# Patent

## Title
Tapered slot antenna end caps

## Abstract

An apparatus includes a first end cap, a second end cap and a tapered slot antenna pair having a first antenna element and a second antenna element. The first end cap is electrically coupled to the first antenna element and comprises conductive material. The second end cap is electrically coupled to the second antenna element and comprises conductive material. The first end cap and the second end cap are configured to provide induction-cancelling, capacitive coupling when the apparatus operates at frequencies below a theoretical cutoff frequency.

## Background
FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
This invention U.S. patent Ser. No. 11/645,261 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 98103.


CROSS-REFERENCE TO RELATED APPLICATIONS
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.
BACKGROUND OF THE INVENTION
The present invention is generally in the field of antennas.
Typical tapered slot antennas suffer from a greatly decreased gain and sensitivity when operating at frequencies below the theoretical cutoff frequency.
A need exists for a tapered slot antenna that does not suffer from a greatly decreased gain and sensitivity when operating at frequencies below the theoretical cutoff frequency.



BRIEF DESCRIPTION OF THE DRAWINGS
All FIGURES are not drawn to scale.
FIG. 1A is a side view of one embodiment of a TSAEC apparatus.
FIG. 1B is a front view of one embodiment of a TSAEC apparatus.
FIG. 1C is a top view of one embodiment of a TSAEC apparatus.
FIG. 1D is a top view of one embodiment of a TSAEC apparatus.
FIG. 1E is a top view of one embodiment of a TSAEC apparatus.
FIG. 1F is a top view of one embodiment of a TSAEC apparatus.
FIG. 1G is a top view of one embodiment of a TSAEC apparatus.
FIG. 1H is a top view of one embodiment of a TSAEC apparatus.
FIG. 1I is a front view of one embodiment of a TSAEC apparatus.
FIG. 1J is a front view of one embodiment of a TSAEC apparatus.
FIG. 1K is a front view of one embodiment of a TSAEC apparatus.
FIG. 1L is a front view of one embodiment of a TSAEC apparatus.
FIG. 1M is a front view of one embodiment of a TSAEC apparatus.
FIG. 1N is a front view of one embodiment of a TSAEC apparatus.
FIG. 2A is a perspective view of one embodiment of a TSAEC cylindrical array.
FIG. 2B is a top view of one embodiment of a TSAEC cylindrical array.



DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to Tapered Slot Antenna End Caps.
DEFINITIONS
The following acronyms are used herein:
Acronym(s):
AE—Antenna Element(s)
EC—End Caps
RF—radio frequency
TSA—Tapered Slot Antenna(s)
TSAEC—Tapered Slot Antenna End Cap(s)
DEFINITION(S)
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
Theoretical Cutoff Frequency—a frequency at which an antenna's largest dimension (or antenna height) is greater than or equal to half of the respective wavelength
The tapered slot antenna end cap (TSAEC) apparatus includes at least one tapered slot antenna (TSA). The at least one TSA of the TSAEC apparatus includes two antenna elements (AE) having a TSA configuration and two end caps (EC). An EC is electrically coupled to each AE to provide capacitive coupling when operating with frequencies lower than a LOF for a TSA, which counteracts inductance created by low frequency RF energy. Thus, a greater antenna sensitivity is achieved when operating below a theoretical cutoff frequency. In one embodiment, the TSAEC apparatus comprises a rectangular plate configuration. In one embodiment, the TSAEC apparatus comprises an oval plate configuration. In one embodiment, the TSAEC apparatus comprises a hollow rectangular plate configuration. In one embodiment, the TSAEC apparatus comprises a hollow oval plate configuration. In one embodiment, the TSAEC apparatus comprises a hollow square plate configuration. In one embodiment, the TSAEC apparatus comprises a square plate configuration. In one embodiment, the TSAEC apparatus comprises a circular plate configuration. In one embodiment, the TSAEC apparatus comprises a hollow circular plate configuration. In one embodiment, the TSAEC apparatus comprises a single plate configuration. In one embodiment, the TSAEC apparatus comprises a stacked plate configuration. In one embodiment, the TSAEC apparatus comprises a folded plate configuration. In one embodiment, the TSAEC apparatus comprises a stacked folded plate configuration. In one embodiment, the TSAEC apparatus comprises a curved plate configuration. In one embodiment, the TSAEC apparatus comprises a stacked curved plate configuration. In one embodiment, the TSAEC apparatus comprises a copper mesh enclosed configuration. In one embodiment, the TSAEC apparatus comprises a radome enclosed configuration. In one embodiment, the TSAEC apparatus comprises a cylindrical array.
FIG. 1A is a side view of one embodiment of a tapered slot antenna end cap apparatus. As shown in FIG. 1A, TSAEC apparatus 100 includes first end cap 130, second end cap 132 and a tapered slot antenna pair (comprising first antenna element 110, second antenna element 120). TSAEC apparatus 100 of FIG. 1A is also referred to as a single plate configuration because first and second end caps 130, 132 form single plates on first and second antenna elements 110, 120. First antenna element 110 and second antenna element 120 comprise a substantially conductive material such as, for example, stainless steel and aluminum. As shown in FIG. 1A, first antenna element 110 and second antenna element 120 are situated in a tapered slot antenna pair configuration. First antenna element 110 has input edge 112, lateral edge 114 and curved edge 116. Lateral edge 114 corresponds to the portion of first AE 110 that is proximate to axis 142 (represented by dashed line L-L on FIG. 1A). Second antenna element 120 has input edge 122, lateral edge 124 and curved edge 126. Lateral edge 124 corresponds to the portion of second AE 120 that is proximate to axis 144 (represented by dashed line M-M on FIG. 1A).
The antenna pair of TSAEC apparatus 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 can also be represented by input edges 112, 122 of antenna elements 110, 120, respectively. 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 TSAEC apparatus 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(ebx−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.

    
    


First end cap 130 is electrically coupled to first AE 110 to provide capacitive coupling when TSAEC apparatus 100 operates at frequencies lower than a LOF for TSAEC apparatus 100, which counteracts inductance (i.e., cancels induction) created by low frequency RF energy. In the embodiment of TSAEC apparatus 100 shown in FIG. 1A, first end cap 130 is also physically coupled to first AE 110 along lateral edge 114. Those skilled in the art shall recognize that first end cap 130 can be physically uncoupled from first AE 110 (while being electrically coupled) without departing from the scope and spirit of TSAEC apparatus (i.e., the end caps and antenna elements do not require a DC connection).
Second end cap 132 is electrically coupled to second AE 120 to provide capacitive coupling when TSAEC apparatus 100 operates at frequencies lower than a LOF for TSAEC apparatus 100, which counteracts inductance created by low frequency RF energy. In the embodiment of TSAEC apparatus 100 shown in FIG. 1A, second end cap 132 is also physically coupled to second AE 120 along lateral edge 124. Those skilled in the art shall recognize that first end cap 132 can be physically uncoupled from second AE 120 (while being electrically coupled) without departing from the scope and spirit of TSAEC apparatus.
FIG. 1B is a front view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1B is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. TSAEC apparatus 100 of FIG. 1B depicts end caps having a rectangular plate configuration. As shown in FIG. 1B, TSAEC apparatus 100 includes an antenna pair (i.e., antenna element 110, antenna element 120) and first and second end caps 130, 132. The antenna pair of TSAEC apparatus 100 has gap height 194.
FIG. 1C is a top view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1C is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. TSAEC apparatus 100 of FIG. 1C depicts end cap 130 having a rectangular plate configuration.
FIG. 1D is a top view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1D is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. TSAEC apparatus 100 of FIG. 1D depicts end cap 130 having an oval plate configuration.
FIG. 1E is a top view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1E is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. TSAEC apparatus 100 of FIG. 1E depicts end cap 130 having a hollow rectangular plate configuration. As shown in FIG. 1E, end cap 130 encloses end cap interior region 134. End cap interior region 134 comprises material different than the material comprising end cap 130. In one embodiment, end cap interior region 134 comprises air. In one embodiment, end cap interior region 134 comprises copper mesh. In one embodiment, end cap interior region 134 comprises a nonconductive material.
FIG. 1F is a top view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1F is substantially similar to TSAEC apparatus 100 of FIG. 1A, 29 and thus, similar components are not described again in detail hereinbelow. TSAEC apparatus 100 of FIG. 1F depicts end cap 130 having a hollow oval plate configuration. As shown in FIG. 311F, end cap 130 encloses end cap interior region 134. End cap interior region 134 comprises material different than the material comprising end cap 130. In one embodiment, end cap interior region 134 comprises air. In one embodiment, end cap interior region 134 comprises copper mesh. In one embodiment, end cap interior region 134 comprises a nonconductive material.
FIG. 1G is a top view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1G is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. TSAEC apparatus 100 of FIG. 1G depicts end cap 130 having a hollow square plate configuration. As shown in FIG. 1G, end cap 130 encloses end cap interior region 134. End cap interior region 134 comprises material different than the material comprising end cap 130. In one embodiment, end cap interior region 134 comprises air. In one embodiment, end cap interior region 134 comprises copper mesh. In one embodiment, end cap interior region 134 comprises a nonconductive material. In one embodiment referred to as a square plate configuration, end cap interior region 134 comprises the same material as end cap 130.
FIG. 1H is a top view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1H is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. TSAEC apparatus 100 of FIG. 1H depicts end cap 130 having a hollow circular plate configuration. As shown in FIG. 1H, end cap 130 encloses end cap interior region 134. End cap interior region 134 comprises material different than the material comprising end cap 130. In one embodiment, end cap interior region 134 comprises air. In one embodiment, end cap interior region 134 comprises copper mesh. In one embodiment, end cap interior region 134 comprises a nonconductive material. In one embodiment referred to as a circular plate configuration, end cap interior region 134 comprises the same material as end cap 130.
