Multi-Rate Digital PLL Timing Recovery With Half-Rate DSP
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Solution Overview
Problem
High-speed data communication systems face challenges in power consumption and latency due to the need for high-speed digital signal processing in SERDES systems, particularly in timing recovery circuits, which are critical for maintaining low Bit Error Rates and handling signal impairments like sinusoidal jitter.
Innovation Solution
Implementing a multi-rate DSP structure that splits timing error signals into sum and difference components, processed at half the update rate, allows for reduced DSP clock rates, lowering latency and power consumption while maintaining performance, and eliminating the need for high-speed libraries and pipelining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-speed DSP clock rates are used for timing recovery circuits, then tracking performance is improved, but power consumption and latency increase
Solution Approach 1:
The timing error signal processing is segmented into two separate paths: a proportional path that processes the current timing error sample, and an integrator path that accumulates timing error samples. This segmentation allows each path to operate at lower clock rates while maintaining overall loop performance, thereby reducing power consumption in the DSP timing recovery circuit.
Solution Approach 2:
The integrator path performs preliminary accumulation of timing error samples before they are combined with the proportional path output. By pre-processing the timing error signal through accumulation, the system reduces the computational burden on subsequent processing stages, allowing for lower DSP clock rates and reduced power consumption while maintaining tracking accuracy.
2Reliability
If high-speed DSP clock rates are used for timing recovery circuits, then tracking performance is improved, but latency increases
Solution Approach 1:
By segmenting the timing error processing into proportional and integrator paths, the system can process signals through parallel pathways that reduce critical path delays. This segmentation eliminates the need for high-speed sequential processing, thereby reducing latency while maintaining tracking performance.
Solution Approach 2:
The integrator performs preliminary accumulation of timing error samples in advance, preparing processed data for subsequent combination with the proportional path. This preliminary action reduces the computational workload and processing time in later stages, thereby reducing overall latency in the timing recovery circuit.
3Speed
If high-speed libraries and pipelining are used in digital control circuits, then processing speed is improved, but device complexity increases
Solution Approach 1:
The system uses periodic accumulation of timing error samples in the integrator path, processing multiple samples over successive clock cycles rather than requiring single-cycle high-speed processing. This periodic action approach achieves adequate processing speed without requiring complex high-speed libraries or extensive pipelining, thereby reducing device complexity.
Data Source
AI summary
Methods and systems to generate control signals for timing recovery of a signal received over baseband communications systems are disclosed. The timing control circuit uses a multi-rate DSP structure for the implementation of the DSP functions in the control loop for use in an ASIC and requires a reduced DSP clock rate, which in turn reduces the need for pipelining and/or high-speed libraries. Thus lower latency, better tracking performance and lower power consumption are achieved. An example embodiment involves splitting the timing error signal, supplied at a given update rate, into a sum and a difference component, and processing each component in separate circuit chains at half the update rate. The resultant half-rate control signals from each separate circuit chain are joined to provide a control signal at the full update rate. Thus, implementations of the present disclosure perform like a full-rate structure, but require a halved DSP clock rate.