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MT Generate FSK Synchronization Parameters (bit array) (G Dataflow)

Last Modified: January 9, 2017

Generates synchronization parameters for FSK demodulation using a synchronization sequence directly represented by the sync bits input array. The generated synchronization parameters cluster avoids phase ambiguity at the demodulator, thus allowing recovery of the actual message bits.

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FSK system parameters

Parameter values defining the FSK system. Wire the FSK system parameters cluster returned by MT Generate FSK System Parameters (M) or MT Generate FSK System Parameters (map) to this cluster. Do not alter the values.

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Note  

If you set the symbol phase continuity element of the FSK system parameters cluster to discontinuous, no pulse-shaping filter can be applied, and the matched filter coefficients parameter is ignored. Refer to MT Generate FSK System Parameters (M) or MT Generate FSK System Parameters (map) for more information about these parameters.

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samples per symbol

An even number of samples dedicated to each symbol. Multiply this value by the symbol rate to determine the sample rate.

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Note  

The demodulation and detector nodes use timing recovery, which is optimized for four or more samples per symbol.

Default: 16

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symbol map

An ordered array that maps each Boolean symbol to its desired deviation frequency. The number of FSK levels in the array is 2 N , where N is the number of bits per symbol.

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symbol phase continuity

Continuity of phase transitions between symbols.

Name Description
continuous

Continuous phase transitions between symbols.

discontinuous

Discontinuous phase transitions between symbols, that is, discontinuous phase FSK (DPFSK).

With discontinuous phase-FSK (DPFSK), modulation consists of selecting the appropriate sinusoid based on the input data. Thus, when switching between symbols, there is a discontinuity in the FSK signal phase. To emulate a hardware-based DPFSK source, this node maintains the phase of each independent sinusoid versus time. Thus, the DPFSK modulator acts like a hardware-based (multiple switched tone generator) FSK modulator.

Default: continuous

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sync bits

An array of synchronization bits used to generate the FSK synchronization parameter cluster. For example, if you specify a preamble word of 1111 1111 1111 1110 for symbol synchronization, you can wire a 16-bit array with the above entries to the sync bits parameter. For reliable symbol synchronization, specify an array of length (10 × bits per symbol).

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Note  

To prevent false synchronization, select a bit pattern with low correlation to nonsynchronized portions of the data stream.

Default: 0

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error in

Error conditions that occur before this node runs. The node responds to this input according to standard error behavior.

Default: no error

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expected sync location

The expected location of the synchronization parameters in symbols. Set this value to -1 to search the entire waveform for the synchronization symbols.

Default: -1

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sync location uncertainty

Number of symbols before or after the expected sync location where the first symbol of the sync sequence may be located. The node ignores this parameter if the expected sync location parameter is set to -1.

Default: 10

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sync indent

Distance that the sync sequence is indented into the information block.

The distance is the number of demodulated symbols preceding the sync sequence. For example, a value of 10 indicates that the output bit stream consists of 10 data symbols, followed by the sync sequence, followed by the remaining data symbols.

Default: 0

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FSK synchronization parameters

Synchronization parameters to pass to the demodulation node.

If the synchronization parameter passed to the demodulation node is left empty, the constellation of the demodulated waveform has a 90° carrier phase ambiguity for two-dimensional modulation schemes (QAM, QPSK, and higher order PSK) and a 180° carrier phase ambiguity for one-dimensional modulation schemes (PAM/ASK/BPSK).

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expected sync location

The expected location of the first symbol of the sync sequence.

This value is an index to the input complex waveform. A value of -1 searches the entire input complex waveform and ignores the sync location uncertainty parameter.

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sync sequence

The mapped symbol pattern. Although the data type is complex, only the real portion is used.

The real portion of the mapped symbols is the frequency deviation of the symbol value, and the imaginary portion is 0. To prevent false synchronization, configure this pattern so that there is a low probability of accidental correlation to nonsynchronized parts of the data stream. If this parameter is left empty, the signal is still demodulated.

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sync location uncertainty

Number of symbols before or after the expected sync location where the first symbol of the sync sequence may be located. The node ignores this parameter if the expected sync location parameter is set to -1.

Default: 10

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sync indent

Distance that the sync sequence is indented into the information block.

The distance is the number of demodulated symbols preceding the sync sequence. For example, a value of 10 indicates that the output bit stream consists of 10 data symbols, followed by the sync sequence, followed by the remaining data symbols.

Default: 0

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error out

Error information. The node produces this output according to standard error behavior.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported


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