Coupled feed metalized frame circularly polarized watch antenna

Abstract

The invention discloses a coupled feed metalized frame circularly polarized watch antenna, which comprises a metalized frame, a circuit board and a feed terminal, and is characterized in that the metalized frame surrounds the periphery of the circuit board, grooves are formed in the metalized frame close to the left and right frames of the circuit board and have a pair of degenerate modes, and a metal floor is arranged on the lower layer of the circuit board and is provided with a feed terminal. A gap is formed between the first coupling excitation unit and the metalized frame, on the upper layer of the circuit board, the first coupling excitation unit and the second coupling excitation unit are close to the upper frame and the right frame of the circuit board respectively, and the first lumped inductor and the second lumped inductor are arranged on the first coupling excitation unit and the second coupling excitation unit respectively; the micro-strip power division structure is connected with the first coupling excitation unit, and the micro-strip power division structure is connected with the second coupling excitation unit; one end of the feed terminal is connected with the microstrip power division structure, and the other end is connected with the metal floor. The groove is loaded on the metalized frame to realize circular polarization, satellite signals can be received in a lossless manner, multipath interference is reduced, and satellite positioning precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of watch antennas, and in particular to a coupled-feed metallized frame circularly polarized watch antenna. Background Art

[0002] With the rapid development of wireless communication technology and the emergence of integrated circuit technology and high-performance, low-power chips, satellite positioning and motion trajectory recording in mobile terminal devices have become important functions of these devices. This requires the use of satellite communication systems. Circularly polarized waves can effectively avoid the Faraday rotation effect when passing through the ionosphere of the Earth's atmosphere. Therefore, satellites use circularly polarized waves to transmit signals to the ground.

[0003] However, due to limitations in size or industrial design, mobile terminal devices have typically used linearly polarized antennas to receive circularly polarized signals transmitted by satellites. This inherently results in a 3dB energy loss and low transmission efficiency. Furthermore, after the circularly polarized waves transmitted by the satellite reach the ground, they undergo multipath reflections and are transformed into waves with opposite rotational directions before being received by the user terminal, potentially leading to misjudgment of position and decreased positioning accuracy. Therefore, designing and researching miniaturized circularly polarized antennas for satellite positioning on wearable terminal devices has practical application value.

[0004] The basic principle of circular polarization is the existence of two orthogonal currents with equal amplitude but a 90-degree phase difference. For a metal-framed watch, the annular metal frame acts as a radiator. The ring itself has a pair of mutually orthogonal degenerate modes, but generally does not have a 90-degree phase difference. Therefore, in addition to exciting these two modes separately through two ports, an additional phase-shifting network is required to provide the required phase difference, which increases the complexity of the entire feed network. Summary of the Invention

[0005] In order to overcome the defects and shortcomings of the prior art, the present invention provides a coupled-fed metallized frame circularly polarized watch antenna. The present invention makes full use of the structure of the metal frame itself to achieve self-phase shift, and the size of the groove can be adjusted to adapt to the operating frequency movement and circular polarization performance deterioration caused by changes in the overall size of the watch, thereby increasing the freedom of antenna design, and has the advantages of easy integration, meeting the circular polarization performance requirements of metal frame terminal equipment, and high radiation efficiency.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a coupled-feed metallized frame circularly polarized watch antenna, comprising: a metallized frame, a circuit board and a feed terminal;

[0008] The metallized frame surrounds the periphery of the circuit board, the upper layer of the circuit board is provided with a first coupling excitation unit, a second coupling excitation unit, a first lumped inductor, a second lumped inductor and a microstrip power splitter structure, the lower layer of the circuit board is provided with a metal floor, and a gap is provided between the metal floor and the metallized frame;

[0009] The metalized frame is provided with grooves on the left and right frames close to the circuit board, and has a pair of degenerate modes;

[0010] The first coupling excitation unit is close to the upper frame of the circuit board and is used to excite the first mode of the degenerate mode;

[0011] The second coupling excitation unit is close to the right frame of the circuit board and is used to excite the second mode of the degenerate mode;

[0012] The first lumped inductor is provided on the first coupling excitation unit, and the second lumped inductor is provided on the second coupling excitation unit;

[0013] The microstrip power division structure is connected to the first coupling excitation unit, and the microstrip power division structure is connected to the second coupling excitation unit;

[0014] One end of the feeding terminal is connected to the microstrip power dividing structure, and the other end is connected to the metal floor.

