Configurable wide scan angle array

An antenna array structure is described that includes at least two antenna arrays co-located on a common planar array reflector. One of the antenna arrays has a first, central scan range. The other antenna array includes antenna elements that can be controlled to scan regions outside of the first, central scan range.

FIELD

The present disclosure relates to antenna arrays such as beam forming antenna arrays.

BACKGROUND

Adaptive beam forming can be used to optimize the propagation path between a base station antenna array and a terminal such as user equipment (UE). Conventional antenna arrays have a scanning range of approximately +/−40°. Beyond that range, the scanning loss in gain may degrade propagation and also form unwanted side lobes that create interference. Furthermore, at lower frequencies (for example 3.5 GHz or 2.4 GHz), conventional antenna arrays that includes a high number of antenna elements arranged in a planar arrays can require a large physical foot print.

It is desirable to provide a planar antenna array which has the ability to cover an extended beam forming scan range of +/−(40° to 70°) in addition to a conventional scan range +/−40°.

SUMMARY

An antenna array structure is described that includes at least two antenna arrays co-located on a common planar array reflector. One of the antenna arrays has a first, central scan range. The other antenna array includes antenna elements that can be controlled to scan regions outside of the first, central scan range. In at least some examples, the antenna array structure is a planar array that can provide a wider scan angle range and improved gain when compared to conventional antenna array structures of similar size. The planar antenna array structure may in some configurations provide an extended scan angle range and a higher gain over that range, allowing for one or both of a better signal level and a reduction in overall size of the antenna array.

An antenna array structure is disclosed according to a first example aspect. The antenna array structure includes a planar array reflector, a central beam forming antenna array located on the planar array reflector and configured to form radio frequency (RF) signals having a beam peak that is adjustable within a central scan angle range relative to a propagation axis that is normal to the array reflector, and a wide beam forming antenna array located on the surface of the planar array reflector and configured to form RF signals with a beam peak that is adjustable within a wide angle scan range that at least partially exceeds the central scan angle range.

In some example embodiments, the central beam forming antenna array includes an array of antenna elements that are polarized approximately parallel to the array reflector, and the wide beam forming antenna array includes an array of antenna elements that are polarized approximately parallel to the propagation axis and orthogonal to the antenna elements of the central beam forming antenna array. In some examples rows of the antenna elements of the central beam forming antenna array alternate with rows of the antenna elements of the wide beam forming antenna array on the array reflector.

In some example embodiments, the central beam forming antenna array includes a first array of first antenna elements and a second array of second antenna elements, wherein each first antenna element is co-located with a respective one of the second antenna element, the first antenna elements and second antenna elements having different polarizations. The first antenna elements and second antenna elements may be polarized orthogonally to each other. Furthermore, the first antenna elements and second antenna elements may each be dipole antenna elements.

In some example embodiments, the central beam forming antenna array includes antenna elements that are polarized parallel to a plane of the array reflector and that are one of: dipole antenna elements; slot antenna elements; slot coupled patch antenna elements; probe fed patch antenna elements; linear polarized antenna element and circular polarized antenna elements.

In some example embodiments of the first aspect, the wide beam forming antenna array includes antenna elements that are polarized in a direction that is normal to a plane of the array reflector and that are one of: monopole antenna elements; configurable monopole antenna elements having parasitic switchable features; folded monopole antenna elements; inverted F antenna elements; and configurable reversible inverted F antenna elements.

In some example embodiments, the wide beam forming antenna array includes an array of configurable reversible inverted F-antenna units. In some examples, each configurable reversible inverted F antenna (RIFA) unit comprises: a feed portion electrically coupling the RIFA unit to an RF feed; at least a first selective grounding portion and a second selective grounding portion, each selective grounding portion being configured to selectively enable or disable an electrical coupling to a ground plane of the planar array reflector; a first conductive arm providing electrical conduction between the feed portion and the first selective grounding portion, extending from the first selective grounding portion towards the feed portion and extending beyond the feed portion; and at least a second conductive arm providing electrical conduction between the feed portion and the second selective grounding portion, extending from the second selective grounding portion towards the feed portion and extending beyond the feed portion. The feed portion, the first selective grounding portion and the first conductive arm together define a first inverted F antenna (IFA) element of the RIFA unit, the feed portion, the second selective grounding portion and the second conductive arm together define at least a second IFA element of the RIFA antenna unit; the feed portion being common to both the first and at least the second IFA elements.

In some examples, the first and second IFA elements are polarized in a direction that is normal to a plane of the array reflector, and oriented to propagate in opposing directions.

In some examples the array structure comprises a controller configured to independently adjust a phase and an amplitude of an RF signal for each of a plurality of first antenna elements that are included in the central beam forming antenna array and each of a plurality of second antenna elements that are included in the wide beam forming antenna array to cause the antenna array structure to form a collective RF signal having a beam peak that corresponds to a desired propagation angle. In some examples, the controller is configured to use the central beam forming antenna array to form the collective RF signal when the desired propagation angle falls within the central scan angle range and to use the wide beam forming antenna array to form the collective RF signal when the desired propagation angle falls within the wide scan angle range. In some examples, the controller is configured to use both the central beam forming antenna array and the wide beam forming antenna array to form the collective RF signal when the desired propagation angle falls within a scan angle range that is within an overlapping region of the central scan angle range and the wide scan angle range. In some examples, the controller is configured to use only the central beam forming antenna array to form the collective RF signal when the desired propagation angle falls within the central scan angle range and to use only the wide beam forming antenna array to form the collective RF signal when the desired propagation angle falls within the wide scan angle range.

