US-12625246-B2 - Continuous-phase modulation based power-efficient tunable joint radar/communications system

US12625246B2US 12625246 B2US12625246 B2US 12625246B2US-12625246-B2

Abstract

Systems, methods, and computer-readable storage media for generating and utilizing radar signals with embedded data are disclosed. Data is encoded onto a CPM waveform, which is then combined with a base radar waveform to produce a radar-embedded communication (REC) waveform. Both the CPM waveform and the base radar waveform may have a continuous phase and constant envelope, resulting in the REC waveform having a continuous phase and constant envelope. The changing (e.g., on a pulse-to-pulse basis) nature of the REC waveform causes RSM of clutter which may result in residual clutter after clutter cancellation, decreasing target detection performance of the radar system. In an aspect, various parameters may be utilized to dynamically adjust the performance of the radar system for a particular operating scenario, such as to enhance radar signal processing or enhance data communication capabilities.

Inventors

Cenk Sahin
Patrick M. McCormick
Justin G. Metcalf
John Jakabosky
Shannon David Blunt
Erik S. Perrins

Assignees

UNIVERSITY OF KANSAS
GOVERNMENT OF THE UNITED STATES, AS REPRESENTED BY THE SECRETARY OF THE AIR FORCE

Dates

Publication Date: 20260512
Application Date: 20200918

Claims (20)

