Patent ID: 12199703

DETAILED DESCRIPTION

As discussed above, sector-splitting multi-beam antennas that use beamforming networks may exhibit beam peak walking where the pointing directions of the generated antenna beams vary as a function of frequency. Beam peak walking can be particularly problematic for antenna arrays that are designed to operate over wide frequency ranges, such as the 1.7-2.7 GHz frequency band. Beam peak walking can lead to a large variation in the power levels of the antenna beams at the outside edges of the sub-sectors as a function of frequency, which is undesirable. Moreover, the problems caused by beam peak walking tend to increase with the number of antenna beams generated by the sector-splitting antenna. In some cases, sector-splitting antennas may be designed to generate three, four, five, six or more antenna beams (per polarization) in order to, for example, split a 120° sector in the azimuth plane into three, four, five, six or more sub-sectors. Beam peak walking issues can be particularly problematic with such higher order sector-splitting antennas.

FIGS.1A and1Bare schematic diagrams that together illustrate the RF signal paths of a conventional Butler Matrix based six-beam sector-splitting antenna1. In particular,FIG.1Ais a schematic block diagram of base station antenna1that illustrates the RF signal paths extending from the RF ports of the antenna to the columns of a multi-column array of radiating elements, andFIG.1Bis a schematic block diagram illustrating how RF signals are distributed to the radiating elements in each column of the multi-column array.

As shown inFIG.1A, the sector-splitting antenna1includes twelve RF connector ports20-1through20-12(also referred to herein as “RF ports”) that are used to input RF signals to the antenna1from external radios, such as remote radio heads. The antenna1further includes an antenna array30that has ten columns32-1through32-10of dual-polarized radiating elements34that are mounted to extend forwardly from a reflector12(only columns32-1and32-10are explicitly numbered inFIG.1Ato simplify the drawing; it will be understood that the columns32are arranged sequentially in numerical order). Each dual-polarized radiating element34includes a first polarization radiator36-1and a second polarization radiator36-2. Herein, when multiple of the same elements are included in an antenna, the elements may be referred to individually by their full reference numeral (e.g., column32-3) and collectively by the first part of their reference numerals (e.g., the columns32). Base station antenna1also includes a pair of beamforming networks (“BFN”)40-1,40-2(one for each polarization) and a pair of feed networks50-1,50-2(again, one for each polarization). In order to simplifyFIG.1A, the beamforming networks40-1,40-2and feed networks50-1,50-2are illustrated as being on opposed ends of the antenna array30. It will be appreciated that the RF connector ports20-1through20-12are typically all located in a bottom end cap (not shown) of antenna1, that the beamforming networks40may be located in any convenient location within antenna1, and the feed networks50-1,50-2connect respective subsets of the RF ports20to the respective beamforming networks40-1,40-2.

The RF connector ports20-1through20-6may comprise, for example, RF connectors, and may be connected to RF ports on one or more radios via, for example, coaxial cables. The radios are typically external to the antenna1and are not shown inFIG.1A. Each beamforming network40is implemented as a 6×6 Butler Matrix. The six first polarization RF connector ports20-1through20-6are connected to the six inputs42-1through42-6of the Butler Matrix40-1, and the six second polarization RF connector ports20-7through20-12are connected to the six inputs42-7through42-12of the Butler Matrix40-2. The six outputs44-1through44-6of Butler Matrix40-1are connected to the ten-column antenna array30by the feed network50-1, and the six outputs44-7through44-12of Butler Matrix40-2are connected to the ten-column antenna array30by the feed network50-2. Only inputs42-1,42-6,42-7and42-12and only outputs44-1,44-6,44-7and44-12are explicitly numbered inFIG.1Ato simplify the drawing; it will be understood that the inputs and outputs to the beamforming networks40are arranged sequentially in numerical order).

As is further shown inFIG.1A, the feed network50-1includes four first-level power dividers52-1through52-4that are each used to connect selected ones of the outputs44-1through44-6of Butler Matrix40-1to respective pairs of columns32of antenna array30. In particular, first-level power divider52-1connects output44-1of Butler Matrix40-1to the third and ninth columns32-3and32-9, first-level power divider52-2connects output44-2of Butler Matrix40-1to the fourth and tenth columns32-4and32-10, first-level power divider52-3connects output44-5of Butler Matrix40-1to the first and seventh columns32-1and32-7, and first-level power divider52-4connects output44-6of Butler Matrix40-1to the second and eighth columns32-2and32-8. Output44-3of Butler Matrix40-1is connected to the fifth column32-5, and output44-4of Butler Matrix40-1is connected to the sixth column32-6. Consequently, the six outputs44-1through44-6of Butler Matrix40-1feed all ten columns32of antenna array30. An additional four first-level power dividers52-5through52-8are provided that connect selected ones of the outputs44-7through44-12of Butler Matrix40-2to respective pairs of columns32each of antenna array30in a similar fashion.

