Patent Publication Number: US-7710325-B2

Title: Multi-band dielectric resonator antenna

Description:
BACKGROUND 
   Many wireless devices, systems, platforms, and components exist and are being developed that are capable of operation within multiple frequency bands. For example, devices such as cellular telephones, personal digital assistants (PDAs), portable computers, and others may include cellular telephone functionality that is operative within one frequency band, wireless networking functionality that is operative within another frequency band, and Global Positioning System (GPS) functionality that is operative within yet another frequency band, all within a single device. Typically, a different antenna would be used for each function. However, the use of multiple separate antennas within a device can require a relatively large amount of space, especially with respect to smaller form factor wireless devices. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1   a ,  1   b , and  2  illustrate embodiments of an arrangement of dielectric resonator antennas in a multi-band dielectric resonator antenna. 
       FIGS. 3-15  and  17  illustrate embodiments of feeding structures utilizing feeding structures to couple to the dielectric resonator antennas shown in  FIGS. 1 and 2 . 
       FIG. 16  illustrates an embodiment of a communication device having a multi-band dielectric resonator antenna. 
   

   DETAILED DESCRIPTION 
   In the following description, reference is made to the accompanying drawings which form a part hereof and which illustrate several embodiments. It is understood that other embodiments may be utilized and structural and operational changes may be made without departing from the scope of the embodiments. 
     FIGS. 1   a  and  2  are top views illustrating arrangements of multi-band dielectric resonator antennas  2  and  12 , respectively.  FIG. 1   a  shows an arrangement of a multi-band antenna  2  having three dielectric resonator antennas  4 ,  6 , and  8 , where the antennas  4 ,  6 , and  8  have a circular shape.  FIG. 1   b  illustrates a lateral cross-sectional view of the dielectric antenna of  FIG. 1   a , where the antennas  4 ,  6 , and  8  are positioned on a substrate  10 . 
     FIG. 2  shows a top view of an alternative embodiment of a multi-band dielectric antenna  12  with three dielectric resonator antennas  14 ,  16 , and  18  having a square or rectangular shape. Each of the dielectric resonator antennas  6 ,  8  and  16 ,  18  and the inner-most elements  4  and  14  have different resonating frequencies. For instance, the outer antennas, e.g., rings,  8  and  18  correspond to the central frequency of the lowest operating frequency band, the internal antennas  4  and  14  have the highest frequency band, and the middle ring antennas  6  and  16  operate at a middle frequency band. The radiation antennas are sequentially and concentrically placed inside the other ring antenna(s) with larger physical size(s) and the dielectric antennas  4  and  14  arranged in the center area. With the described embodiments, the radiation volume of the dielectric resonator antenna is reusable at all frequency bands to minimize the space required for the three separate dielectric resonator antennas. 
   Because the resonating frequency of dielectric radiation antennas are directly related to their electrical properties and physical dimensions, size compactness can be achieved by using dielectric materials with high permittivity (typical ∈ r  in the range from 30 to 100). Furthermore, flexibility in dimensions may be achieved by forming the radiation antennas  4 ,  6 ,  8  and  14 ,  16 ,  18  to be plate-shaped, i.e., having a large area in the x-y dimension but thin in the z dimension). Alternatively, the elements  4 ,  6 ,  8  and  14 ,  16 ,  18  may be rod-shaped, i.e., having a small area in the x-y dimensions but long in the z dimension. Further, because each of the radiation elements  4 ,  6 ,  8  and  14 ,  16 ,  18  operate at different resonating frequency bands, the electromagnetic coupling among the radiation elements is minimal. Other shapes of the dielectric resonator antennas are also possible, such as octagonal and elliptical. However, in certain embodiments, the different dielectric resonator antennas in one multi-band dielectric resonator antenna may all have the same general shape, e.g., circular, square, rectangular, polygonal, elliptical, etc. Further, there may be two dielectric resonator antennas or more than three dielectric resonator antennas in the structure. 
   In the described embodiments each dielectric radiation antenna/element  4 ,  6 ,  8  and  14 ,  16 ,  18  services a different frequency band. The frequency bands that may be targeted by one or more of the dielectric resonator antennas  4 ,  6 ,  8  and  14 ,  16 ,  8  may operate at frequency bands used for cellular wireless communication, such as Global System For Mobile Communications (GSM), General Packet Radio Service (GPRS), Advanced Mobile Phone System (AMPS), Code Division Multiple Access (CDMA), wideband CDMA (WCDMA), CDMA 2000, etc. Similarly, one or more of the antennas  4 ,  6 ,  8  and  14 ,  16 ,  18  may operate at frequency bands used for wireless network communication, such as IEEE 802.11x, Bluetooth, HIPERLAN 1, 2, Ultrawideband, HomeRF, WiMAX, etc. Different bands associated with the radiation elements  4 ,  6 ,  8  in one multi-band antenna  2  may be used to service cellular and wireless communication frequency bands. One or more of the antennas  4 ,  6 ,  8 , and  14 ,  16 ,  18  may operate at frequency bands used for other wireless applications, such as GPS, and mobile television. 
