Broadband dual-frequency operation of circular patch antennas and arrays with a pair of L-shaped slots

By embedding properly arranged L-shaped slots in a circular patch, a novel broadband dual-frequency design is proposed and experimentally studied. With the use of an L-strip microstrip line for feeding the proposed antenna, the impedance bandwidths, determined from 10 dB return loss, of two operating bands can reach about 7.0% to 12.5% for the lower band and 18.9% to 21.5% for the higher band. Operating frequencies across the obtained lower and higher bands are of the same polarization planes, and have a tunable frequency ratio between the center frequencies of the two operating bands ranging from about 1.31-1.61. The application of the proposed antenna to the design of a 2 x 2 broadband dual-frequency patch antenna array is also demonstrated. Details of the proposed broadband dual-frequency design are described, and experimental results of the constructed prototypes are presented and discussed.