Analog Channel

Construct loss model from channel loss metric or impulse response

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Libraries:
SerDes Toolbox / Utilities

Description

The Analog Channel block constructs a loss model using a channel loss metric or an impulse response from another source in a SerDes Toolbox™ model. Analog model inputs are only used for IBIS file construction when using impulse response. For more information, see Analog Channel Loss in SerDes System.

Ports

Input

WaveIn — Input signal

scalar | vector

Input signal, specified as a waveform.

Data Types: double

Output

WaveOut — Modified output data

scalar | vector

Modified output data that includes the effect of a lossy printed circuit board transmission line model according to the method outlined in [1].

Data Types: double

Parameters

Channel Model

Channel model — Source of channel model

Loss model (default) | Impulse response

Source of channel model.

• Select Loss model to model the analog channel from a loss model.

• Select Impulse response to model the analog channel from an impulse response.

Programmatic Use

• Use get_param(gcb,'ChannelType') to view the current Channel model.

• Use set_param(gcb,'ChannelType',value) to set a specific Channel model.

Target frequency (Hz) — Frequency for desired channel loss

20e9 (default) | positive real scalar

Frequency for the desired channel loss, specified as a positive real scalar in hertz. It corresponds to the Nyquist frequency of the system.

Dependencies

This parameter is only available when Loss model is selected as Channel model.

Programmatic Use

• Use get_param(gcb,'TargetFrequency') to view the current value of Target frequency (Hz).

• Use set_param(gcb,'TargetFrequency',value) to set Target frequency (Hz) to a specific value.

Data Types: double

Loss (dB) — Channel loss at target frequency

8 (default) | scalar

Channel loss at the target frequency, specified as a scalar in dB.

Dependencies

This parameter is only available when Loss model is selected as Channel model.

Programmatic Use

• Use get_param(gcb,'Loss') to view the current value of Loss (dB).

• Use set_param(gcb,'Loss',value) to set Loss (dB) to a specific value.

Data Types: double

Impedance (Ohms) — Channel characteristic impedance

positive real scalar

Characteristic impedance of the channel, specified as a positive real scalar in ohms. Impedance (Ohms) depends on the setting of Signaling in the Configuration tab in the SerDes Designer app or in the Configuration block.

• If Signaling is set to Differential, the default value of Impedance (Ohms) is 100.

• If Signaling is set to Single-ended, the default value of Impedance (Ohms) is 50.

Dependencies

This parameter is only available when Loss model is selected as Channel model.

Programmatic Use

• Use get_param(gcb,'Zc') to view the current value of Impedance.

• Use set_param(gcb,'Zc',value) to set Impedance to a specific value.

Data Types: double

Impulse response — User provided impulse response

[zeros(1,63),1/SampleInterval,zeros(1,192)] (default) | matrix

User provided impulse response, specified as a unitless matrix. Impulse response is used to construct a channel loss model from the user-defined impulse response of the system.

You can use user specified impulse response to define your own crosstalk. If you decide to include crosstalk from your custom impulse response, you can specify upto six crosstalk stimuli as new columns in the impulse response.

Dependencies

This parameter is only available when Impulse response is selected as Channel model

Programmatic Use

• Use get_param(gcb,'ImpulseResponse') to view the current value of Impulse response.

• Use set_param(gcb,'ImpulseResponse',value) to set Impulse response to a specific value.

Data Types: double

Impulse sample interval — Sample interval of user provided impulse response

6.25e-12 (default) | positive real scalar

Sample interval of the user provided impulse response, specified as a positive real scalar in seconds.

Data Types: double

Analog Model

Tx R (Ohms) — Single-ended impedance of transmitter analog model

50 (default) | nonnegative real scalar

Single-ended impedance of the transmitter analog model, specified as a nonnegative real scalar in ohms.

Programmatic Use

• Use get_param(gcb,'TxR') to view the current value of Tx R (Ohms).

• Use set_param(gcb,'TxR',value) to set Tx R (Ohms) to a specific value.

Data Types: double

Tx C (F) — Capacitance of transmitter analog model

100e-15 (default) | nonnegative real scalar

Capacitance of the transmitter analog model, specified as a nonnegative real scalar in farads.

