High-gain vehicle-mounted optical transparent antenna with improved directional diagram

Abstract

This invention discloses a high-gain vehicle-mounted optically transparent antenna with improved radiation pattern, operating in the 0.74-0.87 GHz range. The invention includes a substrate, an antenna body, and a system ground plane. The substrate comprises a PET film layer, an OCA adhesive layer, and a PC dielectric substrate. The antenna body consists of two trapezoidal radiating patches, a reverse cancellation strip, a feed line, and a system ground plane located on the same layer as the antenna. The two trapezoidal radiating patches are connected by the reverse cancellation strip, which links their longer base edges. Its transparency is primarily achieved through the use of a transparent substrate material and a metal mesh structure composed of thin and fine metal wires. The cascaded trapezoidal radiating patches and the connected reverse radiation strip achieve performance improvements such as high gain, wide bandwidth, and improved horizontal radiation pattern nulls. This invention can achieve optical transparency of over 70%, radiation efficiency of over 65%, and radiation pattern null improvement of over 3 dB in the operating frequency band.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetic field and microwave, and relates to a high-gain vehicle-mounted transparent antenna with improved radiation pattern, in particular to a high-gain vehicle-mounted transparent antenna with high gain, low sidelobe, improved radiation pattern and optical transparency, which specifically works in a 0.74GHz-0.87GHz frequency band. BACKGROUND

[0002] Antennas are key components of intelligent network connection systems such as wireless communication, wireless network and satellite positioning. In a wireless communication system, antennas play a key role in transmitting and receiving signals. With the rapid development of 5G automotive intelligence, automatic driving and the Internet of Things, new-generation intelligent vehicles have higher and higher requirements for antennas. The performance of an antenna directly determines the overall performance of the entire intelligent network connection vehicle system. Common traditional vehicle-mounted antennas are roughly as follows: whip antennas, shark fin antennas and built-in antennas. Whip antennas are usually commonly installed on old cars, and whip antennas often have a relatively long physical size, which also brings strong signal collection capability. However, it also increases the wind resistance of the vehicle and may cause the antenna to break when passing through low areas or tunnels. Compared with whip antennas, most vehicles currently use more aesthetically pleasing and less wind-resistant shark fin antennas. Shark fin antennas also have the function of releasing static electricity. However, they often have poorer signal reception capability than traditional antennas in some special situations. Built-in antennas, also known as invisible antennas, are widely used because they can be completely integrated with the vehicle body, do not affect the overall appearance of the vehicle and do not cause additional wind resistance. However, due to the placement of the antenna inside the vehicle, the signal reception capability is often affected by the metal frame of the vehicle body. The above-mentioned common vehicle-mounted antennas have certain advantages and disadvantages, so it is particularly important to design a new type of antenna that is aesthetically pleasing, does not affect the wind resistance of the vehicle, has good signal reception capability and high gain.

[0003] Optically transparent antenna is a potential solution to the above problems. It is often used on glass or transparent medium substrate, and is also called glass antenna. As a hot research direction of current antenna, glass antenna has many related researches on expanding its bandwidth, realizing dual polarization, obtaining high isolation and large power capacity, etc. Compared with traditional antennas, glass antenna has the following advantages: first, it is transparent as a whole, has high aesthetic degree and flexible installation; second, its conventional antenna performance indicators (gain, radiation efficiency, bandwidth, directivity, etc.) are comparable to traditional metal antennas; third, it is small in size, light in weight and relatively concealed. At present, researches on glass antenna cover all aspects, but researches on vehicle-mounted glass antenna are not many. Glass antenna can be attached to the car glass to obtain better signal receiving capability due to its good optical transparency. Its close-to-glass placement does not affect the wind resistance and appearance of the car. Therefore, glass antenna is a highly feasible new type of vehicle-mounted antenna alternative.

[0004] However, unlike the application of indoor glass antenna, the front windshield of the vehicle is often designed at a certain angle to reduce wind resistance, but this will also cause the antenna pattern in the horizontal plane to be not omnidirectional but to have nulls at certain specific angles. At the nulls, signals cannot be received and transmitted, which will greatly affect the reliability of the vehicle-mounted antenna. Therefore, a vehicle-mounted transparent antenna with improved horizontal plane pattern nulls is particularly important.

