MT Generate FSK System Parameters (map)
- Updated2023-02-17
- 5 minute(s) read
MT Generate FSK System Parameters (map)
Calculates parameters for use with either MT Modulate FSK or MT Demodulate FSK. This node accepts an input array of symbol values that explicitly specifies the positions of the symbol map.
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Inputs/Outputs
samples per symbol
An even number of samples dedicated to each symbol. Multiply this value by the symbol rate to determine the sample rate.
Default value: 16
symbol values
Array of symbol values with an order that corresponds to the symbol map. The number of FSK levels specified in the array must be 2N, where N is the number of bits per symbol.
This parameter expects an array of integers. The integers 0 to (M-1), inclusive, must all be included only once in the symbol values array, where M is the M-ary number of the modulation. The symbol locations (FSK frequencies) are evenly spaced between -FSK Deviation and +FSK Deviation, inclusive, with the binary representation (LSB first convention) of the integers that populate the symbol values array that corresponds to the placement of the M-ary bits on the I/Q constellation.
For example, for 4-FSK, if you specify FSK deviation as 150k and symbol values as [0 1 3 2], then:
- 00 (symbol value 0) corresponds to -150k
- 01 (symbol value 1) corresponds to -50k
- 11 (symbol value 3) corresponds to 50k
- 10 (symbol value 2) corresponds to 150k
Therefore the generated FSK symbol map reads [-150k -50k 150k 50k]. Similarly, if you specify the symbol values array as [0 1 2 3], the generated FSK symbol map reads [-150k -50k 50k 150k].
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
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
error in
Error conditions that occur before this node runs.
The node responds to this input according to standard error behavior.
Default value: No error
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.
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.
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.
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
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.
error out
Error information.
The node produces this output according to standard error behavior.