Mobile phones and other wirelessly enabled devices continue to shrink in size, or are required to accommodate more functionality into existing form factors. Efficient antenna operation, providing adequate RF bandwidth and gain, is problematic in such environments. Many devices are required to contain more than one antenna and communicate over several different frequencies. Moreover, challenging performance standards may be imposed by regulatory bodies, cellular carriers and/or the dynamics of the marketplace.
Antenna designers are frequently pushed to conform to a plurality of stringent—and possibly inconsistent—design parameters, regarding antenna size, performance and other factors. Accordingly, advancements in antenna design would assist antenna designers and would result in mobile phones and other wirelessly enabled devices that conform to their product requirement specifications.
Techniques for enhancing mobile device antenna performance by application of dielectric loading materials are described herein. In one example, a mobile device includes a ground plane carried within an enclosure. An antenna is connected to the ground plane. Dielectric loading material is provided within at least a portion of an area defined between the ground plane and the antenna. The dielectric loading material results in a shortening of a required antenna length, thereby creating a recovered area, i.e., valuable space that is “recovered” by the use of dielectric loading material. The recovered area can be put to one or more uses. For example, a smaller antenna may make it possible to provide a desired separation space between the antenna and the enclosure. Such a separation space may prevent or reduce adverse hand detuning, which may otherwise result when a user touches the enclosure. Alternatively or additionally, a smaller antenna may allow installation of components (e.g., active components, such as integrated circuits) installed within the recovered area, thereby providing additional functionality to the mobile device. And further, a smaller antenna may simply allow the enclosure of the mobile device to be smaller.
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 as an aid in determining the scope of the claimed subject matter. The term “techniques,” for instance, may refer to device(s), system(s) and/or method(s) as permitted by the context above and throughout the document.
The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components. Moreover, the figures are intended to illustrate general concepts, and not to indicate required and/or necessary elements.
The disclosure describes techniques for enhancing mobile device antenna performance involving dielectric loading of mobile device antennas. In one example, a mobile device, wireless communications device and/or cellular telephone, includes a ground plane, carried within an enclosure. An antenna can be connected to the ground plane; alternatively, such as in a monopole antenna topology, a single connection is provided to drive the antenna element. Dielectric loading material is provided within at least a portion of an area defined between the ground plane and the antenna. The dielectric loading material results in a shortening of a required antenna length for operation at a given frequency. The shortening creates a “recovered area,” in the sense that the area is “recovered” or “reclaimed” for an alternate use.
The recovered areas can be utilized in one or more manners. For example, reduced antenna length may make it possible to increase distance between the antenna and enclosure. This may prevent or reduce adverse detuning, which may otherwise result when a user touches the enclosure. A smaller antenna may allow installation of components into recovered area, thereby providing additional functionality to the mobile device. And further, a smaller antenna may simply allow the enclosure of the mobile device to be smaller.
In one arrangement, an antenna may be supported above a ground plane that is within a printed circuit board (PCB). Dielectric loading material may be located between all or part of the antenna and the PCB. The antenna and dielectric loading material can be kept in place by any appropriate fasteners, such as adhesive glue, clips, heat stakes or other fastening devices, both known and developed for the application. In a further commonly practiced arrangement, the antenna may be implemented as a film or flexible PCB element and carried by, located along side or adjacent to, and/or wrapped about component(s), such as a plastic carrier frame. Such antennas, when somewhat shortened by the use of dielectric loading material, can be positioned further from the enclosure (and thereby in a location less susceptible to adverse hand detuning). In a still further and increasingly common arrangement, the antenna may be printed onto the plastic carrier frame of the mobile device. By appropriately locating dielectric loading material, such antennas may be made more compact, while retaining specification compliance.
In a variation of the antenna dielectric structure discussed above, a second dielectric loading material component can be located adjacent to the antenna, and on a side of the antenna opposite the first dielectric loading material, discussed above. Accordingly, a portion of the antenna may sandwiched between two dielectric loading material components, to thereby provide greater reduction in antenna size, while maintaining specification compliance.
And in a further variation, dielectric loading material can be located between the antenna and a portion of the enclosure nearest to the antenna. This arrangement can reduce adverse hand detuning in particular applications.
