WO2020119349A1 - 天线结构及通信终端 - Google Patents

天线结构及通信终端 Download PDF

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Publication number
WO2020119349A1
WO2020119349A1 PCT/CN2019/116599 CN2019116599W WO2020119349A1 WO 2020119349 A1 WO2020119349 A1 WO 2020119349A1 CN 2019116599 W CN2019116599 W CN 2019116599W WO 2020119349 A1 WO2020119349 A1 WO 2020119349A1
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WO
WIPO (PCT)
Prior art keywords
antenna
capacitor
antenna radiator
tuning circuit
frequency band
Prior art date
Application number
PCT/CN2019/116599
Other languages
English (en)
French (fr)
Inventor
李日辉
蒋锐
侯梓鹏
Original Assignee
维沃移动通信有限公司
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
Application filed by 维沃移动通信有限公司 filed Critical 维沃移动通信有限公司
Publication of WO2020119349A1 publication Critical patent/WO2020119349A1/zh
Priority to US17/344,899 priority Critical patent/US11967780B2/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/50—Structural association of antennas with earthing switches, lead-in devices or lightning protectors
    • 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
    • H01Q9/0442—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with particular tuning means
    • 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
    • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
    • H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
    • H01Q1/242—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use
    • H01Q1/243—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use with built-in antennas
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • 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
    • H01Q5/10—Resonant antennas
    • 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
    • H01Q5/20—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements characterised by the operating wavebands
    • H01Q5/28—Arrangements for establishing polarisation or beam width over two or more different wavebands
    • 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
    • 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
    • H01Q5/335—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 at the feed, e.g. for impedance matching
    • 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
    • H01Q9/0414—Substantially flat resonant element parallel to ground plane, e.g. patch antenna in a stacked or folded configuration
    • 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
    • H01Q9/30—Resonant antennas with feed to end of elongated active element, e.g. unipole
    • H01Q9/42—Resonant antennas with feed to end of elongated active element, e.g. unipole with folded element, the folded parts being spaced apart a small fraction of the operating wavelength

Definitions

  • the embodiments of the present disclosure relate to the field of communication technologies, and in particular, to an antenna structure and a communication terminal.
  • the communication terminal may be provided with two independent antennas, one is a low-frequency antenna, covering a frequency range of 0.7 to 0.96 GHz (Gigahertz); the other is a mid- and high-frequency antenna, covering a frequency range of 1.71 to 2.69 GHz.
  • Embodiments of the present disclosure provide an antenna structure and a communication terminal, to solve the problem that the impedance mismatch loss of the antenna in the related art is large, resulting in poor transmission efficiency of the antenna.
  • an embodiment of the present disclosure provides an antenna structure that is applied to a communication terminal, and the antenna structure includes: an antenna radiator, a signal source, a first capacitor, and a first tuning circuit;
  • the first end of the antenna radiator is grounded
  • Both the first end of the first capacitor and the first end of the first tuning circuit are electrically connected to the connection point of the antenna radiator, and the second end of the first capacitor is electrically connected to the signal source, The second end of the first tuning circuit is grounded;
  • the antenna impedance of the first end of the first capacitor at the target frequency point is located in the first quadrant of the Smith chart, and the target frequency point is at least part of the frequency points in the frequency band covered by the antenna radiator.
  • an embodiment of the present disclosure also provides a communication terminal including the antenna structure provided by the embodiment of the present disclosure as described above.
  • the antenna structure includes: an antenna radiator, a signal source, a first capacitor, and a first tuning circuit; the first end of the antenna radiator is grounded; the first end of the first capacitor and the The first end of the first tuning circuit is electrically connected to the connection point of the antenna radiator, the second end of the first capacitor is electrically connected to the signal source, and the second end of the first tuning circuit is grounded; Wherein, the antenna impedance of the first end of the first capacitor at the target frequency point is located in the first quadrant of the Smith chart, and the target frequency point is at least part of the frequency points in the frequency band covered by the antenna radiator.
  • the antenna impedance of the first end of the first capacitor at the target frequency point is located on the basis of the first quadrant of the Smith chart. Feeding through the high impedance of the first capacitor, on the one hand, can make the antenna structure generate new The resonant mode of the antenna optimizes the resonance mode excited by the antenna structure; on the other hand, the antenna impedance of the second end of the first capacitor can be matched to the matching point close to the Smith chart, which can improve the impedance mismatch loss of the antenna and reduce Impedance mismatch loss can further improve the transmission efficiency of the antenna.
  • FIG. 1a is one of the schematic diagrams of the antenna structure provided by the embodiment of the present disclosure.
  • 1b is a second schematic diagram of an antenna structure provided by an embodiment of the present disclosure.
  • 1c is a third schematic diagram of an antenna structure provided by an embodiment of the present disclosure.
  • 1d is a fourth schematic diagram of an antenna structure provided by an embodiment of the present disclosure.
  • FIG. 2 is a schematic diagram of a Smith chart provided by an embodiment of the present disclosure
  • 3a is a fifth schematic diagram of an antenna structure provided by an embodiment of the present disclosure.
  • 3b is a sixth schematic diagram of an antenna structure provided by an embodiment of the present disclosure.
  • FIG. 4 is a seventh schematic diagram of an antenna structure provided by an embodiment of the present disclosure.
  • FIG. 5 is a schematic diagram 8 of an antenna structure provided by an embodiment of the present disclosure.
  • FIG. 6 is a schematic diagram 9 of an antenna structure provided by an embodiment of the present disclosure.
  • FIG. 7 is a schematic diagram of antenna standing wave ratio coverage provided by an embodiment of the present disclosure.
  • FIG. 8a is a second schematic diagram of a Smith chart provided by an embodiment of the present disclosure.
  • FIG. 8b is a third schematic diagram of a Smith chart provided by an embodiment of the present disclosure.
  • FIG. 9 is a schematic diagram of antenna efficiency provided by an embodiment of the present disclosure.
  • FIG. 10 is a tenth schematic diagram of an antenna structure provided by an embodiment of the present disclosure.
  • FIG. 11 is a fourth schematic diagram of a Smith chart provided by an embodiment of the present disclosure.
  • FIG. 12 is a second schematic diagram of antenna standing wave ratio coverage provided by an embodiment of the present disclosure.
  • FIG 13 is an eleventh schematic diagram of an antenna structure provided by an embodiment of the present disclosure.
  • the antenna structure may include an antenna radiator, a signal source, a first capacitor, and a first tuning circuit.
  • the antenna radiator is mainly used for antenna radiation.
  • the antenna radiator may be a low-frequency antenna radiator.
  • the frequency range covered by the low-frequency antenna radiator may include 0.7-0.96 GHz (Gigahertz).
  • the above frequency range can be divided into several frequency bands (or frequency bands): 0.7 ⁇ 0.746GHz (can be numbered as B12); 0.79 ⁇ 0.86GHz (can be numbered as B20); 0.824 ⁇ 0.894GHz (can be numbered) B5); 0.88 ⁇ 0.96GHz (may be numbered as B8), but not limited to this.
  • the antenna radiator may be a high-frequency antenna radiator.
  • the frequency range that can be covered by the high-frequency antenna radiator may include 1.71 to 2.69 GHz.
  • the above frequency range can be divided into several frequency bands: 1.71 ⁇ 1.88GHz (can be numbered as B3); 1.88 ⁇ 1.92GHz (can be numbered as B39); 1.92 ⁇ 2.17GHz (can be numbered as B1); 2.3 ⁇ 2.4GHz (can be numbered as B40); 2.5 ⁇ 2.69GHz (can be numbered as B41), but not limited to this.
  • the antenna radiator may be a metal frame or a metal shell of the communication terminal, or a metal body arranged in the communication terminal housing, and the material may be a flexible printed circuit (FPC), laser direct molding (Laser) Direct Structuring (LDS), stainless steel, magnesium alloy, etc., are not limited.
  • FPC flexible printed circuit
  • Laser laser direct molding
  • LDS Direct Structuring
  • stainless steel magnesium alloy, etc.
  • a signal source (or feed) can be used to send and receive signals to provide electromagnetic energy.
  • the first capacitor not only has the function of impedance matching, it is a high-impedance feeding element, which can cause the antenna structure to generate a new resonance mode and optimize the resonance mode excited by the antenna structure.
  • the first capacitor has a large capacitance, each resonance mode will be greatly affected, resulting in that the antenna structure cannot operate to the required frequency band. Therefore, in the embodiment of the present disclosure, optionally, the value of the first capacitor is smaller than the second specific value.
  • the value range of the first capacitor may be 0.5 picofarad to 2.7 picofarad.
  • the first capacitor may be a fixed capacitor or a variable capacitor. When the first capacitor is a variable capacitor, the resonance frequency may be further changed to increase the flexibility of the resonance frequency.
  • the resonant frequency of the resonant mode generated by connecting a small capacitor at the antenna feeding point can be lower, and can be equivalent
  • the total length of the antenna radiator is shortened, and the space occupied by the antenna structure in the communication terminal is reduced.
  • the first tuning circuit is mainly used to change the equivalent electrical length of the antenna radiator, thereby changing the resonance frequency of each resonance mode.
  • the impedance of the first tuning circuit is adjustable. In specific implementation, it may be composed of multiple switches and matching elements (such as inductors and capacitors), or may be composed of variable capacitors and inductors, which is not limited in the embodiments of the present disclosure .
  • the arrangement of the antenna radiator, the signal source, the first capacitor, and the first tuning circuit in the embodiments of the present disclosure will be described below.
  • the first end of the antenna radiator is grounded. It should be noted that the embodiments of the present disclosure do not limit the grounding method. In practical applications, the grounding method may include, but is not limited to, grounding by connecting a metal case, a motherboard ground, or a reference ground. In addition, the second end of the antenna radiator is an open end.
  • Both the first end of the first capacitor and the first end of the first tuning circuit are electrically connected to the connection point of the antenna radiator, and the second end of the first capacitor is electrically connected to the signal source, The second end of the first tuning circuit is grounded.
  • the first capacitor is connected between the connection point of the antenna radiator and the signal source; the first tuning circuit is connected between the connection point of the antenna radiator and the ground point.
  • the first end of the first capacitor and the first end of the first tuning circuit may be electrically connected to the same connection point of the antenna radiator, or different connection points, which can be determined according to actual needs, The embodiments of the present disclosure do not limit this.
  • the first end of the first capacitor is electrically connected to the first connection point of the antenna radiator, and the second end of the first tuning circuit is electrically connected to the second connection point of the antenna radiator; or , The first end of the first capacitor and the first end of the first tuning circuit are electrically connected to the same connection point of the antenna radiator.
  • the number of antenna radiator feed-in connection points can be reduced, not only This reduces the need for structural space of the antenna radiator and reduces the influence of parasitic parameters fed into the connection point.
  • the first connection point may be provided between the second end of the antenna radiator and the second connection point, or between the first end of the antenna radiator and the second connection point, depending on the actual situation The demand is determined, and the embodiment of the present disclosure does not limit this.
  • connection point of the antenna radiator if it is connected to a signal source, the connection point may be called a feeding point or a feeding point.
  • FIGS. 1a to 1d To facilitate understanding of the antenna structure of the embodiment of the present disclosure, please refer to FIGS. 1a to 1d.
  • the first end of the first capacitor and the first end of the first tuning circuit are electrically connected to different connection points of the antenna radiator.
  • the first connection point where the first end of the first capacitor is electrically connected to the antenna radiator is C
  • the second end where the second end of the first tuning circuit is electrically connected to the antenna radiator The second connection point is B.
  • the first connection point C is disposed between the first end of the antenna radiator (denoted as D in FIGS. 1a to 1d) and the second connection point B. It can be seen that in FIG. 1a, the length between the second end of the antenna radiator (marked as A in FIGS. 1a to 1d) and the second connection point B is smaller than the second end A and the antenna radiator The length between the first connection points C, that is, the length of AC is greater than the length of AB.
