CN110518347B

CN110518347B - Multi-band vehicle-mounted antenna

Info

Publication number: CN110518347B
Application number: CN201910797039.3A
Authority: CN
Inventors: 程勇; 章鹏
Original assignee: Nanjing University of Posts and Telecommunications
Current assignee: Nanjing University of Posts and Telecommunications
Priority date: 2019-08-27
Filing date: 2019-08-27
Publication date: 2020-10-16
Anticipated expiration: 2039-08-27
Also published as: CN110518347A

Abstract

The invention discloses a multi-band vehicle-mounted antenna, which belongs to the technical field of antennas and comprises a metal floor, a dielectric substrate, a microstrip line feeder, a radiation unit and a ground plane, wherein the radiation unit and the ground plane are printed on the dielectric substrate; the grounding plane is printed on the reverse side of the dielectric substrate and is connected with the metal floor; one end of the microstrip line feeder line is connected to the bottom end of the dielectric substrate, and the other end of the microstrip line feeder line is connected to the metal floor. The three monopoles of the invention are connected together to form a printing structure directly fed by a microstrip line, and the three monopoles with different lengths resonate under different frequencies. The gradual change profile, the gap structure and the capacitive structure are introduced, the impedance matching is improved, the bandwidth is 890MHZ-960MHz, 1710MHz-2690MHz and 3.4G-3.6GHz, the broadband characteristic is realized, the broadband characteristic can be applied to communication frequency bands such as GSM, LTE and 5G, the application range is wide, and the broadband impedance matching circuit has the advantages of novel structure, small size, low manufacturing cost and the like.

Description

Multi-band vehicle-mounted antenna

Technical Field

The invention belongs to the technical field of antennas, and particularly relates to a multi-band vehicle-mounted antenna.

Background

With the increasing demand of entertainment function and driving function, more and more electronic devices are arranged on the automobile, more and more antennas are integrated on the automobile, and the available space of the vehicle-mounted antenna is reduced.

The multi-band antenna is the mainstream trend of modern roof antennas, and integrates multiple frequency band antennas such as GPS, LTE, GSM and the like, and the antennas are integrated in a shark fin-shaped shell.

Meanwhile, the transmission bandwidth of multimedia information such as image, video, audio and the like is expected to be wider and wider, and the development of modern electronic information technology also needs antennas with better performance, which all push the communication system to move towards the broadband and multi-frequency directions.

In order to enable the antenna to implement communication in different frequency bands, many researchers have studied broadband technology and multiband technology of the antenna, and the antenna is often designed as either a broadband antenna, compatible with different frequency bands, or a multiband antenna.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a multi-band vehicle-mounted antenna, which realizes broadband characteristics, can be applied to communication frequency bands such as GSM, LTE, 5G and the like, and has a wide application range.

The technical scheme is as follows: in order to achieve the purpose, the invention provides the following technical scheme:

a multi-band vehicle-mounted antenna comprises a metal floor, a dielectric substrate, a microstrip feeder, a radiation unit and a ground plane, wherein the radiation unit and the ground plane are printed on the dielectric substrate; the grounding plane is printed on the reverse side of the dielectric substrate and is connected with the metal floor; one end of the microstrip line feeder line is connected to the bottom end of the dielectric substrate, and the other end of the microstrip line feeder line is connected to the metal floor.

Further, the dielectric constant range of the dielectric substrate is 4.4, and the metal floor is a rectangular metal plate.

Further, the length of the dielectric substrate is 65-75 mm, the width is 20-30 mm, and the thickness is 1.4-1.8 mm; the metal floor is a rectangular metal plate, the length of the metal plate is 200-400 mm, and the width of the metal plate is 200-400 mm.

