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Thread: CCDF SIGNAL ANALYSIS BW


Permlink Replies: 4 - Pages: 1 - Last Post: Oct 6, 2011 8:25 AM Last Post By: Leyo
Leyo

Posts: 63
Registered: 04/17/07
CCDF SIGNAL ANALYSIS BW
Posted: Sep 29, 2011 9:44 AM
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Hello,

This is has refernce to MXA (N9020A) CCDF measurement.
In CCDF measurement, what is the siginficance of Info BW?. Is is related to the RBW of the MXA? I read about an option to increase this infoBW or signal analysis BW to 40 MHz from 25 MHz.
Suppose I have 4 carrier WCDMA. spaced 5MHz apart. This signal will have 20 Mhz BW (BW od 5 MHz for each WCDMA). I should be able to analyze CCDF etc using 25MHz InfoBW, right?
sleithem

Posts: 25
Registered: 09/30/11
Re: CCDF SIGNAL ANALYSIS BW
Posted: Sep 30, 2011 4:45 PM   in response to: Leyo in response to: Leyo
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Hi,

In CCDF, the info BW is the BW used by the analyzer to generate the CCDF. The preset for the info BW is 5 MHz, but it can be modified by pressing the BW hard key in the CCDF measurement mode.
Therefore, given the entire 20 MHz W-CDMA signal that you have suggested, you would want to change the info BW to 20 MHz in order to obtain power level data for the entire signal. If you are interested in the power measurement for a single carrier with BW of 5 MHz, you would set the info BW to 5 MHz.
The limit of the info BW is based upon the analysis BW of the analyzer that you are using. If you have an analyzer with 25 MHz of analysis BW, the hard cap for the info BW will be limited to 25 MHz (and this would indeed be sufficient for the measurement that you have suggested).
Purchasing option B40 will allow you to increase the analysis bandwidth limit to 40 MHz, which will increase the hard cap for the info BW to 40 MHz.

Also, resolution BW is related to the BW of the IF filter, and not to the info BW.

Thanks, and Best Regards,
Leyo

Posts: 63
Registered: 04/17/07
Re: CCDF SIGNAL ANALYSIS BW
Posted: Sep 30, 2011 7:08 PM   in response to: Leyo in response to: Leyo
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Thanks. Still I am confused with the relation of Info BW and RBW.
Lets take a Wideband signal, say 25 MHz BW centered at 1842 MHz. Have selected the Infow BW as 25 MHz, but the RBW is only 10 MHz. Since the signal is first pass through the RBW of IF filter, it will get filtered by the RBW. So even though Info BW is 25 MHz, won't get the full signal statistics, right?.
sleithem

Posts: 25
Registered: 09/30/11
Re: CCDF SIGNAL ANALYSIS BW
Posted: Oct 3, 2011 5:09 PM   in response to: Leyo in response to: Leyo
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Hi again,

The info BW is independent of the resolution BW. You can think of it as a form of analysis BW. For example, since you have set the info BW to 25 MHz for your 25 MHz signal, the analyzer sweeps the full 25 MHz. This means that the IF filter with RBW of 10 MHz is swept through the entire 25 MHz. This is the same process that would be used to view the signal in swept analyzer mode with a span of 25 MHz and a 10 MHz RBW. However, in this case, the result is used to compute the CCDF. Therefore, although your resolution would be poor (due to the large RBW), you would still have a CCDF based upon the full 25 MHz span. To reveal more of the power variations and produce a more accurate CCDF, you could reduce your RBW sufficiently while maintaining the same info BW.

I hope that helps make the difference between RBW and info BW more clear.
Please let me know if you need more clarification or have additional questions.

Thanks,
Leyo

Posts: 63
Registered: 04/17/07
Re: CCDF SIGNAL ANALYSIS BW
Posted: Oct 6, 2011 8:25 AM   in response to: Leyo in response to: Leyo
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Very clear now....Thanks for your nice explanation.

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