FFE

Models a feed-forward equalizer

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  • FFE block

Libraries:
SerDes Toolbox / Datapath Blocks

Description

The FFE block applies a feed-forward equalizer (FFE) as a finite-impulse response (FIR) filter to a sample-by-sample input signal or an impulse response vector input signal. This filtering reduces distortions due to channel loss impairments.

Ports

Input

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Input baseband signal. The input signal can be a sample-by-sample signal specified as a scalar, or an impulse response vector signal.

Data Types: double

Output

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Estimated channel output. If the input signal is a sample-by-sample signal specified as a scalar, the output is also scalar. If the input signal is an impulse response vector signal, the output is also a vector.

Data Types: double

Parameters

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FFE operating mode:

  • Off — FFE is bypassed and the input waveform remains unchanged.

  • Fixed — FFE applies the FFE tap weights specified in Tap weights to input waveform.

Programmatic Use

Block parameter: Mode
Type: character vector
Values: Fixed | Off
Default: Fixed

Fractional taps for sub-symbol equalization control, specified as T-spaced, T/2-spaced, or T/4-spaced. T represents the symbol time.

Programmatic Use

Block parameter: TapSpacing
Type: character vector
Values: T-spaced | T/2-spaced | T/4-spaced
Default: T-spaced

FFE tap weights, specified as a row vector in volts. The length of the vector specifies the number of taps. The vector element value specifies the strength of the tap at that element position. The tap with the largest magnitude is the main tap and therefore defines the number of pre- and post-cursor taps.

You can use a valid MATLAB expression to evaluate the Initial tap weights (V) row vector.

Example: set_param(gcb,'TapWeights',"zeros[(1,4) 1 zeros(1,15)]") creates an FFE with 20 taps where the fifth tap is the main tap.

Programmatic Use

Block parameter: TapWeights
Type: character vector
Values: row vector
Default: [0,1,0,0,0]

  • Use get_param(gcb,'TapWeights') to view the current FFE Tap weights.

  • Use set_param(gcb,'TapWeights',value) to set FFE to a specific Tap weights vector.

Data Types: double

Select to normalize tap weight vectors so that the sum of the absolute values of the Tap weights vector elements is one.

Click to plot the response of the FFE FIR (finite impulse response) filter.

IBIS-AMI parameters

Select to include Mode as a parameter in the IBIS-AMI file. If you deselect Mode, it is removed from the AMI files, effectively hard-coding Mode to its current value.

Select to include Tap weights as a parameter in the IBIS-AMI file. If you deselect Tap weights, it is removed from the AMI files, effectively hard-coding Tap weights to its current value.

Version History

Introduced in R2019a

See Also

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