Design of wideband opened quarter wavelength microstrip patch antennas for mobile communication system

Abstract

Opened quarter wavelength patch antennas fed by L-shape probe are designed and studied experimentally. The impedance bandwidth, radiation pattern and the gain of the antennas are investigated and compared with the corresponding shorted quarter wavelength patch antennas. The bandwidth of the antenna is 39% (SWR<2), which cover the existing mobile communication bands, PCS, CDMA and 3G with frequency ranging from 1.71GHz to 2.17GHz (SWR<1.4). The radiation patterns are found to be better than the corresponding shorted quarter wavelength patch antennas. The cross polarization level improvement in H-plane is about 10dB and the gain improvement is about 5dB. The E-plane beam squint is a disadvantage for the shorted quarter wavelength patch antennas, the proposed antennas could fill the unwanted beam squint, and the improvement is about 10dB. Besides the opened quarter wavelength patch antennas are having superb performances, this antenna is also simple in construction, which could reduce the manufacturing costs. This antenna design is suitable for the application in the small base station antenna or in the mobile phone, which performance, size and the cost are both the important factors.