SD Toolbox Reference |

Power Spectral Density

Calculates power spectral density, signal-to-noise ratio and effective number of bits of the Sigma-Delta modulator output.

Library

SD Toolbox.

Description

The Power Spectral Density block calculates power spectral density (PSD), signal-to-noise ratio (SNR) and effective number of bits (ENOB) from the Sigma-Delta modulator output.

The PSD and the SNR are calculated over tha last N simulation points using the calcSNR function, skipping the first Nt simulation points. If the total number of simulation points Ntot is larger than N + Nt, the calculation is performed when N + Nt points are available (before the end of the simulation), while if Ntot = N + Nt, the calculation is performed at the end of the simulation. The ENOB is obtained from the SNR with the equation

Graphical output is provided and, if desired, all the results (PSD, signal PSD, noise PSD, SNR and ENOB) are saved in a file, that can then be loaded into the Matlab Workspace for further processing.

Parameters

- Scope Number: Identification number of the Power Spectral Density block; different numbers are required for each Power Spectral Density block used in order to avoid overwriting the same figure
- Sampling Frequency: Frequency of the sampling signal in Hz (fs = 1/Ts, where Ts is the Sample Time)
- Lower Band Bound: Lower limit of the baseband in Hz
- Upper Band Bound: Upper limit of the baseband in Hz
- Signal Frequency: Frequency of the input signal in Hz
- Number of FFT Points: Number of simulation points to be considered for the calculation (N)
- Number of Transient Points: Number of points to be discarded at the beginning of the simulation (Nt)
- Variables Available in the Workspace: Selects if the results of the psotprocessing (PSD, signal PSD, noise PSD, SNR and ENOB) have to saved in a file
- Name of .mat File: Name of the file in which the results of the psotprocessing (PSD, signal PSD, noise PSD, SNR and ENOB) are saved if Variables Available in the Workspace is active
- Scale: Selects if the x-axis of the graphical output has to be linear or logarithmic

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