aDecoupling of Closely Stacked Patch Antennas for Airborne Radio Altimeter Applications

Abstract In this paper, a mutual coupling reduction technique between closely stacked patch antennas is proposed based on high impedance electromagnetic structure (HIES) in C-band (4.2 ∼ 4.4GHz). The considered stacked patch antenna array consists of two dielectric layers, one driven rectangular patch, and four parasitic rectangular patches. The decoupling element composed of two symmetrical rectangular loops embedded into the dielectric and printed at the bottom layer between the driven patches. The decoupling element acting as artificial magnetic conductor (AMC) with very high input impedance. After adding the decoupling unit, the maximum achieved measured port to port isolation is increased from 20 dB to 57dB with 0.15λ0 edge to edge separation distance at the top layer and the realized gain is approximately 10dB. The efficiency of the antennas increased from 91% to 95%. Moreover, the envelop correlation coefficient (ECC) is reduced from 0.0017 to