A Reconfigurable Balanced Filtering Antenna with High Common-Mode Suppression

A reconfigurable planar balanced quasi-Yagi antenna integrated with a bandpass filtering response is presented in this paper. The proposed antenna consists of a balanced stepped-impedance microstrip-slotline transition structure, a driver dipole, a pin diode, a parasitic strip and a bandpass filtering unit. A differential-mode (DM) assband with a sharp filtering performance is realized by introducing a microstrip stub-loaded resonator (SLR). By pin diode over the open-stub of SLR, the effective electrical length of the antenna can be changed, leading to an electrically tunable operating bandwidth. The antenna maintains radiation performance similar to that of the conventional quasi-Yagi antenna. Meanwhile, there are two radiation nulls on both sides of the passband to enhance the selectivity greatly. For the common-mode (CM) signals, the microstrip-slotline transition structure can achieve a good wideband CM suppression without affecting the DM ones, thus simplify the design procedure.