A Broadband Microstrip Antenna with Stable Gain

A low-profile and broadband microstrip antenna with stable gain is proposed and studied. The radiation patch of the proposed antenna is shorted by two rows of shorting pins and is divided into six pieces by three slots. The antenna is fed by a microstrip line through a slot cut on the ground. Two resonance modes with broadside radiation are excited simultaneously. The proposed antenna achieves a broad operating band of 4.05-5.86 GHz and the relative bandwidth of 36.5% with a profile of 0.06 λ0 (λ0 is the center operating wavelength in the free space). It has an extremely stable gain of 5.7-6.5 dBi and stable radiation patterns without null in the operating band.