A Self-Decoupling Mechanism for Closely Spaced Stacked Microstrip Patch Antenna Pair with Co-Directional Surface Currents

TL;DR

This paper introduces a simple, cost-effective broadband self-decoupling mechanism for closely spaced stacked microstrip patch antennas, significantly reducing mutual coupling without complex fabrication or additional circuits.

Contribution

It proposes a novel self-decoupling method using an embedded metallic line that works with co-directional surface currents, unlike traditional approaches.

Findings

Achieves 16.9 dB isolation improvement across 5G NR N78 band

Maintains mutual coupling below -20 dB across N77 and N78 bands

Validates effectiveness through experimental results on multiple configurations

Abstract

This paper presents a simple and cost-effective broadband self-decoupling mechanism to mitigate strong mutual coupling in tightly stacked patch antenna pairs. Unlike conventional decoupling approaches that rely on oppositely directed surface currents between parasitic and driven patches, the proposed method achieves broadband self-decoupling under co-directional surface current distributions by introducing an embedded ultra-narrow metallic coupling line between adjacent parasitic patches. This design effectively mitigates boresight gain reduction and total efficiency degradation typically introduced by conventional decoupling techniques, without requiring additional decoupling circuits or complex fabrication processes. In a tightly spaced two-element array, the proposed method enhances isolation by 16.9 dB across the 5G NR N78 band, reaching a maximum improvement of 40.2 dB. It also supports compact adjacent-band MIMO systems, maintaining mutual coupling levels below -20 dB for antennas operating across both the N77 and N78 bands. Experimental validation on three representative configurations confirms the broadband self-decoupling capability and practical applicability of the proposed technique.