If normal noise filters are used for high-speed differential signaling lines like HDMI, the signal quality will deteriorate, and the signals will not be transmitted properly. For this reason, common mode choke coils (CMCC) are a suitable solution. Because HDMI signals are high speed, we should select a CMCC that is best suited for high-speed signals.
CMCCs are installed near the output pins of the IC at the HDMI source side and near the connectors at the sink side. The source-side CMCC installed near the IC can suppress the common mode noise generated from the transmission ICs at the source side by preventing the propagation of common mode noise at the sink side.
The sink-side CMCC can suppress the common mode noise generated from the HDMI signal wiring of the sink equipment by preventing common mode noise from entering the Wi-Fi antenna.
First, we verified how much HDMI communication affects Wi-Fi. We confirmed that, when HDMI 2.1 communication was started, the Wi-Fi reception sensitivity dropped by 6 to 10 dB in the 2.4 GHz and 5 GHz bands. When noise actually entering the Wi-Fi was confirmed, we found that it overlapped with the 2.4 GHz and 5 GHz bands.
■Wi-Fi Receiver sensitivity