Circularly polarized cavity-backed helical antenna based on rectangular micro-coaxial process

Abstract

The invention discloses a circularly polarized cavity-backed helical antenna based on a rectangular micro-coaxial process. The circularly polarized cavity-backed helical antenna mainly comprises two helical arms, a dielectric substrate printed with the two helical arms, a thin-film resistor on the dielectric substrate, two metal rings on the outer circle of the dielectric substrate, a metal sleeve, a feed rectangular coaxial line balun, a conical metal table, a wave-absorbing material and a radio frequency coaxial connector. The tail ends of the two spiral arms are connected with one ends of the two thin-film resistors respectively, the other ends of the two thin-film resistors are connected with the metal rings respectively, the dielectric substrate is placed above the metal sleeve, and the top and the bottom of the feed rectangular coaxial line balun are connected with the spiral arms and the radio frequency coaxial connector respectively. The feed rectangular coaxial line balun is embedded in the conical metal table, and the wave-absorbing material is placed above the conical metal table. The antenna provided by the invention adopts a metal back cavity structure, and has the characteristics of small overall structure size, high gain and low axial ratio in an ultra-wideband range.

Description

Technical Field

[0001] The invention relates to the field of antenna technology, and in particular to a circularly polarized cavity-backed spiral antenna based on a rectangular micro-coaxial process. Background Art

[0002] In recent years, with the continuous development of wireless communication technology, the functionality of wireless communication systems such as radar systems, anti-interference systems, and terminal communication systems has been continuously improved, which directly increases the design requirements of the transceiver antennas, and it is becoming more and more challenging to achieve these demanding design requirements. At present, the ultra-wide circularly polarized cavity-backed spiral antenna has received widespread attention, which is also due to its wide application in satellite communications, electronic warfare, radar systems, mobile communication base stations, etc.

[0003] Compared with other transmitting and receiving antennas, circularly polarized helical antennas not only have consistent gain and input impedance within several frequency octaves, but also have powerful anti-interference and multipath suppression capabilities. However, with the increase of the operating frequency band, it becomes increasingly difficult to miniaturize it while maintaining the original performance. This has also become a major research hotspot today. Summary of the invention

[0004] The present invention proposes a circularly polarized cavity-backed helical antenna based on a rectangular micro-coaxial process, which can solve at least one of the above-mentioned technical problems.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A circularly polarized cavity-backed spiral antenna based on a rectangular micro-coaxial process of the present invention comprises a dielectric substrate, characterized in that two spiral arms, two thin-film resistors, and a circle of metal rings are printed on the upper surface of the dielectric substrate, and metal rings of the same size are also printed on the lower surface of the dielectric substrate, and metalized vias are provided in the dielectric substrate; the metalized vias are used to connect the metal rings on the front and back surfaces of the dielectric substrate; One end of the thin film resistor is connected to the metal ring, and the other end of the thin film resistor is connected to the spiral arm; The dielectric substrate is placed on the top of the metal sleeve; a conical metal platform is arranged in the metal sleeve, and a wave absorbing material is placed on the top of the conical metal platform; The conical metal platform is embedded with a feeding rectangular coaxial line balun; The output end of the feeding rectangular coaxial line balun is connected to the centers of the two spiral arms, and the input end of the feeding rectangular coaxial line balun is connected to the radio frequency coaxial connector.

[0006] Furthermore, the balun input end of the feeding rectangular coaxial line is connected to the rectangular coaxial line by a section of grounded coplanar waveguide, and air is used as a medium under the grounded coplanar waveguide.

[0007] Furthermore, a supporting structure is provided underneath the center feed line of the grounded coplanar waveguide, and the feeding rectangular coaxial line balun realizes the function of the balun by reversely connecting the inner conductor and the outer conductor, and the feeding rectangular coaxial line balun has a cylindrical air cavity at the reverse connection point between the inner conductor and the outer conductor.

[0008] Furthermore, the feed rectangular coaxial line balun has a release hole and a supporting structure, the output end of the feed rectangular coaxial line balun is connected to a grounded coplanar waveguide structure, the other end of the grounded coplanar waveguide structure is connected to a parallel double-wire structure, and one end of the parallel double-wire structure is connected to a spiral arm.

[0009] Furthermore, a cylindrical air cavity and a screw hole for loading the radio frequency coaxial connector are provided inside the conical metal platform.

[0010] Furthermore, four metal pillars are connected to the conical metal platform, and the absorbing material has four holes for the metal pillars to pass through.

[0011] Furthermore, the dielectric substrate is placed in the groove on the top of the metal sleeve, and two screws are provided to clamp the dielectric substrate.