Programmatic Use

• Use get_param(gcb,'TxC') to view the current value of Tx C (F).

• Use set_param(gcb,'TxC',value) to set Tx C (F) to a specific value.

Data Types: double

Rx R (Ohms) — Single-ended impedance of receiver analog model

50 (default) | nonnegative real scalar

Single-ended impedance of the receiver analog model, specified as a nonnegative real scalar in ohms.

Programmatic Use

• Use get_param(gcb,'RxR') to view the current value of Rx R (Ohms).

• Use set_param(gcb,'RxR',value) to set Rx R (Ohms) to a specific value.

Data Types: double

Rx C (F) — Capacitance of receiver analog model

200e-15 (default) | nonnegative real scalar

Capacitance of the receiver analog model, specified as a nonnegative real scalar in farads.

Programmatic Use

• Use get_param(gcb,'RxC') to view the current value of Rx C (F).

• Use set_param(gcb,'RxC',value) to set Rx C (F) to a specific value.

Data Types: double

Rise time (s) — 20%−80% rise time of stimulus input

10e-12 (default) | positive real scalar

20%−80% rise time of the stimulus input to transmitter analog model, specified as a positive real scalar in seconds.

Programmatic Use

• Use get_param(gcb,'RiseTime') to view the current value of Rise time (s).

• Use set_param(gcb,'RiseTime',value) to set Rise time (s) to a specific value.

Data Types: double

Voltage (V) — Peak-to-peak voltage at input of transmitter analog model

1 (default) | positive real scalar

Peak-to-peak voltage at the input of transmitter analog model, specified as a positive real scalar in volts.

Programmatic Use

• Use get_param(gcb,'VoltageSwingIdeal') to view the current value of Voltage (V).

• Use set_param(gcb,'VoltageSwingIdeal',value) to set Voltage (V) to a specific value.

Data Types: double

Crosstalk

Include crosstalk — Include crosstalk in simulation

off (default) | on

Select to include crosstalk in the simulation. By default, this option is deselected.

Magnitude

Specification — Specify magnitude of near and far end aggressors

100GBASE-CR4 (default) | CEI-25G-LR | CEI-28G-SR | CEI-28G-VSR | Custom

Specify the magnitude of the near and far end aggressors. You can choose to include maximum allowed crosstalk for specifications such as 100GBASE-CR4, CEI-25G-LR, CEI-28G-SR, CEI-28G-VSR, or you can specify your own custom crosstalk integrated crosstalk noise (ICN) level.

Programmatic Use

• Use get_param(gcb,'CrosstalkSpecification') to view the current value of Specification.

• Use set_param(gcb,'CrosstalkSpecification',value) to set Specification to a specific value.

Far end crosstalk ICN (V) — Desired integrated noise level of far end aggressor

15e-3 (default) | nonnegative real scalar

Desired integrated crosstalk noise (ICN) level of the far end aggressor, specified as a nonnegative real scalar in volts. ICN specifies the strength of the crosstalk.

Dependencies

This parameter is only available when you choose Custom as crosstalk Specification.

Programmatic Use

• Use get_param(gcb,'FEXTICN') to view the current value of Far end crosstalk ICN (V).

• Use set_param(gcb,'FEXTICN',value) to set Far end crosstalk ICN (V) to a specific value.

Data Types: double

Near end crosstalk ICN (V) — Desired integrated noise level of near end aggressor

10e-3 (default) | nonnegative real scalar

Desired integrated crosstalk noise (ICN) level of the near end aggressor, specified as a nonnegative real scalar in volts. ICN specifies the strength of the crosstalk.

Dependencies

This parameter is only available when you choose Custom as crosstalk Specification.

Programmatic Use

• Use get_param(gcb,'NEXTICN') to view the current value of Near end crosstalk ICN (V).

• Use set_param(gcb,'NEXTICN',value) to set Near end crosstalk ICN (V) to a specific value.

Data Types: double

FEXT Stimulus

Symbol Time (s) — Symbol time of far end crosstalk stimulus

100e-12 (default) | positive real scalar

Symbol time of the far end crosstalk (FEXT) stimulus, specified as a positive real scalar in seconds.

