CN210957022U

CN210957022U - Horizontal polarization omnidirectional antenna and antenna test system

Info

Publication number: CN210957022U
Application number: CN201922370253.9U
Authority: CN
Inventors: 漆一宏; 于伟; 郑煜铭
Original assignee: GENERAL TEST SYSTEMS Inc
Current assignee: GENERAL TEST SYSTEMS Inc
Priority date: 2019-12-24
Filing date: 2019-12-24
Publication date: 2020-07-07
Anticipated expiration: 2029-12-24

Abstract

The utility model discloses a horizontal polarization omnidirectional antenna and antenna test system, wherein, the antenna includes: the coaxial line antenna comprises a current balun structure and a plurality of folded dipoles, wherein the folded dipoles form a voltage balun structure, a feed layer is connected with an inner core wire of an antenna body of the coaxial line, a grounding layer is connected with a shielding layer of the antenna body of the coaxial line, and the current on the folded dipoles is controlled to flow to a coaxial line outer skin through the current balun structure and the voltage balun structure so as to calibrate various probe antennas. According to the utility model discloses antenna, restrain the common mode current through the two balun forms of voltage balun and current balun, restrain the common mode current effect and show, utilize the voltage balun structure that folding dipole constitutes can reach 15-20% bandwidth, have wide bandwidth, the advantage that the size is little, the omnidirectionality is fine, and can also realize simultaneously that the omnidirectionality is good and restrain the common mode current effect and show these two dot performances in 18% -20% wide bandwidth, simple easy the realization.

Description

Horizontal polarization omnidirectional antenna and antenna test system

Technical Field

The utility model relates to an antenna calibration technical field, in particular to horizontal polarization omnidirectional antenna and antenna test system.

Background

In the related art, the CTIA standard provides an index requirement of omnidirectional performance for a calibration antenna used for a multi-probe antenna measurement darkroom: the out-of-roundness is less than 0.2 dB.

As shown in fig. 1, a horizontally polarized omnidirectional antenna (also referred to as a loop antenna) is provided, and a plurality of radiating elements are combined to achieve high omnidirectional performance of horizontal polarization, but a current on an outer skin of a cable may damage a current balanced by the antenna itself, so that a directional pattern of the antenna is distorted, but the out-of-roundness of the antenna cannot be guaranteed to be less than 0.2 dB. Therefore, when the loop antenna is used, the cable must be covered with a ferrite magnetic ring to reduce the influence of the current on the cable on the performance of the antenna. However, the ferrite magnetic ring sleeved on the cable has a good effect on inhibiting the current on the cable only at a low frequency below 2GHz, and the using frequency band of the calibration antenna covers 0.6-6 GHz. Meanwhile, since the ferrite magnetic material has uncertain loss, the use of it on the calibration antenna causes uncertainty deviation of the final calibration result.

Another way to suppress the current on the coaxial cable is to add a balun (also called balun structure) to the antenna, such as the loop antenna shown in fig. 2. Although the loop antenna with the structure can maintain the directional diagram of the antenna to be basically not deformed without sleeving a ferrite magnetic loop, the choke effect of the balun structure is related to the wavelength of the antenna, so that the choke bandwidth is very narrow, the choke bandwidth is usually only 5% of the bandwidth, the size of the balun structure is large, and if the size of the antenna is too large, on one hand, the phase center of the antenna is shifted, and on the other hand, the omnidirectional performance of the antenna is deteriorated. The loop antenna of the type can only realize the omni-directionality of 0.2dB in a narrow band, and the narrow band antenna is very sensitive to processing errors and environmental influences, so that the loop antenna is expensive in practical application and has high defective rate.

SUMMERY OF THE UTILITY MODEL

The present invention aims at solving at least one of the technical problems in the related art to a certain extent.

Therefore, an object of the present invention is to provide a horizontally polarized omnidirectional antenna, which has an obvious effect of suppressing common mode current, can reach a bandwidth of 15-20%, has the advantages of wide bandwidth and small size, has good omni-directionality, and can simultaneously achieve the performance of two points, i.e., good omni-directionality and an obvious effect of suppressing common mode current, within a wide bandwidth of 18% -20%, and is simple and easy to implement.

