CN114914703A

CN114914703A - Transparent reflective conductive frequency selective electromagnetic medium and multi-band antenna system

Info

Publication number: CN114914703A
Application number: CN202210420452.XA
Authority: CN
Inventors: 盖伊·约瑟夫; 吴吉强; 金利; 吴中林; 刘木林; 姚想喜; 欧迪
Original assignee: Tongyu Communication Inc
Current assignee: Tongyu Communication Inc
Priority date: 2022-04-21
Filing date: 2022-04-21
Publication date: 2022-08-16

Abstract

A transparent reflection conductive frequency selection electromagnetic medium and a multiband antenna system are provided, the electromagnetic medium has a surface structure which is formed by a plurality of medium units which are periodically arranged and is transparent to a first frequency band wireless signal, the shortest working wavelength of the first frequency band is larger than the longest working wavelength of the second frequency band, each medium unit comprises a central subunit and four transmission line branches, the four transmission line branches are uniformly distributed around the central subunit, and the extension direction is matched with the polarization direction of a linear signal; the transmission line branches in the adjacent medium units are connected and enclose a conductive closed loop; the distribution spacing of the dielectric elements matches the distribution spacing of the antenna radiating elements operating in the second frequency band. The effect on the penetrated second frequency band wireless signal can be reduced, the first frequency band wireless signal can be reflected with high performance, and the antenna is suitable for a multi-antenna array with independent reflectors and a multi-band base station antenna system integrating a plurality of antenna array modules.

Description

Transparent reflective conductive frequency selective electromagnetic medium and multi-band antenna system

Technical Field

The present invention relates to wireless communication antenna technology, and more particularly, to a transparent reflective conductive frequency selective electromagnetic medium and a multiband antenna system.

Background

In today's multi-band cellular base station designs, it is desirable to integrate multiple radiating elements corresponding to multiple radio signal bands within the same radome. Typically, in such integrated antenna systems, the high and low frequency arrays share the same back metal reflector that is used to produce a one-way gain pattern in half the space at a given beamwidth required for cellular base station operation.

However, with the development of mobile communication technology and the demand for base station construction, it may be necessary to provide the high frequency array and the low frequency array as independent modules, and construct such an integrated multiband antenna system with such independent modules. In this manner, each module with a dedicated reflector can operate independently and also operate efficiently when two modules are stacked integrated under the same antenna radome.

It is well known that for antenna arrays, the similarity of directional gain and pattern shape within a given operating frequency band is a key performance feature. Therefore, the transparent reflective medium between the two modules must be able to pass high frequency radio signals with minimal pattern distortion and no significant change in directional gain. This requires that the electromagnetic medium be electrically transparent to one of the antenna modules and reflective to the other antenna module, while maintaining the operating performance of both antenna modules.

Disclosure of Invention

The invention aims to solve the technical problem of providing an electromagnetic medium which shows a reflection characteristic for low-frequency signals and a transparent characteristic for high-frequency signals and is suitable for a multi-frequency dual-module communication system or a multi-module communication base station antenna system.

The technical scheme adopted by the invention for solving the technical problems is as follows: a transparent reflective conductive frequency selective electromagnetic medium having a surface structure formed by a plurality of dielectric elements periodically arranged to be reflective to a first band of radio signals and transparent to a second band of radio signals, wherein a shortest operating wavelength of the first band is longer than a longest operating wavelength of the second band, each of the dielectric elements comprises a central sub-element and four transmission line branches connected to the central sub-element, the four transmission line branches are uniformly distributed around the central sub-element, and an extension direction of the four transmission line branches matches with a polarization direction of the radio signals of the first band and the second band; in the adjacent dielectric units, the two transmission line branches of one dielectric unit are connected with the two transmission line branches of the other dielectric unit to form a conductive closed loop; the distribution spacing of the dielectric elements matches the distribution spacing of the antenna radiating elements operating in the second frequency band.

Further, the transmission line branches of adjacent dielectric units are connected directly or via an intermediate transmission line.