FIG.1Billustrates the connections between beamforming networks40-1,40-2and the radiating elements34of column32-5of antenna array30. As shown inFIG.1B, output44-3of Butler Matrix40-1is coupled to a first phase shifter assembly56-1. The first phase shifter assembly56-1includes a 1×4 power divider that divides RF signals input thereto into four sub-components, and also includes an adjustable phase shifter that is configured to impart a phase progression across the four sub-components in order to electronically change the tilt angles of the antenna beams generated by the radiating elements34in column32-5. Each output58of the first phase shifter assembly56-1is coupled to a respective feed board60. A pair of radiating elements34are mounted on each feed board60. A power divider62is provided on each feed board60that sub-divides RF signals input thereto from the respective outputs58of the first phase shifter assembly56-1into first and second sub-components that are passed to the respective first and second radiating elements34mounted on the feed board60. As can be seen, the portion of feed network50-1depicted inFIG.1Bfeeds output44-3of Butler Matrix40-1to the −45° dipole radiators36-1of the radiating elements34in column32-5. A second phase shifter assembly56-2and four additional feed board power dividers62are provided that are used to similarly feed RF signals that are output from output44-9of Butler Matrix40-2to the +45° dipole radiators36-2of the radiating elements34in column32-5. It will be appreciated that each of the other nine columns32of antenna array30are fed in the same manner as shown inFIG.1B.

FIGS.2A-2Care simulated azimuth plots that illustrate three of the six antenna beams generated by the multi-beam antenna1ofFIGS.1A-1B. Each graph shows the antenna beams that are generated by the antenna1when excited with RF signals at frequencies of 1.7 GHz, 2.2 GHz and 2.7 GHz (i.e., at the lowermost frequency, the center frequency and the uppermost frequency of the 1.7-2.7 GHz operating frequency band).FIG.2Aillustrates the leftmost antenna beam for a sector,FIG.2Billustrates the antenna beam that is adjacent the antenna beam ofFIG.2A, andFIG.2Cillustrates the antenna beam that is adjacent the antenna beam ofFIG.2B. In other words,FIGS.2A-2Cillustrate the antenna beams that provide coverage to the left half of the sector. The remaining three antenna beams (at each of the three frequencies) that provide coverage to the right half of the sector are mirror images of the antenna beams shown inFIGS.2A-2C. As shown inFIGS.2A-2C, the beam peak walking increases with increasing scan angle, and exceeds 20° with the outermost antenna beams.

The beam peak walking shown inFIGS.2A-2Coccurs because the phase differences between the six outputs44of each Butler Matrix40are independent of the frequencies of the RF signals input to the Butler Matrix40, but the spacing between the columns32of radiating elements34in array30is frequency dependent. It may be possible to reduce the degree of beam peak walking shown inFIGS.2A-2Cby applying a phase progression along the transmission lines connecting the outputs of the Butler Matrix40to the columns32of radiating elements34. While this phase progression may designed to, for example, reduce the beam peak walking on the left three antenna beams, such a design will increase the beam peak walking for the right three antenna beams.

Pursuant to embodiments of the present invention, sector-splitting multi-beam antennas are provided that include first and second multi-column antenna arrays. These antennas further include a first beamforming network that is coupled to the first antenna array and a second beamforming network that is coupled to the second antenna array. The first beamforming network is configured to generate a first subset of the sector-splitting antenna beams, and the second beamforming network is configured to generate a second subset of the sector-splitting antenna beams. For example, for a six-beam sector-splitting antenna, the first beamforming network may be configured to generate the left three antenna beams and the second beamforming network may be configured to generate the right three antenna beams. A phase progression may be applied along the transmission lines connecting the outputs of each beamforming network to the columns of radiating elements in the respective antenna arrays. Since the first beamforming network is only used to generate the antenna beams that provide coverage to the left side of the sector, the added phase progression may reduce the degree of beam peak walking for the left side antenna beams without impacting the beam peak walking on the right side antenna beams. Similarly, since the second beamforming network is only used to generate the antenna beams that provide coverage to the right side of the sector, the added phase progression may reduce the degree of beam peak walking for the right side antenna beams without impacting the beam peak walking on the left side antenna beams.

