Patent Publication Number: US-8995236-B2

Title: Electronic timepiece with internal antenna

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to an electronic timepiece with an internal antenna. 
     2. Related Art 
     Electronic timepieces that receive signals from positioning information satellites such as GPS (Global Positioning System) satellites to display accurate time are known from the literature. Such electronic timepieces commonly have a ring-shaped antenna for receiving radio signals from the positioning information satellites. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2011-21929, and Japan Patent No. 4551678. 
     The ring-shaped antenna is disposed around the time display part (such as the dial) of the electronic timepiece. The antenna includes an annular base made of a dielectric material (an electrical insulator), and an annular part made of a conductive material formed on the base. 
     If the ring-shaped antenna disposed around the time display is located too close to the time display, viewing the time display may be obstructed. However, disposing the antenna to a position far from the time display requires a large area outside of the time display, and the size of the electronic timepiece increases accordingly. 
     An electronic timepiece may also have a metal case on the exterior. If the ring-shaped antenna is near the metal case, antenna sensitivity drops. If the ring-shaped antenna is located far from the case, a large space is required between the outside of the time display and the inside of the case, and the size of the electronic timepiece increases accordingly. 
     SUMMARY 
     The present invention is directed to the foregoing problem, and achieves a time display that can be easily read and an antenna with good reception performance while suppressing increasing the size of an electronic timepiece that has an internal antenna. 
     One aspect of the invention is an electronic timepiece with internal antenna, including: a case of which at least part is made from a conductive material; an annular antenna housed in the case; a feed part that feeds the antenna housed in the case; and a time display unit disposed inside the antenna in plan view. The antenna has an annular dielectric base, and an antenna element that is made from a conductive material and is fed by the feed part. The base has a sloped surface that slopes toward the time display unit and decreases in height to the time display unit with proximity to the inside. The antenna element is disposed to the sloped surface of the base. 
     Because the base of the antenna has a sloped face and this face decreases in height to the time display unit with proximity to the inside, the time display unit (such a timepiece dial) can be seen from a wide angle of view. Furthermore, because a conductive antenna element through which the antenna is fed is disposed to this slope, the antenna element can be disposed to a position where radio waves from the outside cannot be easily blocked by the case, at least part of which is made from a conductive material. The acceptance angle of the antenna element is therefore wide, and good reception performance can be assured in the antenna. 
     Because using such a slope makes the time display unit easy to see and increases the acceptance angle of the antenna element, there is no need to create a wide area around the outside of the time display unit, and increasing the size of the electronic timepiece can be suppressed. 
     The antenna base in an electronic timepiece with an internal antenna according to another aspect of the invention preferably preferably has a top that is parallel to the time display unit; and the sloped surface is contiguous to the top in plan view. 
     Parallel as used here includes substantially parallel. 
     Further preferably, the electronic timepiece with internal antenna according to another aspect of the invention has a dial ring that is attached to the case, disposed outside the time display unit, made from a non-conductive material that covers the antenna, and the dial ring has a sloped part parallel to the sloped surface of the base of the antenna. Parallel as used here includes substantially parallel. 
     Because the dial ring is made of a non-conductive material, the dial ring does not interfere with signal reception by the antenna. Furthermore, because the dial ring covers the antenna, the antenna is hidden and does not detract from the appearance of the electronic timepiece. The time display unit can also be read from a wide angle of view because the dial ring has a slope parallel to the slope of the base, and this slope also decreases in height to the time display unit to the inside. 
     Note that “annular” as used herein means a continuous, uninterrupted ring, is not limited to circular rings, and includes uninterrupted squares and other polygons. 
     An electronic timepiece with internal antenna according to another aspect of the invention also has a back cover made from a conductive material. The case is a cylindrical body made of a conductive material; the back cover is electrically connected to the body of the case, and electrically connected to the ground of the antenna element of the antenna; and the back cover and case body function as a ground plane. 
     In the electronic timepiece according to this aspect of the invention, the ground potential is stabilized and good reception performance can therefore be assured in the antenna as a result of the case body and the back cover, which have a large volume and area, functioning as a ground plane. 
     In an electronic timepiece according to another aspect of the invention, the case has a cylindrical body made of a conductive material, and a bezel made of a non-conductive material to which a crystal that protects the time display unit is attached; and the bezel is fit to the inside of the case body. 
     Because the bezel that holds the crystal attached to the case is made of a non-conductive material, the bezel does not interfere with signal reception by the antenna. The bezel is fit to the inside of the body, and the bezel increases the distance between the conductive body and the antenna, and more particularly the conductive part of the antenna. The acceptance angle through which the antenna can receive signals is therefore increased, and good reception performance can be assured. 
     In an electronic timepiece according to another aspect of the invention, the antenna element of the antenna is disposed to a position at a greater height from the time display unit than the body of the case. 
     The body of the casein this aspect of the invention is made of a conductive material, but by disposing the body closer in height to the time display unit than the antenna element of the antenna, the body has substantially no effect on the directions from which radio waves can reach the antenna element. The acceptance angle through which the antenna element can receive signals is therefore increased, and good reception performance can be assured. 
     Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overview of a GPS system including an electronic timepiece  100  with an internal antenna according to a first embodiment of the invention. 
         FIG. 2  is a plan view of the electronic timepiece  100 . 
         FIG. 3  is a partial section view of the electronic timepiece  100 . 
         FIG. 4  is an exploded view of part of the electronic timepiece  100 . 
         FIG. 5A  to  FIG. 5C  describe the shape of the antenna  40  in the electronic timepiece  100  and the antenna pattern of the antenna  40 . 
         FIG. 6  describes the relative positions of the antenna  40 , feed pin  44 , and storage battery  27  in the electronic timepiece  100 . 
         FIG. 7  describes the relative positions of the antenna  40 , feed pin  44 , storage battery  27 , and magnetic screens S 1  and S 2  in the electronic timepiece  100 . 
         FIG. 8  describes the relative positions of the antenna  40 , feed pin  44 , storage battery  27 , and magnetic screen S 3  in the electronic timepiece  100 . 
         FIG. 9  is a block diagram showing the circuit configuration of the electronic timepiece  100 . 
         FIG. 10  shows the results of tests checking the advantage of the reception performance of the antenna in the electronic timepiece  100 . 
         FIG. 11  is an oblique view of a different antenna  140  used in an electronic timepiece for comparison. 
         FIG. 12A  is an oblique view of an antenna  240  according to a first variation of the preferred embodiment,  FIG. 12B  is a plan view of the antenna  240 , and  FIG. 12C  is a section view of the antenna  240  through line G-g in  FIG. 12B . 
         FIG. 13  is a graph showing the results of tests checking the advantage of the reception performance of the antenna in the electronic timepiece according to the first variation. 
         FIG. 14  is a section view of an electronic timepiece used for comparison. 
         FIG. 15  is a section view of an antenna according to a second variation of the preferred embodiment. 
         FIG. 16  is a section view of an antenna according to a third variation of the preferred embodiment. 
         FIG. 17  is a section view of an antenna according to a fourth variation of the preferred embodiment. 
         FIG. 18  is a section view of an antenna according to a fifth variation of the preferred embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Preferred embodiments of the present invention are described below with reference to the accompanying figures. Note that the size and scale of parts shown in the figures differ from the actual size and scale for convenience. Furthermore, the following examples are specific preferred embodiments of the invention and describe technically desirable limitations, and the scope of the invention is not limited thereby unless such limitation is specifically stated below. 
     A. Mechanical Configuration of an Electronic Timepiece with Internal Antenna 
       FIG. 1  shows the basic concept of a GPS system that includes an electronic timepiece  100  with an internal antenna according to a preferred embodiment of the invention. 
     The electronic timepiece  100  is a wristwatch that receives signals (radio signals) from at least one of plural GPS satellites  20  and adjusts the time based thereon, and displays the time on the surface (side) (referred to below as the “face”) on the opposite side as the surface (referred to below as the “back”) that contacts the wrist. The back side is also referred to below as the bottom, and the face side as the top. 
     A GPS satellite  20  is an example of a positioning information satellite that orbits the Earth on a specific orbit, and transmits a navigation message superimposed on a 1.57542 GHz RF signal (L1 signal). The 1.57542 GHz signal carrying a superimposed navigation message is referred to herein as simply a “satellite signal.” These satellite signals are right-handed circularly polarized waves. 
     The invention is described below using the GPS system as an example of a satellite positioning system, but the invention is not so limited. More particularly, the invention can be used with Global Navigation Satellite Systems (GNSS) such as Galileo (EU), GLONASS (Russia), and Beidou (China), and other positioning information satellites that transmit satellite signals containing time information, including the SBAS and other geostationary or quasi-zenith satellites. 
     The electronic timepiece  100  may therefore be a wristwatch that receives radio waves (radio signals) from positioning information satellites other than GPS satellites  20 , and adjusts the internal time based thereon. 
     There are currently approximately 31 GPS satellites  20  in the constellation. Only 4 of the 31 satellites are shown in  FIG. 1 . 
     Each GPS satellite  20  superimposes a unique pattern called a C/A code (Coarse/Acquisition Code), which is a 1023-chip (1 ms) pseudorandom noise code unique to a specific GPS satellite  20 , on the satellite signal. This code is used to identify which GPS satellite  20  transmitted a particular satellite signal. Each chip is a value of +1 or −1, and the C/A code appears to be a random pattern. The C/A code superimposed on the satellite signal can therefore be detected by correlating the satellite signal that is actually received with the known pattern of each C/A code. 
     Each GPS satellite  20  carries an atomic clock, and the highly precise time information (“GPS time information” below) kept by the atomic clock is included in the satellite signal transmitted by the GPS satellite  20 . The time difference of the atomic clock onboard each GPS satellite  20  is measured by the ground control segment, and a time correction parameter for correcting this time difference is also included in the satellite signal. The electronic timepiece  100  receives a satellite signal transmitted from one GPS satellite  20 , and adjusts the internal time to the correct time using the GPS time information and time correction parameter contained in the received signal. 
     Orbit information indicating the position of the GPS satellite  20  on its orbit is contained in the satellite signal. The electronic timepiece  100  can calculate its own position using the GPS time information and orbit information. This position calculation assumes that there is some degree of error in the internal time kept by the electronic timepiece  100 . More specifically, in addition to the three parameters for determining the three-dimensional position of the electronic timepiece  100 , this time error is also an unknown. The electronic timepiece  100  therefore generally receives satellite signals from four or more GPS satellites, and calculates its own position using the GPS time information and orbit information contained in each of the received signals. 
       FIG. 2  is a plan view of the electronic timepiece  100 . 
     As shown in  FIG. 2 , the electronic timepiece  100  has an outside case  80 . The case  80  includes a cylindrical body  81  made of metal or other conductive material, and a bezel  82  made of a non-conductive material such as ceramic. The bezel  82  is pressed into the body  81 . 
     An annular dial ring  83  made of a non-conductive material such as plastic is disposed inside the bezel  82 , and a round dial  11  is disposed inside the dial ring  83 . 
     Bar-shaped hour markers are disposed every 30 degrees around the dial ring  83 , and such markers are not disposed to the dial  11 . The information shown on the dial ring  83  and the information shown on the dial  11  may be different from each other, and is not limited to the information shown in the figure. 
