Wireless communication device comprising a wide-beam satellite multi-antenna structure

Abstract

An antenna structure for a wireless communication device is provided, which can operate in a frequency range consistent with satellite communications, while exhibiting wide upper-hemispheric circular-polarized beam coverage and radiation energy levels that meet established human exposure limits. The antenna structure comprises two radiating elements, with one being implemented as a metal frame antenna and another being implemented as an on-ground antenna. There is a dielectric substrate between the on-ground antenna and a ground plane of the wireless communication device. The on-ground antenna is configured as a planar conductor extending parallel to the ground plane and coupled to it at two opposite coupling points, with a feeding point being between the coupling points and coupled to a wireless communication module. The frame antenna is spaced from the on-ground antenna so as to be electromagnetically coupled to it in response to the wireless communication module feeding the second radiating element.

Description

[0001] WIRELESS COMMUNICATION DEVICE COMPRISING A WIDE-BEAM SATELLITE MULTI-ANTENNA

[0002] STRUCTURE

[0003] TECHNICAL FIELD

[0004] The present disclosure relates generally to the field of wireless communications. In particular, the present disclosure relates to a wireless communication device comprising a wide-beam multi-antenna structure capable of performing satellite communications.

[0005] BACKGROUND

[0006] The satellite mode of a mobile device allows it to connect to a telephone network via satellites orbiting the Earth. Low Earth Orbit (LEO) satellites provide satellite-to-cell communications, delivering messages, phone calls and even broadband services to mobile phones. The advantage of a satellite phone is that it can be used in regions where there is no local terrestrial communication infrastructure, such as landline and cellular networks.

[0007] The LEO satellites provide worldwide wireless coverage without any discontinuity. Because the LEO satellites are not geostationary, they move relative to the earth. Any LEO satellite is only in the phone's field of view for a short time, so a call must be ‘handed off to another LEO satellite when it passes over the local horizon. To guarantee connectivity at any satellite and phone positions, at least one LEO satellite must always have direct line of sight in each coverage area, and the mobile phone must always have beam coverage in the form of the (preferably) entire upper hemisphere in all user scenarios.

[0008] Existing mobile phones typically radiate radio frequency (RF) energy via metal frame antennas, which may result in human exposure limits for the specific absorption rate (SAR) being exceed, such as when the mobile phone is held close to a person’s head during a phone call. Existing on-ground antennas (e.g., located on the ground plane or chassis of the mobile phone) have limited gain due to polarisation losses of up to 3 dB: such antennas radiate linearly polarised (LP) beams in directions towards upper hemisphere. However, the LP beams can experience connectivity degradation due to atmospheric attenuation and the use of circularly polarized (CP) transmitting antennas at the LEO satellites. In this sense, CP electromagnetic wave radiation is more robust to such phenomena and enable a mobile phone receiver to decode stronger signals against fading and multipath interference. At the same time, existing CP antennas, such as patch antennas, Planar Inverted-F antennas (PIFAs), slot antennas and any combination thereof, radiate beams in a direction normal to the ground plane or chassis, thereby providing insufficient hemispherical beam coverage for satellite communications when the mobile phone is in the user’s hand close to his / her head, such as during a phone call.

[0009] SUMMARY

[0010] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure.

[0011] It is an objective of the present disclosure to provide an antenna structure for a wireless communication device (e.g., mobile phone) that can operate in a frequency range consistent with satellite communications, while exhibiting wide upper-hemispheric CP beam coverage and reducing the impact of radiation energy on a user’s body (e.g., his / her head), providing radiation levels that meet established human exposure limits for the SAR. The objective above is achieved by the features of the independent claim in the appended claims. Further embodiments and examples are apparent from the dependent claims, the detailed description, and the accompanying drawings.

[0012] According to an aspect, a wireless communication device is provided, which comprises a ground plane, a dielectric substrate provided on the ground plane, a wireless communication module provided on the dielectric substrate, and a conductive frame running around the ground plane. The conductive frame comprises a first radiating element that is configured as an elongated frame portion separated by at least one slot from a remaining part of the conductive frame. The wireless communication device is characterized in that it further comprises a second radiating element provided on or above the dielectric substrate and configured as a planar conductor extending parallel to the ground plane. The second radiating element is coupled to the ground plane at two opposite coupling points and has a feeding point between the two opposite coupling points. The feeding point is coupled to the wireless communication module. The first radiating element is spaced from the second radiating element so as to be electromagnetically coupled to the second radiating element in response to the wireless communication module feeding the second radiating element. In the wireless communication device thus configured, CP beamforming towards the upper hemisphere is achieved by that the first radiating element is passively coupled to the second radiating element. In particular, such CP beamforming may cover an angular range of ±70° in the elevation plane. Furthermore, since the second radiating element is separated from the ground plane by the dielectric substrate, RF energy is less absorbed by a human tissue and more radiated into free space (e.g., SAR < 1.2 W / kg over 10 g at 29 dBm input power).

