Patent Publication Number: US-9887457-B2

Title: Electronically steerable antenna using reconfigurable power divider based on cylindrical electromagnetic band gap (CEBG) structure

Description:
This patent application is a divisional of U.S. Non-Provisional application Ser. No. 13/760,980, filed on Feb. 6, 2013 and entitled “Electronically Steerable Antenna Using Reconfigurable Power Divider Based on Cylindrical Electromagnetic Band Gap (CEBG) Structure,” which is hereby incorporated by reference herein as if reproduced in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to electronically steerable antenna using reconfigurable power divider based on cylindrical electromagnetic band gap (CEBG) structure. 
     BACKGROUND 
     Modern wireless transmitters perform beamsteering to manipulate the direction of a main lobe of a radiation pattern and achieve enhanced spatial selectivity. Conventional beamsteering techniques rely on manipulating the phase of radio frequency (RF) signals through a series of phase shifters and RF switches. The inclusion of phase shifters, RF switches, and other complex components increase the manufacturing cost and design complexity of agile antennas. Accordingly, less complex agile antenna designs are desired. 
     SUMMARY OF THE INVENTION 
     Technical advantages are generally achieved, by embodiments of this disclosure which describe electronically steerable antenna using reconfigurable power diver based on cylindrical electromagnetic band gap (CEBG) structure. 
     In accordance with an embodiment, an apparatus for transmitting wireless signals is provided. In this example, the apparatus includes a central line feed; and a radial waveguide structure coupled to the central line feed. The radial waveguide structure comprises a plurality of radiating elements encircling the central line feed, and a plurality of active elements interspersed between the central line feed and the plurality of radiating elements. 
     In accordance with another embodiment, a method for operating an agile antenna is provided. The agile antenna has a radial waveguide structure affixed to a central line feed. Further, a plurality of active elements are affixed to the surface of the radial waveguide structure, and a plurality of radiating elements are positioned along the circumference of the radial waveguide structure. In this example, the method comprises emitting, from the central line feed, a radio frequency (RF) signal over the radial waveguide structure, and selectively activating fewer than all of the plurality of active elements to direct the propagation of the RF signal towards fewer than all of the radiating elements, thereby beamsteering a wireless signal emitted by the agile antenna. 
     In accordance with yet another embodiment, an antenna configured for beam switching is provided. In this example, the antenna includes a line feed configured to emit a radio frequency (RF) signal, a plurality of radiating elements encircling the line feed, and a plurality of active elements interspersed between the line feed and the plurality of radiating elements. The plurality of radiating elements are configured to convert the RF signal into a wireless signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a diagram of a wireless network for communicating data; 
         FIG. 2  illustrates a diagram of an embodiment agile antenna; 
         FIG. 3  illustrates a top view of the embodiment agile antenna; 
         FIG. 4  illustrates a diagram of an embodiment agile antenna configured to emit a beamsteered wireless signal; 
         FIG. 5  illustrates a side view of the embodiment agile antenna; 
         FIG. 6  illustrates a diagram of an embodiment agile antenna comprising groups of active elements that are controlled by a common switch; 
         FIG. 7  illustrates a diagram of another embodiment agile antenna; 
         FIG. 8  illustrates another side view of the embodiment agile antenna; 
         FIG. 9  illustrates a diagram of a radiating element; 
         FIG. 10  illustrates a diagram of an interconnection between the coaxial line feed and a radial waveguide; 
         FIG. 11  illustrates a flowchart of a method for transmitting a beamsteered wireless signal; and 
         FIG. 12  illustrates a block diagram of an embodiment communications device. 
     
    
    
     Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale. 
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The making and using of embodiments of this disclosure are discussed in detail below. It should be appreciated, however, that the concepts disclosed herein can be embodied in a wide variety of specific contexts, and that the specific embodiments discussed herein are merely illustrative and do not serve to limit the scope of the claims. Further, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of this disclosure as defined by the appended claims. 
