US-12618958-B2 - Radar system and associated apparatus and methods

US12618958B2US 12618958 B2US12618958 B2US 12618958B2US-12618958-B2

Abstract

A radar system includes a radar receiver configured to receive return signals reflected from within a volume of radar coverage. A processor for processing the return signals extracts characteristics from a return signal received in a corresponding coherent processing interval. The extracted characteristics include a set of frequencies and/or a set of times, each frequency and/or time having a respective extracted amplitude of a corresponding set of extracted amplitudes. The processor determines a corresponding amplitude index for each extracted amplitude; and for each extracted amplitude, respectively stores in a memory location addressable via the corresponding amplitude index, a set of return signal related data including information for identifying the corresponding frequency and/or time, and an associated identifier for uniquely identifying, in combination with the amplitude index, that set of return signal related data.

Inventors

Gordon Kenneth Andrew Oswald

Assignees

Gordon Kenneth Andrew Oswald

Dates

Publication Date: 20260505
Application Date: 20220901
Priority Date: 20210901

Claims (20)

1 . A radar system for providing surveillance, the radar system comprising: at least one radar transmitter and at least one radar receiver arranged to provide a volume of radar coverage, wherein the at least one radar transmitter is configured to transmit a sequence of pulses to illuminate the volume of radar coverage, wherein the at least one radar receiver is configured to receive corresponding return signals reflected from within each resolution cell of one or more resolution cells within the volume of radar coverage, and wherein the return signals for each resolution cell are received in a series of coherent processing intervals; and means for processing the return signals, wherein the means for processing the return signals is configured to: extract characteristics from each return signal of a plurality of return signals received in each resolution cell in each coherent processing interval of a plurality of coherent processing intervals, the extracted characteristics comprising a set of frequencies and/or a set of times, each frequency and/or time having a respective extracted amplitude within a corresponding amplitude range; determine a corresponding amplitude index for the amplitude range within which the extracted amplitude falls; for each extracted amplitude: respectively store, in a memory location addressable via the corresponding amplitude index, a set of return signal related data comprising information for identifying the corresponding frequency and/or time, and an associated identifier for uniquely identifying, in combination with the amplitude index, that set of return signal related data; and extract a further characteristic including at least one of a position, heading, speed, acceleration, altitude, scattering cross-section, and/or classification of an object within the volume of radar coverage based on the stored set of return signal related data.
2 . The radar system according to claim 1 , wherein the associated identifier is an integer that is incremented for each successive set of return signal related data stored in association with the corresponding amplitude index.
3 . The radar system according to claim 1 , wherein the means for processing the return signals is further configured to access a stored set of return signal related data by using the corresponding amplitude index as at least part of an address, and optionally the associated identifier for uniquely identifying the set of return signal related data as part of the address.
4 . The radar system according to claim 1 , wherein the extracted characteristics comprise one or more of the set of frequencies and the extracted amplitudes comprise one or more of the corresponding amplitudes in the frequency domain.
5 . The radar system according to claim 1 , wherein the extracted characteristics comprise one or more of the set of times and the set of extracted amplitudes comprises one or more of the corresponding amplitudes in the time domain.
6 . The radar system according to claim 1 , wherein the at least one radar transmitter is configured to transmit the sequence of pulses omnidirectionally.
7 . The radar system according to claim 1 , wherein the amplitude index, the set of return signal related data, and the associated identifier for uniquely identifying, in combination with the amplitude index, the set of return signal related data are stored in association with one another in a vector histogram.
8 . The radar system according to claim 1 , wherein the set of return signal related data comprises at least one of an associated time, frequency, phase, complex amplitude, radial speed, and/or acceleration.
9 . The radar system according to claim 1 , wherein the set of return signal related data is stored as a vector that is identifiable using the corresponding amplitude index, and optionally the associated identifier for uniquely identifying, in combination with the amplitude index, the set of return signal related data.
10 . The radar system according to claim 1 , wherein the means for processing the return signals is further configured to update the stored set of return signal related data to include the extracted further characteristic.
11 . The radar system according to claim 1 , wherein the object is a target in the volume of radar coverage.
12 . The radar system according to claim 1 , wherein the means for processing the return signals is further configured to identify the presence of a target within the volume of radar coverage based on the stored set of return signal related data.
13 . The radar system according to claim 1 , wherein the means for processing the return signals is configured for parallel processing of the return signals and/or for parallel processing of the set of return signal related data.
14 . The radar system according to claim 1 , wherein the volume of radar coverage comprises a plurality of resolution cells; and wherein the means for processing the return signals is configured to classify, based on the set of return signal related data, a return signal received from a cell of the plurality of cells as at least one of: a noise signal corresponding to noise in the at least one resolution cell; a clutter signal; a candidate target; a target signal corresponding to an object of interest in the volume of radar coverage; a multipath signal corresponding to multipath scattering; an interference signal; or a malfunction signal corresponding to a malfunction of the radar system.
15 . The radar system according to claim 14 , wherein the at least one radar receiver comprises a plurality of radar receiver elements and/or comprises a plurality of radar receivers; and wherein the at least one radar receiver is configurable for digital beamforming to form the plurality of resolution cells.
16 . The radar system according to claim 1 , wherein the means for processing the return signals is further configured for identifying a modulation spur, and/or for identifying at least one rotating component of an object comprising a rotor, propeller, jet engine, or wind turbine blade from the set of return signal related data.
17 . The radar system according to claim 1 , wherein the means for processing the return signals is further configured to determine an acceleration of an object from the set of return signal related data, wherein the determination is based on contiguous amplitudes in the frequency domain.
18 . The radar system according to claim 1 , wherein the means for processing the return signals is further configured to determine at least one of an associated range, amplitude, direction and/or Doppler offset of simultaneous and coherent received signals, to identify multipath return signals using the set of return signal related data.
19 . A method of a radar system for providing surveillance, the method comprising: transmitting a sequence of pulses to illuminate a volume of radar coverage, receiving corresponding return signals reflected from each resolution cell of one or more resolution cells within the volume of radar coverage, wherein the return signals for each resolution cell are received in a series of coherent processing intervals; processing the return signals is configured to: extract characteristics from each return signal of a plurality of return signals received in each resolution cell and each coherent processing interval of a plurality of coherent processing intervals, the extracted characteristics comprising a set of frequencies and/or a set of times, each frequency and/or time having a respective extracted amplitude within a corresponding amplitude range; determine a corresponding amplitude index for the amplitude range within which the extracted amplitude falls; for each extracted amplitude: respectively store, in a memory location addressable via the corresponding amplitude index, a set of return signal related data comprising information for identifying corresponding frequencies and/or times, and an associated identifier for uniquely identifying, in combination with the amplitude index, that set of return signal related data; and extract a further characteristic including at least one of a position, heading, speed, acceleration, altitude, scattering cross-section, and/or classification of an object within the volume of radar coverage based on the stored set of return signal related data.
20 . A non-transitory computer-readable medium storing a program including instructions that, when executed by a processor forming part of a radar system, cause the processor to carry out the steps of the method of claim 19 .

