Transmitter with Improved Sensitivity and Shielding
First Claim
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1. A magnetic field transmitter configured to generate a time varying magnetic field in response to a time varying input signal, the magnetic field transmitter comprising:
- a) a transmitter coil winding constructed of a bundle of continuous conductor loops, the bundle having an inner perimeter and an outer perimeter separated by a distance, the transmitter coil winding having a number of turns N, a coil winding resistance R, an effective coil radius Re and a coil winding inductance L, a conductor having a cross-sectional area A, a total length l and a resistivity ρ
, wherein the inner perimeter of the bundle, the coil winding resistance and the coil winding inductance are selected such that;
i) the coil winding resistance and the coil winding inductance produces a break frequency fb for the transmitter coil winding of between 20 Hz and 2000 Hz,where the break frequency is defined by the formula fb=R/(2π
L) wherein the coil winding resistance R is defined by the formula R=ρ
1/A and the coil winding inductance L is defined by the formula L=N2 (uoπ
Re)/2 where the constant uo is the permeability of free space; and
ii) the bundle having an annulus width and an annulus depth which are each smaller than a distance from a center of the bundle to the inner perimeter of the bundle; and
b) a backing plate comprised of low reluctance magnetic material having an upper surface and a lower surface, the lower surface of the backing plate being attached in close proximity to a lower surface of the transmitter coil winding, the backing plate having an outer perimeter that is approximately coincident with the outer perimeter of the transmitter coil winding.
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Abstract
A magnetic field transmitter, especially a transmitter used in conjunction with wireless communications earplugs. In one embodiment, a plate of magnetic material is used behind a coil of electrical conductor to improve the efficiency of the transmitter and to provide electrical and magnetic shielding. The specific dimensions and characteristics of the preferred embodiment of the transmitter described herein provide for efficient wireless communications.
13 Citations
18 Claims
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1. A magnetic field transmitter configured to generate a time varying magnetic field in response to a time varying input signal, the magnetic field transmitter comprising:
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a) a transmitter coil winding constructed of a bundle of continuous conductor loops, the bundle having an inner perimeter and an outer perimeter separated by a distance, the transmitter coil winding having a number of turns N, a coil winding resistance R, an effective coil radius Re and a coil winding inductance L, a conductor having a cross-sectional area A, a total length l and a resistivity ρ
, wherein the inner perimeter of the bundle, the coil winding resistance and the coil winding inductance are selected such that;i) the coil winding resistance and the coil winding inductance produces a break frequency fb for the transmitter coil winding of between 20 Hz and 2000 Hz, where the break frequency is defined by the formula fb=R/(2π
L) wherein the coil winding resistance R is defined by the formula R=ρ
1/A and the coil winding inductance L is defined by the formula L=N2 (uoπ
Re)/2 where the constant uo is the permeability of free space; andii) the bundle having an annulus width and an annulus depth which are each smaller than a distance from a center of the bundle to the inner perimeter of the bundle; and b) a backing plate comprised of low reluctance magnetic material having an upper surface and a lower surface, the lower surface of the backing plate being attached in close proximity to a lower surface of the transmitter coil winding, the backing plate having an outer perimeter that is approximately coincident with the outer perimeter of the transmitter coil winding. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A magnetic field transmitter configured to generate a time varying magnetic field in response to a time varying input signal, the magnetic field transmitter comprising:
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a) a transmitter coil winding constructed of a bundle of continuous conductor loops, having an inner perimeter and an outer perimeter separated by a distance and an annulus width and an annulus depth, the annulus width and the annulus depth being smaller compared to a distance from a center of the bundle to the inner perimeter of the bundle; b) a backing plate of low reluctance magnetic material having a front side and a back side, the transmitter coil winding being fixedly attached in close proximity to the backing plate, the backing plate having a central area perforated with at least one perforation passing through the upper surface and the lower surface; and c) an audio acoustic speaker configured to produce an acoustic output from the input signal and mounted adjacent to the at least one perforation in the backing plate, such that sound generated by the speaker passes through the at least one perforation in the backing plate. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification