This paper presents physical lumped element models for the structures employing a split-ring resonator (SRR) coupled with a pair of microstrip antennas. The results of 3D EM simulations, circuit simulations and measurement results are provided. For experimental verification, a resonator device was fabricated on an FR4 epoxy glass substrate. Mismatch between the values of resonant frequency that are predicted by the models and that are measured is less than 3%. As a benchmarking case for the proposed model, a reference oscillator was designed and implemented. A phase noise of −139.51 dBc/Hz at 3 MHz frequency offset was measured with a center frequency of 1.617 GHz.

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Audio processing had been in demand throughout the electronic era. Recent advances in neural networks increased the demand on audio processing for speech recognition applications. In this work, a rigorous study on the dynamic range and system complexity optimization is presented for a mixed-signal keyword spotting system. The proposed system consists of an analog feature extractor and a neural network based keyword classifier. The results showed that with the proposed method, more than an order of magnitude power saving can be achieved in the analog feature extraction compared to the digital state-ofthe-art counterpart.