the second arc configuration; At least one of the first arc configuration and the second arc configuration is positioned on a circuit board so as not to overlap a center point of the antenna array.

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