serdes.CTLE
Continuous time linear equalizer (CTLE) or peaking filter
Description
The serdes.CTLE
System object™ applies a linear peaking filter to equalize a sample-by-sample input signal or
to analytically process an impulse response vector input signal. The equalization process
reduces distortions resulting from lossy channels. The filter is a real one-zero two-pole
(1z/2p) filter, unless you define the gain-pole-zero (GPZ) matrix.
To equalize the baseband signal using serdes.CTLE
:
Create the
serdes.CTLE
object and set its properties.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
Description
returns a CTLE object
that modifies an input waveform according to the pole zero transfer function defined in
the object.ctle
= serdes.CTLE
sets properties using one or more name-value pairs. Enclose each property name in quotes.
Unspecified properties have default values.ctle
= serdes.CTLE(Name
,Value
)
Example: ctle = serdes.CTLE('ACGain',5)
returns a CTLE object with
gain at the peaking frequency set to 5 dB.
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.
Main
Mode
— CTLE operating mode
2
(default) | 0
| 1
CTLE operating mode, specified as 0
, 1
, or
2
. Mode
determines whether the CTLE is
bypassed or not. If CTLE is not bypassed, then Mode
also
determines what transfer function is applied to the input waveform.
Mode Value | CTLE Mode | CTLE Operation |
---|---|---|
0 | off | serdes.CTLE is bypassed and the input waveform remains
unchanged. |
1 | fixed | serdes.CTLE applies the CTLE transfer function as
specified by ConfigSelect to the input
waveform. |
2 | adapt | If WaveType is set to 'Impulse'
or 'Waveform' , then the Init subsystem calls to the
serdes.CTLE . The serdes.CTLE determines
the CTLE transfer function to maximize the performance metric as specified
by the PerformanceCriteria property and applies the
transfer function to the input waveform for time domain simulation. This
optimized transfer function is used by the CTLE for entire time domain
simulation. For more information about the Init subsystem, see Statistical Analysis in SerDes Systems |
If WaveType is selected as
'Sample' , then serdes.CTLE operates in
the fixed mode. |
Data Types: double
SliceSelect
— Select which corner of 3D GPZ matrix to use
0
(default) | nonegative scalar integer
Select which slice, family, or corner of a 3-D GPZ matrix to use during CTLE configuration.
You must set Specification
to GPZ
to
effectively use SliceSelect
. Depending on how many slices are
available in your GPZ matrix, you can then select the slice you are interested in from
a zero-based index.
You cannot use GPZ for a given slice and the peaking gain, DC gain, or AC gain for another slice.
Data Types: double
ConfigSelect
— Select which member of transfer function family to apply in fixed mode
0
(default) | real integer scalar
Select which member of the transfer function family to apply in fixed mode, specified as a real integer scalar.
Example: ctle = serdes.CTLE('ConfigSelect',5,'Specification','DC Gain and
Peaking Gain')
returns a CTLE object that selects the 6-th element of the
DCGain
and PeakingGain
vector to apply to the
filter transfer function.
Data Types: double
Specification
— Input specification for CTLE response
'DC Gain and Peaking Gain'
(default) | 'DC Gain and AC Gain'
| 'AC Gain and Peaking Gain'
| 'GPZ Matrix'
Defines which inputs will be used for the CTLE transfer function family. There are
five inputs which can be used to define the CTLE transfer function family:
DCGain
, PeakingGain
,
ACGain
, PeakingFrequency
, and
GPZ
.
You can define the CTLE response from any two of the three gains and peaking frequency or you can define the GPZ matrix for the CTLE.
Select
'DC Gain and Peaking Gain'
to specify CTLE response fromDCGain
,PeakingGain
, andPeakingFrequency
.'DC Gain and AC Gain'
to specify CTLE response fromDCGain
,ACGain
, andPeakingFrequency
.'AC Gain and Peaking Gain'
to specify CTLE response fromACGain
,PeakingGain
, andPeakingFrequency
.'GPZ Matrix'
to specify CTLE response fromGPZ
.
