Protective superstrate for planar array antennas

Abstract

A superstate for a planar array antenna that includes a first major surface and an opposing surface facing a substrate of the planar array antenna where the opposing surface includes at least one first surface location and at least one second surface location that is positioned closer to the substrate than the at least one first surface location.

Description

PROTECTIVE SUPERSTRATE FOR PLANAR ARRAY ANTENNASCross-Reference to Related Applications

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63 / 634714 filed April 16, 2024, the content of which is incorporated herein by reference in its entirety.Field

[0002] The present disclosure relates generally to a protective superstrate for planar array antennas and more particularly to a protective superstrate for planar array antennas that facilitate improved antenna performance.Background

[0003] Planar antenna arrays, including those used as terminals for Low Earth Orbit (LEO) satellite communications, typically require continual adjustment of the receiving direction due to movement of the signal producer (e.g., satellite). Such adjustment can be done electronically by tuning (scanning) the beam of a phased array formed by a large number of planar antennas. In this regard, a phase array tends to be the most sophisticated and expensive part of the user terminal, which can be mobile or stationary and can vary in size. Since damage of a single patch antenna can make the whole unit inoperable, the structure requires mechanical and environmental protection. Typical radomes or covers are made of plastic which may be not sufficiently robust. In addition, such materials may have high loss tangent and thus introduce unwanted radio frequency (RF) loss. Finally, plastics can be subject to environmental deterioration, for example, due to heat or ultra-violet (UV) exposure.

[0004] In contrast to plastic, glass offers enhanced mechanical and environmental protection. However, glass has relatively high dielectric permittivity, and as such, a glass superstrate in the immediate proximity of planar antennas may significantly reduce performance of the antenna array due to excitation of surface waves in the substrate and superstrate. Accordingly, it is desirable to design a protective cover or superstrate that incorporates the protective advantages of glass while avoiding negative RF effects of a high permittivity superstrate.SUMMARY

[0005] Embodiments disclosed herein include A superstate for a planar array antenna. The superstate includes a first major surface and at least one opposing surface configured to face a substrate of the planar array antenna. The at least one opposing surface includes at least one first surface location and at least one second surface location that is configured to be positioned closer to the substrate than the at least one first surface location.

[0006] Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the disclosed embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0007] It is to be understood that both the foregoing general description and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and character of the claimed embodiments. The accompanying drawings are included to provide further understanding and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description serve to explain the principles and operations thereof.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a schematic top view of a prior art antenna array;

[0009] FIG. 2 is a schematic side view of an antenna array positioned to receive a wave at a scan angle (0);

[0010] FIGS. 3a-3f are schematic side cutaway views of exemplary protective superstrates in accordance with embodiments disclosed herein;

[0011] FIGS. 4a-4b are charts showing acceptable substrate and superstrate thicknesses for a given antenna configuration in accordance with embodiments disclosed herein;

[0012] FIG. 5 is a series of charts showing real and imaginary parts of input impedance for a given antenna element in accordance with embodiments disclosed herein; and

[0013] FIG. 6 is a series of charts showing real and imaginary parts of input impedance for a given antennal element in accordance with embodiments disclosed herein.DETAILED DESCRIPTION

[0014] Reference will now be made in detail to the present preferred embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0015] Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, for example by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0016] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0017] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0018] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0019] Planar antenna arrays typically include a plurality of planar antennas distributed across a planar surface. These arrays also typically include a substrate, upon which the planarantennas are distributed, and cover or superstate, which can provide mechanical and environmental protection to the antennas. In such configurations, an air gap between the antenna substrate and the cover or superstate can improve performance by, for example, broadening the impedance matching angle for uplink and / or downlink satellite communications. However, in these configurations, the airgap, which may only be in the range of about 0.5 millimeters to about 1 millimeter, must be maintained accurately over the entire surface area of the array which may, for example, be about 50 centimeters by about 70 centimeters.

