Abstract:
A design and physical configuration for multi-frequency, low-profile, capacitively loaded antenna with integrated filters to be used in wireless communications. One element having one to n plates, and one antenna having one to n elements. The range of frequencies covered to be determined by the shape, size, and number of elements in the physical configuration of the antenna. Frequencies covered to be filtered by 1 to n in-line or adjunct filters.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application relates to co-pending application Ser. No. 09/892,928, filed on Jun. 26, 2001, entitled “Multi Frequency Antenna Structure and Methods Reusing the Volume of an Antenna” by L. Desclos et al., owned by the assignee of this application and incorporated herein by reference.  
         [0002]    This application relates to co-pending application Ser. No. 10/076922, entitled “Multi Frequency Antenna Structures with a New E-Field Distribution for Very Low-Profile Antenna Applications” by G. Poilasne et al., owned by the assignee of this application and incorporated herein by reference.  
         [0003]    This application relates to co-pending application Ser. No. TBD (Attorney Dkt. No. 272/126), entitled “Low Profile, Multi-Frequency, Multi-Band, capacitively Loaded Magnetic Dipole Antenna” by G. Poilasne et al., owned by the assignee of this application and incorporated herein by reference. 
     
    
     
       BACKGROUND INFORMATION  
         [0004]    1. Field of the Invention  
           [0005]    The present invention relates generally to the field of wireless communications, and particularly to the design of multi-band antennas.  
           [0006]    2. Background  
           [0007]    Certain applications such as the Global System for Mobile Communications (GSM) and Personal Communications Service (PCS) require that multiple bands be accessible, depending upon the local frequency coverage available from a service provider. In order to utilize a specific band for a specific application (i.e., in the context of a multi-band-capable antenna), an adjunct piece of hardware like a duplexer or filter can be used. The subject of the present invention, however, obviates the need for an adjunct duplexer or filter through an integrated filter. These filters can be either in-line or attached directly to the antenna element.  
           [0008]    Because applications such as GSM and PCS are used in the context of wireless communication devices that have relatively small form-factors, a low profile is also a required feature of these antennas.  
           [0009]    The present invention addresses the requirements of certain wireless communications applications by providing a configuration for multi-band, low-profile, capacitively loaded antennas with integrated filters.  
         SUMMARY OF THE INVENTION  
         [0010]    This invention allows for multiple antenna elements in myriad physical configurations to cover one to n number of frequencies or bands of frequencies.  
           [0011]    In all embodiments of the present invention there are antenna elements with both inductive and capacitive parts. Each antenna element, regardless of variations in physical design of the element, provides a single frequency or band of frequencies.  
           [0012]    In one embodiment a single antenna element has one u-shaped top plate and one bottom plate. In all embodiments, each antenna element produces a specific frequency or band of frequencies based on its relative size and shape. Different physical configurations can also be considered to adapt the antenna and its elements to the physical environment specific to a particular application.  
           [0013]    Once the antenna elements have been cut and folded into the desired form for the purpose of matching a frequency or frequency band, they can then be arranged to target multiple bands. In one embodiment, the antenna elements can be placed one next to the other. In another embodiment, the antenna elements can be stacked, one on top of another. In yet another embodiment, the elements can be inserted one inside the other.  
           [0014]    In all embodiments, integrated filters are used to reject unused bands. In one embodiment, the filter is a formed piece of metal that is attached to the underside of one arm of the antenna element. In another embodiment, the filter is cut out of one arm of the antenna element. Whatever the single embodiment of the filter, all of the various embodiments can be combined in a variety of physical configurations to meet the requirements of a given application. Once the multiple antenna elements have been cut, folded, and arranged to both meet the frequency and space requirements of the specific application, one has a multi-band, low-profile, capacitively loaded antenna with integrated filters.  
