COMMUNICATION DEVICE, ELECTRONIC TIMEPIECE, AND ANTENNA DEVICE

An antenna of an electronic timepiece includes a ring-shaped antenna pattern formed on a top surface or bottom surface of a cover glass and another antenna pattern that is formed beneath the ring-shaped antenna pattern and is capacitively coupled with the ring-shaped antenna pattern. The resonant frequency of the antenna is determined by the antenna patterns.

BACKGROUND OF THE INVENTION

The present invention relates to a communication device, an electronic timepiece, and an antenna device.

When exchanging information between a wristwatch and other devices using radio waves or when receiving satellite radio waves to obtain the time or a time zone, the reception sensitivity of the antenna can pose a challenge. Using a larger antenna is one solution to improving the antenna reception sensitivity. However, wristwatches cannot be increased in size by any significant amount. Therefore, antennas that do not negatively impact the design aesthetics of a wristwatch are in demand.

Conventional wristwatches that receive satellite radio waves such Global Positioning System (GPS) signals typically use rectangle-shaped patch antennas or ring antennas made from a ring-shaped dielectric embedded in the bezel of the wristwatch in order to achieve the required gain and circular polarization properties for the antenna, for example. However, using a patch antenna or a ring antenna tends to increase the diameter or thickness of the wristwatch, thereby having a significant effect on the overall design aesthetics of the wristwatch.

The invention disclosed in Japanese Patent Application Laid-Open Publication No. 2015-8513 provides one example of a wristwatch that uses a dielectric ring antenna. The SOLUTION section in the abstract of this patent document discloses the following: “An electronic device1includes a GPS antenna11that receives externally sent radio waves; an outer case101made at least partially from a non-conductive material; a plate-shaped dial2made from a non-conductive material and housed within the outer case101; a back cover102made from a conductive material and fixed to the outer case101; and a receiver that is housed between the dial2and the back cover102within the outer case101and processes received signals according to the radio waves received by the GPS antenna11. The GPS antenna11includes a line-shaped antenna electrode112arranged around the periphery of the dial2. The back cover102is connected to the ground of the receiver and functions as a reflector that reflects the radio waves.”

The invention disclosed in this patent document makes it possible to arrange a ring antenna under a sheet of cover glass. However, this tends to increase the diameter or thickness of the wristwatch, thereby negatively affecting the design aesthetics of the wristwatch.

Accordingly, the present invention is directed to a scheme that substantially obviates one or more of the above-discussed and other problems due to limitations and disadvantages of the related art.

SUMMARY OF THE INVENTION

Therefore, the present invention aims to provide a communication device, an electronic timepiece, and an antenna device that include a high-performance antenna that does not increase the size or thickness of the device housing.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, in one aspect, the present disclosure provides a communication device, including:

a communication module;

a cover glass covering the communication module and having a transparent window; and

an antenna,

wherein the antenna includes:a first antenna pattern that is looped and formed on a top surface or a bottom surface of the cover glass; anda second antenna pattern beneath the first antenna pattern and capacitively coupled with the first antenna pattern, and

wherein a resonant frequency of the antenna is determined by the first antenna pattern and the second antenna pattern.

In another aspect, the present disclosure provides an antenna device, including:

an antenna line for receiving radio waves from a satellite;

a feed line that is arranged beneath the antenna line and coupled with the antenna line;

a feed point that contacts the feed line; and

a ground line formed centered around a position that has been rotated in a direction +45° or +225° from the feed point about a prescribed rotational axis.

DETAILED DESCRIPTION OF EMBODIMENTS

Next, an embodiment of the present invention will be described in detail with reference to figures.

In the present embodiment, the cover glass of an electronic timepiece is used as a dielectric material for the antenna in order to provide a high-performance antenna that does not increase the overall size or thickness of the electronic timepiece.

FIGS. 1A and 1Billustrate the configuration of an electronic timepiece1and an antenna3thereof according to the present embodiment.

FIG. 1Ais a cross-sectional view of the electronic timepiece1taken along line I-I.

