Effects of radio-frequency exposure (100-kHz to 500-kHz) on very-high-speed digital data transmission system using a copper loop

This paper describes our investigation of the effect of radio frequency (RF) exposure on the performance of a very-high-speed digital data transmission system called the Asymmetrical Digital Subscriber Lines (ADSL) using the uncoded quadrature modulation (QAM) scheme at a rate of approximately 1.6 Mb/s and which operates within the 100- to 5OO-kHz frequency band. The effect of different wideband emissions within the ADSL band, including the background radio noise in the environment and emissions from light dimmers, fluorescent lamps, motors, and other household appliances on the customer´s premises were investigated. Also, the effect of RF exposure caused by radiation from high-power licensed transmitters, such as LORAN-C, coastguard transmitters, and radiobeacons, were investigated. A complete database of information for these transmitters was acquired. The coupled voltage caused by radiation from the transmitters was predicted by using a detailed electromagnetic interference (EMI) model that was developed and experimentally verified. Field surveys near LORAN-C stations in New York, New Jersey, and California were performed. For the study on spurious emission-like background radio noise, light dimmers, invisible fences, and emission from diesel engines, it was found that these sources inside the customer´s premises may not generate potential interference to the system. Minimum distances (critical distance) that should be maintained between the ADSL receiver and the interfering radio transmitters (LORAN-C radiobeacons) were obtained for the 18 ADSL test loops. Initial study of multiple exposure caused by several transmitters radiating at different frequencies, but all within the ADSL band, showed that such an effect should not generate any potential interference within the 100- to 500-kHz band