EP0348636A1 - Antenna for a small radio-controlled watch - Google Patents

Abstract

A magnetic antenna for a radio receiver, in particular for the long-wave receiver of a radio clock, is to be designed so that it can also be installed in the confined spaces of a small housing or used as the antenna of a wristwatch. For this, the core (15) passing through the coil (14) z. B. made of flexible highly permeable material, so that there is a flexible connection to the clock, which can also be designed as a watch strap (28). When dielectric foils are interposed, the strips of a stack core (15) can also serve as the electrodes of the adjustment capacitance of an antenna resonant circuit. A multi-layer laminated ribbon cable (31), which can be integrated into a watch band (28), preferably serves as the antenna line between the coil (14) and the receiver.

Description

The invention relates to an antenna according to the preamble of claim 1, in particular for the radio receiver of a radio clock, as is described in more detail in EP 0 242 717 A2.

In the case of small clocks, such as small style clocks or travel alarm clocks, it is problematic to have a long-wave antenna of sufficient power for the reception of radio-transmitted signals in the small-diameter space that is angled between the clockwork and the inner wall of the watch case or hinged construction parts To accommodate time information.

The realization of a radio-controlled watch as a wristwatch has so far been regarded by experts as not being feasible because of the space required for the construction of the radio receiver (see R. Bermbach and M. Lobjinski "New radio-controlled clocks from the Institute for Data Technology" in FUNKUHREN, published by W. Hilberg, center from page 170); the problem of accommodating a sufficient magnetic core loop antenna volume is not even taken into account there. The space requirement for the receiver has meanwhile been resolved since there have been permanently tuned long-wave receivers for radio clocks integrated on a chip (cf. DE 35 16 810 A1). However, the problem of miniaturization of sufficiently powerful passive antennas for long-wave receivers, which, for example, as in the case of modern consumer radio clocks, should be operated from a single-cell battery, remains unsolved.

In recognition of these circumstances, the invention has for its object to design an antenna of the generic type in such a way that it can be installed even in narrow and angled environmental conditions or can be used as a powerful long-wave antenna for portable devices such as, in particular, a radio-controlled wristwatch.

The object is essentially achieved in that the generic antenna is designed according to the characterizing part of claim 1.

This solution is based on the consideration that the essential obstacle to the realization of a frame antenna suitable for confined spaces is less the volume of the (ferrite) core penetrating the frame coil than the space required for a rigid cylindrical core or for the grouping of several Cores to be arranged in a defined geometric orientation. Therefore, the solution is seen in a flexibly held core for a loop antenna, as can be realized, for example, by means of several flexible strips or soft ferrite cores made of soft magnetic materials of high permeability, such as amorphous metals in sheet or powder form, which can be displaced relative to one another. Depending on the existing installation conditions, such an antenna can be angled in an L-shaped, U-shaped or Z-shaped manner in order to make optimal use of the free spaces available for installing the antenna and at the same time realize different spatial reception orientations. Such a flexible core stack of individual magnetically effective strips can also be designed, for example, bent into a ring cutout, as part of a bangle which represents or receives the antenna for a receiver worn, for example, under clothing or directly on the wrist , for example, can also serve directly as a bracelet antenna of a radio-controlled wristwatch or can be inserted into a watch bracelet.

The capacity for tuning the resonant circuit of the antenna can also be integrated into a layer structure, for example by connecting individual layers which are electrically insulated from one another as reciprocal electrode groups to form a capacitor, and to connect the antenna coil in parallel, to avoid eddy current losses.

For the electrical connection of the coil of such a flexible loop antenna, a structure of multilayer conductive foils laminated onto insulating foils is expediently used, in the middle of which a relatively narrow conductor extends, which is electrically shielded by wider conductive foils extending above and below it can also serve as a return conductor for the antenna connection to the radio clock receiver. Such an electrically tunable ribbon cable is expediently glued to the core in front of the antenna coil, and a miniaturized matching capacitor for the antenna resonant circuit can also be applied in the connection area to the coil connecting wires. The opposite end of the ribbon cable is equipped with plug-in means, which are preferably oriented approximately transversely to the longitudinal extent and thus transversely to the direction of pull of the ribbon cable entering a watch case and are plugged together there with complementary plug-in means for connection to the receiver in the watch case. A soft, elastic encapsulation of the antenna core with its coil expediently also includes the course of the ribbon cable up to the plug-in means positioned in the watch case, so that a clamp-fixing of the bracelet bezel at the entry into the watch case at the same time mechanical fastening and moisture Sealing the connector is used. Such a ribbon cable can e.g. also run between an alarm clock folding stand equipped with the antenna and the clockwork that can be swiveled, in which the receiver is installed.

