ADC Signal Quality Improvement via Oscillator Frequency Adjustment
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Solution Overview
Problem
Analog-to-digital converters (ADCs) in receivers introduce distortion due to high-level input signals and non-linearities, causing harmonic blocking signals that alias onto desired channels, leading to interference and noise, which existing technologies struggle to effectively filter or mitigate.
Innovation Solution
An adjustment mechanism that analyzes ADC output signals using spectral characterization and interference assessment to adjust the frequency of local oscillators and digital downconverters, shifting blocking signals out of the desired channel range, thereby improving the signal-to-interference-plus-noise-and-distortion (SINAD) ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ADC samples intermediate frequency signal, then signal conversion is achieved, but distortion and harmonic blocking signals are introduced
Solution Approach 1:
The patent characterizes the ADC's distortion behavior and uses this harmful effect to predict blocking signal locations. By analyzing the ADC output spectrum and identifying strong signals that could generate harmful harmonics, the system proactively adjusts oscillator frequencies to prevent these harmonics from aliasing onto desired channels, thus converting the understanding of harmful effects into a preventive mechanism
Solution Approach 2:
The system performs spectral characterization of the ADC and identifies potential blocking signals before they cause interference. By analyzing the intermediate frequency signal spectrum and predicting where harmonic blocking signals will alias, the system adjusts oscillator frequencies in advance to prevent the harmful effects from occurring in the first place
2Object-affected harmful factors
If traditional filtering is used to reduce noise, then noise reduction is achieved, but desired signals may also be attenuated
Solution Approach 1:
Instead of using traditional filtering that operates in the frequency domain with fixed characteristics, the patent changes the approach by dynamically adjusting oscillator frequencies in the time domain. This parameter change allows the system to move blocking signals out of alignment with desired channels without applying fixed filters that would attenuate both noise and desired signals
3Object-generated harmful factors
If oscillator frequencies are adjusted dynamically, then interference is reduced, but system complexity increases
Solution Approach 1:
The system implements a feedback mechanism where the ADC output spectrum is continuously analyzed, blocking signal locations are predicted based on characterized ADC distortion behavior, and oscillator frequencies are adjusted accordingly. This closed-loop feedback approach enables automatic interference reduction without requiring complex manual configuration or multiple hardware components
Data Source
AI summary
Improving signal quality by sampling an intermediate frequency signal by an analog-to-digital converter (ADC) and determining spectral characteristic data of the output signal of the ADC, and processing the spectral characteristic data to identify blocking signals and blocking spur signals that interfere with any desired signals. An adjustment is made to the frequency of one or more oscillators to reduce the interference resulting from the blocking signals if a ratio of the desired signal level to the total interfering blocker spur level is below a threshold.