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Selection of a mixer type is a trade off for a particular application. [2] Mixer circuits are characterized by their properties such as conversion gain (or loss), noise figure and nonlinearity. [3] Nonlinear electronic components that are used as mixers include diodes and transistors biased near cutoff.
Diode mixers take advantage of the non-linearity of diode devices to produce the desired multiplication in the squared term. They are very inefficient as most of the power output is in other unwanted terms which need filtering out. Inexpensive AM radios still use diode mixers. Electronic mixers are usually made with transistors and/or diodes ...
This additional diode cell topology is typically used when a low distortion voltage-controlled amplifier (VCA) is required. This topology is rarely used in RF mixer/modulator applications for various reasons, one being that the linearity advantage of the top linearized cascode is minimal due to the near-square wave drive signals to these bases ...
Some mixer designs, such as double-balanced mixers, suppress some high order undesired products, while other designs, such as harmonic mixers exploit high order differences. Examples of nonlinear components that are used as mixers are vacuum tubes and transistors biased near cutoff , and diodes.
One classic design for a harmonic mixer uses a step recovery diode (SRD). [1] The mixer's subharmonic input is first amplified to a power level that might be around 1 watt. That signal then drives a step recovery diode impulse generator circuit that turns the sine wave into something approximating an impulse train.
The name derives from the fact that the analog circuit of diodes originally used to implement this technique takes the shape of a ring: a diode ring. [2] The circuit is similar to a bridge rectifier , except that instead of the diodes facing left or right, they face clockwise or counterclockwise.
Various semiconductor diodes. Left: A four-diode bridge rectifier.Next to it is a 1N4148 signal diode.On the far right is a Zener diode.In most diodes, a white or black painted band identifies the cathode into which electrons will flow when the diode is conducting.
A mixer-based detector (e.g., a Schottky diode-based double-balanced mixer) provides "the ultimate in phase noise floor performance" and "in system sensitivity." since it does not create finite pulse widths at the phase detector output. [2] Another advantage of a mixer-based PD is its relative simplicity. [2]