Patent Grant
8228235
This invention relates generally to the field of high-frequency antennas and particularly to the field of planar and conformal antennas for high frequency microwaves.
Planar (or flat-plate) and conformal antennas for high frequency microwave transmission (e.g. in various parts of 0.1-40 GHz range) are nowadays widely in use, for example in radio broadcasting, mobile communication, and satellite communication. Such antennas can provide circular and linear polarization, based on their specific configurations.
Generally, printed conformal and planar antennas are built on a multilayered substrate structure (e.g. PCB, printed circuit board) and include, inter alia, a dielectric substrate and an array of radiating elements and their respective transmission lines, the number of elements depending on their gain as well as on the overall desired gain of the antenna. The radiating elements and the transmission lines are disposed on either one or both sides of the dielectric substrate. Planar antennas are produced, for example, by printing using so-called “microstrip” technology or photolithography.
U.S. Pat. No. 6,285,323 discloses a flat panel antenna for microwave transmission that comprises at least one PCB, and has radiating elements and transmission lines located on both the first and second sides of the PCB in a complementary manner, such that the transmission lines of the first and second sides overlay one another, and the radiating elements of the second side extend outwards from the terminations of the transmission lines in the opposite directions, at an angle of 180 degrees from the radiating elements of the first side.
US Patent Application No. 2003/0218571 discloses an antenna having linear and circular polarization, which uses dipoles as radiating elements, and has an orthogonal characteristic in both linear and circular polarization, the antenna being embodied in the use of two plates, including the front and rear sides of both plates.
US Patent Application No. 2003/0020665 discloses a planar antenna having a scalable multi-dipole structure for receiving and transmitting high-frequency signals, including a plurality of opposing layers of conducting strips disposed on either side of an insulating (dielectric) substrate.
U.S. Pat. No. 6,163,306 discloses a circularly polarized cross dipole antenna comprising a first L-shaped dipole antenna element including a first pair of strip conductors and a first bending portion and a second L-shaped dipole antenna element including a second pair of strip conductors and a second bending portion. The first L-shaped dipole antenna element is arranged in a first region of four regions delimited by crossing lines virtually set within a single plane and the second L-shaped dipole antenna element is arranged in a second region thereof, which is diagonally opposite to the first region. The first bending portion and the second bending portion are close and opposite to each other, such that the first and second L-shaped dipole antenna elements form a cross. The antenna also comprises a parallel-twin-line feeder extending from the first and second bending portions and provided so as to feed power within the single plane.
Also related to planar antennas are U.S. Pat. Nos. 5,708,446, 5,786,793,6,037,911, 6,166,702, 6,275,192, 6,424,311, 6,518,935, 6,844,851; US Patent Application No. 2003/0063031; PCT Patent Application No. WO01/80358; EP Patent Applications Nos. EP0920074 and EP1271692; and SASAS DRAGAS and MARCO SABBADINI: “A Novel Type of Wide Band Circular Polarised Antenna (Proceedings ESA WPP-222; 27th ESA Antenna Workshop on Innovative Periodic Antennas, Electromagnetic Bandgap, Lefthanded Materials, Fractal and Frequency Selective surface, 9-11 Mar. 2004, Santiago de Compostela.
There is a need in the art for a new planar/conformal antenna.
The present invention provides for planar and conformal antennas for transmitting and/or receiving electromagnetic waves of at least one predefined frequency in the range of 0.1-40 GHz, and a predefined polarization. The antenna according to the invention provides both circular and linear polarization, based on its specific predefined configuration.
According to an embodiment of the invention there is provided a planar or conformal antenna for transmitting and/or receiving electromagnetic waves of at least one predefined frequency and a predefined polarization, the antenna comprising a plane dielectric substrate (PCB) with upper and lower faces; at least one pair of substantially identical upper and lower radiating elements disposed on said upper and lower faces; in each pair of said radiating element in the upper face and the corresponding radiating element in the lower face, the phase center of the lower radiating element substantially coincides with the phase center of the upper radiating element. This allows for high level of antenna performance, e.g. gain of at least 1 dB, 1.5 dB and more, up to 3 dB, when compared to a prior art antenna with the same number of radiating elements, having substantially the same geometrical dimensions; and low axial ratio over a large portion of the radiated beam.
