High-Speed Image Transmission MIPI D-PHY and C-PHY Cable Design Guide

In the field of high-speed image transmission, MIPI (Mobile Industry Processor Interface) has become the mainstream interface standard, with D-PHY and C-PHY being the two most common physical layer specifications. They differ significantly in terms of signal transmission methods, rates, and cable structure design. In engineering practice, selecting the appropriate ultra-fine coaxial cable is crucial for ensuring signal integrity and system reliability. Understanding the characteristics of different PHY specifications helps achieve a balance between performance and reliability when designing high-speed cables.

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Part 1: Transmission Characteristics of D-PHY and C-PHY

D-PHY uses differential signal transmission, where each pair of signal lines transmits data through voltage difference, with typical rates reaching 1.5Gbps to 4.5Gbps and is widely used in camera interfaces (CSI) and display interfaces (DSI). C-PHY, on the other hand, uses a three-wire system for transmission, with each group of three wires transmitting data together, achieving higher data throughput at the same bandwidth, for example, the equivalent rate of C-PHY v1.2 can reach 13Gbps. Different signal structures determine the束 design strategies and the focus of transmission performance.

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Design Considerations for Ultra-fine Coaxial Cable Assemblies

Due to the different signal forms of D-PHY and C-PHY, the cable design needs to be optimized specifically. D-PHY emphasizes differential impedance control, usually requiring 100Ω±10%, so the cable selection must ensure a single-line impedance of about 50Ω. C-PHY pays more attention to the geometric symmetry and phase consistency among the three lines to ensure efficient data transmission. In high-speed applications, extremely thin coaxial cables can reduce crosstalk through independent shielding and precise structure, and multi-layer shielding structures can further enhance signal stability. In addition, due to the limited space in mobile devices, the cable must also consider flexibility and bend life, especially for the three-line combination of C-PHY, which puts higher requirements on termination and processing technology.

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Connectors and Harness Matching

In actual assembly, the match between the connector and the harness directly affects signal integrity. D-PHY mostly uses traditional differential interfaces, such as Hirose or I-PEX connectors; C-PHY usually requires a customized three-wire interface. Asymmetrical interface layout or uneven welding points can cause reflections and signal distortion. Therefore, the harness manufacturer needs to work with the whole machine designer at the early stage of the project to determine the wire diameter, shielding structure, and termination layout together, ensuring overall impedance continuity and stable transmission of high-frequency signals.

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Overall, D-PHY tends to favor traditional differential transmission, with strict requirements for impedance control; C-PHY uses three-phase encoding, which has higher transmission efficiency but complex structural design. Engineers in the design of extremely thin coaxial cable bundles should fully understand the electrical characteristics of different PHY specifications, reasonably select cable materials, shielding methods, and termination strategies, thereby ensuring high-speed signal integrity, anti-interference capability, and the overall reliability of the system.

I amSuzhou Huichengyuan Electronic Technology,Long-term focus on the design and customization of high-speed signal cable harnesses and ultra-fine coaxial cable harnesses. For more information or customization development, please contact Manager Zhang:18913228573（WeChat same number）。