Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-06-16
2002-06-11
Getzow, Scott M. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06405088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a telemetry coil arrangement for receiving data signals in particular from cardiologic implants, comprising a pair of coils disposed one after the other in the direction of reception.
2. Background Art
A telemetry receiver coil arrangement of the generic type is known from U.S. Pat. No. 5,630,835, which discloses an electronic apparatus for the non-invasive communication with an implanted device such as a cardiac pacemaker. An antenna arrangement with two coils connected in opposite directions is provided in the electronic apparatus—which is a so-called “programming head” in the case under regard. This known antenna arrangement with the two coils connected in series in opposition of phase helps suppress the effects of so-called far-field interference signals on the received near-field signals from the implant.
The effect underlying the known prior art bases on the fact that the mentioned interference fields in the form of far-field interference signals are substantially represented by homogeneous electromagnetic fields, whereas the transmitter field of the implant represents a decidedly inhomogeneous electromagnetic field. As a result of the connection, in opposition of phase, of the two coils, the homogeneous signal portions neutralize each other, whereas the inhomogeneous signal portions are only slightly damped. This helps improve the signal-to-noise ratio from 1:1 to an order of magnitude of for instance, 47:1 when only a single receiver coil is used, given the geometry of the two coils specified in the exemplary embodiment of the publication cited at the outset. In theory, even total suppression of homogeneous fields can be attained.
U.S. Pat. No. 5,741,315 teaches, in a telemetric data transmission device, to dispose a receiver coil and a compensation coil of differing diameters on a cup-shaped support such that inhomogeneous signals—namely the signals emitted by the implant—are observed only in the receiver coil, whereas homogeneous signals—namely interference signals—are measured also in the compensation coil.
Since cardiologic implants, for instance a cardiac pacemaker, emit only very weak magnetic fields for data transmission, which have to be received in comparatively interfering surroundings, inhomogeneous interference fields should also be suppressed in a suitable manner. This is not feasible by the coil arrangement specified in U.S. Pat. No. 5,630,835.
SUMMARY OF THE INVENTION
It is the object of the invention to improve the receiving properties of telemetry coil arrangements for the reception of data signals in particular in cardiologic implants.
According to the basic concept of the solution, according to the invention, of this object, the prior art double coil principle can be improved by the coils having differing diameters and/or—in particular with systems of coils of identical diameter—by the coils being put in circuit asymmetrically. Certain directional characteristics can be attained by this measure, which can help improve the suppression of inhomogeneous interference fields. The number of windings on the coils must be adapted in such a way that, in spite of these differing diameters of the coils or the asymmetric circuitry of the coils, voltages induced by homogeneous interference fields will cancel each other, given a corresponding circuitry of the coils. Details of this will become apparent from the description of the exemplary embodiments.
Further problems in telemetry coil arrangements reside in the so-called “zeroes” in the case of lateral displacement of the emitter and receiver coil. Observations show that in the case of certain ranges of lateral or radial displacement between the two coil systems, the voltage of reception becomes zero regardless of the amplitude of the emitter field. As will become apparent from the exemplary embodiments, different coil systems have different zeroes. In the case of at least three coils of at least two different diameters and in the case of corresponding coupling of these coil systems, the coil systems, in a certain situation of reception, can be individually connected to form combinations of coils of optimal receiving properties. The selection from various system configurations can be effected for instance by evaluation of suitable signal parameters such as the amplitude or the signal-to-noise ratio.
Further features, details and advantages of the invention will become apparent from the ensuing description of exemplary embodiments of the subject matter of the invention, taken in conjunction with the attached drawings.
REFERENCES:
patent: 5630835 (1997-05-01), Brownlee
patent: 5741315 (1998-04-01), Lee et al.
patent: 39 36 547 (1991-05-01), None
patent: 0 917 079 (1999-05-01), None
Koch Frank
Merlin Julian
Biotronik Mess- und Therapiegeräte GmbH & Co. Ingenieurbüro Berl
Browdy and Neimark
Getzow Scott M.
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