Patent Publication Number: US-11038278-B2

Title: Lens apparatus and methods for an antenna

Description:
FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT 
     The United States Government has ownership rights in the subject matter of the present disclosure. Licensing inquiries may be directed to Office of Research and Technical Applications, Naval Information Warfare Center, Pacific, Code 72120, San Diego, Calif., 92152; telephone (619) 553-5118; email: ssc_pac_t2@navy.mil. Reference Navy Case No. 104,104. 
    
    
     TECHNICAL FIELD 
     The present disclosure technically relates to antennas. Particularly, the present disclosure technically relates to apparatuses for improving antenna performance. 
     BACKGROUND OF THE INVENTION 
     In the related art, various related art antenna systems have been implemented, such as conical and biconical antennas. Referring to  FIG. 1 , this diagram illustrates, in a side view, an antenna A, in accordance with the prior art. The antenna A typically comprises an upper antenna element  30 , a lower antenna element  40 , and a feed  50  from the lower antenna element  40  to the upper antenna element  30 . The antenna A has an antenna gain G that equals a directivity D of the antenna A multiplied by an efficiency E of the antenna A. The antenna efficiency E is the ability of the antenna A to transfer energy from a feed  50 , such as a radio-frequency (RF) cable or a feed cable, to the antenna A, including energy absorbed by the antenna A, itself, if the antenna A experiences any losses. 
     Related art techniques use multiple antennas to achieve improvement in antenna gain, thereby resulting in undue weight and complexity. Further, related art lens antennas only improve antenna gain in one particular direction. Challenges experienced in the related art include limited performance, e.g., limited gain and limited directionality, e.g., related art directional antennas, wherein electromagnetic energy is directed towards only a specific direction. Therefore, a need exists in the related art for the improving antenna performance, such as by improving antenna gain in all directions. 
     SUMMARY OF INVENTION 
     To address at least the needs in the related art, the present disclosure involves a lens apparatus for improving antenna performance, the apparatus comprising: a lens configured to at least one of focus, refocus, and refract electromagnetic energy for constructively adding gain in a far-field, the lens configured to operably couple with an antenna, whereby electromagnetic energy is omnidirectionally concentrated, whereby antenna gain and directivity are improved, whereby antenna efficiency and antenna frequency range are maintained, and whereby antenna complexity is minimized, in accordance with an embodiment of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
       The above, and other, aspects, features, and benefits of several embodiments of the present disclosure are further understood from the following Detailed Description of the Invention as presented in conjunction with the following several figures of the drawings. 
         FIG. 1  is a diagram illustrating a side view of an antenna, in accordance with the prior art. 
         FIG. 2A  is a diagram illustrating a side view of a lens apparatus, comprising lens, such as a convex lens, operably coupled with an antenna, such as a bicone antenna, in accordance with an embodiment of the present disclosure. 
         FIG. 2B  is a diagram illustrating a cross-sectional side view of a lens apparatus, comprising a lens, such as a convex lens, operably coupled with an antenna, such as a bicone antenna, wherein the lens performs at least one of focus, refocus, and refract electromagnetic energy, as shown in  FIG. 2A , in accordance with an embodiment of the present disclosure. 
         FIG. 3A  is a diagram illustrating a cross-sectional side view of a lens apparatus, comprising a lens, such as a convex lens, operably coupled with an antenna, such as a bicone antenna having a feed and a coupling feature, shown by an inset view, wherein the lens performs at least one of focus, refocus, and refract electromagnetic energy, in accordance with an embodiment of the present disclosure. 
         FIG. 3B  is a diagram illustrating a cross-sectional side view of the coupling feature in the inset view, as shown in  FIG. 3A , in accordance with an embodiment of the present disclosure. 
         FIG. 4  is a diagram illustrating a cross-sectional side view of a lens apparatus having a void, shown with example dimensions, in accordance with an embodiment of the present disclosure. 
         FIG. 5A  is a diagram illustrating a side view of an improved antenna radiation pattern effected by, and exemplifying low frequency performance of, a lens apparatus, in accordance with an embodiment of the present disclosure. 
         FIG. 5B  is a diagram illustrating a side view of an improved antenna radiation pattern effected by, and exemplifying high frequency performance of, a lens apparatus, in accordance with an embodiment of the present disclosure. 
         FIG. 5C  is a diagram illustrating a side view of an improved antenna radiation pattern  105   c  effected by, and exemplifying very high frequency performance of, a lens apparatus, in accordance with an embodiment of the present disclosure. 
