genqamdemod

General quadrature amplitude demodulation

Syntax

z = genqamdemod(y,const)

Description

z = genqamdemod(y,const) demodulates the complex envelope, y, of a quadrature amplitude modulated signal using the signal mapping specified in const.

Examples

General QAM Modulation and Demodulation

Create the points that describe a hexagonal constellation.

inphase = [1/2 1 1 1/2 1/2 2 2 5/2];
quadr = [0 1 -1 2 -2 1 -1 0];
inphase = [inphase;-inphase]; inphase = inphase(:);
quadr = [quadr;quadr]; quadr = quadr(:);
const = inphase + 1i*quadr;

Plot the constellation.

h = scatterplot(const);

Generate input data symbols. Modulate the symbols using this constellation.

x = [3 8 5 10 7];
y = genqammod(x,const);

Demodulate the modulated signal, y.

z = genqamdemod(y,const);

Plot the modulated signal in same figure.

hold on;
scatterplot(y,1,0,'ro',h);
legend('Constellation','Modulated signal');
hold off;

Determine the number of symbol errors between the demodulated data to the original sequence.

numErrs = symerr(x,z)

numErrs = 
0

Input Arguments

y — Complex envelope

scalar | vector | matrix | 3-D array

Complex envelope, specified as a scalar, vector, matrix, or 3-D array of numeric values. If y is a matrix with multiple rows, the function processes the rows independently.

const — Signal mapping

complex vector

Signal mapping, specified as a complex vector.

Data Types: double | single
Complex Number Support: Yes

Output Arguments

z — Message signal

scalar | vector | matrix | 3-D array

Message signal, returned as a scalar, vector, matrix, or 3-D array of numeric values. The message signal consists of integers between 0 and length(const)–1. The datatype of z is the same as the data type of input x.

Data Types: double | single

Extended Capabilities

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

Version History

Introduced before R2006a