Electronic clock

Abstract

To provide an electronic watch that can improve the performance of an antenna when arranging the antenna in a case of a watch formed of conductive material.SOLUTION: An electronic watch comprises: an antenna that has a plate-like first conductor element connected with a power supply part, a plate-like second conductor element overlapping the first conductor element in plan view, and a short circuit part that causes a short circuit between the first conductor element and the second conductor element; and a conductive case that accommodates the antenna and has a side wall. The first conductor element has a short circuit part-side outer edge continuing to the short circuit part, and an antenna open end. In plan view, a first distance between the antenna open end and the side wall is larger than a second distance between the short circuit part-side outer edge and the side wall.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to an electronic timepiece with a built-in antenna. [Background technology]

[0002] BACKGROUND ART Among small electronic timepieces such as wristwatches, there is known an electronic timepiece that includes an antenna for receiving satellite signals and a case for housing the antenna (see Patent Document 1). The antenna in Patent Document 1 has a first conductive element connected to a power supply section, a second conductive element that overlaps the first conductive element in a plan view, and a short-circuit section that shorts the first conductive element and the second conductive element. Patent Document 1 also discloses that the case is made of a conductive material to block external noise, and that the case is made of a metallic material to enhance the luxury feel of the electronic timepiece. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-47144 Summary of the Invention [Problem to be solved by the invention]

[0004] It was desirable to further improve the performance of an antenna when placing an antenna having a first conductive element, a second conductive element, and a short circuit in a watch case made of a conductive material such as metal. [Means for solving the problem]

[0005] The electronic timepiece disclosed herein comprises an antenna having a flat first conductor element connected to a power supply section, a flat second conductor element that overlaps the first conductor element in a planar view, and a short-circuit section that short-circuits the first conductor element and the second conductor element, and a conductive case that houses the antenna and has a side wall, wherein the first conductor element has an outer edge on the short-circuit section side that is continuous with the short-circuit section, and an antenna open end, and in the planar view, a first distance between the antenna open end and the side wall is greater than a second distance between the outer edge on the short-circuit section side and the side wall. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is an explanatory diagram showing an electronic timepiece and a positioning information satellite according to an embodiment. [Figure 2] FIG. 1 is a front view showing an electronic timepiece according to an embodiment. [Figure 3] FIG. 2 is a cross-sectional view showing the electronic timepiece. [Figure 4] FIG. 2 is an exploded perspective view showing the main parts of the electronic timepiece. [Figure 5] FIG. 2 is an exploded perspective view showing the main parts of the electronic timepiece. [Figure 6] FIG. 2 is a perspective view showing the main part of the planar antenna of the electronic timepiece. [Figure 7] FIG. 2 is a perspective view showing the main part of the planar antenna of the electronic timepiece. [Figure 8] FIG. 2 is a perspective view showing the main parts of the planar antenna and solar panel of the electronic timepiece. [Figure 9] 3 is a schematic cross-sectional view of the planar antenna, solar panel, and dial of the electronic timepiece. FIG. [Figure 10] FIG. 3 is a schematic plan view showing the positional relationship between the case and the planar antenna of the electronic timepiece. [Figure 11] FIG. 2 is a block diagram showing a circuit configuration of the electronic timepiece. [Figure 12] FIG. 10 is a diagram showing the electric field distribution of a planar antenna of a comparative example. [Figure 13] 3A and 3B are diagrams illustrating an electric field distribution of the planar antenna according to the embodiment. [Figure 14]10 is a graph showing the relationship between the amount of cutting of the antenna electrode and the amount of improvement in peak gain and radiation efficiency. [Figure 15] 1 is a graph showing the directivity of a planar antenna. [Figure 16] FIG. 10 is a schematic plan view showing a modified planar antenna. [Figure 17] FIG. 10 is a front view showing another modified example of an electronic timepiece. DETAILED DESCRIPTION OF THE INVENTION

[0007] An electronic timepiece 1 according to an embodiment will be described below with reference to the drawings. In this embodiment, the crystal 15 side of the electronic timepiece 1 will be referred to as the front side or upper side, and the back cover 14 side will be referred to as the back side or lower side.

[0008] The electronic watch 1 of this embodiment has a built-in planar antenna 50, which will be described later, and is configured to receive satellite signals from multiple positioning information satellites S, such as GPS satellites and quasi-zenith satellites, that orbit the Earth in a predetermined orbit, as shown in Figure 1, to obtain satellite time information and correct the internal time information.

[0009] 2 and 3, the electronic timepiece 1 has a case 10 that houses a dial 2, hands 3, a date wheel 5, a movement 20, a planar antenna 50, etc. The electronic timepiece 1 also has a crown 6 and two buttons 7 and 8 for external operation.

[0010] The dial 2 is formed into a disk shape using a non-conductive material. The dial 2 in this embodiment is made of polycarbonate resin with a relative dielectric constant of 3. A through hole 2A is formed in the center of the plane of the dial 2, and three coaxial pointer shafts 35, 36, and 37 are arranged in the through hole 2A. Hour hand 31 is attached to pointer shaft 35, minute hand 32 is attached to pointer shaft 36, and second hand 33 is attached to pointer shaft 37. Pointer shafts 35, 36, and 37 and the hour hand 31, minute hand 32, and second hand 33, which are the hands 3, are made of conductive metal members. A rectangular date window 2B is provided at the 3 o'clock position on the dial 2. A date wheel 5 is located on the back side of the dial 2 and can be seen through the date window 2B. The hour hand 31, minute hand 32, second hand 33, and date wheel 5 are driven via a step motor and gear train, which will be described later.

[0011] In this embodiment, the direction perpendicular to the surface of the dial 2, i.e., the axial direction of the pointer shafts 35 to 37, is defined as the first direction, and the direction perpendicular to this first direction is defined as the second direction. Furthermore, in this embodiment, a plan view means that the electronic timepiece 1 is viewed from the first direction, and a side view means that the electronic timepiece 1 is viewed from the second direction.

