Active Antennas and EIRP/TRP (in dBm)

Active Antennas and EIRP/TRP (in dBm)

Transmitter Patterns, EIRP, and TRP

The preferred test method for evaluating a “live antenna” or active transmitter performance, is far field power (EIRP) measurements. We use our calibrated chamber paths and positioners to map out your device’s EIRP in dBm. With this method, your pattern shows EIRP (apparent power) in hundreds of test directions. This type of pattern is a typical final test of a transmitter or transceiver with an integrated or attached antenna. Any issues with antenna performance or the matching network will be discovered. We will also calculate the Total Radiated Power (TRP) of your transmitter, based on the spherically integrated EIRPs in any 3D pattern.

TRP Example

The shape to the left is the EIRP pattern of a 2 Watt (+33 dBm) GSM cellular modem. The device is supposed to be omnidirectional, but the pattern shows otherwise. Also, this device has an FCC mandated maximum peak EIRP of 4 Watts (+36 dBm), which can be seen to be exceeded in the “-X axis” direction of the 3D plot. We also calculate Total Radiated Power (TRP) by integrating over the surface of the spherical pattern. Knowing your TRP along with your conducted launched power, allows antenna radiation efficiency to be calculated. Many modern “wireless” products seek ultra small antennas, and antenna+matching efficiencies can sometimes be very poor (10 to 20%).