Furthermore, the physical extension length of one side edge of the conductive closed loop enclosed by the medium units is less than half of the second frequency band operating wavelength, and the electrical length is greater than half of the second frequency band operating wavelength.

Further, the transmission line branches of the dielectric units have a slow-wave structure for adjusting electrical lengths thereof, or the transmission line branches and the intermediate transmission line have a slow-wave structure.

Furthermore, the central subunit is in a square sheet shape, and the edge of the square central subunit is parallel to the edge of the antenna radiation unit working in the second frequency band.

The invention also provides a multiband antenna system with the transparent reflective conductive frequency selective electromagnetic medium, which comprises a high-frequency antenna unit working in a second frequency band and a low-frequency antenna unit working in a first frequency band, wherein the high-frequency antenna unit and the low-frequency antenna unit are respectively arranged below and above the electromagnetic medium, and the electromagnetic medium is used as a reflector of the low-frequency antenna unit and is transparent to a radiation signal of the high-frequency antenna unit; the extension direction of the transmission line branch of the dielectric element is parallel to the polarization direction of the high-frequency antenna element and the low-frequency antenna element.

Furthermore, a central subunit of the dielectric unit corresponds to the center of the high-frequency antenna unit, the central subunit is in a square sheet shape, and the four transmission line branches are respectively connected to four corners of the square central subunit and are overlapped with a diagonal line of the high-frequency antenna unit.

Furthermore, in the dielectric unit, one or more edge transmission lines parallel to the boundary of the high-frequency antenna unit in the horizontal or vertical direction are connected between two adjacent transmission line branches, and the edge transmission lines have a slow-wave structure for adjusting the electrical length.

Furthermore, the central subunit of the dielectric unit is arranged between two high-frequency antenna units, and the conductive closed loop surrounded by adjacent dielectric units is arranged between four adjacent high-frequency antenna units.

Furthermore, the low-frequency antenna unit is arranged on a supporting part in the low-frequency antenna housing and forms a low-frequency antenna module with an electromagnetic medium below the supporting part, and the high-frequency antenna unit is arranged in the high-frequency antenna housing and forms a high-frequency antenna module with a reflecting plate below the high-frequency antenna unit.

Furthermore, the high-frequency antenna module is an active module, and the low-frequency antenna module is a passive module.

Furthermore, the antenna comprises a plurality of pairs of low-frequency antenna modules and high-frequency antenna modules, and an electromagnetic medium matched with the working frequency band of each pair of low-frequency antenna modules and high-frequency antenna modules is arranged between each pair of low-frequency antenna modules and each pair of high-frequency antenna modules.

The invention has the beneficial effects that: the transmission line branches of the dielectric units are matched with the polarization direction of the wireless signals, the distribution spacing of the dielectric units is matched with the distribution spacing of the antenna radiation units working in the second frequency band, the influence on the penetrating second frequency band wireless signals can be reduced, the first frequency band wireless signals are reflected in a high-performance mode, and the multi-band antenna array is suitable for a multi-antenna array with independent reflectors and a multi-band base station antenna system integrating a plurality of antenna array modules.

Drawings

Fig. 1 is a schematic diagram of embodiment 1 of a dual band antenna system.

Fig. 2 is a partially enlarged view of the area a in fig. 1.

FIG. 3 is a schematic representation of the transparent reflective duality of a frequency selective electromagnetic medium.

Fig. 4 is a schematic diagram of a frequency selective closed loop conductor.

Fig. 5 is a schematic diagram of embodiment 1 of a media unit structure.

Fig. 6 is a schematic diagram of embodiment 2 of the media unit structure.

Fig. 7 is a schematic diagram of embodiment 3 of the media unit structure.

Fig. 8 is a schematic diagram of embodiment 4 of the media unit structure.

Fig. 9 is a schematic diagram of embodiment 5 of a media unit structure.

Fig. 10 is a schematic diagram of embodiment 6 of the media unit structure.

