3Measurement Example 3 - Measuring The Modulation Spectrum In Burst Mode With The Gated Sweep Function - Rohde & Schwarz R&S FSP Series Operating Manual

R&S FSP
2.5.3.3 Measurement Example 3 – Measuring the Modulation Spectrum in Burst Mode
with the Gated Sweep Function
Since transmission systems compliant to IS136 use a TDMA method, the adjacent
channel power must also be measured in burst mode. An IS136 TDMA frame is
divided into 6 time slots. Two of these slots are assigned to a subscriber. This
means that the ratio of transmit time to off-time for IS136 mobile phones is only 1:3
(e.g. time slots 1 and 4)
The R&S FSP supports the measurement of the adjacent channel power in the
TDMA mode with the Gated Sweep function.
Test setup with the R&S Signal Generator SMIQ:
Signal
generator
SMIQ
The R&S SMIQ has to be equipped with options R&S SMIQ-B10 or R&S SMIQ-B20
(modulation coder) and R&S SMIQ-B11 (data generator).
Option R&S SMIQ-Z5 is required to trigger the R&S FSP. This option is connected
to the R&S SMIQ's parallel output port. The BNC output Trigger 1 of the R&S SMIQ-
Z5 provides a TTL trigger signal on the rising edge of the IS136 burst, which is used
to start the R&S FSP sweep in the Gated Sweep mode.
The R&S FSP's IF power trigger is not suitable for IS136. It triggers on every
level edge of the input signal. Since the modulation of the IS136 signal causes
level dips even during the transmit burst, there is no way of ensuring that the
R&S FSP is only triggered on the burst edge.
Settings on signal generator R&S SMIQ:
Switch the signal generator to the IS136 burst mode (time slots 1 and 4 are switched
on, the other time slots are switched off).
The R&S SMIQ is set as follows to generate the signal:
Press the PRESET key.
Press the FREQ key and enter 850 MHz.
Press the LEVEL key and enter -20 dBm.
Press the RETURN key.
Select DIGITAL STANDARD using the spinwheel and press the SELECT key.
Select NADC using the spinwheel and press the SELECT key.
Press the SELECT key.
Select ON using the spinwheel and press the SELECT key.
Press the RETURN key.
Operating Manual 1164.4556.12 - 06
Trigger1
SMIQ-Z5
Par Data Output
RF Inp
FSP
Ext Ref Out
Measurements on Modulated Signals
Ext Gate/Trig IN
Ext Ref IN
Getting Started
2.37