Wideband Filtering Dumbbell-Shaped Slot Antenna With Improved Frequency Selectivity for Both Band-Edges

A novel wideband filtering dumbbell-shaped slot antenna with improved frequency selectivity for both band-edges is proposed in this paper. The filtering slot antenna is composed of a dumbbell-shaped slot, two parasitic patches, eight slot-stubs and a feeding line with a pair of step impedance resonator (SIR) stubs. An additional resonance is generated to increase the bandwidth and a gain null is produced at the upper band-edge to improve the frequency selectivity by loading parasitic patches in the dumbbell-shaped slot. Eight slot-stubs adjacent to the dumbbell-shaped slot are etched to enhance the impedance matching. In addition, the bandwidth is further broadened and two gain nulls are realized at both band-edges by adding a pair of SIR stubs. Moreover, the gain nulls can be adjusted individually by the length of parasitic patches or SIR stubs. As a result, the gain curve of the proposed filtering slot antenna has good flatness and the frequency selectivity for both band-edges is significantly improved. A prototype has been manufactured and measured to verify the validity of the design. The measured impedance bandwidth of |S
₁₁
| <; -10 dB is 62.5% (2.2 GHz - 4.2 GHz). High suppression levels of 26 dB and 30 dB can be achieved in the lower and upper stopbands, respectively.