WO2007075822A2

WO2007075822A2 - Multi-band antenna system with multiple plate conductors

Info

Publication number: WO2007075822A2
Application number: PCT/US2006/048661
Authority: WO
Inventors: Kristen K. Leininger; Eric L. Krenz; James P. Phillips
Original assignee: Motorola, Inc.
Priority date: 2005-12-27
Filing date: 2006-12-20
Publication date: 2007-07-05
Also published as: CN101352022A; WO2007075822A3; KR20080083337A

Abstract

A wireless communication device (200) comprising an antenna system is disclosed. The antenna system includes a first plate conductor (202) and a second plate conductor (204) that can interact capacitively. The first plate conductor (202) and the second plate conductor (204) have surfaces that are at least partially overlapping and are in close proximity to each other. The antenna system further includes one or more feed points (206). In some embodiments, the antenna system will include one or more localized complex impedances (802) coupled to at least one of the first plate conductor (202) and the second plate conductor (204) proximate a respective edge for modifying the corresponding electrical length. In further embodiments, at least one of the first plate conductor (202) and the second plate conductor (204) will form at least a portion of the external housing of the wireless communication device (200).

Description

MULTI-BAND ANTENNA SYSTEM WITH MULTIPLE PLATE CONDUCTORS

FIELD OF THE INVENTION

|0001| The present invention relates in general to antenna systems, and more specifically to a multi-band antenna system, which incorporates multiple plate conductors.

BACKGROUND OF THE INVENTION [0002] Antennas are generally used for the conversion of energy between an electrical signal, which is principally contained within an electrical conductor and an 'electromagnetic wave, which can propagate substantially beyond the electrical conductor. In many devices, the antennas encompass one or more dedicated discrete elements, such as one or more conductors, which are specifically adapted for radiating and receiving electromagnetic waves at one or more desired frequencies. [0003| Historically, the antenna often incorporated structure, such as a stub or a whip, that extended beyond the boundaries of the rest of the device. However, more recently, in at least some instances for aesthetic reasons, the antenna is increasingly being placed internal to and/or within the boundaries of the rest of the device. Aesthetics and usability preferences are increasingly influencing designs in other areas as well, including the overall size and shape of the phone, which is trending toward smaller devices. Enhancements in functionality, which is often necessitating the inclusion of additional elements to support the increased functionality, has also remained a fairly consistent trend. [00041 In some instances these considerations are impacting the types of materials used in the manufacture of the phone. For example, metal materials are increasingly being used in the construction of the housing as a way to maintain structural integrity, while minimizing the amount of material, and hence volume, required to provide the desired structural integrity, which in turn helps to address some of the space constraints associated with increasingly smaller devices. Increased use of metal housing materials can also further enhance the aesthetic appeal of a device. [0005] However some of these changes can have an impact on the requisite and/or desired performance characteristics of an associated antenna system. For example, increasing functionality can result in an antenna system, which needs to support a larger number of frequencies and/or frequency bands. Furthermore, an increase in the use of metal materials (i.e. conductive materials) as part of the external housing can impact the ability of a signal, which might originate from inside the device, from being able to propagate outside the device.

[00061 Furthermore as the overall size of the device decreases, corresponding size limits are placed upon any conductive elements intended to fit within the external size limits of the device, which are used to support the transmission or the reception of wirelessly communicated signals, which are in the form of radio frequency electromagnetic waves.

[0007] The present inventors have recognized that the metallic housing elements, being conductive, could be used to support the desired transmission and reception of electromagnetic signals, either alone or in conjunction with other conductive elements, thereby making available within the device, space which would otherwise have supported the positioning and placement of a dedicated discrete conductive element for use in an antenna system, so that the space is now available for use in the positioning and placement of elements which support other functions. [0008] Furthermore, incorporation of portions of a metallic housing as part of an antenna, enables the respective portions of the housing to be used to radiate or receive electromagnetic signals, as opposed to functioning as an electromagnetic shield which might inhibit the transmission or reception of such signals. Still further, the present inventors have developed an approach for tuning antennas, which incorporate plate conductors, which can be formed at least in part from metallic housing elements, so as to better support the desired frequency ranges, while still allowing the industrial designers a degree of freedom in formulating the various dimensions of the device including the external housing. SUMMARY OF THE INVENTION

