Synthesizing Beam-Scannable Thinned Massive Antenna Array Utilizing Modified Iterative FFT for Millimeter-Wave Communication

In this letter, a modified iterative fast Fourier transform (MI-FFT) technique is presented to synthesize thinned massive array for 5G millimeter-wave (mm-wave) communications. The periodicity of a scannable array factor for a uniformly spaced planar array is discussed and employed to reduce the complexity of array factor computation. A gradual array thinning strategy is introduced to prevent the iterative procedure from being trapped into an endless loop so that a better solution with lower sidelobe level (SLL) can be found. The beamwidth control is also added in the MI-FFT to control the pattern beamwidth. A thinned 128-element planar array with parasitic patch covered microstrip antenna elements is designed with the frequency band from 25.2 to 31.6 GHz. The 128-element positions are optimally selected from a prescribed larger layout by the proposed method, and consequently the obtained thinned array has a much lower SLL and narrower beamwidth than a conventional fully occupied 128-element array.