DADiSP Online Help
Click here to see this page in full context

DADiSP Worksheet Functions > Function Categories > Fourier Transforms and Signal Processing > CHEBWIN

 

CHEBWIN

Purpose:

Multiplies a series with a Dolph-Chebyshev Window.

Syntax:

CHEBWIN(series, ampflag, attn)

series

-

A series or array.

ampflag

-

Optional. An integer, the amplitude correction flag:

0

:

do not correct amplitude (default)

1

:

correct amplitude

2

:

correct RMS amplitude

3

:

correct mean squared amplitude

attn

-

Optional. A real, the sidelobe attenuation from the mainlobe in dB. Defaults to -100.

Alternate Syntax:

CHEBWIN(N, ampflag, attn)

N

-

An integer, the window length.

ampflag

-

Optional. An integer, the amplitude correction flag:

0

:

do not correct amplitude (default)

1

:

correct amplitude

2

:

correct RMS amplitude

3

:

correct mean squared amplitude

attn

-

Optional. A real, the sidelobe attenuation from the mainlobe in dB. Defaults to -100.

Returns:

A series.

Example:

W1: gsin(1000, 0.001, 45)

W2: chebwin(w1)

 

W1 contains a 1000 point sinewave with a frequency of 45 Hz. W2 multiplies the sinewave with a Dolph-Chebyshev window.

Example:

W1: gsin(1000, 0.001, 45)

W2: chebwin(w1, 0, -65)

 

Same as the first example except the sidelobe attenuation is -65 dB.

Example:

W1: chebwin(100, 0, -60)

W2: magspec(w1, 8192);20*log10(curr/max(curr));

 

W1 Creates a 100 point Dolph-Chebyshev window where the sidelobe attenuation is -60 dB. W2 displays the normalized frequency response.

Remarks:

The frequency response of an Nth order Dolph-Chebyshev window with an attenuation of attn decibels is given by:

 

 

The time domain response is determined by computing the inverse Fourier transform and scaling the result to a unitary maximum.

 

The Dolph-Chebyshev windows minimizes the Chebyshev norm of  the sidelobes for a given mainlobe width.

 

The Dolph-Chebyshev window can be regarded as the impulse response of an optimal Chebyshev lowpass filter having a zero-width passband.

 

Because the Dolph-Chebyshev window yields equiripple constant magnitude sidelobes, impulses may result at the end points of the time domain response.

 

Use GCHEBWIN to generate an N point Dolph-Chebyshev window.

 

gchebwin(100, 1/100, -60)

 

creates a 100 point Dolph-Chebyshev window with a sample rate of 0.01 and an attenuation of -60 dB.

 

See TAYLORWIN to multiply a series with a Taylor window.

See Also:

FFT

GCHEBWIN

GHAMMING

GKAISER

PSD

SPECTRUM

TAYLORWIN

WINFUNC