[0005] The present application proposes a high-gain vehicle-mounted transparent antenna with improved pattern, which realizes optical transparency by selecting transparent substrate materials (PC substrate, OCA (Optically Clear Adhesive) glue, PET (polyethylene terephthalate) film) and using a metal mesh composed of fine metal wires to realize electrical interconnection and optical transparency of the metal layer. The optical transparency is related to the spacing of the metal mesh and the thickness of the metal wire. By selecting appropriate metal mesh technology, the antenna radiation efficiency and optical transparency can be effectively balanced. The antenna and the substrate are designed in L shape to better embed into the car window and connect with the feed line. The main radiation part of the antenna is two radiation patches. The length of the radiation patch is adjusted to determine the working frequency of the antenna, and the width of the patch is adjusted to ensure that the bandwidth of the antenna covers the 0.74GHz-0.87GHz frequency band. Its radiation working principle is to adjust the shape and length of the reverse cancellation strip to make the radiation modes of the two series-connected radiation patches same direction to form a high-gain effect by superposition. Finally, by replacing the traditional rectangular radiation patch design with a trapezoidal patch, the nulls in the horizontal plane can be significantly improved (-3dB). SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the existing traditional vehicle-mounted antenna in appearance and low signal receiving capability, and propose a high-gain vehicle-mounted transparent antenna with a rectangular patch. Since the front windshield of the vehicle-mounted vehicle often has an inclination angle when installed, it will cause a signal receiving zero point in the horizontal plane. The present application improves the rectangular radiation patch. The trapezoidal radiation patch can improve the directional diagram zero point and widen the working bandwidth of the antenna.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0008] A high-gain vehicle-mounted transparent antenna with improved directional diagram, comprising a substrate (1), an antenna body, a system floor (2);

[0009] The substrate (1) is "L" shaped, which includes PET film layer (1-1), OCA adhesive layer (1-2), PC dielectric substrate (1-3) from top to bottom; PET film layer (1-1) is used as the growth substrate of metal mesh; OCA adhesive layer (1-2) is used to connect PET film and PC dielectric substrate (1-3);

[0010] The antenna body is located on the upper surface of the substrate (1), which includes two axisymmetric trapezoidal radiation patches (3), a reverse cancellation strip (4) and a microstrip feed line (5);

[0011] The long bottom edges of the two trapezoidal radiation patches (3) are connected with the two ends of the reverse cancellation strip (4) respectively;

[0012] The system floor (2) is located on the upper surface of the substrate (1), and the system floor (2) is "L" shaped, which is combined with the metal frame of the car and is suitable for the feed of the vehicle-mounted antenna;

[0013] The system floor (2) is provided with an "L" shaped slot (6) near the end of the antenna body;

[0014] The "L" shaped slot (6) is provided with an "L" shaped microstrip feed line (5), and the two ends of the microstrip feed line (5) are connected with the short bottom edges of the trapezoidal radiation patches (3) of the antenna body and the system floor (2) respectively;

[0015] The trapezoidal radiation patch (3), the reverse cancellation strip (4), the microstrip feed line (5) and the system floor (2) are made of metal mesh material.

[0016] As a preferred, the long bottom edge of the trapezoidal radiation patch (3) is about 0.12 wavelength, and the wavelength is the wavelength corresponding to the center frequency of the working frequency band. The short bottom edge is about 0.04 wavelength, which can effectively overcome the problem of radiation zero point in the horizontal direction caused by the inclination angle of the front windshield of the vehicle.

[0017] As a preference, the height of the trapezoidal radiation patch (3) is about 0.368 wavelengths;

[0018] As a preference, the reverse cancellation strip adopts a meander line to realize the cancellation of the current, and the total length thereof is about 1.22 wavelengths; the high gain of the antenna is caused by the superposition of the co-directional radiation modes of the two trapezoidal radiation patches (3).

