Abstract:
In some embodiments, a multiband antenna array using electromagnetic bandgap structures is presented. In this regard, an antenna array is introduced having two or more planar antennas situated substantially on a surface of a substrate, a first set of electromagnetic bandgap (EBG) cells situated substantially between and on plane with the antennas, and a second set of EBG cells situated within the substrate below the antennas. Other embodiments are also disclosed and claimed.

Description:
FIELD OF THE INVENTION 
   Embodiments of the present invention generally relate to the field of antennas, and, more particularly to multiband antenna array using electromagnetic bandgap structures. 
   BACKGROUND OF THE INVENTION 
   Today&#39;s wireless communication devices, such as laptop computers, require at least two antennas to transmit and receive external signals. As the number of required antennas increases it will be necessary to isolate the antennas from one another. At the same time the size of wireless devices will likely be expected to decrease. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements, and in which: 
       FIG. 1  is a graphical illustration of an overhead view of a multiband antenna array using electromagnetic bandgap structures, in accordance with one example embodiment of the invention; 
       FIG. 2  is a graphical illustration of a cross-sectional view of a multiband antenna array using electromagnetic bandgap structures, in accordance with one example embodiment of the invention; 
       FIG. 3  is a graphical illustration of a cross-sectional view of a multiband antenna array using electromagnetic bandgap structures, in accordance with one example embodiment of the invention; 
       FIG. 4  is a flow chart of an example method for making a multiband antenna array using electromagnetic bandgap structures, in accordance with one example embodiment of the invention; and 
       FIG. 5  is a block diagram of an example electronic appliance suitable for implementing a multiband antenna array using electromagnetic bandgap structures, in accordance with one example embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that embodiments of the invention can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form in order to avoid obscuring the invention. 
   Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. 
     FIG. 1  is a graphical illustration of an overhead view of a multiband antenna array using electromagnetic bandgap structures, in accordance with one example embodiment of the invention. In accordance with the illustrated example embodiment, antenna array package  100  includes one or more of electromagnetic bandgap (EBG) cells  102  and antennas  104 . In one embodiment, antenna array package  100  represents a package comprising a multi-layer organic substrate that is soldered, along with other components, to a printed circuit board. 
   EBG cells  102  represent multiband EBG structures on the surface of antenna array package  100 . EBG cells  102  are designed to prevent radiating waves from propagating between antennas  104 . One skilled in the art would recognize that EBG cells  102  can enable small scale antenna arrays by allowing discrete antennas to be located near each other. As shown, EBG cells  102  include a spiral patch, however other topologies or a combination of different topologies may be utilized. As shown, four rows of EBG cells  102  separate adjacent antennas  104 , however more or fewer rows may be utilized. EBG cells  102  may have forbidden bandgaps that are customized for the waves to be propagated by antennas  104  by varying the number of turns and trace widths of the spiral patches. In one embodiment, the width of each EBG cell  102  is less than or equal to about 750 um for very low frequencies (˜1 GHz). 
   Antennas  104  represent planar antennas on the surface of antenna array package  100 . Antennas  104  transmit signals into free space through radial wave propagation. While shown as containing four antenna in a square pattern, antenna array package  100  may contain any number of antennas in any pattern. In one embodiment, coaxial cable or coplanar waveguide feed the signals into antennas  104 . In another embodiment, plated through holes (PTH) transmit the signals to antennas  104 . Antennas  104  may transmit the same or different frequencies. Some examples of wireless communication that can use antennas  104  include WiFi, WiMax, Bluetooth, and cellular communications. In one embodiment, antenna array package  100  is part of a multiple inputs multiple outputs (MIMO) radio, where antennas  104  are identical and EBG cells  102  redirect the signals upwards and substantially prevent the signals from propagating sideways. 
     FIG. 2  is a graphical illustration of a cross-sectional view of a multiband antenna array using electromagnetic bandgap structures, in accordance with one example embodiment of the invention. As shown, antenna array package  200  includes EBG cells  202 , antenna  204 , EBG cells  206 , ground plane  208 , and dielectric layers  210  and  212 . 
   EBG cells  202  prevent radiating waves from antenna  204  from propagating to adjacent antennas and vice versa. 
   EBG cells  206  have a forbidden bandgap in the frequency band of antenna  204 . One skilled in the art would recognize that substrate thickness can be less than the quarter wavelength required by traditional planar patch antennas. EBG cells  206  may be the same as or different than EBG cells  202  in size and topology. EBG cells  206  may have one, two, three or more bandgaps below 50 Ghz. In one embodiment, the inductance of EBG cells  206  is varied and enhanced by altering the height of the vias coupling EBG cells  206  with ground plane  208 . 
   As part of a process for making a multiband antenna array using electromagnetic bandgap structures, for example as described in reference to  FIG. 4 , dielectric layers  210  and  212  may be laminated on a core ground plane  208 . In one embodiment, ground plane  208  is a metal layer that is coupled with a ground on a printed circuit board and coupled with EBG cells  202  and  206  through PTH&#39;s. In one embodiment, dielectric layers  210  and  212  are organic substrate layers. 
     FIG. 3  is a graphical illustration of a cross-sectional view of a multiband antenna array using electromagnetic bandgap structures, in accordance with one example embodiment of the invention. As shown, antenna array package  300  includes EBG cells  302 , antenna  304 , EBG cells  306 , ground plane  308 , antenna  310 , and EBG cells  312  and  314 . 
