Re: Bandwidth to Q conversion
Re: Bandwidth to Q conversion
- Subject: Re: Bandwidth to Q conversion
- From: Ethan Funk <email@hidden>
- Date: Thu, 6 Jan 2005 20:09:13 -0700
Equation:
-3 dB (1/2 power or 1/sqrt(2) voltage) Bandwidth = center frequency / Q
example:
Bandpass filter, with a Q = 5, center frequency = 2.0 kHz
-3 dB Bandwidth = 2.0 kHz / 5 = 0.4 kHz or 400 Hz
-3 dB points are 400 Hz apart centered at 2.0 kHz, so...
The filter will have 3 dB attenuation at 1.8 kHz, 0 dB attenuation at 2
kHz and back down to 3 dB at 2.2 kHz. As you move farther away from
the center frequency, the attenuation will continue to drop with an
ever increasing slope.
A high or low pass filter would only have the upper or lower
attenuation point.
The full frequency response equation is a bit more complicated. Let me
know if you need it.
Ethan...
On Jan 6, 2005, at 18:59, Allan Hoeltje wrote:
Maybe I am just blind but I swear I can't find a nice conversion
formula to
go from Q to Bandwidth and Bandwidth to Q. Am I using the correct
terminology? I've Googled and looked in various books but draw a
blank.
-Allan
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