S-Parameters Mixer

Model mixer and local oscillator using S-parameters

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Libraries:
RF Blockset / Equivalent Baseband / Mixers

Description

The S-Parameters Mixer block models the nonlinear mixer described in the block dialog box, in terms of its frequency-dependent S-parameters, the frequencies and reference impedance of the S-parameters, noise data (including phase noise data), and nonlinearity data.

Examples

Radar Tracking System

Model and simulate a radar tracking system.

• Open Script

Parameters

Main

S-Parameters — S-parameters for nonlinear mixer

[0,0;1,0] (default) | 2-by-2-by-M array

S-parameters for the nonlinear mixer, specified as a 2-by-2-by-M array where M is the number of S-parameters.

Frequency (Hz) — Frequency of S-parameters

2.0e9 (default) | M-element vector

Frequency of the S-parameters, specified as an M-element vector with each element unit in hertz. All frequencies must be positive.

Reference Impedance (ohms) — Reference impedance of S-parameters

50 (default) | numeric scalar | numeric vector of length M

Reference impedance of the S-parameters as a numeric scalar or a numeric vector of length M. If you provide a scalar value, then that value is applied to all frequencies.

Complex Number Support: Yes

Interpolation method — Method to interpolate network parameters

Linear (default) | Spline | Cubic

Method to interpolate the network parameters, specified as one of the following:

Method	Description
Linear	Linear interpolation
Spline	Cubic spline interpolation
Cubic	Piecewise cubic Hermite interpolation

Mixer Type — Type of mixer

Downconverter (default) | Upconverter

Type of mixer, specified as Downconverter or Upconverter.

LO frequency (Hz) — Local oscillator frequency

0.9e9 (default) | M-element vector

Local oscillator frequency, specified as an M-element vector with each element unit in hertz.

• If you choose Mixer Type as Downconverter, then the blockset computes the mixer output frequency, f_out, from the mixer input frequency, f_in, and the local oscillator frequency, f_lo, as f_out = f_in – f_lo.

• If you Mixer Type as Upconverter, then f_out = f_in + f_lo.

Note

For a downconverting mixer, the local oscillator frequency must satisfy the condition f_in – f_lo ≥ 1/(2t_s), where t_s is the sample time specified in the Input Port block. Otherwise, an error appears.

Noise Data

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

[0.1 1 10 100]*1e3 (default) | numeric vector

Phase noise frequency offset, specified as a numeric vector with units in hertz.

Data Types: double

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

[-70 -120 -140 -150] (default) | numeric vector

Phase noise level, specified as a numeric vector with units in decibels relative to the carrier per hertz.

Data Types: double

Noise type — Type of noise data

Noise figure (default) | Spot noise data | Noise factor | Noise temperature

Type of noise data, specified as one of the following:

• Noise figure

• Spot noise data

• Noise factor

• Noise temperature

This parameter is disabled if the data source contains noise data.

Noise figure (dB) — Available signal-to-noise ratio at the input to available signal-to-noise ratio at the output

0 (default) | scalar ratio | vector of ratios

Available signal-to-noise ratio at the input to available signal-to-noise ratio at the output, specified as a scalar ratio or a vector of ratios.

Dependencies

To enable this parameter, select Noise figure in Noise type.

Minimum noise figure — Minimum ratio of available signal-to-noise ratio at input to available signal-to-noise ratio at output

0 (default) | scalar ratio | vector of ratios

Minimum ratio of available signal-to-noise ratio at the input to available signal-to-noise ratio at the output, specified as a scalar ratio or a vector of ratios.

Dependencies

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

Optimal reflection coefficient — Optimal source impedance

1+0i (default) | complex scalar | complex vector

Optimal source impedance, specified as a complex scalar or a complex vector.

Dependencies

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

Equivalent normalized noise resistance — Normalized resistance values used to take noise measurement

1 (default) | positive scalar | positive vector

Normalized resistance values used to take noise measurement, specified as a positive scalar or a positive vector.

Dependencies

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

Noise factor — Ratio of available signal-to-noise power at input to available signal-to-noise power at output

1 (default) | scalar ratio | vector of ratios

Ratio of available signal-to-noise power at the input to available signal-to-noise power at the output, specified as a scalar ratio or a vector of ratios.

Dependencies

To enable this parameter, select Noise factor in Noise type.

Noise temperature (K) — Equivalent temperature that produces same amount of noise as mixer

0 (default) | nonnegative scalar | nonnegative vector

Equivalent temperature that produces the same amount of noise as the mixer, specified as a nonnegative scalar or nonnegative vector with units in kelvins.

