Technical data

380 Chapter 13
Power Meter
Making an Average Power Measurement
Power Meter
Making an Average Power Measurement
Average power measurements provide a key metric in transmitter performance.
Transmit power must be set accurately to achieve optimal coverage in wireless
networks. If transmit power is set too high due to inaccurate power measurements,
undesired interference can occur. If transmit power is set too low, coverage gaps or
holes may occur. Either case affects system capacity and translates into decreased
revenue for service providers.
Average power can be measured while the base station is active for the channel of
interest. All other channels should be inactive. Average power is a broadband
measurement, so if there are other signals present it will also measure their power
contributions.
NOTE The test set supports the Agilent 8482A, 8481A, and N8481A/N8482A with Option
CFT power sensors.
CAUTION The maximum power for the RF In (Port 1) and RF Out/SWR (Port 2) ports is
+20 dBm (100 mW). When using the 8481A/8482A or N8481A/N8482A with
Option CFT Power Sensors, the maximum input power applied to the Power Sensor
is +24 dBm (300 mW). When using the 8481D Power Sensor, the maximum input
power is +20 dBm (100 mW). When directly coupled to a base station (BTS) or
Access Network (AN), the test set can be damaged by excessive power applied to
any of these three ports.
To prevent damage in most situations when you directly couple the test set to a base
station, use the high power attenuator between the test set and the BTS.
NOTE If you suspect other signals may be present, it is recommended that you turn off all
the other channels and measure average power on the signal of interest alone.
Another option is to measure channel power (which is inherently less accurate), but
filters out all other channels (signals). You can measure channel power for CDMA
using the CDMA Analyzer or CDMA Over Air tool. For other modulation formats,
use their respective analyzers (that is, GSM, 1xEV-DO, or W-CDMA) or measure
channel power using either the spectrum analyzer or the Channel Scanner tool.
NOTE If you have not done so, measure the loss of the high power attenuator by using the
Insertion Loss measurement. Refer to “Two Port Insertion Loss” on page 123.