Investigation on phase properties of circular microstrip antenna

Phased array antennas for scanning a beam over large angles have numerous applications, which are expected to increase with the expansion of wireless systems and the use of smart antennas. In large arrays, however, the number of phase shifters can be large and at UHF and millimetre wavebands can introduce insertion losses. Alternative approaches to simplify the phase shifter complexity or reduce their number can be beneficial. One possibility is to use the antenna parameters as variables to modify its impedance characteristics, and thus the insertion phase. This possibility is becoming realistic by the use of MEMS technology (see Bozler, C. et al., MTT-S, 2000). Due to this fact, the phase properties of a microstrip antenna, in terms of its dimensions, are studied. The antenna dimensions are modified such that its input impedance match remains acceptable, by keeping S/sub 11/<-10 dB. For the study, both the cavity model and the full wave numerical analysis method are utilized and discussed. Using micromachining techniques, the antenna parameters may be made a source of the phase shift for phase array antennas. With a circular microstrip patch antenna, up to 70 degree phase shift can be achieved.