Design of Compact, Single-Layered Substrate Integrated Waveguide Filtenna With Parasitic Patch

A compact, single-layered substrate-integrated waveguide (SIW) filtenna with parasitic patch is synthesized and designed. A half-mode substrate-integrated rectangular cavity (HMSIRC) is adopted as the first stage resonator to reduce the circuit size. A parasitic patch functioning as the last stage resonator as well as the radiator is arranged closely to the HMSIRC so as to enhance the operational bandwidth and facilitate the filtering performance. Two broadside radiation nulls are realized at both the upper and lower band-edges to sharpen the band-edge roll-off rate: one is generated by the interaction between the HMSIRC and the parasitic patch, and the other is introduced by placing two pairs of shorting posts under the parasitic patch. The standard filter synthesis technology is utilized to guide the filtenna design. The optimized prototype was fabricated and measured. The measured results, in good agreement with simulated values, indicated the proposed filtenna provides a 5.1% fractional bandwidth, a maximum realized gain of 6.3 dBi, and a flat passband gain response along with excellent out-of-band selectivity, even with ultralow profile 0.015 λ
₀
and small volume 0.005 λ
₀
³
.