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System Model for a Mixer (Closed Form): MIXER



MIXER is a generic mixer model used to represent a mixer in RF subcircuit simulation. It includes intermodulation distortion, nonzero input and output reflection coefficient, LO saturation, group delay, and port-to-port isolations.

Equivalent Circuit


Name Description Unit Type Default
ID Element ID   MX#
GCONV Conversion efficiency, dB, at rated LO power PLO (negative for loss) dB -6
P1DB_IN 1-dB compression point at input dB units 10
IP3_IN Third-order IP, 2f2-f1, at input; dB units dB units 20
*RF2IF RF to IF isolation (neg. for loss) dB -20
*IF2RF IF to RF isolation (neg. for loss) dB -20
*LO2IF LO to IF isolation (neg. for loss) dB -20
*LO2RF LO to RF isolation (neg. for loss) dB -20
*IF2LO IF to LO isolation (neg. for loss) dB -90
*RF2LO RF to LO isolation (neg. for loss) dB -90
PLO Available LO power (dB units) for specified conversion gain dB units 10
*S11RFMAG RF input reflection coefficient magnitude   0.0
*S11RFANG RF input reflection coefficient angle Angle 0.0
*S22IFMAG IF output reflection coefficient magnitude   0.0
*S22IFANG IF output reflection coefficient angle Angle 0.0
*S11LOMAG LO input reflection coefficient magnitude   0.0
*S11LOANG LO input reflection coefficient phase angle Angle 0.0
*Z0 Port reference impedance Resistance 50Ω
*TDLY Group delay Time 0.0
NF Noise figure, dB dB 0.0

* indicates a secondary parameter

Parameter Details

DB UNITS. Units listed as dB can be in dBm or dBW, depending on your specified project units.

GCONV. The conversion loss (or gain) at the specified LO power level, GCONV, increases slightly if LO power is increased beyond the specified value. At low LO levels, the IF output is proportional to the LO level.

IP3_IN, P1DB_IN, and Isolations. These are independent of the LO level. They are modeled in the same manner as NL_AMP2.

Implementation Details

The mixer model is fundamentally a multiplier with some additional characteristics that make it behave as an RF or microwave mixer. Note that this element models mixer behavior in a very general manner, and may not precisely model any particular mixer type.

The conversion efficiency saturates much like most types of mixers. At the specified LO level, the conversion efficiency is approximately 1 dB below its maximum value. Saturation is accomplished by clipping the LO waveform; this process generates spurious mixing products involving the fundamental RF and LO harmonics. You can use output filters to adjust the levels of these products.

The IF is unfiltered, so both sum and difference frequencies are produced. You can include an IF output filter to eliminate the undesired product.

The input and output reflection coefficients are constant with frequency.

Many of the comments regarding NL_AMP2 apply to MIXER. In particular, the gain, IP3, and 1-dB compression level are those measured with the specified S11 and S22. Thus, they do not change when S11 or S22 are modified, as long as the source and load impedance are equal to Z0.


This element does not have an assigned layout cell. You can assign artwork cells to any element. See “Assigning Artwork Cells to Layout of Schematic Elements” for details.

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