CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/EP2018/057064, filed on Mar. 20, 2018, which is hereby incorporated by reference in its 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.

