Antenna design with fragmented metallic cover

Abstract

Various example embodiments relate to radio frequency communications. A device may comprise: a base layer comprising at least one antenna cavity with at least one antenna element; and a metallic cover layer comprising a plurality of metallic fragments separated by dielectric material, wherein a width of the plurality of metallic fragments at an inner surface of the metallic cover layer disposed towards the base layer is smaller than the width of the plurality of metallic fragments at an outer surface of the metallic cover layer disposed away from the base layer.

Description

[0001] ANTENNA DESIGN WITH FRAGMENTED METALLIC COVER

[0002] TECHNICAL FIELD

[0003] Various example embodiments generally relate to the field of radio communications. In particular, some example embodiments provide an antenna design for devices with a metallic cover.

[0004] BACKGROUND

[0005] Millimetre -wave (mm-wave) antennas are one of the components enabling high speed data connections over a radio channel. It may be desired to operate antennas in different frequency bands and to enable support for dual-polarization, high isolation, and good realized gain. In addition, it may be desired to implement antennas within an all-metallic industrial design of a device.

[0006] SUMMARY

[0007] 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 or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0008] Example embodiments of the present disclosure enable to achieve a desired antenna radiation beam inclination and to thereby improve performance in radio communication. The foregoing and other benefits may be achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description, and the drawings. According to a first aspect, a device for radio frequency communication is provided. The device may comprise: a base layer comprising at least one antenna cavity with at least one antenna element; and a metallic cover layer comprising a plurality of metallic fragments separated by dielectric material, wherein a width of the plurality of metallic fragments at an inner surface of the metallic cover layer disposed towards the base layer is smaller than the width of the plurality of metallic fragments at an outer surface of the metallic cover layer disposed away from the base layer. This solution integrates the metallic cover layer as a part of antenna and thereby enables to reduce the antenna volume at the base layer, for example in order to reduce thickness of the antenna design.

[0009] In a first possible implementation form of the device according to the first aspect, the device further comprises: a conductive gasket layer between the base layer and the metallic cover layer, wherein the conductive gasket layer comprises at least one aperture aligned with the at least one antenna cavity. This solution improves antenna operation by enabling to ground the metallic cover layer.

[0010] In a second possible implementation form of the device according to the first aspect as such or according to the first implementation form of the first aspect, the base layer comprises a conductive surface, and wherein the conductive gasket layer is configured to be in galvanic contact with the metallic cover layer and the conductive surface of the base layer. This solution improves grounding of the metallic cover layer.

[0011] In a third possible implementation form of the device according to the first aspect as such or according to the first or second implementation form of the first aspect, the base layer comprises an antenna cavity with a plurality of antenna elements. This solution makes implementation of the antenna design easier. In a fourth possible implementation form of the device according to the first aspect as such or according to the first or second implementation form of the first aspect, the base layer comprises a plurality of antenna cavities with respective antenna elements. This solution improves antenna operation by isolating adjacent antenna cavities.

[0012] In a fifth possible implementation form of the device according to the fourth implementation form of the first aspect, the metallic cover layer comprises at least one cavity wall configured to separate the plurality of antenna cavities. This solution improves antenna operation by enabling to achieve a second resonance mode (dielectric resonator antenna, DRA, mode). The operation bandwidth may be increased and isolation between adjacent antenna cavities is also improved.

[0013] In a sixth possible implementation form of the device according to the fifth implementation form of the first aspect, the outer surface of the metallic cover layer comprises engraving along the at least one cavity wall configured to form engraved fragments at the outer surface of the metallic cover layer, wherein dimensions of the engraved fragments correspond to dimensions of the plurality of metal fragments at the outer surface of the metallic cover layer. This solution enables to conceal antenna implementation, while maintaining isolation between adjacent antenna cavities.

[0014] In a seventh possible implementation form of the device according to the first aspect as such or according to any of the third to fourth implementation forms of the first aspect, the plurality of antenna cavities is configured for different frequency bands. This solution enables to implement a multiband antenna.

[0015] In an eighth possible implementation form of the device the seventh implementation form of the first aspect, the plurality of antenna cavities comprise at least one low-band antenna cavity configured for a first frequency band and at least one high-band antenna cavity configured for a second frequency band, wherein the second frequency band is higher than the first frequency band. This solution enables to implement dual -band antenna or antenna array with reduced antenna volume at the base layer.

[0016] In a ninth possible implementation form of the device according to the eighth implementation form of the first aspect, an electrical volume of the at least one low-band antenna cavity is higher than an electrical volume of the at least one high-band antenna cavity. This solution enables to tune the antennas to desired frequency bands.

[0017] In a tenth possible implementation form of the device according to the ninth implementation form of the first aspect, a size of metallic fragments of the metallic cover layer aligned with the at least one high-band antenna cavity is equal to a size of metallic fragments of the metallic cover layer aligned with the at least one low-band antenna cavity, and a height of the at least one high-band antenna cavity is lower than a height of the at least one low-band antenna cavity. This solution enables to tune the low-band and high-band antennas to desired frequency bands while making manufacturing of the metallic cover easier.