In some embodiments, the sector-splitting base station antennas may include a plurality of RF ports, a plurality of columns of radiating elements, a first beamforming network that is coupled between a first subset of the RF ports and a first antenna array, and a second beamforming network that is coupled between a second subset of the RF ports and a second antenna array. The first beamforming network and the first antenna array are configured to generate a first plurality of antenna beams that provide coverage to a first side of a sector of a cell of a cellular communications system but not to a second side of the sector, and the second beamforming network and the second antenna array are configured to generate a second plurality of antenna beams that provide coverage to the second side of the sector but not to the first side of the sector.

In some embodiments, none of the columns of radiating elements in the first antenna array are also in the second antenna array. In other embodiments, some, but not all, of the columns of radiating elements in the first antenna array comprise shared columns of radiating elements that are also in the second antenna array. In such embodiments, the shared columns of radiating elements are in between the columns of radiating elements in the first antenna array that are not in the second antenna array and the columns of radiating elements in the second antenna array that are not in the first antenna array.

Each beamforming network may be implemented, for example, using a Butler Matrix. In some embodiments, at least some of the outputs of each Butler Matrix may be coupled to more than one of the columns of radiating elements. As a result, at least two of the columns of radiating elements in the second antenna array may be positioned within a footprint of the first antenna array.

The sector-splitting base station antenna may be configured to split the sector into a plurality of sub-sectors in the azimuth plane, and the first plurality of antenna beams provide coverage to a first half of the sub-sectors and the second plurality of antenna beams provide coverage to a second half of the sub-sectors that is different from the first half.

According to further embodiments, sector-splitting base station antennas are provided that have a plurality of RF ports, a plurality of columns of radiating elements, and first and second beamforming networks that each include a plurality of inputs and a plurality of outputs. Some of the inputs of the first beamforming network are coupled to respective ones of a first subset of the RF ports and a remainder of the inputs are coupled to respective matched terminations, and the outputs of the first beamforming network are coupled to a first subset of the columns of radiating elements.

Some of the inputs of the second beamforming network may be coupled to respective ones of a second subset of the RF ports and a remainder of the inputs are coupled to respective matched terminations (e.g., 50 ohm resistors), and the outputs of the first beamforming network are coupled to a second subset of the columns of radiating elements. The sector-splitting base station antenna may be configured, for example, to split a sector into six sub-sectors, and the first and second beamforming networks may each have six inputs and six outputs. Some, but not all, of the columns of radiating elements in the first subset of the columns of radiating elements may be shared columns of radiating elements that are also in the second subset of the columns of radiating elements in some embodiments.

Pursuant to further embodiments, sector-splitting base station antennas are provided that include a plurality of RF ports, first and second antenna arrays, a first beamforming network that is coupled between a first subset of the RF ports and the first antenna array and a second beamforming network that is coupled between a second subset of the RF ports and the second antenna array. At least some of the columns of radiating elements of the first antenna array are positioned within a footprint of the second antenna array, and at least some of the columns of radiating elements of the first antenna array are positioned within a footprint of the second antenna array.

In some embodiments, the four rightmost of the columns of the first antenna array are interlaced with the four leftmost of the columns of the second antenna array. In other embodiments, all of the columns of the first antenna array may be interlaced with columns of the second antenna array. The interlaced columns of the two antenna arrays may be vertically aligned in some embodiments, and horizontally staggered in other embodiments.

Pursuant to still further embodiments of the present invention, sector-splitting base station antennas are provided that are configured to split a sector into a plurality of sub-sectors. These antennas include a plurality of RF ports, a plurality of columns of radiating elements, a first beamforming network that is coupled between a first subset of the RF ports and a first subset of the columns of radiating elements, and a second beamforming network that is coupled between a second subset of the RF ports and a second subset of the columns of radiating elements. The first beamforming network is configured to generate a plurality of first polarization antenna beams that provide coverage to a first subset of the sub-sectors and the second beamforming network is configured to generate a plurality of first polarization antenna beams that provide coverage to a second subset of the sub-sectors.

