Tuning low-inductance coils at low frequencies
First Claim
1. A method for obtaining magnetic resonance signals from a microcoil at low frequency comprising the steps of:
- connecting the microcoil in series with a second coil, whereby the microcoil is an effective magnetic resonance transmitter or receiver coil;
forming a resonant circuit of the coils with a capacitor whose capacitance is determined primarily by the inductance of the second coil;
permitting the resonant circuit to resonate at low frequency, with alternating current at a resonance wavelength;
locating the microcoil remotely from the second coil and capacitor; and
connecting electrically the microcoil in parallel with the second coil by means of a transmission line having a length that is an odd multiple of a length corresponding substantially to one-fourth of the resonance wavelength;
whereby the remotely located microcoil presents, in the resonant circuit, as a large impedance in parallel to the second coil.
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Accused Products
Abstract
A method and apparatus for tuning and matching extremely small sample coils with very low inductance for use in magnetic resonance experiments conducted at low frequencies. A circuit is disclosed that is appropriate for performing measurements in fields where magnetic resonance is beneficially utilized. The circuit has a microcoil, an adjustable tuning capacitance, and added inductance in the form of a tuning inductor. The microcoil is an electrical coil having an inductance of about 25 nanohenries (nH) or less. Because additional inductance is purposefully added, the capacitance required for resonance and apparatus function is proportionally and helpfully reduced. The apparatus and method permit the resonant circuit and the magnet to be made extremely small, which is crucial for new applications in portable magnetic resonance imaging, for example.
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Citations
15 Claims
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1. A method for obtaining magnetic resonance signals from a microcoil at low frequency comprising the steps of:
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connecting the microcoil in series with a second coil, whereby the microcoil is an effective magnetic resonance transmitter or receiver coil; forming a resonant circuit of the coils with a capacitor whose capacitance is determined primarily by the inductance of the second coil; permitting the resonant circuit to resonate at low frequency, with alternating current at a resonance wavelength; locating the microcoil remotely from the second coil and capacitor; and connecting electrically the microcoil in parallel with the second coil by means of a transmission line having a length that is an odd multiple of a length corresponding substantially to one-fourth of the resonance wavelength; whereby the remotely located microcoil presents, in the resonant circuit, as a large impedance in parallel to the second coil. - View Dependent Claims (2, 3, 4, 5)
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6. A method for obtaining magnetic resonance signals from a microcoil at low frequency, comprising the steps of:
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connecting the microcoil in series with a tuning coil having an inductance at least ten times larger than the inductance of the microcoil, whereby the microcoil is an effective magnetic resonance transmitter or receiver coil and contributes no substantial inductance needed for resonance; forming a resonant circuit of the coils with a capacitor whose capacitance is determined primarily by the inductance of the tuning coil and; permitting the resonant circuit to resonate at low frequency, with alternating current at a resonance wavelength. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification