Effect of Upper Sideband Impedance on a Lower Sideband Up-Converter

An analysis is given of a lower sideband up-converter which includes a finite circuit reactance X₃₃ at the upper sideband frequency, in addition to the circuit impedances at the input signal and output lower sideband frequencies. The expressions developed for the gain, gain sensitivity to pump power variation, and noise figure show the extent to which gain and gain sensitivity decrease, and noise figure increases when X₃₃ is finite, as compared to the case when X₃₃ is infinite. For a simple circuit configuration the gain-bandwidth product changes markedly when X₃₃ is small at the center frequency. In addition, when second-harmonic pump power is allowed to flow through the varactor diode, the performance of the lower sideband up-converter can be improved.