Nonlinear and smart metamaterials useful to change resonance frequencies
Inventors
Zhang, Xin • ANDERSON, Stephan • Zhao, Xiaoguang • Duan, Guangwu
Assignees
Publication Number
US-12085629-B2
Publication Date
2024-09-10
Expiration Date
2040-10-08
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Abstract
A passive MRI enhancing embodiment includes a plurality of resonators and increases signal-to-noise ratio of radiofrequency signals emitted by a specimen and captured by an MRI machine. The apparatus increases the magnetic field component of radiofrequency energy during signal transmission from the MRI machine to the specimen, and/or reception of signals from the specimen to the MRI machine. Use of the apparatus improves the images generated by the MRI machine, and/or reduces the time necessary for the MRI machine to capture the image. An isolator embodiment has a nonlinear resonator controllably configurable alternately into an isolation configuration and a transmission configuration, and a second resonator. The nonlinear resonator is coupled to a communications port and is substantially communicatively isolated from the second resonator when the nonlinear resonator is in the isolation configuration, and is communicatively coupled to the second resonator when the nonlinear resonator is in the transmission configuration.
Core Innovation
The invention provides a circuit comprising a first resonator with a characteristic resonant frequency and a non-linear resonator that is controllably configurable between two resonance states. In the first resonance state, the non-linear resonator has a resonant frequency equal to that of the first resonator, enabling communicative coupling. In the second resonance state, the non-linear resonator has a different resonance frequency, producing substantial isolation from the first resonator. The configuration between resonance states is controlled by the impedance state of a coupler, such as a varactor or switch, electrically disposed in the non-linear resonator.
The background identifies the problem addressed: traditional MRI systems face limitations in signal-to-noise ratio (SNR) due to noise from various sources, including the MRI machine’s circuitry, which impacts image quality and increases imaging time. Conventional methods to improve SNR, such as increasing the strength of the static magnetic field or optimizing signal processing, are limited by safety concerns and an inability to eliminate noise entirely.
The core innovation introduces metamaterial-based resonator arrays, together with non-linear resonators or isolator circuits, capable of actively shifting between coupled and isolated modes. This enables selective communication or isolation based on resonance state, offering improvements such as enhanced SNR, without requiring increased RF power transmission. The claimed system can be used as a signal magnifying accessory or isolator in MRI systems, improving imaging performance passively without the need for integrated wiring or control from the MRI machine.
Claims Coverage
The patent claims one main inventive feature through a single independent claim, supported by a range of dependent claims specifying resonator types and coupler implementations.
Circuit with configurable isolation and coupling via non-linear resonator
A circuit comprising: - A first resonator with a characteristic resonant frequency. - A non-linear resonator controllably configurable into: - A first resonance state, in which its resonant frequency equals that of the first resonator, enabling inductive and communicative coupling between them. - A second resonance state, in which its resonant frequency is distinct from the first, resulting in substantial isolation between the resonators. The non-linear resonator includes a coupler (such as a varactor or switch) that can assume different impedance states to shift between resonance states. In one configuration, the first resonator couples to a first port and the non-linear resonator to a second port, enabling direction-dependent communication or isolation controlled by resonance state.
The claims broadly cover circuits employing a non-linear resonator, which can selectively couple or isolate from a first resonator using resonance state control mediated by an impedance-switching coupler, as detailed in the claim and supported by dependent claims specifying device embodiments.
Stated Advantages
Increases the signal-to-noise ratio (SNR) of radiofrequency signals emitted by a specimen and captured by an MRI machine, leading to improved image quality.
Reduces the time required for the MRI machine to capture an image.
Operates passively without requiring increased power from the MRI machine.
Enhances specimen safety by substantially avoiding unwanted generation or increase of an electric field.
Provides substantial isolation between resonator circuits when desired, enabling unidirectional signal flow or selective resonance.
Documented Applications
Use as a passive MRI enhancing accessory to increase SNR and improve MRI images.
Use as an isolator circuit for controllably coupling or isolating signals between ports in RF communication or MRI systems.
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