Radio frequency applicator
Inventors
Shmidov, Dima • MacCarini, Paolo • Steinberg, Idan • Thornton, Michael M. • Davis, Christopher Nelson
Assignees
Duke University • Endra Life Sciences Inc
Publication Number
US-12350015-B2
Publication Date
2025-07-08
Expiration Date
2043-11-10
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Abstract
A radio frequency applicator, including a waveguide having a first interior surface comprising a first aperture, a second interior surface opposing the first interior surface, a third interior surface adjacent to the first and second interior surfaces, a fourth interior surface opposing the third interior surface, and a fifth interior surface perpendicular to the first, second, third, and fourth interior surfaces, an aperture antenna, a solid dielectric insert within the waveguide, the solid dielectric insert having a second aperture formed therethrough that is configured for alignment with the first aperture, an RF connector, configured to receive generated RF energy pulses, at least one planar-shaped shim, having a third aperture therethrough configured to align with the first and second apertures, and a radio frequency feed pin connected to the RF connector, disposed within the first, second, and third apertures and affixed to the second interior surface of the waveguide.
Core Innovation
The invention describes a radio frequency (RF) applicator comprising a waveguide with defined interior surfaces and apertures, an aperture antenna, a solid dielectric insert with a matching aperture, a planar-shaped shim or multiple shims with apertures aligned with those of the waveguide and insert, an RF connector to receive RF energy pulses, and a radio frequency feed pin electrically connected to the RF connector and affixed to the second interior surface of the waveguide. The feed pin passes through the apertures and is designed to reduce or eliminate capacitive effects by being physically and electrically connected to the aperture antenna, achieving instead a magnetic loop effect.
The RF applicator utilizes multiple planar shims of varying material properties, including conductive, compressible, and dielectric shims arranged within the waveguide to enable tuning of the resonance frequency. This modular arrangement allows coarse and fine frequency tuning by selecting combinations of shims with specific permittivity and other physical properties, overcoming limitations in prior art.
The problem addressed is that conventional waveguides for thermoacoustic applications suffer from manufacturing, repeatability, and temperature drift issues. In particular, existing devices such as those described in U.S. Pat. No. 10,682,059B1 have feed probes that are not electrically connected to the aperture antenna, causing capacitive effects subject to variations from material differences and temperature changes. These drawbacks make tuning difficult and cause frequency fluctuations over time.
The invention solves these problems by providing an RF applicator design with a feed probe that is electrically connected to the aperture antenna to reduce capacitive effects and generate a magnetic loop effect, thereby lowering reflected power and maximizing transmitted power. The use of multiple, planar-shaped shims within the waveguide enables precise tuning of the resonance frequency while maintaining stable operation under temperature variation.
Claims Coverage
The patent includes three independent claims defining the RF applicator with key inventive features related to the waveguide structure, aperture antenna, dielectric insert, RF connector, shims, and feed pin configuration.
Waveguide and aperture antenna structure
The RF applicator comprises a waveguide with first to fifth interior surfaces forming apertures aligned to define an aperture antenna, with the opening perpendicular and opposing specific interior surfaces.
Solid dielectric insert with aligned aperture
The waveguide houses a solid dielectric insert having an aperture aligned with the waveguide aperture to shape the electromagnetic properties within the guide.
Planar-shaped shim(s) with aligned apertures for frequency tuning
At least one or a plurality of planar-shaped shims, including conductive, compressible, and dielectric types, each having apertures aligned with the waveguide and insert apertures, to tune the resonance frequency by varying permittivity and physical properties.
Radio frequency feed pin electrically connected and affixed
A radio frequency feed pin configured for electrical connection to the RF connector, disposed through the aligned apertures of the waveguide, insert, and at least one shim, and affixed directly to the second interior surface, eliminating capacitive effects.
Material properties of shims and insert
The conductive shim has conductivity in the range 1×10^6 to 1×10^8 Siemens/meter; the compressible shim has bulk modulus between 1.0 MPa and 1.0 GPa and acoustic attenuation between 5 and 200 dB/(MHz*cm); the solid dielectric insert has real relative permittivity between about 20 and 180 and imaginary relative permittivity between about 0 and 18; dielectric shims have specific permittivity ranges similarly defined.
The claims collectively define an RF applicator featuring a waveguide with a solid dielectric insert and multiple planar shims of varying materials and properties, with a feed pin that is electrically connected and affixed to minimize capacitive effects, enabling controllable tuning and stable operation of the device.
Stated Advantages
Reduced or eliminated capacitive effect by electrically connecting feed probe to aperture antenna, resulting in a magnetic loop effect.
Lower reflected power and maximized transmitted power due to magnetic loop effect.
Ability to tune resonance frequency precisely using multiple planar-shaped shims with varying permittivity and physical properties.
Stable tuning and reduced frequency fluctuations despite temperature changes.
Improved manufacturing repeatability and performance stability over prior art waveguides.
Documented Applications
Thermoacoustic imaging, specifically in thermoacoustic imaging systems where RF energy pulses are directed into a region of interest to induce acoustic pressure waves, enabling imaging of thermoelastic properties of tissue.
Medical imaging applications involving generation and detection of RF-induced acoustic signals, such as imaging a liver containing a blood vessel within a human or animal body.
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