阅读说明：本技术 天线、多频带天线、和安装天线的方法 (Antenna, multiband antenna, and method of mounting antenna ) 是由 陈长富 陈海燕 郭鹏斐 吴润苗 于 2020-06-01 设计创作，主要内容包括：本发明涉及一种天线,包括：反射器,包括前侧,所述前侧包括第一区域和不与所述第一区域重叠的第二区域；第一列辐射元件,包括至少一个第一辐射元件,所述第一辐射元件位于所述反射器的前侧并被配置为发出第一频带内的电磁辐射,所述第一列辐射元件被安装以从所述第一区域向前延伸；以及降反射部件,在前方被安装在所述第二区域,其中,所述降反射部件被配置为被所述降反射部件反射的所述第一频带内的电磁辐射弱于被所述反射器的第一区域反射的所述第一频带内的电磁辐射。本发明还涉及多频带天线和安装天线的方法。(The invention relates to an antenna comprising: a reflector comprising a front side comprising a first region and a second region that does not overlap the first region; a first column of radiating elements including at least one first radiating element located on a front side of the reflector and configured to emit electromagnetic radiation within a first frequency band, the first column of radiating elements mounted to extend forward from the first region; and a retro-reflective component mounted in the second region in front, wherein the retro-reflective component is configured to reflect electromagnetic radiation within the first frequency band that is weaker than electromagnetic radiation within the first frequency band that is reflected by the first region of the reflector. The invention also relates to a multiband antenna and a method of mounting an antenna.)

1. An antenna, comprising:

a reflector comprising a front side comprising a first region and a second region that does not overlap the first region;

a first column of radiating elements including at least one first radiating element located on a front side of the reflector and configured to emit electromagnetic radiation within a first frequency band, the first column of radiating elements mounted to extend forward from the first region; and

a reflection reducing member installed in front of the second region,

wherein the retro-reflective component is configured to reflect electromagnetic radiation in the first frequency band that is weaker than electromagnetic radiation in the first frequency band that is reflected by the first region of the reflector.

2. The antenna of claim 1, wherein the down-reflecting component comprises an absorbing material for electromagnetic radiation within the first frequency band.

3. An antenna according to claim 1, wherein a first impedance of the retro-reflective member in the first frequency band is higher than a second impedance of the first region of the reflector in the first frequency band, such that electromagnetic radiation in the first frequency band excites a weaker surface current in the retro-reflective member than in the first region of the reflector.

4. The antenna of claim 1,

the first region has a first boundary extending in a longitudinal direction of the antenna, a lateral distance between the first boundary and a phase center of the at least one first radiating element is 0.3-0.6 times a wavelength corresponding to a center frequency of the first frequency band, and

the second region extends laterally from the first boundary away from the first region.

5. The antenna of claim 1,

the first region has a first boundary extending along a longitudinal direction of the antenna, a lateral distance between the first boundary and a phase center of the at least one first radiating element is 0.2-0.3 times a wavelength corresponding to a center frequency of the first frequency band,

the second region extends laterally from the first boundary away from the first region, an

The antenna also includes a conductive element located at the first boundary extending forward from the reflector.

6. The antenna of claim 1, wherein the length of the second region is the same as the length of the first region.

7. A multi-band antenna comprising:

a reflector;

a first array of radiating elements configured to emit electromagnetic radiation within a first frequency band;

a second array of radiating elements configured to emit electromagnetic radiation within a second frequency band; and

a retro-reflective component covering a first portion of the front surface of the reflector, the retro-reflective component configured to reduce reflection of electromagnetic radiation within the first frequency band by the first portion and to substantially not reduce reflection of electromagnetic radiation within the second frequency band by the first portion,

wherein, in a front view of the antenna, a first region in which the first array of radiating elements extends is adjacent to a second region in which the second array of radiating elements extends, and a third region in which the retro-reflective component extends overlaps the second region and does not overlap the first region.

8. A multi-band antenna comprising:

a reflector;

a first array of radiating elements configured to emit electromagnetic radiation within a first frequency band;

a second array of radiating elements configured to emit electromagnetic radiation within a second frequency band; and

a retro-reflective component positioned on a front surface of the reflector and covering a first portion of the reflector, the retro-reflective component configured to attenuate electromagnetic radiation within the first frequency band reflected by the first portion and to substantially not attenuate electromagnetic radiation within the second frequency band reflected by the first portion,

wherein, in a front view of the antenna, a first area over which the first array of radiating elements extends overlaps a second area over which the second array of radiating elements extends, and a third area over which the retro-reflective component extends overlaps the second area and does not overlap the first area.

9. A method of mounting an antenna configured to produce an antenna beam formed by electromagnetic radiation within a first frequency band, the method comprising:

a reflection reducing member is mounted on a portion of a mounting surface for the antenna, which is close to a side portion of the antenna, wherein,

the mounting surface is capable of reflecting electromagnetic radiation within the first frequency band, an

The retro-reflective component is configured to reduce reflection of electromagnetic radiation within the first frequency band by the mounting surface.

10. A multi-band antenna comprising:

a reflector;

an array of first radiating elements configured to emit electromagnetic radiation within a first frequency band;

an array of second radiating elements configured to emit electromagnetic radiation within a second frequency band different from the first frequency band; and

a retro-reflective component positioned forward of the reflector, the retro-reflective component configured to reduce reflection of incident electromagnetic radiation within the first frequency band more than reflection of incident electromagnetic radiation within the second frequency band.

Technical Field

The present invention relates to communication systems, and more particularly, to an antenna, a multiband antenna, and a method of mounting an antenna.

Background

Beamforming antennas are typically implemented as phased arrays of radiating elements. The size of the radiating elements, and the distance between adjacent radiating elements, is generally proportional to the operating frequency of the signals transmitted and received by the radiating elements, with higher operating frequencies corresponding to smaller radiating elements and smaller spacing between adjacent radiating elements. A multi-band antenna may include multiple arrays of radiating elements, and different arrays of radiating elements may have different operating frequency bands.

Fig. 1A and 1B are schematic diagrams of a conventional multiband antenna assembly 100. The multiband antenna assembly 100 includes a reflector 160, and the reflector 160 may include a metal surface that serves as a ground plane and reflects electromagnetic radiation that reaches the reflector, which may be redirected, e.g., to propagate forward. The antenna assembly 100 may also include additional mechanical and electrical components disposed behind the reflector 160, such as one or more of connectors, cables, phase shifters, Remote Electronic Tilt (RET) units, duplexers, and the like. The antenna including the antenna assembly 100 may be mounted on a raised structure for operation, such as an antenna tower, utility pole, building, water tower, etc., such that the reflector 160 of the antenna extends generally perpendicular to the ground. The antenna also typically includes a radome (not shown) that provides environmental protection.