Another object of the present invention is to provide an antenna testing system.

In order to achieve the above object, the utility model provides a horizontal polarization omnidirectional antenna, include: the coaxial line antenna comprises a current balun structure and a plurality of folded dipoles, wherein the folded dipoles form a voltage balun structure, a feed layer is connected with an inner core wire of an antenna body of the coaxial line, a ground layer is connected with a shielding layer of the antenna body of the coaxial line, and currents on the folded dipoles are controlled to flow to a coaxial line outer skin through the current balun structure and the voltage balun structure together so as to calibrate various probe antennas.

The utility model discloses a horizontal polarization omnidirectional antenna, through the two balun forms of voltage balun and current balun restrain the common mode current, restrain the common mode current effect and be showing, wherein, utilize folding dipole self special structure, construct the self-balancing voltage balun of a broadband, can reach 15-20% bandwidth, have wide bandwidth, advantage that the size is little, and because this kind of balanced structure of constructing the zero potential hardly receives the restriction of antenna wavelength, consequently can play the choking effect in certain bandwidth; the length of the microstrip line between the antenna and the coaxial line is not required to be fixed to be a quarter wavelength, so that the distance between the antenna and the center can be flexibly adjusted according to requirements; in addition, the gain ripple of the horizontal plane is less than 0.2dB, the omni-directionality is good, the performance of the omni-directionality and the effect of inhibiting common-mode current are simultaneously realized in a wide bandwidth of 18% -20%, and the method is simple and easy to realize.

Further, in the circumferential direction of the antenna, each folded dipole includes two end portions extending along the circumferential direction, and at least one end portion is provided with a bent portion extending toward the other end portion.

Further, still include: a plurality of coupling pieces, each of which is disposed at a corresponding position of an end of an adjacent folded dipole.

Further, the corresponding position is a bending position of the adjacent folded dipoles.

Further, the upper layer micro-strip and the lower layer micro-strip of each folded dipole of the plurality of folded dipoles are provided with electroplating through holes.

Further, the current balun structure includes: the choke structure is a preset disc-shaped structure; the microstrip structure is a preset width gradual change structure.

Further, the impedance characteristic of the antenna is obtained by multi-order transformation of the line widths of the plurality of folded dipoles.

Further, still include: a multi-layer PCB (Printed Circuit Board) Board, wherein each of the multi-layer PCB boards is connected through a metal via hole.

Alternatively, the plurality of folded dipoles may be four folded dipoles.

In order to achieve the above object, the utility model discloses another aspect provides an antenna test system, include: a microwave darkroom and an instrument; the antenna as described in the above embodiments.

The utility model discloses an antenna test system, through the two balun forms of voltage balun and current balun restrain the common mode current, restrain the common mode current effect and be showing, wherein, utilize folding dipole self special structure, construct the self-balancing voltage balun of a broadband, can reach 15-20% bandwidth, have wide bandwidth, advantage that the size is little, and because this kind of balanced structure of constructing the zero potential hardly receives the restriction of antenna wavelength, consequently can play the choking effect in certain bandwidth; the length of the microstrip line between the antenna and the coaxial line is not required to be fixed to be a quarter wavelength, so that the distance between the antenna and the center can be flexibly adjusted according to requirements; in addition, the gain ripple of the horizontal plane is less than 0.2dB, the omni-directionality is good, the performance of the omni-directionality and the effect of inhibiting common-mode current are simultaneously realized in a wide bandwidth of 18% -20%, and the method is simple and easy to realize.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic view of a related art loop antenna without a balun structure;

fig. 2 is a schematic diagram of a related art narrowband loop antenna;

fig. 3 is a calibration schematic diagram of a multi-probe antenna measurement darkroom according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a loop antenna composed of four folded dipoles according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a voltage balun constructed from folded dipoles in accordance with one embodiment of the present invention;

fig. 6a is a schematic diagram of the top layer (feed layer) of a dual layer printed PCB antenna according to an embodiment of the invention;

fig. 6b is a schematic diagram of the lower layer (ground plane) of a dual layer printed PCB antenna according to an embodiment of the invention;

