FET up-converter design using load-dependent mixing transconductance

A method for a more accurate prediction of FET up-converter gain is proposed. The method uses an equivalent circuit containing a conversion current source at the upper and lower sideband output frequency. The magnitude of the current is related to the IF input voltage by the mixing transconductance factor that is a function of internal LO voltages in the FET. These voltages depend on the output load impedance at the LO frequency. With this approach, the output network can be optimized for acceptable match at the selected sideband and for desired LO signal rejection, while avoiding those impedance values in the LO frequency range that have been observed to cause severe degradation in conversion gain