The antenna assembly 100 further includes an array of radiating elements 110, an array of radiating elements 120, and an array of radiating elements 130 disposed on a front side of the reflector 160. In some embodiments, some or all of the radiating elements may be dual polarized radiating elements configured to radiate in two different polarizations. In the illustrated embodiment, the operating band of the radiating element 110 may be, for example, 3.1-4.2 GHz or a sub-band thereof. The operating band of the radiating element 120 may be, for example, 1695 to 2690MHz or a sub-band thereof. The operating band of the radiating element 130 may be, for example, 694-960 MHz or a sub-band thereof. Each radiating element 120 includes a respective director 121 to tune the radiation pattern of the array of radiating elements 120 and/or improve its return loss. The array of radiating elements 120 comprises two vertically extending linear arrays that are horizontally adjacent to each other. Depending on the way the radiating elements 120 are fed, the two linear arrays may be configured to form two separate antenna beams (at each polarization) or may be configured to form a single antenna beam (at each polarization). An array of vertically extending radiating elements 110 and 130, respectively, is disposed between the two linear arrays of radiating elements 120. The radiating elements 130 are horizontally staggered on either side of the vertical central axis of the array of radiating elements 130, slightly off that axis, in order to obtain a narrower antenna beam in the azimuth plane.

Disclosure of Invention

It is an object of the present invention to provide an antenna, a multiband antenna, and a method of mounting an antenna.

According to a first aspect of the present invention, there is provided an antenna comprising: a reflector comprising a front side comprising a first region and a second region that does not overlap the first region; a first column of radiating elements including at least one first radiating element located on a front side of the reflector and configured to emit electromagnetic radiation within a first frequency band, the first column of radiating elements mounted to extend forward from the first region; and a retro-reflective component mounted in the second region in front, wherein the retro-reflective component is configured to reflect electromagnetic radiation within the first frequency band that is weaker than electromagnetic radiation within the first frequency band that is reflected by the first region of the reflector.

According to a second aspect of the present invention, there is provided a multiband antenna comprising: a reflector; a first array of radiating elements configured to emit electromagnetic radiation within a first frequency band; a second array of radiating elements configured to emit electromagnetic radiation within a second frequency band; and a retro-reflective component covering a first portion of the front surface of the reflector, the retro-reflective component configured to reduce reflection of electromagnetic radiation within the first frequency band by the first portion and to substantially not reduce reflection of electromagnetic radiation within the second frequency band by the first portion, wherein, in a front view of the antenna, a first area over which the first array of radiating elements extends is adjacent to a second area over which the second array of radiating elements extends, and a third area over which the retro-reflective component extends overlaps the second area and does not overlap the first area.

According to a third aspect of the present invention, there is provided a multiband antenna comprising: a reflector; a first array of radiating elements configured to emit electromagnetic radiation within a first frequency band; a second array of radiating elements configured to emit electromagnetic radiation within a second frequency band; and a retro-reflective component located at a front surface of the reflector and covering a first portion of the reflector, the retro-reflective component configured to attenuate electromagnetic radiation within the first frequency band reflected by the first portion and to substantially not attenuate electromagnetic radiation within the second frequency band reflected by the first portion, wherein, in a front view of the antenna, a first area over which the first array of radiating elements extends overlaps a second area over which the second array of radiating elements extends, and a third area over which the retro-reflective component extends overlaps the second area and does not overlap the first area.

According to a fourth aspect of the present invention, there is provided a method of mounting an antenna configured to generate an antenna beam formed by electromagnetic radiation within a first frequency band, the method comprising: mounting a retro-reflective component on a mounting surface of the antenna and on a side of the antenna, wherein the mounting surface is capable of reflecting electromagnetic radiation within the first frequency band, and the retro-reflective component is configured to reduce reflection of electromagnetic radiation within the first frequency band by the mounting surface.

According to a fifth aspect of the present invention, there is provided a multiband antenna comprising: a reflector; an array of first radiating elements configured to emit electromagnetic radiation within a first frequency band; an array of second radiating elements configured to emit electromagnetic radiation within a second frequency band different from the first frequency band; and a retro-reflective component positioned forward of the reflector, the retro-reflective component configured to reduce reflection of incident electromagnetic radiation within the first frequency band more than reflection of incident electromagnetic radiation within the second frequency band.

Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.

Fig. 1A is a front view of a prior art multiband antenna assembly.

Fig. 1B is a bottom view of the multiband antenna assembly of fig. 1A with the directors for the radiating elements removed.

Fig. 2A is a bottom view of an antenna model used to test radiation patterns in one simulation.

Fig. 2B is a plot of simulated radiation patterns as a function of azimuth for the antenna model of fig. 2A.

Fig. 2C is a bottom view of an antenna model used to test radiation patterns in yet another simulation.

Fig. 2D is a plot of simulated radiation patterns as a function of azimuth for the antenna model of fig. 2C.

Fig. 2E is a bottom view of an antenna model used to test radiation patterns in yet another simulation.

Fig. 2F is a plot of simulated radiation patterns as a function of azimuth for the antenna model of fig. 2E.

Fig. 3A is a schematic diagram of how electromagnetic radiation generated by the antenna model of fig. 2A is reflected by a radome.

Fig. 3B is a schematic diagram of how the electromagnetic radiation generated by the antenna model of fig. 2E is reflected by the radome.

Fig. 3C is a schematic diagram of how electromagnetic radiation generated by an antenna according to one embodiment of the present invention is reflected by a radome.

Figure 4 is a front view of a multiband antenna assembly according to one embodiment of the invention.

Fig. 5A-5E are simplified front views of multi-band antenna assemblies according to further embodiments of the present invention.

Fig. 6A is a perspective view of at least a portion of a reflection reducing member in an antenna according to one embodiment of the present invention.

Fig. 6B is a simplified side view of the reflection reducing component of fig. 6A.

Fig. 6C is a front view of at least a portion of a reflection reducing component in an antenna according to yet another embodiment of the present invention.

Fig. 6D is a simplified side view of the reflection reducing component of fig. 6C.

Fig. 7 is a simplified front view of at least a portion of a reflection reducing component in an antenna according to yet another embodiment of the present invention.

