The effect of capacitive mixing and detection in Schottky-barrier diodes at high, intermediate, or modulation frequencies

At high IF or modulation frequencies a Schottky-barrier diode not only operates as a conductance mixer or detector due to its nonlinear conductance but also as a capacitance mixer or detector due to its nonlinear capacitance. The effect is calculated for a heavily doped Schottky-barrier diode in which the pump amplitude and the signal amplitude are relatively small so that short Taylor expansions of the current and charge characteristics can be used. Beyond an upper corner frequency f1the effect gives rise to a considerable increase in the output signal and to a considerable increase in signal-to-noise ratio. Due to the electronic feedback between input and output, the output conductance g_{out} can be negative foromega_{i} = omega_{P} - omega_{0}when capacitive mixing predominates. At the limit of stability (g_{out} = 0) the noise figureF = 1 + n_{1}omega_{i}/omega_{0}, where n1lies between ½ and 1.