Patent ID: 12218429

DETAILED DESCRIPTION

The present invention will be described below with reference to the drawings, in which several embodiments of the present invention are shown. It should be understood, however, that the present invention may be implemented in many different ways and is not limited to the example embodiments described below. In fact, the embodiments described hereinafter are intended to make a more complete disclosure of the present invention and to adequately explain the scope of the present invention to a person skilled in the art. It should also be understood that the embodiments disclosed herein can be combined in various ways to provide many additional embodiments.

In the drawings, the same reference signs present the same elements. In the drawings, for the sake of clarity, the sizes of certain features may be modified.

It should be understood that the wording in the specification is only used for describing particular embodiments and is not intended to limit the present invention. All the terms used in the specification (including technical and scientific terms) have the meanings as normally understood by a person skilled in the art, unless otherwise defined. For the sake of conciseness and/or clarity, well-known functions or constructions may not be described in detail.

The singular forms “a/an” and “the” as used in the specification, unless clearly indicated, all contain the plural forms. The words “comprising”, “containing” and “including” used in the specification indicate the presence of the claimed features, but do not preclude the presence of one or more additional features. The wording “and/or” as used in the specification includes any and all combinations of one or more of the relevant items listed. As used herein, phrases such as “between X and Y” and “between about X and Y” should be interpreted to include X and Y. As used herein, phrases such as “between about X and Y” mean “between about X and about Y”. As used herein, phrases such as “from about X to Y” mean “from about X to about Y.”

In the specification, when an element is referred to as being “on”, “attached” to, “connected” to, “coupled” with, “contacting”, etc., another element, it can be directly on, attached to, connected to, coupled with or contacting the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on”, “directly attached” to, “directly connected” to, “directly coupled” with or “directly contacting” another element, there are no intervening elements present. In the specification, references to a feature that is disposed “adjacent” another feature may have portions that overlap, overlie or underlie the adjacent feature.

In the specification, words describing spatial relationships such as “up”, “down”, “left”, “right”, “forth”, “back”, “high”, “low” and the like may describe a relation of one feature to another feature in the drawings. It should be understood that these terms also encompass different orientations of the apparatus in use or operation, in addition to encompassing the orientations shown in the drawings. For example, when the apparatus in the drawings is turned over, the features previously described as being “below” other features may be described to be “above” other features at this time. The apparatus may also be otherwise oriented (rotated 90 degrees or at other orientations) and the relative spatial relationships will be correspondingly altered.

The antenna assemblies according to embodiments of the present invention are applicable to various types of base station antennas, for example beamforming antennas. In beamforming antennas, due to uncontrollable errors in the design, manufacture or use of RF control systems (such as a remote radio unit or “RRU”) or antenna feed networks, a calibration circuit is typically required to compensate for the phase differences and/or amplitude differences of the RF signals that are input at different RF ports. This process is often referred to as “calibration”.

Typically, an antenna array and feeding circuits therefor may be integrated on a first printed circuit board as a feed board, while the calibration device is configured as a second printed circuit board placed separately from the first printed circuit board. The feed board may typically be mounted on a first backplane. With the structural strength taken into account, the calibration device also needs to be mounted on a second backplane placed separately from the first backplane. The “backplane” may be any suitable form of plate, such as a metal plate. For the purpose of calibration, a well-known coaxial device may be mounted on the second backplane for electrically connecting a microstrip calibration circuit on the calibration device with the feeding circuit on the feed board. Further, an additional connection device is required to mount the first backplane and the second backplane together. In the mounted state, the first backplane and the second backplane are placed facing each other and spaced apart from each other. However, such connection solution by means of the coaxial device may bring one or more of the following problems: First, the coaxial devices may occupy a large space within the antenna, which may increase the difficulty in the overall design and wiring of the antenna system. Second, it may be time-consuming to install the coaxial devices and the likelihood of installation errors may be increased. Third, the cost of the coaxial devices and the installation costs may increase the overall cost of the antenna. Fourth, there is a relatively strict requirement for the flatness of the first and second backplanes, otherwise the return loss and passive intermodulation performance (PIM) of the antenna may be negatively affected. Fifth, the structural strength can be reduced and/or is low, since the first and second backplanes are mounted spaced apart from each other.

The antenna assembly according to embodiments of the present invention can avoid the connection solution by means of a coaxial device between the microstrip calibration circuit and the feeding circuit. Further, the antenna assembly according to embodiments of the present invention can also achieve high integration and miniaturization of the overall antenna construction.

Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

Referring toFIGS.1and2,FIG.1is a schematic perspective view of a base station antenna100according to some embodiments of the present invention, andFIG.2is a schematic perspective view of an antenna assembly200according to some embodiments of the present invention.

As shown inFIG.1, the base station antenna100is an elongated structure that extends along a longitudinal axis L. The base station antenna100may have a tubular shape with a generally rectangular cross-section. The base station antenna100includes a radome110and a top end cap120. In some embodiments, the radome110and the top end cap120may comprise a single integral unit, which may be helpful for waterproofing the base station antenna100. One or more mounting brackets150are provided on the rear side of the radome110which may be used to mount the base station antenna100onto an antenna mount (not shown) on, for example, an antenna tower. The base station antenna100also includes a bottom end cap130which includes a plurality of connectors140mounted therein. The base station antenna100is typically mounted in a vertical configuration (i.e., the longitudinal axis L may be generally perpendicular to a plane defined by the horizon when the base station antenna100is mounted for normal operation).

As shown inFIG.2, the base station antenna100includes an antenna assembly200that may be slidably inserted into the radome110. The antenna assembly200includes a feed board300, a backplane400, and a calibration board500(not visible as it is underneath the backplane400in the view ofFIG.2). In the embodiment shown inFIG.2, the feed board300is mounted on a first major surface of the backplane400, and the calibration board500is mounted on a second major surface of the backplane400opposite the first major surface.

In some embodiments, the feed board300, the backplane400, and the calibration board500may be mounted in abutment against each other in sequence without the presence of a large gap, particularly a gap brought by the use of coaxial devices. In this text, the coaxial device may be a coaxial connector or a coaxial cable. The gap therebetween may be, for example, less than the thickness of any of the feed board300, the backplane400and the calibration board500. The feed board300may be at least partially abutted against the first major surface of the backplane400, and the calibration board500may be at least partially abutted against the second major surface of the backplane400. Additionally, the feed board300, the backplane400and the calibration board500may be mounted together by other fastening means such as bayonet connection, screw connection, rivet connection, welding and/or adhering.

In some embodiments, the feed board300, the backplane400, and the calibration board500may be placed in close contact with each other in sequence, that is, there is almost no gap therebetween. For installation, an adhesive layer, a fastening device, or the like may be applied therebetween. Therefore, the feed board300, the backplane400, and the calibration board500can be tightly integrated with each other.

The aforesaid assembly solutions of the feed board300, the backplane400and the calibration board500can not only reduce the space occupied by the antenna assembly200within the antenna, thereby improving the integration of the overall antenna construction, but can also reduce the number of backplanes400, for example, to only one backplane400, thereby reducing manufacturing costs, weight and the overall size of the antenna. Further, in the case where only one backplane400is required, the strict requirement for flatness of the first backplane and the second backplane may be avoided.

An antenna array310including a plurality of radiating elements320may be mounted on the feed board300, and the radiating elements320are mounted to extend forwardly (in a forward direction F) from the backplane400. The backplane400may be configured as a reflector of the base station antenna100. The reflector may be used as a ground plane structure for the radiating elements320. The reflector may be made of an electrically conductive material, such as copper, aluminum, etc.

The antenna arrays310may be, for example, linear arrays of radiating elements320or two-dimensional arrays of radiating elements320. The plurality of radiating elements320may include low-band radiating elements and high-band radiating elements, and the low-band radiating elements extend farther forward than the high-band radiating elements. The low-band radiating elements may be configured to transmit and receive RF signals in a first frequency band such as, for example, the 617-960 MHz frequency range or a portion thereof. The high-band radiating elements may be configured to transmit and receive RF signals in a second frequency band such as, for example, the 2.5-2.7 GHz frequency range, the 3.4-3.8 GHz frequency range and/or the 5.1-5.8 GHz frequency range or a portion (or portions) thereof. Dual-polarized radiating elements are typically used on the modern base station antennas, which transmit and receive RF signals with two orthogonal polarizations.

In some embodiments, the antenna arrays310may extend substantially along the entire length of the base station antenna100. In other embodiments, the antenna arrays310may also extend only partially along the length of the base station antenna100. The antenna arrays310may extend in a vertical direction V, which may be the direction of a longitudinal axis L of the base station antenna100or may be parallel to the longitudinal axis L. The vertical direction V is perpendicular to a horizontal direction H and a forward direction F (seeFIG.1).

Next, the feed board300and the calibration board500of the antenna assembly200according to embodiments the present invention will be further described with reference toFIGS.3and4, whereinFIG.3is a simplified schematic view of the calibration board500for the antenna assembly200, andFIG.4is a simplified schematic view of the feed board300for the antenna assembly200.