[0020] In addition, modem array designs may include at least two types of antenna elements that are interleaved on the same substrate. Such configurations can reduce the overall area of the antenna array while accommodating both transmitter and receiver (or satellite uplink and downlink) arrays using different frequencies (e.g., 20 GHz and 30 GHz). For example, FIG. 1 shows a schematic top view of a prior art antenna array 100 comprising two such types of antenna elements.

[0021] Such designs must also account for continual movement of a signal producer / receiver (e.g., satellite) relative to the array, which, in turn, affects the angle (i.e., scan angle) of the signal between both. FIG. 2 shows a schematic side view of an antenna array 100 positioned to receive a wave 200 at a scan angle (0). For example, a satellite positioned directly over an array corresponds to a scan angle of zero whereas a satellite posited closer to the horizon corresponds to a higher scan angle. As scan angles increase, signal quality can be impacted from both an attenuation and impedance matching perspective. This can particularly be the case when a material having relatively high dielectric permittivity, such as glass, is used in a cover or superstrate.

[0022] Applicants have found that operation of such antenna arrays can be optimized with a cover or superstrate having a variable thickness (i.e., different thicknesses in different areas of the array). For example, a glass cover or superstrate having a variable thickness can on, the one hand, provide adequate mechanical and environmental protection to the antenna arrays while at the same time, impart dielectric permittivity and impedance matching appropriate for varying antenna elements and scan angles. In certain exemplary embodiments, such glass covers or superstrates can incorporate or be coupled with a relatively low dielectric permittivity material, such as glass soot.

[0023] FIGS. 3a-3f are schematic side cutaway views of exemplary protective superstrates lOOa-f in accordance with embodiments disclosed herein. Each superstrate includes a first major surface 102a-102f and at least one opposing surface 104a-104f configured to face asubstrate of a planar array antenna. Each of the at least one opposing surfaces includes at least one first surface location 106a-106f and at least one second surface location 108a-108f. The at least one second surface location 108a-108f is configured to be positioned closer to the substrate (not shown) than the at least one first surface location 106a-106f.

[0024] Each of the superstates of FIGS. 3a-3f include a glass layer 110a-l lOf, wherein each glass layer 110a- 11 Of comprises the first major surface 102a-102f and an opposing surface 104a-104f that includes the at least one first surface location 106a-106f. In addition, the glass layers l lOa-l lOd and 11 Of of FIGS. 3a-3d and 3f each comprise at least one second surface location 108a-108d and 108f, wherein the glass layers HOa-l lOd ofFIGS. 3a-3d each comprise a plurality of first surface locations 106a-106d and second surface locations 108a-108d and the glass layer 1 lOf of FIG. 3f comprises a first bent edge and a second bent edge, each of the first and second bent edges comprising a second surface location 108f at each opposing end of the glass layer 11 Of. The plurality of first surface locations 106a- 106d and second surface locations 108a-108d of FIGS. 3a-3d extend along a repeating pattern of opposing surfaces 104a-104d. In particular, the repeating pattern of FIGS. 3a and 3b comprises prisms, the repeating pattern of FIG. 3c comprises cylinders, and the repeating pattern of FIG. 3d comprises hemispheres.

[0025] In contrast to the superstates of FIGS. 3a-3d and 3f, the superstate of FIG. 3e comprises a glass soot layer 112 extending between the glass layer l lOe and a substrate (not shown), the glass soot layer 112 comprising at least one second surface location 108e.

[0026] In FIGS. 3a-3f, the closest distance between the first major surfaces 102a-102f and the first surface location(s) 106a-106f of the second major surfaces 104a-104f is represented by ds of FIG. 3 a and the difference in distance to the substrate (not shown) between the first surface location(s) 106a-106f and the second surface locations 108(a)- 108(f) is represented by dpat of FIG. 3a. In certain exemplary embodiments, the second surface location(s) 108(a)- 108(f) are at least about O.O5Xo closer, such as at least about O.O6Xo closer, and further such as at least about O.O7Xo closer, including from about O.O5Xo closer to about 0.1 OXo closer to the substrate than the first surface location(s) 106a-106f, wherein Xo is the wavelength of a wave received or transmitted by the antenna. In certain exemplary embodiments, a closest distance between the first major surface 102a-102f and the first surface location(s) 106a-106f is not greater than about O.O4Xo, such as not greater than about O.O3Xo, including from about O.O2Xo to about O.O4Xo.