   Antenna array package  300  includes antenna  304  on the surface of, and antenna  310  within, the substrate. By incorporating antenna, and associated grounded EBG cells  312  and  314 , within the substrate, it may be possible to implement more antennas without increasing the footprint of the antenna array package. 
     FIG. 4  is a flow chart of an example method for making a multiband antenna array using electromagnetic bandgap structures, in accordance with one example embodiment of the invention. It will be readily apparent to those of ordinary skill in the art that although the following operations may be described as a sequential process, many of the operations may in fact be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged or steps may be repeated without departing from the spirit of embodiments of the invention. 
   According to but one example implementation, the method of  FIG. 4  begins with lamination ( 402 ) and via-hole formation. In one embodiment, a metal substrate core is laminated and utilized as a ground plane, such as, for example as ground plane  208  is laminated by dielectric layers  210  and  212 . Via-holes may be created in dielectric layer  210  to allow EBG cells  206  to be grounded to ground plane  208 . 
   Next, EBG cells are patterned and formed ( 404 ). In one embodiment, photoresist patterns and electroplating is used to create the spiral patches of EBG cells  206 . In another embodiment, EBG cells  206  are preformed and are placed on the substrate. 
   Next, there is further lamination and via-hole formation ( 406 ). Via-holes may be created in dielectric layer  210  to allow EBG cells  202  to be grounded to ground plane  208 . Via-holes may also be created to feed a signal to antenna  204  to be transmitted. 
   Lastly, antennas and EBG cells are patterned and formed ( 408 ). In one embodiment, photoresist patterns and electroplating is used to create antenna  204  and the spiral patches of EBG cells  202 . In one embodiment, antenna  204  and EBG cells  202  are preformed and are placed on the substrate. Additional steps may be needed to complete the package including, for example, adding ball grid array (BGA) contacts. 
     FIG. 5  is a block diagram of an example electronic appliance suitable for implementing a multiband antenna array using electromagnetic bandgap structures, in accordance with one example embodiment of the invention. Electronic appliance  500  is intended to represent any of a wide variety of traditional and non-traditional electronic appliances, laptops, desktops, cell phones, wireless communication subscriber units, wireless communication telephony infrastructure elements, personal digital assistants, set-top boxes, or any electric appliance that would benefit from the teachings of the present invention. In accordance with the illustrated example embodiment, electronic appliance  500  may include one or more of processor(s)  502 , memory controller  504 , system memory  506 , input/output controller  508 , wireless network controller(s)  510 , input/output device(s)  512 , and antenna array  514  coupled as shown in  FIG. 5 . 
   Processor(s)  502  may represent any of a wide variety of control logic including, but not limited to one or more of a microprocessor, a programmable logic device (PLD), programmable logic array (PLA), application specific integrated circuit (ASIC), a microcontroller, and the like, although the present invention is not limited in this respect. In one embodiment, processors(s)  502  are Intel® compatible processors. Processor(s)  502  may have an instruction set containing a plurality of machine level instructions that may be invoked, for example by an application or operating system. 
   Memory controller  504  may represent any type of chipset or control logic that interfaces system memory  508  with the other components of electronic appliance  500 . In one embodiment, the connection between processor(s)  502  and memory controller  504  may be referred to as a front-side bus. In another embodiment, memory controller  504  may be referred to as a north bridge. 
   System memory  506  may represent any type of memory device(s) used to store data and instructions that may have been or will be used by processor(s)  502 . Typically, though the invention is not limited in this respect, system memory  506  will consist of dynamic random access memory (DRAM). In one embodiment, system memory  506  may consist of Rambus DRAM (RDRAM). In another embodiment, system memory  506  may consist of double data rate synchronous DRAM (DDRSDRAM). 
   Input/output (I/O) controller  508  may represent any type of chipset or control logic that interfaces I/O device(s)  512  with the other components of electronic appliance  500 . In one embodiment, I/O controller  508  may be referred to as a south bridge. In another embodiment, I/O controller  508  may comply with the Peripheral Component Interconnect (PCI) Express™ Base Specification, Revision 1.0a, PCI Special Interest Group, released Apr. 15, 2003. 
   Wireless network controller(s)  510  may represent any type of device that allows electronic appliance  500  to communicate wirelessly with other electronic appliances or devices. In one embodiment, network controller  510  may comply with a The Institute of Electrical and Electronics Engineers, Inc. (IEEE) 802.11b standard (approved Sep. 16, 1999, supplement to ANSI/IEEE Std 802.11, 1999 Edition). In another embodiment, wireless network controller(s)  510  may also include ultra-wide band (UWB), global system for mobile (GSM), global positioning system (GPS), or other communications. 
   Input/output (I/O) device(s)  512  may represent any type of device, peripheral or component that provides input to or processes output from electronic appliance  500 . 
   Antenna array  514  may represent a multiband antenna array using electromagnetic bandgap structures as depicted in  FIG. 1 ,  2 , or  3 . 
   In the description above, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form. 
   Many of the methods are described in their most basic form but operations can be added to or deleted from any of the methods and information can be added or subtracted from any of the described messages without departing from the basic scope of the present invention. Any number of variations of the inventive concept is anticipated within the scope and spirit of the present invention. In this regard, the particular illustrated example embodiments are not provided to limit the invention but merely to illustrate it. Thus, the scope of the present invention is not to be determined by the specific examples provided above but only by the plain language of the following claims.