Monolithically Integrated Directly Pumped Time-Varying Transmission Lines

A novel directly pumped time-varying transmission line (DP-TVTL) is proposed here and implemented on gallium arsenide (GaAs) microwave monolithic integrated circuit (MMIC). Comparing to existing TVTL architectures where the pump wave is launched through the transmission line, the pump wave in the DP-TVTL is directly fed to the different parts of the transmission line through a parallel power division network. The impedance of TVTL is modulated by the pump through diode bridges that isolate the signal path from the pump path. The power division network creates a phase delay emulating that of a traveling-wave delay line yet without launching the physical pump wave on the TVTL. This avoids the loss of the pump energy propagating through the transmission line. It also adds more freedom in the design of the bandgap properties of TVTL and simplifies the combination/separation circuitry for waves at different frequencies in and out of the TVTL. The resulting MMIC TVTL offers exceptional, broadband conversion gain performance of up to 4.2 dB, a low noise figure of 3 dB, and input referred P1dB of 12 dBm when used as a parametric mixer. It may be used in an RF front end as a mixer first receiver or an RF correlator.