[0027] In certain exemplary embodiments, Xo is from about 1.0 to about 1.5 centimeters, corresponding to a frequency range of from about 20 gigahertz (GHz) to about 30 GHz. In such embodiments, the second surface location(s) 108(a)- 108(f) are, for example, at least about0.5 millimeters closer, such as at least about 0.6 millimeters closer, and further such as at least about 0.7 millimeters closer, including from about 0.5 millimeters closer to about 1.5 millimeters closer to the substrate than the first surface location(s) 106a-106f. In these embodiments, a closest distance between the first major surface 102a-102f and the first surface location(s) 106a-106f is not greater than about 0.6 millimeters, such as not greater than about 0.5 millimeters, including from about 0.3 millimeters to about 0.6 millimeters.

[0028] Embodiments disclosed herein include methods of making the superstrates 100a- 1 OOf of FIGS. 3a-3f. For example, the glass layers 110a-l lOf of the superstrates lOOa-lOOf of FIGS. 3a-3f can be made by forming the patterns shown in FIGS. 3a-3f, including forming the first surface location(s) 106a-106f and the second surface locations 108(a)- 108(f). For example, the patterns shown in FIGS. 3a-3f can be formed by hot pressing a glass precursor material in accordance with methods known to persons having ordinary skill in the art. Such methods can also include ion exchanging the glass layers 110a- 11 Of in accordance with methods known to persons having ordinary skill in the art.

[0029] The superstate lOOe of FIG. 3e, which includes a glass soot layer 112, can be made by pressing a soot precursor material and / or adhering the glass soot layer 112 to the glass layer 1 lOe. The adhering can be accomplished, for example, by laser welding the glass soot layer 112 to the glass layer 1 lOe in accordance with methods known to persons having ordinary skill in the art. Such methods may also include heating the glass layer 1 lOe and the glass soot layer 112 to a temperature of at least about 1300°C, such as a temperature of from about 1300°C to about 1500°C. Such heating can increase the density of the glass soot layer 112 from, for example, about 0.7 to about 0.9 grams per cubic centimeter to, for example, about 1.0 to about 1.2 grams per cubic centimeter.

[0030] Alternatively, the superstrate 1 OOe may be prepared by using a paste of soot particles and a solvent such as water or a polar solution (e.g., acetone of methyl ethyl ketone) or with an organic carrier (e.g., pine oil or polymer material). The paste can, for example, be dried at temperatures below about 100°C ( in the case of polar solutions) or de-bonded at organic carrier decomposition temperatures (e.g., about 600°C) and then pre-sintered to higher density as described above to achieve better adhesion to the glass substrate. The soot layer thickness can be controlled by controlling the paste viscosity or by controlling deposition processes using, for example, screen printing.

[0031] The superstrate 1 OOe of FIG. 3e can also be made by vapor depositing a soot precursor material on the glass layer 1 lOe in accordance with methods known to persons having ordinary skill in the art. For example, the soot precursor material can be deposited using a constant orvarying delivery rate of at least one of a fuel, an oxidant, or the soot precursor material. Varying the delivery rate of at least one of a fuel, an oxidant, or a soot precursor material can enable the deposition of a glass soot layer comprising a non-uniform density. This can, in turn, result superstates having differing dielectric permittivity in different areas of the superstate.

[0032] FIGS. 4a-4b are charts showing acceptable substrate and superstate thicknesses for a given antenna configuration in accordance with embodiments disclosed herein. Specifically, the shaded areas of FIGS. 4a-4b show acceptable combinations of substrate and superstate thicknesses for a maximum scan angle (0) of 45°, wherein FIG. 4a shows maximum acceptable combinations where no air gap is present between the superstate and the antennas and FIG. 4b shows maximum acceptable combinations where an air gap is present between the superstate and the antennas. As can be seen by comparing FIGS. 4a and 4b, the air gap enables a larger range of superstate thicknesses for a given maximum scan angle.

