On Signal Processing Algorithms For Pulse & Inter-pulse Binary Phase Coded Radar Altimeter

Airborne radar altimeter, as a special applied domain, has different operation characteristics from conventional radar and radar altimeter. Time waveform and Doppler spectrum spread are significant points. Such characteristics will lead to different signal detection and processing methods.Researching on ground echo model and its distinctions of time domain are relative maturity in airborne incoherent pulse altimeters, incoherent pulse system is popular in early-stage(at present, such system is widespread availability).Corresponding algorithm adopted in target detection and processing borrows ideas from classical point-based target's pulse radar system, such as: The binary integration detection (BI or M/N detection or double threshold detection) etc. Such simple algorithms transplant will make radar altimeter's target detection performance fall down. So studying on area target's detection algorithms for airborne pulse radar altimeter seem to be important. The content concerned is one of the tasks of this dissertation.Along with the technical development in modern radar and further researches on ground echo frequency domain characteristics, all achievements are prerequisite for developing airborne pulse Doppler radar altimeter. At the present, range correlation and velocity filtering processing methods are adopted in most of modern airborne pulse Doppler radar altimeters. Having wide Doppler filter width comparing to airborne pulse Doppler radar Doppler filter, signal processor has low performance. Meantime, it is fixed Doppler filter band that restrict airborne altimeter's flexibility. On the other hand, high repeat frequency for avoiding measuring velocity blurriness leads to high range blurriness. Moreover, simple pulse Doppler radar altimeter system can't satisfy the demands for anti-jamming in complex electromagnetic environment. So studying on a kind of waveforms adapting to airborne pulse Doppler radar altimeter and corresponding signal processing algorithms is major task in this dissertation.In order to estimate performance of target detecting algorithm and its hardware Objectively, an orthogonal base-band echo simulator system based on ground echo simulation is put forward. And simulator system's hardware design and implementation have been finished.Main contents in this dissertation include:1 After studying time and frequency domain echo model and its characteristics for airborne pulse radar altimeter in beam lobe vertical incidence, then target detection and processing algorithms for non-coherent and coherent integration are studied emphatically.2 According to altimeter echo pulse spread in distance, two types of target detection methods, multi-range gate BI detection & double integrator BI detection, are put forward. The former improve detection performance and measurement accuracy of height by means of optimizing weighting factor in adjacent range gate. And the latter has high performance with lower false alarm probability by block integrating. In addition, assessment of detection algorithm performance based on Markov chain is a unique feature.3 Through analyzing echo Doppler spectrum of airborne pulse radar altimeter, relative complete model of echo simulation and its simulation program is created. This program can simulate target echo signal from maximal beam-lobe illuminating circle and clutter loop from blurred range in different height. All these are important for target detection algorithms investigated.4 In response to requirement of radar altimeter's target detection performance, a kind of high PRF inter-pulse m sequence binary phase-coded waveform which combines all advantages of coherent pulse train and m sequence binary phase-coded signal has been presented. Not only does the waveform satisfy pulse Doppler radar altimeter demands, but also has high range and velocity resolution and measuring precision. Meantime, this waveforms signal can solve velocity and range's measuring blurriness better. On the other hand, high anti-interference performance can be obtained.5 Three types of target detection algorithms, including their performance and...