         FIG. 6  is a graph illustrating a simulated antenna gain, as a function of frequency range, at lower frequencies, of an antenna operably coupled with the general or simulated lens apparatus, in relation to a measured (at chamber) antenna gain of an antenna operably coupled with a prototype lens apparatus, in accordance with embodiments of the present disclosure. 
         FIG. 7  is a graph illustrating another simulated antenna gain, as a function of frequency range, at higher frequencies, of an antenna operably coupled with the general or simulated lens apparatus, in relation to a measured (at chamber) antenna gain of an antenna operably coupled with the prototype lens apparatus, in accordance with embodiments of the present disclosure. 
         FIG. 8  is a graph illustrating a return-loss, as a function of frequency range, of an antenna operably coupled with a lens apparatus, in accordance with embodiments of the present disclosure. 
         FIG. 9A  is a diagram illustrating a cross-sectional side view of a lens apparatus that is scalable in at least one of size and shape in at least one plane, wherein the lens apparatus has an aspect ratio, for example, in accordance with an alternative embodiment of the present disclosure. 
         FIG. 9B  is a diagram illustrating a cross-sectional side view of a lens apparatus, that is scalable in at least one of size and shape in at least one plane, wherein the lens apparatus has a higher aspect ratio than that shown in  FIG. 13A , for example , in accordance with an alternative embodiment of the present disclosure. 
         FIG. 9C  is a diagram illustrating a cross-sectional side view of a lens apparatus, that is scalable in at least one of size and shape in at least one plane, wherein the lens apparatus has a lower aspect ratio than that shown in  FIG. 13A , for example, in accordance with an alternative embodiment of the present disclosure. 
         FIG. 10  is a diagram illustrating side views, and cross-sectional side views, of various lens apparatuses, implemented with various lens apparatuses, in accordance with various alternative embodiments of the present disclosure. 
         FIG. 11  is a flow diagram illustrating a method of providing a lens apparatus for improving performance of an antenna, in accordance with an embodiment of the present disclosure. 
         FIG. 12  is a flow diagram illustrating a method of improving performance of an antenna by way of a lens apparatus, in accordance with an embodiment of the present disclosure. 
     
    
    
     Corresponding reference numerals or characters indicate corresponding components throughout the several figures of the drawings. Elements in the several figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be emphasized relative to other elements for facilitating understanding of the various presently disclosed embodiments. Also, common, but well-understood, elements that are useful or necessary in commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present disclosure. 
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
       FIGS. 2A and 2B , illustrate, in a side view, a lens apparatus  100 , comprising a lens  101  and a coupling feature  102 . The lens apparatus  100  shown in  FIGS. 2A and 2B  is operably coupled with an antenna A′, which in this embodiment is a bicone antenna, comprising an upper antenna element  30 ′ and a lower antenna element  40 ′. The lens  101  may be configured to focus, refocus, and/or refract electromagnetic energy for constructively adding gain in a far-field. The lens  101  is configured to operably couple with an antenna A′, whereby electromagnetic energy is omnidirectionally concentrated, whereby antenna gain and directivity are improved, whereby antenna efficiency and antenna frequency range are maintained, and whereby antenna complexity is minimized. 
     Still referring to  FIG. 2A , the lens apparatus  100  maximizes the directivity and antenna efficiency of an antenna A′ by allowing electromagnetic energy to act as a travelling wave by way of a logarithmic curve that is extended across the antenna A′ in an x-plane P x , shown in relation to a z-plane direction P z . The lens  101  comprises at least one shape of a spheroidal shape, a convex shape, a toroidal shape, a ring toroidal shape, a horn toroidal shape, a spindle toroidal shape, a lemniscate shape, a lemnsicate of Bernoulli shape, a lemnsicate of Booth shape, lemniscate of Gerono shape, a paraboloid of revolution shape, and a hyperboloid of revolution shape, for at least one of focusing, refocusing, and refracting electromagnetic energy being radiated from the antenna A′ in the far-field, thereby increasing antenna directivity. In addition, the lens  101  retains the upper antenna element  30 ′ in relation to the lower antenna element  40 ′. The lens  101  is configurable for focusing energy in a given implementation by configuring the lens  101  in relation to parameters, such as shape, material, dielectric properties, and tangent loss properties. The lens  101  has a dielectric constant in a range of at least approximately 2, e.g., approximately 2.1, preferably in a range of at least approximately 5, and at least one tangent loss property, e.g., a tangent loss in a range of approximately 0.0003 to approximately 0.0004. For example, the lens  101  may be made of polypropylene. However, it is to be understood that the lens  101  may be made of other materials having a refractive index appropriate for any given implementation of the lens apparatus  100 . 