In some examples, the central scan angle range is not more than +/−40° relative to the propagation axis that is normal to the array reflector. In some examples, the wide angle scan range is from not less than 35° to not more than 75° and from not more than −35° to not less than −75° relative to the propagation axis that is normal to the array reflector.

According to another example aspect is a method of transmitting an RF signal using an antenna array structure that includes a planar array reflector, a central beam forming antenna array located on the planar array reflector and configured to form radio frequency (RF) signals having a beam peak that is adjustable within a central scan angle range relative to a propagation axis that is normal to the array reflector, and a wide beam forming antenna array located on the surface of the planar array reflector and configured to form RF signals with a beam peak that is adjustable within a wide angle scan range that at least partially exceeds the central scan angle range. The method includes selecting at least one of the central beam forming antenna array and the wide beam forming antenna array based on a desired propagation angle, and adjusting the amplitude and phase of RF signals provided to antenna elements of the selected antenna array to achieve the desired propagation angle for transmitting the RF signal. In at least some examples, selecting at least one of the central beam forming antenna array and the wide beam forming antenna array based on a desired propagation angle comprises: if the desired propagation angle falls with the central scan angle range then selecting the central beam forming antenna and if the desired propagation angle falls outside of the central scan angle range then selecting the wide scan angle array. In some examples, the central scan angle range is not more than +/−40°.

DESCRIPTION OF EXAMPLE EMBODIMENTS

The following is a partial list of acronyms and associated definitions that may be used in the following description:

Directional references herein such as “front”, “rear”, “up”, “down”, “horizontal”, “top”, “bottom”, “side” and the like are used purely for convenience of description and do not limit the scope of the present disclosure. Furthermore, any dimensions provided herein are presented merely by way of an example and unless otherwise specified do not limit the scope of the disclosure. Furthermore, geometric terms such as “straight”, “flat”, “curved”, “point”, “normal”, “orthogonal” and the like, and references to direction of polarization, are not intended to limit the disclosure any specific level of geometric precision, but should instead be understood in the context of the disclosure, taking into account normal manufacturing tolerances, as well as functional requirements as understood by a person skilled in the art.

FIG. 1andFIG. 2illustrate front and side views of an antenna array structure110according to example embodiments. In example embodiments, antenna array structure110may be configured to transmit and receive radio frequency (RF) signals within a predetermined or operating frequency band through a wireless channel. For example, antenna array structure110may be part of a base station system or other interface node and used to exchange RF signals using the operating frequency band with user equipment (UE).

Antenna array structure110includes first and second beam forming antenna arrays, namely a dual polarity central scan angle (CSA) array106and a wide scan angle (WSA) array108, that are co-located on a common planar array reflector112. The antenna array structure110is an active electronically scanned array having a beam peak direction119that can be adjusted relative to an antenna propagation axis121(also known as the antenna boresight) that is normal to the array reflector112. With reference to the three dimensional orthogonal X-Y-Z reference coordinates shown inFIG. 1andFIG. 2, the planar array reflector112extends in the X-Y plane and the antenna propagation axis121extends parallel to the Z axis in a direction that is normal to the X-Y plane. As best shown inFIG. 2, in the illustrated example, the antenna array structure110the beam peak direction119can be described with two angles, namely angle θ, which is the angle of the beam peak direction119from the antenna propagation axis121, and angle φ, which represents the rotation of the the beam peak direction119around the antenna propagation axis121. In the illustrated example, the angle φ denotes the angle of the beam peak direction119from the X-Z plane that is intersected by the antenna propagation axis121, and in the particular example illustrated inFIG. 2, the angle φ=0. In a use case where the antenna array structure110is mounted with X-Z plane in a horizontal direction, the angles φ and θ can describe a direction of beam peak119that corresponds to what is commonly referred to as downtilt.

In example embodiments, the combination of CSA array106and WSA array108enables the propagation angle θ of the beam peak direction to be scanned within a total scan angle range140of +/−θWrelative to an antenna propagation axis121. In some example embodiments, θW=70°, however other angles are also possible. For example, the maximum scan angle θWmay be more than 70° (for example 75°) or less than 70° in some embodiments. In at least some example embodiments, the CSA array106and WSA array108can each be steered to enable downtilt angle φ to be steered away from φ=0, for example +/−40°.

In example embodiments, the planar array reflector112is formed from a conductive material that provides structural rigidity to the antenna array structure110. In one example, the reflector112is formed from aluminum. In some example embodiments, isolated RF feed ports are provided on a back surface of the planar array reflector112to connect each of the antenna elements in CSA array106and WSA array108to a respective RF feed line. In alternative embodiments, the reflector could for example be a multilayer printed circuit board (PCB) that includes a conductive ground plane layer with a ground connection, one or more dielectric substrate layers, and one or more layers of conductive traces for distributing one or both of control and RF signals throughout the planar array reflector112.