           [0015]    This summary does not purport to define the invention. The invention is defined by the claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1A is a diagram illustrating an exemplary single element, capacitively loaded antenna;  
         [0017]    [0017]FIG. 1B is a diagram illustrating a side view of the antenna of FIG. 1A;  
         [0018]    [0018]FIG. 1C is a diagram illustrating a top view of the antenna of FIG. 1A;  
         [0019]    [0019]FIG. 2A is a diagram illustrating the top view of an antenna element that includes a filter element in accordance with the invention;  
         [0020]    [0020]FIG. 2B is a diagram illustrating the antenna element of FIG. 2A with two filter elements in accordance with the invention;  
         [0021]    [0021]FIG. 2C is a diagram illustrating the antenna element of FIG. 2A with three filter elements in accordance with the invention;  
         [0022]    [0022]FIG. 2D is a diagram illustrating a close up view of the filter element of FIG. 2A;  
         [0023]    [0023]FIG. 2E is a diagram illustrating an alternative embodiment of the filter element of FIG. 2D;  
         [0024]    [0024]FIG. 2F is a diagram illustrating another alternative embodiment of the filter element of FIG. 2D;  
         [0025]    [0025]FIG. 2G is a diagram illustrating still another alternative embodiment of the filter element of FIG. 2D;  
         [0026]    [0026]FIG. 3 is a plot of the return loss of an exemplary dual-band antenna;  
         [0027]    [0027]FIG. 4 is a plot of the frequency response of the dual-band antenna of FIG. 3;  
         [0028]    [0028]FIG. 5 is a diagram illustrating the effect of a high pass filter on the frequency response of the dual-band antenna of FIG. 3;  
         [0029]    [0029]FIG. 6 is a diagram illustrating the effect of a low pass filter on the frequency response of the dual-band antenna of FIG. 3;  
         [0030]    [0030]FIG. 7 is a plot of the return loss for a tri-band antenna that incorporates filtering in accordance with the invention;  
         [0031]    [0031]FIG. 8A is a diagram illustrating an antenna element comprising an alternative embodiment of a filter element coupled with the antenna element in accordance with the invention;  
         [0032]    [0032]FIG. 8B is a diagram illustrating the antenna element of FIG. 8A coupled with another alternative embodiment of a filter element in accordance with the invention;  
         [0033]    [0033]FIG. 8C is a diagram illustrating the antenna element of FIG. 8A coupled with still another alternative embodiment of a filter element in accordance with the invention;  
         [0034]    [0034]FIG. 9A is a diagram illustrating the filter element of FIG. 8A coupled with two of the filter elements illustrated in FIG. 8A;  
         [0035]    [0035]FIG. 9B is a diagram also illustrating the filter element of FIG. 8A coupled with two of the filter elements illustrated in FIG. 8A arranged in a different location relative to the filter elements of FIG. 9A;  
         [0036]    [0036]FIG. 9C is a diagram illustrating the filter element of FIG. 8A coupled with two of the filter elements illustrated in FIG. 8B;  
         [0037]    [0037]FIG. 9D is a diagram also illustrating the filter element of FIG. 8A coupled with two of the filter elements illustrated in FIG. 8B arranged in a different location relative to the filter elements of FIG. 9C;  
         [0038]    [0038]FIG. 10A is a diagram illustrating an antenna element comprising the filter element of FIG. 2G and coupled with the filter element of FIG. 8A;  
         [0039]    [0039]FIG. 10B is a diagram illustrating an antenna element comprising the filter element of FIG. 2G and coupled with the filter element of FIG. 8B;  
         [0040]    [0040]FIG. 10C is a diagram illustrating an antenna element comprising the filter element of FIG. 2G and coupled with the filter element of FIG. 8C;  
         [0041]    [0041]FIG. 10D is a diagram illustrating an antenna element comprising the filter element of FIG. 2G and coupled with the filter elements of FIGS. 8B and 8C;  
         [0042]    [0042]FIG. 11A is a diagram illustrating an exemplary single element, multi-band, capacitively loaded antenna;  
         [0043]    [0043]FIG. 11B is a diagram illustrating another exemplary single element, multi-band, capacitively loaded antenna; and  
         [0044]    [0044]FIG. 11C is a diagram illustrating still another exemplary single element, multi-band, capacitively loaded antenna.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0045]    In the following description, for purposes of explanation and not limitation, specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known methods and devices are omitted so as to not obscure the description of the present invention with unnecessary detail.  
         [0046]    In general, an antenna is developed to produce a specific frequency, band of frequencies, or combination of frequencies or bands of frequencies for a targeted application like Global System for Mobile Communications (GSM) or Personal Communications Service (PCS). The target, or resonant, frequency is a result of the inductance and capacitance of the antenna. A capacitively loaded antenna presents various advantages, chief among them excellent isolation. Different versions of capacitively loaded dipole antennas are considered herein, and each can possess different degrees of isolation as well as different bandwidths.  