Embodiments of the present invention will now be discussed in greater detail with reference toFIGS.3A-12, in which example embodiments are shown.

FIGS.3A-3Dillustrate a sector-splitting multi-beam base station antenna100according to embodiments of the present invention. In particular,FIG.3Ais a perspective view of base station antenna100.FIG.3Bis a schematic block diagram of antenna100that illustrates the RF signal paths extending from the RF ports of the antenna to the columns of the antenna arrays130-1,130-2included therein, andFIG.3Cis a schematic block diagram illustrating how RF signals are distributed to the radiating elements in each column of radiating elements.FIG.3Dis an azimuth plot illustrating the antenna beams generated by the sector-splitting multi-beam base station antenna100.

As shown inFIG.3A, the sector-splitting multi-beam base station antenna100includes a housing110. In the depicted embodiment, the housing110is a multi-piece housing that includes a radome112, a top end cap114and a bottom end cap116. A plurality of RF ports120are mounted in the bottom end cap116. The RF ports120may comprise RF connectors that may receive coaxial cables that provide RF connections between the base station antenna100and one or more radios (not shown).

The base station antenna100is an elongated structure that extends along a longitudinal axis L. The azimuth boresight pointing direction of the base station antenna100refers to a horizontal axis extending from the front of base station antenna100to the center, in the azimuth plane, of a sector served by the base station antenna100. When the base station antenna100is mounted for normal use, the longitudinal axis L will typically extend along a vertical axis, although in some cases the base station antenna100may be tilted a few degrees from the vertical to impart a mechanical downtilt to the antenna beams formed by the base station antenna100.

Referring toFIG.3B, the base station antenna100includes twelve RF connector ports120-1through120-12(also referred to herein as “RF ports”) that are used to input RF signals to the antenna100from one or more external radios, such as remote radio heads. The RF connector ports120may comprise, for example, RF connectors. The antenna100further includes first and second antenna arrays130-1,130-2. The first antenna array130-1includes eight columns132-1through132-8of radiating elements134, with eight radiating elements134in each column132. Similarly, the second antenna array130-2includes eight columns132-9through132-16of radiating elements134, with eight radiating elements134in each column132. Each of the radiating elements134may be implemented as a dual-polarized radiating element134, and each radiating element134may be mounted to extend forwardly from a reflector112(only columns132-1and132-16are explicitly numbered inFIG.3Bto simplify the drawing; it will be understood that the columns132are disposed in numerical order). In the illustrated embodiment, each radiating element134comprises a slant −45°/+45° cross-dipole radiating element that includes a first dipole radiator136-1that is configured to transmit and receive signals having a −45° polarization, and a second dipole radiator136-2that is configured to transmit and receive signals having a +45° polarization. The dipole radiators136may be mounted on a feed stalk (e.g., a pair of feedboard printed circuit boards that carry RF signals between the dipole radiators136and an associated feed network). As shown inFIG.3B, the two antenna arrays130-1,130-2are implemented in side-by-side fashion, and no radiating elements134of the first antenna array130-1are within the footprint of the second antenna array130-2.

The antenna100also includes a total of four beamforming networks140-1through140-4(two for each polarization) and a pair of feed networks150-1,150-2(one for each polarization). Each beamforming network140is implemented as a 6×6 Butler Matrix. RF connector ports120-1through120-3are connected to three of the six inputs142of Butler Matrix140-1, and the remaining three inputs142to Butler Matrix140-1are each coupled to a matched termination such as, for example, a 50 Ohm resistor146that is coupled to electrical ground. RF connector ports120-4through120-6are connected to three of the six inputs142of Butler Matrix140-2, and the remaining three inputs142to Butler Matrix140-2are each coupled to a matched termination146. Four of the six outputs of Butler Matrix140-1(namely outputs144-2through144-5) are connected directly to columns132-3through132-6, respectively, of the first antenna array130-1by the feed network150-1. Output144-1of Butler Matrix140-1is connected to a first level power divider152-1, and the outputs of power divider152-1are coupled to columns132-2and132-8, respectively, of the first antenna array130-1. Output144-6of Butler Matrix140-1is connected to a first level power divider152-2, and the outputs of power divider152-2are coupled to columns132-1and132-7, respectively, of the first antenna array130-1. RF connector ports120-4through120-6are connected to the second beamforming network140-2, and the second beamforming network140-2is connected to the second antenna array130-2in the exact same fashion that the first beamforming network140-1is connected to the first antenna array130-1, and hence description of these connections as shown inFIG.3Bwill be omitted. It should be noted that only outputs144-1and144-12are explicitly numbered inFIG.3Bto simplify the drawing; it will be understood that the outputs to the beamforming networks140-1,140-2are arranged sequentially in numerical order).

