Patent Publication Number: US-2022216593-A1

Title: Antenna extender, and electronic device with antenna extender

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/976,818, filed on Aug. 31, 2020, which is a National Stage of International Application No. PCT/EP2018/057064, filed on Mar. 20, 2018, which are hereby incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The embodiments relate to the field of antennas used for wireless communications, and particularly to antennas that fit into tight spaces in electronic devices built with electrically conductive frames. Furthermore the embodiments relate to antenna arrangements that include a plurality of antennas, and to electronic devices that include an antenna or antenna arrangement. 
     BACKGROUND 
     Antennas are needed in all electronic devices that communicate using radio waves. Many such devices are meant to be portable, easily usable, and aesthetically appealing to users. As a consequence their size, design, overall appearance, mechanical robustness, and efficiency in radio communications may pose difficult and possibly mutually contradicting requirements to antenna design. 
     One example of such an electronic device is a portable communications and/or computing device such as a smartphone, a tablet computer, or a laptop computer. Such a device may be relatively flat and somewhat elongated in form, and have two ends, two side edges, as well as a front side and a back side. A large majority portion of the front side is often reserved for a touch-sensitive display. The back side may be covered by a back cover made of plastic, but in many cases the back side includes a layer of glass and/or metal. The circumference along the ends and side edges may also include a metallic frame. The device may be only a few millimeters thick, and the ends and side edges may measure from a few centimeters to a few decimeters. The physical dimensions of an antenna have certain relation to the wavelength of communications, which means that if an antenna is to be used for communications at wavelengths below  6  GHz, it must have physical dimensions in the order of some centimeters. It is difficult to design an antenna of that size so that, on one hand, it would enable efficient communications and high data throughput but on the other hand it would fit easily within a portable communications device. 
     Prior art suggests various antenna structures that may make use of the metallic or otherwise conductive structural parts of the electronic device. However, it has been found that antenna performance is not always optimal over the whole required frequency range and/or all frequency bands on which the electronic device should operate. 
     SUMMARY 
     An object of the embodiments is to provide an antenna that is compact in size, applicable in portable electronic devices, robust against many kinds of operating conditions, and combinable with other antennas included in an electronic device. Another object is that the antenna could be implemented in a confined space among other parts and structures of an electronic device, and yet have good performance Yet another object is to provide an electronic device that includes at least one antenna of its kind. 
     According to a first aspect, an electronic device is provided. The electronic device includes a housing having a first side and a second side, a dielectric cover on the second side, and an electrically conductive peripheral structure along edges of the first and second sides. The electronic device also includes an antenna feed coupled to a portion of the peripheral structure for using the portion as a radiating antenna element. Additionally the electronic device includes a conductive member on (e.g. attached on an inner side or an outer side of) the dielectric cover. Alternatively, the conductive member may be arranged underneath the dielectric cover (e.g. on a further support structure inside the housing). The conductive member has a first dimension along a longitudinal direction of the portion and extending inwards from the portion—with reference to the peripheral structure—by a second dimension, the second dimension being less than twice the first dimension. The electronic device includes an electric coupling between the portion and that part of the conductive member that extends along the longitudinal direction of the portion. The conductive member forms an antenna extender and, hence, can also be called an antenna extender. A purpose of the conductive member, i.e. the antenna extender, is to enlarge the surface area where the electric field is distributed on. In other words, the antenna extender increases the antenna aperture for radiation. It will improve the chassis mode excitation at desired frequency band(s). The antenna extender can be used, for example, to improve radiation efficiency, adjust resonant frequency, increase impedance bandwidth, and modify current distributions and radiation patterns to control, e.g. the effect of the user. 
     The antenna extender allows making an antenna of compact in size, for example in portable electronic devices in which there is little space, because it improves the impedance bandwidth and efficiency of the antenna without requiring more antenna clearance (i.e. more distance between radiating antenna element and ground). The improvement in impedance bandwidth and efficiency also increase robustness against suboptimal operating conditions, because they provide more marginal before the performance of the antenna would fall below acceptable limits. The antenna extender does not occupy such space that would otherwise be needed for other antennas in the same device, which makes the solution very compatible with other antennas. The antenna may even share some structures with other parts of the electronic device, which further emphasizes its suitability for confined spaces. 