Data Types: char
PeakingFrequency
— Approximate frequency at which CTLE transfer function peaks
5e9
(default) | scalar | vector
Approximate frequency at which CTLE transfer function peaks in magnitude,
specified as a scalar or a vector in Hz. If specified as a scalar, it is converted to
match the length of ACGain
, DCGain
, and
PeakingGain
by scalar expansion. If specified as a vector, then
the vector length must be the same as the vectors in ACGain
,
DCGain
, and PeakingGain
.
Data Types: double
DCGain
— Gain at zero frequency
[0 -1 -2 -3 -4 -5 -6 -7 -8]
(default) | scalar | vector
Gain at zero frequency for the CTLE transfer function, specified as a scalar or a
vector in dB. If specified as a scalar, it is converted to match the length of
PeakingFrequency
, ACGain
, and
PeakingGain
by scalar expansion. If specified as a vector, then
the vector length must be the same as the vectors in
PeakingFrequency
, ACGain
, and
PeakingGain
.
Data Types: double
PeakingGain
— Difference between AC and DC gain
[0 1 2 3 4 5 6 7 8]
(default) | scalar | vector
Peaking gain, specified as a vector in dB. It is the difference between
ACGain
and DCGain
for the CTLE transfer
function. If specified as a scalar, it is converted to match the length of
PeakingFrequency
, ACGain
, and
DCGain
by scalar expansion. If specified as a vector, then the
vector length must be the same as the vectors in
PeakingFrequency
, ACGain
, and
DCGain
.
Data Types: double
ACGain
— Gain at the peaking frequency
0
| scalar | vector
Gain at the peaking frequency for the CTLE transfer function, specified as a
scalar or vector in dB. If specified as a scalar, it is converted to match the length
of PeakingFrequency
, DCGain
, and
PeakingGain
by scalar expansion. If specified as a vector, then
the vector length must be the same as the vectors in
PeakingFrequency
, DCGain
, and
PeakingGain
.
Data Types: double
GPZ
— Gain pole zero
matrix
Gain pole zero, specified as a matrix. GPZ
explicitly defines
the family of CTLE transfer functions by specifying the DCGain
(dB) in the first column and then poles and zeros in alternating columns. The poles
and zeros are specified in Hz. Use the argument ConfigSelect
with
zero-based index to select filters defined by rows of the GPZ matrix.
The serdes.CTLE
System object only allows repeated poles or zeros when the
FilterMethod
is set to Cascaded
. Complex
poles or zeros must have conjugates. The number of poles must be greater than number
of zeros for system stability. The System object ignores poles and zeros of 0 Hz and you can use them to zero-pad the
matrix.
You can define multiple slices of CTLE responses by using a 3-D GPZ matrix. You can concatenate and zero-pad two GPZ matrices to extend to the third dimension.
Data Types: double
Complex Number Support: Yes
Advanced
SymbolTime
— Time of single symbol duration
100e-12
(default) | real scalar
Time of a single symbol duration, specified as a real scalar in s.
Data Types: double
SampleInterval
— Uniform time step of waveform
6.25e-12
(default) | real scalar
Uniform time step of the waveform, specified as a real scalar in s.
Data Types: double
WaveType
— Input wave type form
'Sample'
(default) | 'Impulse'
| 'Waveform'
Input wave type form:
'Sample'
— A sample-by-sample input signal.'Impulse'
— An impulse response input signal.'Waveform'
— A bit-pattern waveform type of input signal, such as pseudorandom binary sequence (PRBS).
Data Types: char
PerformanceCriteria
— Criterion used for CTLE optimization
SNR
(default) | maxEyeHeight
| maxMeanEyeHeight
| maxCOM
| eyeAreas
| eyeWidth
| centerEyeHeight
| centerMeanEyeHeight
| centerCOM
Criterion used for CTLE optimization when the serdes.CTLE
Mode
is set to adapt. The performance criteria is calculated
using the optPulseMetric
function.
Data Types: char
OutputOptMetric
— Output optimization metric value
off (default) | on
Output the optimization metric value.
FilterMethod
— Method to calculate time domain filter coefficients
PartialFraction
(default) | Cascaded
Method to calculate rational transfer function time domain filter coefficients:
PartialFraction
filter method uses a partial fraction expansion of the poles and zeros to directly calculate the filter coefficients. Theserdes.CTLE
System object does not allow repeated poles or zeros when theFilterMethod
is set toPartialFraction
.Cascaded
filter method uses an approach that cascades together numerous shorter filters that collectively represent the specified behavior. This results in a more robust filter. Theserdes.CTLE
System object only allows repeated poles or zeros when theFilterMethod
is set toCascaded
.