  • the first connection point C is disposed between the second end of the antenna radiator and the second connection point B. It can be seen that, in FIGS. 1b and 1c, the length between the second end A of the antenna radiator and the second connection point B is larger than that between the second end A of the antenna radiator and the first connection point C
  • the length of AC that is, the length of AC is less than the length of AB.
  • the difference between FIG. 1b and FIG. 1c is mainly that the first connection point C in FIG. 1b is close to the second connection point B, and the first connection point C in FIG. 1c is close to the first end A of the antenna radiator.
  • the first end of the first capacitor and the first end of the first tuning circuit are electrically connected to the same connection point of the antenna radiator, and the connection point is marked as B.
  • the antenna radiator is labeled 10
  • the signal source is labeled 20
  • the first capacitor is labeled 30, and the first tuning circuit is labeled 40.
  • the first end D of the antenna radiator 10 is grounded, and the second end A of the antenna radiator 10 may be an open end.
  • the second terminal of the first capacitor 30 is grounded through the signal source 20, and the second terminal of the first tuning circuit 40 is directly grounded.
  • the antenna radiator 10 is L-shaped, but it should be understood that the present disclosure does not limit the shape of the antenna radiator 10, as in some embodiments, the antenna radiator 10 may also be The linear type or the curved type may be specifically set according to actual needs, which is not limited in the embodiments of the present disclosure.
  • connection point B and the connection point C in FIG. 1a are only examples, and therefore the installation positions of the connection point B and the connection point C are not limited.
  • the antenna impedance of the first end of the first capacitor at the target frequency point is located in the first quadrant of the Smith chart.
  • the target frequency point is at least part of frequency points in the frequency band covered by the antenna radiator. Further, the target frequency point is at least two-thirds frequency points in each frequency band covered by the antenna radiator.
  • the pure resistance line in the Smith chart can be set as the first line, and the straight line formed by two points with a phase of 90 degrees in the outer circumference of the Smith chart can be set as the second line. After that, the four areas divided by the first line and the second line are used as the first, second, third, and fourth quadrants.
  • the first quadrant is an area with inductance and large impedance
  • the second quadrant is an area with inductance and low impedance
  • the third quadrant is an area with capacitive reactance and low impedance
  • the fourth quadrant is an area with capacitive reactance and large impedance.
  • the orthogonal point of the first line and the second line may be referred to as a matching point or a center point.
  • the matching point can be understood as: the matching impedance required by the RF system, when the antenna impedance at the second end of the first capacitor (ie, the antenna impedance at the signal source) matches the matching impedance required by the RF system, ie, the antenna at the second end of the first capacitor
  • the impedance mismatch loss of the antenna structure can be minimized and the transmission efficiency can be maximized.
  • the matching impedance required by the RF system is 50 ⁇ (ohm)
  • the impedance mismatch loss of the antenna structure can be minimized and the transmission efficiency can be maximized .
  • the antenna impedance of the first end of the first capacitor at the target frequency is located in the first quadrant of the Smith chart, which belongs to the region of inductance and large impedance, and resonance in the target frequency band The modalities are few or very poor. After that, it is further fed through the high impedance of the first capacitor.
  • the antenna structure can generate a new resonance mode, thereby optimizing the resonance mode excited by the antenna structure; on the other hand, the antenna at the second end of the first capacitor
  • the impedance matching is close to the matching point of the Smith chart, which can improve the impedance mismatch loss of the antenna, reduce the impedance mismatch loss, and thereby improve the transmission efficiency of the antenna.
  • the total length of the antenna radiator and the connection on the antenna radiator can be defined The setting position of the point is realized.
  • the value range of the total length of the antenna radiator is 3/16 wavelength to 3/8 wavelength of the center frequency point of the first frequency band in the frequency band covered by the antenna radiator;
  • a first length between the second end of the antenna radiator and a connection point electrically connected to the first tuning circuit is less than 1/4 wavelength of the second frequency band in the frequency band covered by the antenna radiator;
  • the center frequency point of the first frequency band is less than the center frequency point of any frequency band except the first frequency band in the frequency band covered by the antenna radiator; the center frequency point of the second frequency band is greater than the The center frequency point of any frequency band except the second frequency band in the frequency band covered by the antenna radiator.
  • the frequency band covered by the antenna radiator includes B3 (1.71 to 1.88 GHz), B39 (1.88 to 1.92 GHz), B1 (1.92 to 2.17 GHz), B40 (2.3 to 2.4 GHz), and B41 (2.5 to 2.69 GHz ), the first frequency band is B3 and the second frequency band is B41.
  • the first frequency band covered by the antenna radiator includes B12 (0.7 ⁇ 0.746GHz), B20 (0.79 ⁇ 0.86GHz), B5 (0.824 ⁇ 0.894GHz) and B8 (0.88 ⁇ 0.96GHz), the first frequency band is B12, the second frequency band For B8.
  • the value range of the total length of the antenna radiator is required to be the center of the first frequency band in the frequency band covered by the antenna radiator 3/16 wavelength to 3/8 wavelength of the frequency point, optionally, the total length of the antenna radiator may be required to be close to 1/4 wavelength of any frequency point in the first frequency band.
  • determining the total length of the antenna radiator in the above manner can not only expand the frequency band covered by the antenna radiator, but also, compared with the related art, the embodiments of the present disclosure can shorten the total length of the antenna radiator, thereby reducing the antenna
  • the structure takes up space in the communication terminal.
  • the first length of the antenna radiator is less than 1/4 wavelength of the second frequency band.
  • the first end of the first capacitor is electrically connected to the first connection point of the antenna radiator
  • the second end of the first tuning circuit is electrically connected to the second connection point of the antenna radiator
  • the first length between the second end of the antenna radiator and the second connection point is less than or equal to 1/4 wavelength of the second frequency band, that is, the length of AB in FIGS. 1a to 1d is less than or equal to 1/4 wavelength of the second frequency band.
  • the length of AB may be less than or equal to 1/4 wavelength at any frequency in the second frequency band.
  • determining the first length of the antenna radiator in the above manner can not only expand the frequency band covered by the antenna radiator, but also, compared with the related art, the embodiments of the present disclosure can increase the first length.
  • the absolute value of the difference between the second length of the antenna radiator and the first connection point and the total length is greater than the first specific value. That is, the second length is at least a first specific value smaller than the total length, that is, the length of AC in FIGS. 1a to 1d is at least a first specific value smaller than the length of AD.
  • the determination of the first specific value may be related to the performance type of the antenna radiator. Specifically, if the antenna radiator is a low-frequency antenna radiator, the first specific value may be 4 mm; if the antenna radiator is a mid-high frequency antenna radiator, the first specific value may be 1 mm. However, it should be understood that the present disclosure does not limit the first specific value, and the specific value may be determined according to actual needs.
  • determining the total length of the antenna radiator and the position of the connection point of the antenna radiator in the above manner helps the antenna impedance of the first end of the first capacitor at the target frequency point to be in the first quadrant of the Smith chart, Furthermore, the antenna structure can generate a new resonance mode, optimize the resonance mode excited by the antenna structure, and improve the impedance mismatch loss of the antenna.
  • the value range of the total length is 16 mm to 22 mm; the value range of the first length is 0 Mm to 12 mm; the value range of the second length is 0 mm to 18 mm;
  • the value range of the total length is 40 mm to 60 mm; the value range of the first length is 0 mm to 35 mm; the second The value range of the length is 0 mm to 50 mm.
  • the specific values of the total length, the first length, and the second length of the antenna radiator may be determined according to actual conditions, which is not limited in the embodiments of the present disclosure. However, it should be understood that the total length of the antenna radiator is always greater than the first length and the second length.
  • the value range of the total length is 18 mm to 20 mm;
  • the value range of the first length is 6 mm to 8 mm ;
  • the value range of the second length is 14 mm to 16 mm;
  • the value range of the total length is 40 mm to 60 mm; the value range of the first length is 25 mm to 30 mm; the second The value range of the length is 33 mm to 45 mm.
  • the antenna impedance of the first end of the first capacitor at the target frequency point can be located in the first quadrant of the Smith chart, and It can make the antenna structure generate a new resonance mode, optimize the resonance mode excited by the antenna structure; and improve the impedance mismatch loss of the antenna.
  • the antenna radiator is a high-frequency antenna radiator
  • the connection point where the antenna radiator is electrically connected to the first end of the first capacitor is electrically connected to the antenna radiator
  • the spacing between the connection points of the first end of a tuning circuit is less than the fourth characteristic value, such as 3mm
  • the first tuning circuit may cause the antenna impedance of the first end of the first capacitor at B40/B41 to enter the Smith chart At the junction of the first quadrant and the second quadrant, the antenna impedance of the first end of the first capacitor at the target frequency point cannot be located in the first quadrant of the Smith chart.
  • the antenna structure further includes a phase adjustment circuit; One end is electrically connected to the connection point of the antenna radiator through the phase adjustment circuit; wherein the phase adjustment range of the phase adjustment circuit includes 0.
  • FIG. 3a and FIG. 3b are identical.
  • FIG. 3a The main difference between FIG. 3a and FIG. 1a is that, in FIG. 1a, the first end of the first capacitor 30 is directly electrically connected to the first connection point C, while in FIG. 3a, the first end of the first capacitor 30 passes through The phase adjustment circuit 50 is electrically connected to the first connection point C.
  • FIG. 3b The main difference between FIG. 3b and FIG. 1d is that in FIG. 1d, the first end of the first capacitor 30 is directly electrically connected to the connection point B, while in FIG. 3b, the first end of the first capacitor 30 passes through the phase adjustment circuit 50. Electrically connected to connection point B.
  • a phase adjustment circuit may be added at the connection point electrically connected to the first end of the first capacitor.
  • the phase adjustment circuit may be implemented by only connecting a small capacitor (such as 0.3 to 0.7 pf) to ground; or, first Connect a series of small inductors and then a small capacitor (such as a series of 2 ⁇ 4nH and 0.3 ⁇ 0.7pf); or, directly lengthen the feed line between the antenna and the feed to adjust the impedance to the first quadrant.
  • the phase adjustment value of the phase adjustment circuit may be 0, that is, the phase adjustment circuit does not adjust the phase.
  • phase adjustment circuit can be selected according to the actual debugging situation.
  • present disclosure does not limit the circuit structure employed by the phase adjustment circuit to achieve a specific phase adjustment value.
  • the first end of the first capacitor and the first end of the first tuning circuit are electrically connected to the same connection point of the antenna radiator, as shown in FIG. 3b, in specific implementation, it may be at point B
  • the first tuning circuit 40 is connected first, and then the phase adjustment circuit 50 is serially connected, that is, the first tuning circuit 40 is connected between the B power and the main floor, and the phase adjustment circuit 50 is connected between the point B and the first capacitor 30.
  • the antenna impedance of the first end of the first capacitor at the target frequency point can be adjusted to the first quadrant of the Smith chart, thereby achieving the antenna impedance of the first end of the first capacitor at the target frequency point
  • the requirement in the first quadrant of the Smith chart can in turn enable the antenna structure to generate a new resonance mode, optimize the resonance mode excited by the antenna structure; and improve the impedance mismatch loss of the antenna.
  • the antenna structure further includes a second tuning circuit, the first end of the second tuning circuit and the first end of the first capacitor or the first end of the first capacitor The two ends are electrically connected, and the second end of the second tuning circuit is grounded.
  • the second tuning circuit may be used to implement double-resonant carrier aggregation (Carrier Aggregation, CA). In this way, by adding a second tuning circuit, double-resonant CA may be realized.
  • the second tuning circuit may be used to adjust the resonance frequency of the target resonance mode of the antenna structure, improve the antenna standing wave ratio of the target frequency band of the target resonance mode, and reduce the mismatch loss. In this way, with the newly added second tuning circuit, the mismatch loss can be reduced, and thus the transmission efficiency of the antenna can be improved.
  • the second tuning circuit includes a tuning element and a first matching element connected in series;
  • the first end of the first matching element is electrically connected to the first end of the first capacitor or the second end of the first capacitor; the second end of the first matching element passes through the tuning element Ground.