[0019] The antenna and the system floor are in the same layer, and the area where the metal exists adopts the design of a metal mesh to realize the transparency thereof, and the transparency of the antenna and the radiation efficiency of the antenna have a contradictory relationship, and preferably, a transparent metal mesh material with a thickness of 4 um and a square resistance of 0.12 Omega / Dot is selected, the theoretical transparency of which can reach about 70%, and the radiation efficiency thereof can reach more than 65%.

[0020] The length of the long bottom side of the trapezoidal radiation patch determines the improvement effect of the radiation pattern null thereof, and the longer the length is, the better the improvement effect of the null is, but also makes the antenna volume larger and the cost higher, and the design of the trapezoidal radiation patch simultaneously increases the width of the radiation patch, thereby bringing a wider impedance matching bandwidth, and therefore, a length of about 0.12 wavelengths is selected for the long bottom side length as a compromise.

[0021] The reverse cancellation strip adopts a meander line mode to realize the mutual cancellation of the currents in the strip, prevent the generation of the radiation mode opposite to the radiation patch, and thereby reduce the antenna gain; the total length of the reverse cancellation strip and the spacing between the meander lines can be well controlled, and as a preference, a strip with 19 meander lines is adopted as the reverse cancellation strip.

[0022] The invention adopts the feeding mode of a coplanar waveguide (CPW), and the impedance matching performance of the antenna can be adjusted by adjusting the size of the slot of the floor and the feeding line of the antenna.

[0023] The application provides a high-gain vehicle-mounted transparent antenna with improved radiation pattern, and the optical transparency principle is that a transparent substrate material (PC substrate, OCA glue, PET film) is selected, and a metal mesh composed of metal wires is used to realize electrical interconnection and optical transparency of the metal layer. The optical transparency is related to the spacing of the metal mesh and the thickness of the metal wire, and by selecting a suitable metal mesh process, the antenna radiation efficiency and optical transparency can be effectively considered. The antenna and the substrate are designed in an L shape to better embed into the vehicle window and be connected with the feed line. The main radiation part of the antenna is two trapezoidal radiation patches, the working frequency of the antenna is determined by adjusting the length of the trapezoidal radiation patch, and the bandwidth of the antenna is ensured to cover the 0.74GHz-0.87GHz frequency band by adjusting the width of the trapezoidal radiation patch. The radiation working principle is that the radiation modes of the two series-connected radiation patches are made to be the same direction by adjusting the shape and length of the reverse cancellation strip, so as to superimpose to form a high-gain effect. Finally, by replacing the traditional rectangular radiation patch design with a trapezoidal patch, the radiation pattern null in the horizontal plane can be obviously improved (3dB improvement).

[0024] The effective effect of the application is that the application is a high-gain vehicle-mounted transparent antenna with improved radiation pattern, which is a planar structure in size and shape, has optical transparency compared with a traditional vehicle-mounted antenna, is more hidden, can be better integrated with the vehicle body to reduce wind resistance, and is convenient to install. In terms of performance, the superposition effect of the double radiation patches in series is used to realize high gain, and the omnidirectional radiation pattern makes it have good signal receiving capability, the design of the trapezoidal radiation patch makes it have wider working bandwidth and improved radiation pattern null performance, and the transparent antenna also has wide application prospects in indoor glass, furniture integration and other application scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a structural schematic diagram of the high-gain vehicle-mounted transparent antenna with improved radiation pattern null of the application;

[0026] Figure 2 is a layer information diagram of the high-gain vehicle-mounted transparent antenna with improved radiation pattern null of the application;

[0027] Figure 3 is a structural schematic diagram of a high-gain vehicle-mounted transparent antenna without improved radiation pattern null (a comparative example);

[0028] Figure 4 is a metal mesh schematic diagram used in the designed high-gain vehicle-mounted transparent antenna;

[0029] Figure 5 is a size marking diagram of a metal mesh unit used in the designed high-gain vehicle-mounted transparent antenna;