[0012] [Exterior structure of electronic watch] Case 10 comprises case main body 11 and back cover 14. Case main body 11 comprises a cylindrical case 12 and a ring-shaped bezel 13 attached to the front side of case 12. Note that in this embodiment, case 12 and back cover 14 are constructed as separate bodies, but this is not a limitation and a one-piece case in which case 12 and back cover 14 are integrated is also possible. Also, in this embodiment, case 12 and bezel 13 are constructed as separate bodies, but this is not a limitation and a structure in which case 12 and bezel 13 are integrated is also possible, which has the advantage of being less expensive. The case 12, bezel 13, and back cover 14 are made of a metallic material, i.e., a conductive material, such as stainless steel, titanium alloy, aluminum, or brass. In this embodiment, the side wall of the conductive case 10 is made up of the case 12.

[0013] A cover crystal 15, which serves as a cover member, is attached to the bezel 13 of the case 10. The cover crystal 15 is a flat glass formed into a disk shape. This cover crystal 15 is made of a transparent material such as mineral glass, sapphire glass, or organic glass. Mineral glass is glass made from silica (silicon dioxide: SiO2), sapphire glass is glass made from alumina (aluminum oxide: Al2O3), and organic glass is a synthetic resin material such as acrylic. The cover crystal 15 of this embodiment is made of plate-shaped sapphire glass. Sapphire glass has a relative dielectric constant of approximately 9 to 11 and is made from single-crystal sapphire made from high-purity alumina. Sapphire glass is characterized by its high hardness and scratch resistance, its extremely smooth surface, excellent light transmittance, and high visibility.

[0014] [Internal structure of an electronic watch] Next, the internal structure of the case 10 of the electronic timepiece 1 will be described. As shown in FIG. 3, the case 10 accommodates the dial 2, a dial ring 16, a movement 20, and the like.

[0015] The dial ring 16 is made of a non-conductive material and has a ring shape in plan view, similar to the dial 2, and is arranged along the outer periphery of the dial 2. In this embodiment, the dial ring 16 is made of polycarbonate resin with a relative dielectric constant of 3. The dial ring 16 covers the outer periphery of the dial 2 so that the outer periphery of the dial 2 is not visible due to the dial ring 16.

[0016] 3, 4, and 5, the movement 20 includes a date indicator 5, a main plate 21, a train wheel bridge 22, a drive mechanism 23, a secondary battery 24, a solar panel 25, a planar antenna 50, an LED board 60, a circuit board 70, a magnetic shield 81, a circuit holder 82, etc. Note that the train wheel bridge 22 and the magnetic shield 81 are not shown in FIG.

[0017] The main plate 21 is made of a non-conductive material such as plastic. As shown in Figures 4 and 5, a solar panel 25, a planar antenna 50, a date indicator 5, and an LED board 60 are arranged between the main plate 21 and the dial 2. That is, the solar panel 25 is arranged on the back side of the dial 2, which is the surface facing the main plate 21, a dielectric board 51 of the planar antenna 50 is arranged on the back side of the solar panel 25, the date indicator 5 and LED board 60 are arranged on the back side of the dielectric board 51, and a second conductive element 53 of the planar antenna 50 is arranged on the back side of the date indicator 5 and LED board 60. The second conductive element 53 also serves as an hour wheel holder and a magnetic shield, as will be described later. Between the main plate 21 and the back cover 14, there are arranged a train wheel bridge 22, a drive mechanism 23, a secondary battery 24, a circuit board 70, a magnetic shield 81, and a circuit holder 82.

[0018] 5, the train wheel bridge 22 comprises two train wheel bridges: a first train wheel bridge 22A that supports the train wheel that drives the hour hand 31, minute hand 32, and second hand 33, and a second train wheel bridge 22B that supports the train wheel that drives the date wheel 5. However, they may also be made into a single train wheel bridge.

[0019] The drive mechanism 23 is attached to the back of the main plate 21, and drives the hour hand 31, minute hand 32, second hand 33, and date indicator 5. That is, as shown in FIG. 4, the drive mechanism 23 has a first step motor 231 and a first wheel train that drive the hour hand 31, a second step motor 232 and a second wheel train that drive the minute hand 32, a third step motor 233 and a third wheel train that drive the second hand 33, and a fourth step motor 234 and a fourth wheel train that drive the date indicator 5. The first wheel train includes a stem 35 to which the hour hand 31 is attached. The second wheel train includes a stem 36 to which the minute hand 32 is attached. The third wheel train includes a stem 37 to which the second hand 33 is attached. In the movement 20, a winding stem 260 connected to the crown 6 is disposed at the 3 o'clock position of the dial 2, and a switching mechanism 261 such as a loveseat is disposed around the winding stem 260. In addition, the step motors 231 to 234 are disposed in positions that do not overlap with the secondary battery 24 in the plan view.

[0020] 4, the base plate 21 and the drive mechanism 23 are disposed between the LED board 60 and the circuit board 70. In addition, a magnetic shield 81 and a circuit holder 82 are disposed on the back surface of the circuit board 70. As shown in FIG. 5, three light emitting elements 611, 612, and 613 each made of a light emitting diode are mounted on the rear surface of the LED substrate 60, which faces the base plate 21. Circuit elements such as semiconductor integrated circuits (ICs), resistors, and capacitors are mounted on both the front and back sides of circuit board 70. Three light receiving elements 711, 712, and 713 made up of phototransistors and circuit elements 741, 742, and 743 are mounted on the front side of circuit board 70, i.e., the side facing dial 2, as shown in Figure 4. These light emitting elements 611 to 613 and light receiving elements 711 to 713 are used to detect the position of each hand.

