Technical data

Chapter 6 111
Channel Analyzer Measurements
Making Adjacent Channel Power (ACP) Measurements
Channel Analyzer Measurements
Making Adjacent Channel Power (ACP)
Measurements
The adjacent channel power (ACP) measurement is also referred to as
the adjacent channel power ratio (ACPR) and adjacent channel leakage
ratio (ACLR). We use the term ACP to refer to this measurement.
ACP measures the total power (rms voltage) in the specified channel
and up to three pairs of offset frequencies. The measurement result
reports the ratios of the offset powers to the main channel power.
The measurement results can help you determine whether the power is
set correctly and whether the transmitter filter is working properly.
Once you have set the limits, you can easily see whether a test falls
within those limits using the mask feature and the color-coded metrics.
You can measure the adjacent channel power on one to three adjacent
channels on each side of your center channel in the CDMA, TDMA,
UMTS (W-CDMA), GSM EDGE and GPRS, AMPS, NMT-450, Tetra,
and iDEN channel bands.
CAUTION When measuring multiple adjacent channels, the combined channel
power must not exceed +33 dBm at the RF Input.
CAUTION The maximum power for the RF Input 50 Ω is 33 dBm (2 W). When
directly coupled to a transmitter, the analyzer can be damaged by
excessive power applied to any of these ports.
To prevent damage in most situations when you directly couple the
analyzer to a transmitter, connect a high power attenuator between the
analyzer RF Input 50 Ω and the transmitter.
NOTE For complex modulation such as CDMA, W-CDMA, GSM, the frequency
error measurement is not accurate.
The following example shows how to make an ACP measurement on a
W-CDMA base station signal broadcasting at 1.955 GHz.
Step 1. Connect the RF Output of the signal generator to the analyzer
RF Input 50 Ω as shown in Figure 6-1.