     Referring to  FIG. 2B , this diagram illustrates, in a side view, where the lens  101  is depicted as being transparent so as to reveal the coupling feature  102 . Also shown in  FIG. 2B  are electromagnetic rays  202 . As can be seen in  FIG. 2B , the lens apparatus  100  focuses and refracts the electromagnetic energy, emanating from a feed  50 ′. 
     Referring to  FIG. 3A , this diagram illustrates, in a cross-sectional side view, an embodiment of the lens apparatus  100 . The electromagnetic energy travels (is transmitted) from the feed  50 ′, such as an RF cable or a feed cable, into the antenna A′, and, subsequently, travels (is transmitted) into at least one of the air, a vacuum, and a partial vacuum. The feed  50 ′, such as an RF cable or a feed cable, is impedance-matched to the lens material, by example only. Once the electromagnetic energy begins to exit (commences transmission from) the antenna, the lens  101  concentrates and transmits the electromagnetic energy into the air. 
     Referring to  FIG. 3B , this diagram illustrates, in a cross-sectional side view, the coupling feature  102  in the inset view I, as shown in  FIG. 3A , in accordance with an embodiment of the lens apparatus  100 . This embodiment of the coupling feature  102  is shown with example dimensions (in both units of centimeters and inches), for accommodating the feed  50 ′ and coupling the upper antenna element  30 ′ with the lower antenna element  40 ′. The lens  101  comprises a material having an index of refraction that causes the electromagnetic energy to change direction, e.g., in a desired direction. The index of refraction for the lens material is expressed as follows: index of refraction n=(speed of light in a vacuum)/(speed of light in the material)=c/v. 
     According to Snell&#39;sLaw of Refraction, when light travels from a material with a refractive index n 1  into a material with a refractive index n 2 , the refracted ray, the incident ray, and the ray, corresponding to a vector that is normal in relation to the interface between the two materials, all lie in the same plane; and the angle of refraction θ 2  is related to the angle of incidence θ 1  by the expression: n 1  sin θ 1 =n 2  sin θ 2 . By example only, the lens  101  changes direction of the electromagnetic energy from the antenna A′ into the air by an angular amount that is based approximately on Snell&#39;s Law, e.g., wherein the incident energy θ 1  changes direction to θ 2  approximately based on the index of refraction of the lens material and the air (or vacuum or partial vacuum). In antennas, due to antenna theory reciprocity, an opposite relationship is true if the electromagnetic energy is travelling in an opposite direction. 
     The lens  101  may take the form of various general lenses. Suitable example shapes of the lens  101  include, but are not limited to, a spheroidal shape, a convex shape, a toroidal shape, a ring toroidal shape, a horn toroidal shape, a spindle toroidal shape, a lemniscate shape, a lemnsicate of Bernoulli shape, a lemnsicate of Booth shape, lemniscate of Gerono shape, a paraboloid of revolution shape, and a hyperboloid of revolution shape. 
       FIG. 4  illustrates, in a cross-sectional side view, an embodiment of the lens  101 , shown with example dimensions (in both units of centimeters and inches). The void V in the lens  101  is nearly completely filled with the coupling apparatus  102 , as shown in  FIG. 3B . In other words, the void V accommodates the coupling feature  102  disposed between the lens  101  and a feed  50 ′ of the antenna A′ as shown in  FIG. 3B . 
     Referring back to  FIG. 3B , the coupling feature  102  is disposed to materially fill in an entire volume from the feed  50 ′ to the lens  101 . The embodiment of the coupling feature  102  shown in  FIG. 3B  is cylindrical in shape so as to fit within the void V and with nearly conical depressions in opposite sides to accommodate the upper antenna element  30 ′ and the lower antenna element  40 ′ as shown in  FIG. 3B . However, it is to be understood that the coupling feature  102  may have any desired shape (e.g., cube shape, rectanguloid shape) that fits within the volume between the upper antenna element  30 ′ and the lower antenna element  40 ′ and the lens  101 . The coupling feature  102  comprises the same material as the lens  101  and has a tight tolerance in relation to the feed  50 ′, whereby the coupling feature  102  is integrated with the lens  101 , and whereby fabrication of the lens apparatus  101  is facilitated. The coupling feature  102  accommodates the feed  50 ′ and couples the upper antenna element  30 ′ with the lower antenna element  40 ′. 
