High-isolation and high-gain microstrip antenna based on double-layer radiation patches

In this paper, we propose a high-isolation and high-gain microstrip antenna whose size is smaller than 0.33λ. Due to two symmetrical feed ports, two orthogonal eigen modes are excited and antenna is dual-polarized. By introducing suitable parasitic radiation patch, not only the total gain increases, but also the isolation between different feed ports is improved. The simulated and measured results demonstrate that, the return loss of the antenna is smaller than -10 dB over the frequency band from 2.45 GHz to 2.80 GHz, and the isolation between two ports is smaller than -20 dB with its minimum value of -50 dB at 2.48 GHz. Besides, when one port is fed and the other is matched, the far field test verifies that the maximum radiation direction is perpendicular to the surface of the antenna with the total gain of 9.49 dB and cross-polarized ratio of 26.5 dB. Thus, high-isolation and high-gain characteristics make that the antenna can be applied to multiple inputs and multiple outputs (MIMO) systems.