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.

Figure 1:  Low-pass filter geometry	Dimensions
	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

Figure 2:  Comparitive results
(a) Published [1, Figure 4] (b) FEKO