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MT Generate PSK System Parameters (map) (G Dataflow)

Last Modified: January 9, 2017

Calculates parameters for use with either MT Modulate PSK or MT Demodulate PSK. This node generates the symbol map for PSK-modulated systems. The node accepts an array of symbol values that explicitly specifies the positions of the symbol map.

Example Symbol Map for PSK

This symbol map corresponds to input symbol values {0, 1, 3, 2} for a quadrature-phase-shift-keying (QPSK) modulation system.

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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 values

An array of symbol values with an order that corresponds to the symbol map. The number of PSK states in the array must be 2 N , where N is the number of bits per symbol.

This node expects an array of integers for the symbol values parameter. The integers 0 through (M-1) must all be included only once in the symbol values array, where M is the M-ary number of the modulation. The binary representation (LSB first convention) of the integers represents the bit pattern that is mapped to the corresponding symbol location in the symbol values array. The symbol locations are generated with equal angles between all M-ary symbol locations and a distance of unity from the origin.

For example, in 8-PSK, if you specify symbol values as [5 4 2 7 3 0 1 6], the generated PSK symbol map is [(-0.383 - 0.924i), (0.383 - 0.924i), (-0.383 + 0.924i), (-0.924 - 0.383i), (0.383 + 0.924i), (0.924 + 0.383i), (0.924 - 0.383i), (-0.924 + 0.383i)].

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differential PSK

A value that indicates how the PSK modulation represents symbols.

Differential operation is used to implement PSK formats such as differential quadrature PSK (DQPSK) and π /4-DQPSK.

Name Description
disable

Symbols are represented as constellation points.

enable

Symbols are represented as the transitions between constellation points.

Default: disable

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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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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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PSK system parameters

Parameter values defining the PSK system. Wire this cluster to the corresponding system parameters clusters of MT Modulate PSK or MT Demodulate PSK.

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samples per symbol

Number of samples per symbol in the modulated output complex waveform. For error-free operation, the samples per symbol must be an even number.

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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

A value that indicates how the PSK modulation represents symbols.

Differential operation is used to implement PSK formats such as differential quadrature PSK (DQPSK) and π /4-DQPSK.

Name Description
disable

Symbols are represented as constellation points.

enable

Symbols are represented as the transitions between constellation points.

Default: disable

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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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bits per symbol

Number of bits represented by each symbol. This value is equal to Log 2 (M), where M is the order of the modulation (for example, for 16-PSK, M = 16).

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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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