CN101752664B - Annular circular polarization ceramic antenna based on quadrature coupling feed - Google Patents

Abstract

The invention discloses an annular circularly polarized ceramic antenna based on orthogonal coupling feeding, including an upper layer microstrip antenna structure, an upper layer dielectric substrate, a middle layer dielectric substrate, a metal floor layer, a lower layer dielectric substrate and a bottom Wilkinson power divider; the upper layer microstrip antenna The structure is a loop antenna. The two metal discs are small discs with two points as the center respectively. The two metal discs are respectively located in the two arcs and the inner circle area; the bottom Wilkinson power splitter layer is composed of high resistance lines, the first low Impedance line, the second low impedance line and chip resistors; the characteristic impedance of the high resistance line is the characteristic impedance z ₀ of the first low impedance line or the second low impedance line times; the upper dielectric substrate, the middle dielectric substrate and the lower dielectric substrate are all ceramic dielectrics. The antenna feed mechanism uses two circular metal sheets to generate two current sources with the same amplitude and are orthogonal to each other, so as to expand the axial ratio bandwidth of the circular metal antenna and increase the degree of freedom of antenna adjustment.

Description

Circular Polarization Ceramic Antenna Based on Orthogonal Coupling Feed

technical field

The invention relates to a satellite navigation and positioning antenna, which can work simultaneously in the B1 frequency band (1561.098MHz) and B1-2 frequency band (1589.742MHz) of China's Beidou second-generation system, and the L1 frequency band (1575.42MHz) of the American GPS system and Compatible receiving antenna for multiple navigation systems in the L1 frequency band (1602.56-1615.50MHz) of European GLONASS.

Background technique

The satellite navigation industry is a national strategic high-tech industry. It is a typical technology-intensive and service-oriented IT industry. Its development prospects are very broad. It has become one of the eight major wireless industries in the world. The rapid information industry has become another new growth point of the third IT economy. The satellite and positioning GPS application industry represented by the US Global Positioning System GPS has gradually become a global high-tech industry. my country's satellite navigation industry is entering a critical moment of rapid industrialization development. It is expected that in the next five to ten years, a global navigation satellite system integrating GPS, GLONASS, GALILEO and Beidou satellite navigation system will be formed.

With the development of various navigation systems, the coexistence of multiple systems and the pace of multi-mode integration will be further accelerated. The era of a single GPS system is changing into the era of a multi-constellation coexisting and compatible Global Navigation Satellite System (GNSS). In the foreseeable future, coverage The satellite navigation systems in the territory of each country will include four major systems: GPS, GLONASS, GALILEO and Beidou satellite navigation system. The advantages and disadvantages of each system are: GPS has been developed for a long time and is widely used, but for the sake of national security, GPS in the United States has not promised the continuity of civilian services; GLONASS has strong anti-jamming ability, but the system is unstable, The coding method is special; GALILEO is relatively accurate, but the technology maturity is relatively late. The Beidou satellite navigation system is a set of satellite navigation and positioning systems with independent intellectual property rights and two-way communication capabilities developed from China's strategic level. Therefore, it is an inevitable trend in the development of the satellite navigation industry to develop application technologies that are compatible with the above-mentioned satellite navigation systems and realize multi-mode integration.

However, the current design of multi-navigation system compatible antennas has the following technical difficulties:

1. Axial ratio/impedance broadband technology

In mobile satellite communication, the launch system on the satellite broadcasts the signal with circularly polarized waves, so that the moving vehicle and the mobile satellite communication equipment terminal equipped by the user can receive the satellite signal in any direction independent of the satellite. The launch system on the Internet covers a large range and does not need to be aimed at a specific terminal. To meet this demand, antennas for mobile satellite communications equipment must have good circular polarization performance over a wide beam.