The above description describes the RF connector ports120, beamforming networks140and first level power dividers152that are used to feed the first polarization dipole radiators136-1of the radiating elements134in the first and second antenna arrays130-1,130-2. As shown at the top ofFIG.3B, the same components are repeated to feed the second polarization dipole radiators136-2of the radiating elements134in the first and second antenna arrays130-1,130-2.

InFIG.3Bthe radiating elements in columns132-1through132-8are drawn using solid lines to indicate that these radiating elements134are part of the first array130-1, and the radiating elements in columns132-9through132-16are drawn using dotted lines to indicate that these radiating elements134are part of the second array130-2.

FIG.3Cillustrates the connections between output144-3of beamforming networks140-1,140-3and the radiating elements134of column132-4of antenna array130-1. As shown inFIG.3C, output144-3of Butler Matrix140-1is coupled to a first phase shifter assembly156-1. Phase shifter assembly156-1includes a 1×4 power divider that divides RF signals input thereto into four sub-components, and also includes an adjustable phase shifter that is configured to impart a phase progression across the four sub-components in order to electronically change the tilt angles of the antenna beams generated by the radiating elements134in column132-4. Each output158of phase shifter assembly156-1is coupled to a respective feed board160. A pair of radiating elements134are mounted on each feed board160. A power divider162is provided on each feed board160that sub-divides RF signals input thereto into first and second sub-components that are passed to the respective first and second radiating elements134mounted on the feed board160. As can be seen, the portion of feed network150-1depicted inFIG.3Cfeeds output144-3of Butler Matrix140-1to the −45° dipole radiators136-1of the radiating elements134in column132-4. A second phase shifter assembly156-2and four additional feed board power dividers162are provided that are used to similarly feed RF signals that are output from output144-15of Butler Matrix140-3to the +45° dipole radiators136-2of the radiating elements134in column132-4. It will be appreciated that each of the other columns132of antenna arrays130-1and130-2are fed in the same manner as shown inFIG.3C.

The base station antenna100operates as follows. The first beamforming network140-1, the first feed network150-1and the first antenna array130-1are used to generate first through third −45° polarized antenna beams138-1through138-3that provide coverage to the three sub-sectors on the left side of the sector, and the second beamforming network140-2, the second feed network150-2and the second antenna array130-2are used to generate fourth through sixth −45° polarized antenna beams138-4through138-6that provide coverage to the three sub-sectors on the right side of the sector. Similarly, the third beamforming network140-3, the third feed network150-3and the first antenna array130-1are used to generate first through third +45° polarized antenna beams that also provide coverage to the three sub-sectors on the left side of the sector, and the fourth beamforming network140-4, the fourth feed network150-4and the second antenna array130-2are used to generate fourth through sixth +45° polarized antenna beams that provide coverage to the three sub-sectors on the right side of the sector.FIG.3Dis a schematic diagram illustrating the first through sixth −45° polarized antenna beams138-1through138-6. As can be seen, the six antenna beams split a 120° sector in the azimuth plane into six sub-sectors that are served by the six antenna beams138. The first through sixth +45° polarized antenna beams will look identical to the first through sixth −45° polarized antenna beams, and hence the +45° antenna beams are not shown separately inFIG.3D.

As discussed above, including a phase progression along the transmission lines connecting the outputs of each Butler Matrix140to the columns132of radiating elements134may reduce the degree of beam peak walking in one direction. As discussed above with reference toFIGS.2A-2C, the beam peak walking of the left three beams results in the beam peaks for the left three antenna beams138-1through138-3generated in response to lower frequency signals pointing at larger azimuth angles than the beam peaks generated in response to higher frequency signals. Since beamforming networks140-1and140-3only generate the left three antenna beams138-1through138-3, the phase progression can be used to decrease the amount of beam peak walking for the left three antenna beams138-1through138-3with no adverse impact on the right three antenna beams138-4through138-6. Similarly, since beamforming networks140-2and140-4only generate the right three antenna beams138-4through138-6, the phase progression can be used to decrease the amount of beam peak walking for the right three antenna beams138-4through138-6with no adverse impact on the left three antenna beams138-1through138-3.

