TECHNICAL FIELD

The present disclosure relates generally to the field of antennas that radiate radio waves. In particular, the present disclosure relates to a cavity-slot antenna apparatus configured to operate in a high band (HB) and a low band (LB) of a radio spectrum, and to a wireless communication apparatus.

BACKGROUND

Electronic devices typically comprise different antennas that support wireless communications in different frequency bands (e.g., cellular frequency bands). To meet consumer demand for compact and aesthetically pleasing electronic devices, device manufacturers always strive to miniaturize the antennas. At the same time, device manufacturers also strive to ensure that the antennas operate effectively in one or more frequency bands of interest and do not interfere with nearby circuits in the electronic devices. For example, if care is not taken, a small antenna, or an antenna that is shaped to fit within a limited housing of an electronic device, may exhibit poor performance or generate radio frequency interference.

Currently, there is a very limited volume (e.g., 22><3x l mm3) for an antenna array in handheld electronic devices. The limited volume imposes strict requirements on the dimensions of the antenna array. Such requirements can be particularly difficult to meet for non-planar cavity-slot antennas (also referred to as cavity-backed slot antennas). In turn, the miniaturization of antennas can lead to several issues, such as limited performance, low isolation, poor cross- polarization ratio, etc.

Therefore, there is still a need for cavity-slot antennas that are sized to fit within a limited volume in handheld electronic devices and, at the same time, exhibit proper performance in different bands (e.g., HB and/LB) of the radio spectrum.

SUMMARY

This summary presents a selection of concepts in a simplified form that are further described below in the detailed description. It is an objective of the present disclosure to provide a cavity-slot antenna that is sized to be integrated in a handheld electronic device (e.g., a smartphone) and configured to operate efficiently in both the HB and the LB of the radio spectrum.

The objective above is achieved by the features of the independent claims in the appended claims. Further embodiments and examples are apparent from the dependent claims, the detailed description and the accompanying drawings.

According to a first aspect, an antenna apparatus is provided. The antenna apparatus comprises a dielectric substrate, and an LB antenna element and an HB antenna element which are arranged adjacent to each other on the dielectric substrate. The LB antenna element comprises an LB resonant cavity and one or more LB feeding elements coupled to the LB resonant cavity. The LB resonant cavity has a top surface, a lateral surface, and one or more slots running over each of the top surface and the lateral surface of the LB resonant cavity. The HB antenna element comprises an HB resonant cavity and one or more HB feeding elements coupled to the HB resonant cavity. The HB resonant cavity has a top surface, a lateral surface, and one or more slots running over the top surface of the HB resonant cavity. The antenna apparatus thus configured may efficiently operate in both the HB and the LB of the radio spectrum. Furthermore, since the LB resonant cavity is provided with one or more 3D slots each running over the top and lateral surfaces of the LB resonant cavity, it is possible to reduce the size of the LB antenna element (without affecting the performance of the antenna apparatus) and, consequently, the whole antenna apparatus, thereby allowing the antenna apparatus to be integrated in a limited housing of a handheld electronic device. Moreover, this configuration of the antenna apparatus provides smaller surface wave excitation.

In one embodiment of the first aspect, each of the one or more slots of the LB resonant cavity is shaped to produce a slant-polarized electromagnetic (EM) wave or a linearly polarized EM wave when the LB resonant cavity is electrically fed via the one or more LB feeding elements, and each of the one or more slots of the HB resonant cavity is shaped to produce a slant- polarized EM wave or a linearly polarized EM wave when the HB resonant cavity is electrically fed via the HB feeding element. Thus, by properly selecting the shape of the slot(s) of each of the HB and LB resonant cavities, it is possible to provide a desired radiation pattern of the antenna apparatus. As one example, the slot(s) of the HB resonant cavity may be shaped to produce the slant-polarized EM wave, while the slot(s) of the LB resonant cavity may be shaped to produce the linearly polarized EM wave, or vice versa. As another example, the slots of both the LB and HB resonant cavities may be shaped to produce the EM waves with the same polarization (i.e., slant polarization or linear polarization). All of this may make the antenna apparatus more flexible in use.

In one embodiment of the first aspect, each of the one or more slots of the LB resonant cavity runs over the lateral surface of the LB resonant cavity perpendicular to the dielectric substrate. Such 3D slot(s) of the LB resonant cavity are easily implemented.

In one embodiment of the first aspect, each of the one or more slots of the LB resonant cavity reaches the dielectric substrate on the lateral surface of the LB resonant cavity. In this embodiment, the 3D slot(s) of the LB resonant cavity completely “cuts” the lateral surface on one or more sides of the LB resonant cavity (i.e., the LB resonant cavity is “open” on one or more sides). As a result, current fed via the LB feeding element(s) to the LB resonant cavity will travel a longer path, thereby making the LB antenna element electrically longer and, consequently, causing the LB antenna element resonating at a lower frequency.

