In this article, grey-box and black-box surrogate modeling are described, with some key findings. The important point is that surrogate modeling has a solid mathematical basis leading to what has become a dramatic increase in our ability to develop engineering models and to engineer systems. In Section 2, a systematic approach to constructing surrogate models is provided. Each step is explained using published methods. Section 3 presents surrogate modeling examples from the domain of circuits and systems.

Demystifying Surrogate Modeling for Circuits and Systems

In this paper, a class of dual-band ring-resonator bandpass filters is proposed based on a single ring resonator. As its most distinctive feature, two pairs of first- and second-order degenerate resonant modes in a ring resonator are simultaneously excited, resulting in a compact dual-mode dual-band bandpass filter with two transmission poles in both passbands. Firstly, two capacitors or parallel-coupled lines are placed at two nonorthogonally excited positions along a ring resonator in order to excite the two first-order degenerate modes and create multiple transmission zeros. Next, a set of perturbations is introduced on the ring to excite the two second-order degenerate modes. In our design, two excitation positions are first placed with between 45°- and 135°-separation on a ring. Simulations show that, with a proper arrangement of the excitation angle, two transmission poles in the first passband can be excited and more transmission zeros can be generated. Four and eight open-circuited stubs are loaded symmetrically along the ring, resulting in synchronous excitation of two poles in the second passband. Of the two designed filters with 135°- and 45°-separation, the one with 45° exhibits much better out-of-band performance with three additional transmission zeros at frequencies lower than the first passband, between the two passbands and higher than the second passband. Finally, two filter prototypes are fabricated and their measured results are found to be in good agreement with theory.

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A Dual-Band Ring-Resonator Bandpass Filter Based on Two Pairs of Degenerate Modes

Two novel balanced filters with wideband common mode suppression using dual-mode ring resonators are proposed in this paper. Two and four transmission zeros close to the passband are realized to improve the selectivity for the differential mode. In addition, over 20-dB common mode suppression can be realized from 0 GHz to $5f_{0}$ ( $f_{0}$ is the center frequency of the passband), due to the all-stop transmission characteristic of the open/shorted coupled lines. To verify the presented concepts, two prototypes ( $\varepsilon_{r}=2.65$ , $h=1.0\ {\rm mm}$ ) with 3-dB fractional bandwidths of 22.9% and 21.9% for the differential mode are designed and fabricated. The theoretical and measured results agree well and show good in-band filtering performance and high selectivity.

Balanced filters with wideband common mode suppression using dual-mode ring resonators

Convergence is a well-known issue for standard space-mapping optimization algorithms It is heavily dependent on the choice of coarse model, as well as the space-mapping transformations employed in the optimization process One possible convergence safeguard is the trust region approach where a surrogate model is optimized in a restricted neighborhood of the current iteration point In this paper, we demonstrate that although formal conditions for applying trust regions are not strictly satisfied for space-mapping surrogate models, the approach improves the overall performance of the space-mapping optimization process Further improvement can be realized when approximate fine model Jacobian information is exploited in the construction of the space-mapping surrogate A comprehensive numerical comparison between standard and trust-region-enhanced space mapping is provided using several examples of microwave design problems

Robust Trust-Region Space-Mapping Algorithms for Microwave Design Optimization

Contemporary design in engineering and industry relies heavily on computer simulation and efficient algorithms to reduce the cost and to maximize the performance and sustainability as well as profits and energy efficiency. Solving an optimization problem correctly and efficiently requires not only the right choice of optimization algorithms and simulation methods, but also the proper implementation and insight into the problem of interest. This book consists of ten self-contained, detailed case studies of real-world optimization problems, selected from a wide range of applications and contributed from worldwide experts who are working in these exciting areas.Optimization topics and applications include gas and water supply networks, oil field production optimization, microwave engineering, aerodynamic shape design, environmental emergence modelling, structural engineering, waveform design for radar and communication systems, parameter estimation in laser experiment and measurement, engineering materials and network scheduling. These case studies have been solved using a wide range of optimization techniques, including particle swarm optimization, genetic algorithms, artificial bee colony, harmony search, adaptive error control, derivative-free pattern search, surrogate-based optimization, variable-fidelity modelling, as well as various other methods and approaches. This book is a practical guide to help graduates and researchers to carry out optimization for real-world applications. More advanced readers will also find it a helpful reference and aide memoire.

Computational Optimization and Applications in Engineering and Industry

This paper deals with a dual-mode ring resonator fed by quarter-wavelength side-coupled lines. The resonator synthesis was developed so as to fix the central frequency, bandwidth, and transmission zeros frequencies, as well as the insertion loss in the passband. Based on this resonator, several bandpass filters were designed, which include the cascaded rings and the combination of such ring resonator with coupled line sections. Simulations are proposed throughout the paper to illustrate the various possibilities offered by the concept. The filters' experimental results in microstrip technology are also presented to validate the idea.

O. Pigaglio

Papers

Quarter-Wavelength Side-Coupled Ring Resonator for Bandpass Filters