CN109075436B

CN109075436B - Ultra-wideband dual-polarized radiating element for base station antenna

Info

Publication number: CN109075436B
Application number: CN201780023220.8A
Authority: CN
Inventors: 胡安·司伽德尔阿尔瓦雷斯; 伊格纳西欧·冈萨雷斯; 唐涛; 布鲁诺·比斯孔蒂尼
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2016-04-12
Filing date: 2017-04-12
Publication date: 2021-06-08
Anticipated expiration: 2037-04-12
Also published as: EP3813192B1; WO2017177927A1; CN109075436A; EP3813192A1; EP3232504A1; EP3232504B1

Abstract

The invention relates to a radiating element for a base station antenna, said radiating element comprising: -a support structure, -at least one pair of dipole arms in a first layer of the support structure, and-at least two parasitic arms in a second layer of the support structure, wherein the distance between the first and second layers is between 0.0004 and 0.1, preferably between 0.002 and 0.02, of the minimum wavelength of the operating band of the radiating element, wherein the area of the perpendicular projection of the parasitic arms from the second layer to the first layer covers at least 60% of the area of the at least one pair of dipole arms.

Description

Ultra-wideband dual-polarized radiating element for base station antenna

Technical Field

The invention relates to a radiating element for a base station antenna, a dual-band radiating structure and a base station antenna.

Background

Ultra-wideband base station antenna systems typically operate over the frequency spectrum of 690-960MHz ("low band" -LB), 1.427-2.4GHz ("mid-band" -MB) and 1.7-2.7GHz ("high band" -HB), which includes most of the cellular network frequency bands in use today. With the increasing demand for deep integration of radio antennas, such as Active Antenna Systems (AAS), new methods for designing ultra-compact ultra-wideband multi-array base station antenna architectures by reducing the depth are required without compromising on the antenna's key points.

For these architectures, multiple LBs, MBs and HBs coexist. However, this coexistence becomes more challenging when trying to reduce the overall antenna geometry (compact design) and maintain RF critical performance. Among many other technical design strategies, one of the key points is the design of the radiating elements for LB, MB, and HB. Ideally, they should be electrically invisible to each other. From this point of view, the physical size of the radiating element is one of the main factors.

In a typical scenario, the MB frequency range (1.427GHz-2.4GHz) is about twice the LB frequency range (690-960MHz), so a dipole designed to operate in MB may resonate and behave like a monopole in LB, producing undesirable effects and degrading the performance of the antenna in the LB band.

If the resonant behavior of the MB dipole is not moved outside the LB band, some undesirable consequences such as spikes and isolation in return loss, phase discontinuities, radiation pattern perturbations, gain drop, etc. may occur due to in-band resonance.

Therefore, there is a need for a radiating element that provides broadband characteristics while having a low profile and being invisible to other frequency bands that coexist in the antenna.

Disclosure of Invention

It is an object of the present invention to provide a radiating element for a base station antenna, a dual band radiating structure and a base station antenna that overcome one or more of the above-mentioned problems of the prior art.

A first aspect of the present invention provides a radiating element for a base station antenna, the radiating element comprising: -a support structure, -at least one pair of dipole arms in a first layer of the support structure, and-at least two parasitic arms in a second layer of the support structure, wherein the distance between the first layer and the second layer is between 0.0004 and 0.1, preferably between 0.002 and 0.02, of the minimum wavelength of the operating band of the radiating element, wherein the area of the perpendicular projection of the parasitic arms from the second layer to the first layer covers at least 60% of the area of the at least one pair of dipole arms. Arranging the parasitic arms formed of a conductive material at a determined distance from the dipole arms has the technical effect of: the total length of the dipole arms may be reduced for a given operating frequency. The overall size of the radiating element in the direction of the dipole arms is thus reduced with respect to prior art devices. This allows, for example, to arrange the radiating element in a second radiating element of a lower frequency band to provide a dual-band radiating structure in a reduced spatial configuration. The parasitic arms are arranged DC/galvanically isolated from the dipole arms. Each parasitic arm is capacitively coupled to at least one corresponding dipole arm.

