A miniature dual-band filter based on microstrip dual-mode resonators

A microstrip dual-band bandpass filter (DBF) with an original miniature design is described. The filter consists of thee microstrip dual-mode resonators, which are rendered dual-mode by splitting their regular strip conductors from one end by longitudinal slots. The formation of one passband of the DBF involves the resonances of even modes of each microstrip double-mode resonator, while the other passband is formed by the resonances of odd modes. The proposed device is simple to manufacture and allows the central frequencies and widths of each passband to be tuned within broad limits. A method of DBF tuning has been developed. Good prospects of the proposed microstrip DBF are confirmed by the high characteristics of its working prototype.