fig. 7 is a graph comparing the omnidirectional performance (out-of-roundness) of antennas in different configurations, according to an embodiment of the present invention;

fig. 8 is a current distribution diagram of an arc parasitic strip and antenna in accordance with one embodiment of the present invention;

fig. 9a is a schematic structural diagram of a current balun with a gradual change structure according to an embodiment of the present invention;

fig. 9b is a schematic diagram of part a of a current balun, according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of an antenna portion position branch change according to one embodiment of the present invention;

fig. 11 is a schematic diagram of a scheme for directly using a folded dipole combination according to an embodiment of the present invention;

fig. 12a is a schematic diagram of a loop antenna composed of three folded dipoles according to an embodiment of the present invention;

fig. 12b is a schematic diagram of a loop antenna composed of five folded dipoles according to an embodiment of the present invention;

fig. 13a is a schematic diagram of a square current balun structure according to an embodiment of the present invention;

fig. 13b is a schematic diagram of a circular current balun structure according to an embodiment of the present invention;

fig. 14a is a schematic illustration of an electroplated via connection scheme in accordance with an embodiment of the present invention;

fig. 14b is a schematic diagram of a coupling scheme according to an embodiment of the present invention;

fig. 15 is a schematic diagram of a three-layer plate implementation loop antenna according to an embodiment of the present invention;

FIG. 16 is a schematic view of a top layer and a bottom layer of a three-layer board connected by plated vias according to one embodiment of the present invention;

fig. 17 is a schematic diagram of a stripline implementation of a folded dipole radiating element according to an embodiment of the present invention;

fig. 18 is a schematic diagram of a coaxial line scheme implementing a loop day according to an embodiment of the present invention;

fig. 19 is a schematic structural diagram of an antenna testing system according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present invention, and should not be construed as limiting the present invention.

The present application is based on the recognition and discovery by the utility model of the following problems:

with the advent of the 5G mobile communication era, the demand for high-speed data services has increased. Compared with the traditional single-probe measurement darkroom, the multi-probe antenna measurement darkroom has the advantage that the measurement speed is greatly improved by using the electric switch, so that the multi-probe antenna measurement darkroom is more and more widely applied to the current OTA measurement. Due to the inconsistency of the wave-absorbing material in the multi-probe antenna measurement darkroom, the inconsistency of the combination of the wave-absorbing material and different probes and the inconsistency of the gains of different probes, the multi-probe antenna measurement darkroom needs to be calibrated before the measurement is carried out in order to ensure the accuracy of the multi-probe measurement darkroom measurement.

In the multi-probe antenna measurement darkroom shown in fig. 3, each probe antenna is a dual polarized antenna consisting of a vertical polarization and a horizontal polarization. Therefore, the calibration of the probe must also include both polarizations. Since the horizontal polarization directions of different probes in the multi-probe darkroom are different, the use of a horizontally polarized omnidirectional antenna as the calibration antenna is the best choice for the calibration of horizontal polarization: when different probes are calibrated, the polarization direction of the calibration antenna is not required to be changed by mechanical rotation, so that the calibration time is shortened, and the accuracy of the measurement system is improved.

Based on the background, the embodiment of the utility model provides a horizontal polarization omnidirectional antenna and antenna test system is provided.

The horizontal polarization omnidirectional antenna and the antenna test system provided by the embodiment of the present invention are described below with reference to the accompanying drawings, and the horizontal polarization omnidirectional antenna provided by the embodiment of the present invention will be described with reference to the accompanying drawings at first.

Fig. 4 is a schematic structural diagram of a horizontally polarized omnidirectional antenna according to an embodiment of the present invention.

As shown in fig. 4, the horizontally polarized omni directional antenna includes: a current balun structure and a plurality of folded dipoles.

The feed layer is connected with the inner core wire of the antenna body of the coaxial line, the grounding layer is connected with the shielding layer of the antenna body of the coaxial line, and the current on the folded dipoles is controlled to flow to the outer skin of the coaxial line through the current balun structure and the voltage balun structure so as to calibrate various probe antennas. The utility model discloses the antenna suppresses common mode current through the two balun forms of voltage balun and current balun, and it is showing to suppress common mode current effect, and the voltage balun structure that utilizes folding dipole to constitute can reach 15-20% bandwidth, has wide bandwidth, the little advantage of size, and the omnidirectionality is fine to can also realize simultaneously that the omnidirectionality is good and suppress that the common mode current effect is showing two dot performance in 18% -20% wide bandwidth, simple easy realization.

It should be noted that the antenna of the embodiments of the present invention can be used (but not limited to) for calibrating a multi-probe antenna measurement system. When using the utility model discloses when the antenna is as calibration antenna, have following advantage: 1. the calibration is more accurate; 2. the calibration operation is more convenient; 3. and the calibration cost is saved. Of course, the utility model discloses the antenna except being used for the calibration, can also be used to other occasions that need horizontal polarization omnidirectional antenna, the suitability is strong.

Specifically, a broadband self-balanced voltage balun is constructed by using a special structure of a folded dipole, as shown in fig. 5. The voltage of the core feed line is marked negative and the feed line is shorted to the ground plane at point a, so the voltage at point a is also negative and the potential at point B is positive. Since the point C and the point B are directly connected by the short-circuit line, the potential at the point C is positive, and similarly, the point C and the point a are short-circuited, and the potential at the point C is negative. And constructing a structure with the same path from the point B to the point C and from the point A to the point C, so that the positive electromotive force and the negative electromotive force of the point C are equal in magnitude and are mutually counteracted, and the point C becomes a zero potential point. Because the coaxial line sheath is grounded and is a zero potential point, no potential difference exists between the C point and the coaxial line sheath, and the current on the folded dipole cannot flow to the coaxial line sheath, so that the effect of choking is achieved. Compared with a quarter-wavelength balun structure, the voltage balun structure has the following advantages:

(1) the wide bandwidth, because the balanced structure of the zero potential is almost not limited by the wavelength of the antenna, the choke effect can be achieved within a certain bandwidth;

(2) the size is small, and the length of the microstrip line between the antenna and the coaxial line is not required to be fixed to be a quarter wavelength, so that the distance between the antenna and the center can be flexibly adjusted according to requirements.

Further, in an embodiment of the present invention, in a circumferential direction of the antenna, each folded dipole includes two end portions extending in the circumferential direction, and at least one end portion is provided with a bending portion extending toward the other end portion. Wherein, the upper layer microstrip and the lower layer microstrip of each folded dipole of the plurality of folded dipoles are provided with electroplating through holes.

It can be understood that, the embodiment of the present invention takes the antenna formed by combining four folded dipoles bent in an arc shape as an example, and the four folded dipoles are spliced in the clockwise direction to form the combined loop antenna as shown in fig. 4. As shown in fig. 6a and 6b, the antenna of the embodiment of the present invention is a dual-layer printed PCB antenna, which is composed of an upper layer and a lower layer, wherein the upper layer is a feed layer and is directly connected to an inner core wire of a coaxial line; the lower layer is a grounding layer, and the tail end of the grounding layer is connected with a shielding layer of the coaxial line. The upper layer micro-strip and the lower layer micro-strip of each folded dipole are connected through the electroplating through hole. In order to further improve the omnidirectional performance of antenna, the embodiment of the utility model provides a on this basis, buckle this model along the circular arc, every folding dipole after the arc is buckled reduces 5mm for comparing before with the distance at center. Figure 7 shows a comparison of the out-of-roundness of four folded dipoles before and after arc bending. The results show that the out-of-roundness of the arc-bent antenna is reduced from 0.7dB to 0.3dB compared to the previous one.

Further, in an embodiment of the present invention, the antenna of the embodiment of the present invention further includes: a plurality of coupling tabs. Each coupling piece of the plurality of coupling pieces is arranged at a corresponding position of the end part of the adjacent folded dipole, wherein the corresponding position is a bending position of the adjacent folded dipole.

It can be understood that the current distribution of the dipole is tapered because of the radiation characteristic of the dipole, i.e. the middle current is large and the two ends are small. In order to further reduce the out-of-roundness of the antenna, arc-shaped coupling microstrip lines are respectively added between the adjacent folded dipoles to compensate the weakened currents at the ends of the dipoles, as shown in fig. 8.