[0018] In an eleventh possible implementation form of the device according to the ninth implementation form of the first aspect, a height of the at least one high-band antenna cavity is equal to a height of the at least one low-band antenna cavity, and: the width of the plurality of metallic fragments is smaller for metallic fragments aligned with the at least one high-band antenna cavity than for metallic fragments aligned with the at least one low-band antenna cavity, a width of a gap between the plurality of metallic fragments at the outer surface of the metallic cover layer is larger for the metallic fragments aligned with the at least one high-band antenna cavity than for the metallic fragments aligned with the at least one low-band antenna cavity, or a thickness of the plurality of metallic fragments is lower for the metallic fragments aligned with the at least one high-band antenna cavity than for the metallic fragments aligned with the at least one low-band antenna cavity. This solution enables to tune the low-band and high-band antennas to desired frequency bands while making manufacturing of the base layer easier. In a twelfth possible implementation form of the device according to any of the fourth to eleventh implementation forms of the first aspect, the base layer comprises a plurality of lo -band antenna cavities and a plurality of high-band antenna cavities with respective antenna elements. This solution enables to implement a dual -band antenna array with reduced antenna volume at the base layer.

[0019] In a thirteenth possible implementation form of the device according to the twelfth implementation forms of the first aspect, the plurality of the low-band antenna cavities is arranged in a first row along the metallic cover layer, and the plurality of the high-band antenna cavities are arranged in a second row along the metallic cover layer parallel to the first row. This solution improves beam steering performance of a dual -band antenna array.

[0020] In a fourteenth possible implementation form of the device according to the thirteenth implementation form of the first aspect, the plurality of low -band antenna cavities and the plurality of high-band antenna cavities are arranged alternately in a row along the metallic cover layer. This solution enables to provide the dual -band antenna in narrower area along the metallic cover.

[0021] In a fifteenth possible implementation form of the device according to the first aspect as such or according to any of the first to fourteenth implementation forms of the first aspect, the width of the plurality of metallic fragments is substantially constant within a first distance from the outer surface of the metallic cover layer. This solution makes manufacturing of the metallic cover easier, while still enabling to reduce the antenna volume at the base layer.

[0022] In a sixteenth possible implementation form of the device according to the first aspect as such or according to any of the first to fifteenth implementation forms of the first aspect, the plurality of metallic fragments is chamfered towards the inner surface of the metallic cover layer. This solution enables to provide part of the electric volume of an antenna cavity at the metallic surface, thereby enabling to reduce the antenna volume at the base layer. Furthermore, the chamfered shape makes manufacturing of the metallic cover easier.

[0023] In a seventeenth possible implementation form of the device according to the first aspect as such or according to any of the first to sixteenth implementation forms of the first aspect, the width of the plurality of metallic fragments is substantially constant within a second distance from the inner surface of the metallic cover layer. This solution enables to provide a more significant part of the electric volume of an antenna cavity at the metallic surface, thereby enabling to reduce the antenna volume at the base layer.

[0024] In an eighteenth possible implementation form of the device according to the first aspect as such or according to any of the first to seventeenth implementation forms of the first aspect, the base layer comprises a printed circuit board (PCB) layer. This solution enables to reduce thickness of the antenna design by providing the antenna cavities within the PCB layer instead of a separate base layer.

[0025] According to a second aspect, a method for manufacturing a device for radio frequency communication is provided. The method may comprise: arranging at least one antenna element at least one antenna cavity of a base layer; stacking the base layer and the at least one antenna element with a metallic cover layer, wherein the metallic cover layer comprises a plurality of metallic fragments separated by dielectric material, wherein a width of the plurality of metallic fragments at an inner surface of the metallic cover layer disposed towards the base layer is smaller than the width of the plurality of metallic fragments at an outer surface of the metallic cover layer disposed away from the base layer. This solution enables manufacturing an antenna with reduced antenna volume at the base layer. In a first possible implementation form of the method according to the second aspect, the method further comprises: stacking a conductive gasket layer between the base layer and the metallic cover layer, wherein the conductive gasket layer comprises at least one aperture aligned with the at least one antenna cavity. This solution enables to manufacture an antenna with improved operation by enabling grounding of the metallic cover layer.

[0026] In second possible implementation form of the method according to the second aspect as such or according to the first or second implementation forms of the second aspect, the metallic cover layer comprises at least one cavity wall configured to separate the plurality of antenna cavities, when stacked with the base layer. This solution enables manufacturing of an antenna with improved operation by enabling isolation of adjacent antenna cavities.

[0027] In a third possible implementation form of the method according to the third implementation form of the second aspect, the method further comprises: engraving the outer surface of the metallic cover layer along the at least one cavity wall to form engraved fragments at the outer surface of the metallic cover, wherein dimensions of the engraved fragments correspond to dimensions of the plurality of metal fragments at the outer surface of the metallic cover layer. This solution enables to conceal antenna implementation, while maintaining isolation between adjacent antenna cavities.

[0028] Implementation forms of the present disclosure can thus provide devices and methods for manufacturing devices with improved antenna design. Any implementation form may be combined with one or more other implementation forms. These and other aspects of the present disclosure will be apparent from the example embodiment(s) described below.

[0029] DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are included to aid further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and, together with the description, help to explain the example embodiments. In the drawings:

[0031] FIG. 1 illustrates an example of an orthographic view of a device with high-band and low-band antenna cavities and a fragmented metallic cover;

[0032] FIG. 2 illustrates an example of a cross-sectional view of an antenna cavity and a fragmented metallic cover;

[0033] FIG. 3 illustrates an example of a cross-sectional view of high-band and low-band antenna cavities with constant size of metallic fragments of a metallic cover;

[0034] FIG. 4 illustrates an example of a cross-sectional view of high-band and low-band antenna cavities with band-dependent size of metallic fragments of a metallic cover;

[0035] FIG. 5 illustrate examples of top views a fragmented metallic cover for low-band (a) and high-band (b) sections of the fragmented metallic cover;

[0036] FIG. 6 illustrates an example of a top view of a fragmented metallic cover configured with rows of low-band and high-band antennas;

[0037] FIG. 7 illustrates an example of a top view of a fragmented metallic cover configured for a rows of alternately arranged low- band and high-band antenna cavities; FIG. 8 illustrates examples of cross-sectional shapes of metallic fragments.

