Compact Low-Profile Wideband Filtering Antenna Without Additional Filtering Structure

In this letter, a compact, low-profile wideband filtering antenna without additional filtering structure is proposed. The antenna is simple in structure and composed of a substrate, a ground plane etched with a semicircular-shaped wide slot, an inverted Y-shaped symmetrical branch, and a microstrip feedline with a quarter impedance matching line at the front end. The inverted Y-shaped symmetrical branches not only introduce a new resonant frequency point at the low-frequency band to expand the impedance matching bandwidth, but also introduce two radiation nulls in the antenna's gain response at both sides of the passband to generate good filtering performance. To verify the performance of the proposed antenna, a prototype is fabricated and measured. The measured results are in good agreement with the simulation results, demonstrating that the proposed filtering antenna has an impedance bandwidth of 33.2% (4.67–6.53 GHz), and a flat gain response in the passband with a peak realized gain of 4.92 dBi with a compact size of 0.65λ
₀
× 0.54λ
₀
× 0.01λ
₀
.