Rohde & Schwarz R&S FSP Series, Руководство по эксплуатации

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Operating Manual 1164.4556.12 - 06 2.33
R&S FSP Getting Started
Measurements on Modulated Signals
Fig. 2-4 Repeatability of adjacent channel power measurements on IS95 signals in
the Fast ACP mode
The following figure shows the passband characteristics of the 30 kHz channel filter
in the R&S FSP.
Fig. 2.19 Frequency response of the 30 kHz channel filter for measuring the power in the IS 95
adjacent channel
ACPR IS95 Repeatability
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
10 100 1000
Sweep time/ms
S
ta
nda
rd dev
/
dB
Adjacent channels
Alternate channels Tx channel
Note on adjacent channel power measurements on IS95 base-station sig-
nals:
When measuring the adjacent channel power of IS95 base-station signals, the
frequency spacing of the adjacent channel to the nominal transmit channel is
specified as ±750 kHz. The adjacent channels are, therefore, so close to the
transmit channel that the power of the transmit signal leaks across and is also
measured in the adjacent channel if the usual method using the 30 kHz resolu-
tion bandwidth is applied. The reason is the low selectivity of the 30 kHz resolu-
tion filter. The resolution bandwidth, therefore, must be reduced considerably,
e.g. to 3 kHz to avoid this. This causes very long measurement times (factor of
100 between a 30 kHz and 3 kHz resolution bandwidth).
This effect is avoided with the time domain method which uses steep IF filters.
The 30 kHz channel filter implemented in the R&S FSP has a very high selectivity
so that even with a ±750 kHz spacing to the transmit channel the power of the
useful modulation spectrum is not measured.