The CSA array106is a rectangular two-dimensional R by M periodic array made up of a plurality of rows116of dual polarity antenna units120(R=4, M=5 in the illustrated example) secured to the planar array reflector112. In an example embodiment, each dual polarity antenna unit120includes a pair of co-located dipole antenna elements122,124, that have orthogonal polarization axes. Thus, CSA array106is made up of two arrays of dipole antenna elements122,124. In the illustrated example, each dipole antenna element122has a +45° polarization in the X-Y plane and each dipole antenna element124has a −45° polarization in the X-Y plane. In example embodiments, the periodic spacing in both the X and Y directions between adjacent dual polarity antenna units120is S1≈λ/2, where λ is an operating wavelength that corresponds to a frequency within the operating frequency band that the antenna array structure110is designed to support. By way of non-limiting example, λ may in one example be a wavelength that corresponds to a frequency within a frequency band of 3.4 GHz to 3.8 GHz. In other example embodiments, array spacing of other than S1≈λ/2 may be used.

Referring toFIG. 2, each of the dipole antenna elements122,124, is connected to a respective RF feed line132. RF feed lines132connect the dipole antenna elements122,124through an amplifying and phase shifting module130to transmit/receive (Tx/Rx) circuitry126. When transmitting signals, each dipole antenna element122,124is fed RF signals generated by the transmit/receive (Tx/Rx) circuitry126through amplifying and phase shifting module130for transmission over a wireless channel. When receiving signals, RF signals received through the wireless channel at each dipole antenna element122,124are sent through amplifying and phase shifting module130to transmit/receive (Tx/Rx) circuitry126. Amplifying and phase shifting module130is configured to apply antenna element excitation weights to enable a magnitude and phase of the RF signal applied to or received from each of the dipole antenna elements122,124to be individually controlled by a controller128.

During operation, the phase and amplitude of the RF signals applied to or received from each of the dipole antenna elements122,124of the dual polarity antenna units120can be independently adjusted by controller128to collectively control the propagation angle θ of the CSA array106in two dimensions (e.g. in the Y-Z plane and the X-Z plane) relative to antenna propagation axis121. In example embodiments, a number of different types of known dual polarity antenna designs can be used for the dual polarity antenna units120of CSA array106, which conventionally have a scan angle range of +/−(30° to 40°) relative to the antenna propagation axis121. Thus, in example embodiments, the CSA array106has a first, central scan angle range134of +/−θCrelative to the antenna propagation axis121. In some example embodiments, θC=40° such that the effective scan angle range134of the CSA array106is +/−40° relative to the antenna propagation axis121, although the central scan angle range134may be greater or less than +/−40° in some embodiments. For example, the effective scan angle range134of the CSA array106is +/−35° in some embodiments, and the effective scan angle range134of the CSA array106is +/−30° in some embodiments.

For purposes of illustrating operation of CSA array106,FIG. 3illustrates a simulated radiation pattern for one row116of 5 dipole antenna elements122wherein amplifying and phase shifting module130applies the following antenna element excitation weights to the RF signal applied to each antenna element122, from left to right, as follows: 1stantenna element122: magnitude weight (M)=0.5V, phase weight (P)=0°; 2ndantenna element122: M=0.8V, P=−50°; 3rdantenna element122: M=1V, P=−100°; 4thantenna element122: M=0.8V, P=−150°; and 5thantenna element122M=0.5V, P=−200°. Plots302represent three azimuth cuts at 3.4 Ghz, 3.6 GHz and 3.8 GHz. As shown inFIG. 3, the resulting transmitted RF signal has a beam peak119at θ=+15°. As shown inFIG. 3, the RF signal pattern has minimal side lobes when the beam peak direction is at 15°. Simulation results show that the side lobes grow when the beam peak119approaches the limits of the central scan angle range134

Referring again toFIG. 1andFIG. 2, as noted above, antenna array structure110also includes WSA array108co-located with dual-polarity array106on planar array reflector112. WSA array108includes antenna elements that can be controlled to scan wide angle regions that fall outside of the narrower central scan range134of the dual-polarity array106.

In the illustrated example WSA array108is a rectangular two-dimensional R+1 by N periodic array made up of a plurality of rows114of monopole antenna elements118(r,c), where 1≤r≤R+1 and 1≤c≤N (R+1=5, N=9 in the illustrated example ofFIG. 1andFIG. 2) secured to the planar array reflector112. The monopole antenna elements118(r,c) each are polarized in a direction that is approximately normal to the planar array reflector112(e.g. parallel to the antenna propagation axis121). In an example embodiment, rows114of monopole antenna elements118(r,c) alternate with rows116of the dual polarity antenna units120. Although different array spacing can be used in different embodiments, in the example shown inFIG. 1andFIG. 2, the periodic spacing in the X direction between adjacent monopole antenna elements118(r,c) within each row114is S2≈λ/4, and the periodic spacing in the Y direction between adjacent monopole antenna elements118(r,c) within each column is S1≈λ/2.

