** File: TPSht_02.hlp
** Index: 41

** More Sheet View Help
   :: Fourier Transformation commands
   :: Data windowing commands


Û  Fourier Transform

    This menu is shown  as Fourier Tfm in
TechPlot.

Û  Forward (Half)

    This command calculates amplitude and
  phase for the half range frequency
  (positive part).  One can use these
  columns to compute the real and
  imaginary part of the Fourier transform
  using the Math | Transform command as
  described below.

Û  Inverse (Half)

    This command performs the inverse
  Fourier transformation.

Û  Forward (Full)

    This command calculates amplitude and
  phase for the full range frequency.

Û  Inverse (Full)

    This command performs the full range
  inverse Fourier transformation.

Û  Convolution

    This command lets you calculate the
  convolution of two columns of data.


Û  Windowing

    This menu contains commands that are
used in the design of finite impulse
response (FIR) filters.

    The following commands are the
commonly used windowing functions, w[n].

Û  Square

    This command performs data windowing
  using the following window function:

    w[n]=1, if 0<=n<=M;

    w[n]=0, otherwise.

Û  Bartlett

    This command performs data windowing
  using the following window function:
    w[n]=1-2*abs(n-0.5M)/M, if 0<=n<=M;
    w[n]=0, otherwise.

Û  Hanning

    This command performs data windowing
  using the following window function:
    w[n]=0.5-0.5*cos(2ãn/M),
            if 0<=n<=M;
    w[n]=0, otherwise.

Û  Hamming

    This command performs data windowing
  using the following window function:

    w[n]=0.54-0.46*cos(2ãn/M),
            if 0<=n<=M;
    w[n]=0, otherwise.

Û  Blackman

    This command performs data windowing
  using the following window function:

    w[n]=0.42-0.5*cos(2ãn/M)
         +0.08*cos(4ãn/M), if 0<=n<=M;
    w[n]=0, otherwise.

Û  Welch

    This command performs data windowing
  using the following window function:

    w[n]=1-sqr(2*(n-0.5M)/(M+2)),
            if 0<=n<=M;
    w[n]=0, otherwise.

Û  Parzen

    This command performs data windowing
  using the following window function:

    w[n]=1-2*abs(n-0.5M)/(M+2),
            if 0<=n<=M;
    w[n]=0, otherwise.