In a first embodiment of the radiating element according to the first aspect, the first layer is parallel to the second layer. Typically, the distance between said first and second layers defines the distance between the respective positions of the dipole arms and the parasitic arms, which distance may vary within the limits provided according to the first aspect. However, it is preferred to keep the first layer parallel to the second layer, i.e. the parasitic arm and the dipole arm have a constant vertical distance, since this configuration can be easily manufactured. For example, the first and second layers may be parallel layers in a continuous support structure of the insulation material.

In a second implementation form of the radiating element according to any of the implementation forms of the first aspect, the support structure comprises a printed circuit board, PCB, and the dipole arms are arranged in a layer of the PCB and the parasitic arms are arranged in another layer of the same PCB. In this embodiment, the support structure may be formed from a PCB, which may be economically and efficiently manufactured. The first and second layers may be disposed on opposite sides of the PCB. Alternatively, one or more of the first and second layers may also be provided in an intermediate layer of the PCB.

In a third embodiment of the radiating element according to the first aspect as such or according to the first embodiment of the first aspect, the support structure comprises, or is, a Molded Interconnect Device (MID), wherein the dipole arm is formed by a first metallization on the MID and the parasitic arm is formed by a second metallization on the MID, wherein the first metallization and the second metallization are arranged opposite to each other. Support structures using MIDs can also be manufactured economically and efficiently. The metallizations forming the dipole arm and the parasitic arm, respectively, may also be provided in parallel layers, for example on the top and bottom surfaces of a planar MID-board.

In a fourth implementation form of the radiating element according to the first aspect as such or according to the first implementation form of the first aspect, the dipole arms are formed by a first set of metal sheets and the parasitic arms are formed by a second set of metal sheets arranged at said distance from the first set of metal sheets. In this embodiment the parasitic arms and the dipole arms are made of metal sheets, which may be separated by an insulating material. This configuration also allows the parasitic arms and dipole arms to be arranged in parallel layers on a support structure which may comprise any insulating material. In such a configuration, the insulating material between the parasitic arm and the dipole arm on the support structure need not be continuous, as long as the distance between the first and second layers is within predetermined limits.

In a fifth embodiment of the radiating element according to any of the embodiments of the first aspect, the parasitic arm is floating. Floating means that the arm is isolated from ground and no signal feed is connected. In this way, the parasitic arm effectively acts as an extension of the dipole arm, which reduces the overall length of the dipole arm for a given operating frequency.

In a sixth implementation form of the radiating element according to any implementation form of the first aspect, the radiating element comprises one or more additional parasitic elements outside the area of the dipole arm and galvanically isolated from the at least two parasitic arms, wherein the additional parasitic elements are provided in the first layer, the second layer or any other layer of the radiating element. The additional parasitic element outside the area of the dipole arm allows to further reduce the overall length of the dipole arm. The additional parasitic element is also floating and thus the total length of the radiating element, i.e. the total length of the dipole arm plus the added length of the additional parasitic element arranged outside the dipole arm, can be reduced. The additional parasitic element may be arranged on any layer of the radiating element, preferably in the first layer or the second layer, or in any intermediate layer between the first and second layer. With the additional parasitic element, the additional parasitic element is most effective in reducing the length of the dipole arm in a layer located within a predetermined distance of the first and second layers.

In a seventh implementation of the radiating element according to any of the implementations of the first aspect, the at least two parasitic arms each comprise a solid region of conductive material. The parasitic arms of the solid areas of conductive material are extremely effective in reducing the overall length of the dipole arms. However, in other preferred embodiments, the solid areas of conductive material in the parasitic arms may also include non-conductive breaks. The non-conductive interruptions may only marginally affect the radiation characteristics of the radiating element, thereby still providing the effect of reducing the length of the radiating element.

In an eighth implementation of the radiating element according to any of the implementations of the first aspect, the support structure comprises a distance holder having a foot for connecting to a reflector of the base station antenna, wherein the distance holder is configured to hold the dipole arm and the parasitic arm at a further predetermined distance from the reflector. The support structure comprises a foot for connection to a reflector of a base station, the support structure providing the effect that the dipole arm and the parasitic arm are arranged within a predetermined distance of the reflector of the base station antenna. In order to maintain low profile characteristics and still good RF performance, the predetermined distance from the reflector should be maintained in the range of 0.15 to a quarter wavelength of the center operating frequency. The reflector may act as a reflector for a plurality of radiating elements in a base station antenna. The footing integrated in the support structure allows easy connection of the radiating element to the reflector. Furthermore, the footing may also comprise electronic circuitry, in particular a feeding system for the radiating element.

