Harmonic Suppression of Microstrip Antenna by Defected Microstrip Structure

In this paper, a microstrip antenna with suppressed harmonics at 3.55 GHz is proposed. To achieve this operation, a short U-shaped defected microstrip structure (DMS) and a long U-shaped DMS are etched on the microstrip-feed line. The second harmonic can be reduced by using the long U-shaped DMS; meanwhile the short U-shaped DMS accomplishes the third harmonic suppression. The return loss of the proposed antenna at the fundamental, the second harmonic and the third harmonic frequencies are simulated and compared to that of the conventional microstrip antenna. It has been confirmed that the proposed antenna obtains outstanding harmonic suppression characteristic in the second- and third-harmonic frequencies.