The discussion herein includes several sections. Each section is intended to be non-limiting; more particularly, this entire description is intended to illustrate components, techniques and arrangements which may be utilized in dielectric loading of mobile device antennas. The sections are not intended to illustrate components which must be utilized in any particular application. The discussion begins with a section entitled “Mobile Device Antennas with Dielectric Loading” describes aspects which provide improved antenna performance by using dielectric loading materials. A section entitled “Dielectrically Loading Both Sides of an Antenna” describes an optional step beyond dielectrically loading one side of an antenna. A section entitled “Dielectric Loading to Reduce Hand Detuning” describes techniques that may be used to further reduce the symptoms of antenna detuning due to contact between the device enclosure and outside objects, such as a user's hand. A section entitled “Flexible PCB and Printed Antennas” describes techniques applicable to these types of antennas. A section entitled “Example Antenna Configurations” describes antennas having differently sized and positioned dielectric elements. Finally, the discussion ends with a brief conclusion.
This brief introduction, including section titles and corresponding summaries, is provided for the reader's convenience and is not intended to limit the scope of the claims, nor the proceeding sections.
Mobile Device Antennas with Dielectric Loading
The mobile device 100 may include a number of components. Many mobile devices contain a printed circuit board (PCB), which provides connectivity to the components. In many applications, the PCB additionally provides a ground plane 102 for the mobile device 100. An antenna 104 is supported a distance from the ground plane 102. In some embodiments, a shorting element or ground connection 106 provides an electrical connection between the ground plane 102 and the antenna 104. For example, the ground connection 106 may be used in inverted F or planar inverted F [PIFA] antenna topologies and some loop antenna topologies. Monopole antenna topologies do not require a ground connection. Accordingly, inclusion of the ground connection 106 depends on a design or topology of the antenna 104. Moreover, the techniques discussed herein regarding use of dielectric loading material are adaptable to most antenna topologies, including antenna topologies with and without ground connections. A feed line 108 may be used to drive the antenna. Depending on the antenna design, the feed line 108 may include two conductors, one of which is connect to each of the ground plane 102 and the antenna 104. An enclosure 110, shown to have arbitrary screen, keyboard and user interface devices, is provided as an example only, and should not be considered to contain required components, features and/or elements.
Significantly, the antenna 104 may be implemented using any desired technology, topology, design and/or materials. An antenna may be selected based on design requirements, costs or other parameters associated with a particular project. Examples of antenna technologies—intended not as a comprehensive list, but for purposes of illustration—include antennas formed as metal printed onto substrates or plastics, antennas formed as conductors in flexible self adhesive films on substrates, and antennas formed as stamped metal elements in an appropriate shape. Accordingly, antenna 104 should be considered to be somewhat diagrammatic in nature, and as such, representative of a wide range of antenna technologies.
Dielectric loading material 114 is located and contained within at least a portion of a region between the ground plane 102 and the antenna 104. The antenna 104, dielectric loading material 114 and ground plane 102 may therefore assume a stacked relationship, with the dielectric loading material sandwiched between the antenna 104 and ground plane 102. The dielectric loading material may be any dielectric material suggested by a particular design. For example, ceramic materials in sheet form provide suitable dielectric properties for many designs. Additionally, dielectric materials in sheet form, such as RF (radio frequency) substrate materials may be used. Such materials are available from vendors, including Taconics (Taconics Headquarters, Advanced Dielectric Division, 136 Coonbrook Road, Petersburgh, N.Y. 12128, USA) or Rogers (Rogers Corporation, One Technology Drive, Rogers, Conn. 06263).
Use of the dielectric loading material 114 within all or part of the region between the ground plane 102 and the antenna 104 allows design and fabrication of an antenna 104 of shorter length 116, as seen in
By using dielectric loading material 114 within all or part of the region between the ground plane 102 and the antenna 104—resulting in an antenna 104 sized for location within a region of shorter length 116—recovered areas 120 and 122 are obtained. Accordingly, an antenna can be sized—and recovered areas 120, 122 created—in part as a function of the nature, type, size and positioning of the dielectric loading material 114. The recovered areas 120, 122 can be utilized in one or more manners. For example, the recovered areas 120, 122—associated with an antenna 104 and dielectric loading material 114 sized to fit within an area of shorter length 116—may provide sufficient separation between the antenna 104 and enclosure 110 to prevent or reduce adverse detuning. For example, user contact with location 112 of the enclosure 110 may not result in detuning if recovered areas 120, 122 are created through the use of dielectric loading material 114. Moreover, an antenna 104 utilizing dielectric loading material 114 may allow installation of components (e.g., active components such as integrated circuits) into recovered area, thereby providing additional functionality to the mobile device 100. And further, an antenna 104 utilizing dielectric loading material 114 may allow the enclosure 110 of the mobile device 100 to be smaller.
