Noise-Shaping DAC Circuit for Quantization Noise Redistribution
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Solution Overview
Problem
Conventional digital-to-analog converters introduce quantization noise that limits communication system performance, requiring a large number of bits and increased size and complexity, which in turn increases costs.
Innovation Solution
A noise shaping module with specific filter transfer functions is incorporated into the system to suppress quantization noise, utilizing a first filter with a transfer function G(z) and a second filter with a transfer function H(z), where the sum of these functions is approximately 1, to equalize noise components in the frequency domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large number of bits are used for the digital-to-analog converter input, then the quantization noise level is reduced, but the digital-to-analog converter size and complexity are increased
Solution Approach 1:
The patent changes the frequency distribution parameter of quantization noise by introducing noise shaping filters with transfer functions G(z) and H(z). This redistributes the noise power spectrum density across different frequency bands, concentrating quantization noise in frequency bands with higher channel attenuation where it has less impact on system performance, thereby reducing the required number of bits
Solution Approach 2:
The patent applies different filtering characteristics to different frequency components of the quantization noise. By using frequency-dependent transfer functions G(z) and H(z), the noise shaping is optimized for specific frequency bands, allowing aggressive noise suppression in critical bands while maintaining signal fidelity elsewhere
2Reliability
If the quantization noise power spectrum density is reduced to meet system requirements, then communication system performance is improved, but the digital-to-analog converter requires more bits and becomes more complex
Solution Approach 1:
The patent modifies the spectral distribution parameter of quantization noise using noise shaping filters. By changing how noise power is distributed across frequency rather than uniformly reducing it, the system achieves better performance in critical frequency bands without requiring a uniform increase in bit depth across all frequencies
Solution Approach 2:
The patent employs feedback mechanisms through the noise shaping filter structure where the quantization noise is filtered and fed back with transfer function H(z). This feedback selectively reinforces or attenuates noise components at different frequencies, shaping the overall noise spectrum to meet system requirements more efficiently
Data Source
AI summary
A noise shaping circuit and method for operating the same includes a first addition module that receives a digital input signal. A first filter module generates a first filtered output signal based on an output of the first addition module. A truncation module generates a truncated output signal based on first filtered output signal. A second filter module generates a second filtered output signal based on the truncated output signal. The second filtered output signal is an input to the first addition module.