       FIGS. 5A, 5B, and 5C  respectively illustrate, an improved antenna radiation pattern  105   a  within an ultra-high frequency (UHF) band (i.e., between 300 megahertz (MHz) and 3 gigahertz (GHz)), the X-band frequency (i.e., approximately 7.0-11.2 GHz), and the Ku band (approximately 12-18 GHz) of an omnidirectional antenna, bicone antenna as modified by an embodiment of the lens apparatus  100 . The lens  101  focuses and refracts electromagnetic energy, and the performance of the lens apparatus  100  improves as the lens size becomes electrically larger in relation to the wavelength (wavelength=velocity of light/frequency), in accordance with an embodiment of the present disclosure. 
     Referring to  FIG. 6 , this graph illustrates a simulated antenna gain, as a function of frequency range, at low frequencies and higher low frequencies, of a simulated antenna operably coupled with the simulated lens apparatus, in relation to a measured (at chamber) antenna gain of an antenna A′ operably coupled with the embodiment of the lens apparatus  100  shown in  FIG. 3A . The data in  FIG. 6  is obtained from tests conducted to validate data simulated by the CST Microwave Studio® software. As such, the measured gain of the antenna A′ is close to the simulated gain of the CST Microwave Studio® software at low frequencies and higher low frequencies. 
     Referring to  FIG. 7 , this graph illustrates a simulated antenna gain, as a function of frequency range, such as low frequencies, medium frequencies, and a high range of high frequencies, of a simulated antenna operably coupled with the simulated lens apparatus, as shown in  FIG. 3A , in relation to a measured (at chamber) antenna gain of an antenna A′ operably coupled with the embodiment of the lens apparatus  100  shown in  FIG. 3A . As such, the measured gain of the antenna A′ is close to the gain simulated by the CST Microwave Studio® software low frequencies, medium frequencies, and a high range of high frequencies. 
     Referring to  FIG. 8 , this graph illustrates a return-loss (in dB), as a function of frequency range (in Hz), e.g., in a range of approximately 10 MHz to approximately 10 GHz, of an antenna A′ operably coupled with a lens apparatus  100 , in accordance with embodiments of the present disclosure. Return loss is a loss of power in a signal that is returned or reflected by a discontinuity in an antenna transmission. By example only, the return loss is approximately −12.44 dB at approximately 1.912 GHz by implementing the lens apparatus  100 . 
       FIGS. 9A, 9B, and 9C  illustrate, in a cross-sectional side view, different embodiments of the lens apparatus  100  with different embodiments of bicone, omnidirectional antennas. The lens apparatus  100  may be used with any known ultrawideband antenna. 
       FIG. 10  is a diagram illustrating side views, and cross-sectional side views, of various lens apparatuses  100 , comprising lenses  101 , such as a convex lens, implemented with various antennas A′, such as bi-element antennas, in accordance with various alternative embodiments of the present disclosure. 
     Referring to  FIG. 11 , this flow diagram illustrates a method M 1  of providing a lens apparatus  100  for improving performance of an antenna A′, in accordance with an embodiment of the present disclosure. The method M 1  comprises: providing a lens  101  configured to at least one of focus, refocus, and refract electromagnetic energy for constructively adding gain in a far-field, providing the lens  101  comprising configuring the lens  101  to operably couple with an antenna A′, as indicated by block  1501 , whereby electromagnetic energy is omnidirectionally concentrated, whereby antenna gain and directivity are improved, whereby antenna efficiency and antenna frequency range are maintained, and whereby antenna complexity is minimized. 
     Still referring to  FIG. 11 , in the method M 1 , providing the lens  100 , as indicated by block  1500 , comprises configuring the lens  100  in at least one shape of a spheroidal shape, a convex shape, a toroidal shape, a ring toroidal shape, a horn toroidal shape, a spindle toroidal shape, a lemniscate shape, a lemnsicate of Bernoulli shape, a lemnsicate of Booth shape, lemniscate of Gerono shape, a paraboloid of revolution shape, and a hyperboloid of revolution shape; providing the lens  100 , as indicated by block  1501 , comprises providing at least one material of polypropylene and the like; providing a lens  100 , as indicated by block  1501 , comprises configuring the lens  100  with at least one dielectric property, such as a dielectric constant in a range of at least approximately 2, e.g., approximately 2.1, preferably in a range of at least approximately 5; providing lens  100 , as indicated by block  1501 , comprises configuring the lens with at least one tangent loss property, such as a tangent loss in a range of approximately 0.0003 to approximately 0.0004; providing the lens  100 , as indicated by block  1501 , comprises configuring the lens  100  with a refractive index in a range of approximately 1.4 to approximately 10. 
