I'm currently working on a passive sonar project.
My goal is to acquire signals of 4 or 6 mics and compute the DOA with estimators such as MUSIC.
I cannot acquire more mics as the compute will be way too complicated.
I made a first board with AD1974 (so 4 mics), but results are quite disappoing : the DOA is not correct, due to signal acquisition problems.
I made simulation programs on computer, everything is fine, but not with acquired signals.
Looks like the pases are not preserved, and looking at the datasheet i cannot find if there is a simultanous sampling on this chip. does it ?
(I should notice : each signal is filtered to conserve only frequencies from 800Hz to 2 Khz)
My mics are not perfect too but i'm concerned about the ADC.
i am then looking for a simultanous sample ADC with the following characreristics :
- DSP interface (SPORT or parallel)
- around 150k to 250 K samples /sec/ channel
- 12 to 16 bits
- autonomous that is should send to DSP data without DSP work (DMA)
- I don"t really need a ADC with PGA as i automatically scale signals after acquisition.
The AD1974 was good for this as it sends data without any DSP intervention, but with the problems of phase.
Looking at other ADC (like AD7656), i need to trigger every conversion from DSP and then read them. This is complex and should lead to DSP work...
Do you have such ADC for this application ?
I saw ADC for imaging but they are quite expensive and way too fast for me.