Q
I have a question relating to the operation of the AD73322L frequency response.I am testing the device with Sine wave tones ranging across the voice band
between 300Hz and 3400Hz and
Am finding that with a sampling rate of 16Khz, I am getting a 25% reduction in
output at 3400 compared
To 300Hz.
Is this attenuation the correct operation of the device? I was expecting a flat
response.
Are there any setings in the registers which affect the frequency response?
I found that 8Khz sampling gave distortion to the wave at 3400Hz so increased
to 16Khz.
A
This is actually the correct or expected frequency response of the device. Ituses a Sinc^3 filter to provide low group delay - however this filter response
is quite "soft" with roll-off in the pass band that continues into the
transition band.
If the device is being used with a DSP as is normally the case, a Sinc^3
compensation filter operating at 16 kHz with decimation to 8 kHz can provide a
flat response out to 3400 Hz and provides a sharp transition band.
The other alternative is the AD74111 which is a mono codec but has a more
traditional filter which gives flat pass band response and sharp transition
band.