[0013] In an exemplary embodiment, the first radiating element has a dimension of i / 4 to i / 2 along the conductive frame, where i is a wavelength of a radio wave radiated by the second radiating element at a first frequency band. The first radiating element thus sized may contribute to more efficient CP beamforming, as the first radiating element radiates the RF energy phase delayed and orthogonally polarized relative to the RF energy radiated by the second radiating element.

[0014] In an exemplary embodiment, the first radiating element is implemented as one of a common-mode wire antenna, a differentialmode wire antenna, a slot-mode antenna, an inverted-F antenna, and a monopole antenna. These antenna types may result in more efficient CP beamforming, improving the CP gain in the directions towards the upper hemisphere.

[0015] In an exemplary embodiment, the wireless communication device further comprises a load circuit coupled to one of two lateral ends of the first radiating element. In this embodiment, the load circuit has a reactance corresponding to a resonant frequency of the first radiating element. By properly loading one of the lateral ends of the first radiating element, it is possible to achieve either right-hand CP (RHCP) or left-hand CP (LHCP) beam coverage, which may make the wireless communication device compatible with various satellite communication systems.

[0016] In an alternative exemplary embodiment, the wireless communication device further comprises a first load circuit releasably coupled to a first lateral end of the first radiating element and a second load circuit releasably coupled to a second lateral end of the first radiating element. The first load circuit has a first reactance, while the second load circuit has a second reactance equal to or different from the first reactance. In this embodiment, the wireless communication device further comprises a switching module provided on the dielectric substrate and configured to turn on and off each of the first load circuit and the second load circuit (i.e. , connect and disconnect each of the first and second load circuits to and from the first radiating element). In this configuration, the wireless communication device may switch between RHCP and LHCP beamforming, thereby making the wireless communication device compatible with various satellite communication systems (e.g., satellite communication services of one service provider may be accessed using RHCP beamforming, while satellite communication services of another service provider may be accessed using LHCP beamforming).

[0017] In one exemplary embodiment of the first aspect, the switching module is further configured to releasably couple the first and second lateral ends to the cellular wireless communication module. In this configuration, the wireless communication device may switch between satellite communication network to cellular wireless communication network. In an exemplary embodiment, the second radiating element is spaced from the first radiating element by a distance equal to or less than i / 2. With such inter-element spacing, the first radiating element radiates the RF energy phase delayed and orthogonally polarized relative to the RF energy radiated by the second radiating element, for which reason gain improvement of up to 3 dB may be achieved with respect to the CP beam formed by the joint operation of the first and second radiating elements.

[0018] In an exemplary embodiment, the second radiating element is shaped as one of a strip, a ring, a semi-ring, and an arc. These different geometries of the second radiating element may provide flexibility in optimizing the beam pattern of the antenna structure (i.e., the combination of the first and second radiating elements) used in the wireless communication device. For example, conductive shapes like arcs, rings, semi-rings and strips have distinct electrical properties and may resonate at different frequencies. Furthermore, such geometries may maximize the use of available space inside the wireless communication device (e.g., the ring-shaped second radiating element may wrap around those internal areas or portions of the wireless communication device which would otherwise remain unused).

[0019] In an exemplary embodiment, the wireless communication device further comprises a camera module comprising a camera lens. In this embodiment, the second radiating element is shaped as the ring, the semi-ring or the arc and extends around the camera lens (e.g., as a part of the camera bezel). The second radiating element thus shaped may be integrated into the wireless communication device (like a mobile phone) in a more compact and efficient manner - without having to reserve an individual space for it.

[0020] In an exemplary embodiment, the second radiating element is configured as a conductive track on the dielectric substrate. Such a conductive track on the dielectric substrate may allow the second radiating element to be integrated into compact, thin, and lightweight device design. Moreover, such a conductive track on the dielectric substrate may be fabricated using standard printed circuit board (PCB) manufacturing processes, making the whole device production more efficient and cost-effective.

