ULTRA-LOW-PROFILE LOW FREQUENCY ANTENNA

Abstract

An ultra-low-profile low frequency antenna including a magnetic core having coil winding channels in three intersecting axial directions orthogonal to each other, defining X-axis (X), Y-axis (Y) and Z-axis (Z), receiving respective X-coil (DX), Y-coil (DY), and Z-coil (DZ). A Z-coil winding channel surrounds the magnetic core around the Z-axis (Z), providing partial grooves confined between two parallel surfaces. The thickness of the magnetic core in the Z-axis (Z) is less than 1.2 mm. Each partial groove has a width in the Z-axis (Z) equal or less than 0.4 mm and its depth in a radial direction perpendicular to the Z-axis (Z) is at least two times of its width. The Z-coil (DZ) is wound within said groove and extends radially from ⅓ to ⅔ of the groove's depth. The outer edge of the Z-coil is at the entrance of the groove.

Claims

1. An ultra-low profile low frequency antenna comprising a magnetic core made of a soft-magnetic non-electro conductive material, the magnetic core having coil winding channels in three intersecting axial directions orthogonal to each other, defining X-axis (X), Y-axis (Y) and Z-axis (Z) orthogonal to each other wherein: the magnetic core includes a flat central region and four corner protuberances spaced apart to each other around said central region, said corner protuberances defining therebetween a X-coil winding channel surrounding the central region around the X-axis (X), and a Y-coil winding channel surrounding the central region around the Y-axis (Y); and a Z-coil winding channel surrounds the magnetic core around the Z-axis (Z), said Z coil winding channel being defined by a discontinuous groove confined between two parallel surfaces which are perpendicular to the Z-axis (Z) providing a rectangular cross section, said discontinuous groove including four partial grooves each included in one of the corner protuberances; a X-coil (DX) is wound around the X-axis (X) contained within the X-coil winding channel, a Y-coil (DY) is wound around the Y-axis (Y) contained within the Y-coil winding channel, and a Z-coil (DZ) is wound around the Z-axis (Z) contained within the Z-coil winding channel; and the X-coil (DX), the Y-coil (DY) and the Z-coil (DZ) being made of conductive wire, and each having a conductive wire entry and a conductive wire exit connected to a respective connection terminal, the magnetic core is monolithic and has a flattened drum-like shape; the thickness of the magnetic core in the Z-axis (Z) direction is of less than 1.2 mm; each partial groove is narrow and deep being the width of each partial groove in the Z-axis (Z) direction equal or less than 0.4 mm and being the depth of each partial groove in a radial direction perpendicular to the Z-axis (Z) direction at least two times the width thereof; and the Z-coil (DZ) is wound within said Z-coil winding channel inserted in said narrow deep groove and extending radially from ⅓ to ⅔ of the depth of the groove and the outer edge of the Z-coil wound in the Z-coil winding channel, is at a distance of the entrance of the groove so that the parallel surfaces extent in cantilever beyond said outer edge.

2. The antenna of claim 1, wherein said connection terminals are directly attached to a flat surface of said corner protuberances.

3. The antenna according to claim 1, wherein an inner edge of said Z-coil is at a distance of said X-coil and Y-coil.

4. The antenna according to claim 1, wherein the conductive wire is an insulated high thermal resistant wire up to 220° C. and has a diameter of 0.020 mm-0.040 mm.

5. The antenna according to claim 1, wherein the antenna is encapsulated by an insulating resin coating with a coating thickness between 0.2 mm.

6. The antenna according to claim 1, wherein the thickness of the magnetic core is less than 1 mm and the width of the partial grooves is of 0.3 mm.

7. The antenna according to claim 1, wherein the extension of the core in the X-axis and in the Y-axis directions is preferably equal or less than 140 mm.sup.2.

8. The antenna according to claim 1, wherein the magnetic core is a high density molded ferrite core or a high density molded ferrite core made of a Nickel Zinc alloy or made of a Manganese Zinc alloy.

9. The antenna according to claim 1, wherein one of the central regions located in a larger face of the core includes a recess defining the X coil winding channel 12X and the opposite region is flat.

10. A method of producing the ultra-low profile low frequency antenna of claim 1 comprising: obtaining a monolithic, flattened drum-like shape magnetic core by: compacting in a mold powder of soft-magnetic non-electro conductive material shaping the magnetic core including a flat central region and four corner protuberances spaced apart to each other around said central region, said corner protuberances defining therebetween a X-coil winding channel surrounding the central region around the X-axis, and a Y-coil winding channel surrounding the central region around a Y-axis (Y); creating a Z-coil winding channel surrounding the magnetic core around the Z-axis by a sawing process, said Z-coil winding channel being defined by a discontinuous groove confined between two surfaces, said discontinuous groove including four partial grooves each included in one of the corner protuberances; oven-sintering the magnetic core producing its crystallization, shrinking and hardening; arranging a X-coil (DX) wound around the X-axis (X) contained within the X-coil winding channel, a Y-coil (DY) wound around the Y-axis (Y) contained within the Y-coil winding channel, and a Z-coil (DZ) wound around the Z-axis (Z) contained within the Z-coil winding channel (12Z); and connecting a conductive wire entry and a conductive wire exit of each of said X-coil, Y-coil and Z-coil to a respective connection terminal, wherein each of the four partial grooves of the magnetic core and previous to the oven-sintering process has a trapezial cross section in a radial sectional plane coincident with the Z-axis (Z), said trapezial cross section being produced by a tapered saw during the sawing process, and being said trapezial cross section defined to become a rectangular cross section after the crystallization, shrinking and hardening.

