HDMI 2.1 Noise Suppression Solutions

HDMI 2.1, an extension of HDMI 2.0, supports significantly higher data rates, making noise suppression critical to maintain signal integrity. This article explores electromagnetic compatibility (EMC) challenges in HDMI 2.1 systems and effective solutions using common mode choke coils (CMCCs).

HDMI 2.1 Overview

HDMI 2.1, designed for digital video and audio transmission, offers a bandwidth approximately 2.7 times that of HDMI 2.0, with per-channel signal speeds doubled. Unlike HDMI 2.0¡¯s three data channels and one clock channel, HDMI 2.1 uses four data channels, eliminating the clock channel. This increased speed necessitates robust noise suppression to prevent signal degradation.

EMC Challenges in HDMI 2.1

Two primary EMI issues affect HDMI 2.1 systems:

• Internal EMC Noise: HDMI signals interfere with Wi-Fi antennas, reducing Wi-Fi sensitivity by 6¨C10dB in the 2.4GHz and 5GHz bands.
• Radiated Noise: Emissions from HDMI devices or cables, with HDMI 2.1 generating noise from 1GHz to 6GHz, compared to 1GHz to 3GHz for HDMI 2.0.

Common Mode Choke Coils for Noise Suppression

Standard noise filters degrade high-speed differential signals like HDMI, making CMCCs the preferred solution. CMCCs suppress common mode noise while preserving differential signal integrity, critical for HDMI 2.1¡¯s high-speed data rates. Placement is key:

• Source-Side CMCC: Near the IC output pins to suppress noise from transmission ICs, preventing propagation to the sink side.
• Sink-Side CMCC: Near connectors to block noise from HDMI wiring entering Wi-Fi antennas.

Suitable CMCCs for HDMI 2.1 include models with high common mode impedance and minimal signal impact, such as those optimized for frequencies up to 6GHz with at least 25dB attenuation in the GHz range.

Performance Results

Testing demonstrates CMCC effectiveness:

• Radiated Noise Reduction: A source-side CMCC significantly reduces HDMI 2.1 noise in the 1¨C6GHz range. Residual noise often stems from other components, like DRAM, rather than HDMI signals.
• Signal Integrity: Eye diagram tests confirm CMCCs do not alter HDMI 2.1 signal waveforms, maintaining quality.
• Common Mode Noise: CMCCs reduce AC common mode noise by up to 47%, enhancing system EMC.

Conclusion

HDMI 2.1¡¯s high-speed signals require careful EMC management to prevent Wi-Fi interference and radiated emissions. CMCCs, strategically placed at source and sink sides, effectively suppress common mode noise without compromising signal integrity. By selecting CMCCs optimized for high-frequency performance, engineers can ensure reliable HDMI 2.1 operation in modern AV systems.