[0033] Examples

[0034] Embodiments disclosed herein will be further described with reference to the following non-limiting examples.

[0035] Example 1:

[0036] A simulation of the effect of substrate and superstate properties on performance of a large antenna array was performed, wherein no air gap was present between the superstate and the antennas. Specifically, a planar antenna having a substrate and a superstate with permittivities of 2.55 and 5.0, respectively, was simulated to be pattered with an array of antennas, each antenna having a width (W) of O.OO2Xo, a length (L) given in FIG. 5, and an antenna-to-antenna distance of O.5Xo, wherein Xo is the wavelength of a wave received by the antenna.

[0037] FIG. 5 is a series of charts showing real and imaginary parts of input impedance for this configuration, wherein the charts on the left side of the figure show simulated real input impedance Re(Zo) and the charts on the right side of the figure show simulated imaginary input impedance Im(Zo) of each antenna element for broadside (perpendicular to the array plane, 0=0) excitation of the array, corresponding to different sizes of the radiating element (printed dipole) ranging from L=O.25Xo to 0.28A.0. The black dashed curve shows the condition Im(Zo)=O or an ideal operation condition. Pink dotted, dashed, and solid lines show, respectively, the condition when the maximum scan angle is 55, 50, and 45 degrees. As can be seen from FIG. 5, the region of acceptable scan angles is relatively low (area below a pink line for the corresponding scan angle) and for vanishing the imaginary part of input impedance(the desired operation condition shown by dashed black line), the real part of input impedance is somewhat low (about 30 ohm).

[0038] Example 2

[0039] A simulation of the effect of substrate and superstate properties on performance of a large antenna array was performed with the same parameters as Example 1, except an gap of O.O5Xo was simulated to be present between the superstate and the antennas.

[0040] FIG. 6 is a series of charts showing real and imaginary parts of input impedance for this configuration, wherein the charts on the left side of the figure show simulated real input impedance Re(Zo) and the charts on the right side of the figure show simulated imaginary input impedance Im(Zo) of each antenna element for broadside (perpendicular to the array plane, 0=0) excitation of the array, corresponding to different sizes of the radiating element (printed dipole) ranging from L=O.25A,o to O.28Xo. The black dashed curve shows the condition Im(Zo)=O or an ideal operation condition. The additional blue dotted curve shows the condition Re(Zo)=5O ohm, which can also be viewed as an ideal impedance matching condition. Pink dotted, dashed, and solid lines show, respectively, the condition when the maximum scan angle is 55, 50, and 45 degrees. With an air gap introduced, the region of acceptable scan angles increases (higher slope of the pink lines) and the real part of input impedance increases.

[0041] Embodiments disclosed herein, such as those illustrated in FIGS. 3a-3f, can enable the air gap effect illustrated in FIG. 6. Embodiments disclosed herein can also enable planar antenna arrays comprising superstates with such air gap effect. Such arrays can, for example, be configured to receive or transmit a wave having a frequency (f) of from about 20 gigahertz (GHz) to about 30 GHz. In addition, embodiments disclosed herein can enable planar antenna arrays, wherein the antenna has an input impedance value of Re(Z) ± Im(Z) ohm, wherein Re(Z) is the real component of input impedance and ranges from about 30 ohm to about 70 ohm, such as from about 40 ohm to about 60 ohm, including about 50 ohm, and Im(Z) is the imaginary component of input impedance and ranges from about -40 ohm to about 40 ohm, such as from about -20 ohm to about 20 ohm, including about 0 ohm, for scan angles (0) ranging from about 0 degrees to about 45 degrees.

