Time-domain Adaptive Beamforming On One Kind Of Non-stationary Pulse Signal

The technology of beamforming is the core part of underwater target positioningresearch and the study of adaptive beamforming algorithm has great significance. Thecurrently used high resolution algorithms can improve the azimuth resolving andtarget detection ability of broadband passive sonar systems, but all of them havecertain restrictions at the same time. MVDR has acceptable performance in lowerSNR conditions. Analytical signal was introduced to time-domain wide band signalsto weight amplitude and phase and therefore same weight vector to be happening withMVDR method based on frequency-domain. In this method, the narrow-band divisionprocess is avoided computational complexity is reduced significantly. The data lengthrequired to obtain stable optimum weighted vector was far less shorter thanfrequency-domain MVDR in rare data conditions.In this paper, Capon adaptive beamforming(minimum variance distortionlessresponse, MVDR) was extended into one kind of non-stationary pulse signal，andMVDR of single Chirp pulse signal with constant amplitude (TMVDR on singleChirp pulse signal，CTMVDR) was realized by using one kind of MVDR in timedomain (Time-domain MVDR,TMVDR).the main works in this paper:(1) Theoreticalanalysis indicated that the condition of realizing TMVDR on single Chirp pulse signalis stable estimation of optimum weight vector which is related to the stability ofself-correlation of Chirp signal serial estimation.(2) Compare the performance ofCBF, MVDR on frequence domain and CTMVDR via computer simulation,accordingly, reflecting the advantages of CTMVDR. And utilizing the accurate timedelay algorithm improve the time delay accuracy of time series.(3) Designed andorganized the experment on the lake,the feasibility and stability of TMVDR on singleChirp pulse signal was validate by the results of data processing.The experiments show that with no more than1024data and sampling rate is lessthan10times nyquist frequency, we can estimate the adaptive optimum weight vector steadily. Contrasting with conventional beamforming(CBF), CTMVDR is effective inbeamforming response, DOA estimation and, clear array gain, target localization withgood precision.Further work commence from the following two aspects, on one hand, we willmake sea experiments to test the CTMVDR in practice; on the other hand, we will tryto extend the MVDR adaptive beamforming method to other non-stationary pulsesignal.