Further, the first monopole is composed of a first rectangular unit, a second rectangular unit, a first trapezoid unit and a third rectangular unit which are connected in sequence, wherein the length W1 of the first rectangular unit is 20-25 mm, the width L1 of the first rectangular unit is 2-5 mm, the length W2 of the second rectangular unit is 2-5 mm, the length L2 of the second rectangular unit is 30-50 mm, the height L3 of the first trapezoid unit is 7-9 mm, the length of the other connecting edge L4 between the bottom edges of the trapezoids is 8-10 mm, the width W3 of the third rectangular unit is 6-8 mm, and the length L5 of the third rectangular unit is 9-11 mm; the first rectangular unit is perpendicular to the second rectangular unit and the third rectangular unit respectively.

Further, the third monopole is composed of a third trapezoid unit, a fourth rectangular unit and a fifth rectangular unit which are connected in sequence, wherein the lower bottom edge W5 of the third trapezoid unit is 6-8 mm, the upper bottom edge W6 of the third trapezoid unit is 3-5 mm, the height of the third trapezoid unit is 12-14 mm, the width W7 of the fourth rectangular unit is in the range of 2-4 mm, the length L9 of the fourth trapezoid unit is 30-40 mm, the width W8 of the fifth rectangular unit is 2-3 mm, and the length L10 of the fifth trapezoid unit is 5-7 mm.

Further, the microstrip feeder includes a feeding structure of the antenna, where the feeding structure of the antenna includes a sixth rectangular unit, a seventh rectangular unit, an eighth rectangular unit, and a ninth rectangular unit connected in sequence, where the sixth rectangular unit and the seventh rectangular unit are connected in parallel, and the eighth rectangular unit and the ninth rectangular unit are perpendicular to the seventh rectangular unit, respectively, where the sixth rectangular unit has a length W9 of 20-30 mm, a width L11 of 3-5 mm, the seventh rectangular unit has a length W10 of 20-30 mm, a width L12 of 3-5 mm, the eighth rectangular unit has a width W11 of 0.5-1.5 mm, a length L13 of 0.5-1.5 mm, a width W12 of 1-3 mm, and a length L14 of 2-4 mm.

Further, an antenna slot is formed on the feed structure of the antenna through etching, the antenna slot is a U-shaped structure and comprises three slots which are sequentially connected, wherein the three slots comprise a bottom slot and vertical slots which are perpendicular to two ends of the bottom slot, the length W13 of the bottom slot is 17-19 mm, the length L15 of the vertical slot is 18-22 mm, and the width W14 of the slot is 2-4 mm.

Furthermore, the sixth rectangular unit is respectively communicated with the first monopole, the second monopole and the third monopole, and the ninth rectangular unit is connected with the metal floor.

Further, the ground plane is composed of a tenth rectangular unit and an eleventh rectangular unit, wherein the tenth rectangular unit has a length W15 of 40-50 mm, a width L16 of 4-6 mm, a length W16 of 15-25 mm, and a width L17 of 3-5 mm.

The invention principle is as follows: nowadays, the mobile communication frequency band mainly includes three frequency bands: 824MHz-960MHz, 1710MHz-2690MHz and 3.4GHz-3.6 GHz. The microstrip antenna is the best choice for the multi-frequency miniaturized antenna due to the advantages of small size, light weight, easy integration, low profile and the like. The traditional monopole antenna can not be simply integrated on an automobile due to reasons such as volume, and the like, and the printed monopole antenna overcomes the volume defect and bandwidth defect of the traditional monopole antenna by printing the traditional monopole antenna on a medium substrate, and has the structural characteristics and performance advantages similar to those of a microstrip antenna, so that the printed monopole antenna is widely applied to mobile communication frequency band antennas. It is well known that both conventional monopole antennas and printed monopole antennas have only one resonant frequency point, the resonant length being one quarter of a wavelength. Therefore, increasing the antenna frequency band, widening the antenna bandwidth, and reducing the antenna size are the main directions for studying printed monopole antennas.