As with dipole antenna elements122,124, in example embodiments each of the monopole antenna elements118(r,c) is also connected by a respective RF feed line130to amplifying and phase shifting module130, which in turn is connected to transmit/receive (Tx/Rx) circuitry126. Amplifying and phase shifting module130is configured to enable an amplitude and phase of the RF signal applied to or received from each of the monopole antenna elements118(r,c) to be individually controlled by controller128.

During operation, the phase and amplitude of the RF signals applied to or received from each of the monopole antenna elements118(r,c) is controlled by controller128to achieve a desired propagation angle θUEfor the beam peak direction119relative to antenna propagation axis121. In example embodiments, the desired propagation angle corresponds to an optimal angle for a particular UE that the antenna array structure110is exchanging the subject RF signals with, referred to hereafter as the UE propagation angle.

A number of different types of known monopole antenna designs can be used for monopole antenna elements118(r,c) of the WSA array108. Monopole antenna elements118(r,c) have a polarization that is normal to the planar array reflector112and orthogonal to the polarizations in the X-Y plane of dipole antenna elements122,124. Accordingly, the monopole antenna elements118(r,c) are not be particularly effective for radiating RF signals within the central scan angle range134covered by CSA array106, however they are effective for radiating RF signals within the wider scan angle ranges138and136that border the central scan angle range134. In example embodiments monopole antenna elements118(r,c) can be controlled by controller128to provide a wide angle scan range136of between approximately +θCto +θw, and a wide angle scan range138of between approximately −θCto −θw, relative to the antenna propagation axis121. Thus, in example embodiments, the WSA array108and the CSA array106collectively provide a total scan angle range140of +/−θWrelative to the antenna propagation axis121. In one example, θC=40° and θW=70°, such that the combination of WSA array108and dual-polarity array106provide the antenna array structure110with a larger overall scan angle range than each of the individual arrays, for example a continuous scan angle range of +/−70°. As noted above, in some examples the continuous scan angle range can be more or less than +/−70°, including for example +/−75°.

For purposes of illustrating operation of WSA array108,FIG. 4illustrates a simulated radiation pattern for one row114of 9 monopole antenna elements118(r,1) to118(r,9) for an example where controller128specifies a UE propagation angle θUE=52°. In the example illustrated inFIG. 4, amplifying and phase shifting module130applies the following antenna excitation weights to the RF signal applied to each of the monopole antenna elements118(r,1) to118(r,9), from left to right in a single row114, as shown in the following table:

For the UE propagation angle θUE=52° ofFIG. 4, dphase=63° and dtaper=0.8. Plots402represent three azimuth cuts at 3.4 Ghz, 3.6 GHz and 3.8 GHz. As shown inFIG. 4, the resulting transmitted RF signal has a beam peak direction119at +52°. Different dphase and dtaper values can be used to achieve different UE propagation angles; for example, simulation results for dphase=95° and dtaper=0.7 resulted in a beam peak at 70° and simulation results for dphase=80° and dtaper=0.8 resulted in a beam peak at 62°.

FIG. 5Ashows an example method for transmitting or receiving an RF signal from antenna array structure110. In example embodiments, antenna array structure110is used to transmit and/or receive RF signals using time division duplexing (TDD) in a multiple input multiple output (MIMO) environment. For example antenna array structure110may be part of a base station that communicates with multiple UEs. Based on predetermined information, a scheduler at the base station determines a time slot to to transmit or receive an RF signal to or from a particular UE. Based on tracked information about the channel between the base station and the UE, the scheduler or the base station determines an optimal angle (the UE propagation angle θUE) to use for the RF signal. The UE propagation angle θUEwill fall within the total scan angle range140of the antenna array structure110(E.g. within +/−θw). In the example ofFIG. 5A, controller128receives the UE propagation angle θUEthat is to be used for a transmitting or receiving the RF signal (block502). The controller128then selects which antenna array should be used to transmit or receive the RF signal based on the UE propagation angle (block504). In particular, if the UE propagation angle θUE falls with the central scan angle range134(e.g. |θUE|<|θc|) then the controller128will select the CSA array106. However, if the UE propagation angle θUEfalls outside of the central scan angle range134but within the wider scan angle ranges136,138, (e.g. |θUE|>|θc| and |θUE|≤|θw|) then the controller128will select the WSA CSA array106.

The controller128then causes the appropriate amplitude and phase weights to be applied to the RF signals that are provided to each of the respective antenna elements of the selected antenna array to achieve the UE propagation angle θUEfor the RF signal (block506). In particular, in cases where the UE propagation angle θUEfalls with the central scan angle range134, the controller128causes the phase and amplitude of the RF signal applied to each of the dipole antenna elements122,124to be individually controlled such that the resulting RF signal transmitted or received by CSA array106has a beam peak at approximately the UE propagation angle θUE. In cases where the UE propagation angle θUEfalls outside the central scan angle range134, the controller128causes the phase and amplitude of the RF signal applied to each of the monopole antenna elements118(r,c) to be individually controlled such that the resulting RF signal transmitted or received by WSA array108has a beam peak at approximately the UE propagation angle θUE.