Fig. 11 is a schematic diagram of embodiment 7 of the media unit structure.

Figure 12 is a schematic view of embodiment 1 of a dual polarized planar array with a transparent reflective electromagnetic medium.

Figure 13 is a schematic view of embodiment 2 of a dual polarized planar array with a transparent reflective electromagnetic medium.

Fig. 14 is a schematic diagram of embodiment 8 of the media unit structure.

Fig. 15 is a schematic diagram of embodiment 9 of a media unit structure.

Fig. 16 is a schematic diagram of embodiment 2 of a dual band antenna system.

Fig. 17 is a schematic diagram of embodiment 1 of a stacking mode of a dual-band antenna system.

Fig. 18 is a schematic diagram of embodiment 2 of a stacking mode of a dual-band antenna system.

Fig. 19 is a schematic diagram of an embodiment of an integrated lf-hf antenna system with separable modules.

Fig. 20 is a side view of an embodiment of a dual-band antenna system.

Fig. 21 is a three-dimensional view of an embodiment of a dual-band antenna system.

Fig. 22 is a distribution of a radiation electric field of the high frequency antenna array at 3.4 GHz.

Fig. 23 is a distribution of a radiation electric field of the high frequency antenna array at 3.6 GHz.

Fig. 24 is a distribution of radiation electric field of the high frequency antenna array at 3.8 GHz.

Fig. 25 is an electric field distribution radiated by a low band antenna element at 850 MHz.

FIG. 26 is a graph of surface current distribution on a media unit at 3.6 GHz.

FIG. 27 is a normalized elevation gain comparison of a low band (P-module) binary array at 850MHz using a conventional metal reflector and ATPR media.

FIG. 28 is a normalized azimuth gain comparison of a low band (P-module) binary array using a conventional metal reflector and ATPR media at 850 MHz.

FIG. 29 is a gain comparison in the 690MHz-960MHz range using a conventional metal reflector and an ATPR medium.

FIG. 30 is the gain in the E-plane at 3400MHz (-45 polarization).

FIG. 31 is the E-plane gain at 3400MHz (+ 45 ° polarization).

FIG. 32 is the E-plane gain (-45 polarization) at 3600 MHz.

FIG. 33 is the E-plane gain (+ 45 polarization) at 3600 MHz.

FIG. 34 is the gain in the E-plane at 3800MHz (-45 polarization).

FIG. 35 is the E-plane gain (+ 45 polarization) at 3800 MHz.

FIG. 36 shows the H-plane gain (-45 polarization) at 3400 MHz.

FIG. 37 is the H-plane gain at 3400MHz (+ 45 ° polarization).

FIG. 38 is the H-plane gain (-45 polarization) at 3600 MHz.

FIG. 39 is the H-plane gain (+ 45 ° polarization) at 3600 MHz.

FIG. 40 is the H-plane gain (-45 polarization) at 3800 MHz.

FIG. 41 is the H-plane gain (+ 45 ° polarization) at 3800 MHz.

The labels in the figure are: 1. the antenna comprises an electromagnetic medium, 1-1 parts of a central subunit, 1-2 parts of transmission line branches, 1-3 parts of an intermediate transmission line, 1-4 parts of a slow wave structure, 1-5 parts of an edge transmission line, 2 parts of a high-frequency antenna unit, 2-1 parts of a high-frequency array feed network, 3 parts of a low-frequency antenna unit, 4 parts of a closed-loop electric conductor, 5 parts of a low-frequency antenna signal, 6 parts of a high-frequency antenna signal, 7 parts of a low-frequency antenna housing, 8 parts of a supporting component, 9 parts of a waterproof isolating layer, 10 parts of a high-frequency antenna housing, 11 parts of a reflecting plate, 12 parts of a high-frequency antenna module, 13 parts of a low-frequency antenna module, 14 parts of a surface current zero point.