In one embodiment of the first aspect, the one or more slots of the LB resonant cavity comprise a first linear slot and a second linear slot. Each of the first linear slot and the second linear slot of the LB resonant cavity runs over each of the top surface and the lateral surface of the LB resonant cavity. The first linear slot and the second linear slot of the LB resonant cavity do not intersect with each other. Thus, it is possible to provide a different configuration of nonintersecting (e.g., parallel or running at an angle to each other without intersection) 3D slots in the LB resonant cavity, thereby changing the performance characteristics of the antenna apparatus. All of this may make the antenna apparatus more flexible in use.

In one embodiment of the first aspect, the one or more slots of the HB resonant cavity comprise a first linear slot and a second linear slot. Each of the first linear slot and the second linear slot of the HB resonant cavity runs over the top surface of the HB resonant cavity. The first linear slot and the second linear slot of the HB resonant cavity do not intersect with each other. Thus, it is possible to provide a different configuration of non-intersecting (e g., parallel or running at an angle to each other without intersection) 2D slots in the HB resonant cavity, thereby changing the performance characteristics of the antenna apparatus. All of this may make the antenna apparatus more flexible in use.

In one embodiment of the first aspect, the one or more slots of the LB resonant cavity comprise a first linear slot and a second linear slot. Each of the first linear slot and the second linear slot of the LB resonant cavity runs over each of the top surface and the lateral surface of the LB resonant cavity. The first linear slot and the second linear slot of the LB resonant cavity intersect with each other. Thus, it is possible to provide a different configuration of intersecting 3D slots in the LB resonant cavity, thereby changing the performance characteristics of the antenna apparatus. All of this may make the antenna apparatus more flexible in use.

In one embodiment of the first aspect, the first linear slot and the second linear slot of the LB resonant cavity form a 3D cross-like slot. By using the 3D cross-like slot, it is possible to produce linearly polarized or slant-polarized EM waves in the LB of the radio spectrum more efficiently.

In one embodiment of the first aspect, the one or more LB feeding elements of the LB antenna element is coupled to the LB resonant cavity in proximity of a point of intersection of the first linear slot and the second linear slot of the LB resonant cavity. By so doing, it is possible to make the LB antenna element even more electrically long, thereby further shifting the resonant frequency of the LB antenna element down in the radio spectrum.

In one embodiment of the first aspect, each of the one or more slots of the HB resonant cavity comprises a first linear slot and a second linear slot. Each of the first linear slot and the second linear slot of the HB resonant cavity runs over the top surface of the HB resonant cavity. The first linear slot and the second linear slot of the HB resonant cavity intersect with each other. Thus, it is possible to provide a different configuration of intersecting 2D slots in the HB resonant cavity, thereby changing the performance characteristics of the antenna apparatus. All of this may make the antenna apparatus more flexible in use.

In one embodiment of the first aspect, the first linear slot and the second linear slot of the HB resonant cavity form a 2D cross-like slot. By using the 2D cross-like slot, it is possible to produce linearly polarized or slant-polarized EM waves in the HB of the radio spectrum more efficiently. In one embodiment of the first aspect, the one or more HB feeding elements of the HB antenna element are coupled to the HB resonant cavity in proximity of a point of intersection of the first linear slot and the second linear slot of the HB resonant cavity. By so doing, it is possible to make the HB antenna element even more electrically long (i.e., the current path along the top surface of the HB resonant cavity is longer), thereby further decreasing the resonant frequency of the HB antenna element (this may be beneficial in some HB use scenarios).

In one embodiment of the first aspect, the antenna apparatus comprises an array of LB antenna elements and an array of HB antenna elements. The array of LB antenna elements comprises said LB antenna element, and the array of HB antenna elements comprises said HB antenna element. The array of LB antenna elements and the array ofHB antenna elements do not overlap with each other. Thus, it is possible to combine said LB antenna element with similar (e.g., in terms of design and/or performance characteristics) LB antenna elements and said HB antenna element with similar (e.g., in terms of design and/or performance characteristics) HB antenna elements in the same antenna apparatus.

In one embodiment of the first aspect, the antenna apparatus comprises an array of LB antenna elements and an array of HB antenna elements. The array of LB antenna elements comprises said LB antenna element, and the array of HB antenna elements comprises said HB antenna element. The array of LB antenna elements and the array of HB antenna elements are interleaved. Thus, it is possible to combine said LB antenna element with other (e.g., in terms of design and/or performance characteristics) LB antenna elements and said HB antenna element with other (e.g., in terms of design and/or performance characteristics) HB antenna elements in the same antenna apparatus.

