Design of a Compact, High Frequency Selective Broadband Substrate Integrated Waveguide Filtering Antenna

This paper presents a compact substrate integrated waveguide (SIW) filtering antenna operating at 4.9 GHz, designed using a stacked configuration of two resonant cavities. The miniaturized antenna has overall dimensions of λ0 × 0.74λ0 × 0.069λ0 (where λ0 is the free-space wavelength at 4.9 GHz). A microstrip stub is introduced between the two resonant cavities to enhance coupling paths, thereby generating radiation nulls at the upper and lower stopbands, which contribute to improved frequency selectivity. Additionally, the designed microstrip stub acts as a first-order resonator, creating an extra resonance point within the passband and achieving an impedance bandwidth of 28%. The antenna maintains stable gain within its passband, with out-of-band suppression exceeding -14 dB.