Duo-binary RF Link for High-Speed Serial Transmission
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Solution Overview
Problem
High-speed serial links in integrated circuits face bottlenecks due to increased wire density, crosstalk, RC delay, and distortion caused by channel properties, leading to limited data rates and complex, power-consuming equalization methods, as well as the need for repeaters that disrupt floor plans and lack portability across technology nodes.
Innovation Solution
A mixed digital-RF high-speed link using duo-binary coding and differential pre-coding, combined with a self-mixing technique at the receiver, allows for efficient long-distance transmission with reduced propagation delay, simplified decoding, and increased data rates up to 10 Gbps without error correction or equalization, using a 60-GHz carrier and differential transmission lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If equalization methods are used to reduce channel distortion, then signal integrity is improved, but device complexity and power consumption increase dramatically
Solution Approach 1:
The patent extracts and removes the complex equalization function from the system, replacing it with a simpler alternative. By using RF modulation instead of baseband transmission, the patent eliminates the need for complex equalizers while maintaining signal integrity through frequency-domain separation of signal components.
Solution Approach 2:
The patent substitutes the mechanical/electrical equalization system with an RF modulation system. Instead of using complex filters and adaptive algorithms to compensate for channel distortion, the patent uses frequency modulation to transmit signals in a regime where channel effects are minimized.
2Reliability
If digital repeaters are added to maintain signal integrity for long distance links, then signal quality is improved, but floor plan is disrupted and power consumption increases
Solution Approach 1:
The patent removes the need for digital repeaters by extracting the signal regeneration function and replacing it with RF modulation. The high-frequency carrier enables signals to traverse long distances without requiring intermediate regeneration stages, eliminating the associated floor plan disruptions and power consumption.
Solution Approach 2:
The patent transitions from baseband signaling to RF modulation, effectively moving the signal to a different frequency dimension. This dimensional change allows the signal to propagate through the channel with minimal distortion, eliminating the need for repeaters that would otherwise be required in the time domain.
3Device complexity
If baseband transmission is used, then system simplicity is maintained, but propagation delay increases to around 40 ps/mm
Solution Approach 1:
The patent changes the frequency parameter of the transmission signal from baseband to RF range. This parameter change reduces the propagation delay from 40 ps/mm to 9 ps/mm by utilizing the frequency-dependent characteristics of the transmission medium, while maintaining relative system simplicity through straightforward modulation and demodulation circuits.
Data Source
AI summary
Binary data is processed through a differential pre-encoder, which includes a simple modulo-2 addition. This step is used to cancel the propagation error that can be introduced by duo-binary modulation and to simplify demodulation. Next the duo-binary encoder introduces controlled Inter Symbol Interference between a previously sent bit and a present bit to compress the spectral density closer to the DC. Next a 60-GHz carrier is modulated and transmitted over differential transmission lines.