Three-Valued LFPS Signal Circuit Without Phase Matching
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Solution Overview
Problem
The existing methods for generating a three-valued Low Frequency Periodic Signaling (LFPS) signal according to the USB 3.0/3.1/3.2 standard face issues due to the use of two-valued NRZ signals, leading to pseudo signals, transient responses, and increased costs associated with two-channel pattern generators, which result in signal reception deviations and increased user burden.
Innovation Solution
A three-valued signal generation device and method utilizing a pseudo LFPS signal and an enable signal to generate a three-valued LFPS signal with voltage levels of low, high, and intermediate levels, employing differential amplifiers and signal synthesis units to produce the desired signal, thereby reducing costs and eliminating the need for phase matching and waveform confirmation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a two-valued NRZ signal is used to generate an LFPS signal, then the signal generation is simple, but the LFPS signal becomes a pseudo signal that does not conform to the USB 3.0/3.1/3.2 standard and lacks an intermediate value
Solution Approach 1:
The patent changes the voltage level parameters of the LFPS signal by introducing three distinct levels (high level VH, intermediate level VI, and low level VL) instead of the conventional two levels. This is achieved through a three-valued signal generation circuit that outputs signals with voltage levels satisfying VH > VI > VL, thereby transforming the signal from a non-compliant two-valued NRZ signal to a compliant three-valued LFPS signal that meets USB 3.0/3.1/3.2 standards
Solution Approach 2:
The patent segments the signal generation process into distinct functional blocks: a pattern generator that generates the base signal, and a three-valued signal generation circuit that transforms the two-valued NRZ signal into a three-valued LFPS signal. This segmentation allows the system to maintain the simplicity of two-valued signal generation while achieving three-valued signal output through the intermediary transformation circuit
2Device complexity
If a two-valued NRZ signal is used to generate a three-valued LFPS signal, then the generation process is simplified, but transient response occurs due to AC coupling and common mode voltage deviation occurs
Solution Approach 1:
The patent applies preliminary action by pre-setting the voltage levels of the LFPS signal through the three-valued signal generation circuit before transmission. The circuit is designed to output signals with predetermined voltage relationships (VH > VI > VL), ensuring that the signal starts with correct voltage levels and avoiding transient responses that would occur with AC coupling. This preliminary configuration of voltage levels prevents subsequent deviations in common mode voltage
3Reliability
If two signals are synthesized using a two-channel pattern generator, then a three-valued LFPS signal can be generated, but glitch noise is generated due to phase difference and skew adjustment is required
Solution Approach 1:
The patent merges the signal generation and signal transformation functions into a single integrated three-valued signal generation circuit. Instead of using two separate channels that would require phase synchronization, the circuit takes a single two-valued NRZ signal and internally generates the three voltage levels through combined logic operations and voltage level conversion, thereby eliminating phase difference issues and glitch noise
Solution Approach 2:
The three-valued signal generation circuit acts as an intermediary between the pattern generator and the transmission medium. It receives a simple two-valued NRZ signal from the pattern generator and transforms it into a compliant three-valued LFPS signal, serving as a mediator that converts between different signal formats without requiring complex phase matching or multiple channels
4Measurement precision
If waveform confirmation using a waveform observation device is performed to match phases, then signal accuracy is improved, but user workload and cost increase
Solution Approach 1:
The three-valued signal generation circuit performs self-service by automatically generating the correct three-valued LFPS signal waveform without requiring external waveform observation or manual phase adjustment. The circuit internally manages the voltage level transitions and timing, making the signal generation process self-sufficient and eliminating the need for user intervention with expensive waveform observation equipment
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 approach allows for the generation of a three-valued LFPS signal specified by the USB 3.0/3.1/3.2 standard at a lower cost using a one-channel pattern generator, reducing the risk of transient responses and user workload, and ensuring correct signal reception.
Implementation Method 1
a first differential amplifier that includes a first enable terminal to which the enable signal is input, a first input terminal to which the pseudo LFPS signal is input, a first output terminal from which a first differential signal is output, and a first inverted output terminal from which a first inverted differential signal obtained by inverting a voltage level of the first differential signal is output
Data Source
AI summary
A three-valued signal generation device includes a first differential amplifier that outputs a differential signal, a second differential amplifier that outputs a differential signal and an inverted differential signal in accordance with a level based on a reference voltage of an inverted pseudo LFPS signal, which is obtained by inverting a logic level of the pseudo LFPS signal, a first signal synthesis unit that synthesizes the differential signal from the first differential amplifier and the inverted differential signal from the second differential amplifier to perform positive logic output of a three-valued LFPS signal, and a second signal synthesis unit that synthesizes the inverted differential signal from the first differential amplifier and the differential signal from the second differential amplifier to perform negative logic output of the three-valued LFPS signal.