     Hands  13  ( 13   a  to  13   c ) that turn on a center pivot  12  and indicate the current time are disposed above the dial  11 . The dial  11  may also be referred to as the time display unit below. 
     Further described below, the case  80  has two openings, one each on the face and the back cover sides. 
     The opening on the face side of the case  80  is covered by a crystal  84  through an intervening bezel  82 , and the dial  11  and hands  13  ( 13   a  to  13   c ) are visible through the crystal  84 . 
     As also shown in  FIG. 1  and  FIG. 2 , the electronic timepiece  100  has a crown  16  and pushers  17 ,  18 . The crown  16  and pushers  17 ,  18  can be manually operated to set the electronic timepiece  100  to at least a mode (time information acquisition mode) that receives satellite signals from at least one GPS satellite  20  and adjusts the internal time, and a mode (positioning information acquisition mode) that receives signals from plural GPS satellites  20 , calculates the current position, and adjusts the time difference of the internal time. The electronic timepiece  100  can also execute the time information acquisition mode and positioning information acquisition mode regularly (automatically). 
       FIG. 3  is a section view showing the internal structure of the electronic timepiece  100 , and  FIG. 4  is an exploded oblique view showing parts of the electronic timepiece  100 . 
     As shown in  FIG. 3 , the case  80  includes a cylindrical body  81  made of metal or other conductive material and a bezel  82  made of a non-conductive material such as ceramic, and the bezel  82  is pressed into the body  81 . The case  80  has a top opening K1 and a bottom opening K2. The top opening K1 of the case  80  is covered by the round crystal  84 , and the bottom opening K2 is covered by a back cover  85  made of SUS (stainless steel), Ti (titanium), or other conductive material. The body  81  and back cover  85  screw together, for example. 
     The ring-shaped dial ring  83  made of plastic or other non-conductive material is disposed to the inside circumference of the bezel  82  below (on the back cover side of) the crystal  84 . The main plate  38  made of plastic or other non-conductive material is disposed inside the inside circumference of the body  81  below the dial ring  83 . 
     A donut-shaped storage space is formed by the main plate  38 , the dial ring  83 , and inside surface of the case  80 . The annular antenna  40  is housed in this space. The antenna  40  is therefore disposed on the inside side of the inside circumference of the bezel  82 , and the top of the antenna  40  is covered by the dial ring  83 . 
     An annular ground plane  90  made of metal is disposed in this space between the antenna  40  and the main plate  38 . The ground plane  90  is electrically connected to the back cover  85  through a conductive spring  24 , and is electrically connected to the body  81  because the back cover  85  is affixed to the body  81 . 
       FIG. 5A  to  FIG. 5C  describe the construction of the antenna  40 . 
       FIG. 5A  is an oblique view of the antenna  40 ,  FIG. 5B  is a plan view of the antenna  40 , and  FIG. 5C  is a section view of the antenna  40  through line G-g in  FIG. 5B . 
     The antenna  40  includes an annular base  401  made of a dielectric material, and an antenna element  415  formed on the base  401 . The antenna element  415  is made of metal or other conductive material. A feed part  404  made of metal or other conductive material is also disposed to the antenna  40 . The antenna element  415  and feed part  404  can be formed by a plating or silver paste printing process. The dielectric constant Σr of the base  401  material can be adjusted to approximately 5-20 by mixing a dielectric material that is used in high frequency applications, such as titanium oxide, with resin. 
     As shown in  FIG. 5C , the base  401  has a pentagonal section including a top T1, outside face T2, bottom T3, slope TP1, and second slope TP2. The antenna element  415  is formed on slope TP1 as shown in the figure. The feed part  404  is formed on the slope TP1, second slope TP2, and bottom T3. The antenna element  415  is electrically connected to a feed pin  44  through the feed part  404 , and a specific potential is thereby supplied to the antenna element  415  of the antenna  40 . 
     As shown in  FIG. 5B , the antenna element  415  has a notch  420 , and thus forms a C-shape with a notch in the ring. The antenna element  415  has an antenna length that resonates to signals (satellite signals) from a positioning information satellite. 
     GPS satellites  20  transmit satellite signals at 1.575 GHz, the length of one wave is approximately 19 cm. Because an antenna length of approximately 1.0-1.2 wavelength is required to receive circularly polarized waves, a loop antenna of approximately 19-24 cm is required to receive a signal from a GPS satellite  20 . Rendering a loop antenna with this antenna length in a wristwatch, however, results in a large wristwatch. 
     The base  401  of the antenna  40  in this embodiment is made from a material with a dielectric constant ∈r of approximately 5-20. When using a base  401  with a dielectric constant ∈r, the wavelength shortening rate of the base  401  will be (Σr) −1/2 . More specifically, the wavelength of the radio waves received by the antenna  40  can be shortened (Σr) −1/2  times by using a dielectric with a dielectric constant of Σr. Because the antenna  40  according to this embodiment of the invention has a base  401  with a dielectric constant of ∈r, the antenna length of the antenna  40  can be shortened (Σr) −1/2  times compared with a configuration not using the base  401 , and the size of the antenna can be reduced. 
     As shown in plan view in  FIG. 5B , the antenna element  415  is a C-shaped element, that is, a ring with notch removed, and functions as an antenna element that converts electromagnetic waves to current. The antenna element  415  is fed by the feed part  404 . The impedance of the circuit electrically connected to the antenna  40  and the impedance of the antenna  40  can be matched by desirably setting the length of the antenna element  415 . 
     The angle between the feed part  404  and the notch  420  is √a, the length of the notch  420  is Δg, the circumferential length of the antenna element  415  is C. If the wavelength of the received circularly polarized waves is λ as described in Japan Patent No. 3982918, then preferably C=1.31└, Φa=40°, and Δg=0.018λ. 
