Radar signal processing for clutter spectrum reduction

Abstract

A pulse-Doppler radar signal processing method comprises the step of receiving time-domain radar data based on reflection measurements of a burst comprising a pulse train emitted into a beam coverage area, wherein the burst comprises a plurality of dwells, each dwell comprising a group of pulses having different pulse repetition intervals (PRI) -; The method comprises the steps of: processing time-domain radar data to correlate range and reflection measurements for each dwell; combining time-domain data for multiple dwells—the combining step includes combining reflection measurements of different dwells for corresponding ranges—; after the combining step, converting time-domain data for multiple dwells to generate frequency-domain burst data; and evaluating frequency-domain burst data to establish the presence of one or more targets within a beam coverage area.

Description

Technology Field

[0001] The present disclosure relates, in some embodiments, to radar signal processing, and more specifically, but non-exclusively, to radar signal processing for reducing clutter spectrum in radar data. Background Technology

[0002] The background technology to which each technology is incorporated by reference in its entirety includes U.S. Patent No. 7864106, which is described as follows.

[0003] Most modern surveillance radars scan the surrounding space using a relatively narrow radiation beam. The total scan time is typically a user-defined parameter of the system. The fraction of scan time allocated to collect target returns from each beam direction is called the time-on-target. During this time fraction, a series of pulses is transmitted by the radar. The interval between the rises of any two consecutive pulses is called the Pulse Repetition Interval (PRI), and the pulse rate is called the Pulse Repetition Frequency (PRF). The detection and measurement process can be realized by using a constant or variable PRF during the time-on-target interval. Maximum SNR can be achieved through the coherent integration of all target returns over the entire time-on-target interval. At first glance, the most attractive way to realize this concept would be to use a single constant Pulse Repetition Frequency (PRF) for transmitting pulse sequences and utilizing target returns. However, this method does not support unambiguous measurement of range or speed, or both.

[0004] Another problem associated with single PRF detection schemes is the issue of blind zones (blind range and Doppler frequency) in the detection map. This problem reflects the periodic nature of transmission and reception in pulse radar detection schemes and is known as the visibility problem.

[0005] In conventional technology, one solution to both ambiguity and visibility problems is to transmit two or more pulse sequences, each having a different PRF, in succession. Each sub-interval with a constant PRF is ambiguous but provides different "scales" for the simultaneously measured target range and Doppler frequency. Combinations of all measurements (each having a different PRF) during the time-on-target interval allow for ambiguity resolution but require independent detection attempts. In other words, the requirement to provide simultaneous detection and measurement of the target leads to dividing the time-on-target interval into several independent sub-intervals, each representing a relatively small portion of the total time-on-target interval. The detection process in each sub-interval, known as the coherent processing interval, or simply CPI, can be optimally performed using coherent integration, but the maximum energy collected from the target reflection is only a fraction of the total energy that can be collected during the entire time-on-target interval. Any logical or arithmetic combination of sub-interval results causes a loss and degradation of detection probability compared to the coherent integration of the signal over the entire time-on-target interval.

[0006] The approval of the above reference(s) herein should not be inferred to mean that these references are related in any way to the patentability of the subject matter disclosed herein.

[0007] The following is a non-exclusive list of some exemplary embodiments of the present disclosure. The present disclosure also includes embodiments that include fewer features than all features of one embodiment, and embodiments that use features from a number of embodiments, even if not listed below.

[0008] Example 1. As a pulse-Doppler radar signal processing method,

[0009] A step of receiving time-domain radar data based on reflection measurements of a burst comprising a pulse train emitted into a beam coverage area—the burst comprises a plurality of dwells, each dwell comprising a group of pulses having different pulse repetition intervals (PRI)—;

[0010] A step of processing the above time-domain radar data to correlate the range and reflection measurements for each dwell;

[0011] A step of combining time domain data for multiple dwells - the combining step includes combining reflection measurements of different dwells for corresponding ranges -;

[0012] After the above combining step, a step of converting the time domain data for a plurality of dwells to generate frequency domain burst data;

[0013] A pulse-Doppler radar signal processing method comprising the step of evaluating frequency domain burst data to establish the presence of one or more targets within the beam coverage area.

[0014] Example 2. A pulse-Doppler radar signal processing method in Example 1, wherein the time domain data for a plurality of dwells is non-coherent.

[0015] Example 3. A pulse-Doppler radar signal processing method, wherein, in Example 1 or Example 2, the combining step comprises identifying a corresponding range gate in a different dwell and combining measurement data of a different dwell for the corresponding range gate.

[0016] Example 4. In Example 3, the processing step is,

[0017] A pulse-Doppler radar signal processing method comprising generating a plurality of range gate vectors for each dwell, each containing a reflection measurement value for a specific range gate.

[0018] Example 5. In Example 4, the combining step comprises identifying corresponding range gate vectors in different dwells; and

[0019] A method comprising concatenating data of corresponding range gate vectors to provide a plurality of range gate vectors for a burst.

[0020] Example 6. In Example 5, for each of the dwell, the plurality of range gate vectors provide a range-pulse map, and the processing step provides a plurality of range-pulse maps, a range-pulse map for each dwell, a pulse-Doppler radar signal processing method.

[0021] Example 7. A pulse-Doppler radar signal processing method in Example 6, wherein the plurality of range gate vectors for the burst provide a burst range-pulse map.

[0022] Example 8. A pulse-Doppler radar signal processing method, wherein in any one of Examples 5 to 7, the transforming step comprises the step of generating a plurality of range-Doppler vectors by applying a Fourier transform to each of the plurality of range gate vectors for a burst.

[0023] Example 9. A pulse-Doppler radar signal processing method in Example 8, wherein the Fourier transform is a Fast Fourier Transform (FFT).

[0024] Example 10. A pulse-Doppler radar signal processing method in Example 8 or Example 9, wherein the converting step follows weighting.

[0025] Example 11. In Example 10, the converting step provides a burst range-Doppler map, a pulse-Doppler radar signal processing method.

[0026] Example 12. A pulse-Doppler radar signal processing method, wherein in any one of Examples 9 to 11, the evaluating step comprises evaluating a range-Doppler map to characterize a cell as indicating the presence or absence of a target.

[0027] Example 13. In any one of Examples 1 to 12, the method comprises the step of emitting the pulse train during a time-on-target associated with a burst, wherein each pulse comprises electromagnetic (EM) radiation;

[0028] A pulse-Doppler radar signal processing method, wherein the receiving step comprises measuring the reflection of the signal from the beam coverage area.

[0029] Example 14. A pulse-Doppler radar signal processing method, wherein in any one of Examples 1 to 13, the receiving step comprises one or more of down-conversion, sampling, and filtering of the measurement value of the reflection to provide the time domain radar data.

[0030] Example 15. A pulse-Doppler radar signal processing method, wherein in any one of Examples 5 to 14, the identifying step comprises determining a corresponding range-gate number for each dwell for an actual range distance.

[0031] Example 16. A pulse-Doppler radar signal processing method, wherein in any one of Examples 12 to 15, the evaluating step comprises comparing each cell of a range-Doppler map with a threshold value.

[0032] Example 17. A pulse-Doppler radar signal processing method according to Example 16, comprising the step of determining a background level for each cell of a range-Doppler map, wherein the threshold value is determined from the background level.

[0033] Example 18. A pulse-Doppler radar signal processing method according to Example 17, wherein the step of determining the background level includes averaging adjacent cell values.

[0034] Example 19. A pulse-Doppler radar signal processing method in Example 18, wherein the threshold value is a value multiplied by a constant selected to provide the sensitivity and false alarm rate required for the background level.

[0035] Example 20. A pulse-Doppler radar signal processing method, wherein in any one of Examples 1 to 19, the method comprises the step of receiving verification time-domain radar data based on reflection measurements of a verification burst including a verification pulse train emitted into the beam coverage area, wherein the verification burst includes a plurality of dwells, and each dwell includes a pulse group having a different PRI.

[0036] Example 21. A pulse-Doppler radar signal processing method in Example 20, wherein the dwell of the verification burst has a different PRI for the dwell of the burst.

[0037] Example 22. A pulse-Doppler radar signal processing method comprising the step of determining the range and velocity of one or more targets by using the time domain radar data and the verification time domain radar data to resolve the ambiguity of the range and / or velocity of one or more targets in Example 20 or Example 21.

[0038] Example 23. In any one of Examples 1 to 22, changing the beam coverage area; and

[0039] A pulse-Doppler radar signal processing method comprising repeating the above method.

[0040] Example 24. As a pulse-Doppler system,

[0041] A radar transmitter configured to emit a burst containing a train of electromagnetic (EM) radiation radar pulses into a beam coverage area—said that the burst comprises a sequential series of dwells having different pulse repetition intervals (PRI);

[0042] A radar receiver configured to detect the reflection of an emitted pulse to measure the reflection timing relative to the emission timing of a radar pulse and to generate burst data; and

[0043] It includes a processor, and the processor,

[0044] Processing the above time-domain radar data to correlate the range and reflection measurements for each dwell;

[0045] Combining time-domain data for multiple dwells—combining includes combining reflection measurements of different dwells for corresponding ranges—;

[0046] After combining time domain data for multiple dwells, converting the time domain data for multiple dwells to generate frequency domain burst data;

[0047] A pulse-Doppler system configured to evaluate frequency domain burst data to identify the range and velocity of any target within the beam coverage area.

[0048] Example 25. As a pulse-Doppler radar signal processing method,

[0049] Step of receiving burst data - burst data includes dwell data of more than one dwell, each dwell having a different pulse repetition interval (PRI) -;

[0050] For each dwell, a step of processing burst data to provide a corresponding dwell range-pulse map;

[0051] For each range-gate of the burst range-gate map,

[0052] Identifying the corresponding range-gate for each of more than one dwell; and

[0053] A step of generating a burst range-pulse map comprising concatenating data from corresponding range-gates of more than one dwell to provide range-gate data for corresponding range-gates of the burst range-gate map;

[0054] A step of converting a burst range-gate pulse map into a burst range-Doppler map; and

[0055] A pulse-Doppler radar signal processing method comprising the step of evaluating a range-Doppler map to characterize a cell as indicating the presence or absence of a target.

[0056] Example 26. As a pulse-Doppler system,

[0057] A radar transmitter configured to emit a burst comprising a series of electromagnetic (EM) radar pulses, each comprising a sequential series of dwells having different pulse repetition intervals (PRI);

[0058] A radar receiver configured to detect the reflection of an emitted pulse to measure the reflection timing relative to the emission timing of a radar pulse and to generate burst data; and

[0059] It includes a processor, and the processor,

[0060] Receiving burst data from a radar receiver;

[0061] Processing burst data to provide a corresponding dwell range-pulse map for each dwell;

[0062] For each range-gate of the burst range-gate map,

[0063] Identifying the corresponding range-gate for each of more than one dwell; and

[0064] Generating a burst range-pulse map by concatenating data from corresponding range-gates of more than one dwell to provide range-gate data for corresponding range-gates of the burst range-gate map;

[0065] Converting a burst range-pulse map to a burst range-Doppler map; and

[0066] A pulse-Doppler system configured to perform an evaluation of a range-Doppler map to characterize a cell as indicating the presence or absence of a target.

[0067] Unless otherwise defined, all technical and / or scientific terms used in this document have the meaning as generally understood by those skilled in the art(s) to which this disclosure pertains. Methods and / or materials similar or equivalent to those described herein may be used to carry out and / or test the embodiments of this disclosure, and exemplary methods and / or materials are described below. In connection with the exemplary embodiments described below, materials, methods, and examples are illustrative and are not intended to be limiting.

[0068] Some embodiments of the present disclosure are implemented as systems, methods, or computer program products. For example, some embodiments of the present disclosure may take the form of entirely hardware embodiments, entirely software embodiments (including firmware, resident software, microcode, etc.), or embodiments combining software and hardware modes, all of which may generally be referred to herein as “circuits,” “modules,” and / or “systems.”

[0069] An embodiment of the method and / or system of some embodiments of the present disclosure may include performing and / or completing selected tasks manually, automatically, or in combination thereof. According to an actual device and / or equipment of some embodiments of the method and / or system of the present disclosure, various selected tasks may be implemented by hardware, by software, by firmware, and / or a combination thereof, for example, using an operating system.

[0070] For example, hardware for performing selected tasks according to some embodiments of the present disclosure may be implemented as a chip or circuit. As software, selected tasks according to some embodiments of the present disclosure may be implemented, for example, by using any suitable operating system, as a plurality of software instructions are executed by a computing device.

[0071] In some embodiments, one or more tasks according to some exemplary embodiments of the method and / or system as described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes volatile memory for storing instructions and / or data and / or non-volatile storage for storing instructions and / or data, for example. Optionally, a network connection is also provided. User interface(s), for example, display(s) and / or user input device(s) are optionally provided.

[0072] Some embodiments of the present disclosure may be described below with reference to flowcharts and / or block diagrams. For example, exemplary methods and / or devices (systems) and / or computer program products according to embodiments of the present disclosure are illustrated. It will be understood that each step of a flowchart and / or a block of a block diagram and / or combinations of steps of a flowchart and / or blocks of a block diagram may be implemented by computer program instructions. Such computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine such that instructions executed through the processor of the computer or other programmable data processing device create means for implementing the functions / operations specified in the flowchart steps and / or block diagram blocks or blocks.

[0073] These computer program instructions may also be stored on a computer-readable medium capable of instructing a computer, other programmable data processing device, or other device (e.g., in memory, local and / or hosted in the cloud) to function in a specific manner, so that the instructions stored on the computer-readable medium can be used to produce a manufactured article comprising instructions that implement a function / operation specified in a flowchart and / or block diagram blocks or blocks.

[0074] Computer program instructions are also executed by one or more computing devices so that a series of work steps are performed, for example, on computing devices, other programmable devices and / or other devices, to generate a computer-implemented process, so that the instructions being executed provide a process for implementing the functions / operations specified in the flowchart and / or block diagram blocks or blocks.

[0075] Some of the methods described herein are generally designed for computer-based use only and may be impossible and / or impractical for human experts to perform purely by hand. Human experts who wish to perform similar tasks by hand may be expected to use various methods that utilize expert knowledge and / or the pattern recognition capabilities of the human brain, for example, which could potentially be more efficient than going through the steps of the methods described herein by hand. Brief explanation of the drawing

[0077] To better understand the subject matter disclosed herein and to illustrate how it can be practically implemented, embodiments will now be described merely as non-limiting examples with reference to the following attached drawings. FIG. 1 is a simplified schematic diagram of a radar system according to some embodiments of the present disclosure. FIG. 2 is a simplified schematic plot of radar transmission according to some embodiments of the present disclosure. FIG. 3 is a simplified schematic plot of radar transmission and detection for a plurality of dwells according to some embodiments of the present disclosure. FIG. 4 is a target detection method according to some embodiments of the present disclosure. FIGS. 5a through 5c are simplified schematic range-pulse maps according to some embodiments of the present disclosure. Figure 6a is a simplified schematic diagram of a range-Doppler map. FIG. 6b is a simplified schematic diagram of a multiple PRI range-Doppler map according to some embodiments of the present disclosure. FIGS. 7a and 7b illustrate a flowchart of a target detection method according to some embodiments of the present disclosure. FIG. 8 is a plot of a clutter frequency spectrum according to some embodiments of the present disclosure. Specific details for implementing the invention

[0078] The present disclosure relates, in some embodiments, to radar signal processing, and more specifically, but non-exclusively, to radar signal processing for reducing clutter spectrum in radar data.

[0079] outline

[0080] Extensive aspects of some embodiments of the present disclosure relate to combining pulse-Doppler radar data acquired in response to a group of emitted electromagnetic (EM) radiation pulses, wherein the pulse groups have different pulse repetition intervals (PRIs) and the combining is performed without phase correction. In some embodiments, a train of EM radiation pulses (referred to herein as "burst") is emitted, each burst comprising a plurality of dwells having different PRIs. Corresponding radar data for the burst (referred to herein as "burst data") comprises the measured reflections of these EM radiation pulses. Different PRIs potentially enable ambiguity resolution (of target range and / or velocity) and / or prevention of blind zones (ranges corresponding to times when the system is transmitting and cannot receive) in the acquired data.

[0081] Generally, in pulse-Doppler radar, time-domain radar data (measured reflections of emitted pulses) for individual dwells are coherently integrated to provide frequency-domain data used to determine velocity by calculating the Doppler shift. Typically, time-domain radar data acquired for different dwells is incoherent, and this incoherence is associated with one or more different PRIs introducing, for example, new timing intervals (phase resets between PRIs), target movement, and sampling. Therefore, individual dwell data are typically processed separately to allow for coherent integration.

[0082] One aspect of some embodiments of the present disclosure relates to combining dwell data in the time domain as opposed to the frequency domain, which effectively increases the observation time and provides increased frequency resolution when converting to the frequency domain.

[0083] A potential benefit of increasing frequency resolution is the reduction of clutter spectral width. Radar measurement signals typically contain a portion of the signal referred to as clutter, which is generated by stationary background scatterers such as the ground, trees, leaves, and buildings. Reducing the clutter spectral width can prevent the overlap between the Doppler frequency of a slow-moving target and the clutter spectrum; otherwise, its identification would be hindered by the clutter signal.

[0084] One aspect of some embodiments of the present disclosure relates to generating a range-Doppler map for a burst of pulse-Doppler radar data (as opposed to generating multiple range-Doppler maps corresponding to multiple dwells, e.g.). The burst range-Doppler map is generated from a burst range-gate (RG) pulse map (PM). Received radar pulse reflection measurement burst data is processed to generate multiple dwell RGPMs. Subsequently, the range gates of the burst RGPM maps are each generated by concatenating data from the corresponding range gates of the multiple dwell RGPMs.

