To conduct an effective radiated spurious measurement, the frequency spectrum to be investigated, the limits to be applied, the equipment setup to be used and the testing procedures to be followed are four important aspects which need to be known or investigated before the actual testing starts. Each of the above aspects is addressed in the following. Also discussed are two commonly used power units, EIRP (Equivalent isotropically radiated power or, alternatively, Effective isotropically radiated power) and ERP.
Many countries, including the United States, require the measurement of radiated spurious emissions of an intentional radiator as part of its regulatory certification. Spurious emissions of a radiator are unwanted emissions on frequencies which are outside the necessary bandwidth during its normal operation excluding out-of-band emissions. Normally, the limits of spurious emissions are specified in terms of field strength, or peak power, or mean power attenuation relative to the mean output power of a transmitter [1-5]. As a result, the radiated spurious emissions of a product are usually measured either by the total power substitution method or the field strength approach.
The total power substitution method is an approach preferred by many regulatory and industry authorities, such as FCC, China MII (Ministry of Information Industry) [3], TIA [4] and 3GPP [5], for making the radiated spurious emissions measurement. TIA [4] provided the detailed measurement procedures for using the total power substitution method. The measurement uncertainty was discussed in [6]. CISPR 16-2-3 [7] discusses the substitution method for measuring the radio disturbance in the frequency range of 30 MHz to 18 GHz. But it fails to provide well defined and consistent measurement procedures
This paper reviews and discusses the equipment setup and measurement procedures for making the radiated spurious emissions measurement by using the substitution method. With a given field strength of a spurious signal at the receiving antenna, two approaches, the FSPL and the site attenuation approaches, are presented and elaborated in the paper for estimating the effective radiated power of the spurious signal and the required input power to the substitution antenna. The calculated results are compared with the measured ones from both broadband EMC antennas and tunable dipoles. The pros and cons of each estimation method and different type of substitution antennas are addressed and discussed as well in the paper.