[0038] FIG. 9 illustrates an orthographic view of an example of shallow engraving of cavity walls to form uniform fragment pattern on outer surface of a metallic cover;

[0039] FIG. 10 illustrates example of performance comparison with stepped and non-stepped metallic fragments at different frequency bands;

[0040] FIG. 11 illustrates example of gain radiation patterns with and without dedicated apertures for antenna cavities in a conductive gasket; and

[0041] FIG. 12 illustrates an example of a method for manufacturing a device for radio communication.

[0042] Like references are used to designate like parts in the accompanying drawings.

[0043] DETAILED DESCRIPTION

[0044] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0045] Millimeter-wave (mm-wave) antennas are one of the components that enable high speed data connection over a radio interface. Mm-wave antennas of a device may be for example configured to operate in two frequency bands, such as band n257+n258 (24.24-29.5 GHz), also referred to as low band (LB), and band n259+n260 (37-43.5 GHz), also referred to as the high band (HB). Mm-wave antennas may be configured to support dual -polarization, high isolation, as well as good realized gain. It may be also desired to implement the antennas such that they are substantially unrecognizable for users.

[0046] The all-metallic industrial design (ID) of the cover of a device, such as a mobile phone, may be considered to be aesthetically pleasing and therefore desired by the users. The all-metallic industrial design however does not generally enable radiation of electromagnetic wave to pass the cover. In an all-metal ID of a communication device, there may be however certain locations that support the electromagnetic radiation though. One potential location for mm-wave antenna is along a slot along the edge of the device . It may be however difficult to provide support for dual polarization in such narrow slot. Another potential location for a mm-wave antenna is the camera-deco region, which may be however far from the edge of the device where an endfire (EF) antenna module may be positioned. Hence, the distance between the broadside and endfire mm-wave modules would be large, possibly resulting in large transmission line loss and lower realized gain.

[0047] Example embodiments of the present disclosure provide an efficient antenna design, which for example enables implementation of a dual-polarized, dual-band, and dual-fed antenna solution with a fragmented metallic cover comprising shaped metal fragments, also referred to as metal pixels, separated by dielectric material. Various ways to improve the bandwidth and efficiency of the antenna are provided, while keeping the antenna(s) unrecognizable to a user.

[0048] According to one approach, a thin (20 pm) metal plate may be provided on top of radiating patch antenna provided at an antenna cavity. The metal plate may comprise uniform slits on top of the metal plate. In such arrangement, the top metal plate would be configured to operate as a frequency selective structure. For antenna array implementation, different antenna elements could be positioned in a single antenna cavity and metal pillars within the cavity could be used to achieve desired modes, e.g., the antenna operating in the TM10 mode (transverse magnetic mode 10) and the antenna cavity operating in the TM 102 mode.

[0049] In such an approach, the TM102 mode of the antenna cavity would require large cavity dimensions which would increases the size of the antenna. In case of array implementation, the large antenna size would result in higher distance between the array elements which reduces the beam steering range. The thickness of the metal plate would be unrealistic for implementation of a metallic cover. The uniform slits in the metal plate act as a frequency selective structure (FSS). Furthermore, using uniform slots or rectangular pixels would not be optimal when considering realistic cover thickness.

[0050] It is generally challenging to integrate a metallic cover (e.g., a back cover) with a radiation source within a printed circuit board (PCB) of the device while maintaining a dedicated cavity. Thickness of the metallic cover may be high, for example about 550 pm, and when considering fragmenting the cover, the desired gap between the fragments may be low, for example about 100 pm. This may increase the capacitance significantly and consequently the radiation efficiency and impedance bandwidth may decrease significantly.

[0051] It may be further desired to enable the device to operate at both LB and HB, optionally with beam steering capability with antenna arrays at respective bands.

[0052] Furthermore, in order to have uniform metal fragment pixel patterns, which would be beneficial for manufacturing, same fragment dimensions might be used for fragments associated with LB and HB antenna elements. It may be generally challenging to achieve correct operating frequency at LB and HB, when dimensions of the metal fragments are the same at both bands Example embodiments of the present disclosure provide an antenna design, where metal fragments of the metallic cover are beneficially shaped to improve performance of the antenna. Furthermore, support for dual-band operation is enabled by dimensioning of the metal fragments or the antenna cavities.

[0053] FIG. 1 illustrates an example of an orthographic view of a device with high-band and low-band antenna cavities and a fragmented metallic cover. Device 100 may comprise a metallic cover 110 (e.g., metallic cover layer), for example as the back cover of device 100. A back cover of device 100 may be configured to cover a surface of device 100 that is opposite to a main display of device 100. Even though device 100 is illustrated as a mobile phone, it is understood that the example embodiments may be applied to any suitable devices, such as tablet computers or other personal digital accessories. For the purpose of illustration, in this example the axis parallel to longer sides of metallic cover 110 is called the x-axis and the axis parallel to shorter sides of metallic cover 110 is called the y-axis.

[0054] Metallic cover 110 may comprise metallic fragments 112 (e.g., metal pixels), arranged for example as one or more groups of metal fragments. Metallic fragments 112 may be separated by dielectric material forming a gap between metallic fragments 112, as will be further described with reference to FIG. 2. The group(s) of metallic fragments 112 may be provided for example as rectangular (e.g., square-shaped) patterns on the outer surface of metallic cover 110. Metallic cover 110 may be therefore fragmented at particular position(s) along the outer surface of metallic cover 110. Other portions of metallic cover might not be fragmented, e.g., comprising a solid metallic surface.

[0055] Device 100 may comprise a base layer, represented throughout the description by printed circuit board (PCB) layer 120. It is however noted that device may comprise a base layer which is separate from a PCB layer of device 110. Therefore, any aspects described with reference to PCB layer 120 may be generally applied to any suitable type of base layer, for example a sheet of insulating or dielectric material. PCB layer 120 may comprise a flat sheet of insulating or dielectric material and layer(s) of conductive circuitry (e.g., copper wires). PCB layer 120 may comprise one or plurality of antenna cavities 122 comprising respective antenna element(s) 124, for example a ring patch antenna element configured to be inductively fed for orthogonal polarizations. PCB layer 120 may comprise a dedicated cavity for each antenna element, as illustrated in FIG. 1. It is however possible to include more than one antenna in one antenna cavity, for example to include all antenna elements in one antenna cavity.

[0056] PCB layer 120 and metallic cover 110 may be connected or assembled together, for example with a conductive gasket 130 (e.g., a conductive gasket layer) illustrated by black in FIG. 1. Conductive gasket 130 may be therefore provided between the PCB layer 120 and metallic cover 110. Conductive gasket 130 may comprise aperture(s) aligned with antenna cavity / cavities of PCB layer 120. When an aperture of conductive gasket 130 is aligned with an antenna cavity of PCB layer 120 a direct path may be provided from at least a portion of antenna cavity 122 perpendicularly towards metallic cover 110 without obstruction by conductive gasket 130.

[0057] PCB layer 120 may comprise a conductive surface, which may be the top layer of PCB layer 120 disposed towards metallic cover 110 and / or conductive gasket 130. The conductive surface may for example comprise a conductive surface finish, such as electroless nickel immersion gold (ENIG) finish, immersion silver (lAg) finish, or immersion tin plating (lAn) finish, or the like. Conductive gasket 130 may be configured to be in galvanic contact with both metallic cover 110 and the conductive surface of PCB 120 layer. Conductive gasket 130 together with the conductive surface of PCB layer 120 helps to ground metallic cover 110, which improves antenna operation.

[0058] Device 100 may therefore comprise a stack of metallic cover 110, conductive gasket 130, and PCB layer 110 with a conductive surface finish. This provides the benefit of reducing in antenna volume in PCB layer 120 as metallic cover 110 is exploited as part of the antenna. In addition, the integration of PCB layer 120 with metallic cover 110 is suitable for realistic implementation.

[0059] In case of dual-band antennas or antenna arrays, the different layers 110, 120, and / or 130 may provide dedicated antenna cavities for LB and HB antenna elements. Even though some example embodiments have been described using two frequency bands (LB, HB) as an example, device 100 may be generally configured for multiband operation. For example, PCB layer 120 may comprise antenna cavities configured for two or more different frequency bands. One or more antenna cavities with respective antenna elements may be provided for each frequency band.

[0060] FIG. 2 illustrates an example of a cross-sectional view of an antenna cavity and a fragmented metallic cover. The cross section is provided between points xi and %2 along the x-axis. As described with reference to FIG. 1, metallic cover 110 may comprise metallic fragments 112, illustrated in FIG. 2 as the T-shaped dotted elements. Metallic fragments 112 may be separated dielectric material 114 (white), which may form part of metallic cover layer 110. Dielectric material 114 may comprise any suitable dielectric material, such as for example injection moulded plastic. A gap filled with dielectric material may be therefore provided between metallic fragments through metallic cover 114 in a direction perpendicular to outer surface of metallic cover 110. The array of metal fragments positioned in close gaps acts as artificial dielectric with higher effective dielectric constant, thereby improving antenna operation.

[0061] The shape of metal fragments 112 may be such that width (w) of metallic fragments 112 is higher at the outer surface of metallic cover 110 than at the inner surface of metallic cover 110. The outer surface of metallic cover 110 may be the surface disposed away from PCB layer 120 and / or conductive gasket 130. The inner surface of metallic cover 110 may be the surface disposed towards PCB layer 120 and / or conductive gasket 130, e.g., towards interior of device 100. The width of metallic fragments 112 may therefore get smaller along thickness (h) of metallic cover 110. This provides the benefit of having a small (e.g., nearly invisible) gap between metallic fragments 112 at the outer surface of metallic cover 110, while providing sufficient electric volume for desired antenna operation by the larger volume of dielectric material 114 between metallic fragments 112 at the inner surface of metallic cover 110. This also reduces the capacitance between metallic fragments 112, thereby improving antenna operation. Providing part of the electric volume at the inner surface metallic cover 110 also reduces antenna volume needed at printed circuit board (PCB), which enables the overall antenna design to be thinner. Furthermore, since the broadside radiation module can be now implemented close to the endfire radiation module, transmission line losses are reduced, resulting in increase of the realized gain. The latter benefit may be provided by any of the example embodiments described herein.

[0062] FIG. 3 illustrates an example of a cross-sectional view of high-band and low-band antenna cavities with constant size of metallic fragments of a metallic cover. The cross section is provided between points yi and yi along the y-axis. A dual-band antenna may be implemented with antenna cavities dedicated to antenna elements of different frequency bands. The metal fragment antenna described with reference to FIG. 1 may be configured for operation at both LB (24.25-29.5 GHz) and HB (37—43.5 GHz). Such a good wideband performance may be provided for example by the presence of TM10 patch mode and dielectric resonator antenna (DRA) TE111 (Transverse Electric 111) mode at the operating frequency bands. The resonant frequency of the TM10 mode patch may be mainly dependent on the ring patch dimension and height from the ground, in this example from the bottom of PCB layer 120. The resonant frequency of the DRA TE111 mode depends in the electrical volume of the cavity and therefore the antenna structure of FIG. 1 may be configured for different frequency bands by adjusting the electrical volume .

