R&S FSQ Signal Analyzer - Rohde & Schwarz

R&S FSQ Getting Started
Standard dev /dB
0,35
0,3
0,25
0,2
0,15
0,1
0,05
0
Tx channel
ACPR IS95 Repeatability
Measurements on Modulated Signals
Alternate channels
Adjacent channels
10 100 1000
Sweep time/ms
Fig. 2.25 Repeatability of adjacent channel power measurements on IS95 signals in the
Fast ACP mode
Note on adjacent channel power measurements on IS95 base-station signals
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 resolution
bandwidth is applied. The reason is the low selectivity of the 30 kHz resolution
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 FSQ 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.
The following figure shows the passband characteristics of the 30 kHz channel filter
in the R&S FSQ.
2.38 Operating Manual 1313.9681.12 - 01