     This embodiment uses a C-shaped antenna element  415  with a notch  420 , but could alternatively use an O-shaped antenna element that is an endless loop. 
       FIG. 3  and  FIG. 4  are referred to again below. 
     As shown in  FIG. 3 , an optically transparent dial  11 , a center pivot  12  passing through the dial  11  and main plate  38 , and hands  13  (second hand  13   a , minute hand  13   b , hour hand  13   c ) that move around the center pivot  12  and display the current time, are disposed inside the inside circumference of the antenna  40 . 
     The center pivot  12  extends in the direction between the face and back along the center axis of the case  80 . The dial  11  is round and made of plastic or other optically transparent non-conductive material. As shown in  FIG. 3 , the dial  11  is disposed between the crystal  84  and main plate  38 . A hole through which the center pivot  12  passes is formed in the center of the dial  11 . The hands  13  are disposed between the crystal  84  and the dial  11  inside the inside circumference of the antenna  40 . 
     A drive mechanism (drive unit)  30  that causes the center pivot  12  to turn and drives the plural hands  13  is disposed below (on the back cover side of) the main plate  38 . The drive mechanism  30  includes a stepper motor M and wheel train, and drives the hands  13  by the stepper motor M causing the center pivot  12  to turn through the wheel train. More specifically, the drive mechanism  30  causes the center pivot  12  to turn so that the hour hand  13   c  turns one revolution in 12 hours, the minute hand  13   b  turns one revolution in 60 minutes, and the second hand  13   a  turns one revolution in 60 seconds. 
     The electronic timepiece  100  has a circuit board  25  inside the case  80 . The circuit board  25  is made of resin or other material including a dielectric, and is disposed below the drive mechanism  30  (that is, between the drive mechanism  30  and the back cover  85 ). 
     A circuit block including a GPS reception unit (radio receiver)  26  and control unit  70  is disposed on the bottom (on the surface facing the back of the wristwatch) of the circuit board  25 . The GPS reception unit  26  is a single-chip IC module, for example, and includes analog and digital circuits. The control unit  70  sends control signals to the GPS reception unit  26  and controls the reception operation of the GPS reception unit  26 , and controls operation of the drive mechanism  30 . 
     A feed pin  44  made of metal or other conductive material is disposed above top side of the circuit board  25 . The feed pin  44  has an internal spring, passes through a through-hole formed in the ground plane  90  and contacts the feed part  404  of the antenna  40 , and passes through a through-hole  38   b  ( FIG. 4 ) formed in the main plate  38  and contacts the circuit board  25 . The feed part  404  of the antenna  40  is therefore electrically connected to the circuit board  25  (more precisely, to wiring disposed to the circuit board  25 ) through the feed pin  44 , and a specific potential is supplied from the circuit board  25  to the antenna  40 . 
     The circuit block including the GPS reception unit  26  and control unit  70  is covered by a shield  91  made of a conductive material. The shield  91  is electrically connected to the ground plane  90  through a circuit support  39 , back cover  85 , and body  81 . The ground potential of the circuit block is supplied to the shield  91 . More specifically, the shield  91 , back cover  85 , body  81 , and ground plane  90  are held at the ground potential of the circuit block, and function as a ground plane. 
     The magnetic screens S 1  and S 2  are disposed between the drive mechanism  30  and main plate  38 , and another magnetic screen S 3  is disposed between the drive mechanism  30  and circuit board  25 . Magnetic screens S 1  and S 2  are referred to below as a first magnetic screen, the magnetic screen S 3  as a second magnetic screen, and magnetic screens S 1  to S 3  are made of a conductive material with high permeability, such as pure iron. 
     If there is a speaker or other object that produces a strong magnetic field on the outside of the electronic timepiece  100 , the magnetic field can cause the stepper motor M to operate incorrectly. Of the parts of the electronic timepiece  100 , metal in the body  81  and back cover  85  produces a magnetic field when magnetized. Circuit blocks on the circuit board  25  can also produce a magnetic field. 
     By covering the stepper motor M with magnetic screens S 1  to S 3  made of a material with high permeability, this embodiment of the invention magnetically shields the drive mechanism  30  and prevents the stepper motor M from operating incorrectly due to the magnetic fields described above. 
     A lithium ion battery or other cylindrically shaped storage battery  27 , a battery compartment  28  for holding the storage battery  27 , and a solar panel  87  that generates power by photovoltaic conversion, are also disposed inside the case  80  of the electronic timepiece  100 . 
     The solar panel  87  is a round disc having plural solar cells (photovoltaic devices) that convert light energy to electrical energy (power) connected in series. The solar panel  87  is disposed inside the inside circumference of the antenna  40  and between the main plate  38  and dial  11 , and a center hole through which the center pivot  12  passes is formed in the center of the solar panel  87 . 
     The storage battery  27  is charged by the power produced by the solar panel  87 . The battery compartment  28  for holding the storage battery  27  is below the circuit board  25  (that is, between the circuit board  25  and back cover  85 ). 
     The crown  16  and pushers  17 ,  18  ( FIG. 2 ) are disposed to the outside of the case  80 . Movement of the crown  16  resulting from the user of the electronic timepiece  100  operating the crown  16  is transferred through the stem  16   a  passing through the case  80  to the drive mechanism  30 . Movement of the pusher  17  (or pusher  18 ) produced by the user of the electronic timepiece  100  pressing the pusher  17  (or pusher  18 ) is transferred to a switch not shown through the corresponding button stem  17   a  (or button stem  18   a ) (see  FIG. 6 ) passing through the case  80 . These switches convert pressure from the pusher  17  (or pusher  18 ) to an electrical signal, and output the signal to the control unit  70 . 
     The crown  16 , stem  16   a , pushers  17 ,  18 , and button stems  17   a  and  18   a  are also referred to below as operating units. 