[0009] The present invention provides an antenna which is adapted to operate in one or more frequency bands. The antenna includes a first plate conductor having a surface and a second plate conductor, the second plate conductor having a surface in close proximity to and at least partially overlapping the surface of the first plate conductor, wherein the first plate conductor and the second plate conductor interact capacitively. The first plate conductor and the second plate conductor each have one or more corresponding edges, which each have an electrical length. The electrical length of at least a respective one of the edges of at least one of the first plate conductor and the second plate conductor are modified by one or more localized complex impedances. The one or more complex impedances are coupled to at least one of the first plate conductor and the second plate conductor proximate the respective edge. The first and second plate conductors each have respective feed points, which are adapted for receiving a differential signal.

[00101 The present invention further provides for a wireless communication device, which includes an antenna and one or more signal generators. The antenna is adapted to operate in one or more frequency bands and includes a first plate conductor having a surface, a second plate conductor having a surface, which is in close proximity to and at least partially overlapping the surface of the first plate conductor, wherein the first plate conductor and the second plate conductor interact capacitively, and one or more respective feed points, associated with each of the first and second plate conductors, the one or more feed points being adapted for receiving a differential signal. At least one of the first plate conductor and the second plate conductor form at least a portion of the external housing of the wireless communication device. The wireless communication device further includes one or more signal generators, which provide the one or more feed points of the antenna with a differential feed. [0011] The present invention still further provides for a wireless communication device, which includes an antenna, which is adapted for operating in one or more frequency bands. The antenna has a first plate conductor having a surface, and a second plate conductor, the second plate conductor having a surface in close proximity to the surface of the first plate conductor. Each of the first and second plate conductors have one or more respective feed points, which are adapted for receiving a differential signal. The wireless communication device additionally includes a substrate having one or more conductive paths located between the first plate conductor and the second plate conductor, where each conductive path includes an inductive length and one or more capacitors, which bridge portions of the inductive length, which together are tuned to convey signals having one or more corresponding predetermined frequencies between the first plate conductor and the second plate conductor. [0012] These and other objects, features, and advantages of this invention are evident from the following description of one or more preferred embodiments of this invention, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS [0013] The present invention is illustrated by way of example, and not limitation, in the accompanying figures, in which like references indicate similar elements, and in which:

[0014] FIG. 1 is a perspective view of an antenna, in accordance with an exemplary embodiment; [0015] FIG. 2 is a perspective view of a wireless communication device, in accordance with a first exemplary embodiment;

[0016] FIG. 3 is a perspective view of a wireless communication device, in accordance with a second exemplary embodiment;

[0017] FIG. 4 is a perspective view of a wireless communication device, in accordance with a third exemplary embodiment;

[0018] FIG. 5 is a perspective view of a substrate, in accordance with an embodiment of the invention;

[0019] FIG. 6 is a perspective view of a wireless communication device with the substrate, in accordance with an embodiment of the invention; [0020] FIG. 7 shows a wireless communications device with one or more additional antennas, in accordance with an embodiment of the invention; and [0021] FIG. 8 shows a first plate conductor and a second plate conductor with complex impedances, in accordance with an embodiment of the invention. [0022] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of the embodiments shown.

