Adaptive Nonlinear Interference Cancellation for ADC Dynamic Range
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Solution Overview
Problem
Existing digital receivers face limitations in tolerating high levels of in-band interference, leading to signal degradation due to analog to digital converter (ADC) bit limitations and linear interference cancellation methods, which fail to effectively separate and cancel coincident interference without reducing signal levels.
Innovation Solution
An adaptive interference cancellation system utilizing a combination of analog and digital stages, where the first stage identifies and characterizes interferers before digitization, and a digital signal processor generates a cancellation waveform to remove interference in real-time, with adjustable parameters and calibration tables to optimize cancellation, and a second digital stage further enhances cancellation, achieving nonlinear interference cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If linear interference cancellation methods are used to separate interference from desired signals, then interference removal is achieved, but signal levels are reduced along with interference due to lack of orthogonality in near or complete signal-interference coincidence
Solution Approach 1:
The patent transforms the interference cancellation approach from linear to nonlinear by changing the mathematical space in which cancellation occurs. Specifically, it maps signals to a nonlinear feature space where interference and desired signals become more distinguishable, allowing cancellation to proceed without degrading the desired signal. This parameter change in the cancellation methodology enables high-level interference removal while preserving signal integrity even in coincident scenarios.
Solution Approach 2:
The patent replaces conventional linear cancellation mechanisms with a nonlinear cancellation system that uses modulation type detection and characterization. Instead of relying on linear subtraction that fails when signals are non-orthogonal, the system substitutes a more sophisticated approach that identifies interferer characteristics and applies targeted nonlinear cancellation, thereby removing interference without the signal degradation that plagues linear methods.
2Object-affected harmful factors
If gain is reduced in front of ADC to prevent saturation from large interferers, then ADC saturation is avoided, but desired signal level is reduced to the point where ADC ENoB limitations degrade signal recovery
Solution Approach 1:
The patent applies preliminary interference cancellation before the ADC conversion process. By detecting and characterizing interferers in advance and generating cancellation waveforms that are subtracted from the received signal prior to digitization, the system removes large interferers beforehand. This preliminary action prevents ADC saturation without requiring gain reduction, thereby maintaining adequate signal levels for accurate ADC conversion and signal recovery within the ADC's dynamic range.
3Object-affected harmful factors
If analog interference cancellation is used, then interference cancellation is achieved, but cancellation is limited to 20 to 30 dB due to imperfections and differences between analog components
Solution Approach 1:
The patent replaces the analog cancellation system with a digital cancellation system. Instead of relying on analog components that suffer from manufacturing tolerances and component variations limiting cancellation to 20-30 dB, the system uses digital signal processing to generate and apply cancellation waveforms. This substitution of digital for analog enables much higher cancellation levels (potentially 60 dB or more) because digital systems are not constrained by analog component imperfections and can achieve precise waveform generation and subtraction.
Data Source
AI summary
Methods and apparatus to cancel an interfering signal using an analog cancellation stage followed by a digital cancellation stage. In an exemplary embodiment, the interfering signal is processed to determine modulation type for removal in the analog domain. The digital stage provides further interference reduction in the digital domain.