| Besides having the same advantages as traditional phased array radar does, wideband phased array radar emploies wideband signal to get high distance resolution ability. Consequently, more detailed target information can be obtained and applied to deal with the related problems such as multiple target resolution, target classification and recognition, and so on. In addition, due to the low probability of interception (LPI) brought by using wideband signal, wideband phased array radars exhibit better anti-interference performance. Introducing digitalization technology to the wideband phased array will make the time delay adjustment convenient, which is required by the wideband beamforming. Hence, the transmitting Digital Beamforming (DBF) and receiving DBF can be implemented readily. The obtained simultaneous multi-beam benefits the flexibility of the phased array resource scheduling. Wideband Digital Array Radar (WB-DAR), combining the digitalization technology and wideband phased array, is an advanced and ideal radar system. It is being needed urgently in the practical applications, and will be applied widely in the field of military electronics.Compared with traditional analog phased arrays, WB-DAR system can be characterized by wideband digitalization, and has innovations in different aspects, such as system architecture, wideband beamforming approach based on the digital delay, digital reconfiguration technology, and so on. All the innovations mentioned above require the support from the development of related key technologies.When the development of WB-DAR is promoted from theoretical research to practical system, it is absolutely necessary to launch the research on key technologies of WB-DAR including general system structure, RF sampling technology, wideband beamforming methods based on digital delay, low sidelobe pulse compression technology, etc. This work will accelerate related theory development and practical application of WB-DAR. Aimed at this topic, the research work discussed in this dissertation was carried out. Main research work includes:1. The general system architecture of WB-DAR was studied. After summarizing and analyzing typical WB-DAR experimental systems, new general system architecture of WB-DAR system based on uniform linear array was proposed. Furthermore, the architectures of key subsystems are analyzed detailedly. Main problems about key subsystems such as main function, architecture, important interfaces and signals, were discussed. This proposed general system architecture has simple structure, definite function partitioning, and takes wideband digitalization characteristics into account extremely. Therefore, it can be used as a scheme template to realize similar systems.2. The RF sampling technology of WB-DAR was investigated. The necessity of performing RF sampling in the WB-DAR was demonstrated firstly. Then some related problems about RF sampling in the single channel were studied. The design methods of high speed mixed-signal circuits were discussed in detail and corresponding design criteria were summarized. Based on these criteria, a high speed data acquisition system was designed and implemented. The good test result proves the validity of the summarized criteria. Furthermore, the aperture jitter, one of the key factor which affects RF sampling performance, was studied. The relationship between the aperture jitter and the ENOB of the RF sampling system of the DAR was demonstrated, and the effect of the aperture jitter on the sidelobe level after the digital beamforming was analyzed. The obtained conclusion is useful for the design and implementation of practical WB-DAR system. In addition, the effect on the beamforming performance, resulted from nonsynchronous sampling between multichannels, was analyzed in theory. After that, a new approach to measure the delay existing in different channel by means of maximum likelihood estimation and Fractional Delay Filter (FDF) was proposed. Although this method needs some extra hardware resource, it is still suitable to be realized on the WB-DAR hardware platform due to the adopted parallel structure.3. The wideband beamforming technology based on digital delay was researched. The analysis model of wideband receiving pattern based on time delay was established to point out the reason why the traditional phase-shift method cannot be applied in the wideband digital beamforming system any longer. In order to meet the practical requirements of WB-DAR system, a new general antenna pattern model was proposed. Theoretical analysis, computer simulation and practical system test were carried out to prove that the proposed method, which combines unit delay with phase-shift, can form wideband receiving beam and improve the aperture transition effect. Considering about the RF sampling characteristic, a real time poly-phase beamforming structure combining anti-aliasing filter and variable fractional delay filter was proposed. This method can simplify the hardware structure effectively and obtain almost continuous adjustment of fractional delay. Comparison among the Lagrange interpolation approach, Least Square (LS) approach and LS combined with spline interpolation approach was made to find out the appropriate method for the design of the combination filter proposed above. Finally, computer simulation result was given to show how much the accuracy of wideband receiving beam pointing was improved after the usage of fractional delay.4. Low sidelobe pulse compression methods were studied. The theoretical analysis of Linear Frequency Modulation (LFM) signal, employed in most of wideband radar systems, was presented. Different methods exhibited in the open literatures were summarized and compared. Then, a new approach to design low sidelobe pulse compression filter was proposed. The proposed pulse compression filter can output narrow pulse of which the Mainlobe to Sidelobe Ratio (MSR) is more than 97dB, and can be implemented on real time processing platform. Besides, the related problems about Signal to Noise Ratio (SNR) loss, mainlobe broadening and Doppler frequency sensitivity were analyzed by computer simulation. A practical test utilizing an experimental platform was performed to prove the effective improvement of MSR.5. The author took an important role in the development of a WB-DAR experiment system and outfield experiment. This experiment system was designed on the basis of the proposed general architecture. The system experiment was finished successfully and some test results were illustrated.
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