  • the antenna structure further includes a second tuning circuit 60 that includes a tuning element 61 and a first matching element 62 connected in series.
  • the first end of the first matching element 62 may be electrically connected to the first end of the first capacitor 30 (connected with a solid line in FIG. 4 ), or the first end of the first matching element 62 may be connected to the first capacitor 30
  • the second end of the is electrically connected (connected with a dotted line in FIG. 4); the second end of the first matching element 62 is grounded through the tuning element 61.
  • connection order of the tuning element 61 and the first matching element 62 may be reversed. That is, the embodiment of the present disclosure does not limit the series connection order of the tuning element 61 and the first matching element.
  • the tuning element is a first switch or a variable capacitor
  • the first matching element includes a second capacitor and/or a first inductor
  • first matching element is the second capacitor or the first inductor, the first end of the first matching element and the first end of the first capacitor or the first The second end of the capacitor is electrically connected;
  • the first matching element includes the second capacitor and the first inductor connected in parallel
  • the first end of the first matching element is electrically connected to the first end of the first capacitor.
  • the tuning element is a first switch
  • the first matching element includes a second capacitor and/or a first inductor; wherein, the first matching element One end is electrically connected to the first end of the first capacitor or the second end of the first capacitor; the second end of the second capacitor is electrically connected to the first switch.
  • the second tuning circuit is composed of the first switch and the second capacitor connected in series, or is composed of the first switch and the first inductor connected in series, and can be used to adjust the target resonance mode of the antenna structure.
  • the resonance frequency improves the antenna standing wave ratio of the target frequency band of the target resonance mode and reduces the mismatch loss.
  • the resonance frequency of the target resonance mode of the antenna radiator can be reduced.
  • the target resonance mode can be expressed as H2 or H3
  • the target frequency band of H2 can be B39
  • the target frequency band of H3 can be B40.
  • the tuning element is a first switch
  • the first matching element is composed of a first inductor and a second capacitor connected in parallel; wherein, the first end of the first matching element is The first end of the first capacitor is electrically connected; the second end of the second capacitor is electrically connected to the first switch.
  • the first matching element is mainly used to generate different impedance characteristics with different frequencies, and therefore, it can be referred to as a frequency-variable impedance element.
  • the second tuning circuit is composed of a first switch, and a first inductance and a second capacitor connected in parallel. Therefore, the second tuning circuit of this embodiment can be used to implement double-resonant CA.
  • the conduction state of the first tuning circuit and the first switch can be controlled so that the antenna radiator simultaneously generates two resonance modes for covering two different frequency bands at the same time.
  • the frequency band covered by the antenna radiator includes In the case of B3, B39, B1, B40, and B41, B39+B41 or B3+B40 can be covered simultaneously.
  • the first matching element may be equivalent to capacitance or high impedance (such as open circuit, very small capacitance, and large inductance).
  • the first matching element may be equivalent to a capacitance in B40 or B41, and the value range of the equivalent capacitance may be From 0.3 picofarads to 1.2 picofarads; the first matching element in B3 or B39 can be adjusted according to the resonant frequency of the new resonant mode produced by the antenna radiator, such as equivalent to high impedance (such as open circuit, very small capacitance, very Large inductance).
  • the first tuning circuit is composed of a variable capacitor; or, the first tuning circuit is composed of a variable capacitor and a fixed inductor connected in series or in parallel.
  • the first tuning circuit may be composed of an independent variable capacitor, or a variable capacitor and a fixed inductor, and the connection relationship between the variable capacitor and the fixed inductor may be series or parallel.
  • the specific value range of the variable capacitor in the first tuning circuit and the specific inductance value of the fixed inductance in the first tuning circuit are related to the operating frequency band of the antenna, which is not limited in the embodiments of the present disclosure .
  • the first tuning circuit includes a first sub-tuning circuit and a second sub-tuning circuit connected in parallel;
  • the antenna radiator when the first sub-tuning circuit is in a first working state and the second sub-tuning circuit is in a first working state, the antenna radiator generates a first resonance mode
  • the antenna radiator When the first sub-tuning circuit is in the second working state and the second sub-tuning circuit is in the first working state, the antenna radiator generates a second resonance mode
  • the antenna radiator When the first sub-tuning circuit is in the first working state and the second sub-tuning circuit is in the second working state, the antenna radiator generates a third resonance mode
  • the antenna radiator When the first sub-tuning circuit is in the second working state and the second sub-tuning circuit is in the second working state, the antenna radiator generates a fourth resonance mode
  • the resonance frequencies of the first resonance mode, the second resonance mode, the third resonance mode, and the fourth resonance mode increase in sequence. That is, F1 ⁇ F2 ⁇ F3 ⁇ F4, where F1 represents the resonance frequency of the first resonance mode, F2 represents the resonance frequency of the second resonance mode, F3 represents the resonance frequency of the third resonance mode, and F4 represents the first Resonance frequency of four resonance modes.
  • the first working state may be represented as an off state
  • the second working state may be represented as an on state, but it is not limited thereto.
  • the first resonance mode may be H1, and at this time, the antenna radiator covers B3; the second resonance mode may be H2, at this time, the antenna radiator covers B39 and B1; the third resonance mode may be H3, at this time, the antenna radiator covers B40; the fourth resonance mode may be H4, at this time, the antenna radiator covers B41.
  • the multi-band coverage of the antenna radiator can be achieved by only two sub-tuning circuits.
  • three or more sub-tuning circuits can achieve more antenna radiators.
  • the embodiments of the present disclosure can not only reduce the number of sub-tuning circuits, thereby saving the cost of the tuning circuit, but also reducing the loss of the tuning circuit and improving the antenna performance.
  • the first sub-tuning circuit includes a second switch and a second matching element;
  • the second sub-tuning circuit includes a third switch and a third matching element;
  • the antenna radiator when both the second switch and the third switch are in an off state, the antenna radiator generates the first resonance mode
  • the antenna radiator When the second switch is in an on state and the third switch is in an off state, the antenna radiator generates the second resonance mode
  • the antenna radiator When the second switch is in an off state and the third switch is in an on state, the antenna radiator generates the third resonance mode
  • the antenna radiator When both the second switch and the third switch are in a conducting state, the antenna radiator generates the fourth resonance mode.
  • the first sub-tuning circuit is composed of the second switch and the second matching element
  • the second sub-tuning circuit is composed of the third switch and the third matching element.
  • the first tuning circuit 40 includes a second switch 41, a second matching element 42, a third switch 43 and a third matching element 44.
  • the second switch 41 and the second matching element 42 constitute a first sub-tuning circuit
  • the third switch 43 and the third matching element 44 constitute a second sub-tuning circuit
  • the first sub-tuning circuit and the second sub-tuning circuit are connected in parallel.
  • the second switch 41 and the third switch 43 may be integrated on one module.
  • both the second switch 41 and the third switch 43 are in an off state, and the middle and high frequency antenna radiator generates a resonance mode H1, which can be used to cover B3;
  • the second switch 41 is in the on state, and the third switches 43 are in the off state.
  • the middle and high frequency antenna radiator generates a resonance mode H2, which can be used to cover B39 and B1;
  • the second switch 41 is in the off state, and the third switches 43 are in the on state.
  • the middle and high frequency antenna radiator generates a resonance mode H3, which can be used to cover B40;
  • Both the second switch 41 and the third switch 43 are in a conducting state, and the middle and high frequency antenna radiator generates a resonance mode H4, which can be used to cover B41.
  • the second matching element includes a second inductor;
  • the third matching element includes a third inductor;
  • the value of the second inductance is greater than the value of the third inductance.
  • the resonance frequency of the second resonance mode generated by the antenna radiator is lower than the first When the second switch 41 is in the off state and the third switch 43 is in the on state, the resonance frequency of the third resonance mode generated by the antenna radiator.
  • the amount of inductance can be further reduced, so that the antenna radiator can cover a higher frequency band.
  • the value range of the second inductance is 8 nH to 22 nH; the value range of the third inductance is 1 nH to 5.6 nH.
  • the embodiments of the present disclosure can increase the inductance of the third inductor, thereby reducing the loss when the third switch is turned on, which can further reduce the switching loss of the antenna structure and improve the antenna performance of B40/B41 .
  • the specific inductance values of the second inductor and the third inductor are related to the operating frequency band of the antenna.
  • the inductance values of the low-frequency antenna and the medium-high frequency antenna are different, which is not limited in the embodiments of the present disclosure.
  • the antenna structure of the first embodiment can refer to FIG. 6. It should be noted that this embodiment takes an example in which the antenna radiator is expressed as a medium-high frequency antenna radiator.
  • a small capacitor C1 is connected at the feed point C of the antenna radiator to achieve antenna bandwidth coverage.
  • the value range of C1 may be 0.5-2.7pf, and optionally, the value range of C1 may be 0.8-1.5pf. It should be understood that C1 corresponds to the aforementioned first capacitor.
  • the first tuning circuit includes K1, K2, L1, and L2. It should be understood that K1 corresponds to the second switch, K2 corresponds to the third switch, L1 corresponds to the second inductance, and L2 corresponds to the third inductance.
  • K1 and K2 are all off (that is, in the off state), the middle and high frequency antenna radiator generates a resonance mode H1, which can be used to cover B3; K1 is turned on, and the inductance L1 is loaded at point B, and the value range of L1 It can be 8 ⁇ 22nH.
  • the value range of L1 can be 10 ⁇ 15nH.
  • the medium and high frequency antenna radiator generates the resonance mode H2, which can be used to cover B39 and B1.
  • the value range of L2 can be 1 ⁇ 5.6nH, optionally, the value range of L2 can be 1.5 ⁇ 3.3nH, the medium and high frequency antenna radiator generates resonance mode H3, which can be used to cover B40; K1 and K2 are turned on at the same time, the inductance is equal to L1 parallel L2 , Further reduced, the high-frequency antenna radiator generates a resonance mode H4, which can be used to cover B41.
  • phase adjustment circuit is not shown in the antenna structure. In this case, the phase adjustment circuit is “directly connected”.
  • FIG. 7 a schematic diagram of antenna standing wave ratio coverage.
  • the inductance at point B decreases, corresponding to the movement of H1 ⁇ H2 ⁇ H3 ⁇ H4, the antenna resonance frequency increases.
  • the standing wave ratio of H1/H2/H3/H4 in the B3/B1/B40/B41 frequency band does not increase overall. It can be seen that the impedance mismatch of the antenna in the embodiment of the present disclosure is significantly improved problem.
  • the antenna structure of this embodiment directs a small capacitor C1 at the feeding point C, which directly excites the resonance modes of H1 and H2, and at the same time improves the impedance mismatch of H3/H4 in the B40/B41 frequency band.
  • the The antenna structure requires that the antenna impedance at point C is mostly in the first quadrant of the Smith chart in the B3/B1/B39/B40/B41 frequency band.
  • the antenna structure utilizes the equivalent small inductance of some segments on the antenna radiator to generate a resonance mode and uses a matching circuit of the feed path to optimize to 50 ohms.
  • FIG. 8a and FIG. 8b are identical.
  • FIG. 8a is a schematic diagram of the impedance change of the antenna impedance of the first end of C1 in the B3/B41 frequency band after passing through C1.
  • the real curve of the antenna impedance in FIG. 8a represents the antenna impedance of the first end of C1 in the B3/B41 frequency band
  • the imaginary curve of the antenna impedance represents the antenna impedance of the first end of C1 in the B3/B41 frequency band through C1
  • the rear antenna impedance is the antenna impedance of the second end of C1 in the B3/B41 frequency band.
  • the antenna impedance of the first end of C1 in the B3/B41 band is located in the first quadrant of the Smith chart.
  • the antenna impedance of B3 is located in the high-impedance area of the inductive zone, and there is no obvious resonance mode in the B3 band.
  • State the minimum standing wave ratio in the frequency band is greater than 5
  • B41 has obvious resonant modal characteristics (the minimum standing wave ratio in the frequency band is less than 4), but it is very bad.
