Hi everyone,
When measuring the phase noise with E5052A, its units is dBc/Hz. But for spurs, there are two kinds of unit (dBc and dBc/Hz). If the unit dBc unit is chosen, the displayed spur level is correlated well with the spur level in the spectrum window. My question is what is the exact mathmetical relation between the two unit?
Any answers is appreciated!
-Ryan
When measuring the phase noise with E5052A, its units is dBc/Hz. But for spurs, there are two kinds of unit (dBc and dBc/Hz). If the unit dBc unit is chosen, the displayed spur level is correlated well with the spur level in the spectrum window. My question is what is the exact mathmetical relation between the two unit?
Any answers is appreciated!
-Ryan
During a phase noise measurement, the E5052A or B looks for data points that are significantly above the surrounding noise levels. This data is flagged as a spurious signal. It is also important to understand that although phase noise is displayed as noise power in a 1 Hz bandwidth, the analyzer does not actually measure using a physical 1Hz bandwidth filter. Particularly at large offset frequencies, the bandwidth is much larger than 1Hz. This allows measurement times to be much faster. It also means that the measured noise power is higher than would be measured if a 1 Hz bandwidth was used. We can correct for this power difference (normalize to 1Hz), since we know the actual measurement bandwidth.
When in phase noise mode, the E5052A/B can handle a spurious signal in 3 different ways:
1. normalized (dBc/Hz). The analyzer treats all signals as noise - a coherent signal is ignored and normalized as if it were noise
2. power (dBc) - when the analyzer finds a data point that trips the spur detector, this point is "un-normalized". That is, this spurious is displayed in its proper amplitude.
3. omit - when the analyzer finds a data point that trips the spur detector, this point is not displayed. The analyzer shows interpolated noise data for this point.
The power correction used for normalization is 10log(actual BW).
for example, if the PN was measured at a particular data point using a 30kHz bandwidth, the correction would be 10log(30000) = 44.8 dB.
If you change to "power (dBc)" mode, you would see a spur at this frequency increase in amplitude by 44.8dB.
In practice, the actual bandwidth used by the analyzer varies with offset frequency, and is not available to the user. Also, you can not directly control this value. So, this info is not of much direct use - unless you want to understand how the analyzer works.
As far as I understand - You explain here how is the measurement made by the Phase Noise application.
I want to measure phase noise using the regular spectrum analyzer mode (in order to find correlation between the modes).
What isn't clear to me is if the BW I should use is the res. BW at the spectrum mode or the BW that the Phase noise application uses ?
Just in case: I am using MXA N9020A
Thank you.
You will need to choose a bandwidth that is narrow enough to reject the carrier - the RBW can be wider at greater offsets from the carrier.
AN 150
http://cp.literature.agilent.com/litweb ... 2-0292.pdf
pages 65-68 has some hints when measuring noise