DETAILED DESCRIPTION [0023] Before describing in detail the particular antenna system and wireless communication device embodiments, it should be observed the apparatus components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to the understanding of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0024] In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or other elements inherent to such process, method, article, or apparatus. An element preceded by "comprises ... a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0025] The term "another", as used herein, is defined as at least a second or more. The terms "including" and/or "having", as used herein, are defined as comprising. The term "coupled", as used herein with reference to electrical technology, is defined as connected, although not necessarily directly, and not necessarily mechanically. [0026] FIG. 1 is a perspective view of an antenna 100, in accordance with an exemplary embodiment. The antenna 100 includes a first plate conductor 102 and a second plate conductor 104. In one embodiment, the first plate conductor 102 and the second plate conductor 104 are metallic plates. The term plate conductor is generally meant to refer to a conductor having a surface with a meaningful length and width, so as to have a plurality of measurable edges, which can each be adapted to be used in the creation of one or more electromagnetic signals, which radiates beyond the boundaries of the corresponding conductor. In connection with the illustrated embodiment, the first plate conductor 102 has a surface that is in close proximity with a surface of the second plate conductor 104. In at least some instances, the surfaces of the plate conductors 102 and 104 are substantially planar. The plate conductors 102 and 104 can be incorporated as separate elements, or can be formed from and/or incorporated as part of other elements. For example, planar conductive surfaces can be found in printed circuit boards, LCD displays and lithium pyramidal batteries, which can be used in connection with the present invention as a plate conductor with the alternative function of forming part of an antenna system for use in a wireless communication device.

[0027] The plate conductors 102 and 104 are generally electrically isolated at one or more frequencies of interest. In some instances, this separation can take the form of a gap. Each of the plate conductors includes one or more respective feed points 108, which are adapted to receive a differential signal that can be produced by a corresponding transmitter 106 capable of producing a differential signal at one or more frequencies of interest. The respective feed points 108 are generally located proximate an edge of the first plate conductor 102 and an edge of the second plate conductor 104. In some instances, each of the plate conductors of the antenna 100 can also be provided with a plurality of feed points.

[0028] In the illustrated embodiment, each plate conductor is incorporated in a different part of a wireless communication device having a two part housing. For example the first plate conductor is incorporated into an upper housing, and the second plate conductor is incorporated into a lower housing. The upper and lower housings are generally rotatable relative to one another, often times about a hinge. In such an instance, the plate conductors of the antenna 100 can exist in multiple orientations, relative to one another. For example, the angle between the plate conductors 102 and 104 can vary from 0 degrees to almost 360 degrees. The embodiment depicted in FIG. 1 shows the plate conductors 102 and 104 in an orientation where the plate conductors are nearly co-linear, such as when a clam shell- type phone is in an open position. In other words, the first plate conductor 102 and the second plate conductor 104 are at an angle that is approximately equal to 180 degrees. In other instances, the angle between the two plate conductors can be approximately zero degrees, such as when a clam shell-type phone is in a closed position. When the angle between the two conductive plates is nearly zero degrees, the first plate conductor 102 and the second plate conductor 104 generally have portions which at least partially overlap. In such an instance the plate conductors are also generally parallel. In this embodiment, the respective feed points 108 can be located at a corresponding edge of the first plate conductor 102 and the second plate conductor 104, proximate the position of a hinge (not shown).

[0029] The antenna 100 is electrically excited by providing a differential signal to the feed points 108. The first plate conductor 102 and the second plate conductor 104 each have an electrical length determined by the geometries of the first and second conductors and by the phase velocity of any electromagnetic energy traversing therethrough. In at least one embodiment, the electrical lengths of the first plate conductor 102 substantially match the electrical lengths of the second plate conductor 104 at each of the corresponding edges. Each edge belonging to the surface of the first plate conductor 102 and the second plate conductor 104 will have an electrical length, which can be different. It should be appreciated that the electrical length of an edge is not necessarily equal to the physical length of the edge. When the antenna 100 is excited, the electrical length of one or more edges belonging to the first plate conductor 102 interacts with the electrical length of the one or more edges belonging to the second plate conductor 104. This interaction produces a resonance at a frequency determined by the dimensions of the plate conductors 102 and 104 and the associated phase velocity. In other words, a resonant structure with a standing wave is created when a differential signal is applied to the first plate conductor 102 and the second plate conductor 104. Sometimes, this is referred to as the first plate conductor 102 being electrically fed against the second plate conductor 104. However in some instances, the natural resonance may not be at the desired predetermined frequency. In some instances this may be the result of the inherent geometries of the plate conductors, in other instances this may be the result of the interaction of the two conductive plates at a particular angle, for example, when the angle between the two conductive plates is nearly zero. To ensure that the antenna 100 produces the radiation signal at the predetermined desired frequency, even when the angle between the two plate conductors is nearly zero, the electrical length of at least one of the first plate conductor 102 and the second plate conductor 104 can be modified by using one or more complex impedances to change the phase velocity. The complex impedances or admittances are placed on at least one of the first plate conductor 102 and the second plate conductor 104. In an embodiment, the complex impedances used are capacitive susceptances. Tn this embodiment, there are one or more pieces of dielectric material that are placed between the first plate conductor 102 and the second plate conductor 104. Deliberate placement of the pieces of dielectric material allows control over the standing wave modes of resonance and thus the radiation. Exemplary values of the predetermined frequencies at which one antenna 100 might radiate are 869 MHz, 960 MHz, 1575MHz, and 1850 MHz, which would accommodate frequencies which support communications in accordance with the standard for various implementations of Global System for Mobile Communications (GSM) as well as the reception of GPS type signals.

[0030] FIG. 2 is a block diagram of a wireless communication device 200, in accordance with a first exemplary embodiment, wherein the device represents a clam- shell type wireless communication device 200 illustrated in a closed position. As noted previously a clam-shell type mobile device employs a hinge mechanism by which the device can transition between an open and closed position. In the illustrated embodiment, the wireless communication device 200 does not include a dedicated discrete antenna, but uses existing components or structures to provide the antenna functionality. The wireless communication device 200 includes a first plate conductor 202 and a second plate conductor 204. The first plate conductor 202 and the second plate conductor 204 share many of the properties of the first plate conductor 102 and the second plate conductor 104 as described in conjunction with FIG. 1. In at least one embodiment, the first plate conductor 202 and the second plate conductor 204 form at least portions of the housing of the wireless communication device 200. As the first plate conductor 202 and the second plate conductor 204 are metallic components, the main housing of the wireless communication device 200 can be largely, and even entirely metallic. The aesthetics of the wireless communication device 200 can sometimes be improved by having a largely and/or entirely metallic housing or keypad. For example, a housing made from the same or similar materials can reduce any potential feeling of discontinuity in the look and feel, when the device is handled by the user, which can sometimes be associated with a transition between different materials.

[0031] Furthermore, a metallic housing tends to be much stronger and require less volume than housings comprised more substantially of plastic elements. Thus they can generally be much thinner and thus provide for more compact wireless devices. The wireless communication device 200 enables the first plate conductor 202 and the second plate conductor 204 to overlap completely and/or nearly completely in a closed position. However, when the wireless communication device 200 is in an open position, the first plate conductor 202 and the second plate conductor 204 may not overlap. The first plate conductor 202 and the second plate conductor 204 are physically separated by a hinge. In at least some embodiments, the hinge can be non- metallic. Correspondingly, the hinge can facilitate the electrical isolation of the first plate conductor 202 and the second plate conductor 204. In other instances, the first plate conductor 202 and the second plate conductor 204 are electrically isolated for electrical signals having one or more particular frequencies by a substrate, which is explained in detail in conjunction with FIG. 5. Respective feed points 208 are located proximate the hinge and are adapted so that they can receive a differential signal. The wireless communication device 200 also includes at least one of a transmitter 206 and a receiver coupled to the feed points. In at least some instances both the transmitter and receiver can be combined as part of a transceiver. The transmitter 206 supplies a differential signal to the feed points 208. In various embodiments, the wireless communication device 200 can include a plurality of transmitters and receivers.

[0032] The antenna functionality of the wireless communication device 200 is met by electrically exciting the first plate conductor 202 and the second plate conductor 204 in relation to each other. The electric excitement of the two plate conductors 202 and 204 cause them to interact and function as a radiator of electromagnetic signals. As noted previously, in connection with FIG. 1, the first plate conductor 202 and the second plate conductor 204 each have an electrical length, which determines the effectiveness of the antenna in transmitting and receiving electromagnetic signals at various frequencies.

[0033] When the wireless communication device 200 is in the open position, i.e., the angle between the first plate conductor 202 and the second plate conductor 204 is substantially greater than 100 degrees, then the wireless communication device 200 acts as a wideband dipole. In this embodiment, the antenna 200 has a broadband response. When the wireless communication device 200 is in the closed position, i.e., the angle between the first plate conductor 202 and the second plate conductor 204 is substantially less than 90 degrees, the resonance bands are controlled by using complex impedances, as in the case of the antenna 100. The closed position of the wireless communication device 200 is further elaborated in conjunction with FIG. 7. [0034] FIG. 3 is a perspective view of a wireless communication device 300, in accordance with a second exemplary embodiment. In this embodiment, the wireless communication device 300 is consistent with a slider-type mobile device. A slider- type mobile device employs a slide mechanism to open and close the mobile device. The wireless communication device 300 includes a first plate conductor 302 and a second plate conductor 304. The first plate conductor 302 and the second plate conductor 304 have properties that are similar to the first plate conductor 102 and the second plate conductor 104 as described in conjunction with FIG. 1. In one embodiment, at least one of the first plate conductor 302 and the second plate conductor 304 form at least a portion of the housing of the wireless communication device 300. In other instances, one or more of the plate conductors can be formed as part of a conductive layer of a printed circuit board, or a surface of a battery pack, etc. The first plate conductor 302 and the second plate conductor 304 can have different configurations, so as they may be non-overlapping, partially overlapping, or substantially overlapping with respect to each other. Respective feed points 308 allow the plate conductors to be driven differentially. The feed points 308 are provided with a differential signal produced by a transmitter 306.

[0035J The antenna functionality of the wireless communication device 300 is met by electrically exciting the first plate conductor 302 and the second plate conductor 304 in relation to each other. The first plate conductor 302 and the second plate conductor 304 interact in the same manner as the first plate conductor 102 and the second plate conductor 104. Hence, the wireless communication device 300 can be made to resonate at a plurality of desired frequencies.

[0036] FIG. 4 is a perspective view of a wireless communication device 400, in accordance with a second exemplary embodiment. In an embodiment, the wireless communication device 400 is a candy bar-type mobile device, which resembles an oblong monolithic block and has a housing shape, which is generally non-changing. The wireless communication device 400 includes a first plate conductor 402 and a second plate conductor 404. In at least one embodiment, the first plate conductor 402 and the second plate conductor 404 are generally collinear, relative to each other. The plate conductors can alternatively be stacked relative to one another, in which case the respective block diagram would more closely resemble the embodiment illustrated in FIG. 2, with the exception that the two elements would generally not rotate relative to one another, via a hinge or otherwise.

[0037] In at least one embodiment, one or more of the first plate conductor 402 and the second plate conductor 404 form at least a portion of the housing of the wireless communication device 400. In another embodiment, the first plate conductor 402, and the second plate conductor 404 are printed circuit board halves of the wireless communication device 400. In yet another embodiment, the first plate conductor 402 can incorporate at least portions of the battery of the wireless communication device 400, and the second plate conductor 404 can be the printed circuit board of the wireless communication device 400. One skilled in the art will readily appreciate that various conductive surfaces might be present in the construction of a typical wireless communication device, which could function as a plate conductor in forming portions of the present antenna structure without departing from the teachings of the present invention.

[0038] Once again, each plate conductor 402 and 404, includes one or more feed points 408, which can be electrically excited so as to transmit a desired electromagnetic signal, which can extend beyond the boundaries of the device. The respective feed points 408 are provided with a differential feed by a transmitter 406, and in turn can function in a manner which is similar to the plate conductors discussed in connection with at least some of the other embodiments. [0039] FIG. 5 is a perspective view of a substrate 500, in accordance with at least some embodiments of the present invention. The substrate 500 is a flexible circuit that is designed to function as a balancer-unbalancer and provide isolation at certain predefined frequencies for the antenna. The substrate 500 includes a conductive layer 502, a plurality of area capacitors 504, and a flexible material 506. The flexible circuit 506 includes a non-conductive low loss material. The substrate 500 is designed so as to include one or more conductive paths, which are formed as part of the conductive layer 502. In the illustrated embodiment a single conductive path is shown. The plurality of area capacitors 504 serve to bridge portions of the inductive length of the conductive path. More specifically, the capacitors 504 are formed by electrically coupling one end 508 of conductor proximate one end of the conductive path, and allowing the other end of the conductor to extend across another portion of the conductive path without being electrically coupled to the same. The area of overlap 510 is separated by an amount of non-conducting material, which has a predetermined dielectric constant over a deliberate area, which is necessary for producing the desired capacitive effect.

