Understanding Filter Specs

[Vindhyachal.Takniki]

1. I have a filter specs which i need to implement. Specs are: (in inverted commas)

"When switch is pressed, the filter is included with range 10Hz-1000Hz and bandwidth of filter is 23% for broad band analysis"


2. I am using labview. I have placed a filter with below specs:
Mode: IIR filter
Order: 6
Type: bandpass
fl = 10Hz
fh=1000Hz
Topology: butterworth

3. In specs i didn't understand the bandwith thing:23%.
When already filter fl & fh are given, what is this 23%.
I think specs are misprinted.

[CoastalMaineBird]

Bandwidth is usually specifed as the frequency difference between the -3dB points (where the output amplitude is 0.707 the input amplitude).

You can specify it in Hz (kHz, MHz, etc.) - for a fixed frequency filter this might make the most sense.

Since you have a tunable filter, the bandwidth is specified as a percentage of the center point.

i.e., if your center is at 1000 Hz, then your -3 dB points should be 885 Hz (-11.5 %) and 1115Hz (+11.5 %).

If your center moves to 2000 Hz, your -3 dB points should be 1770 Hz (-11.5 %) and 2230 Hz (+11.5 %).

Either way, the width of the passband is 23% of the center frequency.

[billko]

What did this have to do with LabVIEW?