[0030] Figure 6 is the reflection coefficient diagram of the high-gain vehicle-mounted transparent antenna with pattern null improvement designed;

[0031] Figure 7 is the horizontal plane radiation pattern of the vehicle-mounted transparent antenna at 800MHz;

[0032] Wherein, 1 is a substrate, 1-1 is a PET film layer, 1-2 is an OCA glue layer, and 1-3 is a PC substrate; 2 is a system floor; 3 is a trapezoidal radiation patch; 4 is a reverse cancellation strip; 5 is a microstrip feed line; and 6 is an "L"-shaped slot. DETAILED DESCRIPTION

[0033] In order to further illustrate, the present application is further described by combining examples and illustrating the structure of the drawings, but the present application is not limited to this embodiment.

[0034] Figure 1 The high-gain vehicle-mounted transparent antenna with pattern null improvement provided by the present application specifically comprises a substrate 1, an antenna body, and a system floor 2.

[0035] The substrate 1 is "L"-shaped and comprises a horizontal portion and a vertical portion; the substrate 1 comprises three parts from top to bottom, which are Figure 2 The PET film layer 1-1, the OCA glue layer 1-2, and the PC substrate layer 1-3 in the substrate 1 are used as the metal mesh growth substrate.

[0036] The antenna body is located on the upper surface of the substrate 1 and comprises two axisymmetrically arranged trapezoidal radiation patches 3, a reverse cancellation strip 4, and a microstrip feed line 5; the long bottom edges of the two trapezoidal radiation patches 3 are connected with the two ends of the reverse cancellation strip 4, respectively; and the radiation main body part is composed of the reverse cancellation strip 4 connecting the two trapezoidal radiation patches 3.

[0037] The system floor 2 is located on the upper surface of the substrate 1, and the system floor 2 is "L"-shaped; after being combined with the automobile metal frame, the system floor 2 is suitable for the feeding of the vehicle-mounted antenna; the system floor and the feed line are designed to be L-shaped so as to be embedded into the metal frame structure of the vehicle window and thus hide the feed line. The system floor 2 comprises a horizontal metal floor and a vertical metal floor; the vertical metal floor has the same shape and size as the vertical portion of the substrate 1, and the vertical metal floor completely covers the vertical portion of the substrate 1; the horizontal metal floor is located at one end of the horizontal portion of the substrate 1, and the length of the horizontal metal floor is less than the length of the horizontal portion of the substrate 1, and the width of the horizontal metal floor is equal to the width of the horizontal portion of the substrate 1.

[0038] The system floor 2 is provided with an "L"-shaped slot near the end of the antenna body;

[0039] The "L" shaped slot is provided with an "L" shaped microstrip feed line 5, both ends of the microstrip feed line 5 are connected with the short bottom edge of the trapezoidal radiation patch 3 of the antenna body and the system floor 2 respectively;

[0040] The trapezoidal radiation patch 3, the reverse cancellation strip 4, the microstrip feed line 5 and the system floor 2 adopt Figure 4 The metal mesh material has a thickness of only H MM =4um, the ultra-thin metal mesh structure is optically transparent, the transparency can reach more than 70%, and the sheet resistance is only 0.12Ω□ / , the low sheet resistance can bring high antenna radiation efficiency.