In one embodiment of the first aspect, the array of LB antenna elements and the array of HB antenna elements are provided in a staggered arrangement. By using the staggered arrangement of the array of LB antenna elements and the array of HB antenna elements, it is possible to make the antenna apparatus more compact.

In one embodiment of the first aspect, the LB antenna element and the HB antenna element are oriented differently from each other. An orientation of antenna implies a certain direction of radiation of the antenna. Thus, the different orientations of the LB and HB antenna elements mean that their radiation will propagate differently (i.e., along different directions of radiation), which may be beneficial in some use scenarios.

In one embodiment of the first aspect, each of the LB resonant cavity and the HB resonant cavity has a cubic shape or a cylindrical shape. Thus, it is possible to select different shapes for each of the LB and HB resonant cavities, which may make the antenna apparatus more flexible in use.

In one embodiment of the first aspect, the LB antenna element is operable in a frequency range of 24.25 GHz to 29.5 GHz, and the HB antenna element is operable in a frequency range of 37 GHz to 43.5 GHz. As a result, the antenna apparatus may be used in different LB and HB use scenarios.

In one embodiment of the first aspect, the LB resonant cavity and the HB resonant cavity are equally sized. This may make the antenna apparatus more compact. Furthermore, since the HB and LB resonant cavities have similar dimensions, it is possible to achieve higher directivity of the HB antenna element.

In one embodiment of the first aspect, the LB resonant cavity is smaller or larger than the HB resonant cavity. By changing the dimensions of the LB resonant cavity (and/or the HB resonant cavity), it is possible to adjust the dimensions of the whole antenna apparatus to the limited volume available for the antenna apparatus in the housing of the handheld electronic device.

According to a second aspect, a wireless communication apparatus is provided. The wireless communication apparatus comprises the antenna apparatus according to the first aspect, and a transceiver connected to the antenna apparatus. By using the antenna apparatus, the wireless communication apparatus may efficiently support wireless communications (e.g., use wireless communication services) in both the HB and the LB of the radio spectrum. Moreover, given that the antenna apparatus may occupy a quite small volume (due to the 3D slot(s) of the LB antenna element) within the wireless communication apparatus, there is no need to significantly increase the dimensions of the wireless communication apparatus.

Other features and advantages of the present disclosure will be apparent upon reading the following detailed description and reviewing the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is explained below with reference to the accompanying drawings in which:

FIGs. 1A and IB show different views of an antenna apparatus in accordance with a first embodiment, namely: FIG. 1 A shows a top view of the antenna apparatus, and FIG. IB shows an isometric view of the antenna apparatus;

FIG. 2 shows a magnified isometric view of an LB antenna element included in the antenna apparatus of FIGs. 1A and IB;

FIG. 3 shows one possible implementation example of an HB antenna element included in the antenna apparatus of FIGs. 1A and IB;

FIG. 4 shows a top view of an antenna apparatus in accordance with a second embodiment;

FIG. 5 shows a top view of an antenna apparatus in accordance with a third embodiment;

FIG. 6 shows a top view of an antenna apparatus in accordance with a fourth embodiment;

FIG. 7 shows a top view of an antenna apparatus in accordance with a fifth embodiment;

FIGs. 8A and 8B shows experimental results obtained for the antenna apparatus of FIG. 5, namely: FIG. 8 A shows a dependence of S parameters on frequency, and FIG. 8B shows a Cross-Polarization Ratio (XPR) on frequency; and

FIG. 9 shows a schematic block diagram of a wireless communication apparatus in accordance with one embodiment.

DETAILED DESCRIPTION

Various embodiments of the present disclosure are further described in more detail with reference to the accompanying drawings. However, the present disclosure may be embodied in many other forms and should not be construed as limited to any certain structure or function discussed in the following description. In contrast, these embodiments are provided to make the description of the present disclosure detailed and complete.

According to the detailed description, it will be apparent to the ones skilled in the art that the scope of the present disclosure encompasses any embodiment thereof, which is disclosed herein, irrespective of whether this embodiment is implemented independently or in concert with any other embodiment of the present disclosure. For example, the apparatuses disclosed herein may be implemented in practice by using any numbers of the embodiments provided herein. Furthermore, it should be understood that any embodiment of the present disclosure may be implemented using one or more of the features presented in the appended claims.

The word “exemplary” is used herein in the meaning of “used as an illustration”. Unless otherwise stated, any embodiment described herein as “exemplary” should not be construed as preferable or having an advantage over other embodiments.