Description

This application is a National Stage Application of PCT/GB2022/052239, filed Sep. 1, 2022, which claims benefit of United Kingdom Application 2112454.0, filed Sep. 1, 2021, and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications. FIELD OF THE INVENTION The present invention relates to a radar system and to associated apparatus and methods. The invention has particular, although not exclusive, relevance to air surveillance radar. BACKGROUND TO THE INVENTION Radar for air surveillance has taken many forms, with a range of functions, from long-range air defence to terminal traffic control. For example, types of radar and corresponding applications include: Staring air defence: Range and Direction FindingScanning air defence and traffic control: Detect and Track with reflecting or phased array antennas, plus cooperative methods.Tracking air defence: Non-cooperative Detect and TrackActive Electronically Scanned Array (AESA) air defence and weapons control: Resource Management, Non-Cooperative Detect and Track Phased array radars are built with solid-state electronics using radio-frequency phase control between the elements of a planar array antenna to form and direct transmit/receive beams, and these are then used in place of parabolic reflectors to support electronic scanning, and with the added potential of target-following modes. AESA radars use a large number of transmit-receive modules to carry out an E-scan function, but with greater flexibility and agility in directing and receiving beams, and of achieving multiple functionality within an array antenna. AESA radars have been the main focus of radar system development in recent decades. However, the demands of agile beam forming, agile waveforms and multiple functions place major and competing demands on the management of radar resources, such as dwell times and the available processing power. Radar engineering design has focused on minimizing the width of scanning beams for azimuth accuracy combined with high sensitivity, on the basis that the arising data must be accurate, detection fast, and the processing burden small. Track filtering has the task of receiving a series of detected positions, with many targets, each being interrogated only once every several seconds; the task being, first, to form correct associations between successive detections, and then to estimate target-specific trajectories from their positions. The probability of false associations and the arising processing burden grows rapidly with the number of targets, their dynamics, and the length of the scan interval. High radar agility, while effective in allowing random and rapid changes in beam direction, runs counter to potential gains that arise from extended dwell times on target. Scanning beams with high detection thresholds incur losses in signal information when the beam is narrowly focused elsewhere in the volume of regard, when signal components fail the threshold test and when short dwell times lead to low-resolution Fourier transforms and Doppler spectra. Intermittent observation is a necessary feature of scanning radar and implies the need to find associations between time-separated detections, which in turn leads to volatile and factorial-scaled burdens in computation. By contrast, persistent observation eliminates or greatly reduces the likelihood of disassociation between successive target scatters: signal sequences can be processed linearly, maintaining and extracting the full information content. Extended dwell time increases routine processing costs, but it permits the acquisition of continuing, coherent target responses, yielding target data with greater resolution and information content than is possible within the short dwell time typical of a scanning radar. Radar Target Information Information acquired by surveillance is created not by calculations at the radar, but when radar transmissions are scattered from objects in the volume of regard. Complex scattered amplitudes are encoded according to the presence, position, shape and motion of the object. The continuing reception of scattered signals acquires information about every object in the volume of regard and its behaviour that, according to the Electromagnetic Uniqueness Theorem is uniquely decodable within the constraints of radar sensitivity and resolution, Tracking is then implicit in the solution. An important fundamental in radar is that, provided that signal processing is linear with respect to complex (in-phase and quadrature) signal amplitudes, any information content is maintained. This is also true with respect to the addition of noise in receiver electronics, in that while random noise may obscure target information, it does not degrade or confuse it: it remains available for association with information at neighbouring times and receiving array elements. Additive noise itself provides a stable ref