[0041] The medium substrate is L-shaped, the width of the far floor is W sub =50mm, the long side is L sub =420mm, the short side W g1 =25mm. The system floor is also L-shaped, the length is L g =73mm, the width is W g1 +W g2 =45mm, the gap width W g2 =20mm. By etching an "L" shaped slot on the system floor and feeding by adding an L-shaped metal microstrip line, the width of the feed line is 1mm, the width of the "L" shaped slot W s =3mm, the length of the two stages of the "L" shaped slot is L s1 =34mm, L s2 =26.5mm, the length of the microstrip feed line 5 is slightly longer than the length of the "L" shaped slot. Two trapezoidal radiation patches 3 are distributed on both sides of the reverse cancellation strip 4, and two trapezoidal radiation patches 3 are set to make the working currents of the two trapezoidal radiation patches 3 in the same direction, so that the radiation patterns are superimposed to improve the antenna gain, and the reverse cancellation strip 4 is designed by bending to make the radiation pattern which should be opposite to the radiation patch 3 to be cancelled inside. The long bottom edges of the two trapezoidal radiation patches are placed close to each other, the long bottom edge W p2 =45mm, the waist length L p2 =138.8mm. The zero point improvement performance of the directional diagram is determined by the width of W p2 , the greater the value of W p2 , the better the effect of improving the zero point of the directional diagram, but considering the cost and the size of the antenna, 45mm is selected as the bottom edge length of the trapezoidal radiation patch as a preferred. The reverse cancellation strip is designed by bending to save space, the line width W b =3mm, the spacing g between the two bending lines is 2.6mm, and the partial line length L b =5.6mm, by changing the total length of the reverse cancellation strip, the radiation phase of the two rectangular radiation patches can be well controlled to realize high gain performance.

[0042] Here, we provide, such as Figure 3 The comparative proportion, in Figure 1 Based on the antenna, the shape of the trapezoidal radiating patch 3 is changed from trapezoidal to long L. p1 =138mm, width W p1 A rectangle with a diameter of 15mm. The length L of the radiating patch. p1 The frequency of the antenna is the primary factor determining its operating frequency, while the bandwidth primarily determines its operating bandwidth.

[0043] Figure 4 This is a microscopic schematic diagram of a metal mesh. The configuration of this regularly arranged ultra-thin metal mesh achieves the optical transparency of the antenna layer, with a transparency of over 70%, which meets the requirement of application in automotive glass without affecting the vision of people inside the vehicle. Figure 5 This is a schematic diagram of a metal mesh unit, which consists of vertically intersecting metal wires with a wire width of W. m Line spacing g M This is related to the metal mesh manufacturing process. These two parameters also affect the transparency of a transparent antenna; generally, narrower linewidths and larger line spacing result in higher transparency, but at the same time, metal loss also increases. Another factor determining metal loss is H. MM H MM The larger the antenna, the lower the metal loss, resulting in higher radiation efficiency and better performance. The main purpose of the PET film layer 1-1 is to attach the metal mesh layer, enabling stable growth; its thickness is H. PET =50um, dielectric constant is 3.4, loss angle is 0.008. OCA adhesive layer 1-2 is used to connect the PET film and the PC substrate, and the thickness is selected as H. OCA =100um adhesive layer, dielectric constant 3.8, loss angle 0.005. PC substrate layer 1-3 thickness H PC =1.5mm, dielectric constant is 2.9, loss angle is 0.01.

[0044] Figure 6 This is a graph showing the reflection coefficient of the present invention as a function of frequency. It can be seen that in the antenna's preset operating frequency band (0.74GHz-0.87GHz), the reflection coefficient reaches below 15dB, and its -10dB impedance bandwidth reaches approximately 300MHz, far exceeding the design target. Figure 7 for Figure 1 This invention and Figure 3 A comparison of the horizontal radiation patterns of the transparent vehicle-mounted antenna without null point improvement shows that the antenna of the present invention also has the characteristics of low sheet resistance, high transparency, high gain, simple structure and easy installation.

[0045] This invention proposes a high-gain automotive transparent antenna with improved radiation pattern. The substrates are all made of transparent materials (PC, OCA, PET), and the metal layer uses a metal mesh design, thus possessing excellent optical transparency and making it well-suited for automotive antenna applications. When installed on the windshield, it offers advantages over traditional antennas, including aesthetics, ease of installation, and no impact on the vehicle's wind resistance. Furthermore, this invention achieves high gain by connecting two radiating patches in series and adjusting the shape of the anti-cancellation strips to ensure the currents in the two radiating patches are in the same direction. High gain translates to strong signal reception / transmission capabilities. Additionally, by changing the shape of the radiating patches to trapezoidal, this invention overcomes the problem of null points in the horizontal radiation pattern caused by the antenna's tilted placement, avoiding situations where there is no signal at certain angles. These advantages of this invention make it more suitable than other solutions for the requirements of high channel capacity, high data throughput, and aesthetically pleasing antenna systems in modern 5G automotive wireless communication systems.