[0040] The plurality of area capacitors 504 in conjunction with the inductance associated with the flexible circuit 506 creates a parallel-resonant (LC) circuit. In one embodiment, the substrate 500 is a dual-band balun object. In another embodiment of the invention, the substrate 500 is a quad-band balun object. The substrate 500 is used in the wireless communication device 200 to electrically isolate the first plate conductor 202 and the second plate conductor 204 at particular desired frequency bands of operation. The one or more conductive paths only enable particular signals having predetermined frequencies to be transmitted between the first plate conductor 202 and the second plate conductor 204. Each of the conductive paths has an inductance determined primarily by its length. [0041] FIG. 6 is a perspective view of the wireless communication device 200 having the substrate 500, in accordance with an embodiment of the invention. The substrate 500 is incorporated between the first plate conductor 202 and the second plate conductor 204 in the wireless communication device 200, in many instances within a gap 602 formed between the two plate conductors. The wireless communication device 200 also includes a hinge between the first conductive element 202 and the second conductive element 204, which generally can coincides with the gap 602. In this instance, the substrate 500 can be located in the hinge of the wireless communication device 200. The substrate 500 enables a physical connection between the first plate conductor 202 and the second plate conductor 204, and allows for an electrical connection at some frequencies, while maintaining an effective electrical isolation at other frequencies.

[0042] A set of conductors 604 is shown bridging the gap 602. In one embodiment, the set of conductors 604 includes metallic wires which extend across the gap 602, and are soldered to the surface of the conductive elements 202 and 204 on each side of the gap 602. The parallel inductance of the set of conductors 604 resonates with the gap capacitance, to produce a "lumped element balun" function that enables the antenna of the wireless communication device 200 to function more efficiently at the desired frequencies. Higher inductance of the set of conductors 604 ensures a higher quality factor for the antenna of the wireless communication device 200. Multiple conductors create multiple LC circuit resonances, which help to create an ultra-wide band response at the desired bands of interest.

[0043] The antenna performance of the wireless communication device 200 improves with the incorporation of the substrate 500. This tuning method can create a multi-band response that is more highly efficient. The substrate 500 enables the wireless communication device 200 to exist with multiple gaps (not shown). This further assists the wireless communication device 200 by increasing the number of feed points.

|0044] FIG. 7 shows the wireless communication device 200 with a second antenna, in accordance with at least one embodiment of the present invention. In addition to the features described above, the wireless communication device 200 can also incorporate traditional antennas, such as the helical antenna 702, to enhance the bandwidth of an already supported band of frequencies or to provide additional frequency bands of resonance. In at least one embodiment, the wireless communication device 200 incorporates an additional helical antenna 702 placed in the space formed between the first plate conductor 202 and the second plate conductor 204, such as in the area of a hinge. The helical antenna 702 provides for the transmission or reception of an electromagnetic signal having still further desired frequencies, which can have the effect of providing communication capabilities in additional frequency bands for the wireless communication device 200 because of the different geometries and associated resonance frequencies of the helical antenna 702. A still further conductive element 704, inserted within the helical antenna 702, can provide still further transmission or reception capabilities, typically in a higher frequency band, as the substantially straight conductor will generally have an electrical length that is shorter than the corresponding helical structure. Placement within the hinge of the additional internal antenna structure is particularly suitable in instances, where the hinge is substantially formed from non-conductive materials. [0045] FIG. 8 shows the plate conductors 202 and 204 with complex susceptances or impedances, in accordance with at least one embodiment of the present invention. As mentioned earlier, when the wireless communication device 200 is in the closed position, i.e., the angle between first plate conductor 202 and the second plate conductor 204 is substantially less than 90 degrees, then the bands of resonance are controlled by means of complex susceptances or impedances. In one embodiment, the complex susceptance used is a capacitance. A resonant structure is created when the first plate conductor 202 and the second plate conductor 204 are in close proximity to each other. Specific tuning is achieved by controlling the standing- wave modes of radiation in this configuration with complex susceptances or impedances. Area capacitors are created by the planned placement of dielectric material 802 between the plate conductors 202 and 204. Controlling the size and location of the area capacitor creates the desired resonances, relative to the particular proximate edges of the first and second plate conductors. In one embodiment, the pieces of dielectric material 802 are located on the periphery of the first plate conductor 202 and the second plate conductor 204 and away from the corners, in which case their effects are more pronounced relative to a particular edge. In other embodiments, the pieces of dielectric material 802 are located away from the periphery and/or closer to one of the corners of the first plate conductor 202 and the second plate conductor 204, in which case the effects may be more pronounced with more than one of the edges. In one embodiment, the dielectric material 802 can be made from a form of Rexolite®. The dielectric material 802 is generally discretely located, localized to a particular area, between the two plate conductors, where they are intended to affect the corresponding electrical lengths. In some embodiments, they may be physically associated with and/or attached to a particular one of the plate conductors 202 and 204, in accordance with various embodiments of the invention.

