Three-frequency flexible metasurface for improving performance of mobile phone antenna in pocket

Abstract

The invention belongs to the technical field of wireless communication, and particularly discloses a three-frequency flexible metasurface applied to improving the performance of a mobile phone antenna in a pocket, the three-frequency flexible metasurface comprises a conductive layer, a dielectric layer and a backflow layer which are sequentially arranged, the conductive layer is composed of three-ring conductive patches in N rows and N columns, N is larger than or equal to 6, and each three-ring conductive patch comprises an outer ring, a middle ring and an inner ring. According to the invention, the three-frequency flexible metasurface design is adopted, and the same-phase superposition of a reflected wave and an incident wave is realized within the reflection phase bandwidth [-90 degrees, 90 degrees], so that the performance of the mobile phone antenna is improved.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a three-band flexible metasurface used to improve the performance of a mobile phone antenna in a pocket. Background Art

[0002] Smartphones, as the most common mobile smart terminals in human society, occupy a pivotal position in wearable devices. Currently, the more successful commercial wearable devices include smartphones, smart watches, smart bracelets and VR glasses. As electronic devices with higher computing power among wearable devices, smartphones have great advantages in efficient data transmission and processing during device communication, and have become the data interaction center in many wearable devices. Therefore, the wireless communication module of smartphones plays a vital role in communication rate and throughput.

[0003] In addition to retaining onboard antennas such as IFA and PIFA for 2G / 3G / 4G communications, commercial mobile phone antennas currently use mid-frame antennas and MIMO technology for 5G communications for aesthetic reasons. At the same time, in order to meet the high speed, low latency, and large connections required by 5G mobile phones, the number of mobile phone antennas has increased significantly. Currently, 5G mobile phones generally have more than 10 antennas to achieve multi-band communications.

[0004] Improving the performance of mobile phone antennas is particularly important in communication between wearable devices. Smartphones are usually placed in clothing pockets. Due to their close contact with the human body, human tissue may interfere with antenna performance, resulting in reduced signal quality or unstable communication. Therefore, there are two factors to consider:

[0005] First, the performance of mobile phone antennas may be affected by the uneven dielectric properties of the human body. The mobile phone antenna in the pocket is basically close to the surface of the human body, and the dielectric constants of different organs and tissues of the human body vary greatly. This uneven dielectric property may cause antenna frequency deviation, poor matching, changes in radiation patterns, etc., which will eventually cause a decline in communication performance or even failure to communicate.

[0006] Second, the absorption of electromagnetic waves by the human body will lead to a series of biological effects. These effects depend on the frequency and energy of the electromagnetic waves. Low-frequency electromagnetic fields mainly produce induced currents in biological tissues, while high-frequency electromagnetic fields may cause tissue heating and affect human health. Currently, many countries use the specific absorption rate (SAR) as an indicator to measure the absorption of radio frequency energy by human tissues. The Chinese standard YD / T1644 requires that the SAR limit for network access testing be an average value of 10g, with a limit of 2W / kg.

[0007] In order to improve the performance of mobile phone antennas and reduce the absorption of electromagnetic waves by the human body without changing the structure of the mobile phone antenna, placing a piece of metal ground on the side of the pocket close to the human body is a feasible solution in theory. However, the metal ground must be at least a quarter wavelength away from the mobile phone antenna to have a reflective effect, which is difficult to achieve in a narrow pocket environment, and placing a metal ground in the pocket also affects the comfort of wearing. Due to its special reflection mechanism, the metasurface can achieve the forward superposition of the incident wave and the reflected wave, which can improve the performance of the mobile phone antenna while achieving a low profile. Therefore, it is of great significance to use metasurfaces to improve the antenna performance in narrow spaces such as pockets and reduce the radiation hazards to the human body.

[0008] At present, the main methods for improving antenna performance are:

[0009] 1. Form an antenna array. By arranging multiple antennas together to form a special array, the antenna gain can be significantly improved, such as MIMO, phased array, etc. However, in this application scenario, the structure of the mobile phone antenna remains unchanged, and this method is obviously not suitable for pocket scenarios.

[0010] Second, optimize the antenna structure, such as optimizing the size, adjusting the feed point, slotting, etc. This method requires adjustments to the mobile phone antenna structure, which usually faces problems such as complex design structure and high cost, which is generally not suitable for mass production in the industry.

[0011] 3. Use a reflector. Placing a reflector such as a metal ground behind the antenna can increase the antenna gain, but this method often requires the distance between the metal ground and the antenna to be a quarter of a wavelength, which is generally difficult to achieve in a narrow pocket environment, and the metal ground has a poor experience in wearing comfort.

[0012] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0013] The purpose of the present invention is to solve the technical problems existing in the background technology. To this end, a three-band flexible metasurface is provided for improving the performance of a mobile phone antenna in a pocket.

[0014] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0015] A three-band flexible metasurface used to improve the performance of a mobile phone antenna in a pocket, comprising a conductive layer, a dielectric layer and a return layer arranged in sequence, wherein the conductive layer is composed of three-ring conductive patches in N rows and N columns, wherein N is greater than or equal to 6, and each three-ring conductive patch comprises an outer ring, a middle ring and an inner ring.

[0016] The following is a technical solution further defined in the present invention: the outer ring of the three-ring conductive patch is a square ring with a side length of 20 mm to 21.9 mm.

[0017] The following is a technical solution further defined in the present invention: the middle ring of the three-ring conductive patch is a square ring with square cut corners, the side length of the square ring is 14mm to 17.2mm, and the side length of the square cut corner is 1.5mm.

[0018] The following is a technical solution further defined by the present invention: the inner ring of the three-ring conductive patch is a square ring with square cut corners, the side length of the square ring is 9.2 mm to 12 mm, and the side length of the square cut corner is 1.5 mm.

[0019] The following is a technical solution further defined by the present invention, wherein the dielectric layer is a square.

[0020] The following is a technical solution further defined by the present invention, wherein the reflux layer is a square.

[0021] The following is a technical solution further limited by the present invention, wherein the thickness of the dielectric layer is 1 to 3 mm.

[0022] The following is a technical solution further defined in the present invention, wherein the thickness of the conductive layer is 0.01 to 0.03 mm, and the thickness of the reflow layer is 0.01 to 0.03 mm.

[0023] The following is a technical solution further defined by the present invention, wherein the dielectric layer is made of a flexible PDMS material.

[0024] The following is a technical solution further limited by the present invention, wherein the conductive layer and the return layer are both conductive cloths woven from conductive fibers.

[0025] Compared with the prior art, the present invention has the following technical effects:

[0026] The three-band flexible metasurface design adopted by the present invention superimposes the reflected wave and the incident wave in the same phase within the reflection phase bandwidth [-90°, 90°], thereby improving the performance of the mobile phone antenna, which is mainly manifested in the following aspects:

[0027] Without changing the structure of the mobile phone antenna itself, the performance of the mobile phone antenna can also be improved (increasing gain, radiation efficiency, and reducing SAR): the maximum gain at 2.4GHz, 3.5GHz, and 5.3GHz is increased by 4.2dB, 4.6dB, and 5.8dB respectively; the radiation efficiency is increased by 16.6%, 11.5%, and 12.1% respectively; the SAR of the mobile phone at the waist and abdomen is 0.032W / kg, 0.053W / kg, and 0.045W / kg respectively;

[0028] Through the working mechanism of the tri-band flexible metasurface, the distance between the mobile phone antenna and the metasurface is less than a quarter of the wavelength, which is conducive to mobile phone communication in pockets: the distance between the tri-band flexible metasurface and the mobile phone antenna is only 1mm, which is much smaller than the quarter wavelength of 2.4GHz 31.25mm;

[0029] The dimensions of the three-band flexible metasurface are designed under a fixed pocket area, and the optimal design of the metasurface under a fixed area is given, which is in line with practical applications: the overall dimension of the three-band flexible metasurface is designed to be 180mm*180mm, which has the best performance improvement;

[0030] The triple-band flexible metasurface adopts a polarization-insensitive structure and flexible material design, which has a stable performance improvement effect on antennas with different polarization modes. It has the property of polarization insensitivity, ensuring stable performance improvement while improving wearing comfort.

[0031] The present invention is further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 It is a schematic diagram of the upper surface structure of a unit in the three-frequency flexible metasurface of the present invention;

[0034] Figure 2 It is a schematic diagram of the lower surface structure of a unit in the three-frequency flexible metasurface of the present invention;

[0035] Figure 3 is a schematic diagram of the use of the tri-band flexible metasurface of the present invention, wherein the tri-band flexible metasurface is placed under the antenna of a mid-frame mobile phone;

[0036] Figure 4 The radiation pattern comparison between the three-band flexible metasurface without using the three-band flexible metasurface and the one with using the three-band flexible metasurface; Figure 3 (a) is the XY plane radiation pattern of the mobile phone antenna using the triple-band flexible metasurface. Figure 3 (b) is the YZ-plane radiation pattern of the mobile phone antenna using the triple-band flexible metasurface;

[0037] Figure 5 This is a comparison of the radiation efficiency of a mobile phone in free space, a mobile phone on the waist and abdomen of a human body, and a mobile phone using a tri-band flexible metasurface on the waist and abdomen of a human body;

[0038] Figure 6 This is a comparison chart of the SAR results of a mobile phone on the human waist and abdomen, and a mobile phone using a triple-band flexible metasurface on the human waist and abdomen; Figure 6 (a) is the SAR image of the mobile phone on the waist and abdomen of the human body. Figure 6 (b) is the SAR image of a mobile phone using a triple-band flexible metasurface on the waist and abdomen of a human body;

[0039] Figure 7 A physical picture of the three-frequency flexible metasurface produced by the present invention;

[0040] Figure 8 The far-field measurement diagram of the mobile phone antenna and the three-band flexible metasurface in a microwave darkroom is shown for the present invention;

[0041] Fig. 9 This is a graph showing the actual measurement of the radiation efficiency of a mobile phone antenna and a three-band flexible metasurface in a reverberation chamber in the present invention. DETAILED DESCRIPTION

[0042] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0043] In the description of the present invention, it is necessary to understand that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0044] like Figure 1-9 As shown, this embodiment provides a three-band flexible metasurface for improving the performance of mobile phone antennas in pockets. The three-band metasurface uses flexible materials as a medium and conductive cloth woven from conductive fibers (silver yarn materials) as a conductive layer and a return layer, which can be integrated into a pocket (metapocket). When a smartphone is placed in a pocket integrated with a metasurface, this metasurface can improve the gain and radiation efficiency of the mobile phone antenna while having little impact on the working frequency band of the mobile phone antenna, improve the radiation performance of the antenna, thereby enhancing the signal reception and transmission capabilities, while reducing the harm of electromagnetic radiation to the human body.

[0045] like Figure 1 , 2As shown in Figures 3 and 4, the three-frequency flexible metasurface of this embodiment has a sandwich structure (i.e., a structure in which layers overlap each other), including a conductive layer (on the upper surface), a dielectric layer (in the middle layer), and a return layer (on the lower surface) arranged in sequence. The dielectric layer is made of flexible PDMS material. Both the conductive layer and the return layer are conductive fabrics woven from conductive fibers (silver yarn material). In the conductive layer, only the three-ring conductive patch is woven from conductive fibers, and in the return layer, the entire surface is woven from conductive fibers.

[0046] The conductive layer is composed of six rows and six columns of three-ring conductive patches, such as Figure 1 , which is a schematic diagram of the upper surface structure of a unit in the three-frequency flexible metasurface, wherein a unit of the three-frequency flexible metasurface includes a three-ring conductive patch. Each three-ring conductive patch includes an outer ring, a middle ring and an inner ring.

