Tuneable and dual-band circular microstrip antenna with stubs

A circular microstrip antenna loaded along its feed axis with either one stub or two stubs has been analyzed using an improved linear transmission line model. When the length of the stub is small, the frequency is tuned over a 9% range in the L-band and, when it is comparable to /spl lambda//4, it exhibits dual-frequency operation. The experimental results are in good agreement with the theoretical results.