Design and implementation of a dualband microwave filter using nonuniform lines.

In this article, we propose a mapping method in which the system function of filter in z-domain is founded by discrete-time domain techniques as well as by chain-scatte ring matrices of various transmission-lines is derived to fulfill a dualbandpass microwave filter based on equal-length nonuniform coupled lines. A dualband filter with the desired bandwidth and low insertion loss is recognized by cascading bandpass and bandstop filters. The five-order Butterworth bandstop filter, which uses a coupled-serial-shunted lines structure, causes the implantation and correct placement of the bandstop filter. The wide-band bandpass filter is implemented by the five-order Chebyshev Type II band-pass filter, which uses serial lines and shunted stubs lines configuration. The design process is finished by using optimization algorithms to tune the values of characteristic impedances of each transmission-line section. Experimental results significantly agree with the theoretical values. Measurement shows that the 3 dB passband widths are about 20% for the frequency of 2.45 GHz and 10% for the frequency of 5.25 GHz. The insertion loss is about 0.831 dB at the frequency of 2.38 GHz and 1.873 dB at the frequency of 5.216 GHz. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 210–215, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22075 [ABSTRACT FROM AUTHOR]