SerDes Echo Cancellation With Independent TX/RX Phase Adjustment
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Solution Overview
Problem
Dual-duplex Serializer/Deserializer (SerDes) links in high-speed communications systems experience bit errors due to transmit echoes, which are difficult to cancel effectively due to the receive signal being significantly weaker than the transmit signal and sensitive to jitter.
Innovation Solution
The implementation of an adjustable delay line and phase interpolators in the SerDes I/O circuit architecture to align the phase of the receive signal with the transmit echo, allowing for efficient cancellation of transmit echoes by creating a relative phase shift between the receive and transmit signals, along with additional circuitry for interference cancellation and equalization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmit operations are performed in dual-duplex SerDes links, then data transmission capability is improved, but transmit echoes cause bit errors due to the receive signal being about 40 dB below the transmit signal
Solution Approach 1:
The patent converts the harmful transmit echo signal into a useful component by capturing it through a tap, processing it through delay lines and phase interpolators to match the receive signal timing, then subtracting it from the received signal to eliminate the echo interference and recover the original data
2Device complexity
If echo cancellation is attempted without precise phase alignment, then echo cancellation complexity is reduced, but cancellation effectiveness deteriorates due to jitter and phase drift between receive and transmit signals
Solution Approach 1:
The patent employs dynamic phase adjustment through phase interpolators that can continuously adjust the phase of the transmit echo signal to track and compensate for phase drift and jitter, ensuring optimal alignment with the receive signal under varying operating conditions
Solution Approach 2:
The system uses feedback mechanisms where the captured transmit echo is processed and compared against the receive signal to dynamically adjust delay and phase parameters, optimizing the cancellation effectiveness in real-time
3Reliability
If independent phase adjustment for transmit and receive signals is implemented, then echo cancellation performance is improved, but device complexity increases due to additional delay circuits and phase interpolators
Solution Approach 1:
The patent divides the phase adjustment function into separate independent control paths for transmit and receive signals, with dedicated delay lines and phase interpolators for each, allowing precise independent optimization of each signal path's timing and phase characteristics
Data Source
AI summary
A Serializer/Deserializer (SERDES) circuit is disclosed. The circuit includes an input/output (I/O) pad for coupling to a duplex SerDes link. An adjustable delay line provides a first component of a relative phase between a receive signal sampling point and a transmit echo signal. A second delay circuit generates a second component of the relative phase. A timing relationship between the receive signal sampling point and the transmit echo signal is based on the sum of the first and second components.