VIDEO LOWPASS FILTERS
SERIES ATLW Stopband Ratio @45dB = 1.32
ATCL Stopband Ratio @45dB = 1.14
ATBW Stopband Ratio @45dB = 1.08
ABW Stopband Ratio @42dB = 1.066
For many years amplitude, Delay and phase corrected filters have found applications in
Television Broadcasting, Cable transmission, Direct Satellite Transmission, Analog and
Digital Image Processing, Analog to Digital conversion and Computer Graphics. Allen
Avionics offers four basic shape factors or stopband ratios in their range of Video
Filters.
ATLW General purpose filters include
amplitude,Phase and Group Delay
equalization to improve pulse and bar
response. Smooth slower roll off reduces
ringing. Can be used as in any Video
bandwidth limiting application. Also used
as anti aliasing pre filters in analog to
digital conversion applications or as post
aliasing filters with the addition of sin x/x
correction.
ATCL More complex filter for applications
requiring a sharper cutoff rate. The tight
control of amplitude, phase and delay of
the ATCL series makes them ideal for
high performance analog and digital
applications.
ATBW Almost a Brickwall Filter. The
ATBW is a good compromise for
sharpness, ringing, insertion loss and
cost. The ATBW stopband ratio of 1.08 is
close to the ABW series Brickwall ratio of
1.066 but has less ringing, Delay
distortion and insertion loss.
ABW A true Brickwall Filter. The ABW
series is the sharpest cutoff Video filter
available anywhere. Tight control of the
Amplitude, Phase and Delay
Characteristics create a filter unmatched
for sharpness, low ringing, insertion loss
and cost. Typical NTSC applications use
this filter to pass 4.20MHz and reject
everything above 4.48MHz which
requires a stopband ratio of 1.066. See
Brickwall data sheet.