Any positioning terminology, such as “left”, “right”, “top”, “bottom”, “above” “below”, “upper”, “lower”, “horizontal”, “vertical”, etc., may be used herein for convenience to describe one element’s or feature's relationship to one or more other elements or features in accordance with the figures. It should be apparentthat the positioning terminology is intended to encompass different orientations of the apparatus disclosed herein, in addition to the orientation(s) depicted in the figures. As an example, if one rotates the apparatus in the figures 90 degrees clockwise, elements or features described as “left” and “right” relative to other elements or features would then be oriented, respectively, “above” and “below” the other elements or features. Therefore, the positioning terminology used herein should not be construed as any limitation of the invention.

Although the numerative terminology, such as “first”, “second”, “third”, “fourth”, etc., may be used herein to describe various embodiments and features, these embodiments and features should not be limited by this numerative terminology. This numerative terminology is used herein only to distinguish one feature or embodiment from another feature or embodiment. For example, a first slot and a second slot which are discussed herein could be renamed a second slot and a first slot, respectively, without departing from the teachings of the invention.

In this disclosure, the term “antenna apparatus” may refer to an apparatus configured to radiate and receive radio waves. The radio waves may refer to a type of electromagnetic radiation that occurs in different frequency bands of the radio spectrum (e g., in the so-called centimeter-wave (cm- wave) and millimeter- wave (mm-wave) bands). The radio waves are used, for example, in wireless communications, such as point-to-point communications, intersatellite links, and point-to-multipoint communications, etc However, the application of the radio waves is not limited to wireless communications only, and they may be also used, for example, for (air, ground or marine) vehicle navigation and control, road obstacle detection, etc. For this reason, the antenna apparatus according to the embodiments disclosed herein may be used in the same use scenarios as the radio waves. More specifically, the antenna apparatus may be implemented as part of a user equipment (UE) that may refer to a wireless customer premises equipment (CPE) (e.g., a wireless router, switch, etc.), a mobile device, a mobile station, a terminal, a subscriber unit, a mobile phone, a cellular phone, a smart phone, a cordless phone, a personal digital assistant (PDA), a wireless communication device, a desktop computer, a laptop computer, a tablet computer, a single-board computer (SBC) (e.g., a Raspberry Pi device), a gaming device, a netbook, a smartbook, an ultrabook, a medical device or medical equipment, a biometric sensor, a wearable device (e.g., a smart watch, smart glasses, a smart wrist band, etc ), an entertainment device (e.g., an audio player, a video player, etc.), a vehicular component or sensor (e.g., a driver-assistance system), a smart meter/sensor, an unmanned vehicle (e.g., an industrial robot, a quadcopter, etc.) and its component (e.g., a self-driving car computer), industrial manufacturing equipment, a global positioning system (GPS) device, an Internet-of- Things (loT) device, an Industrial loT (IIoT) device, a machine-type communication (MTC) device, a group of Massive loT (MIoT) or Massive MTC (mMTC) devices/sensors, or any other suitable device that uses the radio waves for operation. In some embodiments, the UE may refer to at least two collocated and inter-connected UEs thus defined.

The prior art antenna solutions may comprise only one, bulky antenna instead of two different types of antenna elements. Some slot antennas may use a different feeding type, such as Substrate-Integrated Waveguide (SIW), coaxial or ideal feeding. For example, a coaxial feeding element used to feed a slot antenna may not be possible to implement at mm-wave frequencies due to pitch restrictions. Further, the prior art antenna solutions may require additional components, such as parasitic resonators, to improve antenna performance.

To the authors’ knowledge, the prior art does not disclose an antenna apparatus that would comprise a combination of cavity-slot antennas for simultaneous operation in different bands (e g., HB and LB) of the radio spectrum.

The embodiments disclosed herein provide a technical solution that allows mitigating or even eliminating the above-sounded drawbacks peculiar to the prior art. In particular, the embodiments disclosed herein relate to an antenna apparatus that comprises LB and HB cavityslot antennas on a single dielectric substrate. The LB cavity-slot antenna comprises an LB resonant cavity and one or more 3D slots running over the top and lateral surfaces of the LB resonant cavity. The HB cavity-slot antenna comprises an HB resonant cavity and one or more 2D slots running over the top surface of the HB resonant cavity. Each of the LB and HB cavityslot antennas may be fed by using one or more feeding elements. The antenna apparatus thus configured may efficiently operate in both the HB and the LB of the radio spectrum. Furthermore, due to the 3D slot(s), it is possible to reduce the size of the LB cavity-slot antenna (without affecting the performance of the antenna apparatus) and, consequently, the whole antenna apparatus, thereby allowing the antenna apparatus to be integrated in a limited housing of a handheld electronic device (e.g., smartphone).