Fig. 8A to 8C are plots of simulated radiation patterns as a function of azimuth for an antenna comprising a radome at frequencies 3.1GHz, 3.6GHz and 4GHz, respectively, where curves C1, C3, C5 are the radiation patterns produced by an array of radiating elements in an antenna comprising the antenna assembly shown in fig. 1A, and curves C2, C4, C6 are the radiation patterns produced by an array of radiating elements in an antenna comprising the antenna assembly shown in fig. 4.

Fig. 9A is a plot of simulated radiation pattern as a function of azimuth for an antenna including a radome at frequency 806MHz, where curve C7 is the radiation pattern produced by the array of radiating elements in the antenna including the antenna assembly shown in fig. 1A, and curve C8 is the radiation pattern produced by the array of radiating elements in the antenna including the antenna assembly shown in fig. 4.

Fig. 9B is a plot of a simulated radiation pattern at a frequency of 1.695GHz versus azimuth for an antenna including a radome, where curve C9 is the radiation pattern produced by the array of radiating elements in the antenna including the antenna assembly shown in fig. 1A, and curve C10 is the radiation pattern produced by the array of radiating elements in the antenna including the antenna assembly shown in fig. 4.

Note that in the embodiments described below, the same reference numerals are used in common between different drawings to denote the same portions or portions having the same functions, and a repetitive description thereof will be omitted. In some cases, similar reference numbers and letters are used to denote similar items, and thus, once an item is defined in one figure, it need not be discussed further in subsequent figures.

For convenience of understanding, the positions, sizes, ranges, and the like of the respective structures shown in the drawings and the like do not sometimes indicate actual positions, sizes, ranges, and the like. Therefore, the present invention is not limited to the positions, dimensions, ranges, and the like disclosed in the drawings and the like.

Detailed Description

The present invention will now be described with reference to the accompanying drawings, which illustrate several embodiments of the invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, the embodiments described below are intended to provide a more complete disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art. It is also to be understood that the embodiments disclosed herein can be combined in various ways to provide further additional embodiments.

It is understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention. All terms (including technical and scientific terms) used herein have the meaning commonly understood by one of ordinary skill in the art unless otherwise defined. Well-known functions or constructions may not be described in detail for brevity and/or clarity.

When an element is referred to herein as being "on," attached to, "" connected to, "coupled to," or "contacting" another element, etc., it can be directly on, attached to, connected to, coupled to or contacting the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly on," "directly attached to," directly connected to, "directly coupled to," or "directly contacting" another element, there are no intervening elements present. In this context, one feature being disposed "adjacent" another feature may refer to one feature having a portion that overlaps or is above or below the adjacent feature.

In this document, reference may be made to elements or nodes or features being "connected" together. Unless expressly stated otherwise, "connected" means that one element/node/feature may be mechanically, electrically, logically, or otherwise joined to another element/node/feature in a direct or indirect manner to allow for interaction, even though the two features may not be directly connected. That is, "connected" is intended to include both direct and indirect joining of elements or other features, including joining using one or more intermediate elements.

In this document, spatial relationship terms such as "upper", "lower", "left", "right", "front", "back", "high", "low", and the like may describe one feature's relationship to another feature in the drawings. It will be understood that the terms "spatially relative" encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, features originally described as "below" other features may be described as "above" other features when the device in the figures is inverted. The device may also be otherwise oriented (rotated 90 degrees or at other orientations) and the relative spatial relationships may be interpreted accordingly.

Herein, the term "a or B" includes "a and B" and "a or B" rather than exclusively including only "a" or only "B" unless otherwise specifically stated.

In this document, the term "exemplary" means "serving as an example, instance, or illustration," and not as a "model" that is to be reproduced exactly. Any implementation exemplarily described herein is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the detailed description.

In this document, the term "substantially" is intended to encompass any minor variations due to design or manufacturing imperfections, tolerances of the devices or components, environmental influences and/or other factors. The term "substantially" also allows for differences from a perfect or ideal situation due to parasitics, noise, and other practical considerations that may exist in a practical implementation.

In addition, "first," "second," and like terms may also be used herein for reference purposes only, and thus are not intended to be limiting. For example, the terms "first," "second," and other such numerical terms referring to structures or elements do not imply a sequence or order unless clearly indicated by the context.

It will be further understood that the terms "comprises/comprising," "includes" and/or "including," when used herein, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, and/or components, and/or groups thereof.

The radiation pattern produced by the array of radiating elements 110 of the antenna assembly 100 of fig. 1A and 1B may be distorted when the antenna assembly 100 is inserted into a radome to form an antenna. Such distortion may occur, for example, at and/or near the boresight (boresight) pointing direction of the array of radiating elements 110, as illustrated by curves C1, C3, C5 in fig. 8A through 8C. In a simulation experiment, the inventors removed all the elements (including the radiating elements 120 and 130 and parasitic elements for the radiating elements, etc.) of the antenna assembly 100, except the array of the radiating elements 110, located at the front side of the reflector 160, resulting in the antenna model 210 for simulation shown in fig. 2A. The antenna model 210 includes a reflector 211 similar to the reflector 160 in the antenna assembly 100, an array of radiating elements 213 similar to the array of radiating elements 110, and a radome 212. The simulation results of the radiation pattern produced by the array of radiating elements 213 in the antenna model 210 are shown in fig. 2B, where the three curves are the intensity of the radiation pattern as a function of azimuth angle at three frequencies, 3.1GHz, 3.6GHz, and 4GHz, respectively. It can be seen that the radiation pattern of the array of radiating elements 213 in the antenna model 210 is also distorted at and/or near the boresight pointing direction, similar to the radiation pattern produced by the array of radiating elements 110 in the antenna (including the radome) comprising the antenna assembly 100.

In yet another simulation experiment, the inventors removed the radome 212 from the antenna model 210, resulting in the antenna model 220 for simulation shown in fig. 2C. The antenna model 220 includes a reflector 221, similar to the reflector 160 in the antenna assembly 100, and an array of radiating elements 223, similar to the array of radiating elements 110. The simulation results of the radiation pattern produced by the array of radiating elements 223 in the antenna model 220 are shown in fig. 2D, where the three curves are the intensity of the radiation pattern as a function of azimuth angle at three frequencies, 3.1GHz, 3.6GHz, and 4GHz, respectively. It can be seen that unlike the radiation pattern of the array of radiating elements 110 in the antenna (including the radome) comprising the antenna assembly 100, the radiation pattern of the array of radiating elements 223 in the antenna model 220, which does not include a radome, is not distorted near the boresight pointing direction.