[0085] The pulse reflections from the target at different dwells are located at different range gates (of different dwells) and have different Doppler phases (2πfdt) associated with the time delay between dwells. However, in some embodiments, phase correction is not performed when combining dwell data. This is based on the assumption that the clutter is stationary and therefore the clutter signal has a zero Doppler shift and the same phase at all dwells. This assumption allows for the combination of dwell data before converting to the frequency domain for target identification. This enables the identification of a target that provides a reflection with sufficient signal power to be identified at a single dwell against background thermal noise, but also enables identification against background clutter even when the signal power is not sufficiently high.

[0086] In some embodiments, for example, when a target provides a reflection wave sufficiently strong against thermal noise, if the target is identified in the beam coverage area using time-domain combined dwell data, the target range and / or velocity can then be determined using the coherent integration of radar data from a single dwell.

[0087] In some embodiments, even if a target is identified using data from a single dwell, the dwell itself may not be known. In some embodiments, an additional burst, referred to herein as a "verification" burst, is emitted, for example, having a PRI different from that of the original burst. Here, one or more dwells (e.g., all dwells) within the verification burst may have a PRI different from that of all dwells in the initial burst. The verification burst may have the same number of dwells or a different number of dwells as the initial burst. Subsequently, radar data acquired in association with the verification burst may be used to resolve ambiguities in the range and / or Doppler frequency of a target if the target is found in the data of the PRI of the first burst and the data of the PRI of the second burst (where the PRIs are different). In some embodiments, ambiguity resolution may use data from more than two dwells and / or more than two bursts.

[0088] The processing of radar signals described herein may be used, for example, in surveillance and / or tracking radar or ultrasonic systems.

[0089] Before describing at least one embodiment of the present invention in detail, it should be understood that the present invention is not necessarily limited to the application thereof to details of the configuration and arrangement of components and / or methods presented in the following description and / or illustrated in the drawings and / or embodiments. Other embodiments of the present invention may be possible or may be implemented or carried out in various ways.

[0090] FIG. 1 is a simplified schematic diagram of a radar system (100) according to some embodiments of the present disclosure.

[0091] In some embodiments, the system (100) includes a transmitter (102) connected to a transmission antenna (104) and a receiver (108) connected to a receiving antenna (110).

[0092] The transmitter (102) can transmit a sequence of electromagnetic (EM) signals characterized by its PRF (1 / PRI) value through the transmission antenna (104).

[0093] The transmitted EM signal(s) (112) may reach an object (106) that reflects at least a portion of the incident EM signal power, and the echo (114) of the transmitted signal (112) returns to a receiver (108) through a receiving antenna (110). In some embodiments, the transmitting and receiving antennas (104, 110) are each implemented by the same physical device.

[0094] The system (100) may include a processing and memory circuit (PMC) (116) configured to control the operation of a transmitter (102) and a receiver (108) and / or process and / or store data transmitted to and / or received from there. The PMC (116) may generate control signal(s) and transmit them to the transmitter (102). The PMC (116) may process the received data to identify and / or characterize object(s) (106) (e.g., according to one or more features of FIG. 4 and / or FIG. 7).

[0095] Optionally, the transmitter (102) and / or receiver (108) may be configured to transmit and receive signals within a field of view (beam coverage area). The beam coverage area may be changed to scan a physical space larger than the beam coverage area. The beam coverage area may be mechanically changed by movement of the transmitter and / or receiver, executed by one or more actuators that may be controlled, for example, by the PMC (116). Additionally or alternatively, if the direction of the emitted signal can be controlled via the transmitter (102) hardware, the beam coverage area may be electronically changed.

[0096] Optionally, in some embodiments, the system (100) includes a connection to an external processing and / or storage device located, for example, in the cloud (122). Optionally, the system (100) includes a user interface for receiving control commands from a user and / or displaying data to the user. The system (100) may include a housing (120) configured to include and / or protect one or more parts of the system architecture.

[0097] The system (100) can be employed in a surveillance and / or tracking radar, and an ultrasonic system.

[0098] FIG. 2 is a simplified schematic plot of radar transmission (212) according to some embodiments of the present disclosure.

[0099] FIG. 2 illustrates a radar transmission (224) as a plot of intensity (I) over time (t) (e.g., corresponding to the signal (112) emitted by the transmitter (102) of FIG. 1). The radar transmission (224) may include a pulse train having a plurality of different pulse range intervals PRI1, PRI2, PRI3, three different pulse range intervals (PRI) are shown, which increase over time (t) along the pulse train. It should be understood that although shown as a square wave, in some embodiments, an envelope for a carrier wave is shown. Here, the pulses of the pulse train may be formed as high-frequency (e.g., GHz range) sinusoidal carrier waves modulated (e.g., by amplitude modulation) to provide the on / off pulsed envelope shown for the carrier wave. Although three PRIs with increasing PRIs along the pulse train are illustrated, it should be understood that in some embodiments, a different number of PRIs, such as three to twenty PRIs, may be used and / or the PRIs may decrease over time along the pulse train or have a different pattern from the PRIs that increase or decrease.

[0100] FIG. 3 is a simplified schematic plot of radar transmission and detection for a plurality of dwells according to some embodiments of the present disclosure.

[0101] FIG. 3 illustrates radar transmission (PRI1, PRI2) and detection (RG) for a plurality of dwells according to some embodiments of the present disclosure. PRI1 , RG PRI2 It is a simplified schematic plot of ). The time scale of the plot is the same, and the duration It is between the range gates.

[0102] Figure 3 illustrates the detection of two targets, one detected at the first RG (m=1) of the two PRI1 and PRI2, and the other detected at the third RG (m=3) of the two PRIs.

[0103] For ease of example and explanation, the exemplified PRI has a one-to-one mapping between the first four RGs, and targets are detected within these RGs.

[0104] FIG. 4 is a target detection method according to some embodiments of the present disclosure.

[0105] In 400, in some embodiments, radar data is received for a plurality of dwells, and each dwell has a different pulse repetition interval (PRI).

