Patent Publication Number: US-7592962-B1

Title: EPC tapered slot antenna method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of U.S. Ser. No. 11/645,258, entitled “Extended Phase Center Tapered Slot Antenna,” by HORNER et al. filed Nov. 27, 2006, now U.S. Pat. No. 7,397,440, which is hereby incorporated by reference herein in its entirety for its teachings and is hereinafter referred to as the “parent application.” (NC#097529) This application is related to U.S. Pat. No. 7,009,572, issued on Mar. 7, 2006, entitled “Tapered Slot Antenna”, by Rob HORNER et al., Navy Case No. 96507, which is hereby incorporated by reference in its entirety herein for its teachings on antennas. This application is also related to U.S. Ser. No. 11/472,514 filed on Jun. 15, 2006, entitled “Tapered Slot Antenna Cylindrical Array”, by Rob HORNER et al., Navy Case No. 97194, which is hereby incorporated by reference in its entirety herein for its teachings on antennas. This application is also related to U.S. Ser. No. 11/482,301 filed on Jun. 27, 2006, entitled “Tapered Slot Antenna Cylindrical Array”, by Rob HORNER et al., Navy Case No. 98219, which is hereby incorporated by reference in its entirety herein for its teachings on antennas. 

   FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
   This invention (Navy Case No. 098518) is assigned to the United States Government and is available for licensing for commercial purposes. Licensing and technical inquiries may be directed to the Office of Research and Technical Applications, Space and Naval Warfare Systems Center, San Diego, Code 2112, San Diego, Calif., 92152; voice (619) 553-2778; email T2@spawar.navy.mil. Reference Navy Case Number 098518. 

   BACKGROUND OF THE INVENTION 
   The present invention is generally in the field of antennas. 
   Typical tapered slot antennas (TSA) have a relatively short phase center when operating at frequencies below a theoretical cutoff frequency. Thus, typical TSA have limited capabilities when operating as broadband antennas. 
   A need exists for TSA having a relatively long phase center when operating at frequencies below a theoretical cutoff frequency. An exemplary need exists for antennas used in direction finding applications. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     All FIGURES are not drawn to scale. 
       FIG. 1A  is a side view of one embodiment of an EPCTSA. 
       FIG. 1B  is a front view of one embodiment of an EPCTSA. 
       FIG. 1C  is a front view of one embodiment of an EPCTSA. 
       FIG. 1D  is a front view of one embodiment of an EPCTSA. 
       FIG. 1E  is a front view of one embodiment of an EPCTSA. 
       FIG. 2A  is a perspective view of one embodiment of an EPCTSA. 
       FIG. 2B  is a top view of one embodiment of an EPCTSA. 
       FIG. 3A  is a perspective view of one embodiment of an EPCTSA cylindrical array. 
       FIG. 3B  is a top view of one embodiment of an EPCTSA cylindrical array. 
       FIG. 4  is a perspective view of one embodiment of an EPCTSA cylindrical array. 
       FIG. 5  is a flowchart of an exemplary method of manufacturing one embodiment of an EPCTSA. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Described herein is EPC Tapered Slot Antenna Method. 
   DEFINITIONS 
   The following acronyms are used herein: 
   Acronym(s): 
   AE—Antenna Element(s) 
   EPC—Extended Phase Center 
   EPCTSA—Extended Phase Center Tapered Slot Antenna 
   LOF—Lowest Operating Frequency 
   RF—Radio Frequency 
   TSA—Tapered Slot Antenna(s) 
   DEFINITION(S) 
   