Dependencies

To enable this parameter, select Noise temperature in Noise type.

Frequency (Hz) — Domain of frequencies to express noise data

2.0e9 (default) | nonnegative scalar | nonnegative vector

Domain of frequencies to express noise data, specified as a nonnegative scalar in hertz or nonnegative vector with each element unit in hertz. If you provide a scalar value for your noise data, the block ignores the Frequency (Hz) parameter and uses the same noise data for all frequencies. If you provide a vector of values for your noise data, it must be the same size as the vector of frequencies. The block uses the Interpolation method specified in the Main tab to interpolate noise data.

Nonlinearity Data

IP3 type — Type of third order intercept

OIP3 (default) | IIP3

Type of third order intercept, specified as OIP3 (output intercept point) or IIP3 (input intercept point). This parameter is disabled if the data source contains power data or IP3 data.

IP3 (dBm) — IP3 value

inf (default) | scalar | vector

IP3 value, specified as a scalar in dBm for frequency independent nonlinear data or a vector with each element unit in dBm for frequency dependent nonlinear data. This parameter is disabled if the data source contains power data or IP3 data.

1dB gain compression power (dBm) — Output power value at which gain has decreased by 1 dB

inf (default) | scalar | vector

Output power value ($$P_{1dB,out}$$) at which the gain has decreased by 1 dB, specified as a scalar in dBm for frequency independent nonlinear data or vector with each element unit in dBm for frequency dependent nonlinear data. This parameter is disabled if the data source contains power data or IP3 data.

Output saturation power (dBm) — Output power value that mixer produces when fully saturated

inf (default) | scalar | vector

Output power value ($$P_{sat,out}$$) that the mixer produces when fully saturated, specified as a scalar in dBm for frequency independent nonlinear data or a vector with each element unit in dBm for frequency dependent nonlinear data. This parameter is disabled if the data source contains output saturation power data.

Gain compression at saturation (dB) — Decrease in gain value

3 (default) | scalar | vector

Decrease in gain value ($$G{C}_{sat}$$) when the power is fully saturated, specified as a scalar in dB for frequency independent nonlinear data or a vector with each element unit in dB for frequency dependent nonlinear data.

Frequency (Hz) — Frequency points corresponding to third-order intercept or power data

2.0e9 (default) | positive scalar | positive vector

Frequency points corresponding to third-order intercept or power data, specified as a positive scalar or positive vector in units of hertz. This parameter is disabled if the data source contains power data or IP3 data.

Dependencies

• If you specify the frequency as a scalar, then the IP3 (dBm), 1 dB gain compression power (dBm), and Output saturation power (dBm) parameters must all be scalars.

• If you specify the frequency as a vector, then or more of the IP3 (dBm), 1 dB gain compression power (dBm), and Output saturation power (dBm) parameters must also be a vector.

Visualization

Source of frequency data — Frequency data source

Same as the S-Parameters (default) | User-specified

Frequency data source, specified as Same as the S-Parameters or User-specified.

Frequency data (Hz) — Frequency data range

[1e9:1e8:2.9e9] (default) | vector

Frequency data range, specified as a vector with each element unit in hertz.

Dependencies

To enable this parameter, set Source of frequency data to User specified.

Reference impedance (ohms) — Reference impedance

50 (default) | nonnegative scalar

Reference impedance, specified as a nonnegative scalar in ohms.

Plot type — Type of data plot

X-Y plane (default) | Composite data | Polar plane | Z Smith chart | Y Smith chart | ZY Smith chart

Type of data plot to visualize using the given data, specified as one of the following:

• X-Y plane — Generate a Cartesian plot of the data versus frequency. To create linear, semilog, or log-log plots, set the Y-axis scale and X-axis scale accordingly.

• Composite data — Plot the composite data. For more information, see Create Plots Using Equivalent Baseband Library Blocks.

• Polar plane — Generate a polar plot of the data. The block plots only the range of data corresponding to the specified frequencies.

• Z smith chart, Y smith chart, and ZY smith chart — Generate a Smith^® chart. The block plots only the range of data corresponding to the specified frequencies.

Y parameter1 — Type of parameters to plot

S11 (default) | S12 | S21 | S22 | GroupDelay | OIP3 | NF | NFactor | NTemp | PhaseNoise | ...

Type of parameters to plot based on the Plot type you set, specified as one of the following.

Plot type	Y parameter1
X-Y plane	S11, S12, S21, S22, GroupDelay, OIP3, NF, NFactor, NTemp, and PhaseNoise.
Composite data	No Y parameter1 to set.
Polar plane	S11, S12, S21, and S22
Z Smith chart	S11 and S22.
Y Smith chart	S11 and S22.
ZY smith chart	S11 and S22.

