Hameg Instruments HZ530 Manual Del Usuario página 47

Will a spectrum analyzer allow me to make
sensible emissions measurements?
Does a spectrum analyzer's response to pulsed
interference influence the measurement result?
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tage of the HM5000 Spectrum Analyzer series is its fast sweep
rate. The display is "updated" every 23ms which allows very fast
tracking of the test signal.
The main problem with noise floor occurs when you make radiated
emissions measurements. Radiated emissions limits for residen-
tial, commercial, or light industrial environments with a 10-meter
separation between a unit under test and an antenna are 30 to
230 MHz for 30 dB uV/m, and 230 to 1000 MHz for 37 dB uV/m.
A typical maximum receiver noise floor is 1-5 dB uV, whereas for
a spectrum analyzer the noise floor is around 10-20 dB uV. Clearly,
sensible measurements at some frequencies are not easily obtained
with a spectrum analyzer because the noise floor is comparable
with the limit.
You can overcome this limitation by using a 3-meter test distance,
or by use of a pre-selector or preamplifier (which is built-in for
example in the E-Field probe of the HZ530) with the spectrum
analyzer. Each of these methods effectively increases the limit or
reduces the noise floor of the measurement.
On the other hand we observed in many cases clearly noticeable
radiation from the test receiver or measuring equipment itself.
Concerning this phenomena the HM 5000 series spectrum analyzer
has a big advantage due to its strictly analog design. There is no
self generated radiation measurable from the analyzer within its
own sensitivity range.
CISPR 16 contains a curve that defines how quasi-peak detectors
respond to a pulsed signal. The curve is based upon the signal's
pulse repetition frequency (PRF). For a 30MHz to 1000MHz radiated
emissions measurement, the measured value of the input signal can
potentially be reduced by a figure up to about 40dB. This number
is also known as the overload factor. The design of a compliance
receiver ensures this response. However, pulsed signals can over-
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