Delta-Sigma Demodulation With Digital Downconversion for Low Distortion
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Solution Overview
Problem
Traditional demodulator architectures face challenges such as increased noise, distortion, and complexity in processing radio frequency (RF) signals, particularly due to harmonics and nonlinearities in mixers, and require higher sample rates and resolution in analog-to-digital converters (ADCs) for digital down-conversion.
Innovation Solution
The proposed demodulator architecture performs down-conversion after delta-sigma modulation, using a digital downconverter and decimation filter to process the 1-bit output from the delta-sigma modulator, simplifying the system by reducing the order of the delta-sigma modulator and decimation filter, and utilizing a CORDIC for digital local oscillator generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional demodulator architectures are used with mixers and ADCs, then signal processing capability is achieved, but noise and distortion increase due to harmonics and nonlinearities
Solution Approach 1:
The patent replaces the traditional mixer-based frequency conversion mechanism with a digital downconverter that operates on the output of a delta-sigma modulator. This substitution eliminates the nonlinear mixing process that generates harmonics and distortion, achieving frequency conversion in the digital domain where such harmful effects are avoided.
Solution Approach 2:
The patent changes the operating parameters by using a delta-sigma modulator with a low sample rate and low resolution (1-bit output) instead of requiring high sample rates and high resolution ADCs. This parameter change simplifies the conversion process and reduces the introduction of quantization noise and distortion while maintaining signal fidelity through the subsequent digital processing stages.
2Measurement precision
If high sample rates and resolution are used in ADCs for digital down-conversion, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent segments the signal processing function into two distinct stages: first, a simple delta-sigma modulator that performs oversampled 1-bit conversion at low complexity, and second, a digital downconverter with decimation filter that performs the precise frequency conversion and signal reconstruction in the digital domain. This segmentation allows each stage to be optimized independently, avoiding the need for a single complex high-resolution ADC.
Solution Approach 2:
The patent transitions from analog domain processing with high-resolution ADCs to a digital domain approach where the delta-sigma modulator output is processed through digital downconversion and decimation. This dimensional change from analog to digital processing enables precise signal recovery without requiring complex high-resolution analog-to-digital conversion hardware.
3Speed
If traditional mixer operations are used, then frequency conversion is achieved, but distortion increases due to nonlinearities
Solution Approach 1:
The patent substitutes the analog mixer operation with a digital downconverter that performs frequency conversion using digital signal processing. The delta-sigma modulator output is multiplied by a digital local oscillator signal in the digital domain, eliminating the nonlinear mixing process that generates harmonic distortion while maintaining efficient frequency conversion capability.
Data Source
AI summary
Disclosed herein are devices, systems, and methods for improved demodulation. In one embodiment, a demodulator includes an input port configured to receive an analog input signal having a first frequency spectrum, a delta-sigma modulator electrically coupled with the input port, a digital downconverter electrically coupled with the delta-sigma modulator, and a filter electrically coupled with the digital downconverter. The filter is configured for a passband having a second frequency spectrum. The demodulator also includes an output port electrically coupled with the filter. The output port is configured to provide an output signal having the second frequency spectrum.