11. The method according to claim 10, wherein the conductive wire entry and the conductive wire exit of each of said X-coil, Y-coil and Z-coil are connected to the respective connection terminal by a laser welding process.

12. The method according to claim 10. wherein the assembly of the core and coils are embedded in a resin casing and connected to a PCB by a reflow soldering process in an oven.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0056] The foregoing and other advantages and features will be more fully understood from the following detailed description of an embodiment with reference to the accompanying drawings, to be taken in an illustrative and not limitative, in which:

[0057] FIG. 1 shows a first perspective view of the magnetic core of the ultra-low-profile antenna of this invention.

[0058] FIG. 2 is a second perspective view of the magnetic core showing the opposite greater face

[0059] FIGS. 3 and 4, illustrate the association of the magnetic core to a lead frame providing the connecting terminals, FIG. 4 showing the final arrangement of the core in a space of reception of the lead frame.

[0060] FIG. 5 is a perspective view illustrating the arrangement of the extension tabs from the lead frame providing the connecting terminals with regard to the magnetic core.

[0061] FIG. 6 is a perspective view equivalent to FIG. 5 but including the first X-coil wound around the X-coil winding channel.

[0062] FIG. 7 is a perspective equivalent to FIG. 5 but including both the X-coil and Y-coil respectively wound around the X-coil winding channel and Y-coil winding channel.

[0063] FIG. 8 shows another perspective view, equivalent to that of the previous FIGS. 5 to 7, but in this case with the three X-coil, Y-coil and Z-coil respectively wound around the X-coil winding channel, Y-coil winding channel and Z-coil winding channel.

[0064] FIG. 9 is the same figure as FIG. 8, but seen from the bottom showing the layout of the extension tabs of the lead frame from which the connecting terminals will be formed.

[0065] FIG. 10 shows the assembly of the core and extension tabs with the core covered by a layer of epoxy resin and FIG. 11 is the equivalent view but seen from the top part.

[0066] FIG. 12 is equivalent to FIG. 10 but with the extension tabs cut providing the 8 connecting terminals.

[0067] FIG. 13 is a figure equivalent to FIG. 12 but with the connecting terminals folded against the body of the casing provided by the epoxy resin coating.

DETAILED DESCRIPTION OF AN EMBODIMENT

[0068] The foregoing and other advantages and features will be more fully understood from the following detailed description of an embodiment with reference to the accompanying drawings, to be taken in an illustrative and not limitative, in which:

[0069] FIGS. 1 and 2 show the magnetic core 10 of the proposed ultra-low-profile antenna, which is made of a soft-magnetic non-electro conductive material such as a ferrite made of a Nickel Zinc alloy or made of a Manganese Zinc alloy, the core 10 having coil winding channels 12X, 12Y and 12Z in three intersecting axial directions orthogonal to each other.

[0070] The magnetic core 10 includes a central region 12 and four corner protuberances 11 spaced apart to each other around said central region 12. The corner protuberances 11 define therebetween a X-coil winding channel 12X surrounding the central region 12 around the X-axis X, a Y-coil winding channel 12Y surrounding the central region 12 of the core around the Y-axis Y, and a Z-coil winding channel 12Z surrounding the magnetic core 10 around the Z-axis Z, being the X-coil winding channel 12X, the Y-coil winding channel 12Y and the Z-coil winding channel 12Z orthogonal to each other.

[0071] The Z-coil winding channel 12Z is defined by a discontinuous groove confined between two parallel upper and lower surfaces of the core 10 which are perpendicular to the Z-axis Z providing a rectangular cross section, the discontinuous groove including four partial grooves 40 each included in one of the corner protuberances 11.

[0072] As shown in FIGS. 6, 7 and 8, a X-coil DX is wound around the X-axis X contained within the X-coil winding channel 12X, a Y-coil DY is wound around the Y-axis Y contained within the Y-coil winding channel 12Y, and a Z-coil DZ is wound around the Z-axis Z contained within the Z-coil winding channel 12Z.

[0073] The X-coil DX, the Y-coil DY and the Z-coil DZ are made of conductive wire, and each has a conductive wire entry and a conductive wire exit connected to a respective connection terminal 30.

[0074] According to the teachings of present invention, following special features are implemented:

[0075] Firstly, the thickness of the magnetic core 10 in the Z -axis Z direction is of less than 1.2 mm and preferably equal or less than 1 mm.

