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Mixer (First RF System Mixer, Polynomial Model for Nonlinearity)

Symbol

Available in ADS

Parameters

Name

Description

Units

Default

SideBand

Produce UPPER, LOWER, or BOTH sidebands at output port

None

UPPER

ImageRej

Image rejection at output with respect to fundamental

dB

None

LO_Rej1

LO to Input Port Rejection

dB

None

LO_Rej2

LO to Output Port Rejection

dB

None

RF_Rej

Input to Output Port Rejection

dB

None

ConvGain

Conversion Gain, use x + j × y, polar(x,y), dbpolar(x,y) for complex value; see note 2)

None

dbpolar(0,0)

S11

Forward Reflection Coefficient, use x + j × y, polar(x,y), dbpolar(x,y), vswrpolar(x,y) for complex value; see note 2)

None

polar(0,0)

S22

Reverse Reflection Coefficient, use x + j × y, polar(x,y), dbpolar(x,y), vswrpolar(x,y) for complex value; see note 2)

None

polar(0,180)

S33

LO Port Reflection Coefficient, use x + j × y, polar(x,y), dbpolar(x,y), vswrpolar(x,y) for complex value; see note 2)

None

0

PminLO

Minimum LO Power before starvation

None

None

NF

Double sideband noise figure

dB

None

NFmin

Minimum double sideband noise figure at Sopt

dB

None

Sopt

Optimum source reflection for minimum noise figure, use x + j × y, polar(x,y), dbpolar(x,y) for complex value

None

None

Rn

Equivalent noise resistance

 

Z1

Reference impedance for port 1 (real or complex number)

 

Z2

Reference impedance for port 2 (real or complex number)

 

Z3

Reference impedance for port 3 (real or complex number)

 

ImpNoncausalLength

Non-causal function impulse response order

Integer

None

ImpMode

Convolution mode

Integer

None

ImpMaxFreq

Maximum frequency to which device is evaluated

None

ImpDeltaFreq

Sample spacing in frequency

None

ImpMaxOrder

Maximum allowed impulse response order

Integer

None

ImpWindow

Smoothing window

Integer

None

ImpRelTol

Relative impulse response truncation factor

None

None

ImpAbsTol

Absolute impulse response truncation factor

None

None

Range of Usage

NF ≥ 0 dB
NFmin > 0
0 < Sopt < 1
0 < Rn
GainCompFreq > 0

ConvGain > 0

Gain Compression Parameters

Name

Description

Units

Default

GainCompType

Gain compression type: LIST=use model gain compression specifications; FILE=use file-based gain compression data

None

LIST

GainCompFreq

Reference frequency for gain compression (if gain compression is described as a function of frequency)

ReferToInput

Specify gain compression with respect to input or output power of device

None

OUTPUT

SOI

Second order intercept

dBm

None

TOI

Third order intercept

dBm

None

Psat

Power level at saturation

dBm

None

GainCompSat

Gain compression at Psat

dB

5.0

GainCompPower

Power level in dBm at gain compression specified by GainComp

dBm

None

GainComp

Gain compression at GainCompPower

dB

1 dB

GainCompFile

Filename for gain compression data in S2D file format

None

None

Range of Usage for Gain Compression Parameters

When specifying gain compression using model parameters, only certain combination of parameters will produce stable polynomial curve fitting. Recommended parameter combinations are listed here.

Note If unrealistic parameter values are used, the polynomial will become unstable, resulting in oscillations.

  • Third-order intercept and 1dB gain compression parameters:
    TOI, GainCompPower, with GainComp=1dB.
    Range of validity: TOI > GainCompPower + 10.8.
  • Third-order intercept and power saturation parameters:
    TOI, Psat, GainCompSat.
    Range of validity: TOI > Psat + 8.6.
  • 1dB gain compression and power saturation parameters: GainCompPower, with GainComp=1dB, and Psat, GainCompSat.
    Range of validity: Psat > GainCompPower + 3.
  • Third-order intercept, 1dB gain compression and power saturation parameters:
    TOI, GainCompPower with GainComp=1dB, and Psat, GainCompSat.
    Range of validity: Psat > GainCompPower +3, TOI > GainCompPower + 10.8
  • Second-order intercept and third-order intercept parameters: SOI, TOI.