[0042] Embodiments disclosed herein can include using a variety of glass compositions for glass layer 110a- 1 lOf, including but not limited to glass compositions comprising 58-65 weight percent (wt%) SiCh, 14-20wt% AI2O3, 8-12wt% B2O3, l-3wt% MgO, 5-10wt% CaO, and 0.5- 2wt% SrO, alkali free glass compositions comprising 58-65wt% SiCh, 16-22wt% AI2O3, 1- 5wt% B2O3, l-4wt% MgO, 2-6wt% CaO, l-4wt% SrO, and 5-10wt% BaO, alkali free glasscompositions comprising 57-6 lwt% SiC , 17-21wt% AI2O3, 5-8wt% B2O3, l-5wt% MgO, 3- 9wt% CaO, 0-6wt% SrO, and 0-7wt% BaO, or alkali containing glass compositions comprising 55-72wt% SiO2, 12-24wt% AI2O3, 10-18wt% Na2O, 0-10wt% B2O3, 0-5wt% K2O, 0-5wt% MgO, and 0-5wt% CaO, which, in certain embodiments, may also comprise l-5wt% K2O and l-5wt% MgO.

[0043] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiment of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A superstate for a planar array antenna, the superstate comprising: a first major surface and at least one opposing surface configured to face a substrate of the planar array antenna, the at least one opposing surface comprising at least one first surface location and at least one second surface location that is configured to be positioned closer to the substrate than the at least one first surface location.

2. The superstate of claim 1, wherein the at least one second surface location is configured to be at least about O.O5Xo closer to the substrate than the at least one first surface location, wherein Xo is the wavelength of a wave received or transmitted by the planar array antenna.

3. The superstate of claim 2, wherein a closest distance between the first major surface and the at least one first surface location is not greater than about O.O4Xo.

4. The superstate of claim 3, wherein Xo is from about 1.0 to about 1.5 centimeters.

5. The superstrate of claim 1, wherein the superstate comprises a glass layer.

6. The superstrate of claim 5, wherein the glass layer comprises the first major surface and the at least one first surface location.

7. The superstrate of claim 6, wherein the glass layer comprises the at least one second surface location.

8. The superstate of claim 7, wherein the at least one first surface location and the at least one second surface location each comprise a plurality of surface points.

9. The superstate of claim 8, wherein the plurality of surface points extend along a repeating pattern of the at least one opposing surface.

10. The superstate of claim 9, wherein the repeating pattern comprises at least one of prisms, cylinders, or hemispheres.

11. The superstate of claim 7, wherein the glass layer comprises a first bent edge and a second bent edge, each of the first and second bent edges comprising at least one second surface location.

12. The superstate of claim 6, wherein the superstate comprises a glass soot layer configured to extend between the glass layer and the substrate, the glass soot layer comprising the at least one second surface location.

13. The superstate of claim 12, wherein the glass soot layer comprises a non-uniform density.

14. A planar array antenna comprising the superstate of any one of claims 1 to 13.

15. The planar array antenna of claim 14, wherein the planar array antenna is configured to receive or transmit a wave having a frequency (f) of from about 20 gigahertz (GHz) to about 30 GHz.

16. The planar array antenna of claim 15, wherein the planar array antenna has an input impedance value of Re(Z) ± Im(Z) ohm, wherein Re(Z) is the real component of input impedance and ranges from about 30 ohm to about 70 ohm, and Im(Z) is the imaginary component of input impedance and ranges from about -40 ohm to about 40 ohm for scan angles (0) ranging from about 0 degrees to about 45 degrees.

17. A method of making the superstrate of any one of claims 1 to 13, comprising forming the at least one first surface location and the at least one second surface location.

18. The method of claim 17, wherein the superstrate comprises a glass layer and the forming comprises hot pressing a glass precursor material.

19. The method of claim 18, wherein the method comprises ion exchanging the glass layer.

20. The method of claim 17, wherein the superstrate comprises a glass layer and a glass soot layer and the forming comprises pressing a soot precursor material.

21. The method of claim 20, wherein the method comprises adhering the glass soot layer to the glass layer.

22. The method of claim 21, wherein the adhering comprises laser welding the glass soot layer to the glass layer.

23. The method of claim 20, wherein the method comprises heating the glass layer and the glass soot layer to a temperature of at least about 1300°C.

24. The method of claim 17, wherein the superstate comprises a glass layer and a glass soot layer and the forming comprises vapor depositing a soot precursor material on the glass layer.

25. The method of claim 24, wherein the vapor depositing comprises varying a delivery rate of at least one of a fuel, an oxidant, or the soot precursor material.

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