Research On The Design Of Integrated Radar And Communication Signal Based On OFDM Technique

Nowadays weapon platform faces the growing threat and increasing complicated electromagnetic environment. To deal with this situation, weapon platform must be equipped with more and more electronic devices, which will undoubtedly affect its mobility and bring the problem of electromagnetic compatibility leading to the decrease of warfare capability. To decrease the volume and electromagnetic interference of weapon platform, an effective way is to implement the integration of electronic equipment. As two important parts of weapon platform, the integration of radar and communication will be greatly significant.To realize the integration of radar and communication more effectively, the concept of signal energy sharing was proposed. The integrated radar and communication system based on the principle of signal energy sharing is one that can not only detect the targets but also communicate with others with a high data rate by using the common resources.In this article, based on the principle of signal energy sharing and the Orthogonal Frequency Division Multiplexing technique(OFDM), the author does abundant work about signal sharing of the integrated radar and communication. The major work and innovation mainly include the following several aspects:1) The differences and similarities between the radar and communication system are analyzed. The resource restrains in the integrated radar and communication system are also analyzed from the perspective of system. Then the evaluation and design criteria of the radar and communication sharing signal are established.2) By analyzing the shortcomings of existing ways realizing the integrated radar and communication based on OFDM and pseudo-random sequences, a new sharing signal, namely MC-CDMA(Multicarrier CDMA), is designed by combining the OFDM and spread spectrum technique. The use of spread spectrum technique makes the sharing signal have lower intercept probability, stronger communication confidentiality and possess potential multiple access capability. At the same time, the peak to average power ratio of the designed sharing signal is lower 4 d B than the existing OFDM sharing signal.3) The ambiguity function of MC-CDMA sharing signal and LFM signal are analyzed, the former has thumbtack ambiguity function, while the distance and Doppler sidelobe of which is higher. Aiming at this problem, a algorithm for radar signal processing based on the modulation symbols is introduced by utilizing the special time and frequency domain structure of MC-CDMA signal, which is then improved by using the sidelobe suppression technique. Weighting with window function makes the distance sidelobe of MC-CDMA signal reduced by 47 d B. In addition, the algorithm can thoroughly eliminate the effect of modulation information on target detection. Compared with the traditional processing method based on correlation, this algorithm can make the distance sidelobe reduced by 45 d B.4) For that the peak to average power ratio of OFDM signal is relatively large and the intercarrier interference of CE-OFDM(Constant Envelope OFDM) signal needs to be reduced, another new sharing signal, namely CE-MSK-OFDM shared signal, is designed by combining constant envelope modulation technique with fast roll off spectrum characteristic of MSK signal. The signal can make the peak to average power ratio of OFDM signal reduced to 0 d B and effectively decrease the intercarrier interference of CE-OFDM signal.5) The comparisons between the ambiguity function of CE-MSK-OFDM sharing signal and OFDM radar signal modulated with ideal phase code indicate that CE-MSK-OFDM sharing signal is better and that the modulated communication information almost has no negative impact on radar performance of the integrated system. In addition, to facilitate the design of system parameters, the effects of various parameters on the ambiguity function of CE-MSK-OFDM sharing signal are also analyzed by simulation.6) From the perspective of system, the system waveform parameters, working mode and link maintenance are designed and analyzed. Then the frame of integrated radar and communication system based on MC-CDMA and CE-MSK-OFDM are constructed, the radar and communication performance of which two system are also simulated. Simulation results show that the average throughput rate of the link connectivity region is above 2 Mbps, which can be more higher with good beam control. It is obvious that the two sharing signal designed above can meet the requirements of battle application well.