Communications Toolbox™

modem.mskmod - Construct MSK modulator object

Syntax

h = modem.mskmod(property1, value1, ...) h = modem.mskmod(MSKdemod_object) h = modem.mskmod(MSKdemod_object, property1, value1, ...) h = modem.mskmod

Description

The modem.mskmod function creates a modulator object that you can use with the modulate method to modulate a signal. To learn more about the process for modulating a signal, see Using Modem Objects.

h = modem.mskmod(property1, value1, ...) constructs an MSK modulator object h with properties as specified by the property/value pairs.

h = modem.mskmod(MSKdemod_object) constructs an MSK modulator object h by reading the property values from the MSK demodulator object, MSKdemod_object. The properties that are unique to the MSK modulator object are set to default values.

h = modem.mskmod(MSKdemod_object, property1, value1, ...) constructs an MSK modulator object h by reading the property values from the MSK demodulator object, MSKdemod_object. Additional properties are specified using property/value pairs.

h = modem.mskmod constructs an MSK modulator object h with default properties. This syntax is equivalent to:

h = modem.mskmod('Precoding', 'off', ...
  'SamplesPerSymbol', 8, 'InputType', 'bit')

Modem Modulation Method

This object has a method modulate that is used to modulate signals.

The syntax is y = modulate(h, x), where h is the handle to a modulator object and x is a signal. This syntax outputs the baseband signal y.

x can be a multichannel signal. The columns of x are considered individual channels, while the rows are time steps.

When mapping input bits to symbols, the first bit is interpreted as the most significant bit.

For h.inputtype = ‘bit' (i.e., x represents binary input), nBits consecutive elements in each channel or column represent a symbol, where nBits = log₂(h.M). The number of elements in each channel must be an integer multiple of nBits, and elements of x must be 0 or 1. For an input x of size , an output y of size is computed.

For h.inputtype = ‘integer' (i.e., x represents symbol input), elements of x must be in the range [0, h.M-1]. For an input x of size , an output y of size is computed.

See Using Modem Objects for usage examples.

Properties

An MSK modulator object has the following properties. All the properties are writable unless explicitly noted otherwise.

Property	Description
`Type`	Type of modulation object. This is a fixed value, set to `'MSK Modulator'`.
`M`	Constellation size. This is a fixed value, set to `2`.
`Precoding`	Specifies the type of the coherent MSK modulator. The choices are `'off'` for conventional coherent MSK, and `'on'` for precoded coherent MSK.
`SamplesPerSymbol`	Number of samples used to represent an MSK symbol.
`InputType`	Type of input to be processed by the MSK modulator object. The choices are `'bit'` (bit/binary input), and `'integer'` (integer/symbol input). Because the MSK constellation size is two, `'bit'` and `'integer'` are equivalent.

Methods

An MSK modulator object has the following functions for inspection, management, and simulation:

See Using Modem Objects for details and examples of their use.

Examples

% Construct a modulator object for MSK modulation with
% five samples per symbol.
h = modem.mskmod('SamplesPerSymbol', 5)
 
% Construct an MSK modulator object with precoding and
% 10 samples per symbol.
h = modem.mskmod('Precoding', 'on', 'SamplesPerSymbol', 10)
 
% Construct a modulator object from an existing demodulator
% object for MSK demodulation in order to modulate binary
% inputs.
demodObj = modem.mskdemod('SamplesPerSymbol', 6) % existing 
                                   % MSK demodulator object
modObj = modem.mskmod(demodObj)