Optimum Detection Of Anti-Radiation Missile

Anti-radiation Missile (ARM) is a fatal threat to modern radar systems. It has shown great power in several recent regional conflicts. Developing counter-Anti-radiation missile techniques and preventing radar systems from being attacked by ARM is one of the key factors of leading to victory or defeat.The research work of this thesis is supported by the National Defence Foundation. Its main task is to develop practical algorithms for ARM launching detection. ARM launching warning is one of the effective measures for counter-Anti-radiation Missile. The optimum detectors with realization considerations are proposed in the thesis. The detectors are more suitable for pulsed tracking radars to detect an incoming Anti-radiation Missile at the first fire stage while the radar is in its tracking situation.ARM detection can be either made in the radar Range Gate (RG) or in an Interception Gate (IG) specially settled for ARM. Detection of ARM in RG is made by making use of the ordinary radar RG while the radar is in tracking of an aircraft. The radar echoes in RG are composed of two components. One is from aircraft, and the other is from ARM. Detection in this gate is essentially a multi-components signal detection problem. Whereas in IG, the radar echoes is only composed of ARM. In the first flying stage of an ARM, it moves toward the radar in a constant acceleration speed. The echoed signal from an ARM is a Linear Frequency Modulated (LFM) sinusoid wave. Hence, ARM detection is essentially LFM signal detection problems in lower signal to noise ratio.The main achievements of the thesis are as follow:The analytical radar signal model for ARM at its fire stage is established. The likelihood-ratio test based optimum detection criterion and decision-making rules for ARM detection in RG as well as in IG are constructed. The optimum statistical detector is configured based on the classic statistical detection theories. The optimum detection in IG is composed of Dechirping and Fourier transforming. However, in RG, an additional aircraft component canceller is included.The generalized likelihood ratio test based optimum detector, the Radon Wigner Transform (RWT) based detector and the Radon ambiguity transform (RAT) based detector for ARM detection in IG are analyzed. The identity in performance of the three detectors is demonstrated. Based on structure analysis of the simultaneous auto-correlation matrix, a modified method for the matrix construction is proposed. The result shows that a 3dB SNR gain can be obtained for WVD and AF, which improves the detection performance.ARM detection techniques in RG are discussed intensively and the idea of aircraft echo elimination is proposed. Because CLEAN in time domain is more sensitive to parameter estimation errors, a frequency domain CLEAN method called whiten filtering technique is introduced, which overcomes the shortage inherent in time domain CLEAN and improves the robustness of the detection algorithm.Based on the Wiener filtering theory, an adaptive aircraft echo canceller based on linear prediction error filtering (LPEF) is developed. The principle of the canceller is due to the auto-correlation of the input signals. With the method, the highly correlated aircraft echo with a mono frequency component can be eliminated perfectly while the feebly correlated ARM echo with a linearly modulated frequency can be hold. The advantages of this method are its less computation requirement and suitable for real-time processing. Computer simulation results show that reliable detection performance can be attained in lower signal to noise ratio. False alarm and miss detection is under better controlled. ARM echo signal can be detected immediately at the ARM's first launch stage with this detector.Aircraft echo elimination based on Wavelet packet decomposition is proposed. Good elimination result obtained. However, the computation burden is great due to the wavelet packet decomposition and reconstruction of the signal.The performance of the proposed detector is analyzed quantitatively in detection ability and in output signal to noise ratio. The optimum linear envelope detector and the square envelope detector have essentially the same detection performance under the Neyman-Pearson Criterion in spite of the difference in their output SNR.Aimed at the present situation of our air defence radar systems, the idea of preventing radar systems against ARM attack by supplementing ARM detection units for current radar systems is introduced. The basic structure of the ARM detection unit based on the ALPEF with quadratic phase compensation Fourier analysis is given.Some problems related to the detection realization are considered. Complex modulus approximation, which is more computation wasted, is studied. The modifing CORDIC coefficients are given, which improves the precision of modulus approximation.