Variable Quantizer Scaling for Noise Shaping Dynamic Range
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Solution Overview
Problem
Existing signal processing circuits face challenges in reducing quantization noise and increasing dynamic range without causing transient audible phenomena, such as 'pop', due to fixed scaling factors that lead to suboptimal performance at varying input signal levels.
Innovation Solution
A signal processing circuit with a dynamic range optimization circuit that adjusts scaling factors on the fly based on the absolute value of the noise shaping input signal, maintaining a constant ratio between scaling factors to prevent transients and optimize dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed scaling factor is used in the quantizer, then the device complexity is reduced and ease of operation is improved, but the dynamic range is limited and quantization noise increases at varying input signal levels
Solution Approach 1:
The patent implements a dynamic scaling factor that automatically adjusts based on the input signal level. The scaling factor is modified according to the absolute value of the input signal, allowing the quantizer to adapt to varying signal conditions. This dynamic adjustment optimizes the dynamic range and reduces quantization noise while maintaining operational simplicity through automated control.
2Adaptability or versatility
If a dynamic scaling factor is adjusted on the fly to optimize dynamic range, then the adaptability is improved, but transient disturbances occur causing audible pops
Solution Approach 1:
The patent applies preliminary anti-action by pre-adjusting the scaling factor based on the absolute value of the input signal before quantization occurs. The scaling factor is modified in advance according to the signal level, preventing transient disturbances from occurring during the quantization process. This proactive adjustment eliminates audible pops while maintaining optimized dynamic range.
3Manufacturing precision
If the scaling factor is increased to reduce quantization noise, then the manufacturing precision is improved, but the dynamic range decreases when input signal values are low
Solution Approach 1:
The patent implements a dynamic scaling factor that automatically adjusts based on the input signal level. When the input signal level is high, the scaling factor increases to reduce quantization noise and improve precision. When the input signal level is low, the scaling factor decreases to maintain adequate dynamic range. This dynamic adjustment optimizes both quantization precision and dynamic range across varying signal conditions.
Data Source
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AI summary
A signal processing circuit (20) includes a filter (23) generating a quantizer input signal (quantizerinput) from a noise shaping input signal (nshin) and a quantizer output signal (quantizeroutput). A quantizer (24) divides the quantizer input signal by a scaling factor (γ) to produce a noise shaping output signal (nshout) and multiplies the noise shaping output signal by the scaling factor to produce the quantizer output signal. Receiver circuitry (35) scales the quantizer output signal by a second scaling factor (α). A dynamic range optimization circuit (34) compares a current value of the noise shaping input signal to a threshold value, lowers or raises the scaling factor (γ) in response to the comparison, and proportionally lowers or raises the scaling factor (γ) such that a ratio between the scaling factor and second scaling factor (α) remains substantially constant.