1 . A method for receiving data embedded in radar waveform transmission, the method comprising: receiving, by at least one processor, an input radar waveform, wherein the input radar waveform comprises an embedded communication radar waveform generated by in phase combining a continuous phase radar waveform and a continuous phase modulation (CPM) communication waveform comprising data; synchronizing, by the at least one processor, the input radar waveform to a clock associated with the at least one processor to produce a synchronized input radar waveform, the synchronizing determining a synchronization timing associated with the input radar waveform; extracting, by the at least one processor, the CPM communication waveform from the synchronized input radar waveform, wherein the extracting includes performing a de-chirp process on the synchronized input radar waveform based on the synchronization timing to extract the CPM communication waveform; and processing, by the at least one processor, the extracted CPM communication waveform to obtain the data of the CPM communication waveform.
2 . The method of claim 1 , wherein the synchronizing further comprises determining a frequency offset of the input radar waveform.
3 . The method of claim 1 , wherein extracting the CPM communication waveform from the input radar waveform comprises combining the input radar waveform with a complex conjugate of a known radar waveform.
4 . The method of claim 1 , wherein processing the extracted CPM communication waveform to obtain the data of the CPM communication waveform comprises demodulating the CPM communication waveform.
5 . The method of claim 1 , wherein the extracting further comprises applying a compensation transform to the synchronized input radar waveform, the compensation transform comprising a matched filter or a mismatched filter derived from samples of the synchronized input radar waveform, wherein the samples of the synchronized input radar waveform are sampled at one or more delays, and wherein sampled responses are collected into columns of a matrix to generate the compensation transform.
6 . A system for receiving data embedded in radar waveform transmission, the system comprising: a receiver configured to: receive an input radar waveform, wherein the input radar waveform comprises an embedded communication radar waveform generated by in phase combining a continuous phase radar waveform and a continuous phase modulation (CPM) communication waveform comprising data; synchronize the input radar waveform to a clock associated with at least one processor to produce a synchronized input radar waveform, wherein to synchronize the input radar waveform includes to determine a synchronization timing associated with the input radar waveform; extract the CPM communication waveform from the synchronized input radar waveform based on a known radar waveform associated with the continuous phase radar waveform, wherein to extract includes to perform a de-chirp process on the synchronized input radar waveform based on the synchronization timing to extract the CPM communication waveform; and process the extracted CPM communication waveform to obtain the data of the CPM communication waveform; and a memory communicatively coupled to the at least one processor.
7 . The system of claim 6 , wherein the synchronizing further comprises determining a frequency offset of the input radar waveform.
8 . The system of claim 6 , wherein extracting the CPM communication waveform from the input radar waveform comprises combining the input radar waveform with a complex conjugate of the known radar waveform.
9 . The system of claim 6 , wherein processing the extracted CPM communication waveform to obtain the data of the CPM communication waveform comprises demodulating the CPM communication waveform.
10 . The system of claim 6 , wherein the receiver is integrated in a vehicle.
11 . A non-transitory computer-readable storage medium storing instructions that, when executed by one or more processors, cause the one or more processors to perform operations for receiving data embedded in radar waveform transmission, the operations comprising: receiving, by at least one processor, an input radar waveform, wherein the input radar waveform comprises an embedded communication radar waveform generated by in phase combining a continuous phase radar waveform and a continuous phase modulation (CPM) communication waveform comprising data; synchronizing, by the at least one processor, the input radar waveform to a clock associated with the at least one processor to produce a synchronized input radar waveform, the synchronizing determining a synchronization timing associated with the input radar waveform; extracting, by the at least one processor, the CPM communication waveform from the synchronized input radar waveform based on a known radar waveform associated with the continuous phase radar waveform, wherein the extracting includes performing a de-chirp process on the synchronized input radar waveform based on the synchronization timing to extract the CPM communication waveform; and processing, by the at least one processor, the extracted CPM communication waveform to obtain the data of the CPM communication waveform.
12 . The non-transitory computer-readable storage medium of claim 11 , wherein the synchronizing further comprises determining a frequency offset of the input radar waveform.
13 . The non-transitory computer-readable storage medium of claim 11 , wherein extracting the CPM communication waveform from the input radar waveform comprises combining the input radar waveform with a complex conjugate of the known radar waveform.
14 . The non-transitory computer-readable storage medium of claim 11 , wherein processing the extracted CPM communication waveform to obtain the data of the CPM communication waveform comprises demodulating the CPM communication waveform.
15 . A method for performing radar detection using radar-communication waveforms, the method comprising: receiving, by at least one processor, an input radar waveform, wherein the input radar waveform comprises an embedded communication radar waveform generated by in phase combining a continuous phase radar waveform and a continuous phase modulation (CPM) communication waveform comprising data; synchronizing, by the at least one processor, the input radar waveform to a clock associated with the at least one processor to produce a synchronized input radar waveform, the synchronizing determining a synchronization timing associated with the input radar waveform; multiplying, by the at least one processor, the synchronized input radar waveform with a reference signal to produce a modified input radar waveform, wherein the multiplying is performed based on the synchronization timing to produce the modified input radar waveform; generating, by the at least one processor, a first signal corresponding to a real component of the modified input radar waveform and a second signal corresponding to an imaginary component of the modified input radar waveform; performing, by the at least one processor, radar monitoring based on an input radar waveform and a compensation transform derived from samples of the first signal and the second signal; and outputting, by the at least one processor, radar data based on the radar monitoring.
