Definition - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues - primarily having to spend time purging garbage posts from the board. At some point I might start the RF Cafe Forums again if the phpBB software gets better at filtering spam.

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Antonio
Post subject: Definition Posted: Mon Nov 05, 2007 6:42 pm

Captain

Joined: Sat Jun 16, 2007 12:26 am
Posts: 12
Can anyone please define in detail about these???

1) What is the selectivity of a filter?

2) What is the mathematical expression for selectivity?

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jaslovkel
Post subject: Posted: Tue Nov 06, 2007 11:57 am

Captain

Joined: Tue Jun 26, 2007 10:27 am
Posts: 11
Location: Dallas, TX
Hi Antonio,

Selectivity is usually another name for how much attenuation is available in the stopband of a filter in a given frequency range. It depends on what type of filter it is to what the mathematical representation will be. This is because different filter approximations will have different transfer functions. However, the more poles in the transfer function will make the resulting circuit act as the ideal 'brick wall'. A narrowband system will require a filter with very high selectivity while a wideband system will require a low selectivity.

-J

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Antonio
Post subject: Posted: Fri Nov 09, 2007 3:31 am

Captain

Joined: Sat Jun 16, 2007 12:26 am
Posts: 12
Thank you very much for your help.

Posted 11/12/2012