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RFIC Application Selection Guide
Mixer ICs

Translates an information-carrying signal in frequency by outputting the sum or difference frequency of the incident signal and a local oscillator (LO) signal
  1. down-conversion: IAM-915xx
  2. upconversion: 1st choice: HPMX-2006
  can also use: IAM-81xxx
  3. integrated solutions: HPMX-5001 (up and down converters)
  4. millimeter wave: HMMC-3040
  1. Schottky Diodes (better linearity; lower voltage)
2. AT transistors or ATF FETs as active mixers
  Key Parameters
  frequency, conversion gain, intercept point, noise figure
output spectral purity (LO leakage, isolation, n by m products)
  Integrated circuit mixers provide an alternative to traditional diode based passive mixers. The typical implementation uses a structure called a Gilbert cell. An emitter-coupled transistor pair is used to switch the current path between the inner and outer transistors of a collector-cross-coupled quad; this switching creates a double-balanced mixing action.

Gilbert cell-based IC mixers differ significantly from diode mixers. The Gilbert cell is an amplifier, so the mixer now has conversion gain rather than the approximately 7 dB loss of a passive mixer. The switching action of the mixer takes relatively little energy to initiate, so although the IC mixer must be DC biased, its total power budget is often less than that required for a passive mixer driven by a much higher-powered LO. The Gilbert cell is often less sensitive to loading, and doesn't require any bulky transformers, making it an extremely convenient device to use. In trade for these advantages, Gilbert cell-based mixers have higher noise figures (14 dB vs. 7 dB typ.) and lower intercept points (less linearity) than do diode-based mixers.

A second implementation for active mixers is the cascode type. Also referred to as a transconductance mixer, this topology ultimately can be traced back to dual gate designs. The resulting mixer is single balanced, has conversion gain, and typically has lower a noise figure than a Gilbert cell structure. Although in this structure the mixer itself provides no isolation, the matching structures used on the RF and LO ports are high pass, while the match on the IF port is low pass, so the isolation of the overall structure can be better than that of a balanced mixer (40 dB vs 30 dB). These features make the cascode mixer ideal for down-converting applications.

  Product Families
    IAM-81xxx: 5V Gilbert cell
IAM-82xxx: 10V Gilbert cell, higher intercept point
IAM-915xx: 3V cascode type downconverter
HPMX-2006: 3V upconverter with post amplifier
HPMX-5001: includes 3V up/down converting mixers
HMMC-3040: 20-43 GHz double ba,anced mixer and LO amplifier
  Related Topics:
    Gain Blocks as self-oscillating mixers (SOMs)
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this page last updated: 1 October 1999