Quasi-Time-Invariant 3-D Focusing Beampattern Synthesis for Conformal Frequency Diverse Array

Due to the range-angle-dependent beampattern, frequency diverse array (FDA), either in the form of linear array or planar array, has been extensively investigated in recent years. However, the conformal FDA is seldom studied. In this article, a general conformal FDA framework is first developed. Specifically, a hemi-spherical FDA is exploited to illustrate the unique advantage of conformal FDA in terms of the 3-D localization ability. Furthermore, to deal with the intrinsic defect of time-variant range-angle-coupled beampattern of the FDA, an optimized static nonlinear frequency offset (OSNFO) is proposed. The OSNFO not only decouples the conformal FDA beampattern in the range-angle dimension, but also copes with its inherent time-variant problem, resulting in a quasi-time-invariant 3-D focusing beampattern. Numerous simulation results have been provided to demonstrate the superiority and the effectiveness of the OSNFO-conformal FDA.