WO2022037485A1 - 圆极化天线结构及智能穿戴设备 - Google Patents

圆极化天线结构及智能穿戴设备 Download PDF

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Publication number
WO2022037485A1
WO2022037485A1 PCT/CN2021/112445 CN2021112445W WO2022037485A1 WO 2022037485 A1 WO2022037485 A1 WO 2022037485A1 CN 2021112445 W CN2021112445 W CN 2021112445W WO 2022037485 A1 WO2022037485 A1 WO 2022037485A1
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WIPO (PCT)
Prior art keywords
radiator
antenna
circularly polarized
antenna structure
smart
Prior art date
Application number
PCT/CN2021/112445
Other languages
English (en)
French (fr)
Inventor
赵安平
任周游
Original Assignee
安徽华米信息科技有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from CN202021727353.9U external-priority patent/CN212783791U/zh
Priority claimed from CN202010833927.9A external-priority patent/CN111916898A/zh
Application filed by 安徽华米信息科技有限公司 filed Critical 安徽华米信息科技有限公司
Priority to EP21857580.1A priority Critical patent/EP4184713A4/en
Publication of WO2022037485A1 publication Critical patent/WO2022037485A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/27—Adaptation for use in or on movable bodies
    • H01Q1/273—Adaptation for carrying or wearing by persons or animals
    • G—PHYSICS
    • G04—HOROLOGY
    • G04R—RADIO-CONTROLLED TIME-PIECES
    • G04R60/00—Constructional details
    • G04R60/02—Antennas also serving as components of clocks or watches, e.g. motor coils
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/2291—Supports; Mounting means by structural association with other equipment or articles used in bluetooth or WI-FI devices of Wireless Local Area Networks [WLAN]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
    • H01Q5/30—Arrangements for providing operation on different wavebands
    • H01Q5/307—Individual or coupled radiating elements, each element being fed in an unspecified way
    • H01Q5/314—Individual or coupled radiating elements, each element being fed in an unspecified way using frequency dependent circuits or components, e.g. trap circuits or capacitors
    • H01Q5/328—Individual or coupled radiating elements, each element being fed in an unspecified way using frequency dependent circuits or components, e.g. trap circuits or capacitors between a radiating element and ground
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H01Q7/005—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop with variable reactance for tuning the antenna
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
    • H01Q9/0421—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with a shorting wall or a shorting pin at one end of the element
    • G—PHYSICS
    • G04—HOROLOGY
    • G04G—ELECTRONIC TIME-PIECES
    • G04G17/00—Structural details; Housings
    • G04G17/02—Component assemblies
    • G04G17/04—Mounting of electronic components

Definitions

  • the present disclosure relates to the technical field of electronic devices, in particular to a circularly polarized antenna structure and a smart wearable device.
  • Smart wearable devices are popular with more and more users due to their diverse functions. These functions all need to rely on the built-in antenna structure of the smart wearable device to achieve.
  • Satellite positioning antenna As an example, with the development of smart wearable devices, the satellite positioning function has become one of its essential functions.
  • Commonly used satellite positioning systems generally include Global Positioning Satellite System (GPS), Beidou Satellite Navigation System (BDS), and GLONASS Satellite Navigation System (GLONASS).
  • GPS Global Positioning Satellite System
  • BDS Beidou Satellite Navigation System
  • GLONASS GLONASS Satellite Navigation System
  • the transmitting antenna of the satellite to the ground adopts the form of circular polarization.
  • the receiving antenna of the device should also adopt The same circularly polarized antenna as the transmit antenna.
  • smart wearable devices are limited by volume or industrial design, and it is difficult to realize circularly polarized antennas, but linearly polarized antennas are generally used, which leads to poor satellite positioning performance of the device and capture of motion trajectories. Not accurate enough either.
  • Embodiments of the present disclosure provide a circularly polarized antenna structure and a smart wearable device.
  • an embodiment of the present disclosure provides a circularly polarized antenna structure, which is applied to a smart wearable device, and the antenna structure includes:
  • the effective perimeter of the radiator is equal to the wavelength corresponding to the central operating frequency of the antenna structure
  • a feeding terminal one end of which is electrically connected to the radiator, and the other end is connected to the feeding module of the main board;
  • grounding terminal One end of the grounding terminal is electrically connected to the radiator, and the other end is electrically connected to the grounding module of the main board through a first capacitor.
  • connection line between the feeding terminal and the center point of the radiator is a first connection line
  • connection line between the ground terminal and the center point of the radiator is a second connection line
  • first connecting line to the second connecting line forms a first included angle ⁇
  • the first direction is the counterclockwise surrounding direction of the radiator
  • the first included angle ⁇ is 10° ⁇ 80°.
  • the annular structure of the radiator is any one of the following:
  • Circular ring Circular ring, elliptical ring, rectangular ring, triangular ring, diamond ring or polygonal ring.
  • the antenna structure is any one of the following:
  • Satellite positioning antenna Bluetooth antenna, WiFi antenna or 4G/5G antenna.
  • the capacitance value of the first capacitor is 0.2pF ⁇ 1.5pF.
  • the first included angle ⁇ is 25°, and the capacitance value of the first capacitor is 0.5pF.
  • embodiments of the present disclosure provide a smart wearable device, including the circularly polarized antenna structure according to any embodiment of the first aspect.
  • the smart wearable device is a smart watch
  • the smart watch includes:
  • the metal surface frame surrounds the edge of the open end of the casing, and the metal surface frame forms the radiator.
  • the smart watch further includes a screen assembly assembled to the open end of the housing through the metal face frame.
  • the smart wearable device is any one of the following:
  • FIG. 1 is a schematic structural diagram of a circularly polarized antenna structure according to some embodiments of the present disclosure.
  • FIG. 2 is an exploded view of the structure of a smart watch according to an embodiment of the present disclosure.
  • FIG 3 is a cross-sectional view of a smart watch in accordance with one embodiment of the present disclosure.
  • 4A-4D are graphs of current distribution changes in a circularly polarized antenna structure according to an embodiment of the present disclosure.
  • FIG. 5 is a schematic structural diagram of a circularly polarized antenna structure according to an embodiment of the present disclosure.
  • FIG. 6 is a graph of return loss of a circularly polarized antenna structure in accordance with one embodiment of the present disclosure.
  • FIG. 7 is a graph of the antenna efficiency of a circularly polarized antenna structure according to one embodiment of the present disclosure.
  • FIG. 8 is an axial ratio plot of a circularly polarized antenna structure in accordance with one embodiment of the present disclosure.
  • FIG 9 is a graph of the gain of a circularly polarized antenna structure in accordance with one embodiment of the present disclosure.
  • FIG. 10 is a radiation pattern of a circularly polarized antenna structure in the xoz plane according to one embodiment of the present disclosure.
  • FIG. 11 is a radiation pattern of a circularly polarized antenna structure in a yoz plane according to an embodiment of the present disclosure.
  • FIG. 12 is a graph of the gain of the circularly polarized antenna structure in the xoz plane according to an embodiment of the present disclosure.
  • FIG. 13 is a graph of the gain of the circularly polarized antenna structure in the yoz plane according to one embodiment of the present disclosure.
  • FIG. 14 is a cross-sectional view of a smart watch in accordance with another embodiment of the present disclosure.
  • FIG. 15 is a cross-sectional view of a smart watch in accordance with yet another embodiment of the present disclosure.
  • Circularly polarized antennas are commonly used in satellite navigation systems, because the circularly polarized waves generated by the circularly polarized antennas can be received by linearly polarized antennas in any direction, and the circularly polarized antennas can also receive any direction.
  • the incoming wave of the linearly polarized antenna has good antenna performance, so the circularly polarized antenna is generally used in satellite positioning or reconnaissance and interference.
  • Circularly polarized antennas can be divided into left-hand circular polarization (LHCP, Left-Hand Circular Polarization) antennas and right-hand circular polarization (RHCP, Right-Hand Circular Polarization) antennas.
  • LHCP left-hand circular polarization
  • RHCP Right-Hand Circular Polarization
  • the positioning systems include GPS, Beidou, GLONASS, and Galileo.
