3-4 Chapter 3
Making GSM Base Station Measurements
Making the Output RF Spectrum (ORFS) Measurement
The output RF spectrum measurement consists of the following two
measurements:
• Output RF spectrum due to modulation.
For this measurement the average value during at least 40 bits
between bit 87 and 132 (approximately equivalent to the 50% to 90%
portion of the burst, excluding midamble) is retained. The vertical
lines mark the section of the burst over which the measurement is
made. If multiple bursts are examined, an average of the average
values is calculated. The relative power (difference between the
average power of the burst at zero offset and the average power of
the burst at the indicated offset) and the absolute power are
displayed.
• Output RF spectrum due to switching transients.
For this measurement the peak value of the burst is retained. If
multiple bursts are examined, then the maximum of the peak values
is retained. The relative power (difference between the peak power of
the burst at zero offset and the peak power of the burst at the
indicated offset) and the absolute power are displayed.
The GSM standard specifies the tests are run on specified offsets from
the carrier. The instrument identifies this as single offset, multiple
offset or swept modes. The measurement made in these modes is the
same, except for the following:
• Multiple offset mode automatically makes the measurement at all
the specified offset frequencies and lists the results in a table at the
end of the measurement.
• Swept mode makes the measurement in the frequency domain and
shows the GSM burst relative to the limits mask.
To Next Page
Loading...
Need help?
General