Usage
Syntax
Input Arguments
x
— Input baseband signal
scalar | vector
Input baseband signal. If the WaveType
is set to
'Sample'
, then the input signal is a sample-by-sample signal
specified as scalars. If the WaveType
is set to
'Impulse'
, then the input signal is an impulse response vector
signal.
Output Arguments
y
— Equalized CTLE output
scalar | vector
Equalized CTLE output waveform. If the input signal is a sample-by-sample signal specified as scalars, then the output is also scalar. If the input signal is an impulse response vector signal, then the output is also a vector.
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)
Examples
Impulse Response Processing Using CTLE
This example shows how to process the impulse response of a channel using serdes.CTLE
System object™.
Use a symbol time of 100
ps and 16
samples per symbol. The channel has 16
dB loss. The peaking frequency is 11
GHz.
SymbolTime = 100e-12; SamplesPerSymbol = 16; dbloss = 16; DCGain = 0:-1:-26; PeakingGain = 0:26; PeakingFrequency = 11e9;
Calculate the sample interval.
dt = SymbolTime/SamplesPerSymbol;
Create the CTLE object. The object adaptively applies the optimum transfer function for the best eye height opening to the input impulse response.
CTLE1 = serdes.CTLE('SymbolTime',SymbolTime,'SampleInterval',dt,... 'Mode',2,'WaveType','Impulse',... 'DCGain',DCGain,'PeakingGain',PeakingGain,... 'PeakingFrequency',PeakingFrequency);
Create the channel impulse response.
channel = serdes.ChannelLoss('Loss',dbloss,'dt',dt,... 'TargetFrequency',1/SymbolTime/2); impulseIn = channel.impulse;
Process the impulse response with CTLE.
[impulseOut, Config] = CTLE1(impulseIn);
Display the adapted configuration.
fprintf('Adapted CTLE Configuration Selection is %g \n',Config)
Adapted CTLE Configuration Selection is 17
Convert the impulse responses to pulse, waveform, and eye diagram.
ord = 6; dataPattern = prbs(ord,2^ord-1)-0.5; pulseIn = impulse2pulse(impulseIn,SamplesPerSymbol,dt); waveIn = pulse2wave(pulseIn,dataPattern,SamplesPerSymbol); eyeIn = reshape(waveIn,SamplesPerSymbol,[]); pulseOut = impulse2pulse(impulseOut,SamplesPerSymbol,dt); waveOut = pulse2wave(pulseOut,dataPattern,SamplesPerSymbol); eyeOut = reshape(waveOut,SamplesPerSymbol,[]);
Create the time vectors.
t = dt*(0:length(pulseOut)-1)/SymbolTime; teye = t(1:SamplesPerSymbol); t2 = dt*(0:length(waveOut)-1)/SymbolTime;
Plot pulse response comparison, waveform comparison, input, and output eye diagrams.
figure plot(t,pulseIn,t,pulseOut) legend('Input','Output') title('Pulse Response Comparison') xlabel('Symbol Times'),ylabel('Voltage') grid on axis([47 60 -0.1 0.4])
figure plot(t2,waveIn,t2,waveOut) legend('Input','Output') title('Waveform Comparison') xlabel('Symbol Times'),ylabel('Voltage') grid on
figure subplot(211),plot(teye,eyeIn,'b') ax = axis; xlabel('Symbol Times'),ylabel('Voltage') grid on title('Input Eye Diagram') subplot(212),plot(teye,eyeOut,'b') axis(ax); xlabel('Symbol Times'),ylabel('Voltage') grid on title('Output Eye Diagram')
Sample-by-Sample Processing Using CTLE
This example shows how to process impulse response of a channel one sample at a time using serdes.
CTLE
System object™.
Use a symbol time of 100
ps and 16
samples per symbol. The channel has 16
dB loss. The peaking frequency is 11
GHz. Select 12
-th order pseudorandom binary sequence (PRBS), and simulate the first 500
symbols.
