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Transition from Microstrip To Coplanar Waveguide (CPW) simulated in SolidWorks

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Microstrip to Coplanar waveguide transition

In hybrid integrated circuits design, transition between microstrip and CPW is essential. This article demonstrates the application of HFWorks and SolidWorks to design and simulate a transition from microstrip line to coplanar waveguide.

This approach of using HFWorks and SolidWorks is ideal for such applications because the structure can be easily modeled and simulated inside SolidWorks. One of the methods to realize microstrip to CPW transition is based on two couples of microstrip-to-slot line transitions.A broadband transition from microstrip to CPW is presented in this article.The structure fundamentally utilizes two pairs of microstrip-to-slotline transitions to achieve this.At the lower frequency below the passband, the input impedance contains capacitive reactance. To counteract the capacitive reactance, a short-ended microstrip stub is introduced to connect in parallel with the microstrip line.

The S Parameters simulation in HFWorks was used to simulate the transition from microstrip to CPW for hybrid integrated circuits. Figure 1 shows the 3D model of the transition from microstrip line to CPW.

Figure 1 - 3D model of the transition from microstrip line to CPW (a) top view of the model, (b) bottom view of the model

The layout of the transition from Microstrip to CPW is depicted in figure 2, the gemeometrical results are summarized in table 1.

Figure 2 - Layout of the microstrip-to-CPW transition structure with a shortended microstrip stub

Simulation Results

Figure 3 shows a comparison between the simulated results of S parameters and the appropriate measurements of a single microstrip-to-CPW transition. The two results are in goodagreement. The simulated results indicate that, for the return loss ofbetter than 10 dB, a broad bandwidth of 2.05 to 9.96 GHz is achieved.

Figure 3 - Return and insertion loss of the transition from microstrip to CPW (dB)

The maximum and minimum insertion losses of thetransition passband are 1.7 dB and 0.2 dB, respectively.

Conclusion

This article shows how to simulate the transition from microstrip to CPW with wide bandwidth and low insertion loss. Further, good agreement between the simulated and the measured results was achieved. The study proves that the usage of modern simulation tools like HFWorks can help the designers of transition from microstrip to CPW create and validate their designs easily in a computer without the need to create and test multiple prototypes.

References

[1] Ziwen Tao" Broadband Transition Design From Microstrip to CPW", IEEE Microwave and wireless components letters, vol. 25, NO. 11, November 2015, pp 712-714.