As shown inFIG.3, the calibration board500may be configured as a printed circuit board, which may include, for example, a dielectric substrate510, a microstrip calibration circuit520disposed on a first major surface of the dielectric substrate510, and a ground metal layer (not shown) disposed on a second major surface of the dielectric substrate510. In some embodiments, the microstrip calibration circuit520may be implemented in a multi-layer printed circuit board including two dielectric substrates, wherein a first ground metal layer may be disposed on an upper surface of the upper dielectric substrate, a second ground metal layer may be disposed on a lower surface of the lower dielectric substrate, and the calibration circuit520is provided in a metal layer between the two dielectric substrates. As a result, the calibration circuit520is surrounded by the first and second ground metal layers and may thus constitute a stripline network. The stripline network may be advantageous in that it can reduce losses of radiation signals and protect RF transmission lines from external radiation. In some embodiments, the calibration board500may include, for example, two or more printed circuit boards, which may be electrically connected to each other via cables.

The calibration circuit520may include a calibration port530, transmission lines540, power divider/combiners550, and couplers560. The power divider/combiners550may be configured as Wilkinson power dividers/combiners. The couplers560may be configured as directional couplers560. The calibration circuit520may be used to identify any unintended variations in the amplitude and/or phase of the RF signals that are input to the different RF ports580of the antenna.

In some embodiments, a remote radio unit (RRU) (not shown) may input a calibration signal to the calibration port530via a cable. Then, the calibration signal is passed from the calibration port530via the respective transmission lines540to the power dividers550which divide the calibration signal into a plurality of sub-components. The sub-components of the calibration signal are passed by the respective couplers560to the respective feed branches570. The feed branches570may each include an RF port580and a feeding line (hereinafter referred to as a first transmission line590). The RF ports580may each extract a small portion of the calibration signal by means of the couplers560. The first transmission lines590may be electrically connected to the feeding circuit330on the feed board300by means of conductive connections, so that the RF signal input by the RRU to the RF port580may be further fed to the downstream radiating element320. The RRU may read the amplitude and/or phase of the RF signals that are electrically coupled from the calibration circuit520via the couplers560to the RF ports580. Accordingly, calibration of the RF control system can be implemented in terms of the S parameters of the RF ports580and the calibration port530. In other words, the calibration can be implemented in terms of the amplitude and/or phase of the RF signals coupled to the RF ports580and the amplitude and/or phase of the calibration signal at the calibration port530. The RRU may adjust the amplitude and/or phase of the RF signal to be input to the RF port580so as to provide an optimized antenna beam.

In some embodiments, the RRU may first input RF signals into the respective RF ports580via cables. Then, the calibration circuit520may extract, by means of the couplers560, a small amount of each of the RF signals from the respective RF ports580, and then combine these extracted signals to a calibration signal by means of the power combiners550and pass the calibration signal back to the RRU that generates the RF signals. The RRU may adjust the amplitude and/or phase of the RF signals to be input to the RF ports580according to the calibration signal so as to provide an optimized antenna beam.

It should be understood that the calibration board500and the calibration circuit520may include any suitable configuration and/or working mode and are not limited to the embodiments described above.

Refer toFIG.4, which only exemplarily shows one radiating element320and a feeding circuit330therefor mounted on the feed board300. The feed board300may be configured as a printed circuit board, which may include, for example, a dielectric substrate340, a microstrip feeding circuit330provided on a first major surface of the dielectric substrate340, and a ground metal layer (not shown) provided on a second major surface of the dielectric substrate340. The feeding circuit330may include a first feeding interface350, a second feeding interface360, and associated transmission lines (hereinafter referred to as second transmission lines370). The feeding circuit330is configured to transmit the RF signal received from the RF port580to the corresponding radiating element320, and/or the feeding circuit330is configured to transmit the RF signal received from the radiating element320to the respective RF port580. The first feeding interface350may feed sub-components of the RF signal with a first polarization to the respective radiating element320(or a group of radiating elements), and the second feeding interface360may feed sub-components of the RF signal with a second polarization to the respective radiating element320(or a group of radiating elements). In order to enable an effective electrical connection of the first transmission line590on the calibration board500with the respective feeding interfaces on the feed board300and further with the second transmission lines370, conductive structures600,700are additionally provided, as will be discussed in further detail below. Next, some effective electrical connections solutions will be exemplarily described in detail with reference toFIGS.5a,5band6a,6b.

