Demodulator
Model RF to RF demodulator
Libraries:
RF Blockset /
Circuit Envelope /
Systems
Description
The Demodulator block models an RF to RF demodulator. The Demodulator block mask icons are dynamic and indicate the current state of the applied noise parameter. For more information, see Demodulator Icons.
Examples
Parameters
Main
Source of conversion gain — Source parameter of conversion gain
Available power gain
(default)  Open circuit voltage gain
 Polynomial coefficients
Source parameter of conversion gain, specified as one of the following:
Available power gain
— Relates the ratio of power of a single sideband (SSB) at the output to the input power. This calculation assumes a matched load and source termination.Open circuit voltage gain
— Value of the open circuit voltage gain parameter as the linear voltage gain term of the polynomial voltagecontrolled voltage source (VCVS).Polynomial coefficients
— Implements a nonlinear voltage gain according to the polynomial you specify.
Available power gain — Ratio of power of SSB at the output to input power
0 dB
(default)  scalar in dB or a unitless ratio
Ratio of power of SSB at output to input power, specified as a scalar in dB or a unitless ratio. For a unitless ratio, select None.
Dependencies
To enable this parameter, set Source of conversion
gain to Available power
gain
.
Open circuit voltage gain — Open circuit voltage gain
0 dB
(default)  scalar
Open circuit voltage gain, specified as a scalar in dB.
Dependencies
To enable this parameter, set Source of conversion
gain to Open circuit voltage
gain
.
Polynomial coefficients — Coefficients of polynomial specifying voltage gain
[0 1]
(default)  vector
Polynomial coefficients, specified as a vector.
The order of the polynomial must be less than or equal to 9. The
coefficients must be ordered in ascending powers. If a vector has 10
coefficients,
[
,
the polynomial it represents is:a
_{0},a
_{1},a
_{2},
... a
_{9}]
V_{out} = a_{0} + a_{1}V_{in} + a_{2}V_{in}^{2} + ...
+ a_{9}V_{in}^{9}
a_{1}
represents the linear gain term, and higherorder terms are modeled
according to [2].
For example, the vector
[
specifies the relation V_{out} = a_{0} + a_{1}V_{1} + a_{2}V_{1}^{2} + a_{3}V_{1}^{3}. Trailing zeros are omitted. So,
a
_{0},a
_{1},a
_{2},a
_{3}][
defines the same polynomial as
a
_{0},a
_{1},a
_{2}][
.a
_{0},a
_{1},a
_{2},
0]
The default value is [0,1]
, corresponding to the
linear relation V_{out} =
V_{in}.
Dependencies
To enable this parameter, set Source of conversion
gain to Polynomial
coefficients
.
Local oscillator frequency — Local oscillator (LO) frequency
0
Hz
(default)  scalar
Local oscillator (LO) frequency, specified as a scalar in Hz, kHz, MHz, or GHz.
Input impedance (Ohm) — Input impedance of demodulator
50
(default)  scalar
Input impedance of demodulator, specified as a scalar in Ohms.
Output impedance (Ohm) — Output impedance of demodulator
50
(default)  scalar
Output impedance of demodulator, specified as a scalar in Ohms.
Add Image Reject filter — Image reject (IR) filter parameters
off
(default)  on
Select to add the IR filter parameter tab. Clear to remove the tab.
Add Channel Select filters — Channel select (CS) filter parameters
off
(default)  on
Select to add the CS filter parameter tab. Clear to remove the tab.
Ground and hide negative terminals — Ground and hide negative circuit terminals
on
(default)  off
Select to internally ground and hide the negative terminals. Clear to expose the negative terminals. When the terminals are exposed, you can connect them to other parts of your model.
Edit System — Break demodulator block links and replace internal variables by appropriate values
button
Use this button to break demodulator links to the library. The internal variables are replaced by their values which are estimated using demodulator parameters. The Demodulator becomes a simple subsystem masked only to keep the icon.
Use Edit System to edit the internal variables without expanding the subsystem. Use Expand System to expand the subsystem in Simulink^{®} canvas and to edit the subsystem.
Impairments
LO to In isolation — Ratio of magnitude between LO voltage to leaked voltage at input port
(RF)
inf
dB
(default)  scalar
Ratio of magnitude of LO voltage to leaked voltage at input port (RF), specified as a scalar in dB.
Noise figure (dB) — Signaltonoise ratio (SNR) between outputs and input
0
(default)  scalar
Singlesideband noise figure of mixer, specified as a scalar in dB.
To model noise in a circuit envelope model with a Demodulator block, you must select the Simulate noise check box in the Configuration block dialog box.