A conventional monopole antenna is a metal post approximately one-quarter wavelength long that is placed vertically on the ground. By using the mirror image theory, a mirror image monopole under the ground is used to replace the surface current influence of the ground, so the surface current distribution of the monopole can be replaced by the surface current distribution of the upper half part of the equivalent dipole when analyzing the surface current distribution of the monopole. It should be noted that a dipole antenna may radiate throughout space, while a monopole antenna only radiates above ground. When the ground is infinite, according to the free space dipole theory, the upper half radiation area of the monopole antenna can be directly equivalent to the far field radiation field of the monopole antenna:

where r is the distance from the source point to the field point, I_mIs the maximum current, L is the antenna length, β is the phaseBit constant, F_θIs the far field normalized pattern of the antenna. As can be seen from formula (2), when θ is 90 °, F_θIs a constant value, i.e. the horizontal directional pattern of the antenna is a circle, and the monopole antenna is non-directional. Printed monopoles also have similar characteristics as an improvement over conventional monopoles. Conventional monopole antennas cannot be integrated into a limited space due to volume and profile limitations, and therefore, the monopole antennas are generally printed on a dielectric substrate to achieve integration. Meanwhile, the printed monopole is a planar antenna, and the bandwidth is wider than that of the traditional monopole. Therefore, compared with the traditional monopole, the printed monopole antenna also has the advantages of wide frequency band, small volume, easy processing and integration, low price and the like.

The printed monopole is composed of a metal floor, a dielectric substrate and a radiation patch, and mainly comprises a microstrip line feed (a microstrip feed line is directly connected with the radiation patch) and a coplanar waveguide feed (the microstrip feed line, the floor and the radiation patch are on the same plane). The printed monopole can be divided into a circular patch monopole, a rectangular patch monopole, a triangular patch monopole and the like according to different shapes of the metal patches. As is known, a microstrip antenna also consists of a metal floor, a dielectric substrate and a radiation patch, and the difference is that no metal patch is arranged below the printed monopole antenna radiation patch corresponding to the dielectric substrate, and a metal bottom plate is arranged below the microstrip antenna radiation patch corresponding to the radiation patch to form a resonant cavity with the radiation patch. Although the microstrip patch antenna and the printed monopole antenna belong to planar antennas and have similar structural characteristics, the performances of the microstrip patch antenna and the printed monopole antenna are different. The bandwidth of the printed monopole is relatively wide compared to a microstrip patch antenna. In addition, the dielectric plate of the printed monopole antenna is generally very thin, has low dielectric loss and is not easily influenced by the material of the dielectric plate.

According to the monopole theory, the calculation formula of the resonance frequency of the printed monopole and the size of the radiation patch is as follows:

in the formulae (4) and (5),_eis the equivalent dielectric constant of the dielectric plate,_ris the relative dielectric constant of the dielectric plate, W is the width of the monopole antenna, L is the length of the monopole antenna, and the radiation length of the antenna is W/2+ L. The size of the printed monopole antenna can be preliminarily calculated through the expression of the resonant frequency, and then the size is adjusted through simulation software, wherein the radiation length of the printed monopole antenna is one fourth of the wavelength. In order to achieve the required performance in practical applications, the printed monopole antenna needs to be deformed, that is, the radiation patch is changed, and there are two main deformation measures: cutting and loading. For example, when the size of the antenna needs to be reduced, simulation software can be used for displaying the current distribution of the antenna, so that the resonant path of the antenna is obtained, the main radiation area is analyzed, and then the non-main radiation area is properly cut to achieve the purpose of antenna miniaturization. Or a slit can be cut at a reasonable position of the radiation patch, the current distribution of the patch is changed, the effective current path of the antenna is increased, and the resonant frequency of the antenna is reduced. When the frequency band of the antenna needs to be increased, a parasitic unit or other branches can be loaded, resonators of the antenna are added to obtain different resonant frequencies, and when the different resonant frequencies are close to each other, the bandwidth of the antenna can be increased. The antenna can also be multi-frequency by cutting the floor to form a defective structure, and simultaneously, the impedance matching is improved.