In a ninth implementation of the radiating element according to any of the implementations of the first aspect, the distance keeper comprises, or is, a printed circuit board, PCB, perpendicular to the first and second layers of the radiating element, wherein the PCB comprises a balun and a microstrip line, and the balun is configured to electrically connect each arm of the at least one pair of dipole arms to ground, and the microstrip line is configured to feed the at least one pair of dipole arms. The microstrip line of this embodiment serves as a feed transmission line for the dipole arm. The balun may comprise a conductive surface on the opposite side of the PCB to the microstrip line, the function of which is to convert a balanced signal of the dipole arm into an unbalanced signal in the feed line and vice versa.

In a tenth embodiment of the radiating element according to any of the embodiments of the first aspect, the operating band is in the range of 1.4GHz to 2.7 GHz. This operating frequency is preferred because it allows the radiating element of the present embodiment to be arranged in another radiating element operating in the low frequency band, i.e. in the range 690MHz to 960 MHz.

A second aspect of the present invention relates to a dual-band radiating structure having at least a first radiating element and a second radiating element, the first radiating element according to any embodiment of the first aspect having an operating band and the second radiating element having an operating band lower than the operating band of the first radiating element, wherein the first radiating element is arranged inside the second radiating element. The advantage of the dual-band radiating arrangement according to this aspect is that two radiating elements of different frequency bands can be arranged to occupy only a minimum of space. This is particularly advantageous for constructing base station antennas which typically operate in at least two frequency bands, e.g. a first frequency band covered by a first radiating element and a second frequency band covered by a second radiating element. Since the size of the second radiating element for lower frequencies is necessarily large, it is advantageous that the radiating element for the high frequency band can be arranged inside the radiating element of the lower frequency band.

A third aspect of the present invention relates to a base station antenna, comprising: a reflector; at least one radiating element according to any embodiment of the first aspect and/or a dual-band radiating element according to the second aspect; wherein the radiating element and/or the dual-band radiating element is disposed in front of the reflector such that the dipole arm and the parasitic arm are disposed at a predetermined distance from the reflector. The base station antenna of the present aspect may include a plurality of radiating elements and/or dual-band radiating elements that are all disposed within a predetermined distance from a single reflector. This structure therefore allows to construct a base station with at least two or three radiating elements for different operating bands in a small spatial configuration.

Drawings

In order to more clearly illustrate the technical features of the embodiments of the present invention, the drawings that are required to be used in the description of the embodiments will be briefly described below. The drawings in the following description are directed to merely some embodiments of the invention, which may be modified without departing from the scope of the invention as defined in the appended claims.

Figure 1 shows a top perspective view of a radiating element of a first embodiment;

fig. 2 shows a bottom perspective view of the radiating element of the first embodiment;

figure 3 shows a side view of the radiating element of the first embodiment;

fig. 4 shows a side view of the PCB including the feeding system of the first embodiment;

fig. 5 illustrates a top side perspective view of a dual band radiating element of a second embodiment;

fig. 6 shows a bottom perspective view of the dual band radiating element of the second embodiment;

fig. 7 shows a plan view of a base station antenna of the third embodiment;

fig. 8a-c show perspective top and bottom views of three further embodiments of the radiating element.

Detailed Description

A first embodiment of the radiating element is described with reference to fig. 1 to 5.

The radiating element comprises two pairs of dipole arms 2 which are capable of radiating on mutually perpendicular polarisations. The dipole arms 2 are arranged on a top surface of a support structure, which in this embodiment comprises a printed circuit board, PCB, 4. Dipole arm 2 is electromagnetically coupled (but electrically/DC isolated) to parasitic arm 6, which comprises a layer of conductive material, and is disposed on an opposite side of PCB 4. The shape of the parasitic arms is arbitrary, but preferably covers the entire area of the respective dipole arm 2. In the embodiment shown, the parasitic arms are arranged on a bottom layer of the PCB and the dipole arms 2 are arranged on a top layer of the PCB 4. It should be understood, however, that in other embodiments the dipole arms and the parasitic arms may also be provided in other layers (top, bottom or middle layers) of a support structure such as a PCB or a molded interconnect device MID.

As shown in fig. 1, the dipole arms 2 have a curved contour. However, other geometries are possible.

