A design method for circularly polarized antenna

Abstract

The present invention proposes a design method for a circularly polarized antenna, including: determining the material parameters of a main patch and a parasitic patch of a wideband circularly polarized antenna; determining the initial sizes of the main patch and the parasitic patch according to the determined material parameters of the main patch of the wideband circularly polarized antenna; establishing the main patch and the parasitic patch models in electromagnetic simulation software for simulation, and adjusting the size and angle of the main patch and changing the position of the feeding point so that the main patch obtains two impedance matching points; circular polarization is achieved by adjusting the size and angle of the parasitic patch, and a parasitic patch with an optimal axial ratio within the required center frequency setting range is obtained; the parasitic patch and the main patch are combined into the same antenna simulation model, and the size is optimized through joint simulation so that the complete stacked antenna obtains the impedance matching characteristics of the main patch and the axial ratio characteristics of the parasitic patch, and the design of the wideband circularly polarized antenna is completed. The present invention combines the angle-cut circularly polarized antenna with the stacked antenna technology, and the designed antenna is not only simple in structure but also significantly increases the antenna bandwidth, and the axial ratio, standing wave and gain of the obtained antenna unit in the required frequency band meet the requirements.

Description

Technical Field

[0001] The invention belongs to the field of radio frequency antennas, and in particular relates to a design method for a circularly polarized antenna. Background Art

[0002] Microstrip antennas are widely used in various devices and systems due to their advantages such as light weight, small size, thin profile, flexible feeding method, low cost, easy conformality with the target, and diversified functions. Compared with linearly polarized antennas, circularly polarized microstrip antennas have some significant advantages. The transmitting and receiving postures between circularly polarized transmitting and receiving antennas are more flexible, and no polarization alignment is required. In addition, circularly polarized antennas also have the ability to resist multipath interference. For antennas located in complex environments, interference can be effectively reduced. On the other hand, the orthogonality of the rotation direction of circularly polarized antennas can realize spectrum reuse and increase communication capacity. Highly stable circularly polarized antennas are essential key components in meteorological satellites, detection satellites, and navigation satellites. Many researchers have devoted themselves to the research and development of circularly polarized antennas.

[0003] Nowadays, the amount of data transmitted by wireless communication systems is increasing day by day, and there is an urgent need for antennas to have wider working bandwidths to ensure smooth communication links. Narrowband antennas can no longer meet the needs of practical applications. The axial ratio of a circularly polarized microstrip antenna in the direction of maximum gain is an indicator of the circular polarization performance of the antenna. The common part of the axial ratio bandwidth and the impedance bandwidth is the working bandwidth of the circularly polarized antenna. Common antenna methods for circular polarization include single feed point cutting. Compared with the method of realizing circular polarization with dual feed points, this method has a simple antenna feeding structure and is easy to implement, but it can only achieve a good axial ratio at the resonance point. Summary of the invention

[0004] The invention combines a corner-cut circularly polarized antenna with a stacked antenna technology, and proposes a design method for a broadband circularly polarized microstrip antenna.

[0005] The technical solution to achieve the purpose of the present invention is: a design method for a circularly polarized antenna, comprising:

[0006] Determine the material parameters of the main patch and parasitic patch of the broadband circularly polarized antenna;

[0007] According to the determined material parameters of the main patch of the wide-band circularly polarized antenna, the initial size of the main patch is determined;

[0008] According to the initial size of the main patch, a main patch model is established in the electromagnetic simulation software for simulation. By adjusting the size of the main patch, cutting the angle and changing the position of the feeding point, the main patch can obtain two impedance matching points.

[0009] According to the determined material parameters of the parasitic patch of the broadband circularly polarized antenna, the initial size of the parasitic patch is determined;

[0010] A parasitic patch model is established in the electromagnetic simulation software according to the initial size of the parasitic patch for simulation. Circular polarization is achieved by adjusting the size and cut-off angle of the parasitic patch to obtain a parasitic patch with the best axial ratio within the required center frequency setting range.

[0011] The parasitic patch and the main patch are combined into the same antenna simulation model. After joint simulation and size optimization, the complete stacked antenna obtains the impedance matching characteristics of the main patch and the axial ratio characteristics of the parasitic patch, completing the design of the wide-band circularly polarized antenna.

[0012] Preferably, the material parameters of the main patch and the parasitic patch of the wideband circularly polarized antenna include the dielectric material used for the main patch and the parasitic patch, the dielectric material between the main patch and the parasitic patch, the dielectric material between the parasitic patch and the ground plane, the thickness of the dielectric layer between the main patch and the parasitic patch, and the thickness of the dielectric layer between the parasitic patch and the ground plane.

[0013] Preferably, the main patch and the parasitic patch use the same dielectric material.

[0014] Preferably, the thickness of the dielectric layer between the main patch and the parasitic patch is the same as the thickness of the dielectric layer between the parasitic patch and the ground plane.

[0015] Preferably, the initial size of the parasitic patch is determined in the same manner as the initial size of the main patch.

[0016] Compared with the prior art, the present invention has the following significant advantages: the present invention combines the corner-cut circularly polarized antenna with the stacked antenna technology, and provides a design idea and method for a broadband circularly polarized antenna. The designed antenna not only has a simple structure but also significantly increases the antenna bandwidth. The axial ratio, standing wave and gain of the obtained antenna unit meet the requirements in the required frequency band.

[0017] The present invention is described in further detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram for calculating the cutting angle size of circularly polarized microstrip patch antenna.

[0019] Figure 2 Schematic diagram of the main patch antenna structure.

[0020] Figure 3 Antenna standing wave simulation results after determining the optimal dimensions for the main patch antenna.

[0021] Figure 4 Antenna axial ratio simulation results after determining the optimal dimensions for the main patch antenna.

[0022] Figure 5 Antenna gain simulation results after determining the optimal dimensions for the main patch antenna.

[0023] Figure 6 Schematic diagram of the structure of the parasitic patch antenna.

[0024] Figure 7 Simulation results of the antenna axial ratio after determining the optimal dimensions for the parasitic patch antenna.

[0025] Figure 8 Schematic diagram of the antenna structure designed for the present invention.

[0026] Fig. 9 Standing wave simulation results of the antenna designed for the present invention.

[0027] Fig.10 Axial ratio simulation results of the antenna designed for the present invention.

[0028] Fig.11 Gain simulation results of the antenna designed for the present invention. DETAILED DESCRIPTION

[0029] A design method for a circularly polarized antenna, the specific steps are:

[0030] Determine the dielectric material and the thickness of the dielectric layer between the main patch, parasitic patch, and ground plane;

[0031] Calculate the size of the main patch based on the dielectric material and the frequency of the antenna to be designed;

[0032] According to the initial size of the main patch, a main patch model is established in the electromagnetic simulation software for simulation. By cutting the corners and changing the feeding point position, the main patch obtains two impedance matching points: frequency point A and frequency point B.

[0033] Design the parasitic patch and perform modeling and simulation of the parasitic patch in the electromagnetic simulation software. Circular polarization is achieved by adjusting the size and cutting angle of the parasitic patch to obtain a desired center frequency (i.e. ) is the design with the optimal axial ratio near

[0034] By combining the parasitic patch and the main patch into the same simulation model and optimizing the size through joint simulation, the complete stacked antenna can obtain the impedance matching characteristics of the main patch and the axial ratio characteristics of the parasitic patch, resulting in an antenna unit design with excellent axial ratio, standing wave and gain between frequency bands A and B.

[0035] In a further embodiment, the initial size of the parasitic patch is determined in the same manner as the initial size of the main patch, and the calculation formula is as follows:

[0036]

[0037]

[0038] Where c is the speed of light in a vacuum, f0 is the resonant frequency, W is the width of the main patch or parasitic patch, L is the length of the main patch or parasitic patch, h is the thickness of the dielectric layer between the main patch and the parasitic patch or the thickness of the dielectric layer between the parasitic patch and the ground plane, ε r is the relative dielectric constant of the medium used;

[0039]

[0040] In a further embodiment, the calculation formula for the cut-off angle size of the main patch or parasitic patch of the wideband circularly polarized antenna is as follows:

[0041] According to the formula (|ΔS / S|)Q0=1 / 2, the total area S of the cut corners is determined, where Q0 is the total quality factor of the main patch or parasitic patch, and S=W×L is the area of ​​the main patch or parasitic patch;

[0042] According to the formula ΔS = C × C, determine the length of the right angle side C of the cut angle, such as Figure 1 shown.

