Patent Application
20250132505
The present disclosure relates generally to antennas and more specifically to a wideband dual-polarized antenna element and interleaved antenna array.
The use of patch antennas is a convenient and relatively low-cost approach for millimeter wave applications. In a patch antenna, the electric field strength is greatest at the edge of the patch and zero at the center of the patch. The electric field lines between a ground plane and a radiating patch antenna will thus curve or bulge beyond the edges of the patch antenna to create what is denoted as a fringing field. As a result of the fringing field, the effective size of a patch antenna is larger than just the actual patch dimensions. Although patch antennas are a convenient and relatively low-cost antenna architecture, the fringing field radiation from patch antennas may result in relatively narrow bandwidths.
The narrow bandwidth of patch antennas may be problematic for their use in wireless systems employed in millimeter wavelength (mmW) spectrums (e.g., 24 GHz to 48 GHz for 5G NR high bands, also referred to as FR2, although higher frequencies may be used). To cover the entire FR2 band using patch antennas may then require the use of multiple antenna arrays in which each antenna array is dedicated to a particular subset of the FR bandwidth but this increases manufacturing costs and may require excessive space in a mobile device. Alternatively, interleaved patch antennas may be used on different substrate stacks, which again increases manufacturing costs.
The following summary discusses some aspects of the present disclosure to provide a basic understanding of the discussed technology. This summary is not an extensive overview of all contemplated features of the disclosure and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present some concepts of one or more aspects of the disclosure in summary form as a prelude to the more detailed description that is presented later.
In accordance with an aspect of the disclosure, a multi-band antenna element is provided that includes: a ground plane; a first patch antenna element adjacent the ground plane; a first L-shaped probe including a first via and a first feed, wherein the first via extends from the ground plane to the first feed, the first patch antenna element is positioned between the first feed and the ground plane, and a plane defined by the first feed is orthogonal to the first via; a second patch antenna element, wherein the first feed is positioned between the second patch antenna element and the first patch antenna element, and wherein the first L-shaped probe is configured to parasitically excite the second patch antenna element; and a third patch antenna element including a first linear slot, wherein the second patch antenna element is positioned between the third patch antenna element and the first feed, the first patch antenna element is configured to parasitically excite the third patch antenna element, and the second patch antenna element is configured to parasitically excite the first linear slot.
In accordance with another aspect of the disclosure, a multi-band antenna method of operation is provided that includes: exciting a first low-band patch antenna to resonate at a first frequency within a low band; parasitically exciting a second low-band patch antenna to resonate at a second frequency within the low band responsive to the exciting of the first low-band patch antenna; exciting an L-shaped probe with a high-band signal; parasitically exciting a high-band patch antenna to resonate at a third frequency within a high band responsive to the exciting of the L-shaped probe, wherein a lowest frequency of the high band is greater than a highest frequency of the low band; and parasitically exciting a slot in the second low-band patch antenna to resonate at a fourth frequency within the high band responsive to the exciting of the L-shaped probe.
In accordance with yet another aspect of the disclosure, a linear antenna array is provided that includes: a plurality of multi-band antenna elements, wherein each multi-band antenna element is configured to transmit and receive across a low band and across a high band, wherein a lowest frequency of the high band is greater than a highest frequency of the low band; and a plurality of high-band antenna elements, wherein each high-band antenna element is configured to transmit and receive across the high band, the high-band antenna elements and the multi-band antenna elements alternate in order with respect to each other across the linear antenna array, and a spacing between each high-band antenna element to a neighboring one of the multi-band antenna elements is sized according to a maximum scan angle that is less than or equal to 90 degrees, and wherein the scan angle is defined with respect to a normal to a plane of the linear antenna array.
Other aspects, features, and implementations of the present disclosure will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary implementations of the present disclosure in conjunction with the accompanying figures. While features of the present disclosure may be discussed relative to certain implementations and figures below, all implementations of the present disclosure can include one or more of the advantageous features discussed herein. In other words, while one or more implementations may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various implementations of the disclosure discussed herein. In similar fashion, while exemplary implementations may be discussed below as device, system, or method implementations it should be understood that such exemplary implementations can be implemented in various devices, systems, and methods.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various implementations and to explain various principles and advantages in accordance with the present disclosure.
Implementations of the present disclosure and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures.
