A Partition-Based Method for Harmonic Beamforming of Time-Modulated Planar Array

Because of the multiplication of antennas, harmonic beamforming based on the time-modulated planar array (TMPA) requires a much longer modulation period than the time-modulated linear array (TMLA). Two additional constraints should also be fulfilled: 1) avoid aliasing in the frequency domain; the modulation frequency should be larger than the transmitted signal's bandwidth and 2) accurately extract harmonics; the bandpass filter (BPF) bandwidth should be no less than the modulation frequency. If the bandwidth of the transmitted signal increases, the processor and radio frequency (RF) switch should be accordingly improved, thus increasing the overall costs. In this article, we propose a method based on partition subarrays for TMPA harmonic beamforming. Upon modulating subarrays separately and simultaneously, we obtain an equivalent beam. In our scheme, a TMPA is divided into S subarrays, such that the modulation frequency and the maximum bandwidth of the transmitted signal can be S times the original ones, making filtering much easier. Our approach has three major advantages: 1) it greatly reduces the requirement of BPF by enlarging the frequency interval; 2) it allows the transmission of larger bandwidth signals with the same hardware; and 3) the efficiency of the antenna is improved. Numerical simulations verified the proposed method.