TELETEXT FILTERS
A RANGE OF DIP PULSE SHAPING FILTERS
FOR TELETEXT SYSTEMS
To avoid data errors the fast pulses produced by data generators need to be band limited prior to
insertion into a video channel.
When conventional low pass filters are used unacceptable time domain ringing of the pulse results.
This range of filters is designed to band limit while avoiding this problem.
Due to technical and historic reasons three types of filter are in current use. They are based on the
Gaussian, Raised Cosine and Cosine Roll-off realisations. Each has a slightly different
characteristic. The cosine roll-off type is the only one that band limits the frequency spectrum to
5.5 MHz so ensuring that a 625 line video system is transparent to the pulse.
FX055AD
Filter Type
Attenuation at 5.5 MHz
Impedance
Temperature Range
Aqueous Washable
Package
FX055BD
FX055CD
Gaussian
3.0 dB
75 ohms
0°C to 70°C
Yes
DR00110A
Raised cosine Cosine Roll-off
5.0 dB
75 ohms
0°C to 70°C
Yes
DR00110A
19.0 dB
75 ohms
0°C to 70°C
Yes
DR00110A
© Faraday Technology. As part of continual product improvement the specifications, details and dimensions shown in this publication are subject to change without notice
Fara163d
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Dec-99(A)
FARADAY [ FARADAY TECHNOLOGY ]