Although the example described above have assumed a discrete transition at +/−θCbetween the central scan angle range134of the CSA array106and the wide scan angle range136,138of the WSA array108, in at least some example embodiments there can be an overlap between the central scan angle range134of the CSA array106and the wide scan angle range136,138of the WSA array108. In such an example, in block504the controller128may select both the CSA array106and the WSA array108, and cause both the CSA array106and the WSA array108to simultaneously transmit (or receive) the RF signal in block506. By way of non-limiting example, the overlap region may be +/−(θC+/−5°), such that when |θc−5°|≤|θUE|≤θc+5°|, both CSA array106and the WSA array108are used to transmit the RF signal in a scheduled time slot with appropriate phase and amplitude adjustment factors being individually applied to the RF signals for each of the dipole antenna elements122,124and monopole antenna elements118(r,c) to collectively achieve the UE propagation angle θUE. In some example embodiments, the overlap region overlap may be similar to what is found in overlap between cell site coverage ‘sectors’ in cellular networks, primarily to avoid dropped connections in these areas of transition between sectors.

In summary, in example embodiments the antenna array structure110includes three independent arrays co-located on planar array reflector112. In particular, CSA array106includes two arrays, namely a first array of dipole antenna elements122and a second array of dipole antenna elements124. The dipole antenna elements122and dipole elements124are each polarized parallel to the planar array reflector112and orthogonal to each other. A third array is provided by WSA array108whose monopole antenna elements118(r,c) are each polarized orthogonal to the dipole antenna elements122,124. The two orthogonal arrays of the CSA array106are capable of forming beams within a central scan angle range of an axis121that is normal to planar array reflector112, and the WSA array108is capable of forming beams at angle that fall outside of central scan angle range.

In at least some example embodiments the use of an planar antenna array structure110having co-located CSA array106and WSA array108provides a structure that can effectively form beams over a greater range of propagation angles than many conventional planar arrays. Furthermore, in a conventional array a high antenna element density may be required to reduce unwanted sidelobes wide beam steering angles. In the case of antenna array structure110, an increase in gain can result from an overlap in the WSA array individual antenna element pattern and the CSA array individual element pattern, permitting the pattern beam widths for the individual antenna elements to be somewhat reduced compared to a conventional 65 degree cellular antenna. As will be described in further detail below, WSA array individual element pattern gain can be further increased when a configurable antenna element is used.

Accordingly, in some example embodiments the antenna elements of the CSA array106and WSA array108may be configured to have reduced antenna element radiation beamwidth, and higher gain. This can allow for the reduction of the overall array size. Reduced array size can be an important factor in the context of lower frequencies which have larger bandwidth and hence require larger antenna elements.

In this regard,FIG. 5Bis a plot of one antenna element of the CSA, and its 3 dB beamwidth approximately represents the scan angle range of CSA array106. Lines510represent regions where the coverage patterns of the WSA array108overlaps with that of the CSA array106, and line512represents the normal (boresight) boresight axis of the CSA array106. The combination of WSA array108with CSA array106allows the gain of the CSA array106to be reduced in the areas that can be covered by the WSA array108. For example, the CSA array106may be implemented using antenna elements that have a scan angle range of <65°, but which have a greater beam focus and gain near the boresight axis of 0°. This can allow a reduction in the number of rows or columns of antenna units120required for the CSA array106in the absence of WSA array108.

In the WSA array108described above, the monopole antenna elements118(r,c) have an X-axis spacing of S2≈λ/4 and a Y-axis spacing of S1≈λ/2, and the propagation angle θ of the WSA array108relative to antenna propagation axis121may be controlled to a greater extent in the Z-X plane than the Z-Y plane. In other example embodiments, the monopole antenna elements118(r,c) are arranged to also allow the propagation angle θ of the WSA array108to be controlled to a similar degree in both the Z-Y-plane and the Z-X plane, allowing improved two dimensional control of the propagation angle θ relative to antenna propagation axis121.

In this regard,FIG. 6illustrates a further antenna array structure610that is identical to antenna array structure110described above except for differences in the WSA array108that will now be described. Antenna array structure610includes additional monopole antenna elements118between the dual polarity antenna units120in each row116such that alternating columns614of the WSA array108have an inter-monopole antenna element spacing of S2≈λ/4. In this regard, as seen inFIG. 6, the 2nd, 4th, 6thand 8thcolumns614of WSA array108each include 9 monopole antenna elements118that have a Y-axis spacing of S2≈λ/4 between adjacent elements, while the 1st, 3rd, 5th, 7thand 9thcolumns of WSA array108each include 5 monopole antenna elements118that have a Y-axis spacing of S1≈λ/2 between adjacent elements.

The combination of columns614of monopole antenna elements118with Y-axis spacing of S2≈λ/4 and rows114of monopole antenna elements118with Y-axis spacing of S2≈λ/4 enables the WSA array108to scan wide angles θCto θWin both the Z-Y plane and the Z-X plane, allowing two dimensional control of wide angle beam forming relative to the antenna propagation axis121.

