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h = modem.pammod(property1, value1,
...)
h = modem.pammod(PAMdemod_object)
h = modem.pammod(PAMdemod_object,
property1, value1, ...)
h = modem.pammod
The modem.pammod 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.pammod(property1, value1, ...) constructs a PAM modulator object h with properties as specified by the property/value pairs.
h = modem.pammod(PAMdemod_object) constructs a PAM modulator object h by reading the property values from the PAM demodulator object, PAMdemod_object. The properties that are unique to the PAM modulator object are set to default values.
h = modem.pammod(PAMdemod_object, property1, value1, ...) constructs a PAM modulator object h by reading the property values from the PAM demodulator object, PAMdemod_object. Additional properties are specified using property/value pairs.
h = modem.pammod constructs a PAM modulator object h with default properties. It constructs a modulator object for BPAM modulation, and is equivalent to:
h = modem.pammod('M', 2, 'SymbolOrder', 'binary', ...
'InputType', 'integer') 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 (complex envelope) 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.
A PAM 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 'PAM Modulator'. |
| M | M-ary value. |
| Constellation | Ideal signal constellation. This property is not writable and is automatically computed based on M and PhaseOffset. |
| SymbolOrder | Type of mapping employed for mapping symbols to ideal constellation points. The choices are 'binary' (binary mapping), 'gray' (Gray mapping), and 'user-defined' (custom mapping). |
| SymbolMapping | A list of integer values from 0 to M-1 that correspond to ideal constellation points. This property is writable only when SymbolOrder is set to 'user-defined'. Otherwise, it is automatically computed. |
| InputType | Type of input to be processed by the PAM modulator object. The choices are 'bit' (bit/binary output), and 'integer' (integer/symbol output). |
A PAM modulator object has the following functions for inspection, management, and simulation:
See Using Modem Objects for details and examples of their use.
% Construct a modulator object for 4-PAM modulation.
h = modem.pammod('M', 4)
% Construct an object to modulate binary data using
% 16-PAM modulation.
% The constellation has Gray mapping.
h = modem.pammod('M', 16, 'SymbolOrder', 'Gray', ...
'InputType', 'Bit')
% Construct a modulator object from an existing
% demodulator object for PAM demodulation in order to
% modulate binary inputs.
demodObj = modem.pamdemod('M', 8)
modObj = modem.pammod(demodObj, 'InputType', 'Bit')modem, modem.dpskdemod, modem.dpskmod, modem.genqamdemod, modem.genqammod, modem.mskdemod, modem.mskmod, modem.oqpskdemod, modem.oqpskmod, modem.pamdemod, modem.pskdemod, modem.pskmod, modem.qamdemod, and modem.qammod

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