       
       Conductive Launch Structure—a structure that is capable of conducting electricity between antenna elements of an antenna pair or multiple antenna pairs of a TSA or TSA array; the structure located along an axis between a LOF phase center and a launch end of a TSA; the structure extends phase center of a TSA beyond LOF ordinary phase center (i.e., toward a launch end) 
       Feed End—Portion of a TSA from which an input signal is received 
       Launch End—Portion of a TSA distal to the feed end 
       Lowest Operating Frequency—theoretical cutoff frequency for a TSA having specific dimensions (and not having a conductive launch structure) 
       Lowest Operating Frequency (LOF) Phase Center—phase center for frequencies lower than the theoretical cutoff frequency for a TSA having specific dimensions regardless of having a conductive launch structure 
       Lowest Operating Frequency Extended Phase Center—phase center for frequencies lower than the theoretical cutoff frequency for a TSA having specific dimensions, wherein the TSA has a conductive launch structure; (the conductive launch structure creates a new launch point or phase center) 
       Lowest Operating Frequency Ordinary Phase Center—phase center for frequencies lower than the theoretical cutoff frequency for a TSA having specific dimensions, wherein the TSA does not have a conductive launch structure 
       Phase Center—location on a TSA representing a launch point of RF energy from the TSA relative to a feed axis; 
       Theoretical Cutoff Frequency—a frequency at which an antenna&#39;s largest dimension (or antenna height) is greater than or equal to half of the respective wavelength 
     
  
   The extended phase center tapered slot antenna (EPCTSA) includes at least one tapered slot antenna. The at least one TSA includes two antenna elements (AE) and a conductive launch structure that electrically couples the two AE at location between a LOF ordinary phase center (i.e., phase center for frequencies lower than the theoretical cutoff frequency for a TSA) and a launch end of the at least one TSA. In one embodiment, the conductive launch structure comprises a single loop. In one embodiment, the conductive launch structure comprises a double loop. In one embodiment, the conductive launch structure comprises a square loop. In one embodiment, the conductive launch structure comprises a curved loop. In one embodiment, the EPCTSA comprises two TSA, wherein each TSA comprises two AE and a conductive launch structure that electrically couples the two AE at a location between a LOF ordinary phase center and a launch end of the TSA. In one embodiment, the EPCTSA comprises two TSA, wherein a conductive launch structure electrically couples all four AE. In one embodiment, the conductive launch structure comprises conductive material and at least one lump sum (passive) circuit element. In one embodiment, the EPCTSA comprises sixteen TSA having a cylindrical array configuration, wherein each TSA comprises two antenna elements (AE) and a conductive launch structure that electrically couples the two AE at a location between a LOF ordinary phase center and a launch end of the TSA. 
     FIG. 1A  is a side view of one embodiment of an EPCTSA. As shown in  FIG. 1A , EPCTSA  100  includes an antenna pair (i.e., antenna element  110 , antenna element  120 ) and conductive launch structure  130 . The antenna pair of EPCTSA  100  has gap height  194 , a feed end and a launch end. The feed end of the antenna pair corresponds to the portion of the antenna pair that is proximate to axis  140  (represented by dashed line K-K on  FIG. 1A ). The feed end receives and transmits signals. The launch end of the antenna pair corresponds to the portion of the antenna pair that is proximate to axis  146  (represented by dashed line N-N on  FIG. 1A ). Note that the launch end only denotes a location on the antenna pair versus an actual launch point of a particular frequency. The feed end can be operatively coupled to an input/output (I/O) feed such as a coaxial cable. An I/O feed can be used to transmit and receive RF signals to and from EPCTSA  100 . RF signals can be transmitted from the feed end toward the launch end, wherein the RF signals launch from the antenna pair at a point between the feed end and the launch end depending on the signal frequency. RF signals having higher frequencies (and are greater than the LOF) launch closer to the feed end and RF signals having lower frequencies (and are greater than the LOF) launch closer to the launch end. 
   In one embodiment, AE  110 ,  120  have curvatures that can each be represented by the following Equation 1:
 
 Y ( x )= a ( e   bx −1);  (Equation 1)
         where, a and b are parameters selected to produce a desired curvature. In one embodiment, parameters “a” and “b” are approximately equal to 0.2801 and 0.1028, respectively.       

