HYBRID NOTCH ANTENNA

Abstract

Described is a hybrid notch antenna comprising a flared notch antenna structure and a transverse electromagnetic (TEM) horn structure having walls disposed through or attached to the notch antenna structure member such that the TEM horn is integrated with the notch antenna to form a hybrid TEM/notch antenna.

Claims

1. A hybrid notch antenna comprising: a flared notch element provided from a member disposed in a first plane and having a notch therein; at least two conductive walls disposed through, or attached to, the member on either side of the notch.

2. The antenna of claim 1, wherein the at least two conductive walls form a transverse electromagnetic (TEM) horn structure integrated with the flared notch element.

3. The antenna of claim 2, wherein the TEM horn structure is provided having a shape and position selected to affect an impedance of the hybrid notch antenna to extend a bandwidth of the hybrid notch antenna.

4. The antenna of claim 2 wherein a dielectric insulator is disposed in the notch of said flared notch element.

5. The antenna of claim 4 wherein said dielectric insulator encapsulates the notch of said flared notch element.

6. The antenna of claim 2, wherein the flared notch element and the integrated TEM horn structure form a first antenna element.

7. The antenna of claim 6 further comprising additional transmit antenna elements, wherein each additional antenna element is formed from an additional flared notch element and an additional TEM horn structure.

8. The antenna of claim 6 further comprising second, third, and fourth antenna elements, wherein each of the second, third, and fourth antenna elements are formed from second, third, and fourth flared notch elements and TEM horn structures, respectively.

9. The antenna of claim 8, wherein the first, second, third, and fourth transmit antenna elements are oriented to form a four-antenna rosette.

10. The system of claim 9, wherein each of the plurality of hybrid TEM/notch antenna elements are configured to generate various polarizations in response to alternating amplitudes and phases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The foregoing and other objects, features and advantages will be apparent from the following more particular description of the embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the embodiments.

[0015] FIG. 1 is an isometric view of hybrid transverse electromagnetic (TEM)/notch antenna according to an example embodiment.

[0016] FIG. 2A is another isometric view of hybrid transverse electromagnetic (TEM)/notch antenna illustrating sample dimensions according to an example design and embodiment.

[0017] FIG. 2B illustrates sample performance metric for the example TEM/notch antenna of FIG. 2A according to example embodiments.

[0018] FIG. 3 is an isometric view of a plurality or array of hybrid TEM/notch antennas disposed symmetrically about an axis according to embodiments described herein.

[0019] FIG. 4 is a front view of the array of FIG. 3 according to embodiments described herein.

[0020] FIG. 5. is an isometric view of a single hybrid antenna in which the outer edges of the notch are shaped to accept TEM plates, and which uses dual coaxial feeds and a dielectric insert according to an example embodiment.

DETAILED DESCRIPTION

[0021] Referring to FIG. 1, a hybrid transverse electromagnetic (TEM)/notch antenna 100 comprises a flared notch element 110 disposed over a ground plate 120 and in a first plane perpendicular to the ground plane 120. The flared notch element 110 comprises first and second members 115a-b having first-member and second-member tapered surfaces 106a-b. The first member 115a is positioned across from the second member 115b such that the first-member tapered surface 106a faces the second-member tapered surface 106b. The first and second members 115a-b (collectively, a notch member 115) are positioned to define a notch 116.

[0022] In embodiments, a first conductive wall 105a and a second conductive wall 105b are disposed through the first and second members 115a-b, respectively, and are aligned along a second plane perpendicular to the first plane. The pair of first and second conductive walls 105a-b can be considered a transverse electromagnetic (TEM) horn structure integrated with the flared notch element 110. The TEM horn structure 105a-b is provided having a shape selected to affect the impedance of the hybrid notch antenna 100 to increase the bandwidth of the hybrid notch antenna 100.

[0023] In embodiments, the notch member 115 can have a height H.sub.NE extending from the ground plane 120. The notch member 115 can have a width W.sub.NE. These dimensions can be made as large as possible (subject to installation and packaging constraints) to obtain the widest possible bandwidth.

[0024] In additional embodiments, the TEM horn structures 105a-b can have a height H.sub.TEM. Additionally, the TEM horn structures 105a-b are spaced away from the ground plane 120 (i.e., such that the TEM horn structures 105a-b are not in physical contact with the ground plane 120). Further, the TEM horn structures 105a-b can have a width W.sub.TEM. In some embodiments, the TEM horn structures 105a-b can be slanted from first and second top corners 126a-b toward first and second bottom corners 126a-b of the notch member 115. The TEM horn size, interior angle, and position relative to the ground plane are adjusted using numerical simulations to optimize performance in terms of VSWR vs. frequency and/or radiation pattern shape.

[0025] In embodiments, the ground plane 120, the notch plates 115a and 115b, and the TEM plates 105a and 105b may be any material such as Copper or Aluminum, that is a good conductor at the frequencies of operation.

[0026] The hybrid transverse electromagnetic (TEM) horn/notch antenna 100 can be configured, via the flared notch element 110 and the TEM horn structures 105a-b, to provide greater bandwidth than traditional notch antennas. The TEM horn structures 105a-b form a tuning element that increases the bandwidth of the notch 110, resulting in a reduced VSWR at low frequencies, thus extending the low frequency cutoff (the lowest frequency at which VSWR is within acceptable limits).

[0027] For example, referring to FIG. 2A, illustrating dimensions of the notch member 115 and the TEM horn structures 105a-b, the TEM/notch antenna 100 can experience a return loss vs. frequency from a 50 Ohm source as shown in FIG. 2B. Since 10 dB return loss is a generally-accepted rule-of-thumb for being able to use an antenna for high-power radiation, it is evident that without the TEM plates 105a-b, the notch 110 is only useful for frequencies above 7 GHz, whereas with the TEM plates added, it is useful for frequencies of 4.5 GHz and above. The combined structure reduced the low-end cutoff by about without increasing the overall antenna size as compared to the notch alone. Therefore, a simple notch antenna would need to be approximately 4/3 times as large in all linear dimensions to achieve the same performance. It is anticipated that the methods proposed by Schuneman (U.S. Pat. No. 6,850,203 B1), Fisher (U.S. Pat. No. 7,088,300 B2), McGrath (U.S. Pat. No. 7,652,631 B2) and others may be combined with this invention to obtain further performance improvement.

[0028] Referring to FIG. 3, a hybrid transverse electromagnetic (TEM)/notch antenna array 300 comprises a rosette of hybrid TEM/notch antenna elements 310a-d (hybrid antenna elements, collectively 310) disposed over a ground plane 320. Although four hybrid TEM/notch antenna elements are shown, a skilled artisan understands that an antenna array (e.g., the array 300) can comprise any number of hybrid antenna elements 310. Each of the hybrid antenna elements 310 can be substantially similar to the hybrid transverse electromagnetic (TEM)/notch antenna 100 of FIG. 1. For example, each of the hybrid antenna elements 310a-b comprises a notch member 315 (e.g., the notch member 115 of FIG. 1) comprising a notch 316. The notch member 315 is disposed over the ground plane 320 and in a first plane perpendicular to the ground plane 320. Additionally, TEM horn structures 305 can be integrated with the notch members 315. As shown here, the TEM horns are plates 305a and 305b associated with notch 310a; plates 305c and 305d associated with notch 310b; plates 305e and 305f associated with notch 310c; and plates 305g and 305h associated with notch 310d. Plates may be trimmed along their intersections, for example plates 305a and 305h.

[0029] Referring to FIG. 4, hybrid antenna elements 410a-d are shown oriented diagonally with respect to an observer. A combination of the four elements 410a-d can produce arbitrary antenna polarizations. For radiation in or near the direction perpendicular to the ground plane (e.g., ground plane 120 of FIG. 1), a first antenna pair comprising elements 410a & 410d, with feeds at locations 430a & 430d, produces electric fields that are oriented orthogonal to a second antenna pair comprising elements 410b & 410c, with feeds at locations 430b & 430c. Pluses and minuses indicate the orientation of the feed connections. By controlling the relative phases of each pair, arbitrary polarizations may be produced. For example, if feeds 430a through 430d are driven with relative phases of 0, 0, 180, and 180, the resulting radiation will be vertically polarized. Relative phases of 0, 180, 180, and 0 will produce horizontal polarization. Relative phases of 0, 90, 180, and 270 or 0, 90, 180, and 270 will produce circular polarization. Other combinations of phases with unequal amplitudes may produce any linear or elliptical polarization.

[0030] Referring to FIG. 5, a single flared notch 500 comprises notch arms 515a-b having interior surfaces shaped according to a typical exponential shape. Outside surfaces of the notch arms 515a-b are trimmed to accept metal plates 505a and 505b that form a TEM horn portion. The plates 505a-b may be attached to the notch arms 515a-b by any convenient method, for example, soldering, welding, bonding, or with fasteners such as screws or rivets. The plates 505a-b may be formed as bent pieces of sheet metal, with the additional portions 507a and 507b included for mechanical rigidity. An interior of the notch 500 may be partially filled with a dielectric insert 540. The dielectric insert 540 can: (1) ensure precise spacing between the arms 515a and 515b; and (2) allow the antenna to radiate high power. The dielectric insert 540 can comprise an insulator material that has a high dielectric breakdown strength and low radio frequency loss, for example thermoset resins. An additional feature is the use of twin feeds 550a and 550b configured to supply equal signals with opposite phase, to increase a supplied radio frequency power above the limit of a single coaxial input, as described in McGrath et al. (U.S. application Ser. No. 15/896,668, filed on Feb. 14, 2018).

[0031] One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.