Optical Disc Variable Gain Amplifier Digital Envelope Detection
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Solution Overview
Problem
Conventional optical disc apparatuses require two analog-to-digital converters (ADCs) for envelope detection and binary data generation, leading to a large analog circuit size and high costs, despite the trend towards miniaturization and digital circuit dominance.
Innovation Solution
An optical disc apparatus with an amplitude control mechanism using a Variable Gain Amplifier (VGA) followed by digital sampling, binary data generation, amplitude detection, and envelope generation, allowing for the extraction of the envelope from a signal after VGA processing, thereby reducing the analog circuit scale and enabling a digital envelope generating circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two ADCs are used for envelope detection and binary data generation, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
A single ADC is designed to perform multiple functions: it converts the amplified signal for both envelope detection and binary data generation. The envelope detection unit and binary data generating unit share the same ADC output, eliminating the need for separate ADC circuits and reducing overall device complexity while maintaining measurement precision for both functions
Solution Approach 2:
The patent merges the envelope detection path and binary data generation path by having both units receive their input from the same ADC. This consolidation reduces the number of analog-to-digital conversion circuits from two to one, directly addressing the contradiction between measurement precision and device complexity
2Ease of manufacture
If digital circuit configuration is adopted, then ease of manufacture is improved, but analog circuit scale reduction is limited without proper architecture
Solution Approach 1:
The patent replaces analog envelope detection circuitry with a digital implementation. The envelope detecting unit operates in the digital domain after the ADC, using digital signal processing techniques to extract envelope information. This substitution reduces analog circuit scale and improves ease of manufacture while maintaining the necessary functionality
Solution Approach 2:
The invention changes the operational domain of envelope detection from analog to digital parameters. By performing envelope detection on digital samples rather than analog signals, the system achieves better manufacturability and reduced analog circuit complexity while preserving measurement accuracy through digital processing
Data Source
AI summary
A variable gain amplifier (203: VGA) for amplifying an amplitude of a signal extracted by a pickup (202), an A/D converter (204) for converting the amplified signal into digital, and an amplitude detecting circuit (206) for detecting amplitude information from the digital information, are provided. A gain control circuit (205) for calculating a control value for the VGA (203) is calculated from the detected amplitude information, and an envelope generating circuit (207) for executing an operation of absorbing transfer characteristics of the VGA (203) from the control value for the VGA (203) and the amplitude information, are provided to generate an envelope extracted by the pickup (202). When the characteristics of the VGA (203) vary, a degree of the variation is calculated from the amplitude information of the signal extracted by the pickup (202) and amplitude information obtained by fixing the control value for the VGA (203), and characteristic correction is executed.