Y parameter2 — Type of parameters to plot

S11 | S12 | S21 | S22 | GroupDelay | OIP3 | NF | NFactor | NTemp | ...

Type of parameters to plot based on the Plot type you set, specified as one of the following.

Plot type	Y parameter1
X-Y plane	S11, S12, S21, S22, GroupDelay, OIP3, NF, NFactor, NTemp, and PhaseNoise.
Composite data	No Y parameter1 to set.
Polar plane	S11, S12, S21, and S22
Z Smith chart	S11 and S22.
Y Smith chart	S11 and S22.
ZY smith chart	S11 and S22.

Y format1 — Plot format

Magnitude (decibels) (default) | Magnitude (linear) | Angle(degrees) | Angle(radians) | Real | Imaginary

Plot format, specified as one of the following.

Y parameter1	Y format1
S11, S12, S21, and S22.	Magnitude (decibels), Magnitude (linear), Angle(degrees), Angle(radians), Real, and Imaginary.
GroupDelay	ns, us, ms, s, and ps.
OIP3	dB, dBm, W, and mW.
NF	Magnitude (decibels)
NFactor	None
NTemp	Kelvin
PhaseNoise	dBc/Hz

Dependencies

To enable Y format1, set Plot type to X-Y plane.

Y format2 — Plot format

Magnitude (decibels) (default) | Magnitude (linear) | Angle(degrees) | Angle(radians) | Real | Imaginary

Plot format, specified as one of the following.

Y parameter1	Y format1
S11, S12, S21, and S22.	Magnitude (decibels), Magnitude (linear), Angle(degrees), Angle(radians), Real, and Imaginary.
GroupDelay	ns, us, ms, s, and ps.
OIP3	dB, dBm, W, and mW.
NF	Magnitude (decibels)
NFactor	None
NTemp	Kelvin
PhaseNoise	dBc/Hz

Dependencies

To enable Y format1, set Plot type to X-Y plane.

X parameter — Frequency plot

Freq (default)

Frequency plot, specified as Freq.

X format — Frequency plot format

Hz (default) | Auto | kHz | MHz | GHz | THz

Frequency plot format, specified as one of the following.

Auto	Hz	kHz	MHz
GHz	THz

Y scale — Y-axis scale

Linear (default) | Log

Y-axis scale, specified as Linear or Log.

Dependencies

To enable this parameter, set Plot type to X-Y plane.

X scale — X-axis scale

Linear (default) | Log

X-axis scale, specified as Linear or Log.

Dependencies

To enable this parameter, set Plot type to X-Y plane.

Plot — Plot specified data

button

Plot specified data using the plot button.

More About

Network Parameters

The S₂₁ parameter values describe the conversion gain as a function of frequency, referred to the mixer input frequency. The other S-parameters also refer to the mixer input frequency.

In the S-Parameters field of the block dialog box, provide the S-parameters for each of M frequencies as a 2-by-2-by-M array. In the Frequency field, specify the frequencies for the S-parameters as an M-element vector. The elements of the vector must be in the same order as the S-parameters. The figure shows the correspondence between the S-parameters array and the vector of frequencies.

The S-Parameters Mixer block interpolates the given S-parameters to determine their values at the modeling frequencies the Output Port block calculates. For more details about how the Output Port block calculates the modeling frequencies, see Map Network Parameters to Modeling Frequencies.

RF Blockset™ Equivalent Baseband software computes the reflected wave at the mixer input ($$b_1$$) and at the mixer output ($$b_2$$) from the interpolated S-parameters as

$$\left[\begin{array}{c}{b}_1(f_{in})\\ b_2(f_{out})\end{array}\right]=\left[\begin{array}{cc}{S}_{11}& S_{12}\\ S_{21}& S_{22}\end{array}\right]\left[\begin{array}{c}{a}_1(f_{in})\\ a_2(f_{out})\end{array}\right]$$

where

• $$f_{in}$$ and $$f_{out}$$ are the mixer input and output frequencies, respectively.

• $$a_1$$ and $$a_2$$ are the incident waves at the mixer input and output, respectively.

The interpolated S₂₁ parameter values describe the conversion gain as a function of frequency, referred to the mixer input frequency.

Active Noise

You can specify active block noise in one of the following ways:

• Spot noise data in the S-Parameters Mixer block dialog box.

• Noise figure, noise factor, or noise temperature value in the S-Parameters Mixer block dialog box.