[0021] In this embodiment, a high-potential power supply voltage VDD and a low-potential power supply voltage VSS are supplied to the circuit board 70 via a secondary battery 24 and a constant voltage circuit (not shown). In this embodiment, the power supply voltage VDD is set to ground potential. Alternatively, the power supply voltage VSS may be set to ground potential. The LED substrate 60 and the circuit substrate 70 are electrically connected by conductive members 651, 652, 653, and 654, each of which is made up of a coil spring, and thus power is supplied to the light emitting elements 611, 612, and 613.

[0022] As shown in FIG. 4, the secondary battery 24 is a button-type lithium ion battery formed in a circular shape when viewed from above, and is disposed in a cutout portion 71 of the circuit board 70. Solar panel 25 is a solar cell panel used in wristwatches, and can be, for example, a film-type solar cell in which amorphous silicon thin film 252 is laminated on resin film substrate 251. Solar panel 25 has through-holes 25A through which pivots 35-37 are inserted, and two electrode terminals. These electrode terminals and circuit board 70 are electrically connected by coil springs 255 and 256, as shown in FIG. 5. Therefore, the current generated by solar panel 25 charges secondary battery 24 via coil springs 255 and 256 and circuit board 70.

[0023] [Flat antenna] The planar antenna 50 receives satellite signals from GPS satellites and, in this embodiment, is configured as a planar inverted-F antenna. A typical planar inverted-F antenna is a square patch antenna with a short-circuiting plate. It achieves resonance characteristics with half the dimensions of a square patch antenna, allowing for antenna miniaturization. However, the antenna directivity of an inverted-F antenna is tilted obliquely from the zenith direction compared to a patch antenna. When built into a watch, it is easily affected by the metal case, significantly degrading antenna performance. Therefore, it could only be used in combination with a ceramic bezel. Ceramic materials such as zirconia, which transmit radio waves, have color restrictions and limited flexibility, limiting the design of the watch. When using a planar inverted-F antenna, reducing the size of the antenna electrode and increasing the distance between the antenna electrode and the metal case reduces the influence of the metal case, improving antenna performance. However, in watches with built-in solar panels, the solar panel has a conductive layer, so it must be smaller than the antenna electrode for antenna performance reasons. Making the solar panel smaller also reduces the power generation area, which can lead to the issue of reduced solar power generation. However, in an inverted-F antenna, radio waves are mostly radiated from the open end of the antenna opposite the short-circuited part. As a result of extensive research, the inventors have found that the most effective way to reduce the influence of the metal case is to separate the open end of the antenna electrode from the metal case. For this reason, the planar antenna 50 of this embodiment has a structure in which only the open end of the antenna electrode is cut out in order to ensure both the power generation area of ​​the solar panel 25 and antenna performance. The configuration of the planar antenna 50 will be described below with reference to Figures 6 to 10 in addition to Figures 3 to 5.

[0024] The planar antenna 50 is disposed so as to overlap the cover glass 15 in a planar view. As also shown in Figures 3 and 9, the planar antenna 50 is configured to include a dielectric substrate 51, a plate-shaped first conductor element 52, a second conductor element 53 disposed so as to overlap the first conductor element 52 in a planar view, and a short-circuit portion 54 that short-circuits the first conductor element 52 and the second conductor element 53. A through-hole 50A, through which the pointer shafts 35 to 37 are inserted, is formed at the center of the plane of the planar antenna 50. That is, the through-hole 50A is formed by passing through the plate-shaped first conductive element 52, the dielectric substrate 51, and the second conductive element 53. The planar antenna 50 also serves as a support substrate that supports the solar panel 25 made of film.

[0025] The dielectric substrate 51 is a synthetic resin member that serves as an antenna substrate. If the material of the dielectric substrate 51 is one of polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polycarbonate (PC), and syndiotactic polystyrene (SPS), electroless plating is easily adhered to the substrate, and the dielectric loss tangent can be made low, making the substrate suitable for an antenna substrate. A protrusion is formed on the back surface of the dielectric substrate 51, that is, the surface facing the main plate 21. The protrusion comprises an inner circumference protrusion 51A formed on the inner circumference side of the date indicator 5 in a plan view, and an outer circumference protrusion 51B formed on the outer circumference side of the date indicator 5. The dielectric substrate 51 has the function of pressing the date indicator 5 against the main plate. A recess 51C is formed in the inner circumference protrusion 51A, in which the LED substrate 60 is disposed.

[0026] The first conductor element 52 is formed on almost the entire surface of the dielectric substrate 51, that is, on the solar panel 25 side. The first conductor element 52 can be formed from a thin metal plate such as copper or an iron alloy, but in this embodiment it is made of a metal coating formed on the surface of the dielectric substrate 51. The metal coating can be formed by plating, for example, copper, silver, nickel, aluminum, or the like. The second conductive element 53 can be formed of a metal coating like the first conductive element 52, but in this embodiment it is made of a magnetically shielded plate that also serves as an hour wheel holder. The magnetically shielded plate that makes up the second conductive element 53 is a conductive plate made of pure iron coated with a nickel film, and as will be described later, comes into contact with the short-circuiting portion 54. The first conductive element 52 functions as the radiating member of the planar inverted-F antenna, and the second conductive element 53 functions as the ground member of the planar inverted-F antenna.

[0027] As shown in Figure 9, the short-circuit portion 54 is composed of a side short-circuit portion 54A formed on the side of the dielectric substrate 51 and a back short-circuit portion 54B formed on the back surface of the dielectric substrate 51, specifically on the bottom surface of the outer peripheral protrusion 51B. A power supply terminal 55 is formed on the outer peripheral protrusion 51B, spaced apart from the short-circuit portion 54. The power supply terminal 55 is electrically connected to the first conductive element 52 via the side surface of the dielectric substrate 51. One end of the feed element 56 abuts against the feed terminal 55. The other end of the feed element 56 abuts against the circuit board 70 and is electrically connected to a receiving IC mounted on the circuit board 70. Note that in FIG. 3, the feed element 56 is schematically illustrated as penetrating the second conductive element 53 and the dielectric substrate 51 to contact the first conductive element 52. However, in reality, as shown in FIGS. 4 to 7, the feed terminal 55 of the first conductive element 52 extends to the underside of the dielectric substrate 51 via the side surface, and the upper end of the feed element 56 is in contact with this feed terminal 55. The feed element 56 is a pin-shaped connector made of a conductive material such as metal, and contains a coil spring. The biasing force of the coil spring keeps the feed element 56 in contact with the underside of the feed terminal 55.

