Explicit Size-Reduction-Oriented Design of a Compact Microstrip Rat-Race Coupler Using Surrogate-Based Optimization Methods
In this paper, an explicit size reduction of a compact rat-race coupler implemented in a microstrip technology is considered. The coupler circuit features a simple topology with a densely arranged layout that exploits a combination of high- and low-impedance transmission line sections. All relevant dimensions of the structure are simultaneously optimized in order to explicitly reduce the coupler size while maintaining equal power split at the operating frequency of 1 GHz and sufficient bandwidth for return loss and isolation characteristics. Acceptable levels of electrical performance are ensured by using a penalty function approach. Two designs with footprints of 350 mm2 and 360 mm2 have been designed and experimentally validated. The latter structure is characterized by 27% bandwidth. For the sake of computational efficiency, surrogate-based optimization principles are utilized. In particular, we employ an iterative construction and re-optimization of the surrogate model involving a suitably corrected low-fidelity representation of the coupler structure. This permits rapid optimization at the cost corresponding to a handful of evaluations of the high-fidelity coupler model.
KeywordsMicrowave couplers Rat-race couplers Coupler optimization Surrogate-based optimization Computer-aided design Compact coupler Compact microstrip resonant cells
- 1.Koziel, S., Bekasiewicz, A., Kurgan, P.: Size reduction of microwave couplers by EM-driven optimization. In: International Microwave Symposium (2015)Google Scholar
- 2.Zheng, S.Y., Yeung, S.H., Chan, W.S., Man, K.F., Leung, S.H.: Size-reduced rectangular patch hybrid coupler using patterned ground plane. IEEE Trans. Microwave Theory Techn. 57(1), 180–188Google Scholar
- 11.Koziel, S., Yang, X.S., Zhang, Q.J. (eds.): Simulation-Driven Design Optimization and Modeling for Microwave Engineering. Imperial College Press, London (2013)Google Scholar
- 17.CST Microwave Studio, ver. 2013. CST AG, Darmstadt (2013)Google Scholar
- 22.Koziel, S., Bekasiewicz, A., Kurgan, P.: Rapid multi-objective simulation-driven design of compact microwave circuits. Microwave Opt. Techn. Lett. 25(5), 277–279 (2015)Google Scholar