[0021] In an exemplary embodiment, the planar conductor serving as the second radiating element is divided by at least one gap into at least two sub-conductors. Each of the at least one gap is between the two opposite coupling points. Adding one or more gaps to the planar conductor may enhance the performance and functionality of the second radiating element in particular and the whole antenna structure in general. More specifically, the gap(s) may enable radiation at additional frequency band wavelengths n, with the dimensions of the sub-conductors proportional ton / 2 orn / 4. Moreover, the gap(s) define radiation and frequency bandwidth characteristics of the second radiating elements (e.g., these discontinuities may be used for enhancement of the frequency bandwidth). Additionally, the gap(s) may affect the distribution of current along the planar conductor, thereby influencing the radiation pattern of the second radiating element.

[0022] In an exemplary embodiment, the wireless communication device further comprises a third radiating element provided on or above the dielectric substrate and configured as a planar conductor extending parallel to the ground plane. The third radiating element is spaced from the second radiating element so as to be electromagnetically coupled to the second radiating element in response to the wireless communication module feeding the second radiating element. By using the third radiating element, dual-band (dual-resonant) operation of the wireless communication device may be achieved, which in turn means that the wireless communication device may simultaneously operate for receiving (RX) and transmitting (TX) (with TX and RX beam shapes being the same, i.e., the TX and RX beams have the same angular directions).

[0023] In an exemplary embodiment, when the load circuit is coupled to one of the lateral ends of the first radiating element, the third radiating element is spaced from the second radiating element by a distance equal to or less than 2, where A is a wavelength of a radio wave radiated by the third radiating element at a second frequency band. With such inter-element spacing, electromagnetic coupling between the second and third radiating elements may be enhanced, which in turn may result in more efficient dual-band operation of the wireless communication device. In an alternative exemplary embodiment, when the device comprises the first and second load circuits coupled to the first and second lateral ends of the first radiating element, respectively, and the switching module for alternately switching them on and off, the third radiating element is spaced from the second radiating element by a distance equal to or less than 2. With such inter-element spacing, electromagnetic coupling between the second and third radiating elements may be enhanced, which in turn may result in more efficient dual-band operation of the wireless communication device.

[0024] In an exemplary embodiment, the third radiating element is configured as a conductive track on the dielectric substrate. Similar to the second radiating element, the third radiating element in the form of the conductive track on the dielectric substrate may be integrated into compact, thin, and lightweight device design, as well as may be fabricated using standard PCB manufacturing processes, making the whole device production more efficient and cost-effective.

[0025] In an exemplary embodiment, the planar conductor serving as the third radiating element is divided by at least one gap into at least two sub-conductors. Similar to the gap(s) in the second radiating element, the gap(s) in the third radiating element may enhance the performance and functionality of the third radiating element in particular and the whole antenna structure in general. More specifically, the gap(s) may enable radiation at additional frequency band wavelengthsn, with the dimensions of the sub-conductors proportional ton / 2 orn / 4. Furthermore, the gap(s) define radiation and frequency bandwidth characteristics of the second radiating elements (e.g., these discontinuities may be used for enhancement of the frequency bandwidth). Additionally, the gap(s) may affect the distribution of current along the planar conductor, thereby influencing the radiation pattern of the second radiating element.

[0026] In an exemplary embodiment, the first radiating element further comprises a wall extending over and parallel to the ground plane from an upper end of the elongated frame portion towards the second radiating element by a distance of less than i / 4. The use of such a wall may increase electromagnetic coupling between the first radiating element and the second radiating element, thereby improving the conversion of linear polarization to circular polarization, as well as provide additional gain improvement for LHCP and RHCP beams.

[0027] Other features and advantages of the present disclosure will be apparent upon reading the following detailed description and reviewing the accompanying drawings.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present disclosure is explained below with reference to the accompanying drawings in which:

[0030] FIG. 1 shows, in a simplified view, the surroundings of an antenna structure in a mobile phone, with the antenna structure comprising a first radiating element in the form of a top metal frame antenna and a second radiating element in the form of an on-ground antenna according to a first exemplary embodiment;

[0031] FIGs. 2A and 2B show different schematic views of the antenna structure used in the mobile phone, namely: FIG. 2A shows an isometric view of the antenna structure; and FIG. 2B shows a sectional view of the antenna structure, as obtained along line A-A in FIG. 2A;

[0032] FIG. 3 schematically shows an electric field distribution in the antenna structure;

[0033] FIGs. 4A-4C show far-field radiation (gain) patterns for three different antenna structures in the principal (horizontal and vertical) planes, with the first antenna structure being represented only by the on-ground antenna wrapping around a camera lens in the mobile phone, the second antenna structure being represented by the combination of the on-ground antenna and the top metal frame antenna in the mobile phone, and the third antenna structure being represented by the combination of the on- ground antenna and the top metal frame antenna provided with a top horizontal wall extending from its upper end; FIGs. 5A-5F show equivalent circuits of different on-ground antennas which may be used in the antenna structure of the mobile phone;