If you specify block noise as spot noise data, the block uses the data to calculate noise figure. The block first interpolates the noise data for the modeling frequencies using the specified Interpolation method. It then calculates the noise figure using the resulting values.

Phase Noise

The S-Parameters Mixer block applies phase noise to a complex baseband signal. The block first generates additive white Gaussian noise (AWGN) and filters the noise with a digital FIR filter. It then adds the resulting noise to the angle component of the input signal.

The blockset computes the digital filter by:

1. Interpolating the specified phase noise level to determine the phase noise values at the modeling frequencies.

2. Taking the IFFT of the resulting phase noise spectrum to get the coefficients of the FIR filter.

Note

If you specify phase noise as a scalar value, then the blockset assumes that the phase noise is the phase noise is constant at all modeling frequencies and does not have a 1/f slope. This assumption differs from that made by the Mathematical Mixer block.

Nonlinearity

You can introduce nonlinearities into your model by specifying parameters in the Nonlinearity Data tab of the S-Parameters Mixer block dialog box. Depending on which of these parameters you specify, the block computes up to four of the coefficients $$c_1$$, $$c_3$$, $$c_5$$, and $$c_7$$ of the polynomial $$F_{AM/AM}(s)=c_{1}s+c_3{\left|s\right|}^{2}s+c_5{\left|s\right|}^{4}s+c_7{\left|s\right|}^{6}s$$ that determines the AM/AM conversion for the input signal $$s$$. The block automatically calculates $$c_1$$, the linear gain term. If you do not specify additional nonlinearity data, the block operates as a mixer with a linear gain. If you do, the block calculates one or more of the remaining coefficients as the solution to a system of linear equations, determined by the following method.

1. The block checks whether you have specified a value other than Inf for:

   • The third-order intercept point ($$OIP3$$ or $$IIP3$$).

   • The output power at the 1-dB compression point ($$P_{1dB,out}$$).

   • The output power at saturation ($$P_{sat,out}$$).

   In addition, if you have specified $$P_{sat,out}$$, the block uses the value for the gain compression at saturation ($$G{C}_{sat}$$). Otherwise, $$G{C}_{sat}$$ is not used. You define each of these parameters in the block dialog box, on the Nonlinearity Data tab.

2. The block calculates a corresponding input or output value for the parameters you have specified. In units of dB and dBm,

   $$\begin{array}{c}{P}_{sat,out}+G{C}_{sat}=P_{sat,in}+G_{lin}\\ P_{1dB,out}+1=P_{1dB,in}+G_{lin}\\ OIP3=IIP3+G_{lin}\end{array}$$

   where $$G_{lin}$$ is $$c_1$$ in units of dB.

3. The block formulates the coefficients $$c_3$$, $$c_5$$, and $$c_7$$, where applicable, as the solutions to a system of one, two, or three linear equations. The number of equations used is equal to the number of parameters you provide. For example, if you specify all three parameters, the block formulates the coefficients according to the following equations:

   $$\begin{array}{c}\sqrt{P_{sat,out}}=c_1\sqrt{P_{sat,in}}+c_3{\left(\sqrt{P_{sat,in}}\right)}^3+c_5{\left(\sqrt{P_{sat,in}}\right)}^5+c_7{\left(\sqrt{P_{sat,in}}\right)}^7\\ \sqrt{P_{1dB,out}}=c_1\sqrt{P_{1dB,in}}+c_3{\left(\sqrt{P_{1dB,in}}\right)}^3+c_5{\left(\sqrt{P_{1dB,in}}\right)}^5+c_7{\left(\sqrt{P_{1dB,in}}\right)}^7\\ 0=\frac{c_1}{IIP3}+c_3\end{array}$$

   The first two equations are the evaluation of the polynomial $$F_{AM/AM}(s)$$ at the points $$(\sqrt{P_{sat,in}},\sqrt{P_{sat,out}})$$ and $$(\sqrt{P_{1dB,in}},\sqrt{P_{1dB,out}})$$, expressed in linear units (such as W or mW) and normalized to a 1-Ω impedance. The third equation is the definition of the third-order intercept point.

   The calculation omits higher-order terms according to the available degrees of freedom of the system. If you specify only two of the three parameters, the block does not use the equation involving the parameter you did not specify, and eliminates any $$c_7$$ terms from the remaining equations. Similarly, if you provide only one of the parameters, the block uses only the solution to the equation involving that parameter and omits any $$c_5$$ or $$c_7$$ terms.

If you provide vectors of nonlinearity and frequency data, then the block calculates the polynomial coefficients using values for the parameters interpolated at the center frequency.

Version History

Introduced before R2006a