[0047] For a unit of the three-frequency flexible metasurface: the outer ring of the three-ring conductive patch is a square ring with a side length of 20mm to 21.9mm, wherein the inner side length of the square ring is 20mm and the outer side length is 21.9mm. The middle ring of the three-ring conductive patch is a square ring with a square cut corner, and the side length of the square ring is 14mm to 17.2mm, wherein the inner side length of the square ring is 14mm and the outer side length is 17.2mm; the side length of the square cut corner is 1.5mm. The inner ring of the three-ring conductive patch is a square ring with a square cut corner, and the side length of the square ring is 9.2mm to 12mm, wherein the inner side length of the square ring is 9.2mm and the outer side length is 12mm; the side length of the square cut corner is 1.5mm. The dielectric layer and the return layer are square with a side length of 30mm. The height of the dielectric layer is 3mm. The thickness of the conductive layer is 0.03mm. The thickness of the return layer is 0.03mm.

[0048] Table 1 Figure 1 Specific parameter values ​​of the medium- and triple-frequency flexible metasurfaces, in mm:

[0049] w w1 w2 w3 w4 w5 30 21.9 20 17.2 14 12 w6 b1 b2 b3 b4 9.2 1.5 1.5 1.5 1.5

[0050] like Figure 4 As shown, after using the triple-band flexible metasurface, the maximum gains at 2.4 GHz, 3.5 GHz, and 5.3 GHz were increased by 4.2 dB, 4.6 dB, and 5.8 dB, respectively.

[0051] like Figure 5 As shown, when using the triple-band flexible metasurface, the radiation efficiency at 2.4 GHz, 3.5 GHz, and 5.3 GHz is increased by 16.6%, 11.5%, and 12.1%, respectively.

[0052] like Figure 6As shown in the figure, when the three-band flexible metasurface is not used, the SAR of the mobile phone at the waist and abdomen is 0.346W / kg, 0.478W / kg, and 0.446W / kg at 2.4GHz, 3.5GHz, and 5.3GHz respectively. When the three-band flexible metasurface is used, the SAR of the mobile phone at the waist and abdomen is 0.032W / kg, 0.053W / kg, and 0.045W / kg at 2.4GHz, 3.5GHz, and 5.3GHz respectively.

[0053] The practical application of the present invention is further described below:

[0054] First, in order to make the product of the present invention adapt to the sizes of most mobile phones on the market, the overall size of the three-band flexible metasurface is designed to be 180mm*180mm. Figure 3 and 7 As shown, it is composed of six rows and six columns of metasurface units, with a total of 36 metasurface units, and the size of one metasurface unit is designed to be 30mm*30mm. Most common mobile phone sizes are 70mm*150mm. Considering the randomness of the position and direction of the mobile phone in the pocket, as well as the common pocket size, a 180mm*180mm three-band flexible metasurface is most preferred. This can not only adapt to most mobile phone sizes, ensure a stable antenna performance improvement effect, but also reduce production costs. At the same time, considering the stability and durability of the present invention in practical applications, a PDMS material with good flexibility is selected as the substrate dielectric material, so that it can be integrated into pockets and other clothing while improving the wearing comfort.

[0055] Second, since the uncertainty of the position of the mobile phone in the pocket is too high, it is necessary to consider the influence of polarization mismatch after the antenna passes through the tri-band flexible metasurface. However, the tri-band flexible metasurface designed by the present invention has the property of being polarization insensitive (such as Figure 1 As shown in the figure, any polarization direction angle will not have a significant impact on the antenna performance, ensuring the stability of the antenna performance.

[0056] The central frequencies of the triple-frequency flexible metasurface designed in the present invention are 2.4 GHz, 3.5 GHz, and 5.3 GHz, and the reflection phase bandwidths [-90°, 90°] are 2.39 GHz to 2.43 GHz, 3.47 GHz to 3.53 GHz, and 5.19 GHz to 5.46 GHz.

[0057] Third, in order to maximize the performance of the antenna, the number of units in the three-band flexible metasurface is also a consideration. Too small a number of units will not significantly improve the performance, while too large a number of units will increase the thickness of the structure, which is not conducive to wearable applications. Taking the above into consideration, the number of units in the metasurface of the present invention is 6*6 (such as Figure 3 and 7This ensures the effectiveness of performance improvement and enhances wearability.

