Design of a compact filter-antenna using DGS structure for modern wireless communication systems

A compact filter-antenna for modern wireless communication systems is designed in this letter. The filter-antenna comprises a microstrip square open-loop resonator, a DGS square open-loop resonator, a coupled line, and a Γ-shaped antenna. The Γ-shaped antenna is excited by a coupled line that is treated as the admittance inverter in filter design, which performs not only a radiator, but also the last resonator of the bandpass filter. Therefore, near-zero transition loss is achieved between the filter and the antenna. Measured results show that the filter-antenna achieves an impedance bandwidth of 23.7% (2.25-2.855GHz) at a reflection coefficient S11<;-10 dB.