FIR Reflection Cancellation in Unmatched High-Speed Links
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Solution Overview
Problem
High-speed data communication systems with unterminated receivers face bandwidth limitations and increased power consumption due to slow absorption of signal reflections, leading to performance degradation and error-prone signaling.
Innovation Solution
A circuit with a transmitter, transmission line, and receiver, where either the transmitter or receiver includes a Finite Impulse Response (FIR) filter to cancel reflected signals, allowing for pre-cancellation or cancellation at the receiver's sampling point, effectively eliminating residual reflections and enhancing symbol transmission rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If source-termination is used to reduce power consumption, then power consumption decreases, but transmission bandwidth is limited due to slow absorption of signal reflections
Solution Approach 1:
The patent applies preliminary anti-action by using an FIR filter to generate a cancellation signal that preemptively counteracts the reflected signal before it corrupts the data. The cancellation signal is created based on previous transmitted symbols and is subtracted from the received signal, thereby preventing the harmful reflection effect rather than merely responding to it after occurrence
Solution Approach 2:
The FIR filter acts as an intermediary component between the transmission line and the receiver. It processes the received signal by filtering out the reflected signal components, thereby mediating the interaction between the unterminated transmission line and the data recovery process, enabling high-speed communication without far-end termination
2Reliability
If double termination is used to minimize signal reflections, then reflection settling time decreases, but power consumption increases
Solution Approach 1:
The patent extracts the termination function from the physical hardware at the far-end and relocates it to the signal processing domain through an FIR filter. Instead of using a physical termination resistor at the receiver end, the system mathematically extracts and cancels the reflection components from the received signal, thereby eliminating the need for far-end termination hardware and its associated power consumption
Solution Approach 2:
The patent replaces the mechanical/electrical termination system (physical resistors at both ends of the transmission line) with a digital signal processing system (FIR filter). This substitution transforms the reflection control mechanism from a passive electrical component-based approach to an active signal processing approach, reducing power consumption while maintaining reflection control
3Device complexity
If unterminated receiver is used to reduce circuit complexity, then device complexity decreases, but error-free signaling rate is limited by reflection settling time
Solution Approach 1:
The system performs preliminary action by using the FIR filter to predict and cancel reflection effects before they impact data recovery. The filter processes previous transmitted symbols to generate cancellation signals in advance, preparing the received signal for accurate data extraction without requiring complex termination circuits
Data Source
AI summary
A circuit includes a transmitter, a transmission line, and a receiver coupled to the transmitter through the transmission line, the transmission line used to transmit data at high-speed rates. At least one of the transmitter or receiver has associated therewith an unmatched termination, wherein either the transmitter or the receiver includes a finite impulse response (FIR) filter configured to cancel a reflected signal at a cancellation point situated at an input of the receiver, at an input of a driver, or at an output of the driver, the driver being coupled to an output of the transmitter, such that the reflected signal is substantially removed from the signal detected by the receiver.