     Disclosed herein is an agile antenna that beamsteers wireless transmissions by selectively activating/de-activating active elements on a radial-waveguide using direct current (DC) switches. Notably, the active elements may be relatively low complexity and/or inexpensive active/electromechanical components (e.g., diodes, microelectromechanical system (MEMS), etc.), and hence embodiment agile antenna designs of this disclosure may achieve cost and/or complexity savings over conventional agile antenna designs that rely on phase shifters and radio frequency (RF) switches to effectuate beamsteering. More specifically, embodiment agile antennas include a plurality of radiating elements encircling a radial waveguide upon which a plurality of active elements are affixed. The active elements may be activated/deactivated by DC switches in order to direct the propagation of an RF signal across the waveguide and towards selected radiating elements, thereby determining the primary direction of the main lobe of the emitted radiation pattern. 
     U.S. Patent Application Publication 2007/0080891 (hereinafter “the &#39;891 application”) discusses an agile antenna that uses a circular via configuration to effectuate beamsteering, and is incorporated herein by reference as if reproduced in its entirety. The agile antenna design discussed in the &#39;891 application utilizes a dipole feed design in which propagation of the RF signal is directed via a series of parasitic reflectors and radiators towards a centralized radiating element. As a result, the agile antenna provided by the &#39;891 application is only capable of vertical polarization, and is limited to azimuth beam direction coverage. Conversely, embodiment agile antennas provided herein utilize a coaxial feed line, and as well as a series of inter-connected active elements (acting like a power divider) to direct the RF signal towards selected radiating elements positioned along the circumference of the radial waveguide. As a result of these (and other) design principals, embodiment agile antennas described herein are capable of achieving various polarizations (e.g., single, dual, circular, elliptical, etc.) as well as achieving full beam coverage. This flexibility is achieved thanks to the freedom of choice of the radiator element in the design principle. 
       FIG. 1  illustrates a network  100  for communicating data. The network  100  comprises an access point (AP) no having a coverage area  112 , a plurality of user equipments (UEs)  120 , and a backhaul network  130 . The AP no may comprise any component capable of providing wireless access by, inter alia, establishing uplink (dashed line) and/or downlink (dotted line) connections with the UEs  120 , such as a base station, an enhanced base station (eNB), a femtocell, and other wirelessly enabled devices. The UEs  120  may comprise any components capable of establishing a wireless connection with the AP  110 . The backhaul network  130  may be any component or collection of components that allow data to be exchanged between the AP no and a remote end (not shown). In some embodiments, the network  100  may comprise various other wireless devices, such as relays, femtocells, etc. 
       FIG. 2  illustrates an agile antenna  200  comprising a radial waveguide structure  205 , a line feed  210 , a plurality of active elements  220 , and a plurality of radiating elements  230 . The active elements  220  may be any component or collection of components that has the ability to (collectively or independently) change the flow of current over the radial waveguide structure  205 . In an embodiment, active elements include active components that rely on a source of energy (e.g., DC power) to change the flow of current, such as (for example) a PIN diode. In the same or other embodiments, active elements include electromechanical components that change the flow of current using moving parts or electrical connections, such as (for example) MEMS components. As shown, the line feed  210  protrudes from the center of the radial waveguide structure  205 , the radiating elements  230  are affixed around the circumference of the radial waveguide structure  205 , and the active elements  220  are affixed to the surface of the radial waveguide structure  205 . The line feed  210  emits an RF electrical signal, which radiates outwardly over the radial waveguide structure  205 . The active elements  220  are interspersed between the line feed  210  and the radiating element  230 , and may be selectively activated/deactivated for the purpose of directing propagation of the RF signal towards selected ones of the plurality of radiating elements  230 . 
       FIG. 3  illustrates a top view of the agile antenna  200  illustrating how the diodes  220  encircle the coaxial line feed  210 . Notably, different patterns of the active elements  220  are activated to direct the RF signal towards different radiating elements  230 , which effectively beamsteers the wireless transmission.  FIG. 4  illustrates a top view of an agile antenna  410  configured to emit a wireless signal  415 . As shown, selected active elements are activated/de-activated to direct propagation of the RF signal towards the radiating elements  431 - 433 , which controls the direction of the wireless signal  415 . Notably, whether a given RF signal propagates over active elements in the “On Mode” (e.g., activated diodes, etc.) or in the “Off Mode” (e.g., deactivated diodes, etc.) may depend on the wavelength of the RF signal. For instances, RF wavelengths within a certain range propagate over activated diodes, while RF wavelengths outside that range propagate over de-activated diodes. The diagram  420  shows the radiation pattern of the agile antenna  410 . 
