Dual-band bandpass filters using equal-length coupled-serial-shunted lines and Z-transform technique

• Published in: IEEE transactions on microwave theory and techniques Vol. 52; no. 4; pp. 1111 - 1117
• Main Authors: Tsai, L.-C., Hsue, C.-W.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.04.2004; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Band pass filters; Bandwidth; Digital filters; Dual band; Microstrip filters; Microwave filters; Microwave frequencies; Passband; Transfer functions; Wideband
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2004.825680

A synthesizing method is presented to design and implement digital dual-band filters in the microwave frequency range. A dual-band filter consists of a bandstop filter and a wide-band bandpass filter in a cascade connection, wherein the transfer functions of both the bandpass filter and bandstop filter are expressed in the Z domain. The bandstop filter is implemented by using a coupled-serial-shunted line structure, while the wide-band bandpass filter is constructed by using a serial-shunted line configuration. In particular, the bandwidth of each passband of the dual-band filter is controllable by adjusting the characteristics of both the bandpass filter and bandstop filter. By neglecting the dispersion effect between microstrip lines of different widths over a wide bandwidth, a dual-band filter is realized in the form of microstrip lines and its frequency responses are measured to validate this method.