Traditional helical antennas are often used in satellite navigation systems to generate circularly polarized wave propagation. Since the antenna needs to extend upward from the surface of the grounded metal plate to a height of λ0/4～λ0/2 (where λ0 is the antenna operating wavelength ) a helix, so it's poorly styled and adds aerodynamic drag. The low-profile microstrip antenna can make up for the above shortcomings, but the traditional single-feed microstrip circularly polarized antenna still has the following disadvantages: (1) There is not enough beam width to ensure a wide enough coverage for mobile satellite communications; (2) When having sufficient beam width, the impedance bandwidth is insufficient. Although the radiation beam width of the microstrip antenna is reduced by using a high dielectric constant dielectric material or using microstrip slot technology to produce a wide radiation beam, this method reduces the impedance bandwidth and cannot meet the requirements.

2. Miniaturization technology

Miniaturization technology is a major challenge in the design of multi-system navigation-compatible antennas. Regardless of electrical performance or mechanical size, miniaturization technology is indispensable. In terms of electrical performance, the satellite navigation system requires that the radiation beam of the antenna be sufficiently wide, and usually, a small-sized antenna can produce a wide radiation beam. From the perspective of mechanical size, when multiple antenna units are combined, the size of the entire antenna will inevitably increase, which will not only increase the aerodynamic resistance, but also increase the difficulty of antenna assembly, and affect the mechanical properties of the antenna. Strength puts forward higher requirements.

3. Antenna gain enhancement technology

Satellite navigation and positioning systems such as Beidou, GPS and GLONASS require the antenna not only to have a wide beam range, but also to have a high gain. Common gain requirements are: within the range of elevation angle 20°-90°, the gain is greater than 0dBic, and within the range of elevation angle 5°-20°, the gain is greater than -3dBic. In order to meet this requirement, it is first necessary to improve the impedance matching of the port to ensure that the radio frequency signal can be fed into each antenna unit and reduce the reflected signal energy. On the basis of ensuring good port matching, the radiation efficiency of the antenna should be improved, so that the signal fed into the antenna can be fully transmitted, and the energy loss in the antenna unit, including dielectric loss and metal loss, can be reduced.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art, provide a receiving antenna compatible with multiple satellite navigation and positioning systems, and achieve good performances such as impedance bandwidth, axial ratio bandwidth, gain and small volume.

The invention utilizes the circularly polarized ceramic antenna with orthogonal coupling feed to realize the performance of the circularly polarized antenna. The impedance bandwidth, axial ratio bandwidth and gain bandwidth of the antenna all cover Beidou B1, GPS L1, Beidou B1-2 and Beidou B1-2. The four frequency bands of three global satellite positioning systems such as GLONASS L1 are also characterized by miniaturization, compact structure, and easy processing and application.

The purpose of the present invention is achieved through the following technical solutions:

A circularly polarized ceramic antenna based on orthogonal coupling feeding, including an upper microstrip antenna structure, an upper dielectric substrate, a middle dielectric substrate, a metal floor layer, a lower dielectric substrate and a bottom Wilkinson power divider; an upper dielectric substrate and a middle layer The dielectric substrates are stacked together to form a dielectric composite substrate of an annular metal radiator. The upper microstrip antenna structure and the metal floor layer are respectively attached to the upper and lower sides of the dielectric composite substrate; the lower surface of the metal floor layer is connected to the lower dielectric substrate, and the bottom Wilkinson power divider Attached to the lower surface of the lower dielectric substrate;

The microstrip antenna structure of the upper layer comprises a loop antenna, and two sections of circular arcs protruding outward are provided on the inner circle boundary of the loop antenna 1. The included angle between the point and the center of the ring antenna is 90°; the two metal discs are small discs with two points as the centers respectively, and the two metal discs are respectively located in the two arcs and the inner circle area;

