Reactive Impedance Surface TM Mode Slow Wave for Patch Antenna Miniaturization [AMTA Corner]

This paper presents a two-layer mushroom-like reactive impedance surface (RIS) and its application to patch-antenna miniaturization. A reactive impedance surface, known as a meta-substrate, has been shown to present the ability to miniaturize printed antennas when serving as the substrate for the antenna. However, the area of conventional reactiveimpedance- surface substrates is usually much larger than that of the miniaturized antenna. Here, a reactive impedance surface with very small unit-cell dimensions (a cell area reduction of 95.6%, compared to a traditional reactive impedance surface) is proposed, and utilized to design a miniaturized antenna over a reactive-impedance-surface substrate with the same size as the antenna itself. The two-layer mushroom-like reactive impedance surface is analyzed theoretically and numerically. The reflection phase diagram of the reactive-impedance-surface substrate and the reactive impedance surface/PEC parallel plate waveguide are studied to verify the analytic model. It is shown to have a high propagation constant near the resonant frequency of the reactive impedance surface. The effect of vias in the mushroom-like reactive impedance surface is also discussed. Applying the two-layer reactive-impedance-surface substrate and an optimized miniaturized patch antenna topology, several UHF-band patch antennas, working around 400 MHz, were designed and fabricated. Using this approach, a miniaturized antenna with dimensions λ₀/11.4×λ₀/11.4×λ₀/74, including the reactive-impedance-surface substrate, was developed.