A Novel Tri-Band Patch Antenna With Broadside Radiation and Its Application to Filtering Antenna

A tri-band patch antenna utilizing the TM
₁₀
mode together with modified TM
₂₀
and TM
₃₀
modes of a single patch is proposed in this communication. Through asymmetrically loading a stub on one radiating edge of the patch and cutting a rectangular slot offset from the other one, the current distributions of the TM
₂₀
and TM
₃₀
modes are perturbed, resulting in broadside radiation for all the first three modes of a single patch. Each operational frequency can be effectively controlled through varying the dimensions of the patch, slot, and loading stub. Good impedance matching is achieved simultaneously in three operational bands through aperture coupling. A prototype is designed, fabricated, and measured for validation. Based on this tri-band antenna, a new tri-band filtering antenna is further developed, showing good selectivity and broadside radiation characteristic.