Software-Defined Radio Front End Using Tone-Based Duplexerless Isolation
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Solution Overview
Problem
Conventional wireless communication systems face challenges in reducing self-interference in full duplex Frequency Division Duplex (FDD) systems, particularly due to the large size and complexity of duplexers required for high isolation, which are exacerbated by the increased interference and bandwidth demands of 4G technologies.
Innovation Solution
A reconfigurable software-defined radio front end that uses a combination of feed-forward cancellation and digital residual interference cancellation methods, including the injection of tones to characterize the receive channel and processing with an infinite impulse response filter to generate an interference cancellation signal, allowing for software-controlled operation across different bands and modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional filter-based duplexers are used to attenuate self-interference, then isolation between transmit and receive signals is improved, but device size and weight increase significantly
Solution Approach 1:
The patent replaces the mechanical filter-based duplexer system with an electronic self-interference cancellation system. The cancellation system uses signal processing techniques including feed-forward cancellation and digital residual interference cancellation to achieve the required isolation without physical filters, thereby eliminating the large metal housing with air-filled cavities and significantly reducing weight.
Solution Approach 2:
The patent introduces an intermediary cancellation signal that is 180 degrees out of phase with the self-interference signal. This cancellation signal is generated by sampling the transmit signal, processing it through IIR filters to match the receive channel characteristics, and then subtracting it from the received signal, thereby eliminating the need for large physical isolation components.
2Reliability
If filter-based duplexers are used to meet isolation requirements, then transmit-to-receive isolation is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical filter assemblies with software-controlled digital signal processing. The system uses microprocessors to implement feed-forward cancellation and digital residual interference cancellation algorithms, replacing the need for complex multi-band filter designs and switch networks with programmable logic and algorithms.
Solution Approach 2:
The cancellation system is designed to be multi-band and reconfigurable through software control. The same hardware platform can operate across multiple frequency bands and standards (including LTE-Advanced) by loading different filter coefficients and cancellation parameters, eliminating the need for multiple dedicated duplexers for different bands.
3Reliability
If large duplexers are used to handle increased interference from high-power transmitters, then isolation is improved, but loss of energy increases
Solution Approach 1:
The patent eliminates the energy losses inherent in physical filter components by using electronic cancellation. The cancellation system processes signals in the digital domain where energy loss is minimal, avoiding the insertion losses and heat generation associated with large-power handling in conventional filter-based duplexers.
4Adaptability or versatility
If multiple duplexers are used for multi-band operation, then adaptability to different frequency bands is improved, but device complexity and size increase
Solution Approach 1:
The patent implements a universal cancellation platform that can operate across multiple frequency bands and communication standards. The system uses software-controlled IIR filters with reconfigurable coefficients that can be adjusted to match the characteristics of different bands, allowing a single hardware platform to provide multi-band operation without requiring multiple dedicated duplexers or complex switch networks.
Solution Approach 2:
The cancellation system is dynamically reconfigurable through software control. Filter coefficients, cancellation parameters, and processing algorithms can be adjusted in real-time to optimize performance for different frequency bands and operational modes, providing adaptability without the static complexity of multiple fixed duplexers.
Data Source
AI summary
The present application describes a computer-implemented method for configuring a front end including receiving a first signal and a second signal containing interference; characterizing the receive channel using the first tone; processing the compensated first signal using an infinite impulse response filter based on the characterized receive channel to generate an interference cancelling signal; and coupling the interference cancelling signal to the second signal to generate an interference cancelled receive signal. The present application also describes a computer-implemented apparatus for a front end.