Equivalent circuits of a transistor mixer

Both resistive and reactive effective parameters of a transistor mixer are expressed in terms of oscillator amplitude and the small-signal quiescent parameters. The frequencies of the three signals in a mixer, being different, give rise to three effective equivalent circuits: one in respect of the intermediate-frequency output, one as presented to the radio-frequency source and one as presented to the oscillator source. The proposed circuits offer a convenient means of mixer-circuit design up to the frequencies at which the small-signal equivalent circuit is applicable.