SymbolTime = 100e-12; SamplesPerSymbol = 16; dbloss = 16; DCGain = 0:-1:-26; PeakingGain = 0:26; PeakingFrequency = 11e9; ConfigSelect = 15; prbsOrder = 12; M = 500;
Calculate the sample interval.
dt = SymbolTime/SamplesPerSymbol;
Create the CTLE object. Since we are processing the channel one sample at a time, the input waveform is '
sample
'
type. The object adaptively applies the optimum filter transfer function for the best eye height opening.
CTLE = serdes.CTLE('SymbolTime',SymbolTime,'SampleInterval',dt,... 'Mode',2,'WaveType','Sample',... 'DCGain',DCGain,'PeakingGain',PeakingGain,... 'PeakingFrequency',PeakingFrequency,... 'ConfigSelect',ConfigSelect);
Create the channel impulse response.
channel = serdes.ChannelLoss('Loss',dbloss,'dt',dt,... 'TargetFrequency',1/SymbolTime/2);
Initialize PRBS generator.
[dataBit,prbsSeed] = prbs(prbsOrder,1);
Loop through one symbol at a time.
inSymbol = zeros(SamplesPerSymbol,1); outWave = zeros(SamplesPerSymbol*M,1); for ii = 1:M % Get new symbol [dataBit,prbsSeed] = prbs(prbsOrder,1,prbsSeed); inSymbol(1:SamplesPerSymbol) = dataBit-0.5; % Convolve input waveform with channel y = channel(inSymbol); % Process one sample at a time through the CTLE for jj = 1:SamplesPerSymbol outWave((ii-1)*SamplesPerSymbol+jj) = CTLE(y(jj)); end end
After truncating the first 75 symbols to allow equalization, use the function reshape on the array of symbols to create the eye diagram.
foldedEye = reshape(outWave(75*SamplesPerSymbol+1:M*SamplesPerSymbol),SamplesPerSymbol,[]);
t = dt*(0:SamplesPerSymbol-1);
figure,plot(t,foldedEye,'b');
Copyright 2019 The MathWorks, Inc.
Define CTLE from 3D GPZ Matrix
Create a GPZ matrix from a uniform number of poles and zeros.
G = [-3;-4;-5;-6]; P = [-15321428571 -13848214285;... -15600000000 -14100000000;... -15878571428 -14351785714;... -16157142857 -14603571428]; Z = [-5574642857;-4960100000;-4435821428;-3981285714]; gpz1 = serdes.CTLE.GainPoleZeroToGPZ(G,P,Z);
Create a second GPZ matrix from a varying number of poles.
G = [0;-1;-2]; P = {[-23771428571,-13092857142];... [-17603571428,-13344642857];... [-17935714285,-13596428571,-15321428571]}; Z = {-10492857142;-7914982142;-6845464285}; gpz2 = serdes.CTLE.GainPoleZeroToGPZ(G,P,Z);
Combine the two matrices into a 3D GPZ matrix.
gpz = serdes.CTLE.CombineSlices(gpz1,gpz2)
gpz = gpz(:,:,1) = 1.0e+10 * -0.0000 -1.5321 -0.5575 -1.3848 0 0 -0.0000 -1.5600 -0.4960 -1.4100 0 0 -0.0000 -1.5879 -0.4436 -1.4352 0 0 -0.0000 -1.6157 -0.3981 -1.4604 0 0 gpz(:,:,2) = 1.0e+10 * 0 -2.3771 -1.0493 -1.3093 0 0 -0.0000 -1.7604 -0.7915 -1.3345 0 0 -0.0000 -1.7936 -0.6845 -1.3596 0 -1.5321 0 0 0 0 0 0
Create a CTLE from the 3D GPZ matrix.
CTLE3D = serdes.CTLE('Specification','GPZ Matrix','GPZ',gpz,'FilterMethod','Cascaded')
CTLE3D = serdes.CTLE with properties: Main Mode: 2 Specification: 'GPZ Matrix' GPZ: [4x6x2 double] SliceSelect: 0 ConfigSelect: 0 Use get to show all properties
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 R2019aR2023b: Slice Select
you can now select which slice, family, or corner of a 3-D GPZ matrix to use during CTLE configuration.
See Also
AGC | serdes.AGC
| CTLE | DFECDR | serdes.DFECDR | SaturatingAmplifier | optPulseMetric
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