[0046] The above is merely a specific embodiment of the present invention, used only to illustrate the design method and core design concept of the present invention. However, the decoupling scheme proposed in this invention is not limited to high-gain antennas operating in the specific frequency band of this embodiment. The operating frequency of the antenna can be adjusted by adjusting the length of the antenna radiating patch, and the operating bandwidth can be adjusted by adjusting the width of the antenna radiating patch. Furthermore, it is not limited to a specific dielectric substrate and can be applied to different application scenarios depending on the specific application, such as indoor windows and other application scenarios requiring antenna transparency. In addition, transparent antennas with different transparency can be obtained by adjusting the density of the metal mesh in the metal mesh process to suit applications with different transparency requirements. It should be noted that for those skilled in the art, optimizations and improvements can still be made to the present invention without departing from the principle of the present invention, and these optimizations and improvements will also fall within the protection scope of the claims of the present invention. The present invention does not limit the scope of specific embodiments. For those skilled in the art, as long as various changes occur within the spirit and scope of the present invention as defined and determined by the appended claims, all inventions conceived based on the design concept of the present invention are protected.

Claims

1. A high-gain vehicle-mounted optically transparent antenna with improved radiation pattern, characterized in that... Includes substrate (1), antenna body, and system floor (2); The substrate (1) is "L" shaped and includes, from top to bottom, a PET film layer (1-1), an OCA adhesive layer (1-2), and a PC dielectric substrate (1-3) as a metal mesh growth substrate. The antenna body is located on the upper surface of the substrate (1), and includes two axially symmetrical trapezoidal radiating patches (3), a reverse cancellation strip (4), and a microstrip feed line (5). The long base edges of the two trapezoidal radiation patches (3) are respectively connected to the two ends of the reverse canceling strip (4); The system floor (2) is located on the upper surface of the substrate (1), and the system floor (2) is "L" shaped. When combined with the automotive metal frame, it is suitable for feeding the vehicle antenna. The system floor (2) has an "L" shaped slot (6) near the antenna body. The "L"-shaped slot is provided with an "L"-shaped microstrip feed line (5), and the two ends of the microstrip feed line (5) are respectively connected to the short bottom edge of the trapezoidal radiating patch (3) of the antenna body and the system ground plane (2). The trapezoidal radiating patch (3), the anti-cancellation strip (4), the microstrip feed line (5), and the system floor (2) are made of metal mesh material; the anti-cancellation strip (4) is a bent line, and the total length of the anti-cancellation strip (4) is 1.22 wavelengths. The wavelength referred to is the wavelength corresponding to the center frequency of the working frequency band. By adjusting the shape and length of the anti-cancellation strip (4), the radiation modes of the two trapezoidal radiating patches (3) are made to be in the same direction, thereby superimposing to form a high gain.

2. The antenna as described in claim 1, characterized in that... The trapezoidal radiating patch (3) has a long base of 0.12 wavelengths, which refers to the wavelength corresponding to the center frequency of the working frequency band, and a short base of 0.04 wavelengths.

3. The antenna as described in claim 1, characterized in that... The height of the trapezoidal radiating patch (3) is 0.368 wavelengths, and the wavelength referred to is the wavelength corresponding to the center frequency of the working frequency band.

4. The antenna as described in claim 1, characterized in that... The metal mesh material has a thickness of 4 μm and a sheet resistance of 0.12 Ω / □.

5. The antenna as described in claim 1, characterized in that... The counteracting effect of the counteracting strip (4) can be controlled by adjusting the total length of the counteracting strip (4) and the spacing between the bends.

6. The antenna as described in claim 1, characterized in that... The reverse offset strip (4) is a strip that is bent 19 times.

7. The antenna as described in claim 1, characterized in that... The impedance matching performance of the antenna is adjusted by adjusting the size of the "L"-shaped slot (6) of the system floor (2) and the microstrip feed (5) of the antenna.

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