  • the satellite positioning antennas of these systems all use right-handed circularly polarized antennas.
  • the satellite positioning function can be used in various application scenarios such as motion assistance, trajectory detection, and positioning.
  • the smart wearable device is limited by the volume or industrial design, and it is difficult to realize the circularly polarized antenna. Inverted-F Antenna (Inverted-F Antenna), slot antenna, etc., but the linearly polarized antenna has low receiving efficiency for the circularly polarized wave emitted by the satellite, which leads to the poor positioning accuracy and trajectory detection performance of the smart wearable device, which is difficult to meet High-accuracy positioning requirements.
  • some smart watches in the related art use circularly polarized antennas to realize satellite positioning antennas.
  • the scheme is to feed an inverted-F antenna (IFA) under the metal ring on the upper surface of the watch, and to generate circular polarization through the coupling of another parasitic antenna unit (that is, the ground branch of the IFA) and the metal ring of the watch.
  • IFA inverted-F antenna
  • another parasitic antenna unit that is, the ground branch of the IFA
  • Antenna performance In this circular polarization design, in order to generate a ring current on the metal ring, there are special requirements for the length of the IFA antenna and parasitic antenna element: the length of the IFA and/or the parasitic antenna element needs to be close to (1/4) of the metal ring.
  • the "effective annular current” referred to here refers to that the generated annular current can circulate and rotate along the metal ring relatively uniformly with the change of the phase, so as to realize the current of the circularly polarized antenna.
  • the annular current on the metal ring is realized by the coupling between the IFA antenna unit, the parasitic antenna unit and the metal ring, the coupling gap between the IFA antenna, the parasitic antenna unit and the watch metal ring is There are higher design requirements, which increases the difficulty of antenna design.
  • the IFA antenna and the parasitic antenna unit are FPC (Flexible Printed Circuit) or LDS (Laser Direct Structuring) antennas placed on the antenna bracket, which undoubtedly occupy the limited space of the watch, which is not suitable for the limited space of the watch. Limited smart wearable devices are difficult to apply.
  • FPC Flexible Printed Circuit
  • LDS Laser Direct Structuring
  • the embodiments of the present disclosure provide a simple and effective circularly polarized antenna structure, which can be used for smart wearable devices, thereby realizing a circularly polarized antenna of the device.
  • the smart wearable device described in the following embodiments of the present disclosure may be in any form of device suitable for implementation, such as watch-type devices such as smart watches and smart bracelets; for example, smart glasses, VR glasses, AR Glass-like equipment such as glasses; wearable equipment such as smart clothing and wearing pieces; etc., which are not limited in this disclosure.
  • the circularly polarized antenna structure of the present disclosure includes a main board 100 and a ring-shaped radiator 200 .
  • the main board 100 is the main PCB board of the device, on which a processor and corresponding control circuit modules are integrated. etc. (not shown in the drawings).
  • the radiator 200 is an annular metal radiator, such as a metal ring, and the radiator 200 is disposed above or outside the main board 100 to form a gap with the main board 100 .
  • the radiator 200 is electrically connected to the mainboard 100 through the feeding terminal 110 and the grounding terminal 120 , the feeding terminal is connected to the feeding module of the mainboard 100 through the feeding point 111 , and the grounding terminal 120 is connected to the grounding module of the mainboard 100 through the first capacitor 121 , thus forming a circularly polarized antenna structure.
  • the feeding terminal 110 can bridge the gap formed between the main board 100 and the radiator 200 , that is, one end of the feeding terminal 110 is electrically connected to the radiator 200 and the other end is connected to the feeding module of the main board 100 .
  • the feeding terminal 110 and the radiator 200 may be formed separately or integrally formed, which is not limited in the present disclosure.
  • the feeding terminal 110 and the radiator 200 are integrally formed, and the free end of the feeding terminal 110 is electrically connected to the feeding module of the main board 100 through the elastic member on the main board 100 , wherein the feeding terminal 110 and the main board 100 are electrically connected.
  • the connections form the feed point 111 .
  • the ground terminal 120 can also bridge the gap formed between the main board 100 and the radiator 200 , that is, one end of the ground terminal 120 is electrically connected to the radiator 200 , and the other end is connected to the ground module of the main board 100 . It can be understood that, the ground terminal 120 and the radiator 200 may be formed separately or integrally formed, which is not limited in the present disclosure.
  • the ground terminal 120 is connected with the first capacitor 121 , and the radiator 200 is grounded through the first capacitor 121 .
  • the first capacitor 121 may be disposed on the mainboard 100 , one end of which is connected to the other end of the ground terminal 120 , and the other end is connected to the grounding module of the mainboard 100 .
  • the effective perimeter of the radiator is equal to the wavelength corresponding to the central operating frequency of the antenna structure. Therefore, when implementing antenna structures with different frequencies, it is necessary to set the effective perimeter of the radiator.
  • the length is equal to the wavelength corresponding to that frequency.
  • the physical perimeter of the radiator 200 around a circle is the effective perimeter of the radiator 200 .
  • the assembly structure around the radiator 200 and the surrounding materials will increase the effective perimeter of the radiator, that is, reduce the resonant frequency of the radiator.
  • the radiator 200 is assembled with a plastic material (eg, a plastic bracket or a nano-injected material)
  • the material will increase the effective circumference of the radiator.
  • the screen near the radiator 200 also has the effect of increasing the effective perimeter of the radiator, such as the glass cover of the screen assembly.
  • the effective perimeter of the radiator 200 is increased is the dielectric constant of the plastic material and the glass cover plate (the dielectric constant of plastic and nano-injection molding materials is generally between 2-3, and the dielectric constant of the glass cover plate is generally between 6 and 6). -8) is greater than the dielectric constant in air, the introduction of high dielectric constant material will increase the current intensity near the radiator, thereby increasing the effective circumference of the radiator 200 . That is, when the radiator 200 achieves the same resonance frequency, the actual physical circumference of the radiator 200 can be reduced. Therefore, those skilled in the art can understand that the "effective circumference" in the embodiments of the present disclosure refers to the effective electrical length when the radiator actually generates a resonant electric wave, and is not limited to be understood as the physical length.
  • At least one inventive concept of the antenna structure of the present disclosure is to directly feed the annular radiator 200 and use the grounded first capacitor 121 to draw the current generated by the radiator 200 to form a rotating annular current, thereby forming a circle polarized waves.
  • the principle and performance exploration of the circularly polarized wave will be described in detail below, and will not be described in detail here.
  • the antenna structure includes a main board and a ring-shaped radiator.
  • the feed terminal and the ground terminal are connected between the main board and the radiator, one end of the feed terminal is electrically connected to the radiator, the other end is connected to the feed module of the main board, one end of the ground terminal is electrically connected to the radiator, and the other end is It is electrically connected to the grounding template of the mainboard through the first capacitor.
  • the current of the radiator is pulled through the first capacitor, so that the ring-shaped radiator generates a rotating effective ring current, thereby forming a circularly polarized wave and realizing a circularly polarized antenna structure.
  • the circularly polarized antenna structure Compared with the linearly polarized antenna structure, the circularly polarized antenna structure has higher receiving efficiency, so that the positioning is more accurate when the satellite positioning function is realized. And by directly feeding the ring radiator, no other coupling antenna structure is required, which greatly simplifies the structure and cost of the circularly polarized antenna, and is easier to implement on smart wearable devices with small volume and space such as smart watches.
  • the smart wearable device takes a smart watch as an example
  • the antenna structure takes a satellite positioning antenna of the smart watch as an example.
  • the smart watch includes a casing, the casing includes a frame 310 and a bottom casing 320 , and electrical components such as a battery 400 and a main board 100 are placed inside the casing.
  • the frame 310 in this embodiment may be a non-metal frame made of non-metallic materials such as plastic or ceramic, or may be a metal frame made of metal materials.
  • the bottom case 320 in this embodiment can be made of a non-metallic material such as plastic, or a metal material, which is not limited in the present disclosure.
  • the open end on the upper side of the case is generally used as the display area of the watch.
  • the radiator 200 of the antenna structure is realized by the metal frame of the watch.
  • the metal face frame is arranged on the end face of the open end of the casing, that is, the metal face frame surrounds the edge of the open end of the casing. Used to assemble the screen assembly 500.
  • the metal frame is used as the radiator 200 of the antenna structure, which greatly reduces the occupation of the internal space of the watch by the antenna structure, and effectively increases the volume of the radiator, thereby greatly enhancing the radiation performance of the antenna.
  • the feeding terminal 110 and the grounding terminal 120 are integrally formed with the metal surface frame. During assembly, they are electrically connected to corresponding circuits through elastic members 130 such as elastic sheets provided on the main board 100 . module.
  • the screen assembly 500 is fixedly assembled to the open end of the housing through a metal frame.
  • the structure of the watch is simplified in FIG. 1, and only the related structure of the circularly polarized antenna is shown.
  • a circularly polarized antenna can be implemented in two ways: the first way is that the ring current generated when the effective circumference of the radiator is an integer multiple of the wavelength corresponding to the operating frequency can form circular polarization; the second way is Two mutually orthogonal line currents of equal amplitude and 90° out of phase can form circular polarization.
  • the circularly polarized antenna in this embodiment is implemented in the first way.
  • taking the GPS signal whose center operating frequency is 1.575 GHz as an example the wavelength of the GPS signal can be obtained by calculating the center operating frequency. Based on the influence of the watch case, screen and other components on the wavelength, the actual physical perimeter of the metal face frame at the effective wavelength can be designed.
  • the metal face frame whose effective perimeter is one GPS signal wavelength
  • the metal face frame is directly fed with electricity, and the first capacitor 121 is used to effectively draw the generated current, so that a single direction is formed inside the metal face frame. Rotating rotating current field.
  • Fig. 4A-Fig. 4D the current distribution of the rotating current generated by the metal face frame in one cycle is shown, and Fig. 4A-Fig. 4D are the current distribution when the phase is at 0°, 90°, 180° and 270°, respectively picture.
  • the denser the lines in the figure represent the greater the current density, and the sparser the lines represent the lower the current density. 4A-4D, it can be seen that under the action of the first capacitor 121, a ring current that rotates counterclockwise is generated inside the metal surface frame.
  • the display screen of the watch is defined as the xy plane, and the direction perpendicular to the display screen of the watch pointing to the sky is the +z direction, so that the xyz space rectangular coordinate system can be established.
  • the counterclockwise surrounding direction of the radiator 200 is defined as the first direction
  • the connection line between the feed terminal 110 and the center point of the radiator 200 is the first connection line
  • the ground terminal 120 and the radiator 200 The line connecting the center points of , is the second connecting line
  • the included angle from the first connecting line along the first direction, that is, turning counterclockwise to the second connecting line, is the first included angle ⁇ .
  • the first connection line may be a connection line between the projection of the feeding terminal 110 on the plane where the radiator 200 is located (for example, the xy plane in FIG. 5 ) and the center point of the radiator 200 on the plane.
  • the second connection line may be the connection line between the projection of the ground terminal 120 on the plane and the center point of the radiator 200 on the plane, which is not limited in the present disclosure.
  • the effective circumference of the radiator is equal to the wavelength corresponding to the operating frequency.
  • the current distribution of the resonant wave there must be two current zero points and two current zeros on the entire circumference. current peaks (also visible through Figures 4A-4D). Therefore, at a certain moment, the entire circumference can be divided into four regions according to the current distribution, namely:
  • the above current distribution is a periodic current variation distribution.
  • the periodic current distribution will periodically rotate in the annular metal frame with time, that is, the above-mentioned circularly polarized wave is formed.
  • a left-handed circularly polarized wave is generated, and when the current rotates in the counterclockwise direction in the metal surface frame, a right-handed circularly polarized wave is generated.
  • the current in the metal frame is rotated under the action of the first capacitor 121, when the first included angle , that is, the "pulling" current rotates counterclockwise; on the contrary, when the first angle , the "pull” current rotates clockwise.
  • the phase of the current across the first capacitor 121 is 90° ahead of the phase of the voltage across the first capacitor 121 in the AC circuit, so when the first included angle , the above-mentioned phase advance of 90° will cause the current on the ring radiator 200 to rotate in the counterclockwise direction, thereby realizing a right-hand circularly polarized antenna.
  • the 90° advance of the current phase at both ends of the first capacitor 121 will cause the current on the ring radiator 200 to rotate in a clockwise direction, thereby realizing a left-hand circularly polarized antenna.
  • the circular current generating the circularly polarized wave has a periodic distribution feature on the entire circumference of the ring radiator.
  • the circularly polarized antenna should satisfy the following laws: when the first clamp Horn When the current rotates counterclockwise, a right-handed circularly polarized wave is generated; and when the first included angle When the current rotates clockwise, a left-handed circularly polarized wave is generated.
  • " ⁇ " means the union of the two.
  • the first included angle ⁇ is preferably Of course, those skilled in the art can understand that in other embodiments, the first included angle ⁇ can also be set to Thus, a left-hand circularly polarized antenna is formed.
  • connection line between the feed terminal and the center point of the radiator is the first connection line
  • connection line between the ground terminal and the center point of the radiator is the second connection line
  • first connection line is the connection line between the ground terminal and the center point of the radiator.
  • the angle between the first connection line and the second connection line in the counterclockwise direction is the first included angle.
  • the antenna structure of the present disclosure can realize circularly polarized waves in different directions by adjusting the first included angle, and meet the design requirements of circularly polarized antennas in different directions.
  • the circularly polarized wave can be decomposed into two mutually orthogonal linearly polarized waves with equal amplitude and a phase difference of 90°.
  • the current zero point of the first-order mode wave corresponds to the other The current peak value of the first-order mode wave. Therefore, in order to improve the effect of the first capacitor 121 on the circular polarization, the position of the first capacitor 121 should be as far away as possible from these current zero positions, that is, the distance from the first included angle ⁇ is 0°, 90°, 180° and 270° position.
  • the satellite positioning antenna of this embodiment only considers right-handed circular polarization, and for smart watches, it is considered that there are many other devices in the watch, such as the FPC of the screen and heart rate, the side buttons of the watch, and For speakers, etc., in order to avoid the influence of these components on the antenna performance, the feeding terminal 110 and the grounding terminal 120 should be made as close as possible, so as to avoid the influence of the above-mentioned components between the feeding point and the grounding point on the antenna performance. Therefore, in one embodiment, the first included angle ⁇ is preferably 10° ⁇ 80°.
  • the first included angle is in the range of 0° to 90° to form a right-hand circularly polarized wave. Since the transmitting antenna for satellite positioning adopts a right-handed circularly polarized wave, the same The right-hand circularly polarized antenna structure for receiving can improve the antenna efficiency and positioning accuracy.
  • the first included angle is further optimized to be 10° to 80°, so that the position of the first capacitor is far away from the current zero position of the two orthogonal components of the circularly polarized wave (that is, the position where the first included angle ⁇ is 0°) or the current
  • the peak position that is, the position where the first included angle ⁇ is 90°
  • the peak position can maintain the independence of the two orthogonal component waves, thereby improving the radiation efficiency of the circularly polarized antenna and improving the antenna performance.
  • the antenna structure can be further optimized below.
  • Axial Ratio is an important parameter to characterize the performance of a circularly polarized antenna.
  • Axial ratio refers to the ratio of two orthogonal electric field components of a circularly polarized wave. The smaller the axial ratio, the better the circularly polarized performance. Conversely, a larger axial ratio indicates a worse circular polarization performance.
  • one criterion for performance of the circularly polarized antenna is that the axial ratio should be less than 3dB.
  • the capacitance value of the first capacitor, the first included angle ⁇ and the operating frequency with an axial ratio less than 3dB satisfy the following relationship:
  • the working frequency with the axial ratio less than 3dB decreases with the increase of the first included angle ⁇ ; when the first included angle ⁇ is fixed, the working frequency with the axial ratio less than 3dB decreases with increasing capacitance value.
  • the first angle ⁇ is less than 45°
  • the operating frequency with an axial ratio less than 3dB has a smaller change trend with the capacitance value of the first capacitor; on the contrary, when the first angle ⁇ is greater than 45°, the axial ratio is less than 3dB.
