Folded Dipole Patch Antenna Miniaturization for 434 MHz Hyperthermia
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Solution Overview
Problem
Conventional antennas for biomedical applications, particularly in hyperthermia treatments, are not miniaturized, leading to large sizes that complicate impedance matching and are not suitable for sub-GHz frequencies, necessitating a compact antenna design with stable radiation performance near the human body.
Innovation Solution
A miniaturized folded dipole patch antenna is designed with a dielectric circuit board, meander paths, a lumped inductor, and parallel metallic strips, configured to resonate at 434 MHz without requiring complex impedance matching networks, using a single inductor to achieve resonance and reduce size by 93%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional antenna designs are used for sub-GHz frequencies, then radiation performance is achieved, but antenna size becomes large and complex impedance matching is required
Solution Approach 1:
The antenna structure is divided into multiple meander paths that are segmented and arranged in a compact configuration. The dipole antenna is split into two meander paths with multiple segments, allowing the electrical length to be extended within a reduced physical footprint, thus achieving sub-GHz resonance without large dimensions
Solution Approach 2:
The meander paths are nested within a compact planar structure where the antenna elements are folded back on themselves multiple times. This nesting approach allows the antenna to fit within a small area while maintaining the required electrical length for low-frequency operation
2Volume of moving object
If antenna size is reduced for miniaturization, then compact design is achieved, but impedance matching becomes complex due to small input resistance and large reactance
Solution Approach 1:
The antenna design changes key parameters including the addition of a lumped inductor element and adjustment of meander path dimensions to naturally achieve impedance matching. By modifying the electrical characteristics through parameter adjustment rather than adding complex matching networks, the small antenna achieves good impedance match at the feed point
Solution Approach 2:
The antenna structure is designed to self-match impedance through its inherent geometry and the integrated lumped inductor element. The meander paths and inductor work together to provide the necessary reactance cancellation and resistance matching without requiring external matching networks, making the antenna self-sufficient
3Reliability
If multiple lumped elements are added for frequency shifting, then resonance frequency is adjusted below desired frequency, but parametric analysis complexity increases
Solution Approach 1:
Instead of adding multiple lumped elements for frequency shifting, the design extracts and utilizes the inherent capacitance of the meander path geometry combined with a single strategically placed lumped inductor. This approach achieves the desired frequency shifting below the resonance frequency with minimal elements, reducing parametric analysis complexity
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 antenna achieves efficient impedance matching and stable radiation performance, providing good penetration depth and effective field strength, suitable for hyperthermia applications, while being compact enough for biomedical implants.
Implementation Method 1
Increasing inductance of the antenna shifts the resonance below a desired resonance frequency
Implementation Method 2
The folded dipole patch antenna is configured to resonate in a frequency range of about 434 MHz upon application of an input signal at the coaxial feed port
Data Source
AI summary
A folded dipole patch antenna for use in a hyperthermia applicator is described. The antenna includes a dielectric circuit board, and a folded dipole microstrip antenna. The dielectric circuit board has a top side and a bottom side. The folded dipole microstrip antenna is formed on the top side and includes two meander paths mirror each other. A pair of parallel metallic strips is located on the bottom side. A coaxial feed port is connected to the pair of parallel metallic strips. The antenna is configured to resonate in a frequency range of about 434 MHz upon application of an input signal at the coaxial feed port. The folded dipole patch antenna has a small size and does not require an impedance matching circuit. The hyperthermia applicator is configured to emit microwave energy toward a target tissue within a human body.