Helix-Shaped Cross-Dipole Elements for Multi-Band RF Scattering Control
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Solution Overview
Problem
Multi-band base station antennas face challenges in reducing the impact of scattering of RF signals from one frequency band by radiating elements of other frequency bands, which affects antenna beam shape, beamwidth, and gain, making it difficult to compensate for these effects across varying frequencies.
Innovation Solution
The use of 'cloaking' radiating elements with helix-shaped dipole arms and parasitic elements that are designed to be transparent to RF energy in specific frequency bands, reducing current formation and scattering by acting as filters to block or suppress RF energy from nearby radiating elements operating in higher frequency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple arrays of radiating elements are deployed to support service in different frequency bands, then the capacity and coverage of the base station are improved, but the arrays interact with each other causing scattering of RF signals which degrades antenna beam shape, beamwidth, and gain
Solution Approach 1:
A helical structure is introduced as an intermediary component between the low-band and high-band radiating elements. This helix acts as a frequency selective surface that allows low-band signals to pass through while blocking high-band signals, thereby preventing the harmful interaction and scattering between the two frequency bands while maintaining both services
Solution Approach 2:
The radiating elements are designed with spatially varying properties - the helical structure is positioned specifically in the region where low-band and high-band arrays interact. The helix provides frequency-selective transparency locally, allowing low-band RF energy to pass through while blocking high-band energy, thus addressing the scattering problem in the critical interaction zone without affecting other parts of the antenna system
2Productivity
If the number of base station antennas is increased to accommodate increasing volume of cellular communications, then the capacity is improved, but the weight and wind loading on the antenna tower increase beyond acceptable limits
Solution Approach 1:
Multiple base station antenna functions (low-band service, high-band service, and frequency isolation) are merged into a single integrated antenna structure. The low-band and high-band radiating elements are combined in one antenna assembly with the helical frequency selective surface, eliminating the need for separate antenna towers or structures for different frequency bands
Solution Approach 2:
The base station antenna is designed as a multi-functional unit that simultaneously provides low-band service, high-band service, and frequency band isolation through the helical structure. This universal antenna design supports multiple frequency bands and services within a single structure, reducing the total number of antennas and their associated weight and wind loading
3Reliability
If different arrays of radiating elements are used for different frequency bands, then the performance in each frequency band is optimized, but the interaction between arrays makes it challenging to meet customer requirements relating to the size and width of the base station antenna
Solution Approach 1:
The helical structure serves as a compact intermediary element that enables close spacing between low-band and high-band arrays. By providing frequency-selective blocking in a space-efficient helical configuration, it allows the arrays to be positioned closer together without causing harmful interactions, thus reducing the overall antenna width while maintaining frequency band 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
This design significantly reduces the impact of scattering between different frequency band radiating elements, maintaining antenna beam integrity and performance across multiple frequency bands, while being cost-effective and manufacturable using metal wires.
Implementation Method 1
at least a first portion of the first conductor has a helix-shape... configured to suppress formation of currents in the second operating frequency band on the first dipole arm
Data Source
AI summary
A base station antenna includes first and second RF ports, a first array of radiating elements that are configured to transmit and receive RF signals in a first operating frequency band, where each of the radiating elements in the first array is coupled to the first RF port, and a second array of radiating elements that are configured to transmit and receive RF signals in a second (higher) operating frequency band, where each of the radiating elements in the second array is coupled to the second RF port. A first of the radiating elements in the first array includes a first dipole radiator that has a center-fed first dipole arm that comprises a first conductor, where at least a first portion of the first conductor has a helix-shape.