A Compact Frequency-Reconfigurable Differential-fed Microstrip Antenna

A compact differential-fed microstrip antenna with continuous frequency-tuning performance is presented in this paper. The continuous frequency-tuning capability of the developed antenna is realized by loading a pair of varactor diodes that are located on two shorted strips, along each of the radiation edges of the microstrip antenna. By changing the capacitance value of the varactor diodes, the impedance bandwidth of the developed antenna could achieve a continuously varying in the range of 1.60-2.39GHz, i.e., a fractional bandwidth of 39.6%. Meanwhile, the antenna exhibits low cross-polarization levels below −40dB and stable directional radiation capability over the whole operational bandwidth.