Output Rf Spectrum Measurement Description; How Is An Output Rf Spectrum (Orfs) Measurement Made - Agilent Technologies 8960 10 Series Reference Manual

Output RF Spectrum Measurement Description

Output RF Spectrum Measurement Description

How is an output RF spectrum (ORFS) measurement made?

ORFS is a narrow-band measurement that provides information about the distribution of the mobile station
transmitter's out-of-channel spectral energy due to modulation and switching as defined in ETSI 05.05,
section 4.2.1 and ETSI 11.10, section 13.4.2.
The test set's measurements include both ORFS due to modulation and ORFS due to switching. Switching and
modulation measurements may be performed from the same burst, if the user requests both modulation and
switching results at the same frequency offsets measurement throughput is improved. Measurements are
made using a 30 kHz IF bandwidth, 5-pole synchronously tuned filter.
ORFS due to modulation measures out of channel interference during the useful part of the burst excluding
the midamble. The measurement returns relative results in (dB) using the power in a 30 kHz bandwidth at
zero offset as the reference. The user may set from 0 to 22 offsets.
ORFS due to switching measures out of channel interference over the entire burst, plus up to 10 additional
bits on either side of the 147 bit wide normal burst. The measurement returns absolute power results (dBm)
for each offset indicating the maximum value over the entire burst. The user may set from 0 to 8 ORFS due to
switching offsets.
The number of measurements to be averaged for each offset may be different. The test set internally controls
all other aspects of the measurement, including calibration, there is no user calibration required.
TX power (average power), 30 kHz bandwidth power at zero offset, ORFS due to modulation average power,
and ORFS due to switching maximum power are included in an ORFS measurement, when both modulation
and switching measurements are made. (TX power is performed using the same method as the "Transmit
Power Measurement Description" on page 106, which synchronizes the measurement with the burst
amplitude).
ORFS due to modulation
When multiple offsets for the ORFS due to modulation measurement are set, the DSP averages the power
across the appropriate time segments (40 bits) of the burst with a 30 kHz resolution bandwidth, 5-pole,
synchronously tuned filter placed at the center frequency of the burst and compares it to a time segment of the
response of the same filter placed at some frequency offset. The result is a relative power measurement using
the 30 kHz bandwidth power at zero offset as a reference. For each user specified offset, the DSP retunes the
filter and measures the 30 kHz bandwidth power and compares it to the reference, giving a relative power
measurement of signal power over the entire burst. The DSP processes the data and makes the results
available to the user. The 30 kHz bandwidth power at zero offset is measured only if the user requests at least
one ORFS due to modulation measurement.
For offsets up to 1.799999 MHz, an ORFS due to modulation measurement uses the 30 kHz resolution
bandwidth filter required in GSM 05.05. At 1800 kHz offset frequency the ORFS due to modulation
measurement is made using 30 kHz resolution bandwidth filter, not the 100 kHz resolution bandwidth filter
required by ETSI.
The ORFS due to modulation measurement measures both the front and back data portions of the burst.
Measurements occur from bit 15 to 60 and from bit 87 to 132. GSM 11.10 recommends that this measurement
be performed on only the back section of the burst. Measuring both the front and back of the burst has the
speed advantage of providing two modulation measurements per burst.
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