Compact Single-Aperture Antenna for Direction-Finding Navigation
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Solution Overview
Problem
Current radio-navigation systems face challenges in providing simultaneous GPS-based position, velocity, attitude measurements, and direction-finding capability in a small form-factor with a single-aperture multi-mode antenna, as existing systems require large multi-aperture arrays or are unable to reject interference effectively, and existing single-aperture antennas have limited operational fields of view and rely on phase interferometry which is sensitive to baseline length.
Innovation Solution
A compact single-aperture multi-mode direction-finding antenna with improved gain and phase symmetry, utilizing a conductive vertical extension and conductive posts to enhance pattern symmetry, allowing for accurate angle-of-arrival measurements over the entire hemisphere and simultaneous interference rejection, while eliminating the need for an analog mode-forming network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single-aperture antenna is used, then the system size is reduced, but the operational field of view is limited and measurement precision deteriorates
Solution Approach 1:
The patent segments the antenna structure into multiple arms (at least two arms) with specific geometric configurations, allowing the single aperture to support multiple orthogonal modes (TM and TE modes) that provide enhanced direction-finding capability across a wider field of view while maintaining compact size
Solution Approach 2:
The patent utilizes modal decomposition in the electromagnetic domain, transforming the problem from spatial dimension to modal dimension by exciting and detecting multiple orthogonal modes (TM0, TE1, etc.) within the single aperture, thereby achieving enhanced measurement precision without increasing physical size
2Measurement precision
If phase interferometry is used, then direction-finding capability is achieved, but the system becomes sensitive to baseline length and requires large multi-aperture arrays
Solution Approach 1:
The patent replaces the mechanical/spatial baseline-based phase interferometry system with an electromagnetic modal-based system. Instead of relying on physical baseline length between apertures, the invention uses the inherent orthogonal electromagnetic modes within a single aperture to achieve direction-finding, thereby eliminating baseline length sensitivity and reducing system complexity
3Volume of moving object
If existing single-aperture antennas are used, then the system is compact, but interference rejection capability is insufficient
Solution Approach 1:
The patent segments the electromagnetic field within the single aperture into multiple orthogonal modes (TM and TE modes), allowing independent processing and comparison of modal coefficients to detect and reject interfering signals while maintaining compact antenna size
Solution Approach 2:
The patent implements a feedback mechanism where the measured modal coefficients are processed to determine angle-of-arrival information and interference characteristics, with the results used to enhance signal processing and improve interference rejection capability in the compact single-aperture configuration
Data Source
AI summary
A radio-based navigation system uses a small multi-mode direction-finding antenna and a direction-finding receiver to determine platform position, velocity, attitude and time while simultaneously providing protection against narrowband and broadband sources of interference. Global Navigation Satellite System (GNSS) signals such as those from a Global Positioning System (GPS) provide attitude measurements with a compact multi-mode direction-finding antenna (e.g., a small two-arm spiral with improved angle-of-arrival performance over the entire hemisphere enhanced through use of a conductive vertical extension of the antenna ground plane about the antenna perimeter and/or conductive posts placed evenly around the antenna perimeter) that provides protection against jammers. The multi-mode spiral may be treated as an array of rotationally-symmetric antenna elements. The GPS receiver architecture may be modified for direction-finding and thereby attitude determination by increasing the number of input signals from one to at least two while minimizing the required number of correlators and mixers.