CN101170213B - Low Profile Cavity Backed Circular Slot One Point Short Circularly Polarized Antenna - Google Patents

Abstract

The invention relates to a cavity-backed circular polarization antenna of an annular slot one-point short circuit with low profile. The prior cavity-backed circular polarization antenna based on annular slot one-point short circuit has complicated structure, large volume, non-planar integration, as well as high cost. Two surfaces of a medium substrate of the invention are plated with metal layers, the upper metal layer is etched with a micro-strip line used for feeding, and a common ground and coplanar waveguide transmission line, and as the micro-strip line, the middle metal belt of the coplanar waveguide transmission line extends outwardly. The upper metal layer, the medium substrate, and the lower metal layer are opened with a plurality of metallized through holes arranged as a circularity, so as to form a cavity, and the coplanar waveguide transmission line dives into the cavity. The lower metal layer is etched with a circular ring shaped radiation slot of one-point short circuit in corresponding cavity area. Compared with the cavity-backed circular polarization antenna composed by the prior metal cavity, the invention adopts common PCB process to manufacture, the manufacturing cost is low, and can realize seamless integration with the micro-strip circuit, thereby improving systemic integrated level.

Description

Low Profile Cavity Backed Circular Slot One Point Short Circularly Polarized Antenna

technical field

The invention belongs to the field of microwave technology, and relates to a low-profile cavity-backed annular gap one-point short-circuit circularly polarized antenna based on substrate integrated waveguide technology, which can be used as a radio frequency transceiver front-end antenna and is widely used in mobile communications, satellite communications, Radar and other wireless communication systems are used to solve the polarization mismatch problem caused by the Faraday electromagnetic rotation effect, and can also play a role in suppressing rain and fog interference and anti-multipath reflection.

Background technique

As a key component of a communication system, antennas are widely used in wireless communication occasions. Due to the Faraday rotation effect of radio wave propagation in space and the uncertainty of the position of the receiving antenna in mobile communication, if a traditional single-polarized antenna is used as the transceiver unit, the polarization matching alignment of the transceiver antenna is required to achieve better reception. Effect. The constant-amplitude rotating field radiated by circularly polarized antennas can be decomposed into two orthogonal linearly polarized waves with equal amplitude and 90-degree phase difference, which are widely used in wireless communications to solve the problem of polarization mismatch. At the same time, due to the rotation reversal characteristic when the circularly polarized wave is incident on the symmetrical target, the circularly polarized antenna is used in the field of mobile communication and satellite communication, and it also plays the role of suppressing rain and fog interference and anti-multipath reflection. Therefore, designing a high-performance circularly polarized antenna can not only avoid polarization mismatch and obtain good receiving effect, but also greatly relieve the index pressure of subsequent RF circuits, significantly improve system performance and reduce system cost. Especially in wireless communication applications where volume and weight are strictly limited, such as satellite communication and radio frequency identification, it is particularly important to design a high-performance circularly polarized antenna with a low profile.

There are various ways to implement circularly polarized antennas, including microstrip patch antennas, microstrip slotted antennas, waveguide slotted antennas, cavity-backed circularly polarized antennas, and helical antennas. Circularly polarized antennas in the form of microstrips have the advantages of low profile and easy conformality, and are most widely used. Its feeding methods mainly include slot coupling feeding and coaxial waveguide feeding. Among them, slot coupling feeding is mainly realized by multi-layer PCB technology, which is expensive and not very stable for domestic technology. Although the coaxial feeding method is simple, it cannot be seamlessly integrated with the planar circuit, resulting in a larger volume. The waveguide slot slotted circularly polarized antenna is suitable for array antenna applications. The single radiating unit is small in size and the array is compact in size. The array antenna has excellent characteristics such as narrow main lobe width, shapeable pattern, and low cross-polarization level. It is widely used Applied to microwave millimeter wave radar communication system, etc. However, antennas based on traditional metal waveguide technology are large in size, complex in processing technology, and high in cost, which limits their widespread use; cavity-backed circularly polarized antennas are generally implemented on a planar substrate with feed, radiation elements, and an additional metal cavity on the back This kind of antenna has high gain and good directivity, but it also has complex processing, high cost and large volume. In order to solve these problems, Sievenpiper et al. proposed to form a cavity structure by embedding metal strips on the substrate, and at the same time use coaxial to feed it at a suitable position to form a cavity-backed circularly polarized antenna. Compared with the previous cavity-backed circularly polarized antenna, this implementation method is greatly reduced in size, but its processing cost is still high, and it cannot be integrated in a plane; the helical antenna is mainly used in space applications of earth stations and satellite links. It has the advantages of high gain, low axial ratio, and wide axial ratio bandwidth, but its three-dimensional helical radiation structure determines its disadvantages such as large volume and incapable of plane integration. Based on the current research status of circularly polarized antennas, it is still necessary to study the use of new technologies and new structures to achieve low-cost, low-profile, high-performance circularly polarized antennas.

