2. Electromagnetic Compatibility (a) An electrical product you are developing has undergone an electric field radiated emission test in order to comply with the European Union Directive for electromagnetic compatibility for CE Marking. The test result exceeds the electric field radiated emission limit for 10 m test distance of 30 dBuv/m by 10 dB at a frequency of 53 MHz and is found to be due to radiation from a 1 m long signal cable. Calculate the common mode interference current on the signal cable that could cause the test failure. [10 Marks] (b) What design measures could be taken to reduce the common mode interference current on the signal cable and which would be the simplest measure to implement requiring minimal design changes? How does the chosen measure reduce common mode interference current and does it affect the differential mode current of the intentional signals carried by the cable? [8 Marks) (c) Having eliminated the cable radiation, it is found that the test result still exceeds the electric field radiated emission limit by 5 dB at a frequency of 53 MHz due to radiation from an aperture in the product metal enclosure. The aperture longest dimension is 50 mm. What change in the aperture dimension is required to achieve a further reduction of 5 dB in the electric field emission? 17 Marks) 2. Electromagnetic Compatibility (a) An electrical product you are developing has undergone an electric field radiated emission test in order to comply with the European Union Directive for electromagnetic compatibility for CE Marking. The test result exceeds the electric field radiated emission limit for 10 m test distance of 30 dBuv/m by 10 dB at a frequency of 53 MHz and is found to be due to radiation from a 1 m long signal cable. Calculate the common mode interference current on the signal cable that could cause the test failure. [10 Marks] (b) What design measures could be taken to reduce the common mode interference current on the signal cable and which would be the simplest measure to implement requiring minimal design changes? How does the chosen measure reduce common mode interference current and does it affect the differential mode current of the intentional signals carried by the cable? [8 Marks) (c) Having eliminated the cable radiation, it is found that the test result still exceeds the electric field radiated emission limit by 5 dB at a frequency of 53 MHz due to radiation from an aperture in the product metal enclosure. The aperture longest dimension is 50 mm. What change in the aperture dimension is required to achieve a further reduction of 5 dB in the electric field emission? 17 Marks)
