Compact dual-band quasi-elliptic bandpass filter with transmission-zero control

A novel compact dual-band bandpass filter based on a simple defected ground structure is proposed. This filter offers quasi-elliptic responses at both the passbands, and all its four transmission zeros near the passbands can be controlled to design for a wide range of center frequencies and bandwidths, without degrading the in-band performance in general. In this paper two dual-band bandpass filters are designed to demonstrate the effectiveness of the approach. The measurement shows a very good agreement with the simulation results. In addition, the implemented filters have sizes less than 0.24γ × 0.17γ and around 30 dB rejection in the stopband between passbands.