     Still referring to  FIG. 11 , the method M 1  further comprises providing a coupling feature  102 , as indicated by block  1502 , for coupling an upper antenna element  30 ′ with a lower antenna element  40 ′ and for accommodating a feed  50 ′. Providing the coupling feature  102 , as indicated by block  1502 , comprises configuring the coupling feature  102  with at least one of a refractive index matching that of the lens  101  and a material matching that of the lens  101 . 
     Still referring to  FIG. 11 , the method M 1  further comprises providing the antenna A′ operably coupled with the lens  101 , as indicated by block  1503 , wherein providing the antenna A′, as indicated by block  1503 , comprises providing at least one of a biconical antenna, an inverse biconical antenna, a dish antenna, an omnidirectional antenna, an omnidirectional antenna system, a spherical antenna, a bi-spherical antenna, an ellipsoidal antenna, a bi-ellipsoidal antenna, a bow-tie antenna, a diamond-shaped antenna, a bi-diamond-shaped antenna, a semi-circular antenna, a bi-semicircular antenna, a circular antenna, a bi-circular antenna, an elliptical antenna, and a bi-elliptical antenna. 
     Referring to  FIG. 12 , this flow diagram illustrates a method M 2  of improving performance of an antenna A by way of a lens apparatus  100 , in accordance with an embodiment of the present disclosure. The method M 2  comprises: providing a lens apparatus  100  for improving antenna performance, as indicated by block  1600 , providing the lens apparatus  100  comprising: providing a lens  101  configured to at least one of focus, refocus, and refract electromagnetic energy for constructively adding gain in a far-field, providing the lens  101  comprising configuring the lens  101  to operably couple with an antenna A′, as indicated by block  1601 ; A′, as indicated by block  1602 ; and at least one of focusing, refocusing, and refracting the electromagnetic energy from the antenna A′ to the air by the lens  101 , as indicated by block  1603 , thereby omnidirectionally concentrating electromagnetic energy, thereby improving antenna gain and directivity, thereby maintaining antenna efficiency and antenna frequency range, and thereby minimizing antenna complexity. 
     Still referring to  FIG. 12 , in the method M 2 , providing the lens apparatus  100 , as indicated by block  1600 , further comprises providing a coupling feature  102  for coupling an upper antenna element  30 ′ with a lower antenna element  40 ′ and for accommodating a feed  50 ′. Providing the coupling feature  102  comprises configuring the coupling feature  102  with at least one of a refractive index matching that of the lens  101  and a material matching that of the lens  101 . 
     Still referring to  FIG. 12 , in the method M 2 , providing the lens apparatus  100 , as indicated by block  1600 , further comprises providing the antenna A′ operably coupled with the lens  101 , wherein providing the antenna A′ comprises providing at least one of a biconical antenna, an inverse biconical antenna, a dish antenna, an omnidirectional antenna, an omnidirectional antenna system, a spherical antenna, a bi-spherical antenna, an ellipsoidal antenna, a bi-ellipsoidal antenna, a bow-tie antenna, a diamond-shaped antenna, a bi-diamond-shaped antenna, a semi-circular antenna, a bi-semicircular antenna, a circular antenna, a bi-circular antenna, an elliptical antenna, and a bi-elliptical antenna. 
     In embodiments of the present disclosure, the lens apparatus  100  may be matched in impedance with the antenna A′. The lens apparatus  100  facilitates low-level and high-level testing of an antenna system and associated radio frequency (RF) components, e.g., in a production setting, wherein measurement of quality and fidelity is improved, facilitates processing and presenting measured test data, and facilitates modifying and improving test procedures. 
     In embodiments of the present disclosure, the lens apparatus  100  is operable with an antenna, whereby a communications range is improvable. The lens apparatus  100  is operable by facilitating obtaining measured data for verifying system performance and providing insight into how the antenna system will behave in real-world conditions. The lens apparatus  100  is operable by facilitating testing performance of an antenna and RF system by using various RF test equipment, such as a vector network analyzer (VNA), a spectrum analyzer, and an RF signal generator, to test performance of antenna and RF system. The lens apparatus  100  is operable by facilitating test component performance at different temperatures as per mission requirements by using a thermal chamber. 
     It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.