Accordingly, the inventors believe that distortions in the radiation pattern of the array of radiating elements 110 in an antenna (including a radome) comprising the antenna assembly 100 may be caused by the reflection of electromagnetic radiation between the radome and the reflector. As shown in fig. 3A, the electromagnetic radiation emitted by the radiation element 33 travels forward to the radome 32, and a part of the electromagnetic radiation does not continue to radiate forward through the radome 32, but is reflected by the radome 32 so that it is redirected to travel backward (a possible path of such electromagnetic radiation is schematically shown in the figure by a dotted line, and the arrow thereon indicates the traveling direction of the electromagnetic radiation). The reflected electromagnetic radiation travels backwards at the reflector 31, is reflected by the reflector 31 such that it is redirected to travel forwards such that it is superimposed on the electromagnetic radiation subsequently emitted directly from the radiating element 33. The superimposed electromagnetic radiation will not be in phase with the subsequently emitted electromagnetic radiation and therefore may not combine constructively, resulting in distortion of the radiation pattern produced by the array of radiating elements 33.

Thus, in yet another simulation experiment, the inventors reduced the width of the reflector 211 in the antenna model 210 such that the width of the reflector is substantially the width required by the array of radiating elements 233, resulting in the antenna model 230 for simulation shown in fig. 2E. The antenna model 230 includes a reflector 231 that is significantly narrower than the reflector 211 in the antenna model 210, an array of radiating elements 233 similar to the array of radiating elements 213 in the antenna model 210, and a radome 232 similar to the radome 212 in the antenna model 210. Fig. 3B shows a similar situation as the antenna model 230. The electromagnetic radiation emitted by the array of radiating elements 33 travels forward to the radome 32, and a portion of the electromagnetic radiation is reflected by the radome 32 so that it travels backward. However, many of the reflected electromagnetic radiation does not reach the reduced width reflector 34 and is therefore not redirected by the reflector 34 and is thus not superimposed on the electromagnetic radiation directly emitted from the array of radiating elements 33. The simulation results of the radiation pattern of the array of radiating elements 233 in the antenna model 230 are shown in fig. 2F, where the three curves are the intensity of the radiation pattern as a function of azimuth angle at three frequencies, 3.1GHz, 3.6GHz, and 4GHz, respectively. It can be seen that the radiation pattern of the array of radiating elements 233 in the antenna model 230 with the narrower reflector 231 is much improved over the radiation pattern of the array of radiating elements 213 in the antenna model 210 with the wider reflector 211, although not smooth, near the boresight pointing direction of the array of radiating elements 233.

From the above simulation experiments, it can be determined that at least one reason for the distortion of the radiation pattern of the array of radiating elements 110 in the antenna assembly 100 is that the reflector 160 is too wide for the array. One solution is to narrow the reflector 160 to fit the width of the array of radiating elements 110, as shown in fig. 2E, 3B. In a multi-array antenna, the reflector serves not only one of the arrays, but all of the arrays in the multi-array antenna. For example, in the antenna assembly 100, the reflector 160 serves an array of radiating elements 120 and an array of radiating elements 130 in addition to the array of radiating elements 110. Therefore, the actual width of the reflector 160 cannot be reduced to fit the width of the array of radiating elements 110.

The antenna according to the present invention can solve the above-mentioned problems. As shown in fig. 3C, the antenna according to one embodiment of the present invention includes a reflector 31, an array of radiation elements 33, a reflection reducing member 35, and a radome 32. The array of radiating elements 33 comprises an array of radiating elements 33 extending substantially in the longitudinal direction of the reflector 31. Each radiating element 33 may include a feed/support rod extending forward from the reflector 31, and a radiating arm extending generally parallel to the reflector 31 and configured to emit electromagnetic radiation within a first frequency band. In some embodiments, each radiating element 33 may be a cross-dipole radiating element that radiates with two different polarizations. In other embodiments, other types of radiating elements may be used, such as patch radiating elements. The retro-reflective member 35 is configured such that electromagnetic radiation in the first frequency band that is reflected by the retro-reflective member 35 is weaker than electromagnetic radiation in the first frequency band that is reflected by the area of the reflector 31 covered by the retro-reflective member 35. The retro-reflective members 35 may reduce or attenuate the reflection of electromagnetic radiation within the first frequency band by at least 30% (e.g., by approximately 30%, 50%, 80%, etc.) of the area of the reflector 31 covered by the retro-reflective members 35. The down-reflecting members 35 are provided on the front surface of the reflector 31 and on the left and right sides of the array of radiating elements 33 in the front view of the antenna. Similarly to the case of the reflector 34 with a reduced width shown in fig. 3B, in this embodiment, the electromagnetic radiation emitted by the array of radiating elements 33 travels forward to the radome 32, and a portion of the electromagnetic radiation is reflected backward by the radome 32. The backward reflected electromagnetic radiation may pass to the retro-reflecting component 35 without being totally reflected to travel forward, so that the reflected electromagnetic radiation is not totally superimposed on the electromagnetic radiation directly emitted from the radiating element 33. Thus, the radiation pattern of the array of radiating elements 33 may be improved.

The first part of the reflector 31, which is not covered by the retro-reflective part 35, is an active part of the array of radiating elements 33. For an array of radiating elements, the width of the active portion of the reflector required for this may be, for example, slightly greater than the width of the array of radiating elements 33. For example, the width of the reflector (i.e., the width of the effective portion) required by a row of the radiating elements may be 0.6 to 1.2 times (the lateral distance from the phase center of the radiating element to the boundary of the effective portion is 0.3 to 0.6 times) the wavelength corresponding to the center frequency of the electromagnetic radiation emitted by the radiating element (herein, simply referred to as "center wavelength"), and is usually 0.8 to 1 times (the lateral distance from the phase center of the radiating element to the boundary of the effective portion is 0.4 to 0.5 times) the center wavelength. If the space is limited, the width of the effective portion can be reduced to 0.5 to 0.6 times the center wavelength (the distance from the phase center of the radiation element to the boundary of the effective portion is 0.25 to 0.3 times the center wavelength), and a conductor 36 (conductive element) as a parasitic element extending forward from the reflector can be added at the boundary of the effective portion to compensate for the lack of the width of the effective portion. In the embodiment shown in fig. 3C, a reflection-reducing member 35 may be provided on the front surface of the second portion of the reflector 31 except for the active portion to the array of the radiation elements 33. It is to be understood that in another embodiment, the reflection reducing member 35 may be provided only on the front surface of a third portion (e.g., the region a5 described below) of the reflector 31 near the effective portion. The retro-reflective member 35 may attenuate surface currents on the reflector 31 excited by electromagnetic radiation emitted by the radiating elements 33 such that the second portion of the reflector 31 will reflect less of the electromagnetic radiation emitted by the radiating elements 33, thereby improving the radiation pattern of the array of radiating elements 33.