[0063] Even though some example embodiments have been described using particular frequency ranges as examples of high and low bands, it is appreciated that the example embodiments may be generally applied to any suitable frequency ranges. In general, one or more first antenna elements may be configured, together with respective antenna cavity / cavities and portion of metallic cover 110, for operation at a first frequency band. One or more second antenna elements may be configured, together with respective antenna cavity / cavities and portion of metallic cover 110, for operation at a second frequency band, where the second frequency band is higher than the first frequency band.

[0064] As the electrical volume requirement of the DRA mode is different at different frequency bands, it may be difficult to implement a co-located antenna, e.g., a single LB and HB antenna element in same antenna cavity, with the fragmented metallic cover described herein. It may be therefore desired to implement a dual-fed, dual-band antenna by separate LB and HB antenna elements, as illustrated in FIG. 3.

[0065] For example, low-band (LB) antenna 302 may comprise a first portion of metallic cover 110 and a first portion of PCB layer 120. High-band (HB) antenna 304 may comprise a second portion of metallic cover 110 and a second portion of PCB layer 120. Conductive gasket 130 may be provided between metallic cover 110 and PCB layer 120 for the LB and HB antennas. Conductive gasket 130 may comprise dedicated apertures for antenna cavities of different bands. For example, a dedicated aperture may be provided for each low-band antenna cavity and for each high-band antenna cavity. A dedicated aperture of conductive gasket 130 may be aligned with a single antenna cavity 124.

[0066] One option for implementing LB and HB antennas is to use constant metal pixel size for both LB and HB elements, as illustrated in FIG. 3. The size of the antenna cavity may be however varied. The use of constant metal fragment size for LB and HB helps to achieve uniform pixel pattern. A fragmented metallic cover may be easier to manufacture with uniform fragment dimensions. The size of metallic fragments 112 aligned (e.g., in a direction perpendicular to outer surface of metallic cover 110) with LB antenna cavity 122-1 may be therefore equal to the size of metallic fragments of the metallic cover layer aligned with HB antenna cavity 122-2. For example, the shape and area covered at the outer surface of metallic cover 110 by different metallic fragments 112 may be equal. Furthermore, different metal fragments 112 may have similar cross-sections. However, the height of LB antenna cavity 122-1 may be higher than the height of HB antenna cavity 122-2. This enables to have desired electrical volume for operation at the LB and HB frequencies, respectively. The electrical volume of LB antenna cavity 122-1 may be higher than the electrical volume of HB antenna cavity 122-2. A cavity wall 126 may be formed between LB antenna cavity 122-1 and HB antenna cavity 122-2. The cavity wall may comprise separate metal fragments, which may together form a similar shape as metal fragments 112. Alternatively, as solid metal fragment 112 may be provided as cavity wall 126, as will be further described with reference to FIG. 9.

[0067] Alternatively, or additionally, the width of the gap (e.g., width of dielectric material 114) between metallic fragments 112 at the outer surface of metallic cover 110 may be larger for metallic fragments 112 that are aligned with HB antenna cavity 122- 2 than for metallic fragments 112 aligned with the LB antenna cavity 122-1. Alternatively, or additionally, the thickness of metallic fragments 112 may be lower for metallic fragments aligned with HB antenna cavity 112 than for metallic fragments 112 aligned with low-band antenna cavity 122-2. These features provide the benefit of enabling to obtain desired relative electric volumes for the LB and HB antenna cavities.

[0068] FIG. 4 illustrates an example of a cross-sectional view of high-band and low-band antenna cavities with band-dependent size of metallic fragments of a metallic cover. Another option for implementing LB and HB antennas is to use non-uniform metal fragment dimensions for LB and HB antenna elements. The cross-section of FIG. 4 may be therefore provided as an alternative to the cross-section of FIG. 3. The electrical volume of the antenna cavity at PCB layer 120 may be however the same for LB and HB elements. Note that the electrical volume may be different from the physical volume of the cavity. The electrical volume may refer to the effective volume created when a physical volume (e.g., an antenna cavity) is loaded with dielectric 3 material. The electrical volume may be defined for example by Ve— Vpep, where Veand Vpare the electrical and physical volumes, respectively, and eris the relative permittivity of the dielectric material.

[0069] The height of HB antenna cavity 122-2 may be therefore equal to the height of LB antenna cavity 122-1. The width of metallic fragments 112 may be however smaller for metallic fragments 112 aligned with HB antenna cavity 122-2 than for metallic fragments 112 aligned with LB antenna cavity 122-1. This provides the benefit of easier manufacture of PCB layer 120, because the cavity height is the same for antenna cavities configured to operate at different frequency bands. Again, the electrical volume of LB antenna cavity 122-1 may be higher than the electrical volume of HB antenna cavity 122-2.

[0070] FIG. 5 illustrates examples of top views low-band (a) and high-band (b) sections of a fragmented metallic cover. In case of LB antenna, an antenna cavity dedicated to an antenna element may be larger than in case of HB antenna. Therefore, with uniform metal fragment dimensions, also the number of metal fragments 112 associated with a LB antenna element may be larger (e.g., 25) than the number of metal fragments 112 associated with a HB antenna element (e.g., 9). Also, the width (WLB) of the group of metal fragments 112 associated with LB antenna cavity 122-1 may be higher than the width (WHB) of the group of metal fragments 112 associated with HB antenna cavity 122-2. In one example, WLB = 4.5 mm and HB = 2.83 mm. The width of the respective LB and HB sections of metallic cover 110 may be, for example. WLB ANT = 5.4 mm and WHB ANT = 3.60 mm. The width (WLB) of the group of metal fragments 112 associated with LB antenna cavity 122-1 may for example in the range of 5.0 mm to 6.0 mm. The width (WHB) of the group of metal fragments 112 associated with HB antenna cavity 122-2 may for example in the range of 3.0 mm to 4.0 mm.

