Research On Anti-Jamming Technology Among Distributed Radar Stations

Making use of distributed launch radar stations as its irradiation sources, and receiving the echo by its radar array, the distributional receiving coherent radar realizes the high-resolution imaging of the target and accurate parameter measurement. The anti-jamming radar station’s communication guarantees for the real-time collaborative work of the distributional receiving coherent radar. Therefore, using the spread spectrum technology of multi-carrier and FFH-OFDM as an entry point, this paper studies the anti-jamming technology of radar inter-station communication from three respects: anti-jamming communication technology, signal detection technology of receivers, and interference suppression technology. Mainly considering the effects of multi-path fading, narrow-band jamming, and single-tone jamming on the complex communication between radar stations, this paper studies several aspects as follows:First, Fast Frequency Hopping Orthogonal Frequency Division Multiple Access(FFH-OFDM) is used to improve the traditional Multiple Carrier Direct Sequence Code Division Multiple Access(MC-DS-CDMA), leading to a type of improved spread spectrum technology of multi-carrier. The improved technology, possessing the characteristics of both FFH-OFDM and MC-DS-CDMA, realizes the direct spread spectrum in the time domain, and the fast frequency hopping in the frequency domain. Thus, it has the characteristics of two-dimensional spread spectrum, and avoids the disadvantage of the traditional MC-DS-CDMA that it lacks the diversity of frequency domain. The anti-jamming performance of this improved technology is analyzed both theoretically and simulatedly.Second, three sorts of signal detection algorithm of the FFH-OFDM receiver are studied around the improved technology, especially the signal detection algorithm based on QR decomposition. This paper improves the traditional signal detection algorithm based on QR decomposition, puts forward a new type of signal detection algorithm which is fit for the improved technology, and verifies the performance of this signal detection algorithm in the environment of distributed radar inter-station communication. The algorithm implements the QR decomposition of the matrix of spreading channel by Gram-Schmidt algorithm, and reduces the error propagation through adopting the iterative method to implement the layered detection of the signal. The usage of this signal detection algorithm achieves the dehopping of FFH and the despreading of the spread spectrum in the time domain simultaneously.Last, this paper studies the interference suppression technology in regard to the improved algorithm above, from the aspects of the interference detection and the interference suppression. The performances of three sorts of interference detection algorithm, CME, FCME, and the self-adaptive multi-thresholding algorithm, are analyzed respectively. Because the improved spread spectrum technology implements the fast frequency hopping by FFH-OFDM, the transmission signal is able to traverse all the sub-carriers in a single symbol period, and thus the narrow-band jamming and single-tone jamming can only interfere with some partial band of the transmission signal. Therefore, the interference detection algorithm is used in this paper to detect the interfered part of the band, in order to limit the amplitude of it and reduce the energy of the interference signal, and consequently suppress the interference.