Research On Frequency Diverse Array Parameters Optimization Design And Target Localization

Phased-array antennas have been widely used in many modern communication, radar, and navigation systems. Unlike conventional phased-array antenna, the frequency diverse array(FDA) antenna employs a small amount of frequency increment compared to the carrier frequency across the array elements. FDA achieves range-dependent beamforming, which can be used to suppress range-dependent interferences and clutter or improve detection performance. In the study of the frequency diverse array, the main contributions of this thesis can be summarized as follows:(1) The detection performance of FDA radar is derived and simulated.The likelihood ratio test target detector for FDA radar, distributed MIMO radar and phased array radar are derived separately. Additionally the detection performances of FDA radar based on multiple pulses is also investigated. The results show that FDA radar has the better detectable performance than distributed MIMO radar and phased array radar in low Signal-to-Noise ratio(SNR). The detection performance improves as the increase of the number of elements.(2) The FDA radar estimation performance bound is derived, and a simple transmit subaperturing strategy is proposed.Two different data models including before and after matched filtering are investigated separately. This thesis derives FDA radar Cramér-Rao lower bounds(CRLBs) for estimating direction, range(time delay) and velocity(Doppler shift). As the FDA radar has range-angle coupling, we proposed a simple transmit subaperturing strategy, which divides the whole array into two subarrays, each uses a distinct frequency increment. Assuming temporally White Gaussian noise and linear frequency modulated transmit signal, extensive simulation examples are performed. When compared to conventional phased-array radar, FDA can yield better CRLBs for estimating the direction, range and velocity. Moreover, the impacts of element number and frequency increment are also analyzed.(3) An optimal subarray design strategy for FDA radar target localization via CRLB minimization is proposed.To decouple the range and angle response of targets, we divide the FDA transmit array elements into multiple subarrays. For a given number of array elements and subarrays, the optimal array division and frequency increments design strategies are formulated as a constrained CRLB minimization problem. Then it is converted into an unconstrained optimization problem and further resolved by iteratively utilizing the Nelder-Mead algorithm.(4) The FDA manifold geometric and ambiguity properties are analyzed with differential geometry. An augmentation approach is proposed to resolve the manifold ambiguities in direction of arrival estimation.The FDA resolution and detection capabilities are derived as a function of the manifold length and first curvature for the sources with unequal powers. The ambiguity inherent in a linear FDA manifold is analyzed. Under the same conditions, FDA has better detection and resolution capabilities than conventional phased array. Since FDA offers a range-dependent beampattern, some manifold vectors that are linearly dependent in phased array will be linearly independent in the FDA. For these reasons, when compared to phased-array radar, FDA radar can resolve more sources.