[0076] Each partial groove 40 is narrow and deep, being the width of each partial groove 40 in the Z-axis Z direction equal or less than 0.4 mm, and preferably around 0.3 mm, and being the depth of each partial groove 40 in a radial direction perpendicular to the Z-axis Z direction at least two times the width thereof.

[0077] Likewise, the Z-coil DZ is wound within said Z-coil winding channel 12Z inserted in said narrow deep groove 40 and extends radially from ⅓ to ⅔ of the depth of the groove 40. The outer edge of the Z-coil wound in the Z-coil winding channel 12Z is at a distance of the entrance of the groove 40 (see FIGS. 8 and 9) so that the parallel surfaces extent in cantilever beyond said outer edge.

[0078] As can also be seen in FIGS. 8 and 9 the inner edge of said Z-coil is at a distance of said X-coil and Y-coil.

[0079] The conductive wire for the coil is an insulated high thermal resistant wire up to 220° C. and has a diameter comprised in a range between 0.020 mm-0.040 mm.

[0080] As can be seen in FIGS. 1 and 2 one of the central regions located in one of the larger faces of the core 10 includes a recess defining the X-coil winding channel 12X while the other opposite central region (see FIG. 2) is flat. This allows the magnetic core be manufactured without risk of breakage in this central part, as this central part has a total thickness of about 0.60 mm. Taking into account the small diameter of the insulated conductive wire and the development in width of each of the X coil and Y-coil the lack of a recess for the X-coil in one of the larger faces of the core is avoidable since this does not impose an excessive bulging of the superimposed wound coils DX and DY.

[0081] As illustrated in FIGS. 5 to 9, connection terminals 30 are directly attached to a flat surface of said corner protuberances.

[0082] FIGS. 3 and 4 show how the core 10 is attached to a lead frame 50 which has cut out some extension tabs 51 from which the connecting terminals 30 will be obtained by cutting.

[0083] The core 10 with its coils DX, DY and DZ is encapsulated by an insulating resin coating 60 with a coating thickness between 0.2 and 0.3 mm. This can be seen in FIGS. 10 to 13.

[0084] FIGS. 12 and 13 show the connection terminals 30 folded against the electro-insulant material, defining connection terminals overlapped to recessed portions 61 the casing 60 of the antenna.

[0085] In a second aspect this invention refers to a production method of an ultra-low profile low frequency antenna, the method including according to know procedures:

[0086] obtaining a magnetic core by:

[0087] compacting in a mold an amorphous powder of soft-magnetic non-electro conductive material shaping the magnetic core 10 including a flat central region 12 and four corner protuberances 11 spaced apart to each other around said central region 12, said corner protuberances 11 defining therebetween a X-coil winding channel 12X surrounding the central region 12 around the X-axis X, and a Y-coil winding channel 12Y surrounding the central region 12 around a Y-axis Y;

[0088] creating a Z-coil winding channel 12Z surrounding the magnetic core 10 around the Z-axis Z by a cutting or sawing process, said Z-coil winding channel 12Z being defined by a discontinuous groove confined between two upper and lower surfaces of the core 10, said discontinuous groove comprising four partial grooves 40 each included in one of the corner protuberances 11;

[0089] oven-sintering the magnetic core 10 producing its crystallization, shrinking and hardening;

[0090] arranging a X-coil DX wound around the X-axis X contained within the X-coil winding channel 12X, a Y-coil DY wound around the Y-axis Y contained within the Y-coil winding channel 12Y, and a Z-coil DZ wound around the Z-axis Z contained within the Z-coil winding channel 12Z; and

[0091] connecting a conductive wire entry and a conductive wire exit of each of said X-coil, Y-coil and Z-coil to a respective connection terminal 30.

[0092] According to this invention and mainly for the purpose of manufacturing a magnetic core with the dimensions and configuration previously explained, previous to the oven-sintering process each of the four partial grooves 40 of the magnetic core 10 is cut to have a trapezial cross section in a radial sectional plane coincident with the Z-axis Z, said trapezial cross section being produced by a tapered saw during the sawing process, being said trapezial cross section defined to finally take a rectangular cross section shape after the crystallization, shrinking and hardening due to the oven sintering process.

[0093] In addition, the connection of the wire entry and the conductive wire exit of each of said X-coil DX, Y-coil DY and Z-coil DZ to the respective connection terminal 30 can be performed by a laser welding process.

[0094] As a final step, the assembly of the core 10 and coils DX, DY and DZ can be embedded in a resin casing 60 and connected to a PCB (not shown) by a reflow soldering process in an oven.

[0095] The ultra-low-profile triaxial antenna of this invention has been particularly designed for its integration in a smartphone, in particular to operate as a key-less system. Therefore, a mobile phone (or other portable computer device) integrating the proposed antenna will also include a software application installed therein providing a user interface for controlling operation of the proposed ultra-low-profile triaxial low frequency antenna.

[0096] It will be understood that various parts of one embodiment of the invention can be freely combined with parts described in other embodiments, even being said combination not explicitly described, provided there is no harm in such combination.

[0097] The scope of the present invention is defined in the following set of claims.