Thus, base station antenna100can significantly improve performance. However, the two antenna arrays130-1,130-2included in base station antenna100have a total of sixteen columns132of radiating elements134, which may significantly increase the width of base station antenna100as compared to conventional base station antenna1, and which also increases the weight and cost of antenna100. Additionally, antenna arrays130-1and130-2each only include eight columns132of radiating elements134as compared to the ten columns32of radiating elements34included in conventional base station antenna1. However, the reduction in beam peak walking may be worth the increased cost, particularly in higher-order sector-splitting applications.

FIG.4is a schematic block diagram illustrating the connections between the RF connector ports and the antenna arrays of a base station antenna200according to further embodiments of the present invention. WhileFIG.4does not illustrate the connections between the outputs of the beamforming networks/first level power dividers and the radiating elements in each column of the antenna arrays, it will be understood that these connections may be the same as shown inFIG.3Cfor the corresponding connections in base station antenna100. This is also true with respect to base station antennas that are discussed below with respect toFIGS.5-10, respectively. The base station antenna200may generate six antenna beams having narrower azimuth beamwidths as compared to the antenna beams generated by the base station antenna100.

As can be seen, base station antenna200is similar to base station antenna100, but includes eight additional first level power dividers152, as well as eight second level power dividers154that are not present in base station antenna100. The eight additional first level power dividers152allow each beamforming network140to be connected to ten columns132of radiating elements134instead of eight columns132as is the case with base station antenna100. As a result, the azimuth beamwidths of the antenna beams generated by base station antenna200may be narrower than the azimuth beamwidths of the antenna beams138generated by base station antenna100. Each second level power divider154is used to combine signals from two different beamforming networks140and to feed the combined signals to a respective column132of radiating elements134. As shown inFIG.4, the four middle columns132-7through132-10of radiating elements134each receive RF signals from two different beamforming networks140, and hence are part of both the first antenna array130-1and the second antenna array130-2. In other words, the four middle columns132-7through132-10of radiating elements134are shared across both antenna arrays130so that the number of columns132in each antenna array130can be increased without increasing the number of radiating elements134. However, beam-to-beam isolation may be reduced, and additional power loss (and hence gain) is incurred in the second level power dividers154. As base station antenna200may otherwise be identical to base station antenna100, further description thereof will be omitted.

FIG.5is a schematic block diagram illustrating the connections between the RF connector ports and the antenna arrays of a base station antenna300according to further embodiments of the present invention. Base station antenna300is similar to base station antenna200, but instead of sharing columns132of radiating elements across the first and second antenna arrays130-1,130-2, in base station antenna300, each antenna array130includes ten columns132of radiating elements134, none of which are shared with the other antenna array130. The four columns132-7through132-10of antenna array130-1that are closest to the middle of the base station antenna300are interlaced with respective ones of the four columns132-11through132-14of antenna array130-2that are closest to the middle of the base station antenna300. By “interlaced” it is meant that the radiating elements134in a column132of the first antenna array130-1are positioned relative to a column132of the second antenna array130-2so that so that a vertical axis exists that intersects the radiating elements134in both columns, and so that the radiating elements134in the two columns alternate as they extend with respect to the vertical axis. Thus, the radiating elements134in two interlaced columns132may be aligned along a vertical axis (as shown inFIG.5), or the radiating elements134of the two columns132may be staggered a small amount in the horizontal direction (as shown inFIG.6). It can also be seen that each of columns132-8through132-10of antenna array130-1is between (when viewed along a horizontal axis) a pair of columns132of antenna array130-2. For example, column132-8of antenna array130-1is between columns132-11and132-13of antenna array130-2, and column132-10of antenna array130-1is between columns132-13and132-15of antenna array130-2. Similarly, each of columns132-11through132-13of antenna array130-2is between (when viewed along a horizontal axis) a pair of columns132of antenna array130-1.

Since base station antenna300does not share columns132of radiating elements134between two antenna arrays130, the second level power dividers154that are included in base station antenna200are not necessary in base station antenna300. As base station antenna300may otherwise be identical to base station antenna200, further description thereof will be omitted.

