Multifactor analysis of variance (ANOVA) investigation into GTEM to open area test site correlation for FCC Part 15 radiated emissions tests

The Gigahertz Transverse Electromagnetic Cell (GTEM) is gaining widespread acceptance in radiated emissions testing for electromagnetic compatibility (EMC). The FCC now allows for the data taken in the GTEM to be submitted as final compliance radiated data as long as the GTEM has proven to be correlated to a listed OATS for the product family under test. The correlation must be proven and filed with the FCC. The ability to take final compliance measurements in the GTEM can be instrumental in reducing the cycle time of the regulatory compliance approval process, which will lead to shorter time to market for the product. The Compliance Group at Motorola Paging in Boynton Beach, FL primarily tests small belt-worn pagers and their derivatives. A pager can easily fit into the 1 dB field contour region of a 5305 GTEM cell. The objective of this research was to investigate the correlation between the GTEM and the FCC-listed OATS to (1) reduce cycle time of regulatory compliance tests by qualifying the GTEM as an alternate EMC test site with the FCC and (2) to establish confidence that all emissions that are tested and passed in the GTEM will pass on the open area test site. For paging products, there are four primary contributors to variation in readings from GTEM to OATS: (1) unit-to-unit variation, (2) frequency of emissions, (3) product to product, and (4) the differences in the methods. A four-factor analysis of variance (ANOVA) experiment was designed to investigate the effects of these contributors.