Detailed Description

The technical scheme of the invention is clearly and completely described below with reference to the accompanying drawings and the detailed description. The specific contents listed in the following examples are not limited to the technical features necessary for solving the technical problems to be solved by the technical solutions described in the claims. Meanwhile, the list is that the embodiment is only a part of the present invention, and not all embodiments.

The electromagnetic medium 1 disclosed in the present invention shall be referred to as a high frequency transparent low frequency reflective (HBT-LBR) medium and may also be referred to as an Active Transparent Passive Reflective (ATPR) medium when the high frequency radio module consists of a high frequency active antenna system and a low frequency passive antenna system.

As shown in fig. 1 and 2, an electromagnetic medium 1 has a periodic surface structure formed by a plurality of medium units arranged periodically, and a conductive closed-loop structure is formed between the medium units. In this embodiment, the first frequency band is an operating frequency band of the low frequency antenna, the second frequency band is an operating frequency band of the high frequency antenna, and the shortest operating wavelength of the first frequency band is greater than the longest operating wavelength of the second frequency band. The surface structure exhibits the effect of being reflective to wireless signals in the first frequency band and transparent to wireless signals in the second frequency band.

Fig. 4 is a schematic illustration of the principle of one conductive closed loop structure in a periodic surface structure. The electrically conductive closed loop structure is formed by a closed loop electrical conductor 4, the frequency behavior of which is dependent on the metrology parameters a and w, and a set of electrical components, such as component C shown in fig. 3. Where the element C may be an inductor, a capacitor, or a series or parallel combination of such elements, these elements may be created by electrical characteristics such as the shape, structure, material, etc. of the transmission line in a conductive closed loop configuration, and may be distributed or a combination of distributed and distributed electrical characteristics. The sides of the conductive closed loop structure match the polarization direction of the radio signal, which as shown is +45 ° and-45 ° polarization directions, respectively.

Fig. 5 is a schematic view of one of the dielectric elements forming a conductive closed loop structure. Each medium unit comprises a central subunit 1-1 and four transmission line branches 1-2 connected to the central subunit, the four transmission line branches are uniformly distributed around the central subunit, and the extending direction of the four transmission line branches is matched with the polarization direction of the wireless signals. The transmission line branches are sides of a conductive closed loop structure. In the adjacent dielectric units, the two transmission line branches of one dielectric unit are connected with the two transmission line branches of the other dielectric unit to form a conductive closed loop.

The distribution spacing of the dielectric elements matches the distribution spacing of the antenna radiating elements operating in the second frequency band. When the distribution pitch of the antenna radiation elements is comparable to the size of the dielectric elements, the structure shown in fig. 5 may be adopted, in which the pitch d is _v =d _h The transmission line branches of adjacent dielectric elements may be directly connected. When the distribution pitch of the antenna radiation elements is larger than the size of the dielectric elements, for example, the vertical distribution pitch is larger than the size of the dielectric elements. An intermediate transmission line 1-3 can be connected to the transmission line branch 1-2, as shown in fig. 6, when d _h ≠ d _v The transmission line branches of adjacent dielectric elements are connected via an intermediate transmission line.

The dielectric element formed by the transmission line branches and the reactive elements therein, which may be an electrical characteristic of the transmission line structure, and the periodic structure thereof may be arranged such that the high frequency signal currents have a longer transmission length over a relatively short physical distance with respect to the operating wavelength of the antenna. When dielectrically coupled to the high-frequency antenna element, a plurality of surface current zeros, which are equivalent to open points on the transmission line, may be structurally formed. Such open points may create isolated short transmission line segments that appear as capacitively coupled stubs or disconnected conductive surfaces on the high frequency element and allow high frequency signals to pass through the dielectric structure with minimal degradation of antenna performance.

Further said electromagnetic medium may be arranged such that the circumference of the closed loop of any part of the electromagnetic medium contained within the boundaries of the high frequency antenna element or array of elements is greater in electrical length than half the operating wavelength and wherein the physical extension a and width w of one side of the smallest conductive closed loop is physically smaller (a < lambda/2) but the electrical length is greater than half the considered high frequency operating wavelength (lambda/2).

As shown in fig. 7-11, the transmission line branches of the dielectric elements may be provided with slow-wave structures, which are typically formed by bending the transmission lines, and which may be used to adjust the electrical length of the transmission lines. The electrical characteristics on the dielectric elements may be further arranged such that the equivalent electrical length le on one side of element a is greater than the free-space operating wavelength of the high-band antenna array (a < λ/2, le > λ). In the embodiment shown in fig. 7, the transmission line branch 1-2 has two slow wave structures 1-4 and the intermediate transmission line 1-3 has one slow wave structure 1-4. At least one current zero may be formed on the transmission line branch 1-2 and any two conductive paths between nodes above the high frequency element have at least two current zeros for the high frequency operating wavelength.

The dielectric elements may be arranged to match the centre of the high frequency antenna element 2 such that one dielectric element or a group of dielectric elements of the structure is substantially symmetrical with respect to the centre of the high frequency antenna element or the centre of a sub-array of said high frequency antenna elements. Fig. 12 shows a part of a dual polarized planar array with the edges of the conductive closed loop, i.e. the transmission line branches of the dielectric elements, crossing the diagonal of the antenna radiating elements and with a distribution pitch matching the horizontal and vertical pitch of the array. This configuration is advantageous for increasing the reflective surface of the low band medium while maintaining good cross polarization and pattern gain at the high band.

Figure 13 illustrates a portion of a dual-polarized planar array in which the central sub-element of the dielectric element is interposed between two high frequency antenna elements, shared between adjacent antenna elements of the conductive closed loop, and rotated 45 to match the polarization of the antenna and to match the horizontal and vertical spacing of the array.

The central sub-unit 1-1 of the dielectric unit is a square sheet, the edge of which is parallel to the edge of the antenna radiation unit (high-frequency antenna unit 2) operating in the second frequency band, and has the function of adjusting the beam width and the gain. Fig. 8-11 show different embodiments of the size ratio of the central subunit 1-1 of the dielectric element to the high frequency antenna element 2. In the embodiment shown in fig. 10, the center sub-unit is substantially the same size as the high-frequency antenna unit and can resonate with the high-frequency antenna unit. The central sub-unit is a radiation element which can be used as a director of the high-frequency antenna unit below the central sub-unit, so that the narrower beam width is realized, and the directivity is enhanced. The reduced size of the central subunit allows for greater wave width and half power angles, but a relative reduction in gain. The specific size of the central subunit is selected according to the performance requirements of the antenna. For example, in the embodiment shown in fig. 11, the central sub-element is much smaller than the high-frequency antenna element, and has less radiation effect, but there may be more slow-wave structures within the boundary of the high-frequency antenna element. The dielectric element may also be a non-radiating element so that it is almost completely transparent to high frequency signals.

The electromagnetic medium 1 is also configured to reflect off the low band antenna array while achieving the dielectric transparency characteristic for the high band antenna array. In a preferred embodiment of low band reflection; the directional gain of a low frequency antenna may be controlled by the density of the distribution of conductive elements on the electromagnetic medium, where a group of elements or sub-elements form an electrical path along a given wave polarization that is at least longer than half the operating wavelength of the low frequency band under consideration. For example, as shown in fig. 14 and 15, one or more edge transmission lines 1-5 having a slow-wave structure for adjusting an electrical length may be added between two adjacent transmission line branches 1-2 in parallel with a horizontal or vertical boundary of the high-frequency antenna unit. This allows for an increased density of conductive elements distribution while maintaining the electromagnetic dielectric structure matched to the polarization of the high frequency antenna array. For specific design requirements such as high gain, radiation beamwidth coverage, etc.

One embodiment of a multi-band antenna system is shown in fig. 1, 2 and 16, having a high frequency antenna element operating in a second frequency band and a low frequency antenna element operating in a first frequency band, the high frequency antenna element and the low frequency antenna element being arranged below and above an electromagnetic medium 1, respectively, the electromagnetic medium 1 acting as a reflector for the low frequency antenna element and being transparent to a radiation signal of the high frequency antenna element; the extension direction of the transmission line branch of the dielectric element is parallel to the polarization direction of the high-frequency antenna element and the low-frequency antenna element.

