Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Reexamination Certificate
2000-02-03
2001-06-05
Arana, Louis (Department: 2862)
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
C324S322000
Reexamination Certificate
active
06242917
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a magnetic resonance transmission antenna of the type having at least two transmission elements that individually generate respective, linearly polarized, discrete magnetic fields that are superimposed to form a circularly polarized, overall magnetic field.
2. Description of the Prior Art
Magnetic resonance transmission antennas of the above general type are wellknown, for example, in German OS 44 34 948, German OS 43 22 352, German OS 41 38 690, U.S. Pat. Nos. 5,144,241 and 5,606,259.
In these known antennas, currents that are offset in phase by 90° are supplied into two transmission elements in order to generate the circularly polarized, overall magnetic field. To this end, a transmission current is divided into two sub-currents that are offset in phase by 90° relative to one another and that are set to the same amplitude in matching circuits. The sub-currents are then supplied into the transmission elements. The transmission elements are decoupled from one another in a complicated way in order to avoid unwanted couplings and to thus obtain a purely circularly polarized, overall magnetic field.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a simply constructed magnetic resonance transmission antenna that generates a purely circularly polarized, overall magnetic field.
This object is inventively achieved in a magnetic resonance transmission antenna having transmission elements that are coupled to one another such that a transmission current fed into one of the transmission elements generates a phase-offset coupled current in the other of the transmission elements. Given a suitable coupling, the overall magnetic field generated by the transmission elements is then also circularly polarized.
In contrast to conventional antennas, thus, the coupling between the transmission elements is intentionally intensified in order to obtain a phase offset between the emitted, discrete magnetic fields via the coupling of the transmission elements and thus to obtain a circularly polarized, overall magnetic field. Given exactly two transmission elements, in particular, the coupling must be such that the coupled current is of the same magnitude as the transmission current, and such that the phase offset exactly corresponds to the angular offset of the discrete magnetic fields.
Optionally, the coupling between the transmission antennas can be inductive, capacitive or mixed inductive-capacitive.
The efficiency of the magnetic resonance transmission antenna is especially high when the transmission elements are tuned to a common resonant frequency.
REFERENCES:
patent: 4887038 (1989-12-01), Votruba et al.
patent: 4968937 (1990-11-01), Akgun
patent: 5006805 (1991-04-01), Ingwersen
patent: 5128615 (1992-07-01), Oppelt et al.
patent: 5144241 (1992-09-01), Oppelt et al.
patent: 5270656 (1993-12-01), Roberts et al.
patent: 5280249 (1994-01-01), Kess
patent: 5473252 (1995-12-01), Renz et al.
patent: 5602557 (1997-02-01), Duerr
patent: 5606259 (1997-02-01), Potthast et al.
patent: 5708361 (1998-01-01), Wang et al.
patent: OS 42 38 831 (1994-05-01), None
Nistler Juergen
Renz Wolfgang
Arana Louis
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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