Multi-Bit Sigma-Delta Speaker Array for Low-Distortion Digital Audio
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Solution Overview
Problem
Conventional all-digital speaker systems based on PWM modulation suffer from nonlinear distortion and low over-sampling rates, limiting their ability to achieve true digitization, integration, and low power dissipation.
Innovation Solution
An all-digital speaker system utilizing multi-bit Σ-Δ modulation, including an A/D converter, interpolation filter, Σ-Δ modulator, dynamic mismatch regulator, differential buffer, and speaker array, which converts analog signals into multi-bit digital signals, shapes noise, eliminates code errors, and enhances load driving ability, thereby reducing hardware complexity and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If PWM modulation technique is used in digital amplifier, then digitization of speaker system is promoted, but nonlinear distortion components are generated in the expecting band
Solution Approach 1:
The patent replaces the analog PWM modulation circuit with a fully digital Σ-Δ modulation system implemented in FPGA. The Σ-Δ modulator converts PCM digital signals to PWM duty cycle control signals through digital filtering and modulation, eliminating the need for analog components while achieving true all-digitalization. This substitution resolves the nonlinear distortion issue by using digital signal processing instead of analog circuitry.
2Device complexity
If low over-sampling rate (200 KHz-400 KHz) is used in PWM modulation, then hardware complexity is reduced, but SNR of coded signal is difficult to improve
Solution Approach 1:
The patent changes the over-sampling rate parameter to 1.536 MHz, which is significantly higher than conventional 200-400 KHz rates. This parameter change enables the system to achieve high SNR through digital filtering while maintaining manageable hardware complexity through FPGA implementation. The higher sampling rate provides better noise shaping and filtering performance.
Solution Approach 2:
The FPGA platform provides multi-functionality by integrating the Σ-Δ modulator, digital filter, and PWM generation circuitry into a single device. This universal platform handles multiple signal processing functions simultaneously, achieving high performance without proportionally increasing hardware complexity.
3Device complexity
If analog components are photo etched on silicon chip for PWM modulation, then integration is achieved, but true all-digitalization level is not reached
Solution Approach 1:
The patent substitutes all analog components with digital logic circuits implemented in FPGA. The Σ-Δ modulator, digital filter, and PWM generator are all realized through digital logic, achieving true all-digitalization. This eliminates the need for photo-etched analog components while maintaining high integration through the FPGA platform.
Data Source
AI summary
The present invention disclosed an all-digital speaker system device based on multi-bit Σ-Δ Modulation, comprising an A/D converter, an interpolation filter, a Σ-Δ modulator, a dynamic mismatch regulator, a differential buffer and a speaker array. The present invention takes advantage of the Σ-Δ modulation technique to effectively reduce the cost and complexity of the hardware realization of the speaker system device, thus realizing the full digitalization of the whole sound transmission link and the integration of the system device with low power dissipation and volume. Furthermore, the system device according to the present invention is provided with a better control ability on the local sound field, thus providing a better practicable method for the voice secret transmission.