Mitigation method/Results/Conclusion Mitigation method As this problem was caused by the conducted disturbance wave from the IP-STB, four ferrite cores (Attenuation > 20 dB @ 10-100 MHz) were installed on the component video cable as shown in Figure 1.13-4. Figure 1.13-5 shows the variation of the D/U ratio after the installation of those ferrite cores. As the figure shows, the D/U ratio rose to about 45 dB, and this problem was solved. Miti(08)_F1.13-4 Figure 1.13-4 – Mitigation by ferrite cores 60 Video signal Audio signal Signal strength [dBμV] 50 D/U = 45 dB D/U = 25 dB 40 30 20 10 0 90 91 92 93 94 95 96 Frequency [MHz] Miti(08)_F1.13-5 IP - STB_ON After mitigation (Ferrite core) Figure 1.13-5 – Variation of D/U ratio after mitigation Conclusion In this NGN trial, communication and broadcasting equipments are connected by cables such as a video cable; therefore, both equipments can become disturbance sources. By checking the spectrum of measured signals, in this case, it was found that the IP-STB was a disturbance source. The requirements of video ports should be defined to prevent EMC problems on NGN services. – 3 – Case study 1.13