     In a first implementation form of the electronic device, the dielectric cover is a dielectric plate and the conductive member is mechanically supported by the dielectric plate. This involves an advantage that the mechanical structure can be made robust and relatively easy to manufacture. It also involves the advantage that the distance between the conductive member and a grounded part of the electric device, such as a display, can be made as large as possible. This improves the impedance bandwidth and efficiency. 
     In a further implementation form of the electronic device, the dielectric plate is made of plastic, glass, ceramic, wood, or another dielectric substance, as desired, and has an inner surface and an outer surface, and the conductive member is a piece of conductive material fixedly attached to the inner surface of the dielectric plate. This involves advantages that the outer appearance of the device can be made very appealing, and that the mechanical structure can be made robust and relatively easy to manufacture. 
     In a further implementation form of the electronic device, the dielectric plate is transparent or translucent and includes a decorative layer on the inner surface, and the conductive member is indirectly attached to the inner surface of the dielectric plate through being attached to the decorative layer. This involves an advantage that the advantageous outer appearance of the device does not need to be compromised even if a conductive member of this kind is used as an antenna extender. 
     In a further implementation form of the electronic device, the electronic device includes a dielectric support structure inside the dielectric cover, and the conductive member is mechanically supported by the dielectric support structure. This involves an advantage that the design and mechanical structure of the antenna extender can be particularly well tailored according to operating frequencies and other affecting factors, and/or that some dielectric part inside the electronic device can efficiently double as a support structure for the antenna extender. 
     In a further implementation form of the electronic device, the electric coupling is a galvanic coupling including at least one of: a direct contact between the portion and the conductive member; a coupling through a conductive gasket between the portion and the conductive member; a coupling through two or more discrete contact members between the portion and the conductive member; a weld-, solder-, or glue joint between the portion and the conductive member. This involves an advantage that a secure electric coupling can be made in a wide variety of alternatives concerning the parts and materials in the surrounding structure. 
     In a further implementation form of the electronic device, the electric coupling is a non-galvanic coupling including at least one of a capacitive coupling and an inductive coupling. This involves an advantage that no direct contact needs to be made between certain parts, which makes it easier to design and assemble the structure and helps to avoid any problems that suboptimal contacts could cause. 
     In a further implementation form of the electronic device, a crossover frequency of the non-galvanic coupling is in the order of tens to hundreds of megahertz. This involves an advantage that sufficient electromagnetic connection can be made at frequencies that are useful taken the other dimensions of the antenna structure. 
     In a further implementation form of the electronic device, the portion includes a radiating antenna element of an antenna structure that is one of the following: a monopole antenna, a dipole antenna, a folded dipole antenna, a capacitive coupling element antenna, an inverted-F antenna, a loop antenna, and a slot antenna. This involves an advantage that the most suitable antenna type can be selected for a particular implementation. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a CCE antenna, 
         FIG. 2  illustrates an inverted-F antenna, 
         FIG. 3  illustrates a monopole or inverted-L antenna, 
         FIG. 4  illustrates certain structural parts of an electronic device, 
         FIG. 5  illustrates a cross section of the structure of  FIG. 4 , 
         FIG. 6  illustrates some structural parts of an electronic device with an antenna extender, 
         FIG. 7  illustrates a cross section of the structure of  FIG. 6 , 
         FIG. 8  illustrates some structural parts of an electronic device with an antenna extender, 
         FIG. 9  illustrates a cross section of the structure of  FIG. 8 , 
         FIG. 10  illustrates the dimensioning of an antenna extender, 
         FIG. 11  illustrates the dimensioning of another antenna extender, 
         FIG. 12  illustrates an equivalent circuit of an antenna extender, 
         FIG. 13  illustrates an antenna extender with a contact member, 
         FIG. 14  illustrates examples of shapes of antenna extenders, 
         FIG. 15  illustrates some structural parts of an electronic device with an antenna extender, and 
         FIG. 16  illustrates measured performance of antennas with and without antenna extenders. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device may include an inner part enclosed in an outer cover. Typically the inner part or chassis includes the electronic components needed for the operation of the electronic device, while the role of the outer cover is to provide mechanical support and protection as well as an appealing outer appearance. If the electronic device is equipped for wireless communications, it must have one or more antennas built into it. The provision of an electrically conductive peripheral structure, such as the so-called ring or outer frame that forms a part of the structure and outer appearance of many sophisticated smartphones, allows using one or more sections of the electrically conductive peripheral structure as radiating antenna elements. According to established vocabulary, a radiating antenna element is a structural part to which an oscillating electric current of high frequency is coupled for transmitting a radio signal, and/or to which a received radio signal induces an oscillating electric current of high frequency that can in turn be converted into the received signal. 