Contents of the invention

The object of the present invention is to provide a low-profile cavity-backed annular slot one-point short-circuit circularly polarized antenna based on substrate integrated waveguide technology. This new type of circularly polarized antenna has good radiation performance, high gain, and low profile. Seam plane integration, simple structure, easy design, easy processing, and low cost. Compared with the existing cavity-backed circularly polarized antenna based on one-point short-circuit of the annular slot, the volume of the circularly polarized antenna is greatly reduced, and the manufacturing cost is significantly reduced.

The low-profile, cavity-backed annular slot one-point short-circuit circularly polarized antenna of the present invention includes a dielectric substrate, and the two sides of the dielectric substrate are coated with metal layers, which are respectively an upper metal layer and a lower metal layer, wherein the lower metal layer is used as a ground layer; The metal layer is etched with a microstrip line and a coplanar waveguide transmission line for feeding. The coplanar waveguide transmission line is a common ground coplanar waveguide structure, and the middle metal strip extends outwards as a microstrip line; it runs through the upper metal layer and the dielectric substrate. There are through holes on the chip and the lower metal layer, and the inner wall of the through hole is plated with metal to form a metallized through hole; a plurality of metallized through holes are arranged in a circular order to form a circular substrate integrated waveguide cavity, forming a circular substrate The hole spacing of the adjacent metallized through holes of the chip integrated waveguide cavity is the same; the coplanar waveguide transmission line extends into the substrate integrated waveguide cavity, and the center of the substrate integrated waveguide cavity is located at the center line of the metal strip of the coplanar waveguide transmission line The upper and lower metal layers are etched in the area of the substrate-integrated waveguide cavity with a circular radiation slit with a short circuit, the radiation slit is set concentrically with the substrate-integrated waveguide cavity, and the center of the short-circuit point is connected to the center of the radiation slit Perpendicular to the centerline of the metal strip in the feed structure.

The diameter of the metallized through hole is less than one-tenth of the air wavelength corresponding to the center frequency of the antenna, and the ratio of the diameter of the metallized through hole to the center-to-center distance of two adjacent metallized through holes is greater than 0.5.

The low-profile cavity-backed annular slot one-point short-circuit circularly polarized antenna of the present invention uses substrate-integrated waveguide technology to manufacture a substrate-integrated waveguide cavity structure equivalent to a traditional metal cavity on a common dielectric substrate, thereby greatly improving the The volume of the cavity-backed circularly polarized antenna is reduced. Unlike traditional cavity-backed antennas that require precise machining, this new type of antenna, including the feed network, can be manufactured using ordinary PCB technology, significantly reducing manufacturing costs, and can be seamlessly integrated with microstrip circuits. Structurally, the substrate is a dielectric substrate with double-sided metal layers, and a series of metallized through holes are arranged at uniform intervals on the dielectric substrate to form a circular substrate integrated waveguide cavity equivalent to a traditional metal cavity. . The microstrip line used for feeding is etched on the upper metal layer of the double-sided metal layer, and then the electromagnetic wave is introduced into the circular substrate integrated waveguide cavity through the coplanar waveguide structure. The lower metal layer of the double-sided metal layer corresponds to the area of the integrated waveguide cavity of the substrate and etches a circular radiation gap with a short circuit to radiate electromagnetic energy.

Specific working principle: The electromagnetic wave is fed by the microstrip line, and then introduced into the circular substrate integrated waveguide cavity formed by the substrate integrated waveguide technology through the coplanar waveguide transmission line, thereby exciting multiple modes in the cavity resonance. Since the cavity is a two-dimensional symmetric structure, two second-order degenerate modes that are orthogonal to each other must be excited. At this time, by adjusting the position and width of the short-circuit point on the annular slit, the two mutually orthogonal degenerate resonance modes can be separated, and the energy can be radiated through the slit to form an antenna. Adjusting the size of the cavity, the radius of the annular gap, and the position and width of the short-circuit point can adjust the phase difference of the electromagnetic waves radiated by the mutually orthogonal resonance modes to 90 degrees at the required frequency, so that the radiated electromagnetic waves form a circle polarization.

