Wideband mutual coupling reduction and scan blindness elimination in a microstrip patch phased array antenna with truncated soft surface structures

This article introduces a new type of soft surface as truncated soft surface (TSS) for the mutual coupling reduction in stacked aperture-coupled microstrip patch phased array antennas. Also, a meandered TSS (MTSS) is introduced with a reduced size compared to the TSS. Conventional soft surfaces not only prevent the propagation of waves in the soft longitudinal direction but also guide the waves in the transversal direction. So, the mutual coupling decreases in the soft longitudinal direction and increases in the transversal direction. Truncation in the transversal direction prevents the waves from guidance on TSSs. Simulation results show that using this technique helps to decrease the mutual coupling in the E-plane of a phased array antenna without any noticeable increase in the H-plane coupling. Also, there is no blind spot in the desired scan range and the embedded element pattern will not have any null in the scan range. Using this technique, the acceptable scan range for an antenna substrate with a low relative permittivity of 2.33, can be increased up to 45 degrees. Finally, measurement results show that using TSS leads to an 8-dB decrement in the E-plane mutual coupling.