       FIGS. 1, 2, and 3  illustrate electronic devices that include an inner part, or chassis,  101  and a radiating antenna element, which may be a portion of an electrically conductive peripheral structure. It is typical to the inner part or chassis  101  that it includes a relatively extensive ground plane, for which reason it may be considered as a grounded region that has an effect on the performance of the radiating antenna element. 
     In  FIG. 1  the radiating antenna element  102  is a straight portion of the electrically conductive peripheral structure, the whole length of which is located at a distance  103  from a straight edge of the inner part or chassis  101 . An antenna feed  104  is at or close to a middle point of the radiating antenna element  102 . Neither of these (antenna element being straight; antenna feed being close to the middle) is a strict requirement, and variations are possible. The antenna of  FIG. 1  could be called a CCE (Capacitive Coupling Element) antenna. 
     In  FIG. 2  the radiating antenna element  201  is otherwise located at a distance  202  from a straight edge of the inner part or chassis  101 , but at one end of the radiating antenna element  201  there is a direct contact to the (ground plane of the) inner part or chassis  101 . A ground contact of this kind could be located anywhere along the length of the antenna element  201 . In  FIG. 2  an antenna feed  203  is closer to that end of the radiating antenna element  102  that has the contact than to its free end. Again, variations to all these features are possible. The antenna of  FIG. 2  is an IFA (Inverted-F Antenna). 
     In  FIG. 3  the radiating antenna element  301  is located at a distance  302  from a straight edge of the inner part or chassis  101 . An antenna feed  303  is located at one end of the radiating antenna element  301 , which makes the antenna a monopole or an ILA (inverted-L antenna). 
       FIGS. 4 and 5  are further illustrations of a structure that may follow the principle of  FIG. 1  above. The radiating antenna element  102  is a portion of an electrically conductive peripheral structure of the electronic device. The inner part or chassis  101  is illustrated in a simplified manner as a thick slab, a portion of which is shown in  FIGS. 4 and 5 . A first dielectric cover  401  covers a first (front) side of the electronic device, and a second dielectric cover  402  covers a second (back) side of the electronic device. In the assembled configuration the slightly inwards curved outer edges of the first  401  and second  402  dielectric covers come against respective grooves in the radiating antenna element  102 , so that a streamlined outer appearance of the electronic device is achieved. 
     The distance  103 ,  202 , or  302  at which the radiating antenna element is located from an adjacent grounded structure can be called the ground clearance or antenna clearance. The optimal magnitude of a ground clearance depends on the operating frequency and bandwidth. As a general rule on the operating frequencies smaller than 6 GHz that are common in smartphones and other widely used wireless communications devices a ground clearance of 5 to 10 millimeters could be close to an optimum. However, it may be desirable to cover a whole side surface, for example a front surface, of an electronic device with a (touch-sensitive) display. A display needs an associated ground plane, and this ground plane may define the effective outer dimensions of what is considered as the inner part or chassis  101  in  FIGS. 1 to 3 . As a consequence there may be as little as 1 to 2 millimeters, or even less, available as the ground clearance. 
