MT Add Phase Noise VI
Models and applies common sources of phase noise present in communications systems components. This VI creates phase noise by first generating white noise and then applying a 1/f (inverse f) filter to specify the noise shape. The output of the filter is scaled such that the generated noise density is equal to the specified offset frequency. The phase component of the input signal is then modulated by the filtered noise.
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input complex waveform specifies the modulated complex baseband waveform data.
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offset frequency specifies the offset frequency in hertz for the specified noise density. This is the frequency at which the 1 Hz bandwidth spectral density of the ideal inverse-f noise waveform is equal to specified noise density. Valid entries for this parameter must be in the range 0.7 mHz to f s/2, where f s is the sampling frequency (1/dt) of the input complex waveform. The default is 200,000 Hz (200 kHz). |
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noise density specifies the single sideband noise contribution in a 1 Hz bandwidth relative to the total power at the specified offset frequency (Hz). The default is –120 dBc/Hz. |
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inverse f exponent for noise shape specifies the exponent of the desired 1/f curve. The inverse f curve specifies the spectral shape of the phase noise. Specify a value in the range –3.0 to 3.0. The default is 2. |
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seed in specifies a seed for the noise sample generator. Set this value to –1 (xFFFFFFFF) to reseed the noise generator with a random seed. The random signal generator is reseeded on first call to this VI and when reset? is set to TRUE. When reset? is FALSE this parameter is ignored on subsequent calls. The default is -1 (xFFFFFFFF). |
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reset? specifies whether the VI reuses the noise shaping filter and reseeds the noise generator on subsequent calls. When reset? is TRUE (default), the VI designs/redesigns noise-shaping IIR filter and reseeds the noise generator using the seed in parameter value. When reset? is FALSE, the VI uses the previously designed IIR filter, and reseeds the noise generator with the seed out parameter, upon each subsequent call. The VI always resets on first call. The default is TRUE. |
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error in (no error) can accept error information wired from previously called VIs. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
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output complex waveform returns the signal-plus-noise complex baseband waveform data.
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seed out returns the seed used in the subsequent call to this VI when reset? set to FALSE.
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error out passes error or warning information out of a VI to be used by other VIs. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
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Details
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Note Multiregion inverse f rolloff noise shapes can be implemented by calling the MT Add Phase Noise VI multiple times in series
on a signal, with each call defining the inverse f rolloff and desired level at a specific offset frequency. When combining individual
MT Add Phase Noise VIs in this way, refer to the following considerations:
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