       FIG. 6  shows the relative positions of the case  80 , antenna  40 , feed pin  44 , storage battery  27  (battery compartment  28 ) and operating units (crown  16 , stem  16   a , pushers  17 ,  18 , and button stems  17   a  and  18   a ) when seen in plan view (that is, when the electronic timepiece  100  is seen from the direction perpendicular to the dial  11 ). 
     As shown in  FIG. 6 , the battery compartment  28  is disposed so that the storage battery  27  (the storage battery  27  housed in the battery compartment  28 ) and the antenna  40  do not overlap when seen in plan view. The feed pin  44  is also disposed to a position not overlapping the storage battery  27  held in the battery compartment  28  when seen in plan view. 
     For structural reasons, the battery compartment  28  cannot be disposed to a position superimposed with the operating units (more specifically, the stem  16   a ) in plan view. 
     The feed pin  44  also cannot be disposed to a position superimposed with the operating units (more specifically, the stem  16   a  and button stems  17   a ,  18   a ) in plan view. 
     As a result, the battery compartment  28  and feed pin  44  are disposed where they are not superimposed with the operating units in plan view. For structural reasons, the battery compartment  28  is also disposed where it is not superimposed with the circuit block including the GPS reception unit  26  and control unit  70  (not shown in  FIG. 6 ). 
     The location of the feed pin  44  is also limited by the relationship to the magnetic screens S 1  to S 3  described below. 
     The location of the feed pin  44  is therefore determined with consideration for its position relative to the magnetic screens S 1  to S 3  described below, and the relative position of the storage battery  27  to the operating units. 
       FIG. 7  shows the relative positions of the antenna  40 , feed pin  44 , storage battery  27 , magnetic screens S 1  and S 2 , and stepper motor M in plan view.  FIG. 8  shows the relative positions of the antenna  40 , feed pin  44 , storage battery  27 , magnetic screen S 3 , and stepper motor M in plan view. 
     As shown in  FIG. 7 , the magnetic screens S 1  and S 2  are disposed superimposed with at least part of each stepper motor M. As shown in  FIG. 8 , magnetic screen S 3  is disposed superimposed with at least part of each stepper motor M. Asa result, each stepper motor M is magnetically shielded from the magnetic fields produced from the outside of the drive mechanism  30 , and incorrect operation of the stepper motors M due to these magnetic fields can be prevented. 
     B. Circuit Configuration of the Electronic Timepiece with Internal Antenna 
       FIG. 9  is a block diagram showing the circuit configuration of the electronic timepiece  100 . 
     As shown in  FIG. 9 , the electronic timepiece  100  includes a GPS reception unit  26  and a control display unit  36 . The GPS reception unit  26  executes processes related to receiving satellite signals, locking onto GPS satellites  20 , generating positioning information, and generating time correction information, for example. The control display unit  36  executes processes including keeping the internal time and adjusting the internal time. 
     A solar panel  87  charges the storage battery  27  through the charging control circuit  29 . 
     The electronic timepiece  100  has regulators  34  and  35 , and the storage battery  27  supplies drive power through a regulator  34  to the control display unit  36 , and supplies drive power through another regulator  35  to the GPS reception unit  26 . 
     The electronic timepiece  100  also has a voltage detection circuit  37  that detects the voltage of the storage battery  27 . 
     Regulator  35  could be split into a regulator  35 - 1  (not shown) that supplies drive power to the RF unit  50  (described below), and a regulator  35 - 2  (not shown) that supplies drive power to a baseband unit  60  (described below). In this implementation, regulator  35 - 1  could be disposed in the RF unit  50 . 
     The electronic timepiece  100  also has the antenna  40  described above and a SAW (surface acoustic wave) filter  32 . As described with reference to  FIG. 1 , the antenna  40  receives satellite signals from plural GPS satellites  20 . However, because the antenna  40  also receives noise in addition to the satellite signals, the SAW filter  32  extracts the satellite signals from the signals received by the antenna  40 . In other words, the SAW filter  32  functions as a bandpass filter that passes signals in the 1.5 GHz waveband. 
     The GPS reception unit  26  includes the RF (radio frequency) unit  50  and baseband unit  60 . As described below, the GPS reception unit  26  executes a process that extracts satellite information including GPS time information and orbit information contained in the navigation message from the 1.5 GHz satellite signal extracted by the SAW filter  32 . 
     The RF unit  50  includes a LNA (low noise amplifier)  51 , mixer  52 , VCO (voltage controlled oscillator)  53 , PLL (phase-locked loop) circuit  54 , IF (intermediate frequency) amplifier  55 , IF filter  56 , and A/D converter  57 . 
     The satellite signal passed by the SAW filter  32  is amplified by the LNA  51 . The satellite signal amplified by the LNA  51  is mixed by the mixer  52  with the clock signal output by the VCO  53 , and down-converted to a signal in the intermediate frequency band. The PLL circuit  54  phase compares a clock signal obtained by frequency dividing the output clock signal of the VCO  53  with a reference clock signal, and synchronizes the output clock signal of the VCO  53  to the reference clock signal. As a result, the VCO  53  can output a stable clock signal with the frequency precision of the reference clock signal. Note that several megahertz, for example, can be selected as the intermediate frequency. 
     The signal from the mixer  52  is amplified by the IF amplifier  55 . However, mixing by the mixer  52  also produces a high frequency component of several GHz in addition to the IF signal. The IF amplifier  55  therefore amplifies both the IF signal and the high frequency component of several GHz. The IF filter  56  therefore passes the IF signal and removes the high frequency component of several GHz (more accurately, attenuates the signal to a specific level or less). The IF signal passed by the IF filter  56  is converted to a digital signal by the A/D converter  57 . 
