Agilent Technologies 54503A Podręcznik Użytkownika Pobierz pdf (Strona 122)

100

101

122 Chapter2

Making Measurements

Example 9: Adjacent Channel Power Measurement

wide

is measured with the channel power function, using the

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.

center

is the same as P

wide

except the channel power

bandwidth should be equal to the channel bandwidth.

Use the same units as P

wide

carr

is measured in zero span with:

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 ∆f

1 α–

------------

W ∆f()0dB=,≤

for ∆f

1 α+

-------------

W ∆f() ∞–dB=,≥

for all other ∆fW∆f()10dB log

---





π 2 ∆fT 1–()

2α

----------------------------------





sin–=,

1 2 ... 117 118 119 120 121 122 123 124 125 126 127 ... 715 716

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