[0034] FIGs. 6A-6C schematically explains how lateral ends of the top metal frame antenna may be asymmetrically loaded to provide LHCP and RHCP beamforming, namely: FIG. 6A shows a schematic top view of the antenna structure with the loaded top metal frame antenna; FIG. 6B shows a general equivalent circuit of the asymmetrically loaded top metal frame antenna; and FIG. 6C shows a specific equivalent circuit of the asymmetrically loaded top metal frame antenna implemented as a wire antenna;

[0035] FIG. 7 schematically illustrates how the asymmetric loading of the top metal frame antenna included in the antenna structure of the mobile phone may affect the SAR and the LHCP gain (G) of the antenna structure;

[0036] FIGs. 8A-8F show far-field radiation (gain) patterns for the antenna structure with the differently asymmetrically loaded (for LHCP beamforming) top frame antenna in the principal planes, namely: FIGs. 8A-8C show the total, LHCP beam-related and RHCP beam-related gains, respectively, in the azimuth plane; and FIGs. 8D-8F show the total, LHCP beam-related and RHCP beam-related gains, respectively, in the elevation plane;

[0037] FIG. 9 shows a schematic top view of the mobile phone with an antenna structure implemented according to a second exemplary embodiment; and

[0038] FIG. 10 shows a schematic top view of the mobile phone with an antenna structure implemented according to a third exemplary embodiment.

[0039] DETAILED DESCRIPTION

[0040] 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.

[0041] 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 device 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.

[0042] 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.

[0043] 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 apparent that 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 imaginatively 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 present disclosure. Furthermore, although the numerative terminology, such as “first”, “second”, etc., may be used herein to describe various embodiments, elements or features, it should be understood that these embodiments, elements or features should not be limited by this numerative terminology. This numerative terminology is used herein only to distinguish one embodiment, element or feature from another embodiment, element or feature. For example, a first radiating element discussed below could be called a second radiating element, and vice versa, without departing from the teachings of the present disclosure.

[0044] In the embodiments disclosed herein, it is to be understood that there may be a plurality of ways in which the two elements may be coupled, i.e., the two elements may be directly (galvanically) coupled or connected to each other, or there may be an intermediary between the two elements that indirectly couples them to each other (e.g., a transistor, a voltage converter, a capacitor, etc.). At the same time, if coupling is specifically called electromagnetic, it is to be understood as the interaction of the two elements by means of an electromagnetic field.

[0045] According to the embodiments disclosed herein, a wireless communication device may refer to a (mobile) user device or (mobile) user equipment (UE), such as a mobile station, a terminal, a subscriber unit, a mobile phone, a cellular phone, a smart phone, a cordless phone, a satellite phone, a personal digital assistant (PDA), a laptop computer, a tablet computer, a wearable device (e.g., a smart watch, smart glasses, a smart wrist band, etc.), or any other suitable device that uses the radio waves for operation.

[0046] As used in the embodiments disclosed herein, a radiating element may refer to antenna element configured to radiate and receive radio waves in a frequency band consistent with satellite communications. The radiating element may be implemented as an isolated portion or part of a conductive (e.g., metal) frame of a (mobile) user device or user equipment (UE), in which case it is referred to as a (metal) frame antenna in the art. Alternatively, the radiating element may be implemented as a differently shaped planar conductor arranged over a ground plane of the (mobile) user device or UE, in which case it is referred to as an on-ground antenna in the art.

[0047] The exemplary embodiments disclosed herein relate to an antenna structure for a wireless communication device (e.g., mobile phone) that may operate in a frequency range consistent with satellite communications, while exhibiting wide upper- hemispheric CP beam coverage and radiation energy levels that meet established human exposure limits for the SAR. For this purpose, the antenna structure comprises two radiating elements, with one being implemented as a frame antenna and another being implemented as an on-ground antenna. There is a dielectric substrate between the on-ground antenna and a ground plane of the wireless communication device. The on-ground antenna is configured as a planar conductor extending parallel to the ground plane and coupled to the ground plane at two opposite connection points, with a feeding point being between the two opposite coupling points and coupled to a wireless communication module. The frame antenna is spaced from the on-ground antenna so as to be electromagnetically coupled to it in response to the wireless communication module feeding the second radiating element.