[0028] The back-surface short-circuit portion 54B, which is laminated on the bottom surface of the outer peripheral protrusion 51B, is in contact with the surface of the metal second conductive element 53. The second conductive element 53 is electrically connected to the ground terminal of the circuit board 70 via the connection element 57, and functions as the ground member of the plate-shaped inverted-F antenna, as described above. Furthermore, because the second conductive element 53 is made of metal, it also serves as a magnetic shield that covers the dial 2 side of the step motors 231-234.

[0029] In this embodiment, when the planar antenna 50 is incorporated into the case body 11, a short-circuit portion 54 is provided at the 12 o'clock direction relative to the through-hole 2A of the dial 2 in a plan view. Therefore, in the first conductive element 52 that serves as the antenna electrode, an antenna open end 58 is formed on the opposite side of the short-circuit portion 54, that is, at the 6 o'clock direction relative to the through-hole 2A of the dial 2 in a plan view. This antenna open end 58 is formed inside the outer periphery of the dielectric substrate 51. Here, as shown in FIGS. 6 and 10, the antenna open end 58 is an edge that is approximately parallel to the line connecting the 3 o'clock and 9 o'clock positions on the dial 2. That is, in comparison with the dielectric substrate 51, which is approximately circular in plan view, the first conductive element 52 has a shape in which a bow-shaped region surrounded by an arc with a central angle θ1 and a chord connecting both ends of the arc has been removed, and the chord portion serves as the antenna open end 58. Therefore, as shown in FIGS. 9 and 10, the first conductive element 52 has the antenna open end 58 and an outer edge 59 on the short-circuit portion side that is continuous with the short-circuit portion 54. Then, if a first distance between the antenna open end 58 and the case 12, which is the side wall, is L1 and a second distance between the outer edge 59 on the short-circuit portion 54 side and the case 12, which is the side wall, is L2, then L1 > L2. Note that L1 and L2 are radial dimensions that are perpendicular to antenna open end 58 and pass through through hole 50A. Short-circuit portion 54 is formed in a partial range in the circumferential direction along the side surface of dielectric substrate 51, and when an imaginary line is set connecting through hole 50A with the center position of short-circuit portion 54 in the circumferential direction, i.e., the midpoint between both edges of short-circuit portion 54 in the circumferential direction, antenna open end 58 is provided perpendicular to this imaginary line. Therefore, L1 and L2 are dimensions along the imaginary line.

[0030] 4, 5, and 8, the solar panel 25 has a cut portion 253 formed by cutting the 6 o'clock position portion to match the shape of the first conductive element 52. The solar panel 25 is formed to be slightly smaller than the first conductive element 52 in a plan view, and the outer periphery of the first conductive element 52 is exposed to the outside of the solar panel 25.

[0031] As shown in FIG. 9 , the second conductive element 53, i.e., the magnetically shielding plate that also serves as an hour wheel holder, does not have a cutout like the first conductive element 52. The distance between the outer periphery of the second conductive element 53 and the case 12 is the same as the second distance L2. Therefore, the distance between the outer edge of the second conductive element 53 on the opposite side of the short-circuiting portion 54 (i.e., the outer edge at the 6 o'clock position) and the case 12 is the same as the distance between the outer edge of the second conductive element 53 on the short-circuiting portion 54 side (i.e., the outer edge at the 12 o'clock position) and the case 12. Therefore, the second conductive element 53, which serves as the ground plate, has a larger planar size than the first conductive element 52, which serves as the antenna electrode. This causes the directivity of the planar antenna 50 to point toward the zenith, i.e., toward the cover crystal 15, thereby improving antenna performance even when a conductive case 10 is used. Furthermore, because solar panel 25 has a partial cutout on the 6 o'clock side, if dielectric substrate 51, which serves as the antenna base, is made of a resin material such as white, the difference in color between the solar panel 25 portion and the portion where dielectric substrate 51 is exposed without solar panel 25 may be visible through translucent dial 2. For this reason, a color-matching sheet 27 similar in color to solar panel 25 is placed between the exposed portion of dielectric substrate 51 and dial 2. Because the amorphous silicon thin film 252 portion of solar panel 25 is dark purple, color-matching sheet 27 is also made of a dark purple polyester film or the like.

[0032] [Circuit configuration of electronic clock] FIG. 11 is a block diagram showing the circuit configuration of the electronic timepiece 1. The electronic timepiece 1 has a GPS receiving unit 300, a control display unit 400, and a power supply unit 500, all of which are arranged on a circuit board 70.

[0033] [GPS receiver] The GPS receiver 300 receives and processes satellite signals from GPS satellites via the planar antenna 50 and SAW filter 230. The SAW filter 230 is a bandpass filter that passes 1.5 GHz satellite signals. A separate LNA may be inserted between the planar antenna 50 and the SAW filter 230 to improve reception sensitivity. The SAW filter 230 may also be built into the GPS receiver 300. SAW is an abbreviation for Surface Acoustic Wave, and LNA is an abbreviation for Low Noise Amplifier.

[0034] The GPS receiver 300 processes satellite signals that have passed through the SAW filter 230, and includes an RF circuit 310, a baseband circuit 320, a crystal oscillator circuit 330 with a temperature compensation circuit, and a flash memory 340. RF is an abbreviation for Radio Frequency. The crystal oscillator circuit 330 is abbreviated as TCXO in FIG. 11.