• Fig. 1 in unterbrochener Axial-Längsschnittdarstellung eine flexib­le magnetische Antenne in der Ausgestaltung als Funkuhren-Arm­band,
• Fig. 2 in stark überhöhter Querschnittsdarstellung eine Armband-An­tenne gemäß Fig. 1 unter Berücksichtigung einer auf dem Streifen-Kern vor der Spulen-Stirn aufliegenden Antennen-­Flachbandleitung,
• Fig. 3 die Flachbandleitung gemäß Fig. 2 in unterbrochener und abgebrochener Draufsicht-Darstellung, bei fortgelassener Umguß-Einlassung und fortgelassener oberer Abschirm-Leitfolie samt darunter angeordneter Isolierfolie und ohne Berücksichti­gung des im Spulen-Anschlußbereich montierten Abstimmkonden­sators,
• Fig. 4 in abgebrochener Längsschnittdarstellung die Klemmbefestigung der Armband-Einfassung am Rande eines Uhrengehäuses mit quer zur Zugbeanspruchungs-Richtung orientierten Steckmitteln für die elektrische Verbindung vom Uhrwerks-Empfänger zur Antennen-Flachbandleitung;
• Fig. 5 im Armband-Ausschnitt einen auch quer zu seiner Längserstrek­kung flexibel eingefaßten Kern und
• Fig. 6 einen relativ steifen Kern im Anschluß zwischen flexiblen Armband-Teilen.

Additional alternatives and further developments as well as further features and advantages of the invention result from the further claims and, also taking into account the explanations in the summary, from the following description of the drawings abstracted to the essentials, in particular not to measure Enlarged in true-to-scale proportions, preferred exemplary embodiments of the inventive solutions for the case of wristwatch antennas that can be connected to a wristwatch housing are outlined. It shows:

• 1 shows an interrupted axial longitudinal sectional view of a flexible magnetic antenna in the form of a radio watch bracelet,
• 2 in a greatly exaggerated cross-sectional view of a bracelet antenna according to FIG. 1, taking into account an antenna ribbon cable resting on the strip core in front of the coil end,
• 3 shows the ribbon cable according to FIG. 2 in an interrupted and broken top view, with omitted encapsulation and omitted upper shielding guiding foil including insulating foil arranged underneath and without taking into account the tuning capacitor mounted in the coil connection area,
• 4 shows a broken longitudinal section of the clamp fastening of the bracelet bezel on the edge of a watch case with plug means oriented transversely to the direction of the tensile stress for the electrical connection from the clockwork receiver to the antenna ribbon cable;
• Fig. 5 in the bracelet cutout a core and also flexibly edged transversely to its longitudinal extent
• Fig. 6 shows a relatively rigid core in the connection between flexible bracelet parts.

An autonomous (wrist) radio-controlled watch 11, which is only symbolically outlined in the drawing, is equipped with a radio receiver 12 for receiving and decoding time information which, if necessary, serves to correct the time currently displayed by the radio-controlled watch 11. The receiver 12 is fed from an antenna 13 designed as an LC resonant circuit. This is constructed as a layered core frame antenna, that is to say from a coil 14 which is penetrated by a flexible core 15.

The core 15 is preferably layered as a vertical stack of very thin strips 16 of amorphous, soft magnetic, highly permeable material, such as those under the trade name VITROVAC from Vacuumschmelze GmbH (D-6450 Hanau) as extremely thin and spring-hard flexible sheets, in particular for the construction of low-loss transformers in switched-mode power supplies and for magnetic switches of pulse power supplies are launched on the market and are characterized by low sensitivity to mechanical stresses.

