Does anyone know of a reasonably good SPICE model of a mixer? Something that I can use in LTSpice? It doesn't have to be accurate (meaning it doesn't need to be based on intermodulation tables) since all I am doing is trying to learn about feedback systems that contain RF elements. However, I would like it to have all 3 inputs (LO,RF and IF). I know you can multiply two voltages in SPICE etc to emulate mixing, but that is a bit too basic for what I am doing.