Signal Detecting And Processing For MMW Precise Detection System

There are two regimes of Millimeter Wave (MMW) precise detection system:the active detection system (ADS) and the passive detection system (PDS). In this dissertation, ADS means high range resolution Radar, which can obtain the exact information about objects, such as speed, azimuth anddistance etc. Signal processing plays an important role in both ADS and PDS, thus advanced signal processing technique is one of the most prominent procedures to improve the exactness of both detection systems. The key techniques of ADS signal processing include the follows:quadrature sampling of IF signal, digital pulse compression, moving target detection, waveform design. PDS does not eradiate electromagnetic wave and thus lead to no electromagnetic pollution and no object speckle fluctuation. These proeperies make PDS a high concealment system and enable it to detect the objects covered with microwave absorbing materials. High resolution imaging technique is an important research issue of PDS, however, small antenna aperture limits the imaging resolution of PDS. Therefore it is necessary to improve the resolution by software processing. To take both advantages of ADS and PDS, it is natural to integrate them into an active/passive compound detecting system enabling us to obtain more detailed object information.This dissertation focuses on signal processing techniques used in ADS and PDS. The research results include the following five parts:In the first part, two regimes of MMW precise detection system are briefly introduced, including the principles of Stepped Frequency (SF) Radar and Chirp Stepped Frequency (Chirp-SF) Radar, system parameter analysis on ADS. As to PDS, characteristics of MMW Alternating Current (AC) radiometer are investigated, and its parameter design is implemented for AC radiometer.The second part emphasizes on researching IF bandpass sampling and digital quadrature transform for SF Radar. Additionally the algorithm for polyphsae filtering principle is presented, including fractional delay filter, which is used for digital quadrature transform in polyphase filtering. Moreover, their image-rejection performance is also analyzed. The hardware for band-pass sampling and polyphsae filtering are carried out and outfield test for the hardware are also brought through.There is heavy distance-speed coupling between SF signals and Chirp-SF signals, so it is necessary to imply speed compensation. The third part of this dissertation puts forward an algorithm for speed compensation by waveform design, and the ideal is to add a group of Pulse Doppler (PD) signal in SF Radar. When object speed is little, SF is used for speed and range detection without PD, while object speed is relatively large, only PD is used for speed detection. This compensation algorithm can also be used for the speed compensation of Chirp-SF signal.The resolution of passive MMW image obtained from PDS is relatively low due to present techno-level, thus the forth part of the dissertation discusses super-resolution processing of passive MMW image. Firstly the regularizing principles of image reconstruction are investigated, and then half-quadratic regularization algorithm for MMW image with high resolution restoration is introduced according to degenerative factor of MMW imaging. Finally several deterministic criteria of image quality are given to evaluate the MMW reconstruction images from different algorithms.The fifth part ends this dissertation with an introduction of mathematical morphologic and its applications in MMW image restoration. This algorithm is well suitable for image edge detection that compensates the edge information back to smoothened image. Otherside, dislocation error in level direction is another degradation factor brought in with PDS scanning movement, and the Module-1 range algorithm can conquer it.Summarily, the problems discussed in this dissertation are indispensable bases of the active/passive compound detecting system and the results will contribute to the development of above mentioned system.