       FIG. 6  illustrates some parts of an electronic device according to an embodiment in an exploded view.  FIG. 7  is a cross section of these parts along a plane that goes through the antenna feed  601 . The electronic device includes a housing having a first side and a second side. The first side is the lower side in  FIGS. 6 and 7 , and the second side is the upper side. The electronic device includes a dielectric cover  602  on the second side, and an electrically conductive peripheral structure along edges of the first and second sides. A portion  603  of the electrically conductive peripheral structure is seen in  FIGS. 6 and 7 . The antenna feed  601  is coupled to the portion  603  of the electrically conductive peripheral structure for using the portion  603  as a radiating antenna element. 
     As a difference to  FIGS. 4 and 5 , the electronic device of  FIGS. 6 and 7  includes a conductive member  604  covered by and arranged on the dielectric cover  602 . In this example the conductive member  604  is arranged on the inside (the inner surface) of the dielectric cover  602 . However, in a further embodiment, the conductive member  604  may be arranged on the outside (the outer surface) of the dielectric cover  602 . The conductive member  604  has a first dimension  605  along a longitudinal direction of the portion  603  of the electrically conductive peripheral structure that is used as a radiating antenna element. The conductive member  604  extends inwards from the portion  603  by a second dimension  606 . Here “inwards” is defined as inwards with reference to the peripheral structure of the electronic device; in other words, “inwards” means towards the center of the electronic device. 
     Of the dimensions of the conductive member  604 , the second dimension  606  is less than twice the first dimension  605 . The significance of these dimensions is discussed in more detail later. The conductive member  604  can be alternatively called an antenna extender. The expressions conductive member and antenna extender are used interchangeably. 
     An electric coupling exists between the portion  603  of the electrically conductive peripheral structure that is used as a radiating antenna element and that part of the conductive member  604  that extends along the longitudinal direction of the portion. In the structure of  FIGS. 6 and 7 , one long edge of the conductive member  604  is in direct mechanical contact with a part of the portion  603 , which ensures the electric coupling. Other ways of making such an electric coupling are discussed in more detail later. 
     In the structure of  FIGS. 6 and 7 , the dielectric cover  602  is a dielectric plate, and the conductive member  604  is mechanically supported by the dielectric plate. For example, the dielectric plate that includes the dielectric cover  602  can be made of, for example, plastic or glass, and it may have an inner surface and an outer surface. The conductive member  604  may be fixedly attached to the inner surface of the dielectric cover  602 , for example by gluing or by ultrasonic welding. The conductive member  604  could also be attached in other ways, such as being embedded in the material of the dielectric cover  602 . The actual way of attaching has little practical significance. Fixed attaching of this kind is based on an assumption that the conductive member  604  is a piece of conductive material, such as a piece of a metal foil or plate. An alternative would be to form the conductive member  604  on some surface of the dielectric cover  602  using conductive paint or other substance that is not in the form of a discrete, solid piece of conductive material before becoming attached to the dielectric cover  602 . 
     Using the dielectric cover  602  as a mechanical support for the conductive member  604  involves an advantage that no other structural parts are needed for that purpose. It may also enable easy assembling of the electronic device, because the conductive member  604  may be attached to the inner surface of the dielectric cover  602  first, so that when at a later assembling stage the dielectric cover  602  and the electrically conductive peripheral structure are brought together, the electric coupling between the conductive member  604  and the portion  603  that is used as a radiating antenna element is automatically made. An electrically conductive gasket can be used to ensure the electric coupling, but this is not necessarily required. The use of plastic, glass, ceramic, wood, or other dielectric material as the material of the dielectric cover  602  may enable achieving a very appealing outer appearance of the electronic device at a reasonable level of manufacturing costs. Plastic as the material involves the additional advantage that ultrasonic welding, moulding, or other known method based on partly melting some of the plastic substance are available for fixedly attaching the conductive member  604  to the dielectric cover  602 . 