In the illustrated embodiment, the down-reflecting member 35 is located on the front surface of the reflector 31. It is to be understood that in another embodiment, the retro-reflective member 35 may be located at the front side of the reflector 31 and at the rear side of the radiating arm of the radiating element 33, i.e. between the reflector 31 and the radiating arm of the radiating element 33 in the front-rear direction. In the illustrated embodiment, the down-reflecting components 35 are located on the left and right sides of the array of radiating elements 33. It will be appreciated that in another embodiment, the down-reflecting feature 35 may be provided only on one side of the array of radiating elements 33, and the radiation pattern of the array of radiating elements 33 may also be improved.

In a multi-band antenna, to reduce the effect of the down-reflecting component 35 on the array of other radiating elements included in the antenna assembly, the down-reflecting component 35 is further configured to not substantially reduce or attenuate the reflection of electromagnetic radiation in a second frequency band, different from the first frequency band, by the area of the reflector 31 covered by the down-reflecting component 35. By "substantially not reduced" or "substantially not attenuated" herein is meant not reduced or attenuated at all, and reduced or attenuated by less than or substantially equal to 5%.

In one embodiment, the retro-reflective component 35 may comprise an absorbing material for electromagnetic radiation within the first frequency band. In another embodiment, the retro-reflective member 35 may have a high impedance relative to electromagnetic radiation within the first frequency band such that electromagnetic radiation within the first frequency band excites a relatively weak surface current in the retro-reflective member 35, thereby enabling the retro-reflective member 35 to reduce reflection of electromagnetic radiation within the first frequency band by the reflector 31 itself. In this embodiment, the down-reflecting member 35 may form an Electromagnetic Bandgap (EBG) structure with the portion of the reflector 31 covered therewith. The reflectivity of the EBG structure for electromagnetic radiation in the first frequency band may be lower than the reflectivity of the reflector 31 for electromagnetic radiation in the first frequency band (in case the angles of incidence of the electromagnetic radiation in the first frequency band with respect to the EBG structure and the reflector 31 are the same). As shown in fig. 6A to 6D, the EBG structure includes a ground plane 61, a dielectric plate 62 located on the ground plane 61, and a conductor element array. The array of conductor units comprises a plurality of conductor units arranged in an array substantially equally spaced from each other, each conductor unit comprising a capacitive element 63 and an inductive element 64 electrically connected to each other such that the array of conductor units has a high impedance in the first frequency band. In the above-described embodiment, the reflector 31 may be used as the ground plane 61, and the reflection reducing member 35 may include the conductor element array and the dielectric plate at the front surface of the reflector 31.

Fig. 6A and 6B show an EBG structure. The array of conductor elements includes a plurality of "mushroom" shaped conductor elements arranged in an array. The capacitive element 63 in each conductor unit is located on the front surface of the dielectric plate 62. The inductive element 64 in each conductor unit penetrates the dielectric sheet 62 in the thickness direction of the dielectric sheet 62, and electrically connects the ground plane and the capacitive element 63 corresponding to the inductive element 64. A via may be provided through the dielectric plate 62, the dimensions of which may be much smaller than those of the capacitive element 63, and the inductive element 64 may be implemented as a conductor filled in the via, or as a metal (e.g. copper) plated on the wall of the via. Capacitors are formed between adjacent capacitive elements 63 and/or between capacitive elements 63 and the ground plane. These capacitors, in combination with the inductive element 64, form an LC circuit that can have a high impedance for the frequencies targeted, thereby suppressing surface currents within these frequencies. The conductor elements are arranged periodically in the array in order to suppress surface currents. The more conductor units are arranged periodically, the stronger the suppression of the surface current. The number of the conductor units arranged periodically is more than or equal to 5, so that an effective suppression effect can be obtained. For example, in an embodiment in which the reflection reducing member 35 is implemented as an EBG structure, the EBG structure includes 5 or more conductor units in the lateral direction (i.e., width direction) of the reflector 31 on one side of the array of the radiation elements 33.

Fig. 6C and 6D show still another EBG structure. In this EBG structure, the capacitive element 63 and the inductive element 64 in each conductor unit are located on the front surface of the dielectric plate 62. The capacitive element 63 may be implemented as a patch conductor of larger size and the inductive element 64 may be implemented as a patch conductor of much smaller size than the capacitive element 63. Capacitors are formed between adjacent capacitive elements 63, between adjacent inductive elements 64, between adjacent capacitive elements 63 and inductive elements 64, and/or between capacitive elements 63 and a ground plane, and inductive elements 64 form inductors. The number of the conductor units arranged periodically may be greater than or equal to 5 to obtain an effective surface current suppressing effect.

It should be understood that in the EBG structure shown in fig. 6C and 6D, it is also possible to have the inductive element penetrating the dielectric plate 62 as shown in fig. 6A and 6B, i.e., the conductor unit may include both the inductive element at the front surface of the dielectric plate and the inductive element penetrating the dielectric plate. It should be understood that the shapes and sizes of the capacitive and inductive elements shown in the drawings are merely illustrative and that the EBG structure may be implemented in other forms. The EBG structure can be easily manufactured using a manufacturing process of a PCB and is low in manufacturing cost.

When designing an EBG structure, equivalent capacitance and inductance values may be calculated based on the targeted frequency (which may be, for example, the center frequency of the operating band of the array of radiating elements 33), thereby determining the shape and size of the capacitive and inductive elements in the EBG structure to enable significant suppression of the EBG structure with respect to current at the targeted frequency. The relative bandwidth of the frequencies for which the EBG structure is intended (the ratio of the difference between the highest and lowest frequencies within the frequency band to the center frequency) is typically 5% to 7%, while the relative bandwidth of the radiating elements is typically large, and may be 30% to 50% (e.g., the relative bandwidth of the radiating element 110 in the antenna assembly 100 is about 30%). Therefore, if the surface current suppression is performed for the entire frequency band of the radiation element 110, the EBG structure may be applied to a wider frequency band.

