LFPS Translation Circuit for Optical USB Interconnects
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Solution Overview
Problem
The existing USB 3 and USB 3.1 standards' Low Frequency Periodic Signalling (LFPS) protocol is not directly suitable for optical links due to the inability to translate the electrical idle state, which limits the transmission over optical connections and restricts the interconnection length.
Innovation Solution
A circuit arrangement and method that translate LFPS sequences into non-return-to-zero (NRZ) signals suitable for optical data transmission, enabling the extension of USB host-to-device interconnection lengths by converting LFPS into a format compatible with optical links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If LFPS protocol is used for USB 3 communication, then power management and signal initiation are improved, but compatibility with optical links is lost due to inability to translate electrical idle state
Solution Approach 1:
The patent introduces an intermediary translation mechanism that converts LFPS electrical idle state into a format suitable for optical transmission. The circuit arrangement includes a translator that mediates between the electrical domain (LFPS protocol) and optical domain, enabling compatibility without losing power management capabilities. This intermediary translation layer allows the optical link to carry LFPS signals while maintaining the original protocol's functionality.
2Device complexity
If passive galvanic cable connection is used, then simplicity is maintained, but interconnection length is limited to approximately 1.5 m
Solution Approach 1:
The patent replaces the mechanical/electrical galvanic connection system with an optical transmission system. By substituting electrical signals with optical signals through light-emitting and light-receiving components, the system achieves extended transmission distances while maintaining relative simplicity. The optical link eliminates the 1.5m length limitation inherent in passive galvanic cables.
3Length of stationary object
If active galvanic cable connection with repeaters is used, then interconnection length is extended, but device complexity increases due to full protocol support requirements
Solution Approach 1:
The patent replaces complex active galvanic repeaters with simpler optical transmission components. By using light-emitting components and light-receiving components with integrated translation functionality, the system achieves extended reach without requiring full protocol-level repeaters. The optical domain naturally supports longer distances, eliminating the need for complex active regeneration equipment.
4Adaptability or versatility
If LFPS sequence is transmitted directly over optical link, then electrical idle state transmission is attempted, but transmission fails due to optical systems supporting only two signalling states
Solution Approach 1:
The patent changes the parameter representation of the LFPS signal to make it compatible with optical transmission. Instead of attempting to transmit the electrical idle state directly (which requires three states), the system translates the signal into a format that uses only two optical states (light present/absent or high/low intensity). This parameter transformation enables reliable optical transmission while preserving the original LFPS information.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for the successful transmission of USB 3 and USB 3.1 compliant data over optical links, extending the interconnection lengths beyond passive galvanic cable limitations and enabling low-power implementation of optical transmitters and receivers.
Implementation Method 1
at least one light-emitting component (1110, 1210) for converting electrical signals to optical signals
Implementation Method 2
at least one light-receiving component (1120, 1220) for converting optical signals to electrical signals
Data Source
Figure 1
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AI summary
In order to enable Low Frequency Periodic Signalling (LFPS) over at least one optical link, a circuit arrangement (TC) for controlling at least one light-emitting component (LD) as well as a corresponding method are proposed, said method comprising the steps of: - monitoring at least one differential input (IN+, IN-) for the presence of an electrical idle state by means of at least one IDLE detector (ID); - triggering at least one time delay block (TD) by means of the IDLE detector (ID) when the EI state at the differential input (IN+, IN-) gets interrupted or is resumed; - detecting whether the differential input (IN+, IN-) is driven by a L[ow]F[requency]P[eriodic]S[ignalling] or by a S[uper]S[peed] / e[nhanced]S[uper]S[peed] signallingby means of at least one signal type detector (SD), said signal type detector (SD) having a decision latency time being less than the time delay provided by the time delay block (TD); - making a decision whether LFPS or SS / ess signalling is to be transmitted by means of at least one decision circuit (DT), said decision being based on information from the IDLE detector (ID) and/or from the signal type detector (SD); - at least one input stage (IS) being connected to the decision circuit (DT); and - driving the light-emitting component (LD) by means of at least one output stage (OS), said output stage (OS) being connected downstream at least one input stage (IS) and being turned on or turned off by the decision circuit (DT). A corresponding circuit arrangement (RC) and method for processing an optical signal (SI) received from at least one light-receiving component (PD) are also proposed.