In-band Full Duplex Transceiver Self-Interference Cancellation
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Solution Overview
Problem
Current in-band full duplex methods face challenges in achieving efficient self-interference cancellation, particularly in wideband systems, due to limitations in antenna separation techniques and the deterioration of electrical balance duplex performance as system bandwidth widens, making it difficult to apply to small devices and maintaining effective signal cancellation across various frequency bands.
Innovation Solution
The proposed solution involves an in-band full duplex transceiver design that includes a hybrid transformer with impedance matching units and a finite impulse response (FIR) filter, which phase-inverts and combines signals to cancel self-transmitting interference, using a controller to set attenuation degrees based on frequency domain conversions to minimize interference across different frequency bandwidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If antenna region SIC technique is used to physically separate transmitting and receiving antennas, then self-interference cancellation performance is improved, but device size increases and it cannot be applied to small devices
Solution Approach 1:
The patent introduces an electrical balance duplex (EBD) circuit as an intermediary component that electrically separates the transmitting and receiving signal paths without requiring physical distance. The EBD circuit uses reactive components (inductors and capacitors) to create signal cancellation paths that mimic the effect of physical separation, enabling self-interference cancellation in compact device form factors
Solution Approach 2:
The patent replaces the mechanical/physical separation approach (antenna region SIC) with an electrical field-based approach (electrical balance duplex). Instead of relying on physical distance to attenuate self-interference, the invention uses electrical circuitry with reactive components to create phase-inverted cancellation signals, substituting mechanical separation with electrical field manipulation
2Device complexity
If electrical balance duplex (EBD) technique is used for self-interference cancellation, then device complexity is reduced, but SIC gain deteriorates as system bandwidth becomes wider
Solution Approach 1:
The patent enhances the static EBD circuit by adding dynamically adjustable components. Variable capacitors and inductors are introduced that can be tuned to optimize cancellation performance across different frequency bands and bandwidth conditions. This dynamic adjustment capability allows the circuit to adapt to varying system requirements, maintaining high SIC gain across wide bandwidths while preserving the relatively simple circuit architecture
Solution Approach 2:
The patent modifies the fixed parameter EBD circuit by introducing adjustable electrical parameters. The reactive components (capacitors and inductors) are made variable, allowing their impedance values to be changed based on operating conditions. This enables optimization of the cancellation network for different bandwidth scenarios, preventing SIC gain deterioration as system bandwidth increases while maintaining circuit simplicity
3Device complexity
If existing EBD technique is applied to wideband systems, then device simplicity is maintained, but frequency-dependent SIC performance becomes uneven across different frequency bandwidths
Solution Approach 1:
The patent segments the wideband operating range into multiple frequency sub-bands, each handled by dedicated EBD cancellation networks with optimized component values. Instead of using a single fixed EBD circuit for the entire wideband, the invention divides the frequency spectrum and applies tailored cancellation parameters to each segment, ensuring consistent SIC performance across all frequency bands while maintaining overall circuit simplicity through modular design
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design improves self-interference cancellation (SIC) gain in wideband systems, reduces quantization errors, and enhances the overall performance of in-band full duplex transceivers, enabling effective operation across a broader range of frequencies while being applicable to smaller devices.
Implementation Method 1
a hybrid transformer including a first end connected to an antenna, outputting the transmitting signal to the antenna, and outputting a received signal provided through the antenna to a receiver
Implementation Method 2
an impedance matching unit including a plurality of balance networks connected to a second end of the hybrid transformer, and matching impedance of the antenna
Implementation Method 3
a finite impulse response (FIR) filter for receiving the transmitting signal, and canceling a self-transmitting interference signal included in a signal output by the receiving output end
Data Source
AI summary
Disclosed is an in-band full duplex transceiver. The in-band full duplex transceiver may include a transmitter, a hybrid transformer, and an impedance matching unit. The hybrid transformer may include a first end connected to an antenna, may output a transmitting signal to the antenna, and may output a received signal provided through the antenna to the receiver. The impedance matching unit may include balance networks connected to a second end of the hybrid transformer and matching impedance of the antenna.