[0035] The RF circuit 310 is a typical RF section for GPS reception that includes a PLL, VCO, LNA, mixer, IF amplifier, IF filter, A / D converter, etc. Note that PLL is an abbreviation for Phase Locked Loop, VCO is an abbreviation for Voltage Controlled Oscillator, and IF is an abbreviation for Intermediate Frequency.

[0036] The baseband circuit 320 is a typical baseband unit for GPS reception that includes a DSP, CPU, RTC, SRAM, etc. The baseband circuit 320 is also connected to a TCXO 330 and flash memory 340. Note that DSP is an abbreviation for Digital Signal Processor, CPU is an abbreviation for Central Processing Unit, RTC is an abbreviation for Real Time Clock, and SRAM is an abbreviation for Static Random Access Memory.

[0037] Baseband circuit 320 receives the digitally converted received signal from RF circuit 310, performs correlation processing, positioning calculations, etc. to acquire satellite time information and positioning data, and uses leap seconds stored in SRAM to correct the acquired satellite time information, i.e., Z count, to calculate UTC (Coordinated Universal Time), which is the time data. Baseband circuit 320 then outputs the positioning data and time data to control unit 410. The clock that forms the basis of the local oscillation signal is supplied from the TCXO 330 to the RF circuit 310 via the baseband circuit 320 .

[0038] Flash memory 340 stores a time difference database that associates location information specified by latitude and longitude with time difference information for that location. When GPS receiver 300 acquires location information in positioning mode, it acquires time difference information, i.e., the time difference from UTC, based on the location information (latitude, longitude) and outputs it to control unit 410.

[0039] [Control display section] The control display unit 400 includes a control unit (CPU) 410, a drive circuit 420 that drives the hands and the like, and a crystal oscillator 430.

[0040] The control unit 410 includes an RTC 411, a ROM 412, and a storage unit 413, and keeps time, and outputs control signals to the GPS receiving unit 300 to control its operation. The RTC 411 keeps internal time using a reference signal output from the crystal oscillator 430. Various programs executed by the control unit 410 are stored in the ROM 412. In this embodiment, the internal time kept by the RTC 411 is UTC, which is Coordinated Universal Time. If reception in the timekeeping mode or positioning mode is successful, the control unit 410 updates the RTC 411 with the UTC output from the GPS receiver unit 300. The memory unit 413 stores the satellite time information, positioning information, and time difference information output from the GPS receiving unit 300. To this end, the control unit 410 calculates the time at the current location using UTC and the time difference information, and drives the drive mechanism 23 using the drive circuit 420 to indicate the calculated time with the hour hand 31, minute hand 32, and second hand 33.

[0041] [Power supply section] The power supply unit 500 supplies power to the GPS receiving unit 300 and the control display unit 400, and includes a solar panel 25, a charge control circuit 510, a secondary battery 24, a first voltage conversion unit 520, a second voltage conversion unit 530, and a voltage detection circuit 540. The charge control circuit 510 controls the charging of the secondary battery 24 with the power generated by the solar panel 25 . The secondary battery 24 supplies driving power to the control display unit 400 via the first voltage conversion unit 520 and supplies driving power to the GPS receiving unit 300 via the second voltage conversion unit 530 . The voltage detection circuit 540 monitors the output voltage of the secondary battery 24 and outputs it to the control unit 410. Therefore, the control unit 410 can grasp the voltage of the secondary battery 24 detected by the voltage detection circuit 540 and control the reception process.

[0042] [Antenna performance test] Next, the results of a simulation comparing the antenna performance of the planar antenna 50 of this embodiment, in which the aforementioned L1 and L2 satisfy L1>L2, and a comparative example, in which L1=L2, will be described with reference to FIGS. 12 to 15. Figures 12 and 13 show the electric field distribution at the 6 o'clock position of the planar antenna 50, that is, on the antenna open end 58 side, with Figure 12 being a comparative example and Figure 13 being an example of this embodiment. Comparing Figures 12 and 13, it can be seen that in Figure 13, where the antenna open end 58 is further away from the body 12, which is the side wall, the electric field at the antenna open end 58 at the 6 o'clock position is stronger, and radiation toward the zenith is greater.

[0043] FIG. 14 is a graph showing the results of a simulation of the amount of improvement in peak gain and radiation efficiency versus the amount of electrode cut at the antenna open end 58. The amount of electrode cut is L3 in Figure 10, which is the dimension from the outer edge of the dielectric substrate 51 to the antenna open end 58. Peak gain is the antenna gain in the direction of maximum radiation, and radiation efficiency is the antenna radiation efficiency in all directions. The white circles in Figure 10 represent simulated values ​​of peak gain, and the dotted line is an approximation curve connecting the white circles. The black circles in Figure 10 represent simulated values ​​of radiation efficiency, and the solid line is an approximation curve connecting the black circles. The vertical axis in Figure 14 shows the percentage improvement when L3 = 0 mm is used as the reference. When the first conductive element 52 (the antenna electrode) is not cut (L3 = 0 mm), cutting the antenna electrode at the 6 o'clock position to move the antenna open end 58 away from the inner circumferential surface of the case 12 maximizes the effect at approximately L3 = 0.75 mm. This indicates that the antenna performance improvement effect is observed when L3 is between 0 and 2 mm. The wavelength of a GPS satellite signal is approximately 190 mm, and the antenna performance improvement effect is observed when L3 is 2 mm or less, i.e., approximately 0.01 wavelength or less. Since L3 = L1 - L2, the electrode cut amount L3, which is the difference between the first distance L1 and the second distance L2, is less than 0.01 times the wavelength of the GPS satellite signal received by the planar antenna 50. When L3 is greater than 2 mm, the antenna performance degrades because the planar antenna 50 becomes too small, less than the resonant wavelength (1 / 4 wavelength), resulting in degraded antenna characteristics. Furthermore, as shown in FIG. 14, the improvement in peak gain is greater than that in radiation efficiency, which indicates that the antenna directivity is improved so that it faces the zenith. If the antenna electrode before cutting is a flat circle, antenna open end 58 with L3 = 0.75 mm will be a chord with a central angle of 26.6 degrees if the antenna electrode diameter is 28 mm, and a chord with a central angle of 25.7 degrees if the antenna electrode diameter is 30 mm. Furthermore, antenna open end 58 with L3 = 2 mm will be a chord with a central angle of 43.6 degrees if the antenna electrode diameter is 28 mm, and a chord with a central angle of 42.1 degrees if the antenna electrode diameter is 30 mm. Because the diameter of antenna electrodes that can be incorporated into wristwatches is approximately 28 to 30 mm, antenna open end 58 may be configured with a chord with a central angle of 45 degrees or less.

