Multiple-input multiple-output (MIMO) radar equipped with a frequency diverse array (FDA) can produce a range-dependent beampattern and increase the degrees-of-freedom of the antenna array. In this paper, a new method of designing the MIMO radar beampattern with sparse frequency waveforms is proposed for the FDA, which randomly samples multiple distance points such that the MIMO radar beampattern with the both sparse frequency spectrum and constant modulus constraints are realized by the proposed beampattern design framework. The main steps are as follows. We first obtain the covariance matrix of the transmitted signal by a given ideal beampattern, and formulate the problem of designing the realizable beampattern as a nonconvex optimization problem, which includes the constraints of the both constant modulus of transmitted signals and sparse frequency spectrum. Then, a cyclic optimization algorithm is proposed, which guarantees the monotonic decrease of the objective function as the algorithm proceeds. The simulation results illustrate that the proposed method can achieve smaller errors than the traditional method, which does not consider the frequency diversity.

Beampattern Optimization for Frequency Diverse Array With Sparse Frequency Waveforms

Based on the orthogonal frequency division multiplexing (OFDM) technique, an intelligent waveform is designed, which is suitable for simultaneously performing data transmission and radar sensing. In view of the inherent high peak-to-mean envelope power ratio (PMERP) and poor peak-to-side-lobe ratio (PSLR) problems in the OFDM based radar and communication (RadCom) waveform design, we propose two technologies to deal with that. To be specific, we adopt Gray code technology to reduce the PMERP and simultaneously choose an optimal cyclic sequence to improve the PSLR of RadCom waveform. In our method, the optimal cyclic sequence is dynamically generated to continuously provide the best waveform according to the change of communication data. In addition, to meet the requirements of different radar detection tasks, two simple methods are utilized to adjust the bandwidth of RadCom waveform. To verify the advantages of the designed waveform, we conduct several simulation experiments to compare with some existing RadCom waveforms. The results show that our designed RadCom waveform can simultaneously achieve lower PMERP and higher PSLR. In addition, our designed RadCom waveform has a thumbtack type fuzzy function and shows the good ability to do multitarget detection.

/pdf/radar-communication-integrated-waveform-design-based-on-ofdm-kpt7hlr1sx.pdf

Radar Communication Integrated Waveform Design Based on OFDM and Circular Shift Sequence

As a new competitive technology, radar-embedded communication (REC) can achieve the covert communication while improving the spectrum utilization. The embedded communication waveform has always been the core of REC. Traditional waveform design methods use eigen-decomposition to construct REC waveforms after converting research targets. However, the constructed REC waveforms are not orthogonal, which would reduce the communication reliability. Besides, converting targets would affect the low probability of detection (LPD) performance of REC. To solve these problems, this paper proposes a new waveform design method based on singular value decomposition (SVD). We compare the proposed method with the traditional ones in terms of communication reliability, LPD performance and robustness. Analysis and simulation results show that the SVD waveform generated by the proposed method is better than the traditional REC waveforms. We also provide a method to measure the level of similarity between SVD waveform and radar waveform. Then we can adjust the similarity to control the trade-off between reliability and concealment.

A New Radar-Embedded Communication Waveform Based on Singular Value Decomposition

This paper focuses on the waveform design for a radar-embedded communication (REC) system which can achieve covert communication while improving the spectrum utilization. In order to solve the problem that the conventional embedded communication waveforms are not orthogonal, this paper proposes the orthogonal weighted-combining (OWC) strategy and the orthogonal dominant-projection (ODP) strategy. Furthermore, the OWC strategy can be broken into two strategies: constrained weighted-combining (CWC) strategy and improved weighted-combining (IWC) strategy. Theoretical analysis and simulation results have shown that these three strategies can dramatically improve communication reliability. Moreover, the performance of the strategies mentioned above has been assessed by the low probability of intercept (LPI) metric. Comparing to the traditional strategies, the IWC strategy shows better LPI performance while the CWC strategy and ODP strategy remain unchanged. Additionally, the ODP strategy can also reduce computational complexity and response delay, which is rather important in the REC system. Any of the three strategies can be selected in accordance with the needs of the application scenario.

https://www.mdpi.com/2079-9292/8/10/1107/pdf

Orthogonal Waveform Design for Radar-Embedded Communications

In order to improve the covertness of radar embedded communication based on the eigenvalue decomposition radar embedded communication waveform design scheme, a new waveform design scheme that combines the idea of shaped design is constructed. In this paper, the background and concept of radar embedded communication are introduced in detail. Three existing waveform design schemes are analyzed. Using de-correlation filter receivers, a weighted waveform design scheme for shaped non-dominant subspace feature vectors is constructed and analyzed. The communication covertness and reliability is illustrated. Both the theoretical analysis and the simulation show that this scheme improves the covertness of communication.

/pdf/a-new-shaped-waveform-design-scheme-for-radar-embedded-3udaouy1tt.pdf

A New Shaped Waveform Design Scheme for Radar Embedded Communication

According to the Tag application with function of covert communication, a method for sparse frequency waveform design based on radar-embedded communication is proposed. Firstly, sparse frequency waveforms are designed based on power spectral density fitting and quasi-Newton method. Secondly, the eigenvalue decomposition of the sparse frequency waveform sequence is used to get the dominant space. Finally the communication waveforms are designed through the projection of orthogonal pseudorandom vectors in the vertical subspace. Compared with the linear frequency modulation waveform, the sparse frequency waveform can further improve the bandwidth occupation of communication signals, thus achieving higher communication rate. A certain correlation exists between the reciprocally orthogonal communication signals samples and the sparse frequency waveform, which guarantees the low SER (signal error rate) and LPI (low probability of intercept). The simulation results verify the effectiveness of this method.

/pdf/sparse-frequency-waveform-design-for-radar-embedded-3mwuk7zddn.pdf

Chaoyun Mai

Papers

Sparse Frequency Waveform Design for Radar-Embedded Communication