Unintentional Modulation Of Radar Emitter Signals

Unintentional modulation of radar emitter signals is a very important issue in the field of modern electronic warfare. It's caused by the phase noise generated from the various hardware components and the circuit of the radar transmitter. This issue focuses on seeking the radar source of the signal in the increasingly complex electromagnetic environment. The transmitter platform recognition and tracking can be realized, which provides favorable conditions for the battlefield analysis. Intercepting and analyzing the conventional parameters are the key in the traditional radar emitter signal reconnaissance, and the individual characteristics of the unintentional modulation from the difference of the hardware will be ignored as a faint noise. On the contrary, unintentional modulation that reflects the inherent properties of radar emitter is the emphasis when studying the unintentional modulation of radar emitter signal.Analysis and examination of unintentional modulation are a significant aspect of radar emitter individual identification. This issue appears a few times, but there is not an unified theory about it. Focussing on the different radar emitters whose mode and type are same, this article will discuss the unintentional modulation of radar emitter signal. The main work and research are as follows.1. The principle of unintentional modulation of radar emitter signals is introduced. Then the mechanism is analyzed which shows the phase noise of radar transmitter is the main source. The structure and phase noise model of radar transmitter are analyzed, and the total output phase noise distribution is researched through the analysis of the radar transmitter.2. In order to analyze the unintentional modulation characteristics of radar emitter signal, Continuous Wave(CW) radar emitter signal, Binary Phase Shift-Key(BPSK) radar emitter signal and Linear Frequency Modulation(LFM) radar emitter signal are used in this paper, and then implementation analysis and simulation experiments are achieved respectively.3. Based on the time-frequency atom decomposition algorithm, the feature extraction techniques of radar emitter signals'unintentional modulation are researched, and then frequency domain features are extracted.4. Two kinds of time-frequency atom dictionaries are constructed firstly. Focussing on the different CW radar emitter signals whose mode and type are same, a method of unintentional modulation feature extraction is proposed based on the Gabor atom dictionary characteristics. The parameters of the optimal Gabor atoms and the similarity are considered as the unintentional modulation feature parameters. Introduction of time-frequency parameters, the unintentional modulation information of radar emitter signals shows a global and local performance in time-frequency domain.5. Aiming at LFM radar emitter signal, the adaptive ability of Chirp atom is stronger than Gabor atom's. A method of unintentional modulation feature extraction of different LFM radar emitters whose mode and type are same is proposed based on the Chirp atom dictionary characteristics. The parameters of the optimal Chirp atoms and the similarity are also considered as the unintentional modulation feature parameters.This paper was supported by the National Natural Science Foundation of China (60702026) and Youth Science and Technology Foundation of Sichuan (09ZQ026-040).