IMT Mixer

Model mixer using intermodulation table (IMT)

Since R2019b

• 

Libraries:
RF Blockset / Circuit Envelope / Elements

Description

Use the IMT Mixer to perform frequency translation defined in an intermodulation table (see [1], [2], [3], and [4]) for a single tone carrier mixed with a local oscillator (LO) signal. The block includes nonlinear amplification, device and phase noise, and mixer spur visualization. For a single tone carrier F_car nonlinearly modulated with an LO signal of frequency F_LO, the mixer output intermodulation products occur at frequencies:

$$F_{\text{out}}(M,N)=\left|M\times F_{\text{car}}\pm N\times F_{\text{LO}}\right|$$

where:

• F_car – input RF signal carrier frequency

• F_LO – local oscillator frequency

• M and N are nonnegative integers (0,1,…, order of nonlinearity)

For a downconverter, the desired output tone is $$\left|F_{\text{car}}-F_{\text{LO}}\right|$$, and for an upconverter it is $$\left|F_{\text{car}}+F_{\text{LO}}\right|$$. All other combinations of M and N represent the spurious intermodulation products.

IMT Mixer block mask icons are dynamic and indicate the current state of the applied noise parameter. For more information, see IMT Mixer Icons.

Parameters

Main

Carrier frequency (Hz) — Carrier frequency

1e9 (default) | scalar

Carrier frequency, specified as a scalar in hertz. When multiple carriers exist on the input connection, this carrier frequency is selected as the RF signal input. Distance between adjacent carriers must be greater than $$(1-1e^{-8})F_{\text{c}}$$.

Data Types: double

Local oscillator frequency (Hz) — Local oscillator (LO) frequency

0.9e9 (default) | scalar

Local oscillator (LO) frequency, specified as a scalar in hertz.

Reference input power (dBm) — Reference input power

-10 (default) | scalar

Reference input power, specified as a scalar in dBm. The expression for the normalized input signal for the specified reference input power is:

$${10}^{(\frac{(-P_{\text{rf}}+20\log 10(\frac{1}{\sqrt{R_{\text{in}}}})+30)}{20})}$$

Intermodulation tables assume that the spur levels are measured for a reference input and output power. For example, if you increase the input power by 10 dB, the spurs due to second order non-linearity will increase by 20 dB, the spurs due to third order non-linearity will increase by 30 dB, and so forth.

Nominal output power (dbm) — Nominal LO power

-20 (default) | scalar

Nominal output power, specified as a scalar in dBm. The expression for the normalized output signal for the specified reference input power is:

$$2\text{x}{10}^{(\frac{(P_{\text{if}}-20\log 10(\frac{1}{\sqrt{R_{\text{out}}}})-30)}{20})}$$

Use data file — Specify data file to use

off (default) | on

Select this parameter to specify the data file you want to use to extract the spur table. Clear to specify your own spur values. The data file may contain any combination of IMT table, AC data, and colored spot noise in S2D or P2D format. See [4].

Data file — Data file

samplespur1.s2d (default)

Data file, specified as IMT data, AC data, and colored spot noise. To learn about the combination of inputs a data file can have and how this block extracts and calculates the parameters, see Block Parameters When Using Data File.

Dependencies

To set this parameter, first select Use data file.

Input impedance (Ohm) — Input impedance of mixer

50 (default) | real scalar

Input impedance of mixer, specified as a real scalar.

Output impedance (Ohm) — Output impedance of mixer

50 (default) | real scalar

Output impedance of mixer, specified as a real scalar.

Ground and hide negative terminals — Ground RF negative circuit terminals

on (default) | off

Select this parameter to internally ground and hide the negative terminals. To expose the negative terminals, clear this parameter. If the terminals are exposed, the input signal is not referenced to the ground.

IMT

IMT table — IMT spur visualization

[99 99 99; 99 0 99; 99 99 99] (default) | square matrix

IMT spur visualization, specified as a square matrix.

Output signal power (dBm) — Signal power of desired output tone

0 (default) | scalar

Signal power of the desired output tone when plotting intermodulation products, specified as a scalar.