According to an embodiment of the invention, the antenna is configured for providing circular polarization, and each of the radiating elements is capable of radiating electromagnetic waves of a circular polarization. According to another embodiment of the invention, the radiating elements comprise bend-shaped elements. According to yet another embodiment of the invention, the above-mentioned bend-shape is an L-shape.
According to an embodiment of the invention, the antenna is configured for providing linear polarization, and the radiating elements comprise radiating elements having first and second branches arranged at an acute angle with respect to each other.
According to an embodiment of the invention there is provided an antenna for transmitting and/or receiving electromagnetic waves of at least one predefined frequency and a predefined polarization, the antenna comprising a multi-layered substrate structure having a dielectric substrate with upper and lower faces; at least one pair of substantially identical upper and lower radiating elements disposed on said upper and lower faces of the dielectric substrate; each radiating element transmitting and/or receiving electromagnetic waves with a phase center located at a predefined position; each radiating element comprising a radiating element and a transmission line, the geometrical dimensions of which depend on said predefined frequency; in each pair of said radiating element in the upper face and the corresponding radiating element in the lower face:
According to yet another embodiment of the invention there is provided a method for providing a planar antenna for transmitting and/or receiving electromagnetic waves of at least one predefined frequency and a predefined polarization, the antenna having a dielectric substrate with upper and lower faces; at least one pair of substantially identical upper and lower radiating elements disposed on said upper and lower faces of the dielectric substrate; said radiating elements comprising radiating elements having first and second branches the method comprising:
According to one embodiment of the invention there is provided an antenna for transmitting and/or receiving electromagnetic waves of at least one predefined frequency and a circular polarization, the antenna comprising at least a first support having upper and lower faces and at least one pair of substantially identical upper and lower radiating elements disposed on said upper and lower faces, respectively, each radiating element being capable of transmitting and/or receiving electromagnetic waves of circular polarization with a phase center located at a predefined position.
According to another embodiment of the invention there is provided an antenna for transmitting and/or receiving electromagnetic waves of at least one predefined frequency and a circular polarization, the antenna comprising at least a first support having upper and lower faces and at least one pair of substantially identical upper and lower radiating elements disposed on said upper and lower faces, respectively, each radiating element being capable of transmitting and/or receiving electromagnetic waves of circular polarization with a phase center located at a predefined position, and the radiating elements on each face of said first and second supports are arranged such that the distance between the phase centers of at least one pair located on the first support and another, adjacent pair located on the second support is in a range of about 0.4λ0-0.5λ0, λ0 being the wavelength of the predefined frequency in air.
According to yet another embodiment of the invention there is provided an antenna for transmitting and/or receiving electromagnetic waves of at least one predefined frequency and a predefined polarization, the antenna comprising a multi-layered substrate structure having at least a first and second dielectric substrate layer each having at least an upper and a lower face; each face carrying at least one radiating element capable of transmitting and/or receiving electromagnetic waves of circular polarization with a phase center located at a predefined position; at least a first radiating element carried on one face is paired with at least a second radiating element carried on a different face and oppositely located with respect to a plane perpendicular to the plane of the dielectric substrates, such that the phase center of the first radiating element substantially coincides with the phase center of the at least radiating element.
According to an embodiment of the present invention there is provided a method for providing a planar antenna for transmitting and/or receiving electromagnetic waves of at least one predefined frequency and a required linear polarization, the antenna having at least a first and second dielectric substrate, at least one face of each substrate carrying at least one radiating element capable of transmitting and/or receiving electromagnetic waves of circular polarization with a phase center located at a predefined position, the method comprising:
According to another embodiment of the present invention there is provided an antenna for transmitting and/or receiving electromagnetic waves of at least one predefined frequency and a circular polarization, the antenna comprising at least a first and second support, each with upper and lower faces, and at least one, first radiating element disposed on at least the upper or lower faces of the first support, and at least a second radiating element disposed on at least the upper or lower faces of the second support; said first and second radiating elements are capable of transmitting and/or receiving electromagnetic waves of a circular polarization with a phase center located at a predefined position such that the phase center of the first radiating element substantially coincides with the phase center of the second radiating element.
In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:
a-3b are schematic illustrations of the structure of an element of the antenna of
a-4d are schematic illustrations of the structure of elements of the antenna of
a-5e illustrate simulated characteristics of an antenna element according to an embodiment of the invention;
a-7c illustrate simulated characteristics of an antenna element according to another embodiment of the invention.
a-9c are schematic illustrations of the structure of an antenna according to yet another embodiment of the invention;
a-10b illustrate another antenna according to another embodiment of the invention; and
In the non-limiting example of
a-3b illustrate schematically in greater detail the structure of paired radiating elements 21 of the antenna of
The following is a description of the design of a single radiating element in the circular polarization configuration, in accordance with an embodiment of the invention. In the following example, the PCB material has relative permittivity ∈r=2.2 and width w=0.5 mm. Note that the invention is not bound by the following example.
As demonstrated in the non-limiting example of
The lengths A and B of the X and Y branches are substantially identical and are defined by the following equation:
A,B=K1λ0 [1]
Wherein K1 is in the range of 0.3 to 0.35, e.g. K1=0.33, and wherein λ0 is the wavelength of the operating frequency in air. Thus, in the abovementioned operating frequency (8 GHz), A and B equal 12.5 mm.
The width C of the X and Y branches is defined as follows:
C=K2λ0 [2]
Wherein K2 is in the range of 0.10 to 0.20, e.g. K2=0.106. In the example of
The feed point 25 is connected to one of the branches, the Y branch in the example of
It should be noted that the invention is not limited by the specific example of the radiating element 21 as shown in
According to an embodiment of the present invention, the radiating element is configured for generating electromagnetic field with circular polarization and for that purpose it has a substantially L-shape with first and second branches and a feed point located on said second branch, such that the electric current generated in the second branch is phase delayed in 90° with respect to the electric current generated in the first branch.
Having described the design of a single radiating element, there follows a description of the design of a paired radiating element in the circular polarization configuration, according to an embodiment of the invention:
As mentioned before, the paired elements 21 disposed on both the upper and lower faces of the PCB 10 are oppositely aligned in a relatively compact space, in a complementary manner, such that the phase centers of the upper and lower elements substantially coincide, yielding a high level of antenna performance. According to an embodiment of the invention, the upper and lower elements are oppositely and adjacently aligned in the following manner:
Length D between the X branch of said upper radiating element and the X branch of said lower radiating element, and the length E between the Y branch of said upper radiating element and the Y branch of said lower radiating element, are defined by the following equations:
D=K3λ0 [3]
E=K4λ0 [4]
Wherein K3 and K4 are in the range of 0.3 to 0.6, e.g. K3 and K4 equal 0.41 λ0. Note that D and E need not be identical. Also note that upper and lower radiating elements need not be in full symmetry with each other. Note that D and E values other than the above specified values can be used. For example, in the case D or E exceeds 0.6λ0, the gain of the antenna may increase due to the increase in the equivalent surface of the antenna. However the axial ratio (the measure of the antenna circularity on its axis of symmetry) is increased.
According to the present invention and as illustrated in
0.5λ0<F<1λ0 [5]
In the above discussion with reference to
The phase center of an antenna can be determined by measurements, computed simulations, and calculations. As discussed in “Antenna Handbook, Volume II Antenna Theory”, ed. Y. T. Lo, Van Nostrand Reinhold, New York, in chapter 8, the analytical formulations for locating the phase center of an antenna typically exist for only a limited number of antenna configurations. Experimental techniques are known in the art for locating the phase center of an antenna, as well as simulation tools such as the CST Microwave Studio™ software commercially available from CST Computer Simulation Technology GmbH, Germany.
a-5e illustrate simulated characteristics of a pair of radiating elements according to an embodiment of the invention, in the circular polarization configuration shown in
a shows the gain of a single pair of radiating elements. Note that typically the characterizing gain of prior art radiating elements having substantially the same geometrical dimensions as described above with reference to
According to yet another embodiment of the invention there is provided an antenna suitable for linear polarization. There follows a description of the design of a single radiating element as well as the paired radiating elements in the linear polarization configuration.
