Design of a wide stopband bandpass filter with the two-path coupled lines

A compact bandpass filter with a wide stopband has been proposed. This filter consists of two two-path coupled lines and a bandpass filter. Moreover, the two-path coupled lines employed for a wide stopband are connected at input/output ports separately. Therefore, the harmonics passed by the bandpass filter can be suppressed. A design example with 1 GHz for the central frequency is provided. In addition, a wide stopband, more than six times as the central frequency ƒ
0
, is obtained.