   Different feeding schemes may be used for the dielectric resonator antennas  4 ,  6 ,  8  and  14 ,  16 ,  18  to couple the signal to a transceiver.  FIGS. 3-8  illustrate different feeding structures that may be used to couple to the antenna  4 ,  6 ,  8  and  14 ,  16 ,  18  signal. 
     FIG. 3  illustrates a top cross-sectional view of a feeding structure embodiment. A dielectric resonator antenna  20 , e.g.,  4 ,  6 ,  8  and  14 ,  16 ,  18 , is coupled to a probe  22  feeding structure. There is a separate probe  22  for each antenna  4 ,  6 ,  8  and  14 ,  16 ,  18  in a multi-band antenna  2 ,  12 . 
     FIG. 4  illustrates a top cross-sectional view of a feeding structure embodiment. A substrate  30  has a dielectric resonator antenna  32 , e.g.,  4 ,  6 ,  8  and  14 ,  16 ,  18 , coupled to a feeding line  34  feeding structure. In the embodiment of  FIG. 4 , the dielectric resonator antenna  32  is coupled directly to the feeding line  34  or feeding structure. In one embodiment, each of the antennas, e.g., e.g.,  4 ,  6 ,  8  and  14 ,  16 ,  18 , in one multi-band antenna  2  and  12  may have their own separate feeding line or each of the antennas, e.g.,  4 ,  6 ,  8  and  14 ,  16 ,  18 , in one multi-band antenna  2  and  12 , may be coupled to directly (or indirectly through a coupling slot) to a same shared feeding line. 
     FIG. 5  illustrates a top cross-sectional view of a feeding structure embodiment. A substrate  40  is placed beneath a dielectric resonator antenna  42 , e.g.,  4 ,  6 ,  8  and  14 ,  16 ,  18 , coupled to a feeding structure comprising a coupling slot  44  coupled to a feeding line  46 . The dielectric resonator antenna  42  is placed on the top of the ground plane of the substrate  40 . The coupling slot  44 , etched on the ground plane of the substrate  40 , couples the electromagnetic signal between the feeding line and the dielectric resonator antenna  42 . In one embodiment, each of the antennas  4 ,  6 ,  8  and  14 ,  16 ,  18  in one multi-band antenna  2  and  12  may have their own coupling slot  44  and feeding line  46 . Alternatively, each of the antennas  4 ,  6 ,  8  and  14 ,  16 ,  18  may have their own coupling slot coupled to a shared feeding line. The feeding line  46  may comprise a coplanar waveguide signal line or a microstrip signal line. 
     FIG. 6  illustrates a top cross-sectional view of a feeding structure embodiment. A substrate  50  of a multi-band antenna is placed beneath the dielectric resonator antennas  52 ,  54 , and  56 , each coupled to a dedicated coupling slot  58 ,  60 , and  62 , respectively. The dielectric resonator antennas  52 ,  54 ,  56  are placed on the top of the ground plane of the substrate  50 , and the coupling slots  58 ,  60 ,  62  are etched on the ground plane of the substrate  50 . The coupling slots  58 ,  60 , and  62  are coupled to a shared feeding line  64 . Thus the different signals for the different antennas  52 ,  54 , and  56  are transmitted through a common feeding line  64  via separate coupling slots  58 ,  60 , and  62 . 
   In a further embodiment, each of the antennas  52 ,  54 , and  56  may be associated with a separate feeding line tuning stub  66 ,  68 , and  70 , respectively, coupled to the feeding line  64  to perfect the impedance match if the impedance in the signal from the antenna  52 ,  54 , and  56  does not match the impedance in the feeding line  64 . 
     FIG. 7  illustrates an equivalent electric circuit diagram of an embodiment of a tri-band antenna  80 , where each of the three dielectric resonator antennas  82 ,  84 , and  86  are coupled to a corresponding separate feeding line  88 ,  90 , and  92 , respectively, via a feeding coupling  94 ,  96 , and  98 , respectively. 