Fig. 7 shows a conductor cell array in yet another EBG structure, and an EBG structure having such a conductor cell array can support a wider frequency band. The array of conductor elements includes first and second sub-arrays laterally adjacent to one another, wherein the first sub-array is configured to suppress current at frequencies within a first frequency band and the second sub-array is configured to suppress current at frequencies within a second frequency band, such that the combined array of conductor elements can be configured to suppress current at frequencies within both the first and second frequency bands. For example, in an embodiment in which the reflection reducing member 35 is implemented by an EBG structure capable of supporting a wider frequency band, at least a part of the operating frequency band of the radiation element 33 may be divided into a first sub-band and a second sub-band. In various embodiments of the present invention, the first sub-band and the second sub-band may be adjacent, spaced apart, or partially overlapping. A first sub-array of the array of conductor elements of the EBG structure has a higher impedance than the reflector 31 within the first sub-band, and a second sub-array has a higher impedance than the reflector 31 within the second sub-band. Shown in fig. 7 is a front view of a reflection reducing component 35 located to one side of the array of radiating elements 33. In the transverse direction of the reflector 31 the first sub-array comprises N conductor elements and the second sub-array comprises M conductor elements, wherein M and N are each greater than or equal to 5. The size and/or shape of the conductor elements from different sub-arrays may be different. The length of the first and second sub-arrays in the longitudinal direction of the reflector 31 (i.e. the direction of extension of the array of radiating elements 33) may be both L, where L may be greater than or substantially equal to the length of the array of radiating elements 33. It should be understood that the array of conductor elements in an EBG structure supporting a wider frequency band may include more sub-arrays for different frequency bands (sub-bands).

Figure 4 is a front view of a multiband antenna assembly 400 according to one embodiment of the invention. The multiband antenna assembly 400 includes a reflector 460, an array of radiating elements 410 having a first operating frequency band (e.g., 3.1-4.2 GHz or a sub-band thereof), an array of radiating elements 420 having a second operating frequency band (e.g., 1695-2690 MHz or a sub-band thereof), an array of radiating elements 430 having a third operating frequency band (e.g., 694-960 MHz or a sub-band thereof), and a retro-reflective component 450. The reflector 460 includes non-overlapping (when viewed from the front) regions a1 and a region a2, region a1 being located in the middle, region a2 extending from each side of region a1 away from region a1 to a respective side of the reflector 460. In the longitudinal direction of the reflector 460, the array of radiating elements 410 extends over the entire area a1, the array of radiating elements 420 extends over the entire area a2, the array of radiating elements 430 extends over the entire reflector 460, and the retro-reflective member 450 extends over the entire area a 2. The retro-reflective component 450 reduces the width of the active portion of the reflector for the array of radiating elements 410 to the width of region a 1.

Fig. 8A to 8C are graphs of simulated radiation patterns of an antenna including a radome as a function of azimuth at frequencies of 3.1GHz, 3.6GHz, and 4GHz, respectively. These three frequencies are all frequencies within the operating frequency band of the radiating element 410 (or radiating element 110). Curves C1, C3, C5 correspond to the radiation pattern of the array of radiating elements 110 in the antenna comprising the antenna assembly 100 shown in fig. 1A. Curves C2, C4, C6 correspond to the radiation pattern of the array of radiating elements 410 in the antenna comprising the antenna assembly 400 shown in fig. 4, wherein the retro-reflective component 450 is implemented as the EBG structure shown in fig. 6A and 6B for frequencies at the center frequency of the operating band 3.1-4.2 GHz, 3.65 GHz. It can be seen that the radiation pattern of the array of radiating elements 410 in the antenna assembly 400 is improved over the radiation pattern of the array of radiating elements 110 in the antenna assembly 100.

In order to test the effect of the reflection reducing component on the other arrays of radiating elements included in the antenna assembly, the inventors also simulated the radiation patterns produced by the other arrays of radiating elements. Fig. 9A and 9B show plots of the intensity of electromagnetic radiation as a function of azimuth for an antenna comprising a radome at two frequencies of 806MHz and 1.695GHz, respectively. 806MHz is the frequency within the operating band of radiating element 430 (or radiating element 130), curve C7 corresponds to the radiation pattern produced by the array of radiating elements 130 in the antenna including antenna assembly 100 shown in fig. 1A, and curve C8 corresponds to the radiation pattern produced by the array of radiating elements 430 in the antenna including antenna assembly 400 shown in fig. 4. The 1.695GHz is the frequency within the operating band of radiating element 420 (or radiating element 120), curve C9 corresponds to the radiation pattern produced by the array of radiating elements 120 in the antenna including antenna assembly 100 shown in fig. 1A, and curve C10 corresponds to the radiation pattern produced by the array of radiating elements 420 in the antenna including antenna assembly 400 shown in fig. 4. In the antenna assembly 400, the down-reflecting component 450 is implemented as an EBG structure shown in FIGS. 6A and 6B for a frequency of 3.65GHz, the center frequency of the operating band 3.1-4.2 GHz. It can be seen that the reflection reducing component 450 for the array of radiating elements 410 in the antenna assembly 400 has little effect on the radiation pattern of the other array of radiating elements (i.e., the array of radiating elements 420, 430).

In some embodiments, the retro-reflective member 450 may not extend within the entire area a 2. A retro-reflective member 450 may be disposed in a portion of region a2 proximate to region a1 to break/attenuate surface currents on reflector 460 excited by electromagnetic radiation emitted by radiating elements 410, thereby improving the radiation pattern of the array of radiating elements 410. Fig. 5A shows a multiband antenna assembly 500. The antenna assembly 500 includes a reflector 540, an array of radiating elements 510 to 530, and a reflection reducing component 550. The reflector 540 includes a region a5, and a region a1 and a region a2 that do not overlap with each other. Region a1 is centrally located, regions a2 and a5 extend from each side of region a1 away from region a1, respectively, region a2 extends to each side of reflector 540, and region a5 extends laterally less far than region a2, i.e., region a5 partially overlaps region a2 at a region a1 adjacent to region a 2. The array of radiating elements 510 extends over the entire area a1, the array of radiating elements 520 extends over the entire area a2, the array of radiating elements 530 extends over the entire reflector 540, and the retro-reflective component 550 extends over the entire area a 5.