Add phase noise — Add phase noise
off
(default)  on
Select this parameter to add phase noise to your demodulator system.
Phase noise frequency offset (Hz) — Phase noise frequency offset
1
(default)  scalar  vector  matrix
Phase noise frequency offset, specified as a scalar, vector, or matrix with each element unit in Hz.
If you specify a matrix, each column corresponds to a nonDC carrier frequency of the CW source. The frequency offset values bind the envelope bandwidth of the simulation. For more information, see Configuration.
Dependencies
To enable this parameter, select Add phase noise.
Phase noise level (dBc/Hz) — Phase noise level
Inf
(default)  scalar  vector  matrix
Phase noise level, specified as a scalar, vector, or matrix with element in dBc/Hz.
If you specify a matrix, each column corresponds to a nonDC carrier frequency of the CW source. The frequency offset values bind the envelope bandwidth of the simulation. For more information, see Configuration.
Dependencies
To enable this parameter, select Add phase noise.
Automatically estimate impulse response duration — Automatically estimate impulse response duration
on
(default)  off
Select to automatically estimate impulse response for phase noise. Clear to specify the impulse response duration using Impulse response duration.
Dependencies
To enable this parameter, select Add phase noise.
Impulse response duration — Impulse response duration
1e10
s
(default)  scalar
Impulse response duration used to simulate phase noise, specified as a scalar in s, ms, us, or ns.
Note
The phase noise profile resolution in frequency is limited by the duration of the impulse response used to simulate it. Increase this duration to improve the accuracy of the phase noise profile. A warning message appears if the phase noise frequency offset resolution is too high for a given impulse response duration. This message also specifies the minimum duration suitable for the required resolution.
Dependencies
To set this parameter, first clear Automatically estimate impulse response duration.
Plot phase noise characteristics — Phase noise magnitude response
button
The block plots the phase noise characteristics based in the parameters specified on the Impairments tab and either the Envelope bandwidth parameter in the Configuration block when available or the value specified in the Phase noise frequency offset (Hz) parameter.
Dependencies
To enable this parameter, select Add phase noise.
Nonlinearity
Selecting Polynomial coefficients
for
Source of conversion gain in the
Main tab removes the
Nonlinearity parameters.
Nonlinear polynomial type — Polynomial nonlinearity
Even and odd order
(default)  Odd order
Polynomial nonlinearity, specified as one of the following:
Even and odd order
: The Demodulator can produce secondorder and thirdorder intermodulation frequencies, in addition to a linear term.Odd order
: The Demodulator generates only "oddorder" intermodulation frequencies.The linear gain determines the linear a_{1} term. The block calculates the remaining terms from the values specified in IP3, 1dB gain compression power, Output saturation power, and Gain compression at saturation. The number of constraints you specify determines the order of the model. The figure shows the graphical definition of the nonlinear Demodulator parameters.
Intercept points convention — Intercept points convention
Input
(default)  Output
Intercept points convention, specified as
Input
(input referred) or
Output
(output referred). Use this
specification for the intercept points IP2,
IP3, the 1dB gain compression
power, and the Output saturation
power.
IP2 — Secondorder intercept point
inf
dBm
(default)  scalar
Secondorder intercept point, specified as a scalar in dBm, W, mW, or
dBW. The default value, inf dBm
, corresponds to an
unspecified point.
Dependencies
To enable this parameter, set Nonlinear polynomial
type to Even and odd
order
.
IP3 — Thirdorder intercept point
inf dBm
(default)  scalar
Thirdorder intercept point, specified as a scalar in dBm, W, mW, or
dBW. The default value inf dBm
corresponds to an
unspecified point.
1dB gain compression power — 1dB gain compression power
inf dBM
(default)  scalar
1dB gain compression power, specified as a scalar in dBm, W, mW, or dBW.
Dependencies
To set this parameter, select Odd order
in Nonlinear polynomial type.
1dB gain compression power — 1dB gain compression power
inf dBM
(default)  scalar
1dB gain compression power, specified as a scalar in dBm, W, mW, or dBW.
Dependencies
To set this parameter, select Odd order
in Nonlinear polynomial type.
Gain compression at saturation — Gain compression at saturation
inf dBm
(default)  scalar
Gain compression at saturation, specified as scalar in dBm, W, mW, or dBW.
When Nonlinear polynomial type is
Odd order
, specify the gain compression
at saturation.
Dependencies
To set this parameter, first select Odd
order
in Nonlinear polynomial
type. Then, change the default value of
Output saturation power.
IR Filter
Select Add Image Reject filter in the Main tab to see the IR Filter parameters tab.
