A hybrid equivalent circuit model and plane wave spectrum method for decoupling surface designs in multi-band shared-aperture antenna arrays

Abstract

Shared-aperture antenna arrays are attractive for 5G base stations, owing to their compact size and multi-band frequency coverage. Decoupling surfaces are effective for suppressing crossband mutual coupling. However, their designs typically rely on full-wave simulations of scattering parameters, which may not ensure a good radiation performance and is time-consuming. A systematic methodology based on the hybrid equivalent circuit model and plane wave spectrum method is proposed for decoupling surface designs. The decoupling surface is represented by its equivalent circuit and the spectral expression converts the electromagnetic field into a circuit problem. Both the scattering parameter and radiation pattern can be solved with the circuit, offering an efficient design method that ensures consistent radiation patterns between the model and full-wave simulations. A double-layer decoupling surface with wide stopbands, high transmission property, and sharp roll-off transition was realised. Furthermore, to reduce the overall profile height, the reflection phase of the decoupling surface was tuned. A triple-band shared-aperture base station antenna array was developed. Simulated and measured results demonstrate the array works properly in the 0.69–0.96 GHz, 1.7–2.7 GHz, and 3.3–3.8 GHz frequency bands with stable radiation patterns, and crossband mutual coupling is well suppressed, validating the effectiveness of the proposed methodology.