Single-Arm Spiral Antenna Feed Structure for Wideband Broadside Beams
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Solution Overview
Problem
Conventional spiral antennas require baluns or transformers for feed lines and suffer from reduced bandwidth due to shifting emission beams with frequency changes, limiting their usability and efficiency.
Innovation Solution
Single-arm spiral antennas that can be directly coupled to a coaxial link without baluns or transformers, featuring a ground element proximate to the central node, allowing for wideband operation with bidirectional or unidirectional performance and conic configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional spiral antennas use two or more spiral arms, then they can transmit and receive RF energy, but they require baluns or transformers which increase device complexity and cost
Solution Approach 1:
The patent extracts and eliminates the balun or transformer component from the conventional spiral antenna system. By using a single spiral arm fed by a coaxial cable directly, the design removes the need for the balun/transformer that converts unbalanced to balanced lines, thereby reducing device complexity while maintaining the essential antenna functionality through the ground element and spiral geometry
Solution Approach 2:
The patent employs asymmetry by using a single spiral arm instead of the conventional two or more arms. This asymmetric configuration, when combined with a ground element, creates the necessary balanced-to-unbalanced transformation without requiring a separate balun component, thus simplifying the overall device structure
2Adaptability or versatility
If spiral arrays are used to shift emission beam off broadside, then directional coverage is improved, but beam squint occurs with frequency changes reducing bandwidth
Solution Approach 1:
The patent changes the geometric parameters of the spiral arm, specifically using an Archimedean spiral configuration where the radius increases linearly with the angle. This parameter choice, combined with the ground element positioning, enables the antenna to maintain a fixed broadside beam direction across a wide frequency range (2-12 GHz), eliminating beam squint while preserving directional radiation characteristics
3Device complexity
If single-arm spiral antenna is used, then device complexity is reduced, but theoretical bandwidth modes become zero according to conventional theory
Solution Approach 1:
The patent introduces a ground element as an intermediary component that enables the single spiral arm to function effectively. The ground element, positioned near the inner end of the spiral and connected to the coaxial shield, provides the necessary reference plane and electromagnetic boundary conditions that allow the single-arm configuration to achieve wideband operation (2-12 GHz), overcoming the theoretical limitation that predicted zero useful modes
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 single-arm spiral antennas achieve wideband frequency response from 2 to 12 GHz with low cross-polarization and minimal beam squint, reducing cost, complexity, and weight, while maintaining efficient radiation patterns.
Implementation Method 1
the single-arm spiral antenna can be generally planar for bidirectional performance... operate over a wide frequency range
Implementation Method 2
a ground element positioned below the inner end of the spiral shape which couples to a coaxial shield conductor
Data Source
AI summary
Provided herein are various enhanced antenna structures for radio frequency communications. In one example, an antenna a spiral antenna element having a single arm configured to couple to a radio frequency link at a central node. The antenna also includes a ground element comprising a conical frustum sharing an axis at the central node of the spiral antenna element and configured to couple to a ground reference for the radio frequency link.