Emulating Parametric Amplification with Switched-inductor Network and Current Source

Parametric amplification conventionally relies on a time-varying capacitor (usually a varactor diode) that is part of the LC tank. The capacitance is varied at twice the resonant frequency of an LC tank. While this approach is elegant, it has very limited power-handling capabilities (order of a few hundred milliwatts) and inherent losses, which are limited by the available varactor technology. Building on an explicit energy-balance analysis of the time-varying capacitor, we show that the term v(t)dC/dt that appears in the expression for current of a time-varying capacitor, can be replaced by an externally programmed current source without altering the resonator dynamics. We first show the equivalence between a time-varying capacitor and a fixed capacitor that is shunted by a current pulse source. Subsequently, a hardware-friendly realization based on a switching inductor network is presented, which stores the magnetic energy before the occurrence of voltage extremes and releases it at the time of occurrence. Circuit simulations confirm identical voltage growths in the case of the ideal time-varying capacitor and the switched-inductor version. However, the switched-inductor version is able to withstand significantly higher power. In addition, the switched-inductor version avoids the inherent nonlinearities of the varactor, providing a practical route to broadband, high-power time-varying matching networks.