CN111370865B

CN111370865B - Feed network and corresponding terminal

Info

Publication number: CN111370865B
Application number: CN201811589022.0A
Authority: CN
Inventors: 赵鑫
Original assignee: Shanghai Chuanggong Telecom Technology Co Ltd
Current assignee: Shanghai Chuanggong Telecom Technology Co Ltd
Priority date: 2018-12-25
Filing date: 2018-12-25
Publication date: 2022-02-25
Anticipated expiration: 2038-12-25
Also published as: CN111370865A

Abstract

The invention discloses a feed network and a corresponding terminal, comprising a feed wire and an antenna elastic sheet; the first end of the feed wire is electrically connected with the radio frequency coaxial base, the second end of the feed wire is grounded, and the feed wire is an annular wire; the feed wire enables the antenna wire to be excited to form a plurality of low-order modes; the antenna spring sheet is used for electrically connecting the feed wire with the antenna wire; to reduce the cost of BOM.

Description

Feed network and corresponding terminal

Technical Field

The present invention relates to the field of communications, and in particular, to a feeding network and a corresponding terminal.

Background

The Total screen mobile phone has very small antenna clearance which may be only 2.5-3.5 mm, the efficiency of the antenna is low, and the Total Radiated Power (TRP) index is difficult to reach the standard requirement. The TRP is an integral value of radio frequency radiation power of the mobile phone on a three-dimensional spherical surface in space, and reflects the emission characteristics of the mobile phone in all directions. The total radiation power is limited to an upper limit, the maximum total radiation power is limited by the mobile phone, and the output power of the radio frequency module of any mobile phone cannot exceed 2W (33 dBm). The closer the total radiated power of the handset is to this value, the better the signal transmission capability is, and the greater the radiation is. The index is usually mutually restricted with an SAR (Specific Absorption Rate) index (an index reflecting radiation absorbed by a human body), and a qualified mobile phone has good transmitting capacity and a low SAR value.

Currently, a tunnel (antenna tuner) or an adjustable capacitor is generally added to expand a low frequency bandwidth and improve antenna efficiency. But this increases the Bill of Material (Bill of materials) cost of the handset.

Content of application

The embodiment of the invention provides a feed network and a corresponding terminal, which are used for reducing the BOM cost.

The feed network provided by the embodiment of the invention comprises a feed wire and an antenna elastic sheet;

the first end of the feed wire is electrically connected with the radio frequency coaxial base, the second end of the feed wire is grounded, and the feed wire is an annular wire; the feed wire enables the antenna wire to be excited to form a plurality of low-order modes;

the antenna spring sheet is used for electrically connecting the feed line and the antenna line.

In an optional embodiment, the second end of the feeding trace is provided with a plurality of grounding points, and the positions of the grounding points are all different;

the feed trace is grounded with one of the plurality of ground points.

In an optional embodiment, M grounding points of the plurality of grounding points are electrically connected to M first lumped elements, respectively, and the feeding trace is grounded through one of the first lumped elements, where M is less than or equal to N, and N is the number of all the grounding points.

In an optional embodiment, at least one of the plurality of grounding points is electrically connected to the antenna tuner, and the feeding trace is grounded through the antenna tuner.

In an alternative embodiment, at least one second lumped element is further included;

the second lumped element is electrically connected with a feed line between the radio frequency coaxial base and the antenna elastic sheet, and the second lumped element is used for adjusting the characteristic impedance of the feed line.

In an alternative embodiment, the number of the second lumped elements is 2, one of the second lumped elements is connected in series to the feed trace, and the other second lumped element is connected in parallel to the feed trace.

In an alternative embodiment, the length of the feeding trace satisfies the following formula:

wherein c is the wave velocity in vacuum; f is the high-frequency resonant frequency of the antenna; epsilon gamma is the relative dielectric constant of the PCB medium; and L is the length of the feed line.

In an optional embodiment, the feed trace includes a first segment of trace, a second segment of trace and a third segment of trace, which are connected end to end in sequence, and the first segment of trace, the second segment of trace and the third segment of trace form three sides of a rectangle.

In an optional embodiment, the length of the first segment of wire is 2.6mm, the length of the second segment of wire is 5.7mm, the length of the third segment of wire is 4.2mm, and the wire width of the feed network is 0.3 mm.

The invention also provides a terminal which comprises the feed network and the antenna.

In an optional embodiment, the antenna includes the antenna trace and a parasitic element, one end of the parasitic element is grounded, and one end of the antenna trace is electrically connected to the feed trace through the antenna spring.

The feeding network in the above embodiment of the present invention includes a feeding trace and an antenna spring. The first end of the feed wire is electrically connected with the radio frequency coaxial base, and the second end of the feed wire is grounded. The feed line is a loop line, so that the antenna line is excited to a plurality of low-order modes. The antenna spring sheet is used for electrically connecting the feed line and the antenna line. The feed line is in a high-order mode, the antenna line is excited to a low-order mode by the feed line, and the feed line is set to be a ring line in the embodiment of the invention, so that the mode of the feed line is multiplexed, and under the excitation of the high-order mode of the ring feed line, the antenna line is excited to a common mode with half wavelength, a differential mode with one wavelength and a high-order common mode with three-half wavelength, namely, a plurality of low-order modes are excited, so that the low-frequency bandwidth is widened, an antenna tuner or adjustable capacitor in a circuit can be omitted, the BOM cost is reduced and the cost advantage of products is improved under the condition of realizing the expansion of the antenna bandwidth. Meanwhile, due to the annular arrangement of the feed wiring, the medium-high frequency hot spot distribution can be dispersed, and the SAR of the antenna can be reduced.

Drawings

Fig. 1 is a schematic structural diagram of a feed network according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a feeding trace according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a feeding network including a plurality of grounding points according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a PCB according to an embodiment of the present invention;

fig. 5 is a schematic diagram illustrating a positional relationship between a feed trace, an antenna spring and an antenna according to an embodiment of the present invention;

fig. 6 is a schematic diagram of an antenna provided in an embodiment of the present invention;

fig. 7 is a schematic diagram of S11 of the antenna according to the embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The feed network in the embodiment of the invention can be suitable for terminals with communication functions, such as mobile phones, tablet computers, notebook computers and the like, and not only can be suitable for the design of a main antenna, but also can be applied to the design of a three-in-one antenna and a diversity antenna. In the embodiment of the invention, the main antenna of the full-screen mobile phone is taken as an example for introduction.

Fig. 1 shows a schematic structural diagram of a feed network in an embodiment of the present invention. As shown in fig. 1, the feeding network includes a feeding trace 1 and an antenna spring piece 2. The first end of the feed line 1 is electrically connected with the radio frequency coaxial base 3, and the second end of the feed line 1 is grounded. As can be seen from fig. 1, the feed trace is a loop trace, which can excite the antenna trace to generate a plurality of low-order modes. The antenna spring 2 is located above the feed trace 1, and is used for electrically connecting the feed trace 1 with an antenna trace (not shown).

The feed line is in a high-order mode, the antenna line is excited to a low-order mode by the feed line, and the feed line is set to be a ring line in the embodiment of the invention, so that the mode of the feed line is multiplexed, and under the excitation of the high-order mode of the ring feed line, the antenna line is excited to a common mode with half wavelength, a differential mode with one wavelength and a high-order common mode with three-half wavelength, namely, a plurality of low-order modes are excited, so that the low-frequency bandwidth is widened, an antenna tuner or adjustable capacitor in a circuit can be omitted, the BOM cost is reduced and the cost advantage of products is improved under the condition of realizing the expansion of the antenna bandwidth. Meanwhile, due to the annular arrangement of the feed wiring, the medium-high frequency hot spot distribution can be dispersed, and the SAR of the antenna can be reduced.

The electrical length of the feed line needs to meet the requirement of exciting a high-order mode, that is, the total length of the feed line meets the principle of half-wave dipole λ/4, that is, the satisfied calculation formula is as follows:

wherein c is the wave velocity in vacuum; f is the high-frequency resonant frequency of the antenna; ε γ is the dielectric constant of PCB (Printed Circuit Board); and L is the length of the feed line.

In the embodiment of the invention, the feed wire 1 starts from the radio frequency coaxial base 3 and comprises a first wire section 11, a second wire section 12 and a third wire section 13 which are sequentially connected end to end until the third wire section is grounded. The first section of wire 11, the second section of wire 12 and the third section of wire 13 form three sides of a rectangle. In a specific embodiment, as shown in fig. 2, the width of the whole feeding network is 0.3mm, the length of the first section of wire is 2.6mm, the length of the second section of wire is 5.7mm, and the length of the third section of wire is 4.2 mm.

The total length of the feed track can be set to 12.5mm, and its equivalent electrical length can also be fine-tuned by lumped elements.

In order to achieve fine adjustment of the equivalent electrical length of the feed line, in the embodiment of the invention, a plurality of grounding points are arranged at the second end of the feed line, the positions of the grounding points are different from each other, and one of the grounding points can be selected by the feed line to be grounded.

For example, as shown in fig. 3, the second end of the feed track is provided with three grounding points, a first grounding point 14, a second grounding point 15 and a third grounding point 16. The feed track may be grounded from any one of the first, second and

third ground points

14, 15, 16.

Preferably, M of the plurality of grounding points are electrically connected to the M first lumped elements, respectively, and the feeding trace is grounded through one of the first lumped elements, where M is less than or equal to N, and N is the number of all the grounding points. For example, two grounding points selected from the three grounding points in fig. 3 may be electrically connected to a first lumped element respectively. Optionally electrically connecting the first ground to a first lumped element; or alternatively, the third ground is electrically connected to a first lumped element. The first grounding point can be connected with an inductor of 1 nH-2 nH in series or connected with a resistor of 0 omega in series; or, the third grounding point is connected with an inductor in series or a resistor in series. Thus, when the electrical length of the feeding wire is insufficient, the electrical length can be lengthened by connecting the inductor in series; the resonance frequency of the formed equivalent circuit can also be adjusted by connecting the capacitors in series.

Further, under the condition that the OTA requirement is particularly strict, at least one of the grounding points may be electrically connected to the antenna tuner, and the feeding wire is grounded through the antenna tuner. For example, the second grounding point 15 in fig. 3 is connected to an antenna tuner, and since the antenna tuner is used in conjunction with two grounded lumped elements, the feed trace is grounded through the lumped elements of the antenna tuner. The feed wire is grounded by connecting the antenna tuner, the low-frequency bandwidth is further expanded by adjusting the antenna tuner, or the resonance is heavier than a plurality of frequency bands by different matching tuning of the antenna tuner.

In order to adjust the characteristic impedance of the feeding trace, the embodiment of the present invention provides a second lumped element on the feeding trace. The second lumped element is arranged between the radio frequency coaxial base and the antenna elastic sheet and is electrically connected with the feed routing. The whole feed line is arranged in a clearance area of the mobile phone PCB, and in order to reduce the influence and loss of the radio frequency microstrip line on the high-frequency mode of the feed line, the distance from the radio frequency coaxial base to the second lumped element is as short as possible. In the embodiment of the invention, the distance from the radio frequency coaxial base to the second lumped element is 0.8 mm.

For example, the number of the second lumped elements is 2, one of the second lumped elements is connected in series to the feeding trace, and the other one of the second lumped elements is connected in parallel to the feeding trace. As shown in fig. 3, the second lumped element 17 is a series access feed trace and the second lumped element 18 is a parallel access feed trace.

Fig. 4 shows a PCB comprising the above described feed network in an embodiment of the invention. In order to facilitate the connection between the lumped element and the antenna tuner, the positions of the feed trace connecting the lumped element and the radio frequency coaxial base are set to match in fig. 4. As shown in fig. 4, the first matching bit 41, the second matching bit 42, and the third matching bit 43 are located at the ground end of the feed trace 1. The first matching bit 41 is used to connect a first lumped element. The second matching bit 42 is used to connect a first lumped element. The third matching bits 43 comprise matching bits of the antenna tuner and matching bits of the lumped elements used in conjunction with the antenna tuner for connecting one antenna tuner and two lumped elements. The fourth matching bit 44 and the fifth matching bit 45 are located between the rf coaxial base 3 and the antenna spring 2, the fourth matching bit 44 is used to connect a second lumped element in series to the feeding trace, and the fifth matching bit 45 is used to connect a second lumped element in parallel to the feeding trace.

In addition, because the clearance area of the PCB is very limited, in order to reduce the effect of a parallel plate capacitor formed by the antenna elastic sheet, the metal battery compartment and the injection-molded metal middle shell, and also in order to reduce the coupling effect of the antenna elastic sheet and the FPC wiring and steel sheet on the back of the mobile phone screen, the antenna elastic sheet needs to be transversely placed on the PCB, so that the antenna elastic sheet is located in the clearance area of the PCB as much as possible.

The embodiment of the invention also provides a terminal, which comprises the feed network and the antenna. The positional relationship between the feed trace, the antenna spring and the antenna is shown in fig. 5. The feed line 1 is located on the PCB5, the feed line 1 is provided with an antenna spring 2, and the feed line 1 is electrically connected with the antenna 6 through the antenna spring 2.

Fig. 6 shows a schematic diagram of an antenna in an embodiment of the invention. As shown in fig. 6, the antenna includes an antenna trace 61 and a parasitic element 62. One end 621 of the parasitic element 62 is grounded, and one end of the antenna trace is electrically connected to the feed trace through the antenna spring.