  • the working frequency has a large variation trend with the capacitance value of the first capacitor.
  • Capacitance (unit: pF, picofarad) can be located in 0.2pF ⁇ 1.5pF.
  • the circularly polarized antenna can be optimized by adjusting the first angle ⁇ and the capacitance value of the first capacitor.
  • the optimization goal is: the working frequency range of the antenna meets the frequency of the satellite positioning antenna, and the axis of the frequency range is at the same time. ratio below 3dB.
  • FIG. 6 shows the return loss curve of the antenna of the wristwatch of the present example when the watch is worn on the arm
  • FIG. 7 shows the antenna efficiency curve of the wristwatch of the present example when the wristwatch is worn on the arm. It can be seen from FIG. 6 and FIG. 7 that the antenna of this embodiment has good return loss and antenna efficiency in the satellite positioning frequency range (eg, 1.56-1.61 GHz, with a bandwidth of 50 MHz).
  • the axial ratio of the antenna in this embodiment is lower than 3dB in the satellite positioning frequency range, which can meet the right-hand circular polarization requirements of satellite positioning antennas such as GPS, Beidou, and GLONASS.
  • the gain of the right-handed polarized wave should be at least 10dB higher than that of the left-handed polarized wave.
  • the gain of the wave is more than 15 dB higher than that of the left-handed polarized wave, and has good right-handed circular polarization performance, which further proves that the antenna of the embodiment of the present disclosure has better antenna performance.
  • the following takes the GPS satellite positioning antenna with a center operating frequency of 1.575 GHz as an example to further illustrate the performance of the antenna.
  • Fig. 10 shows the radiation pattern of the right-handed circularly polarized wave of the antenna on the xoz plane when the wristwatch is worn on the arm
  • Fig. 11 shows the right-handed circularly polarized wave of the antenna on the yoz plane when the wristwatch is worn on the arm Radiation pattern of chemical waves.
  • the maximum gain of the antenna in this example occurs above the arm, which can just meet the three main application scenarios of the watch when the watch is worn on the arm, that is: when the wrist is raised to observe the watch, the direction of the watch (+z direction) point to the sky; in the case of running or walking, the 6 o'clock direction of the arm swing points to the sky; and the 9 o'clock direction of the arm swing points to the sky. Therefore, the example antenna has good radiation efficiency as a satellite positioning antenna, which greatly improves the antenna performance.
  • the radiation of the antenna has a good symmetry on the xoz plane, which also shows that the antenna in this example has a good consistency for wearing on the left and right hands, and can satisfy both the left and right hands. The needs of users wearing watches.
  • Figure 12 shows the gain variation curve of the antenna radiated on the xoz plane shown in Figure 10 with the angle ⁇ when the wristwatch of this example is worn on the arm
  • Figure 13 shows the antenna radiated on the yoz plane shown in Figure 11 Wave gain curve with angle ⁇ . It can be seen from Figure 12 and Figure 13 that the gain of the right-handed polarized wave and the total gain of the antenna have good consistency within the range of ⁇ of ⁇ 60° no matter on the xoz plane or the yoz plane, which further proves that The example right-hand circularly polarized antenna has good antenna performance in space, which can meet the needs of fast satellite search and accurate navigation.
  • the radiator of the above smart watch is not limited to be realized by using a metal surface frame, and can also be realized by using a metal frame, or other casing parts such as a metal middle frame.
  • the radiator 200 is provided as a part of the middle frame of the watch, that is, the radiator 200 and the frame 310 together form the middle frame structure of the watch.
  • the other structures and assembling methods of the watch in this embodiment can refer to the above, and will not be repeated.
  • the radiator 200 is arranged at the position of the middle frame, so that the volume of the radiator can be effectively increased, thereby greatly enhancing the radiation efficiency of the antenna.
  • the radiator 200 can also be implemented in any other suitable structural form, for example, the frame 310 in FIG. Frame watch structure, as shown in Figure 15.
  • the present disclosure will not repeat them.
  • the antenna structure of the present disclosure is not limited to being applied to a smart watch, but can also be any other smart wearable device suitable for implementation, such as a smart bracelet, a smart earphone, etc., which is not limited in the present disclosure.
  • the radiator can also be implemented by other structures, and the annular structure of the radiator does not need to be limited to a ring, and any other form of ring can be implemented.
  • the ring structure of the radiator may also be an elliptical ring, a rectangular ring, a rounded rectangular ring, a diamond ring, a triangular ring or other polygonal rings, which is not limited in the present disclosure.
  • the antenna structure of the present disclosure is not limited to implementing satellite positioning antennas, but can also be any other antenna types suitable for implementation, such as Bluetooth antennas, WiFi antennas, or 4G/5G antennas. If the device volume and space allow, the antenna structure of the present disclosure can be used to implement any type of circularly polarized antenna, which is not limited in the present disclosure.
  • the circularly polarized antenna structure provided by the embodiments of the present disclosure can implement a circularly polarized antenna on the smart wearable device, thereby improving the antenna receiving efficiency and antenna performance of the smart wearable device, and improving the positioning accuracy.
  • the structure of the circularly polarized antenna is simple, and there is no need to couple other structures, which greatly simplifies the structure and cost of the circularly polarized antenna, and is easier to implement on a smaller smart wearable device.
  • the antenna structure according to the embodiment of the present disclosure has better circular polarization performance, which can further improve the positioning accuracy.
  • embodiments of the present disclosure provide a smart wearable device, the smart wearable device includes the circularly polarized antenna structure in any of the above embodiments, so that a circularly polarized antenna can be implemented on the smart wearable device, and the smart wearable device can be improved.
  • Device antenna performance In a second aspect, embodiments of the present disclosure provide a smart wearable device, the smart wearable device includes the circularly polarized antenna structure in any of the above embodiments, so that a circularly polarized antenna can be implemented on the smart wearable device, and the smart wearable device can be improved.
  • Device antenna performance is provided.
  • the smart wearable device may be any wearable device suitable for implementation, such as a smart watch, a smart bracelet, a smart earphone, or smart glasses, which is not limited in the present disclosure.
  • the smart wearable device is a smart watch, and the structure of the smart watch can be realized by referring to the above-mentioned embodiments in FIG. 2 , FIG. 14 and FIG. 15 , which will not be repeated in this disclosure.
  • the smart watch includes the circularly polarized antenna structure in any of the above embodiments as a satellite positioning antenna.
  • the smart watch includes a GPS satellite positioning antenna, and the GPS satellite positioning antenna is implemented by the circularly polarized antenna structure in the above embodiment.
  • any other antenna types suitable for implementation can also be implemented, which will not be repeated in this disclosure.
  • the smart wearable device provided by the embodiments of the present disclosure includes a circularly polarized antenna structure, thereby realizing a circularly polarized antenna on the smart wearable device, improving the antenna receiving efficiency and antenna performance of the smart wearable device, and improving the positioning accuracy.
  • the structure of the circularly polarized antenna is simple, and there is no need to couple other structures, which greatly simplifies the structure and cost of the circularly polarized antenna, and is easier to implement on a smaller smart wearable device.
  • the smart wearable device according to the embodiment of the present disclosure has better performance of the circularly polarized antenna, and further improves the positioning accuracy.
  • the face frame and/or frame on the smart watch is used to form a radiator.
  • the face frame and/or frame can be used as a decorative structure for the watch to improve the aesthetics of the device; And/or the frame is used as a radiator, which can reduce the occupation of the internal space of the watch by the antenna structure, and effectively increase the volume of the radiator, thereby greatly enhancing the radiation performance of the antenna.