倍，贴片电阻的阻抗值为z₀的2倍；The bottom Wilkinson power divider layer is made up of high resistance lines, first low impedance lines, second low impedance lines and chip resistors; the high resistance lines and chip resistors are connected into a ring structure, the first low impedance lines and the second One end of the low-impedance line is respectively connected to the projection points of the two metal discs on the lower surface of the lower dielectric substrate, and the other ends of the first low-impedance line and the second low-impedance line are respectively connected to the high-impedance line and the chip resistor; the first low-impedance The characteristic impedance of the line and the second low impedance line are z ₀ ; the characteristic impedance of the high resistance line is the characteristic impedance z ₀ of the first low impedance line or the second low impedance line

times, the impedance value of the chip resistor is 2 times of z ₀ ;

The upper dielectric substrate, the middle dielectric substrate, the lower dielectric substrate and the metal floor layer are located at the lower ends of the two metal discs. The metal disc is connected together with the first low-impedance line and the second low-impedance line;

The upper dielectric substrate, the middle dielectric substrate and the lower dielectric substrate are all ceramic dielectrics.

To further achieve the object of the present invention, the dielectric constant of the upper dielectric substrate is higher than that of the middle dielectric substrate.

The metal disc is copper or silver, and is used to couple and feed the microstrip antenna on the upper layer.

Compared with the prior art, the present invention has the following advantages and technical effects:

(1) The antenna adopts double-feed coupling feeding and three-layer dielectric to expand the axial ratio bandwidth and impedance bandwidth. In the embodiment, when the axial ratio is less than 1.65, the frequency range is 1.55-1.685 GHz, and the bandwidth reaches 135 MHz; when the gain is greater than 2.5 dB, the frequency range is 1.545-1.615 GHz, and the gain bandwidth reaches 70 MHz; and the return loss is 1.55 The frequency range of ~1.7GHz is less than -15dB, making the impedance bandwidth greater than 250MHz.

(2) The antenna is fed by a circular metal plate orthogonally coupled, which avoids the difficult problem of high impedance matching caused by the high dielectric constant of the ceramic dielectric and the loop antenna, increases the degree of freedom of adjustment, and facilitates the debugging of the production link.

(3) The antenna uses a power divider to share the floor with the antenna, which effectively reduces the thickness of the antenna, making the structure more compact and convenient for processing and production.

(4) The antenna adopts ceramic dielectric and loop antenna structure, which effectively reduces the volume of the antenna and expands the beam width.

(5) The antenna adopts orthogonal coupling feeding technology and low-loss three-layer ceramic material to improve the matching performance and radiation efficiency of the antenna, so that the antenna of the present invention has good antenna gain.

Description of drawings

Fig. 1 is the structure schematic diagram of the annular circularly polarized ceramic antenna based on orthogonal coupling feeding of the present invention;

Fig. 2 a is the schematic diagram of microstrip antenna structural layer;

Figure 2b is a schematic diagram of the underlying Wikinson power divider;

Fig. 3 a is the return loss schematic diagram of the present invention;

Figure 3b is a schematic diagram of the axial ratio of the present invention;

Fig. 3c is a schematic diagram of gain of the present invention.

Detailed ways

The implementation of the present invention will be described in detail below in conjunction with the accompanying drawings, but the scope of protection required by the present invention is not limited to the following embodiments.

As shown in Figures 1, 2a, and 2b, the circularly polarized ceramic antenna based on orthogonally coupled feed is implemented in the form of a microstrip circuit, including an upper layer microstrip antenna structure, an upper layer dielectric substrate 13, a middle layer dielectric substrate 14, The metal floor layer 8, the lower dielectric substrate 15 and the bottom Wilkinson power divider. The upper dielectric substrate 13 and the middle dielectric substrate 14 are stacked together to form a dielectric composite substrate of an annular metal radiator. The upper microstrip antenna structure and the metal floor layer 8 are respectively attached to the upper and lower sides of the dielectric composite substrate; the lower surface of the metal floor layer 8 is connected to the lower surface. The dielectric substrate 15 is connected, and the bottom Wilkinson power divider is attached to the lower surface of the lower dielectric substrate 15 .

