Noise-Figure Reduction in Mixer Stages

This paper presents some aspects of random noise reduction in mixer stages connected with the application of proper circuit design and feedback, taking into account the intercorrelation of noise components. The noise figure of diode mixer stages is derived from their basic operational data. Conditions conducive to optimal gain are shown to be coincident with those of minimum noise, the diode's contribution approaching zero im the most favorable case. The noise of triode and multigrid mixer stages is shown to be reducible to the value for a comparable triode amplifier stage by the application of proper feedback. In some cases this reduction amounts to 15 decibels or more. Oscillator noise and push-pull stages are discussed.