Multi-channel Simulation

Note: This feature was previously known as Multi-channel Eye Diagram

Add advanced effects to simulated Transmitter and Crosstalk data sources, and add equalization to the Receiver for eye diagram simulation.

In this topic:

Overview

The following flow diagram shows how simulated Jitter, Noise, and Emphasis can be added to transmitter to stimulate your DUT.

  1. Add and configure ONE Transmit (TX) component to a channel.

  2. Add and configure ONE Receiver (RX) component to a channel.

  3. Add and configure Cross-Talk (XT TX) components to the transmitter and/or receiver.

  4. Click Draw Eye to simulate how the channel reacts to these effects.

The simulation effects are computed using a run-time version of MATLAB® which is installed with PLTS.

Note: With a Multi-channel Simulation selected, you can view the enhanced Bit Pattern Waveforms. Learn how.

Create/Edit a Multi-channel Simulation Configuration

  1. Open a data set in either Differential or Single-ended Eye Diagram view.

  2. Click Tools, then Multi-channel Simulation.

Multi-channel Simulation dialog box help

  1. Drag one of the TX (Transmit), RX (Receiver),  XT TX (Crosstalk), or Diff Tx/Rx AMI components from the Add components pane (in yellow/red circle above) to one of the port slots (yellow shaded area).

  2. Right-click on a slot component to Edit or Delete the properties of that component.

  3. From any AMI component, load an IBS file with vendor-supplied modeling.

  4. From a TX and XT TX (Source) component, optionally add the following effects:

  5. From the RX Settings dialog box, add one of several equalization choices.

  6. When finished, click Draw Eye to begin the simulation. An appropriate new plot is added as the last plot on the current Eye Diagram view window.

Notes

  • Draw Eye is NOT available unless the Channel setup contains at least ONE TX component AND ONE RX component.

  • When viewing a Differential Eye Diagram, a TDDxx plot is created; NOT a TCCxx plot.

Configurations

From this dialog, Multi-channel configurations are created, modified, and saved to your PC for reuse at a later time.

The multi-channel simulation configuration is dependent on a specific DUT configuration. When you select another data set with a different DUT configuration, this window will automatically update the multi-channel simulation configurations that match the current DUT configuration in the list. This allows you to use one configuration to simulate the eye diagrams of many data sets that have the same DUT configuration.

Existing configurations  Select the configuration to be used or modified. The configurations that appear are those that are resident in PLTS memory. Configuration1 is an empty configuration if none are present.

Add a new configuration with name...  Type a name in the field, then click Add. The configuration is added to the Existing configurations and selected.

Delete  Select a configuration, then click Delete to remove the configuration from PLTS memory.

Rename  Select a configuration, type a new name in Rename selected configuration, then click Rename.

Save  After modifying one or more configurations, click Save to store the selected configurations on your PC. When more than one configuration exists, the Select configurations to save dialog is launched. Select one or more configurations to save in the file.

Load  Recall a configuration from your PC hard drive.

 

 

AMI settings dialog box help

Right-click on an AMI slot component to Edit or Delete the properties of that component.

This dialog is used to load a vendor-supplied model for the following components:

  • TX AMI (Transmitter) - appears with the Bit Pattern tab

  • XT TX AMI (Crosstalk transmitter) - appears with the Bit Pattern tab

  • RX AMI (Receiver) - appears alone

  • XT RX AMI (Crosstalk receiver) - contains NO user-specified settings

The yellow areas represent the vendor-supplied AMI models

See Also

Learn more about the IBIS-AMI standard.

 

Browse  Click to navigate to the (*.ibis) file to be loaded. The associated (*.ami) file and supporting files are loaded automatically.

View  Click to see a text-file representation of the IBIS and AMI files.

Component - Shows the root parameter name in the AMI file.

Corner settings - Used to simulate the corner cases. For AMI parameters defined as Corner, PLTS will pick one of the three supplied values (<typ value>, <slow value>, <fast value>) in the parameter definition file for any given model instance. This selection is governed by the same internal corner variable that controls the selection of the "Typ", "Min", "Max" model data.

  • <typ value> corresponds to "Typ"

  • <slow value> corresponds to "Min" (slow or weak performance)

  • <fast value> corresponds to "Max" (fast or strong performance).

  • <slow value> does not have to be less than <fast value>.

