In the documentation for the Keysight DSOX1204G, it has the interesting note for the sampling rate of:

2 GSa/s (half channels)
1 GSa/s (all channels)

So, if I use all 4 channels on the scope, I get GSa/s, and if I use only two channels I get 2 GSa/s. I would assume at the core of the scope there's some low resolution ADC with a convert line that is tied to a 1GHz signal. For the 2 GSa/s are they just tying two ADCs together at the inputs but putting the convert lines 180 degrees out of phase, or is it something more interesting?

  • 2
    \$\begingroup\$ Yes, current scopes work by having multiple slower rate ADCs (with fast analog bandwidth) which can cooperate to take samples at a higher rate for a given channel, or be assigned to different channels. For a given model (cost) you can operate it to maximize speed or channels, or you buy a different more expensive model with a different product of rate * channels. \$\endgroup\$ – Chris Stratton Jan 10 at 1:41

Daniel from Keysight here - this is a very common behavior for this range of oscilloscope. Essentially, manufacturers (like us) build out acquisition boards to handle two channels at a time.

So, a four channel scope has two acquisition boards*. When you use two channels on the same board, the ADC has to cut its sampling in half. It spends 50% on one channel and 50% on the other.

If you'd like to dig in more, I highly recommend this talk given by one of our ADC designers:


**Acquisition systems would be more accurate, as it's often just one PCB. However, each "path" will have chips/ASICs/ADCs/processors that handle two signals per chip.*

  • \$\begingroup\$ That seems to be it. I was just hoping for something more interesting. \$\endgroup\$ – b degnan Jan 17 at 17:04
  • 1
    \$\begingroup\$ Nope, sorry! Time domain interleaving :) \$\endgroup\$ – Daniel Bogdanoff - Keysight Jan 17 at 17:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.