Decoupling Between Extremely Closely Spaced Patch Antennas by Mode Cancellation Method

• Published in: IEEE transactions on antennas and propagation Vol. 69; no. 6; pp. 3074 - 3083
• Main Authors: Sun, Libin, Li, Yue, Zhang, Zhijun
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antenna arrays; Boundary conditions; Closely spaced patch antennas; Couplings; Decoupling; Inductance; Microstrip antennas; mode cancellation method (MCM); multiple-input multiple-output (MIMO); Mutual coupling; Patch antennas; Topology
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2020.3030922

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 2.394-2.530 GHz, with an extremely close edge-to-edge distance of <inline-formula> <tex-math notation="LaTeX">0.016~\lambda _{0} </tex-math></inline-formula> and center-to-center distance of <inline-formula> <tex-math notation="LaTeX">0.44~\lambda _{0} </tex-math></inline-formula>. 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.