       FIGS. 8 and 9  illustrate parts of an electronic device according to a further embodiment that includes a housing having a first side and a second side, and a dielectric cover  602  on the second side. The electronic device includes an electrically conductive peripheral structure along edges of the first and second sides, and an antenna feed  601  coupled to a portion  603  of the peripheral structure for using the portion  603  as a radiating antenna element. 
     The electronic device of  FIGS. 8 and 9  includes a conductive member  804  covered by and arranged underneath the dielectric cover  602 . For example, the electronic device includes a dielectric support structure  801  underneath the dielectric cover  602 , and the conductive member  804  is mechanically supported by the dielectric support structure  801 . Hence, the conductive member  804  is, in this embodiment, not arranged on the dielectric cover  602  but on the separate dielectric support structure  801  arranged underneath the dielectric cover  602 . The dielectric support structure  801  may be part of (or may, in turn, be supported by) any other part of the electronic device, like a wall of a battery compartment, a conductive shielding can of high-frequency parts, a speaker box, or the like. 
     The conductive member  804  has a first dimension  605  along a longitudinal direction of the above-mentioned portion  603  of the peripheral structure of the electronic device. The conductive member  804  extends inwards from the portion  603  by a second dimension  606 , so that again the “inwards” direction is taken with reference to the peripheral structure. The second dimension  606  is less than twice the first dimension  605 . There is an electric coupling between the portion  603  of the peripheral structure and that part of the conductive member  804  that extends along the longitudinal direction of the portion. 
     In the embodiment of  FIGS. 8 and 9  the electric coupling includes an elastic, electrically conductive gasket  901  located between the portion  603  of the peripheral structure and that part of the conductive member  804  that extends along the longitudinal direction of the portion. An electrically conductive gasket of this kind could be used also in the embodiment of  FIGS. 6 and 7 , or in any other embodiment. The electrically conductive gasket  901  may be held in place by glue, or by locking it into a groove, or the like, or by any other manner that ensures both holding in place and making an electric coupling. Other alternatives for making the desired electric coupling may involve at least one of soldering, welding, or gluing with electrically conductive glue. 
       FIGS. 10 and 11  illustrate the concept of the dimensions of the conductive member. In  FIGS. 10 and 11 , the portion  603  of the conductive peripheral structure that is used as the radiating antenna element is shown schematically as a horizontal bar.  FIGS. 10 and 11  illustrate embodiments in which there is a ground connection at one end of the portion  603 , but there are also embodiments in which there is no such ground connection. The first dimension  605  of the conductive member is its dimension along a longitudinal direction of the portion  603 . The conductive member extends inwards (with reference to the peripheral structure) from the portion by a second dimension  606 . In  FIG. 10  the second dimension  606  is about twice the first dimension  605 , while in  FIG. 11  the first dimension  605  is significantly larger than the second dimension  606 . If there is a ground connection like in  FIGS. 10 and 11 , it may be advantageous to place the conductive member so that its distance from the ground connection in the longitudinal direction of the portion of the conductive peripheral structure is the largest possible. 
       FIG. 12  illustrates an equivalent circuit in which point  1201  represents the radiating antenna element and point  1202  represents a conductive member of the kind described above. Point  1203  represents the “open” end of the conductive member, i.e. that part that is furthest away from the radiating antenna element. The so-called open-end impedance Z between point  1203  and the local ground potential is typically large, in the order of at least 100 ohms, or even at least 1 kilo-ohm. 
     The electric coupling between the radiating antenna element and the conductive member is represented by a contact member  1204  in  FIG. 12 . In general, the electric coupling may be considered to take place over an area A across a distance d through a material, the dielectric constant (or relative permittivity) of which is ε r  (epsilon-subscript-r). If the electric coupling is a direct galvanic coupling through for example a direct metal-to-metal contact, the value of ε r  is very large or infinite. 
