lineareq

Construct linear equalizer object

Syntax

eqobj = lineareq(nweights,alg)
eqobj = lineareq(nweights,alg,sigconst)
eqobj = lineareq(nweights,alg,sigconst,nsamp)

Description

The lineareq function creates an equalizer object that you can use with the equalize function to equalize a signal. To learn more about the process for equalizing a signal, see Adaptive Algorithms.

eqobj = lineareq(nweights,alg) constructs a symbol-spaced linear equalizer object. The equalizer has nweights complex weights, which are initially all zeros. alg describes the adaptive algorithm that the equalizer uses; you should create alg using any of these functions: lms, signlms, normlms, varlms, rls, or cma. The signal constellation of the desired output is [-1 1], which corresponds to binary phase shift keying (BPSK).

eqobj = lineareq(nweights,alg,sigconst) specifies the signal constellation vector of the desired output.

eqobj = lineareq(nweights,alg,sigconst,nsamp) constructs a fractionally spaced linear equalizer object. The equalizer has nweights complex weights spaced at T/nsamp, where T is the symbol period and nsamp is a positive integer. nsamp = 1 corresponds to a symbol-spaced equalizer.

Properties

The table below describes the properties of the linear equalizer object. To learn how to view or change the values of a linear equalizer object, see Accessing Properties of an Equalizer.

    Tip   To initialize or reset the equalizer object eqobj, enter reset(eqobj).

PropertyDescription
EqTypeFixed value, 'Linear Equalizer'
AlgTypeName of the adaptive algorithm represented by alg
nWeightsNumber of weights
nSampPerSymNumber of input samples per symbol (equivalent to nsamp input argument). This value relates to both the equalizer structure (see the use of K in Fractionally Spaced Equalizers) and an assumption about the signal to be equalized.
RefTap (except for CMA equalizers)Reference tap index, between 1 and nWeights. Setting this to a value greater than 1 effectively delays the reference signal and the output signal by RefTap-1 with respect to the equalizer's input signal.
SigConstSignal constellation, a vector whose length is typically a power of 2
WeightsVector of complex coefficients. This is the set of wi values in the schematic in Symbol-Spaced Equalizers.
WeightInputsVector of tap weight inputs. This is the set of ui values in the schematic in Symbol-Spaced Equalizers.
ResetBeforeFilteringIf 1, each call to equalize resets the state of eqobj before equalizing. If 0, the equalization process maintains continuity from one call to the next.
NumSamplesProcessedNumber of samples the equalizer processed since the last reset. When you create or reset eqobj, this property value is 0.
Properties specific to the adaptive algorithm represented by algSee reference page for the adaptive algorithm function that created alg: lms, signlms, normlms, varlms, rls, or cma.

Relationships Among Properties

If you change nWeights, MATLAB maintains consistency in the equalizer object by adjusting the values of the properties listed below.

PropertyAdjusted Value
Weightszeros(1,nWeights)
WeightInputszeros(1,nWeights)
StepSize (Variable-step-size LMS equalizers)InitStep*ones(1,nWeights)
InvCorrMatrix (RLS equalizers)InvCorrInit*eye(nWeights)

An example illustrating relationships among properties is in Linked Properties of an Equalizer Object.

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See Also

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