Design of A Size-Reduced, Tunable Yagi Antenna

A Yagi antenna with frequency tunability using variable capacitance elements is investigated. This antenna is size reduced with the use of top loading to decrease the height of the driver and the two directors. Folding is used to decrease the spacing between the elements of the Yagi antenna. Then, varactors are added onto the bottom of each director to electrically tune the resonant frequencies of the two directors. The total frequency tunable bandwidth is increased by combining the tunable bands of each director. The total frequency tunable bandwidth of 19.8% is achieved.