The electronic timepiece1is worn on the arm and therefore includes a time display unit4that includes components such as a dial51, a long hand42, and a short hand41.

The electronic timepiece1also includes a metal case6constituted by a hollow cylinder-shaped, ring-shaped frame61and a back cover64. Moreover, a cover glass2is fitted into an opening in the top surface of the ring-shaped frame61, thereby forming a housing. The ring-shaped frame61and the back cover64are made from a conductive metal material such as brass, stainless steel, or a titanium alloy. Furthermore, the ring-shaped frame61and the back cover64are connected to the ground terminal of a clock module7, which will be described next.

The clock module7is arranged within the housing of the electronic timepiece1. The time display unit4that includes the components such as the dial51, the long hand42, the short hand41, and a ring-shaped dial cover53(a ring-shaped member) is arranged above the clock module7, facing the cover glass2.

The clock module7drives the long hand42and the short hand41to display the time and also receives satellite signals from a GPS satellite8(seeFIG. 4, which will be described later). Moreover, the clock module7includes components such as a circuit board (not illustrated in the figure) on which a circuit device that handles the processing for displaying the time and the GPS feature is mounted, a drive mechanism (not illustrated in the figure) that includes a step motor and a gear train for driving components such as the long hand42and the short hand41, and a battery (not illustrated in the figure) that supplies power to the components listed above.

In the present embodiment, a ring-shaped antenna pattern31(a first antenna pattern) which is part of the antenna3(seeFIG. 3A, which will be described later) is formed along the periphery of the bottom surface of the cover glass2. Moreover, an antenna pattern32(a second antenna pattern) of a prescribed length and the same diameter as the antenna pattern31is formed directly below the antenna pattern31on the dial cover53. In this way, the antenna pattern32is capacitively coupled with the antenna pattern31.

The electronic timepiece1receives satellite signals from the GPS satellite8via the antenna3, decodes the received satellite time information, and corrects the internal time information of the electronic timepiece1.

FIG. 1Bis a top view of the electronic timepiece1.

The disk-shaped dial51is arranged in the center portion of the top surface of the electronic timepiece1. The dial51is made from a non-conductive material such as a synthetic resin or a higher quality ceramic material that is formed into a disk shape, for example. The long hand42, the short hand41, and a small hand44or the like are arranged on the dial51. The indicators such as the long hand42, the short hand41, and the small hand44are driven by the drive mechanism that includes the step motor and the gear train.

The ring-shaped dial cover53is arranged around the periphery of the top surface of the dial51. The antenna pattern32is formed on the dial cover53and has a prescribed length along the peripheral direction thereof, and the circular antenna pattern31is formed above the antenna pattern32on the bottom surface of the cover glass2.

In the present embodiment, the antenna pattern31(which is an electrode) is formed in a ring shape slightly inside of the outer periphery of the bottom surface of the cover glass2of the electronic timepiece1. The antenna pattern32of the prescribed length is formed below the electrode of the antenna pattern31(on the dial cover53, for example) and faces the antenna pattern31, and power is capacitively fed to one end of the antenna pattern32. In this way, the antenna pattern31functions as a feed unit for the antenna3(seeFIG. 3). The metal case6of the electronic timepiece1functions as the ground plane of the antenna3. This allows the electronic timepiece1to receive radio waves via the ring-shaped patch antenna.

The circumferential length of the antenna pattern31is substantially equal to the wavelength of the received radio waves in the cover glass2. In other words, the length of the antenna pattern31is substantially determined by the permittivity of the cover glass2and the frequency of the received radio waves, and this length determines the resonant frequency of the antenna3.

The capacitance of the antenna pattern31and the antenna pattern32is set such that the impedances thereof are matched at 50Ω. The circumferential length of the antenna pattern32may be set to approximately 30°, for example. Moreover, setting the pattern width of the antenna patterns31and32to less than or equal to 20 μm makes the antenna pattern31invisible to the naked eye, thereby having no effect on the design aesthetics of the electronic timepiece1.