  • the impedance matching by C1 it is close to the matching point of the Smith chart. It can be seen that the impedance matching by C1 not only excites the resonance mode of H1/H2, but also improves the impedance mismatch problem of B40/B41.
  • FIG. 8b is the antenna impedance at the signal source of the embodiment of the present disclosure, that is, the second end of C1 is within the frequency band covered by the antenna radiator.
  • the antenna impedance of the second end of C1 in the frequency band covered by the antenna radiator is close to the matching point of the Smith chart, which can improve the antenna impedance mismatch problem.
  • the opening of the impedance curve of each antenna is only an example (for example, the opening of the impedance curve of H1 in the B3 frequency band can be left, and the opening of the impedance curve of H4 in the B41 frequency band can be upward), it will be affected by the position of the feed point Different.
  • the embodiments of the present disclosure do not limit this.
  • the length of AB in order to tune H4 up to B41, is required to be less than 1/4 wavelength of B41, generally 0-12 mm, and an optional value of 6-8 mm.
  • the length of the AB segment in this embodiment may be longer.
  • the maximum length of the AB in the related art is 7 mm, while in this embodiment, it may be up to 12 mm.
  • the sense value of L2 can be made larger, for example, the related art is 0nH, and in this embodiment is 3nH.
  • the multi-band coverage of the antenna radiator can be achieved through two sub-tuning circuits, so that the number of switches can be reduced, and the loss of the switches can be reduced.
  • the reason that the AB segment can be set longer than related technologies can include: 1.
  • the total length of the AD segment has been shortened, the inductance required for tuning to B41 can be greater; 2.
  • C1 can improve the mismatch of B41.
  • this embodiment in order to tune H1 to B3 at the lowest, this embodiment requires the antenna length of the AD segment to be close to 1/4 wavelength of B3, about 16 to 22 mm, and an optional value of 18 to 20 mm. Therefore, compared with the related art, the total length of the antenna in this embodiment may be smaller, that is, the antenna space occupied is smaller.
  • the reason why the AD segment of this embodiment can be set shorter is that: by stringing C1 at the feeding point, the antenna structure can generate a new resonance mode, thereby optimizing the resonance mode excited by the antenna structure , Making the resonant frequency of the resonant mode lower. In this way, at the same resonant frequency, this embodiment can shorten the length of AD because C1 is connected in series.
  • the length of AC is required to be at least 1 mm smaller than that of AD, generally 0 to 18 mm, that is, the length of AC can be greater than, equal to, or less than AB, and the optional value is 14 to 16 mm.
  • B and C can also share a single feed point, that is, a single feed point, it is required that the AB length is less than the 1/4 wavelength of B41, generally 0-12mm, typical value 6-8mm, this can reduce the feed connection point
  • the quantity not only reduces the need for structural space, but also reduces the influence of parasitic parameters fed into the connection points.
  • the length of the CD will significantly affect the resonance frequency of the antenna radiator. Specifically, a decrease in CD will significantly increase the resonance frequency of H1/H2/H3. The CD length of the related art has little effect on the resonance frequency.
  • the first tuning circuit may cause the impedance of B40/B41 to enter the junction of the first quadrant and the second quadrant.
  • a phase adjustment circuit needs to be added at point C.
  • the implementation method can be that only a small capacitor (such as 0.3 to 0.7pf) is connected to ground, or a small inductance is connected first and then a small capacitor (such as 2 to 4nH and 0.3 to 0.7pf). , Or directly lengthen the feed line between the antenna and the feed, so that the B40/B41 impedance is adjusted to the first quadrant.
  • the specific value inside the phase adjustment circuit can be selected according to the actual debugging situation.
  • the above antenna size requirements are only examples.
  • large metal devices are added to the antenna area, high-dielectric materials such as plastic/printed circuit board (PCB), antenna feed
  • PCB plastic/printed circuit board
  • antenna feed The influence of electrical lines, etc., will cause a great change in the length of the antenna.
  • the antenna structure of this embodiment can be applied to a "full screen" mobile terminal, and the metal outer frame serves as an antenna radiator.
  • the antenna radiation fracture can be 1.5mm, the antenna is about 1.5mm from the metal ground of the whole machine (commonly known as the antenna clearance distance), and only 1.2mm from the screen (the screen has obvious absorption antenna efficiency of about 0.8 ⁇ 1.5db) .
  • point B can be pre-parallel connected inductance 30nH.
  • point C can be pre-parallel connected with a 0.3pf capacitor.
  • the free space antenna efficiency can be as shown in Figure 9, the antenna peak efficiency can reach about -4dB, the average efficiency in the B3/B39/B1/B40/B41 band -4.4/-5/-4.3/-4.2/-3.1dB , To meet the antenna efficiency requirements of mobile terminals, and is a high-performance antenna.
  • Embodiment 1 The main difference between this embodiment and Embodiment 1 is that a second tuning circuit is newly added, and the second tuning circuit of this embodiment is mainly used to implement double-resonant carrier aggregation (Carrier Aggregation, CA).
  • CA Carrier Aggregation
  • the second tuning circuit of this embodiment includes K3, L3, and C2.
  • K3 corresponds to the first switch
  • L3 corresponds to the first inductor
  • C2 corresponds to the second capacitor.
  • the antenna radiator when K1 is turned on, K2 is not turned on (that is, in the H1 or H2 state), and K3 is turned on, the antenna radiator can generate two new resonance modes H5 and H6, and exist at the same time, can be used for Cover CA requirements of B39+B41.
  • the antenna radiator can be used to cover the CA requirements of B3+B40.
  • the parallel L3 and C2 can be equivalent to the capacitor in the B40 or B41 frequency band, and generally require 0.3p ⁇ 1.2p; the parallel L3 and C2 in the B3/B39 frequency band can be adjusted according to the resonance frequency of H5, For example, equivalent to high impedance (open circuit, small capacitance, large inductance).
  • K1, K2, and K3 can be integrated on one module, and the common terminal is grounded.
  • FIG. 12 for the schematic diagram of the standing wave ratio of the resonance modes H5 and H6 at the signal source in this embodiment.
  • the antenna structure does not include a phase adjustment circuit.
  • the phase adjustment circuit can be set according to actual needs. It should be noted that when B and C share a feed point (ie, a single feed point), then point B should be combined with the first tuning of K1 and K2. Circuit, and then serial phase adjustment circuit, and then connect the common connection point of C2, L3 and C1.
  • Embodiment 1 The main difference between this embodiment and Embodiment 1 is that a second tuning circuit is newly added, and the second tuning circuit of this embodiment is mainly used to adjust the resonance frequency of the target resonance mode of the antenna structure to improve the target resonance mode.
  • the antenna standing wave ratio of the target frequency band reduces the mismatch loss.
  • the second tuning circuit of this embodiment includes K3 and C2 connected in series. Among them, K3 corresponds to the aforementioned first switch, and C2 corresponds to the aforementioned second capacitor.
  • the second tuning circuit of this embodiment can be used to adjust the resonance frequencies of H2 and H3 to better improve the antenna standing wave ratio of B39 and B40 and reduce the mismatch loss. If C2 is turned on, the resonance frequency of H2 and H3 decreases.
  • the difference between the tuning frequency of point C and point B is that although the tuning range is narrower, the switching loss of point C is very low, which is suitable for fine tuning in a small range.
  • C2 can also be replaced by inductive tuning (that is, C2 is a matching device, specifically an inductor or a capacitor), and only the appropriate adjustment of L1, L2, and antenna length can achieve the above effects.
  • C2 can also be connected to the other end of C1, which can also achieve a similar effect.
  • Embodiment 1, Embodiment 2 and Embodiment 3 only take the antenna radiator as a medium-high frequency antenna radiator for example, but the antenna radiator of the embodiment of the present disclosure may also be expressed as a low-frequency antenna radiator.
  • the low-frequency antenna radiator can generate a resonance mode H1/H2/H3/H4 for covering B12 (0.7 ⁇ 0.746GHz)/B20(0.79 ⁇ 0.86GHz)/ B5 (0.824 ⁇ 0.894GHz)/B8(0.88 ⁇ 0.96GHz).
  • the length of AB is required to be less than 1/4 wavelength of B8, generally 0 to 35 mm, and a typical value of 25 to 30 mm.
  • the antenna length of the AD segment is required to be close to the 1/4 wavelength of B12, about 40 to 60 mm, and the typical value is 45 to 55 mm.
  • the length of AC is required to be at least 4mm smaller than that of AD, generally 0-50mm, that is, the length of AC can be greater than, equal to, or less than AB, with a typical value of 33-45mm.
  • the AC length is required to be less than 1/4 wavelength of B8, generally 0 ⁇ 35mm, typical value 28 ⁇ 35mm, this can reduce the feed connection point
  • the quantity not only reduces the need for structural space, but also reduces the influence of parasitic parameters fed into the connection points.
  • the antenna impedance at point C is mostly in the first quadrant of the smith circle in the B3/B1/B39/B40/B41 frequency band, and then a new resonance mode is excited or matched to 50 ohms through a small capacitor C1.
  • An embodiment of the present disclosure also provides a terminal including the antenna structure as described above.
  • the communication terminal may be a mobile phone, a tablet computer (Tablet Personal Computer), a personal digital assistant (PDA), a mobile Internet device (MID) or a wearable device (Wearable Device) Wait.