         [0047]    [0047]FIG. 1A illustrates a three dimensional view of one embodiment of a single-element, capacitively loaded antenna  10  in accordance with the systems and methods described herein. In this configuration there is a top plate  11 , a grounding plate  12 , and a grounding point  13  electrically connecting top plate  11  with ground plate  12 . Top plate  11  also comprises a cutout “u” shape between the two arms of the top plate. This cutout comprises part of the capacitive part  14  of antenna  10 .  
         [0048]    [0048]FIG. 1B illustrates a side-view of one embodiment of single-element, capacitively loaded antenna  10 , in accordance with the systems and methods described herein. Again, top plate  11 , grounding point  13 , and ground plane  12  are illustrated, but this time from the side. The space between the top plate and grounding plane comprise an inductive part  15  of antenna  10 .  
         [0049]    [0049]FIG. 1C illustrates a top-view of one embodiment of single-element, capacitively loaded antenna  10 , in accordance with the systems and methods described herein. As can be seen, top plate  11  comprises two arms, or plates  16  and  18 , respectively. Top plate  11  also comprises a connecting section  9  that connects plates  16  and  18 .  
         [0050]    The characteristics and operation of antenna  10  are fully disclosed in Co-pending U.S. patent application Ser. No. TBD (Attorney Dkt. no. 272/126), which as mentioned above is fully incorporated herein by reference in its entirety. Specifically, FIGS.  6 A- 6 C and the accompanying description detail the various characteristics and operation of a single element, capacitively loaded antenna, such as antenna  10 . These figures and the accompanying description are specifically incorporated herein by reference as though set forth in full.  
         [0051]    Antenna  10  can be used as one element of a multi-element antenna configured to operate in a plurality of frequency bands. Essentially, Once the elements comprising antenna  10  have been cut and folded into the desired form for the purpose of matching a frequency or frequency band, it can be combined with other single element antennas and arranged to target multiple bands. For example, a plurality of single element antennas, such as antenna  10 , can be placed one next to the other, stacked one on top of another, and/or inserted one inside the other. FIGS.  7 A- 7 B,  8 A- 8 D, and  9 A- 9 C of Co-pending U.S. patent application Ser. No. TBD (Attorney Dkt. no. 272/126) and the accompanying descriptions detail various configurations and arrangements for constructing a multi-band antenna comprising a plurality of single element antennas, such as antenna  10 . These figures and the accompanying descriptions are specifically incorporated herein by reference as though set forth in full. As illustrated in FIG. 3B of Co-pending U.S. patent application Ser. No. TBD (Attorney Dkt. no. 272/126), the frequency coverage for the resulting multi-band antenna is then the combined frequency coverage for each of the single element antennas  10  combined to form the multi-band antenna. Thus, for example, a dual-band antenna configured to cover the 800 MHz band and the 1900 MHz band can be formed by combining a single element antenna  10  with coverage in the 800 MHz range with a single element antenna  10  with coverage in the 1900 MHz range.  
         [0052]    In FIG. 3 of the present application, however, we see that simply combining single element antennas can result in unsatisfactory performance if some type of filtering is not also included. FIG. 3 illustrates a return loss plot of a dual band antenna prior to incorporating filtering. As can be seen, one antenna element  10  comprising the dual-band antenna has a response at frequency band  1  (band  1 ) as illustrated by return loss trace  31 . The other antenna element  10  has a response at frequency band  2  (band  2 ) as illustrated by return loss trace  32 . But there are also smaller responses  33  and  34  on the return loss trace due to energy in one band being coupled to the other band. This unwanted coupled energy is due to poor isolation between the two antenna elements  10  that comprise the dual-band antenna. In other words, when one of the elements is excited and therefore begins to resonate at its operating frequency, energy from the excited element is coupled to the other antenna element. This coupling from one element to the other results in the smaller responses  33  and  34 , which degrade the performance of the dual-band antenna. With proper isolation, the responses  33  and  34  are suppressed, because little or no energy is coupled from one antenna element to the other.  
         [0053]    [0053]FIG. 4 illustrates a plot  37  of the frequency response of a dual-band antenna that results when one of the antenna elements that comprise the dual-band antenna is excited with a signal. As can be seen, the response actually comprises two responses  35  and  36 , one for each band of coverage. Plot  37  illustrates that the rejection between the two frequency bands is poor. The rejection is dependent upon many factors, including: the specific geometry of the antenna; the separation in frequency between the two excited bands, e.g., band  1  and band  2 ; and the frequency characteristics of the feed lines feeding the respective antenna elements in terms of their inherent filtering characteristics. The isolation and rejection of the dual-band antenna can, however, be improved with the use of filtering as described herein.  