     FIG. 8  illustrates an equivalent electric circuit diagram of the embodiment of  FIG. 6  of a tri-band antenna  110 , where each of the three dielectric resonator antennas  112 ,  114 , and  116  are coupled to a shared feeding line  118  via feeding couplings  120 ,  122 , and  124 , respectively. 
   In the embodiments of  FIGS. 3-8 , each feeding line may pass through a separate port to transfer the signal to a coupled communication transceiver. 
     FIG. 9  illustrates a top cross-sectional view of a feeding structure embodiment for a dual-polarization embodiment. Feeding structures comprising ports  150  and  152  are coupled to a dielectric resonator antenna  154 , e.g.,  4 ,  6 ,  8  and  14 ,  16 ,  18 . Feeding port  150  transmits that portion of the signal having horizontal polarization and feeding port  152  transmits that portion of the signal having vertical polarization. Probes may extend through the ports  150  and  152  to couple to the dielectric resonator antenna  154  to transmit the signal. There would be a separate pair of ports  150 ,  152  or other feed structures, such as a probe or strip, for each antenna, e.g.,  4 ,  6 ,  8  and  14 ,  16 ,  18 , in the multi-band antenna  2 ,  12 . 
     FIG. 10  illustrates a top cross-sectional view of an additional dual-polarization feeding structure embodiment. Feeding structures comprising coupling slots  170  and  172  are coupled to feeding lines  174  and  176 , which are coupled to a dielectric resonator antenna  178 , e.g.,  4 ,  6 ,  8  and  14 ,  16 ,  18 . Feeding slot  170  transmits that portion of the signal having horizontal polarization and coupling slot  172  transmits that portion of the signal having vertical polarization. 
     FIG. 11  illustrates a top cross-sectional view of a feeding structure to improve polarization purity. The feeding structure comprises two feeding paths  190  and  192  extending from feeding port  196 . The ends of the feeding paths  190  and  192  are coupled to a dielectric resonator antenna  198 , e.g.,  4 ,  6 ,  8  and  14 ,  16 ,  18 , and separated by a gap. The feeding paths  190  and  192  have a phase difference, such as 180 degrees. In the embodiment of  FIG. 11 , the signal from the antenna  196  is unbalanced. A balun (not shown) may be used to convert an unbalanced signal from the antenna  198  to a balanced signal for transmission through the feeding paths  190  and  192 . 
     FIG. 12  illustrates a top cross-sectional view of a feeding structure to improve polarization purity. The feeding structure comprises two feeding paths  220  and  222  extending from feeding ports  224  and  226 , respectively. The ends of the feeding paths  220  and  222  are coupled to a dielectric resonator antenna  228 , e.g.,  4 ,  6 ,  8  and  14 ,  16 ,  18 , and separated by a gap. The feeding paths  190  and  192  have a phase difference, such as 180 degrees. In the embodiment of  FIG. 12 , the signal from the antenna  228  is balanced. 
   In certain embodiments, different antennas, e.g.,  4 ,  6 , and  8 , in a multi-band antenna  2  may use the feeding structure embodiments of  FIGS. 11 and 12 , depending on whether the signal is unbalanced ( FIG. 11 ) or balanced ( FIG. 12 ). 
   In  FIGS. 9 ,  10 ,  11  and  12 , if the two feeding points have 90 degree phase difference, circular polarization may be implemented for GPS and mobile TV applications. 
     FIGS. 13 ,  14 , and  15  illustrate top cross-sectional views of feeding structure embodiments using dummy structures to improve the field distribution symmetry of the antenna signal and polarization purity. 
     FIG. 13  illustrates a feeding structure comprising a coupling slot  250  coupled to a feeding line  252 , where the coupling slot  250  is coupled to a dielectric resonator antenna  254 , e.g.,  4 ,  6 ,  8  and  14 ,  16 , and  18 . A dummy structure comprising slot  256  has the same feeding structure as coupling slot  250  and is not coupled to any feeding signal.  FIG. 17  illustrates the coupling slot and dummy structures of  FIG. 13  as implemented in multiple dielectric resonator antennas of  FIG. 6 . With respect to  FIG. 17 , a substrate  450  of a multi-band antenna is placed beneath the dielectric resonator antennas  452 ,  454 , and  456 , each coupled to a dedicated coupling slot  458 ,  460 , and  462 , respectively. The dielectric resonator antennas  452 ,  454 ,  456  are placed on the top of the ground plane of the substrate  450 , and the coupling slots  458 ,  460 ,  462  are etched on the ground plane of the substrate  450 . The coupling slots  458 ,  460 , and  462  are coupled to a shared feeding line  464 . Antennas  454  and  456  include dummy structures  461  and  459 , respectively, such as the slots and dummy structures shown in  FIG. 13 . 
