UNAOHM
32
EP2500 (Rev. 0)
Faster access to the measurement is allowed by pressing the key
DIGITAL (35)
.
7.19.3
Carrier-to-Noise Ratio (C/N)
To measure the C/N ratio set the instrument to the measurement or expanded spectrum mode. Press
MORE
, then
C/N
. The measurement result appears on the top of the display (see
Figure 15
). To
alternately set the measurement of the analogue or digital carriers, press the multifunction key
ANLG
/
DIGI
. The key
CARR
/
NOISE
enables the Shaft Encoder and numerical keys
(8)
to alternately
set the carrier and noise frequency. The noise frequency should be selected close to the carrier but free
from any signal. To exit from the C/N mode, press
BACK
.
Figure 15
C/N ratio measurement display
Press
EXEC
to carry out the measurement.
If the measurement is not valid (for example, Noise is higher than Carrier) the value is substituted by
ERROR.
7.19.4
QPSK, QAM or OFDM Demodulator for Digital Signals
For the use of the QPSK card refer to section 9.1.1. For the use of the QAM card refer to section 9.1.5
and for the use of the OFDM card refer to section 9.1.3 in this manual.
7.19.5
QAM and OFDM CH BER Estimation
When either card (QAM or OFDM) is missing, the unit provides the operator with a channel BER
estimation for the missing digital signal.
Because BER depends on actual link quality such as C/N ratio, mismatching and interference found
throughout the link, the unit measures the actual C/N ratio from which it derives the BER considering
the modulation parameters as well. The unit can be set for BER estimation of both OFDM and QAM
signals depending on the card fitted.
To enter Channel BER estimation mode press
DIGITAL (35)
, then
BER
.
When either cards is missing from the unit, a menu pertaining to the missing modulating card will
appear on the screen for BER estimation.
7.19.5.1
OFDM CH BER Estimation
When an OFDM card is fitted inside the unit a display as per
Figure 16
will appear on the screen. The
measurement digits shown in square brackets in
Figure 16
will not appear in the actual display.
C/N
1740 SC0:6.50 pr 00
1750.2 13V k M20
EXEC
CARR
ANALOG
BACK
C/N: 21.5 dB