  • Tablet Personal Computer Tablet Personal Computer
  • PDA personal digital assistant
  • MID mobile Internet device
  • Wearable Device Wearable Device

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Abstract

本申请提供一种天线结构及通信终端，该天线结构包括：天线辐射体、信号源、第一电容和第一调谐电路；所述天线辐射体的第一端接地；所述第一电容的第一端和所述第一调谐电路的第一端均与所述天线辐射体的连接点电连接，所述第一电容的第二端与所述信号源电连接，所述第一调谐电路的第二端接地；其中，所述第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限，所述目标频点为所述天线辐射体覆盖的频带中的至少部分频点。

Description

天线结构及通信终端
相关申请的交叉引用
本申请主张在2018年12月12日在中国提交的中国专利申请号No.201811521027.X的优先权，其全部内容通过引用包含于此。
技术领域
本公开实施例涉及通信技术领域，尤其涉及一种天线结构及通信终端。
背景技术
通信终端内通常使用高低频拆分天线，通过将覆盖不同频段范围的天线分布设置在通信终端的不同区域，以更好的利用整机空间。如，通信终端内可以设置有2个独立的天线，一个是低频天线，覆盖频率范围0.7～0.96GHz(吉赫)；另一个是中高频天线，覆盖频率范围1.71～2.69GHz。
然而，随着“全面屏”移动终端的普及，天线的空间被极大的压缩，导致天线的阻抗失配损耗较大，导致天线的传输效率较差。
发明内容
本公开实施例提供一种天线结构及通信终端，以解决相关技术中的天线的阻抗失配损耗较大，导致天线的传输效率较差的问题。
为解决上述问题，本公开是这样实现的：
第一方面，本公开实施例提供了一种天线结构，应用于通信终端，所述天线结构包括：天线辐射体、信号源、第一电容和第一调谐电路；
所述天线辐射体的第一端接地；
所述第一电容的第一端和所述第一调谐电路的第一端均与所述天线辐射体的连接点电连接，所述第一电容的第二端与所述信号源电连接，所述第一调谐电路的第二端接地；
其中，所述第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限，所述目标频点为所述天线辐射体覆盖的频带中的至少部分频点。
第二方面，本公开实施例还提供一种通信终端，该通信终端包括如上所述的本公开实施例提供的天线结构。
在本公开实施例中，天线结构包括：天线辐射体、信号源、第一电容和第一调谐电路；所述天线辐射体的第一端接地；所述第一电容的第一端和所述第一调谐电路的第一端均与所述天线辐射体的连接点电连接，所述第一电容的第二端与所述信号源电连接，所述第一调谐电路的第二端接地；其中，所述第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限，所述目标频点为所述天线辐射体覆盖的频带中的至少部分频点。这样，本公开在第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限的基础上，通过第一电容的高阻抗馈入，一方面，可以使得天线结构产生新的谐振方式，优化天线结构激发的谐振模态；另一方面，可以将第一电容的第二端的天线阻抗匹配至靠近史密斯圆图的匹配点，从而可以改善天线的阻抗失配损耗问题，降低阻抗失配损耗，进而可以提高天线的传输效率。
附图说明
为了更清楚地说明本公开实施例的技术方案，下面将对本公开实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本公开的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，还可以根据这些附图获得其他的附图。
图1a是本公开实施例提供的天线结构的示意图之一；
图1b是本公开实施例提供的天线结构的示意图之二；
图1c是本公开实施例提供的天线结构的示意图之三；
图1d是本公开实施例提供的天线结构的示意图之四；
图2是本公开实施例提供的史密斯圆图的示意图之一；
图3a是本公开实施例提供的天线结构的示意图之五；
图3b是本公开实施例提供的天线结构的示意图之六；
图4是本公开实施例提供的天线结构的示意图之七；
图5是本公开实施例提供的天线结构的示意图之八；
图6是本公开实施例提供的天线结构的示意图之九；
图7是本公开实施例提供的天线驻波比覆盖示意图之一；
图8a是本公开实施例提供的史密斯圆图的示意图之二；
图8b是本公开实施例提供的史密斯圆图的示意图之三；
图9是本公开实施例提供的天线效率的示意图；
图10是本公开实施例提供的天线结构的示意图之十；
图11是本公开实施例提供的史密斯圆图的示意图之四；
图12是本公开实施例提供的天线驻波比覆盖示意图之二；
图13是本公开实施例提供的天线结构的示意图之十一。
具体实施方式
下面将结合本公开实施例中的附图，对本公开实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本公开一部分实施例，而不是全部的实施例。基于本公开中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本公开保护的范围。
本申请中的术语“第一”、“第二”等是用于区别类似的对象，而不必用于描述特定的顺序或先后次序。此外，术语“包括”和“具有”以及他们的任何变形，意图在于覆盖不排他的包含，例如，包含了一系列步骤或单元的过程、方法、系统、产品或设备不必限于清楚地列出的那些步骤或单元，而是可包括没有清楚地列出的或对于这些过程、方法、产品或设备固有的其它步骤或单元。此外，本申请中使用“和/或”表示所连接对象的至少其中之一，例如A和/或B和/或C，表示包含单独A，单独B，单独C，以及A和B都存在，B和C都存在，A和C都存在，以及A、B和C都存在的7种情况。
以下对本公开实施例的天线结构进行说明。
在本公开实施例中，天线结构可以包括天线辐射体、信号源、第一电容和第一调谐电路。
其中，天线辐射体主要用于天线辐射。具体实现时，一种实施方式中，所述天线辐射体可以表现为低频天线辐射体。低频天线辐射体可覆盖的频率范围可以包括0.7～0.96GHz(吉赫)。在实际应用中，上述频率范围可以划分为几个频带(或称为频段)：0.7～0.746GHz(可以编号为B12)；0.79～0.86GHz (可以编号为B20)；0.824～0.894GHz(可以编号为B5)；0.88～0.96GHz(可以编号为B8)，但不仅限于此。
另一种实施方式中，所述天线辐射体可以表现为中高频天线辐射体。中高频天线辐射体可覆盖的频率范围可以包括1.71～2.69GHz。在实际应用中，上述频率范围可以划分为几个频带：1.71～1.88GHz(可以编号为B3)；1.88～1.92GHz(可以编号为B39)；1.92～2.17GHz(可以编号为B1)；2.3～2.4GHz(可以编号为B40)；2.5～2.69GHz(可以编号为B41)，但不仅限于此。
具体实现时，天线辐射体可以是通信终端的金属边框或者金属外壳，也可以是布置于通信终端壳体内的金属体，材质可以是柔性电路板(Flexible Printed Circuit，FPC)、激光直接成型(Laser Direct Structuring，LDS)、不锈钢、镁合金等，不做限定。
信号源(或称为馈源)可以用于收发信号，提供电磁波能量。
在本公开实施例中，第一电容不仅仅具有阻抗匹配的作用，它是高阻抗的馈入元件，可以使得天线结构产生新的谐振方式，优化天线结构激发的谐振模态。当第一电容具有大容值时，各谐振模态将会受到很大影响，导致该天线结构无法操作到所需的频带。因此，在本公开实施例中，可选的，所述第一电容的取值小于第二特定值。可选地，所述第一电容的取值范围可以为0.5皮法至2.7皮法。在实际应用中，第一电容可以为固定电容或可变电容，当第一电容表现为可变电容时，可以进一步改变谐振频率，提高谐振频率的灵活度。
这样，通过在天线馈电点串小电容，不仅改变了天线谐振产生方式，还可以起到阻抗匹配的作用。另外，相比传统的平面倒F型天线(inverted-F antenna，IFA)产生的谐振模态，通过在天线馈电点串小电容产生的谐振模态的谐振频率可以更低，进而可以在同等谐振频率下缩短天线辐射体的总长度，减小天线结构在通信终端的占用空间。
第一调谐电路主要用于改变天线辐射体的为等效电长度，从而改变各谐振模态的谐振频率。另外，第一调谐电路的阻抗可调，具体实现时，可以由多路开关和匹配元件(如电感、电容)组成，也可以是由可变电容和电感组成，本公开实施例对此不作限定。
以下对本公开实施例中的天线辐射体、信号源、第一电容和第一调谐电路的设置方式进行说明。
所述天线辐射体的第一端接地。需要说明的是，本公开实施例并不限制接地方式，在实际应用中，接地方式可以但不仅限于包括通过连接金属壳体、主板地或参考地的方式接地。另外，所述天线辐射体的第二端是开路端。
所述第一电容的第一端和所述第一调谐电路的第一端均与所述天线辐射体的连接点电连接，所述第一电容的第二端与所述信号源电连接，所述第一调谐电路的第二端接地。
也就是说，第一电容连接在天线辐射体的连接点和信号源之间；第一调谐电路连接在天线辐射体的连接点和接地点之间。
具体实现时，所述第一电容的第一端和所述第一调谐电路的第一端可以电连接所述天线辐射体的同一连接点，或者，不同连接点，具体可根据实际需求决定，本公开实施例对此不作限定。可选的，所述第一电容的第一端电连接所述天线辐射体的第一连接点，所述第一调谐电路的第二端电连接所述天线辐射体的第二连接点；或者，所述第一电容的第一端和所述第一调谐电路的第一端电连接所述天线辐射体的同一连接点。
在所述第一电容的第一端和所述第一调谐电路的第一端电连接所述天线辐射体的同一连接点的情况下，可以减少天线辐射体馈入连接点的数量，不仅降低了对天线辐射体结构空间的需求，也减少了馈入连接点的寄生参数影响。
另外，在所述第一电容的第一端电连接所述天线辐射体的第一连接点，所述第一调谐电路的第二端电连接所述天线辐射体的第二连接点的情况下，第一连接点可以设置在所述天线辐射体的第二端和第二连接点之间，或者，设置在所述天线辐射体的第一端和第二连接点之间，具体可根据实际需求决定，本公开实施例对此不作限定。
需要说明的是，对于天线辐射体的连接点，若其连接有信号源，则该连接点可以称为馈电点或馈点。
为方便理解本公开实施例的天线结构，请参阅图1a至图1d。
其中，在图1a至图1d所示的天线结构中，所述第一电容的第一端和所 述第一调谐电路的第一端电连接所述天线辐射体的不同连接点，在图1a至图1d中，记所述第一电容的第一端电连接所述天线辐射体的第一连接点为C，记所述第一调谐电路的第二端电连接所述天线辐射体的第二连接点为B。
进一步地，在图1a中，第一连接点C设置在所述天线辐射体的第一端(图1a至图1d中记为D)和第二连接点B之间。可见，在图1a中，所述天线辐射体的第二端(图1a至图1d中记为A)和第二连接点B之间的长度，小于所述天线辐射体的第二端A和第一连接点C之间的长度，即AC的长度大于AB的长度。
在图1b和图1c中，第一连接点C设置在所述天线辐射体的第二端和第二连接点B之间。可见，在图1b和图1c中，所述天线辐射体的第二端A和第二连接点B之间的长度，大于所述天线辐射体的第二端A和第一连接点C之间的长度，即AC的长度小于AB的长度。图1b和图1c的区别主要在于：图1b中的第一连接点C靠近第二连接点B，而图1c中的第一连接点C靠近天线辐射体的第一端A。
在图1d中，所述第一电容的第一端和所述第一调谐电路的第一端电连接所述天线辐射体的同一连接点，并记该连接点为B。
在图1a至图1d中，天线辐射体标号为10，信号源标号为20，第一电容标号为30，第一调谐电路标号为40。
如图1a至图1d所示，天线辐射体10的第一端D接地，天线辐射体10的第二端A可以为开路端。第一电容30的第二端通过信号源20接地，第一调谐电路40的第二端直接接地。
在图1a至图1d中，天线辐射体10呈L型，但应理解的是，本公开并不因此限制天线辐射体10的形状，如在某些实施方式中，天线辐射体10也可以呈直线型或者弯曲型，具体可根据实际需要设定，本公开实施例对此不作限定。
