Design of Short Microstrip Leaky-Wave Antenna With Suppressed Back Lobe and Increased Frequency Scanning Region

We demonstrate a short (1.08lambda
_o
) microstrip leaky-wave antenna (MLWA) with suppressed back lobes and doubled frequency scanning region. The configuration of the proposed LWA contains three parts: the conventional open structure MLWA, the added monopole connected to the end of the MLWA on a defected ground plane, and the Yagi-Uda-like elements fabricated along the monopole. Because of the open structure of the MLWA, the reflected power produces a large back lobe radiated backwardly. By using the method of the added monopole connected to the end of the antenna, the remainder power could radiate through the added monopole without reflecting at the end. In addition, the Yagi-Uda-like elements fabricated along the added monopole enlarge the frequency scanning region due to the Yagi-Uda antenna characteristic. Compare to the conventional MLWA, the back lobe of the proposed LWA is suppressed about 8 dB at 5.0 GHz. The frequency scanning region of the H-plane (YZ-plane) of the proposed LWA can scan from 34deg to 57deg (total 23deg) while the frequency is operated from 4.6 GHz to 5.0 GHz; meanwhile the conventional MLWA scans from 30deg to 41deg (only 11deg) at the same frequency region.