NF FRA5087, Instruction Manual

Page: 82 / 194

4.3 Integration
FRA5087
4-8
100 1k 10k 100k
-120
-100
-80
-60
-40
-20
0
Frequency(Hz)
G
a
in
(d
B)
Number of times of
integrations=1
Number of times of
integrations=100
Fig. 4-5 Effect of integration
b)
Automatic integration
Assume that the SN ratio is poor only for the limited frequency range within the range of
frequency sweep, and also assume that the number of times of integrations has been set
manually so that satisfactory measurement accuracy can be obtained in this limited frequency
range, then it comes that the required measurement time is excessively long in that
integration operation that are not necessary in the other part of the frequency range should
also be done.
The FRA5087 has a special capability called automatic (auto) integration, which provides a
capability of automatically setting integration times during the measurement. The use of
automatic integration capability will lead to automatic selection of optimum integration times
as well as reduction of the measurement period of time.
Set the analysis channel, which is
to be referred to for determining the integration count, to be focused, by [COHERENCE
MODE] of the [Measure][BASIC FUNCTION] menu. Select the coherence estimated value
(variance estimated value) of measurement data to be at “SHORT”(0.9) or ”LONG”(0.99) in
[MODE], and then repeat integration operations until the set value is satisfied. Note,
however, that the integration at a certain frequency will terminate when the number of times
of integration reaches the value set in [MAX INTEGRATION TIME].
The coherence estimated value (coh
2
) expresses a statistical cross characteristic between two
(2) varying signals and corresponds to the square of the cross correlation coefficients of
individual Fouler frequency components of the two signals. It is generally judged that
measurement data are more reliable when the coherence estimated value is closer to 1.0. (The
closer the chop to 1.0, the more reliable the measurement data.)