AMI Parameters

  • Parameter list - shows a hierarchy of all of the Reserved_Parameters and optional Model_Specific parameters defined in an AMI model file.

  • Click the parameters to reveal the values to the right and information about the parameter below.

  • To modify a parameter value, select a different value in the dropdown list (for Format List) or select “User specified” , then edit the value. A modified value is used in the Eye Diagram generation and is save with other settings in a configuration file.

 

TX (source) and XT TX (crosstalk source) Settings dialog box help

Click a box to show the dialog settings:

Bit Pattern  Jitter  AWGN   Emphasis

Show  Check individual boxes to create additional eye diagram plots with ONLY the selected effects at each node. These eye diagrams are in addition to a plot of the simulated transmitted signal.

Bit Pattern tab

 

Phase relative to TX (deg)  (Appears ONLY on the XT dialog)

Enter a phase to offset from the transmitted port. This allows the XT TX setting to be more visible in the resulting Eye Diagram.

Same as TX  (Appears ONLY on the XT TX dialog)

  • Check to use the same remaining settings as the TX channel.

  • Clear, then enter independent values.

  • With an AMI model, the Amplitude settings are fixed at (500, -500) mV according to the IBIS AMI standard.

  • Learn more about the Bit Pattern settings.

Symbol Rate (GBd)/Select  Enter a baud symbol rate in the text box or click on the Select button to select a baud symbol rate from the drop down menu.

Pattern Format  (Appears ONLY on the TX dialog)

Select between NRZ (2-level pulse amplitude modulation-PAM2) or PAM4 (4-level pulse amplitude modulation-PAM4).  Learn more about PAM4 signaling.

Filter  (Appears ONLY when PAM4 is the selected Pattern Format)

Filter Type  Select between the following filter types:

  • Bessel4  selects the fourth order Bessel filter type that provides a constant propagation delay across the input frequency range.

  • Butterworth1 - 4  selects the Butterworth first through fourth order filter type. This filter type is known for its flat response in the pass band.

Filter Bandwidth  Bandwidth of the selected filter.

Click Default Setup to reset the setup to its default setting.

Pattern Length (bits)  Select the desired pattern length from the drop down menu.

Pattern Loop Count  Set the number of times to loop through the pattern.

Rise/Fall Time (ps)  Set the rise and fall times (in picoseconds) of the transitions.

S.E. Amplitude (mV)  Eye diagram Y-axis scaling in millivolts. Negative voltages are allowed for differential eye diagrams; these scale values are doubled.

  • High - Sets the upper plot scale.

  • Low- Sets the lower plot scale.

Samples per bit  Set the number of samples for each bit.

Jitter tab with NRZ Pattern Format

Jitter is typically divided into deterministic and random jitter.

Learn more in the MATLAB documentation.

Same as TX  (Appears ONLY on the XT dialog)

  • Check to use the same remaining settings as the TX channel.

  • Clear, then enter independent values.

Random Jitter  Check to enable random jitter.

Random Std (ps) - Standard deviation of the random jitter in picoseconds. Used only when enabled.

Periodic Jitter Check to enable periodic jitter.

Add and Remove  Several periodic jitter components with varying properties can be added. Click Add, then change the subsequent settings.

Periodic amplitude (ps) - Amplitude of each sinusoidal component of the periodic jitter in picoseconds.

Periodic frequency (Hz) - Frequency of each sinusoidal component of the periodic jitter in Hz. The default is 1 kHz.

Periodic phase - Phase of each sinusoidal component of the periodic jitter.

Dirac Jitter (ISI) Check to enable Dirac jitter.

Add and Remove  Several Dirac jitter components with varying properties can be added. Click Add, then change the subsequent settings.

Dirac delta (ps) - Time delay of each Dirac component in seconds.

Dirac probability - Probability of each Dirac component.  Sum must be one.

Jitter tab with PAM4 Pattern Format

The following selections are displayed when PAM4 is selected as the Pattern Format in the Bit Pattern tab.

Same as TX  (Appears ONLY on the XT dialog)

  • Check to use the same remaining settings as the TX channel.

  • Clear, then enter independent values.

Random jitter  Check to enable random jitter.

RJ (ps) - Standard deviation of the random jitter in picoseconds. Used only when enabled.

F/2 jitter  Check to enable F/2 jitter.