[0058] Fourth, since the distance between the mobile phone antenna and the three-band flexible metasurface when placed in the pocket is random, it is necessary to consider the impact of the distance between the antenna and the three-band flexible metasurface on performance improvement. However, one of the advantages of the design of the present invention is that the antenna performance is less affected by distance. The change in distance in the pocket is basically from 1mm to 3mm, and the change in gain improvement is from 4.2dB to 4dB, 4.6dB to 4.2dB, and 5.8dB to 5.1dB. The degree of antenna performance improvement is less affected by the spacing, which increases the freedom of the mobile phone's position in the pocket.

[0059] In summary, the present invention realizes the low profile of the mobile phone antenna in a narrow pocket environment, improves the gain and radiation efficiency of the three frequency bands, and reduces the harm of electromagnetic radiation to the human body. At the same time, the flexible material enables the invention to be integrated into pockets and other clothing to achieve true "invisible" communication. The three-band flexible metasurface designed by the present invention improves the performance of mobile phone antennas, provides greater possibilities for improving communication transmission rate and throughput, and at the same time better guarantees the electromagnetic safety of the human body, and has greater application value.

[0060] It should be noted that the present invention Figure 7 , 8 9 are respectively a physical picture of the processed and produced three-band flexible metasurface, a microwave darkroom far-field measurement picture of a mobile phone antenna and a three-band flexible metasurface, and a reverberation chamber radiation efficiency measurement picture of a mobile phone antenna and a three-band flexible metasurface, which are only used for technical personnel in this field to understand the experimental environment of the product of the present invention and the test data.

[0061] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, all equivalent changes made according to the shape, structure and principle of the present invention without departing from the content of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A three-band flexible metasurface for improving the performance of a mobile phone antenna in a pocket, characterized in that: It comprises a conductive layer, a dielectric layer and a return layer arranged in sequence, wherein the conductive layer is composed of three-ring conductive patches in N rows and N columns, wherein N≥6, and each three-ring conductive patch comprises an outer ring, a middle ring and an inner ring.

2. A three-band flexible metasurface for improving the performance of a mobile phone antenna in a pocket as claimed in claim 1, characterized in that: The outer ring of the three-ring conductive patch is a square ring, and the side length thereof is 20 mm to 21.9 mm.

3. The triple-band flexible metasurface for improving the performance of a mobile phone antenna in a pocket as claimed in claim 1, characterized in that: The middle ring of the three-ring conductive patch is a square ring with square cut corners, the side length of the square ring is 14 mm to 17.2 mm, and the side length of the square cut corner is 1.5 mm.

4. The triple-band flexible metasurface for improving the performance of a mobile phone antenna in a pocket as claimed in claim 1, characterized in that: The inner ring of the three-ring conductive patch is a square ring with square cut corners, the side length of the square ring is 9.2 mm to 12 mm, and the side length of the square cut corner is 1.5 mm.

5. The triple-band flexible metasurface for improving the performance of a mobile phone antenna in a pocket as claimed in claim 1, characterized in that: The dielectric layer is in a square shape.

6. The triple-band flexible metasurface for improving the performance of a mobile phone antenna in a pocket as claimed in claim 1, characterized in that: The reflow layer is square.

7. The triple-band flexible metasurface for improving the performance of a mobile phone antenna in a pocket as claimed in claim 1, characterized in that: The thickness of the dielectric layer is 1 to 3 mm.

8. The triple-band flexible metasurface for improving the performance of a mobile phone antenna in a pocket as claimed in claim 1, characterized in that: The thickness of the conductive layer is 0.01-0.03 mm, and the thickness of the reflow layer is 0.01-0.03 mm.

9. The triple-band flexible metasurface for improving the performance of a mobile phone antenna in a pocket as claimed in claim 1, characterized in that: The dielectric layer is made of flexible PDMS material.

10. The triple-band flexible metasurface for improving the performance of a mobile phone antenna in a pocket as claimed in claim 1, characterized in that: The conductive layer and the return layer are both conductive cloths woven from conductive fibers.

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