comm.MSKModulator System object

Package: comm

Modulate using MSK method

Description

The MSKModulator object modulates using the minimum shift keying method. The output is a baseband representation of the modulated signal. The initial phase offset property sets the initial phase of the output waveform, measured in radians.

To modulate a signal using minimum shift keying:

  1. Define and set up your MSK modulator object. See Construction.

  2. Call step to modulate the signal according to the properties of comm.MSKModulator. The behavior of step is specific to each object in the toolbox.

Construction

H = comm.MSKModulator creates a modulator System object™, H. This object modulates the input signal using the minimum shift keying (MSK) modulation method.

H = comm.MSKModulator(Name,Value) creates an MSK modulator object, H, with each specified property set to the specified value. You can specify additional name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).

Properties

BitInput

Assume bit inputs

Specify whether the input is bits or integers. The default is false.

When you set the BitInput property to false, the step method input must be a column vector with a double-precision or signed integer data type and of values equal to -1 or 1.

When you set the BitInput property to true, the step method input requires double-precision or logical data type column vector of 0s and 1s.

InitialPhaseOffset

Initial phase offset

Specify the initial phase of the modulated waveform in radians as a real, numeric scalar value. The default is 0.

SamplesPerSymbol

Number of samples per output symbol

Specify the upsampling factor at the output as a real, positive, integer scalar value. The default is 8. The upsampling factor indicates the number of output samples that the step method produces for each input sample.

OutputDataType

Data type of output

Specify output data type as one of double | single. The default is double.

Methods

cloneCreate MSK modulator object with same property values
getNumInputsNumber of expected inputs to step method
getNumOutputsNumber of outputs from step method
isLockedLocked status for input attributes and nontunable properties
releaseAllow property value and input characteristics changes
resetReset states of the MSK modulator object
stepModulate using MSK method

Examples

expand all

Modulate an MSK signal with bit inputs and phase offset

% Create an MSK modulator, an AWGN channel, and an MSK demodulator.  Use a
% phase offset of pi/4.
 hMod = comm.MSKModulator('BitInput', true, ...
                    'InitialPhaseOffset', pi/4);
    hAWGN = comm.AWGNChannel('NoiseMethod', ...
                    'Signal to noise ratio (SNR)','SNR',0);
    hDemod = comm.MSKDemodulator('BitOutput', true, ...
                    'InitialPhaseOffset', pi/4);
 % Create an error rate calculator, account for the delay caused by the Viterbi algorithm
    hError = comm.ErrorRate('ReceiveDelay', hDemod.TracebackDepth);
    for counter = 1:100
      % Transmit 100 3-bit words
      data = randi([0 1],300,1);
      modSignal = step(hMod, data);
      noisySignal = step(hAWGN, modSignal);
      receivedData = step(hDemod, noisySignal);
      errorStats = step(hError, data, receivedData);
    end
    fprintf('Error rate = %f\nNumber of errors = %d\n', ...
      errorStats(1), errorStats(2))
Error rate = 0.000000
Number of errors = 0

Algorithms

This object implements the algorithm, inputs, and outputs described on the MSK Demodulator Baseband block reference page. The object properties correspond to the block parameters.

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