A novel differential equation model for a microstrip low‐pass filter

Abstract

AbstractHow to extract equivalent circuit parameters from full‐wave results is becoming an increasingly important aspect of microstrip filter design. In this paper, a microstrip low‐pass filter that is made of six stubs is analyzed by a novel differential equation whose coefficients are determined from full‐wave numerical solutions. In comparison with the conventional nonuniform transmission line equation, the novel differential equation has two additional terms—dependent series voltage and shunt current sources—which represent local radiation effect from discontinuities of the nonuniform transmission line itself. A whole structure of the above microstrip low‐pass filter can be regarded as a special case with a finite‐length non‐uniform transmission line. Thus, the novel differential equation can be used to analyze this kind of microstrip low‐pass filter. The novel differential equation established at a frequency of 10 GHz could cover a very wide frequency range from 6 GHz to 15 GHz. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 368–370, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10609