[0012] Furthermore, a second wave absorbing material is adhered to the side wall of the metal sleeve.

[0013] Furthermore, the radio frequency coaxial connector is connected to the balun input end of the feeding rectangular coaxial line.

[0014] Furthermore, the conical metal platform has four screw holes in it so that the radio frequency coaxial connector is fixed on the conical metal platform.

[0015] It can be seen from the above technical scheme that the purpose of the present invention is to provide an ultra-wideband circularly polarized cavity-backed spiral antenna based on a rectangular micro-coaxial process, which absorbs the reflected current by loading a thin film resistor at the end of the spiral arm printed on a dielectric substrate, thereby reducing the return loss and axial ratio of the antenna at the low frequency of the working frequency band, and also reducing the volume of the antenna. At the same time, a feeding rectangular coaxial line balun based on a rectangular micro-coaxial process is designed to achieve the miniaturization of the antenna. By placing absorbing materials in the metal cavity, a lower axial ratio is achieved in the entire frequency band, and by loading a suitable metal back cavity structure, the antenna has a higher gain and a good radiation pattern.

[0016] Compared with the prior art, the present invention has the following significant advantages: 1. The present invention absorbs the reflected current at the end of the spiral arm by loading a thin film resistor on the dielectric substrate, thereby reducing the return loss and the axial ratio at the low frequency of the working frequency band, thereby solving the size problem caused by improving the performance at the low frequency, thereby reducing the lateral size, and the feeding rectangular coaxial line balun structure designed by the rectangular micro-coaxial process has the advantages of miniaturization, low loss and high power capacity. The use of this feeding structure greatly reduces the cross-sectional height of the antenna, and compared with the traditional structure, miniaturization is truly achieved.

[0017] 2. The present invention realizes high and stable gain and good circularly polarized radiation by loading a metal back cavity structure and absorbing materials of suitable shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 is a top view of the present invention; Figure 3 It is a front view of the present invention; Figure 4 It is a front view of the feeding structure of the present invention; Figure 5 It is the S parameter simulation diagram of the present invention; Figure 6 is a gain simulation diagram of the present invention; Figure 7 It is the axial ratio simulation diagram of the present invention; Figure 8 It is a simulation diagram of the gain changing with the Theta angle at 18 GHz and Phi=0° in the Phi direction of the present invention; Fig. 9 It is a simulation diagram of the gain changing with the Theta angle at 20 GHz and Phi=0° in the Phi direction of the present invention; Fig.10 It is a simulation diagram of the gain changing with the Theta angle at 30 GHz, when the Phi direction Phi=0°; Fig.11 It is a simulation diagram of the gain changing with the Theta angle at 40 GHz with Phi=0° in the Phi direction of the present invention; Fig.12 It is a simulation diagram of the gain changing with the Theta angle at 50 GHz and Phi=0° in the Phi direction of the present invention; Fig.13 It is a simulation diagram of the gain changing with the Theta angle at 18 GHz, 20 GHz, 30 GHz, 40 GHz, 50 GHz, and 60 GHz with Phi=0° in the Phi direction of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0020] like Figure 1 The figure is a schematic structural diagram of an ultra-wideband circularly polarized cavity-backed spiral antenna based on a rectangular micro-coaxial process according to an embodiment of the present invention. The antenna structure includes a dielectric substrate 1, and the upper surface of the dielectric substrate 1 is printed with two spiral arms 3, two thin film resistors 6, and a circle of metal rings 2. The lower surface of the dielectric substrate 1 is printed with a metal ring 2. The dielectric substrate 1 has a metalized via 4, including a metal sleeve 5. There are two screws 21 on the top of the metal sleeve 5. The center 8 of the two spiral arms 3 is connected to the parallel double-wire structure 14 at the output end of the feed rectangular coaxial line balun, and the grounded coplanar waveguide 9 at the input end of the feed rectangular coaxial line balun is connected to the RF coaxial connector 22. The feed rectangular coaxial line balun is embedded in a conical metal platform 15, and the conical metal platform 15 is placed in the metal sleeve 5. An absorbing material 19 is placed on the top of the conical metal platform 15.

[0021] like Figure 2 As shown, the ends 7 of the two spiral arms 3 are respectively connected to one end of the thin film resistor 6, the other end of the thin film resistor 6 is connected to the outer metal ring 2, and then connected to the metal ring 2 on the lower surface of the dielectric substrate 1 through the metallized via 4, thereby achieving grounding, and further achieving the effect of increasing bandwidth, reducing size and reducing axial ratio by utilizing the thin film resistor 6 to absorb reflected current.

