bessel filter

[aasif bashir dar]

why do we gennerally use bessel filters after the PIN or APD at the receiver side. why not any other filter types?????????????
with regards

[Karan Ahuja]

Hi.
It is not necessary that we always use Bessel. It the the application or the requirement that decides the type of filter we must use on the receiver side.
However talking about the bessel filter, it certainly has an advantage that is it preserves the and helps in pulse shaping which means that it helps in preserving the wave shape of filtered signals in the passband.
Hope this is helpful to you.
Thanks
Regards

[Karan Ahuja]

I want to add that the Bessel filter is a linear form of filter that provides a maximally flat group delay or propagation delay across the frequency spectrum, but offers a slower transition from pass-band to stop-band than for other forms of filter of the same order.
However, the Bessel filter is not used as widely as the Butterworth of Chebyshev filters, although the fact that it has a maximally flat group delay means that Bessel filters are often used in audio applications such as audio cross-over networks.

http://www.radio-electronics.com/info/rf-technology-design/rf-filters/bessel-rf-filter-basics.php

[Aabid Baba]

Hello Aasif,
This question had been in my mind also because if you look every design presented in optisystem sample examples only low pass Bessel is used. The reason i guess is the performance or the gain flattering provided by this filter. Also i think Karan has mentioned an important point about preserving the shape of the transmitted signal.
Regards

[burhan num mina llah]

Hello Aasif Bashir

As far as Bessel filter is concerned i agree with most of the responses. Undoubtedly it is used as a default filter for most of the optisystem projects as Karan has mentioned. The reason may be that the Bessel filter is a linear form of filter that provides a maximally flat group delay or propagation delay across the frequency spectrum, but offers a slower transition from pass-band to stop-band than for other forms of filter of the same order.
Also i agree that it has a maximally flat group delay means that Bessel filters are often used in audio applications such as audio cross-over networks as mentioned by other forum members.

I believe it is application specific. Hope this is helpful to you.

Regards

Burhan

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