FIG.6is a schematic block diagram illustrating the connections between the RF connector ports and the antenna arrays of a base station antenna400according to further embodiments of the present invention. Base station antenna400is similar to base station antenna300in that each antenna array130includes ten columns132of radiating elements134, none of which are shared with the other antenna array130. However, the columns132in antenna arrays130-1,130-2are arranged somewhat differently in base station antenna400. Additionally, the four columns132-7through132-10of antenna array130-1that are closest to the middle of the base station antenna400are again interlaced with respective ones of the four columns132-11through132-14of antenna array130-2that are closest to the middle of the base station antenna400. However, in base station antenna300columns132-7through132-10are horizontally aligned and vertically staggered with respect to columns132-11through132-14, respectively, whereas in base station antenna400columns132-7through132-10are both horizontally staggered and vertically staggered with respect to columns132-11through132-14, respectively. This design may provide a slight increase in isolation between antenna arrays130-1and130-2. As base station antenna400may otherwise be identical to base station antenna300, further description thereof will be omitted

FIG.7is a schematic block diagram illustrating the connections between the RF connector ports and the antenna arrays of a base station antenna500according to further embodiments of the present invention. Base station antenna500is similar to base station antenna400. However, in base station antenna500, columns132-7through132-10of antenna array130-1of base station antenna500are horizontally staggered to a greater degree with respect to columns132-11through132-14, respectively, and columns132-1through132-16of antenna array130-1are vertically staggered with respect to columns132-15through132-20of antenna array130-2. As base station antenna500may otherwise be identical to base station antenna400, further description thereof will be omitted.

FIG.8is a schematic block diagram illustrating the connections between the RF connector ports and the antenna arrays of a base station antenna600according to further embodiments of the present invention. InFIG.8, the RF ports120, beamforming networks140and first level power dividers152are only shown for one polarization in order to simplify the drawing. It will be appreciated that RF ports120, beamforming networks140and first level power dividers152are repeated for the second polarization, in the same manner shown inFIGS.3B and4-7. The RF ports120, beamforming networks140and first level power dividers152for the second polarization are also omitted in similar fashion fromFIGS.9and10below to simplify those drawings. Base station antenna600differs from the other base station antennas discussed above in that base station antenna600interlaces all ten columns132-1through132-10of antenna array130-1with the ten columns132-11through132-20of antenna array130-2. Consequently, the average spacing between adjacent columns132is reduced, resulting in a narrower base station antenna. The closer average spacing between columns132acts to increase coupling between radiating elements134in adjacent columns132, which can degrade some performance parameters, such as cross-polarization discrimination. Thus, base station antenna600illustrates how antenna size and performance can be traded off to suit the needs of various applications.

FIG.9is a schematic block diagram illustrating the connections between the RF connector ports and the antenna arrays of a base station antenna700according to further embodiments of the present invention. InFIG.9, the RF ports120, beamforming networks140and first level power dividers152are only shown for one polarization in order to simplify the drawing. Base station antenna700is similar to base station antenna400. However, in base station antenna700, columns132-1through132-6of antenna array130-1are staggered vertically with respect to adjacent columns, as are columns132-15through132-20of antenna array130-2. This may increase isolation between radiating elements134in adjacent columns132, which can improve various performance parameters, such as cross-polarization discrimination.

FIG.10is a schematic block diagram illustrating the connections between the RF connector ports and the antenna arrays of a base station antenna800according to further embodiments of the present invention. The base station antenna800ofFIG.10is a five beam (per polarization) sector splitting antenna, and hence generates one less beam per polarization than the base station antennas ofFIGS.3A-9discussed above. As shown, the connections between the RF connector ports and the antenna arrays are very similar to the connections in the previously described embodiments, with the major difference being that four ports on beamforming networks140-2and140-4are coupled to matched terminations instead of only three as in the other embodiments described herein.

