Ring Antenna Array Element with Mode Suppression Stubs
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Solution Overview
Problem
Conformal phased array antennas face challenges with mutual coupling that limit their scan volume and frequency coverage, particularly between orthogonally polarized feed lines, leading to reduced scan performance and poor axial ratio values when scanned near the horizon.
Innovation Solution
The implementation of tuned conductive elements, or stubs, between feed lines to suppress in-band cross-coupling resonance, utilizing design features such as quantity, length, width, angular separation, and location, which are configured to resonate outside the desired frequency band, thereby reducing cross-coupling between feed lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If feed lines are placed close together in conformal phased array antennas, then device complexity and size are reduced, but mutual coupling between feed lines increases causing reduced scan performance and poor axial ratio values
Solution Approach 1:
A conductive element is introduced as an intermediary between the first and second feed lines. This element is configured to resonate at frequencies outside the operating band, creating a electromagnetic barrier that suppresses cross-coupling between the feed lines while allowing the antenna to maintain its compact conformal structure.
Solution Approach 2:
The conductive element's dimensions (length and width) are specifically designed to resonate at frequencies outside the operating band. By changing the resonant frequency parameter of the added element, the solution suppresses cross-coupling in the operating band without affecting the antenna's primary function.
2Device complexity
If feed lines are placed close together in conformal phased array antennas, then device complexity and size are reduced, but cross-coupling between orthogonally polarized feed lines increases
Solution Approach 1:
The conductive element serves as a mediator placed between the orthogonally polarized feed lines. Its resonant frequency is tuned to be outside the operating band, where it creates electromagnetic interference that cancels out the cross-coupling signals between the feed lines, effectively blocking harmful electromagnetic interaction.
Solution Approach 2:
The conductive element exploits electromagnetic resonance phenomena to convert potential harmful cross-coupling into beneficial mode suppression. By resonating at frequencies outside the operating band, it creates electromagnetic fields that actively cancel the cross-coupling modes, turning a structural limitation into a solution.
3Reliability
If conductive element dimensions are increased to improve mode suppression, then cross-coupling reduction improves, but device size and weight increase
Solution Approach 1:
Instead of increasing the size of the conductive element, the solution changes the resonant frequency parameter by adjusting the element's dimensions to resonate outside the operating band. This allows effective mode suppression with a compact element that does not significantly increase the antenna's overall weight.
Solution Approach 2:
The conductive element is integrated into the existing antenna structure on the circuit board, utilizing the available two-dimensional space efficiently. The element is positioned and dimensioned to achieve the required mode suppression without adding significant volume or weight to the antenna assembly.
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 enables dual-band phased arrays with improved mode suppression, achieving cross-coupling levels of −6 dB or lower, enhancing scan performance and frequency coverage while maintaining a lightweight and thin design.
Implementation Method 1
The conductive element is configured to resonate outside the frequency band to reduce cross-coupling between the first feed element and the second feed element
Data Source
AI summary
A radio frequency (RF) circuit for a ring antenna array element includes first and second feed elements, and a conductive element disposed between the first and second feed elements. The first and second feed elements are electrically couplable to a conductive resonator for a frequency band. The first feed element is configured to conduct an electromagnetic current. The conductive element is configured to resonate outside the frequency band to reduce cross-coupling between the first feed element and the second feed element due to the electromagnetic current.