另外，图1a中连接点B和连接点C的设置位置仅为示例，并不因此限制连接点B和连接点C的设置位置。
在本公开实施例中，所述第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限。其中，所述目标频点为所述天线辐射体覆盖的频带 中的至少部分频点。进一步地，所述目标频点为所述天线辐射体覆盖的每个频带中的至少三分之二的频点。
为方便理解，以下结合图2对史密斯圆图(Smith Chart)的象限的划分进行说明。
如图2所示，可以将史密斯圆图中的纯电阻线设为第一线，将通过史密斯圆图的外周中的相位为90度的二点构成的直线设为第二线。之后，将第一线和第二线划分的4个区域作为第一、第二、第三、第四象限。
其中，第一象限为具有感抗且阻抗较大的区域，第二象限为具有感抗且阻抗较小的区域。第三象限为具有容抗且阻抗较小的区域，第四象限为具有容抗且阻抗较大的区域。
另外，需要说明的是，第一线和第二线的正交点可以称为匹配点或中心点。匹配点可以理解为：射频系统要求的匹配阻抗，当第一电容的第二端的天线阻抗(即信号源处的天线阻抗)匹配至射频系统要求的匹配阻抗，即第一电容的第二端的天线阻抗匹配至史密斯圆图的匹配点时，天线结构的阻抗失配损耗可以降至最低，传输效率可以达到最高。示例性的，若射频系统要求的匹配阻抗为50Ω(欧姆)，则当第一电容的第二端的天线阻抗匹配至50Ω时，天线结构的阻抗失配损耗可以将至最低，传输效率可以达到最高。
由前述内容可知，在本公开实施例中，第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限，属于感抗且阻抗较大的区域，目标频段内的谐振模态几乎没有或者很差。之后，进一步通过第一电容的高阻抗馈入，一方面，可以使得天线结构产生新的谐振方式，进而优化天线结构激发的谐振模态；另一方面，可以将第一电容的第二端的天线阻抗匹配至靠近史密斯圆图的匹配点，从而可以改善天线的阻抗失配损耗问题，降低阻抗失配损耗，进而可以提高天线的传输效率。
在本公开实施例中，为达到第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限要求，可以通过限定天线辐射体的总长度，以及天线辐射体上的连接点的设置位置实现。
可选的，所述天线辐射体的总长度的取值范围是所述天线辐射体覆盖的频带中的第一频带的中心频点的3/16波长至3/8波长；
所述天线辐射体的第二端与电连接所述第一调谐电路的连接点之间的第一长度小于所述天线辐射体覆盖的频带中的第二频带的1/4波长；
其中，所述第一频带的中心频点小于所述天线辐射体覆盖的频带中除所述第一频带之外的任一频带的中心频点；所述第二频带的中心频点大于所述天线辐射体覆盖的频带中除所述第二频带之外的任一频带的中心频点。
示例性的，若天线辐射体覆盖的频带包括B3(1.71～1.88GHz)、B39(1.88～1.92GHz)、B1(1.92～2.17GHz)、B40(2.3～2.4GHz)和B41(2.5～2.69GHz)，则第一频带为B3，第二频带为B41。
若天线辐射体覆盖的频带包括B12(0.7～0.746GHz)、B20(0.79～0.86GHz)、B5(0.824～0.894GHz)和B8(0.88～0.96GHz)，则第一频带为B12，第二频带为B8。
在实际应用中，为了将天线辐射体的谐振模态最低调谐至第一频带，要求所述天线辐射体的总长度的取值范围是所述天线辐射体覆盖的频带中的第一频带的中心频点的3/16波长至3/8波长，可选地，可以要求天线辐射体的总长度接近于第一频带中任一频点的1/4波长。
可见，通过上述方式确定天线辐射体的总长度，不仅可以扩大天线辐射体覆盖的频带范围，另外，相比于相关技术，本公开实施例可以缩短天线辐射体的总长度，进而可以减小天线结构在通信终端的占用空间。
对于天线辐射体的第一长度的设置，由于第一电容可以改善第二频带的阻抗失配，因此，在实际应用中，为了将天线辐射体的谐振模态最高调谐至第二频带，可以要求天线辐射体的第一长度小于第二频带的1/4波长。
需要说明的是，在所述第一电容的第一端电连接所述天线辐射体的第一连接点，所述第一调谐电路的第二端电连接所述天线辐射体的第二连接点的情况下，所述天线辐射体的第二端与第二连接点之间的第一长度小于或等于第二频带的1/4波长，即图1a至图1d中的AB的长度小于或等于第二频带的1/4波长。具体实现时，AB的长度可以小于或等于第二频带中任一频点的1/4波长。
可见，通过上述方式确定天线辐射体的第一长度，不仅可以扩大天线辐射体覆盖的频带范围，另外，相比于相关技术，本公开实施例可以增长第一 长度。
进一步地，在所述第一电容的第一端电连接所述天线辐射体的第一连接点，所述第一调谐电路的第二端电连接所述天线辐射体的第二连接点的情况下，所述天线辐射体的第二端与所述第一连接点之间的第二长度，与所述总长度的差的绝对值大于第一特定值。也就是说，第二长度比总长度至少小第一特定值，即图1a至图1d中的AC的长度比AD的长度至少小第一特定值。
其中，第一特定值的确定可以与天线辐射体的表现类型相关。具体地，若天线辐射体表现为低频天线辐射体，则第一特定值可以为4mm；若天线辐射体表现为中高频天线辐射体，则第一特定值可以为1mm。但应理解的是，本公开对第一特定值并不作限定，具体可根据实际需求确定。
应理解的是，在所述第一电容的第一端和所述第一调谐电路的第一端电连接所述天线辐射体的同一连接点的情况下，如图1d所示，天线辐射体设置单馈点B。
这样，通过上述方式确定天线辐射体的总长度，以及天线辐射体的连接点的设置位置，有助于第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限，进而可以使得天线结构产生新的谐振方式，优化天线结构激发的谐振模态；同时改善天线的阻抗失配损耗问题。
具体实现时，可选的，在所述天线辐射体为中高频天线辐射体的情况下，所述总长度的取值范围为16毫米至22毫米；所述第一长度的取值范围是0毫米至12毫米；所述第二长度的取值范围是0毫米至18毫米；
在所述天线辐射体为低频天线辐射体的情况下，所述总长度的取值范围为40毫米至60毫米；所述第一长度的取值范围是0毫米至35毫米；所述第二长度的取值范围是0毫米至50毫米。
需要说明的是，在实际应用中，所述天线辐射体的总长度、第一长度和第二长度的具体取值可以根据实际情况决定，本公开实施例对此不作限定。但应理解的是，天线辐射体的总长度始终大于第一长度和第二长度。
可选地，在所述天线辐射体为中高频天线辐射体的情况下，所述总长度的取值范围为18毫米至20毫米；所述第一长度的取值范围是6毫米至8毫米；所述第二长度的取值范围是14毫米至16毫米；
在所述天线辐射体为低频天线辐射体的情况下，所述总长度的取值范围为40毫米至60毫米；所述第一长度的取值范围是25毫米至30毫米；所述第二长度的取值范围是33毫米至45毫米。
这样，通过上述方式确定天线辐射体的总长度，以及天线辐射体的连接点的设置位置，可以使得第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限，进而可以使得天线结构产生新的谐振方式，优化天线结构激发的谐振模态；同时改善天线的阻抗失配损耗问题。
考虑到某些场景下，仅通过确定天线辐射体的总长度，以及天线辐射体的连接点的设置位，不能使得第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限。示例性的，在所述天线辐射体为中高频天线辐射体，且在所述天线辐射体电连接所述第一电容的第一端的连接点，与所述天线辐射体电连接所述第一调谐电路的第一端的连接点之间的间距小于第四特征值，如3mm的情况下，第一调谐电路可能使得第一电容的第一端在B40/B41的天线阻抗进入史密斯圆图的第一象限和第二象限交界处，不能使得第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限。
因此，为达到第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限的要求，可选的，所述天线结构还包括相位调整电路；所述第一电容的第一端通过所述相位调整电路与所述天线辐射体的连接点电连接；其中，所述相位调整电路的相位调整范围包括0。
为方便理解，请一并参阅图3a和图3b。
其中，图3a和图1a的主要区别在于，在图1a中，第一电容30的第一端直接与第一连接点C电连接，而在图3a中，第一电容30的第一端通过相位调整电路50与第一连接点C电连接。
图3b和图1d的主要区别在于，在图1d中，第一电容30的第一端直接与连接点B电连接，而在图3b中，第一电容30的第一端通过相位调整电路50与连接点B电连接。
具体实现时，可以在与第一电容的第一端电连接的连接点增加一个相位调整电路，相位调整电路的实现方式可以是只并小电容(如0.3～0.7pf)到地；或者，先串小电感再并小电容(如串2～4nH并0.3～0.7pf)；或者，直接加长 天线至馈电之间的馈电线路从而调整阻抗至第一象限。
当然，在某些实施方式中，相位调整电路的相位调整值可以为0，即相位调整电路不对相位进行调整。
应理解的是，相位调整电路的具体表现形式和具体相位调整值可以根据实际调试情况进行选择。另外，本公开并不限制相位调整电路为达到特定相位调整值所采用的电路结构。
在所述第一电容的第一端和所述第一调谐电路的第一端电连接所述天线辐射体的同一连接点的情况下，如图3b所示，具体实现时，可以在B点先并第一调谐电路40，再串相位调整电路50，即第一调谐电路40连接在B电和主地板之间，而相位调整电路50连接在B点和第一电容30之间。
这样，通过增加相位调整电路，可以将第一电容的第一端在目标频点的天线阻抗调整至史密斯圆图的第一象限，从而达到第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限的要求，进而可使得天线结构产生新的谐振方式，优化天线结构激发的谐振模态；同时改善天线的阻抗失配损耗问题。
在本公开实施例中，可选的，所述天线结构还包括第二调谐电路，所述第二调谐电路的第一端与所述第一电容的第一端或所述第一电容的第二端电连接，所述第二调谐电路的第二端接地。
在本公开实施例中，第二调谐电路可以用于实现双谐振的载波聚合(Carrier Aggregation，CA)，这样，通过新增第二调谐电路，可以实现双谐振的CA。或者，第二调谐电路可以用于调节天线结构的目标谐振模态的谐振频率，改善目标谐振模态的目标频带的天线驻波比，减少失配损耗。这样，通过新增的第二调谐电路，可以降低失配损耗，进而可以提高天线的传输效率。
可选的，所述第二调谐电路包括串接的调谐元件和第一匹配元件；
其中，所述第一匹配元件的第一端与所述第一电容的第一端或所述第一电容的第二端电连接；所述第一匹配元件的第二端通过所述调谐元件接地。
为方便理解，请一并参阅图4。在图4中，天线结构还包括第二调谐电路60，第二调谐电路60包括串接的调谐元件61和第一匹配元件62。其中， 第一匹配元件62的第一端可以与第一电容30的第一端电连接(图4中用实线连接)，或者，第一匹配元件62的第一端可以与第一电容30的第二端电连接(图4中用虚线连接)；第一匹配元件62的第二端通过调谐元件61接地。
需要说明的是，在其他实现方式中，调谐元件61和第一匹配元件62的连接顺序可以调换。即本公开实施例并不限制调谐元件61和第一匹配元件的串接顺序。
以下对第二调谐电路的具体结构和功能进行说明。
可选的，所述调谐元件为第一开关或可变电容；
所述第一匹配元件包括第二电容和/或第一电感；
其中，在所述第一匹配元件为所述第二电容或所述第一电感的情况下，所述第一匹配元件的第一端与所述第一电容的第一端或所述第一电容的第二端电连接；
在所述第一匹配元件包括并联的所述第二电容和所述第一电感的情况下，所述第一匹配元件的第一端与所述第一电容的第一端电连接。
具体实现时，一种实施方式中，可选的，所述调谐元件为第一开关，所述第一匹配元件包括第二电容和/或第一电感；其中，所述第一匹配元件的第一端与所述第一电容的第一端或所述第一电容的第二端电连接；所述第二电容的第二端与所述第一开关电连接。
在本实施方式中，第二调谐电路由串接的第一开关和第二电容组成，或者，由串接的第一开关和第一电感组成，可以用于调节天线结构的目标谐振模态的谐振频率，改善目标谐振模态的目标频带的天线驻波比，减少失配损耗。
