Broadband 4-Bay Antenna Array with Compensating Stubs
Solution Overview
Problem
Existing broadband FM antenna arrays face challenges in achieving frequency-independent performance across the 20 MHz FM band while maintaining low fabrication costs and ensuring optimal vertical and horizontal polarization patterns.
Innovation Solution
A broadband 4-bay antenna array design utilizing Rototiller-style brass dipole arms with compensating stubs and a unique feed harness configuration, including coaxial stubs and impedance compensating components, to achieve a 1.15:1 VSWR and in-phase radiation across the FM band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a broadband FM antenna array is designed to achieve frequency-independent performance across the 20 MHz FM band, then the impedance matching and radiation pattern stability improve, but the device complexity and fabrication cost increase
Solution Approach 1:
The antenna array is divided into four separate bay elements, each with its own feed stub and compensating stub. This segmentation allows independent optimization of each element's impedance matching while maintaining overall broadband performance across the FM band, resolving the contradiction between frequency-independent performance and structural complexity.
Solution Approach 2:
Each bay element is equipped with local compensating stubs tuned to specific frequencies within the FM band. This local quality adjustment enables precise impedance control at each element while maintaining overall system broadband performance, reducing the need for complex global tuning mechanisms.
2Manufacturing precision
If compensating stubs and impedance compensating components are added to control element arm locus impedances, then the impedance matching improves, but the manufacturing complexity increases
Solution Approach 1:
The compensating stubs are designed with specific electrical lengths and characteristic impedances that are optimized for the FM band. By carefully selecting these parameters during the design phase, the antenna achieves excellent impedance matching (VSWR < 1.15:1) across the entire FM band without requiring complex adaptive tuning mechanisms, thereby reducing manufacturing complexity while maintaining high precision.
3Stability of the object's composition
If a rigid feed harness with multiple coaxial stubs is used to connect the center feed input port to each antenna element, then the phase consistency and radiation pattern stability improve, but the device complexity and fabrication cost increase
Solution Approach 1:
The rigid feed harness is pre-configured with four coaxial feed stubs, each connected to a specific bay element with precise electrical lengths. This preliminary configuration ensures that all four elements are fed with equal phase and amplitude across the FM band, eliminating the need for on-site phase tuning and reducing installation complexity while maintaining stable radiation patterns.
4Adaptability or versatility
If the antenna array is designed to radiate ideal vertical and horizontal polarization patterns over the entire FM band, then the communication coverage improves, but the manufacturing precision requirements increase
Solution Approach 1:
The four bay elements are arranged in an asymmetric configuration relative to the vertical tower axis, with elements positioned at different heights and orientations. This asymmetric arrangement, combined with the specific feed harness configuration, produces ideal vertical and horizontal polarization patterns across the FM band while being tolerant to moderate manufacturing tolerances, reducing the stringency of precision requirements.
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 design achieves broadband performance with minimal construction costs, maintaining ideal radiated patterns and impedance matching across the FM band, allowing for scalable arrays and reduced on-site tuning requirements.
Implementation Method 1
Internal to the dipole arm, the first of several compensating stubs are used to control and improve impedance bandwidth
Implementation Method 2
A rigid feed harness may be provided which connects the center feed input port to each of the first, second, third and fourth antenna elements
Implementation Method 3
radiating an ideal relative field, vertically and horizontally polarized azimuth pattern and elevation pattern
Data Source
AI summary
A broadband multi-bay antenna array comprising an upper antenna element group and a lower antenna element group. Each of the upper antenna group and lower antenna group comprises a pair of antenna elements separated by a distance of one-half wavelength at mid-band wavelength. Radiating elements of the first antenna in each pair are positioned in a first orientation and radiating elements of the second antenna in each pair are positioned in a second orientation which differs from the orientation of the first antenna by 180 degrees (flipped over). A center feed input port is positioned between the upper antenna element group and the lower antenna element group and is electrically coupled to each of the first, second, third and fourth antenna elements.