Trouble Shooting Guide, Advanced
4/00021-3/FEA 209 544/25 C
Ericsson Mobile Communications AB
43(78)
The transmitter RF-powerlevel as a function of time, it can be seen in Fig. 13.1.
Fig. 13.1
Time mask for normal duration burst 147 bits 542.8 µS.
Thereisalsoashorteraccess burst 87 bits 321.2 µS. (not present).
Both have the same time period-length for the RF-level shift.
According to the principle of TDMA and the bursty nature of the signal, the outputRF
spectrum results from two effects:
The RF-power level shift at upramp and downramp. Designated: Spectrum due to Switching
Transients.
The digital modulation process. Designated: Spectrum due to the Modulation and wide
band noise.
13.2 Consequences in spectrum and testing
In digital TDMA-systems as EGSM 900 and GSM1800 the transmitted RF-signal is repeated
over time, in a synchronous time pattern.
The active time intervals in the system, for the transmitter and the receiver respectively, are
called Timeslot (TS).
In the system, the timeslots are allocated on RF-carriers, in two frequency duplex at an
Absolute Radio Frequency Channel Number (ARFCN).
This combination of time and frequency TS / ARFCN, is called a physical channel.
The system also has the ability to change the ARFCN each time the physical channel is
opened, in a programmable so called frequency hopping pattern controlled by the switch.
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