[0015] As a preferred technical solution, the first coupling excitation unit and the second coupling excitation unit have the same shape.

[0016] As a preferred technical solution, the first coupling excitation unit and the second coupling excitation unit have the same shape, both are T-shaped, and both are provided with horizontal branches parallel to the frame and vertical branches perpendicular to the frame;

[0017] The horizontal branch of the first coupling excitation unit is parallel to the upper frame of the circuit board, and a gap is provided between the horizontal branch and the upper frame. The vertical branch of the first coupling excitation unit is connected in series with the first lumped inductor.

[0018] The horizontal branch of the second coupling excitation unit is parallel to the right frame of the circuit board, with a gap between the horizontal branch and the right frame. The vertical branch of the second coupling excitation unit is connected in series with the second lumped inductor.

[0019] As a preferred technical solution, the vertical branches of the first coupling excitation unit are provided with slots for connecting the first lumped inductor in series, and the vertical branches of the second coupling excitation unit are provided with slots for connecting the second lumped inductor in series.

[0020] As a preferred technical solution, the microstrip power splitter structure adopts a T-shaped structure, including an input end, a first output end and a second output end, the input end is connected to one end of the feed terminal, the first output end is connected to the first coupling excitation unit, and the second output end is connected to the second coupling excitation unit.

[0021] As a preferred technical solution, the feed terminal adopts a coaxial line, the outer conductor of the coaxial line is connected to the metal floor, and the inner conductor of the coaxial line is connected to the microstrip power splitter structure.

[0022] As a preferred technical solution, the metallized frame is provided with grooves on the left and right frames close to the circuit board, and the grooves are provided with symmetrical distribution.

[0023] As a preferred technical solution, the antenna operates in the L1 frequency band of the GPS satellite positioning system, and the metallized frame has a pair of degenerate modes in the L1 frequency band of GPS.

[0024] As a preferred technical solution, the electrical length of the perimeter of the metallized frame corresponds to a wavelength of the operating frequency of the first mode and the second mode antenna.

[0025] The present invention also provides a smart watch device, which is provided with the above-mentioned coupled-feed metallized frame circularly polarized watch antenna.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] The present invention realizes circular polarization by adding grooves on the metallized frame, making full use of the structure of the metallized frame itself to realize self-phase shift, avoiding the use of a complex and large-sized feeding phase shift network, and facilitating integration into a watch to receive satellite signals more losslessly, reduce multipath interference, and improve satellite positioning accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic top view of the coupled-feed metallized frame circularly polarized watch antenna of the present invention;

[0029] Figure 2 This is a bottom-up schematic diagram of the coupled-feed metallized frame circularly polarized watch antenna of the present invention;

[0030] Figure 3 This is a schematic diagram of the overall structure of the coupled-feed metallized frame circularly polarized watch antenna of the present invention;

[0031] Figure 4 Schematic diagram of current distribution of a pair of degenerate modes of the annular metal frame of the present invention;

[0032] Figure 5 Schematic diagram of the electric field distribution of a pair of degenerate modes of the annular metal frame of the present invention;

[0033] Figure 6 The S of the metal frame circular polarization watch antenna coupled with feeding of the present invention is 11 Schematic diagram of the curve;

[0034] Figure 7 Schematic diagram of the axial ratio curve of the coupled-fed metallized frame circularly polarized watch antenna of the present invention;

[0035] Figure 8 Schematic diagram of the efficiency curve of the coupled-fed metallized frame circularly polarized watch antenna of the present invention;

[0036] Figure 9 Schematic diagram of the current change of the antenna in one cycle;

[0037] Figure 10 is the radiation pattern of the plane antenna with phi = 0 at 1.575 GHz;

[0038] Figure 11 The axial ratio distribution diagram of the phi=0 planar antenna at 1.575GHz;

[0039] Figure 12 This is the axial ratio distribution diagram of the phi=90° planar antenna at 1.575GHz.

