RF Front End Self-Interference Cancellation Using Phase and Time Delay Segmentation
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Solution Overview
Problem
Current methods for cancelling self-interference in full duplex radio (FDR) RF front ends are ineffective due to difficulties in achieving precise phase differences and high resolution time delays, leading to degraded cancellation performance.
Innovation Solution
Incorporating a phase shift circuit into the RF front end structure, which includes an attenuator and a true time delay circuit, to adjust the phase and time delay of the self-interference signal, allowing for effective subtraction of the self-interference signal from the received signal at the low noise amplifier (LNA).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a true time delay circuit is used to cancel self-interference signal, then time delay adjustment is achieved, but the circuit complexity and difficulty in achieving high resolution increase
Solution Approach 1:
The patent divides the time delay adjustment function into two separate components: a coarse adjustment stage using a true time delay circuit and a fine adjustment stage using a phase shifter. This segmentation allows each component to operate at lower resolution requirements, reducing overall circuit complexity while maintaining high precision cancellation capability.
Solution Approach 2:
The patent transitions from a single-dimension time delay approach to a two-dimension approach by adding phase shift as a separate dimension of adjustment. This allows independent control of time delay and phase, simplifying the requirements for each individual component while achieving high overall precision.
2Reliability
If phase shift circuit is added to adjust non-linear phase shift, then self-interference cancellation performance is improved, but device complexity increases
Solution Approach 1:
The patent introduces a phase shifter as an intermediary component between the true time delay circuit and the signal subtraction point. This intermediary specifically addresses the non-linear phase shift characteristic of self-interference signals, enabling accurate cancellation without requiring the main time delay circuit to handle phase complications.
3Measurement precision
If high resolution time delay is implemented, then self-interference signal modelling is improved, but the burden on true time delay circuit increases
Solution Approach 1:
The patent segments the precision requirements between two components: the true time delay circuit handles coarse time delay with relaxed resolution requirements, while the phase shifter handles fine-tuning with high resolution. This segmentation reduces the performance burden on the true time delay circuit while maintaining overall high precision signal modelling.
Data Source
AI summary
The apparatus includes a transmission signal divider for dividing and transmitting a received signal to a transmission antenna and an attenuator, an attenuator for applying a predetermined attenuation factor to the transmitted signal divided to the attenuator, a phase shifter for phase-shifting the signal to which the attenuation factor is applied by a predetermined phase, and a time delayer for time-delaying the phase-shifted signal by a predetermined time.