Information Reproduction Apparatus Using Maximum Likelihood Detection
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Solution Overview
Problem
Conventional information reproduction apparatuses face challenges in reducing interpolation errors and maintaining stability due to increased timing recovery loop delay, noise emphasis, and large circuit scales, particularly in synchronizing clocks and equalizing signals for precise data and timing recovery from analog signals.
Innovation Solution
An information reproduction apparatus that includes a data reading unit, a first clock generation unit for generating an asynchronous clock, a timing detection unit for obtaining timing error information, and branch metric calculation units to calculate plural branch metrics, allowing for pseudo-synchronization of the second clock with the first signal's timing, thereby simplifying the clock generator construction and reducing circuit scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If interpolation is used for timing recovery to synchronize the clock with the analog signal timing, then timing synchronization precision is improved, but interpolation errors increase and noise is emphasized
Solution Approach 1:
The patent replaces the conventional interpolation-based timing recovery mechanism with a maximum likelihood sequence detection approach. Instead of using interpolators to generate pseudo-synchronized clocks, the system uses branch metric calculation units that compute metrics based on the analog signal and timing error information, then selects the most likely sequence through comparison. This substitution eliminates interpolation operations and their associated errors and noise emphasis while achieving accurate timing recovery.
Solution Approach 2:
The patent introduces branch metric calculation units as intermediary components between the A/D converter and the timing recovery logic. These units calculate branch metrics using the analog signal and timing error information without requiring interpolation, serving as a mediator that bridges the asynchronous sampling and synchronous timing requirements while avoiding interpolation errors.
2Measurement precision
If a complex clock generator and FIR filter are used to achieve precise timing recovery and equalization, then data reproduction precision is improved, but circuit scale increases
Solution Approach 1:
The patent extracts and removes the complex FIR filter and traditional clock generator from the system. By using maximum likelihood sequence detection with branch metric calculation, the system achieves precise timing recovery and equalization without requiring these large-scale components. The timing error information is obtained directly through comparison with the analog signal, eliminating the need for complex filtering and clock generation circuits.
Solution Approach 2:
The branch metric calculation units perform multiple functions simultaneously: they calculate timing error information, perform equalization, and enable sequence detection all in one operation. This multi-functionality replaces what would traditionally require separate FIR filters, clock generators, and timing recovery logic, significantly reducing circuit scale while maintaining data reproduction precision.
3Measurement precision
If the timing recovery loop delay is increased to improve timing accuracy, then timing recovery precision is improved, but system stability deteriorates
Solution Approach 1:
The patent inverts the conventional timing recovery approach by not using a feedback loop with interpolation and delay elements. Instead of adjusting the clock based on delayed timing error information, the system calculates branch metrics directly from the current analog signal and timing error information, then selects the most likely sequence. This inversion eliminates the timing recovery loop delay while maintaining high timing recovery precision through direct comparison and maximum likelihood detection.
Data Source
AI summary
There is provided an information reproduction apparatus that can suppress degradations in the qualities of reproduced data and timing from due to interpolation errors when performing interpolation timing recovery, and that can avoid degradation in the stability of the system due to an increase in the timing recovery loop delay. An information reproduction apparatus (100) for reproducing data and timing from an analog signal including data information and timing information is provided with an expected value generator (106) for outputting plural expected values, and a maximum likelihood detector (107) for outputting data that corresponds to a sequence of the highest likelihood with an output sequence of an A/D converter among the plural expected value sequences, at the timing of a second clock.