In the example embodiments described above, the CSA array106that covers the central scan angle range +/−θCcomprises two arrays of co-located, orthogonally polarized dipole antenna elements122,124. In other example embodiments, different types of antenna elements can be used in place of dipole antenna elements122,124, so long as they are polarized approximately parallel to the plane of the planar array structure112(e.g. in the X-Y plane). For example, other types of single polarized antenna elements that could be used for the CSA array106include: slot antenna elements, slot coupled patch antenna elements, probe fed patch antenna elements, right hand or left hand circular polarized antenna elements, or any suitable single linear polarized antenna element.

In the example embodiments described above, the WSA array108is made up of monopole antenna elements that are polarized approximately normal to the plane of the planar array structure112(e.g. in the Z-axis). Different types of antenna elements can to implement the WSA array108, so long as they are polarized approximately normal to the plane of the planar array structure112. Examples of other possible antenna elements include configurable monopole antenna elements with parasitic switchable features, folded monopole antenna elements, and, in particular example embodiments, a configurable reversible inverted F-antenna (IFA) element.

In this regard,FIGS. 7 and 8illustrate diagrammatic views of an example of a configurable reversible IFA (RIFA) unit700that may be used to implement the monopole antenna elements118(r,c) and118in the antenna array structures110,610described above. The antenna unit700is shown on common array reflector112. The antenna unit700may be electrically coupled or uncoupled to the ground plane of common array reflector112. In some example embodiments, the antenna unit700may be formed from a conductive material printed or otherwise provided on a surface of a substrate. A first and at least a second IFA antenna element770are defined in the antenna unit700, as explained further below.

The antenna unit700is electrically coupled to an RF signal port704via a feed portion706. RF signal port704is connected to a respective RF line132. The longitudinal axis of the feed portion706defines an axis of symmetry (indicated by dotted line S inFIG. 7) of the antenna unit700. The antenna unit700includes a plurality of selective grounding portions712; the example inFIG. 7shows first and second selective grounding portions712. Each selective grounding portion712is configured so that the selective grounding portion712can enable or disable an electrical coupling to the ground plane. For example,FIG. 8shows a switchable element716(e.g., a switchable PIN diode) at the end of the selective grounding portion712, to selectively enable or disable an electrical coupling, for example to the ground plane. In some example embodiments, the switchable element716may be a tunable element which can be variably tuned by controller128. For example, in some embodiments, the switchable element716may be tuned to function as an electrical short or a non-zero impedance, or may include a tuning or varactor diode.

The antenna unit700also includes a plurality of conductive arms714; the example inFIG. 7shows first and second conductive arms714. The number of conductive arms714corresponds to the number of selective grounding portions712. Each conductive arm714provides electrical conduction between the feed portion706and a respective one selective grounding portion712, and extends from the respective one selective grounding portion712towards the feed portion706and beyond the feed portion706. It should be noted that the conductive arms714may not be distinct from each other. For example, the conductive arms714may overlap with each other, such that the conductive arms714have an overlapping common portion713. Such a configuration will be discussed in detail further below.

In the example shown, the conductive arms714may be formed integrally with the feed portion706and the selective grounding portions712. Thus, although described as different portions of the antenna unit700, the feed portion706, selective grounding portions712and conductive arms714may not be distinct or physically separate portions of the antenna unit. Conceptually, the antenna unit700shown inFIG. 7may also be thought of as having one arm that provides electrical conduction between the feed portion706and both selective grounding portions712, and extending from both selective grounding portions712. For ease of understanding, the present disclosure will refer to the antenna unit700as having a plurality of conductive arms714with respective lengths as indicated, and with each conductively arm714corresponding to a respective plurality of selective grounding portions712.

The feed portion706, together with one conductive arm714, and the respective selective grounding portion712, define one IFA element770of the antenna unit700. As noted above, the conductive arm714of the IFA element770is considered to be the conductive portion of the antenna unit700that extends from the grounding portion712of that IFA element770towards the feed portion706and extending beyond the feed portion706, explained further below. The feed portion706is common to all IFA elements770, such that the IFA elements770are not discrete elements of the antenna unit700. For example, as shown inFIG. 9, the feed portion706, first selective grounding portion712(1), and first conductive arm714(1), together define a first IFA element770(1); the feed portion706, second selective grounding portion712(2), and second conductive arm714(2), together define a second IFA element770(2). The elements included in IFA elements770(1) and770(2) are conceptually indicated by respective dashed boxes. Thus, as can be seen inFIG. 9, the first IFA element770(1) and second IFA element770(2) include respective first and second conductive arms714(1),714(2) that extend from the corresponding first and second selective grounding portions712(1),712(2) towards and extending beyond the common feed portion706. As shown inFIG. 9, the conductive arms714(1) and714(2) may overlap at least partially over a common portion713of their length. In some embodiments, common portion713can be an integral conductive portion of the RF antenna unit700that is common to the first and second conductive arms714(1) and714(2). Thus, conceptually, IFA elements770(1) and770(2) can be seen to overlap at least partially, in addition to sharing the common feed portion706.

