# FFT Spectrum (Mag-Phase » Single-shot) (G Dataflow)

Version:

Computes the single-sided, scaled amplitude spectrum of a time-domain signal.

## unwrap phase

A Boolean specifying whether to unwrap the phase.

 True Unwraps the phase. False Does not unwrap the phase.

Unwrapping eliminates discontinuities that have an absolute value greater than pi.

Default: False

## signal

The input time-domain signal, usually in volts.

This input can be a 1D array of double-precision floating-point numbers or a 1D array of complex double-precision floating-point numbers.

The time-domain record must contain at least three cycles of the signal for a valid estimate.

## error in

Error conditions that occur before this node runs. The node responds to this input according to standard error behavior.

Default: No error

## dt

The sample period of the time-domain signal, usually in seconds.

Set this input to 1/fs, where fs is the sampling frequency of the time-domain signal.

Default: 1

## magnitude

The magnitude of the single-sided power spectrum.

## phase

The single-sided amplitude spectrum phase, in radians.

## error out

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

## df

The frequency interval of the power spectrum. The unit of this output is Hz if the sample period is in seconds.

## Algorithm for Calculating the Amplitude Spectrum

To compute the single-sided, scaled amplitude spectrum, this node first uses the following equation to compute the two-sided amplitude spectrum:

$\begin{array}{cc}A\left(i\right)=\frac{X\left(i\right)}{N}& i=0,\text{\hspace{0.17em}}1,\text{\hspace{0.17em}}...,\text{\hspace{0.17em}}N-1\end{array}$

where

• A is the two-sided amplitude spectrum
• X is the discrete Fourier transform of signal
• N is the number of points in signal

Then, this node uses the following equation to convert the two-sided amplitude spectrum to the single-sided amplitude spectrum:

$B\left(i\right)=\left\{\begin{array}{cc}A\left(0\right)& i=0\\ \sqrt{2}A\left(i\right)& i=1,\text{\hspace{0.17em}}2,\text{\hspace{0.17em}}...,\text{\hspace{0.17em}}⌊\frac{N}{2}-1⌋\end{array}$

where B is the single-sided amplitude spectrum and is the floor operation.

This node computes the magnitude of the single-sided amplitude spectrum B as magnitude = B and the phase as phase(B).

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported