CN109346830B - All-metal four-arm equiangular spiral circularly polarized antenna unit - Google Patents

Abstract

The invention provides an all-metal four-arm equiangular helical circularly polarized antenna unit, comprising a radiating arm of an all-metal equiangular helical structure, a metal reflection cavity, a coaxial feeder, and a cylindrical resonant cavity; The feed probe is used as coaxial cable feed and is connected to a central metal feed ring, and the pair of upper dipole arms in the radiating arm is fed in parallel through the metal feed ring; The lower dipole arm is connected to the coaxial ground terminal, so as to ensure that the spatial positions of the four dipole arms and the phases of the electromagnetic waves on the arms are orthogonal, so as to form the conditions required for circular polarization. In order to solve the problem of unbalanced feeding of coaxial lines, the coaxial feeding line is designed as a coaxial tapered balun structure, so that the impedance of the load and the feeding line are matched. In order to realize the unidirectional radiation function of the antenna, a metal reflection cavity is added on the back of the antenna. The invention has the characteristics of wide frequency band, small size, high gain, and can be embedded, and is suitable for modern communication systems and electronic countermeasure fields.

Description

An all-metal four-arm equiangular helical circularly polarized antenna unit

technical field

The present invention relates to the technical field of modern wireless communication, and more particularly relates to an all-metal four-arm equiangular helical circularly polarized antenna unit.

Background technique

As the performance of military equipment and aerospace vehicles continues to move towards high precision and high speed, higher requirements are constantly put forward for the quality of antenna real-time communication. Efficient, real-time, anti-jamming and high-capacity communication antennas will become the general trend of future antenna research and development. Circularly polarized antennas have remarkable anti-rain and fog, anti-electromagnetic interference, anti-multi-aperture attenuation and other characteristics, and have been widely used in the fields of unmanned driving technology, remote video communication, global positioning system and signal shielding.

Helical antennas are widely used because of their wide frequency band, wide angle circular polarization, high gain, good impedance matching, and low cost. In addition, the antenna of this structure can change the direction pattern by changing the size, and can quickly adapt to different applications. This structure is often used in radio communications. However, the traditional helical structure antenna also has the disadvantages of large volume, complex structure, difficult manufacture, high processing cost and weak concealment.

In order to overcome the shortcomings of the above-mentioned early helical antennas, a planar helical antenna with frequency-invariant characteristics is designed. Antennas with planar helical structure commonly seen in engineering now include: slotted helical antenna, equiangular helical antenna, and Archimedes helical antenna. These antennas have stable and excellent characteristics in a wide frequency band that cannot be replaced by other antennas. In engineering applications, it is generally necessary to add a back cavity to convert the bidirectional radiation of this type of antenna into unidirectional radiation, so as to improve the directional radiation capability, normal gain and antenna efficiency of the antenna. However, most of the existing helical antennas use microstrip antennas. Microstrip antennas are not easy to achieve broadband functions, have low efficiency, are prone to medium loss, and are less adaptable to the environment than metal conductors.

SUMMARY OF THE INVENTION

The present invention aims to solve the above-mentioned technical problems at least to a certain extent. To this end, the present invention proposes a wide-band, small-size, embeddable, high-gain all-metal four-arm equiangular helical circularly polarized antenna unit, in order to meet the requirements of modern wireless communication technology such as antenna bandwidth and anti-interference ability. Require.

To achieve the above object, the present invention adopts the following technical solutions:

An all-metal four-arm equiangular helical circularly polarized antenna unit, its structural features are:

The radiation arm of the all-metal equiangular spiral structure is used as the radiation area, the cylindrical resonant cavity is used as the transmission area, and the coaxial feeder is used as the feed area, and the radiation area, the transmission area and the feed area are used to realize the reception and transmission of energy;

In the radiating arm, the ends of every two equiangular spiral arms are converged and inlaid with a metal disc to form a dipole arm; the starting ends of the two dipole arms are respectively connected to three-quarter circumference metal The long rectangular metal block and the short rectangular metal block at both ends of the gap of the feeding ring form a dipole; the upper dipole and the lower dipole which are located in different planes up and down and are symmetrically distributed in the center constitute the radiation arm;

The metal reflection cavity is set directly below the radiation arm, and the top is open, and the cylindrical resonant cavity is set at the center of the end of the long rectangular metal block of the lower dipole; the coaxial feeder uses the coaxial feeder probe as the inner conductor, Taking the outer conductor of the tapered balun structure as the ground terminal, the inner conductor and the outer conductor are vertically arranged and penetrate upward from the bottom center of the metal reflection cavity to: the top of the inner conductor passes through the cylindrical resonant cavity and the upper dipole. The metal feeding ring is connected, and the top of the outer conductor is connected with the metal feeding ring of the lower dipole, so that the spatial positions of the four dipole arms of a pair of dipoles and the phases of the electromagnetic waves on the arms are orthogonal.

The structural feature of the present invention also lies in:

The outer conductor of the tapered balun structure has a notch that is gradually cut downward at 0-20° from the top.

The metal reflection cavity is an all-metal hollow cube structure, and the depth is the same as the distance between the lower dipole and the ground.

The equiangular helical structure of the equiangular helical arm is drawn by the general formula of the equiangular helical antenna, and the rotation angle of any two equiangular helical arms is 45°.

The top of the inner conductor is connected to the long rectangular metal block on the upper dipole metal feeding ring, and the top of the outer conductor is connected to the long rectangular metal block on the lower dipole metal feeding ring.

The thickness of the equiangular helical arm, the metal disc, and the metal feeding ring are the same.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. In order to realize the miniaturization of the antenna and improve the efficiency of the antenna, the present invention adopts a non-frequency-variable antenna with a self-complementary structure, emphasizing the influence of the equiangular helical structure on the electrical performance in angle;

2. In the present invention, metal discs are inlaid at the end of the radiation arm, which can cancel the residual currents each other, thereby minimizing the bad reflection from the end, optimizing the pattern and the axial ratio of the antenna;

3. The present invention adopts the coaxial feeder to feed vertically. This feeding method is completed by a single vertical coaxial feeder probe on the ground, so as to avoid designing a feeding network under the antenna; The design allows flexibility in the metal ratio, growth rate, and other helical parameters of the antenna;

4. In order to avoid the unity of the feed point in the vertical feed mode of the coaxial feeder, the present invention connects the coaxial feed probe to a central metal feed ring, and the pair of upper dipole arms is subjected to Parallel feeding, connecting another pair of lower dipole arms in parallel with the coaxial ground terminal, so as to ensure that the spatial positions of the four dipole arms and the phases of the electromagnetic waves on the arms are orthogonal to form the required circular polarization. condition;

5. In order to match the impedance between the antenna and the feeder to satisfy the balance of feeding, and at the same time to avoid the problem that high-frequency current flows out of the surface of the outer conductor when the coaxial feeder is feeding, the feeding cannot be balanced. The conductor adopts a coaxial tapered balun structure, and the outer conductor of the coaxial feeder is gradually cut at an angle of 0-20°, and at the same time, the coaxial line is gradually changed to be equivalent to a double transmission line, so as to achieve balanced feeding. The opening of the cut gradually changes, and the characteristic impedance of the feeder also changes with the cut line, so that the impedance of the load and the feeder are matched;

6. Since the antenna is an equiangular helical structure, there will be two-way radiation. In order to make the antenna realize one-way radiation, have higher efficiency, and improve the gain, the present invention adds a metal reflection cavity with an all-metal hollow cube structure on the back of the antenna.

Description of drawings

Fig. 1 is the three-dimensional structure schematic diagram of the present invention;

Fig. 2 is the structural representation of the upper dipole in Fig. 1;

Fig. 3 is the structural representation of lower dipole among Fig. 1;

Fig. 4 is the structural representation of the coaxial feeder in Fig. 1;

Fig. 5 is the return loss diagram of the present invention;

Fig. 6 is the voltage standing wave ratio diagram of the present invention;

Fig. 7 is the axial ratio diagram of the present invention;

Figure 8 is a gain diagram of the present invention.

In the figure, 1 isometric spiral arm; 2 metal disc; 3 metal feed ring; 4 long rectangular metal block; 5 short rectangular metal block; 6 cylindrical resonant cavity; 7 inner conductor; 8 outer conductor; 9 metal reflection space cavity.

Detailed ways

In order to make the purposes, 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 embodiments of the present invention. Obviously, the described embodiments are part of the present invention. examples, but not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Please refer to FIG. 1 to FIG. 4 , according to the requirements of modern wireless communication on indicators such as bandwidth and anti-interference, an all-metal four-arm equiangular helical circularly polarized antenna unit is designed. The antenna unit has a wide impedance bandwidth, Wide-axis ratio bandwidth, circular polarization and other properties, but also has the advantages of small size, can be installed, high gain, simple feeding, low loss, etc., and all use metal materials, which can strengthen the physical strength of the entire antenna, in harsh environments Under the conditions of use time is more durable. Choosing an all-metal structure can save materials and reduce costs while ensuring the necessary support strength of the structure, and on the other hand, a single processing material can also reduce the complexity of antenna processing.

The above-mentioned antenna unit uses the radiating arm of the all-metal equiangular helical structure as the radiation area, the cylindrical resonant cavity 6 as the transmission area, and the coaxial feeder as the feed area, and uses the radiation area, transmission area and feed area to achieve energy reception. and send;

In the radiation arm, the ends of every two equiangular helical arms 1 converge and inlaid with a metal disc 2 to form a dipole arm; the starting ends of the two dipole arms are respectively connected to three-quarter circumference metal plates. The long rectangular metal block 4 and the short rectangular metal block 5 at both ends of the gap of the feeding ring 3 form a dipole; the upper and lower dipoles are located in different planes up and down, symmetrically distributed in the center, and have the same external dimensions. The poles constitute the radiating arm; wherein, the equiangular spiral arm 1, the metal disc 2, and the metal feeding ring 3 have the same thickness;

The metal reflection cavity 9 is set directly below the radiation arm, the top is open, the cylindrical resonator 6 is set at the center of the end of the long rectangular metal block 4 of the lower dipole; the coaxial feeder uses the coaxial feeder probe as the inner conductor 7, Taking the outer conductor 8 of the tapered balun structure as the ground terminal, the inner conductor 7 and the outer conductor 8 are erected, and penetrate upward from the bottom center of the metal reflection cavity 9 to: the top of the inner conductor 7 passes through the cylindrical resonant cavity 6 and the upper part. The long rectangular metal block 4 on the dipole metal feeding ring 3 is connected, and the top of the outer conductor 8 is connected with the long rectangular metal block 4 on the lower dipole metal feeding ring 3, which ensures a pair of dipoles. The spatial positions of the four dipole arms and the phases of the electromagnetic waves on the arms are orthogonal to form the conditions required for circular polarization. The rectangular metal block on the metal feed ring 3 is fed by the coaxial feed line, and then the pair of dipoles of the radiating arm are fed in parallel through the metal feed ring 3, and finally the radiating arm and the metal reflection cavity 9 are fed in parallel. Radiate energy upwards.

The basic model of the above equiangular helical structure is a double-arm structure. One of the helical arms of the dipole arm can be drawn by the general formula (1) of the equiangular helical antenna, and the other helical arm can be obtained by its rotation angle δ:

为天线臂旋转角度。δ为两螺旋臂之间的角度差，当δ＝90°时，两偶极子臂之间的夹缝与其中任一偶极子臂形成自互补结构。由于天线的极化方向与其螺旋方向一致，天线单元沿z轴极化方向为逆时针的右旋圆极化，沿-z轴极化方向相反。同时因为天线的可用辐射区域由天线的波长决定，所以它的最大半径r_max和最小半径r₀与天线设计的频段有关，天线的最佳设计绕长为1.5圈，α为0.221时可以获取最优的方向图。The other dipole arm can be obtained by rotating this one dipole arm by 180° around the z-axis. Among them, r ₀ is the inner diameter of the helical arm, and the size is related to the highest operating frequency of the antenna. Usually, r ₀ =c/(4·f _h ) is taken, and r _max is the outer radius of the helical arm, and the size is related to the lowest operating frequency of the antenna. , usually take r _max =c/(4·f _l ), α is a constant that measures the degree of coiling tightness of the helical arm, and can also control the handedness of the helical arm. When α>0, the spiral is clockwise; when α<0 , spiral counterclockwise.

is the rotation angle of the antenna arm. δ is the angle difference between the two helical arms. When δ=90°, the gap between the two dipole arms forms a self-complementary structure with any of the dipole arms. Since the polarization direction of the antenna is consistent with its helical direction, the polarization direction of the antenna element along the z-axis is a counterclockwise right-hand circular polarization, and the polarization direction along the -z-axis is opposite. At the same time, because the available radiation area of the antenna is determined by the wavelength of the antenna, its maximum radius r _max and minimum radius r ₀ are related to the frequency band of the antenna design. The optimal design winding length of the antenna is 1.5 turns. When α is 0.221, the maximum Excellent orientation map.

On the basis of the above double-arm structure, in order to form the self-complementary structure of the four-arm type in this embodiment, one of the helical arms can be rotated at an angle of δ=45° to form the other helical arm of the dipole arm, and then the obtained dipole arm can be converted into the other helical arm of the dipole arm. The pole arms are rotated 90°, 180°, and 270° in turn around the z-axis, thereby forming the four arms of the antenna. Adding a metal disc at the end of the antenna can cancel the residual currents, thereby minimizing the bad reflections from the end, optimizing the pattern and the axial ratio of the antenna.

As shown in FIG. 4 , since the four-arm equiangular helix antenna is a self-complementary structure, the impedance is constant and high, so impedance matching needs to be performed while balancing the feeding. For coaxial feeder feeding, a balun design is required. Considering that the gradient balancer has relatively superior performance, a wide range of applications, and is easy to implement on coaxial feeders, the gradient balancer is selected and designed as a coaxial cone. Cut the balun structure. The outer conductor 8 of the tapered balun structure is processed by a special process, and it is gradually cut downward at 0-20° from the top. Finally, the gradual change of the coaxial feeder is equivalent to a double transmission line, so as to realize balanced feeding. At the same time, as the cutout of the outer conductor 8 changes gradually, the characteristic impedance of the feeder also changes with the cutout line, so that the impedance of the load and the feeder are matched.

In addition, the planar equiangular helical antenna radiates bidirectionally along the z-axis and -z-axis, so the pattern is bidirectional and approximates a "8" shape. Because there are two radiation lobes, the gain is low. In order to realize unidirectional radiation of the antenna, have higher efficiency, and improve the gain, the embodiment of the present invention adds a metal reflection cavity 9 with an all-metal hollow cube structure on the back of the antenna, and obtains the corresponding wavelength λ= according to the center frequency of the antenna f=4GHz 75mm, the cavity depth can generally be designed to be 1/4 of the wavelength corresponding to the center frequency of the antenna, and the distance from the lower dipole to the ground is the same. Therefore, the theoretical cavity depth is 18.75mm, and the optimal cavity depth is obtained after optimization. It is 18.4mm, and the thickness of the back cavity is 2mm.

After the simulation test, it can be obtained from Figure 5 and Figure 6 that the impedance bandwidth of the antenna is 2.87GHz to 5.5GHz, and the voltage standing wave ratio bandwidth is 2.7GHz to 6GHz. It can be seen from Fig. 7 and Fig. 8 that the axial ratio bandwidth of the antenna is 2 GHz to 6 GHz, and the maximum antenna gain in the normal direction is 8.9 dB.

Therefore, considering various parameters comprehensively, the available working bandwidth of the all-metal four-arm equiangular helical circularly polarized antenna unit of the embodiment of the present invention is 2.87GHz-5.5GHz, the absolute bandwidth is 2.63GHz, and the relative bandwidth is 62.8%. It can be seen from this that the present invention achieves the design goals of a broadband antenna with small size, high gain, and excellent axial ratio and pattern.

Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, The scope of the invention is defined by the claims and their equivalents.

Claims (5)

1. an all-metal four-arm equiangular spiral circularly polarized antenna unit, is characterized in that: The radiation arm of the all-metal equiangular helical structure is used as the radiation area, the cylindrical resonator cavity (6) is used as the transmission area, and the coaxial feeder is used as the feed area, and the radiation area, the transmission area and the feed area are used to realize the reception and transmission of energy ; In the radiating arm, the ends of each two equiangular spiral arms (1) are converged and inlaid with a metal disc (2) to form a dipole arm; the starting ends of the two dipole arms are respectively connected to the quarters. The long rectangular metal block (4) and the short rectangular metal block (5) at both ends of the metal feeding ring (3) with the perimeter of the third circumference form a dipole; The upper dipole and the lower dipole constitute the radiation arm; The metal reflection cavity (9) is arranged directly below the radiation arm, and the top is open, and the cylindrical resonator (6) is arranged at the center of the end of the long rectangular metal block (4) of the lower dipole; The coaxial feeder probe is the inner conductor (7), and the outer conductor (8) of the tapered balun structure is used as the ground terminal. The cut incision, the inner conductor (7) and the outer conductor (8) are vertical, and penetrate upwards from the bottom center of the metal reflection cavity (9) to: the top of the inner conductor (7) passes through the cylindrical resonant cavity (6) ) is connected to the metal feed ring (3) of the upper dipole, and the top of the outer conductor (8) is connected to the metal feed ring (3) of the lower dipole, so that the four dipoles of a pair of dipoles are connected The spatial position of the sub-arm and the phase of the electromagnetic wave on the arm are orthogonal. 2. The all-metal four-arm equiangular helical circularly polarized antenna unit according to claim 1, wherein the metal reflection cavity (9) is an all-metal hollow cube structure, and the depth is the same as that of the lower dipole. The same distance from the ground. 3. The all-metal four-arm equiangular spiral circularly polarized antenna unit according to claim 1, wherein the equiangular spiral structure of the equiangular spiral arm (1) is drawn by the general formula of the equiangular spiral antenna , the rotation angle of any two equal-angle helical arms (1) is 45°. 4. The all-metal four-arm equiangular helical circularly polarized antenna unit according to claim 1, wherein the top of the inner conductor (7) is connected to the upper dipole metal feed ring (3). The long rectangular metal block (4) is connected, and the top of the outer conductor (8) is connected with the long rectangular metal block (4) on the lower dipole metal feeding ring (3). 5. The all-metal four-arm equiangular spiral circularly polarized antenna unit according to claim 1, characterized in that: the equiangular spiral arm (1), the metal disc (2), the metal feed ring (3) ) of the same thickness.

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