A Differentially Fed Broadband Multimode Microstrip Antenna

A differentially fed microstrip antenna is proposed. The antenna is mainly composed of four strips, two rows of shorting pins, and four pieces of parasitic patches. The TM10, antiphase TM20, and TM12 modes are excited and matched simultaneously over a broadband. The experimental results show that, though the proposed antenna has a low profile of 0.052λ0 (λ0 is the free-space wavelength at the center frequency), it has the -10 dB impedance operating band of 4.25-6.27 GHz and the relative bandwidth of 38.4%. The variation of the measured gain which is 7.21±0.36 dBi is less than 1 dB over the whole operating band. The proposed antenna achieves good performances of broadside radiation with the measured front-to-back ratio of larger than 17 dB, stable radiation patterns without null, and stable gain in the operating band.