Radar Antenna Feed Structure Using Anisotropic Substrate
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Solution Overview
Problem
Highly coupled dipole array antennas face issues with unwanted common-mode currents due to their vertical feed structure, limiting their bandwidth and scan range while maintaining a low profile, and existing solutions like optical fiber feeds are expensive and limited to receive-only applications.
Innovation Solution
Incorporating elongate electrically conductive elements within the dielectric substrate to surround the feed structure, which presents a high impedance to vertically polarized electric fields, thereby suppressing unwanted currents and enhancing the antenna's performance by distributing these elements beneath the antenna elements and coupling capacitively to the ground plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a vertical feed structure is used to connect dipole array elements to driving circuit, then the antenna can achieve low profile, but unwanted common-mode currents are excited over the feed structure
Solution Approach 1:
A dielectric substrate with embedded electrically conductive elements is introduced as an intermediary between the vertical feed structure and the electromagnetic environment. This intermediary structure presents high impedance to vertically polarized electric fields, suppressing common-mode currents without requiring ferrite materials or optical fiber feeds, thereby maintaining low profile while eliminating harmful currents
Solution Approach 2:
The invention changes the electromagnetic parameters of the feed structure environment by incorporating a dielectric substrate with specific permittivity properties and embedded conductive elements. This modifies the impedance characteristics presented to electric fields, transforming the feed structure from one that supports common-mode currents to one that suppresses them, all while maintaining the same low-profile physical dimensions
2Object-generated harmful factors
If optical fiber feeding is used to suppress common-mode currents, then unwanted currents are eliminated, but the solution becomes expensive and limited to receive-only applications
Solution Approach 1:
The invention replaces expensive optical fiber feed structures with a cost-effective dielectric substrate containing embedded conductive elements. This economical solution achieves the same current suppression function using standard microwave engineering materials and techniques, making the antenna suitable for both transmit and receive applications without the limitations of optical fiber systems
Solution Approach 2:
The invention substitutes the optical fiber mechanical feed system with an electromagnetic field-based solution using dielectric and conductive elements. This replacement eliminates the need for optical-to-electrical conversion components, enabling full-duplex transmit and receive operation while reducing system complexity and cost
3Length of stationary object
If highly coupled dipole array is used for low profile application, then antenna profile is reduced, but bandwidth and scan range are limited due to feed structure currents
Solution Approach 1:
The dielectric substrate with embedded conductive elements acts as a mediator that decouples the constraint between low profile and performance. By suppressing common-mode currents at the feed structure level, it enables the highly coupled dipole array to achieve both low profile and enhanced bandwidth and scan range without compromise
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 approach effectively suppresses common-mode currents, allowing for high bandwidth and scan range capabilities while maintaining a low profile and reducing noise, thus improving the antenna's efficiency and cost-effectiveness.
Implementation Method 1
The dielectric substrate may selectively present an impedance to electric fields polarised in a first direction, parallel to the feed structure, which is relatively high compared to an impedance presented to electric fields polarised orthogonally to that first direction
Implementation Method 2
The elongate elements may couple capacitively to the ground plane
Data Source
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AI summary
A radar or other microwave antenna comprises at least one antenna element, a feed structure for the element extending to the antenna element substantially normally thereto through a dielectric substrate, and characterised in that the dielectric substrate is anisotropic whereby to reduce unwanted common-mode currents in the feed structure. The anisotropy may be provided by elongate conductive elements distributed through the dielectric substrate and aligned with their longitudinal axes parallel to the feed structure.