[0043] Specifically, the total quality factor Q0 of the main patch or parasitic patch is calculated by the following formula

[0044]

[0045] Q r ,Q d ,Q c ,Q sw The quality factor values ​​corresponding to radiation, dielectric, conductor loss, and surface wave are respectively:

[0046]

[0047]

[0048] Where a and b are the length and width of the main patch or parasitic patch, σ is the conductivity of the metal of the main patch or parasitic patch; δ is the dielectric loss angle, u0 is the magnetic permeability in vacuum, and h is the thickness of the dielectric layer between the main patch and the parasitic patch or the thickness of the dielectric layer between the parasitic patch and the ground plane. For thin microstrip antennas, h<<λ0, Q sw The effect of can often be approximately ignored, r is the antenna center resonant frequency, λ0 is the wavelength of the antenna center resonant frequency, ε r is the relative dielectric constant of the medium.

[0049] In a further embodiment, for a coaxially fed patch antenna, that is, a main patch or a parasitic patch fed by a coaxial line, after determining the patch length L and width W, during the modeling and simulation process, the position of the coaxial line feeding point is determined. The position of the feeding point will affect the input impedance of the antenna and cause the electric field to change by half a wavelength in the direction. Therefore, from the center point of L to both sides, the impedance gradually increases. When the antenna input impedance is 50Ω, the position of the feeding point in the direction is calculated by the following formula, where dl is the distance from the center position of the patch where the feeding point position is offset.

[0050]

[0051]

[0052] The wideband circularly polarized antenna is the structure of the existing antenna. The specific structural form of the antenna is not the focus of protection of the present invention. The present invention combines the cut-angle circularly polarized antenna with the stacked antenna technology. The designed antenna is not only simple in structure but also significantly increases the antenna bandwidth. The obtained antenna unit meets the requirements in terms of axial ratio, standing wave and gain in the required frequency band.

[0053] Example

[0054] This embodiment takes the design of an antenna unit of a Ku-band phased array antenna as an example for illustration. The main technical index requirements of the antenna unit are as follows:

[0055] a) Antenna operating bandwidth: Ku band (center frequency 15.5 GHz), bandwidth not less than 2 GHz;

[0056] b) Polarization: right-hand circular polarization;

[0057] c) Standing wave ratio: within the working bandwidth and scanning range, the active standing wave ratio is not greater than 2;

[0058] d) Directional gain: not less than 5dB.

[0059] Use a material with a dielectric constant of 3.48 as the plate. First determine the dielectric thickness and antenna position, and calculate the antenna size according to the formula:

[0060]

[0061]

[0062] Where c is the speed of light in a vacuum, f0 is the resonant frequency, W is the width of the main patch or parasitic patch, L is the length of the main patch or parasitic patch, h is the thickness of the dielectric layer between the main patch and the parasitic patch or the thickness of the dielectric layer between the parasitic patch and the ground plane, ε r is the relative dielectric constant of the medium used;

[0063]

[0064] According to h = 0.962mm, f0 = 15.5Ghz

[0065] We get W = 6.462 mm, L = 4.776 mm

[0066] This is the theoretical size of the main patch. Modeling and corner cutting simulation optimization were performed in HFSS. The final main patch impedance matching was obtained at two frequencies: 14.1 GHz and 17.9 GHz. The antenna structure and various simulation results are shown in Figure 1. Figures 3 to 5 shown.

[0067] Design the parasitic patch with the same initial size as the main patch, adjust the size through the corner cutting simulation, and finally get the design with the best axial ratio at 15.5GHz. Figure 6 , 7 shown.

[0068] Add parasitic patches to the main patch to optimize the antenna standing wave, axial ratio and gain parameters. The final antenna model after HFSS optimization simulation is as follows Figure 8 shown.

[0069] At this time, the various simulation indicators of the antenna are as follows Figures 9-11 shown.

[0070] It can be seen that the indicators of this unit antenna are excellent. The bandwidth is greater than 2Ghz at the center frequency of 15.5Ghz, the gain is greater than 5dB in the range of 13.39Ghz to 16.81Ghz, and the circular polarization axial ratio is less than 4dB in the range of 14.02Ghz to 16.5Ghz. When forming a phased array, the axial ratio performance within the array working bandwidth can be improved to below 0.1dB according to the rotation arrangement of the array.

