Double-Differential Patch Antenna for IBFD Self-Interference Cancellation
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Solution Overview
Problem
Current in-band full duplex (IBFD) transceivers face challenges in achieving high RF isolation between transmit and receive chains, which limits spectral efficiency and increases self-interference, requiring additional analog and digital cancellation stages.
Innovation Solution
A double-differential fed dual-polarized patch antenna with a 3 dB/180° ring hybrid coupler configuration provides enhanced interport isolation, achieving 90 dB and 80 dB isolation in 20 and 40 MHz bandwidths respectively, mitigating self-interference at the antenna stage and reducing the need for complex cancellation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional feeding networks (Wilkinson power divider, meandering strips) are used to achieve differential excitation, then device complexity is reduced, but RF isolation between ports deteriorates (achieves only 40-60 dB)
Solution Approach 1:
The patent introduces a 3 dB/180° ring hybrid coupler as an intermediary component between the feed ports and the patch antenna. This coupler acts as a mediator that provides precise amplitude and phase control, achieving 90 dB RF isolation between transmit and receive chains while maintaining a relatively simple overall structure. The hybrid coupler's inherent 180° phase difference and 3 dB splitting ratio enable effective self-interference cancellation without requiring complex meandering strips or unequal length microstrip lines.
2Object-affected harmful factors
If additional analog and digital cancellation stages are added to compensate for insufficient RF isolation, then spectral efficiency deteriorates, but RF isolation between ports is improved
Solution Approach 1:
The patent implements self-interference cancellation at the antenna level through the 3 dB/180° ring hybrid coupler configuration, which performs the cancellation action before the signal enters the receive chain. This preliminary cancellation at the RF front-end achieves 90 dB isolation, eliminating the need for complex subsequent analog and digital cancellation stages, thereby preserving spectral efficiency while effectively suppressing self-interference.
3Area of stationary object
If closely spaced feed lines are used on the identical edge of the radiating patch to achieve compactness, then device area is reduced, but RF isolation deteriorates due to strong RF coupling
Solution Approach 1:
The patent changes the feeding parameters by employing a 3 dB/180° ring hybrid coupler that provides precise amplitude and phase control. This parameter change enables the feed lines to be closely spaced without suffering from strong RF coupling, as the hybrid coupler's inherent phase and amplitude characteristics compensate for the coupling effects, maintaining 90 dB isolation while achieving a compact antenna footprint.
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
The proposed antenna design significantly improves spectral efficiency by achieving high self-interference cancellation at the antenna level, alleviating RF leakage and enabling efficient full-duplex communication with improved signal-to-noise ratio.
Implementation Method 1
The proposed patch antenna is double-differential fed using two 3 dB/180° hybrid ring couplers, which intrinsically provide desirable amplitude and phase balance
Implementation Method 2
double-differential fed dual-polarized patch antenna with a 3 dB/180° ring hybrid coupler configuration provides enhanced interport isolation
Data Source
AI summary
A system may include a double differential-fed dual-polarized 2.4 GHz, microstrip patch antenna with extremely high interport isolation for shared antenna architecture based in-band full duplex (IBFD) transceivers. The presented antenna configuration is based on four ports linearly polarized single radiating element with differential feeding for both transmit (Tx) and receive (Rx) operation. The double differential feeding using two identical 3 dB/180° ring hybrid couplers with nice amplitude/phase balance effectively suppresses the interport RF leakage to achieve very high isolation. Strong amplitude and phase balance of 3 dB/180° ring hybrid coupler can provide a better SIC performance as compared to DFN based on Wilkinson power divider with un-equal length microstrip lines, thus supplying an elite level of suppression in means of self-interference at Tx.