Self-Decoupled Dual-Frequency Patch Antennas via Hybrid Coupling Interface Technique

This letter presents a novel hybrid coupling interface (HCI) technique to achieve self-decoupling between two dual-frequency patch antennas (DFPAs) for the first time, with no need to introduce external structures. To this end, a decoupling condition based on a detailed network analysis indicates the key to realizing self-decoupling at two operating frequencies simultaneously is that the DFPA must have two independent coupling interfaces (CIs), which is different from the single-band self-decoupling achieved by using mixed coupling in a single CI. Then, an actual DFPA with HCI, composed of a rectangular patch and a short-circuited λ/4 microstrip resonator, is proposed and constructed in a two-element array with another one, which demonstrates that decoupling can be realized by adjusting the radius of the shorting pin conveniently. Finally, experimental results show that the in-band isolation between two antennas can be enhanced beyond 15 dB across two operating frequency ranges of 3.77–3.94 GHz (4.4%) and 4.59–4.72 GHz (2.8%).