[0106] In 402, in some embodiments, the dwell data received in step 400 is processed to provide a range-pulse map for each dwell. Here, each range-pulse map is a matrix of data, i.e. It could be, and here l is the PRI index, n is the pulse index, and m is the RG index.

[0107] For a whole burst having L different PRI pulse trains l 0 to L-1 It can have a range between

[0108] n and m may differ for different PRI pulse trains, for example, as illustrated in Fig. 3, the RG for two different PRIs has the same duration but different PRIs. This generates data for a different number of range gates for two different PRIs.

[0109] In 404, in some embodiments, a combined range-pulse map, also referred to as a "burst range-pulse map," is generated for a plurality of dwells. Here, the burst pulse RG map is a matrix It could be, and here d is the RG index and d is the pulse index.

[0110] Generation is for each RG index d Regarding this, it may include concatenating corresponding data for each of the multiple dwell range-pulse maps.

[0111] FIGS. 5a through 5c are simplified schematic range-pulse maps according to some embodiments of the present disclosure.

[0112] FIGS. 5A and 5B illustrate a simple scenario in which the RG indices of the two dwell range-pulse maps and burst range-pulse maps correspond. FIGS. 5A and 5B illustrate map data for PRI1 and PRI2, respectively, as illustrated in FIG. 3.

[0113] In some embodiments, radar measurement data is processed upon reception (e.g., in real time) and arranged into a map. Thus, FIGS. 5a and 5b illustrate the reception of data and processing into a map for the time scale exemplified in FIG. 3. Here, four detections (pulses) occurred in the time scale and were processed into the PRI1 map of FIG. 5a, and only three occurred in the same time scale and were processed into the PRI2 map of FIG. 5b.

[0114] FIG. 5c illustrates a combined dwell range-pulse map that combines pulse data from the maps of FIG. 5a and FIG. 5b by, for example, concatenation.

[0115] Now, returning to FIG. 4, in 406, in some embodiments, the burst range-pulse map is converted into a burst range-Doppler map. For example, it is converted by applying a weighting and Fourier transform (e.g., Fast Fourier Transform (FFT)).

[0116] Figure 6a is a simplified schematic diagram of a range-Doppler map.

[0117] FIG. 6b is a simplified schematic diagram of a multiple PRI range-Doppler map according to some embodiments of the present disclosure.

[0118] FIG. 6a illustrates a range-Doppler map according to the prior art, where the map corresponds, for example, to a single dwell. FIG. 6b illustrates a burst range-pulse map, where the clutter spectrum (626) is reduced in width compared to the clutter spectrum (624) of FIG. 6b.

[0119] Now, returning to FIG. 4, at 408, one or more targets are identified using a burst range-Doppler map (e.g., according to one or more features of steps 718 to 724 of FIG. 1). Referring again to FIG. 6a and 6b, the narrowing of the clutter spectrum as illustrated means that the target (628) obscured by clutter in FIG. 6a is outside the clutter spectrum in FIG. 6b.

[0120] FIGS. 7a and 7b illustrate a flowchart of a target detection method according to some embodiments of the present disclosure.

[0121] In 700, in some embodiments, a radar pulse train is transmitted toward a beam coverage area, for example, by a transmitter (e.g., transmitter (102) of FIG. 1). The period during which the transmission is toward the beam coverage area may be referred to as "time-on-target," and the pulse train is referred to as a burst. A burst may include a plurality of pulse groups having the same PRI, each group referred to as a "dwell," as exemplified and / or described in relation to, for example, the burst (212) of FIG. 2. Here, each group has a different PRI from the other group.

[0122] In 702, in some embodiments, EM radiation reflected from a beam coverage area is measured. The EM radiation is received by one or more antennas (e.g., antenna (110) of FIG. 1) and measured by one or more EM sensors.

[0123] In 704, in some embodiments, EM sensor measurements are processed to provide dwell data for a plurality of dwells. Here, processing may include one or more of frequency down-conversion, filtering, splitting the signal into two channels called in-phase and orthogonal, demodulation (or pulse compression), and digitization (e.g., analog-to-digital conversion (ADC) of the measurement signal including sampling the analog measurement at a sampling rate). Here, the processing steps may occur in an order different from the order listed above.

[0124] For example, a narrowband signal collected at a receiver can be modeled as follows in some embodiments:

[0125] Equation 1

[0126] In the above equation, t is time, and A is the amplitude, and f c is the carrier frequency, and Φ is the phase, and N is the noise. This model is the amplitudeA The bandwidth of f c It uses the assumption that the number of digits is smaller than that.

[0127] Down-conversion to baseband is the received signal of Equation 1 Refer to the carrier signal Carrier frequency mixed with This is performed by removing, and a complex baseband representation can be produced:

[0128] Equation 2

[0129] In the above formula, is the complex envelope of the signal, and is the desired signal, is noise.

[0130] Discretization in time is a specific time complex signal It may include sampling, which generates discrete samples:

[0131] Equation 3

[0132] Data for a single dwell (also referred to here as a single "PRF") can subsequently be represented as a complex value entity:

[0133] Equation 4

[0134] In the above formula, l is the index of PRI / dwell, and is the sampling time within the dwell, and Equation 3, which can be constant within the measurement period Corresponding to It is the amplitude for the nth dwell, and is a constant phase within the measurement period, for example It can be the initial phase of the signal for the i-th dwell, where Equation 1's It can be related to, is a Doppler frequency shift introduced by the relative motion between the transmitter and the receiver, and is of Equation 1 It is sampled complex noise corresponding to.

[0135] In 706, in some embodiments, the pulse data processed for each dwell is a signal matrix It can be expressed as such, and when this matrix is ​​plotted, it is called a range-pulse map. Figures 5a and 5b illustrate an exemplary range-pulse map. Here, the x-axis is the range-gate for the dwell, and the y-axis is the pulse index for the dwell. Figures 5a and 5b show data for two emitted pulses, and, for example, Figures 5a and 5b correspond to Figure 3.

