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

Impact of Thermal Noise on Communication System Performance

Model thermal noise in a super-heterodyne RF receiver and measure its effects on a communications system noise figure and bit error rate.

• Open Model

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 voltage-controlled 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, [a0,a1,a2, ... a9], the polynomial it represents is:

V_out = a₀ + a₁V_in + a₂V_in² + ...  + a₉V_in⁹

a₁ represents the linear gain term, and higher-order terms are modeled according to [2].

For example, the vector [a0,a1,a2,a3] specifies the relation V_out = a₀ + a₁V₁ + a₂V₁² + a₃V₁³. Trailing zeros are omitted. So, [a0,a1,a2] defines the same polynomial as [a0,a1,a2, 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) — Signal-to-noise ratio (SNR) between outputs and input

0 (default) | scalar

Single-sideband 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 non-DC 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 non-DC 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

1e-10 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 second-order and third-order intermodulation frequencies, in addition to a linear term.

• Odd order: The Demodulator generates only "odd-order" intermodulation frequencies.

  The linear gain determines the linear a₁ term. The block calculates the remaining terms from the values specified in IP3, 1-dB 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 1-dB gain compression power, and the Output saturation power.

IP2 — Second-order intercept point

inf dBm (default) | scalar

Second-order 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 — Third-order intercept point

inf dBm (default) | scalar

Third-order intercept point, specified as a scalar in dBm, W, mW, or dBW. The default value inf dBm corresponds to an unspecified point.

1-dB gain compression power — 1-dB gain compression power

inf dBM (default) | scalar

1-dB 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.

1-dB gain compression power — 1-dB gain compression power

inf dBM (default) | scalar

1-dB 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 two-port S-parameters 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 frequency-domain 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.

$$R_{\text{ratio}}=\frac{\sqrt{1+{\epsilon }^2}+\epsilon }{\sqrt{1+{\epsilon }^2}-\epsilon }$$

where:

• $$\epsilon =\sqrt{{10}^{(0.1R_{\text{p}})}-1}$$

• 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) | 2-tuple vector

Passband frequencies for bandpass filters, specified as a 2-tuple 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) | 2-tuple vector

Stopband frequencies for bandstop filters, specified as a 2-tuple 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) | 2-tuple vector

Stopband edge frequencies for bandstop filters, specified as a 2-tuple 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

1e-10s (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 two-port S-parameters 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 frequency-domain 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.

$$R_{\text{ratio}}=\frac{\sqrt{1+{\epsilon }^2}+\epsilon }{\sqrt{1+{\epsilon }^2}-\epsilon }$$

where:

• $$\epsilon =\sqrt{{10}^{(0.1R_{\text{p}})}-1}$$

• 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) | 2-tuple vector

Passband frequencies for bandpass filters, specified as a 2-tuple 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) | 2-tuple vector

Stopband frequencies for bandstop filters, specified as a 2-tuple 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) | 2-tuple vector

Stopband edge frequencies for bandstop filters, specified as a 2-tuple 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

1e-10s (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 R2018a

R2022b: 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.