   Conductive launch structure  130  electrically couples antenna element  110  and antenna element  120  at a location between a LOF ordinary phase center (which can be represented by the intersection of the curved edges of AE  110 ,  120  and dashed line L-L  142  on  FIG. 1A ) and the launch end. The LOF ordinary phase center is a phase center for frequencies lower than the theoretical cutoff frequency for a TSA having specific dimensions (and not having a conductive launch structure). Thus, for TSA that do not have conductive launch structures, frequencies lower than the theoretical cutoff frequency launch at locations proximate to the intersection of the LOF ordinary phase center. The distance between the LOF ordinary phase center and the feed end (relative to the X-axis) is typically a relatively short distance (depicted by length  152  in  FIG. 1A ) and varies depending on TSA dimensions and frequency of interest. For example, a TSA having the dimensions of 12 inches by 12 inches has a LOF ordinary phase center approximately 4.5 inches from the feed end (toward the launch end) along the X-axis in  FIG. 1A . 
   Conductive launch structure  130  comprises a conductive material. In EPCTSA  100 , the distance between the LOF extended phase center (which can be represented by the intersection of the curved edges of AE  110 ,  120  and dashed line M-M  144  on  FIG. 1A ) and the feed end (relative to the X-axis) is a distance (depicted by length  154  in  FIG. 1A ) that is longer than length  152 . Conductive launch structure  130  has a launch structure height (depicted by length  162  in  FIG. 1A ). 
     FIG. 1B  is a front view of one embodiment of an EPCTSA. EPCTSA  100  of  FIG. 1B  is substantially similar to EPCTSA  100  of  FIG. 1A , and thus, similar components are not described again in detail hereinbelow. EPCTSA  100  of  FIG. 1B  depicts a conductive launch structure having a single square loop configuration. As shown in  FIG. 1B , EPCTSA  100  includes an antenna pair (i.e., antenna element  110 , antenna element  120 ) and conductive launch structure  130 . The antenna pair of EPCTSA  100  has gap height  194 . Conductive launch structure  130  has a launch structure width (depicted by length  172  in  FIG. 1B ). 
     FIG. 1C  is a front view of one embodiment of an EPCTSA. EPCTSA  100  of  FIG. 1C  is substantially similar to EPCTSA  100  of  FIG. 1A , and thus, similar components are not described again in detail hereinbelow. EPCTSA  100  of  FIG. 1C  depicts a conductive launch structure having a double square loop configuration. As shown in  FIG. 1C , EPCTSA  100  includes an antenna pair (i.e., antenna element  110 , antenna element  120 ) and conductive launch structures  130 ,  132 . Conductive launch structures  130 ,  132  both comprise conductive material. As shown in  FIG. 1C , conductive launch structures  130 ,  132  have a square loop configuration. Conductive launch structures  130 ,  132  are situated on AE  110 ,  120  at approximately equal distances from the launch end of EPCTSA  100  with respect to the X-axis. Those of ordinary skill in the art shall recognize that conductive launch structures  130 ,  132  can be situated on AE  110 ,  120  at unequal distances from the launch end of EPCTSA  100  with respect to the X-axis without departing from the scope or spirit of the present EPCTSA. 
     FIG. 1D  is a front view of one embodiment of an EPCTSA. EPCTSA  100  of  FIG. 1D  is substantially similar to EPCTSA  100  of  FIG. 1A , and thus, similar components are not described again in detail hereinbelow. EPCTSA  100  of  FIG. 1D  depicts a conductive launch structure having a curved loop configuration. Conductive launch structure  130  comprises conductive material. As shown in  FIG. 1D , conductive launch structure  130  has a curved loop configuration. 
     FIG. 1E  is a front partial schematic view of one embodiment of an EPCTSA. EPCTSA  100  of  FIG. 1E  is substantially similar to EPCTSA  100  of  FIG. 1A , and thus, similar components are not described again in detail hereinbelow. EPCTSA  100  of  FIG. 1E  depicts a conductive launch structure having a lump sum (passive) circuit element configuration. Conductive launch structure  130  comprises conductive material. As shown in  FIG. 1E , conductive launch structure  130  further comprises inductor  134 , resistor  136  and capacitor  138 . In one embodiment, lump sum circuit elements (e.g., inductors, resistors and capacitors) are used to control a transition frequency (i.e., frequency at which RF energy encounters an equal impedance match between AE  110 ,  120  and conductive launch structure  130 ) of EPCTSA  100 . In one embodiment, a combination of at least two of the following components are used to control a transition frequency: inductor, resistor and capacitor. In one embodiment, lump sum circuit elements are designed to create a low-pass filter effect for conductive launch structure  130 . In one embodiment, lump sum circuit elements are designed to create a high-pass filter effect for conductive launch structure  130 . In one embodiment, lump sum circuit elements are designed to create a bandpass filter effect for conductive launch structure  130 . 