This core 15 is clamped transversely to the surface extension of its strips 16 by a border 17, as symbolized in the drawing by the triangles of tension direction. This border 17, for example designed as a plastic shell molded around the core 15, expediently also covers the coil 14 in order to fix it in position on the core 15 and to mechanically protect it against environmental influences. If the border 17 is flexible in order to give the antenna 13 different geometric shapes - for example for installation in limited space conditions or for configuration as a bracelet - the axial length 18 of the coil 14 is relatively limited in order to avoid the area of the non-flexible core 15 to keep small, which is stiffened by the applied coil 14. On the other hand, a coil 14 that applies as little as possible over the core 15 is to be aimed at for electromagnetic reasons, because the field strength decreases quadratically over the distance from the core 15, that is to say winding layers of the coil 14 that are further away only make very small contributions from the field-strengthening effect of the core 15 experienced. The coil 14 is expediently even introduced into a core constriction 48, as taken into account in FIGS. 5 and 6.

Also in the interest of the flexibility of a stack core 15, a free space 19 is left in front of the ends 16 of the strips 16 opposite the border 17 surrounding them. This enables a longitudinal displacement of individual strips 16 against one another when the core 15 is bent about its longitudinal axis.

If instead or in addition a flexibility of the antenna armband 28 transverse to the longitudinal extension of the strips 16 is desired, the core 15 (FIG. 5) consists of individual or stacked strips 16 in frontal succession, with engagement of convexly rounded ends 49 each in concavely adapted joint sockets 50 of the adjoining strip 16. The strips 16 (or the external ones) can also be replaced by a filling 51 made of soft ferrite powder in the assigned part of the flexible border 17 in the course of the bracelet 28. If flexibility in the direction of the longitudinal axis is not so important, the individual joint part strips 16 preferably consist of (sintered) ferrite.

If a relatively stiff core 15, for example a single or multi-layer ferrite body, is given, then it may be expedient for aesthetic reasons to design it in its bezel 17 geometrically as a visual counterpart to the clock 11 itself (FIG. 6) and in anatomically adapt to an arm as a curved ring cutout. The connection to the clock 11 is then made via partial bracelets 28-28 which can be connected to the antenna core 15 via closures or articulated members 29.

In order to avoid signs of abrasion as far as possible when mutually parallel shifting of stacked strips 16 of a flexible core 15 and at the same time to reduce electromagnetic eddy current losses in the ferrite core 15, the individual layers of the strips 16 are provided with interposed insulating layers 20, for example foils or lacquer layers, mechanically and electrically separated from each other.

For this insulation 20, a flexible material with a large dielectric constant is expediently used, such as is available on the market as the so-called X7R ceramic for the construction of small layer capacitors of high capacitance. If the core 15 is also to be bent with small radii, common dielectrics such as mica or foils of polyester or polycarbonate and the like are more advantageous.

This insulating material can be coated or coated with electrically conductive electrodes in order to integrate the tuning capacitance 21 into the strip stack antenna 13 and to connect it electrically to the ends of the coil 14 within the protective enclosure 17, for example via welded connections 22. This reduces the capacitance value and thus the installation space requirement of an external tuning capacitor 23, provided that this cannot even be completely eliminated by the integrated capacitance 21.

Even the electrically conductive core strips 16 themselves can serve as the capacitor electrodes on both sides of dielectric insulating films 20, so that the additional layering of separate capacitor electrodes on both sides of the insulating films 20 is unnecessary. As is known from the technology of the layer capacitors as such, these electrode strips 16, in the interest of a large effective electrode area and thus a high capacitance value, are alternately interconnected in such a way that electrode groups 24.1, 24.2, which mesh with one another in alternating fashion, result. Of these, the outer strip 16.1 or 16.2 can serve as a conductor for closing the coil connections 22.1, 22.2 to antenna connections 25.1, 25.2 leading to the outside. Flexible interconnections 26.1, 26.2 between the electrode strips 16 of the electrode groups 24 in the area of the associated free spaces 19.1, 19.2 ensure that the strips 16 can be displaced alternately in parallel with one another when the ferrite core 15 is subjected to bending stress.