FIG. 1I is a front view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1I is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. As shown in FIG. 1I, TSAEC apparatus 100 includes first end cap 130, second end cap 132, third end cap 136 and fourth end cap 138. TSAEC apparatus 100 of FIG. 1I has a stacked plate configuration because third and fourth end caps 136, 138 are stacked in relation to first and second end caps 130, 132, respectively. The stacked plate configuration provides a means of creating additional capacitive coupling.
FIG. 1J is a front view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1J is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. As shown in FIG. 1J, TSAEC apparatus 100 includes first end cap 130 and second end cap 132. TSAEC apparatus 100 of FIG. 1J has a folded plate configuration because first and second end caps 130, 132 are folded. The folded plate configuration provides a means of creating capacitive coupling.
FIG. 1K is a front view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1K is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. As shown in FIG. 1K, TSAEC apparatus 100 includes first end cap 130, second end cap 132, third end cap 136 and fourth end cap 138. TSAEC apparatus 100 of FIG. 1K has a stacked folded plate configuration because third and fourth end caps 136, 138 are stacked in relation to first and second end caps 130, 132, respectively and all end caps have a folded plate configuration. The stacked folded plate configuration provides a means of creating capacitive coupling.
FIG. 1L is a front view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1L is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. As shown in FIG. 1L, TSAEC apparatus 100 includes first end cap 130 and second end cap 132. TSAEC apparatus 100 of FIG. 1L has a curved plate configuration because first and second end caps 130, 132 are curved. The curved plate configuration provides a means of creating capacitive coupling.
FIG. 1M is a front view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1M is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. As shown in FIG. 1M, TSAEC apparatus 100 includes first end cap 130, second end cap 132, third end cap 136 and fourth end cap 138. TSAEC apparatus 100 of FIG. 1M has a stacked circular plate configuration because third and fourth end caps 136, 138 are stacked in relation to first and second end caps 130, 132, respectively and all end caps have a curved plate configuration. The stacked curved plate configuration provides a means of creating capacitive coupling.
FIG. 1N is a front view of one embodiment of a TSAEC apparatus of FIG. 1A. TSAEC apparatus 100 of FIG. 1N is substantially similar to TSAEC apparatus 100 of FIG. 1A, and thus, similar components are not described again in detail hereinbelow. As shown in FIG. 1N, TSAEC apparatus 100 includes TSAEC enclosure 150, first end cap 130 and second end cap 132. TSAEC apparatus 100 of FIG. 1N has an enclosed configuration because TSAEC enclosure 150 encloses TSAEC apparatus 100. In one embodiment, TSAEC enclosure 150 comprises copper mesh. The copper mesh embodiment provides additional capacitive coupling, which provides additional counter-inductance when operating at or below the lowest operating frequency. In one embodiment, TSAEC apparatus 100 is designed to optimize the balance between capacitance generated by the end caps and inductance created when operating at frequencies below the lowest operating frequency. In one embodiment, TSAEC enclosure 150 comprises a radome.
FIG. 2A is a perspective view of one embodiment of a TSAEC cylindrical array. EPCTSA 200 of FIG. 2A depicts a TSAEC cylindrical array having multiple TSA in a cylindrical configuration. As shown in FIG. 2A, TSAEC cylindrical array 200 comprises first end cap 230, second end cap 232 and sixteen TSA in a cylindrical configuration. First end cap 230 is electrically coupled to lateral edges of sixteen first antenna elements of the sixteen TSA in a manner similar to TSAEC apparatus 100 of FIG. 1A. Second end cap 232 is electrically coupled to lateral edges of sixteen second antenna elements of the sixteen TSA in a manner similar to TSAEC apparatus 100 of FIG. 1A.
FIG. 2B is a top view of one embodiment of a TSAEC cylindrical array of FIG. 2A. TSAEC cylindrical array 200 of FIG. 2B is substantially similar to TSAEC cylindrical array 200 of FIG. 2A, and thus, similar components are not described again in detail hereinbelow.

## Claims

1. An apparatus, comprising:
a tapered slot antenna pair having a first antenna element and a second antenna element;
a first end cap, electrically coupled to said first antenna element, comprising conductive material;
a second end cap, electrically coupled to said second antenna element, comprising conductive material;
wherein said first end cap and said second end cap comprise a hollow plate configuration having an end cap interior region
wherein said first end cap and said second end cap are configured to provide induction-cancelling, capacitive coupling when said apparatus operates at frequencies below a theoretical cutoff frequency.

2. The apparatus of claim 1, wherein said hollow plate configuration comprises a hollow rectangular plate configuration.

3. The apparatus of claim 1, wherein said hollow plate configuration comprises a hollow oval plate configuration.

4. The apparatus of claim 1, wherein said hollow plate configuration comprises a hollow square plate configuration.

5. The apparatus of claim 1, wherein said hollow plate configuration comprises a hollow circular plate configuration.

6. The apparatus of claim 1, wherein said end cap interior region comprises a material selected from the group consisting of air, copper mesh and nonconductive material.

7. An apparatus, comprising:
at least two tapered slot antenna pairs having a cylindrical configuration, wherein each tapered slot antenna pair comprises a first antenna element and a second antenna element;
a first end cap, operatively coupled to a lateral edge of each of said first antenna elements of said at least two tapered slot antenna pairs, comprising conductive material;
a second end cap, operatively coupled to a lateral edge of each of said second antenna elements of said at least two tapered slot antenna pairs, comprising conductive material;
wherein said first end cap and said second end cap are configured to provide induction-cancelling, capacitive coupling when said apparatus operates at frequencies below a theoretical cutoff frequency.

8. An apparatus, comprising:
a tapered slot antenna pair having a first antenna element and a second antenna element;
a first end cap, electrically coupled to said first antenna element, comprising conductive material;
a second end cap, electrically coupled to said second antenna element, comprising conductive material;
wherein said first end cap and said second end cap comprise a stacked plate configuration
wherein said first end cap and said second end cap are configured to provide induction-cancelling, capacitive coupling when said apparatus operates at frequencies below a theoretical cutoff frequency.

9. The apparatus of claim 8, wherein said stacked plate configuration comprises a stacked folded plate configuration.

10. The apparatus of claim 8, wherein said stacked plate configuration comprises a stacked curved plate configuration.

11. An apparatus, comprising:
a tapered slot antenna pair having a first antenna element and a second antenna element;
a first end cap, electrically coupled to said first antenna element, comprising conductive material;
a second end cap, electrically coupled to said second antenna element, comprising conductive material;
wherein said first end cap and said second end cap comprise a folded plate configuration
wherein said first end cap and said second end cap are configured to provide induction-cancelling, capacitive coupling when said apparatus operates at frequencies below a theoretical cutoff frequency.

12. An apparatus, comprising:
a tapered slot antenna pair having a first antenna element and a second antenna element;
a first end cap, electrically coupled to said first antenna element, comprising conductive material;
a second end cap, electrically coupled to said second antenna element, comprising conductive material;
wherein said first end cap and said second end cap comprise a curved plate configuration
wherein said first end cap and said second end cap are configured to provide induction-cancelling, capacitive coupling when said apparatus operates at frequencies below a theoretical cutoff frequency.

13. An apparatus, comprising:
a tapered slot antenna pair having a first antenna element and a second antenna element;
a first end cap, electrically coupled to said first antenna element, comprising conductive material;
a second end cap, electrically coupled to said second antenna element, comprising conductive material;
wherein said first antenna element, second antenna element, first end cap, and second end cap are enclosed by an enclosure
wherein said first end cap and said second end cap are configured to provide induction-cancelling, capacitive coupling when said apparatus operates at frequencies below a theoretical cutoff frequency.

14. The apparatus of claim 13, wherein said enclosure comprises copper mesh.

15. The apparatus of claim 13, wherein said enclosure comprises a radome.

16. An antenna array, comprising:
more than one tapered slot antenna pairs arranged a cylindrical configuration, each of said tapered slot antenna pairs having a first antenna element and a second antenna element;
a first end cap, electrically coupled to each of said first antenna elements, comprising conductive material;
a second end cap, electrically coupled to each of said second antenna elements, comprising conductive material;
wherein said first end cap and said second end cap are configured to provide induction-cancelling, capacitive coupling when the antenna array operates at frequencies below a theoretical cutoff frequency.