Abstract
Fabrication tolerances, as well as uncertainties of other kinds, e.g., concerning material parameters or operating conditions, are detrimental to the performance of microwave circuits. Mitigating their impact requires accounting for possible parameter deviations already at the design stage. This involves optimization of appropriately defined statistical figures of merit such as yield. Although important, robust (or tolerance-aware) design is an intricate endeavor because manufacturing inaccuracies are normally described using probability distributions, and their quantification has to be based on statistical analysis. The major bottleneck here is high computational cost: for reliability reasons, miniaturized microwave components are evaluated using full-wave electromagnetic (EM) models, whereas conventionally utilized analysis methods (e.g., Monte Carlo simulation) are associated with massive circuit evaluations. A practical approach that allows for circumventing the aforementioned obstacles offers surrogate modeling techniques, which have been a dominant trend over the recent years. Notwithstanding, a construction of accurate metamodels may require considerable computational investments, especially for higher-dimensional cases. This paper brings in a novel design-centering approach, which assembles forward surrogates founded at the level of response features and trust-region framework for direct optimization of the system yield. Formulating the problem with the use of characteristic points of the system response alleviates the issues related to response nonlinearities. At the same time, as the surrogate is a linear regression model, a rapid yield estimation is possible through numerical integration of the input probability distributions. As a result, expenditures related to design centering equal merely few dozens of EM analyses. The introduced technique is demonstrated using three microstrip couplers. It is compared to recently reported techniques, and its reliability is corroborated using EM-based Monte Carlo analysis.
Highlights
Microwave design workflows, including optimization procedures, are most often concerned with nominal designs, where possible uncertainties of geometry and material parameters are not accounted for
The numerical results obtained using the proposed design centering approach as well as the reference algorithms outlined in Section 3.2 have been gathered in Table 2 through
As the surrogate is a linear regression model, a rapid yield estimation is possible through numerical integration of the input probability distributions
Summary
Microwave design workflows, including optimization procedures, are most often concerned with nominal designs, where possible uncertainties of geometry and material parameters are not accounted for. Fabrication tolerances, incomplete knowledge of material characteristics (e.g., dielectric permittivity of the substrate) or operating conditions (temperature, geometrical distortions, input signal power), might all alter the electrical performance parameters of the system [1,2]. Fabrication tolerances result from from manufacturing inaccuracies (e.g., chemical etching in the case of microstrip components), and its quantification can be performed using probability distribution, e.g., uniform or Gaussian, with a given maximum deviation or variance, respectively. Tolerance-based parameter deviations may hamper fulfilling the assumed performance specifications by the system under design. The same can be said about making the design more robust, which involves a reduction of appropriately defined statistical figures of merit [3]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
