Research On Key Problems In Efficient Modulation Radar-Communication Integration System

The traditional weapon platform, which is equipped with single functional system, had to endure much electromagnetic threat from different aerial battle platforms and of different modalities. The operational performance and the synthetical survivability of the platform are both facing serious challenge. In the thesis, we discuss the efficient modulation radar-communication integration system by adopting the advanced modulation technique and signal processing algorithms to overcome the bandwidth limition, achieve the high data rate, improve the target detection performance, and realize the miniaturization and multi-functions of the system. Combining the technical characteristics of traditional radar system and efficient modulation communication system, the design scheme of dual frequency electronic integration system is mainly proposed. In order to adapt to the different scenarios, some improvement for the system are made. The design scheme of an Extended Binary Phase Shift Keying (EBSPK)/M-ary Position Phase Shift Keying (MPPSK) MODEM based transceiver for radar-communications is presented too. The issues of range and velocity measurements, the different type of target detection and tracking, digital data transmission of the system are mainly investigated. Then we discuss the following aspects:1. For dual-frequency continuous wave (CW) radar, ambiguity may occur in ranging measurement. In order to solve this problem and integrate radar and communication system, a new dual-frequency electronic integration system based on EBPSK-MODEM is put forward. Several working modes and the power allocation problem of the system are introduced. The effects of modulation parameters and dual-frequency difference on distance and accuracy measurement and communication performance are discussed. Simulation results demonstrate that the integration system can output a radar measurement with both high-precision and wide-range. The integration system can also be used as spectra efficient digital communication by utilizing the advance of EBPSK modulator and the impacting filter aided demodulator. The system could entry into different modes to accomplish particular tasks.2. The design scheme of EBSPK/MPPSK MODEM based transceiver for Radar-Communications which is suitable for simultaneously performing both data transmission and range measurement is proposed. In particular, operating principles of EBSPK/MPPSK transmitter and receiver are introduced. Also, Constant False Alarm Rate (CFAR) target detection performances of the transceiver are discussed when target velocity and time delay take different values. Simulation results demonstrate that, the SNR improvement of the transceiver is better than that of the Linear Frequency Modulation (LFM) system when the relative value of Doppler shift is higher than5×10-7. At the target velocity v=2000m/s, for the non-fluctuation and Swerlingl targets, the SNR performance of EBPSK transceiver is 3dB better than that of the LFM system. At the echo delays τ=0.5μs, the SNR performance of EBPSK transceiver is improved by approximately 2.5dB. CFAR target decetion probability of MPPSK signal is worse than EBPSK signal for ranging applications, but the spectral utilization and data rate for communication operation is higher.3. The average ambiguity function (AAF) of EBPSK pulse signal is deduced. Several Swerling targets decetion probabilities of this signal are analyzed. Furthermore, a new method of velocity measurement based on modified Chinese Remainder Theorem (CRT) algorithm in dual-frequency pulse Doppler (PD) radar is proposed. Finally, a processing algorithm that allows for estimating the velocity of multiple reflecting objects with EBPSK signals is discussed. Results indicate that the unambiguous distance of EBPSK pulse signal is limited by the number of data frames. The velocity ambiguity function is influenced by EBPSK moudulated date frame and pulse train. The dual-frequency PD radar system base on a modified CRT algorithm has the capability of wide range and high precise velocity measurement. Multiple target Doppler estimation algorithm (MTDEA) does not require any specific coding of the transmit data. This algorithm achieves a high dynamic range, limited only by the sidelobes from the Fourier transformation which can be improved with a Hamming window.4. Impulse response of range-extended target is estimated. EBPSK pulse signal is selected to approach the optimum echo signal. The mutual information between the optimum echo signal and radar target scatterer parameters is optimal. Furthmore, under the condition of known or unknown Doppler, two design algorithms of optimized SNR based EBPSK waveforms coding with peak-to-average ratio (PAR) and energy constraint are proposed, respectively. Design algorithm of optimized SNR based EBPSK cognitive waveform with low PAR constraint is presented. Finally, using the correlation of echo pulse Doppler at different sampling time, a maneuvering target decision method based on Kalman filtering is presented. Results indicate that, under the condition of unknown Doppler, range extended target detection performances of optimized waveforms are better than un-optimized waveform. The performances of optimized SNR based EBPSK cognitive waveform is improved by approximately 4dB as compared with un-optimized waveform. The maneuvering target detection performance of EBSPK transceiver for echo decision method based on Kalman filtering is improved by approximately 2.4dB as compared with the transceiver for peak decision method. In the presence of clutter, the performance of the new method is improved by approximately 4dB.5. Algorithm design problems of maneuvering target and multi extended target tracking based on EBPSK transceiver are discussed. The Doppler component of the measurements may be used in combination with the target position measurement as an additional discriminant of measurement origin. An efficient Doppler data association (DDA) method which utilises both position and Doppler measurements for multi-target tracking is developed. The proposed DDA method is demonstrated using the linear multi-target integrated probabilistic data association algorithm (LMIPDA) in multi-target tracking scenario. Trackers modified by this method can provide a substantial reduction in the number of confirmed false tracks, and, in a lower computational load in the presence of clutter and multiple targets. LMIPDA algorithms that use position-only measurements confirm a considerable number of false tracks, while LMIPDA-DDA that incorporate Doppler measurements using the DDA method, does not. Tracking mean square error (MSE) of LMIPDA-DDA method is one order smaller than traditional filtering method, is half of LMIPDA method.