Rohde & Schwarz CMU-K20, Operating Manual

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CMU-K20/-K21/-K22/-K23/-K24 General Settings
1115.6088.12 3.7 E-10
mum and Max./Min. on the other hand, if the measurement extends over more
than one statistic count (repetition mode Continuous, measurement time longer
than one statistic count).
After evaluation of the different traces, the burst power is logarithmized and
plotted in a semi-logarithmic diagram.
The
Display Mode is set in the Control tab of the configuration popup-menus
assigned to the measurement groups Power, Modulation, and Spectrum.
Calculation of
average quantities
The Average traces in the Power, Modulation, and Spectrum menus are ob-
tained as follows:
Let c be the number of bursts forming one statistics cycle (one Statistic Count)
and assume that n bursts have been measured since the start of the measure-
ment. In calculating the
Average trace, the following two situations are distin-
guished:
n
≤≤≤≤
c Single shot measurement or continuous measurement during the
first statistics cycle: At each test point,
Average trace no. n is cal-
culated from Average trace no. n – 1 and Current trace no. n ac-
cording to the following recurrence:
) , , 1 ( ) (
1
) 1 (
1
) ( c n n Curr
n
n Avg
n
n
n Avg
K
= + −
−
=
The Average trace represents the arithmetic mean value over all
n bursts measured.
n > c Continuous measurement after the first statistics cycle: At each
test point,
Average trace no. n is calculated from Average trace
no. n – 1 and Current trace no. n according to:
) ( ) (
1
) 1 (
1
) ( c n n Curr
c
n Avg
c
c
n Avg
> + −
−
=
Scalar quantities are averaged in analogy to Average traces. The formulas hold
for n = 1 where the average trace becomes equal to the current trace (statistics
off).
Calculation of
statistical quanti-
ties In Power and Modulation measurements the statistical functions Average, Mini-
mum, Maximum and Minimum/Maximum are applied to a set of test points de-
pending on two independent parameters:
•
The time, i.e. the abscissa values t
i
, i ranging from 1 to the total number of
test points comprising the trace.
•
The burst number ranging from 1 to the number n of the current burst.
The result of the statistical operations depends on the parameter range consid-
ered and – in the case of statistics functions evaluated over several parameters
– on the order of evaluations. This is why the definition of statistical quantities
deserves some attention and is explained in the relevant sections in chapter 4.
Some particular examples are:
1. In the Power menu, the quantity Average Burst Power denotes the average
power of the current burst. i.e. the arithmetical mean value of all test points t
i
located in the useful part of the burst (lower area 1 in the power template in
chapter 4).
2. In the Modulation menu quantities such as the Frequency Error , Phase Error
RMS, Phase Error Peak etc. are first calculated for the current burst and
entered in the Current column of the output table . The results in the Mini-
mum/Maximum column correspond to the extreme value of the Current re-
sults calculated over all bursts measured. The results in the Average column
correspond to the average of the Current results calculated according to the
prescription in paragraph Calculation of average quantities above.
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