Inset microstrip-line fed dual frequency microstrip patch antenna

In this paper, a novel single-feed dual-frequency microstrip patch antenna is presented and discussed. With proper selection of slot loading and inset feed, dual frequency operation of a patch antenna, with a frequency ratio between 1.03∼1.2 can be achieved, whilst maintaining an input impedance of 50 Ω at both frequencies. The main advantage of this design is that it can be fed directly through the use of a 50 Ω inset microstrip feed line, thus allowing easier integration with associated planar microwave circuitry and antenna arrays. The design technique and measured results for the patch configuration are shown, in which it is demonstrated that a return loss of below -15 dB at both frequencies can be achieved. The measured radiation pattern achieves low cross polarisation levels of below -20 dB at both design frequencies.