式中f_c是工作频率，对同时工作在中国北斗二代B1频段、B1-2频段，美国的GPS系统L1频段（1575.42MHz）和欧洲GLONASS的L1频段（1602.56-1615.50MHz）的多个导航系统可取f_c=1.575GHz；是多层介质叠放之后的等效相对介电常数，h_i是上层介质基板13、中层介质基板14、下层介质基板15的厚度，e_ri是各层介质的相对介电常数，n是天线所用介质层的数目，本例n=3。在环形天线1内圆边界上设有向外突出的两段圆弧2、3，两段圆弧2、3分别以环形天线1内圆边界上两点A、B为圆心，两点A、B分别与环形天线1的圆心的连线的夹角为90°；两金属圆片4、5是分别以两点A、B为圆心的小圆片，两金属圆片4、5的分别位于两圆弧2、3与内圆区域内。The upper layer microstrip antenna structure includes a loop antenna 1, the inner diameter of the ring is R _in , the outer diameter is R _out , the average radius of the ring is (R _in +R _out )/2 and the dielectric constant of the upper dielectric substrate 13 and the middle dielectric substrate together determine the resonant frequency of the antenna, the specific formula is

In the formula, f _c is the working frequency, for multiple navigations working simultaneously in the B1 frequency band and B1-2 frequency band of the second generation of Beidou in China, the L1 frequency band (1575.42MHz) of the GPS system in the United States and the L1 frequency band (1602.56-1615.50MHz) of the European GLONASS The system can take f _c =1.575GHz; is the equivalent relative permittivity after multilayer dielectric stacking, h _i is the thickness of the upper dielectric substrate 13, the middle dielectric substrate 14, and the lower dielectric substrate 15, e _ri is the relative permittivity of each layer of dielectric, n is the antenna The number of dielectric layers used, n=3 in this example. Two sections of circular arcs 2 and 3 protruding outward are arranged on the inner circle boundary of the loop antenna 1, and the two sections of arcs 2 and 3 are respectively centered on two points A and B on the inner circle boundary of the loop antenna 1, and the two points A, The included angle between B and the line connecting the center of the loop antenna 1 is 90°; the two metal discs 4 and 5 are small discs with two points A and B as the centers respectively, and the two metal discs 4 and 5 are respectively located at Two arcs 2, 3 and the inner circle area.

倍，贴片电阻12的阻抗值为特征阻抗Z₀的2倍；这样就可使得Wilkinson功分器的输入端和输出端接入与低阻抗微带线特征阻抗Z₀相等的负载时完全匹配。The bottom Wilkinson power splitter layer is composed of a high-resistance line 11 , a first low-impedance line 11x , a second low-impedance line 11y and a patch resistor 12 . The high-resistance line 11 and the chip resistor 12 are connected to form a ring structure. One end of the first low-impedance line 11x and the second low-impedance line 11y are respectively connected to the projection points of the two metal discs 4 and 5 on the lower surface of the lower dielectric substrate 15. The other ends of the first low-impedance line 11x and the second low-impedance line 11y are respectively connected to the high-impedance line 11 and the chip resistor 12 . Specifically, the two ends of the high-impedance line 11 are respectively connected to the other end of the first low-impedance line 11x and the second low-impedance line 11y, and the two ends of the chip resistor 12 are welded to the first low-impedance line 11x and the second low-impedance line respectively. 11y and the connection point of high resistance line 11. The characteristic impedance of the high-impedance line 11 is equal to the characteristic impedance _Z0 of the first low-impedance line 11x and the second low-impedance line 11y.

times, the impedance value of the chip resistor 12 is twice the characteristic impedance Z ₀ ; in this way, the input and output ends of the Wilkinson power divider can be completely matched when they are connected to a load equal to the characteristic impedance Z ₀ of the low-impedance microstrip line .