[0040] Among them, 1-metallized frame, 2-circuit board, 3-square metal floor, 4-gap, 5-first groove, 6-second groove, 7-third groove, 8-fourth groove, 9-first coupling excitation unit, 10-second coupling excitation unit, 11-first lumped inductor, 12-second lumped inductor, 13-microstrip power divider structure, 14-feed terminal. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0042] Example

[0043] like Figure 1-Figure 3 As shown, this embodiment provides a coupled-feed metallized frame circularly polarized watch antenna, which is suitable for smart terminal devices, especially smart watch devices with metal frames. The watch antenna includes: a metallized frame 1, a circuit board 2 and a feed terminal 14;

[0044] A metallized frame 1 surrounds a circuit board 2. The circuit board 1 includes a dielectric layer and metal layers printed on both sides of the dielectric layer. The upper metal layer is printed with a first coupling excitation unit 9, a second coupling excitation unit 10, a first lumped inductor 11, a second lumped inductor 12, and a microstrip power divider structure 13. The lower metal layer serves as a square metal floor 3. There is a certain gap 4 between the square metal floor 3 and the metallized frame 1, and there is no direct electrical connection.

[0045] In this embodiment, the metalized frame 1 can be formed by assembling four vertical copper-clad dielectric plates, each of which has one side covered with copper. Together, the four metal rectangular strips form a complete square ring. Alternatively, a continuous metal ring structure can be formed by directly using a ring of pure metal with a certain thickness.

[0046] In this embodiment, the circuit board 2 is a printed circuit board (PCB) for carrying circuits and electronic components;

[0047] In this embodiment, the first coupling excitation unit 9 and the second coupling excitation unit 10 have the same shape, both of which are T-shaped and consist of horizontal branches parallel to the frame and vertical branches perpendicular to the frame. The first coupling feeding unit 9 is close to the upper frame for exciting the first mode, and the second coupling feeding unit 10 is close to the right frame for exciting the second mode. The sizes of the first coupling feeding unit and the second coupling feeding unit are adjustable, and the length and width of the T-shape can be adjusted to obtain optimal impedance matching and circular polarization performance.

[0048] Specifically, the horizontal branches of the first coupling excitation unit 9 are parallel to the upper frame of the circuit board with a certain gap, and a small gap is opened on its vertical branches, and the first lumped inductor 11 is connected in series to compensate for the capacitance brought by the first coupling excitation unit to the input impedance and improve the impedance matching characteristics;

[0049] The second coupling excitation unit 10 is perpendicular to the first coupling excitation unit 9, and its horizontal branch is parallel to the right frame of the circuit board. There is also a certain gap between them. A second lumped inductor 12 is also connected in series with the vertical branch to compensate for the capacitance of the second coupling excitation unit to the input impedance and improve the impedance matching characteristics.

[0050] In this embodiment, one end of the feed terminal 14 is connected to the input end of the microstrip power splitter structure 13, and the other end is connected to the square metal ground through the circuit board. The feed terminal 14 is divided into two signals with equal amplitude and phase through the T-shaped microstrip power splitter structure, and is fed to the vertical branch ends of the first coupling excitation unit and the second coupling excitation unit respectively.

[0051] Specifically, the feeding terminal is preferably a 50Ω coaxial line, the outer conductor of the coaxial line is connected to the square metal floor 3, and the inner conductor passes through the circuit board 2 and is connected to the microstrip power splitter structure 13, and then is divided into two microstrip lines respectively connected to the vertical branches of the first coupling excitation unit 9 and the second coupling excitation unit 10;

[0052] The antenna of this embodiment is used for satellite positioning and navigation, and operates in the L1 frequency band of the GPS satellite positioning system. The metallized frame has a pair of degenerate modes near the L1 frequency band of the GPS, represented by the first mode and the second mode, as shown in FIG. Figure 4As shown, this pair of degenerate modes has a circular current distribution, and the currents of the two are orthogonal to each other. The electrical length of the perimeter of the metallized frame corresponds to one wavelength of the operating frequency of the first mode and the second mode antenna;