[0022] Reference Figure 3 As shown, by designing a suitable groove on the top of the metal sleeve 5, the dielectric substrate 1 can be placed on the metal sleeve 5, and screws are installed on the top of the metal sleeve 5 to clamp the dielectric substrate 1. The metal sleeve 5 and the conical metal platform 15 together form a metal back cavity structure, so that the antenna can obtain good directional radiation capability and higher gain, and in order to make the dielectric substrate 1 more stable, four metal pillars 18 are loaded on the conical metal platform 15 as a supporting structure. In order to obtain a lower axial ratio to achieve better circular polarization, a 1mm thick absorbing material 19 is placed on the conical metal platform 15 and a 1mm thick absorbing material 23 is placed on the side wall of the metal sleeve 5 to absorb part of the electromagnetic waves radiated downward, and the absorbing material 19 has four holes 20 for the four metal pillars 18 to pass through. There is a cylindrical air cavity 16 in the conical platform to reduce the influence of energy leakage at the reverse connection on the performance of the feeding rectangular coaxial line balun. In addition, there are four screw holes 17 in the conical platform, and the RF coaxial connector 22 is fixed to the conical metal platform 15 by screws.

[0023] like Figure 4 As shown, energy is input to the grounded coplanar waveguide 9 at the input end of the feeding rectangular coaxial line balun through the RF coaxial connector 22. Air is used as the medium below the grounded coplanar waveguide 9 at the input end of the feeding rectangular coaxial line balun, and a support structure 10 is placed below the grounded coplanar waveguide 9 at the input end of the feeding rectangular coaxial line balun to prevent the RF coaxial connector 22 from collapsing the grounded coplanar waveguide 9 at the input end of the feeding rectangular coaxial line balun. The grounded coplanar waveguide 9 at the input end of the feeding rectangular coaxial line balun is connected to the rectangular coaxial line, and then the inner and outer conductors of the coaxial line are reversed and extended to the grounded coplanar waveguide 13 at the output end of the feeding rectangular coaxial line balun in the form of a rectangular coaxial line. All rectangular coaxial lines have release holes 12. A section of parallel double-wire structure 14 is connected through the grounded coplanar waveguide 13 at the output end of the feeding rectangular coaxial line balun, and then the parallel double-wire structure 14 is connected to the center 8 of the spiral arm on the dielectric substrate 1, thereby realizing the feeding of the antenna and the characteristics of low profile size.

[0024] In an example of the present invention, in order to verify the effectiveness of the above-mentioned ultra-wideband circularly polarized cavity-backed spiral antenna based on rectangular micro-coaxial process, the following structural dimensions are taken as an example for explanation: the antenna structure includes a dielectric substrate 1, the upper surface of the dielectric substrate 1 is printed with two spiral arms 3, two thin film resistors 6, and a circle of metal rings 2, the lower surface of the dielectric substrate 1 is printed with a metal ring 2, the dielectric substrate 1 has a metalized via 4, including a metal sleeve 5, the top of the metal sleeve 5 has two screws 21, the center 8 of the two spiral arms 3 is connected to the parallel double-wire structure 14 at the output end of the feed rectangular coaxial line balun, the grounded coplanar waveguide 9 at the input end of the feed rectangular coaxial line balun is connected to the RF coaxial connector 22, the feed rectangular coaxial line balun is embedded in a conical metal platform 15, the conical metal platform 15 is placed in the metal sleeve 5, and the top of the conical metal platform 15 is placed with an absorbing material 19.

[0025] The dielectric substrate 1 has a diameter of 16.8 mm and a thickness of 0.254 mm. The selected material is RP220B, with a dielectric constant of 2.2 and a loss tangent of 0.0009. The equation of the spiral arm 3 printed on the dielectric substrate 1 is r=r0+α1(φ), where r0=0.17 is the radius of the center of the spiral arm 3 from the origin, α1=0.25 is the spiral growth rate of the spiral arm 3, φ is the rotation angle of the spiral arm 3, the arm width of the spiral arm 3 is 0.35 mm, and the thickness is 0.018 mm, which plays the role of transmitting 18-60 GHz electromagnetic waves. The thin film resistor 6 connected to the end 7 of the spiral arm 3 has a resistance of 120Ω, and its resistance can maintain good stability in the entire frequency band. The width of the metal ring printed on the dielectric substrate 1 is 0.6 mm and the thickness is 0.018 mm. The height of the outermost metal sleeve 5 is 13.348 mm, the diameter is 22 mm, and the diameter of the metal back cavity is 14 mm. The lower surface diameter of the conical metal platform 15 is 13mm, the upper surface diameter is 4.3mm, and the height is 2mm. The four metal pillars on it are slightly different in size, and their average length is 1mm, width is 0.32mm, and height is 3.2mm. The absorbing material 19 on the conical metal platform 15 has a thickness of 1mm, and the absorbing material 23 on the side wall of the metal sleeve 5 has a thickness of 1mm, a width of 2.3mm, and a length of 43.98mm. The length of the feeding rectangular coaxial line balun is 11.648mm, the width is 4mm, and the thickness is 0.9mm.