The antenna 13 from the coil 14 with the core 15 and optionally the resonance capacitance 21 can be connected via lines 27 to the radio receiver 12 of the clock 11, in whose housing this antenna 13 is inserted. If it is a portable radio-controlled watch 11 and in particular a training as a wristwatch, the flexible antenna 13 is expediently also designed as a bracelet 28 by its bezel 17, as outlined in the drawing by articulated links 29.

These can be connected directly - or if necessary via interposed extension members - to the croissants of a wristwatch case if these croissants are electrically insulated from one another, so that additional connecting lines (27) are unnecessary. However, it is sufficient to design a bracelet half or an intermediate piece of a bracelet 28 as an antenna 13. In order to be able to exchange defective bracelets 28 easily and inexpensively, provision can also be made for the antenna 13 to be designed as one or on an envelope-shaped flexible hollow body through which the replacement bracelet 28 is threaded without also exchanging the antenna 13 and the receiver 12 or to have to readjust its antenna resonant circuit.

Thus, a (wrist) radio-controlled clock 11 can be realized, when designing the size or design for installation space required for a receiving antenna 13 no longer has to be taken into account. Such a layered antenna 13 designed as a bracelet 28 or arranged on the bracelet provides an astonishingly high performance compared to conventional cylindrical ferrite cores as coil carriers, because the antenna voltage is proportional to and approximately proportional to the core cross section and above all the (very large) permeability of the core material to the core length and roughly inversely proportional to the core thickness. The core 15 carrying the coil 14 can, however, be of small thickness because of the high permeability, with, in the interest of good flexibility of the bracelet 28, the long axial length of the core 15 in relation to the magnetically effective thickness of the stacked core strips 16 as such.

Under certain circumstances, however, the electrical connection of the antenna 13 to the receiver 12 sketched in FIG. 1 to the watch case via wristband articulated sliders 29 is not sufficiently reliable, for example due to movements or dirt deposits between the articulated members. Free cables 27 can also interfere aesthetically or electrically, especially since they must be equipped with connectors for connection to the watch case, which would have to be designed to be moisture-proof with considerable construction effort.

It would also make it more difficult that such antenna connection lines 27 would have to be shielded between the receiver 12 and the magnetic antenna 13 in order to avoid interference.

It is therefore more expedient to implement the electrical function of the lines 27 or the contact joint members 29 according to FIGS. 2 to 4 and 6 by means of a multi-layer ribbon cable 31 which is electrically matched to the antenna resonant circuit, for example in the manner of the laminated multilayer films such as those marketed by DuPont under the trade name PYRALUX. However, the structure is now such that at least one narrow conductor 32 is sandwiched between two outer wide conductive foils 33 in an electrically insulated manner. These conductive foils 33 protrude laterally on both longitudinal edges approximately by the width of the narrow, central conductor 32, so that there is a good shielding effect of the outer conductive foils 33 for the inner conductor 32. The narrow conductor 32 and the conductive foils 33 are expediently formed as metallic laminations on insulating plastic carrier foils 34.

In the interest of a connection that is simple to manufacture but durable, the entirety of this layer structure of the ribbon cable 31 is fastened in the region in front of the coil end 35 to the surface of the flexible strip core 15 passing through the coil 14 by means of an insulating adhesive layer 36. Here are at the connection end 37 (see Fig. 3) of the ribbon cable 31 in the upper shielding foil 33 '(omitted for the illustration of Fig. 3) and in the insulating foil 34˝ above the lower foil 33˝ recesses, here around the coil connecting wires 22 to be able to connect to the central conductor 32 and to the lower shielding foil 33˝ serving as a return conductor. If a shielding capacitor 23 is required for antenna tuning, it is also expediently arranged in this connection area between the ribbon cable 31 and the antenna coil 14, for example as a surface-mounted chip capacitor, conductively connected between the conductor 32 and the conductive foil 33˝.

The overmolded antenna mount 17 then also surrounds this connection of the ribbon cable 31 equipped with the capacitor 23 to the antenna coil 14 on the surface of the flexible antenna core 15.