[0044] Fig. 15 is a graph showing the directivity of planar antenna 50, with the dotted line showing the directivity when L3 = 0 mm and the solid line showing the directivity when L3 = 0.75 mm. As shown in Fig. 15, when L3 = 0.75 mm, the directivity is more oriented in the 0 degree direction, i.e., the zenith direction (first direction). This makes it easier for planar antenna 50 placed inside case 10 to receive signals from cover glass 15, which is in the zenith direction, and reduces the influence of body 12, which is a conductive sidewall.

[0045] Furthermore, the simulation confirmed that the antenna radiation efficiency deteriorated by 0.2 dB when the second conductor element 53 serving as the ground plate was also cut out by 0.75 mm, similar to the first conductor element 52. Therefore, it was also confirmed that the antenna performance improved when the planar size of the second conductor element 53 serving as the ground plate was larger.

[0046] [Effects of the embodiment] According to the electronic watch 1 of this embodiment, in the flat-shaped first conductor element 52 that serves as the antenna electrode, the first distance L1 between the antenna open end 58 located opposite the short-circuit portion 54 and the case 12, which is the side wall of the case, is made larger than the second distance L2 between the outer edge 59 on the side of the short-circuit portion 54 with the second conductor element 53 and the case 12, which is the side wall of the conductive case.As a result, the antenna directivity is directed upward, and the performance of the planar antenna 50 for the electronic watch 1, which is placed inside a conductive case and therefore needs to receive radio waves from the cover crystal 15 side, i.e., from above, can be improved. That is, in order to improve the reception performance of a planar antenna 50 in a small electronic timepiece 1 such as a wristwatch, it is effective to use a planar inverted-F antenna including a planar first conductive element 52 that serves as a radiation electrode, a planar second conductive element 53 that serves as a ground plate, and a short-circuiting portion 54 that shorts the conductive elements 52, 53, and to increase the area of ​​each of the conductive elements 52, 53. Meanwhile, it is preferable to use a conductive case 10 made of metal or the like for the watch case 10 that houses the planar antenna 50, taking into consideration design and strength. When the planar antenna 50, which is a planar inverted-F antenna, is placed inside the conductive case 10, it is preferable to increase the area of ​​the first conductive element 52 and the second conductive element 53 to improve the performance of the planar antenna 50, but if the first conductive element 52 is close to the case 12, which is the side wall of the conductive case 10, it will be affected by the conductive case 12. In contrast to this, in the present embodiment, the antenna open end 58 of the first conductor element 52 is separated from the conductive case 10, thereby preventing deterioration of the antenna performance, and further, the portion of the first conductor element 52 other than the antenna open end 58 is brought closer to the body 12 than the antenna open end 58, thereby increasing the area of ​​the first conductor element 52, thereby improving the antenna performance. Furthermore, first conductor element 52, which serves as the antenna electrode, is separated from case 10 only at antenna open end 58, i.e., the 6 o'clock side, and other parts of first conductor element 52 are not cut. Therefore, even if amorphous silicon thin film 252, which is the conductor part of solar panel 25, is made smaller than first conductor element 52 in a planar view, the reduction in the area of ​​amorphous silicon thin film 252 can be kept to a minimum, and the amount of power generation can be secured.

[0047] The antenna open end 58 is farther from the body 12 than the outer edge 59 on the short-circuit portion 54 side by the difference between the first distance L1 and the second distance L2, and if this difference in distance becomes large, the planar antenna 50 will become too small compared to the 1 / 4 wavelength which is the resonant wavelength, and the antenna characteristics will deteriorate. In contrast, in this embodiment, by setting the difference between the distances L1 and L2 to 0.01 times the wavelength of the received radio wave or less, it is possible to prevent the planar antenna 50 from becoming too small and to prevent deterioration of the antenna characteristics.

[0048] A part of the solar panel 25 is cut to form a cut portion 253, and the amorphous silicon thin film 252, which is the conductive portion of the solar panel 25, is smaller than the first conductive element 52 in a plan view, so that even if the solar panel 25 is placed on the front side of the first conductive element 52, the influence on the antenna performance can be reduced.

[0049] Because the second conductor element 53 is made of a metal body, i.e., a conductor plate, it can be formed separately from the first conductor element 52, and it is easy to form the second conductor element 53 in a size larger than the first conductor element 52. Furthermore, because the second conductor element 53 can be made larger than the first conductor element 52 in a plan view, the antenna directivity can be directed upward, and the antenna performance can be further improved.

[0050] [Other embodiments] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the present invention. For example, the planar shape of the first conductive element 52 that serves as the antenna electrode is not limited to that of the above embodiment. For example, the antenna open end 58B may be formed in a curved shape, as in the first conductive element 52B of the electronic timepiece 1B shown in Fig. 16. In this first conductive element 52B, the antenna open end 58B is also positioned away from the side wall of the case 10, improving antenna performance. Furthermore, because the antenna open end 58B is formed in a curved shape, it is less susceptible to the influence of the case 10 over a wider area than the antenna open end 58 of the first embodiment.