FIG. 2is an exploded perspective view schematically illustrating the electronic timepiece1according to the present embodiment.

The electronic timepiece1includes, in order from top to bottom, the cover glass2, the dial cover53, the clock module7which is fitted into the opening in the top surface of the ring-shaped frame61, and the back cover64that is fitted onto an opening in the bottom surface of the ring-shaped frame61. Note that in this exploded perspective view, some of the components illustrated inFIG. 1such as the dial51are not shown.

The antenna pattern31is formed in a ring shape on the bottom surface of the cover glass2. The dial cover53is arranged below the antenna pattern31, and the antenna pattern32of the prescribed length is formed on the top surface of the dial cover53. One end of the antenna pattern32is connected to a feed pin73, which is also connected to the interior of the clock module7.

FIG. 3Ais an enlarged cross-sectional view of the antenna3.

The antenna pattern31is formed running along an area near the outer edge of the bottom surface of the cover glass2. The antenna pattern32is formed facing the antenna pattern31on the top surface of the dial cover53, and a portion of the antenna pattern32is also formed on the bottom surface of the dial cover53. Moreover, as indicated by the dashed line, a non-conductive ring54made from a dielectric, for example, may be sandwiched between the cover glass2and the antenna pattern32.

The end of the antenna pattern32formed on the bottom surface of the dial cover53is connected to the feed pin73, which runs through a through hole611and is connected to a communication unit71inside the clock module7. The feed pin73is formed in the clock module7and connects to the antenna pattern32via the through hole611. The side faces of the feed pin73are insulated such that even if these side faces contact the ring-shaped frame61, no power is conducted thereto.

The clock module7includes components such as the feed pin73, the communication unit71, and a clock unit72. The electronic timepiece1receives satellite signals from the GPS satellite8via the antenna3that includes the antenna patterns31and32. The communication unit71decodes satellite time information included in the satellite signals, thereby making it possible to display the correct current time.

FIG. 3Bis an enlarged perspective view of the dial cover53.

The majority of the antenna pattern32is formed on the top surface of the dial cover53; however, a portion of the dial cover53is formed in a recess531in the bottom surface of the dial cover53. The feed pin73contacts this recess531, thereby making it possible to supply power to the antenna pattern32. The recess531also makes it possible to easily detect the rotation angle of the dial cover53when assembling the electronic timepiece1. Moreover, this notch531ensures that the antenna pattern32does not contact the ring-shaped frame61and conduct power thereto.

FIG. 4schematically illustrates the configuration of the antenna3and a circuit of the electronic timepiece1.

The antenna3is a ring-shaped patch antenna that includes the antenna pattern31, the cover glass2that is made from a dielectric and determines the resonant frequency of the antenna pattern31, the antenna pattern32that is capacitively coupled with the antenna pattern31, the feed pin73that connects the antenna pattern32to the communication unit71, and the housing that includes the back cover64.

When radio waves are received from the GPS satellite8, for example, the navigation data radio waves transmitted from the GPS satellite8resonate at a frequency that is determined by the permittivity of the loop-shaped antenna pattern31and the cover glass2as well as by the positional relationship of the back cover64relative to those components. The resulting power is first transmitted to the antenna pattern32due to the capacitive coupling between the antenna patterns31and32and then transmitted to the communication unit71via the feed pin73. The communication unit71decodes the satellite time information from the received navigation data and then sends this satellite time information to the clock unit72. The clock unit72then corrects the time displayed on the time display unit4according to the satellite time information.

The antenna3of the present embodiment does not require a substantial increase in volume of any of the antenna components, thereby making it possible to design the electronic timepiece1to be small and thin.

FIG. 5is an enlarged cross-sectional view of an antenna3according to Modification Example 1.

In Modification Example 1, an antenna pattern31A is formed on the top surface of a cover glass2. The rest of the configuration is the same as in the embodiment described above.

In Modification Example 1, although the electrode of the antenna pattern31A must be protected, the resulting antenna3exhibits the best performance out of the embodiment described above and Modification Examples 2 and 3, which will be described below.