具体实现时，通过控制第一开关导通，进而导通第二电容或第一电感，从而可以降低天线辐射体的目标谐振模态的谐振频率。其中，目标谐振模态可以表现为H2或H3，H2的目标频带可以为B39，H3的目标频带可以为B40。
另一种实施方式中，可选的，所述调谐元件为第一开关，第一匹配元件由并联的第一电感和第二电容组成；其中，所述第一匹配元件的第一端与所述第一电容的第一端电连接；所述第二电容的第二端与所述第一开关电连接。
在本实施方式中，第一匹配元件主要用于随着频率不同产生不同的阻抗 特性，因此，可以称为频变阻抗元件。
而第二调谐电路由第一开关，以及并联的第一电感和第二电容组成，因此，本实施方式的第二调谐电路可以用于实现双谐振的CA。
具体实现时，可以通过控制第一调谐电路和第一开关的导通状态，使得天线辐射体同时产生两个谐振模态，用于同时覆盖两个不同频带，如在天线辐射体覆盖的频带包括B3、B39、B1、B40和B41的情况下，可以同时覆盖B39+B41，或者同时覆盖B3+B40。
在实际应用中，第一匹配元件可以等效于电容或高阻抗(如开路、很小电容、很大电感)。示例性的，在天线辐射体覆盖的频带包括B3、B39、B1、B40和B41的情况下，第一匹配元件在B40或B41内可以等效于电容，且该等效电容的取值范围可以为0.3皮法至1.2皮法；第一匹配元件在B3或B39内可以根据天线辐射体产生新的谐振模态的谐振频率进行调整，如等效于高阻抗(如开路、很小电容、很大电感)。
以下对本公开实施例中的第一调谐电路的具体结构进行说明。
一种实施方式中，可选的，所述第一调谐电路由可变电容组成；或者，所述第一调谐电路由可变电容和固定电感串联或并联组成。
也就是说，在实际应用中，第一调谐电路可以由独立的可变电容组成，或者，由可变电容和固定电感组成，且可变电容和固定电感的连接关系可以为串联或并联。
需要说明的是，第一调谐电路中的可变电容的具体取值范围，第一调谐电路中的固定电感的具体的电感值，与天线的操作频段有关，本公开实施例对此不做限定。
另一种实施方式中，可选的，所述第一调谐电路包括并联的第一子调谐电路和第二子调谐电路；
其中，在所述第一子调谐电路处于第一工作状态，所述第二子调谐电路处于第一工作状态的情况下，所述天线辐射体产生第一谐振模态；
在所述第一子调谐电路处于第二工作状态，所述第二子调谐电路处于第一工作状态的情况下，所述天线辐射体产生第二谐振模态；
在所述第一子调谐电路处于第一工作状态，所述第二子调谐电路处于第 二工作状态的情况下，所述天线辐射体产生第三谐振模态；
在所述第一子调谐电路处于第二工作状态，所述第二子调谐电路处于第二工作状态的情况下，所述天线辐射体产生第四谐振模态；
其中，所述第一谐振模态、所述第二谐振模态、所述第三谐振模态和所述第四谐振模态的谐振频率依序升高。也就是说，F1＜F2＜F3＜F4，其中，F1表示第一谐振模态的谐振频率，F2表示第二谐振模态的谐振频率，F3表示第三谐振模态的谐振频率，F4表示第四谐振模态的谐振频率。
具体实现时，第一工作状态可以表现为断开状态，第二工作状态可以表现为导通状态，但不仅限于此。
示例性的，在天线辐射体覆盖的频带包括B3、B39、B1、B40和B41的情况下，第一谐振模态可以为H1，此时，天线辐射体覆盖B3；第二谐振模态可以为H2，此时，天线辐射体覆盖B39和B1；第三谐振模态可以为H3，此时，天线辐射体覆盖B40；第四谐振模态可以为H4，此时，天线辐射体覆盖B41。
可见，在本公开实施例中，可以仅通过两路子调谐电路，实现天线辐射体的多频带覆盖，相比于相关技术中通过三路或三路以上子调谐电路，才能实现天线辐射体的多频带覆盖，本公开实施例不仅可以降低子调谐电路的数量，进而节省调谐电路的成本，也降低了调谐电路的损耗，提高了天线性能。
可选的，所述第一子调谐电路包括第二开关和第二匹配元件；所述第二子调谐电路包括第三开关和第三匹配元件；
其中，在所述第二开关和所述第三开关均处于断开状态的情况下，所述天线辐射体产生所述第一谐振模态；
在所述第二开关处于导通状态，第三开关处于断开状态的情况下，所述天线辐射体产生所述第二谐振模态；
在所述第二开关处于断开状态，第三开关处于导通状态的情况下，所述天线辐射体产生所述第三谐振模态；
在所述第二开关和所述第三开关均处于导通状态的情况下，所述天线辐射体产生所述第四谐振模态。
在本实施方式中，第一子调谐电路由第二开关和第二匹配元件组成，第 二子调谐电路由第三开关和第三匹配元件组成。为方便理解，请一并参阅图5。
在图5中，第一调谐电路40包括第二开关41、第二匹配元件42、第三开关43和第三匹配元件44。其中，第二开关41和第二匹配元件42构成第一子调谐电路，第三开关43和第三匹配元件44构成第二子调谐电路，且第一子调谐电路和第二子调谐电路并联。
需要说明的是，在实际应用中，为减小第二开关41和第三开关43的占用面积和降低开关成本，可以将第二开关41和第三开关43集成在一个模块上。
具体实现时，第二开关41和第三开关43均处于断开状态，中高频天线辐射体产生谐振模态H1，可用于覆盖B3；
第二开关41处于导通状态，第三开关43均处于断开状态，中高频天线辐射体产生谐振模态H2，可用于覆盖B39和B1；
第二开关41处于断开状态，第三开关43均处于导通状态，中高频天线辐射体产生谐振模态H3，可用于覆盖B40；
第二开关41和第三开关43均处于导通状态，中高频天线辐射体产生谐振模态H4，可用于覆盖B41。
进一步地，所述第二匹配元件包括第二电感；所述第三匹配元件包括第三电感；
其中，所述第二电感的取值大于所述第三电感的取值。
这样，第二开关41处于导通状态，第三开关43均处于断开状态时，天线辐射体覆盖的频带，与第二开关41处于断开状态，第三开关43均处于导通状态时，天线辐射体覆盖的频带不同，且第二开关41处于导通状态，第三开关43均处于断开状态时，所述天线辐射体产生的所述第二谐振模态的谐振频率，低于第二开关41处于断开状态，第三开关43均处于导通状态时，所述天线辐射体产生的所述第三谐振模态的谐振频率。
另外，当第二开关41和第三开关43均处于导通状态，第二电感并联第三电感，可以进一步减小电感量，从而可以使得天线辐射体覆盖更高频带。
具体实现时，可选的，所述第二电感的取值范围为8纳亨(nH)至22 纳亨；所述第三电感的取值范围为1纳亨至5.6纳亨。
可见，相比于相关技术，本公开实施例可以增大第三电感的电感量，从而可以降低第三开关导通时损耗，进而可以进一步降低天线结构的开关损耗，提高B40/B41的天线性能。
需要说明的是，第二电感和第三电感的具体的电感值与天线的操作频段有关，比如作为低频天线和中高频天线的电感值是不同的，本公开实施例对此不做限定。
需要说明的是，本公开实施例中介绍的多种可选的实施方式，彼此可以相互结合实现，也可以单独实现，对此本公开实施例不作限定。
为方便理解，示例说明如下。
实施例一
本实施例一的天线结构可以参考图6所示。需要说明的是，本实施例以天线辐射体表现为中高频天线辐射体为例进行说明。
在图6中，在天线辐射体的馈点C串小电容C1，即可实现天线带宽覆盖。其中，C1的取值范围可以为0.5～2.7pf，可选地，C1的取值范围可以为0.8～1.5pf。应理解的是，C1相当于前述的第一电容。
第一调谐电路包括K1、K2、L1和L2。应理解的是，K1相当于前述第二开关，K2相当于前述第三开关，L1相当于前述第二电感，L2相当于前述第三电感。
具体实现时，K1和K2全off(即处于断开状态)，中高频天线辐射体产生谐振模态H1，可用于覆盖B3；K1导通，此时B点加载电感L1，L1的取值范围可以为8～22nH，可选地，L1的取值范围可以为10～15nH，中高频天线辐射体产生谐振模态H2，可用于覆盖B39和B1；K2导通，L2的取值范围可以为1～5.6nH，可选地，L2的取值范围可以为1.5～3.3nH，中高频天线辐射体产生谐振模态H3，可用于覆盖B40；K1和K2同时导通，电感量等于L1并联L2，进一步减小，中高频天线辐射体产生谐振模态H4，可用于覆盖B41。
在图6中，天线结构未示出相位调整电路，此时，相位调整电路内部为“直接连通”。
天线驻波比覆盖示意图可以参考图7。在图7中，随着B点电感的减小，对应H1→H2→H3→H4移动，天线谐振频率升高。但可以看到，H1/H2/H3/H4在B3/B1/B40/B41频带内的驻波比整体来看是没有变高的，可见，本公开实施例显著改善了的天线的阻抗失配问题。
本实施例的天线结构在馈电点C串小电容C1，直接激发了H1和H2的谐振模态，同时改善了H3/H4在B40/B41频带内的阻抗失配；另外，本实施例的天线结构要求C点的天线阻抗在B3/B1/B39/B40/B41频带内大部分位于smith圆图的第一象限。而在相关技术中，天线结构是利用天线辐射体上的部分段的等效小电感作用产生谐振模态并利用馈电通路的匹配电路优化至50欧。
为方便理解，请一并参阅图8a和图8b。
其中，图8a是C1的第一端在B3/B41频带内的天线阻抗经C1后的阻抗变化示意图。应理解的是，图8a中的天线阻抗实曲线表示C1的第一端在B3/B41频带内的天线阻抗，天线阻抗虚曲线表示C1的第一端在B3/B41频带内的天线阻抗经C1后的天线阻抗，即C1的第二端在B3/B41频带内的天线阻抗。由图8a可见，C1的第一端在B3/B41频带内的天线阻抗位于史密斯圆图的第一象限，此时B3的天线阻抗位于感性区的高阻抗区，B3频带内没有明显的谐振模态(频带内的最小驻波比大于5)，经过C1的高阻抗馈入后被激发出谐振模态。而B41此时已经具有明显的谐振模态特征(频带内的最小驻波比小于4)，但很差，经过C1的阻抗匹配后靠近史密斯圆图的匹配点。可见，经C1进行阻抗匹配后，不仅激发了H1/H2的谐振模态，也改善B40/B41的阻抗失配问题。
图8b是本公开实施例的信号源处，即C1的第二端在天线辐射体覆盖的频带内的天线阻抗。由图8b可见，C1的第二端在天线辐射体覆盖的频带内的天线阻抗均靠近史密斯圆图的匹配点，从而可以改善天线阻抗的失配问题。
需要说明的是，各天线阻抗曲线的开口朝向仅为示例(比如H1在B3频带内的阻抗曲线开口可以朝左，H4在B41频带内的阻抗曲线开口可以朝上)，它会受到馈点位置的不同而不同。本公开实施例并不对此做出限定。
在本实施例中，为了将H4最高调谐至B41，要求AB的长度小于B41 的1/4波长，一般0～12mm，可选值6～8mm。与相关技术相比，本实施例的AB段长度可以更长，如相关技术AB的长度最大是7mm，而本实施例可以到12mm。同时L2的感值可以做的更大，比如相关技术是0nH，而本实施例是3nH。
这样，AB长度增加可以降低开关断开时的损耗，L2的感值增加可以降低开关导通时的损耗。另外，本实施例可以通过两路子调谐电路既可以实现天线辐射体的多频带覆盖，从而可以减少开关的数量减小，进而可减小开关的损耗。
其中，AB段相比于相关技术，可以设置更长的原因可以包括：1、AD段总长度已经缩短，则调谐至B41所需的电感可以更大；2、C1可以改善B41的失配。
另外，与相关技术不同的是，为了将H1最低调谐至B3，本实施例要求AD段的天线长度要求接近于B3的1/4波长，约16～22mm，可选值18～20mm。因此，相比于相关技术，本实施例的天线总长度可以更小，即占用的天线空间更小。其中，相比于相关技术，本实施例的AD段可以设置更短的原因在于：通过在馈电点串C1，使得天线结构可以产生新的谐振方式，进而优化了天线结构激发的谐振模态，使得谐振模态的谐振频率更低，这样，在同等谐振频率下，本实施例因为串了C1，从而可以缩短AD的长度。
AC的长度要求比AD至少小1mm以上，一般0～18mm，即AC可以大于、等于、小于AB的长度，可选值14～16mm。
另外，B和C也可以共同一个馈点即单馈点时，此时要求AB长度小于B41的1/4波长，一般0～12mm，典型值6～8mm，这样可以减小馈入连接点的数量，不仅降低了对结构空间的需求，也减少了馈入连接点的寄生参数影响。
在本实施例中，CD的长度将显著影响天线辐射体的谐振频率，具体地，CD减小会使得H1/H2/H3谐振频率明显升高。而相关技术的CD长度对谐振频率影响较小。
需要说明的是，当BC<3mm时，第一调谐电路可能使得B40/B41的阻抗进入第一象限和第二象限交界处。此时需要C点增加一个相位调整电路，实 现方式可以是只并小电容(如0.3～0.7pf)到地，或者先串小电感再并小电容(如串2～4nH并0.3～0.7pf)，或者直接加长天线至馈电之间的馈电线路，从而使得B40/B41阻抗调整至第一象限。其中，相位调整电路内部具体的值可以根据实际调试情况进行选择。当B和C共馈点时，则B点应该先并第一调谐电路，然后再串这个相位调整电路(即开关电路连在B点和主地之间，而相位调整电路加在B点和电容之间)。