[0026] Figure 5 The S11 parameter simulation result of the antenna in this example shows that S11<-10dB in the entire passband of the antenna (18-60GHz).

[0027] Figure 6 This is the simulation result of the antenna gain. The overall gain in the passband is above 3.5dBi, and the maximum gain can reach 8.18dBi.

[0028] Figure 7 This is the simulation result of the axial ratio of the antenna, which completely covers the entire passband (18-60GHz) with an axial ratio less than 3dB.

[0029] Figure 8-13 They are respectively the simulation diagrams of the gain changing with the Theta angle at 18 GHz, 20 GHz, 30 GHz, 40 GHz, 50 GHz and 60 GHz with Phi=0° in the Phi direction. From the above diagrams, it can be observed that the antenna has a stable 3dB beamwidth.

[0030] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A circularly polarized cavity-backed helical antenna based on a rectangular micro-coaxial process, comprising a dielectric substrate, characterized in that: Two spiral arms, two thin-film resistors, and a circle of metal rings are printed on the upper surface of the dielectric substrate, and metal rings of the same size are also printed on the lower surface of the dielectric substrate. Metallized vias are provided in the dielectric substrate; the metallized vias are used to connect the metal rings on the front and back sides of the dielectric substrate; One end of the thin film resistor is connected to the metal ring, and the other end of the thin film resistor is connected to the spiral arm; The dielectric substrate is placed on the top of the metal sleeve; a conical metal platform is arranged in the metal sleeve, and a wave absorbing material is placed on the top of the conical metal platform; The conical metal platform is embedded with a feeding rectangular coaxial line balun; The top of the feeding rectangular coaxial line balun is connected to the centers of the two spiral arms, and the bottom of the feeding rectangular coaxial line balun is connected to the radio frequency coaxial connector.

2. The circularly polarized cavity-backed helical antenna based on rectangular micro-coaxial technology according to claim 1, characterized in that: The balun input end of the feeding rectangular coaxial line is connected to the rectangular coaxial line by a section of grounded coplanar waveguide, and air is used as a medium under the grounded coplanar waveguide.

3. The circularly polarized cavity-backed helical antenna based on rectangular micro-coaxial technology according to claim 2, characterized in that: The center feed line of the grounded coplanar waveguide is supported by a supporting structure below. The feeding rectangular coaxial line balun realizes the function of the balun by reversely connecting the inner conductor and the outer conductor. The feeding rectangular coaxial line balun has a cylindrical air cavity at the reverse connection of the inner conductor and the outer conductor.

4. The circularly polarized cavity-backed helical antenna based on rectangular micro-coaxial technology according to claim 3 is characterized in that: The feeding rectangular coaxial line balun has a release hole and a supporting structure. The output end of the feeding rectangular coaxial line balun is connected to a grounded coplanar waveguide structure, the other end of the grounded coplanar waveguide structure is connected to a parallel double-wire structure, and one end of the parallel double-wire structure is connected to a spiral arm.

5. The circularly polarized cavity-backed helical antenna based on rectangular micro-coaxial technology according to claim 1, characterized in that: The conical metal platform has a cylindrical air cavity and a screw hole for loading the radio frequency coaxial connector inside.

6. The circularly polarized cavity-backed helical antenna based on rectangular micro-coaxial technology according to claim 1, characterized in that: Four metal pillars are connected to the conical metal platform, and the absorbing material has four holes for the metal pillars to pass through.

7. The circularly polarized cavity-backed helical antenna based on rectangular micro-coaxial technology according to claim 1, characterized in that: The dielectric substrate is placed in the groove on the top of the metal sleeve, and two screws are provided to clamp the dielectric substrate.

8. The circularly polarized cavity-backed helical antenna based on rectangular micro-coaxial technology according to claim 1, characterized in that: The side wall of the metal sleeve is adhered with a wave absorbing material 2.

9. The circularly polarized cavity-backed helical antenna based on rectangular micro-coaxial technology according to claim 4, characterized in that: The radio frequency coaxial connector is connected to the balun input end of the feeding rectangular coaxial line.

10. The circularly polarized cavity-backed helical antenna based on rectangular micro-coaxial technology according to claim 4, characterized in that: The conical metal platform has four screw holes in it so that the radio frequency coaxial connector can be fixed on the conical metal platform.

Images