         [0054]    To improve the isolation and filtering of a multi-band antenna, a high or low pass filter can, for example be included in one or more feed lines powering the various elements comprising the multi-band antenna. Alternatively, the filters can be integrated with the antenna elements. FIG. 2A illustrates a top-view of one embodiment of a single antenna element  17  that comprises one element of a multielement, multi-frequency, capacitively loaded antenna, in accordance with the systems and methods described herein. As with antenna  10  in FIG. 1, antenna element  17  also comprises a top plate  11 , a ground plate, and a grounding contact; however, for ease of illustration, the ground plate and grounding contact are omitted from FIGS.  2 A- 2 C  
         [0055]    Top plate  11  of antenna element  17  is configured in a “U” shape, as with antenna  10 , comprising two plates  28  and  29  formed such that they are adjacent to and substantially parallel to each other, although it is possible for the two plates  28  and  29  to be oriented in some other manner. A filter element  20  has been added to plate  28  in order to improve the isolation of antenna element  17  relative to at least one other element comprising the multi-element, multi-frequency, capacitively loaded antenna. In this particular embodiment, filter element  20  comprises a cutout  19  that runs the width of plate  28  and that divides plate  28  into two parts. The first part is a cutout plate  21 , and the second part is the part formed form the rest of top plate  11 , which can be termed the base plate. It will be understood that so configured, cutout plate  21  becomes a parasitic element of antenna element  17 . Cutout plate  21  is powered through electro-magnetic coupling, indicated by line  27 , with the base plate.  
         [0056]    The position and width of cutout  19  can then be tailored to provide the desired filtering characteristics to filter element  20 . Essentially, the desired filtering characteristics are those that will allow proper performance of antenna element  17 , while improving the isolation and/or rejection, for example, with respect to other antenna elements. Once the geometry of a filter element  20  is defined, the filter element can be replicated in order to add a plurality of filter elements  20  to antenna element  17 . Additional filter elements  20  may be added, for example, to further improve the isolation and/or rejection of antenna element  17 .  
         [0057]    Accordingly, FIG. 2B illustrates a top-view of antenna element  17  that comprises two filter elements  20  that divide plate  28  into two cutout plates  22  and  23 , each driven by electro-magnetic coupling  27 . FIG. 2C illustrates a top-view of antenna element  17  that comprises three filter elements  20  that divide plate  28  into three cutout plates  24 ,  25 , and  26 , each driven by electro-magnetic coupling  27 . More filter elements  20  can be added as required, and each can be driven by electro magnetic coupling  27 . Thus, the electromagnetic coupling can actually be configured to drive form 1 to n cutout plates as required by a particular invention.  
         [0058]    Again, once the geometry for a particular filter element  20  is defined, it can be replicated as required to add a plurality of such elements to an antenna element  17 . Further, different geometries can be defined to provide different filtering characteristics. For example, FIG. 2D illustrates a close up view of the embodiment of a filter element  20  illustrated in FIG. 2A. FIG. 2E, on the other hand, illustrates an alternative embodiment of filter element  20  comprising a different geometry. As with the embodiment of FIG. 2D, the filter element  20  illustrated in FIG. 2E also comprise a cutout  19  that forms a cutout plate  21  and a base plate  11 . Again, electro-magnetic coupling  27  powers cutout plate  21 . This creates an example of more complex filter including an inductance and capacitance.  
         [0059]    [0059]FIG. 2F illustrates another alternative embodiment of a filter element  20 . Again, the filter element  20  of FIG. 2F comprises a cutout  19  that divides plate  28  into a cutout plate  21  and a base plate  11 , with cutout plate  21  being powered by electro-magnetic coupling  27 . This creates an example of more complex filter including an inductance and capacitance.  
         [0060]    [0060]FIG. 2G illustrates still another embodiment of filter element  20 . In this embodiment, filter element  20  comprises a plurality of cutouts  19   a - 19   d . But cutouts  19   a - 19   d  do not separate plate  28  into two different plates as with previous embodiments. The filter that results from filter element  20  in FIG. 2G is a second order filter. Thus, the geometries of cutouts  19   a - 19   d  can be configured to result in poles in the filter&#39;s transfer function at the desired frequencies.  
