3Scan On A Fixed Frequency In The Time Domain - R&S ESU Series Operating Manual

R&S ESU
Frequency range
9 MHz ... 15 MHz
15 MHz ... 45 MHz
45 MHz ... 70 MHz
> 70 MHz
Table 4-2
The A/D converter has 14 bit resolution, which in combination with the built-in prese-
lector allows the high dynamic range which is needed for compliance with CISPR
16-1-1.
The prescan is used to get a detailed overview of the emission spectrum. It normally
occupies the longest time of the whole emission test. Using partial fast fourier trans-
form (FFT) of frequency sections, this time is reduced by factors. The prescan result
is then analyzed and the critical frequencies can be determined. On the critical fre-
quencies, if further maximization with antenna mast and turntable movement is
needed, the R&S ESU can be used in its conventional measurement function with
quasipeak and/or average detection to provide a measurement result which fully
complies with CISPR 16 standards.
4.5.5.3 Scan on a Fixed Frequency in the Time Domain
It is also possible to carry out the scan in the time domain, i.e. at a fixed frequency.
Time domain analysis is generally used to examine the time characteristics of inter-
ferences. Evaluating the detected voltage with an oscilloscope is useful in order to
correctly set the receiver measurement time. By doing so, you can determine
whether and how strongly a narrowband interference fluctuates and whether it is
amplitude-modulated or pulsed. You can also determine the pulse rate of a broad-
band interference. You can set the measurement time to a value that is greater than
or equal to the reciprocal of the pulse rate.
Thermostat-controlled, software-controlled and other electrically controlled instru-
ments generate discontinuous interferences. CISPR 14 and EN 55014 contain limit
values for RFI voltage with click rate weighting in the range 0.15 MHz to 30 MHz.
Clicks can usually be measured using click rate analyzers. However, a factor that is
often critical in click rate measurements is the occurrence of successive pulses
whose individual pulse heights cannot be exactly assigned by using the time con-
stants of the quasipeak weighting and can thus lead to the limit value being
exceeded.
Time domain analysis can determine the pulse height and duration, which can be
useful in such cases. It meets the requirements of CISPR 16-1 with regard to accu-
racy of the pulse duration measurement when the pulse duration is 10 ms and
longer. Triggering can be performed internally – level set with display line – or exter-
nally with a TTL level.
The result memory capacity is 2.000.000 measured values per trace in time domain
analysis. The measured values are stored internally and can, for example, then be
analyzed by zooming in on them with the marker. At a measurement time of 5 ms
per measured value, the memory depth is large enough to record the peak value
and quasipeak value continuously for two hours. Thus, measurement objects such
as washing machines can be evaluated for click interferences.
Operating Manual 1302.6163.12 - 03
Max. Resolution
Bandwidth
120 kHz
200 kHz
500 kHz
1 MHz
Frequency range vs. limitation of resolution bandwidth and FFT width
Instrument Functions
Receiver Mode
FFT width
1 MHz
2 MHz
4 MHz
7 MHz
4.53