     The baseband unit  60  includes, for example, a DSP (digital signal processor)  61 , CPU (central processing unit)  62 , SRAM (static random access memory)  63 , and RTC (real-time clock)  64 . A TCXO (temperature compensated crystal oscillator)  65  and flash memory  66  are also connected to the baseband unit  60 . 
     The temperature compensated crystal oscillator (TCXO)  65  generates a reference clock signal of a substantially constant frequency regardless of temperature. Time zone information, for example, is stored in flash memory  66 . The time zone information defines the time difference between the current location and UTC based on specific coordinates (such as latitude and longitude). 
     The baseband unit  60  executes a process that demodulates the baseband signal from the digital signal (IF signal) output from the A/D converter  57  of the RF unit  50  when set to the time information acquisition mode or the positioning information acquisition mode. 
     In addition, when the time information acquisition mode or the positioning information acquisition mode is set, the baseband unit  60  executes a process that generates a local code of the same pattern as each C/A code, and correlates the local codes to the C/A code contained in the baseband signal, in the satellite search step. The baseband unit  60  adjusts the timing when the local code is generated to find the peak correlation to each local code, and when the correlation equals or exceeds a threshold value, confirms synchronization with the GPS satellite  20  matching the local code (that is, confirms locking onto a GPS satellite  20 ). Note that the GPS system uses a CDMA (Code Division Multiple Access) method whereby all GPS satellites  20  transmit satellite signals on the same frequency using different C/A codes. The GPS satellites  20  that can be locked onto can therefore be found by identifying the C/A code contained in the received satellite signal. 
     To acquire the satellite information from the satellite signal of the GPS satellite  20  that was locked onto in the time information acquisition mode or the positioning information acquisition mode, the baseband unit  60  executes a process that mixes the baseband signal with the local code of the same pattern as the C/A code of the GPS satellite  20  that was locked. 
     The navigation message containing the satellite information of the GPS satellite  20  that was locked onto is demodulated in the mixed signal. The baseband unit  60  then executes a process to detect the TLM word (preamble data) of each subframe in the navigation message, and acquire (such as store in SRAM  63 ) satellite information such as the orbit information and GPS time information contained in each subframe. The GPS time information as used here is the week number (WN) and Z count, but the Z count data alone could be acquired if the week number was previously acquired. The baseband unit  60  then generates the time adjustment information required to correct the internal time based on the satellite information. 
     In the time information acquisition mode, the baseband unit  60  more specifically calculates the time based on the GPS time information, and generates time correction information. The time correction information in the time information acquisition mode may be the GPS time information, or information about the time difference between the GPS time and internal time. 
     However, in the positioning information acquisition mode, the baseband unit  60  more specifically calculates the position based on the GPS time information and orbit information, and acquires the location information (more specifically calculates the latitude and longitude of the electronic timepiece  100  when the satellite signals were received). Next, the baseband unit  60  references the time difference (time zone) information stored in flash memory  66 , and acquires the time difference at the coordinates (such as latitude and longitude) of the electronic timepiece  100  determined from the positioning information. The baseband unit  60  thus generates satellite time data (GPS time information) and time zone (time difference) data as the time correction information. The time correction information used in the positioning information acquisition mode may thus be the GPS time information and time zone information as described above, but the time difference between the internal time and the GPS time could be used instead of the GPS time information. 
     Note that the baseband unit  60  can generate the time correction information using the GPS time information from one GPS satellite  20 , or the baseband unit  60  can generate the time correction information from satellite information from a plurality of GPS satellites  20 . 
     Operation of the baseband unit  60  is synchronized to the reference clock signal output by the TCXO  65 . The RTC  64  generates the timing for satellite signal processing, and counts up at the reference clock signal output from the TCXO  65 . 
     The control display unit  36  includes a control unit  70 , crystal oscillator  73 , and drive circuit  74 . 
     The control unit  70  includes a storage unit  71  and a RTC (real-time clock)  72 , and controls various operations. The control unit  70  can be rendered with a CPU, for example. The control unit  70  outputs control signals to the GPS reception unit  26 , and controls reception by the GPS reception unit  26 . The control unit  70  also controls operation of regulators  34 ,  35  based on output from the voltage detection circuit  37 . The control unit  70  also controls movement of the hands  13  through the drive circuit  74 . 
     Reception data is stored in the storage unit  71 . The control unit  70  adjusts the internal time based on the received data. The internal time is the time kept in the electronic timepiece  100  by the RTC  72 . The RTC  72  operates continuously, and counts up at the reference clock signal generated by the crystal oscillator  73 . The control unit  70  can therefore update the internal time and continue moving the hands even when power is not supplied to the GPS reception unit  26 . 
     When the time information acquisition mode is set, the control unit  70  controls operation of the GPS reception unit  26 , corrects the internal time based on the GPS time, and stores the time in the storage unit  71 . More specifically, the internal time is corrected to UTC (Coordinated Universal Time) by adding a UTC offset to the acquired GPS time. 
     When the positioning information acquisition mode is set, the control unit  70  controls operation of the GPS reception unit  26 , corrects the internal time based on the satellite time data (GPS time) and time zone (time difference) data, and stores the time in the storage unit  71 . 
     C. Benefit of the Embodiment 
     As shown in  FIG. 3  and  FIG. 5 , the electronic timepiece  100  according to this embodiment of the invention has a case  80  with a body  81  made from a dielectric material, an annular antenna  40  contained inside the case  80 , a feed part  404  that feeds the antenna  40  in the case  80 , and a dial  11  that is disposed inside of the antenna  40  and displays the time. The antenna  40  has an annular base made from a dielectric, and this base  401  has a top T1 parallel to the dial  11 , and a slope TP1 that is continuous to the top T1 and is inclined to the dial  11  so that the height from the dial  11  decreases to the inside (that is, with proximity to the center pivot  12 ). The antenna  40  has an antenna element  415  that is made of a conductive material and is fed by the feed part  404 , and the antenna element  415  is disposed to the slope TP1 of the base  401 . 
