Table Of Contents

MT Generate PSK Synchronization Parameters (number array) (G Dataflow)

Last Modified: January 9, 2017

Generates synchronization parameters for PSK demodulation using a synchronization sequence defined by a sync numbers array in which each number represents a group of bits. The generated synchronization parameters cluster avoids phase ambiguity at the demodulator, thus allowing recovery of the actual message bits.

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PSK system parameters

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

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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 coordinates in the complex plane. The number of PSK states in the array must be 2 N , where N is the number of bits per symbol.

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differential PSK

Status of the differential PSK.

Name Description
disable

Disables bit sequence encoding.

enable

Enables bit sequence encoding.

Default: enable

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PSK type

Type of PSK modulation.

Name Description
normal

Sets the modulation type to regular PSK.

shifted

Rotates the constellation by π /M each symbol.

offset

Sets the modulation type to offset quadrature phase-shift keying (OQPSK). This modulation scheme is a form of phase-shift keying in which four different phase angles are used. This scheme is sometimes referred to as staggered quadrature phase-shift keying (SQPSK). For offset PSK, the ideal symbol timing for Q is offset by 1/2 of a symbol period from the ideal symbol timing for I. offset is currently only supported for M= 4.

Default: normal

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sync numbers

An array of synchronization numbers in which the binary representation of each number is used to generate the sync bit array. By default, the internal conversion of each sync number into the corresponding synchronization bit sequence is performed with the most significant bit first (left-aligned) approach.

For example, if you specify a preamble word of 1111 1111 1111 1110 for symbol synchronization, you can specify sync numbers as an array with a single element xFFFE. Specify the bits per sync number value to be 16. You can also specify sync numbers as an array of two elements (xFF and xFE), and specify the bits per sync number value as 8. 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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bits per sync number

Number of bits corresponding to each sync number in the sync numbers array.

Default: 32

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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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PSK synchronization parameters

Synchronization parameters to pass to the demodulation node.

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Note  

The node always uses normal PSK when creating the PSK synchronization parameters cluster, even if the PSK type specified when creating the PSK synchronization parameters cluster is shifted or offset. This supplies an absolute phase reference for MT Demodulate PSK during the process of symbol synchronization.

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 array from the specified synchronization bits or synchronization numbers.

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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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