Low-Pass Microstrip Filter

A low-pass microstrip filter is analysed in FEKO and the results compared to published media.

This article analyses a microstrip low-pass filter that was originally analysed in [1].  The filter was implemented using CADFEKO with the substrate being approximated with a semi-infinite Green’s function layer.  Figure 1 presents the FEKO model and dimensions, while Figure 2 presents a comparison between the results of the FEKO S-parameter computation and the results from [1, Figure 4].

The FEKO simulated results compare well with the published results, validating the simulation techniques.  Small differences between the FEKO and published results may be attributed to uncertainties between the published and CADFEKO geometries, e.g. length of the port stubs and the spacing between the port elements along the centre track.

 Low-pass filter geometry

Figure 1: Low-pass filter geometry


  • Substrate: RT/Duroid
  • εr = 2.2
  • h = 0.794 mm
  • w1 = 2.413 mm
  • w2 = 2.413 mm
  • w3 = 2.54 mm
  • L1 = 12.257 mm
  • L2 = 5.65 mm
comparative results

Figure 2: Comparative results

[1] A.C. Polycarpou, P.A. Tirkas, and C.A. Balanis, “The Finite-Element Method for Modeling Circuits and Interconnects for Electronic Packaging,” IEEE Trans. on Microwave Theory and Techniques, Vol. 45, No. 10, October 1997
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