Chapter 3 71
Making EDGE (with GSM) Measurements
Making the Output RF Spectrum Measurement
Making the Output RF Spectrum
Measurement
Purpose
The Output RF Spectrum measurement is the EDGE (with GSM)
version of adjacent channel power (ACP). Either a single offset is
measured with corresponding traces or up to 15 offsets are measured
and a table is displayed.
The output RF spectrum measurements determine the spectral energy
emitted into the adjacent channels. Excessive amounts of energy
spilling into an adjacent frequency channel could interfere with signals
being transmitted to other MS or BTS. The measurements are divided
into two main groups: spectrum due to the 0.3 GMSK modulation and
noise, and spectrum due to switching transients (burst ramping).
Since GSM is a TDMA format, RF power is being switched on and off
depending on whether the actual burst is being transmitted. The
switching of power causes spectral splatter at frequencies other than
that being transmitted by the carrier. Fast transitions in the time
domain causes switching transients that have high frequency content
associated with them.
NOTE The default output RF spectrum measurements do not perform tests at
frequency offsets greater than 1800 kHz from the carrier.
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