The current induced on the microstrip line is consistent with the current on the antenna in direction, and forms a circle of uniform current along the horizontal plane together with the current on the antenna. Therefore, as can be seen from fig. 7, the out-of-roundness of the antenna in the horizontal direction is significantly reduced (from 0.3dB to 0.09dB) after the arc parasitic strip (coupling patch) is added.

Further, in an embodiment of the present invention, the current balun structure includes: choke structures and microstrip structures. Wherein, the choke structure is a preset disc-shaped structure; the microstrip structure is a preset width gradual change structure.

It will be appreciated that in the galvanic balun configuration shown in figure 9(a), the inner core of the coaxial line is connected to the top layer and the outer core is connected to the bottom layer. The balun structure is composed of two parts, namely A and B, specifically:

(a) the main function of part a is choke, and since the feed layer is very close (1mm) to the ground plane, a high current in the feed layer will cause a large current to appear in the ground plane and the coaxial line through coupling. Therefore, to reduce the current on the coaxial line due to the fringe field leakage, the ground layer can be designed as a "big disk" structure relative to the top layer. As shown in fig. 9(b), the balun structure prevents most of the electric field in the top layer from bypassing the transmission line in the bottom layer to reach the back side of the bottom layer, so as to reduce the current flowing to the coaxial line sheath from the antenna, thereby suppressing the common mode current on the coaxial line.

(b) The part B is a microstrip structure, and the width of the grounding layer is designed into a structure with gradually changed width to enhance impedance matching and effectively save the occupied area of the antenna.

Further, in an embodiment of the present invention, the impedance characteristic of the antenna is obtained by multi-order transformation of line widths of the plurality of folded dipoles.

It can be understood that the impedance of the four parallel-folded dipoles is about 292/4-73 Ω. Therefore, in order to match with the coaxial line of 50 Ω, as shown in fig. 10, the line width of the folded dipole is subjected to multi-stage conversion to change the impedance characteristic of the antenna, and the line widths at both ends of the folded dipole are widened to increase the current at the ends of the dipole.

It should be noted that, (1) the utility model discloses the antenna has carried out the arc with folding dipole and has buckled to better omnidirectional radiation performance has been realized. In addition, according to different application backgrounds and performance requirements, a folded dipole scheme without an arc-shaped bend may also be directly used, for example, as shown in fig. 11, which is not limited herein.

(2) The embodiment of the present invention designs and uses 4 folded dipoles as shown in fig. 4 to form a loop antenna, and according to different requirements, the folded dipole units with different quantities can be used to form the antenna, as shown in fig. 12(a) and 10(b), the PCB antenna composed of 3 folded dipole units and 5 folded dipole units is used, and no specific limitation is made here.

(3) The current balun designed by the embodiment of the utility model uses a gradually changing diamond-shaped structure on the ground plane, as shown in fig. 13; of course, the ground plane of the current balun may be designed to have any shape such as a square shape or a disk shape, and is not particularly limited herein.

(4) The feeding layer and the ground layer of the folded dipole of the embodiment of the present invention are connected by electroplating via holes, as shown in fig. 14(a), of course, the feeding layer and the ground layer of the folded dipole can also be connected by current coupling according to different requirements. As shown in fig. 14(b), the feeding layer and the ground layer of the antenna are not directly connected by an electrical path, but are directly connected by metal such as a plated hole, and are connected by microstrip line coupling.

(5) The embodiment of the present invention relates to a double-layer PCB board scheme (as shown in fig. 6), which can be implemented by using three or more boards according to different application scenarios, for example, a folded dipole radiation unit of a loop antenna, a 3-board PCB scheme shown in fig. 15, and a top layer and a bottom layer which are ground planes connected by a metal via hole, as shown in fig. 16.

(6) In addition to the PCB solution of the above embodiment, the design of the probe can be realized by means of a strip line according to the characteristics of the PCB itself. The PCB stripline shown in fig. 17 implements a folded dipole radiating element of the loop antenna. The PCB here is a three-layer circuit board, unlike the previous three-layer board PCB solutions, where the top and bottom layers of the stripline solution are not connected with metallized vias, i.e., open borders as shown in fig. 17.