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Abstract

本公开涉及电子设备技术领域，具体涉及一种圆极化天线结构及智能穿戴设备。圆极化天线结构应用于智能穿戴设备，包括：主板；环形的辐射体，所述辐射体的有效周长等于所述天线结构的中心工作频率对应的波长；馈电端子，其一端与所述辐射体电性连接，另一端连接所述主板的馈电模块；以及接地端子，一端与所述辐射体电性连接，另一端通过第一电容与所述主板的接地模块电性连接。本公开天线结构可在智能穿戴设备上实现圆极化天线，提高设备的天线接收效率和天线性能，提高定位准确性。

Description

圆极化天线结构及智能穿戴设备 技术领域
本公开涉及电子设备技术领域，具体涉及一种圆极化天线结构及智能穿戴设备。
背景技术
智能穿戴设备由于其功能多样受到越来越多用户的欢迎。这些功能都需要依靠智能穿戴设备内置的天线结构来实现。
以卫星定位天线为例，随着智能穿戴设备的发展，卫星定位功能已经成为其必不可少的功能之一。常用的卫星定位系统一般包括全球卫星定位系统(GPS)、北斗卫星导航系统(BDS)、格洛纳斯卫星导航系统(GLONASS)。
为了增强卫星到地面的传输效率(例如增强穿透能力和覆盖面积等)，卫星向地面的发射天线采用圆极化的形式，同样，为了增强定位天线的接收能力，设备的接收天线也应当采用与发射天线相同的圆极化天线。然而，相关技术中，智能穿戴设备受限于体积或工业设计，难以实现圆极化天线，而是普遍采用线极化天线，这就导致设备的卫星定位性能较差，对运动轨迹的抓取也不够准确。
发明内容
本公开实施方式提供了一种圆极化天线结构及智能穿戴设备。
第一方面，本公开实施方式中提供了一种圆极化天线结构，应用于智能穿戴设备，所述天线结构包括：
主板；
环形的辐射体，所述辐射体的有效周长等于所述天线结构的中心工作频率对应的波长；
馈电端子，其一端与所述辐射体电性连接，另一端连接所述主板的馈电模块；以及
接地端子，一端与所述辐射体电性连接，另一端通过第一电容与所述主板的接地模块电性连接。
在一些实施方式中，所述馈电端子与所述辐射体的中心点的连线为第一连线，所述 接地端子与所述辐射体的中心点的连线为第二连线；沿第一方向，所述第一连线至所述第二连线形成第一夹角β；
其中，所述第一方向为所述辐射体的逆时针环绕方向，
Figure PCTCN2021112445-appb-000001
或者，
Figure PCTCN2021112445-appb-000002
在一些实施方式中，所述第一夹角β为10°～80°。
在一些实施方式中，所述辐射体的环形结构为以下任意之一：
圆形环状、椭圆环状、矩形环状、三角形环状、菱形环状或多边形环状。
在一些实施方式中，所述天线结构为以下任意之一：
卫星定位天线、蓝牙天线、WiFi天线或4G/5G天线。
在一些实施方式中，所述第一电容的电容值为0.2pF～1.5pF。
在一些实施方式中，所述第一夹角β为25°，所述第一电容的电容值为0.5pF。
第二方面，本公开实施方式提供了一种智能穿戴设备，包括根据第一方面中任一实施方式所述的圆极化天线结构。
在一些实施方式中，所述智能穿戴设备为智能手表，所述智能手表包括：
壳体，所述主板设于所述壳体内；和
金属面框，环绕设于所述壳体的敞口端的边缘，所述金属面框形成所述辐射体。
在一些实施方式中，所述智能手表还包括屏幕组件，所述屏幕组件通过所述金属面框装配于所述壳体的敞口端。
在一些实施方式中，所述智能穿戴设备为以下任意之一：
智能手环、智能手表、智能耳机或智能眼镜。
附图说明
为了更清楚地说明本公开具体实施方式或现有技术中的技术方案，下面将对具体实施方式或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本公开的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是根据本公开一些实施方式中圆极化天线结构的结构原理图。
图2是根据本公开一个实施方式中智能手表的结构爆炸图。
图3是根据本公开一个实施方式中智能手表的剖面图。
图4A-图4D是根据本公开一个实施方式中圆极化天线结构的电流分布变化图。
图5是根据本公开一个实施方式中圆极化天线结构的结构原理图。
图6是根据本公开一个实施方式中圆极化天线结构的回波损耗曲线图。
图7是根据本公开一个实施方式中圆极化天线结构的天线效率曲线图。
图8是根据本公开一个实施方式中圆极化天线结构的轴比曲线图。
图9是根据本公开一个实施方式中圆极化天线结构的增益曲线图。
图10是根据本公开一个实施方式中圆极化天线结构在xoz平面的辐射图。
图11是根据本公开一个实施方式中圆极化天线结构在yoz平面的辐射图。
图12是根据本公开一个实施方式中圆极化天线结构在xoz平面的增益曲线图。
图13是根据本公开一个实施方式中圆极化天线结构在yoz平面的增益曲线图。
图14是根据本公开另一个实施方式中智能手表的剖面图。
图15是根据本公开又一个实施方式中智能手表的剖面图。
具体实施方式
下面将结合附图对本公开的实施方式进行清楚、完整地描述，显然，所描述的实施方式是本公开一部分实施方式，而不是全部的实施方式。基于本公开中的实施方式，本领域普通技术人员在没有做出创造性劳动的前提下所获得的所有其他实施方式，都属于本公开保护的范围。此外，下面所描述的本公开不同实施方式中所涉及的技术特征只要彼此之间未构成冲突就可以相互结合。
圆极化天线较为普遍的应用于卫星导航系统中，这是由于圆极化天线所产生的圆极化波可以被任何方向的线极化天线所接收，同时圆极化天线也可以接收任何方向的线极化天线的来波，具有良好的天线性能，故卫星定位或侦察和干扰中普遍采用圆极化天线。圆极化天线可分为左旋圆极化(LHCP,Left-Hand Circular Polarization)天线和右旋圆极化(RHCP，Right-Hand Circular Polarization)天线，以卫星定位天线为例，全球主要的 卫星导航定位系统包括GPS、北斗、GLONASS、伽利略，这些系统的卫星定位天线均采用右旋圆极化天线。
随着智能穿戴设备的发展，卫星定位功能已经成为必不可少的功能之一。以智能手表为例，卫星定位功能可以用于运动辅助、轨迹检测、定位等多种应用场景。然而，相关技术中，智能穿戴设备受限于体积或工业设计，难以实现圆极化天线，在市售的相关智能穿戴设备中，其卫星定位天线多采用线极化天线来实现，例如IFA(Inverted-F Antenna，倒F天线)、缝隙天线等，但是线极化天线对卫星发射的圆极化波接收效率较低，这就导致智能穿戴设备的定位精度和轨迹检测性能较差，难以满足高准确性的定位需求。
为了解决上述问题，相关技术中的一些智能手表采用圆极化天线实现卫星定位天线。其方案是通过在手表上表面金属圈的下方对一个倒F天线(IFA)进行馈电，并通过另外一个寄生天线单元(即IFA的接地分支)和手表的金属圈进行耦合产生的圆极化天线性能。在该圆极化设计中，为了在金属圈上产生环形电流，对IFA天线和寄生天线单元的长度有特殊的要求：需要IFA和/或寄生天线单元的长度接近金属圈的(1/4)弧长左右才能达到“牵引”金属圈上的电流呈现出有效的环形电流的效果。这里所说的“有效的环形电流”指的是所产生的环形电流可以随着相位的变化较均匀地沿着金属圈循环转动，以实现该圆极化天线的电流。在该方案中因为金属圈上的环形电流都是通过IFA天线单元、寄生天线单元和金属圈之间的耦合来实现的，所以对IFA天线、寄生天线单元以及手表金属圈相互之间的耦合缝隙有较高的设计要求，这就增加了天线设计的难度。再有，在该方案中，IFA天线和寄生天线单元是被放置在天线支架上的FPC(Flexible Printed Circuit)或者LDS(Laser Direct Structuring)天线，该支架无疑侵占了手表的有限空间，对于体积受限的智能穿戴设备难以应用。