FIGs. 1A and IB show different views of an antenna apparatus 100 in accordance with a first embodiment. More specifically, FIG. 1 A shows a top view of the antenna apparatus 100, while FIG. IB shows an isometric view of the antenna apparatus 100. As follows from FIGs. 1A and IB, the antenna apparatus 100 comprises a dielectric substrate 102, as well as an LB antenna element 104 and an HB antenna element 106 which are arranged adjacent to each other on the dielectric substrate 102. In order not to overload FIGs. 1A and IB, the dielectric substrate 102 is shown as a plane. However, it is assumed that the dielectric substrate 102 may also extend, for example, upwards until the top of each of the LB antenna element 104 and the HB antenna element 106 (i.e., the LB antenna element 104 and the HB antenna element 106 may be embedded, at least partly, in the dielectric substrate 102). As the dielectric substrate 102, a Liquid Crystal Polymer (LCP) or a Printed Circuit Board (PCB) substrate may be used. In some embodiments, the dielectric substrate 102 may have a ground plane on its back surface opposite to the surface on which the LB antenna element 104 and the HB antenna element 106 are arranged. It should be also noted that the antenna apparatus 100 may be additionally coated, from top, with a dk element to reduce the dimensions of both the LB antenna elements 104 and the HB antenna element 106. For example, the Dk element may be represented by plastic, ceramic, or Artificial Dielectric Layer (ADL) (the ADL provides a way to increase a permittivity (dk) of a plastic by adding small patches that create extra capacitance). The LB antenna element 104 and the HB antenna element 106 are both cavity-slot antennas designed for operation in the LB and HB of the radio spectrum, respectively. For example, the LB may correspond to the frequency range of 24.25 GHz to 29.5 GHz, while the HB may correspond to the frequency range of 37 GHz to 43.5 GHz. The antenna apparatus 100 may be used for both end-fire and broadside radiation

The LB antenna element 104 comprises an LB resonant cavity 108, and the HB antenna element 106 comprises an HB resonant cavity 110. The LB resonant cavity 108 has a cross-like slot 112 formed therein, and the HB resonant cavity 110 has a cross-like slot 114 formed therein. The slot 112 runs over the top and lateral surfaces of the LB resonant cavity 108, while the slot 114 runs only over the top surface of the HB resonant cavity 110. For this reason, the slot 112 may be called “3D slot”, while the slot 114 may be called “2D slot”. Each of the slots 112 and 114 may be considered as a combination of two, vertical and horizontal, slots that intersect with each other at a right angle to form the cross.

The LB antenna element 104 further comprises four feeding elements 116 coupled to the LB resonant cavity 108, and the HB antenna element 106 further comprises four feeding elements 118 coupled to the HB resonant cavity 110. As shown in FIG. IB, each of the feeding elements 116 is implemented as a leg extending inside the LB resonant cavity 108 and coupled to the LB resonant cavity 108 in the proximity of the point of intersection of the horizontal and vertical slots forming the 3D slot 112. Similarly, each of the feeding elements 118 is implemented as a leg extending inside the HB resonant cavity 110 and coupled to the HB resonant cavity 110 in the proximity of the point of intersection of the horizontal and vertical slots forming the 2D slot 114. However, such an implementation of the feeding elements 116 and 118 should not be construed as any limitation of the present disclosure; in some other embodiments, the feeding elements 116 and 118 may be coupled to the outside of the LB resonant cavity 108 and the HB resonant cavity 110, respectively. Each of the feeding elements 116 and 118 may be also coupled (at the other end) to a current source, e.g., by means of microstrips and/or waveguides (e g., coplanar waveguides) running over the dielectric substrate 102. When the LB antenna element 104 and the HB antenna element 106 are differentially fed via the feeding elements 116 and 118, respectively (see the positive pole “+” and the negative pole in FIG. 1A), this will cause each of the 3D slot 112 and the 2D slot 114 to produce a slanted-polarized EM wave (the slant polarization is schematically shown as dashed ovals in FIG. 1A).

For each of the LB antenna element 104 and the HB antenna element 106, the slot and cavity dimensions should be approximately g/2, where Xg is the wavelength in a medium or the guided wavelength which generally is Xg= Xg/Sqrt(dk), where dk is the permittivity of the medium or plastic where the LB antenna element 104 and the HB antenna element 106 are placed. Let us assume that the LB resonant cavity 108 and the HB resonant cavity 110 are equally sized, with slot dimensions a and b being equal to 1.75 mm and 2.25, respectively. For the LB antenna element 104, a height h (see FIG. IB) is also part of the slot dimensions. The height h is assumed to be 0.8 mm. Therefore, the total length of each of the horizontal and vertical slots forming the 3D slot 112 is, for example, 2.25+0.8x2=3.85 mm. The total length of each of the horizontal and vertical slots forming the 2D slot 114 is equal to a. In general, the total length of the 3D slot 112 may be, for example, between kg/4 and kg, whereupon the 3D slot 112 should have a width 5 below kg/2 (e.g., may be equal to 0.5 mm in this numerical example). Resonance may be tuned by modifying the dimensions of the 3D slot 112 or by folding the 3D slot 112 along the wall of the LB resonant cavity 104.