[0051] 17, the antenna open end 58C on the 6 o'clock side may be formed in a shape that follows the decorative member of the dial 2. For example, the electronic timepiece 1C in FIG. 17 has a subdial 2C on the 6 o'clock side of the dial 2. The antenna open end 58C of the first conductive element 52C is formed with a straight portion 581 that follows the scale 2D at the 5 o'clock and 7 o'clock positions on the dial 2 and continues to the outer periphery of the subdial 2C, and a curved portion 582 that follows the outer periphery of the subdial 2C. In this first conductive element 52C, the curved surface portion 582 of the antenna open end 58C is also positioned away from the side wall of the case 10, thereby improving the antenna performance. Furthermore, the antenna open end 58C is formed along the scale 2D and the subdial 2C, making the antenna open end 58C less noticeable. Furthermore, even if the dielectric substrate 51 is exposed in the area surrounded by the antenna open end 58C, it is surrounded by the decorative members of the scale 2D and the subdial 2C, making the color difference less noticeable and improving the design. That is, the shape of the antenna open end of the first conductive element only needs to be such that a certain range including a point opposite to outer edge 59 of the short-circuiting portion that is continuous with short-circuiting portion 54 is separated from body 12, which is the side wall of the case. For example, the antenna open end may be cut into a flat trapezoidal shape, and the shape of the antenna open end and the electrode cut dimensions can be set taking into consideration the effect of improving antenna performance by separating the antenna open end from the side wall of the conductive case and the effect of degrading antenna performance due to a reduction in the area of ​​the first conductive element. The shape of the dielectric substrate 51 may be formed to match the shape of the first conductive element 52, and the dielectric substrate 51 on the antenna open end side may be disposed away from the side wall of the conductive case. By eliminating the dielectric substrate 51 on the open end side, which has the greatest effect on antenna performance, it is possible to improve the antenna performance, albeit slightly.

[0052] The difference between the first distance L1 and the second distance L2 of the first conductive elements 52, 52B, 52C is preferably 0.01 times or less the wavelength of the radio wave received by the planar antenna 50, but is not necessarily limited to 0.01 times or less. In the above embodiment, the 6 o'clock position portion of the solar panel 25 is cut to form the cut portion 253, but it is also possible to cut only the amorphous silicon thin film 252 without cutting the resin film substrate 251. If the resin film substrate 251 and the amorphous silicon thin film 252 are cut, they can be cut together later using a mold or the like, reducing processing costs, and if the resin film substrate 251 is left, changes in color tone can be suppressed. In the above embodiment, the color-tuning sheet 27 is provided to cover a portion of the solar panel 25 that is larger than the conductor portion, specifically the portion where the dielectric substrate 51 is exposed, but a color-tuning sheet may also be provided to cover the portion of the first conductor element 52 that is exposed on the outer periphery of the solar panel 25. In other words, the color-tuning sheet may be provided in a portion where a color different from the conductor portion of the solar panel 25, i.e., the amorphous silicon thin film 252, is visible when the dial 2 is viewed. Furthermore, instead of providing the color-adjusting sheet 27, the back surface of the dial 2 that overlaps with the exposed portion of the dielectric substrate 51 and the conductive element 52 may be colored to make the color difference less noticeable. Also, the electronic timepiece may not be equipped with a solar panel 25.

[0053] In the first embodiment, the second conductor element 53 of the planar antenna 50 was made of a magnetically resistant plate, but the second conductor element 53 may be formed in a plate shape with approximately the same area as the first conductor element 52 and may function as a ground member of a plate-shaped inverted-F antenna. In the above-described embodiments, the antenna receives satellite signals transmitted from GPS satellites, but the signals received by the antenna are not limited to this. For example, the antenna may receive satellite signals transmitted from satellites of other global navigation satellite systems (GNSS) such as Galileo, GLONASS, and Beidou, geostationary satellite-based augmentation systems (SBAS), and regional navigation satellite systems (RNSS) that can be searched only in specific regions, such as quasi-zenith satellites. The antenna is not limited to one that receives satellite signals, but may also be an antenna that receives other radio waves, such as Bluetooth (registered trademark), BLE (Bluetooth Low Energy), Wi-Fi (registered trademark), NFC (Near Field Communication), LPWA (Low Power Wide Area), etc. In other words, the planar antenna 50 incorporated into the electronic timepieces 1, 1B, 1C can be set appropriately depending on the type of signal to be received, the size of the timepiece, how it fits in with other components, etc.

[0054] Summary of this disclosure The electronic timepiece disclosed herein comprises an antenna having a flat first conductor element connected to a power supply section, a flat second conductor element that overlaps the first conductor element in a planar view, and a short-circuit section that short-circuits the first conductor element and the second conductor element, and a conductive case that houses the antenna and has a side wall, wherein the first conductor element has an outer edge on the short-circuit section side that is continuous with the short-circuit section, and an antenna open end, and in the planar view, a first distance between the antenna open end and the side wall is greater than a second distance between the outer edge on the short-circuit section side and the side wall. According to the electronic watch disclosed herein, in the flat first conductive element that is connected to the power supply section and serves as the antenna electrode, the first distance between the open end of the antenna located opposite the short-circuit section and the side wall of the case is made larger than the second distance between the outer edge on the short-circuit section side and the side wall of the conductive case.This means that the antenna directivity is directed upward, improving the performance of the planar antenna for electronic watches that are placed inside a conductive case and therefore need to receive radio waves from the cover crystal side, i.e., from above.

[0055] In the electronic timepiece of this disclosure, it is preferable that the difference between the first distance and the second distance be 0.01 times or less the wavelength of the radio wave received by the antenna. The open end of the antenna is located farther from the side wall of the case than the outer edge of the short-circuited portion by the difference between the first distance and the second distance. If this difference in distance becomes too large, the antenna will be too small compared to the quarter wavelength, which is the resonant wavelength, and the antenna characteristics will deteriorate. Therefore, by setting the difference in these distances to 0.01 times the wavelength of the received radio wave or less, the antenna can be prevented from becoming too small, preventing deterioration of the antenna characteristics.

