ADC Spur Cancellation Using Adaptive I/Q Multi-Tone Filtering
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Solution Overview
Problem
Analog-to-Digital Converters (ADCs) produce spurious signals that degrade the Signal-to-Noise Ratio (SNR), limiting their performance, and existing filtering techniques are inadequate, especially when unwanted signals occur within the signal bandwidth, and conventional adaptive filtering is slow and computationally intensive.
Innovation Solution
Systems and methods generate digital signals to track and cancel unwanted multi-tones by learning coefficients for in-phase and quadrature components, allowing simultaneous cancellation of multiple signals, and include mechanisms for frequency error estimation and Received Signal Strength Indicator (RSSI) to decide on cancellation activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional adaptive filtering techniques are used to cancel spurious signals, then spurious signal cancellation is achieved, but the filtering process is slow and computationally intensive
Solution Approach 1:
The patent changes the computational parameters by using a simplified error metric (total power of unwanted signal) and closed-form coefficient solutions, transforming the computationally intensive iterative process into a faster calculation that directly computes optimal coefficients based on current signal estimates
Solution Approach 2:
The patent extracts and separately processes the unwanted signal components (multi-tone interference) from the desired signal, allowing independent cancellation of spurious signals without processing the entire composite signal through complex filtering operations
2Object-generated harmful factors
If learning rate coefficients are used in adaptive filtering, then spurious signal tracking is achieved, but the convergence time is extended
Solution Approach 1:
The patent skips the gradual iterative learning process by directly computing coefficients that cancel the currently detected unwanted signal, rushing through the adaptation process in discrete steps rather than slow continuous learning
Solution Approach 2:
The patent performs preliminary detection of unwanted signal parameters (frequency, amplitude, phase) and pre-computes cancellation coefficients before the actual cancellation is applied, preparing the solution in advance rather than reacting slowly to signal changes
3Object-generated harmful factors
If continuous adaptive filtering is applied during signal reception, then spurious signal cancellation is maintained, but power consumption increases
Solution Approach 1:
The patent applies periodic action by updating cancellation coefficients at specific intervals or when unwanted signals are detected, rather than continuously processing every incoming signal sample, thereby maintaining cancellation effectiveness while reducing overall power consumption
Solution Approach 2:
The patent implements dynamic adaptation where the filtering operation is activated or adjusted based on the presence and strength of unwanted signals, allowing the system to consume more power only when necessary for cancellation rather than maintaining constant high power operation
4Object-generated harmful factors
If low-pass filters are used to filter unwanted signals, then frequency separation is achieved, but signals within the bandwidth cannot be effectively distinguished
Solution Approach 1:
The patent applies local quality by targeting specific frequency components identified as unwanted signals with cancellation coefficients, rather than applying a broad low-pass filter that affects all frequencies above a threshold, thereby preserving desired signals within the bandwidth while removing specific spurious components
Data Source
AI summary
Systems and methods for adaptive filtering in an Analog-to-Digital Converter (ADC) address the issue of spurious tones affecting the Signal-to-Noise Ratio (SNR). In an illustrative, non-limiting embodiment, a system may include a processor configured to execute program instructions for estimating and compensating spurious signals in the ADC output. The system may identify the frequency, phase, and amplitude of spurious signals using Gi-Gq computation. In some cases, the ADC output path and spurious estimation processing may be oversampled to compensate for high-frequency spurs (e.g., closely below the ADC's Nyquist frequency). Also, such a system may operate before or during the reception of the signal, ensuring no impact on the useful signal reception and reducing power consumption. In another illustrative, non-limiting embodiment, a method may include adaptive filtering or cancellation of unwanted tones by learning and applying coefficients to the in-phase (I) and quadrature (Q) components of a digital signal.