FIG. 2 shows a magnified isometric view of the LB antenna element 104 included in the antenna apparatus 100. As can be seen, the 3D slot 112 of the LB antenna element 104 is “folded” along the lateral surface (i.e., each side wall) of the LB resonant cavity 108 (for this reason, the 3D slot 112 may be called “folded slot”, and the LB antenna element 104 may be correspondingly called “folded slot antenna”). Thus, unlike the HB resonant cavity 110, the LB resonant cavity 108 is “open” on its sides. This ’’opening” of the HB resonant cavity 110 will cause currents fed via the feeding elements 116 to travel a longer patch, as schematically shown with the arrows in FIG. 2 only for one (left) “fold” of the 3D slot 112. This, in turn, will make the LB antenna element 104 electrically longer, so that it resonates at a lower frequency. With this configuration of the LB antenna element 104, HB resonance is avoided. Both the slanted and linear polarizations may be excited in the same band. Hence, filtering may not be needed. Because the size of the LB antenna element 104 is reduced (due to the 3D slot), both antenna elements may be approximately the same size (see FIGs. 1A and IB). Given this, higher directivity of the HB antenna element 106 may be achieved. Further, if the LPC/PCB substrate is used, its width of even 2.5 mm is sufficient for good antenna performance. For comparison, the width and height of the prior art cavity-slot antenna may be almost twice those of the antenna apparatus 100.

Although each of the LB resonant cavity 108 and the HB resonant cavity 110 is shown in FIGs. 1A and IB as having a cubic shape, this should not be construed as any limitation of the present disclosure. In one other embodiment, each of the LB resonant cavity 108 and the HB resonant cavity 110 may have a cylindrical shape, i.e., a circular cross-section in its top view.

Similarly, approximately the same dimensions of the LB resonant cavity 108 and the HB resonant cavity 110 are shown in FIGs. 1A and IB only to stress out the miniaturization advantage provided by using the 3D (folded) slot 112 in the LB resonant cavity 108. However, in some other embodiments, the LB resonant cavity 108 and the HB resonant cavity 110 may have different dimensions (e.g., any of the parameters a, b, s and/or h may be smaller for the LB resonant cavity 108 than for the HB resonant cavity 110).

Other embodiments are possible, in which the 3D slot 112 runs over the lateral surface of the LB resonant cavity 108 at a different angle (not equal to 90 degrees, as shown in FIGs. 1A and AB) relative to the dielectric substrate 102, and/or in which the LB antenna element 104 and the HB antenna element 106 are oriented differently from each other. In case of different orientations, each of the LB antenna element 104 and the HB antenna element 106 will have a different direction of radiation, which may be beneficial in some use scenarios.

In general, the antenna apparatus 100 may exhibit the following performance characteristics: tilting may be ±45 degrees for an LB beam and ±40 degrees for an HB beam. The beams may be tilted even more but grating lobes will arise. The design of the antenna apparatus 100 may enable smaller surface wave excitation. Hence, a more evenly distributed E-field is provided, which results in improved radiation patterns.

FIG. 3 shows one possible implementation example of the HB antenna element 106 included in the antenna apparatus 100. It should be noted that the LB antenna element 104 may be implemented in a similar manner. As follows from FIG. 3, the HB resonant cavity 110 of the HB antenna element 106 may be made of an array 300 of patterned layers stacked one upon another. Each patterned layer (expect for an uppermost patterned layer 302) of the array 300 of patterned layers is configured as a rectangular (e.g., square) planar frame, so that when the patterned layers are stacked one upon another, the (hollow) interior of the HB resonant cavity 110 is formed. The uppermost patterned layer 302 is shaped to form the 2D slot 114. It should be obvious that when fabricating the LB resonant cavity 108 of the antenna element 104 in this way, the patterned layers arranged under the uppermost layer 302 should be also shaped in consideration of the 3D (folded) slot 112. Each patterned layer of the array 300 of patterned layers may be made of an electrically conductive material (e g., metal). To ensure that the patterned layers are rigidly fixed to each other, pins 304 (e.g., rivets, bolts, etc.) may be used, each of which may pass through aligned holes formed in the patterned layers of the array 300 of patterned layers.