[0053] In this embodiment, the metallized frame has symmetrically distributed grooves. Specifically, four grooves are symmetrically arranged on the metallized frame, namely a first groove 5, a second groove 6, a third groove 7, and a fourth groove 8. The four grooves are only distributed on two sides. The grooves separate the degenerate modes of the metallized frame, causing the two modes to have a 90° phase difference. The grooves are only distributed on the left and right bezels of the watch, where the current of the first mode is stronger. The grooves extend the current path. Therefore, the groove loading can mainly shift the first mode to a low frequency, while the second mode remains unchanged, thereby generating a phase difference between the two modes.

[0054] In this embodiment, the antenna is excited by coupling feeding. The coupling feeding unit needs to be loaded at a position where the mode electric field is strong to better excite the corresponding mode. Figure 5 As shown, the electric field distribution of the two modes is obtained. In the electromagnetic field, the location of strong current corresponds to the electric field zero point, and the location of strong electric field corresponds to the current zero point. Modifying the mode characteristics requires modifying the structure where the current is strong, and excitation requires the location of strong electric field. The two modes are orthogonal, so the current zero point of the first mode is located at the upper and lower frames, and the current zero point of the second mode is located at the left and right frames. Therefore, the groove is loaded on the left and right frames, and the two coupling units need to be placed on two adjacent edges to excite the two modes respectively.

[0055] In this embodiment, the size of the groove can be adjusted to control the degree of mode separation. Deepening the groove and widening the groove width will result in a greater degree of mode separation and a larger phase difference. Reasonable control of the groove size can make the two modes of the metallized annular frame have a 90° phase difference in the target operating frequency band, thereby achieving optimal circular polarization performance.

[0056] In this embodiment, the watch has an overall size of 41.1 mm x 41.1 mm. The thickness of the metalized frame and circuit board is 0.8 mm. The dielectric material is FR-4 sheet material with a dielectric constant of 4.3 and a loss tangent of 0.02. The circuit board 2 measures 39.5 mm x 39.5 mm, the metal floor 3 measures 37.75 mm x 37.75 mm, and the gap 4 between the square metal floor 3 and the metalized frame 1 is 1.75 mm wide.

[0057] The watch antenna of this embodiment uses its metallized frame as a radiator, and by introducing a groove structure on the frame, a metallized square ring radiator with a groove is formed. Circular polarization is achieved through self-phase shift, which can be used for GPS satellite positioning and navigation, maximizing the use of the watch's own structure, and the antenna has a high radiation efficiency.

[0058] like Figure 6 As shown, the antenna's |S 11 |Simulation results. As can be seen from the figure, the antenna operates in the GPS L1 frequency band, with a center frequency of 1.575GHz, a -6dB impedance bandwidth of 201.8MHz, and a relative bandwidth of 12.8%.

[0059] like Figure 7 As shown in the figure, the axial ratio simulation results of the antenna are obtained. It can be seen from the figure that the 3dB axial ratio bandwidth of the antenna is 25.7MHz, the relative axial ratio bandwidth is 1.6%, and the optimal axial ratio at 1.575GHz is 0.42dB;

[0060] like Figure 8 As shown in the figure, the efficiency simulation results of the antenna are obtained. It can be seen from the figure that the antenna can achieve an efficiency higher than 62% in the GPS L1 band, and 62.8% at the frequency of 1.575GHz;

[0061] like Figure 9 As shown, the current distribution within one cycle of the antenna is obtained, which rotates counterclockwise and realizes right-hand circular polarization.

[0062] like Figure 10 As shown in the figure, the simulation results of the left-hand gain and right-hand gain of the antenna at 1.575GHz in the phi=0 plane are obtained. Figure 10 It can be seen that the antenna radiates right-hand circularly polarized waves upward. The right-hand gain and left-hand gain just above the center frequency are 0.98 dBic and -34.28 dBic, respectively, and the cross-polarization ratio is greater than 33.3 dB.

