Researches On The Detection Of Weak Targets By Signal Integration

An efficient method to improve detection perfonnance of radar signals is to enhance available energy returned from targets by integration, where performance is depend the utilization of non- stationaiy properties. Focussing on applications of time-frequency analysis and long t~m ~oh~uit signal integration techniques, this diss~tation investigates the methods for realization of matching filter and issues of motion compensation techniques for long tarn integration detection. ~ main contents of the dissertation are descnl,ed as followin& Firstly, a biief introduction of the puipose, backgrntmd and significance of the ~~rks in this disseitation is concerned. For integral detection of ~ak moving targets using multiple dwelling beamfomis of phased array radar or staring mode of conventional radar, a motion compensation way for range migration by anploying range cells stretching and joint time-frequency is established in chapter 2. With no r&p駌ernent on the knowledge a priori of target motion parameters, the provided method takes returned signals of multiple range resolution cells as transient signals, and make use of combined processing in time and frequency domains to compensate the envelop delay ezTors, and to proceed the coherent integration detection. The joint time-frequency processing based method fit into the circumstances where divergent doppler resolution units of target are presented. In chapter 3, An equivalent wide-pulse technique with range resolution capability is proposed to overcome the effect of range migration on low observable target detection using long-tam coherent integration. This method utilizes both simultaneously and sequentially stepped frequency signals to synthesize a narrow pulse in receiver while canying out coherent integration against each individual component, a woxking mode by emitting in wide and receiving in narrow. The advantages over those available methods is it achieves long integration time while possesses range and velocity resolution capabilitie& Chapter 4 proposes a novel long-term coherent integration method for detection of weak non- linear frequency modulated (NLFM) signal returned from low observable maneuvering target The method exploits the time-frequency tiling property of adaptive wavelet transform for the extended NLFM signal model, and is practically realizable. The unitary and linear phase wavelet basis function together with joint one order linear approaching procedure are presented to pursuit the signal trace in time-frequency plane. Additionally, dechirping transform is employed in subband outputs to achieve ABSTRACT the low computational complexity implementation. Simulation results demonstrate the efficacy of the proposed AWF based detector. In accordance with need of an actual application and based upon the prominent scatterer model of high resolution radar, chapter 5 investigated a practical detection and distinction method for sea- surface moving target at lower speed by using integration techi黴ue~ togethering with radial range carelation information to reduce false alarm resulted from sea-spike echoes when radar beamfocm working at low scraped angle. A simulation method of sea clutter data is also concemecL In chapter 6, a waveform detector is considered by discernment of the difference of modulus maxima evolution behaviors between signal and rarxlom noise in multiscale space and a practical noise rumval algorithm is given too. In comparing with one using...