16 . The method of claim 15 , further comprising: sampling, by the at least one processor, the first signal and the second signal to generate the samples of the first signal and the second signal; and generating, by the at least one processor, the compensation transform based on the samples of the first signal and the second signal.
17 . The method of claim 15 , further comprising: band pass filtering the modified input radar waveform; generating a complex lowpass equivalent signal based on the modified input radar waveform subsequent to performing the band pass filtering, wherein the complex lowpass equivalent signal comprises the real component of the modified input radar waveform and the imaginary component of the modified input radar waveform; and performing, by the at least one processor, lowpass filtering of the real component and the imaginary component to produce the first signal and the second signal.
18 . The method of claim 15 , wherein the first signal and the second signal are sampled at one or more delays, and wherein sampled responses are collected into columns of a matrix to generate the compensation transform.
19 . The method of claim 15 , wherein generating the compensation transform comprises: determining a first mismatched filter for an alignment range; and deriving one or more additional range-dependent mismatched filters for one or more other ranges by: time shifting the first mismatched filter by one or more time shifts to produce one or more time shifted filters; and multiplying each of the one or more time shifted filters by a value corresponding to a relative range difference between the alignment range and a range of interest corresponding to a particular one of the one or more time shifted filters.
20 . The method of claim 15 , further comprising: extracting, by the at least one processor, the CPM communication waveform from the synchronized input radar waveform; and processing, by the at least one processor, the extracted CPM communication waveform to obtain the data of the CPM communication waveform.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a national phase application under 35 U.S.C. § 371 of International Application No. PCT/IB2020/058731 filed Sep. 18, 2020, which claims priority to U.S. Provisional Patent Application No. 62/903,615 filed Sep. 20, 2019. The entire contents of each of the above-referenced disclosures is specifically incorporated by reference herein without disclaimer. GOVERNMENT INTEREST This invention was made with government support under Grant Nos. FA9550-17-D-0001 and FA8650-14-D-1722 awarded by the United States Air Force. The government has certain rights in the invention. TECHNICAL FIELD The present disclosure is related to the design and processing of joint radar and communications waveforms. More specifically, the present disclosure is related to improved techniques for both embedding of communication symbols into physical radar waveforms and the processing of said waveforms. BACKGROUND The radio spectrum is a fixed resource with an exponentially increasing demand from commercial communication applications. To meet the increased demand for commercial communication applications, the radar spectrum has been eroded, which has created additional strain on defense applications that must already operate in congested and contested environments. As such, improving spectral efficiency (e.g., dynamic spectrum access) or developing methods to share spectrum between multiple functions (e.g., radar and communication sharing spectrum) has been the subject of ongoing research. Generally speaking, spectrum sharing can take two forms: cohabitation or co-design. The former tends primarily to address the interference that separately operated systems could cause to one another and the latter involves cooperative control within the same system. At first glance, communications and radar may appear to be similar. However, successful communication requires maximizing the entropy embedded in the transmitted waveform while radar waveforms require coherent, restrictive forms to maximize detection performance. Thus, a dual-function system that performs radar and communication simultaneously involves a performance trade-off between these functions. Approaches that utilize time-sharing or frequency sub-banding may be suitable for some applications; however, the notion of radar/communication spectrum sharing necessitates the use of some manner of waveform diversity. As a general principle, waveform diversity involves the exploitation of the available time, frequency, coding, spatial, and polarization degrees-of-freedom. For example, other work has examined the embedding of low probability of intercept (LPI) communications into radar clutter, using a small set of different radar waveforms where each represents a different communication symbol, modulating a communication signal onto the spatial sidelobes of a radar beam, using fourth Generation (4G) communication signals to also serve as short-range radar emissions for automotive applications, dual radar/communication emissions from a common transmit aperture, tandem hopping of communications within spectral gaps of the radar emission, and phase-modulating a linear FM (LFM) waveform. As is the case with most radar applications, some communication systems require spectrally contained symbols with high power efficiency (e.g., aeronautical telemetry). To meet this need, a family of constant envelope signaling schemes was developed, collectively denoted as continuous-phase modulation (CPM). The continuous phase feature of CPM signals leads to high spectral efficiency while the constant envelope feature translates to robustness against the distortion introduced by non-linear components in the transmitter (e.g., the power amplifier). As a result, the transmitter power amplifier can be operated in saturation such that the available power is efficiently converted into radiated power. Due to its favorable features, CPM is used in the Bluetooth wireless standard and two variants of shaped-offset quadrature phase-shift keying (SOQPSK) modulation, a type of CPM, are standardized for military applications (SOQPSK-MIL) and aeronautical telemetry (SOQPSK-TG). Maintaining both power efficiency and spectral efficiency is of great interest for radar systems to maximize “energy on target” and to limit the spectral roll-off for sufficient spectral containment. A CPM-based framework was utilized to implement arbitrary polyphase radar codes as physically realizable continuous frequency modulated (FM) waveforms. The polyphase-coded FM (PCFM) implementation resulted in significantly superior spectral containment compared to derivative phase-shift keying (DPSK) and minimum-shift keying (MSK) implementations. It was subsequently demonstrated that the resulting FM waveform can be optimized via a determination of an underlying optimal code. Additionally, the notion of pulse agility (or waveform agility), in which the radar waveform is allowed to change on a pulse-to-