[0071] FIG. 6 illustrates an example of a top view of a fragmented metallic cover configured with rows of LB and HB antennas. As noted above, PCB layer 120 may comprise multiple LB antenna cavities and multiple HB antenna cavities with respective antenna elements. A first row 601 may comprise multiple LB antennas 302, for example four LB antennas 302 as in the example of FIG. 6. A second row 602 may comprise multiple HB antennas 304, for example six HB antennas 304 as in the example of FIG. 6. The rows may be parallel to each other and provided along metallic cover 110. Such an interleaved antenna array enables to improve beam steering performance, because the distance between adjacent HB antenna elements (HB-HB distance) and adjacent LB antenna elements (LB-LB distance) can be freely configured.

[0072] The width of HB antennas 304 may be lower than the width of LB antennas 302, at least in the direction of the rows. The number of HB antennas 304 may be therefore higher than the number of LB antennas 302. The distance between adjacent groups of metal fragments 112 may be equal among both the LB and HB antennas. The distance between adjacent groups of metal fragments 112 (e.g., also the LB-HB distance) may be equal to width of a single metal fragment 112. This provides the benefit of enabling to create a uniform pattern of metal fragments 112 at the outer surface of metallic cover 110. Another benefit of the interleaved array is that both LB and HB arrays can have optimum array separation distance so than the beam steering range without grating lobe is wider. Furthermore, providing dedicated antenna cavities for different antenna elements helps to minimize coupling between the antenna elements, which increases the realized gain.

[0073] FIG. 7 illustrates an example of a top view of a fragmented metallic cover configured for the rows of alternately arranged LB and HB antennas. Again, PCB layer 120 may comprise multiple LB antenna cavities and multiple HB antenna cavities with respective antenna elements. LB antennas 302 and HB antennas 304 may be arranged in a single row along metallic cover 110. LB antennas 302 and HB antennas 304 may be arranged alternately in the row such that at least one HB antenna 304 is between two LB antennas 304, or such that at least one LB antenna 302 is between two HB antennas 302. If the number of LB antennas 302 is lower than the number of HB antennas, each LB antenna 302 may be provided between two HB antennas 304. This provides the benefit of reducing width of the dual-band antenna. However, when LB and HB array elements are provided alternately, the separation between adjacent LB antenna elements (LB-LB distance) and adjacent HB antenna elements (HB- HB distance) is larger than in the interleaved array of FIG. 5. The increased separation between array element decrease the beam steering range due to grating lobe when compared to the arrangement with rows of LB or HB antennas.

[0074] FIG. 8 illustrates examples of cross-sectional shapes of metallic fragments. The shape of the cross-section of metallic fragments 112, either along the x-axis, the v-axis. or both may be according to FIGs 8(a)(b)(c).

[0075] FIG. 8(a) provides an example of a chamfered metallic fragment 112. The width of metallic fragment 112 may be substantially constant within distance di from the outer surface of metallic cover 110. Metallic fragment 112 may be chamfered from distance towards the inner surface of metallic cover 110. The width of metallic fragment 112 may therefore decrease towards the inner surface, e.g., starting from distance di. The portion with substantially constant width near the outer surface provides the benefit of easier manufacturing of the gap between metal fragments 112. The chamfering, which is also relatively easy for manufacturing, decreases the overall capacitance and enables to provide the desired electrical volume forthe respective antenna cavity.

[0076] FIG. 8(b) provides an example of a stepped metallic fragment 112. The width of metallic fragment 112 may be again substantially constant within distance di from the outer surface of metallic cover 110. Metallic fragment 112 may be stepped such that the width of metallic fragment 112 is also substantially constant within distance di from the inner surface of metallic cover 110 (di < di). The cross-section of metal fragment 112 may comprise a horizontal portion, which is perpendicular to surface of metallic fragment 112 within distances di and di from the outer and inner surfaces of metallic cover 110, respectively. The step may be curved, for example as illustrated with the solid line, or a rectangular step, as illustrated with the dotted line. In the latter example, the sum of distances di and di may be equal to thickness of metallic cover 110. The portion with substantially constant width near the outer surface provides the benefit of easier manufacturing of the gap between metal fragments 112. Stepping increases the distance between metallic fragments, which is in this example maximized with the rectangular step. On the other hand, curving the step makes manufacturing of metallic fragment 112 easier. FIG. 8(c) provides an example of a stepped and chamfered metallic fragment 112. Metallic fragment 112 is now chamfered, within distance A from the outer surface of metallic cover 110, towards the inner surface of metallic cover 110. Metallic fragment 112 may be again stepped such that the width of metallic fragment 112 is substantially constant within distance di from the inner surface of metallic cover 110 (di < di). The width of metallic fragment 112 may therefore decrease towards the inner surface, e.g., until distance di from the inner surface. The cross-section of metal fragment 112 may comprise a horizontal portion, which is perpendicular to surface of metallic fragment 112 within distances di and di from the outer and inner surfaces of metallic cover 110, respectively. The step may be curved or rectangular, as described with reference to FIG. 8(b). In case of rectangular step, the sum of distances di and di may be equal to the thickness of metallic cover 110. The chamfered portion near the outer surface of metallic cover 110 further increases the distance between metallic fragments 112, thereby enabling to provide the desired electrical volume for the respective antenna cavity with even thinner structure.