[0136] signal matrix can be provided by representing a complex value entity according to Equation 4 from the received data (e.g., generated by processing radar reflection measurements) for each dwell / PRI used. Here is a PRI index, and is the pulse number in the signal, and is a range gate, and is the sampling time of the signal of the range gate m of pulse n, and is given as follows:

[0137] Equation 5

[0138] In the above formula, is the pulse rate interval and is the duration of a single-range gate.

[0139] The range-pulse map represents the power received from each emitted pulse after processing (e.g., down-conversion, sampling, filtering) across all ranges during a coherent single dwell. The x-axis represents the range (or "fast-time") and the y-axis represents the pulse number (or "slow-time"). Signal peaks on the x-axis represent the range(s) where the target exists.

[0140] In 708, in some embodiments, the data of individual dwells is combined into a single matrix of range-pulse data for multiple dwells, for example. This single matrix may be represented as a range-pulse map for multiple dwells, for example, a burst dwell. For each range-gate of the burst range-pulse map, the generation may include the following:

[0141] In 710, a corresponding RG is identified for each dwell. In some embodiments, the range gate number and range distance for a specific dwell are determined while considering, for example, one or more of range folding, offset correction, and discretization to the range gate. Actual range For, the corresponding data for each dwell l (corresponding range-gate number Identifying the data (e.g., as described in step 712) enables a combination of time-domain pulse-range data.

[0142] Identification can be done, for example, according to Equation 6, where the range-gate number is a specific dwell and range It can be determined regarding:

[0143] Equation 6

[0144] In the above formula, is distance Defines an area of ​​interest that can be divided into sub-intervals. is the distance corresponding to each range-gate:

[0145] Equation 7

[0146] is the duration for each range-gate distance in time-domain data, and is the speed of light.

[0147] silver It is defined as the unambiguous range for the i-th PRI, and the maximum range (distance) at which a target can be located before range ambiguity occurs (ambiguity occurs, for example, when a radar signal can be confused with an echo from a subsequent pulse).

[0148] Equation 8

[0149] In the above formula, is the speed of light and silver This is the pulse repetition interval for the nth dwell.

[0150] In Equation 6 Operations are range range interval It ensures that it folds. This accounts for range ambiguity, which appears as echoes from a target beyond an unambiguous range "wrap around" the next range interval due to the periodic nature of pulse transmission. Modulo operation It helps determine the effective range of the target within a single unambiguous range interval for a given PRI. This is the actual range The range gate number corresponding to the reflected wave measured within the radar's unambiguous range Resolves ambiguity by mapping to.

[0151] Equation 6 is range folding (modulo operation), offset correction ( ), and dilution to the range gate ( While considering ) Range gate number for the target located at Calculate.

[0152] In 712, data from the corresponding RG of a dwell is concatenated to provide data for the corresponding multiple dwell (burst) RGs. Here, for each RG of the burst range-pulse map, data from the identified corresponding RGs of multiple dwells is concatenated, for example, corresponding RG vectors of different dwells are concatenated.

[0153] In 714, in some embodiments, the burst range-pulse map is converted to the frequency domain, for example, by coherent integration. For example, a matrix B g,h Each range-gate vector By applying weights and Discrete Fourier Transforms (e.g., Fast Fourier Transform (FFT)) to each range gate This is done by generating a signal spectrum for.

[0154] All range gates All combinations of spectra for are burst range-pulse maps / matrix B g,h Each range gate vector for By determining the given folded range-Doppler map (matrix It can provide ).

[0155] Equation 9

[0156]

[0157] In the above formula, is each range-gate in the contiguous range-gate vector (corresponding to pulses for different dwell times) It is the number of data cells for, is the index of the Doppler frequency, and is the number of Doppler frequencies, and is a weighting factor, and is the number of range gates in the burst range-pulse map.

[0158] In some embodiments, a weighting factor is selected to provide a desired level of spectral sidelobe. A spectral sidelobe is a location where signal power (e.g., of a detected target) leaks from a specific Doppler and a specific range gate to another Doppler location, potentially obscuring and interfering with the detection of other targets at that masked Doppler frequency. There may be a trade-off between main lobe width and sidelobe suppression. A wider main lobe has lower frequency resolution for the target but generates less leakage into the sidelobe, preventing masking at other frequencies. The weighting factor may be selected based on how important determining the accurate velocity of the target is for identifying other targets for a particular application.

[0159] A range-Doppler map of real values ​​is generated. For example, here, the index and For each pair of By setting , a K×D matrix P of real values ​​is defined.

[0160] In 716, in some embodiments, for each cell, by performing steps 718 to 722, a clutter narrow-range Doppler map of real values The target is detected in.

[0161] In 718, the background level is estimated. Here, the background level is determined for different cells and / or regions (including one or more cells) of the range-Doppler map. In some embodiments, the background level is determined by averaging the values ​​of multiple cells.

[0162] For example, for a specific cell, the background level can be determined as the average of multiple surrounding cells by averaging the values ​​of adjacent cells. Here, the cells being averaged may be immediate neighbors or a larger number of neighboring cells. The background level for a cell may include the value of the cell itself.

[0163] Here, Equation 10 determines the background level by averaging immediately adjacent cells. Provides an example for determining:

[0164] Equation 10

[0165] In 720, in some embodiments, a threshold level for a cell is determined from the background level according to system requirements. The threshold can be selected based on a desired trade-off between sensitivity and false alarm rate. Here, in some embodiments, the threshold is determined as a multiple of the background level. In some embodiments, the multiple is a constant. A lower threshold (e.g., a lower constant) is associated with higher sensitivity and a higher false alarm rate, and a higher threshold (e.g., a higher constant) is associated with lower sensitivity but a lower false alarm rate.

[0166] In 722, the cell value is compared to a threshold, and if it is higher than the threshold, the cell is characterized as containing the target.

[0167] Steps 718 through 722 can be repeated for each cell in the burst range-Doppler map.

[0168] Optionally, in some embodiments, information regarding the target is used. The information may include the presence of the target within the beam coverage area and / or an approximate range and / or velocity provided by the cell coordinates of the cell characterized as containing the target.

[0169] In some embodiments, information regarding the identified target(s) is conveyed to the user. For example, through a user interface (e.g., UI (118) of FIG. 1).

[0170] In some embodiments, once the presence of a target is established, the target range and / or velocity may be determined from the acquired burst data. For example, data for multiple dwells may be individually coherently integrated, and frequency domain data is used to characterize the range and / or velocity of the target (e.g., using conventional radar technology(s). However, this may produce ambiguous results because, if a specific dwell (e.g., due to a combination of time domain data) is unknown, the target may be detected based on data from a single dwell.

[0171] In some embodiments, an additional verification burst is subsequently transmitted, and the burst has a different PRI that may differ from the PRI of the initial burst. The dwell data of the subsequent verification burst may be used to resolve ambiguities (e.g., range and Doppler ambiguities) using the detection data from both bursts. Ambiguity resolution may be achieved by locating the target using two different PRIs (in the initial burst, the target appears to have been found in a single dwell).

[0172] The unambiguous range and Doppler of the target, for more than one PRF (e.g., PRF1, PRF2), the unambiguous range Ambiguous range interval until found ( , ) ambiguous range from dwell( It can be discovered using an unfolding process that is added multiple times to ), where:

[0173] Equation 11

[0174] Equation 12

[0175] In some embodiments, information regarding the identified target(s) is used to acquire additional data. For example, whereby, if target(s) are identified in the beam coverage area, additional radar pulses may be emitted toward the same beam coverage area. The additionally acquired radar data may then be used to provide more accurate values ​​for the range and / or velocity of the target(s) (e.g., as described with respect to verification bursts). For example, this may be done by performing coherent integration for individual dwells and then combining the dwell data in the frequency domain to find the range and velocity of the target(s), for example, according to conventional radar technology.

[0176] In 724, the system beam coverage area may be changed by moving the transmitter and / or receiver (e.g., by physically moving and / or electronically orienting them). Here, steps 700 through 722 may be repeated sequentially for different beam coverage areas to provide target scanning of the area, for example.

[0177] FIG. 8 is a plot of a clutter frequency spectrum according to some embodiments of the present disclosure.

[0178] FIG. 8 illustrates the clutter spectrum for an individual PRI range-Doppler map ("one dwell") and the clutter spectrum of a burst (including four dwells) range-Doppler map ("four dwells") generated according to the description in this document for the acquired measurements. In the plot, the power (y-axis) of the clutter spectrum is normalized to show the relative width of the spectrum.

[0179] general details

[0180] As used in this document, the term "approximately" means ±20%.

[0181] The terms "comprise," "comprising," "include," "including," and "having," as well as their conjugations, mean "includes but is not limited thereto."

[0182] The term "consisting of" means "includes and is limited thereto."

[0183] Singular forms used herein, such as "a," "an," and "the," include plural references unless otherwise clearly indicated by the context.

[0184] In this application, various quantifications and / or expressions may include the use of ranges. The form of a range should not be interpreted as an inflexible limitation on the scope of this disclosure. Accordingly, descriptions containing ranges should be deemed to specifically disclose individual numbers as well as all possible sub-ranges within said range. For example, a description of a range such as 1 to 6 should be deemed to have specifically disclosed sub-ranges such as 1 to 3, 1 to 4, 1 to 5, 2 to 4, 2 to 6, 3 to 6, etc., and individual numbers within the mentioned range and / or sub-ranges such as 1, 2, 3, 4, 5, and 6. Whenever a numerical range is indicated in this document, it means that any cited numeric number (fraction or integer) within the indicated range is included.

[0185] It may be seen that certain features described in the context of separate embodiments (e.g., for clarity) may also be provided in combination in a single embodiment. Various features of the disclosure described in the context of a single embodiment (e.g., for brevity) may also be provided separately or in any suitable sub-combination, or may be suitable for use with any other described embodiments. Features described in the context of various embodiments are not considered essential features of such embodiments unless the embodiment would not operate without such elements.

[0186] Although the present disclosure has been described in relation to specific embodiments thereof, it will be apparent to those skilled in the art that many alternatives, modifications, and variations are apparent. Accordingly, the present application is intended to encompass all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims.

[0187] All references mentioned in this specification (e.g., publications, patents, patent applications) are incorporated herein by reference in their entirety, for example, as each individual publication, patent, or patent application is individually indicated to be incorporated herein by reference. Any citation or identification of any reference in this application shall not be construed as an acknowledgment that such reference is available as prior art for the present disclosure. Additionally, any priority document(s) and / or documents related to this application (e.g., co-filed) are incorporated herein by reference in their entirety.

[0188] Where section titles are used in this document, they should not be interpreted as necessarily restrictive.

