The inverse Fast Fourier Transform (IFFT) function.  There are two forms.

Syntax

c = Ifft(Signal, length)

r,i = Ifft(Real,Imag)*This form is deprecated and will be removed in a future release *

Arguments

Name

Description

Signal

A vector containing the complex frequency domain representation of a signal.

length (optional)

The length of the output vector if specified as a positive integer.  If omitted or zero, the length will be the input signal length.  If the length is specified as ‘pad’, the length will be rounded up (zero padding the input) if necessary to obtain a power of 2.

Real

A vector containing real component of the frequency domain data.

Imag

A vector containing the imaginary component of the frequency domain data.

Output

Name

Description

c

A vector containing the inverse FFT.

r

A vector of the real component of the inverse FFT.  It has the same length as the input vectors.

i

A vector containing the imaginary component of the inverse FFT.  It has the same length as the input vectors.

Example 1

Given a vector signal, compute the inverse FFT.

Syntax

c = Ifft(signal)

Result

c is the inverse FFT vector.

Example 2

Given vectors real and imag, compute the inverse FFT.

Syntax

r,i = Ifft(real,imag)

Result

r and i contain the real and imaginary components of the inverse FFT, respectively.

Comments

The second form is provided to support the Templex syntax.  It is deprecated and will be removed in a future release. Real and Imag are assumed to be evenly sampled and must have the same number of elements.

If the vector length is modified with the length parameter, samples are either removed or appended (as zeros) symmetrically with respect to the Nyquist frequency.  This preserves the conjugate symmetry for a real signal so that the Ifft output remains real.  The inverse FFT is scaled so that its normalized FFT matches that of the input.  This preserves the time domain amplitude of each frequency component.

See Also:

Fft

FftImag

FftMag

FftPhase

FftReal