F/2 Jitter (PK-PK) - Every second bit, whether it is a zero or a one, is longer or shorter by the value entered in the F/2 Jitter (PK-PK) field. For example, 0.05 UI will make every second bit 5% (5% of the unit interval based on the data rate) longer or shorter.

AWGN tab with NRZ Pattern Format

White Gaussian noise is injected from the data source. Learn more in the MATLAB documentation.

Same as TX  (Appears ONLY on the XT dialog)

  • Check to use the same remaining settings as the TX channel.

  • Clear, then enter independent values.

Symbol SNR (dB)  Set the symbol signal-to-noise ratio in dB.

AWGN tab with PAM4 Pattern Format

When the Pattern Format is PAM4, the random noise level can be set in mV, uV, or nV.

Emphasis tab

See Pre/De-emphasis example

Concepts:

In serial data transmission, pre-emphasis/de-emphasis is often used to compensate for losses over the channel which are larger at higher frequencies. The high frequency content is emphasized compared to the low frequency content which is de-emphasized. This is a form of transmitter equalization.

The dB value can control how much the signal is enhanced or declined.

A 2-tap FIR filter is automatically applied with the specified dB values.

Pre-emphasis is used to enhance the first bit level after a transition.  

  • E is the amplitude after enhancement.

  • D is the original amplitude without pre-emphasis.

De-emphasis is used to decline all the bit levels except the first bit after a transition.

  • E is the original amplitude without de-emphasis.

  • D is the declined amplitude.

Same as TX  (Appears ONLY on the XT TX dialog)

  • Check to use the same remaining settings as the TX channel.

  • Clear, then enter independent values.

Choose emphasis method:

None - Emphasis is disabled.

Specify Pre-emphasis  Enter a value in dB. A 2-tap FIR filter is automatically applied.

Specify De-emphasis  Enter a value in dB. A 2-tap FIR filter is automatically applied.

Specify FIR (filter) taps   The filter function is implemented in MATLAB as a direct form II transposed structure. Learn more in the MATLAB documentation.

Specify M-script file  Add pre/de-emphasis with a custom MATLAB script file. Learn more in the MATLAB documentation.

RX Settings dialog box help

Channel equalization is a simple way of mitigating the detrimental effects caused by a frequency-selective and dispersive communication link between transmitter and receiver. Learn more about Equalization in this Keysight App Note: http://literature.cdn.Keysight.com/litweb/pdf/5990-3585EN.pdf

Choose from:

CTLE (Continuous-time Linear Equalizer)

Specify the equalizer using poles and zeros.

 

Show RX signal before equalization

  • Check to also show a plot without equalization applied.

  • Clear to show only a plot with equalization.

Edit poles and zeros.  Click Edit to show the following dialog:

  • Number of Poles - Select 2 or 3 poles.

  • DC Gain - Adc

  • Zero 1 or 2 frequency (GHz) ωz1  or ωz2  

  • Pole 1 frequency (GHz) ω1  

  • Pole 2 frequency (GHz) ω2  

  • Pole 3 frequency (GHz) ω3  

  • Preset - Click the "+" button to add a name for the current CTLE configuration. Click the "-" button to delete the currently selected Preset.

RX AMI Settings

Show RX input waveform - When checked, an additional eye diagram at the input of the RX is shown after simulation.

The remainder of these settings are identical to the TX AMI settings.

FFE  (Feed-forward equalizer)

Learn more about FFE Equalization in this Keysight App Note: http://literature.cdn.Keysight.com/litweb/pdf/5990-3585EN.pdf

Show RX signal before equalization

  • Check to also show a plot without equalization applied.

  • Clear to show only a plot with equalization.

Feed-forward equalizer (FFE)

Optimized  The Pre/Post cursor taps are selected automatically. Specify the number of taps that you need.

File Tap file (for FFE or DFE) - To load a *.tap file, click Browse, then navigate to *.tap files. Learn more about Tap Files

Manual - Click edit to launch the Edit FFE Taps dialog box where you can create and edit filter taps.

DFE (Decision-feedback Equalizer)

Learn more about DFE Equalization in this Keysight App Note: http://literature.cdn.Keysight.com/litweb/pdf/5990-3585EN.pdf

 

Show RX signal before equalization

  • Check to also show a plot without equalization applied.

  • Clear to show only a plot with equalization.

