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A Non-Reciprocal Component with Distributedly Modulated Capacitors


The requirement of using ferrite magnetic material for non-reciprocal microwave components like circulators and isolators prevents the designs from being small, lossless and broadband especially at the lower end of the microwave frequency spectrum. Active non-reciprocal components may have good isolation and can be integrated, but they are very poor in noise performance. A circuit with distributedly modulated capacitors (DMC) - time-varying capacitors distributed along a transmission line and modulated by a carrier wave - provides a novel realization of lossless and broadband non-reciprocity. The circuit is compatible with modern integrated circuit technology. Decent gain and low noise for receiving path are also possible as bonus advantages. Studies on the estimations of the isolation and the receiving insertion performance of the DMC circuit are focused in this thesis to show its ability to serve for a non-reciprocal component. A prototype made on Rogers circuit board has verified the theory's prediction on the performance, which is capable of achieving >13 dB isolation between the transmitting and the receiving paths and <5 dB receiving insertion loss over the frequency range of 0.5 -- 1.8 GHz.

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