     FIG. 14  illustrates feeding structure comprising a feeding probe  270  coupled to a dielectric resonator antenna  272 , e.g.,  4 ,  6 ,  8  and  14 ,  16 , and  18  to transmit and receive the signal. A dummy structure, i.e., dummy probe  274 , has the same feeding structure as probe  270  and is not coupled to any feeding signal. 
     FIG. 15  illustrates a feeding structure comprising a feeding line  290  coupled to a dielectric resonator antenna  292 , e.g.,  4 ,  6 ,  8  and  14 ,  16 , and  18 , to transmit and receive the signal. A dummy structure comprising dummy line  294  has the same feeding structure as feeding line  290  and is not coupled to any feeding line. 
   Each dummy structure may be positioned parallel to a corresponding driven feeding structure and in a similar location with respect to an opposite side of the antenna being driven. 
   In a further embodiment, the polarization feeding structures of  FIGS. 11-15  may be used in a dual polarization feeding structure, such that one feeding structure having a coupled feeding structure and dummy structure in the embodiments of  FIGS. 11-15 , are used for the horizontal polarization feeding structure and another of the same feeding structure would be used for the vertical polarization feeding structure. 
   Further, as discussed above, different antennas, e.g.,  4 ,  6 , and  8  in the multi-band antenna  2  may use different feeding structures in  FIGS. 3-15  and different feeding structure arrangements, where the feeding structures may utilize feeding structure technologies, such as direct feeding with microstrip line structures, slot feeding with microstrip line, slot coupling with coplanar waveguide transmission line, etc. Some or all of the dielectric resonator antennas may be feed by a separate port. Alternatively, some or all of the dielectric resonator antennas may share the same feeding port by being coupled to a shared feeding line. 
     FIG. 16  illustrates an embodiment of a communication device  300  having a transceiver  302  for receiving and transmitting the signals in the different frequency bands through a multi-band dielectric resonator antenna  304 , such as multi-band dielectric resonator antennas  2  and  12 . The communication device  300  may comprise a laptop, palmtop, or tablet computer having wireless capability, a personal digital assistant (PDA) having wireless capability, a cellular telephone, pagers, satellite communicators, cameras having wireless capability, audio/video devices having wireless capability, network interface cards (NICs) and other network interface structures, integrated circuits, and/or in other formats. 
   The transceiver  302  has the capability to handle signals transmitted and received in the different frequency bands provided by the antennas within the multi-band dielectric resonator antenna  304 . The transceiver  302  may comprise multiple transceiver structures, such as a global positioning system (GPS) receiver, a cellular transceiver, a mobile TV receiver, a WiMAX transceiver, and a wireless network transceiver that are all operable within different frequency bands. The cellular transceiver may be configured in accordance with one or more cellular wireless standards (e.g., Global System For Mobile Communications (GSM), General Packet Radio Service (GPRS), Advanced Mobile Phone System (AMPS), Code Division Multiple Access (CDMA), wideband CDMA (WCDMA), CDMA 2000, and/or others). Similarly, the wireless network transceiver may be configured in accordance with one or more wireless networking standards (e.g., IEEE 802.11x, Bluetooth, HIPERLAN 1, 2, Ultra Wideband, HomeRF, WiMAX, and/or others). 
   The GPS receiver structure of the transceiver  302  may not be capable of transmitting signals and only receive signals from the multi-band dielectric resonator antenna  304 . The cellular transceiver and the wireless network transceiver structures of the transceiver  302  receive signals from and deliver signals to the multi-band dielectric resonator antenna  304 . The transceiver  302 , e.g., GPS receiver, mobile TV receiver, cellular transceiver, and wireless network transceiver may each include functionality for processing both vertical polarization signals and horizontal polarization signals. For example, the transceiver  302  may include a combiner to combine vertical polarization receive signals and horizontal polarization receive signals during receive operations. The transceiver  302  may also include a divider to appropriately divide transmit signals into vertical and horizontal structures during transmit operations. The combiner and/or divider could alternatively be implemented within the antenna itself (or as a separate structure). The transceiver  302 , such as in the GPS receiver structure, may include functionality for supporting the reception of circularly polarized signals from the multi-band dielectric resonator antenna  304 . 
   It should appreciated that other types of receivers, transmitters, and/or transceivers may alternatively be coupled to the multi-band dielectric resonator antenna  304 . In one embodiment, the multi-band dielectric resonator antenna  304  may be implemented on the same chip or integrated circuit substrate as the transceiver  302 . 
   The foregoing description of various embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Many modifications and variations are possible in light of the above teaching.