Design method — Simulation type
Ideal
(default)  Butterworth
 Chebyshev
Simulation type. Simulates an ideal, Butterworth, or Chebyshev filter of the type specified in Filter type and the model specified in Implementation.
Filter type — Filter type
Lowpass
(default)  Highpass
 Bandpass
 Bandstop
Filter. Simulates a lowpass, highpass, bandpass, or bandstop filter type of the design specified in Design method.
Implementation — Implementation
LC Tee
 LC Pi
 Transfer function
 Constant per carrier
 Frequency Domain
Implementation, specified as one of the following:
LC Tee
: Model an analog filter with an LC lumped Tee structure when the Design method is Butterworth or Chebyshev.LC Pi
: Model an analog filter with an LC lumped Pi structure when the Design method is Butterworth or Chebyshev.Transfer Function
: Model an analog filter using twoport Sparameters when the Design method is Butterworth or Chebyshev.Constant per carrier
: Model a filter with either full transmission or full reflection set as constant throughout the entire envelope band around each carrier. The Design method is specified as ideal.Frequency Domain
: Model a ideal filter using convolution with an impulse response. The Design method is specified as ideal. The impulse response is computed independently for each carrier frequency to capture the ideal filtering response. When a transition between full transmission and full reflection of the ideal filter occurs within the envelope band around a carrier, the frequencydomain implementation captures this transition correctly up to a frequency resolution specified in Impulse response duration.Note
Due to causality, a delay of half the impulse response duration is included for both reflected and transmitted signals. This delay impairs the filter performance when the Source and Load resistances differ from the values specified in filter parameters.
By default, the Implementation is
Constant per carrier
for an ideal filter
and LC Tee
for Butterworth or
Chebyshev.
Passband edge frequency — Passband edge frequency
2 GHz
(default)  scalar
Passband edge frequency, specified as a scalar in Hz, kHz, MHz, or GHz.
Dependencies
To enable this parameter, set Design method
to Ideal
and Filter
type to Lowpass
or
Highpass
.
Implement using filter order — Implement using filter order
on
(default)  off
Select this parameter to implement the filter order manually.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
.
Filter order — Filter order
3
(default)  scalar
Filter order, specified as a scalar. For a Filter
type of Lowpass
or
Highpass
, the filter order is the number
of lumped storage elements. For a Filter type of
Bandpass
of
Bandstop
, the number of lumped storage
elements is twice the filter order.
Note
For even order Chebyshev filters, the resistance ratio $$\frac{{R}_{\text{load}}}{{R}_{\text{source}}}>{R}_{\text{ratio}}$$ for Tee network implementation and $$\frac{{R}_{\text{load}}}{{R}_{\text{source}}}<\frac{1}{{R}_{\text{ratio}}}$$ for Pi network implementation.
$${R}_{\text{ratio}}\text{\hspace{0.17em}}=\text{\hspace{0.17em}}\frac{\sqrt{1+{\epsilon}^{2}}+\epsilon}{\sqrt{1+{\epsilon}^{2}}\epsilon}$$
where:
$$\epsilon \text{\hspace{0.17em}}=\text{\hspace{0.17em}}\sqrt{{10}^{(0.1{R}_{\text{p}})}1}$$
R_{p} is the passband ripple in dB.
Dependencies
To enable this parameter, select Implement using filter
order and set Design method to
Butterworth
or
Chebyshev
.
Passband frequency — Passband frequency for lowpass and highpass filters
scalar
Passband frequency for lowpass and highpass filters, specified as a
scalar in Hz, kHz, MHz, or GHz. The default passband frequency is
1 GHz
for Lowpass
filters and 2 GHz
for
Highpass
filters.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
and Filter
type to Lowpass
or
Highpass
.
Passband frequencies — Passband frequencies for bandpass filters
[2 3] GHz
(default)  2tuple vector
Passband frequencies for bandpass filters, specified as a 2tuple vector in Hz, kHz, MHz, or GHz. This option is not available for bandstop filters.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
and Filter
type to Bandpass
.
Passband attenuation (dB) — Passband attenuation
10*log10(2)
(default)  scalar
Passband attenuation, specified as a scalar in dB. For bandpass filters, this value is applied equally to both edges of the passband.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
.
Stopband frequencies — Stopband frequencies for bandstop filters
[2.1 2.9]GHz
(default)  2tuple vector
Stopband frequencies for bandstop filters, specified as a 2tuple vector in Hz, kHz, MHz, or GHz. This option is not available for bandpass filters.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
and Filter
type to Bandstop
.
