IBFD Antenna Layout for Isolation and Direction Finding
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Solution Overview
Problem
In-band full-duplex (IBFD) systems face challenges in achieving high isolation between co-located transmitter and receiver to avoid self-interference, and existing directional phased arrays are expensive and complex to manufacture and operate, lacking direction-finding capabilities.
Innovation Solution
An IBFD antenna design incorporating omnidirectional radiation patterns and circular modes with probe-fed wide-angle short horn antennas, providing direction-of-arrival estimation and adaptive beamforming capabilities, which eliminates the need for baluns and allows simultaneous transmit and receive operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional IBFD antennas are used to suppress self-interference, then isolation between transmitter and receiver is improved, but direction-finding capability is lost
Solution Approach 1:
The antenna system is segmented into multiple independent antenna elements (at least two elements) that can be individually controlled. Each element contributes to both the omnidirectional radiation pattern for SI suppression and the directional information for DoA estimation, allowing the system to achieve both goals simultaneously through separate functional contributions from different segments
Solution Approach 2:
The antenna system is designed to perform multiple functions simultaneously: it provides omnidirectional radiation for self-interference suppression while also enabling direction-of-arrival estimation through the same antenna elements. The circular mode operation and array configuration allow the system to be universal in its capability to handle both SI cancellation and directional finding without requiring separate dedicated structures
2Adaptability or versatility
If directional phased arrays are used to provide direction-finding capability, then direction-of-arrival estimation is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The system changes the operational parameters of the antenna elements by exciting circular modes and controlling the phase and amplitude of signals at different frequencies. By manipulating these parameters (frequency, phase, amplitude) across multiple antenna elements, the system achieves direction-finding capability through post-processing of frequency responses rather than requiring complex physical array structures
Solution Approach 2:
The patent replaces complex mechanical or physical phased array structures with a simpler antenna configuration that achieves direction-finding through signal processing. Instead of using complex beamforming hardware and mechanical adjustments, the system substitutes a straightforward antenna array with circular mode operation and computational methods to extract directional information from frequency response data
3Productivity
If the same frequency band is used for transmit and receive operations, then spectral utilization is improved, but self-interference increases
Solution Approach 1:
The system converts the harmful self-interference signal into useful information by using the transmitted signal itself as a reference for direction-of-arrival estimation. The same signal that causes interference also provides the frequency response data needed to determine the direction of remote users, turning the harmful SI into a beneficial resource for enhancing communication links
Solution Approach 2:
The antenna system creates different radiation patterns for different functions: an omnidirectional pattern for transmit operations to minimize self-interference coupling, and directional sensitivity for receive operations to estimate direction of arrival. By creating locally optimized quality characteristics (omnidirectional vs. directional) for different operational modes, the system enables simultaneous transmit and receive on the same frequency
Data Source
AI summary
Described is an in-band full-duplex (IBFD) antenna having direction finding capability. The IBFD antenna includes a transmit antenna having an omnidirectional radiation pattern and a receive antenna configured to provide a plurality of difference beams. The IBFD antenna may be disposed on a moving platform to cover all angles around the moving platform.