Beneficial effects: The low-profile cavity-backed annular slot one-point short-circuit circularly polarized antenna based on the substrate integrated waveguide technology has the following advantages:

a. This new type of cavity-backed circularly polarized antenna retains the excellent radiation characteristics of the traditional metal-backed circularly polarized antenna, such as high gain. At the same time, the entire antenna, including the cavity-backed structure and feed network, can be on the same dielectric substrate Realized, not only the volume of the antenna is greatly reduced, but also the entire antenna can be seamlessly integrated with the system, which improves the integration degree of the system.

b. This new cavity-backed circularly polarized antenna has a simple structure, and the entire structure is realized on a common dielectric substrate. In the design process, it is only necessary to adjust the radius of the radiation slot, the position of the short-circuit point, and the radius of the circular substrate integrated waveguide cavity composed of metal through holes to obtain the required performance. Few structural parameters greatly shorten the design and optimization time.

c. This new type of cavity-backed circularly polarized antenna is simple and convenient to manufacture, and can be realized with ordinary PCB technology. Compared with traditional cavity-backed antennas that require precision machining, the manufacturing speed is fast and the cost is low.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the three-dimensional structure schematic diagram of the present invention;

Fig. 3 is a schematic diagram of the upper metal layer structure of the present invention;

Fig. 4 is a schematic diagram of the structure of the lower metal layer of the present invention;

Fig. 5 is a comparison diagram of return loss simulation and test results of an embodiment of the present invention;

Fig. 6 is a comparison diagram of the simulation test results of axial ratio and gain of an embodiment of the present invention;

Fig. 7 is a test result diagram of the radiation pattern in the X-Y plane at 12 GHz according to an embodiment of the present invention;

Fig. 8 is a test result diagram of the radiation pattern in the X-Z plane at 12 GHz according to an embodiment of the present invention;

Detailed ways

As shown in Figures 1 and 2, the low-profile cavity-backed annular gap one-point short-circuit circularly polarized antenna includes a Rogers5880 dielectric substrate 1 with a thickness of 0.5 mm, and the two sides of the dielectric substrate 1 are coated with metal layers, which are respectively the upper metal layer 7 And the lower metal layer 8, wherein the lower metal layer 8 is used as the formation layer. As shown in Figure 3, the upper metal layer 7 is etched with a microstrip line 2 for feeding and a coplanar waveguide transmission line 3 (the dotted box includes the part), and the coplanar waveguide transmission line 3 is a common ground coplanar waveguide structure, and the middle metal strip Extend outward, as the microstrip line 2. The length and width of the microstrip line 2 are 4 mm and 1.45 mm respectively, and the two air gaps of the coplanar waveguide transmission line 3 both have a width of 0.7 mm and a length of 8.2 mm. A through hole with a diameter of 1 mm is opened through the upper metal layer 7 , the dielectric substrate 1 and the lower metal layer 8 , and the inner wall of the through hole is plated with metal to form a metallized through hole 4 . A plurality of metallized through-holes 4 are sequentially arranged in a circle with a radius of 11.9 mm to form a circular substrate-integrated waveguide cavity, and the metallized through-holes 4 arrays constituting the circular substrate-integrated waveguide cavity have the same hole spacing. is 1.35mm. The coplanar waveguide transmission line 3 extends into the substrate-integrated waveguide cavity, its top is 6.0 mm away from the center of the cavity, and the center line of the middle metal strip coincides with one diameter of the substrate-integrated waveguide cavity. As shown in Figure 4, the lower metal layer 8 is etched with a circular radiation slot 5 with a width of 1 mm and a radius of 6.2 mm in the region of the substrate-integrated waveguide cavity, the center of which coincides with the center of the circular substrate-integrated waveguide cavity. There is a short circuit 6 with a length of 1.0 mm on the annular radiation slot 5 (the dotted circle frame includes the part), and the center line between the center of the short circuit 6 and the center of the radiation slot is perpendicular to the center line of the metal strip in the feed structure .

