A Wideband Filtering Antenna with Ultra-Wideband Harmonic Suppression

A wideband filtering antenna with ultra-wideband harmonic suppression is proposed. Two H-shaped parasitic patches are placed in the dumbbell-shaped slot antenna to enhance the bandwidth of the antenna. Four slot-stubs are etched to improve the impedance matching. In addition, two radiation nulls are produced by adding a pair of step impedance resonator (SIR) stubs. The ultra-wideband harmonic suppression is achieved by loading a double-head hammer-shaped stub on the feedline. The antenna has an overall size of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.64 \lambda_{0} \times 0.4 \lambda_{0} \times 0.008 \lambda_{0}$</tex>. The impedance bandwidth of antenna is 2.2-3.89 GHz (55.5<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">%</sup>), and the out-of-band suppression level is greater than 17 dB. The reflection coefficient of the antenna is greater than −3 dB in 4–17 GHz (5.7 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{0},f_{0}$</tex> is the center frequency).