Before the core end 37, the ribbon cable 31, as taken into account in FIG. 3, can initially emerge with a constant width in the interest of high bending strength, in order to then transition into a more flexible zone of a line taper 38. This finally ends in a again widened connection area 39 with a conductor eye 39 in the area of a guide foil recess 41 and a pair of eyes 42 through the guide foils 33 on both sides of this recess 41. Plug-in means 43 (sockets or pins) are inserted into these eyes 40, 42 In order (in FIG. 4) to be able to be connected mechanically and electrically in the edge region of, for example, a wristwatch housing 44 with connecting conductors 45 insulated there to the radio clock receiver 12 in the plugging direction transverse to the longitudinal extension of the ribbon cable 31.

For this antenna connection via the ribbon cable 31, a housing clamp connection 46 is provided for moisture-proof compression mounting of the elastic encapsulation 17, which ends with the connection region 39 of the ribbon cable 31 in a connection cavity 47. In this housing-fixed counter contacts to the plug-in means 43 in the ribbon cable eyes 40, 42 are arranged insulated. This results in a moisture-proof and mechanically highly stressable electrically high-quality antenna connection to the receiver 12 in, for example, a wristwatch housing 44.

An expedient additional measure to compensate for the change in inductance due to the relative permeability of the core material under mechanical (bending) stress in the sense of retuning the angular frequency thus changed is not shown separately in the drawing. For this purpose, a compensation control can act on the resonant circuit capacitance in the receiver 12, for example by means of a switchable capacitance cascade or via the corresponding activation of a capacitance diode.

Claims (15)

1. antenna (13), for a small radio clock (11),
characterized,
that it is equipped with a flexible enclosure (17) for a core (15) with a coil (14). 2. Antenna according to claim 1,
characterized,
that its border (17) is designed as a bracelet (28) or as a part thereof. 3. Antenna according to claim 2,
characterized,
that it is designed as a hollow body for receiving a bracelet (28). 4. Antenna according to one of the preceding claims,
characterized,
that flexible bracelets (28) connect to a curved core (15). 5. Antenna according to one of claims 1 to 4,
characterized,
that as a flexible core (15) soft ferrite powder is provided in an elastic plastic enclosure (17). 6. Antenna according to one of claims 1 to 4,
characterized,
that thin strips (16) of highly permeable amorphous metal are stacked to form the core (15). 7. Claim 6
characterized by a border (17) with a free space (19) in front of the end faces of the strips which allows a mutual longitudinal displacement of flexible strips (16) stacked one on top of the other. 8. Antenna according to one of the preceding claims,
characterized,
that strips (16) with convex front ends (49) engage in concave joint pans (50) of adjacent strips (16) arranged in front of them. 9. Antenna according to claim 8,
characterized,
that insulations (20) made of material with a high dielectric constant are arranged between the strip (16), on both sides of which electrodes of a resonance capacitance (21) connected in parallel with the coil (14) are provided. 10. Antenna according to claim 9,
characterized,
that the electrodes of a resonance capacitance (21) or a tuning capacitance (23) are the magnetic material strips (16) themselves. 11. Antenna according to one of claims 5 to 10,
characterized,
that it is equipped with a tuning capacity (23), which is designed to compensate for an angular frequency change due to mechanically induced change in permeability of the core (15). 12. Antenna according to one of the preceding claims,
characterized,
that a thin coil (14) and possibly its resonance or balancing capacitances (21, 23) are connected to the radio clock receiver (12) via a multilayer ribbon cable (31) running on or in the bracelet (28). 13. Antenna according to claim 12,
characterized,
that one end (37) of the ribbon cable (31) in front of an end (35) of the coil (14) on the core (15) and the other end is designed with plug-in means (43). 14. Antenna according to claim 12 or 13,
characterized,
that the ribbon cable (31) extends into the vicinity of its connection area (39) in an elastic casing (17) which is compressible by a clamping connection (46) on the radio-controlled watch housing (44) approximately transversely to its longitudinal extent. 15. Antenna according to one of claims 12 to 14,
characterized,
that a conductor (32) runs in the center region of the ribbon cable (31), on both sides of which shielding guiding foils (33) extend, which can also be connected as return conductors and which extend substantially over the width of the inner conductor (32).

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