Switched Interference Cancellation Circuit for Wireless Coexistence
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Solution Overview
Problem
Advanced wireless devices with multiple radios operating on the same, adjacent, or harmonic frequencies face co-existence issues due to interference, which existing active interference cancellation methods struggle to effectively address, especially when the coupling path signal is stronger than the desired signal, leading to saturation in LNA and ADC.
Innovation Solution
A method and circuit for interference cancellation in wireless communications devices that involves receiving a reference signal, selecting a target interference type, configuring a filter using computed coefficients, and canceling interference using an output of the filter, with the ability to operate in both analog and digital domains to handle fundamental and out-of-band interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If active interference cancellation is implemented in baseband, then the system complexity is reduced, but the cancellation performance deteriorates due to LNA and ADC saturation from the strong coupling path signal
Solution Approach 1:
The interference cancellation system is segmented into multiple domains: analog domain for coupling path cancellation and digital domain for residual interference cancellation. This segmentation allows each domain to handle specific types of interference appropriately, preventing saturation while maintaining cancellation performance.
Solution Approach 2:
An intermediate analog cancellation stage is introduced before the digital baseband processing. This intermediary analog cancellation unit weakens the strong coupling path signal before it reaches the LNA and ADC, preventing saturation and enabling subsequent digital processing to effectively cancel residual interference.
2Device complexity
If a single interference cancellation method is used, then the device complexity is reduced, but the adaptability to different interference types deteriorates
Solution Approach 1:
The interference cancellation system is designed with multi-functionality to handle multiple interference types (fundamental frequency interference and out-of-band interference) using a unified architecture that combines analog and digital cancellation methods, making the system adaptable to different interference scenarios.
Solution Approach 2:
The system dynamically selects and applies different cancellation strategies based on the detected interference type. The interference cancellation circuit adapts its operation mode (analog-only, digital-only, or combined) according to the specific interference characteristics, optimizing performance for each scenario.
3Reliability
If analog interference cancellation is used, then the cancellation performance is improved, but the device complexity and power consumption increase
Solution Approach 1:
The cancellation system is segmented into analog and digital parts, where the analog part handles the most critical coupling path cancellation and the digital part handles residual interference. This segmentation allows the analog circuit to be simpler while maintaining overall high cancellation performance.
Solution Approach 2:
The system uses digital copying of the reference signal to generate the cancellation signal in the analog domain, avoiding the need for complex analog signal generation circuits while maintaining cancellation accuracy.
Data Source
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AI summary
Aspects of the disclosure are directed to interference cancellation and wireless communication. A method of performing analog interference cancellation in a wireless communications device having a transmitter and a receiver includes receiving a reference signal representative of an interfering signal transmitted by the transmitter, selecting a first target interference type from one of a plurality of interference types affecting a an RF signal received by the receiver, configuring a first filter of an interference cancellation circuit using a coefficient computed based on the first target interference type, and cancelling interference in the RF signal using an output of the first filter. Coefficient computation may be performed in a switched manner between analog and digital domain, simultaneously in multiple domains, or in a cascaded manner that provides digital interference cancellation.