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Calculates the maximum possible peak amplitude, after pulse-shape filtering and resampling, of a waveform for the QAM modulation scheme.

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QAM system parameters

Parameter values defining the QAM system. Wire this parameter to the corresponding system parameters cluster of MT Modulate QAM, MT Demodulate QAM, or MT Detect QAM.

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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 value must be an even number.

Default: 16

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symbol map

An ordered array that maps each symbol to its desired coordinates in the complex plane. The number of QAM states in the array is 2 N , where N is the number of bits per symbol. The vector length for the symbols farthest from the origin is 1.

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pulse shaping filter coefficients

An ordered array of filter coefficients corresponding to the desired filter response for the pulse-shaping filter used in modulation. The number of coefficients depends on the pulse-shaping filter characteristics specified in the pulse-shaping filter. Refer to MT Generate Filter Coefficients for more information about pulse-shaping filter coefficients.

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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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waveform scaling factor

Inverse of the maximum amplitude of the I/Q waveform based on the specified system parameters.

For the frequency modulation schemes (FSK, MSK, and CPM), there is no known analytical method to calculate the maximum amplitude that accounts for effects such as resampling, filtering, and so on. Empirically, a waveform scaling factor of 0.8 should be sufficient for most of your applications. This value results in a maximum dynamic range loss of about 2 dB on third-party (non-NI) RF signal generator devices.

If you receive errors related to this value, your signal might be aliased. For more information about aliasing, refer to MT Modulate CPM or MT Modulate FSK.

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error out

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