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iqcoef2imbal

Convert compensator coefficient to amplitude and phase imbalance

Description

[A,P] = iqcoef2imbal(C) converts compensator coefficient C to its equivalent amplitude and phase imbalance.

example

Examples

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Use iqcoef2imbal to estimate the amplitude and phase imbalance for a given complex coefficient. The coefficients are an output from the step function of the IQImbalanceCompensator.

Create a raised cosine transmit filter to generate a 64-QAM signal.

M = 64;
txFilt = comm.RaisedCosineTransmitFilter;

Modulate and filter random 64-ary symbols.

data = randi([0 M-1],100000,1);
dataMod = qammod(data,M);
txSig = step(txFilt,dataMod);

Specify amplitude and phase imbalance.

ampImb = 2; % dB 
phImb = 15; % degrees

Apply the specified I/Q imbalance.

gainI = 10.^(0.5*ampImb/20);
gainQ = 10.^(-0.5*ampImb/20);
imbI = real(txSig)*gainI*exp(-0.5i*phImb*pi/180);
imbQ = imag(txSig)*gainQ*exp(1i*(pi/2 + 0.5*phImb*pi/180));
rxSig = imbI + imbQ;

Normalize the power of the received signal

rxSig = rxSig/std(rxSig);

Remove the I/Q imbalance using the comm.IQImbalanceCompensator System object™. Set the compensator object such that the complex coefficients are made available as an output argument.

hIQComp = comm.IQImbalanceCompensator('CoefficientOutputPort',true);
[compSig,coef] = step(hIQComp,rxSig);

Estimate the imbalance from the last value of the compensator coefficient.

[ampImbEst,phImbEst] = iqcoef2imbal(coef(end));

Compare the estimated imbalance values with the specified ones. Notice that there is good agreement.

[ampImb phImb; ampImbEst phImbEst]
ans = 2×2

    2.0000   15.0000
    2.0178   14.5740

Input Arguments

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Coefficient used to compensate for an I/Q imbalance, specified as a complex-valued vector.

Example: 0.4+0.6i

Example: [0.1+0.2i; 0.3+0.5i]

Data Types: single | double

Output Arguments

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Amplitude imbalance in dB, returned as a real-valued vector with the same dimensions as C.

Phase imbalance in degrees, returned as a real-valued vector with the same dimensions as C.

More About

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Extended Capabilities

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C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2014b