Abstract
The employment of numerical optimization techniques for parameter tuning of microwave components has nowadays become a commonplace. In pursuit of reliability, it is most often carried out at the level of full-wave electromagnetic (EM) simulation models, incurring considerable computational expenses. In the case of miniaturized microstrip circuits, densely arranged layouts with strong cross-coupling effects make EM-driven tuning imperative to achieve the optimum performance. The process is even more challenging due to a typically large number of geometry parameters, and the lack of reasonable initial designs. The latter often encourages the use of global search procedures, which may be prohibitively expensive. In this paper, a novel automated framework for reliable optimization of miniaturized microwave components is proposed. Our methodology is based on design specification management, where the performance requirements imposed on the system are temporarily relaxed if the current design is unlikely to be improved (e.g., due to being away from the target operating frequency). The specifications are re-adjusted at each iteration of the algorithm, and eventually converge to their original values. Using two examples of compact microstrip couplers and a power divider, the presented technique is demonstrated to significantly improve the efficacy of local search routines under challenging design scenarios.
Highlights
The employment of numerical optimization techniques for parameter tuning of microwave components has nowadays become a commonplace
Tight performance requirements imposed on modern microwave systems, partially dictated by the demands pertinent to emerging application areas, e.g., wireless s ensing[9], Internet of Things (IoT)[10], microwave imaging11, 5G12, autonomous v ehicles[13], wearable devices[14], can only be met if meticulous development of the circuit architecture is supplemented by careful tuning of its parameters
A novel design specification adjustment procedure through intelligent decision-making has been introduced to improve the reliability of EM-driven optimization of miniaturized microwave components
Summary
The purpose of this section is to introduce the design specification adjustment scheme with automated decisionmaking, as a tool for improving the reliability of microwave design optimization procedures. Establishing the threshold Fr.min as described above accounts for a typical improvement of the objective function assuming that design requirements are adjusted to satisfy the condition Dc < Dc.max As mentioned before, the latter is set to ensure that the operating frequencies of the system can be relocated to the current target frequencies using local search. The meaning of the last statement is that the coefficient a is, as a matter of fact, obtained through an auxiliary optimization procedure, in which it is adjusted (lowered) as much as necessary to eventually ensure that Fr ≥ Fr.min and Dc ≤ Dc.max for the vector xtmp generated by (8) At this point, the specifications have been relaxed to ensure that the target operating frequencies are sufficiently close to those at the design x(i) (in the sense of (6)), and the local improvement of the design (when starting from x(i)) is at least equal to Fr.min. The pseudocode of the proposed optimization procedure, as well as the flow diagram have been shown in Figs. 3 and 4, respectively
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