Programmatic Use

• Use get_param(gcb,'UIFEXT') to view the current value of Symbol Time (s) in FEXT stimulus.

• Use set_param(gcb,'UIFEXT',value) to set Symbol Time (s) in FEXT stimulus to a specific value.

Data Types: double

Delay (s) — Delay offset of far end crosstalk stimulus

0 (default) | nonnegative real scalar

Delay offset of the far end crosstalk (FEXT) stimulus, specified as a positive real scalar in seconds.

Programmatic Use

• Use get_param(gcb,'DelayFEXT') to view the current value of Delay (s) in FEXT stimulus.

• Use set_param(gcb,'DelayFEXT',value) to set Delay (s) in FEXT stimulus to a specific value.

Data Types: double

Modulation — Modulation levels of far end crosstalk stimulus

NRZ (default) | PAM3 | PAM4 | PAM5 | PAM6 | PAM7 | PAM8 | PAM9 | PAM10 | PAM11 | PAM12 | PAM13 | PAM14 | PAM15 | PAM16

Modulation levels of the far end crosstalk (FEXT) stimulus, specified between NRZ (2-level) and PAM16 (16-level).

Programmatic Use

• Use get_param(gcb,'ModulationFEXT') to view the current value of Modulation in FEXT stimulus.

• Use set_param(gcb,'ModulationFEXT',value) to set Modulation in FEXT stimulus to a specific value.

PRBS Order — PRBS order of far end crosstalk stimulus

7 (default) | 9 | 11 | 13 | 15 | 20 | 23 | 31 | 47

Pseudorandom binary sequence (PRBS) order of the far end crosstalk (FEXT) stimulus.

Programmatic Use

• Use get_param(gcb,'OrderFEXT') to view the current value of PRBS Order in FEXT stimulus.

• Use set_param(gcb,'OrderFEXT',value) to set PRBS Order in FEXT stimulus to a specific value.

Data Types: double

NEXT Stimulus

Symbol Time (s) — Symbol time of near end crosstalk stimulus

100e-12 (default) | positive real scalar

Symbol time of the near end crosstalk (NEXT) stimulus, specified as a positive real scalar in seconds.

Programmatic Use

• Use get_param(gcb,'UINEXT') to view the current value of Symbol Time (s) in NEXT stimulus.

• Use set_param(gcb,'UINEXT',value) to set Symbol Time (s) in NEXT stimulus to a specific value.

Data Types: double

Delay (s) — Delay offset of near end crosstalk stimulus

0 (default) | nonnegative real scalar

Delay offset of the near end crosstalk (NEXT) stimulus, specified as a positive real scalar in seconds.

Programmatic Use

• Use get_param(gcb,'DelayNEXT') to view the current value of Delay (s) in NEXT stimulus.

• Use set_param(gcb,'DelaynEXT',value) to set Delay (s) in NEXT stimulus to a specific value.

Data Types: double

Modulation — Modulation levels of near end crosstalk stimulus

NRZ (default) | PAM3 | PAM4 | PAM5 | PAM6 | PAM7 | PAM8 | PAM9 | PAM10 | PAM11 | PAM12 | PAM13 | PAM14 | PAM15 | PAM16

Modulation levels of the near end crosstalk (NEXT) stimulus, specified between NRZ (2-level) and PAM16 (16-level).

Programmatic Use

• Use get_param(gcb,'ModulationNEXT') to view the current value of Modulation in NEXT stimulus.

• Use set_param(gcb,'ModulationNEXT',value) to set Modulation in NEXT stimulus to a specific value.

PRBS Order — PRBS order of near end crosstalk stimulus

9 (default) | 7 | 11 | 13 | 15 | 20 | 23 | 31 | 47

Pseudorandom binary sequence (PRBS) order of the near end crosstalk (NEXT) stimulus.

Programmatic Use

• Use get_param(gcb,'OrderFEXT') to view the current value of PRBS Order in FEXT stimulus.

• Use set_param(gcb,'OrderFEXT',value) to set PRBS Order in FEXT stimulus to a specific value.