To form a patch antenna, one or more metal layers may be patterned. The metal layers are stacked with respect to intervening dielectric layers. The patterning of each metal layer to form a patch antenna is analogous to the patterning of metal layers to form leads or other types of conductors in integrated circuit applications. Patch antennas are thus a relatively low-cost and convenient antenna architecture for mobile devices. But as noted previously, the fringing field radiation from a patch antenna typically results in a relatively narrowband performance. Such narrowband performance may be problematic with respect to designing a multi-band antenna element that can provide adequate performance across a relatively wide frequency band such as the FR2 band (approximately 24 GHz to 48 GHz).
Despite the potentially narrowband behavior of patch antennas, a patch-based multi-band antenna element is disclosed herein that advantageously provides wideband coverage across both a low band and a high band. The resulting multi-band antenna element may be advantageously incorporated into a wide variety of communication devices such as a user equipment (UE), a base station, an automobile, customer premises equipment (CPE), and so on. As implied by their names, a center frequency of the low band is lower in frequency as compared to a center frequency of the high band. More specifically, a lowest frequency of the high band is greater than a highest frequency of the low band. The following discussion will be directed to a multi-band antenna element designed to provide wideband coverage across a low band of the Frequency Range 2 (FR2) band (e.g., from 24.25 GHz to 29.5 GHZ) and across a high band of FR2 band (e.g., from 37 GHz to 48 GHz) but it will be appreciated that the multi-band antenna elements disclosed herein may be readily adapted for additional frequency bands that are either higher in frequency or lower in frequency as compared to the FR2 band. With respect to the 24.25 GHz to 29.5 GHz low band and the 37 GHz to 48 GHz high band, note that the lowest frequency of the high band is approximately 1.25 times greater than the highest frequency of the low band. Such a relatively small separation between the low band and high band presents a challenge to constructing a wideband multi-band antenna element for an antenna array that can adequately cover both the low band and the high band. The wideband multi-band antenna element disclosed herein advantageously accommodates both the high band and the low band despite such a relatively small separation.
Not only does the multi-band antenna element provide wideband coverage but it also provides enhanced cross-polarization isolation. The multi-band antenna element may thus receive or transmit according to a first linear polarization without a significant coupling to a second linear polarization that is orthogonal to the first linear polarization. Conversely, the multi-band antenna element may receive or transmit according to the second linear polarization without a significant coupling to the first linear polarization. In addition to the multi-band antenna element itself, an interleaved antenna array is disclosed herein that includes a plurality of multi-band antenna elements interleaved or alternating with high-band antenna elements. The multi-band antenna element will now be discussed in more detail, followed by a discussion of the interleaved antenna array.
The multi-band patch antennas disclosed herein may include a stack of a first patch antenna element, a second patch antenna element, and a third patch antenna element. Each patch antenna element may be formed by the patterning of a corresponding metal layer. The first and third patch antenna elements are sized so as to be resonant at respective first and second frequencies within the low band. The second patch antenna element is sized so as to be resonant at a first frequency within the high band. The high band extends from a lowest high-band frequency to a highest high-band frequency. Similarly, the low band extends from a lowest low-band frequency to a highest high band frequency that is lower in frequency than the lowest high-band frequency.
Since the metal layers are stacked akin to a layers of a cake, the patch antennas elements have the same stacking. For example, the metal layers may range from a first metal layer to a fourth metal layer (not counting a metal layer for an underlying ground plane). The first metal layer is adjacent a bottom-most dielectric layer that separates the first metal layer from the ground plane layer although what is low and high is of course a matter of perspective. With regard to this stacking, the first patch antenna element may be formed in the first (nearest to bottom) metal layer whereas the third patch antenna element may formed in the fourth (nearest to highest) metal layer. Since both the first and third patch antennas elements are sized to be resonant at respective first and second frequencies within the low band, the first patch antenna element may also be denoted herein as a first low-band patch antenna element whereas the third patch antenna element may also be denoted as a second low-band patch antenna element.
