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 Using Adaptive Equalizer Functions and Objects.

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).

Property Description

EqType Fixed value, 'Linear Equalizer'

AlgType Name of the adaptive algorithm represented by alg

nWeights Number of weights

nSampPerSym Number 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.

SigConst Signal constellation, a vector whose length is typically a power of 2

Weights Vector of complex coefficients. This is the set of w_i values in the schematic in Symbol-Spaced Equalizers.

WeightInputs Vector of tap weight inputs. This is the set of u_i values in the schematic in Symbol-Spaced Equalizers.

ResetBeforeFiltering If 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.

NumSamplesProcessed Number 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 alg See reference page for the adaptive algorithm function that created alg: lms, signlms, normlms, varlms, rls, or cma.

Property	Description
`EqType`	Fixed value, `'Linear Equalizer'`
`AlgType`	Name of the adaptive algorithm represented by `alg`
`nWeights`	Number of weights
`nSampPerSym`	Number 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.
`SigConst`	Signal constellation, a vector whose length is typically a power of 2
`Weights`	Vector of complex coefficients. This is the set of w_i values in the schematic in Symbol-Spaced Equalizers.
`WeightInputs`	Vector of tap weight inputs. This is the set of u_i values in the schematic in Symbol-Spaced Equalizers.
`ResetBeforeFiltering`	If `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.
`NumSamplesProcessed`	Number 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 `alg`	See 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.

Property	Adjusted Value
`Weights`	`zeros(1,nWeights)`
`WeightInputs`	`zeros(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.

Examples

For examples that use this function, see Equalizing Using a Training Sequence, Example: Equalizing Multiple Times, Varying the Mode, and Example: Adaptive Equalization Within a Loop.