[0046] The antenna structure of the wireless communication device 200 can be tuned by various different methods, either individually or in combination. One method of tuning the antenna structure of the wireless communication device 200 is to move the pieces of dielectric material 802 relative to the area of overlap, such as away from the periphery of the first plate conductor 202 and the second plate conductor 204 so as to be more proximate the center, as noted above. Another method by which the antenna structure of the wireless communication device 200 can be tuned to a more desired frequency includes shifting the feed points 206 to a position more proximate the center of the plate conductors 202 and 204. Yet another method of tuning the antenna structure of the wireless communication device 200 can involve changing the type of dielectric material 802, and consequently the dielectric constant of the material. Yet another method of tuning the antenna structure of the wireless communication device 200 can involve adding impedance matching components at the feed points 206. Yet a still further method of tuning the antenna structure of the wireless communication device 200 can include changing the size or shape (i.e geometry) of the first plate conductor 202 and the second plate conductor 204. [0047] It will be apparent to a person ordinarily skilled in the art that although the various embodiments of the invention have been described using the wireless communication device 200, they are equally applicable to any other communication device, such as the wireless communication devices 300 and 400, without deviating from the scope of the invention.

[0048] Various embodiments of the present invention can be used to provide the following advantages, such as a wireless communication device that incorporates a more substantial metallic housing, where portions of the metallic housing of the wireless communication device can form at least part of an antenna, thereby eliminating the need for at least some separate discrete antenna elements. In turn, this can allow for a wireless communication device that is smaller in size. Alternatively, a wireless communication device of the same size can use the saved space to incorporate additional elements necessary for supporting additional functionality.

[0049] Further, the substrate 500 provides a degree of freedom in the placement of the gap 602, thereby providing flexibility in the design process of the wireless communication device. By shifting the gap 602 towards one of the ends of the phone the efficiency of any radiated signal can be more efficiently managed including allowing for the more precise focus and steering of the radiated energy in the desired direction.

[0050] In another embodiment, the wireless communication device 200 can include more than one gap. In such an embodiment, the wireless communication device 200 could have more than two plate conductors, where a particular pair of the plate conductors is associated with each gap. In this case, each of the pairs of conductive elements may be treated in the manner described above.

[0051] In the foregoing specification, the invention and its benefits and advantages have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.

Claims

1. An antenna operating in one or more frequency bands, the antenna comprising: a first plate conductor having a surface; a second plate conductor, the second plate conductor having a surface in close proximity to and at least partially overlapping the surface of the first plate conductor, wherein the first plate conductor and the second plate conductor interact capacitively; and one or more respective feed points, associated with each of the first and second plate conductors, the one or more feed points being adapted for receiving a differential signal; and wherein the first plate conductor and the second plate conductor each having one or more corresponding edges, which each have an electrical length, the electrical length of at least a respective one of the edges of at least one of the first plate conductor and the second plate conductor being modified by one or more localized complex impedances, the one or more complex impedances being coupled to at least one of the first plate conductor and the second plate conductor proximate the respective edge.

