A Teflon-Filled Open-Ended Circular Waveguide Focal-Plane-Array Used for Sway Compensation in W-band 50dB-Gain Backhaul Reflector Antennas

The paper introduces a novel focal plane array (FPA) design aimed at enhancing the reliability of millimeter-wave backhaul communication links by compensating for the impact of antenna mounting structures' sways. This FPA is analyzed for an offset parabolic reflector antenna with the 40-cm aperture diameter at W-band frequencies (92-96 GHz). The FPA-fed reflector antenna generates multiple closely-overlapping beams to compensate for the expected antenna tilt range, equivalent to seven beamwidths. This study addresses major challenges associated with FPA design implementation at these high frequencies, including (i) the need for a small (≤ 0.75 λ) inter-element spacing for the required beam overlap, and (ii) manufacturing complexities of an array element ensuring optimal reflector illumination and impedance matching in the presence of mutual coupling effects. An analytical approach to the FPA pattern shaping for optimal reflector illumination is proposed and successfully validated via numerical optimization and measurements. Furthermore, our analysis of the total reflector-FPA system shows promising results, i.e. 56 - 68% antenna aperture efficiency (49 - 50 dBi directivity) for all beams with compliance to the radiation emission constraints (ETSI class 3) within ±89°.