Mixer type — Mixer type

Upconverter (default) | Downconverter

Mixer type, specified as Upconverter or Downconverter.

For a single tone carrier F_car nonlinearly modulated with an LO signal of frequency F_LO, the mixer output intermodulation products occur at frequencies:

$$F_{\text{out}}(M,N)=\left|M\times F_{\text{car}}\pm N\times F_{\text{LO}}\right|$$

where:

• F_car – input RF signal carrier frequency

• F_LO – local oscillator frequency

• M and N are nonnegative integers (0,1,…, order of nonlinearity)

For a downconverter, the desired output tone is $$\left|F_{\text{car}}-F_{\text{LO}}\right|$$, and for an upconverter it is $$\left|F_{\text{car}}+F_{\text{LO}}\right|$$. All other combinations of M and N represent the spurious intermodulation products.

Plot — Visualize IMT table values using specified signal power and mixer type

button

Visualize IMT table values using specified signal power and mixer type.

Noise

Simulate noise — Simulate device or phase noise

on (default) | off

Select this parameter to simulate noise as specified in block parameters or in file.

If the noise is specified in an .s2p file, then it is used for simulation.

Noise type — Noise type

Noise figure (default) | Spot noise data

Noise type, specified as Noise figure or Spot noise data.

Dependencies

To set this parameter, first select Simulate noise.

Noise distribution — Noise distribution

White (default) | Piece-wise linear | Colored

Noise distribution, specified as:

• White – Spectral density is a single nonnegative value. The power value of the noise depends on the bandwidth of the carrier, and the bandwidth depends on the time step. This is an uncorrelated noise source.

• Piece-wise linear – Spectral density is a vector of values [p_i]. For each carrier, the noise source behaves like a white uncorrelated noise. The power of the noise source is carrier dependent.

• Colored – Depends on both carrier and bandwidth. This is a correlated noise source.

Dependencies

To set this parameter, first select Simulate noise.

Noise figure (dB) — Noise figure

0 (default) | scalar

Noise figure, specified as a scalar in decibels.

Dependencies

To set this parameter, first select Simulate noise.

Frequencies (Hz) — Frequency data

0 (default) | scalar | vector

Frequency data, specified as a scalar for white noise or vector for piece-wise linear or colored noise in hertz.

Dependencies

To set this parameter, first select Select noise then select Piece-wise linear or Colored in Noise distribution.

Minimum noise figure (dB) — Minimum noise figure

0 (default) | scalar | vector

Minimum noise figure, specified as a scalar or vector in decibels.

Dependencies

To set this parameter, first select Spot noise data in Noise type.

Dependencies

To set this parameter, first select Select noise then select Spot noise data in Noise Type.

Optimal reflection coefficient — Optimal reflection coefficient

0 (default) | scalar | vector

Optimal reflection coefficient, specified as a scalar or a vector.

Dependencies

To set this parameter, first select Select noise then select Spot noise data in Noise Type.

Equivalent normalized noise resistance — Equivalent normalized noise resistance

0 (default) | scalar | vector

Equivalent normalized noise resistance, specified as a scalar or vector.

Dependencies

To set this parameter, first select Select noise then select Spot noise data in Noise Type.

Add LO phase noise — Add phase noise

off (default) | on

Select this parameter to add phase noise to your system with a continuous wave source.

Dependencies

To set this parameter, select Simulate noise.

Phase noise frequency offset (Hz) — Phase noise frequency offset

1 (default) | scalar | vector

Phase noise frequency offset with respect to LO signal, specified as a scalar or vector with each element unit in hertz.

The frequency offset values must be bounded by the envelope bandwidth of the simulation. For more information see Configuration.

Dependencies

To enable this parameter, first select Simulate noise then select Add phase noise.

Phase noise level (dBc/Hz) — Phase noise level

-Inf (default) | scalar | vector | matrix

Phase noise level, specified as a scalar or vector or matrix with elements in decibel per hertz.