The resulting stacking of the first and second low-band patch antennas along with their respective sizing provides a wideband coverage across the low band that extends from the lowest frequency in the low band to the highest frequency in the low band. In one implementation, the first low-band patch antenna element may be excited through a first pair of vias that directly couple to the first low-band patch antenna element. Each via in the first pair of vias may be deemed to form a corresponding port to the first and second low-band patch antenna elements. The first pair of vias are positioned so that one of the vias excites the first low-band patch antenna element according to a first linear polarization whereas a second one of the vias excites the first low-band patch antenna element according to a second linear polarization that may be orthogonal to the first linear polarization. The second low-band patch antenna element is parasitically excited by the first low-band patch antenna element such that no vias are necessary to drive the second low-band patch antenna element. Recall that the second low-band patch antenna element is formed in the fourth metal layer that is relatively remote from the ground metal layer (the bottom-most metal layer). The parasitic excitation of the second low-band patch antenna element is thus advantageous with respect to avoiding the use of relatively-long vias that would couple to the second low-band patch antenna element. Such relatively-long vias may undesirably act as secondary dipole antennas and also lower bandwidth due to their parasitic inductance.
Although the wideband multi-band antenna element is described herein with respect to four metal layers (not counting a separate ground plane), it will be appreciated that additional metal layers may be used. However, it is advantageous to use only four metal layers to lower construction costs and complexity. Given the desirable restriction to four metal layers, an analogous pair of stacked patch antennas to cover the high band is not used in many examples. For example, suppose that a second metal layer in the stack of metal layers is used to form a first high-band patch antenna element. Such a high-band patch antenna element may be too shielded by the other structures in the metal layer stack and thus have too low of an antenna gain. The second metal layer is thus used to form a planar feed of an L-shaped probe. The L shape of the L-shaped probe is completed by a corresponding via that extends from the ground plane to the planar feed. Since the planar feed is formed from the second metal layer, it defines a plane that projects orthogonally from the corresponding via to form the L shape. In alternative implementations, an analogous pair of L-shaped probes may be used to excite the first low-band patch antenna element in lieu of the use of the first pair of vias.
The second metal layer may be patterned to form two feed portions for two corresponding L-shaped probe. Each L-shaped probe is positioned appropriately for the exciting of a corresponding linear polarization in a high-band patch antenna element formed in a third metal layer in the stack of metal layers. Since the metal layers are stacked in order, the second metal layer is higher than the first metal layer. Similarly, the third metal layer is higher than the second metal layer. Finally, the fourth metal layer is higher than the third metal layer. The high-band patch antenna element is an example of the second patch antenna element discussed above. A first one of the L-shaped probes parasitically excites the high-band patch antenna element to be resonant according to the first linear polarization at a first frequency within the high band. Similarly, a second one of the L-shaped probes parasitically excites the high-band patch antenna element to be resonant according to the second polarization at the first frequency within the high band. The high-band patch antenna element is thus a dual-polarized high-band patch antenna element.
But note that the mere use of the dual-polarized high-band patch antenna element without more may result in a fairly narrowband performance within the high band. For example, if the high-band patch antenna element is sized so that the first frequency in the high band is relatively close to the lowest frequency of the high band, then operation solely with the high-band patch antenna element may not be satisfactory for the higher frequencies in the high band. A second high-band patch antenna element could be stacked with respect to the high-band patch antenna element but then more than four metal layers may be needed. Alternatively, the fourth metal layer could be patterned with parasitic elements positioned around the second low-band patch antenna element and sized so as to be resonant at a relatively high second frequency within the high band. But such additional elements then increase the size of the multi-band antenna element.
To solve this dilemma, the second low-band patch antenna element is patterned with at least one slot antenna configured to resonate at a second frequency within the high band. For example, the second low-band patch antenna element may include a pair of intersecting linear slots that are parasitically excited by the high-band antenna and may thus share its dual-polarized ports. In this fashion, an advantageously compact yet high performance dual-polarized multi-band antenna element is provided.
A cross-sectional view of an example wideband multi-band antenna element 100 is shown in
The first metal layer 120 is patterned to form a first low-band patch antenna element 200 as shown in plan view in
Multi-band antenna element 100 is configured for coverage across the low band that is distinct from the high band. In the following discussion, the low band extends from the 24.25 GHz to 29.5 GHz whereas the high band extends from 37 GHz to 48 GHz. However, it will be appreciated that such low band and high band frequencies are merely illustrative and that the multi-band antenna element 100 may be readily adapted to provide coverage for alternative low bands and high bands. With respect to the low band, first low-band patch antenna element 200 has a diameter dimensioned so as to be resonant at approximately 27.5 GHz. As noted earlier, a single patch antenna element such as the first low-band patch antenna element 200 may be relatively narrowband. Thus, the multi-band antenna element 100 includes an additional low-band patch antenna element to cover the entirety of the low band as will be explained further herein.
