FDTD Analysis of Transmission Line Loaded with Time-Varying Shunt Capacitors for Mixer Applications

This paper presents a finite-difference time-domain (FDTD) approach for modeling time-varying media having variable capacitors with temporal dependence. The lumped variable capacitors are placed in parallel with the transmission line, and their capacitance is periodically modulated. The propagating wave in the transmission line undergoes modulation due to the temporal changes of the media. The spectrum of the modulated wave shows new frequencies acting as a mixer. The physical properties of the modulating medium, such as the operating and switching frequencies, the capacitances of the switching states, the gap between the lumped capacitors and the number of capacitors, are parametrically studied. Lumped time-varying capacitors on a transmission line can be used for magnet-less mixer, isolator, etc.