field test unit no 001 "model T"

[Aziz]

SAT is Self Adjusting Threshold ......my implementation was a digital version of the differential integrator. It consists of a fast and slow integration of the incoming ADC values followed by a simple subtraction. The output converges to zero so dc offsets are removed .... This means if you don't move the detector you will only be integrating the noise from the front end.However this method integrates all the wideband energy it does not resolve other factors that are absolutely critical like ground response.
Moodz

Thanks. I know now, what you are meaning with SAT.
Aziz

[moodz]

I don't integrate in the dsp ... I calculate the peak and average sum of magnitudes of the filtered baseband spectrum ... The demod low pass has already done the "integration" to remove non target modulation energy. Works the same as a radio ...where you don't integrate either. Integration is a method of filtering the baseband ...ie target signal ...but if you are already at baseband then integration is not required.
Moodz

Actually the sum of magnitudes on the filtered spectrum could be classed as a form of integration ...up to your own personal interpretation

Moodz

[moodz]

Hi Moodz,

trying to figure out, what SAT was or meant to.

What is SAT???
Aziz

SAT is Self Adjusting Threshold ......my implementation was a digital version of the differential integrator. It consists of a fast and slow integration of the incoming ADC values followed by a simple subtraction. The output converges to zero so dc offsets are removed .... This means if you don't move the detector you will only be integrating the noise from the front end.However this method integrates all the wideband energy it does not resolve other factors that are absolutely critical like ground response.
Moodz

[moodz]

In the frequency domain (FD) we integrate digitally over the FD response. Integration is an essential part of "collecting" all the spectral energy of the response. Particularly, if we have a wide band response.

If we do all the digital demodulation in software, we don't need analog integrators anymore.

Aziz

I don't integrate in the dsp ... I calculate the peak and average sum of magnitudes of the filtered baseband spectrum ... The demod low pass has already done the "integration" to remove non target modulation energy. Works the same as a radio ...where you don't integrate either. Integration is a method of filtering the baseband ...ie target signal ...but if you are already at baseband then integration is not required.
Moodz

[Aziz]

Hi Moodz,

trying to figure out, what SAT was or meant to.

What is SAT???
Aziz

[Aziz]

This is correct ... however ... integration is a time domain method ... it can be done post ADC ... but as Aziz said the frequency domain is where the action happens. That is not to say that integration is not a useable method ... it may not be optimal.

moodz.

In the frequency domain (FD) we integrate digitally over the FD response. Integration is an essential part of "collecting" all the spectral energy of the response. Particularly, if we have a wide band response.

If we do all the digital demodulation in software, we don't need analog integrators anymore.

Aziz

[moodz]

moodz,

so with a sampling rate of 192 khz, would equal a sample every 5.2 us, so our sampling window would have to be 26 us wide to sample 5 times, so we'll still need some sort of integrator to help out , would this be correct ?

which adc chip for the 192 Khz?


Philip

This is correct ... however ... integration is a time domain method ... it can be done post ADC ... but as Aziz said the frequency domain is where the action happens. That is not to say that integration is not a useable method ... it may not be optimal.

moodz.

[moodz]

It's a DAC only!!! I need ADC too.
Sad.
Aziz

bugga ...back to 24 bits again. LOL

[hdphilip]

moodz,

so with a sampling rate of 192 khz, would equal a sample every 5.2 us, so our sampling window would have to be 26 us wide to sample 5 times, so we'll still need some sort of integrator to help out , would this be correct ?

which adc chip for the 192 Khz?


Philip

[Aziz]

Dont forget the bacteria$hit nuggets with this card .... item no 220896231564 on ebay.

384 Khz sampling at 32 bits theres heaps of others too and the price is not too much for a high end card ( around $150 )

moodz.

It's a DAC only!!! I need ADC too.
Sad.
Aziz

[Aziz]

Dont forget the bacteria$hit nuggets with this card .... item no 220896231564 on ebay.

384 Khz sampling at 32 bits theres heaps of others too and the price is not too much for a high end card ( around $150 )

moodz.

Thanks Paul,

haven't seen it yet. That would make UD of the UD detectors.
*LOL*
ASIO interface is nice and offers a very low latency interface.
Aziz

[moodz]

Hi all,

to give hdphilip an idea:
I'm using the second option with the sound card solution:
multichannel (dual-channel)"Fast demod" with 96 kHz sampling rate at 24 bits

When I get the 192 kHz sound card, it will support it as well of course. It will help to find easier the fly$hit targets.

Aziz

Dont forget the bacteria$hit nuggets with this card .... item no 220896231564 on ebay.

384 Khz sampling at 32 bits theres heaps of others too and the price is not too much for a high end card ( around $150 )

moodz.

[Aziz]

Hi all,

to give hdphilip an idea:
I'm using the second option with the sound card solution:
multichannel (dual-channel)"Fast demod" with 96 kHz sampling rate at 24 bits

When I get the 192 kHz sound card, it will support it as well of course. It will help to find easier the fly$hit targets.

Aziz

[moodz]

Are you guys talking about this or something else ??

http://uk.farnell.com/digilent/chipk...ard/dp/1893211

Thats the one. There is also a MAX32 version for more money and more memory.

[moodz]

moodz

what kind of sampling rate are you getting? and do you plan on using all of the adc channels?

philip

The sample rate can be anything you want from a few hertz to mega hertz ... its not the sample rate that matters its where and when you sample ... the maths is the same whether direct sampling with a fast ADC or demod and sample with slow ADC. The great revelation is that everyone has been barking up particular trees with all the techniques to date .... if you stand back and view the whole forest ( with a sprinkle of DSP) you can see all the detail of all the trees at the same time.

To answer your question ...there are main 3 sampling rates I will investigate ... dependant on front ends, time and funds available.

1. multichannel "Slow demod" with 8 Khz to 100 Hz sampling at 24 to 31 bits resolution.

2. multichannel "Fast demod" with 192 Khz sampling at 24 bits.

3. multiplexed "Fast direct sample" with 4 Mhz sampling at 24 bits.

1. is the cheapest and simplest to implement.
3. is the most expensive.

moodz