Design Of Broadband/Dual-Band Circularly Polarized Microstrip Slot Antennas

As a key component of the wireless radio systems, Antenna has critical influenceson the performance of the system. Circularly polarized (CP) antennas are widely usedin many systems, such as satellite communication systems, GPS, remote sensingsystems and electronic warfare systems. In circularly polarized communication systemapplications, microstrip antennas are particularly attractive due to their low profile,light weight, easy integration with RF circuits and easy to achieving circularlypolarized radiation. In this thesis, three CP microstrip slot antennas for wirelesscommunication systems are addressed.Firstly, a broadband CP slot antenna fed by microstrip line is presented. As slightperturbation segments for generating CP radiation, the metal strip connected withmicrostrip line and the horizontal strip connected with the center circular slot areintroduced. The measured|S11|≤-10dB impedance band can be up to41.3%(4.79-7.04GHz), and the simulated3dB AR bandwidth is15.6%(5.08-5.94GHz).Secondly, the broadband CP slot antenna fed by the coplanar waveguide (CPW) ispresented. As the perturbation segments for generating CP radiation, a narrow slot isdeposited at the corner of a square metal loop. In addition, by adjusting the length ofthe narrow slot, the3dB AR bandwidth can be significantly enhanced. The measured|S11|≤-10dB impedance band can be up to35.6%(1.80-2.58GHz), and the simulated3dB AR bandwidth is17.5%(2.08-2.48GHz).Finally, the microstrip CP slot antenna fed by CPW is proposed for dual-band CPradiation. The HFSS software is utilized to analyze and optimize the antennaparameters. It can be obtained that the antenna possesses the simulated10dB returnloss impedance bandwidth of17.6%(1.86-2.22GHz) and25.2%(2.78-3.58GHz). Thesimulated3dB AR bandwidths for the lower and upper bands can be up to17.6%(1.86-2.22GHz) and23.3%(2.88-3.64GHz), respectively.