| The function of battlefield surveillance radar is real-time, accurate, all-weather reconnaissance and monitoring the activities of the battlefield, the weapons and configuration of logistics supplies and identified the target value of properties and determine all kinds of military targets. In terms of anti-interception performance, mobility and operation proposal, reliability, and other tactical and technical index, it is to be putted forward the very high request towards battlefield surveillance radar.Multiple-input multiple-output (MIMO) radar is the improved product of traditional phased array radar. As it is a new type of radar system developed in recent years, MIMO radar is the research focus on the current international. In the orthogonal waveform MIMO radar, the elements on transmit are divided into a number of subarrays in pitch direction. The subarrays transmit mutual orthogonal waveforms, and a wide and low gain beam is formed on transmit. And the DBF is employed to form both receive and effective transmit beams. These new technologies bring some new performance improvements, in the area of battlefield surveillance MIMO radar has big advantages, such as better anti-interception performance, better velocity resolution, advanced ability of low speed target detection under strong clutter.This dissertation investigates the DBF, weak, low speed target detection under strong clutter and array calibration technique in MIMO radar. The main research focus on the following issues:1. Three kinds of equivalent structures of DBF for MIMO radar are introduced first. An adaptive digital beamforming algorithm for MIMO radar system is studied in this paper. SMI algorithm based on MIMO radar is recommended, for the algorithm can operate in high speed, and it is easy to implementation. From the perspective of interference degrees of freedom, the paper discussed of the adaptive module location of the MIMO radar processing system to eliminate the active jamming in space. And match filter has no effect on interference degrees of freedom of MIMO radar, so the location of adaptive module is after the match filter, because the match filter increases the calculation greatly. 2. The technology of low speed target detection under strong clutter for battlefield surveillance MIMO radar is studied. The key of target detection that uses Doppler processing is the separation of clutter spectrum and the target. In the case of sufficiently high Doppler Frequency of MIMO radar system, target detection is mainly influenced by the wind speed. When the wind is weak, we can use Long time coherent integration to improve Doppler Frequency to compress the clutter spectrum. In order to reduce the effects of Doppler Frequency sidelobe, we can use a window conducted in slow time. Meanwhile the window brings the effects of mainlobe broadening and SNR loss. The rule of choosing the window is based on the SCNR of the radar echo. Accumulation time increases to a certain degree, the clutter spectrum compression effect will not improve anymore. So the accumulation of time in target detection has a criticality and the article gives the calculation of the critical value. The effects of MTI filter for low speed target detection is also studied.3. A self-calibration algorithm for MIMO radar in the presence of mutual coupling is investigated. The algorithm can provide accurate DOA estimation, and the mutual coupling coefficients for both transmit array and receive array calibration can be achieved simultaneously. It just uses a one-dimensional search and could reduce the computation burden. The computer simulation illustrate that the algorithm is effective.In addition, the Cramer-Rao Bound( CRB) is studied also, and the noise distribution is not changed in the equivalent MIMO virtual array. |
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