Low-Sidelobe Range-Angle Beamforming With FDA Using Multiple Parameter Optimization

In this paper, we propose an equivalent transmit beamforming method in joint range and angle domains at the receiver of the colocated transmit-receive system where frequency diverse array (FDA) acts as transmit antenna. FDA employs a small frequency offset across the array elements and introduces additional degrees-of-freedom in range domain, which can significantly enhance the beamforming flexibility. However, the transmit beampattern of conventional FDA is range-angle-time dependent. In this work, the time-varying problem is first solved by using a series of filters and mixers at the receiver. In the sequel, a subarray-based FDA framework, termed as multisub-FDA, is established and then a range-angle-decoupled equivalent transmit beamforming method is devised based on particle swarm optimization, which incorporates the frequency offset of each subarray and the corresponding weight vector into the optimization problem. With the proposed approach, the array is capable of generating focused beampattern with low sidelobe in both range and angle domains. Numerical results show that the proposed algorithm improves the beamforming performance, range resolution, and sidelobe suppression.