Claims

Claim 1 A pulse-Doppler radar signal processing method comprising: receiving time-domain radar data based on reflection measurements of a burst including a pulse train emitted into a beam coverage area, wherein the burst includes a plurality of dwells, each dwell including a pulse group having a different pulse repetition interval (PRI); processing the time-domain radar data to associate a range with a reflection measurement for each dwell; combining the time-domain data for the plurality of dwells, wherein the combining step includes combining reflection measurements of different dwells for a corresponding range; after the combining step, converting the time-domain data for the plurality of dwells to generate frequency-domain burst data; and evaluating the frequency-domain burst data to establish the presence of one or more targets within the beam coverage area. Claim 2 A pulse-Doppler radar signal processing method according to claim 1, wherein the time domain data for the plurality of dwells is incoherent. Claim 3 A pulse-Doppler radar signal processing method according to claim 1 or 2, wherein the combining step comprises identifying a corresponding range gate in a different dwell and combining measurement data of the different dwell with respect to the corresponding range gate. Claim 4 A pulse-Doppler radar signal processing method according to paragraph 3, wherein the processing step comprises generating a plurality of range gate vectors for each dwell, each containing a reflection measurement value for a specific range gate. Claim 5 A pulse-Doppler radar signal processing method according to claim 4, wherein the combining step comprises: identifying corresponding range gate vectors in different dwells; and concatenating data of the corresponding range gate vectors to provide a plurality of range gate vectors for the burst. Claim 6 A pulse-Doppler radar signal processing method according to claim 5, wherein for each of the dwells, the plurality of range gate vectors provide a range-pulse map, and the processing step provides a plurality of range-pulse maps, a range-pulse map for each dwell. Claim 7 A pulse-Doppler radar signal processing method according to claim 6, wherein the plurality of range gate vectors for the burst provide a burst range-pulse map. Claim 8 A pulse-Doppler radar signal processing method according to any one of claims 5 to 7, wherein the transforming step comprises generating a plurality of range-Doppler vectors by applying a Fourier transform to each of the plurality of range gate vectors for the burst. Claim 9 A pulse-Doppler radar signal processing method according to claim 8, wherein the Fourier transform is a Fast Fourier Transform (FFT). Claim 10 A pulse-Doppler radar signal processing method according to claim 8 or 9, wherein the converting step follows weighting. Claim 11 In claim 10, the above-mentioned converting step provides a burst range-Doppler map, a pulse-Doppler radar signal processing method. Claim 12 A pulse-Doppler radar signal processing method according to any one of claims 9 to 11, wherein the evaluating step comprises evaluating the range-Doppler map to characterize the cell as indicating the presence or absence of a target. Claim 13 A pulse-Doppler radar signal processing method according to any one of claims 1 to 12, comprising the step of emitting the pulse train during a time-on-target associated with a burst, wherein each pulse comprises electromagnetic (EM) radiation; and the receiving step comprising measuring the reflection of the signal from the beam coverage area. Claim 14 A pulse-Doppler radar signal processing method according to any one of claims 1 to 13, wherein the receiving step comprises one or more of down-conversion, sampling, and filtering of the measurement value of the reflection to provide the time domain radar data. Claim 15 A pulse-Doppler radar signal processing method according to any one of claims 5 to 14, wherein the identifying step comprises determining a corresponding range-gate number for each dwell for an actual range distance. Claim 16 A pulse-Doppler radar signal processing method according to any one of claims 12 to 15, wherein the evaluating step comprises comparing each cell of the range-Doppler map with a threshold value. Claim 17 A pulse-Doppler radar signal processing method according to claim 16, comprising the step of determining a background level for each cell of the range-Doppler map, wherein the threshold value is determined from the background level. Claim 18 A pulse-Doppler radar signal processing method according to claim 17, wherein the step of determining the background level includes averaging adjacent cell values. Claim 19 A pulse-Doppler radar signal processing method according to claim 18, wherein the threshold value is a value multiplied by a constant selected to provide the sensitivity and false alarm rate required for the background level. Claim 20 A pulse-Doppler radar signal processing method according to any one of claims 1 to 19, comprising the step of receiving verification time-domain radar data based on reflection measurements of a verification burst including a verification pulse train emitted into the beam coverage area, wherein the verification burst includes a plurality of dwells, and each dwell includes a pulse group having a different PRI. Claim 21 A pulse-Doppler radar signal processing method according to claim 20, wherein the dwell of the verification burst has a different PRI for the dwell of the burst. Claim 22 A pulse-Doppler radar signal processing method according to claim 20 or 21, comprising the step of determining the range and velocity of one or more targets by using the time domain radar data and the verification time domain radar data to resolve ambiguity in the range and / or velocity of one or more targets. Claim 23 A pulse-Doppler radar signal processing method comprising, in any one of claims 1 to 22, changing the beam coverage area; and repeating the method. Claim 24 A pulse-Doppler system comprising: a radar transmitter configured to emit a burst containing a train of electromagnetic (EM) radiation radar pulses into a beam coverage area—said that the burst comprises a sequential series of dwells having different pulse repetition intervals (PRI); a radar receiver configured to detect the reflection of the emitted pulses to measure the reflection timing relative to the emission timing of the radar pulses and to generate burst data; and a processor, wherein the processor comprises Processing the above time-domain radar data to correlate the range and reflection measurements for each dwell; Combining time domain data for multiple dwells—the combining includes combining reflection measurements of different dwells for corresponding ranges—; After the time domain data for the plurality of dwells is combined, the time domain data for the plurality of dwells is converted to generate frequency domain burst data; A pulse-Doppler system configured to evaluate the above frequency domain burst data to identify the range and velocity of any target within the beam coverage area. Claim 25 A pulse-Doppler radar signal processing method comprising: receiving burst data, wherein the burst data comprises dwell data of more than one dwell, and each dwell has a different pulse repetition interval (PRI); processing the burst data to provide a corresponding dwell range-pulse map for each dwell; and for each range-gate of the burst range-gate map, Identifying a corresponding range-gate for each of the above-mentioned excess dwells; and A step of generating a burst range-pulse map comprising concatenating data from the corresponding range-gates of the one or more dwells to provide range-gate data for the corresponding range-gates of the burst range-gate map; A step of converting the above burst range-gate pulse map into a burst range-Doppler map; and A pulse-Doppler radar signal processing method comprising the step of evaluating the range-Doppler map to characterize a cell as indicating the presence or absence of a target. Claim 26 A pulse-Doppler system comprising: a radar transmitter configured to emit a burst comprising a series of electromagnetic (EM) radar pulses, each comprising a sequential series of dwells having different pulse repetition intervals (PRI); a radar receiver configured to detect the reflection of the emitted pulses to measure the reflection timing relative to the emission timing of the radar pulses and to generate burst data; and a processor, wherein the processor comprises Receiving burst data from the above radar receiver; Processing the burst data to provide a corresponding dwell range-pulse map for each dwell; For each range gate of the above burst range-gate map, Identifying a corresponding range-gate for each of the above-mentioned excess dwells; and Generating a burst range-pulse map by concatenating data from the corresponding range-gates of the one or more dwells to provide range-gate data for the corresponding range-gates of the burst range-gate map; Converting the above burst range-pulse map into a burst range-Doppler map; and A pulse-Doppler system configured to perform an evaluation of the range-Doppler map to characterize a cell as indicating the presence or absence of a target.

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