         [0061]    As mentioned, the filters can be high or low pass filters depending on the embodiments and what frequencies need to be rejected. Thus, for example, returning to the frequency response of  37  of a dual-band filter designed in accordance with the systems and methods described herein, one antenna element can include a high pass filter to filter out the lower frequency band (band  1 ), while the other antenna element includes a low pass filter to filter out the higher frequency band (band  2 ). FIG. 5 illustrates the pass and reject bands of a high-pass filter and the effect the filter has on the two frequency responses of a dual-band antenna. The shaded region  51  indicates the portion of the response that is suppressed by the filtering. Accordingly, a filter element  20  can be configured such that it provides the transfer function  53  illustrated in FIG. 5.  
         [0062]    As mentioned, the filtering can be in the feed line or included in antenna element  17  as described in FIG. 2A- 2 G. In either event, however, filter elements  20  can be added to the antenna element to increase the rejection of the filter. Adding filter elements  20  increases the slope  52  of the transfer function  53 , which allows greater rejection of band  1  signals.  
         [0063]    [0063]FIG. 6, on the other hand, illustrates the pass and reject band of a low pass filter, which can be incorporated into the feed line or in the antenna element  17 . Like the high-pass filter, additional filtering sections  20  can be added to increase the isolation between the two frequency responses, by increasing the slope  52  of transfer function  53 . The shaded region  51  indicates the part of the frequency response that is suppressed by the filtering.  
         [0064]    [0064]FIG. 7 illustrates the return loss plot of a tri-band antenna comprising three antenna elements  17  and filtering in accordance with the present invention. The filtering can be included in one or more feed lines and/or in the three antenna elements  17  as described above. The three separate return loss plots  71 ,  72 , and  73  show no additional responses, which is an indication of adequate filtering.  
         [0065]    Other types of filtering elements can be used in accordance with the systems and methods described herein, besides those illustrated, for example, in FIGS.  2 A- 2 G. FIG. 8A illustrates one embodiment of an antenna element  17  that forms a part of a multi-element, multi-frequency, capacitively loaded antenna, in accordance with the present invention. Again, only top plate  11  of antenna element  17  is shown for simplicity. Antenna element  17  also includes a filter element  81  that serves to reject unsupported frequencies. As shown in the blown up view of FIG. 8A, filter element  81  comprises a bottom plate  84  that is electro-magnetically connected with plate  16  of top plate  11 . Filter element  81  also comprises a plate  85  that extends down from plate  16  in a substantially perpendicular orientation to plate  16 . Other orientations for plate  85  relative to plate  16  are of course possible.  
         [0066]    Preferably, plate  85  is a capacitive plate, i.e., plate  85  preferably forms a capacitance such that filter element  81  is a capacitive filter element with the desired filtering characteristics. In one embodiment, therefore, plate  85  can, like top plate  11 , comprise a cutout section  86  so that plate  85  comprises a “u” shape. So formed, plate  85  can generate a capacitive part of filter element  81  in the same manner that top plate  11  forms a capacitive part  14  of antenna  10  as illustrated in FIG. 1C.  
         [0067]    Other, more complex, filter elements can be generated from the relatively simple capacitive filter element  81 . For example, an Inductive-Capacitive (LC)-filter  82  is illustrated in FIG. 8B. Like filter element  81 , filter element  82  can comprise a bottom plate  84  and a capacitive plate  85 . In addition, filter element  82  can also include a second plate  87 . This second plate  87  can be configured to form an inductive part of filter element  82  in much the same way that ground plate  12  can be configured to form an inductive part  15  of antenna  10  in FIG. 1B.  
         [0068]    [0068]FIG. 8C illustrates another possible filter element  83  configured, as with filter elements  81  and  82  to reject unsupported frequencies. In filter element  83 , bottom plate  84  has been cut so as to form a second order filter with capacitive plate  85 .  
         [0069]    Once the basic filter elements are designed, they can be added as needed to antenna element  17 . For example, two filter elements  81  can be used if required by a particular implementation as indicated in FIG. 9A. As indicated in FIG. 9B, the location of the various filter elements can also be selected based on a particular application&#39;s requirements. Thus, one filter element  81  can be added to one arm of filter element  17 , while another is added to the connecting section between the two arms. Similar configurations can be implemented using filter elements  82  as indicated in figured  9 C and  9 D.  