       FIG. 13  shows how the elements of  FIG. 12  may be considered in practice. The contact member  1204  is located between the portion  603  of the conductive peripheral structure used as the radiating antenna element and the conductive member, for which the reference  604  is used in  FIG. 13 . This is an example only and is not meant to limit the consideration to only those kinds of conductive members that are similar to the conductive member  604  of the embodiment in  FIG. 6 . The area A is proportional to the dimension of the conductive member  604  in the longitudinal direction of the portion  603 . If there are two or more discrete contact members between the portion and the conductive member, like two or more discrete conductive gaskets distributed along the longitudinal direction of the electric connection, the area A is proportional to the distance between the two discrete contact members farthest away from each other. 
     If the electric coupling is a non-galvanic coupling, it may include at least one of a capacitive coupling or an inductive coupling. An exemplary calculation can be made for a capacitive coupling. For example, if the contact area A is 1.5 mm x 12 mm, the distance d is 0.1 mm, and the material in between is air, the contact capacitance would be about 1.7 pF. That would correspond to a crossover frequency of about 90 MHz, assuming that the open end impedance is  1  kΩ. This means that a sufficient electromagnetic coupling between the radiating antenna element and the conductive member is achieved at frequencies higher than 90 MHz. In general, a crossover frequency of a non-galvanic coupling of the kind may be in the order of tens to hundreds of megahertz. 
     In the embodiments described so far, the antenna extender or conductive member has a rectangular shape. This is not a requirement, but the conductive member may take a wide variety of shapes.  FIG. 14  illustrates some examples of such shapes, which include various rectangles, polygons with less or more corners than four, diamond shapes, trapezoidal shapes, shapes obtained by cutting a portion out of some otherwise regular shapes, partly round or curved shapes, and irregular shapes. The shape may be selected for example based on the shape of an available space for the antenna extender in the electronic device. The small white circles in the shapes of  FIG. 14  may be considered as examples of discrete contact members, or they may be examples of weld-, solder-, or glue joints between the conductive member and the portion of the conductive peripheral structure that is used as a radiating antenna element. 
       FIG. 15  illustrates an embodiment in which a dielectric cover  602  on a second side of an electronic device includes a dielectric plate that is transparent or translucent and includes a decorative layer  1501  on its inner surface. The conductive member  604  is indirectly attached to the dielectric plate through being attached to the decorative layer  1501 . A conductive gasket  901  ensures the electric coupling between the conductive member  604  and the portion  603  of the conductive peripheral structure that is used as a radiating antenna element. 
     Yet another possible embodiment could involve a conductive member made as a transparent electrically conductive layer on an outer surface of a dielectric plate that constitutes (a part of) a dielectric cover on the second side of the electronic device. 
       FIG. 16  illustrates measured total efficiencies of systems in which an electronic device includes an antenna, the radiating antenna element of which is a portion of the conductive peripheral structure along sides of the electronic device. In each case the solid line illustrates the measured total efficiency when no antenna extender of the kind described was used. The corresponding dashed line illustrates the measured total efficiency when an antenna extender of the kind described was used. The general improvement in the system&#39;s peak total efficiency was in the order of 1 dB, when the antenna extender was used. This is a result of the so-called chassis mode excitation improving and the antenna resonant frequency being optimized for the desired frequency band. In these measurements a rectangular antenna extender was used, and the dimensioning of the antenna extender was such that its dimension in the longitudinal direction of the radiating antenna element was about twice its dimension in the perpendicular direction. 
     The selection of the type of the radiating antenna element of the antenna structure is not limited by the embodiments. As an example, the antenna structure may be one of the following: a monopole antenna, a dipole antenna, a folded dipole antenna, a capacitive coupling element antenna, an inverted-F antenna, a loop antenna, and/or a slot antenna. 
     Elements have been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those of ordinary skill in the art. In the description, the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfil the functions of several items. The mere fact that certain measures are recited in mutually different embodiments does not indicate that a combination of these measured cannot be used to an advantage. 
     Although the embodiments and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments. 
     Although elements have been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention, and are contemplated to cover any and all modifications, combinations, or equivalents that fall within the scope of the invention.