基于上述相关技术存在的缺陷，本公开实施方式提供了一种结构简单且有效的圆极化天线结构，该天线结构可用于智能穿戴设备，从而实现设备的圆极化形式的天线。可以理解的是，本公开下述实施方式中所述的智能穿戴设备，可以是任何适于实施的设备形式，例如智能手表、智能手环等watch类设备；又例如智能眼镜、VR眼镜、AR眼镜等glass类设备；再例如智能服饰、佩戴件等穿戴类设备；等，本公开对此不作限制。
如图1所示，在一些实施方式中，本公开的圆极化天线结构包括主板100和环形的辐射体200，主板100为设备主PCB板，其上集成有处理器和相应的控制电路模块等(附图未示出)。辐射体200为环形的金属辐射体，例如金属环圈，辐射体200设置在主板 100上方或外侧，从而与主板100之间形成缝隙。辐射体200与主板100通过馈电端子110和接地端子120电性相连，馈电端子通过馈电点111与主板100的馈电模块连接，接地端子120通过第一电容121连接主板100的接地模块，从而形成圆极化天线结构。
馈电端子110可以跨接于主板100和辐射体200之间形成的缝隙，也即，馈电端子110一端电性连接于辐射体200上，另一端连接于主板100的馈电模块。可以理解的是，馈电端子110和辐射体200可以是分开形成，也可以是一体成型，本公开对此无需限制。在一个示例中，馈电端子110与辐射体200一体成型，馈电端子110的自由端则通过主板100上的弹性构件与主板100的馈电模块电性连接，其中馈电端子110与主板100连接形成馈电点111。
接地端子120同样可以跨接于主板100和辐射体200之间形成的缝隙，也即，接地端子120的一端电性连接于辐射体200上，另一端连接于主板100的接地模块。可以理解的是，接地端子120和辐射体200可以是分开形成，也可以是一体成型，本公开对此无需限制。
继续参照图1，接地端子120连接有第一电容121，辐射体200通过第一电容121接地。第一电容121可设置在主板100上，其一端与接地端子120的另一端连接，另一端与主板100的接地模块连接。
对于环形辐射体的圆极化天线结构，所述辐射体的有效周长即等于所述天线结构的中心工作频率对应的波长，因此在实现不同频率的天线结构时，需要设置辐射体的有效周长等于该频率对应的波长。
值得说明的是，在自由空间下，辐射体200环绕一周的物理周长即为辐射体200的有效周长。但是在装配结构下，辐射体200周围的装配结构和其周围的材料将增大辐射体的有效周长，也即会减小辐射体的谐振频率。例如辐射体200与塑料材料(例如塑料支架或者纳米注塑材料)装配时，该材料会增加辐射体的有效周长。同时，辐射体200附近的屏幕也会起到增加辐射体有效周长的效果，例如屏幕组件的玻璃盖板等。
辐射体200的有效周长被增加的原因是塑料材料和玻璃盖板的介电常数(塑料和纳米注塑材料的介电常数一般在2-3之间，玻璃盖板的介电常数一般在6-8之间)大于空气中的介电常数，高介电常数材料的引入将增加辐射体附近的电流强度，进而增加辐射体200的有效周长。即辐射体200在实现相同谐振频率的情况下，可以减小辐射体200的实际物理周长。因此，本领域技术人员可以理解，本公开实施方式所述的“有效周长” 指的是辐射体实际产生谐振电波时的有效电长度，并不局限于理解为物理长度。
本公开天线结构的至少一个发明构思在于：通过对环形辐射体200直接馈电，并且利用接地的第一电容121对辐射体200产生的电流进行牵引，使其形成旋转的环形电流，从而形成圆极化波。对于圆极化波产生的原理和性能探究在下文进行详细说明，在此暂不详述。
通过上述可知，本公开实施方式提供的圆极化天线结构，应用于智能穿戴设备，天线结构包括主板和环形的辐射体，辐射体的有效周长等于天线结构的中心工作频率对应的波长。馈电端子和接地端子连接于主板与辐射体之间，馈电端子的一端与辐射体电性连接，另一端连接主板的馈电模块，接地端子的一端与辐射体电性连接，另一端则通过第一电容与主板的接地模板电性连接。通过第一电容实现对辐射体的电流进行牵引，使得环形辐射体产生旋转的有效环形电流，从而形成圆极化波，实现圆极化天线结构。相较线极化天线结构，圆极化天线结构的接收效率更高，从而在实现卫星定位功能时定位更加准确。并且通过对环形辐射体直接馈电，无需设置其他耦合天线结构，大大简化了圆极化天线的结构和成本，更易于在智能手表等体积空间较小的智能穿戴设备上实现。
下面结合图1至图3的一个具体实施方式，对本公开天线结构的实施以及原理进行详细说明。在本实施方式中，智能穿戴设备以智能手表为例，天线结构以智能手表的卫星定位天线为例。
如图2所示，智能手表包括壳体，壳体包括边框310和底壳320，壳体内部放置电池400和主板100等电气元件。值得说明的是，本实施方式中的边框310可为塑料或陶瓷等非金属材料制成的非金属边框，也可以为金属材料制成的金属边框。本实施方式中的底壳320即可采用塑胶等非金属材质，也可以采用金属材质制成，本公开对此不作限制。壳体上侧的敞口端一般作为手表的显示区域，在本实施方式中，天线结构的辐射体200利用手表的金属面框来实现。金属面框设置在壳体的敞口端的端面上，即，金属面框环绕设于壳体的敞口端的边缘，由于其金属质感，一方面可以起到很好的装饰作用，另一方面可以用来装配屏幕组件500。在本实施方式中，利用金属面框作为天线结构的辐射体200，还大大减少了天线结构对手表内部空间的占用，而且有效增加辐射体的体积，进而大大增强天线的辐射性能。
如图3所示，在本实施方式中，馈电端子110和接地端子120与金属面框一体成型，在装配时，通过主板100上设置的诸如弹片的弹性构件130电性连接于相应的电路模块。屏幕组件500通过金属面框固定装配于壳体的敞口端。为便于对天线结构的说明，图1 中对手表结构进行了简化，仅示出圆极化天线相关结构。
下面基于图1所示结构，对本实施方式中圆极化天线的实现原理进行说明。
首先，圆极化天线可以通过两种方式实现：第一种方式是辐射体的有效周长为工作频率对应波长的整数倍的情况下产生的环电流可以形成圆极化；第二种方式是等幅且相位相差90°的两个相互正交的线电流可以形成圆极化。本实施方式的圆极化天线正是通过第一种方式实现，在本实施方式中，以中心工作频率为1.575GHz的GPS信号为例，通过中心工作频率即可计算得到GPS信号的波长，同时基于手表壳体、屏幕等组件对于波长的影响，即可设计出在有效波长情况下的金属面框的实际物理周长。
对于有效周长为一个GPS信号波长的金属面框，本公开实施方式中通过对金属面框直接馈电，并且利用第一电容121对产生的电流进行有效牵引，使得金属面框内部形成单方向转动的旋转电流场。
如图4A-图4D所示，示出了金属面框产生的旋转电流在一个周期的电流分布，图4A-图4D分别是相位在0°，90°，180°和270°时的电流分布图。图中线条越密集的地方表示电流密度越大，线条越稀疏的地方表示电流密度越小。观察图4A-图4D中电流零点的位置变化即可知，在第一电容121的作用下，金属面框内部产生逆时针旋转的环形电流。在圆极化波的传播方向为+z(图4A-图4D中，垂直于纸面向外)方向时，根据右手螺旋定则，即可知逆时针旋转的环形电流所产生的圆极化波为右旋圆极化波，从而形成有效的右旋圆极化天线。
下面进一步对本实施方式的圆极化天线的天线性能及影响因素进行说明。为便于说明，定义手表的显示屏幕为xy平面，垂直于手表显示屏幕指向天空的方向为+z方向，从而可以建立xyz空间直角坐标系。再有，如图5所示，定义辐射体200的逆时针环绕方向为第一方向，馈电端子110与辐射体200的中心点的连线为第一连线，接地端子120与辐射体200的中心点的连线为第二连线，从第一连线沿第一方向，即逆时针转动至第二连线的夹角为第一夹角β。作为一个示例，所述第一连线可以为馈电端子110在辐射体200所在平面(例如，图5中的xy平面)的投影与辐射体200在该平面的中心点的连线，所述第二连线可以为接地端子120在所述平面的投影与辐射体200在该平面的中心点的连线，本公开对此不作限制。