[0056] In the electronic watch of the present disclosure, it is preferable that a solar panel overlapping the first conductor element in the planar view is arranged on the surface side of the first conductor element, and that the conductor portion of the solar panel is smaller than the first conductor element in the planar view. The conductor portion of the solar panel is smaller than the first conductor element in a planar view, so even if the solar panel is placed on the front side of the first conductor element, the influence of the conductor portion of the solar panel on antenna performance can be reduced.

[0057] The electronic timepiece of the present disclosure preferably has a color-tuning sheet that covers a portion of the first conductive element that is larger than the conductive portion of the solar panel. By covering the part of the solar panel that is larger than the conductor part with the color-matching sheet, the difference in color between the conductor part of the solar panel and the exposed part other than the conductor part can be eliminated, improving the design.

[0058] In the electronic timepiece of the present disclosure, it is preferable that a decorated dial is arranged on the surface side of the first conductive element so as to overlap the first conductive element in the planar view, and that the open end of the antenna has a shape that follows the decoration of the dial in the planar view. By shaping the open end of the antenna to match the decoration of the dial, the outer edge of the open end of the antenna is not conspicuous, preventing a decrease in design.

[0059] In the electronic timepiece of this disclosure, the second conductive element is preferably a conductive plate that is larger than the first conductive element in the plan view. By configuring the second conductive element from a conductive plate, it can be formed separately from the first conductive element, and therefore can be formed larger in size than the first conductive element. Furthermore, by making the second conductive element larger than the first conductive element in a plan view, the antenna directivity can be directed upward, further improving antenna performance.

[0060] In the electronic timepiece of the present disclosure, it is preferable that the distance between the outer edge of the second conductor element opposite the short-circuit portion and the side wall is the same as the distance between the outer edge of the second conductor element on the short-circuit portion side and the side wall. The outer edge of the second conductor element on the opposite side of the short-circuit portion corresponds to the antenna open end of the first conductor element, and the distance between the outer edge of this second conductor element and the side wall is the same as the distance between the outer edge of the second conductor element on the short-circuit portion side and the side wall.As a result, the second conductor element can be made larger than the first conductor element, thereby improving antenna performance.

[0061] In the electronic timepiece of the present disclosure, it is preferable that the electronic timepiece has a hand that displays the time, and that the antenna has a through hole, through which the hand stem passes, at a position different from the short-circuit portion. By forming the through hole through which the hand stem passes at a position on the antenna different from the short-circuited portion, for example, at a position approximately midway between the short-circuited portion and the open end of the antenna, the antenna can be formed to be the same size as the range of hand movement, i.e., the dial. [Explanation of symbols]

[0062] 1...Electronic watch, 1B...Electronic watch, 1C...Electronic watch, 2...Dial, 2A...Through-hole, 2B...Date window, 2C...Sub-dial, 2D...Scale, 3...Hand, 5...Date indicator, 10...Case, 11...Case body, 12...Body, 14...Back cover, 15...Cover crystal, 20...Movement, 25...Solar panel, 25A...Through-hole, 27...Tinting sheet, 31...Hour hand, 32...Minute hand, 33...Second hand, 35...Hand shaft, 36...Hand shaft, 37...Hand shaft, 50...Flat antenna, 50 A...through hole, 51...dielectric substrate, 52...first conductor element, 52B...first conductor element, 52C...first conductor element, 53...second conductor element, 54...short circuit portion, 54A...side short circuit portion, 54B...back short circuit portion, 58...antenna open end, 58B...antenna open end, 58C...antenna open end, 59...outer edge, 251...resin film substrate, 252...amorphous silicon thin film, 253...cut portion, 581...straight portion, 582...curved portion, L1...first distance, L2...second distance.

Claims

1. an antenna having a flat-plate-shaped first conductive element connected to a power supply portion, a flat-plate-shaped second conductive element overlapping the first conductive element in a plan view, and a short-circuit portion shorting the first conductive element and the second conductive element; a conductive case that houses the antenna and has a sidewall; the first conductive element has an outer edge on the short-circuit portion side that is continuous with the short-circuit portion, and an antenna open end, An electronic timepiece characterized in that, in the plan view, a first distance between the open end of the antenna and the side wall is greater than a second distance between the outer edge on the short-circuit portion side and the side wall.

2. 2. The electronic timepiece according to claim 1, An electronic timepiece characterized in that the difference between the first distance and the second distance is 0.01 times or less the wavelength of the radio wave received by the antenna.

3. 3. The electronic timepiece according to claim 1, a solar panel is disposed on a front surface side of the first conductive element so as to overlap with the first conductive element in the plan view; An electronic timepiece characterized in that the conductor portion of the solar panel is smaller than the first conductor element in the plan view.

4. 4. The electronic timepiece according to claim 3, An electronic timepiece comprising a color-adjusting sheet that covers a portion of the first conductive element that is larger than the conductive portion of the solar panel.

5. 5. The electronic timepiece according to claim 1, a dial plate having decoration is disposed on a front surface side of the first conductive element so as to overlap with the first conductive element in the plan view; An electronic timepiece characterized in that the antenna open end has a shape that conforms to the decoration of the dial when viewed in plan.

6. 6. The electronic timepiece according to claim 1, The electronic timepiece is characterized in that the second conductive element is a conductive plate and is larger than the first conductive element in the plan view.

7. 7. The electronic timepiece according to claim 6, The distance between the outer edge of the second conductive element opposite the short circuit portion and the side wall is An electronic timepiece characterized in that the distance between the outer edge of the second conductive element on the short-circuit portion side and the side wall is the same.

8. 8. The electronic timepiece according to claim 1, Equipped with hands that display the time, An electronic timepiece characterized in that the antenna has a through hole through which the hand stem passes, at a position different from the short-circuiting portion.

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