Application Example: GSM AM Suppression Test
R&S
®
SMW-K550
15
User Manual 1178.3263.02 ─ 01
Within the available BS RF bandwidth, the up to 4 wanted signals are allocated sym-
metrically around the center frequency. The interfering signal is sent on the center fre-
quency. The inner two wanted signals are spaced at 6 MHz away form the interferer.
The remaining wanted signals are located at the edges of the maximum supported
bandwidth and at least at 600 Hz away form the inner two.
The frequency distribution is illustrated on
Figure 4-2
.
Figure 4-2: Frequency allocation of the wanted and the interfering signals
GSM frequency bands and channels
According to
TS 51.021
, a GSM band contains a set of adjacent channels, each with a
bandwidth of 200 kHz. The channel numbers and the assignment between channel
numbers and frequencies are band-specific.
In all frequency bands, the downlink frequencies are higher than the corresponding
uplink frequencies. The difference between downlink and uplink frequencies is termed
the duplex spacing; it is also band-specific.
For an overview the GSM bands with their channel numbers and the downlink and
uplink center frequencies, see
TS 51.021
.
Cabling and synchronization issues
As a rule, always use short RF cables of equal length. If a trigger signal is required,
feed the BS signal to the R&S
SMW.
In test setups with more than one instrument, all instruments usually use the same ref-
erence clock. While testing BS receivers, the clock signal is provided by the DUT.
Additional reference frequency is not required.
4.3 How to Generate Signals for GSM AM Suppression
Tests
The following is an example on how to select the correct system configuration and con-
figure the instrument in general. Not all GSM-related settings configurations are shown.
The example uses predefined settings and PN sequences as data source; channel
coding is not used.
How to Generate Signals for GSM AM Suppression Tests
