Frequency Diverse Array Signal Generation and Beamforming Based on Dual Optical Combs

In contrast to phased array (PA), frequency diverse array (FDA) offers enhanced flexibility in beam scanning across both directional and distance dimensions. However, the existing FDA signal generation techniques encounter several challenges, including limited bandwidth, spurious distortion, and complexities in multi-channel tuning. In this paper, an FDA signal generation and beamforming method based on dual optical frequency combs (OFCs) is proposed. In the experiment, five-channel FDA signals with a center frequency of 8 GHz and a frequency offset of 1 MHz are generated. The power level flatness of the FDA signals remains below 2.5 dB with a remarkable spurious suppression ratio of 27.2 dB, indicating the ability of the proposed method to generate high-quality FDA signal, so as to realize the desired beamforming and scanning. The demonstrated beampattern exhibits a distinctive 'S' shape, which is influenced by the distance and angle. Similarly, the generation of broadband FDA is demonstrated experimentally. Moreover, 'X'-shaped beampattern can be realized by altering the distribution of the element, including the multi-carrier FDA and symmetrical FDA. The features of broad operational bandwidth, flexible frequency tunability and high spectrum purity make the proposed method a promising solution for various future applications.