Interferometer Technology And Broadband Measurement System

Interferometer has been a well developed system in direction finding. Accordding to phase differences which were receiveed by some antenna elements when expected signals arrive the array, we could get the DOA information by determining those differences. Correlation interferometer is one of the interferometer direction finding technologies, it obtains DOA information in a more convenient way, instead of computing directly, it compares determined phase differences with samples in the storage.Along with the rapid development of wideband telecommunication technology, getting DOA information of wideband signal is becoming more and more important. Interferometer has been widely used in the wideband radra and telecommunications system for its merits such as: high performance of anti-jamming, high sensitivity and accuracy, available for pitch attitude determining, insensitive of polarization error. Particularly correlation interferomete, for its high speed and accuracy, it takes the core position in wideband direction finding system nowadays. Correlation interferomete aided with other direction finding methods could realize real time monitoring, analyzing and tracing for multiple signals in wideband frequency area.This dissertation mainly focus on wideband interformeter. It will introduce phase interferometer and correlation interferometer, including their system configuration, algorithm and accuracy analysis.First of all, the principle of phase interformeter is presented through 1D single baseline interformeter system. After analyzing its deducing process, two problem appears, first :"Phase Ambiguity"and second:"Mirrorimage Ambiguity". To solve these issues, 2D variable baseline interferometer system is broughted. When 2D variable baseline interferometer accompanied by DTF processing, it could finally come into the structure of wideband phase interferomete system.A lot of factors could effect the direction finding result, in order to obtain the ideal one, it's strongly recommand that we make the relation between them clear. This dissertation deduces the relation of some factors such as:incident angle, length of short and long baseline, SNR, position of array elements, system error. Among them, the relation between length of long baseline and SNR is based on the curve fitting method after tremendous independent experiment, meanwhile the influence of postions of elements is received via maximum likelihood estimate.Wideband correlation interferometer is the key of the dissertation. It soon gives a detailed account of the system. Wideband correlation interferometer algorithm based in channelizing is also presented. It's found that pitch attitude is invalid when direct correlation operation is adpoted between observing phase vector and samples in some frequency coverage. The dissertation provides improved algorithm to solve it. Making a reference to the error model in chapter three, the relation between antenna aperture, number of elements, SNR, resolving capability of signal path and degree of direction finding accuracy.At last, the dissertation provide a detailed introduction to a practice wideband correlation interferometer system which is under developping by the author. After that, it shows the flow of work under fixed-frequency models of the system. Cosidering the important mark of the system: Direction Finding Time, this dissertation gives two solution,and also realization of algorithm in sofeware is introduced which is based on solution one.