Microstrip Patch Filtering Antenna with High Roll-off Rat

Abstract

This paper presents a compact filtering microstrip patch antenna with integrated band-rejection functionality. The design incorporates a dual-layer configuration combining a driven radiator and a parasitic superstrate, achieving a vertical profile of 0.08λ. Three strategically positioned grounding vias and a U-shaped aperture integrated into the primary radiator collectively optimize lower-band suppression (>21.7 dB) while improving transition steepness at the lower operational boundary. Concurrently, the superimposed parasitic layer serves dual purposes: enforcing abrupt roll-off characteristics (>21.9 dB suppression) at the upper band edge and enhancing radiative efficiency.Engineered for the n77 spectrum (3.28–3.85 GHz), the prototype demonstrates a fractional bandwidth of 16% with an average realized gain of 8.0 dBi across the operational band. The architecture exhibits superior spectral confinement, delivering over 21.7 dB rejection in the lower stopband and exceeding 21.9 dB suppression in the upper stopband, outperforming conventional designs in adjacent frequency isolation and in-band performance uniformity.