The upper dielectric substrate 13, the middle dielectric substrate 14, the lower dielectric substrate 15, and the metal floor layer 8 are located at the lower ends of the two metal discs 4, 5 and are provided with two circular digging holes 9, 10, which are respectively used to set two feeding coaxial lines. 6, 7; two feeding coaxial lines 6, 7 respectively connect the two metal discs 4, 5 with the first low-impedance line 11x and the second low-impedance line 11y; two circular digging holes 9, 10 and The axes of the two feeding coaxial lines 6 and 7 are concentric.

计算得到，其中c是光在真空中的速度，f是工作频率，e_eff是等效介电常数，它由微带线宽度、介质厚度和介质相对介电常数决定，其计算公式为h是介质厚度，w是微带线宽度），保证同轴线6中的相位比同轴线7中相位超前90°。Wilkinson功分器的使用，提高了天线的圆极化性能，拓展了天线的轴比带宽。The positions of the two feeding coaxial lines 6 and 7 should meet the requirements of equal amplitude and phase quadrature between the two feeding points, that is, when the first low-impedance line 11x and the second low-impedance line 11y of the bottom Wilkinson power divider When the amplitudes of the signals are the same and the phases are in quadrature, the angle formed by the line between the centers of the two feeding coaxial lines 6, 7 and the center of the loop antenna 1 is 90 degrees, and the two feeding coaxial lines 6, 7 and the center of the loop antenna 1 form an angle of 90 degrees. The larger the distance between the arcs 2 and 3, the smaller the input impedance, which can be obtained through an optimization algorithm such as a genetic algorithm (Genetic Algorithm) according to the feed port impedance of the antenna. The diameters of the metal discs 4 and 5 and the radii of the arcs 2 and 3 jointly affect the impedance matching of the antenna: the greater the distance between the two arcs 2 and 3 and the metal discs, the greater the input impedance of the antenna; but The relationship between the diameters of the metal discs 4 and 5 and the input impedance does not satisfy a linear relationship, and an optimization algorithm such as a genetic algorithm (Genetic Algorithm) needs to be used in combination with the radii of the arcs 2 and 3 to optimize during the design process. Due to the adoption of the coupling feeding method, the problem of high input impedance caused by the loop antenna working in TM ₁₁ mode and the use of high dielectric constant materials is eliminated, making it easier for the input impedance of the antenna to match the impedance of the feed port. The two feed points are 90° to the line connecting the center of the loop antenna, and the distance from the center of the circle is equal, which can stimulate two mutually orthogonal modes, which satisfies one of the conditions for right-handed circular polarization. In order to ensure that the antenna produces right-handed circular polarization, the microstrip line 11x connected to the coaxial line 6 of the Wilkinson power divider is 1/4 longer than the microstrip line 11y connected to the coaxial line 7 (l is the lower dielectric substrate 15 The equivalent wavelength in can be obtained by the formula

Calculated, where c is the speed of light in vacuum, f is the operating frequency, e _eff is the equivalent dielectric constant, which is determined by the width of the microstrip line, the thickness of the medium and the relative permittivity of the medium, and its calculation formula is h is the thickness of the medium, w is the width of the microstrip line), to ensure that the phase in the coaxial line 6 is 90° ahead of the phase in the coaxial line 7. The use of the Wilkinson power divider improves the circular polarization performance of the antenna and expands the axial ratio bandwidth of the antenna.

The upper microstrip antenna structure shares the metal floor layer 8 with the bottom Wilkinson power divider layer, effectively reducing the volume of the antenna and making the structure more compact.