需要说明的是，如果B点或者C点预先加载电感或电容，则AD的长度可以继续加长或剪短。
另外，上述天线尺寸要求仅为示例。在实际应用中，随着通信终端中天线环境的变化，比如天线净空的大小，天线区域加入大的金属器件，高介电的材料如塑胶/印刷电路板(Printed Circuit Board，PCB)，天线馈电线路的影响等，都会引起天线长度的很大变化。而且应用于不同的终端设备中尺寸也存在差异。需要根据实际的天线环境调整尺寸要求。
本实施例的天线结构可以应用于“全面屏”移动终端，金属外边框作为天线辐射体。
在实际应用中，天线辐射断口可以为1.5mm，天线距离整机的金属地约1.5mm(俗称天线净空距离)，距离屏幕仅1.2mm(屏幕此时有明显吸收天线效率约0.8～1.5db)。AD＝18.5mm，AC＝15.5mm，AB＝7mm，L1＝13nH，L2＝2.7nH，C1＝1pf。K1和K2全off，天线谐振模态H1；K1导通，谐振模态H2，K2导通，谐振模态H3；K1和K2同时导通，谐振模态H4。
为了微调频率和静电保护，B点可以预并联电感30nH。为了略微优化H4的驻波比，C点可以预并联0.3pf电容。自由空间的天线效率可以如图9所示，天线峰值效率均可达到-4dB左右，B3/B39/B1/B40/B41频带内平均效率-4.4/-5/-4.3/-4.2/-3.1dB，满足移动终端的天线效率需求，且属于高性能的天线。
实施例二
本实施例与实施例一的主要区别在于，新增了第二调谐电路，且本实施例的第二调谐电路主要用于实现双谐振的载波聚合(Carrier Aggregation，CA)。
如图10所示，本实施例的第二调谐电路包括K3、L3和C2。其中，K3 相当于前述第一开关，L3相当于前述第一电感，C2相当于前述第二电容。
具体实现时，当K1导通，K2不导通(即处于H1或H2状态)，且K3导通时，天线辐射体可以产生两个新的谐振模态H5和H6，且同时存在，可用于覆盖B39+B41的CA需求。
当K1和K2均不导通，仅K3导通时，天线辐射体可以用于覆盖B3+B40的CA需求。
其中，并联的L3和C2在B40或B41频带内可以等效于电容，且一般需要0.3p～1.2p；并联的L3和C2在B3/B39频带内则可以根据H5的谐振频率需要进行调整，比如等效于为高阻抗(开路、很小电容、很大电感)。
在实际应用中，为减小开关的占用空间和降低开关成本，可以将K1、K2和K3集成在一个模块上，公共端接地。
本实施例的C点的天线阻抗，即C1的第一端的天线阻抗经过L3、C2、C1后的阻抗变化示意图可以参考图11。此时K1和K3导通，L3和C2在B39频带内等效于开路，在B41频带内等效于并电容。
本实施例的信号源处的谐振模态H5和H6的驻波比示意图可以参考图12。
在图10中，天线结构未包括相位调整电路。但在某些实现方式中，可以根据实际需求设置相位调整电路，需要说明的是，当B和C共馈点时(即单馈点)，则B点应该先并K1和K2的第一调谐电路，然后再串相位调整电路，再接C2、L3和C1的公共连接点。
实施例三
本实施例与实施例一的主要区别在于，新增了第二调谐电路，且本实施例的第二调谐电路主要用于调节天线结构的目标谐振模态的谐振频率，改善目标谐振模态的目标频带的天线驻波比，减少失配损耗。
如图13所示，本实施例的第二调谐电路包括串接的K3和C2。其中，K3相当于前述第一开关，C2相当于前述第二电容。本实施例的第二调谐电路可以用于调节H2和H3的谐振频率，以更好的改善B39和B40的天线驻波比，减小失配损耗。如导通C2则H2和H3谐振频率降低。
C点与B点调谐频率的区别在于虽然调谐范围更窄，但是C点的开关损耗很低，适合于小范围微调。
当然，在其他实施方式中，也可以将C2换成电感调谐(即C2为匹配器件，具体可以是电感或者电容)，只需要适当调整L1，L2，天线长度，也可以达到上述效果。另外，C2也可以连接至C1的另一端，也可以达到相似的效果。
实施例一、实施例二和实施例三仅以天线辐射体为中高频天线辐射体为例进行说明，但本公开实施例的天线辐射体也可以表现为低频天线辐射体。
在天线辐射体表现为低频天线辐射体的情况下，低频天线辐射体可以产生谐振模态H1/H2/H3/H4，用于覆盖B12(0.7～0.746GHz)/B20(0.79～0.86GHz)/B5(0.824～0.894GHz)/B8(0.88～0.96GHz)。
为了将H4最高调谐至B8，要求AB的长度小于B8的1/4波长，一般0～35mm，典型值25～30mm。为了将H1最低调谐至B12，要求AD段的天线长度要求接近于B12的1/4波长，约40～60mm，典型值45～55mm。AC长度要求比AD至少小4mm以上，一般0～50mm，即AC可以大于、等于、小于AB的长度，典型值33～45mm。另外，B和C也可以共同一个馈点即单馈点时，此时要求AC长度小于B8的1/4波长，一般0～35mm，典型值28～35mm，这样可以减小馈入连接点的数量，不仅降低了对结构空间的需求，也减少了馈入连接点的寄生参数影响。此时仍然要求C点的天线阻抗在B3/B1/B39/B40/B41频带内大部分位于smith圆图的第一象限，然后通过串小电容C1激发新的谐振模态或匹配至50欧。
本公开实施例还提供一种终端，该终端包括如上所述的天线结构。
其中，天线结构可以参考上述描述，此处不再赘述。应理解的是，由于采用了前述天线结构，因此本公开实施例提供的终端具有上述天线结构的所有效果，此处不再赘述。
在实际应用中，通信终端可以是手机、平板电脑(Tablet Personal Computer)、个人数字助理(personal digital assistant，简称PDA)、移动上网装置(Mobile Internet Device，MID)或可穿戴式设备(Wearable Device)等。
以上，仅为本公开的具体实施方式，但本公开的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本公开揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本公开的保护范围之内。因此，本公开的保护范围应 以权利要求的保护范围为准。

Claims (19)

  1. 一种天线结构，应用于通信终端，包括：天线辐射体、信号源、第一电容和第一调谐电路；
    所述天线辐射体的第一端接地；
    所述第一电容的第一端和所述第一调谐电路的第一端均与所述天线辐射体的连接点电连接，所述第一电容的第二端与所述信号源电连接，所述第一调谐电路的第二端接地；
    其中，所述第一电容的第一端在目标频点的天线阻抗位于史密斯圆图的第一象限，所述目标频点为所述天线辐射体覆盖的频带中的至少部分频点。
  2. 根据权利要求1所述的天线结构，其中，所述目标频点为所述天线辐射体覆盖的每个频带中的至少三分之二的频点。
  3. 根据权利要求1所述的天线结构，其中：
    所述第一电容的第一端电连接所述天线辐射体的第一连接点，所述第一调谐电路的第二端电连接所述天线辐射体的第二连接点；或者，
    所述第一电容的第一端和所述第一调谐电路的第一端电连接所述天线辐射体的同一连接点。
  4. 根据权利要求1所述的天线结构，其中：
    所述天线辐射体的总长度的取值范围是所述天线辐射体覆盖的频带中的第一频带的中心频点的3/16波长至3/8波长；
    所述天线辐射体的第二端与电连接所述第一调谐电路的连接点之间的第一长度小于所述天线辐射体覆盖的频带中的第二频带的1/4波长；
    其中，所述第一频带的中心频点小于所述天线辐射体覆盖的频带中除所述第一频带之外的任一频带的中心频点；所述第二频带的中心频点大于所述天线辐射体覆盖的频带中除所述第二频带之外的任一频带的中心频点。
  5. 根据权利要求4所述的天线结构，其中，在所述第一电容的第一端电连接所述天线辐射体的第一连接点，所述第一调谐电路的第二端电连接所述天线辐射体的第二连接点的情况下，所述天线辐射体的第二端与所述第一连接点之间的第二长度，与所述总长度的差的绝对值大于第一特定值。
  6. 根据权利要求5所述的天线结构，其中：
    在所述天线辐射体为中高频天线辐射体的情况下，所述总长度的取值范围为16毫米至22毫米；所述第一长度的取值范围是0毫米至12毫米；所述第二长度的取值范围是0毫米至18毫米；
    在所述天线辐射体为低频天线辐射体的情况下，所述总长度的取值范围为40毫米至60毫米；所述第一长度的取值范围是0毫米至35毫米；所述第二长度的取值范围是0毫米至50毫米。
  7. 根据权利要求1所述的天线结构，还包括相位调整电路；所述第一电容的第一端通过所述相位调整电路与所述天线辐射体的连接点电连接；
    其中，所述相位调整电路的相位调整范围包括0。
  8. 根据权利要求7所述的天线结构，还包括第二调谐电路，所述第二调谐电路的第一端与所述第一电容的第一端或所述第一电容的第二端电连接，所述第二调谐电路的第二端接地。
  9. 根据权利要求8所述的天线结构，其中，所述第二调谐电路包括串接的调谐元件和第一匹配元件；
    其中，所述第一匹配元件的第一端与所述第一电容的第一端或所述第一电容的第二端电连接；所述第一匹配元件的第二端通过所述调谐元件接地。
  10. 根据权利要求9所述的天线结构，其中：
    所述调谐元件为第一开关或可变电容；
    所述第一匹配元件包括第二电容和/或第一电感；
    其中，在所述第一匹配元件为所述第二电容或所述第一电感的情况下，所述第一匹配元件的第一端与所述第一电容的第一端或所述第一电容的第二端电连接；
    在所述第一匹配元件包括并联的所述第二电容和所述第一电感的情况下，所述第一匹配元件的第一端与所述第一电容的第一端电连接。
  11. 根据权利要求1至10中任一项所述的天线结构，其中，所述第一调谐电路包括并联的第一子调谐电路和第二子调谐电路；
    其中，在所述第一子调谐电路处于第一工作状态，所述第二子调谐电路处于第一工作状态的情况下，所述天线辐射体产生第一谐振模态；
    在所述第一子调谐电路处于第二工作状态，所述第二子调谐电路处于第一工作状态的情况下，所述天线辐射体产生第二谐振模态；
    在所述第一子调谐电路处于第一工作状态，所述第二子调谐电路处于第二工作状态的情况下，所述天线辐射体产生第三谐振模态；
    在所述第一子调谐电路处于第二工作状态，所述第二子调谐电路处于第二工作状态的情况下，所述天线辐射体产生第四谐振模态；
    其中，所述第一谐振模态、所述第二谐振模态、所述第三谐振模态和所述第四谐振模态的谐振频率依序升高。
  12. 根据权利要求11所述的天线结构，其中，所述第一子调谐电路包括第二开关和第二匹配元件；所述第二子调谐电路包括第三开关和第三匹配元件；
    其中，在所述第二开关和所述第三开关均处于断开状态的情况下，所述天线辐射体产生所述第一谐振模态；
    在所述第二开关处于导通状态，第三开关处于断开状态的情况下，所述天线辐射体产生所述第二谐振模态；
    在所述第二开关处于断开状态，第三开关处于导通状态情况下，所述天线辐射体产生所述第三谐振模态；
    在所述第二开关和所述第三开关均处于导通状态的情况下，所述天线辐射体产生所述第四谐振模态。
  13. 根据权利要求12所述的天线结构，其中，所述第二匹配元件包括第二电感；所述第三匹配元件包括第三电感；
    其中，所述第二电感的取值大于所述第三电感的取值。
  14. 根据权利要求13所述的天线结构，其中，所述第二电感的取值范围为8纳亨至22纳亨；所述第三电感的取值范围为1纳亨至5.6纳亨。
  15. 根据权利要求1至10中任一项所述的天线结构，其中：
    所述第一调谐电路由可变电容组成；或者，
    所述第一调谐电路由可变电容和固定电感串联或并联组成。
  16. 根据权利要求1至10中任一项所述的天线结构，其中，所述第一电容的取值小于第二特定值。
  17. 根据权利要求16所述的天线结构，其中，所述第一电容的取值范围为0.5皮法至2.7皮法。
  18. 根据权利要求16所述的天线结构，其中，所述第一电容为固定电容或可变电容。
  19. 一种通信终端，包括权利要求1至18中任一项所述的天线结构。
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