Design of wideband antenna for mobile communications

Abstract

Circular polarization design of single feed microstrip wideband antenna is studied by simulation and experiment in this project. One of the fabricated configuration attains Left Hand Circular Polarization (LHCP) in Axial Ratio bandwidth (< 3 dB) of about 4.55% within the impedance matching bandwidth (14.92%) when the substrate thickness is about 0.05λo. The comparison of low permittivity substrate like air (εr =1) is studied. It is found that larger permittivity thus can result in a smaller physical antenna size at a fixed operating frequency. That’s why a relatively higher dielectric constant (εr = 10.02) of substrate is adopted here. The objectives of this project are not only considering the antenna size, but also enhancing impedance bandwidth and providing relatively high gain antenna. Adding a U-slot cavity on the radiating patch is one of methods to broaden the impedance bandwidth by adjusting the dimension and position of the U-slot. In addition, using different size of ground plane can affect the gain of antenna. In order to prove those performances, simulations and fabrications are presented in this report. For the experiment, two prototype antennas with different size of ground plane are fabricated for evaluation.