Has the advantages that: compared with the prior art, the multi-band vehicle-mounted antenna adopts the coaxial cable of 50 omega to be connected with the microstrip feeder of the antenna so as to feed. In order to simulate the environment of a car roof, the antenna is vertically arranged on a horizontal grounding plane, three monopoles are connected together to form a printed structure directly fed by a microstrip line according to the fact that the radiation length of the antenna is one fourth of the wavelength corresponding to the required working frequency, and the monopoles with different lengths resonate at different frequencies. The gradual change profile, the gap structure and the capacitive structure are introduced, the impedance matching is improved, the bandwidth is 890MHZ-960MHz, 1710MHz-2690MHz and 3.4G-3.6GHz, the broadband characteristic is realized, the broadband characteristic can be applied to communication frequency bands such as GSM, LTE and 5G, the application range is wide, and the broadband impedance matching circuit has the advantages of novel structure, small size, low manufacturing cost and the like.

Drawings

FIG. 1 is a schematic perspective view of a multiband vehicle antenna;

FIG. 2 is a front view of a first monopole of a multi-band vehicle antenna;

FIG. 3 is a front view of a second monopole of a multi-band vehicle antenna;

FIG. 4 is a front view of a third monopole of the multiband vehicle antenna;

FIG. 5 is a front view of a feed structure of the multiband vehicle antenna;

FIG. 6 is a front view of a multi-band vehicle antenna slot;

FIG. 7 is a rear view of a multi-band vehicle antenna;

FIG. 8 is a reflection coefficient diagram of a multiband vehicle antenna;

FIG. 9 is the E-plane radiation pattern of the multiband vehicle antenna at frequency 900 MHz;

FIG. 10 is the radiation pattern of the H-plane at frequency 900MHz for a multiband vehicle antenna;

FIG. 11 is the radiation pattern of the E-plane of the multiband vehicle antenna at frequency 2.5 GHz;

FIG. 12 is the radiation pattern of the H-plane of the multiband vehicle antenna at frequency 2.5 GHz;

FIG. 13 is the radiation pattern of the E-plane of the multiband vehicle antenna at frequency 3.5 GHz;

FIG. 14 is the radiation pattern of the H-plane of the multiband vehicle antenna at frequency 3.5 GHz;

reference numerals: 1-metal floor; 2-a dielectric substrate; 3-a first monopole; 4-a second monopole; 5-a third monopole; 6-microstrip line feed line; 7-antenna slot.

Detailed Description

For a better understanding of the contents of the present patent application, the technical solutions of the present invention will be further described below with reference to the accompanying drawings and specific examples.

As shown in fig. 1, a multiband vehicle-mounted antenna comprises a metal floor 1, a dielectric substrate 2 and a radiation unit printed on the dielectric substrate 2, wherein the antenna is manufactured on the dielectric substrate 2 with a dielectric constant range of 4.4, the metal floor 1 is used for the directional radiation of the antenna, the metal floor 1 is a rectangular metal plate, and the radiation unit comprises a first monopole 3, a second monopole 4 and a third monopole 5; the first monopole 3, the second monopole 4, the third monopole 5 and the microstrip line feeder 6 are printed on the front surface of the dielectric substrate 2, as shown in fig. 3, and the ground plane is printed on the back surface of the dielectric substrate 2 and connected to the metal floor 1. The microstrip line feed 6 comprises a feed structure of the antenna and an antenna slot 7 etched in the feed structure of the antenna.

The dielectric substrate 2 has a length in the range of 65-75 mm, a width in the range of 20-30 mm, and a thickness in the range of 1.4-1.8 mm.

The microstrip line feeder 6 is used as a radio wave signal feed source of the antenna, one end of the microstrip line feeder 6 is connected to the bottom end of the dielectric substrate 2, and the other end of the microstrip line feeder 6 is connected to the metal floor 1; the length range of the metal floor 1 is 200-400 mm, and the width range is 200-400 mm.

Referring to FIG. 1, the metal floor 1 is a rectangular metal plate, the length of the metal plate is within the range of 200-400 mm, and the width of the metal plate is within the range of 200-400 mm.