     Because the base  401  of the antenna  40  has a slope TP1, and the height of the slope TP1 to the dial  11  decreases as the slope TP1 descends to the inside, the entire dial  11  can be read from a wide angle of view. 
     Furthermore, because the antenna element  415  of the antenna  40  that is fed is disposed to this slope TP1, the antenna element  415  can be located to a position where external radio waves are not easily blocked by the conductive body  81  of the case  80 . The acceptance angle through which the antenna  40  can receive signals is therefore increased, and good reception performance can be assured. Furthermore, because providing such a slope TP1 makes the dial  11  easy to read and increases the acceptance angle of the antenna  40 , a wide space does not need to be provided around the outside of the dial  11 , and increasing the size of the electronic timepiece  100  can be suppressed. 
     Providing this slope TP1 also makes the electronic timepiece  100  appear thinner, and improves its appearance. This effect is not limited to when the information display part is a dial  11 , and can also be achieved when a digital information display is disposed inside the antenna. 
       FIG. 10  is a graph showing the results of tests confirming the benefit of the reception performance of the antenna in the electronic timepiece  100  according to this embodiment of the invention. In  FIG. 10  solid curve CA denotes the directivity of the antenna  40  in the electronic timepiece  100  according to this embodiment of the invention. Dotted curve CB denotes the directivity of the antenna  140  in an electronic timepiece with an antenna  140  used for comparison. 
     As shown in  FIG. 11 , the comparison antenna  140  has a C-shaped loop antenna element  1415  with a notch  1420  disposed to the top of a base  401  that is the same as the base  401  in this embodiment of the invention. This antenna element  1415  is fed by a feed part  404 . Other aspects of this configuration are identical to this embodiment of the invention. 
     In  FIG. 10  the gain of the antennas  40 ,  140  is normalized so that the peak gain of the antenna  40  according to the invention denoted by curve CA is 0 dB. Compared with the comparison antenna  140 , the gain of the antenna  40  according to the invention is substantially equal in the direction of the zenith, average gain in all directions is good at 0.1 dB, the acceptance angle of the antenna  40  is greater, and the antenna  40  is practical for use in a wristwatch that could be oriented in many different directions when the user is walking, for example. 
     Only the body  81  of the case  80  is made from a conductive material in this embodiment, and the bezel  82  is made from a non-conductive material. However, the bezel  82  could be made from a conductive material. 
     When the bezel  82  is made from a conductive material, the reception performance of the antenna is degraded by the proximity of conductive material to the antenna element  415 . However, by disposing the antenna element  415  to the slope TP1 of the base  401 , the acceptance angle of the antenna  40  is increased, and some distance can be assured between the antenna element  415  and the bezel  82  by disposing the antenna element  415  to the inside slope TP1 instead of the top T1 of the base  401 . As described above, however, a bezel  82  made of a non-conductive material is preferable. 
     As shown in  FIG. 3  and  FIG. 4 , the electronic timepiece  100  has a dial ring  83  that is attached to the case  80 , disposed outside the dial  11 , and made of a non-conductive material covering the antenna  40 , and the dial ring  83  has a sloped part parallel to the slope TP1 of the base  401  of the antenna  40 . Because this dial ring  83  is non-conductive, it does not interfere with the antenna  40  receiving signals. Furthermore, because the dial ring  83  covers the antenna  40 , the antenna  40  is hidden and does not detract from the appearance of the electronic timepiece  100 . The dial  11  can also be read from a wide angle range because the dial ring  83  has a slope parallel to the slope TP1 of the base  401 , and this slope also decreases in height to the dial  11  to the inside. 
     The case  80  in this embodiment has a cylindrical body  81  made of a conductive material, a bezel  82  made of a non-conductive material to which the crystal  84  that protects the dial  11  is attached, and the bezel  82  is fit to the inside of the body  81 . Because the bezel  82  that holds the crystal  84  attached to the case  80  is made of a non-conductive material, the bezel  82  does not interfere with signal reception by the antenna  40 . The bezel  82  is fit to the inside of the body  81 , and the bezel  82  increases the distance between the antenna  40 , and more particularly the antenna element  415 , and the conductive body  81 . The acceptance angle through which the antenna  40  can receive signals is therefore increased, and good reception performance can be assured. The results of tests confirming the benefit of the reception performance of the antenna are described below with reference to a first variation of the preferred embodiment. 
     The fed antenna element  415  of the antenna  40  is disposed to a position that is higher above the dial  11  than the body  81  of the case  80 . The body  81  of the case  80  is made from a conductive material, but by disposing the body  81  at a position closer in height to the dial  11  than the antenna element  415  of the antenna  40 , the body  81  has substantially no effect on the directions from which radio waves can be received by the antenna element  415 . The acceptance angle through which the antenna element  415  can receive signals is therefore increased, and good reception performance can be assured. 
     The electronic timepiece  100  also has a back cover  85  made of a conductive material, the back cover  85  is electrically connected to the body  81  of the case  80 , electrically connected to the ground of the antenna element  415  of the antenna  40 , and the back cover  85  andbody  81  function as a groundplane. The groundpotential is stabilized, and good reception performance can therefore be assured in the antenna, as a result of the body  81  of the case  80  and the back cover  85 , which have a large volume and area, functioning as a ground plane in the electronic timepiece  100 . 
     Other Embodiments 
     The invention is not limited to the foregoing embodiment, and can be varied in many ways such as described in the following variations. One or more of the variations described below can also be desirably combined. 