Stopband edge frequencies — Stopband edge frequencies for ideal bandstop filters
[2.1 2.9] GHz
(default)  2tuple vector
Stopband edge frequencies for bandstop filters, specified as a 2tuple vector in Hz, kHz, MHz, or GHz. This option is not available for ideal bandpass filters.
Dependencies
To enable this parameter, set Design method
to Ideal
and Filter
type to Bandstop
.
Stopband attenuation (dB) — Stopband attenuation
40
(default)  scalar
Stopband attenuation, specified as a scalar in dB. For bandstop filters, this value is applied equally to both edges of the stopband.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
and Filter
type to Bandstop
.
Source impedance (Ohm) — Input source resistance
50
(default)  scalar
Input source resistance, specified as a scalar in Ohms.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
.
Load impedance (Ohm) — Output load resistance
50
(default)  scalar
Output load resistance, specified as a scalar in Ohms.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
.
Automatically estimate impulse response duration — Automatically estimate impulse response duration
on
(default)  off
Select to automatically estimate impulse response for phase noise. Clear to manually specify the impulse response duration using Impulse response duration.
Dependencies
To enable this parameter, set Design method
to Ideal
and
Implementation to Frequency
domain
.
Impulse response duration — Impulse response duration
1e10
s
(default)  scalar
Impulse response duration used to simulate phase noise, specified as a scalar in s, ms, us, or ns. You cannot specify impulse response if the amplifier is nonlinear.
Note
The phase noise profile resolution in frequency is limited by the duration of the impulse response used to simulate it. Increase this duration to improve the accuracy of the phase noise profile. A warning message appears if the phase noise frequency offset resolution is too high for a given impulse response duration. The message also specifies the minimum duration suitable for the required resolution.
Dependencies
To enable this parameter, clear Automatically estimate impulse response duration.
Export — Save filter design to a file
button
Use this button to save filter design to a file. Valid file types are
.mat
and .txt
.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
.
CS Filter
Select Add Channel Select filters in the Main tab to see the CS Filter parameters.
Design method — Simulation type
Ideal
(default)  Butterworth
 Chebyshev
Simulation type. Simulates an ideal, Butterworth, or Chebyshev filter of the type specified in Filter type and the model specified in Implementation.
Filter type — Filter type
Lowpass
(default)  Highpass
 Bandpass
 Bandstop
Filter. Simulates a lowpass, highpass, bandpass, or bandstop filter type of the design specified in Design method.
Implementation — Implementation
LC Tee
 LC Pi
 Transfer function
 Constant per carrier
 Frequency Domain
Implementation, specified as one of the following:
LC Tee
: Model an analog filter with an LC lumped Tee structure when the Design method is Butterworth or Chebyshev.LC Pi
: Model an analog filter with an LC lumped Pi structure when the Design method is Butterworth or Chebyshev.Transfer Function
: Model an analog filter using twoport Sparameters when the Design method is Butterworth or Chebyshev.Constant per carrier
: Model a filter with either full transmission or full reflection set as constant throughout the entire envelope band around each carrier. The Design method is specified as ideal.Frequency Domain
: Model a filter using convolution with an impulse response. The Design method is specified as ideal. The impulse response is computed independently for each carrier frequency to capture the ideal filtering response. When a transition between full transmission and full reflection of the ideal filter occurs within the envelope band around a carrier, the frequencydomain implementation captures this transition correctly up to a frequency resolution specified in Impulse response duration.Note
Due to causality, a delay of half the impulse response duration is included for both reflected and transmitted signals. This delay impairs the filter performance when the Source and Load resistances differ from the values specified in filter parameters.
By default, the Implementation is
Constant per carrier
for an ideal filter
and LC Tee
for Butterworth or
Chebyshev.
Passband edge frequency — Passband edge frequency
2 GHz
(default)  scalar
Passband edge frequency, specified as a scalar in Hz, kHz, MHz, or GHz.
Dependencies
To enable this parameter, set Design method
to Ideal
.
Implement using filter order — Implement using filter order
on
(default)  off
Select this parameter to implement the filter order manually.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
.
Filter order — Filter order
3
(default)  scalar
Filter order, specified as a scalar. This order is the number of
lumped storage elements in lowpass
or
highpass
. In bandpass
or
bandstop
, the number of lumped storage elements
are twice the value.
Note
For even order Chebyshev filters, the resistance ratio $$\frac{{R}_{\text{load}}}{{R}_{\text{source}}}>{R}_{\text{ratio}}$$ for Tee network implementation and $$\frac{{R}_{\text{load}}}{{R}_{\text{source}}}<\frac{1}{{R}_{\text{ratio}}}$$ for Pi network implementation.
$${R}_{\text{ratio}}\text{\hspace{0.17em}}=\text{\hspace{0.17em}}\frac{\sqrt{1+{\epsilon}^{2}}+\epsilon}{\sqrt{1+{\epsilon}^{2}}\epsilon}$$
where:
$$\epsilon \text{\hspace{0.17em}}=\text{\hspace{0.17em}}\sqrt{{10}^{(0.1{R}_{\text{p}})}1}$$
R_{p} is the passband ripple in dB.
