120 Chapter2
Making Measurements
Example 9: Adjacent Channel Power Measurement
Now that the parameters are set, you can activate the measurement.
1. Press
AUTO ACP MEASURE to activate the measurement. The
measured values are displayed in the upper left part of the graticule.
2. Press VIEW TBL TRAC so that table (TBL) is selected. The display will
change from showing the signal trace to showing a table of the ACP
measurements.
PDC Measurements of Mobiles According to the
RCR-27B Standard
The following information is applicable as of September 1993. The
two-bandwidth method, as described in standard RCR-27B, was not
strictly followed by Agilent Technologies in the development of the
built-in adjacent channel power functions (ACP). We believe that
following the standard exactly as written will not make the intended
measurements. If you are not familiar with the standard, you may want
to skip over the following paragraph and proceed to the final paragraph
in this section.
One example of the differences between the standard and the Agilent
Technologies implementation is that the standard calls for 10 kHz/3
kHz resolution bandwidths and the implementation uses 3 kHz/1 kHz
resolution bandwidths. This is because a 10 kHz resolution bandwidth
is not adequatelyselective for measurements. Another difference is that
the ratio M
r
in the implementation is compensated to account for the
fact that the peak response to noise exceeds the average response to
noise by an amount that depends on the product of the noise bandwidth
and the observation time (the burst width). Without this compensation,
the two-bandwidth method did not effectively separate impulsive from
noise-like power. There are other minor differences between the
standard and the implementation as well.
The most significant difference is the way that the standard calls for
measuring the ratio of the power in the adjacent channels to the main
channel. The standard measures the power in the adjacent channels
using a peak detector, and computes its ratio to the average power in
the main channel when "on," measured with a power meter. The Agilent
Technologies implementation takes the ratio with the power in the
main channel measured in the same way as the power in the adjacent
channels. We believe that this latter method provides a more
meaningful ratio and meets the intention of the standard. However, the
Agilent Technologies implementation results in an ACP ratio that is
7.25 dB more negative than the standard method. This is due to the
difference between measuring power of a noise-like signal with a peak
detector versus using a true averaging power detector.
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