Fig. 17 is a schematic diagram of an embodiment in which components in a dual-band antenna system are stacked. The electromagnetic medium comprises a high-frequency antenna array and a low-frequency antenna array, and an electromagnetic medium 1 is arranged between the high-frequency antenna array and the low-frequency antenna array. The relative position of the electromagnetic medium may be optimized for specific high frequency radio and low frequency radio wavelengths using electromagnetic simulation software. In a preferred embodiment, the electromagnetic medium can be placed 0.25 λ above the high band array and 0.18 λ below the low band array to produce the desired reflection effect at the low band while being transparent to the high band.

The low-frequency antenna unit 3 is arranged on a supporting part 8 in a low-frequency antenna housing 7 and forms a low-frequency antenna module with the electromagnetic medium 1 below the supporting part, and the high-frequency antenna unit 2 is arranged in a high-frequency antenna housing 10 and forms a high-frequency antenna module with a reflecting plate 11 below the high-frequency antenna housing. The electromagnetic medium 1 has a waterproof isolation layer 9 thereunder.

In the embodiment shown in fig. 18, the low-frequency antenna module is a passive module (p-module) and the high-frequency antenna module is an active module (a-module). The electromagnetic medium 1 (ATPR) may be integrated in a waterproof isolating layer 9 forming a housing for the low band antenna. This structure enables the high frequency antenna module and the low frequency antenna module to be separated.

Fig. 19 is an embodiment of a multi-module antenna system. Two high-frequency antenna modules 12 (only one is shown in the figure) can be correspondingly arranged on one low-frequency antenna module 13, and the modules are separable and independent structures. More modules may be provided as needed.

For testing the performance, one high frequency antenna module (a-module) and one low frequency antenna module (p-module) were provided, arranged according to the arrangement of fig. 17, 18. The antenna array electric field profiles of fig. 22-25 demonstrate the effectiveness of the p-module reflector (ATPR) and its effect on antenna performance. It can be seen that the radio waves radiated by the a-module antenna can pass through the electromagnetic medium, while the radio waves radiated by the P-antenna are reflected by the medium, thereby producing the desired unidirectional pattern gain for each antenna module. In particular, as shown in fig. 26, the high-frequency transparent behavior of the medium achieved by the slow-wave structure, in which four current zeros appear around the center of the high-frequency antenna element at 3.6GHz, forms an X-shaped conductive part electrically isolated from the rest of the medium, and is thus electromagnetically transparent to the radiated waves originating from the high-frequency antenna element at the frequency point in question.

FIGS. 27-41 show performance testing of the electromagnetic medium (ATPR) of the present invention. It can be seen that the electromagnetic medium (ATPR) reflects off the low band antenna array and is transparent to the high band antenna array, respectively, and the electromagnetic medium can be used as a low band reflector transparent to the high band antenna array.

By optimizing the ATPR medium design and by gradually refining various boundary conditions of the overall structure, the impact of the structure of the present invention on the performance of the high frequency antenna module can be minimized while ensuring satisfactory performance of the low frequency antenna module, thereby achieving good overall performance of both modules. It will be apparent to those skilled in the art that the low band reflection behavior and high band transparency behavior of the medium in terms of antenna performance characteristics, such as directional gain, pattern beamwidth, X-polarization level, front-to-back ratio, impedance bandwidth coverage, etc., can be optimized by appropriate selection of medium geometry and reactive component characteristics, and by adjusting the relative heights of the medium with respect to the low band and high band array positions.

