Digital Speaker Array Channel Equalization and Beam Control
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Solution Overview
Problem
Digital speaker systems face challenges with nonlinear distortion and low over-sampling rates in PWM modulation, leading to poor signal quality and beam steering limitations, especially in reverberant environments where frequency response fluctuations and multi-path interferences are prevalent, affecting the accuracy and stability of sound field reproduction.
Innovation Solution
A method for channel equalization and beam controlling in digital speaker arrays that involves converting analog and digital signals into PCM-coded signals, using weighted impulse responses for equalization, and regulating channel weights for beam-forming, combined with multi-bit Σ-Δ modulation and dynamic mismatch shaping to improve SNR and beam directivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If PWM modulation is used in digital speaker systems, then the system achieves digitization and integration, but nonlinear distortion components are generated in the desired band due to inherent nonlinear defects of the modulation structure
Solution Approach 1:
The patent changes the modulation parameter from traditional PWM to multi-bit Σ-Δ modulation, which fundamentally alters the modulation structure to eliminate inherent nonlinear defects. This parameter change allows the system to maintain digitization while avoiding the generation of nonlinear distortion components in the desired band.
Solution Approach 2:
The patent converts the high-frequency noise inherent in Σ-Δ modulation into a beneficial feature by using noise shaping to push quantization noise out of the audio band. The noise that would normally be harmful is redirected to frequencies above the audible range, where it can be easily filtered out, thereby improving signal quality in the desired band.
2Device complexity
If the over-sampling rate of PWM modulation is reduced for hardware realization, then the system complexity is decreased, but the SNR of the coded signals cannot be further increased due to the limitation of the over-sampling rate
Solution Approach 1:
The patent changes the modulation architecture from PWM to multi-bit Σ-Δ modulation, which fundamentally alters how oversampling and noise shaping work. This parameter change enables the system to achieve high SNR even at lower oversampling rates because the noise shaping mechanism is more efficient in pushing quantization noise out of the audio band.
Solution Approach 2:
The patent replaces the mechanical/PWM-based modulation approach with a digital Σ-Δ modulation approach. This substitution allows for more flexible and efficient noise management through digital signal processing, enabling high SNR performance without requiring excessively high oversampling rates that would increase hardware complexity.
3Object-generated harmful factors
If dynamic mismatch shaping technique is used to eliminate high-order harmonic components, then the total harmonic distortion ratio is reduced, but the frequency response fluctuation in audio band of each channel is not equalized, causing great deviation between system restoration signal spectrum and sound source signal real spectrum
Solution Approach 1:
The patent integrates multiple functions into a single channel equalization and beam controlling device. The device simultaneously performs frequency response equalization across all channels and beam forming operations, ensuring that both harmonic distortion is reduced and frequency response flatness is maintained across the audio band.
Solution Approach 2:
The patent implements feedback mechanisms in the channel equalization process, where the system measures the actual frequency response of each channel and adjusts the equalization parameters accordingly. This feedback loop ensures that frequency response fluctuations are compensated while maintaining low harmonic distortion through coordinated beam forming.
4Device complexity
If simple channel delay regulation is used for beam steering, then the beam-forming method is simple to implement, but the beam control ability is weak and cannot accomplish steering control of multiple beams or achieve good directional control in reverberant environments with multi-path scattering
Solution Approach 1:
The patent changes the beam-forming approach from simple delay regulation to a comprehensive channel equalization and beam controlling method. This parameter change enables the system to regulate both magnitude and phase of transmission signals, achieving superior beam steering control and the ability to form multiple beams simultaneously.
Solution Approach 2:
The patent creates a universal beam controlling device that can handle multiple beam steering scenarios, including free-field environments and reverberant environments with multi-path scattering. The device simultaneously performs channel equalization, beam forming, and adaptive control, making it versatile across different acoustic conditions.
Data Source
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AI summary
The present invention discloses a method and device of channel equalization and beam controlling for a digital speaker array system. The method comprises the following steps: (1) converting digital format; (2) performing channel equalization; (3)controlling beam-forming; (4) performing multi-bit Σ-Δ modulation; (5)performing thermometer code conversion; (6) performing dynamic mismatch-shaping processing; (7) extracting the channel information to send to the digital power amplifier and drive the array sound. The device of the invention comprises: a sound source, a digital converter, a channel equalizer, a beam-former, a Σ-Δ modulator, a thermometer coder, a dynamic mismatch shaper, a extraction selector, a multi-channel digital power amplifier and a speaker array, wherein each unit connects to each other serially. The invention achieves the full-digital of the system and reduces the volume, power dissipation and cost, and enhances the electro-acoustic conversion efficiency and the anti-interference ability thereof, and improves the frequency response flatness in audio band of the system, accomplishes the beam directionality control of the digital array, and provides an effective realizing way for the special sound effect.