A New Deformed Marchand-Balun Monopole Antenna with Band-Adjustable Structure

A design of Marchand-balun monopole antenna with band-adjustable structure and high gain was presented. The antenna is composed of a deformed Marchand-balun structure, two folded rectangular tubes, a band-adjustable structure and a ground. A kind of U-type folded Marchand-balun was skillfully integrated in the tubes of the antenna to excite the monopole differentially, which can enhance the impedance bandwidth. The Gain (~7.0 dB) was also enhanced by utilizing the folded structure of the tubes. By using the band-adjustable structure which connects the two folded rectangular tubes as a short-circuit structure, the antenna has adaptive band shifting from 1.08 GHz to 1.43 GHz. Moreover, the frequency band of the proposed antenna can change from dot frequency mode(narrow band) to wide band mode by adjust the position of the band-adjustable structure. The proposed antenna can be easily formed an array for home radar chain (HRC) and personal communications service (PCS).