6GHz BW, but only 1.6Gsps, I thought you had to have 3x-5x sampling for accurate BW?

Thread Starter

ballsystemlord

Joined Nov 19, 2018
149
Hello,
I like to browse the electronics websites for fun. I noticed this new part, ADC09SJ1300AAV . It's quoted as having a sampling rate of 1.3Gsps, and a BW of 6GHz on the product page and in the datasheet.
Now in seeking to buy an oscilloscope, I was warned that you have to have 3x-5x the sampling rate in order to get a certain BW, baring using interpolation or something like that.

So what's going on here?
Am I misreading something?

Thanks!
 

MrChips

Joined Oct 2, 2009
30,458
Simple answer. This is the ADC component, not a complete oscilloscope.

The specs give the sampling rate of 1.3Gsps. This means that the Nyquist limit is half of that.
It is good to know that the ADC bandwidth is not a limiting factor.
 

ronsimpson

Joined Oct 7, 2019
2,890
you have to have 3x-5x the sampling rate in order to get a certain BW
That is true for a one shot capture. If the signal you are looking at repeats you can see much faster signals that the sampling rate.
If you have a 6ghz band with ADC and you are sampling at 1ghz, then you will need to see 10 to 20 samples to get a good looking picture. The way this is done is, first sample as fast as possible after the trigger. Next pass you delay 100pS and start sampling, with each pass you delay another 100pS. After 10 reads you have data that looks just like you samples at 10ghz.
 

MrChips

Joined Oct 2, 2009
30,458
This is how sampling oscilloscopes worked, long before single event capture came along.
The time sweep would delay the acquisition by picoseconds on every sweep and thus was able to build up a picture of GHz waveforms.
 
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