In one embodiment, a multi-band antenna may include only two arrays having respective operating frequency bands. Fig. 5B shows a multiband antenna assembly 501. The antenna assembly 501 includes a reflector 540, an array of radiating elements 510 and 520, and a reflection reducing component 550. In antenna assembly 501, reflector 540 includes regions a1, a2, and a5 similar to those in antenna assembly 500. The array of radiating elements 510 extends over the entire area a1, the array of radiating elements 520 extends over the entire area a2, and the retro-reflective component 550 extends over the entire area a 5.

In one embodiment, the extended area of the retro-reflective component for the array of target radiating elements may not overlap with the extended areas of the other arrays of radiating elements. Fig. 5C shows a multiband antenna assembly 502. The antenna assembly 502 includes a reflector 540, an array of radiating elements 510 and 520, and a reflection reducing component 550. The reflector 540 includes regions a1, a2, and a5 that do not overlap with one another. Region a1 is located in the middle, region a5 extends from the side of region a1 in a direction away from region a1, and region a2 extends from the side of region a5 away from region a1 in a direction away from region a5 to the side of reflector 540. The array of radiating elements 510 extends over the entire area a1, the array of radiating elements 520 extends over the entire area a2, and the retro-reflective component 550 extends over the entire area a 5.

In one embodiment, the array of target radiating elements may not be located in the middle of the antenna assembly. Fig. 5D shows a multiband antenna assembly 503. The antenna assembly 503 includes a reflector 540, an array of radiating elements 510 and 520, and a reflection reducing component 550. The reflector 540 includes regions a1 and a2, which do not overlap with each other, and a 5. Region a2 is located in the middle of the reflector, and region a1 extends from each side of region a2 away from region a2 to the corresponding side of reflector 540. Each portion of region a5 may extend a lateral distance substantially equal to one-half or less of the lateral width of the corresponding portion of region a2 (not shown). The array of radiating elements 510 extends over the entire area a1, the array of radiating elements 520 extends over the entire area a2, and the retro-reflective component 550 extends over the entire area a 5.

In one embodiment, the area over which the array of radiating elements of the target extends may overlap with the area over which other arrays of radiating elements extend. Fig. 5E shows the multiband antenna assembly 504. The antenna assembly 504 includes a reflector 540, an array of radiating elements 510 and 530, and a reflection reducing component 550. The reflector 540 includes regions a1 and a5, which do not overlap with each other, and A3. The region a1 is located in the middle of the reflector 540, and the region a5 extends a predetermined distance from each side of the region a1 in a direction away from the region a1 but does not extend all the way to the corresponding side of the reflector 540. The area a3 extends across the entire reflector 540. The array of radiating elements 510 extends throughout the area a1, the array of radiating elements 530 extends throughout the area A3, and the retro-reflective component 550 extends throughout the area a 5.

In addition, the invention also provides a method for mounting the antenna. The antenna may also present problems addressed by the present invention when mounted on a large mounting surface capable of reflecting electromagnetic radiation, such as a metal surface of a vehicle roof, aircraft, etc., which may at least partially act as a reflector. In this case, the above-described reflection reducing member may be applied on the mounting surface. The method for mounting the antenna comprises the following steps: a reflection reducing member is mounted on a mounting surface of the antenna and on a side portion of the antenna. For convenience, beauty, cost, and the like, the down-reflecting member may be applied only to a portion of the mounting surface close to the antenna, that is, the down-reflecting member is mounted such that the down-reflecting member extends from a side portion of the antenna to a direction away from the antenna by a predetermined distance.

In addition, embodiments of the present invention may also include the following examples:

1. an antenna, comprising:

a reflector comprising a front side comprising a first region and a second region that does not overlap the first region;

a first column of radiating elements including at least one first radiating element located on a front side of the reflector and configured to emit electromagnetic radiation within a first frequency band, the first column of radiating elements mounted to extend forward from the first region; and

a reflection reducing member installed in front of the second region,

wherein the retro-reflective component is configured to reflect electromagnetic radiation in the first frequency band that is weaker than electromagnetic radiation in the first frequency band that is reflected by the first region of the reflector.

2. The antenna of claim 1, wherein the down-reflecting component comprises an absorbing material for electromagnetic radiation within the first frequency band.

3. The antenna of claim 1, wherein a first impedance of the retro-reflective member in the first frequency band is higher than a second impedance of the first region of the reflector in the first frequency band, such that electromagnetic radiation in the first frequency band excites a surface current in the retro-reflective member that is weaker than a surface current excited in the first region of the reflector.

4. The antenna of claim 1, wherein the antenna is further characterized,

the first region has a first boundary extending in a longitudinal direction of the antenna, a lateral distance between the first boundary and a phase center of the at least one first radiating element is 0.3-0.6 times a wavelength corresponding to a center frequency of the first frequency band, and

the second region extends laterally from the first boundary away from the first region.

5. The antenna of claim 1, wherein the antenna is further characterized,

the first region has a first boundary extending along a longitudinal direction of the antenna, a lateral distance between the first boundary and a phase center of the at least one first radiating element is 0.2-0.3 times a wavelength corresponding to a center frequency of the first frequency band,

the second region extends laterally from the first boundary away from the first region, an

The antenna also includes a conductive element located at the first boundary extending forward from the reflector.

6. The antenna of claim 1, wherein the length of the second region is the same as the length of the first region.

7. The antenna of claim 1, wherein the second region extends the entire length of the reflector.

8. The antenna of claim 1, wherein the front side of the reflector further comprises a third region, the antenna further comprising:

a second column of radiating elements comprising at least one second radiating element configured to emit electromagnetic radiation within a second frequency band, the second column of radiating elements mounted to extend forward from the third region of the front side of the reflector and adjacent to the first column of radiating elements,

wherein the second region is non-overlapping with the third region and the second region is located between the first region and the third region.

9. The antenna of claim 1, wherein the front side of the reflector further comprises a third region, the antenna further comprising:

a second column of radiating elements comprising at least one second radiating element configured to emit electromagnetic radiation within a second frequency band, the second column of radiating elements mounted to extend forward from the third region of the front side of the reflector and adjacent to the first column of radiating elements, wherein the second region overlaps the third region and is adjacent to the first column of radiating elements

The retro-reflective member is further configured to reflect electromagnetic radiation within the second frequency band substantially the same as a third region of the reflector.

10. The antenna of claim 3, wherein the reflection reducing member and the second region form an electromagnetic bandgap structure.