Dependencies
To enable this parameter, select Implement using filter order.
Passband frequency — Passband frequency for lowpass and highpass filters
scalar
Passband frequency for lowpass and highpass filters, specified as a
scalar in Hz, kHz, MHz, or GHz. By default, the passband frequency is
1 GHz
for Lowpass
filters and 2 GHz
for
Highpass
filters.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
and Filter
type to Lowpass
or
Highpass
.
Passband frequencies — Passband frequencies for bandpass filters
[2 3] GHz
(default)  2tuple vector
Passband frequencies for bandpass filters, specified as a 2tuple vector in Hz, kHz, MHz, or GHz. This option is not available for bandstop filters.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
and Filter
type to Bandpass
.
Passband attenuation (dB) — Passband attenuation
10*log10(2)
(default)  scalar
Passband attenuation, specified as a scalar in dB. For bandpass filters, this value is applied equally to both edges of the passband.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
.
Stopband frequencies — Stopband frequencies for bandstop filters
[2.1 2.9] GHz
(default)  2tuple vector
Stopband frequencies for bandstop filters, specified as a 2tuple vector in Hz, kHz, MHz, or GHz. This option is not available for bandpass filters.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
and Filter
type to Bandstop
.
Stopband edge frequencies — Stopband edge frequencies for ideal bandstop filters
[2.1 2.9] GHz
(default)  2tuple vector
Stopband edge frequencies for bandstop filters, specified as a 2tuple vector in Hz, kHz, MHz, or GHz. This option is not available for ideal bandpass filters.
Dependencies
To enable this parameter, set Design method
to Ideal
and Filter
type to Bandstop
.
Stopband attenuation (dB) — Stopband attenuation
40
(default)  scalar
Stopband attenuation, specified as a scalar in dB. For bandstop filters, this value is applied equally to both edges of the stopband.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
and Filter
type to Bandstop
.
Source impedance (Ohm) — Input source resistance
50
(default)  scalar
Input source resistance, specified as a scalar in 0hms.
Load impedance (Ohm) — Output load resistance
50
(default)  scalar
Output load resistance, specified as a scalar in Ohms.
Automatically estimate impulse response duration — Automatically estimate impulse response duration
on
(default)  off
Select to automatically estimate impulse response for phase noise. Clear to specify the impulse response duration using Impulse response duration.
Dependencies
To enable this parameter, set Design method
to Ideal
and
Implementation to Frequency
domain
.
Impulse response duration — Impulse response duration
1e10
s
(default)  scalar
Impulse response duration used to simulate phase noise, specified as a scalar in s, ms, us, or ns. You cannot specify impulse response if the amplifier is nonlinear.
Note
The phase noise profile resolution in frequency is limited by the duration of the impulse response used to simulate it. Increase this duration to improve the accuracy of the phase noise profile. A warning message appears if the phase noise frequency offset resolution is too high for a given impulse response duration. The message also specifies the minimum duration suitable for the required resolution
Dependencies
To set this parameter, first clear Automatically estimate impulse response duration.
Export — Save filter design to a file
button
Use this button to save filter design to a file. Valid file types are
.mat
and .txt
.
Dependencies
To enable this parameter, set Design method
to Butterworth
or
Chebyshev
.
Algorithms
Demodulator Icons
This table shows you how the icons on this block will vary based on how you set the Noise figure (dB) and Add LO phase noise parameters on the block.
Noise figure (dB)  Add LO phase noise: off  Add LO phase noise: on 

0 


10 


References
[1] Razavi, Behzad. RF Microelectronics. Upper Saddle River, NJ: Prentice Hall, 2011.
[2] Grob, Siegfried, and Lindner, Jurgen. “Polynomial Model Derivation of Nonlinear Amplifiers.” Department of Information Technology, University of Ulm, Germany.
Version History
Introduced in R2018aR2022b: Estimate impulse response duration using phase noise offset frequencies
The Deodulator block estimates the impulse response duration using the Phase noise frequency offset (Hz) parameter and visualizes the phase noise characteristics when you click the Plot phase noise characteristics button.
R2021b: Demodulator block icon updated
Starting in R2021b, the Deodulator 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 Demodualtor block, the software replaces the block icon with the R2021b version.
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