Reference is now made to
According to an embodiment of the invention, the radiating elements of the linear polarization configuration comprises bend-shaped elements having first and second branches arranged at an acute angle with respect to each other. The upper and lower radiating elements are arranged in a substantially symmetrical arrangement on both faces of the PCB, such that the first branches of the upper and lower elements are in parallel; and the electrical length of each of said first branches is about 0.5λ0, wherein λ0 is the wavelength of said predefined frequency in air. In other words, each of the first branches of the upper and lower radiating elements, by itself, operates as a radiating element in linear polarization.
In the following example, the PCB material has relative permittivity ∈r=2.2 and width w=0.5 mm. Note that the invention is not bound by the following example. The geometrical dimensions of the acute-angled branches according to the following example are as follows:
The length G of the first branch is defined by the following equation:
G=K5λ0 [7]
Wherein K5 is in the range of 0.3 to 0.4, e.g. K5=0.36, and wherein λ0 is the wavelength of the operating frequency in air. Thus, in the abovementioned example (operating frequency of 8 GHz), G equals 13.5 mm.
The length H between the first branches of the upper and lower elements is defined by the following equation:
H=K6λ0 [8]
Wherein K6 is in the range of 0.3 to 0.35, e.g. K6=0.32, and wherein λ0 is the wavelength of the operating frequency in air. Thus, in the abovementioned operating frequency (8 GHz), H equals 12 mm.
The width I of the radiating element is defined by the following equation:
I=K7λ0 [9]
Wherein K7 is in the range of 0.015 to 0.025, e.g. K7=0.02, and wherein λ0 is the wavelength of the operating frequency in air. Thus, in the abovementioned operating frequency (8 GHz), 1 equals 1 mm. note that the invention is not limited by the specific example of
a-7c illustrate simulated characteristics of an antenna paired element according to the embodiment of the invention shown in
A variety of applications require various and sometime variable polarization. In the field of telecommunication, for example, data-link between ground stations and satellites is typically done with linear polarization, and sometime the polarization is required to vary, e.g. between −45 and +45 degrees with respect to the horizon.
According to an embodiment of the invention shown in
Covering entirely one face of the antenna with a polarizer P, has substantially no effect on the adaptation of the antenna. In the frequency range of 8 to 9 GHz, the return loss is substantially similar to the one shown in
Referring now to
In the resultant multi-layered antenna 900, the aperture of the antenna is shared by the superposition of the electromagnetic fields generated by the RCP and LCP printed circuits. According to another embodiment of the invention, a delay is provided between the ports (connectors) by a delay line or a phase shifter (not shown in
It should be noted that according to the present invention as described above, the radiation pattern of each of the radiating elements (elements 21 as illustrated in
According to an embodiment of the invention, the arrangement of the pairs of radiating elements disposed onto the same PCB is defined by the following equation:
M=K8λ0 [10]
wherein K8 is in the range of 0.8-1.0 and λ0 is the wavelength of the operating frequency in air. Note that M defines the distance between the phase centers of adjacent paired elements on top of the same PCB.
According to the embodiment illustrated herein, the arrangement of pairs of radiating elements disposed onto different PCBs is defined by the following equation:
N=K9λ0 [11]
wherein K9 is in the range of 0.4-0.5 and λ0 is the wavelength of the operating frequency in air. N defines the distance between the phase centers of associated pairs of elements—the RCP pair of elements and the LCP pair of elements, each disposed onto a different PCB. Hence, any change in the value of M will affect the superposition and the interference between the RCP and LCP waves.
