Empty Millimeter Wave Radiometer Signal Processing

The detection and identification of low altitude helicopters by means of passive millimeter-wave (MMW) radiometer is presented in this paper, with the project named as "the signal processing of MMW radiometer against low altitude helicopters". The model of output signal is proposed here on the basis of comprehensive analysis to radiometer systems, and the methods of data pretreatment and feature extractions are simulated and researched based on the theories of digital signal processing and wavelet analysis.The structure of this paper is as follows:(1) The principle of the alternating current (AC) total-power radiometer is introduced and the technical specifications of the radiometer which operates at 94 GHz and is designed for the detection of low altitude helicopters are summarized. Then the model of the signal at the output terminal of radiometer is set up.(2) The characteristics of Fast Fourier Transform (FFT) and wavelet analysis in the application of noise reduction are demonstrated and the output signal of radiometer is pretreated by a relatively better method which is chosen after extensive analysis to the noise reduction performance of different methods.(3) The type of helicopter is confirmed through feature extraction to the rotors and the proper method used for confirming the extract positions of helicopters is provided through wide analysis to a range of different feature extraction approaches.