If you specify a matrix, each column should correspond to a non-DC carrier frequency of the CW source. The frequency offset values must be bounded by the envelope bandwidth of the simulation. For more information see Configuration.

Dependencies

To enable this parameter, first select Simulate noise then select Add phase noise.

Automatically estimate impulse response duration — Automatically estimate impulse response duration

on (default) | off

Select this parameter to automatically calculate impulse response for frequency-dependent noises. Clear this parameter to manually specify the impulse response duration using Impulse response duration.

Dependencies

To enable this parameter, first select Simulate noise then select Add phase noise.

Impulse response duration — Impulse response duration

1e-10s (default) | scalar

Impulse response duration used to simulate frequency-dependent noise, specified as a scalar in seconds. The time should be an integer multiple of the step size in the configuration block, Tduration = NTstep.

Dependencies

To set this parameter, first clear Automatically estimate impulse response duration.

Algorithms

Block Parameters When Using Data File

This table shows you how the block extracts the block parameters if you choose to use a data file. The way the block extracts the parameters depends on the contents of the data file.

Contents of Data File	Reference input power (dBm)	Nominal output power (dBm)	IMT Table	Noise
IMT, AC, and noise data	Block extracts value from IMT header of data file	Block extracts value from data file	Block extracts value from data file	Block extracts value from data file
IMT data	Block extracts value from IMT header of data file	User provides value or block uses default value	Block extracts value from data file	User provides value or block uses default value
AC and IMT data	Block extracts value from IMT header of data file	Block extracts value from data file	Block extracts value from data file	User provides value or block uses default value
Noise and IMT	Block extracts value from IMT header of data file	User provides value or block uses default value	Block extracts value from data file	Block extracts value from data file
AC Data	User provides value or block uses default value	Extracted from the data file	User provides value or block uses default value	User provides value or block uses default value
AC and Noise	User provides value or block uses default value	Extracted from the data file	User provides value or block uses default value	Extracted from the data file
Noise	User provides value or block uses default value	User provides value or block uses default value	User provides value or block uses default value	Extracted from the data file

Consider the default data file samplespur1.s2d. This data file contains IMT, AC, and noise data. When you specify the block to use this data file by selecting the Use data file parameter, the block extracts the reference input power, nominal output power, IMT, and noise data from the data file. This image shows the block mask with the extracted Reference input power (dBm) and Nominal output power (dbm) parameters.

To verify the extracted data, inspect the data file using this command

edit(samplespur1.s2d)

This image shows the real value of the mixer gain at the Carrier frequency (Hz) of 1 GHz and the Reference input power (dBm).

The block extracts the Nominal output power (dbm) from the data file using this equation.

IMT Mixer Icons

This table shows you how the icons on this block will vary based on how you set the Simulate noise and Add LO phase noise parameters on the block.

Simulate noise	Add LO phase noise: off	Add LO phase noise: on
off		Not applicable. For more information, see Dependencies.
on

References

[1] https://www.mathworks.com/help/rf/examples/visualizing-mixer-spurs.html

[2] https://www.microwavejournal.com/articles/3430-the-use-of-intermodulation-tables-for-mixer-simulations

[3] Faria, Daniel., Lawrence Dunleavy, and Terje Svensen. "The Use of Intermodulation Tables for Mixer Simulations". Microwave Journal, April 2002. https://www.microwavejournal.com/articles/3430-the-use-of-intermodulation-tables-for-mixer-simulations.

[4] "RF Mixing / Multiplication: Frequency Mixers". Electronic Notes. https://www.electronics-notes.com/articles/radio/rf-mixer/rf-mixing-basics.php.

Version History

Introduced in R2019b

R2022a: Extract reference input power and nominal output power from data file

You can now extract reference input power and nominal output power from a data file. For more information, see Block Parameters When Using Data File.

R2021b: IMT Mixer block icon updated

Starting in R2021b, the IMT Mixer block icon has updated. The block icons are now dynamic and show the current state of the noise parameter.

When you open a model created before R2021b containing a IMT Mixer block, the software replaces the block icon with the R2021b version.