Making an Average Power Measurement

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 and 8481A 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 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"

NOTE: Connect the Power Meter as close as possible to the power amplifier/duplexer output. Do not use a coupled port. The levels of the sensors do not function well at the levels provided by a coupled port.