Notably, in some embodiments the feed portion706, and the common portion713, are common to both the first IFA element770(1) and the second IFA element770(2). Thus, although the antenna unit700is considered to define first and second IFA elements770(1),770(2), the first and second IFA elements770(1),770(2) are not discrete elements of the antenna unit700. It should be noted that, in some embodiment, there may not be an overlapping common portion713(e.g., the conductive arms714(1),714(2) may not be collinear and hence may not overlap), however the feed portion706remains common to the first and second IFA elements770(1),770(2) in all embodiments.

In some example embodiments, the antenna unit700has two IFA elements770, for example as shown in the examples ofFIGS. 7-11. In other examples, the antenna unit700has more than two IFA elements770, for example four IFA elements770. Other numbers of IFA elements770may be defined in the antenna unit700. Regardless of number, the IFA elements770may be arranged symmetrically about the axis of symmetry defined by the feed portion706. Such an arrangement may be useful in order to achieve a more symmetric radiation pattern for the antenna unit700. In the case where the antenna unit700has two IFA elements770, the two IFA elements770may be arranged with respective conductive arms714extending away from and opposite to each other, with both conductive arms714polarized normal to the array reflector112. In example embodiments, the IFA elements770may be arranged asymmetrically about the axis defined by the feed portion706. For example, in the case where the antenna unit700has two IFA elements770, IFA elements770may be arranged in a rotation angle other than 180° relative to each other. For example, the IFA elements770may be arranged at 90° relative to each other. In the case where the antenna unit700has four IFA elements770, the four IFA elements770may be arranged with a separation of 90° between adjacent IFA elements770, if arranged symmetrically; or at some other angle of separation, if asymmetrically.

Each selective grounding portion712may be selectively coupled to the substrate702via a respective switchable element716. Generally, the switchable element716may be any suitable element that can selectively enable or disable an electrical coupling with the substrate702, for example by creating a virtual, RF open circuit or closed circuit. As shown in the example ofFIG. 9, the switchable element716may be a DC switching PIN diode or other PIN diodes known in the art. The PIN diode can be biased either on or off (e.g., via a control signal from a processor of a wireless communication device in which the antenna unit700is implemented) to selectively enable or disable the electrical coupling to the substrate702. In some examples, the switchable element716may selectively enable or disable an electrical coupling by creating a physical open circuit or closed circuit, such as with the use of microelectromechanical system (MEMS) devices.

Thus, conceptually as shown inFIGS. 10 and 11, the antenna unit700is formed by superimposing and mirroring a plurality of IFA elements770about a single RF signal port704of the antenna unit700, with each IFA element770being independently controllable to be connected to ground or not by controlling the switchable elements716. The overlapping nature of the IFA elements770results in a more compact design for the antenna unit700, which may save space and allow more antennas or other components to be installed. Further, no RF switching component is required.

An IFA element770whose grounding portion712is not electrically coupled to the ground plane of substrate112(e.g., whose PIN diode is biased off) may be considered to be inactive and may have reduced or negligible contribution to the overall radiation pattern of the antenna unit700. Portions of an inactive IFA element770may be considered parasitic elements for an active IFA element.

This is conceptually illustrated inFIGS. 10 and 11. For simplicity, the switchable elements716are not shown inFIGS. 10 and 11.FIG. 10shows an antenna unit700substantially identical to that shown inFIG. 7that includes IFA elements770(1) and770(2) superimposed and symmetrically located around the feed portion706.FIG. 10shows that the electrical coupling between the second selective grounding portion712(2) and the ground plane of substrate112is enabled, and the electrical coupling between the first selective grounding portion712(1) and the ground plane substrate112is disabled. As a result, only the second IFA element770(2) is active. The second IFA element770(2) has parasitic artifacts due to portions of inactive IFA element770(1). The first selective ground portion712(1) and an extending portion of the first conductive arm714(1) (both indicated as dark-colored portions) are high impedance open stubs. Specifically, the first selective ground portion712(1), when not coupled to the ground plane, presents a relatively high impedance parasitic stub to the conductive arm714(2) of the second IFA element770(2). Similarly, the first conductive arm714(1) is shorted by the connection to ground at the second selective grounding portion712(2), so the extended portion of the first conductive arm714(1) is an open circuit stub that presents a relatively high impedance parasitic stub to the grounding portion712(2) of the second IFA element770(2). The active second IFA element770(2) is defined by the second conductive arm714(2), whose length extends from the second selective grounding portion712(2) towards and beyond the feed portion706. The active IFA element770(2), is conceptually illustrated inFIG. 11(with parasitic elements removed for ease of understanding). It should be noted that the IFA element770(2) shown inFIG. 11is substantially identical to a conventional IFA element such as IFA element15seen inFIG. 7. Thus, conceptually, the antenna unit700shown inFIG. 10could be formed from multiple superimposed IFA elements770.

In the example shown inFIG. 10, the antenna unit700may have different switched states, defined by different grounding portions712being electrically coupled or not electrically coupled to the ground plane (via coupling to the substrate112), with different radiation patterns being achievable using different switched states, as illustrated in further examples below. In this way, the radiation pattern of the antenna unit700can be configurable.

