Fourier Analysis

Discrete or continuous time Fourier analysis

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Libraries:
Simscape / Electrical / Control / General Control

Description

The Fourier Analysis block performs a Fourier analysis on the input signal in either discrete or continuous time.

Equations

A periodic function x(t) can be decomposed to an infinite sum of sine and cosine functions as

$$x(t)=\frac{a_0}{2}+{\displaystyle \sum _{n=1}^{\infty }[a_n\cos (nt)+b_n\sin (nt)]}$$

where:

• a₀ is the DC component.

• a_n and b_n are constant Fourier coefficients.

• n is the harmonic number.

The coefficients a_n and b_n are defined as:

$$a_n=\frac{2}{T_0}{\displaystyle \underset{t_0}{\overset{t_0+T_0}{\int }}x(t)\cos (n{\Omega }_{0}t)dt,}n=0,1,\mathrm{...}$$

$$b_n=\frac{2}{T_0}{\displaystyle \underset{t_0}{\overset{t_0+T_0}{\int }}x(t)\sin (n{\Omega }_{0}t)dt},n\text{ = 1,2, }\mathrm{...}$$

$${\Omega }_0=\frac{2\pi }{T_0}$$

$$T_0=\frac{1}{f}$$

where f is the fundamental frequency.

These equations define the magnitude and angle corresponding to the harmonic number:

$$\left|X_n\right|=\sqrt{a_n{}^2+b_n{}^2}$$

$${\theta }_n=-{\tan }^{-1}\left[\frac{a_n}{b_n}\right]$$

Note

If you use this block for continuous-time operations and set the Sample time (-1 for inherited) parameter to 0, you should also specify the value of the Buffer size parameter to ensure it covers the moving time window.

Ports

Input

u — Fourier analysis input

scalar | vector

Input signal to be analyzed. The input can be a single signal or multiple multiplexed signals. Input signals can be AC currents or voltages in an electrical system.

Data Types: single | double

Output

Magnitude — Signal magnitude

scalar | vector

Signal magnitude corresponding to the harmonic number.

Data Types: single | double

Angle — Signal angle

scalar | vector

Signal angle corresponding to the harmonic number.

Data Types: single | double

Parameters

Fundamental frequency (Hz) — Signal fundamental frequency

60 (default) | positive scalar | vector with positive values

Fundamental frequency of the signal, in Hz. If you specify the fundamental frequency using a vector, it must match the input vector dimensions.

Harmonic numbers — Signal harmonic numbers

[1 2] (default) | vector with elements ≥ 0

Specify signal harmonic numbers. Vector elements must be greater than or equal to 0.

Initial magnitude — Initial signal magnitude

1 (default) | vector with elements ≥ 0

Specify the initial magnitude of the signal. Vector elements must be greater than or equal to 0.

Initial phase (rad) — Initial signal phase

0 (default) | vector

Initial phase angle of the signal, in rad.

Buffer size — Buffer size

8192 (default) | scalar

Size of the buffer.

Dependencies

To enable this parameter, set Sample time (-1 for inherited) to 0.

Sample time (-1 for inherited) — Block sample time

-1 (default) | 0 | positive scalar

Time between consecutive block executions. During execution, the block produces outputs and, if appropriate, updates its internal state. For more information, see What Is Sample Time? and Specify Sample Time.

For inherited discrete-time operation, set this parameter to -1. For discrete-time operation, set this parameter to a positive integer. For continuous-time operation, set this parameter to 0.

If this block is in a masked subsystem or a variant subsystem that supports switching between continuous operation and discrete operation, promote this parameter to ensure correct switching between the continuous and discrete implementations of the block. For more information, see Promote Block Parameters on a Mask.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018b