         [0070]    In general, it should be remembered that once a filter element is defined, whether it is a cutout filter element  20  or one that is coupled with antenna element  17 , such as filter elements  81 - 83 , the filter element can be combined with other similar filter elements or with other types of filter elements to provide the required filtering. Thus, in FIG. 10A for example, a cutout filter element  101  is combined with a filter element  81 . In FIG. 10B cutout filter  101  is combined with a filter element  82 . In FIG. 10C filter element  101  is combined with a filter element  83 . In FIG. 10D, three filter elements  101 ,  82 , and  83  are combined. But only a small number of the possible combinations of filter elements are illustrated by the embodiments of FIGS.  10 A- 10 D. Therefore, the embodiments of FIG. 10A- 10 D should not be viewed as limiting the possible combinations of filter elements. Rather, it should be apparent that any number of filter elements, of any type, can be combined as required by a particular implementation.  
         [0071]    It should also be remembered, that the individual antenna elements disclosed herein can be combined to form multi-element, multi-band antennas, such as those disclosed in FIGS.  7 A- 7 B,  8 A- 8 D, and  9 A- 9 C of Co-pending U.S. patent application Ser. No. TBD (Attorney Dkt. no. 272/126). Thus, one or more filter elements can be added to the antenna elements of the various multi-element, multi-band antennas disclosed in FIGS.  7 A- 7 B,  8 A- 8 D, and  9 A- 9 C as required by a particular application and as described above.  
         [0072]    Further, several embodiment of a single element, multi-band antennas are disclosed in FIGS.  11 B- 11 C and the accompanying description of Co-pending U.S. patent application Ser. No. TBD (Attorney Dkt. no. 272/126). These figures and the accompanying descriptions are specifically incorporated herein by reference as if set forth in full. In these embodiments, a single top plate is configured to form multiple antenna elements, each with their own frequency range or band of operation. These single elements, multi-band antennas can also be combined with other antenna elements, such as those disclosed in Co-pending U.S. patent application Ser. No. TBD (Attorney Dkt. no. 272/126). For example, FIGS. 14A and 14B of Co-pending U.S. patent application Ser. No. TBD (Attorney Dkt. no. 272/126) and the accompanying description, incorporated herein by reference in the entirety, illustrate how antenna elements can be stacked with the antenna elements of FIGS.  11 B- 11 C. It will be apparent, however, that filter elements, such as those described above, can also be added to such single element, multi-band antennas, whether alone or combined with other antenna elements, in accordance with the methods disclosed herein.  
         [0073]    [0073]FIG. 11A is a diagram of one possible embodiment of such a single element, multi-band antenna  100 . Antenna  100  comprises a top plate  170  that has been cut so that it comprises cutouts  110  and  112 . The cutouts form three arms  114 ,  116 , and  118 , which form two antenna elements. Arms  114  and  116  form the capacitive part  102  of the first element, while arms  116  and  118  form the capacitive part  104  of the second element. The inductive parts of the two elements,  106  and  108  respectively, are formed between ground plate  120  and top plate  170  in the same manner as described in relation to antenna  10 . Antenna  100  also comprises a ground contact (not shown) between top plate  170  and ground plate  120 . Filter elements, such as those described above, can then be added as required, and in accordance with the methods described herein, to antenna  100 .  
         [0074]    [0074]FIG. 11B illustrates another exemplary single element, multi-band antenna  124 . Cutouts  128  and  146  form three arms  136 ,  138 , and  140 , which form two antenna elements. Arms  136  and  138  form the capacitive part  128  of the first element, and arms  138  and  140  from the capacitive part  132  of the other. Antenna  124  also comprise a ground plate and ground contact that are not shown in FIG. 11B for simplicity. But the ground plate, in conjunction with the top plate  172 , forms the inductive parts,  134  and  130 , of the two antenna elements respectively. Again, filter elements, such as those described above, can be added as required, and in accordance with the methods described herein, to antenna  124 .  
         [0075]    [0075]FIG. 11C illustrates another exemplary single element, multi-band antenna  148 . Cutouts  158  and  160  form three arms  162 ,  164 , and  166 , which form two antenna elements. Arms  162  and  164  form the capacitive part  150  of the first element, and arms  164  and  166  from the capacitive part  154  of the other. Antenna  148  also comprise a ground plate and ground contact that are not shown in FIG. 11C for simplicity. But the ground plate, in conjunction with the top plate  174 , forms the inductive parts,  156  and  152 , of the two antenna elements respectively. Again, filter elements, such as those described above, can be added as required, and in accordance with the methods described herein, to antenna  148 .  
         [0076]    While embodiments and implementations of the invention have been shown and described, it should be apparent that many more embodiments and implementations are within the scope of the invention. Accordingly, the invention is not to be restricted, except in light of the claims and their equivalents. We claim: