The circuit is a microstrip balanced diode mixer design. Besides linear S-Parameters, large-signal results are calculated via two Mixer tasks, namely, the spectra of the steady-state solution and the conversion loss as a function of RF power.
The model represents a balanced diode mixer. Two diodes with identical device parameters are biased in series by a common DC source. It is decoupled from AC by a quarter-wavelength transmission line. The branchline coupler at the input provides LO and RF signals to the diodes with a 90 degree phase shift. Open stubs at the IF output suppress unwanted frequencies, especially, the LO and the third harmonic of the LO.