Undersampling ADC and DSP Separation for Wideband Bitstreams
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Solution Overview
Problem
Wide band communication systems require high-end analog to digital converters (ADCs) that are complex, power hungry, and expensive due to the need to sample signals at the Nyquist rate to avoid aliasing, which limits their efficiency and cost-effectiveness.
Innovation Solution
An apparatus comprising an ADC and a digital signal processor (DSP) that undersamples signals to create a superposition signal, allowing for the extraction of information from aliased components using orthogonal signal separation techniques, enabling the separation of bitstreams from different frequency bands without filtering out high-frequency content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signals are sampled at the Nyquist rate to avoid aliasing, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent intentionally allows aliasing to occur during undersampling, then converts this previously harmful effect into a beneficial feature by using orthogonal encoding schemes. Different frequency bands are encoded with orthogonal codes, and the digital signal processor exploits the orthogonal properties to separate and recover the original signals from the aliased superposition, transforming the aliasing problem into a solution that enables lower sampling rates.
Solution Approach 2:
The patent changes the sampling rate parameter from the traditional Nyquist rate to a lower rate that intentionally causes aliasing. This parameter change is compensated by introducing orthogonal encoding in the frequency domain, allowing the system to operate at lower sampling rates while maintaining signal recovery capability through digital signal processing.
2Measurement precision
If signals are sampled at the Nyquist rate to avoid aliasing, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent converts the harmful aliasing effect into a beneficial mechanism by using orthogonal encoding. Different frequency bands are modulated with orthogonal codes, and even though they alias and superpose in the time domain, their orthogonal properties allow the digital signal processor to separate them perfectly, enabling power-efficient undersampling without sacrificing measurement accuracy.
Solution Approach 2:
The patent replaces the traditional approach of using high-speed analog-to-digital converters (mechanical/electrical sampling system) with a digital signal processing approach that uses orthogonal coding and correlation. This substitution moves the complexity from the analog sampling domain to the digital processing domain, enabling lower power consumption in the ADC while maintaining signal fidelity.
3Measurement precision
If high-end ADCs are used to sample wide band signals at Nyquist rate, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent transforms the aliasing phenomenon from a harmful distortion into a useful mechanism for cost reduction. By encoding different frequency bands with orthogonal codes and allowing them to alias into a lower sampling rate, the system achieves wideband signal processing with lower-cost, lower-performance ADCs that would normally be insufficient for the application.
Solution Approach 2:
The patent changes the sampling rate parameter to a lower value that reduces ADC cost and complexity. This parameter change is made feasible by introducing orthogonal encoding in the frequency domain, which compensates for the reduced sampling rate and enables accurate signal recovery despite the lower performance requirements of the ADC.
Data Source
AI summary
A system includes an ADC configured to generate a superposition signal by the ADC being configured to under-sample an input signal at a sampling frequency in which the input signal that is input to the analog to digital converter has a bandwidth and the sampling frequency is less than a Nyquist rate for the bandwidth of the input signal. The system includes a digital signal processor (DSP) configured to digitally process the superposition signal to separate the superposition signal into a plurality of bitstreams, where each of the plurality of bitstreams corresponds to information in a different one of a plurality of separable, distinct frequency bands within the input signal. The information in the superposition signal for at least one of the said plurality of bitstreams is present in the input signal at frequencies greater than the sampling frequency, and the DSP is configured to output said plurality of bitstreams.