On Which Factors Cut Off Frequency Of Rectangular Low Pass Filter Depends

[Abdullah Baig]

Dear Members
I have two questions please guide me.I am working on Radio over Fiber System.

(Q-1)–I want to inquire On Which Factors Cut Off Frequency Of Rectangular Low Pass Filter Depends
When i set cut off frequency 0.1*Bit rate then it shows good eye diagram while when i move towards 0.2*Bitrate—–0.75*Bitrate the eye diagram gradually starts rough and distorted???

(Q-2)–is it practically possible to set the cut off freq 0.1*Bitrate or 0.2*Bit rate or 0.3 *Bitrate???

Best Regards

[Ravil]

Hi Abdullah,

In general, the cut-off frequency of any low-pass filter depends on 2 parameters: internal resistance and its capacitance. Rectangular filter is considered as an ideal filter in this case, I think.

This cut-off frequency defines the passband of your signal. Your bit rate will be defined by signal bandwidth and type of coding you are using.

[Heitor Galvao]

The Bessel filter transfer function depends on two factors of insertion loss and order parameter of a normalizing constant. While the transfer function of a rectangular filter depends also on the insertion parameter, depth parameter, a center frequency and bandwidth.
It is interesting to note that in the “help” of the Bessel filter he makes an important observation:
Important: Previous versions older than OptiSystem 7.0 used a different equation to estimate the 3 dB bandwidth. The following table provides the multiplication factor that has to be multiplied by the current bandwidth in order to obtain the same results of versions older than OptiSystem 7.0:
(attached image)

[Ibn Aziz]

Heitor Galvao is right i endorsed his views.

[Ajay Vyas]

Abdullah Baig
May I know which type of work you are doing on RoF link. Can be share it

[Author]

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