The parasitic arms 6 are floating, i.e. they are galvanically isolated from ground and any other feeding signals.

The dipole arm 2 is a dipole leg 8, the dipole leg 8 being formed in this embodiment by two PCBs stacked together.

Referring to fig. 3 and 4, more details of the dipole feet 8 are described. The dipole feet 8 of each PCB comprise microstrip lines 10, which microstrip lines 10 allow feeding of a respective pair of dipole arms 2. Furthermore, on the side of the microstrip line 10 of the PCB of the dipole foot 8, this surface is metallized to form a balun structure 12. The electrically balun structure 12 is realized by capacitively connecting two points on the metallized surface, or as shown in the embodiment, electrically connected to the dipole arm 2. This allows an additional adjustment of the resonance frequency of the dipole arm 2. In other words, the dipole feet 8 provide a capacitive feed to the dipole arms 2 and, in addition, an electrically conductive connection of the dipole arms 2 to ground.

Below the dipole feet, a further feed PCB 14 is provided to serve as an interface between the microstrip line 10 and the antenna feed network and to provide mechanical support for the radiating elements.

The relationship between the dipole arm 2 and the parasitic arm 6 coupled thereto is defined as follows: the projection of the dipole arm 2 onto the parasitic arm 6 should overlap at least 60% of the surface of the dipole arm 2. The parasitic arm layer should be located below the dipole arm at a distance between 0.0004 and 0.1, preferably between 0.002 and 0.02, of the smallest wavelength of the operating band of the radiating element. As shown in the first embodiment, the distance may be constant, since the layers of the dipole arms and the layers of the parasitic arms are parallel. However, in other embodiments, the distance may also vary within given limits.

The length and area of the parasitic arm 6 determine the bandwidth and resonant frequency of the radiating element. The parasitic arm 6 may have any shape, but preferably the parasitic arm is solid. There are at least two parasitic arms 6 per dipole element, but other embodiments are not limited to only two parasitic arms per dipole element. The additional parasitic arms may be used to further increase the operating bandwidth of the dipole element.

The radiating element as described above is intended to operate in a multi-band architecture, as will be described in the context of fig. 5 and 6.

Fig. 5 and 6 depict a multiband arrangement of a second embodiment comprising as one part the radiating element of the first embodiment. The first radiating element is disposed inside the lower frequency cup-shaped radiating element 20. For example, the radiating element of the first embodiment may operate in the mid-band, while the second radiating element 20 of the dual-band radiating arrangement operates in the low-band. More details about the second radiating element 20 of the low frequency band are found in parallel PCT patent applications, patent application numbers: described in PCT/EP2016/057963, which is hereby incorporated by reference in its entirety.

It is clear that the dual-band radiating arrangement of the second embodiment is optimized for the available space, since the radiating element for the intermediate band is arranged inside the radiating element 20 of the low band.

The low frequency radiating element 20 acts as a sub-reflector for the first radiating element disposed inside the low frequency radiating element. To ground the first radiating element to the sub-reflector, the orthogonal PCB of the lower band radiating element is capacitively coupled to the lower plane of the low frequency radiating element 20.

As shown in fig. 6, the combined radiating element is also fed through a crossed PCB 8, which also forms the foot of the first radiating element. In the mentioned parallel PCT patent application, application No.: further details are described in PCT/EP 2016/057963.

Referring to fig. 7, a base station antenna of a third embodiment is described. The base station antenna comprises a reflector 30 and a plurality of radiating elements. Along the center line of the reflector 30, a first radiating element and a dual band radiating element according to the second embodiment are disposed. Furthermore, there is a third type of radiating element arranged on a longitudinal side of the reflector 30. The third type of radiating element has a high-band operating band, i.e. from 1710 to 2690 Mhz.

As shown in fig. 7, the overall arrangement of the base station antenna is spatially optimized because the radiating element portions of the low and intermediate bands are made up of dual-band radiating elements, as described above. The same reflector 30 is used for all radiating elements.

With reference to fig. 8a to 8c, further embodiments of the radiating element are described. Fig. 8a shows a radiating element similar to the first embodiment, but the parasitic element comprises a non-conductive interruption 40 within the solid area of the conductive material. The embodiment of fig. 8b comprises two parasitic arms 42 for each dipole arm. The amount of the area of the two parasitic arms 42 covers at least 60% of the area of the dipole arm. The embodiment of fig. 8c includes an additional parasitic element 44. An additional parasitic element 44 is arranged on the top side of the PCB in the same layer as the dipole arm 2. The additional parasitic element 44 further increases the operating band frequency of the dipole.

