Parametric conversion with distributedly modulated capacitors (DMC) for low-noise and non-reciprocal RF front-ends

Transmission lines with time-varying reactance exhibit interesting behaviors such as parametric amplification and mixing [1]. In this paper, such a transmission line realized with distributedly modulated capacitors (DMC) is demonstrated with its active conversion gain, low noise figure as well as non-reciprocity. DMC is offered a great potential to operate in an RF front-end either as a broadband low-noise amplifier (LNA) or an integrated circulator. A practical implementation is presented with varactors and microstrip lines connected in double-balanced fashion. DMC shows in simulations that 9 dB gain with below 0.5 dB noise figure over the input signal frequency of 1 to 6 GHz is achievable when it is optimized for gain and noise performance. Alternatively when the circuit is optimized for isolation, greater than 13 dB isolation can be achieved from 500 MHz to 1.8 GHz, which has been verified with the experiment.