Notes/Equations
  1. The Mixer component is similar to Mixer2. The key difference is that Mixer supports frequency conversion AC analysis or FCAC analysis for small-signal AC or S-parameter analysis, while Mixer2 does not. This capability allows small-signal frequency traditionally done at only one frequency to be somewhat extended to deal with more than one frequency. In terms of convergence, Mixer2 is typically more robust than Mixer, as the power detection is implemented differently.
  2. If NFmin, Sopt, and Rn are used to characterize noise, the following relation must be satisfied for a realistic model.

    A warning message will be issued if Rn does not meet this criterion. If the noise parameters attempt to describe a system that requires negative noise (due to Rn being too small), the negative part of the noise will be set to zero and a warning message will be issued.
  3. Use the function polar(mag,ang) or dbpolar(dB, ang), or VSWR polar(VSWR, ang) to convert these specifications into a complex number.
  4. For an S-parameter or a noise figure sinusoidal ripple, use the function ripple (mag, intercept, period, variable); for example ripple(0.1, 0, 10 MHz, freq).
    Example: S21=dbpolar(10+ripple( ),0.)
  5. Z1, Z2 and Z3 the reference impedance parameters for ports 1, 2 and 3 are used in conjunction with the parameters S11/S21/S12/S22. This is because S-data is always used with respect to a particular reference impedance.
  6. This model passes DC in the sense that a DC source at the RF input passes through the mixer to give a signal at the IF output.
  7. In harmonic balance simulations, the PminLO parameter sets a threshold for the effect of the LO power on the mixer's conversion gain. The default value of PminLO is -100 dBm. The mixer will provide the expected conversion gain if the LO power is significantly greater (~20 dB) than the value of PminLO. If the LO power is less than this amount, the mixer's conversion gain will deteriorate in a nonlinear fashion.
  8. Gain compression can be specified by using the gain compression model parameters, or this information can be contained in an S2D format file. All S2D gain compression types are supported by this model. Gain compression types 1 through 6 can also be described using the gain compression model parameters. Gain Compression 7 information must be contained in an S2D file. The GainCompType parameter instructs the model where to look for this data-in an S2D file or use model parameters.
    For S2D data file format information refer to Working with Data Files.
  9. Mixer operation with the SOI and TOI parameters is described in this note.
    First consider an amplifier. Consider two input tones at f1 and f2 (assume f1<f2) and at the same power level. Do a 2-tone HB simulation. The output will have first-order tones at f1 and f2. It also have second-order intermod products at f2-f1 and at f1+f2. It will also have third-order intermod products at 2 × f1-f2 (will be smaller than f1 by f2- f1) and 2 × f2-f1 (will be greater than f2 by f2-f1). Drawing a picture of this frequency plan can be helpful. Based on these tones we can calculate the SOI and TOI of the amplifier. The general equation is IPn= (n × P1-Pn)/(n-1) where P1 is the power level of the first-order tone and Pn is the power level of the nth-order tone. For SOI, we can use the power levels at f1 and f2-f1 or we can use the power levels at f2 and f1+f2. For TOI, we can use the power levels at f1 and 2 × f1-f2 or we can use the power levels at f2 and 2 × f2-f1.
    For a mixer, everything is the same, except that everything is being shifted down (down- converting mixer) or up (up-converting mixer) by the LO frequency fLO due to mixing. Therefore, all these frequencies will either have fLO subtracted or added. Note that this means that from an HB point of view, we're calculating SOI off of second- and third-order intermod products and calculating TOI off of second- and fourth-order intermod products. For example, TOI can be calculated from a P1 at f1-fLO (second- order as far as the HB simulation is concerned) and a Pn at 2 × f1-f2-fLO (fourth-order as far as the HB simulation is concerned).
    Also, note that the mixer must be output-matched in order to validate SOI and TOI.
    For more information about SOI and TOI, refer to the Amplifier2 component documentation.
  10. Frequency Conversion AC (FCAC) analysis requires a single frequency at every node of a circuit. If Sideband=BOTH is specified for Mixer, the simulator will use SideBand=LOWER for FCAC analysis.
  11. When Mixer is used in Transient analysis for single sideband applications, it is recommended that the user set Sideband=BOTH and insert a high-order filter to suppress the undesired sideband.
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