Summary: 108 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 47, NO. 1, JANUARY 1999
Fig. 4. Magnitude of S-parameters for the edge-coupled filter.
excitation are transferred into the circuit without any loss. The S21
is almost unity, whereas S11 is very small, as would be expected.
B. Edge-Coupled Filter
In order to further prove the accuracy of the excitation modeling
introduced here, using a more complicated structure, the analysis of
the microstrip edge-coupled filter shown in [5, Fig. 6] is considered.
The measurements performed by Shibata et al.  are used as a
standard for comparison.
As seen in Fig. 4, there is a clear agreement between the introduced
excitation modeling and measured data. The use of traveling current
waves with truncation yields completely meaningless results because
the minimum operation frequency is 1 GHz with the corresponding
length of the truncated cosine portion being 29.14 mm. This is
almost 46 times bigger than the size of the rooftop in the direction
of the propagation for the definition (lx = w=4 = 0:318 mm
and lz = l=20 = 0:636 mm). Even at the maximum operating
frequency, which is 15 GHz, extra rooftops are still required to
cover the missing portion. For the maximum operating frequency,