[0048] FIG. 1 shows, in a simplified view, the surroundings of an antenna structure in a mobile phone 100, with the antenna structure being implemented according to a first exemplary embodiment. More specifically, the mobile phone 100 comprises a ground plane 102 (also referred to as a chassis in the art), a dielectric substrate (not shown in FIG. 1) that is assumed to be provided on the ground plane 102 and carry a wireless communication module 104 (e.g., in the form of a radio-frequency integrated circuit (RFIC) chip), and a metal frame 106 extending along the edges of the ground plane 102 and, consequently, the dielectric substrate. The dielectric substrate is also assumed to carry a battery 108 and a camera module 110 comprising a camera lens 112. The dielectric substrate may be, for example, a printed circuit board (PCB). The wireless communication module 104 is assumed to be powered by the battery 108.

[0049] In the first exemplary embodiment, the antenna structure comprises a combination of two radiating elements 114 and 116, where the first radiating element 114 is an elongated top frame portion separated by two (e.g., dielectric-filled) slots 118 from a remaining part of the conductive frame 106, while the second radiating element 116 is a ring-like planar conductor extending substantially parallel to the ground plane 102 and wrapping around the camera lens 112. The second radiating element 116 is coupled (e.g., by means of vertical pins extending through the dielectric substrate) to the ground plane 102 at two opposite coupling points 120, 122 and has a feeding point 124 between the coupling points 120 that is coupled to the wireless communication module 104. The first radiating element 114 is spaced from the second radiating element 116 so as to be electromagnetically coupled to it in response to the wireless communication module 104 feeding the second radiating element 116. In other words, the spacing between the first and second radiating elements 114, 116 is such that the first radiating element 114 is passively fed via the second radiating element 116. Due to these spacing and configurations, the first and second radiating elements 114, 116 may provide CP beamforming in the mobile phone 100, as will be discussed later in more detail.

[0050] In other embodiments, the elongated frame portion serving as the first radiating element 114 may be separated from the remaining part of the metal frame 106 by a single U-like slot, and / or the second radiating element 116 may be implemented as a conductive track running on the dielectric substrate in any suitable place (not only in vicinity of the camera module 110).

[0051] As also follows from FIG. 1, the metal frame 106 may be further cut to form two (or more) additional opening slots 126, so that the metal frame 106 has at least one other separated frame portion which may be used as a radiating element 128 suitable, for example, for performing cellular communications. There may also be coupling points 130 between the metal frame 106 (i.e., the radiating elements 114, 128) and the ground plane 102 to create grounding points.

[0052] FIGs. 4A-4C show far- field radiation (gain) patterns for three different antenna structures of the mobile phone 100, which were simulated in the principal (horizontal and vertical) planes. More specifically, FIGs. 4A and 4B show the radiation patterns in different elevation planes, while FIG. 4C shows the radiation patterns in the azimuth plane. It is contemplated that the first antenna structure includes only the second radiating element 116 (i.e., an on-ground antenna) wrapped around the camera lens 110, the second antenna structure includes the combination of the first radiating element 114 (i.e., a metal frame antenna) and the second radiating element 116, and the third antenna structure is similar to the second antenna structure with the addition of the wall 202 to the first radiating element 114. In each of the FIGs. 4A-4C, the curves corresponding to the first antenna structure are designated as “400”, the curves corresponding to the second antenna structure are designated as “402”, and the curves corresponding to the third antenna structure are designated as “404”. One can see that the combination of the first and second radiating elements 114 and 116 are advantageous over only the second radiating element 116, and the addition of the wall 202 to the first radiating element 114 may provide further gain improvement (see the thick black arrows in the radiation patterns).

[0053] FIGs. 5A-5F show equivalent circuits of different antenna elements, each of which may be used as the second radiating element in the antenna structure of the mobile phone 100. More specifically, FIG. 5A shows a ring-shaped antenna element (i.e., which corresponds to the second radiating element 116 shown in the preceding figures), FIG. 5B shows an arc-shaped antenna element 400, FIG. 5C shows a strip-like antenna element 402 having different or equal loads Z, and Z2(e.g., different combinations of active and / or reactive circuit components), FIG. 5D shows a simple strip-like antenna element 404, FIG. 5E shows an arcshaped antenna element 406 having one or more gaps or discontinuities 408, and FIG. 5F shows a strip-like antenna element 410 having one or more gaps or discontinuities 412. It should be noted that in each of the antenna elements shown in FIGs. 5A-5F, the feed point 124 may be positioned differently (not just midway between the coupling points 120, 122) if necessary and dependent on the particular application; the same is true for the gap(s) 408 and 412.