Adaptive Eq with LMS - A specific number of known symbols are used to determine the best coefficients for the linear equalizer to compensate for the unrealistic channel. This is also known as a training sequence, because the RX component uses the training sequence to automatically adapts the filter taps to compensate for the channel effects. After the training, the filter taps are used to do the real equalization work on the RX signal.  

Learn more about Adaptive Equalization with LMS in MATLAB online help: http://www.mathworks.com/help/comm/ug/equalization.html#a1050772711b1

Tap File (for FFE or DFE) - To load a *.tap file, click Browse, then navigate to *.tap files. Learn more about Tap Files

Manual - Click edit to launch the Edit DFE Taps dialog box where you can create and edit filter taps.

Automatic Taps - Check to use automatic tap values or uncheck to use manual entry tap values.

  • When unchecked (manual entry), enter tap values in the text box separated by commas, spaces, or semicolons. The unchecked tap values are used by the DCA.
  • When checked (automatic), enter the desired number of taps in the Number of Taps text box. PLTS generates the tap values with the automatic optimization algorithm.

Advanced... - Opens the Decision Feedback Equalizer (DFE) Setup dialog to enter the maximum and minimum tap limit values. Enter the values directly into each text box or use the "+" and "-" keys to change the values.

Equalization Combinations

The following two equalizations use combinations of the above CTLE, DFE, and FFE equalizations. The equalizations are processed sequentially. Either CTLE or FFE, then DFE.  See the individual equalization types for help with each component.

CTLE =>DFE

See CTLE and DFE equalizations.

FFE=> DFE

See FFE and DFE equalizations.

Customize with M-script

Provide a MATLAB script file that describes your custom equalization.
 

 

Edit FFE Taps dialog box help

Appears when Edit Taps (Manual) is clicked on the RX FFE Settings dialog.

  1. Click Add.

  2. Select the new Tap.

  3. Specify a Value

  4. Click Apply

  5. To remove the last Tap, select the Tap, then click Remove.

 

Edit DFE Taps dialog box help

Appears when Edit Taps (Manual) is clicked on the RX DFE Settings dialog.

  1. Click Add.

  2. Select the new Tap.

  3. Specify a Value

  4. Click Apply

  5. To remove the last Tap, select the Tap, then click Remove.

Tap File Format

Use Input Tap files to specify the tap values to used in FFE or DFE equalization.

When Optimized is selected, the Tap values are selected automatically by PLTS. When a path and filename is specified for Output taps, the tap values that were automatically selected are output to the file. This file can then be specified for Input taps in subsequent equalization simulations.

The following file was Output from a FFE->DFE equalization. Two taps each are specified for Precursor, Postcursor, and DFE Taps.

This same format is used for Input files.

Example

  1. Click File, then Open then navigate to  [DEMO] E8362B BTL 10MHz-20GHz.dut.

  2. On Analysis Type, select Eye Diagram (single ended).

  3. Click Tools, then Multi-channel Simulation

  4. Drag a Tx component to port 1.

  5. Right click the Tx channel, then click Edit, then make the following Pattern settings: .5 Gbps, 80 ps rise/fall time, PRBS 2^9  -1, 0~200 signal amplitude.

  6. Turn OFF Tx jitter, pre-emphasis, and noise of the Tx component.

  7. Drag a RX component to port 2.

  8. Turn OFF RX equalization. This allows us to see ONLY the Tx signal transmitted through the backplane channel. Later we can see only the effect of crosstalk by comparison.

  9. Click Draw Eye

  1. Right click the TX component of port 1, then click Edit.

  2. Change to port 3 so that we can simulate only the eye diagram of T23 crosstalk.

  3. Leaving the other settings unchanged.

  4. Click Draw Eye

  1. Move the TX back to port 1.

  2. Add a XT TX component to port 3. Note that the small “hill” in the crosstalk picture of step 2 is the rising and falling edge of the crosstalk eye. If the transmission channel delay is very close to the XT TX channel delay and there’s no user-specified XT TX delay, the XT TX eye will synchronize with the transmission eye and we can’t clearly see the crosstalk effect.

  3. To clearly see the effect of the crosstalk, add 180 degrees (half bit period) phase shift to the XT TX compared to TX.

  4. Click Draw Eye

The crosstalk “hill” should be in the center area of the transmission channel eye diagram.

Last Modified:

5-Nov-2019

Added automatic tap values to RX settings for DFE

6-Dec-2013

AMI features with 2014

18-Dec-2012

New features with 2013

21-Oct-2011

New topic