Claims

1. A transparent reflective electrically conductive frequency selective electromagnetic medium, the electromagnetic medium (1) having a surface structure formed by a periodic arrangement of a plurality of dielectric elements that is reflective for radio signals in a first frequency band and transparent for radio signals in a second frequency band, wherein the shortest operating wavelength in the first frequency band is greater than the longest operating wavelength in the second frequency band, characterized in that: each medium unit comprises a central subunit (1-1) and four transmission line branches (1-2) connected to the central subunit, the four transmission line branches are uniformly distributed around the central subunit, and the extending direction of the four transmission line branches is matched with the polarization directions of the wireless signals of the first frequency band and the second frequency band; in the adjacent dielectric units, the two transmission line branches of one dielectric unit are connected with the two transmission line branches of the other dielectric unit to form a conductive closed loop; the distribution spacing of the dielectric elements matches the distribution spacing of the antenna radiating elements operating in the second frequency band.

2. A transparent reflective conducting frequency selective electromagnetic medium as claimed in claim 1 wherein: the transmission line branches (1-2) of adjacent dielectric elements are connected directly or via an intermediate transmission line (1-3).

3. The transparent reflective conductive frequency selective electromagnetic medium of claim 1 or 2, wherein: the physical extension length of one side edge of the conductive closed loop enclosed by the medium units is less than half of the working wavelength of the second frequency band, and the electrical length is greater than half of the working wavelength of the second frequency band.

4. A transparent reflective conducting frequency selective electromagnetic medium as claimed in claim 3, wherein: the transmission line branches (1-2) of the dielectric units have slow-wave structures (1-4) for adjusting their electrical lengths, or the transmission line branches (1-2) and the intermediate transmission lines (1-3) each have a slow-wave structure (1-4).

5. A transparent reflective conducting frequency selective electromagnetic medium as claimed in claim 1 wherein: the central subunit (1-1) is in a square sheet shape, and the edge of the square central subunit is parallel to the edge of the antenna radiation unit working in the second frequency band.

6. A multiple frequency band antenna system having a transparent reflective conductive frequency selective electromagnetic medium as claimed in any one of claims 1 to 5, wherein: the antenna comprises a high-frequency antenna unit working in a second frequency band and a low-frequency antenna unit working in a first frequency band, wherein the high-frequency antenna unit and the low-frequency antenna unit are respectively arranged below and above the electromagnetic medium (1), and the electromagnetic medium (1) is used as a reflector of the low-frequency antenna unit and is transparent to a radiation signal of the high-frequency antenna unit; the extension direction of the transmission line branch of the dielectric element is parallel to the polarization direction of the high-frequency antenna element and the low-frequency antenna element.

7. The multi-band antenna system of claim 6, wherein: the center subunit of the dielectric unit corresponds to the center of the high-frequency antenna unit, the center subunit is in a square sheet shape, and the four transmission line branches are respectively connected to the four corners of the square center subunit and are overlapped with the diagonal line of the high-frequency antenna unit.

8. The multiple-band antenna system of claim 7, wherein: in the dielectric unit, one or more edge transmission lines (1-5) parallel to the boundary of the high-frequency antenna unit in the horizontal or vertical direction are connected between two adjacent transmission line branches (1-2), and the edge transmission lines have slow-wave structures for adjusting the electrical length.

9. The multi-band antenna system of claim 6, wherein: the central subunit of the dielectric unit is arranged between the two high-frequency antenna units.

10. The multi-band antenna system of claim 6, wherein: the low-frequency antenna unit (3) is arranged on a supporting part (8) in a low-frequency antenna housing (7) and forms a low-frequency antenna module with an electromagnetic medium (1) below the supporting part (8), and the high-frequency antenna unit (2) is arranged in a high-frequency antenna housing (10) and forms a high-frequency antenna module with a reflecting plate (11) below the high-frequency antenna housing.

11. The multiple-band antenna system of claim 10, wherein: the high-frequency antenna module is an active module, and the low-frequency antenna module is a passive module.

12. The multi-band antenna system of claim 11, wherein: there are a plurality of pairs of low-frequency and high-frequency antenna modules, between each pair of low-frequency and high-frequency antenna modules there being an electromagnetic medium (1) adapted to its operating frequency band.