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Adjacent Channel Power Measurement
Another common transmitter measurement is that of adjacent channel power ratio. This is
defined as the ratio of the amount of leakage power in an adjacent channel to the total trans
-
mitted power in the main channel. The current trend is to use this measurement to replace
the traditional two-tone intermodulation distortion (IMD) test for system non-linear behav
-
ior.
The specification for ACPR requires comparing the power in the RF channel to the power
at several offset frequencies. The result can be expressed either in power ratio or power
density. In order to calculate the upper and lower adjacent channel values, the Site Master
requires four parameters:
q
Main channel center frequency
q
Main channel bandwidth
q
Adjacent channel bandwidth
q
Channel spacing
Required Equipment
q
Site Master Model S114C or S332C
q
30 dB, 50 Watt, bi-directional, DC –18 GHz, N(m) – N(f), Attenuator
q
Test Port extension cable, Anritsu 15NNF50 – 1.5C
Procedure
Step 1. Using the test port extension cable and 30 dB attenuator connect the Site Master
to the appropriate transmitter test port. The measurement can be accomplished
with our without the 30 dB attenuator. The attenuator is recommended for addi
-
tional protection.
Step 2. Press the
ON/OFF key on the Site Master.
5-4
Chapter 5 Spectrum Analyzer Measurements
1.98 MHz 1.98 MHz
885 kHz 885 kHz
1.23 MHz
30 kHz
Figure 5-1. Example ACPR Specification