[0054] FIGs. 6A-6C schematically explains how lateral ends of the top metal frame antenna (i.e., the first radiating element 114) may be asymmetrically loaded to provide LHCP and RHCP beamforming. More specifically, FIG. 6A shows a schematic top view of the antenna structure with the loaded top metal frame antenna, FIG. 6B shows a general equivalent circuit of the asymmetrically loaded top metal frame antenna, and FIG. 6C shows a specific equivalent circuit of the asymmetrically loaded top metal frame antenna implemented as a wire antenna. Said loading may be performed by connecting any suitable load circuit to one or both lateral ends of the first radiating element 114, for example, via the coupling points 130. Each load circuit may comprise one or more active elements and / or passive elements. In the embodiment shown in FIGs. 6A-6C, a first load circuit in the form of a capacitor Cl is coupled to the left lateral end of the first radiating element 114 and a second load circuit in the form of a capacitor C2 is coupled to the right lateral end of the first radiating element 114. In other embodiments, only one of the lateral ends (right or left) of the first radiating element 114 may be coupled to a corresponding load circuit. In general, the load circuit(s) coupled to the lateral end(s) of the first radiating element 114 is assumed to have a reactance corresponding to a resonant frequency of the first radiating element 114.

[0055] Referring to the embodiment shown in FIGs. 6A-6C, the mobile phone 100 is assumed to further comprise a switching module (not shown) provided on a dielectric substrate (e.g., the one also carrying the second radiating element 116) and configured to (e.g., alternately) switch on and off each of the first load circuit (i.e., Cl) and the second load circuit (i.e., C2), i.e., connect and disconnect C 1 and C2 to and from the first radiating element 114. Optionally, the switching module may be further configured to releasably couple the lateral ends (near the coupling points 130) of the first radiating element 114 to the wireless communication module 104.

[0056] Let us now explain how said asymmetrical loading of the first radiating element 114 may result in different circular polarization (i.e., LHCP or RHCP).

[0057] In response to feeding from the wireless communication module 104, surface currents I are induced in the second radiating element 116 and excite an EM field along the ground plane 102, which in turn result in a voltage induced at each of the lateral ends of the first radiating element 114. If the lateral ends of the first radiating element 114 are open (i.e., not loaded anyhow) or equally loaded (i.e., Cl = C2) and the entire antenna structure is assumed to be symmetrical, the induced voltage at each lateral end will be the same, i.e., VI = V2 = VO. However, if one of the lateral ends of the first radiating element 114 is asymmetrically loaded Cl =£ C2, the induced voltages at the lateral ends of the first radiating element 114 are defined as follows: where Z is the impedance of the first radiating element 114 at its lateral end, and is the angular frequency.

[0058] Therefore, the voltage difference applied to the first radiating element 114 is proportional to the difference in reactive loads, namely:

[0059] After simplification, one can obtain:

[0060] In a practical case, one can use either Cl = Cres, C2 = 0 or C2 = Cres, Cl = 0 to make the first radiating element 114 resonant at a desired radiation frequency (i.e., Cresis defined based on the resonant frequency of the first radiating element 114). The choice between these two cases defines LHCP or RHCP polarizations.

[0061] In case of RHCP beamforming, Cl = Cres, C2 = 0, resulting in:

[0062] In case of LHCP beamforming, C2 = Cres, Cl = 0, resulting in:

[0063] Thus, switching the excitation phase of the first radiating element 114 by 180°, AV' = —AV", is achieved by switching the capacitors: from Cl = Cres, C2 = 0 to C2 = Cres, Cl = 0. This allows the polarization to be controlled from LHCP to RHCP and vice versa, asymmetrically loading the first radiating element 114.

[0064] It should be also noted that the resonant frequency of the first radiating element 114 defines the current magnitude excited therein and, as a result, defines the LHCP / RHCP gain and the SAR.

[0065] FIG. 7 schematically illustrates how the asymmetric loading of the metal frame antenna (i.e., the first radiating element 114) included in the antenna structure of the mobile phone 100 may affect the SAR and the LCHP gain (G) of the antenna structure. More specifically, FIG. 7 corresponds to the case of LHCP beamforming, i.e., C2 = Cres, Cl = 0. As can be seen, the gain G is maximal at point A corresponding to C2 = 2.2 pF (which in turn corresponds to the resonance frequency of the first radiating element 114 at 2 GHz). However, at point A, the SAR is the highest, SAR = 1.8 W / kg. The SAR may be reduced to 1.3 W / kg (see point B in FIG. 7) by detuning capacitor C2 to 1.75 pF (which in turn corresponds to the resonant frequency of the first radiating element 114 at 2.1 GHz). Although the gain G is reduced in point B, it is still 1.5 dB better compared to the reference case, with no metal frame antenna. A further increase in the capacitance of the capacitor C2 above the maximal point decreases the resonance frequency of the first radiating element 114 below the operational frequency band. At that, coupling between the first radiating element 114 and the second radiating element 116 remains high, causing a relatively high SAR, but leading to the wrong phasing of the electric fields E±and E2(see FIG. 3). This results in a significant reduction of the co-polarized LHCP gain (see point C in FIG. 7), while increasing a cross-polarized RHCP gain. It should be noted that realistic implementation losses also affect the SAR: for example, if the load circuit (in this case, the capacitor C2) introduces an additional 1 dB loss due to impedance mismatching, this reduces the SAR by 1 dB.