FIG. 6is an enlarged cross-sectional view of an antenna3according to Modification Example 2.

In Modification Example 2, an antenna pattern31B is formed on the top surface of a cover glass2, and an antenna pattern32B is formed on the bottom surface of the cover glass2. A through hole532is formed in a dial cover53B, and the antenna pattern32B is connected to a feed pin73via this through hole532.

In Modification Example 2, the distance between the antenna patterns31B and32B is fixed, thereby making it possible to reduce variations in the performance of the antenna.

FIG. 7includes an enlarged cross-sectional view of an antenna3and a perspective view of a dial cover53C according to Modification Example 3.

In Modification Example 3, an antenna pattern32C is formed beneath the dial cover53C. More particularly, a groove533is formed in the bottom surface of the dial cover53C, and the antenna pattern32C is formed inside the groove533.

In Modification Example 3, capacitance can still be adjusted as necessary, and the dial cover53C has a simpler structure than the dial cover53illustrated inFIG. 3B, thereby making it possible to produce the component at a lower cost.

In Embodiment 1 and each of the modification examples described above, the case of the clock module7and the dial cover53may in most cases be made from a dielectric material. However, if the permittivity of these components is too high, the dielectric material may potentially affect the function of the antenna3.

FIGS. 8A and 8Billustrate the structure of an analog wristwatch1A.

FIG. 8Ais a top view of the wristwatch1A. Similar to the electronic timepiece1illustrated inFIG. 1B, a circular dial51is arranged in the center of the wristwatch1A, and components such as a long hand42and a short hand41are arranged on the dial51. The wristwatch1A also includes a crown65arranged at the 3 o'clock position.

FIG. 8Bis a cross-sectional view of the wristwatch1A taken along line VIII-VIII.

In the wristwatch1A, a back cover is fitted onto the rear surface of a hollow cylinder-shaped, ring-shaped frame61, and a cover glass2is fitted into an opening in the top surface of the ring-shaped frame61, thereby forming a housing. A clock module7is arranged within the housing of the wristwatch1A. The shaft of the crown65extends into the interior of the clock module7.

Therefore, a feed unit that includes a feed pin73of an antenna such as one of those illustrated inFIGS. 2, 3, and 5 to 7is arranged at a position that is separated from at least the shaft of the crown65so that the feed unit does not positionally interfere with the shaft of the crown65.

Furthermore, as illustrated inFIG. 8A, the analog wristwatch1A includes a side switch66arranged at the 2 o'clock position, a side switch67arranged at the 4 o'clock position, and a side switch68arranged at the 8 o'clock position. Like the shaft of the crown65, the mechanisms of the side switches66to68extend into the interior of the clock module7. Similar side switches are often used in digital wristwatches as well.

Therefore, the feed unit that includes the feed pin73of an antenna such as one of those illustrated inFIGS. 2 and 3is arranged at a position that is separated from the mechanisms of the side switches66to68so that the feed unit does not positionally interfere with these mechanisms. This makes it possible to improve the manufacturability of the wristwatch1A and also makes it possible to reduce costs by simplifying the internal mechanisms.

FIGS. 9A and 9Billustrate a method of achieving circular polarization in a glass antenna according to Modification Example 4.

FIG. 9Ais a top view of an electronic timepiece1daccording to Modification Example 4.

As illustrated inFIG. 9A, a circular antenna pattern31dthat forms a radiating line in the electronic timepiece1dis formed on the bottom surface of a cover glass2. The radius R1and the width W1of the antenna pattern31dare set according to the permittivity of the cover glass2such that that the antenna pattern31eresonates at a required frequency F1. In Modification Example 4, assuming that the required GPS frequency is 1.57542 GHz and the relative permittivity εr of the cover glass2is 10, the radius R1=15.6 mm and the width W1=0.2 mm.

Furthermore, an arc-shaped antenna pattern32dthat has a radius of R2and forms a feed line is arranged at the position shown on the left side ofFIG. 9A.