     FIG. 2A  is a perspective view of one embodiment of an EPCTSA. EPCTSA  200  of  FIG. 2A  has a double TSA, single conductive launch structure configuration.  FIG. 2B  is a top view of one embodiment of an EPCTSA of  FIG. 2A . As shown in  FIGS. 2A and 2B , a first TSA comprises AE  210 ,  220  and a second TSA comprises AE  212 ,  222 . Conductive launch structure  230  electronically couples AE  210 ,  220 ,  212 ,  222 . Conductive launch structure  230  comprises conductive elements  232 ,  234 ,  236 . Conductive element  232  is operatively coupled to AE  210 ,  212 . Conductive element  236  is operatively coupled to AE  220 ,  222 . Conductive element  234  is operatively coupled to conductive elements  232 ,  236 . 
     FIG. 3A  is a perspective view of one embodiment of an EPCTSA cylindrical array. EPCTSA  300  of  FIG. 3A  depicts an EPCTSA cylindrical array having a multiple double TSA, single conductive launch structure configuration. As shown in  FIG. 3A , EPCTSA cylindrical array  300  comprises eight conductive launch structures and sixteen TSA having a cylindrical configuration. In one embodiment, EPCTSA cylindrical array  300  comprises eight EPCTSA  200  of  FIG. 2A  having a cylindrical configuration, wherein each conductive launch structure of said eight conductive launch structures electrically couples a unique pair of said sixteen tapered slot antennas. 
     FIG. 3B  is a top view of one embodiment of an EPCTSA cylindrical array of  FIG. 3A . EPCTSA cylindrical array  300  of  FIG. 3B  is substantially similar to EPCTSA cylindrical array  300  of  FIG. 3A , and thus, similar components are not described again in detail hereinbelow. AE  310  of  FIG. 3B  is analogous to AE  210  of  FIGS. 2A and 2B . AE  312  of  FIG. 3B  is analogous to AE  212  of  FIGS. 2A and 2B . Conductive launch structure  330  of  FIG. 3B  is analogous to conductive launch structure  230  of  FIGS. 2A and 2B . 
     FIG. 4  is a perspective view of one embodiment of an EPCTSA cylindrical array. EPCTSA  400  of  FIG. 4  depicts an EPCTSA cylindrical array having multiple TSA, wherein each TSA has a conductive launch structure having a single square loop configuration. As shown in  FIG. 4 , EPCTSA cylindrical array  400  comprises sixteen conductive launch structures and sixteen TSA having a cylindrical configuration. In one embodiment, EPCTSA cylindrical array  400  comprises sixteen EPCTSA  100  of  FIGS. 1A and 1B  having a cylindrical configuration. 
     FIG. 5  is a flowchart of an exemplary method of manufacturing one embodiment of an EPCTSA. Boxes  510 ,  520 ,  530 ,  540 ,  550  of flowchart  500  of  FIG. 5  show an exemplary method of manufacturing one embodiment of an EPCTSA. While flowchart  500  is sufficient to describe one embodiment of an exemplary EPCTSA, other embodiments of the EPCTSA may utilize procedures different from those shown in flowchart  500 . 
   Referring to  FIG. 5 , at Procedure  510  in flowchart  500 , the method provides a first antenna element of a tapered slot antenna pair. After Procedure  510 , the method proceeds to Procedure  520 . At Procedure  520  in flowchart  500 , the method provides a second antenna element of the tapered slot antenna pair. After Procedure  520 , the method proceeds to Procedure  530 . At Procedure  530  in flowchart  500 , the method operatively couples an input feed to the tapered slot antenna pair. After Procedure  530 , the method proceeds to Procedure  540 . At Procedure  540  in flowchart  500 , the method electronically couples a conductive launch structure to the first and second element at a location between a lowest operating frequency phase center and a launch end of the tapered slot antenna pair. After Procedure  540 , the method proceeds to Procedure  550 . At Procedure  550  in flowchart  500 , the method operatively couples support elements to the first and second antenna elements of the tapered slot antenna pair. After Procedure  550 , the method ends.