[0066] In a preferred embodiment, when the first radiating element 114 is asymmetrically loaded (either at one or both lateral ends, as discussed above), the distance si between the first and second radiating elements 114 and 116 is equal to or less than i / 2.

[0067] FIGs. 8A-8F show far-field radiation (gain) patterns for the antenna structure with the differently asymmetrically loaded (for LHCP beamforming) top frame antenna (i.e., first radiating element 114) in the principal planes. More specifically, the FIGs. 8A-8C show the total, LHCP beam-related and RHCP beam-related gains, respectively, in the azimuth plane, while FIGs. 8D- 8F show the total, LHCP beam-related and RHCP beam-related gains, respectively, in the elevation plane. In the radiation pattern legends, “cam deco” refers to “on-ground antenna”, “C=open” refers to “C=0”, “C=shorf ’ refers to “C=infinity”, and “p” refers to “picofarad”. As can be seen, by tuning C2 (which is designated as “test C” in the radiation patterns), it is possible to increase the gain of the LCHP beam and, consequently, reduce the gain of the RHCP beam, thereby making the entire antenna structure to operate mostly as an LHCP antenna. This additionally confirms the above-given conclusion: the asymmetric loading of the first radiating element 114 results in either LHCP or RHCP beamforming.

[0068] FIG. 9 shows a schematic top view of (part of) the mobile phone 100 with an antenna structure implemented according to a second exemplary embodiment. In this embodiment, the antenna structure comprises a combination of three radiating elements, namely: the first radiating element 114, a second radiating element 900 and a third radiating element 902. Like the second radiating element 116, each of the second and third radiating elements 900 and 902 is assumed to be implemented as a planar conductor extending on or over a common or different dielectric layer or substrate (not shown) substantially parallel to the ground plane 102. Each of the second and third radiating elements 900 and 902 is shaped as an arc for illustrative purposes only. The second radiating element 900 has two opposite coupling points 904 and 906, through which it is coupled to the ground plane 102. The second radiating element 900 is coupled to the wireless communication module 104 via a feeding point 908. The second radiating element 900 is spaced from the first radiating element 114 by the distance si. The third radiating element 902 is spaced from the second radiating element 900 by a distance si selected such that the third radiating element 902 is electromagnetically coupled to the second radiating element 900 when the latter is fed by the wireless communication module 104 via the feeding point 908. Optionally, the second radiating element 900 may comprise one or more differently shaped gaps 910, and / or the third radiating element 902 may comprise one or more differently shaped gaps 912. The gaps 910 and 912 may be aligned with each other, if required.

[0069] As noted earlier, the presence of two on-ground antennas, i.e., the second and third radiating elements 900 and 902, allows the antenna structure to operate at low-band resonance and high-band resonance. This in turn makes it possible to use the antenna structure for receiving (RX) and transmitting (TX) radio signals. In this case, TX and RX beam shapes will be the same, i.e., they will have the same angular directions. Given below are some exemplary characteristics of such dual-resonance operation in case of LHCP beamforming:

[0070] Such dual-band operation is required when the antenna structure needs to perform frequency-division duplexing (FDD). In a time-division duplexing (TDD) scenario, single-band operation is sufficient, which means that the antenna structure according to the first exemplary embodiment may be used.

[0071] FIG. 10 shows a schematic top view of the mobile phone 100 with an antenna structure implemented according to a third exemplary embodiment. Like the antenna structure according to the second exemplary embodiment, the antenna structure according to the third exemplary embodiment comprises a combination of three radiating elements, namely: the first radiating element 114, a second radiating element 1000 and a third radiating element 1002. Similarly, each of the second and third radiating elements 1000 and 1002 is assumed to be implemented as a planar conductor extending on or over a common or different dielectric layer or substrate (not shown) substantially parallel to the ground plane 102. Each of the second and third radiating elements 1000 and 1002 is shaped as a strip of the same or different length. The second radiating element 1000 has two opposite coupling points 1004 and 1006, through which it is coupled to the ground plane 102. The second radiating element 1000 is coupled to the wireless communication module 104 via a feeding point 1008. The second radiating element 1000 is spaced from the first radiating element 114 by the distance si. The third radiating element 1002 is spaced from the second radiating element 1000 by the distance si selected as described above. Optionally, the second radiating element 1000 may comprise one or more differently shaped gaps 1010, and / or the third radiating element 1002 may comprise one or more differently shaped gaps 1012. The gaps 1010 and 1012 may be aligned with each other, if required.

