Decoupling Between Extremely Closely Spaced Patch Antennas by Mode Cancellation Method

In this article, an inductance-based decoupling scheme is proposed to reduce the mutual coupling between extremely closely spaced microstrip antennas. The original strong coupling can be effectively suppressed by simply inserting a lumped inductance in between. To offer a systemic design guideline for this decoupling strategy, a mode cancellation method, based on the synthesis of common mode (CM) and differential mode (DM), is proposed. The inserted inductance plays a role of tuning CM and DM impedances to a similar status, which has an equivalent decoupling effect according to the theory of microwave network. Alternatively, the lumped inductance could also be replaced by an inductive connecting strip for a concise topology. To validate the proposed decoupling concept, a prototype is simulated, fabricated, and measured. The experimental results show that the poor isolation of 5 dB is improved to better than 15.4 dB across the entire matched bandwidth of 2394-2.530 GHz, with an extremely close edge-to-edge distance of 0.016 lambda(0) and center-to-center distance of 0.44 lambda(0). Furthermore, the validation of extending to large-scale 1-D and 2-D arrays is also discussed. Featuring simple structure, compressed dimension, strong-coupling suppression, and good radiation performance, the proposed decoupling scheme possesses promising potential for antenna array applications.

Automated summary

An inductance-based decoupling scheme is proposed to reduce mutual coupling between closely spaced microstrip antennas. The inserted inductance adjusts CM and DM impedances to achieve decoupling effects, showing promising potential for antenna array applications. The proposed decoupling concept is validated through simulation, fabrication, and measurement, demonstrating improved isolation and good radiation performance.