2. The antenna of claim 1, wherein the one or more complex impedances are capacitive impedances.

3. The antenna of claim 1, wherein the respective surfaces of the first plate conductor and the second plate conductor are substantially planar, and substantially parallel with respect to one another.

4. The antenna of claim 1, wherein each of the one or more corresponding edges have an electrical length which interacts to produce a radiated signal having a predefined frequency.

5. The antenna of claim 1, wherein at least one of the first plate conductor and the second plate conductor form at least part of a housing of a wireless communication device.

6. The antenna of claim 1, wherein the first plate conductor forms at least part of a battery assembly of a wireless communication device, and wherein the second plate conductor forms at least part of a printed circuit board of the wireless communication device.

7. A wireless communication device comprising an antenna operating in one or more frequency bands comprising: a first plate conductor having a surface; a second plate conductor having a surface, which is in close proximity to and at least partially overlapping the surface of the first plate conductor, wherein the first plate conductor and the second plate conductor interact capacitively; and one or more respective feed points, associated with each of the first and second plate conductors, the one or more feed points being adapted for receiving a differential signal; and one or more signal generators, the one or more signal generators providing the one or more feed points of the antenna with a differential feed; and wherein at least one of the first plate conductor and the second plate conductor form at least a portion of the external housing of the wireless communication device.

8. The wireless communication device claim 7, wherein the respective surfaces of the first plate conductor and the second plate conductor are substantially planar, and substantially parallel with respect to one another.

9. The wireless communication device of claim 7, wherein the surface of the first plate conductor and the surface of the second plate conductor have one or more corresponding edges, each of the one or more corresponding edges having an electrical length which interact to produce a radiated signal having a predefined frequency.

10. The wireless communication device of claim 7, wherein the first plate conductor and the second plate conductor form at least a portion of the housing of the wireless communication device.

1 1. The wireless communication device of claim 7 further comprising a substrate having one or more conductive paths, wherein the substrate is coupled to at least one of the first plate conductor and the second plate conductor.

12. The wireless communication device of claim 1 1, wherein the substrate is a flexible circuit, where the one or more conductive paths, each have an inductive length and the flexible circuit further has one or more capacitors, which bridge portions of the inductive length, and together with the inductive length of one or more of the conductive paths form one or more filters that are tuned to limit the conveyance of signals having a frequency corresponding to one or more of the frequency bands within which the antenna is intended to operate.

13. The wireless communication device of claim 7 further comprising a second antenna, wherein the second antenna is placed between the first plate conductor and the second plate conductor, the second antenna providing at least one of an additional frequency band or an extension of the bandwidth of an existing frequency band.

14. The wireless communication device of claim 13, wherein the second antenna is a helical antenna.

15. A wireless communication device comprising: an antenna operating in one or more frequency bands comprising: a first plate conductor having a surface; a second plate conductor, the second plate conductor having a surface in close proximity to the surface of the first plate conductor; one or more respective feed points, associated with each of the first and second plate conductors, the one or more feed points being adapted for receiving a differential signal; and a substrate having one or more conductive paths located between the first plate conductor and the second plate conductor, each conductive path having an inductive length and one or more capacitors, which bridge portions of the inductive length, which are tuned to convey signals having one or more corresponding predetermined frequencies between the first plate conductor and the second plate conductor.

16. The wireless communication device of claim 15 further comprising one or more conductors, the one or more conductors being used for connecting one or more points on the first conductive element to one or more points on the second conductive element.

17. The wireless communication device of claim 15, wherein multiple physical configurations of the wireless communication device allow for the surface of the first plate conductor and the surface of the second plate conductor to exist in one of a non- overlapping position, a partially overlapping position and a completely overlapping position.

18. The wireless communication device of claim 15, wherein the first plate conductor and the second plate conductor form at least a portion of the housing of the wireless communication device.

19. The wireless communication device of claim 15, wherein the wireless communication device comprises a two part housing including an upper housing and a lower housing, which are adapted to move relative to one another, and the first plate conductor forms part of the upper housing and the second plate conductor forms part of the lower housing.

20. The wireless communication device of claim 15, wherein the substrate is a flexible circuit.