FIG. 4 shows a top view of an antenna apparatus 400 in accordance with a second embodiment. Similar to the antenna apparatus 100, the antenna apparatus 400 comprises a dielectric substrate 402, as well as an LB antenna element 404 and an HB antenna element 406 which are arranged adjacent to each other on the dielectric substrate 402. The dielectric substrate 402 may be implemented similar to the dielectric substrate 102. The LB antenna element 404 and the HB antenna element 406 are both cavity-slot antennas designed for operation in the LB and HB of the radio spectrum, respectively. The LB antenna element 404 comprises an LB resonant cavity 408, and the HB antenna element 406 comprises an HB resonant cavity 410. Each of the LB resonant cavity 408 and the HB resonant cavity 410 may be made of an electrically conductive material (e.g., metal) on an LCP or PCB substrate used as the dielectric substrate 402. The antenna apparatus 400 differs from the antenna apparatus 100 in the shapes of a 3D slot 412 running over the top and lateral surfaces of the LB resonant cavity 408 and a 2D slot 414 running over the top surface of the HB resonant cavity 410. In particular, each of the 3D slot 412 and the 2D slot 414 is in the form of a cross pattee (which is one example of the cross-like shape). Also, the LB antenna element 404 comprises four feeding elements 416 coupled to the LB resonant cavity 408, and the HB antenna element 406 further comprises four feeding elements 418 coupled to the HB resonant cavity 410. The feeding elements 416 and 418 may be implemented similar to the feeding elements 116 and 118, respectively. Similarly, when the LB antenna element 404 and the HB antenna element 406 are differentially fed via the feeding elements 416 and 418, respectively, this will cause each of the 3D slot 412 and the 2D slot 414 to produce a slanted-polarized EM wave (the slant polarization is schematically shown as dashed ovals in FIG. 4).

FIG. 5 shows a top view of an antenna apparatus 500 in accordance with a third embodiment. Similar to the antenna apparatuses 100 and 400, the antenna apparatus 500 comprises a dielectric substrate 502, as well as an LB antenna element 504 and an HB antenna element 506 which are arranged adjacent to each other on the dielectric substrate 502. The dielectric substrate 502 may be implemented similar to the dielectric substrate 102. The LB antenna element 504 and the HB antenna element 506 are both cavity-slot antennas designed for operation in the LB and HB of the radio spectrum, respectively. The LB antenna element 504 comprises an LB resonant cavity 508, and the HB antenna element 506 comprises an HB resonant cavity 510. Each of the LB resonant cavity 508 and the HB resonant cavity 510 may be made of an electrically conductive material (e g., metal) on an LCP or PCB substrate used as the dielectric substrate 502. The antenna apparatus 500 differs from the antenna apparatuses 100 and 400 in the shapes of a 3D slot 512 running over the top and lateral surfaces of the LB resonant cavity 508 and a 2D slot 514 running over the top surface of the HB resonant cavity 510. In particular, each of the 3D slot 512 and the 2D slot 514 is in the form of a crux decussata or X-cross. Also, the LB antenna element 504 comprises four feeding elements 516 coupled to the LB resonant cavity 508, and the HB antenna element 506 further comprises four feeding elements 518 coupled to the HB resonant cavity 510. The feeding elements 516 and 518 may be implemented similar to the feeding elements 116 and 118, respectively. Due to the shapes of the 3D slot 512 and the 2D slot 514, when the LB antenna element 504 and the HB antenna element 506 are differentially fed via the feeding elements 516 and 518, respectively, this will cause each of the 3D slot 512 and the 2D slot 514 to produce a linearly polarized EM wave (the linear polarization is schematically shown as dashed ovals in FIG. 5).

Those skilled in the art would recognize that the present disclosure is not limited to the crosslike shapes of the slots in the LB and HB resonant cavities, as shown in FIGs. 1A, IB, 2-5. In some embodiments, other cross-like shapes of the slots may be used, such, for example, as a Maltese cross, an alisee pattee cross, etc. Moreover, the present disclosure is not limited to the cross-like shape of the slots in the LB and HB resonant cavities. For example, any other configurations of two or more intersecting slots in each of the LB and HB resonant cavities may be used, such, for example, as a Y-like 3D slot in the LB resonant cavity and a Y-like 2D slot in the HB resonant cavity. Beyond that, each of the LB and HB resonant cavities may have two or more non-intersecting slots (e.g., extending parallel to each other or at an angle to each other but without intersection).

It should be also noted that the number of the feeding elements used for feeding each of the LB and HB resonant cavities may vary depending on particular applications. For example, even one feeding element may be used for feeding each of the LB and HB resonant cavities.