[0077] In general, the width of metallic fragments 112 at the inner surface of metallic cover 110 may be smaller than the width metallic fragments 112 the outer surface. Metallic fragments 112 may be chamfered towards the inner surface, either near the outer surface (e.g., within di) or near the inner surface (e.g., within di), or both. Alternatively, the width of metallic fragments may be substantially constant either near the outer surface (e.g., within di) or near the inner surface (e.g., within di), or both. In addition to chamfering, edges of metal fragments may be blended or rounded to reduce the capacitance and to improve bandwidth performance. It may be generally desired to maximize the distance between metallic fragments 112 to obtain lower capacitance, while keeping the gap as small as possible at the outer surface. However, less optimal solutions with respect to the capacitance may be more beneficial in terms of manufacturing.

[0078] FIG. 9 illustrates an orthographic view of an example of shallow engraving of cavity walls to form uniform fragment pattern on outer surface of a metallic cover. Though the gaps between metallic fragments 112 may be small, the cavity walls might be still recognizable when looking at the outer surface of metallic cover 110 at certain angles. It may be generally desired to make the antenna as unrecognizable as possible. Together with uniform fragment size, shallow laser engraving, optionally with injection moulding, may be used to create fragment-like portions at the outer surface at the positions of the cavity wall, as illustrated in FIG. 9.

[0079] Metallic cover 110 may therefore comprise cavity wall(s) 126 configured to separate antenna cavities 122, e.g., two LB antenna cavities as in FIG. 9 or LB antenna cavity 122-1 and HB antenna cavity 122-2. The cross-section perpendicular to the longitudal direction of the cavity wall may correspond to cross-sectional shape of metal fragments 112. Engraving may be provided along the cavity wall to cause the cavity wall to appear as a row of engraved fragments 912 (dotted) at the outer surface of metallic cover 110. The engraving may be therefore configured to form engraved fragments 912 at the outer surface of metallic cover 110. Dimensions of engraved fragments 912 may correspond to dimensions of metallic fragments 112 at the outer surface metallic cover 110. For example, an area of the outer surface of metallic cover 110 covered by a metal fragment 112 may be equal, both with respect to size and shape, to an area of the outer surface of metallic cover 110 covered by an engraved fragment 912.

[0080] Therefore, at the outer surface of metallic cover the dual -band antenna may appear as a uniform pattern of metallic fragments having substantially identical sizes, whereas at the inner surface of metallic cover 110 the pattern of groups of metallic fragments (cf., FIG. 6 or FIG. 7) may be visible. This provides the benefit of hiding the dual -antenna solution at the outer surface of metallic cover 110. Note that there may not be a dielectric gap between engraved fragments 912 provided along the cavity wall(s). This provides the benefit of improving antenna performance as the antenna operates better with a solid wall between antenna cavities. Furthermore, providing the appearance of uniform fragments without the actual dielectric gap enables to tune the dielectric slightly to optimize coupling between antenna elements. FIG.10 illustrates example of performance comparison with stepped and non-stepped metallic fragments at different frequency bands. The left and right graphs illustrate the bandwidth potential (GHz) for LB and HB, respectively. It is observed that the antenna with stepped metal fragments (cf., FIG. 8(b)) provides much better performance compared to non-stepped metallic fragments with rectangular cross-sectional.

[0081] FIG. 11 illustrates example of gain radiation patterns with and without dedicated apertures for antenna cavities in a conductive gasket. The realized gain radiation pattern (dB) is illustrated with respect to different beam steering directions (-90° ...90°) of a HB antenna array with a fragmented metallic cover, with (solid line) and without (dotted line) dedicated cavities in conductive gasket 130. It is observed that providing a dedicated aperture in conductive gap, as opposed to a common aperture for multiple antenna cavities, significantly improves the beam steering performance.

[0082] FIG. 12 illustrates an example of a method for manufacturing a device for radio communication. As noted above, an antenna, e.g., a dual -band antenna may be advantageously manufactured based on the example embodiments described herein.

[0083] At operation 1201, the method may comprise arranging at least one antenna element at at least one antenna cavity of a printed circuit board layer.

[0084] At operation 1202, the method may comprise stacking the printed circuit board layer and the at least one antenna element with a metallic cover layer, wherein the metallic cover layer comprises a plurality of metallic fragments separated by dielectric material, wherein a width of the plurality of metallic fragments at an inner surface of the metallic cover layer disposed towards the printed circuit board layer is smaller than the width of the plurality of metallic fragments at an outer surface of the metallic cover layer disposed away from the printed circuit board layer.

[0085] The method may further comprise : stacking a conductive gasket layer between the printed circuit board layer and the metallic cover layer, wherein the conductive gasket layer comprises at least one aperture aligned with the at least one antenna cavity.

[0086] The method may further comprise: engraving the outer surface of the metallic cover layer along the at least one cavity wall to form engraved fragments at the outer surface of the metallic cover, wherein dimensions of the engraved fragments correspond to dimensions of the plurality of metal fragments at the outer surface of the metallic cover layer.

[0087] The shape of metallic fragments 112 may be configured according to any of the examples of FIG.8, for example to obtain a desired balance between antenna performance and speed and / or cost of manufacturing.

[0088] Any range or device value given herein may be extended or altered without losing the effect sought. Also, any embodiment may be combined with another embodiment unless explicitly disallowed.

[0089] Although the subject matter has been described in language specific to structural features and / or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[0090] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items. The steps or operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the example embodiments described above may be combined with aspects of any of the other example embodiments described to form further example embodiments without losing the effect sought.

