Mixed-Signal Interference Cancellation in Wireless Transceivers
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Solution Overview
Problem
In wireless transceivers, especially those employing carrier aggregation, interference from modulated spurs and intermodulation distortions (IMD2) degrades signal quality due to non-linearities and cross-talk, which existing all-digital cancellation techniques struggle to effectively mitigate, especially in complex RF front-ends with limited isolation and high data rate demands.
Innovation Solution
A mixed-signal interference cancellation approach is used, where an interference reference signal is generated in the analog domain and processed in the digital domain to cancel modulated spurs and IMD2, leveraging existing receive chains for interference detection and mitigation, reducing hardware requirements and increasing cancellation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If all-digital cancellation techniques are used to mitigate interference, then implementation simplicity is improved, but cancellation performance deteriorates due to inability to effectively handle non-linearities and cross-talk in complex RF front-ends
Solution Approach 1:
The interference cancellation system is segmented into two distinct domains: an analog domain for generating interference reference signals (capturing non-linear characteristics) and a digital domain for processing and subtracting the interference. This segmentation allows each domain to handle tasks it is best suited for, resolving the contradiction between simplicity and performance.
Solution Approach 2:
An analog interference reference signal generator acts as an intermediary component that captures the non-linear characteristics and cross-talk of the RF front-end. This intermediary bridges the gap between the analog RF domain and the digital processing domain, enabling effective interference cancellation while maintaining system simplicity.
2Reliability
If dedicated interference cancellation hardware is added to improve cancellation performance, then interference mitigation capability is improved, but device complexity and production costs increase
Solution Approach 1:
The analog interference reference signal generator is designed to be a multi-functional component that can serve both the primary receive chain and the interference cancellation function. By reusing existing hardware resources for dual purposes, the system achieves improved interference mitigation without proportionally increasing device complexity or production costs.
Solution Approach 2:
The system uses its own existing receive chain hardware to generate the interference reference signal, rather than requiring completely separate dedicated cancellation hardware. The receive chain serves itself by providing both the signal to be received and the reference for canceling interference, reducing overall hardware requirements.
3Measurement precision
If analog domain interference reference signal generation is used, then interference detection accuracy is improved for non-linear distortions, but signal processing complexity increases
Solution Approach 1:
The system replaces complex digital signal processing methods with a simpler analog domain approach for generating interference reference signals. By using analog circuitry to naturally capture non-linear characteristics and cross-talk, the system achieves high detection accuracy without the computational complexity of purely digital methods.
Data Source
AI summary
A method and apparatus for cancelling an interference in a received signal. The apparatus may include a plurality of receivers and one or more transmitters. The first receiver is configured to process a received signal. The first receiver includes a mixer to down-convert the received signal using a first local oscillator signal having a first frequency. The received signal includes a wanted signal and an unwanted signal. The second receiver is configured to process the received signal and generate an interference reference signal. The second receiver includes a mixer to down-convert the received signal using a second local oscillator signal having a second frequency. The apparatus includes an interference canceller configured to cancel, in a digital domain, at least in part interference caused by non-linear characteristics of the first receive chain in a presence of the unwanted signal from the down-converted received signal by the first receive chain.