Data Types: double

More About

Integrated Crosstalk Noise (ICN)

ICN is a frequency domain metric where the crosstalk is multiplied by a weighting function and then numerically integrated from 50 MHz to the baud rate (f_b). If there are multiple aggressors, their power are summed together before combining with the weighting function.

The time domain signal does not excite all frequencies evenly. The power spectral density (PSD) of a baseband time domain excitation follows a sinc-squared type response. The weighting function mimics the excitation of the PSD and shapes the PSD by including the effects of the receiver bandwidth and the transmitter rise time.

The total ICN is calculated by root-sum-squaring the FEXT ICN and NEXT ICN values together.

$$\begin{array}{l}{W}_{ft}(f)=\left(\frac{A_{ft}^2}{4f_b}\right){\text{sinc}}^2\left(\frac{f}{f_b}\right)\left[\frac{1}{1+{\left(f/f_{ft}\right)}^4}\right]\left[\frac{1}{1+{\left(f/f_{ft}\right)}^8}\right]\\ {\sigma }_{fx}={\left(2\Delta f{{\displaystyle \sum _n{W}_{ft}(f_n)10}}^{-MDFEX{T}_{loss}(f_n)/10}\right)}^{1/2}\\ {\sigma }_{nx}={\left(2\Delta f{{\displaystyle \sum _n{W}_{ft}(f_n)10}}^{-MDNEX{T}_{loss}(f_n)/10}\right)}^{1/2}\\ {\sigma }_x=\sqrt{{\sigma }_{fx}^2+{\sigma }_{nx}^2}\end{array}$$

Algorithms

Creating Far End Crosstalk

The impact felt on a victim line from a far end crosstalk aggressor is proportional to the rate of change of the aggressor waveform [2]. So, you can estimate the shape of a FEXT time domain signal with the derivative of the through response lossy impulse response.

$$I_{\text{FEXT}}(t)=k_{\text{FEXT}}\frac{dI(t)}{dt}$$

where, k_FEXT is a scale factor that scales the I_FEXT(t) so that it has user specified ICN value.

To calculate the ICN of the signal, transform the signal to frequency domain using Fourier transform.

$$H_{\text{FEXT}}(f)=ℱ\left[I_{\text{FEXT}}(t)\right]$$

The magnitude of the scale factor k_FEXT is: $$k_{\text{FEXT}}(f)=-\frac{IC{N}_{\text{FEXT}}}{\mathbb{I}ℂ{\mathbb{N}}_{\text{FEXT}}\left(H_{\text{FEXT}}(f)\right)}$$,

where $$\mathbb{I}ℂ\mathbb{N}$$ is the integrated crosstalk noise operator.

The sign of k_FEXT is negative since in typical transmission lines in inhomogeneous dielectrics, the inducting coupling is generally greater than capacitive coupling. As a result, the forward crosstalk pulse has the opposite magnitude from the magnitude of the aggressor signal.

Creating Near End Crosstalk

To calculate the near end crosstalk, note that the frequency domain NEXT response is similar in shape (not in magnitude) to the victim's return loss (S₁₁ or S₁₁).

$$H_{\text{NEXT}}(f)=k_{\text{NEXT}}·S_{11}(f)$$

Then the scale factor k_NEXT is: $$k_{\text{NEXT}}=-\frac{IC{N}_{\text{NEXT}}}{\mathbb{I}ℂ\mathbb{N}\left(S_{11}(f)\right)}$$

And the time domain NEXT signal is derived from the inverse Fourier transform.

$$I_{\text{NEXT}}(t)={ℱ}^{-1}\left[k_{\text{NEXT}}·S_{11}(f)\right]$$

References

[1] IEEE 802.3bj-2014. "IEEE Standard for Ethernet Amendment 2: Physical Layer Specifications and Management Parameters for 100 Gb/s Operation Over Backplanes and Copper Cables." URL: https://standards.ieee.org/standard/802_3bj-2014.html.

[2] Stephen Hall and Howard Heck. Advanced Signal Integrity for High-Speed Digital Designs. Hoboken, NJ: Wiley Press, 2009.

Version History

Introduced in R2019a