The Study Of Dual Polarization Microstrip Antenna On Millimeter-wave

With the increasing development of millimeter wave technology, the applicationof millimeter wave system is becoming widely used. Dual-polarization has becomea trend for the most modern radar system due to the characteristics that it can makefull use of the polarization information of the radar signal. Hence, dual-polarizationmillimeter wave antenna should be designed to meet the requirements of thedevelopment of modern millimeter wave radar system. The design in this article isbased on the microstrip antenna because of the traits of it such as low profile, lowcost, and small volume. The author designed two kinds of antenna units and arraywith different feed mode—coplanar waveguide (CPW)-fed and slot-coupled fed.Firstly, the design and analysis of a simple CPW-fed antenna is carried out. Afterthe analysis of the electric current on the conductor surface, the reason of poorisolation between the ports has been found. And then by adding two parallelmicrostrip and three small rectangle slot, the isolation of the new antenna is lessthan-20dB across the operating band. Besides, the purpose of using a stud insteadof the parallel microstrip is to decrease the cross-polarization to-20dB. Meanwhile,the DGS is applied to the CPW for better impedance matching, and then the antennaunit is suitable for millimeter-wave radar.Secondly, the article designs three antenna units and a2×2antenna array with acombination of the slot-coupled fed and the coupled fed. The first antenna is asimple structure and its impedance bandwidth is7%. After employing coplaneparasitic patches and spatial parallel parasitic patch, the bandwidth is broadening to12%and20.53%, respectively. Then, the “pair-wise anti-phase” technology is usedto design the array antenna. The impedance bandwidth of the proposed antenna is6.13%at the center frequency of37.5GHz, the isolation is less than-30dB and thecross-polarization is-23.6dB. The gain of the antenna is11.5dB. The measure datais compared with the simulated results.Finally, the study uses the VBScript to combine the Genetic Algorithm and theAnsoft HFSS. The method of this article employed is overlapping subpatches whichensure the electrical contact between subpatches. The object of optimization is the slot-coupled antenna, meanwhile the purpose of this method is to broaden thebandwidth. At last, the impedance bandwidth of the antenna is extended from2.64GHz to3.99GHz. The feasibility of this method is confirmed.