The above description is only an embodiment of the present invention, and the scope of the present invention is not limited thereto. Any changes or substitutions may be readily made by those skilled in the art. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A radiating element for a base station antenna, the radiating element comprising:

a support structure (4) for supporting the support structure,

at least one pair of dipole arms (2) in a first layer of the support structure (4), and

at least two parasitic arms (6) in a second layer of the support structure (4),

wherein the distance between the first layer and the second layer is between 0.0004 and 0.1 of the minimum wavelength of the operating band of the radiating element,

wherein the area of the perpendicular projection of the parasitic arm (6) from the second layer to the first layer covers at least 60% of the area of the at least one pair of dipole arms (2), the area of the parasitic arm (6) and the area of the at least one pair of dipole arms (2) each being larger than the area of the at least one pair of dipole arms (2) covered by the area of the perpendicular projection of the parasitic arm (6) from the second layer to the first layer;

said parasitic arms being floating, galvanically isolated from ground and from feed signals, each of said parasitic arms (6) being capacitively coupled to at least one corresponding dipole arm;

wherein the support structure (4) comprises a distance holder having a foot for connecting to a reflector (30) of the base station antenna, wherein the distance holder is configured to hold the dipole arm (2) and the parasitic arm (6) at a further predetermined distance from the reflector (30); wherein the distance keeper comprises crossed printed circuit boards, PCBs, wherein the crossed PCBs are perpendicular to the first and second layers of the radiating element, each PCB of the crossed PCBs comprising a balun (12) and a microstrip line (10), the balun (12) being configured to galvanically connect a respective pair of dipole arms (2) to ground, the microstrip line (10) being configured to feed the respective pair of dipole arms (2).

2. The radiating element of claim 1, wherein a distance between the first layer and the second layer is between 0.002 and 0.02 of a minimum wavelength of an operating band of the radiating element.

3. The radiating element of claim 1, wherein the first layer is parallel to the second layer.

4. The radiating element of any of claims 1-3, wherein the support structure (4) comprises a printed circuit board, PCB, and wherein the dipole arm (2) is provided in a layer of the PCB and the parasitic arm (6) is provided in another layer of the same PCB.

5. The radiating element according to any of claims 1-3, wherein the support structure (4) comprises a Molded Interconnect Device (MID), wherein the dipole arm (2) is formed by a first metallization on the MID and the parasitic arm (6) is formed by a second metallization on the MID, wherein the first and second metallizations are arranged opposite to each other.

6. The radiating element of any of claims 1-3, wherein the dipole arm (2) is formed from a first set of metal sheets and the parasitic arm (6) is formed from a second set of metal sheets arranged at said distance from the first set of metal sheets.

7. The radiating element of any of claims 1-3, comprising one or more additional parasitic elements (44) outside the area of the dipole arm (2) and galvanically isolated from the at least two parasitic arms (6), wherein the additional parasitic elements (44) are provided in the first layer, the second layer or any other layer of the radiating element.

8. The radiating element according to any of claims 1-3, wherein the at least two parasitic arms (6) each comprise a solid area of electrically conductive material.

9. The radiating element of any of claims 1-3, wherein the operating band is in the range of 1.4GHz to 2.7 GHz.

10. A dual band radiating device comprising a first radiating element and a second radiating element (20), the first radiating element being according to any one of claims 1-9, the first radiating element having an operating frequency band, and the second radiating element (20) having an operating frequency band lower than the operating frequency band of the first radiating element, wherein the second radiating element (20) is cup-shaped and configured to act as a sub-reflector for the first radiating element, the first radiating element being arranged inside the second radiating element (20), and wherein the second radiating element (20) is configured to be fed through the crossover PCB.

11. A base station antenna, comprising:

a reflector (30);

-a radiating element according to any of claims 1 to 9 and/or a dual band radiating arrangement according to claim 10;

wherein the radiating element and/or the dual band radiating arrangement is arranged in front of the reflector (30) such that the dipole arm (2) and the parasitic arm (6) are arranged at a predetermined distance to the reflector (30).