如图5所示，由于环形辐射体实现圆极化的条件是辐射体的有效周长等于工作频率对应的波长，根据谐振波的电流分布可知，在整个圆周上必然存在两个电流零点和两个 电流峰值(通过图4A-图4D也可以看到)。因此在某个时刻可根据电流分布将整个圆周分为四个区域，即：
Figure PCTCN2021112445-appb-000003
在该区域中电流从0°的零值达到90°的峰值；
Figure PCTCN2021112445-appb-000004
在该区域中电流从90°的峰值降至180°的零值；
Figure PCTCN2021112445-appb-000005
在该区域中电流从180°的零值达到270°的峰值；
Figure PCTCN2021112445-appb-000006
在该区域中电流从270°的峰值降至360°的零值。
上述电流分布为一个周期的电流变化分布，在第一电容121的作用下，该周期性电流分布将随着时间在环形的金属面框中周期性旋转，也即上述的形成圆极化波。并且，电流在金属面框中沿顺时针方向旋转时，则产生左旋圆极化波，而电流在金属面框中沿逆时针方向旋转时，则产生右旋圆极化波。
进一步的，由于金属面框中的电流在第一电容121作用下产生旋转，当第一夹角
Figure PCTCN2021112445-appb-000007
时，即“牵引”电流逆时针旋转；相反，当第一夹角
Figure PCTCN2021112445-appb-000008
时，则“牵引”电流顺时针旋转。这是由于在交流电路中第一电容121两端的电流的相位比其两端电压的相位超前90°，因此当第一夹角
Figure PCTCN2021112445-appb-000009
时，上述的相位90°超前将导致环形辐射体200上的电流沿着逆时针方向旋转，进而实现右旋圆极化天线。同理，当第一夹角
Figure PCTCN2021112445-appb-000010
时，第一电容121两端的电流相位的90°超前将导致环形辐射体200上的电流沿着顺时针方向旋转，进而实现左旋圆极化天线。
同时，结合圆极化波在环形辐射体存在时，产生圆极化波的环形电流在环形辐射体整个圆周上具有一个周期分布的特征，可知圆极化天线应当满足如下规律：当第一夹角
Figure PCTCN2021112445-appb-000011
时，电流逆时针旋转，产生右旋圆极化波；而当第一夹角
Figure PCTCN2021112445-appb-000012
时，电流顺时针旋转，产生左旋圆极化波。其中，“∪”表示两者并集。
至此，考虑到卫星定位天线均采用右旋圆极化天线，因此当天线结构作为卫星定位天线时，也应当形成右旋圆极化天线。因此，作为卫星定位天线时，第一夹角β优选为
Figure PCTCN2021112445-appb-000013
当然，本领域技术人员可以理解，在其他实施方式中，第一夹角β也可以设置为
Figure PCTCN2021112445-appb-000014
从而形成左旋圆极化天线。
通过上述可知，本公开实施方式提供的圆极化天线结构，馈电端子与辐射体中心点的连线为第一连线，接地端子与辐射体中心点的连线为第二连线，第一连线至第二连线逆时针方向的夹角为第一夹角，通过调整第一夹角的大小，也即改变第一电容的位置，可实现不同方向的圆极化天线。当第一夹角为0°～90°或者180°～270°时，辐射体上电流为逆时针旋转，从而形成右旋圆极化天线；当第一夹角为90°～180°或者270°～360°时，辐射体上电流为顺时针旋转，从而形成左旋圆极化天线。本公开天线结构通过对第一夹角的调整，即可实现不同方向的圆极化波，满足不同方向圆极化天线的设计需求。
通过前述可知，圆极化波可以分解为等幅且相位相差90°的两个相互正交的线极化波，同时根据谐振波的电流分布可知，其中一阶模式电波的电流零点即对应另一阶模式电波的电流峰值。因此，为了提高第一电容121对圆极化的作用效果，应当使得第一电容121的位置尽可能远离这些电流零点位置，也即远离第一夹角β为0°、90°、180°和270°的位置。
另外，由于本实施方式的卫星定位天线仅考虑右旋圆极化，同时对于智能手表而言，考虑到手表中存在较多的其他器件，例如屏幕和心率的FPC、手表的侧边按键、以及扬声器等，为了避免这些器件对天线性能的影响，应当使得馈电端子110和接地端子120尽可能接近，从而避免上述器件位于馈电点和接地点之间对天线性能产生影响。因此，在一个的实施方式中，第一夹角β优选为10°～80°。
本公开实施方式提供的圆极化天线结构，第一夹角位于0°～90°范围内以形成右旋圆极化波，由于卫星定位的发射天线采用右旋圆极化波，因此同样采用右旋圆极化天线结构进行接收可以提高天线效率以及定位准确性。第一夹角进一步优化为10°～80°，使得第一电容的位置远离圆极化波的两个正交分量的电流零点位置(也即第一夹角β为0°的位置)或者电流峰值位置(也即第一夹角β为90°的位置)，以保持两个正交分量波的独立性，进而提高圆极化天线的辐射效率，提高天线性能。
在上述将第一夹角β的范围确定为10°～80°之后，下面可进一步对天线结构进行优化。
轴比(Axial Ratio，AR)是表征圆极化天线性能的一个重要参数，轴比是指圆极化波的两个正交电场分量的比值，轴比越小表示圆极化性能越好，相反，轴比越大表示圆极化性能越差。在本实施方式的应用场景中，圆极化天线性能的一个衡量标准是轴比应当小于3dB。
另一方面，由于本实施方式的圆极化天线的一个核心在于利用第一电容对金属面框的电流进行牵引，不同电容值大小的电容所能实现的牵引效果也存在差异。通过大量对比实验研究，第一电容的电容值大小、第一夹角β以及轴比小于3dB的工作频率满足如下关系：
当第一电容的电容值固定不变时，轴比小于3dB的工作频率随着第一夹角β的增大而降低；当第一夹角β固定不变时，轴比小于3dB的工作频率随着电容值的增加而降低。此外，当第一夹角β小于45°时，轴比小于3dB的工作频率随第一电容的电容值变化趋势较小；相反，当第一夹角β大于45°时，轴比小于3dB的工作频率随第一电容的电容值变化趋势较大。并且，当第一夹角β小于45°时可设置电容值较大的第一电容；反之，当第一夹角β大于45°时可设置电容值较小的第一电容，第一电容的容值(单位：pF，皮法)可位于0.2pF～1.5pF。
基于上述特征，可通过调整第一夹角β和第一电容的电容值来对圆极化天线进行优化，优化目标为：天线的工作频率范围满足卫星定位天线的频率，同时该频率范围的轴比低于3dB。
在一个示例中，当第一夹角β为25°，第一电容的电容值为0.5pF时，满足优化需求，即实现右旋圆极化且工作频率范围轴比低于3dB的卫星定位天线。图6示出了本示例的手表在手臂佩戴状态下天线的回波损耗曲线，图7示出了本示例的手表在手臂佩戴状态下的天线效率曲线。通过图6和图7可以看到，本实施方式的天线在卫星定位频率范围(例如，1.56-1.61GHz，带宽为50MHz)下均具有良好的回波损耗和天线效率。图8示出了本示例的手表在手臂佩戴状态下天线的轴比随频率的变化曲线，图9示出了本示例的手表在手臂佩戴状态下天线的右旋和左旋增益随频率的变化曲线。通过图8可以看到，本实施方式的天线在卫星定位频率范围下轴比均低于3dB，可以满足GPS、北斗、格洛纳斯等卫星定位天线的右旋圆极化需求。同时，对于一个性能较好的右旋圆极化天线，其右旋极化波的增益应当至少比左旋极化波的增益高10dB以上，而通过图9可知，本示例的天线右旋极化波的增益比左旋极化波的增益高出15dB以上，具有良好的右旋圆极化性能，进一步证明了本公开实施方式的天线具有更好的天线性能。