FIG. 9Bis a cross-sectional view of the electronic timepiece1daccording to Modification Example 4 taken along line IX-IX. The antenna pattern32dis formed on the inner surface of a dial cover53arranged beneath the cover glass2.

Next,FIG. 9Awill be described in more detail. The antenna pattern32d(the feed line) is capacitively coupled to the antenna pattern31d(the radiating line) as appropriate. The magnitude of this capacitive coupling is determined by factors such as the width W2of the antenna pattern32das well as an angle β1that corresponds to the length of the antenna pattern32d.Furthermore, a feed point74is formed at the center of the feed line, and the power supplied from the feed line to the radiating line due to the capacitive coupling therebetween is supplied symmetrically about the feed point74.

To circularly polarize the antenna, for right-hand circularly polarized waves the pattern width of the radiating line should be increased at a position at a prescribed angle of γ1=+45° and/or +225° relative to the feed point74in order to increase the capacitance with the ground at that position. For left-hand circularly polarized waves, γ1=−45° and/or −225° relative to the feed point74.

Furthermore, in Modification Example 4, portions with a slightly increased pattern width are formed at 30° intervals around the entire radiating line starting from a position at +45° relative to the feed point74, and the widths and arc lengths of these portions are adjusted to achieve the appropriate impedance matching. Forming these portions of slightly increased pattern width at 30° intervals makes it possible to match the positions of these portions with the 12 hour positions of a clock, thereby making it possible to match the design of the clock face.

FIG. 10shows the right-hand circularly polarized (RHCP) radiation gain performance of Modification Example 4. As shown inFIG. 10, Modification Example 4 exhibits sufficient gain performance for receiving right-hand circularly polarized waves, with the peak gain (0 dB) achieved in the zenith direction.

FIGS. 11A and 11Billustrate a method of achieving circular polarization in a glass antenna according to Modification Example 5.

As illustrated inFIG. 11A, an antenna pattern31ethat forms a radiating line in an electronic timepiece le is formed on the bottom surface of a cover glass2, and the radius R1and the width W1of the antenna pattern31eare set according to the permittivity of the cover glass2such that the antenna pattern31eresonates at a required frequency F1.

FIG. 11Bis a cross-sectional view of the electronic timepiece le according to Modification Example 5 taken along line XI-XI.

An arc-shaped antenna pattern32e(a feed line) of radius R2is formed on the inner surface of a dial cover53arranged beneath the cover glass2.

Next,FIG. 11Awill be described in more detail. The radius R2of the antenna pattern32e(the feed line) as well as an angle β1that corresponds to the line length are set according to the permittivity ε1of the dial cover53such that that the antenna pattern32eresonates at a frequency F1. The feed line and the radiating line are capacitively coupled as appropriate, and the magnitude of this capacitive coupling is determined by factors such as the width W2and the angle β1.

To circularly polarize this antenna, an angle al relative to a feed point74should be less than β1/2 (that is, α1<(β1/2)) for right-hand circularly polarized waves or greater than β1/2 (that is, α1>(β1/2)) for left-hand circularly polarized waves. In Modification Example 5, α1is set to 100° (which is less than β1/2=127.5°) in order to receive right-hand circularly polarized waves.

Moreover, in Modification Example 5 the resonance of the feed pattern is used in order to achieve circular polarization, and therefore the relative permittivity εr of the dial cover53must satisfy formula (1) below.

C0: speed of light in vacuum

FIG. 12shows the RHCP radiation gain performance of Modification Example 5. As shown inFIG. 12, Modification Example 5 exhibits sufficient gain performance for receiving right-hand circularly polarized waves, with the peak gain (0 dB) achieved in the zenith direction.

FIGS. 13A and 13Billustrate a method of achieving circular polarization in a glass antenna according to Modification Example 6.

As illustrated inFIG. 13A, an antenna pattern31fthat forms a radiating line in an electronic timepiece1fis formed on the bottom surface of a cover glass2, and the radius R1and the width W1of the antenna pattern31fare set according to the permittivity of the cover glass2such that the antenna pattern31fresonates at a required frequency F1.

