MT Generate FSK System Parameters (M)

Calculates parameters for use with either MT Modulate FSK or MT Demodulate FSK. This node generates the symbol map for FSK-modulated systems. This node accepts an M-ary value that specifies a predefined symbol map with the number of distinct symbol map values to use as symbols.

1378

Inputs/Outputs

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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.

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

Default value: 16

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M-FSK

The M-ary number, which is the number of distinct frequency deviations, to use as symbols. This value must be a positive power of 2.

Default value: 2

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FSK deviation

Maximum FSK frequency deviation. At baseband frequencies, deviations for individual symbols are evenly spaced in the interval [-fd, fd], where fd represents the frequency deviation.

Default value: 150,000

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symbol phase continuity

Continuity of phase transitions between symbols.

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 value: continuous

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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.

Standard Error Behavior

Default value: No error

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FSK system parameters

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

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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. Applying Carson's rule for FSK modulation, the 98% FSK bandwidth is given by the following formula:

0.5 × (1 + r) × symbol rate + peak frequency deviation

where 0 ≤ r ≤ 1 is the filter parameter.

To satisfy the Nyquist criterion, use the following guideline.

samples per symbol = 2 × ceil(1.5 × bandwidth/symbol rate) to obtain 3× oversampling.

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symbol map

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

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symbol phase continuity

Continuity of phase transitions between symbols.

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 value: continuous

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bits per symbol

Number of bits represented by each symbol. This value is equal to Log2(M), where M is the order of the modulation. Example: For 16-FSK, M = 16.

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error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior