Circularly polarized millimeter wave radar antenna and radar device

Abstract

The utility model provides a circularly polarized millimeter wave radar antenna and radar equipment, and belongs to the technical field of antennae, the circularly polarized millimeter wave radar antenna comprises a microstrip antenna array, the microstrip antenna array is composed of a plurality of periodic antenna units, the antenna unit of each period comprises a plurality of elbow structures, each elbow structure comprises a right-angle elbow and an oblique-angle elbow, the antenna is used for radiating and propagating traveling waves; and the impedance structure is located at the tail end of the microstrip antenna array, the impedance structure is an equivalent resonance circuit, and parameters of the resonance circuit are adjusted to obtain required impedance matching. The feed structure of the antenna can be simplified, the energy loss is reduced, and the working bandwidth is improved.

Description

Technical Field

[0001] The present application relates to the field of antenna technology, and in particular to a circularly polarized millimeter wave radar antenna and radar equipment. Background Art

[0002] Antennas play an important role in wireless communications, as they are responsible for transmitting and receiving radio waves. Circularly polarized antennas are a special type of antenna that can use traveling wave antennas as their single element to transmit and receive circularly polarized electromagnetic waves, and are suitable for various communications and radar applications, such as automotive millimeter wave radars and indoor scene radars.

[0003] However, there are some problems with existing circularly polarized array antennas. The feeding structure they use is complex, which leads to increased losses during energy transmission. In addition, when the traveling wave antenna terminal is connected to a load, the transmission loss in the millimeter wave band is also large, resulting in very little power incident on the terminal and weak reflection effect, but this also requires the operating frequency band of this type of antenna to be wider. Utility Model Content

[0004] The present application provides a circularly polarized millimeter-wave radar antenna and a radar device, which are used to solve the problems of complex feeding structure, large energy loss and limited working bandwidth in existing circularly polarized millimeter-wave radar antennas.

[0005] In a first aspect, the present application provides a circularly polarized millimeter wave radar antenna, the circularly polarized millimeter wave radar antenna comprising:

[0006] A microstrip antenna array, which is composed of a plurality of periodic antenna units, each periodic antenna unit includes a plurality of elbow structures, each elbow structure includes a right-angle elbow and an oblique angle elbow, for achieving radiation and propagation of traveling waves;

[0007] The impedance structure is located at the end of the microstrip antenna array. The impedance structure is an equivalent resonant circuit. The parameters of the resonant circuit are adjusted to obtain the required impedance matching.

[0008] In one embodiment of the present application, the antenna units of each period include a first right-angle elbow, a second right-angle elbow, a third right-angle elbow and a fourth right-angle elbow, and the physical length of the antenna units of each period is equal to twice the vertical distance of the first right-angle elbow plus the horizontal distance between the first right-angle elbow and the second right-angle elbow, plus the horizontal distance between the third right-angle elbow and the fourth right-angle elbow.

[0009] In one embodiment of the present application, based on left-hand circular polarization, the horizontal distance between the first right-angle elbow and the second right-angle elbow is equal to 1 minus one quarter, multiplied by the medium wavelength of the circularly polarized millimeter-wave radar antenna in its frequency band, and then minus the vertical distance of the first right-angle elbow.

[0010] In one embodiment of the present application, based on right-hand circular polarization, the horizontal distance between the first right-angle elbow and the second right-angle elbow is equal to 1 plus one-quarter, multiplied by the medium wavelength of the circularly polarized millimeter-wave radar antenna in its frequency band, and then subtracted from the vertical distance of the first right-angle elbow.

[0011] In one embodiment of the present application, based on left-hand circular polarization, the horizontal distance between the third right-angle elbow and the fourth right-angle elbow is equal to 1 plus one-quarter, multiplied by the medium wavelength of the circularly polarized millimeter-wave radar antenna in its frequency band, and then subtracted from the vertical distance of the first right-angle elbow.

[0012] In one embodiment of the present application, based on right-hand circular polarization, the horizontal distance between the third right-angle elbow and the fourth right-angle elbow is equal to 1 minus one quarter, multiplied by the medium wavelength of the circularly polarized millimeter-wave radar antenna in its frequency band, minus the vertical distance of the first right-angle elbow.

[0013] In one embodiment of the present application, the vertical distance of the first right-angle elbow is equal to one quarter of the medium wavelength of the circularly polarized millimeter-wave radar antenna in its frequency band.

[0014] In one embodiment of the present application, increasing the horizontal distance between the first right-angle elbow and the second right-angle elbow, or reducing the horizontal distance between the third right-angle elbow and the fourth right-angle elbow is equivalent to increasing the parameters of the resonant circuit to reduce the resonant frequency of the resonant circuit.

[0015] In one embodiment of the present application, reducing the horizontal distance between the first right-angle elbow and the second right-angle elbow, or increasing the horizontal distance between the third right-angle elbow and the fourth right-angle elbow is equivalent to reducing the parameters of the resonant circuit to increase the resonant frequency of the resonant circuit.

[0016] In a second aspect, the present application further provides a radar device, comprising a circularly polarized millimeter wave radar antenna as described in any one of the first aspects.

[0017] The circularly polarized millimeter-wave radar antenna and radar device provided by the present application adopt a microstrip antenna array composed of multiple periodic antenna units. Each period of the antenna unit includes multiple elbow structures, including right-angle elbows and bevel elbows, which help to achieve radiation and propagation of traveling waves. Through the design of the microstrip antenna array, the radiation efficiency and performance stability of the antenna can be improved, thereby reducing energy loss. The impedance structure at the end of the microstrip antenna array is an equivalent resonant circuit. The function of the impedance structure is to adjust the inductance value of the resonant circuit to achieve the required impedance matching. Through good impedance matching, the reflection and loss of energy can be reduced, and the transmission efficiency and performance stability of the antenna can be improved.

[0018] Therefore, the present application can simplify the feeding structure of the antenna, reduce energy loss, and improve the working bandwidth, thereby solving the problems of complex feeding structure, large energy loss and limited working bandwidth of existing circularly polarized millimeter-wave radar antennas. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present application or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 is a structural diagram of a circularly polarized millimeter-wave radar antenna provided in an embodiment of the present application;

[0021] Figure 2 yes Figure 1 Schematic diagram of the size of an antenna unit in one period;

[0022] Figure 3 The structure of the circularly polarized millimeter wave radar antenna provided in the embodiment of the present application is Figure 1 ;

[0023] Figure 4 The structure of the circularly polarized millimeter wave radar antenna provided in the embodiment of the present application is Figure 2 ;

[0024] Figure 5 The structure of the circularly polarized millimeter wave radar antenna provided in the embodiment of the present application is Figure 3 ;

[0025] Figure 6 The structure of the circularly polarized millimeter wave radar antenna provided in the embodiment of the present application is Figure 4 ;

[0026] Figure 7is a schematic diagram of antenna return loss provided in an embodiment of the present application;

[0027] Figure 8 is the cross-polarization antenna pattern provided in the embodiment of the present application;

[0028] Fig. 9 is a schematic diagram of a left-handed circularly polarized antenna provided in an embodiment of the present application;

[0029] Fig.10 It is a schematic diagram of a right-hand circularly polarized antenna provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0032] In wireless communications, the polarization of an antenna refers to the change in direction of the electric field vector when an electromagnetic wave propagates. When an electromagnetic wave propagates along the propagation direction, the trajectory of the electric field vector's change in space over time can describe different polarization states. If the trajectory of the electric field vector's change is a straight line, it is called linear polarization; if it is a circle, it is called circular polarization; if it is an ellipse, it is called elliptical polarization. The electromagnetic waves transmitted or received by the antenna must conform to a specific polarization direction. For example, if an antenna is vertically polarized, it can only effectively receive or send vertically polarized electromagnetic waves, but it is less effective for horizontally polarized electromagnetic waves. Similarly, a left-hand circularly polarized antenna can only receive or send left-hand circularly polarized electromagnetic waves, and does not respond well to right-hand circularly polarized signals.

[0033] Therefore, the polarization direction of the antenna is crucial to the wireless communication system. Ensuring polarization matching between the transmitter and the receiver can effectively improve the signal transmission efficiency and quality.

[0034] In order to solve the problems of complex feeding structure, large energy loss and limited working bandwidth of existing circularly polarized millimeter-wave radar antennas, the present application provides a circularly polarized millimeter-wave radar antenna and radar equipment, which adopts a microstrip antenna array composed of multiple periodic antenna units. The antenna unit of each period includes multiple elbow structures, including right-angle elbows and bevel elbows, which help to achieve radiation and propagation of traveling waves. Through the design of the microstrip antenna array, the radiation efficiency and performance stability of the antenna can be improved, thereby reducing energy loss. The impedance structure at the end of the microstrip antenna array is an equivalent resonant circuit. The function of the impedance structure is to adjust the inductance value of the resonant circuit to achieve the required impedance matching. Through good impedance matching, the reflection and loss of energy can be reduced, and the transmission efficiency and performance stability of the antenna can be improved.

[0035] Combine the following Figure 1-Figure 10 The circularly polarized millimeter wave radar antenna and radar device of the present application are described.

[0036] Please refer to the figure, Figure 1 1 is a structural diagram of a circularly polarized millimeter wave radar antenna provided in an embodiment of the present application. A circularly polarized millimeter wave radar antenna comprises a microstrip antenna array 10 and an impedance structure 20.

[0037] Exemplarily, the microstrip antenna array 10 is composed of a plurality of periodic antenna units 101, each periodic antenna unit 101 includes a plurality of elbow structures 102, each elbow structure 102 includes a right-angle elbow 1021 and an oblique angle elbow 1022, for achieving radiation and propagation of traveling waves.

[0038] Specifically, the design of the right-angle elbow 1021 and the angled elbow 1022 can achieve specific radiation characteristics by changing the propagation direction and shape of the electromagnetic wave. A plurality of periodic antenna units 101 are combined to form an integral microstrip antenna array 10, which can be used for signal transmission and reception in a wireless communication system.

[0039] Exemplarily, the impedance structure 20 is located at the end of the microstrip antenna array 10. The impedance structure 20 is an equivalent resonant circuit, and the parameters of the resonant circuit are adjusted to obtain the desired impedance matching.

[0040] Impedance matching is a very important technology and plays a vital role in wireless communication systems. When the output impedance of the antenna array does not match the input impedance of the transmission line or the RF circuit, it will increase the reflection loss during signal transmission, reduce the overall system performance, and affect the signal quality. Therefore, by introducing the impedance structure 20 for impedance matching, the reflection loss can be effectively reduced, and the signal transmission efficiency and system performance can be improved. Specifically, the impedance structure 20 is equivalent to a resonant circuit, and the output impedance of the microstrip antenna array can be adjusted to the desired value by adjusting parameters such as the inductance value so that it matches the input impedance of the transmission line or the RF circuit. In this way, the signal can be transmitted to the maximum extent, the signal loss can be reduced, and the overall performance of the system can be improved.

[0041] The design principle of the circularly polarized millimeter wave radar antenna described in this application is as follows:

[0042] First, there are discontinuities or bending points (i.e., elbow structures 102) on the microstrip series feed line, and the locations of these discontinuities or bending points will cause radiation. After the end is connected to the impedance structure 20, electromagnetic waves will propagate along the line to form a traveling wave antenna. In a microstrip antenna, since the line width is much smaller than the wavelength, the parasitic radiation of the straight microstrip line can be ignored.

[0043] Secondly, at the discontinuity or bending point in the microstrip antenna, the current of the electromagnetic wave will be concentrated on both sides of the microstrip line, forming magnetic field radiation. This formed magnetic field radiation can be equivalent to a single magnetic flux element located on the center line of the microstrip line, and the magnetic flux element is used to describe the magnetic field distribution in the electromagnetic field. At the same time, for the right-angle elbow 1021, its shape will produce a magnetic field radiation in a 45-degree direction, which can be equivalent to an equivalent magnetic flux element in a 45-degree direction.

[0044] By properly designing the distance between the right-angle elbows 1021 in the microstrip antenna, radiation in different polarization modes can be achieved, including horizontal polarization, vertical polarization, right-hand circular polarization and left-hand circular polarization. This design method can effectively control the polarization characteristics of the microstrip antenna, thereby meeting the requirements of different communication systems for polarization modes.

[0045] Therefore, the selection of the distance between the discontinuity points or bending points in the microstrip antenna design and the appropriate right-angle elbows can affect the polarization mode of the antenna, thereby achieving the desired polarization characteristics and providing wireless communication systems with signal transmission options in different directions and polarities.

[0046] The following is a description based on the above design principles through specific embodiments.

[0047] Please refer to Figure 2 , Figure 2 yes Figure 1 Schematic diagram of the dimensions of an antenna unit in a period. Figure 2One period of antenna units 101 is shown, and the antenna units 101 of this period include a first right-angle elbow ①, a second right-angle elbow ②, a third right-angle elbow ③, and a fourth right-angle elbow ④.

[0048] In antenna design, an antenna unit is usually composed of a complete unit, which is called a period. The physical length within this period is represented by L, that is, the physical length of the antenna unit 101. The physical length L refers to the actual length occupied by the antenna structure in space, usually expressed in length units. The physical length L is an important parameter of the antenna unit, which can directly affect the operating frequency, frequency band, radiation characteristics, etc. of the antenna. By adjusting the physical length L of the antenna unit, the antenna operating frequency can be adjusted and optimized, so that the antenna can perform well in a specific frequency band.

[0049] Exemplarily, the physical length L of the antenna unit 101 of each period is equal to twice the vertical distance S of the first right-angle elbow ① plus the horizontal distance D between the first right-angle elbow ① and the second right-angle elbow ②, plus the horizontal distance C between the third right-angle elbow ② and the fourth right-angle elbow ④, that is,

[0050] L=2*S+D+C. (1)

[0051] After simplifying the electric field component ratio of the first right-angle elbow ①, the second right-angle elbow ②, the third right-angle elbow ③ and the fourth right-angle elbow ④ in the xy plane where the antenna is located, we get:

[0052]

[0053] Among them, E1 / E2 represents the ratio between the two components of the electric field synthesized by the four elbows in the x and y planes, j represents the imaginary unit, θ represents the angle between the electric field direction and the x-axis, and β represents the phase coefficient, whose value is a constant.

[0054] In order to achieve circular polarization, the ratio of E1 / E2 needs to be ±j. When the broadside antenna θ=0, the following formula can be obtained:

[0055]

[0056] Wherein, the value of N is an odd value such as 1, 3, 5, etc., which means that in the antenna array, the number of antenna units 101 adopts an odd value to achieve reverse circular polarization. g Represents the medium wavelength of the antenna in its frequency band. According to the antenna array principle, in order to make the antenna normal radiation strongest, the following equation must be satisfied:

[0057] β*L=2mπ; (4)

[0058] Wherein, m is a positive integer.

[0059] When realizing circular polarization in the normal direction (i.e., the direction perpendicular to the antenna surface), the phases of the two spatial orthogonal field components must be orthogonal. When m = 2, substituting this value into equation (4) (i.e., β*L = 2mπ), the condition for circular polarization of a period in the normal direction is obtained as follows:

[0060] Left-hand circular polarization: The horizontal distance D between the first right-angle elbow and the second right-angle elbow is equal to 1 minus one-fourth, multiplied by the medium wavelength λ of the circularly polarized millimeter-wave radar antenna in its frequency band. g , minus the vertical distance S of the first right-angle elbow, that is

[0061]

[0062] Left-hand circular polarization: The horizontal distance C between the third right-angle elbow and the fourth right-angle elbow is equal to 1 plus one-fourth, multiplied by the medium wavelength λ of the circularly polarized millimeter-wave radar antenna in its frequency band. g , minus the vertical distance S of the first right-angle elbow, that is

[0063]

[0064] Right-hand circular polarization: The horizontal distance D between the first right-angle elbow and the second right-angle elbow is equal to 1 plus one-fourth, multiplied by the medium wavelength λ of the circularly polarized millimeter-wave radar antenna in its frequency band. g , minus the vertical distance S of the first right-angle elbow, that is

[0065]

[0066] Right-hand circular polarization: The horizontal distance C between the third right-angle elbow and the fourth right-angle elbow is equal to 1 minus one-fourth, multiplied by the medium wavelength λ of the circularly polarized millimeter-wave radar antenna in its frequency band. g , minus the vertical distance S of the first right-angle elbow, that is

[0067]

[0068] When the vertical distance S of the first right-angle elbow is taken as the medium wavelength λ of the circularly polarized millimeter-wave radar antenna in its frequency band g One quarter of the time, By substituting this into the above equations (3), (5) to (8), the values ​​of D and C can be obtained.

[0069] In antenna design, due to the existence of the elbow structure, there will be a certain difference between the physical length and electrical length of the antenna unit. In order to better optimize the performance of the antenna structure, the values ​​of D and C calculated above can be fine-tuned.

[0070] The physical length refers to the actual length of the antenna element, while the electrical length refers to the equivalent length used in circuit theory, taking into account factors such as the speed at which electromagnetic waves propagate in the antenna structure. Due to the existence of the elbow structure, there is a certain difference between the two. Therefore, by fine-tuning the values ​​of D and C, the antenna structure can be made to better match the required frequency characteristics and radiation characteristics in practical applications, thereby achieving optimization.

[0071] One implementation method is to add an impedance structure 20 at the end of the microstrip antenna array 10, such as Figure 1 As mentioned above, the impedance structure 20 may be in a fan-shaped shape. The impedance structure 20 may also be in other shapes, such as Figure 3-Figure 6 Therefore, the present application does not limit the shape of the impedance structure 20 .

[0072] The function of the impedance structure 20 is: when energy is transmitted to the end of the microstrip antenna array 10, the impedance structure 20 absorbs most of the energy, thereby reducing the signal reflected back to the port, so that the antenna has a wider working bandwidth. Specifically, by adding the impedance structure 20 at the end of the microstrip antenna array 10, the reflected wave at the end of the antenna can be effectively reduced, so that the antenna can maintain an efficient working state in a wider frequency range. The antenna designed in this way can transmit signals more efficiently, improve performance, and have a wider working bandwidth, which is suitable for signal transmission requirements of different frequencies.

[0073] For example, after adding a fan-shaped impedance structure 20 at the end of the microstrip antenna array 10, its return loss is as follows: Figure 7 shown. Figure 7 The working bandwidth shown can reach 3.3 GHz. The working bandwidth refers to the frequency range in which the system can work normally. In radar applications, for radar systems in the millimeter wave frequency band, the working bandwidth of 3.3 GHz is sufficient to cover the target objects that need to be detected and tracked.

[0074] It should be noted that the principle of adding the impedance structure 20 at the end of the microstrip antenna array 10 is that the impedance structure 20 is equivalent to a resonant circuit, which means that the impedance structure 20 has a specific impedance characteristic at a specific frequency. By adjusting the parameters of the resonant circuit, the desired impedance matching can be obtained.

[0075] The calculation formula for the resonant circuit is: Where L0 represents inductance, C0 represents capacitance, and f represents resonant frequency.

[0076] The impedance structure 20 can fine-tune the values ​​of D and C calculated above by adjusting its parameters. The parameters are, for example, the resistance value, capacitance value, inductance value, etc. of the load. By changing the parameters of the impedance structure 20, the impedance matching of the entire antenna system can be affected, and then the values ​​of D and C can be adjusted to achieve better antenna performance and matching effect. For example:

[0077] Increasing the horizontal distance D between the first right-angle elbow and the second right-angle elbow, or reducing the horizontal distance C between the third right-angle elbow and the fourth right-angle elbow is equivalent to increasing the inductance value of the resonant circuit to reduce the resonant frequency f of the resonant circuit.

[0078] Reducing the horizontal distance D between the first right-angle elbow and the second right-angle elbow, or increasing the horizontal distance C between the third right-angle elbow and the fourth right-angle elbow is equivalent to reducing the inductance of the resonant circuit to increase the resonant frequency f of the resonant circuit.

[0079] Therefore, by using the impedance structure 20 and fine-tuning the values ​​of D and C obtained by the above calculation, the effect diagram of the circularly polarized millimeter wave radar antenna can be obtained, as shown in FIG. Figure 8 As shown, Figure 8 The antenna main polarization and cross polarization patterns are shown. It can be seen that the difference between the two polarization modes is only 0.5dB. The main polarization refers to the main polarization mode considered when designing the antenna, while the cross polarization refers to another polarization mode perpendicular to the main polarization.

[0080] Please refer to Fig. 9 , Fig.10 , Fig. 9 is a schematic diagram of a left-handed circularly polarized antenna provided in an embodiment of the present application, Fig.10 It is a schematic diagram of a right-hand circularly polarized antenna provided in an embodiment of the present application.

[0081] Fig. 9 and Fig.10 The axial ratio effect diagram under different polarization modes is shown. The axial ratio is a parameter used to measure the uniformity of the antenna's radiation intensity in different directions. Generally speaking, the smaller the axial ratio, the better the polarization effect within the antenna's radiation range. It can be seen that within the antenna's operating frequency band, the axial ratios of different polarization modes are all within 4dB, indicating that the antenna's radiation performance in different directions is relatively uniform and meets the design requirements.

[0082] It can be seen from this that Figure 8 The antenna shown has a small difference in performance between main polarization and cross polarization. Fig. 9 and Fig.10 The axial ratio effect shown also meets the requirements, indicating that the polarization characteristics and radiation performance of the antenna design within the working frequency band are relatively stable, and the power radiation distribution in the primary and secondary radiation directions is relatively uniform.

[0083] In some embodiments of the present application, the present application further provides a radar device, wherein the radar device includes the circularly polarized millimeter wave radar antenna as described in any of the above embodiments.

[0084] Circularly polarized millimeter wave radar antennas can be used in millimeter wave radar systems. They are designed to achieve circular polarization processing of electromagnetic wave signals. The main feature of circularly polarized signals is that the polarization direction remains unchanged during propagation and is not affected by the antenna or propagation path. This feature gives circularly polarized antennas some advantages in radar systems, such as being able to effectively deal with multipath propagation and scattering of signals, and improving the system's anti-interference ability and target detection performance.

[0085] Therefore, a circularly polarized millimeter-wave radar antenna is used in this radar device, which can achieve more reliable and efficient signal transmission and target detection.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. 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 application.

Claims

1. A circularly polarized millimeter wave radar antenna, characterized in that: The circularly polarized millimeter wave radar antenna comprises: A microstrip antenna array, which is composed of a plurality of periodic antenna units, each periodic antenna unit includes a plurality of elbow structures, each elbow structure includes a right-angle elbow and an oblique angle elbow, for achieving radiation and propagation of traveling waves; The impedance structure is located at the end of the microstrip antenna array. The impedance structure is an equivalent resonant circuit. The parameters of the resonant circuit are adjusted to obtain the required impedance matching.

2. The circularly polarized millimeter wave radar antenna according to claim 1, characterized in that: The antenna units of each period include a first right-angle elbow, a second right-angle elbow, a third right-angle elbow and a fourth right-angle elbow, and the physical length of the antenna units of each period is equal to twice the vertical distance of the first right-angle elbow plus the horizontal distance between the first right-angle elbow and the second right-angle elbow, plus the horizontal distance between the third right-angle elbow and the fourth right-angle elbow.

3. The circularly polarized millimeter wave radar antenna according to claim 2, characterized in that: Based on left-hand circular polarization, the horizontal distance between the first right-angle elbow and the second right-angle elbow is equal to 1 minus one quarter, multiplied by the medium wavelength of the circularly polarized millimeter-wave radar antenna in its frequency band, and then minus the vertical distance of the first right-angle elbow.

4. The circularly polarized millimeter wave radar antenna according to claim 2, characterized in that: Based on right-hand circular polarization, the horizontal distance between the first right-angle elbow and the second right-angle elbow is equal to 1 plus one-quarter, multiplied by the medium wavelength of the circularly polarized millimeter-wave radar antenna in its frequency band, and then subtracted from the vertical distance of the first right-angle elbow.

5. The circularly polarized millimeter wave radar antenna according to claim 2, characterized in that: Based on left-hand circular polarization, the horizontal distance between the third right-angle elbow and the fourth right-angle elbow is equal to 1 plus one-quarter, multiplied by the medium wavelength of the circularly polarized millimeter-wave radar antenna in its frequency band, and then subtracted from the vertical distance of the first right-angle elbow.

6. The circularly polarized millimeter wave radar antenna according to claim 2, characterized in that: Based on right-hand circular polarization, the horizontal distance between the third right-angle elbow and the fourth right-angle elbow is equal to 1 minus one quarter, multiplied by the medium wavelength of the circularly polarized millimeter-wave radar antenna in its frequency band, and then minus the vertical distance of the first right-angle elbow.

7. The circularly polarized millimeter wave radar antenna according to any one of claims 3 to 6, characterized in that: The vertical distance of the first right-angle elbow is equal to one quarter of the medium wavelength of the circularly polarized millimeter-wave radar antenna in its frequency band.

8. The circularly polarized millimeter wave radar antenna according to claim 2, characterized in that: Increasing the horizontal distance between the first right-angle elbow and the second right-angle elbow, or reducing the horizontal distance between the third right-angle elbow and the fourth right-angle elbow is equivalent to increasing the parameters of the resonant circuit to reduce the resonant frequency of the resonant circuit.

9. The circularly polarized millimeter wave radar antenna according to claim 2, characterized in that: Reducing the horizontal distance between the first right-angle elbow and the second right-angle elbow, or increasing the horizontal distance between the third right-angle elbow and the fourth right-angle elbow is equivalent to reducing the parameters of the resonant circuit to increase the resonant frequency of the resonant circuit.

10. A radar device, characterized in that: The radar device comprises the circularly polarized millimeter wave radar antenna as described in any one of claims 1 to 9.

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