Half-Rhombic Antenna Frequency Agility via Apex Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Portable HF antennas face challenges in covering a wide frequency range due to size and complexity, with existing solutions like wire antennas experiencing high impedance at even harmonics, leading to inefficient power radiated and requiring multiple people for deployment.
Innovation Solution
A half-rhombic antenna with an addressable switch at the apex, which is open at odd multiples and closed at even multiples of the lowest frequency, along with a tuning element at the feedpoint to adjust impedance, allowing for efficient operation across the HF range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If broadband solutions such as log-periodic beams or discone antennas are used, then wide frequency coverage is achieved, but the antenna becomes large and complex requiring permanent installation
Solution Approach 1:
The antenna uses a simple dipole structure that is segmented into controllable sections through the use of switches. Rather than employing a complex broadband structure, the simple dipole is divided into effective segments (full length or half length) that can be selectively activated, achieving frequency agility through segmentation of a simple rather than complex structure
Solution Approach 2:
The single dipole antenna structure serves multiple frequency functions (resonating at both odd and even harmonics) through the switchable configuration. This universal structure replaces the need for different antenna structures for different frequency bands, achieving multi-functionality through a single adaptable element rather than multiple specialized elements
2Reliability
If a power resistor load is incorporated at the apex of a folded dipole to reduce high impedance at anti-resonance, then VSWR improves at even harmonics, but radiated power loss increases by 20 dB or higher
Solution Approach 1:
Rather than using a static resistor that continuously dissipates power, the invention uses a dynamic switch that only alters the antenna configuration when operating at even harmonics. The switch connects the center tap to one end of the dipole, creating a half-wave resonant structure that naturally achieves low VSWR without continuous power dissipation, eliminating the energy loss associated with resistive loading
Solution Approach 2:
The invention extracts and eliminates the power-dissipating resistor from the system. Instead of using resistive loading to manage impedance, the solution removes the resistor entirely and uses reactive switching to achieve impedance matching, thereby eliminating the harmful energy loss while maintaining the benefit of improved VSWR at even harmonics
Data Source
AI summary
A half-rhombic antenna includes an addressable switch at the apex. The addressable switch is opened or closed base on the operating frequency of the antenna. The addressable switch is open when operating at odd multiples of the lowest frequency and closed when operating at even multiples of the lowest frequency. The feedpoint includes a tuning element to adjust impedance within a range defined by the operating range of the switched antenna.