[0063] like Figure 11 and Figure 12 As shown, the axial ratio distribution simulation results of the antenna at 1.575 GHz in the planes of phi = 0 and phi = 90° are obtained. As can be seen from the figure, the antenna has a 3dB axial ratio beamwidth of 104°.

[0064] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A coupled-fed metallized frame circularly polarized watch antenna, characterized in that: include: Metallized frame, circuit board and feed terminals; The metallized frame surrounds the periphery of the circuit board, the upper layer of the circuit board is provided with a first coupling excitation unit, a second coupling excitation unit, a first lumped inductor, a second lumped inductor and a microstrip power splitter structure, the lower layer of the circuit board is provided with a metal floor, and a gap is provided between the metal floor and the metallized frame; The metalized frame is provided with grooves on the left and right frames close to the circuit board, and has a pair of degenerate modes; The first coupling excitation unit is close to the upper frame of the circuit board and is used to excite the first mode of the degenerate mode; The second coupling excitation unit is close to the right frame of the circuit board and is used to excite the second mode of the degenerate mode; The first lumped inductor is provided on the first coupling excitation unit, and the second lumped inductor is provided on the second coupling excitation unit; The microstrip power division structure is connected to the first coupling excitation unit, and the microstrip power division structure is connected to the second coupling excitation unit; One end of the feeding terminal is connected to the microstrip power dividing structure, and the other end is connected to the metal floor.

2. The coupled-fed metallized frame circularly polarized watch antenna according to claim 1, characterized in that: The first coupling excitation unit and the second coupling excitation unit have the same shape.

3. The coupled-fed metallized frame circularly polarized watch antenna according to claim 2, characterized in that: The first coupling excitation unit and the second coupling excitation unit have the same shape, both are T-shaped, and both are provided with horizontal branches parallel to the frame and vertical branches perpendicular to the frame; The horizontal branch of the first coupling excitation unit is parallel to the upper frame of the circuit board, and a gap is provided between the horizontal branch and the upper frame. The vertical branch of the first coupling excitation unit is connected in series with the first lumped inductor. The horizontal branch of the second coupling excitation unit is parallel to the right frame of the circuit board, with a gap between the horizontal branch and the right frame. The vertical branch of the second coupling excitation unit is connected in series with the second lumped inductor.

4. The coupled-fed metallized frame circularly polarized watch antenna according to claim 3, characterized in that: The vertical branches of the first coupling excitation unit are provided with slots for connecting in series with a first lumped inductor, and the vertical branches of the second coupling excitation unit are provided with slots for connecting in series with a second lumped inductor.

5. The coupled-fed metallized frame circularly polarized watch antenna according to claim 1, characterized in that: The microstrip power splitter structure adopts a T-shaped structure, including an input end, a first output end and a second output end. The input end is connected to one end of the feed terminal, the first output end is connected to the first coupling excitation unit, and the second output end is connected to the second coupling excitation unit.

6. The coupled-fed metallized frame circularly polarized watch antenna according to claim 1, characterized in that: The feeding terminal adopts a coaxial line, the outer conductor of the coaxial line is connected to the metal floor, and the inner conductor of the coaxial line is connected to the microstrip power dividing structure.

7. The coupled-fed metallized frame circularly polarized watch antenna according to claim 1, characterized in that: The metalized frame is provided with grooves on the left and right frames close to the circuit board, and the grooves are provided with symmetrical distribution.

8. The coupled-fed metallized frame circularly polarized watch antenna according to claim 1, characterized in that: The antenna operates in the L1 frequency band of the GPS satellite positioning system, and the metallized frame has a pair of degenerate modes in the L1 frequency band of the GPS.

9. The coupled-fed metallized frame circularly polarized watch antenna according to claim 1, characterized in that: The electrical length of the perimeter of the metalized frame corresponds to a wavelength of the operating frequency of the first mode and the second mode antenna.

10. A smart watch device, characterized in that: A coupled-fed metallized frame circularly polarized watch antenna as described in any one of claims 1 to 9 is provided.

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