Intentional emitters above 2400 MHz: how best to measure the transmitted signal level for FCC Part 15 compliance

This paper investigates the commonly used methods for measurement of the intentional signal levels emitted by Part 15 radio frequency (RF) devices operating above 2400 MHz, and that have built-in antennas that are soldered directly to a printed circuit (PC) board and are not normally removable. In this paper, we look at what the Federal Communication Commission (FCC) rules really require, and the extent of the possible errors involved in the different ways of measuring the intentional signal fundamental and harmonics. The reliability of the measurements for preventing interference to licensed radio services maybe improved by making radiated emission measurements whenever possible to compare the maximum field strengths to the FCC field-strength limits; determine the transmitter output from the EIRP at the higher frequencies; and, apply the FCC guidance on measurements for direct sequence spread spectrum systems only to direct sequence spread spectrum transmitters.