     Notably, embodiment agile antennas constructed in accordance with embodiments of this disclosure utilize direct current (DC) switches, and therefore are less complex than conventional agile antennas (which rely on phase shifters and RF switches to effectuate beamsteering).  FIG. 5  illustrates a side view of the agile antenna  200 . As shown, the diodes  220  are controlled by a microcontroller  250  via a series of DC switches  240 . Notably, beamsteering related processing in the agile antenna  200  may be akin to manipulating a power divider, and therefore may be far less complex than the baseband processing (e.g., computing phase/amplitude shifts, etc.) inherent to conventional agile antennas. As a result, the microcontroller  250  may be of lower complexity and consume less power than the processors included in conventional agile antenna designs. 
     In some configurations, the number of DC switches required to effectuate beamsteering is reduced by using a common switch to activate groups of active elements.  FIG. 6  illustrates a diagram showing how groups of active elements  220  in the agile antenna  200  can be controlled by a common switch. As shown in  FIG. 6 , groups of active elements  220  (as indicated by the dashed lines) are controlled by the same switch such that fewer switches (e.g., twenty switches in  FIG. 6 ) are used to control beamsteering. 
       FIG. 7  illustrates the agile antenna  200  in greater detail than  FIG. 2 . As shown, the radial waveguide structure  205  includes transitional elements  206 , DC feed circuits  207 , and RF chokes  208 . The transitional elements provide a conductive interface to each of the radiating elements  230 . The DC feed circuits  207  interconnect groups of active elements  220  to a common ground and/or to a common metallic via, such that DC current can activate/de-active the active elements  220 . The RF chokes  208  may include any components configured to block RF frequency signal without blocking the DC signal. Further, the radiating elements  230  may include one or more feed patches  232 , which are interconnected to the transitional elements  206  of the radial waveguide structure  205  via a series of conductive feed paths  231 .  FIG. 8  illustrates a side view of the agile antenna  200 .  FIG. 9  illustrates a radiating element  230 , and demonstrates differences between the feed side  910  and the patch side  920  of the radiating elements  230 . As shown, the feed side  910  includes a conductive feed path  231 , which feeds the RF signal to the feed patches  232  on the path side  920  of the radiating element  230 .  FIG. 10  illustrates an interconnection between the coaxial line feed  210  and the radial waveguide  205 . 
       FIG. 11  illustrates a flowchart  1100  of a method for beamsteering a wireless transmission in accordance with aspects of this disclosure, as might be performed by an agile antenna (or operator thereof). The method  1100  begins at step  1110 , where an RF signal is emitted from the coaxial line feed of the agile antenna. Thereafter, the method  1100  proceeds to step  1120 , where active elements of the agile antenna are selectively activated/deactivated in order to direct propagation of the RF signal over the radial waveguide. Notably, the RF signal is directed towards selected radiating elements for the purpose of beamsteering the emitted wireless signal. Next, the method  1100  proceeds to step  1130 , where the RF signal is converted into a wireless signal by the excited radiating elements. 
       FIG. 12  illustrates a block diagram of an embodiment of a communications device  1200  including a processor  1204 , a memory  1206 , and a switching interface  1214 , which may (or may not) be arranged as shown in  FIG. 12 . The processor  1204  may be any component capable of performing computations and/or other processing related tasks, and may be equivalent to the microcontroller  250  (discussed above). The memory  1206  may be any component capable of storing programming and/or instructions for the processor  1204 . The switching interface  1214  may be any component or collection of components that allows the processor  1204  to manipulate or otherwise control a series of DC switches for the purpose of effectuating beamsteering on an agile antenna. 
     Although the description has been described in detail, it should be understood that various changes, substitutions and alterations can be made without departing from the spirit and scope of this disclosure as defined by the appended claims. Moreover, the scope of the disclosure is not intended to be limited to the particular embodiments described herein, as one of ordinary skill in the art will readily appreciate from this disclosure that processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, may perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.