The specific structural geometric parameters are as follows:

where r _c is the radius of the circular cavity of the substrate integrated waveguide, L _ms and W _ms are the length and width of the feeding microstrip line respectively, L _cpw and g _cpw are the length and width of the coplanar waveguide slot respectively, r _s and W _s are the radius and width of the circular slot, respectively, a _s is the length of the short-circuit point on the circular slot, L _c is the distance between the top of the coplanar waveguide and the center of the cavity, and α is the center of the feeding metal strip d is the diameter of the through hole, _dp is the center distance of the through hole, and h is the thickness of the substrate.

L _ms (mm) 4.0 W _ms (mm) 1.45

L _cpw (mm)8.2 g _cpw (mm)0.7

r _s (mm)6.2 W _s (mm)1.0

α _s (mm)0.8 α(deg)90

L _c (mm)6.0 r _c (mm)11.9

d(mm) _1.0dp (mm)1.35

h(mm)0.5

The specific manufacturing process of the coplanar waveguide single-point fed cavity-backed circularly polarized antenna is as follows: first, select a substrate with corresponding parameters, and etch the microstrip line and coplanar waveguide transmission line for feeding on the upper metal layer of the substrate , and then etch a short-circuited annular gap at a suitable position on the lower metal layer of the substrate, and finally punch a series of metallized through holes at uniform intervals around a short-circuited annular gap on the entire substrate to form a center and a circle. A circular substrate integrated waveguide cavity whose center coincides with the center of the shaped slit. Choose an appropriate hole diameter and hole spacing to avoid energy leakage in the cavity. This new cavity-backed circularly polarized antenna retains the high-gain radiation characteristics of traditional metal-backed circularly polarized antennas. The operating frequency of the antenna can be adjusted conveniently by selecting the appropriate size of the radiation slot and the size of the circular substrate integrated waveguide cavity. The entire antenna is completely realized by ordinary PCB technology and can be fully and seamlessly integrated with the system.

Figures 5 to 8 show the performance test results of the circularly polarized antenna. The simulation test results in Fig. 5 show that the antenna can effectively radiate energy in the working frequency band whose center frequency is 12 GHz. The simulation test results in Figure 6 all show that the antenna has a 3dB axial ratio bandwidth of 90MHz in the working frequency band and a gain of up to 8.0dBi. The test results of the pattern in Figures 7 to 8 show that the antenna exhibits good right-handed circular polarization radiation characteristics in both the X-Y plane and the X-Z plane when the operating frequency is 12 GHz, with high gain, good directivity, and low cross-polarization level .

Claims (2)

1. A one-point short-circuit circularly polarized antenna with a low-profile cavity-backed annular gap, including a dielectric substrate, characterized in that: the two sides of the dielectric substrate are coated with metal layers, which are respectively an upper metal layer and a lower metal layer, wherein the lower metal layer As the ground layer; the upper metal layer is etched with a microstrip line for feeding and a coplanar waveguide transmission line. The coplanar waveguide transmission line is a common ground coplanar waveguide structure, and the middle metal strip extends outwards as a microstrip line; it runs through the upper metal layer, the dielectric substrate and the lower metal layer have through holes, and the inner wall of the through hole is plated with metal to form a metallized through hole; a plurality of metallized through holes are arranged in a circular order to form a circular substrate integrated waveguide cavity. The hole spacing of the adjacent metallized through holes constituting the circular substrate integrated waveguide cavity is the same; the coplanar waveguide transmission line extends into the substrate integrated waveguide cavity, and the center of the substrate integrated waveguide cavity is located at the metal strip of the coplanar waveguide transmission line on the center line of the strip; the lower metal layer etches a circular radiation slit with a short circuit in the area of the substrate integrated waveguide cavity, the radiation slit is set concentrically with the substrate integrated waveguide cavity, the center of the short-circuit point and the radiation slit The line connecting the center of the circle is perpendicular to the center line of the metal strip in the feed structure, and the circular substrate integrated waveguide cavity works in the second-order resonance mode. 2. The low-profile cavity-backed annular slot one-point short-circuit circularly polarized antenna as claimed in claim 1, wherein the diameter of the metallized through hole is less than one tenth of the air wavelength corresponding to the center frequency of the antenna work First, the ratio of the diameter of the metallized through hole to the center-to-center distance of two adjacent metallized through holes is greater than 0.5.

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