To transmit and receive according to a first linear polarization, a first via 145 couples to the first low-band patch antenna element 200 as may also be seen in
Analogous to how the first metal layer 120 is patterned to form the first low-band patch antenna element 200, the third metal layer 130 may be patterned to form a high-band patch antenna element 300 as shown in plan view in
To provide the parasitic drive to the high-band patch antenna element 300, the second metal layer 125 is patterned to form rectangular feeds 400 and 170 as shown in
Note the advantages of the L-shaped probes. As noted earlier, the alternative of driving the high-band patch antenna element 300 directly with vias may result in the vias acting as secondary dipole antennas due to their relatively long length as such vias would span from the ground plane formed by the first metal layer 115 to the third metal layer 130. In addition, such relatively long vias may have substantial parasitic inductance that then limits the bandwidth for the high band. Not only does the use of the L-shaped probes 180 and 415 avoid such lengthy vias, the parasitic capacitance of the rectangular feeds 400 and 170 may function to resonate out the parasitic inductance of the corresponding vias 150 and 410. Accordingly, the rectangular feeds 400 and 170 advantageously increase the high band bandwidth.
The fourth metal layer 135 may be patterned to form a second low-band patch antenna element 500 as shown in
To increase the bandwidth of the potentially narrowband high-band patch antenna 300, the fourth metal layer 135 could be patterned to form smaller parasitic patches that surround the second low-band patch antenna element 500. In such an implementation, the second low-band patch antenna element 500 may be a rectangular patch antenna element. But the surrounding smaller parasitic patches would increase the overall size of the multi-band antenna element 100, which may be undesirable with respect to integrating the multi-band antenna element 100 into an array of antennas. To maintain a compact size for the multi-band antenna element 100, the second low-band patch antenna element 500 is thus configured with a horizontally-aligned linear slot 505 and a vertically-aligned linear slot 510 that together extend the bandwidth of the high band. More generally, the slot 505 has a longitudinal axis that is orthogonal to a longitudinal axis of the slot 510. Each slot 505 and 510 may be symmetric with respect to a center of the second low-band patch antenna 500.
Note that the resonant frequency of a slot antenna is a function of the longitudinal length of the slot. Since the high-band patch antenna element 300 may be sized so as to be resonant at 45 GHz, the slots 505 and 510 may be sized to extend the coverage at the lower end of the high band. For example, each slot 505 and 510 may have a length so as to be resonant at 39 GHz. The second low-band patch antenna element 500 thus also functions as a pair of high-band slot antenna elements. As compared to the fringing field of a patch antenna element, a slot antenna element has an “anti-fringing” electric field that is strongest at the center of the slot and weakest at the end of the slot. The interaction of the fringing field of the high-band patch antenna element 300 with the anti-fringing field of the slot antenna elements advantageously increases the bandwidth of the high band performance. The longitudinal axis of each slot 505 and 510 is orthogonal to the resulting polarization. For example, if the first polarization is a vertical polarization, it may be seen that the slot 505 will radiate vertically-polarized electromagnetic waves. In such an implementation, slot 510 is aligned for the radiation of horizontally-polarized electromagnetic waves.
Another factor limiting the performance at the upper edge of the high band is the parasitic capacitance of the second low-band patch antenna element 500. To tune away this parasitic capacitance, each slot 505 and 510 ends in an inductive stub (which may also be denoted as a sub-slot) that is orthogonally aligned to a longitudinal axis of the slot. For example, an upper end of the slot 510 couples to a rectangular stub 515 that has a longitudinal axis that is orthogonal to a longitudinal axis of the slot 510. Similarly, a lower end of the slot 510 couples to a rectangular stub 520 that has a longitudinal axis that is orthogonal to the longitudinal axis of the slot 510. The stubs 515 and 520 are antisymmetric such that the stub 515 extends to the right of the slot 510 whereas the stub 520 extends to the left of the slot 510. Similarly, a left end of the slot 505 couples to a rectangular stub 525 that has a longitudinal axis that is orthogonal to the longitudinal axis of the slot 505. Finally, a right end of the slot 505 couples to a rectangular stub 530 that has a longitudinal axis that is orthogonal to the longitudinal axis of the slot 505. The stubs 525 and 530 are aligned in an antisymmetric fashion such that the stub 525 extends upwards whereas the stub 530 extends downwards. The inductive load from the stubs 515 through 530 lowers the bandwidth-limiting effect from the parasitic capacitance of the second low-band patch antenna element 500. In addition, the stubs extend the dimensions of their respective slots to accommodate the lower band edge of the high band (extending performance to 37 GHz). In other examples, there are two stubs, extending in opposite directions, from the end of each of the slots 505 and 510 (e.g., in “T” configuration at each end, or an “I” configuration when viewed as a whole).
