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HDMI Cable Principle Analysis

Shenzhen KW-LINK Electronic Co.,Ltd | Updated: Jun 05, 2017

    HDMI is a fully digital interface for both the consumer electronics and PC applications. It can transmit uncompressed audio signals and video signals, because the audio and video signals using the same cable transmission, thus greatly simplifying the number of interface cables, has been popular in the home appliances and PC.HDMI CABLE

    HDMI interface from the emergence of a number of versions have evolved from HDMI 1.1 to HDMI 1.4, although the appearance of the interface has not changed, but the function and bandwidth has been a qualitative improvement. Mainstream HDMI interface version of HDMI 1.3 (a, b, c), but with the popularity of 3D video, HDMI 1.4 version of the device is also a large number of listed, as the focus of the promotion of various products. HDMI 1.4 brings several major innovative features, including HDMI Ethernet channel, audio return channel, HDMI 3D video playback and 4k × 2k ultra-high resolution support.

In the cable, HDMI before there is no version of the points, HDMI 1.4 version contains five types of cables, each with its different features and performance characteristics. HDMI 1.4 version is divided into standard HDMI cable, standard with Ethernet network function HDMI cable, car HDMI cable, high-speed HDMI cable, high-speed Ethernet network with HDMI cable five. Standard HDMI cable is to support 1080p, high-speed HDMI support, including 4k × 2k, 3D video, Deep Color and other advanced display technology, this cable is actually the previous version of HDMI 1.3, their bandwidth requirements in the HDMI 1.3 version of the Within the bandwidth provided. And high-speed attached to the Ethernet function HDMI also has a dedicated data channel, which is to provide equipment between the network function of the HDMI Ethernet channel, the cable structure has changed, this will be described later. In the HDMI standard, but also detailed provisions of the five types of cable certification label. In this evaluation of the sample, we also selected a number of HDMI 1.4 version of the cable, but are not strictly in accordance with the HDMI standard implementation.HDMI CABLE

    Usually the most common HDMI interface for the TYPE A type, the width of 13.9mm, a total of 19 pins, and there is a dual link TYPE B-type interface is rare, the width of 21.2mm. HDMI uses four parallel TMDS differential signal channels, the transmission chain consists of three data channels and a clock channel. Three of the data channels are used to transmit red, green and blue data signals, the first four channels used to transmit the clock, the clock frequency is the data rate of 1/10. HDMI TMDS technology, differential signal common mode bias voltage of +3.3 V, port impedance of 50 ohms, rated amplitude jump to 500mV (+2.8V ~ +3.3V), the voltage swing between 150mV ~ 800mV change The In addition, there are DDC (monitor data channel) data and clock lines in HDMI to transmit bi-directional communication signals and HDCP (high bandwidth digital copyright protection) signal transmission. DDC bus is the key to HDMI compatibility, if any device is not compatible with HDMI 1.3, the entire system will automatically reduce the HDMI through the DDC channel to HDMI 1.2 or lower to ensure compatibility. DDC is very busy in the HDMI cable, they not only carry the handshake communication data, but also continue to pass HDCP encryption key. If HDCP is compatible, it is necessary to continuously decode the key-encrypted digital signal.HDMI CABLE