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Making Measurements
Example 9: Adjacent Channel Power Measurement
P
is measured with the channel power function, using the
wide
same trace data as was used by the ACP measurement.
That means with the channel power bandwidth set to
(2×channel spacing + channel bandwidth), or 792 kHz.
The units should be W, mW, or a similar unit.
P
is the same as P
center
bandwidth should be equal to the channel bandwidth.
Use the same units as P
P
is measured in zero span with:
carr
Resolution bandwidth........................ ≥300 kHz
Video bandwidth ...................................... 3 MHz
Sweep time ............................................... 30 ms
Use the units you would like for the final answer, such
as nW.
For many users, the built-in ACP function without all the computations
gives useful information. To measure according to the standard
requires the computations shown above.
NADC Measurements of Mobiles According to the
IS-54 Standard
The following information is applicable as of February 1995. The IS-54
standard requires a measurement method that we call the gated
method. In order to make time-selective measurements, an external
TTL-type trigger input is required when using the gated method. If the
device under test does not have a trigger output, you can use the
Agilent 85902A burst trigger adapter to provide a trigger. This
accessory is connected to the signal directly (see Figure 2-56); it may be
more convenient for some users to connect the Agilent 85902A to the
second IF output (310.7 MHz) of a spectrum analyzer equipped with
Option 001. See Figure 2-57.
The IS-54 standard also requires that the received spectrum be
weighted in the same manner as it would be in a receiver. The
weighting function used is the root-raised-cosine weighting, with
parameters T and α. W is the weighting in dB. It is a function of ∆f, the
offset of the frequency of the spectral component from the center of the
channel. The relationship is as follows:
for all other ∆f W ∆f
122
except the channel power
wide
wide
1 α
–
for ∆f
≤
----------- - W ∆f
(
)
,
=
2T
α
1
+
for ∆f
≥
------------ - W ∆f
(
)
,
=
2T
1
1
(
)
×
,
=
10dB log
-- -
10
2
.
0dB
∞
– dB
π 2 ∆f T
(
)
–
1
–
sin
--------------------------------- -
2α
Chapter 2
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