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Thread: Infiniium software BW is very slow ...


Permlink Replies: 2 - Pages: 1 - Last Post: Jul 8, 2012 1:07 AM Last Post By: Guest Threads: [ Previous | Next ]
Guest
Infiniium software BW is very slow ...
Posted: Jul 2, 2012 1:46 AM
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Hi,

Sorry for my poor english.

I have one Oscilloscope MSO9404A 4 GHz, 20 GSa/s. Very often I do not need all the bandwidth (4 GHz) of the oscilloscope to effetture measures, but much less. To decrease the noise, I use the "Bandwidth Limit" but it's is very very slow. For 50 MHz, 100MHz, 200Mhz, 500MHz it is unusable, the filtering is done in software and it's very slow.

In recent firmware (Ex: 3.50.0003) provides a hardware limitation of the band. Using this mode, the slowdown is not present but there is only a limitation to 20 MHz. Agilent can not implement even 50 MHz, 100 MHz, 200 MHz, 500 MHz ?



Thanks very much.

secureasm
algoss


Posts: 602
Registered: 11/03/06
Re: Infiniium software BW is very slow ...
Posted: Jul 4, 2012 12:22 PM   in response to: Guest in response to: Guest
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The 20MHz HW BW limit is a relic from before my time. Something like that has been part of scope HW for a very long time. The 9000 series scopes are the highest BW scopes that have that capability, that I'm aware of. Adding other bandwidth options could certainly be done, but would require a multi-path switch in an input path that also wants to get to 4GHz, so that's probably not going to happen.

The processing time necessary to do a SW filter is a function of the ratio between the sample rate and the requested BW. The lower the BW, the more taps required, and the longer the processing time. Lower sample rate - fewer taps.

Here's my recommendation:
  • Use a Low-Pass filter function rather than InfiniiSim. You'll have a lot more control over the filter parameters.
  • Reduce the sample rate when you're filtering. If you want a 100MHz filter, for example, reduce the sample rate to 1GHz or maybe even 500MHz. That will reduce the filter processing time by a factor of at least 20.

Let me know how you make out.

Al
Guest
Re: Infiniium software BW is very slow ...
Posted: Jul 8, 2012 1:07 AM   in response to: algoss in response to: algoss
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Hi,
algoss wrote:
The 20MHz HW BW limit is a relic from before my time. Something like that has been part of scope HW for a very long time. The 9000 series scopes are the highest BW scopes that have that capability, that I'm aware of. Adding other bandwidth options could certainly be done, but would require a multi-path switch in an input path that also wants to get to 4GHz, so that's probably not going to happen.

Also I think it's something unlikely, however a band limit to 100 or 200 MHz could be useful instead of 20 MHz.

algoss wrote:
The processing time necessary to do a SW filter is a function of the ratio between the sample rate and the requested BW. The lower the BW, the more taps required, and the longer the processing time. Lower sample rate - fewer taps.

It's a true, but in some cases you can not compromise, high sample rate with low BW (< 4Ghz), we are not at the LHC.
algoss wrote:
Here's my recommendation:
  • Use a Low-Pass filter function rather than InfiniiSim. You'll have a lot more control over the filter parameters.

Low pass filter work very well thanks for your suggestion.
algoss wrote:
  • Reduce the sample rate when you're filtering. If you want a 100MHz filter, for example, reduce the sample rate to 1GHz or maybe even 500MHz. That will reduce the filter processing time by a factor of at least 20.

I Try even this solution.

Thanks very much.

secureasm

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