[0072] It is worth noting that the geometries or shapes of the second and third radiating elements are shown in FIGs. 9 and 10 for illustrative purposes only and should not be construed as any limitation of the present disclosure - in some other embodiments, the second and third radiating elements may be shaped differently (e.g., the second radiating element may be shaped as a strip, while the third radiating element may be shaped as an arc or ring).

[0073] Although the exemplary 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.

Claims

CLAIMS1. A wireless communication device comprising: a ground plane; a dielectric substrate provided on the ground plane; a wireless communication module provided on the dielectric substrate; a conductive frame running around the ground plane and comprising a first radiating element, the first radiating element being configured as an elongated frame portion separated by at least one slot from a remaining part of the conductive frame; and a second radiating element provided on or above the dielectric substrate and configured as a planar conductor extending parallel to the ground plane; wherein the second radiating element is coupled to the ground plane at two opposite coupling points and has a feeding point between the two opposite coupling points, the feeding point being coupled to the wireless communication module; and wherein the first radiating element is spaced from the second radiating element so as to be electromagnetically coupled to the second radiating element in response to the wireless communication module feeding the second radiating element.

2. The device of claim 1 , wherein the first radiating element has a dimension of i / 4 to i / 2 along the conductive frame, where i is a wavelength of a radio wave radiated by the second radiating element at a first frequency band.

3. The device of claim 1 or 2, wherein the first radiating element is implemented as one of a common-mode wire antenna, a differential-mode wire antenna, a slot-mode antenna, an inverted-F antenna, and a monopole antenna.

4. The device of any one of claims 1 to 3, further comprising a load circuit coupled to one of two lateral ends of the first radiating element, the load circuit having a reactance corresponding to a resonant frequency of the first radiating element.

5. The device of any one of claims 1 to 3, wherein the first radiating element has a first lateral end and a second lateral end, and wherein the device further comprises: a first load circuit releasably coupled to the first lateral end and having a first reactance; a second load circuit releasably coupled to the second lateral end and having a second reactance, the second reactance being equal to or different from the first reactance; and a switching module provided on the dielectric substrate and configured to switch on and off each of the first load circuit and the second load circuit.

6. The device of claim 5, wherein the switching module is further configured to releasably couple each of the first lateral end and the second lateral end to the wireless communication module.

7. The device of any one of claims 4 to 6, wherein the second radiating element is spaced from the first radiating element by a distance equal to or less than Xi / 2.

8. The device of any one of claims 1 to 7, wherein the second radiating element is shaped as one of a strip, a ring, a semi-ring, and an arc.

9. The device of claim 8, further comprising a camera module comprising a camera lens, and wherein the second radiating element is shaped as the ring, the semi-ring or the arc and extends around the camera lens.

10. The device of claim 8, wherein the second radiating element is configured as a conductive track on the dielectric substrate.

11. The device of any one of claims 1 to 10, wherein the planar conductor serving as the second radiating element is divided by at least one gap into at least two sub-conductors, the at least one gap being between the two opposite coupling points.

12. The device of any one of claims 1 to 11, further comprising a third radiating element provided on or above the dielectric substrate and configured as a planar conductor extending parallel to the ground plane, the third radiating element being spaced from the second radiating element so as to be electromagnetically coupled to the second radiating element in response to the wireless communication module feeding the second radiating element.

13. The device of claim 12, wherein the device comprises the load circuit according to claim 4, and wherein the third radiating element is spaced from the second radiating element by a distance equal to or less than 2, where is a wavelength of a radio wave radiated by the third radiating element at a second frequency band.

14. The device of claim 12, wherein the device comprises each of the first load circuit, the second load circuit and the switching module according to claim 5, and wherein the third radiating element is spaced from the second radiating element by a distance equal to or less than b / 2.

15. The device of any one of claims 12 to 14, wherein the third radiating element is configured as a conductive track on the dielectric substrate.

16. The device of any one of claims 12 to 15, wherein the planar conductor serving as the third radiating element is divided by at least one gap into at least two sub-conductors.

17. The device of any one of claims 1 to 16, wherein the first radiating element further comprises a wall extending over and parallel to the ground plane from an upper end of the elongated frame portion towards the second radiating element by a distance of less than i / 4.

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