As shown in fig. 2, the first monopole 3 is composed of a first rectangular unit, a second rectangular unit, a first trapezoidal unit and a third rectangular unit, which are connected in sequence, wherein the length W1 of the first rectangular unit is 20-25 mm, the width L1 of the first rectangular unit is 2-5 mm, the length W2 of the second rectangular unit is 2-5 mm, the length L2 of the second rectangular unit is 30-50 mm, the height L3 of the first trapezoidal unit is 7-9 mm, the length of the other connecting edge L4 between the bottom edges of the trapezoids is 8-10 mm, the width W3 of the third rectangular unit is 6-8 mm, and the length L5 of the third rectangular unit is 9-11 mm. The first rectangular unit is perpendicular to the second rectangular unit and the third rectangular unit respectively.

Referring to fig. 3, the second monopole 4 has a trapezoid structure and is a second trapezoid unit, wherein the height W4 of the second trapezoid unit is 6-8 mm, the length of the lower base L6 is 25-35 mm, and the length of the upper base L7 is 17-19 mm.

As shown in fig. 4, the third monopole 5 is composed of a third trapezoidal unit, a fourth rectangular unit and a fifth rectangular unit which are connected in sequence, wherein the lower base W5 of the third trapezoidal unit is 6-8 mm, the upper base W6 is 3-5 mm, the height is 12-14 mm, the width W7 of the fourth rectangular unit is in the range of 2-4 mm, the length L9 is 30-40 mm, the width W8 of the fifth rectangular unit is 2-3 mm, and the length L10 is 5-7 mm.

Referring to fig. 5, the feeding structure of the antenna comprises a sixth rectangular unit, a seventh rectangular unit, an eighth rectangular unit and a ninth rectangular unit, which are connected in sequence, wherein the sixth rectangular unit and the seventh rectangular unit are connected in parallel, the eighth rectangular unit and the ninth rectangular unit are perpendicular to the seventh rectangular unit, respectively, the sixth rectangular unit has a length W9 of 20-30 mm, a width L11 of 3-5 mm, a length W10 of 20-30 mm, a width L12 of 3-5 mm, a width W11 of 0.5-1.5 mm, a length L13 of 0.5-1.5 mm, a width W12 of 1-3 mm, and a length L14 of 2-4 mm.

The sixth rectangular unit is respectively communicated with the first monopole 3, the second monopole 4 and the third monopole 5, and the ninth rectangular unit is connected with the metal floor 1.

As shown in fig. 6, the antenna slot 7 is a U-shaped structure, and includes three slots connected in sequence, including a bottom slot and vertical slots perpendicular to two ends of the bottom slot, where the length W13 of the bottom slot is 17-19 mm, the length L15 of the vertical slot is 18-22 mm, and the slot width W14 is 2-4 mm.

Referring to fig. 7, the ground plane is formed of tenth and eleventh rectangular units, wherein the tenth rectangular unit has a length W15 of 40-50 mm, a width L16 of 4-6 mm, a length W16 of 15-25 mm, and a width L17 of 3-5 mm.

Referring to fig. 8, a simulation experiment is performed on the novel multi-band vehicle-mounted antenna by using an electromagnetic simulation software HFSS. The experimental reflection coefficient S11 characteristic is that S11< -10dB is between 834 and 1000MHz, 1680 and 3050MHz and 3.3-3.68GHz, thus realizing the broadband characteristic.

In conjunction with fig. 9-14, the novel multi-band vehicle-mounted antenna is simulated by using the electromagnetic simulation software HFSS. An antenna radiation pattern is given. Fig. 5-10 show that at three frequency points (0.9GHz, 2.2GHz, 3.5GHz), the simulation results of the antenna on the E plane and the H plane are well matched, and omnidirectional radiation on the H plane can be kept, so that the requirement of omnidirectional radiation of the vehicle-mounted antenna is met. At 0.9GHz, the antenna is approximately 8-shaped in an E-plane upper directional diagram and is similar to a half-wave dipole antenna, but due to floor reflection, an antenna directional diagram slightly inclines upwards, the inclination is continuously increased along with the increase of frequency, the secondary lobe of the antenna is reduced, and the main lobe is increased. When the frequency point is 3.5GHz, the maximum radiation direction of the antenna is inclined to 0 degree.