The use of configurable RIFA units700for antenna elements118(r,c),118of WSA arrays108may, in some examples, provide additional main beam gain with a reduced number of array elements. In addition to controlling the amplitude and phase of the RF signal at the feed port704of each RIFA unit700, the controller128also controls which of the IFA elements770(1),770(2) of each RIFA unit700is active by controlling the switchable elements716. This provides further control of the propagation direction of the individuals RIFA units700. By way of example, in the example ofFIGS. 10 and 11, activating the IFA element770(2) of a RIFA unit700results in a propagation direction in the plus X-axis direction (plus θ), whereas activating the other IFA element770(1) results in a propagation direction in the minus X-axis direction (minus θ). Including selectable antenna elements in the +/−Y axis direction in RIFA units700can further wide angle steering abilities of the WSA array108.

In the example of simple monopole antenna elements described above in respect of the embodiments ofFIGS. 1 to 6, a maximum antenna element spacing of S2=λ/4 was required for the antenna elements118of WSA array108. The use of configurable RIFA units700for antenna elements118of the WSA array108can permit the inter-antenna unit spacing to be increased to λ/4, and the number of columns and/rows of elements to be reduced. By way of illustration,FIG. 12Ais a representation of the scan angle range for a WSA array108that uses RIFA units700. Switching between IFA elements770(1) and770(2) allows the antenna element gain in a desired main beam direction (illustrated by line782) to be increased, while the gain in the unwanted direction (illustrated by line784) can be decreased, thereby decreasing sidelobes. This feature is further illustrated in the 3-D rendering of a simulated signal inFIG. 12B. Pattern gain is formed in main beam direction782and decreased in the unwanted beam direction784, which reduces the gain of unwanted sidelobes that would otherwise have been created in a λ/2 element spacing configuration if simple monopole elements were used. This enables inter-unit spacing S2to be increased from λ/4 to λ/2 and permits a reduction in the number of antenna elements while keeping the main beam gain the same or higher. Note that the configurable WSA antenna element, such as the RIFA, can also be configured to a complimentary state to that shown inFIG. 12B, with the enhanced gain in the784direction and reduced gain in the782direction. That state would be used for the case where the WSA main beam is directed towards the direction784.

Some example dimensions of the antenna unit700are now described with reference toFIG. 8. Generally, the antenna unit700may be designed with specific dimensions in order to emit or receive wireless RF signals within a desired operating frequency or frequency band. For example, the antenna unit700may have at least one IFA element770with an operating frequency of 2.4 GHz, or an operating frequency of 5.5 GHz, or any operating frequency within the range of about 700 MHz to 20 GHz or higher, for example about 2.4 GHz to about 5.5 GHz. In some examples, IFA elements770designed to operate at different operating frequencies may be used in a singled antenna unit700(e.g., in an antenna unit700with an asymmetrical configuration). In example embodiments, different antenna units700with IFA elements770operating at different frequencies may be used together within a single communication device.

In the example ofFIG. 8, each IFA element770has substantially the same dimensions, and substantially the same operating frequency (e.g., 5 GHz) and antenna characteristics. In this example, the IFA elements770are each formed of substantially rectilinear lengths. Each conductive arm714may have substantially equal length L1(e.g., about 0.65 times the operating wavelength λ), substantially equal width W (e.g., about 0.16λ) and at substantially equal spacing H (e.g., about 0.5λ) from the substrate702. The grounding portions712may all be located a distance L2(e.g., about 0.71λ) from the central axis of symmetry, and the conductive arms714may each extend a distance L3(e.g., about 0.3λ) from each respective grounding portion712. In the present disclosure, “substantially equal” and “about” can include a range within normal manufacturing tolerances, for example +/−5%. In other example embodiments, the IFA elements770may have different dimensions (e.g., having grounding portions712at different spacing from the axis of symmetry) and/or have different operating characteristics.

In some example embodiments, the antenna unit700may be made from a conductive material such as copper, a copper alloy, aluminum or an aluminum alloy. The antenna unit700may be formed as one integral piece.

The disclosed antenna array structures may be useful for one or more of achieving a higher scan angle, as well as smaller array size, including for lower operating frequencies.

The disclosed antenna array structures may be implemented in various applications that use antennas, such as telecommunication applications (e.g., transceiver applications in wireless network base stations or wireless local area network access points). The dimensions described in this application for the various elements of the antenna unit are non-exhaustive examples and many different dimensions can be applied depending on both the intended operating frequency bands and physical packaging constraints.

The present disclosure may be embodied in other specific forms without departing from the subject matter of the claims. The described example embodiments are to be considered in all respects as being only illustrative and not restrictive. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. Selected features from one or more of the above-described embodiments may be combined to create alternative embodiments not explicitly described, features suitable for such combinations being understood within the scope of this disclosure.

All values and sub-ranges within disclosed ranges are also disclosed. Also, although the systems, devices and processes disclosed and shown herein may comprise a specific number of elements/components, the systems, devices and assemblies could be modified to include additional or fewer of such elements/components. For example, although any of the elements/components disclosed may be referenced as being singular, the embodiments disclosed herein could be modified to include a plurality of such elements/components. The subject matter described herein intends to cover and embrace all suitable changes in technology. It is therefore intended that the appended claims encompass any such modifications or embodiments.