Claims

1. A design method for a circularly polarized antenna, characterized in that: include: Determine the material parameters of the main patch and parasitic patch of the broadband circularly polarized antenna; According to the determined material parameters of the main patch of the wide-band circularly polarized antenna, the initial size of the main patch is determined; According to the initial size of the main patch, a main patch model is established in the electromagnetic simulation software for simulation. By adjusting the size of the main patch, cutting the angle and changing the position of the feeding point, the main patch can obtain two impedance matching points. According to the determined material parameters of the parasitic patch of the broadband circularly polarized antenna, the initial size of the parasitic patch is determined; A parasitic patch model is established in the electromagnetic simulation software according to the initial size of the parasitic patch for simulation. Circular polarization is achieved by adjusting the size and cut-off angle of the parasitic patch to obtain a parasitic patch with the best axial ratio within the required center frequency setting range. The parasitic patch and the main patch are combined into the same antenna simulation model. After joint simulation and size optimization, the complete stacked antenna obtains the impedance matching characteristics of the main patch and the axial ratio characteristics of the parasitic patch, completing the design of the wide-band circularly polarized antenna.

2. The design method of a circularly polarized antenna according to claim 1, characterized in that: The material parameters of the main patch and the parasitic patch of the wideband circularly polarized antenna include the materials used for the main patch and the parasitic patch, the dielectric material between the main patch and the parasitic patch, the dielectric material between the parasitic patch and the ground plane, the thickness of the dielectric layer between the main patch and the parasitic patch, and the thickness of the dielectric layer between the parasitic patch and the ground plane.

3. The design method of a circularly polarized antenna according to claim 2, characterized in that: The main patch and the parasitic patch are made of the same material.

4. The design method of a circularly polarized antenna according to claim 2, characterized in that: The thickness of the dielectric layer between the main patch and the parasitic patch is the same as the thickness of the dielectric layer between the parasitic patch and the ground plane.

5. The design method of a circularly polarized antenna according to claim 1, characterized in that: The initial size of the parasitic patch is determined in the same manner as the initial size of the main patch.

6. The design method of a circularly polarized antenna according to claim 5, characterized in that: The calculation formulas for the initial size of the parasitic patch and the initial size of the main patch are as follows: Where c is the speed of light in a vacuum, f0 is the resonant frequency, W is the width of the main patch or parasitic patch, L is the length of the main patch or parasitic patch, h is the thickness of the dielectric layer between the main patch and the parasitic patch or the thickness of the dielectric layer between the parasitic patch and the ground plane, ε r is the relative dielectric constant of the medium used; 7. The design method of a circularly polarized antenna according to claim 1, characterized in that: The method for determining the cut-angle size of the main patch or parasitic patch of the wideband circularly polarized antenna is specifically as follows: According to the formula (|ΔS / S|)Q0=1 / 2, the total area S of the cut corners is determined, where Q0 is the total quality factor of the main patch or the parasitic patch, S=W×L is the area of ​​the main patch or the parasitic patch, W is the width of the main patch or the parasitic patch, and L is the length of the main patch or the parasitic patch; According to the formula ΔS=C×C, determine the length C of the right angle side of the cut corner.

8. The design method of a circularly polarized antenna according to claim 7, characterized in that: The total quality factor Q0 of the main patch or parasitic patch is calculated by the following formula: Q r ,Q d ,Q c ,Q sw They correspond to the quality factor values ​​of radiation, dielectric, conductor loss, and surface wave respectively.

9. The design method of a circularly polarized antenna according to claim 8, characterized in that: The quality factor values ​​of radiation, dielectric, conductor loss, and surface wave are as follows: Among them, a and b are the length and width of the main patch or parasitic patch, ε r is the relative dielectric constant of the medium used, σ is the conductivity of the main patch or parasitic patch metal; δ is the dielectric loss angle, u0 is the magnetic permeability in vacuum, h is the thickness of the dielectric layer between the main patch and the parasitic patch or the thickness of the dielectric layer between the parasitic patch and the ground plane, and f r is the center resonant frequency of the antenna, and λ0 is the wavelength of the center resonant frequency of the antenna.

10. The design method of a circularly polarized antenna according to claim 1, characterized in that: When modeling and simulating the main patch and parasitic patch, the initial feeding point position is: Where dl is the distance from the center of the patch where the feed point is offset, h is the thickness of the dielectric layer between the main patch and the parasitic patch or the thickness of the dielectric layer between the parasitic patch and the ground plane, W is the width of the main patch or the parasitic patch, L is the length of the main patch or the parasitic patch, and ε r is the relative dielectric constant of the medium used.

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