serdes.SaturatingAmplifier

Models a saturating amplifier

Description

The serdes.SaturatingAmplifier System object™ scales the input waveform according to a voltage in versus voltage out response. The voltage in versus voltage out response is specified either by the soft clipping response defined by Limit and Linear Gain properties or by the VinVout property. serdes.SaturatingAmplifier System object applies memoryless nonlinearity to incoming waveform.

To limit the voltage output to a specific value:

1. Create the serdes.SaturatingAmplifier object and set its properties.

2. Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?

Creation

Syntax

SatAmp = serdes.SaturatingAmplifier

SatAmp = serdes.SaturatingAmplifier(Name,Value)

Description

SatAmp = serdes.SaturatingAmplifier returns an amplifier object that modifies the input signal so that the output voltage is clipped to 1.2 V.

SatAmp = serdes.SaturatingAmplifier(Name,Value) sets properties using one or more name-value pairs. Enclose each property name in quotes. Unspecified properties have default values.

Example: SatAmp = serdes.SaturatingAmplifier('Limit',5) returns a saturating amplifier object that limits the output waveform at 5 V.

Properties

Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

Mode — Amplifier operating mode

1 (default) | 0

Amplifier operating mode, specified as 0 or 1. Mode determines whether the amplifier is bypassed or not.

Mode Value	Saturating Amplifier Mode	Saturating Amplifier Operation
0	Off	serdes.SaturatingAmplifier is bypassed and the input waveform remains unchanged.
1	On	serdes.SaturatingAmplifier scales the input waveform according to a voltage in versus voltage out response.

Data Types: double

Specification — Input specification for limiting amplifier output

'Limit and Linear Gain' (default) | 'VinVout'

Input specification for limiting amplifier output:

• 'Limit and Linear Gain' — Creates a soft clipping voltage in versus voltage out response with the values specified in the Limit and Linear Gain properties.

• 'VinVout' — Generates output voltages corresponding to input voltage specified in the VinVout property. The serdes.SaturatingAmplifier System object maps the input voltage to the output voltages using a memoryless nonlinearity response. If any input voltage point falls outside the specified values, the output for that particular input voltage is linearly interpolated.

Data Types: char

Limit — Clipping voltage for limiting amplifier

1.2 (default) | real positive scalar

Clipping voltage for the limiting amplifier, specified as a real positive scalar in V.

Data Types: double

LinearGain — Amplifier gain in linear region

1 (default) | real positive scalar

Amplifier gain in the linear region, specified as a unitless real positive scalar.

Data Types: double

VinVout — Input and corresponding output voltage responses

N×2 matrix | N×2×M matrix

Input and corresponding output voltage responses, specified as an N×2 matrix (2-D) or N×2×M matrix (3-D) in volts. N is the number of voltage samples and M is the number of slices.

If VinVout is a 3-D matrix, you can select which slice of the VinVout is to use. To know more about defining 3-D VinVout matrix, see Define Saturating Amplifier with 3D VinVout Matrix.

Data Types: double

Slice select — Select which corner of 3D GPZ matrix to use

0 (default) | nonegative scalar integer

Select which slice, family, or corner of a 3-D VinVout matrix to use during CTLE configuration.

You must set Specification to VinVout to effectively use SliceSelect. Depending on how many slices are available in your VinVout matrix, you can then select the slice you are interested in from a zero-based index.

Data Types: double

Usage

Syntax

y = SatAmp(x)

Description

y = SatAmp(x)

Input Arguments

x — Input baseband signal

scalar | vector

Input baseband signal.

Output Arguments

y — Clipped output voltage

scalar | vector

Clipped output voltage, as specified by the serdes.SaturatingAmplifier object.

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

Specific to serdes.SaturatingAmplifier

CombineSlices

Combine multiple VinVout matrices in a single 3-D VinVout matrix

Common to All System Objects

step	Run System object algorithm
release	Release resources and allow changes to System object property values and input characteristics
reset	Reset internal states of System object

Examples

Clipping Input Waveform Using SaturatingAmplifier

This example shows how to clip an incoming sine wave using the serdes.SaturatingAmplifier system object™.

Define an input sine wave with a frequency of 250 Hz.

Fs = 10000;
L = 100;
t = (0:L-1)'/Fs;
x = sin(2*pi*250*t);

Construct the SaturatingAmplifier system object with a linear gain of 2, and gain limit of 0.8 V.

linearGain = 2;
limit = 0.8;
SaturatingAmplifier = serdes.SaturatingAmplifier('Mode',1,...
          'Limit',limit,'LinearGain',linearGain);
y = SaturatingAmplifier(x);

Plot the input and modified waveforms.

figure, plot(t,x,t,y)
legend('Input','Output')
title('Clipping Waveform Using Saturating Amplifier');
xlabel('Time (s)');
ylabel('Amplitude (V)');

Define SaturatingAmplifier with VinVout Table

This example shows how to define a serdes.SaturatingAmplifier system object™ using the VinVout property.

Define an input sine wave with a frequency of 250 Hz.

t = (0:99)/10000;
x = sin(2*pi*250*t);

Define the Voltage In/Voltage Out matrix.

M = [-0.6194   -0.8000
     -0.4129   -0.6954
     -0.2065   -0.3966
      0         0
      0.2065    0.3966
      0.4129    0.6954
      0.6194    0.8000];

Define the saturating amplifier with the VinVout table.

SatAmp = serdes.SaturatingAmplifier('Mode',1,'Specification','VinVout','VinVout',M);

Modify the input waveform with the saturating amplifier.

y = SatAmp(x);

Plot the input and modified output waveforms.

figure; 
plot (t,x,t,y)
legend ('SaturatingAmplifier input','SaturatingAmplifier output');
grid on;
xlabel('Time (Seconds)');
ylabel('Amplitude (Volts)');

Define Saturating Amplifier with 3D VinVout Matrix

Define a 2D VinVout matrix.

LinearGain1 = 1;
Limit1 = 0.7;
N1 = 11;
VinVout1 = serdes.utilities.SoftClipper(LinearGain1, Limit1,N1);

Define a second 2D VinVout matrix.

LinearGain2 = 1.1;
Limit2 = 0.75;
N2 = 7;
VinVout2 = serdes.utilities.SoftClipper(LinearGain2, Limit2,N2);

Combine the two matrices to create a 3D matrix.

VinVout = serdes.SaturatingAmplifier.CombineSlices({VinVout1,VinVout2});

Create a saturating amplifier from the 3D VinVout matrix.

satamp= serdes.SaturatingAmplifier(...
    'Specification','VinVout',...
    'SliceSelect',1,... %Zero-based index
    'VinVout',VinVout);

More About

Memoryless Nonlinearity

A memoryless nonlinearity (MNL) is a function where the output at the time t is only dependent on the input at the same time t. This means that the function has no memory of prior inputs and is thus memoryless. In the serdes.SaturatingAmplifier System object, the input voltages are mapped to the output voltage using the MNL response through a lookup table with linear interpolation between data points. This response must be a function where each input value is uniquely mapped to an output value.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

IBIS-AMI codegen is not supported in MAC.

Version History

Introduced in R2019a

R2023b: Slice Select

You can now select which slice, family, or corner of a 3-D GPZ matrix to use during CTLE configuration.