Optical Disc Phase Error Detection Using Segmented Sampling
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Solution Overview
Problem
Current optical disc technologies face challenges in maintaining stable reproduction clock signal generation as linear density increases, leading to degraded reproduction capability due to widened intersymbol interference and overlapping phase information, which results in high bit error rates and synchronization issues.
Innovation Solution
An optical disc apparatus that includes a synchronizer, adaptive equalizer, maximum likelihood decoder, phase-advance and phase-delay waveform generators, and a metric detector to accurately detect phase errors and control the phase of the digital reproduction signal, allowing for stable reproduction clock signal generation even at higher linear densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If linear density of recording data is increased to improve storage capacity, then recording density per volume is improved, but reproduction capability is degraded due to widened intersymbol interference and overlapping phase information
Solution Approach 1:
The patent segments the phase error detection process into multiple sampling points (at least two different sampling points) within the bit period. This segmentation allows the system to capture phase information from different positions of the reproduction signal, enabling accurate phase error detection even when intersymbol interference widens due to increased linear density. By dividing the detection task across multiple points, the system maintains reproduction capability while supporting higher recording densities.
Solution Approach 2:
The patent uses more sampling points than the minimum single point conventionally used. By sampling at multiple points (excessive action), the system obtains redundant phase information that can be processed to accurately determine phase error despite the presence of intersymbol interference. This partial redundancy ensures that at least some sampling points provide reliable phase information even when others are degraded by interference from adjacent bits.
2Device complexity
If conventional phase error detection is used at increased linear density, then device complexity is reduced, but bit error rate increases due to inability to detect proper phase information
Solution Approach 1:
The patent implements a feedback mechanism where phase error is detected at multiple sampling points and this information is fed back to control the reproduction clock signal phase. The system continuously monitors phase error at multiple points and adjusts the clock signal accordingly, creating a closed-loop control system. This feedback approach ensures that phase synchronization is maintained even at increased linear densities where conventional open-loop detection would fail, thereby maintaining low bit error rates without requiring fundamentally more complex hardware.
3Ease of operation
If single point phase error detection is used for simplicity, then ease of operation is improved, but synchronization stability deteriorates due to overlapping phase information from multiple edges
Solution Approach 1:
The patent segments the phase error detection into multiple sampling points within each bit period. This segmentation allows the system to capture phase information from different positions, and by processing these multiple measurements, the system can identify the correct phase error signal that corresponds to the current bit's edge rather than overlapping information from adjacent bits. This maintains synchronization stability while keeping the operation relatively simple through systematic processing of the segmented measurements.
Data Source
AI summary
An optical disc apparatus includes a synchronizer that generates a reproduction clock signal synchronized with a reproduction signal of information recorded in an optical disc medium, and generates a digital reproduction signal synchronized with the reproduction clock signal, an adaptive equalizer that generates a post-adaptive-equalization digital reproduction signal, and a maximum likelihood decoder that performs maximum likelihood decoding of the post-adaptive-equalization digital reproduction signal to generate a binary signal. The apparatus also includes an expected waveform generator that generates an expected waveform from the binary signal, a phase-advance waveform generator that generates a phase-advance waveform, a phase-delay waveform generator that generates a phase-delay waveform, and a metric detector that detects a phase error. In the optical disc apparatus, the synchronizer controls the phase of the digital reproduction signal using the phase error.