Planar Fractal Loop Antenna for Wideband Satellite Positioning
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Solution Overview
Problem
Existing wide bandwidth antennas for satellite ranging systems have a three-dimensional architecture, leading to a high profile that is not suitable for applications requiring a small form factor, and often lack a common phase center across different frequency bands, which is critical for accurate positioning measurements.
Innovation Solution
A planar slot array antenna with a multi-arm radiating structure of interconnected spiral slots that flare into fractal loop configurations, using a leaky wave microstrip multiple turn spiral feed network to achieve a wide bandwidth and a common phase center, while maintaining a low profile and reducing signal variation in the azimuth plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a three-dimensional architecture with a stack of individual planar antennas or a complex patch antenna structure is used to achieve wide bandwidth, then the bandwidth is improved, but the antenna profile becomes high which is not suitable for aircraft or other applications requiring a small form factor
Solution Approach 1:
The patent transitions from three-dimensional stacked antenna architectures to a two-dimensional planar fractal loop structure. The fractal geometry enables wide bandwidth performance within a single planar layer, eliminating the need for multiple stacked layers and thereby reducing the antenna profile while maintaining wide bandwidth capability across 1175-1610 MHz
Solution Approach 2:
The patent employs fractal geometry with specific dimensional parameters and self-similar patterns that inherently provide wide bandwidth characteristics. By optimizing the fractal loop dimensions, spacing, and feed network parameters, the antenna achieves wide bandwidth performance without requiring a three-dimensional stacked architecture
2Adaptability or versatility
If a three-dimensional antenna structure is used to achieve wide bandwidth, then the bandwidth is improved, but the phase center alignment across different frequency bands deteriorates, which is critical for accurate positioning measurements
Solution Approach 1:
The planar fractal loop antenna structure serves multiple functions simultaneously: it provides wide bandwidth performance, maintains a common phase center across all frequency bands (1175-1610 MHz), and ensures accurate positioning measurements. The symmetric fractal geometry inherently maintains phase center stability while supporting multi-frequency operation
Solution Approach 2:
The patent optimizes specific geometric parameters of the fractal loop structure, including loop dimensions, spacing between loops, and feed network configuration, to simultaneously achieve wide bandwidth and maintain a stable common phase center across all operating frequency bands for accurate GPS, GLONASS, and GALILEO positioning
3Adaptability or versatility
If conventional wide bandwidth antenna structures are used, then the bandwidth is improved, but the signal variation in the azimuth plane increases, affecting positioning accuracy
Solution Approach 1:
The patent employs surface wave suppression structures positioned at specific locations around the perimeter of the planar fractal loop antenna. These localized suppression elements target and reduce surface wave effects that cause signal variation in the azimuth plane, thereby stabilizing the radiation pattern while maintaining wide bandwidth performance
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 antenna provides a wide bandwidth, a common phase center, reduced signal variation, and improved polarization purity across the frequency band of interest, ensuring accurate positioning measurements and suitability for applications like aircraft and vehicles.
Implementation Method 1
A leaky wave microstrip multiple turn spiral feed network is used to excite the radiating structure of the antenna
Implementation Method 2
The spacing between the elements, the lengths of the elements and the feed location of the elements are selected to provide a desirable electromagnetic coupling between the elements
Implementation Method 3
each slot begins as a spiral and flares into a fractal loop configuration
Implementation Method 4
the geometric and electrical phase centers are aligned
Implementation Method 5
a surface wave suppression region enclosing the slotted array and a plurality of through openings disposed between the surface wave suppression region and the peripheral edge of the antenna to reduce defraction of the emitted signal at the peripheral edge
Data Source
Figure 1
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Figure 3A
AI summary
An antenna is provided for acquiring RF signals from various satellite ranging systems including GPS, GLONASS, GALILEO and OmniSTAR®. The antenna configuration includes a radiating structure of multi-arm spiral slots terminated with fractal loops. A leaky wave microstrip spiral feed network is used to excite the radiating structure of the antenna. The fixed beam phased array of aperture coupled slots is optimized to receive a right hand polarized signal. The proposed antenna is made out of a single PCB board. The antenna has a very uniform phase and amplitude pattern in the azimuth plane from 1.15 to 1.65 GHz, therefore providing consistent performance at GPS, GLONASS, GALILEO and OmniSTAR® frequencies. The antenna also has a common phase center at the various frequencies from 1175 MHz to 1610 MHz and substantially the same radiation pattern and axial ratio characteristics.