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CPM, in Digital Baseband sublibrary of Modulation
The GMSK Demodulator Baseband block demodulates a signal that was modulated using the Gaussian minimum shift keying method. The input is a baseband representation of the modulated signal.
The BT product, Pulse length, Symbol prehistory, and Phase offset parameters are as described on the reference page for theGMSK Modulator Baseband block.
Internally, this block creates a trellis description of the modulation scheme and uses the Viterbi algorithm. The Traceback length parameter, D, in this block is the number of trellis branches used to construct each traceback path. D influences the output delay, which is the number of zero symbols that precede the first meaningful demodulated value in the output.
If the input signal is sample-based, then the delay consists of D+1 zero symbols.
If the input signal is frame-based, then the delay consists of D zero symbols.
The input can be either a scalar or a frame-based column vector and must be of type single or double. If the Output type parameter is set to Integer, then the block produces values of 1 and -1. If the Output type parameter is set to Bit, then the block produces values of 0 and 1.
The input signal can be an upsampled version of the modulated signal. The Samples per symbol parameter is the upsampling factor. It must be a positive integer. For more information, see Upsampled Signals and Rate Changes in Communications Blockset User's Guide.
Determines whether the output consists of bipolar or binary values.
The product of bandwidth and time.
The length of the frequency pulse shape.
The data symbols used by the modulator before the start of the simulation.
The initial phase of the modulated waveform.
The number of input samples that represent each modulated symbol.
The number of trellis branches that the Viterbi Decoder block uses to construct each traceback path.
The output data type can be boolean, int8, int16, int32, or double.
CPM Demodulator Baseband, Viterbi Decoder
[1] Anderson, John B., Tor Aulin, and Carl-Erik Sundberg. Digital Phase Modulation. New York: Plenum Press, 1986.
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