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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.

GaAs TUNNET diodes with 75‐nm thick undoped transit‐time layer and 14‐nm thick n+ electric‐field‐inducing layer, fabricated with molecular layer epitaxy, were oscillating in fundamental‐mode, metal, rectangular WR‐1.0 (0.254 × 0.127 mm) resonant cavities at 706 GHz. The continuous wave output power was ‐67 dBm, at the bias current of 600 mA. The frequency range of continuous wave fundamental‐mode TUNNETT diodes fabricated with molecular layer epitaxy extends from 60 GHz (+13 dBm) to 706 GHz. Modulation experiments of lower frequency, 86‐GHz and 163‐GHz, TUNNETTs have shown that TUNNETTs are suitable for broadband communication and other systems at the modulation rate exceeding 2 Gbps. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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