A new approach to coupling/decoupling networks for EMC testing

Testing of immunity to EN61000-4-6 and of emission to EN55022 is achieved using coupling and decoupling networks (CDNs). The paper describes several improvements to the configuration, construction and connection of such networks. Firstly, it is shown that embodying the whole of the 150 Ω source impedance within the CDN, together with built-in voltage measurement, substantially reduces the energising required and so reduces the system cost. At the same time this simplifies the calibration. Secondly, the factors limiting frequency response are analysed, and it is shown that with a carefully-designed CDN and a sufficiently small EUT it is certainly practicable to extend the maximum injection frequency to 400 MHz. Lastly, it is described how a limited set of CDNs can be adapted to meet a large variety of practical applications in telecommunications, computing, and process control by appropriate CDN internal design and linking within the CDN connectors