为进一步对本示例天线的性能进行说明，下面以中心工作频率为1.575GHz的GPS卫星定位天线为例，对天线性能做进一步说明。
图10示出了本示例手表在手臂佩戴状态下天线在xoz平面上右旋圆极化波的辐射图，图11示出了本示例手表在手臂佩戴状态下天线在yoz平面上右旋圆极化波的辐射图。 从图10和图11可以看出，本示例的天线最大增益出现在手臂的上方，恰好可以满足手表在手臂佩戴状态下最主要的三个应用场景，也即：抬腕观察手表时，手表方向(+z方向)指向天空；跑步或者走路情况下，手臂摆动时6点钟方向指向天空；以及手臂摆动时9点钟方向指向天空。因此，本示例天线作为卫星定位天线具有很好的辐射效率，大大提高天线性能。再有，通过图10还可以看到，天线的辐射在xoz平面上具有很好的对称性，这也说明本示例天线对左手和右手的佩戴具有较好的一致性，可以同时满足左手和右手佩戴手表的用户需求。
图12示出了本示例手表在手臂佩戴状态下，天线在图10所示的xoz平面上辐射波随角度θ的增益变化曲线，图13示出了天线在图11所示的yoz平面上辐射波随角度θ的增益变化曲线。通过图12和图13可以看到，无论在xoz平面还是yoz平面上，右旋极化波的增益和天线的总增益均在θ为±60°的范围内具有良好的一致性，也进一步证明了本示例右旋圆极化天线在空间上具有良好的天线性能，可以满足快速搜星和准确导航的需求。
上述对本公开实施方式的圆极化天线结构的结构和原理进行了详细说明，在上述实施方式的基础上，本公开还可以有其他适于实施的替代实施方式。
在一些替代实施方式中，上述智能手表的辐射体并不局限于利用金属面框来实现，也可以利用金属边框来实现，或者利用金属中框等其他壳体部分来实现。例如图14所示的实施方式中，辐射体200设置为手表中框的一部分，即辐射体200与边框310共同形成手表的中框结构。本实施方式中手表的其他结构和装配方式参见前述即可，不再赘述。本实施方式中辐射体200设置在中框位置，从而可以有效增加辐射体的体积，进而大大增强天线的辐射效率。当然，本领域技术人员可以理解，辐射体200还可以利用其他任何适于实施的结构形式实现，比如，图14中的边框310也可以构成辐射体200，从而形成仅有辐射体200的金属中框手表结构，如图15所示。对于其它类似的构成辐射体的结构，本公开对此不再赘述。
在另一些实施方式中，本公开的天线结构并不局限于应用于智能手表，还可以是其他任何适于实施的智能穿戴设备，例如智能手环、智能耳机等，本公开对此不作限制。同时可以理解，当天线结构应用于其他形式的智能穿戴设备时，辐射体也可以相应利用其他结构来实现，并且辐射体的环形结构也无需限定为圆环，其他任何形式的环形均可实现。例如在一些示例中，辐射体的环形结构还可以是椭圆环、矩形环、圆角矩形环、菱形环、三角形环或者其他多边形环，本公开对此无需限制。
在又一些替代实施方式中，本公开的天线结构也不局限于实现卫星定位天线，还可以是其他任何适于实施的天线类型，例如蓝牙天线、WiFi天线或者4G/5G天线等。在设备体积和空间允许的情况下，本公开的天线结构可以用于实现任何类型的圆极化天线，本公开对此不作限制。
通过上述可知，本公开实施方式提供的圆极化天线结构，可以在智能穿戴设备上实现圆极化天线，从而提高智能穿戴设备的天线接收效率和天线性能，提高定位准确性。并且，实现圆极化天线的结构简单，无需耦合其他结构，大大简化了圆极化天线的结构和成本，更容易在体积较小的智能穿戴设备上实现。再有，根据本公开实施方式的天线结构具有更好的圆极化性能，可进一步提高定位准确性。
第二方面，本公开实施方式提供了一种智能穿戴设备，该智能穿戴设备包括上述任一实施方式中的圆极化天线结构，从而可以在智能穿戴设备上实现圆极化天线，提高智能穿戴设备天线性能。
智能穿戴设备可以是任何适于实施的穿戴设备，例如智能手表、智能手环、智能耳机或智能眼镜等，本公开对此不作限制。
在一个示例中，智能穿戴设备为智能手表，智能手表的结构可参见上述图2、图14和图15的实施方式实现，本公开对此不再赘述。智能手表包括上述任一实施方式中的圆极化天线结构作为卫星定位天线。在一个示例中，智能手表包括GPS卫星定位天线，该GPS卫星定位天线通过上述实施方式中的圆极化天线结构实现。当然，还可以实现其他任何适于实施的天线类型，本公开对此不再赘述。
通过上述可知，本公开实施方式提供的智能穿戴设备，包括圆极化天线结构，从而在智能穿戴设备上实现圆极化天线，提高智能穿戴设备的天线接收效率和天线性能，提高定位准确性。并且，实现圆极化天线的结构简单，无需耦合其他结构，大大简化了圆极化天线的结构和成本，更容易在体积较小的智能穿戴设备上实现。再有，根据本公开实施方式的智能穿戴设备具有更好的圆极化天线性能，进一步提高定位准确性。并且，智能穿戴设备为智能手表时，利用智能手表上的面框和/或边框形成辐射体，一方面面框和/或边框可以作为手表装饰结构，提高设备美观度；另一方面利用面框和/或边框作为辐射体，可以减少天线结构对手表内部空间的占用，而且有效增加辐射体的体积，进而大大增强天线的辐射性能。
显然，上述实施方式仅仅是为清楚地说明所作的举例，而并非对实施方式的限定。 对于所属领域的普通技术人员来说，在上述说明的基础上还可以做出其它不同形式的变化或变动。这里无需也无法对所有的实施方式予以穷举。而由此所引伸出的显而易见的变化或变动仍处于本公开的保护范围之中。

Claims (10)

  1. 一种圆极化天线结构，应用于智能穿戴设备，所述天线结构包括：
    主板；
    环形的辐射体，所述辐射体的有效周长等于所述天线结构的中心工作频率对应的波长；
    馈电端子，其一端与所述辐射体电性连接，另一端连接所述主板的馈电模块；以及
    接地端子，一端与所述辐射体电性连接，另一端通过第一电容与所述主板的接地模块电性连接。
  2. 根据权利要求1所述的天线结构，其中，所述馈电端子与所述辐射体的中心点的连线为第一连线，所述接地端子与所述辐射体的中心点的连线为第二连线；沿第一方向，所述第一连线至所述第二连线形成第一夹角β；
    其中，所述第一方向为所述辐射体的逆时针环绕方向，
    Figure PCTCN2021112445-appb-100001
    或者，
    Figure PCTCN2021112445-appb-100002
  3. 根据权利要求2所述的天线结构，其中，所述第一夹角β为10°～80°。
  4. 根据权利要求1至3任一项所述的天线结构，其中，所述辐射体的环形结构为以下任意之一：
    圆形环状、椭圆环状、矩形环状、三角形环状、菱形环状或多边形环状。
  5. 根据权利要求1至3任一项所述的天线结构，其中，所述天线结构为以下任意之一：
    卫星定位天线、蓝牙天线、WiFi天线或4G/5G天线。
  6. 根据权利要求1至3任一项所述的天线结构，其中，
    所述第一电容的电容值为0.2pF～1.5pF。
  7. 一种智能穿戴设备，包括根据权利要求1至6任一项所述的圆极化天线结构。
  8. 根据权利要求7所述的智能穿戴设备，其中，所述智能穿戴设备为智能手表，所述智能手表包括：
    壳体，所述主板设于所述壳体内；和
    金属面框，环绕设于所述壳体的敞口端的边缘，所述金属面框形成所述辐射体。
  9. 根据权利要求8所述的智能穿戴设备，其中，
    所述智能手表还包括屏幕组件，所述屏幕组件通过所述金属面框装配于所述壳体的敞口端。
  10. 根据权利要求7所述的智能穿戴设备，其中，所述智能穿戴设备为以下任意之 一：
    智能手环、智能手表、智能耳机或智能眼镜。
PCT/CN2021/112445 2020-08-18 2021-08-13 圆极化天线结构及智能穿戴设备 WO2022037485A1 (zh)

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