     Variation 1 
     A first variation of the preferred embodiment is described with reference to  FIG. 12 .  FIG. 12A  is an oblique view of an antenna  240  according to a first variation of the preferred embodiment,  FIG. 12B  is a plan view of the antenna  240 , and  FIG. 12C  is a section view of the antenna  240  through line G-g in  FIG. 12B . 
     This antenna  240  has an annular dielectric base  401  as described in the foregoing embodiment, and antenna elements  2402  and  2403  formed on the base  401 . These antenna elements  2402  and  2403  are made of metal or other conductive material. 
     A feed part  404  made of metal or other conductive material as in the foregoing embodiment is also disposed to the antenna  240 . The antenna elements  2402  and  2403  and feed part  404  can be formed by a plating or silver paste printing process. 
     Antenna element  2402  is formed on the top T1 of the base  401 , and antenna element  2403  is formed on the slope TP1. The feed part  404  is formed on the slope TP1, second slope TP2, and bottom T3 of the base  401 . The other antenna element  2403  is electrically connected through the feed part  404  to the feed pin  44 , and a specific potential is thereby supplied to the antenna element  2403  of the antenna  240 . The antenna element  2402  is not fed by the feed part  404 . 
     As shown in  FIG. 12B , the antenna element  2402  has a notch  2405 , and is a C-shaped loop element, that is, a loop with a portion of the ring removed. The antenna element  2402  has an antenna length that resonates to signals (satellite signals) from a positioning information satellite. 
     As shown in  FIG. 12B , the antenna element  2403  is an arc-shaped element when seen in plan view, and is formed with a specific gap to antenna element  2402 . These two antenna elements  2402  and  2403  are electromagnetically coupled, and function as an antenna element that converts electromagnetic waves to current. The one antenna element  2403  is the part that is made of a conductive material and is fed by the feed part  404 , and may also be referred to as the driven element. The impedance of the circuit electrically connected to the antenna  240  and the impedance of the antenna  240  can be matched by desirably setting the length of the antenna element  2403 . 
       FIG. 13  is a graph showing the results of tests confirming the benefit of the reception performance of the antenna in the electronic timepiece according to this variation of the invention. In  FIG. 13  solid curve CC denotes the directivity of the antenna  240  in the electronic timepiece according to this variation of the invention. Dotted curve CD denotes the directivity of the antenna  240  in an electronic timepiece used for comparison. 
     In the electronic timepiece shown in  FIG. 14  and used for comparison, the bezel  82  is fit to the outside of the body  81  of the case  80 , that is, the reverse of the first embodiment and variation thereof described above. Other aspects of the comparison are the same as in this first variation. 
     In  FIG. 13  the gain of the antenna  240  in the first variation and the comparison is normalized so that the peak gain of the antenna  240  according to the variation denoted by curve CC is 0 dB. The gain of the antenna  240  according to the first variation in the direction of the zenith is 1.1 dB and better than the comparison antenna  240 , and average gain in all directions is good at 2.8 dB. The acceptance angle of the antenna  240  in the first variation is greater, and is practical for use in a wristwatch that could be oriented in many different directions when the user is walking, for example. This is because, as in the embodiment described above, the bezel  82  is fit inside the body  81  in the first variation, and the bezel  82  increases the distance between the antenna  240 , and more particularly the antenna element, and the conductive body  81 . 
     Variation 2 
       FIG. 15  is a section view of the antenna in variation 2, and is the same as the view in  FIG. 5C  and  FIG. 12C . The base  401  of the antenna in this variation does not have a second slope TP2, and slope TP1 continues to the bottom T3. The top T1 of the base  401  is smaller than in the preferred embodiment above and the first variation. The slope TP1 is therefore larger in this second variation than in the preferred embodiment above and the first variation. The antenna element  2402  (C-shaped loop element) is also formed in addition to the antenna element  2403  (driven element) on the slope TP1. A conductive part of the antenna is not formed on the top T1. Because the top T1 of the base  401  is small in this configuration, the dial  11  is prevented from being hidden by the dial ring  83 , and visibility is thus improved. 
     Variation 3 
       FIG. 16  is a section view of the antenna in variation 3, and is the same as the view in  FIG. 5C  and  FIG. 12C . 
     In this embodiment of the invention all of the antenna element  415  (C-shaped loop element) and part of the feed part  404  are embedded in the base  401 . This configuration can be manufactured by insert molding. Insert molding enables manufacturing the antenna element at a lower cost than using a plating or silver paste printing process. The base  401  in this variation also does not have a second slope TP2, and has a vertical inside face. 
     Variation 4 
       FIG. 17  is a section view of the antenna in variation 4, and is the same as the view in  FIG. 5C  and  FIG. 12C . In this embodiment the antenna element  415  (C-shaped loop element) is affixed to the base  401  by flexible tape  500 . This configuration can be manufactured, for example, by forming the antenna element  415  on flexible tape  500 , and affixing the flexible tape  500  to the base  401 . This manufacturing method enables manufacturing the antenna at a lower cost than when the antenna element is formed by a plating or silver paste printing process. The base  401  in this variation also does not have a second slope TP2, and has a vertical inside face. 
     Variation 5 
       FIG. 18  is a section view of the antenna in variation 4, and is the same as the view in  FIG. 5C  and  FIG. 12C . The base  401  in this variation also does not have a second slope TP2, and has a vertical inside face. 
     Variation 6 
     The antenna is round in the foregoing embodiments, but could be square or other annular shape. A square annular antenna is desirable for an angular wristwatch having a digital information display unit disposed inside the antenna, for example. 
     Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom. 
     The entire disclosure of Japanese Patent Application No. 2012-209025, filed Sep. 24, 2012 is expressly incorporated by reference herein.