FIG. 6 shows a top view of an antenna apparatus 600 in accordance with a fourth embodiment. Similar to the antenna apparatuses 100, 400 and 500, the antenna apparatus 600 comprises a dielectric substrate 602, as well as an LB antenna element 604 and an HB antenna element 606 which are arranged adjacent to each other on the dielectric substrate 602. The dielectric substrate 602 may be implemented similar to the dielectric substrate 102. The LB antenna element 604 and the HB antenna element 606 are both cavity-slot antennas designed for operation in the LB and HB of the radio spectrum, respectively. The LB antenna element 604 comprises an LB resonant cavity 608, and the HB antenna element 606 comprises an HB resonant cavity 610. Each of the LB resonant cavity 608 and the HB resonant cavity 610 may be made of an electrically conductive material (e.g., metal) on an LCP or PCB substrate used as the dielectric substrate 602. The antenna apparatus 600 differs from the antenna apparatuses 100, 400 and 500 in the shapes of a 3D slot 612 running over the top and lateral surfaces of the LB resonant cavity 608 and a 2D slot 614 running over the top surface of the HB resonant cavity 610. In particular, each of the 3D slot 612 and the 2D slot 614 is in the form of a straight line. Moreover, the antenna apparatus 600 is characterized by that the LB antenna element 604 comprises two feeding elements 616 coupled to the LB resonant cavity 608, and the HB antenna element 606 comprises two feeding elements 618 coupled to the HB resonant cavity 610. The feeding elements 616 and 618 may be implemented similar to the feeding elements 116 and 118, respectively. Due to the shapes of the 3D slot 612 and the 2D slot 614, when the LB antenna element 604 and the HB antenna element 606 are differentially fed via the feeding elements 616 and 618, respectively, this will cause each of the 3D slot 612 and the 2D slot 614 to produce a linearly polarized EM wave (the linear polarization is schematically shown as dashed ovals in FIG. 6).

Those skilled in the art would recognize that the present disclosure is not limited to the linear shape of the slots in the LB and HB resonant cavities, as shown in FIG. 6. In some embodiments, the slots of the LB and HB resonant cavities may be shaped as any curved line (e.g., arc-shaped, C-shaped, U-shaped, etc.).

FIG. 7 shows a top view of an antenna apparatus 700 in accordance with a fifth embodiment. As shown in FIG. 7, the antenna apparatus 700 comprises a dielectric substrate 702 (e.g., an LCB or PCB substrate), as well as the array of the interleaved LB and HB antenna elements 104 and 106 arranged on the dielectric substrate 702. The antenna elements 104 and 106 are shown only by way of example, and any combination of the above-described antenna elements 104, 106, 404, 406, 504, 506, 604 and 606 may be used in the antenna apparatus 700. Although the array of the interleaved LB and HB antenna elements 104 and 106 is shown as a ID array, this should not be construed as any limitation of the present disclosure; in some other embodiments, the array of the interleaved LB and HB antenna elements 104 and 106 may be in the form of a matrix. Moreover, the LB and HB antenna elements 104 and 106 may be provided in a staggered arrangement, if required and depending on particular applications. At the same time, the LB and HB antenna elements 104 and 106 should not be necessarily interleaved; instead, the array may be divided into two non-overlapping subarrays each comprising the LB antenna elements 104 or the HB antenna elements 106. FIGs. 8A and 8B shows experimental results obtained for the antenna apparatus 500. More specifically, FIG. 8A shows a dependence of S-parameters on frequency, and FIG. 8B shows a dependence of a Cross-Polarization Ratio (XPR) on frequency. To obtain these experimental results, the dielectric substrate 502 of the antenna apparatus 500 was provided with a rectangular ground plane on its back surface. S-parameters are well-known in the art, whereupon their description is omitted herein. As follows from FIGs. 8A and 8B, the design of the antenna apparatus 500 may provide the improved XPR and isolation for linear polarizations. The linear polarization will present the improved XPR and isolation, since the currents are aligned with the rectangular ground plane. It should be noted that, for the slanted polarization provided by the antenna apparatus 100, the isolation and the XPR will not as good, but both the slanted and linear polarizations provided by the antenna apparatuses 100 and 500, respectively, will have identical performance and radiation patterns.

FIG. 9 shows a schematic block diagram of a wireless communication apparatus 900 in accordance with one embodiment. The wireless communication apparatus 900 may be implemented as part of a UE (e.g., smartphone), or implemented as an individual device. As shown in FIG. 9, the apparatus 900 comprises a transceiver 902 and an antenna 904. The antenna 904 may be implemented as any of the antenna apparatuses 100, 400-700. The transceiver 902 is configured to perform wireless communications, e.g., with another UE by using the antenna 904.

Although the embodiments of the present disclosure are described herein, it should be noted that any various changes and modifications could be made in the embodiments of the present disclosure, without departing from the scope of legal protection which is defined by the appended claims. In the appended claims, the word “comprising” does not exclude other elements or operations, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.