This embodiment of the invention allows using two substantially identical printed antenna boards in combination, in an efficient manner, to provide over the same area right-hand or left-hand circular polarization, or both, as required.
As illustrated in
In the foregoing discussion, embodiments of the invention were presented with respect to a rectangular grid, e.g. as illustrated in
a-10b illustrate another example of a combination of two substantially identical printed antenna boards according to another embodiment of the invention. In
The invention was described in detail with reference to a planar configuration, in which the radiating elements are disposed onto both faces of a planar support. It should be noted that the invention is not limited by the above-described planar configuration and other arrangements are possible within the scope of the invention. For example, the invention can be implemented as a conformal antenna, which conforms to a surface whose shape is determined by considerations other than electromagnetic, for example, aerodynamic or hydrodynamic, or other non-planar configurations.
The invention was described in detail with reference to the operating frequencies falling within the range of 8-9 GHz. It should be noted that the invention is not limited by this specific example, and is suitable to operate in a variety of frequencies, with the necessary modifications and alterations, e.g. change of the operating frequency would result in change in the geometrical dimensions of the radiating elements and their respective planar layout and arrangement. The invention was described with reference to a printed configuration (utilizing a PCB), however it should be noted that the invention is not limited by this configuration. It should also be noted that in the range of relatively lower frequencies (e.g. 1 GHz and less), λ equals 30 cm or more, thus allowing the use of radiating elements made of metal, as well as the use of air spacers, foam layers, etc. The invention was mainly described with reference to a single PCB configuration, in which the PCB has the radiating elements disposed on both its faces. It should be noted that the invention can be implemented in another configuration, in which two PCBs and more are adjacently used, each having the radiating elements disposed on one or both faces, such that the phase centers of adjacent radiating elements substantially coincide.
The invention was described with reference to a central feed scheme, in which all radiating elements printed over a certain area are fed via a common feed point. It should be understood that the invention is not limited by this example and other feed schemes are possible within the scope of the present invention. For example, by separating respective transmission lines over the same PCB, different radiating element pairs disposed over the same PCB could be operable with different polarization (e.g. some with RCP and some with LCP). Hence a single printed-board antenna made of circular polarization elements could provide linear polarization.
According to one embodiment of the invention, each PCB is fed via dedicated connectors (elements 18a and 18b in
According to another embodiment of the invention, each PCB carries radiating elements arranged substantially as illustrated in
Thus, according to a first, broad aspect of the present invention, there is provided an antenna made of two or more spaced apart PCBs, each having one or more radiating elements disposed on one or both its faces, such that the phase center of at least one from among the plurality of radiating elements disposed on one face of a PCB coincides with a phase center of a radiating element disposed onto the other face of the same PCB or on a different, adjacent PCB.
According to another broad aspect of the invention, there is provided an antenna made of one or more PCBs, having one or more radiating elements disposed on one or both its faces, such that the phase center of at least one from among the plurality of radiating elements disposed on one face of the PCB coincides with a phase center of a radiating element disposed onto the other face of the same PCB or on a different PCB, thereby constituting a first pair of radiating elements. The antenna further comprises at least one second, substantially identical pair of radiating elements. The at least second pair is operable with a circular polarization different from that of the first pair (e.g. RCP/LPC), such that the aperture of the antenna is made of a superposition of electromagnetic fields corresponding to the first and second pair. The distance between the phase centers of the first and second pairs is preferably about 0.4λ wherein λ0 is the wavelength of the operating frequency in air.
It should be clear to anyone versed in the art that the reference to the second PCB as being ‘substantially identical’ to the first PCB excludes the portions of the PCBs onto which the connectors are located. This is illustrated e.g. in
The present invention has been described with a certain degree of particularity, but those versed in the art will readily appreciate that various alterations and modifications may be carried out without departing from the scope of the following Claims:
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| Number | Date | Country |
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| Number | Date | Country | |
|---|---|---|---|
| 20060170596 A1 | Aug 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10800019 | Mar 2004 | US |
| Child | 11338883 | US |