The point at which feed line 108 is connected to the PCB, within which the ground plane 102 is located, may be considered to be a design parameter. In particular, by selecting a point at which the feed line 108 attaches to the PCB, the relative sizes of the recovered areas 120, 122 may be adjusted. For example, if a ground plane within the PCB is generally co-extensive with the PCB, then attachment of the feed line 108 to a central location on the PCB will result two similarly sized recovered areas. As a further example, attachment of the feed line to an off-center location on the PCB will result in one recovered area that is larger than the other recovered area. As a still further example, attachment of the feed line to a location near one edge of the PCB will result in one recovered area that is much larger than the other recovered area. Thus, while in the example of
Two holes 410, 412 may be defined in the dielectric loading material 404, as one option to provide passage for a ground connection (as seen in
An antenna and dielectric region 608 encompasses an antenna associated with one or more dielectric loading material(s) in one or more locations. The dielectric loading material(s) used within the antenna and dielectric region 608 results in a shorter antenna than would be the case without use of dielectric loading material. Accordingly, use of dielectric loading material within the antenna and dielectric region 608 may result in recovered areas 610, 612, i.e., areas that represent a degree to which the antenna with dielectric loading material is shorter than an antenna without dielectric loading material. The relative sizes of the recovered areas 610, 612 may be adjusted. For example, one recovered area may be made larger and the other recovered area made correspondingly smaller by variation of a point at which a feed line driving the antenna is attached to a printed circuit board and associated ground plane. Thus, while in the example of
Referring to
In particular, a mobile device 1000 includes an enclosure 1002. A carrier frame 1004 may be made of plastic or other material, as indicated by a particular set of design requirements. In an example implementation, a notch 1006 may be defined in the carrier frame 1004 to support dielectric loading material 1008 and a PCB 1010 having a ground plane.
A second recess or notch 1012 may optionally be defined in the carrier frame 1004 to define a location within which a flexible thin film PCB antenna 1014 is carried. The flexible thin film PCB antenna 1014 may be attached to the carrier frame 1004 by any desired fastener, such as flange fasteners 1016, 1018, adhesive or simply frictional fastening, which secures the flexible thin film PCB antenna 1014 between the carrier frame 1004 and the enclosure 1002. The flexible thin film PCB antenna 1014 may be located along, or carried by, one or more sides of the carrier frame 1004—as seen in
Alternatively, the antenna 1014 of
An antenna 1112 may be supported by the carrier frame 1104. Optionally, the antenna may be supported within a second notch 1114 defined on the surface of the carrier frame 1104. The antenna may be secured in place by a small quantity of adhesive, a pin, a clip, heat-welding or other fastening means.
With the dielectric block removed (i.e., dielectric equal to air) the length of the antenna 1202 is 1040 mils. When the dielectric block 1204 had a dielectric constant of 10, the length of antenna 1202 was reduced to 700 mils, without degrading the matched bandwidth of 13.7%. The length and volume of the antenna 1202 (due to the dielectric 1204) was reduced to 67.3% of the original dimensions, as shown in Table 1. In this example, reduction of the antenna from 1040 mils to 700 mils provides a recovered area of 340 mils.
If a dielectric constant of the dielectric material 1304 was changed to ∈r=30, a length of the antenna 1302 could be further reduced to a 575 mils, or a 55.3% of the length of an antenna without dielectric loading. This size reduction is achieved at an expense of usable antenna bandwidth, i.e., the bandwidth of the antenna is reduced to 8.6%. However, this result still considerably exceeds the required bandwidth for Bluetooth or Wi-Fi antennas at 2.45 GHz. Moreover, such a bandwidth reduction would also not be a problem for GPS antennas or other antenna applications where small percentage bandwidth is acceptable. This bandwidth reduction effect may constrain the use of very high dielectric constant materials (e.g. ∈r=30) in applications where very broadband antennas are required such as cellular pentaband antennas.
Although the subject matter has been described in language specific to structural features and/or methodological 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. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claims.