The antenna is arranged on the side edge or the bottom edge of the mobile phone as far as possible, and electromagnetic waves radiate at the positions, so that the antenna efficiency can be improved. The electrical length of the antenna wiring needs to meet the requirement that resonance is formed in a low-frequency band, and meanwhile, a high-order mode generated by feeding wiring feeding excites a low-order mode of the low frequency, and the two modes are mutually superposed to jointly influence the passive resonance of the low frequency of the antenna.

The feed trace may increase the bandwidth of the low frequency band excited by the antenna trace. And the bandwidth expansion of the high frequency band is realized by depending on the parasitic unit. Because the mobile phone antenna is the deformation of the half-wave dipole antenna model, the ground of the mobile phone can also participate in the radiation of electromagnetic waves. The parasitic unit in the embodiment of the invention is led out from the screw post at the side of the mobile phone in a grounding way, and can better participate in radiation through the contact of the side elastic sheet or the step, thereby improving the antenna efficiency.

On the other hand, the antenna wire generates a low-frequency broadband resonance waveform together with the self resonance mode under the excitation of the feed wire. Meanwhile, the frequency doubling and frequency tripling of the low-frequency resonance can also influence the high-frequency resonance of the feed wire. And the antenna wiring uses the side of the mobile phone as much as possible and extends fully to the two sides, which is beneficial to improving the antenna efficiency.

In a specific embodiment, when the first matching bit of the feed trace is connected in series with a 1.2nH inductor, S11 of the antenna is shown in fig. 7. The passive efficiency of the antenna is shown in table 1, corresponding to S11 of fig. 7.

TABLE 1

The passive efficiency of the antenna in table 1 is mostly-6 to-3, and the passive efficiency of the general antenna in the prior art is mostly-10 to-8, so that it can be seen that the passive efficiency of the antenna is improved by the feed line of the embodiment of the present invention.

In the embodiments of the present invention, the "upper" and the "lower" correspond to the upper side and the lower side of the picture, that is, the "upper surface" refers to the surface corresponding to the upper side of the device in the picture, and the "lower surface" refers to the surface corresponding to the lower side of the device in the picture.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A feed network is characterized by comprising a feed wire and an antenna elastic sheet;

the first end of the feed wire is electrically connected with the radio frequency coaxial base, the second end of the feed wire is grounded, and the feed wire is an annular wire; the annular feed wire enables the antenna wire to be excited to form a plurality of low-order modes;

the feed wiring is in a high-order mode; the length of the feed wire satisfies the following formula:

wherein c is the wave velocity in vacuum; f is the high-frequency resonant frequency of the antenna corresponding to the antenna routing; epsilon gamma is the relative dielectric constant of the medium of the PCB where the feed network is positioned; l is the length of the feed line;

the antenna elastic sheet is positioned on the feed wire and used for electrically connecting the feed wire with the antenna wire.

2. The feed network of claim 1, wherein the second end of the feed trace is provided with a plurality of grounding points, and the plurality of grounding points are all at different positions;

the feed trace is grounded with one of the plurality of ground points.

3. The feeding network of claim 2, wherein M grounding points of the plurality of grounding points are electrically connected to M first lumped elements, respectively, and the feeding trace is grounded through one of the first lumped elements, wherein M is less than or equal to N, and N is the number of all the grounding points.

4. The feed network of claim 2, wherein at least one of the plurality of ground points is electrically connected to an antenna tuner, the feed trace being grounded through the antenna tuner.

5. The feed network of claim 1, further comprising at least one second lumped element;

6. The feed network of claim 5, wherein the number of second lumped elements is 2, one of the second lumped elements being serially connected into the feed trace and the other of the second lumped elements being connected in parallel into the feed trace.

7. The feed network of claim 1, wherein the feed traces include a first segment, a second segment, and a third segment that are connected end-to-end in sequence, the first segment, the second segment, and the third segment forming three sides of a rectangle.

8. The feed network of claim 7, wherein the first segment of traces have a length of 2.6mm, the second segment of traces have a length of 5.7mm, the third segment of traces have a length of 4.2mm, and the feed network has a trace width of 0.3 mm.

9. A terminal, characterized in that it comprises a feeding network and an antenna according to any of claims 1 to 8.

10. The terminal of claim 9, wherein the antenna comprises the antenna trace and a parasitic element, one end of the parasitic element is grounded, and one end of the antenna trace is electrically connected to the feed trace through the antenna spring.