(7) As shown in the schematic diagram of the coaxial line scheme in fig. 18, in addition to the PCB scheme and the open waveguide scheme, the coaxial line may be bent to implement the folded dipole radiation unit, and they are combined to form a loop antenna.

To sum up, the embodiment of the present invention provides a horizontally polarized omnidirectional antenna, which suppresses common mode current through the dual balun form of the voltage balun and the current balun, and has significant effect of suppressing common mode current, wherein a self-balanced voltage balun with a wide band is constructed by using a special structure of the folded dipole, which can reach 15-20% of bandwidth, and has the advantages of wide bandwidth and small size, and because the balanced structure constructing a zero potential is almost not limited by the wavelength of the antenna, the antenna can play a role of choking within a certain bandwidth; the length of the microstrip line between the antenna and the coaxial line is not required to be fixed to be a quarter wavelength, so that the distance between the antenna and the center can be flexibly adjusted according to requirements; in addition, the gain ripple of the horizontal plane is less than 0.2dB, the omni-directionality is good, the performance of the omni-directionality and the effect of inhibiting common-mode current are simultaneously realized in a wide bandwidth of 18% -20%, and the method is simple and easy to realize.

Next, an antenna test system according to an embodiment of the present invention will be described with reference to the drawings.

As shown in fig. 19, the antenna test system 10 includes: a microwave anechoic chamber and meter 100 and an antenna 200 as described in the previous embodiments.

According to the embodiment of the utility model provides an antenna test system, restrain the common mode current through the two balun forms of voltage balun and current balun, restrain the common mode current effect and be showing, wherein, utilize folding dipole self special structure, construct the self-balancing voltage balun of a broadband, can reach 15-20% bandwidth, have wide bandwidth, advantage that the size is little, and because this kind of balanced structure who constructs the zero potential hardly receives the restriction of antenna wavelength, consequently can play the choking effect in certain bandwidth; the length of the microstrip line between the antenna and the coaxial line is not required to be fixed to be a quarter wavelength, so that the distance between the antenna and the center can be flexibly adjusted according to requirements; in addition, the gain ripple of the horizontal plane is less than 0.2dB, the omni-directionality is good, the performance of the omni-directionality and the effect of inhibiting common-mode current are simultaneously realized in a wide bandwidth of 18% -20%, and the method is simple and easy to realize.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art without departing from the scope of the present invention.

Claims

1. A horizontally polarized omnidirectional antenna, comprising:

the coaxial line antenna comprises a current balun structure and a plurality of folded dipoles, wherein the folded dipoles form a voltage balun structure, a feed layer is connected with an inner core wire of an antenna body of the coaxial line, a ground layer is connected with a shielding layer of the antenna body of the coaxial line, and currents on the folded dipoles are controlled to flow to a coaxial line outer skin through the current balun structure and the voltage balun structure together so as to calibrate various probe antennas.

2. The antenna according to claim 1, wherein each folded dipole comprises two end portions extending along the circumferential direction in the circumferential direction of the antenna, and a bent portion extending toward the other end portion is provided on at least one end portion.

3. The antenna of claim 2, further comprising:

a plurality of coupling pieces, each of which is disposed at a corresponding position of an end of an adjacent folded dipole.

4. An antenna according to claim 3, wherein the corresponding location is a location of a bend of the adjacent folded dipole.

5. The antenna of claim 1, wherein the upper and lower microstrips of each of the plurality of folded dipoles are provided with plated vias.

6. The antenna of claim 1, wherein the current balun structure comprises:

the choke structure is a preset disc-shaped structure;

the microstrip structure is a preset width gradual change structure.

7. The antenna of claim 1, wherein the impedance characteristic of the antenna is obtained by a line width multi-order transformation of the plurality of folded dipoles.

8. The antenna of claim 1, further comprising:

the PCB comprises a plurality of layers of PCBs, wherein each layer of PCB of the plurality of layers of PCBs is connected through a metal through hole.

9. The antenna of claim 1, wherein the plurality of folded dipoles is four folded dipoles.

10. An antenna test system, comprising:

a microwave darkroom and an instrument;

an antenna as claimed in any one of claims 1 to 9.