The upper dielectric substrate 13 , the middle dielectric substrate 14 and the lower dielectric substrate 15 are all ceramic dielectrics, wherein the dielectric constant of the upper dielectric substrate 13 is higher than that of the middle dielectric substrate 14 . The upper dielectric substrate 13 has the characteristics of high dielectric constant, which can effectively reduce the volume of the antenna. The dielectric constant of the middle dielectric substrate 14 is lower than that of the upper dielectric substrate 13, which effectively reduces the influence of high impedance caused by the upper dielectric substrate 13 with high dielectric constant characteristics, expands the impedance bandwidth, and ensures that the antenna match. The dielectric constant of the middle dielectric substrate 14 is smaller than that of the upper dielectric substrate 13, which can reduce the overall dielectric constant and expand the bandwidth of the antenna.

The results obtained after implementation are shown in Figure 3. It can be seen from Figure 3a that in the 1.55-1.615GHz frequency band where Beidou B1, B1-2, GPS L1, and GLONASS L1 are located, the return loss S11<-15dB, as can be seen from Figure 3b, in the above frequency band The axial ratio AR<1.65dB. It can be seen from Figure 3c that in the 1.55-1.615GHz frequency band, the gain Gain>2.5dB, and the maximum gain is 4.1dB at 1.575GHz. This shows that the impedance bandwidth, axial ratio bandwidth and gain bandwidth of the antenna cover the frequency bands of Beidou B1/B1-2, GPSL1 and GLONASS L1, which makes the antenna have good performance in the above frequency bands.

Claims (3)

1. the annular circular polarization ceramic antenna based on quadrature coupling feed is characterized in that comprising upper strata microstrip antenna structure, upper layer medium substrate, middle level medium substrate, metal floor layer, layer dielectric substrate and bottom Wilkinson power splitter; Upper layer medium substrate and middle level medium substrate stack the medium composite base plate that forms the endless metal radiant body, and upper strata microstrip antenna structure and metal floor layer are respectively attached to this medium composite base plate upper and lower surface; Metal floor layer lower surface is connected with the layer dielectric substrate, and bottom Wilkinson power splitter is attached to the layer dielectric base lower surface;

Described upper strata microstrip antenna structure is a loop aerial, is provided with two sections outwards outstanding circular arcs on loop aerial internal circle circle, two sections circular arcs respectively with on loop aerial internal circle circle 2 be the center of circle, 2 angles with the line in the center of circle of loop aerial are 90 °; Two metal disks are to be the sequin in the center of circle with 2 respectively, and two metal disks lay respectively at two circular arcs and internal circle circle area surrounded inside;

Described bottom Wilkinson power splitter layer is made up of high resistant line, first low-impedance line, second low-impedance line and Chip-R; High resistant line and Chip-R connect into loop configuration, one end of first low-impedance line and second low-impedance line is connected at layer dielectric base lower surface subpoint with two metal disks respectively, and the other end of first low-impedance line and second low-impedance line is connected with Chip-R with the high resistant line respectively; The characteristic impedance of first low-impedance line and second low-impedance line is z ₀The characteristic impedance of high resistant line is the characteristic impedance z of first low-impedance line or second low-impedance line ₀

Doubly, the resistance value of Chip-R is z ₀2 times;

The upper layer medium substrate, middle level medium substrate, layer dielectric substrate and the metal floor layer that are positioned at two metal disk lower ends are provided with two circular boreholes, are respectively applied for two feed coaxial lines are set; Two feed coaxial lines link together two metal disks and first low-impedance line, second low-impedance line respectively;

Upper layer medium substrate, middle level medium substrate and layer dielectric substrate are ceramic dielectric;

First low-impedance line and the second low-impedance line length differ 1/4 times of the effective wavelength of operating frequency in the layer dielectric substrate.

2. the annular circular polarization ceramic antenna based on quadrature coupling feed according to claim 1 is characterized in that: the dielectric constant height of the permittivity ratio middle level medium substrate of described upper layer medium substrate.

3. the annular circular polarization ceramic antenna based on quadrature coupling feed according to claim 1 is characterized in that: described metal disk is copper sheet or silver strip.

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