Claims

1. A multi-band vehicle-mounted antenna, characterized in that: the antenna comprises a metal floor (1), a dielectric substrate (2), a microstrip line feeder (6), a radiation unit and a ground plane, wherein the radiation unit and the ground plane are printed on the dielectric substrate (2), and the radiation unit comprises a first monopole (3), a second monopole (4) and a third monopole (5) which are printed on the front surface of the dielectric substrate (2); the grounding plane is printed on the reverse side of the dielectric substrate (2) and is connected with the metal floor (1); one end of the microstrip line feeder (6) is connected to the bottom end of the dielectric substrate (2), and the other end of the microstrip line feeder is connected to the metal floor (1); the first monopole (3) consists of a first rectangular unit, a second rectangular unit, a first trapezoid unit and a third rectangular unit which are connected in sequence, wherein the first rectangular unit is 20-25 mm in length and 2-5 mm in width, the second rectangular unit is 2-5 mm in length and 30-50 mm in length, the first trapezoid unit is 7-9 mm in height, the other connecting edge between the bottom edges of the trapezoids is 8-10 mm in length, and the third rectangular unit is 6-8 mm in edge width and 9-11 mm in length; the first rectangular unit is vertical to the second rectangular unit and the third rectangular unit respectively; the third monopole (5) is composed of a third trapezoidal unit, a fourth rectangular unit and a fifth rectangular unit which are connected in sequence, wherein the lower bottom edge of the third trapezoidal unit is 6-8 mm, the upper bottom edge of the third trapezoidal unit is 3-5 mm, the height of the third trapezoidal unit is 12-14 mm, the width of the fourth rectangular unit is within the range of 2-4 mm, the length of the fourth rectangular unit is 30-40 mm, the width of the fifth rectangular unit is 2-3 mm, and the length of the fifth rectangular unit is 5-7 mm; the microstrip line feeder comprises a feeding structure of the antenna, the feeding structure of the antenna comprises a sixth rectangular unit, a seventh rectangular unit, an eighth rectangular unit and a ninth rectangular unit which are sequentially connected, wherein the sixth rectangular unit and the seventh rectangular unit are connected in parallel, the eighth rectangular unit and the ninth rectangular unit are respectively perpendicular to the seventh rectangular unit, the sixth rectangular unit is 20-30 mm in length and 3-5 mm in width, the seventh rectangular unit is 20-30 mm in length and 3-5 mm in width, the eighth rectangular unit is 0.5-1.5 mm in width and 0.5-1.5 mm in length, and the ninth rectangular unit is 1-3 mm in width and 2-4 mm in length; etching the feed structure of the antenna to form an antenna slot (7), wherein the antenna slot (7) is of a U-shaped structure and comprises three slots which are sequentially connected, wherein the three slots comprise a bottom slot and vertical slots which are perpendicular to two ends of the bottom slot, the length of the bottom slot is 17-19 mm, the length of the vertical slots is mm, and the width of the slots is 2-4 mm; the sixth rectangular unit is respectively communicated with the first monopole (3), the second monopole (4) and the third monopole (5), and the ninth rectangular unit is connected with the metal floor (1).

2. The multiple band-type vehicle-mounted antenna according to claim 1, characterized in that: the dielectric constant range of the dielectric substrate (2) is 4.4, and the metal floor (1) is a rectangular metal plate.

3. The multiple band-type vehicle-mounted antenna according to claim 1, characterized in that: the length of the medium substrate (2) is 65-75 mm, the width is 20-30 mm, and the thickness is 1.4-1.8 mm; the metal floor (1) is a rectangular metal plate, the length of the metal plate is 200-400 mm, and the width of the metal plate is 200-400 mm.

4. The multiple band-type vehicle-mounted antenna according to claim 1, characterized in that: the ground plane is composed of a tenth rectangular unit and an eleventh rectangular unit, wherein the tenth rectangular unit is 40-50 mm long and 4-6 mm wide, and the eleventh rectangular unit is 15-25 mm long and 3-5 mm wide.