Radiated spurious emissions measurement by substitution method

The total power substitution method is a measurement approach preferred by FCC and other authorities for evaluating the radiated spurious emissions of an RF product. This paper reviews and discusses the setup and procedures for conducting radiated spurious emissions measurement by using this approach. Two estimation methods, the free space path loss (FSPL) method and the site attenuation method, are also presented and elaborated in the paper. With a given field strength of a spurious signal at the receiving antenna, its effective radiated power (ERP) and the required input power to the substitution antenna can be estimated beforehand to save testing time and efforts. The calculated results are compared with the measured ones from both broadband EMC antennas and tunable dipoles. The pros and cons of each method are addressed as well.