11. The antenna of claim 10, wherein the reflection reducing member comprises:

an array of conductor units comprising a plurality of conductor units arranged in an array substantially equally spaced from each other, each conductor unit comprising a capacitive element and an inductive element electrically connected to each other such that the array of conductor units has a higher impedance in the first frequency band than the first region of the reflector.

12. The antenna of claim 11, wherein the reflection reducing member further comprises a dielectric plate positioned at a front side of the reflector, wherein,

the reflector provides a ground plane that is,

the capacitive element of each conductor unit is located on the front surface of the dielectric plate, an

The inductive element of each conductor unit penetrates through the dielectric plate in the thickness direction of the dielectric plate and electrically connects the reflector and the capacitive element corresponding to the inductive element.

13. The antenna of claim 11, wherein the reflection reducing member further comprises a dielectric plate positioned at a front side of the reflector, wherein,

the reflector provides a ground plane, an

The capacitive element and the inductive element of each conductor unit are located on the front surface of the dielectric plate.

14. The antenna of claim 11, wherein the array of conductor elements comprises at least 5 conductor elements in a transverse direction perpendicular to a longitudinal direction of the antenna.

15. The antenna of claim 11, wherein the array of conductor elements comprises first and second sub-arrays, the first frequency band comprising first and second sub-bands, wherein,

the first sub-array has a higher impedance within the first sub-band than the first region of the reflector,

the second sub-array has a higher impedance within the second sub-band than the first area of the reflector, an

The first and second sub-arrays are adjacent in a lateral direction perpendicular to a longitudinal direction of the antenna.

16. The antenna of claim 15, wherein each of the first and second sub-arrays includes at least 5 conductor elements in the lateral direction.

17. A multi-band antenna comprising:

a reflector;

a first array of radiating elements configured to emit electromagnetic radiation within a first frequency band;

a second array of radiating elements configured to emit electromagnetic radiation within a second frequency band; and

a retro-reflective component covering a first portion of the front surface of the reflector, the retro-reflective component configured to reduce reflection of electromagnetic radiation within the first frequency band by the first portion and to substantially not reduce reflection of electromagnetic radiation within the second frequency band by the first portion,

wherein, in a front view of the antenna, a first region in which the first array of radiating elements extends is adjacent to a second region in which the second array of radiating elements extends, and a third region in which the retro-reflective component extends overlaps the second region and does not overlap the first region.

18. The antenna according to claim 17, wherein the third region overlaps the second region at a portion of the second region close to the first region in a front view of the antenna.

19. The antenna of claim 17, wherein the first region includes first and second opposing borders, wherein the second region includes first and second subregions, wherein the third region includes first and second subregions, wherein the first subregion of the second region and the first subregion of the third region each extend from the first border in a direction away from the first region, and wherein the second subregion of the second region and the second subregion of the third region each extend from the second border in a direction away from the first region.

20. The antenna of claim 19, wherein the first sub-region of the third region and the second sub-region of the third region extend a distance less than the distance that the first sub-region of the second region and the second sub-region of the second region extend, respectively.

21. The antenna of claim 17, wherein the reflection reducing member and the first portion form an electromagnetic bandgap structure.

22. A multi-band antenna comprising:

a reflector;

a first array of radiating elements configured to emit electromagnetic radiation within a first frequency band;

a second array of radiating elements configured to emit electromagnetic radiation within a second frequency band; and

a retro-reflective component positioned on a front surface of the reflector and covering a first portion of the reflector, the retro-reflective component configured to attenuate electromagnetic radiation within the first frequency band reflected by the first portion and to substantially not attenuate electromagnetic radiation within the second frequency band reflected by the first portion,

wherein, in a front view of the antenna, a first area over which the first array of radiating elements extends overlaps a second area over which the second array of radiating elements extends, and a third area over which the retro-reflective component extends overlaps the second area and does not overlap the first area.

23. The antenna of claim 22, wherein the antenna further comprises,

at least one frequency in the second frequency band being lower than each frequency in the first frequency band, an

In a front view of the antenna, the first region is located at a middle portion of the second region, and the third region is located at an edge portion of the second region.

24. The antenna of claim 22, wherein the reflection reducing member and the first portion form an electromagnetic bandgap structure.

25. A method of mounting an antenna configured to produce an antenna beam formed by electromagnetic radiation within a first frequency band, the method comprising:

a reflection reducing member is mounted on a portion of a mounting surface for the antenna, which is close to a side portion of the antenna, wherein,

the mounting surface is capable of reflecting electromagnetic radiation within the first frequency band, an

The retro-reflective component is configured to reduce reflection of electromagnetic radiation within the first frequency band by the mounting surface.

26. The method of claim 25, further comprising: the reflection reducing member is installed such that the reflection reducing member extends a predetermined distance from a side portion of the antenna in a direction away from the antenna.

27. The method of claim 25, wherein the down-reflecting component comprises an absorbing material for electromagnetic radiation within the first frequency band.

28. The method of claim 25, wherein the down-reflecting feature forms an electromagnetic bandgap structure with the portion of the mounting surface covered by the down-reflecting feature.

29. A multi-band antenna comprising:

a reflector;

an array of first radiating elements configured to emit electromagnetic radiation within a first frequency band;

an array of second radiating elements configured to emit electromagnetic radiation within a second frequency band different from the first frequency band; and

a retro-reflective component positioned forward of the reflector, the retro-reflective component configured to reduce reflection of incident electromagnetic radiation within the first frequency band more than reflection of incident electromagnetic radiation within the second frequency band.

30. The antenna of claim 29, wherein the reflection reducing components are positioned on either side of the array of first radiating elements.

31. The antenna of claim 29 or 30, wherein the reflection reducing component is not located behind the array of first radiating elements.

32. The antenna according to any one of claims 29 to 31, wherein the reflection reducing member comprises a plurality of conductor units arranged in an array, each conductor unit comprising a capacitive element and an inductive element electrically connected to each other.

33. The antenna of claim 32 wherein a first impedance of the array conductor elements in the first frequency band is higher than a second impedance of the array conductor elements in the second frequency band.

34. The antenna of claim 32 wherein a first impedance of the array conductor elements within the first frequency band is higher than a second impedance of a portion of the reflector that is not behind the retro-reflective component.

Although some specific embodiments of the present invention have been described in detail by way of illustration, it should be understood by those skilled in the art that the above illustration is only for the purpose of illustration and is not intended to limit the scope of the invention. The various embodiments disclosed herein may be combined in any combination without departing from the spirit and scope of the present invention. It will also be appreciated by those skilled in the art that various modifications may be made to the embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.