Shorted Spiral Antenna Layout for Wideband 50-Ohm Low Bands
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Solution Overview
Problem
Existing low band antenna designs have limited bandwidth at the center frequency and require a 150-ohm input impedance, which is not compatible with most commercial radios that have a 50-ohm impedance, and often consist of multiple linear regions.
Innovation Solution
A wideband, low-frequency spiral antenna with a substrate, a shorting portion, and a tuning stub, featuring a spiral element with curved arms and a ground plane, designed to operate with a 50-ohm input impedance, providing additional bandwidth and a lower resonant frequency without the need for a cavity backing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear regions are used to achieve resonance at desired center frequency, then the antenna can resonate at the target frequency, but the bandwidth at the center frequency is limited
Solution Approach 1:
The patent employs spiral curved regions instead of linear regions to achieve resonance. The spiral geometry with its continuous curvature allows the antenna to resonate at the desired center frequency while simultaneously providing broader bandwidth coverage, resolving the contradiction between frequency precision and bandwidth adaptability
Solution Approach 2:
The patent transitions from two-dimensional linear antenna regions to a three-dimensional spiral structure that extends in multiple dimensions. This dimensional change enables the antenna to achieve both precise resonance at the center frequency and enhanced bandwidth through the spatial complexity of the spiral configuration
2Adaptability or versatility
If spiral antenna design is used to achieve wide bandwidth, then the bandwidth is improved, but the input impedance becomes around 150 ohms which is incompatible with standard 50-ohm commercial radios
Solution Approach 1:
The patent applies different characteristics to different parts of the spiral antenna structure. By varying the geometry, dimensions, and configuration in specific local regions of the spiral, the antenna achieves both wide bandwidth and impedance transformation to match standard 50-ohm commercial radio interfaces
Solution Approach 2:
The patent modifies key geometric parameters of the spiral antenna, such as the spiral arm width, spacing between arms, number of turns, and overall size, to simultaneously achieve wide bandwidth operation and transform the input impedance to be compatible with standard 50-ohm commercial radio interfaces
3Measurement precision
If multiple linear regions are used to achieve desired resonance, then the antenna can be tuned to center frequency, but the structural complexity increases
Solution Approach 1:
The patent combines multiple resonant functions into a single integrated spiral structure. Instead of using separate linear regions that would require individual tuning, the unified spiral geometry provides continuous resonance characteristics across the desired frequency range, reducing structural complexity while maintaining frequency tuning capability
Data Source
AI summary
An antenna may include a ground plane, a tuning stub, and a shorted spiral antenna element connected to the tuning stub. The shorted spiral antenna element may include a plurality of spiral traces shorted together by a shorting element extending radially outward to contact each of the spiral traces.