Decoupling of Closely Spaced E-Plane Patch Antennas Using Compact Shorted Stepped-Impedance Strips

This letter proposes a shorted stepped-impedance strip (SSIS) decoupling approach for closely spaced E-plane patch antennas. By introducing a pair of SSISs between the two antennas, band-stop decoupling is achieved through the combined effect of the inductive/capacitive characteristics of the SSISs and their capacitive coupling with the patches. An equivalent-circuit model of the antenna is established to reveal the analytical relationship between the decoupling null and the circuit parameters, and to clarify the correspondence of these parameters to the SSIS placement and geometrical dimensions. The proposed antenna has a center-to-center spacing of only 0.295λ0, and the effective length of each SSIS is about λe/6. Measured results show that the antenna achieves a maximum isolation of 34 dB and a 20-dB isolation bandwidth of 8.3%.