Quadrature Audio Band Processing for Flexible EQ and Companding
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Solution Overview
Problem
Existing audio processing circuits in smartphones lack flexibility and control, particularly in equalization and companding, which limits the adjustment of frequency response and signal amplitude, leading to suboptimal audio quality and potential loudspeaker damage.
Innovation Solution
A novel circuit that processes audio signals by using quadrature sources, low pass filters, and companding techniques to allow for adjustable frequency band processing, enabling greater control over the audio signal's amplitude and phase, and allowing for the creation of a multi-band equalizer or compandor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional audio processing circuits are used in smartphones, then the device size remains small, but the flexibility and control over frequency response and signal amplitude are limited
Solution Approach 1:
The audio signal is divided into multiple frequency bands using quadrature sources and low pass filters. Each frequency band can be processed independently, allowing selective adjustment of amplitude and phase for different frequency ranges. This segmentation enables flexible audio processing while maintaining manageable circuit complexity through modular design.
Solution Approach 2:
The circuit employs dynamically adjustable parameters including quadrature source frequencies, filter cutoff frequencies, and companding gain values. These dynamic controls allow real-time adjustment of frequency response and signal amplitude, providing adaptability for different audio conditions and user preferences without requiring complex fixed circuitry.
2Reliability
If equalization and companding are applied to protect loudspeakers, then loudspeaker damage is prevented, but audio quality may be compromised without precise control
Solution Approach 1:
The companding circuit monitors signal amplitude across frequency bands and dynamically adjusts gain to prevent excessive levels that could damage loudspeakers. The feedback mechanism continuously adapts the processing parameters based on actual signal conditions, providing both protection and high-fidelity audio reproduction by maintaining optimal signal levels.
Solution Approach 2:
The system dynamically changes processing parameters including quadrature source frequencies, filter characteristics, and companding gain values based on signal conditions. This parameter adaptation enables precise control over audio quality while maintaining loudspeaker protection, as the circuit can optimize its behavior for different audio content and environmental conditions.
3Manufacturing precision
If multiple frequency bands are processed independently, then audio quality and user preference matching improve, but the processing complexity increases
Solution Approach 1:
The circuit merges multiple frequency band processing paths into a unified architecture using shared quadrature sources and systematic filtering. By combining the processing of multiple frequency bands through a common framework with coordinated quadrature sources and filters, the system achieves high-fidelity multi-band control while reducing overall complexity compared to completely separate processing chains.
Data Source
AI summary
A circuit and method is disclosed for filtering an audio signal. The circuit has a first quadrature source and multipliers for multiplying the input signal by the I and Q outputs of the quadrature source. The multiplied inputs are then passed through a pair of low pass filters, which may have an adjustable Q factor. The outputs of the low pass filters are then multiplied in a second pair of multipliers by the I and Q outputs, respectively, of a second quadrature source, which will typically be of the same frequency, but different amplitude and phase, of the first quadrature source. The twice-multiplied signals are then summed by an adder to provide an output signal. The circuit may be modified to include a companding circuit between the low pass filters and the second pair of multipliers that determines the amplitude of the input signal, filters it, and compands the signal in a compandor. The compandor may have adjustable parameters. The circuit thus allows for far greater flexibility and control of the processing of the input signal than prior art circuits.