Beam-steering of microstrip antenna using single-layer FSS based phase-shifting surface

In this article, beam-steering of microstrip antenna (MSA) is demonstrated in a cost-effective manner using a single-layer, low-loss passive frequency selective surface (FSS) based on a phase-shifting surface (PSS). A quasi-periodic spatial PSS is constructed by arranging four rows of eight split-ring resonators (SRR) shaped unit cells having different geometrical parameters but identical dimensions and placed adjacent to each other with a periodicity (p) of 0.18 lambda, where lambda is the wavelength corresponding to the resonant frequency (4.5 GHz) of the fundamental unit cell. The geometrical parameters of the SRRs are tailored to control the surface impedance and the transmission phase across the surface area to reshape the phase front of the transmitted waves. A directive MSA operating at 5.5 GHz, is also designed and integrated with this PSS to demonstrate the beam-steering capability. On rotating/shifting the PSS over the MSA, beam-steering in the elevation plane is accomplished across -30 degrees to +30 degrees without degrading its reflection coefficient characteristics, with a maximum gain of 8.9 dBi. The best antenna performance in terms of beam tilt and gain is achieved when the PSS is vertically placed and fixed above the MSA. The MSA integrated with the non-uniform metasurface exhibits 75% radiation efficiency with a front to back ratio of 55.5 (17.4 dB). A prototype is fabricated and measured as a proof of concept. The measured results are consistent with full-wave simulation results.