Digital Signal Selection Circuit for Noise-Free Audio Switching
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Solution Overview
Problem
Car audio systems experience switching noise when selecting the same sound source for both front and rear speakers, as existing analog selectors propagate noise between channels.
Innovation Solution
A signal selecting circuit that converts analog signals to digital signals and uses a digital selector to output signals, allowing for noise-free switching by controlling the selection and conversion of signals without changing the unchanged output channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If analog selectors are used to select sound sources for front and rear speakers, then sound source selection is achieved, but switching noise occurs when the same sound source is selected for both channels
Solution Approach 1:
The patent replaces the mechanical analog switching system with a digital signal processing system. Analog-to-digital converters (ADCs) convert the analog audio signals to digital domain, where a digital selector (multiplexer) performs the channel selection. This substitution eliminates the switching noise inherent in analog mechanical switches because digital switching occurs in the digital domain without the contact bounce and electromagnetic interference characteristic of mechanical analog switches.
Solution Approach 2:
The patent introduces digital signal processing as an intermediary between the analog audio sources and the output channels. The ADCs and digital selector act as intermediaries that process the audio signals in the digital domain, preventing direct analog switching between channels. This intermediary digital processing stage isolates the selection logic from the analog signal paths, thereby preventing noise propagation to unchanged channels.
2Object-generated harmful factors
If digital signal processing is used to select sound sources, then switching noise is prevented, but system complexity increases due to additional converters and control circuits
Solution Approach 1:
The patent segments the audio processing system into distinct functional modules: analog-to-digital conversion stage, digital selection stage, and digital-to-analog conversion stage. Each module performs a specific function independently. The ADCs convert analog signals to digital, the digital selector performs channel routing in the digital domain, and DACs convert back to analog for output. This segmentation allows noise-free digital switching while organizing the complexity into manageable, modular components.
Solution Approach 2:
The digital selector serves multiple functions: it routes different audio sources to different output channels, enables independent channel selection, and prevents noise propagation simultaneously. The control circuit that generates selection signals also manages both the analog and digital selection processes, providing multi-functionality that reduces overall system complexity despite the added digital processing stage.
Data Source
AI summary
A signal selecting circuit is disclosed which outputs a first and a second digital signals by converting a first and a second analog signals into digital signals, the first and the second analog signals being the same or different signals selected from a plurality of analog signals, the signal selecting circuit comprising: an analog signal selection circuit that, based on an analog selection signal, selects the first and the second analog signals from the plurality of analog signals; a first AD converter that converts the first analog signal outputted from the analog signal selection circuit into a third digital signal to output the third digital signal; a second AD converter that converts the second analog signal outputted from the analog signal selection circuit into a fourth digital signal to output the fourth digital signal; a digital signal selection circuit that, based on a digital signal, selectively outputs one or both of the third and the fourth digital signals as the first and the second digital signals; and a control circuit that, based on an output selection signal for selecting the first and the second digital signals, outputs the analog selection signal and the digital selection signal.