It will be appreciated that the stubs need not be rectangular because alternative stub implementations may be shaped to orthogonally extend from the slot ends in an antisymmetric fashion. For example, an alternative second low-band patch antenna element 600 is shown in
To achieve the desired resonant frequencies, the various patches, slots, and stubs are sized accordingly. In one implementation, the first low-band patch antenna element 200 may thus have a diameter of 3.2 mm. Similarly, the first low-band patch antenna element 300 may have a diameter of 1.9 mm. In addition, the second low-band patch antenna element 500 may have a diameter of 3.3 mm. The slots 505 and 510 may have a length of 2.7 mm and a width of 0.4 mm. Each rectangular stub may have a length of 0.45 mm and a width of 0.35 mm. Note, however, that the resonant frequencies produced by these features depend upon a number of factors such as the dielectric constant for the insulating layers in the multi-band antenna element 100. It will thus be appreciated that these dimensions are merely illustrative.
Referring again to
A linear antenna array will now be discussed in which a plurality of multi-band antenna elements as disclosed herein is interleaved with a plurality of high-band antenna elements. Each multi-band antenna element in the array may be implemented as discussed for multi-band antenna 100. An example high-band antenna element 700 is shown in
The use of circular patch antennas in both the multi-band antenna elements and the high-band antenna elements leads to an advantageously-compact linear array 800 as shown in
There is thus an alternating series of two multi-band antenna elements and two high-band antenna elements to the left of the third multi-band antenna element 815. An analogous alternating series sits to the right of the third multi-band antenna element 815 as formed by a high-band antenna element 840, a fourth multi-band antenna element 820, a high-band antenna element 845, and the fifth multi-band antenna element 825. It may thus be seen that the mutual coupling between the center multi-band antenna element 815 and the antenna elements to its left is advantageously symmetric with the mutual coupling between the center multi-band antenna element 815 and the antenna elements to its right. Each high-band antenna element in the array 800 may be implemented as discussed for the high-band antenna 700. Similarly, each multi-band antenna element in the array 800 may be implemented as discussed for the multi-band antenna element 100.
A spacing between adjacent antennas in the array 800 will now be discussed. Note that the spacing (which may be represented by a variable d) affects the desired directivity of the array 800 in a broadside direction 850. The broadside direction 850 is normal to a plane defined by the array 800. In that regard, it can be shown that a maximum scan angle θ from the broadside direction 850 is function of a ratio (d/λ) of the spacing d and the band wavelength λ as defined by the following Equation (1):
For example, suppose that the maximum scan angle θ is 45 degrees. It follows from Equation (1) that the ratio d/λ would then be less than or equal to approximately 0.585. For such a maximum scan angle, the spacing d between adjacent antenna elements in array 800 may be approximately 3 mm. The corresponding spacing between successive multi-band antenna elements in array 800 would then be approximately 6 mm for a maximum scan angle of 45 degrees. Assuming that both the high-band and the multi-band antenna elements have the same number of input ports (which would be two each for the multi-band antenna element 100 and the high-band antenna element 700), the ports to the high-band antenna elements 830 and 845 may be terminated in some implementations. Although array 800 is a linear array, it will be appreciated that it may be scaled to instead form a planar (two-dimensional) array in alternative implementations. Note that array 800 advantageously provides relatively optimum array factors in both the low band and in the high band. Moreover, the resulting directivity for the high band may help to mitigate the higher propagations losses for the high band. In addition, the use of array 800 enables the aggregation of carriers of any desired bandwidth across the low and high bands. With respect to the FR2 low band and high band defined herein in which the lowest frequency of the high band is approximately 1.25 times larger than the highest frequency of the low band, array 800 advantageously provides wideband coverage across both the low band and the high band with optimized radiation patterns.
An example multi-band antenna method of operation will now be discussed with reference to the flowchart of
The disclosure will now be summarized in the following example clauses.
In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples. The description herein is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.
