Balanced Passive Cancellation for Full Duplex Self-Interference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Full-duplex wireless communication systems face significant challenges due to high self-interference, which requires high isolation between transmitter and receiver components to prevent the transmitter signal from interfering with the receiver signal, limiting their performance and bandwidth.
Innovation Solution
The implementation of a transceiver circuit with balanced passive cancellation using power dividers, circulators, and power combiners to split and combine signals in differential and common modes, ensuring equal propagation lengths and symmetry between paths to effectively cancel self-interference without additional signal processing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high transmitter power is used to improve transmission distance and coverage, then transmission capability is improved, but self-interference to the receiver increases
Solution Approach 1:
The patent applies passive cancellation to convert the harmful self-interference signal into a beneficial cancellation mechanism. By creating two equal-magnitude signals with opposite phases through the power divider and circulator network, the transmitted signal that causes interference is transformed into a cancellation signal that actively neutralizes the interference at the receiver input, allowing high power transmission without proportional increase in interference.
Solution Approach 2:
The patent introduces asymmetry in the signal path configuration to achieve cancellation. The circulator components create asymmetric signal routing where the transmitted signal follows different paths (direct path vs. reflected path through circulator) that result in equal magnitude but opposite phase at the receiver, enabling the high power signal to interfere constructively with its own inverted version rather than with the received signal.
2Measurement precision
If high receiver sensitivity is used to improve signal detection capability, then reception performance is improved, but susceptibility to transmitter interference increases
Solution Approach 1:
The passive cancellation system converts the harmful transmitter interference into a beneficial cancellation signal. The power divider splits the transmitted signal into two paths, one of which is routed through the circulator to create an inverted version that equals the direct path signal in magnitude but opposes it in phase. This transformed interference signal is then combined at the receiver input to cancel the harmful interference, allowing high sensitivity operation without proportional increase in interference susceptibility.
3Object-generated harmful factors
If additional SI cancellation components are added to reduce self-interference, then isolation performance is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing transmitter components multi-functional to avoid adding complexity. The power divider, already necessary for signal distribution, is configured to also generate the cancellation signal path. The circulator components, used for signal routing, simultaneously provide the phase inversion function needed for cancellation. This universal use of existing components achieves self-interference cancellation without adding dedicated cancellation hardware, maintaining system simplicity while improving isolation performance.
4Volume of moving object
If compact antenna subsystems are used to reduce device size, then miniaturization is achieved, but signal bandwidth may be limited
Solution Approach 1:
The patent segments the signal paths into multiple independent routes (direct path and circulator-reflected path) that can be independently optimized. This segmentation allows the compact antenna subsystem to handle wide bandwidth signals by distributing the signal processing across multiple paths, preventing bandwidth limitation that would otherwise result from miniaturization. The segmented approach maintains signal integrity across wide frequency ranges despite reduced physical size.
Data Source
AI summary
System and method embodiments are provided for implementing balanced passive cancellation of self-interference (SI) for full-duplex (FD) communications. In an embodiment, a transceiver circuit for FD communications comprises an antenna comprising a first port and a second port, a transmitter, and a power divider coupled to the transmitter and comprising a first output and a second output. The transceiver circuit further comprises a receiver, a power combiner coupled to the receiver and comprising a first input and a second input, and a first circulator coupled to the first output of the power divider, the first port of the antenna, and the first input of the power combiner. The transceiver circuit also comprises a second circulator coupled to the second output of the power divider, the second port of the antenna, and the second input of the power combiner.