Furthermore, an antenna pattern32fthat forms a feed line is arranged at the position shown on the left side ofFIG. 13A.

FIG. 13Bis a cross-sectional view of the electronic timepiece1faccording to Modification Example 6 taken along line XIII-XIII.

The antenna pattern32f(the feed line) is arc-shaped with a radius of R2and is formed in eight separate portions on the inner surface of a dial cover53arranged beneath the cover glass2.

Next,FIG. 13Awill be described in more detail. The antenna pattern32f(the feed line) is capacitively coupled to the antenna pattern31f(the radiating line) as appropriate. The magnitude of this capacitive coupling is determined by factors such as the width W2of the antenna pattern32fas well as an angle β1that corresponds to the length of the antenna pattern32f.In Modification Example 6, the angle β1=50°.

Furthermore, a feed point74is formed at the center of the feed line, and the power supplied from the feed line to the radiating line due to the capacitive coupling therebetween is supplied symmetrically about the feed point74.

To circularly polarize this antenna, for right-hand circularly polarized waves, ground patterns G045and G225of a prescribed width W3and angle β45are formed at a position of γ1=+45° and/or +225° relative to the feed point74. This increases the capacitance with the antenna pattern31f(the radiating line), thereby circularly polarizing the antenna. For left-hand circularly polarized waves, ground patterns of a prescribed width W3and angle β45may be formed at a position of γ1=31 45° and/or −225° relative to the feed point74. In Modification Example 3, the angle β45is set to 26° at the positions at γ1=+45° and +225.

Furthermore, in Modification Example 6, the antenna pattern32fis divided at 45° intervals around the entire circumference thereof starting from the feed point74, and ground patterns G045, G090, G135, G180, G225, G270, and G315are formed at the corresponding positions. The widths and arc lengths of each these portions are adjusted to achieve the appropriate impedance matching. Adjusting the lengths and widths of these radiating patterns and ground patterns makes it possible to fine-tune the antenna frequency as well as adjust the circular polarization characteristics and impedance properties of the antenna without having to change the antenna pattern31f.

FIG. 14shows the RHCP radiation gain performance of Modification Example 6. As shown inFIG. 14, Modification Example 6 exhibits sufficient gain performance for receiving right-hand circularly polarized waves, with the peak gain (0 dB) achieved in the zenith direction.

As described above, conventional patch antennas and ring antennas tend to affect the size and thickness of the device housing. In at least one aspect of the present invention, the timepiece housing itself functions as an antenna, and therefore the antenna structure either does not increase the size of the timepiece at all or only increases the size of the timepiece by a very small amount, while also making it possible to provide a wristwatch antenna with excellent performance. The antenna of the present embodiment does not require a substantial increase in volume of any of the antenna components, thereby making it possible to design a small, thin timepiece.

MODIFICATION EXAMPLES

The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention. For example, modifications such as (a) to (e) below are possible.

(a) The present invention is not limited to an analog electronic timepiece and may also be applied to a digital electronic timepiece. In this case, the antenna pattern31and the antenna pattern32may be arranged around the periphery of a liquid crystal panel, for example.

(b) The antenna pattern31does not necessarily have to be circular in shape. The antenna pattern31may be any polygonal shape including quadrilaterals or may be irregular in shape.

(c) The present invention is not limited to electronic timepieces and may be applied to any communication device.

(d) The antenna communication standard and frequency bands that can be used for communication are not limited to GPS or ultra high frequencies. The antenna may use any communication standard/frequency band suitable for use in a communication device. In other words, communication standards such as Bluetooth (registered trademark) and Wi-Fi (registered trademark) as well as the frequency bands used for these communication standards may be used.

(e) Any configuration in which the antenna pattern31A is formed on a glass surface may be used, or the antenna pattern31A may be integrated into existing timepiece components such as the bezel ring.

It will be apparent to those skilled in the art that various modification and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations that come within the scope of the appended claims and their equivalents. In particular, it is explicitly contemplated that any part or whole of any two or more of the embodiments and their modifications described above can be combined and regarded within the scope of the present invention.