[0091] The term 'comprising' is used herein to mean including the method, blocks, or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[0092] Although subjects may be referred to as ‘first’ or ‘second’ subjects, this does not necessarily indicate any order or importance of the subjects. Instead, such attributes may be used solely for the purpose of making a difference between subjects.

[0093] It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from scope of this specification.

Claims

CLAIMS1. A device for radio frequency communications, the device comprising: a base layer comprising at least one antenna cavity with at least one antenna element; and a metallic cover layer comprising a plurality of metallic fragments separated by dielectric material, wherein a width of the plurality of metallic fragments at an inner surface of the metallic cover layer disposed towards the base layer is smaller than the width of the plurality of metallic fragments at an outer surface of the metallic cover layer disposed away from the base layer.

2. The device according to claim 1, further comprising: a conductive gasket layer between the base layer and the metallic cover layer, wherein the conductive gasket layer comprises at least one aperture aligned with the at least one antenna cavity.

3. The device according to claim 2, wherein the base layer comprises a conductive surface, and wherein the conductive gasket layer is configured to be in galvanic contact with the metallic cover layer and the conductive surface of the base layer.

4. The device according to any of claims 1 to 3, wherein the base layer comprises an antenna cavity with a plurality of antenna elements.

5. The device according to any of claims 1 to 3, wherein the base layer comprises a plurality of antenna cavities with respective antenna elements.

6. The device according to claim 5, wherein the metallic cover layer comprises at least one cavity wall configured to separate the plurality of antenna cavities.

7. The device according to claim 6, wherein the outer surface of the metallic cover layer comprises engraving along the at least one cavity wall configured to form engraved fragments at the outer surface of the metallic cover layer, wherein dimensions of the engraved fragments correspond to dimensions of the plurality of metal fragments at the outer surface of the metallic cover layer.

8. The device according to any of claims 4 to 7, wherein the plurality of antenna cavities is configured for different frequency bands.

9. The device according to claim 8, wherein the plurality of antenna cavities comprise at least one low-band antenna cavity configured for a first frequency band and at least one high-band antenna cavity configured for a second frequency band, wherein the second frequency band is higher than the first frequency band.

10. The device according to claim 9, wherein an electrical volume of the at least one low-band antenna cavity is higher than an electrical volume of the at least one high-band antenna cavity.

11. The device according to claim 9, wherein a size of metallic fragments of the metallic cover layer aligned with the at least one high-band antenna cavity is equal to a size of metallic fragments of the metallic cover layer aligned with the at least one low-band antenna cavity, and wherein a height of the at least one high-band antenna cavity is lower than a height of the at least one low-band antenna cavity.

12. The device according to claim 9, wherein a height of the at least one high-band antenna cavity is equal to a height of the at least one low-band antenna cavity, and wherein: the width of the plurality of metallic fragments is smaller for metallic fragments aligned with the at least one high-band antenna cavity than for metallic fragments aligned with the at least one low-band antenna cavity, a width of a gap between the plurality of metallic fragments at the outer surface of the metallic cover layer is larger for the metallic fragments aligned with the at least one high-band antenna cavity than for the metallic fragments aligned with the at least one low-band antenna cavity, or a thickness of the plurality of metallic fragments is lower for the metallic fragments aligned with the at least one high- band antenna cavity than for the metallic fragments aligned with the at least one low-band antenna cavity.

13. The device according to any of claims 5 to 12, wherein the base layer comprises a plurality of low -band antenna cavities and a plurality of high-band antenna cavities with respective antenna elements.

14. The device according to claim 13, wherein the plurality of the low-band antenna cavities is arranged in a first row along the metallic cover layer, and wherein the plurality of the high-band antenna cavities is arranged in a second row along the metallic cover layer parallel to the first row.

15. The device according to claim 13, wherein the plurality of low-band antenna cavities and the plurality of high-band antenna cavities are arranged alternately in a row along the metallic cover layer.

16. The device according to any of claims 1 to 15, wherein the width of the plurality of metallic fragments is substantially constant within a first distance from the outer surface of the metallic cover layer.

17. The device according to any of claims 1 to 16, wherein the plurality of metallic fragments is chamfered towards the inner surface of the metallic cover layer.

18. The device according to any of claims 1 to 17, wherein the width of the plurality of metallic fragments is substantially constant within a second distance from the inner surface of the metallic cover layer.

19. The method according to any of claims 1 to 17, wherein the base layer comprises a printed circuit board layer.

20. A method for manufacturing a device for radio frequency communications, the method comprising: arranging at least one antenna element at least one antenna cavity of a base layer; stacking the base layer and the at least one antenna element with a metallic cover layer, wherein the metallic cover layer comprises a plurality of metallic fragments separated by dielectric material, wherein a width of the plurality of metallic fragments at an inner surface of the metallic cover layer disposed towards the base layer is smaller than the width of the plurality of metallic fragments at an outer surface of the metallic cover layer disposed away from the base layer.

21. The method according to claim 20, further comprising: stacking a conductive gasket layer between the base layer and the metallic cover layer, wherein the conductive gasket layer comprises at least one aperture aligned with the at least one antenna cavity.

22. The method according to claim 20 or 21, wherein the metallic cover layer comprises at least one cavity wall configured to separate the plurality of antenna cavities, when stacked with the base layer.

3. The method according to claim 22, further comprising: engraving the outer surface of the metallic cover layer along the at least one cavity wall to form engraved fragments at the outer surface of the metallic cover, wherein dimensions of the engraved fragments correspond to dimensions of the plurality of metal fragments at the outer surface of the metallic cover layer.

Images