Shunt Coupled Spiral Inductor

A spiral inductor on a substrate is simulated in a shunt configuration and its S-parameters extracted.

This article presents FEKO simulations that are representative of RF components that are constructed on a dielectric.  The model that is simulated here is a shunt coupled spiral inductor that was also analysed by Polycarpou et al [1].

Figure 1 depicts the shunt coupled spiral inductor and S-parameter results from [1, Figure 6].  Figure 2 presents the FEKO method of moments (MoM) simulation model and the FEKO simulated results.  The model was constructed with CADFEKO.  The substrate was modelled as a semi-infinite plane Green’s function for the MoM solution and as a finite dielectric block for the finite difference time domain (FDTD) solution.

The FEKO results compare favourably with the published results  [1, Figure 6], validating the FEKO model and simulation techniques.  Small differences in the results are due to uncertainties in the model dimensions between the published model and the FEKO model, e.g. length of the main transmission line, exact dimensions of the right angle coupling between the spiral and the w3 line from the main transmission line.

Simulation model

Figure 1: Simulation model and results, [1, Figure 6]


  • Alumina substrate:
    • εr = 9.8
    • h = 0.635 mm
  • w1 = 0.635 mm
  • w2 = 0.2 mm
  • w3 = 0.6 mm
  • R1 = 1.9 mm
  • R2 = 1.3 mm
  • R3 = 0.7 mm

Figure 2: FEKO shunt coupled spiral inductor simulation

Method of moments

(a) Method of moments model

 Computed S-parameters

(b) Computed S-parameters

The results from [1] are for a FEM full-wave solution. By comparing the FEKO results to the published FEM results and getting the degree of correlation shown in Figure 2(b), it is reasonable to assume that the results are accurate for the real-world problem being analysed.

[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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