FIG.11is a schematic block diagram of a 6×6 beamforming network900that may be used in the base station antennas according to embodiments of the present invention. As shown inFIG.11, the beamforming network900includes six inputs which are labeled142-1through142-6and six outputs which are labeled144-1through144-6. The first and second inputs142-1,142-2are coupled to a −120° hybrid coupler910, the third and fourth inputs142-3,142-4are coupled to a +120° hybrid coupler920, and the fifth and sixth inputs142-5,142-6are coupled to a +180° hybrid coupler930. The first output of the −120° hybrid coupler910is coupled to the first input of a first 3×3 hybrid coupler940-1and the second output of the −120° hybrid coupler910is coupled to the first input of a second 3×3 hybrid coupler940-2. The first output of the +120° hybrid coupler920is coupled to the second input of the first 3×3 hybrid coupler940-1and the second output of the +120° hybrid coupler920is coupled to the second input of the second 3×3 hybrid coupler940-2. The first output of the +180° hybrid coupler930is coupled to the third input of the first 3×3 hybrid coupler940-1and the second output of the +180° hybrid coupler930is coupled to the third input of the second 3×3 hybrid coupler940-2. The outputs of the first and second 3×3 hybrid couplers940-1,940-2are numbered to show how they correspond to the outputs144-1through144-6of the beamforming network900.

As described above, phase compensation may be applied to reduce beam peak walking in the base station antennas according to embodiments of the present invention. In example, embodiments, such phase compensation may be accomplished by adding different configurations of microstrip stubs to microstrip transmission lines that connect the beamforming networks to the antenna arrays in the base station antennas according to embodiments of the present invention. The different configurations of microstrip stubs may be selected to exhibit different phase slope versus frequency characteristics, which allows the output phase for each microstrip transmission line as a function of frequency to be optimized to reduce beam peak walking.

FIG.12is a schematic diagram illustrating such phase compensation may be achieved. In particular, a pair of microstrip transmission lines1000,1010are shown inFIG.12. Transmission line1000includes an input1002(which may be connected to a beamforming network), an output1004(which may be coupled to a column of radiating elements), and a plurality of tuning stubs1006. Similarly, transmission line1010includes an input1012(which may be connected to a beamforming network), an output1014(which may be coupled to a column of radiating elements), and a plurality of tuning stubs1016. The tuning stubs1006,1016have different configurations. The graph inFIG.12illustrates the phase of RF signals that are input to the respective transmission lines1000,1010at the respective outputs of transmission lines1000,1010as a function of frequency. As shown in the graph, the slopes of the two responses differ (and hence the lines on the graph cross), which allows a designer to optimize the phase output as a function of frequency in order to reduce beam peak walking.

While the above-described embodiments are described with respect to splitting a 120° sector of a traditional three-sector base station, it will be appreciated that embodiments of the present invention are not limited thereto. For example, in other embodiments, the sector-splitting base station antennas may be used to split a sector of a four-sector base station, used in applications that provide coverage along relatively straight highways, tunnels, bridges, railways or the like, or used in specialized applications such as stadiums or other large venues.

It will be appreciated that many modifications may be made to the above example embodiments without departing from the scope pf the present invention. As one example, each of the embodiments discussed above included two beamforming networks per polarization. Embodiments of the present invention are not limited thereto. For example, in other embodiments, three or more beamforming networks may be provided per polarization. As one example, a six-beam (per polarization) sector-splitting antenna could include three beamforming networks which are each coupled to a respective pair of RF ports (per polarization). Each beamforming network may be coupled to a respective antenna array. The antenna arrays may or may not share columns, and may include interlace columns.

The base station antennas described above include “columns” of radiating elements. Most typically, each “column” may comprise a vertically-oriented linear array of radiating elements where the radiating elements extend along a vertical axis. However, it will be appreciated that in some cases the columns may be so-called “staggered” linear arrays of radiating elements in which some of the radiating elements are offset horizontally from other of the radiating elements by a small amount. As explained in U.S. Provisional Patent Application Ser. No. 62/722,238, filed Aug. 24, 2018, the entire content of which is incorporated herein by reference, such staggered linear arrays may be included in base station antennas to, for example, improve the stability of the azimuth beamwidth across the frequency band of operation.

It will be appreciated that the present specification only describes a few example embodiments of the present invention and that the techniques described herein have applicability beyond the example embodiments described above. It should also be noted that the antennas according to embodiments of the present invention may be used in applications other than sector-splitting such as, for example, in venues such as stadiums, coliseums, convention centers and the like. In such applications, the multiple beams are more usually configured to cover a 60°-90° sector.

Embodiments of the present invention have been described above with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (i.e., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.).

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and/or groups thereof.

Aspects and elements of all of the embodiments disclosed above can be combined in any way and/or combination with aspects or elements of other embodiments to provide a plurality of additional embodiments.