Refer toFIGS.5aand5b, which show a first assembly solution of the feed board300, the backplane400, and the calibration board500. In the first assembly solution, the antenna assembly200may include a metal conductor600as the conductive structure and a dielectric element610. The metal conductor600may be configured as any form of metal elements, such as a copper wire, a copper bar, an aluminum pin, or the like. The dielectric element610may be made of any suitable dielectric material, such as mica, ceramic, rubber, paper, polystyrene, or the like. The metal conductor600is configured as an impedance-matched transmission line, which may be designed to have an impedance of 50 ohms.

The backplane400may include a first opening410, the feed board300has a second opening380corresponding to the first opening410, and the calibration board500has a third opening595corresponding to the first opening410. The dielectric element610may be disposed within the first opening410, at least partially surrounding, the metal conductor600and electrically isolating the metal conductor600from the backplane400. As shown, the dielectric element610may entirely surround the metal conductor600. A length of the dielectric element610is approximately equal to a width/thickness of the backplane400. An inner peripheral wall of the backplane400that defines the first opening410, the dielectric element610, and the metal conductor600may be abutted against each other in sequence. In this way, the inner peripheral wall of the backplane400that defines the first opening410, the dielectric element610, and the metal conductor600may commonly form an equivalent coaxial cable segment, wherein the inner peripheral wall corresponds to an outer conductor of the coaxial cable, the dielectric element610corresponds to an insulating medium of the coaxial cable, and the metal conductor600corresponds to an inner conductor of the coaxial cable.

The metal conductor600may extend, at one end, through the first opening410and the second opening380up to the feeding circuit330on the feeding board300, and then be welded (e.g., soldered) to a first welding region390(in this way the feed interfaces350,360are formed) to thereby be electrically connected to the second transmission line370. Further, the metal conductor600may extend, at the opposite end, through the first opening410and the third opening595to the feed branch570on the calibration board500, and then be welded to a second welding region592to thereby be electrically connected to the first transmission line590. In this way, the second transmission line370on the feed board300is electrically connected to the first transmission line590on the calibration board500. In some embodiments, the backplane400may be a reflector of the base station antenna, thereby realizing a common ground between the feed board300and the calibration board500.

In the first assembly solution, since a conventional coaxial device is not used, the gap between the feed board300and the backplane400and/or the gap between the backplane400and the calibration board500can be reduced or even eliminated, thereby reducing the size/volume of the antenna assembly200, which improves the integration of the antenna.

Refer toFIGS.6aand6b, which show a second assembly solution for the feed board300, the backplane400, and the calibration board500. In the second assembly solution, the antenna assembly200may include a printed circuit board component700that includes a dielectric layer710, a printed trace720on a first side of the dielectric layer710, and a ground metal layer on a second side of the dielectric layer710. The printed trace720is configured as an impedance-matched transmission line segment, which may be designed to have an impedance of 50 ohms.

The backplane400may include a first opening410, the feed board300may have a second opening380corresponding to the first opening410, and the calibration board500may have a third opening595corresponding to the first opening410. The printed circuit board component700may extend, at one end, through the first opening410and the second opening380up to the feeding circuit330on the feeding board300, and the printed trace720of the printed circuit board component700may be welded to a first welding region390(in this way the feed interfaces350,360are formed) to thereby be electrically connected to the second transmission line370. The ground metal layer of the printed circuit board component700may be electrically connected to a ground region on the feed board300. Further, the printed trace720of the printed circuit board component700may extend, at the opposite end, through the first opening410and the third opening595to the feed branch570on the calibration board500, and then be welded to a second welding region592to thereby be electrically connected to the first transmission line590. The ground metal layer of the printed circuit board component700may be electrically connected to a ground region on the calibration board500. In this way, the second transmission line370on the feed board300is electrically connected to the first transmission line590on the calibration board500. In some embodiments, the backplane may be a reflector of the base station antenna, thereby realizing a common ground between the feed board300and the calibration board500.

In the second assembly solution, as the RF performance of the printed traces720on the printed circuit board component700is independent of the backplane400, the requirement for flatness of the backplane400is reduced, thereby reducing manufacturing difficulty and costs. Further, the flatness of the backplane400and/or the design accuracy of the first opening410of the backplane400have almost no effect on the RF performance of the printed circuit board component700.

Furthermore, since a conventional coaxial device is not used, the gap between the feed board300and the backplane400and/or the gap between the backplane400and the calibration board500may be reduced or even eliminated, thereby reducing the size/volume of the antenna assembly200and improving the integration of the antenna.

Although exemplary embodiments of the present invention have been described, those skilled in the art should appreciate that many variations and modifications are possible in the exemplary embodiments without materially departing from the spirit and scope of the present invention. Accordingly, all such variations and modifications are intended to be included within the scope of the present invention.