The disclosure generally relates to the field of antenna design technology and, more particularly, relates to a cone-based multi-layer wideband antenna.
An antenna is often known to work as a transducer that converts electrical signals on a transmission line to radio waves and vice versa. In general, the antenna size and operating frequency of the antenna are related. For example, for the antenna to have relatively low operating frequency, the size of the antenna needs to be relatively large. Therefore, it can be expected for antenna designers to encounter a tradeoff in realizing a compact or miniaturized antenna while maintaining low operating frequencies of the antenna.
Further, a single conventional antenna often cannot operate at a relatively wide frequency range or bandwidth, and multiple different antennas are thus needed for covering the desired frequency range. Through the development of certain classes of antennas (e.g., conical antennas), it is possible for a single antenna to operate over a large bandwidth. But, the size-frequency tradeoff still exists, which does not cope with the growing need for compact wide band antennas that operate at lowest possible frequencies. That is, the design of an antenna satisfying the requirement of being wideband, having a reduced size, and operating at low frequencies can be rather difficult.
The disclosed cone-based multi-layer antenna is designed to solve the aforementioned size-frequency tradeoff problem and other problems encountered during antenna design.
One aspect of the present disclosure provides an antenna. The antenna includes a cone-based member having a multi-layer structure. The multi-layer structure includes a first layer conical structure, and the first layer conical structure has a height and a base radius configured to provide a desired impedance of the antenna.
In some embodiments, the cone-based member further includes multiple layers of conical structures over the first layer conical structure.
In some embodiments, the multiple layers of conical structures and the first layer conical structures are arranged such that the antenna has a cross-sectional shape with a large scale curvature at one or more sides. Further, the first layer conical structure can be a cone, and the multiple layer of conical structures can be truncated cones.
In some embodiments, the multiple layers of conical structures and the first layer conical structures are arranged such that the antenna has a cross-sectional shape with a large scale virtual curvature at one or more sides, where a non-uniform meander line is arranged along the large scale virtual curvature. Further, the first layer conical structure can be a cone, and the multiple layer of conical structures can be circular discs.
In some embodiments, the antenna further includes an inverted cone-based member, and the inverted cone-based member is symmetric to the cone-based member. Further, a source can be disposed between the cone-based member and the inverted cone-based member.
In some embodiments, different meander lines are arranged along different large scale virtual curvatures to allow the antenna to operate at different frequency bandwidths.
In some embodiments, the antenna further includes a ground plane, and a meander line structure is configured in the ground plane to form a resonating structure on the ground plane.
Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure.
Various objectives, features, and advantages of the present disclosure can be more fully understood with reference to the detailed descriptions of the following drawings accompanying the present disclosure. Like reference numerals refer to like elements. It shall be noted that the following drawings are merely examples for illustrative purposes according to various disclosed embodiments and are not intended to limit the scope of the present disclosure.
Reference will now be made in detail to exemplary embodiments of the invention, which are illustrated in the accompanying drawings. Herein after, embodiments consistent with the disclosure will be described with reference to drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. It is apparent that the described embodiments are some but not all of the embodiments of the present invention. Based on the disclosed embodiments, persons of ordinary skill in the art may derive other embodiments consistent with the present disclosure, all of which are within the scope of the present invention. Further, in the present disclosure, the disclosed embodiments and the features of the disclosed embodiments may be combined or separated under conditions without conflicts.
As discussed above, it can be difficult to design a compact wideband antenna operating at lowest possible frequencies for application in modern communication. Directed towards the size-frequency tradeoff problem set forth during the design of low-frequency wideband antennas, the present disclosure provides an improved antenna that combines features of conical antenna and meander line antenna. The disclosed antenna may have a relatively small size and is able to operate at a relatively wide range of low frequencies.
Conical antennas have been studied for wideband coverage, and a single conical antenna can operate at a wide operating frequency range (also referred to as “wide bandwidth or wideband”) by proper configuration.
As shown in
The conical structure 101 may be a full cone, spanning 360 degrees. Further, the conical structure 101 may be symmetric about the cone axis and have a straight sidewall (i.e., lateral surface). The conical structure 101 may be made of a conductive material. The ground plane 103 may also be made of a conductive material. For example, the ground plane 103 may be a copper plate printed on a printed circuit board (PCB). Further, the ground plane 103 may be separated from the vertex of the conical structure 101 by a preset distance, and the ground plane 103 may be disposed in parallel with the top surface of the conical structure 101.
Referring to
Both the aforementioned monocone antenna and biconical antenna are known for their wideband coverage. Based on this wideband coverage feature, a cone-based multi-layer antenna showing desired or predetermined impedance (e.g., 50 ohm), low operating frequency, and the compact size is described later in the present disclosure. Further, approaches to reduce the space occupied by the antenna while maintaining its low operating frequencies are provided.
Return loss is often used as a parameter for evaluating power transferred from a transmission line to an antenna, and a high return loss is often desired for antennas. For example, a return loss greater than 10 dB indicates that at least 90% of the input power is delivered to the antenna and the reflected power is less than 10%.
For maximal power transfer (high return loss), the impedance of the antenna needs to match the impedance of the transmission line. Because the impedance of the commonly used transmission line (and of a transceiver to which the transmission line is coupled) is around 50 ohm, an antenna with impedance of approximately 50 ohm is desired to achieve satisfying impedance matching and thus maximal power transfer.
For example, a monocone antenna with a half-cone angle of around θ=40 degrees may have impedance of around 50 ohms, and for a monocone antenna having a half-cone angle of around 23 degrees, the impedance of the antenna is around 100 ohms. Thus, for a monocone antenna to have desired impedance matching, its half-cone angle may be designed to be approximately 40 degrees.
When the impedance of the antenna and the impedance of the transmission line are not well matched, power may be reflected back to the source and thus generate a standing wave. The greater the mismatch, the greater the percentage of the reflection. That is, though the monocone antenna in
To maintain the impedance of the antenna to be approximately 50 ohms while reducing the base radius, for example, by half, the present disclosure provides an improved wide band cone-based antenna by introducing a multi-layer structure into the antenna. In one embodiment,
As shown in
In some embodiments, the first layer conical structure 401, the second layer conical structure 402, and the third layer conical structure 403 may each have a shaped sidewall. In some other embodiments, the first layer conical structure 401, the second layer conical structure 402, and the third layer conical structure 403 may each have a straight sidewall. Optionally, the first layer conical structure 401, the second layer conical structure 402, and the third layer conical structure 403 may each be designed to be hollow, without a supporting member filling the corresponding inner space.
Further, the first layer conical structure 401 that is closest to the ground plane 400b may be used for the 50 ohm impedance matching, where the 50 ohm impedance matching here may refer to the matching of the disclosed antenna to a 50 ohm transmission line (e.g., coaxial cable). In some embodiments, the first layer conical structure 401 may be a full cone spanning 360 degrees, and in this case, the height and the base radius of the first layer conical structure 401 may need to be designed to yield impedance of approximately 50 ohms.
For example, the height of the first layer conical structure 401 may be designed to be h/2, and the base radius of the first layer conical structure 401 may be designed to be r=0.85 h/2, such that the half-cone angle of the first layer conical structure 401 is calculated to be approximately 40 degrees, which corresponds to the antenna impedance of approximately 50 ohms. Thus, a relatively satisfying antenna impedance matching performance may be ensured.
The second layer conical structure 402 may be, for example, a truncated cone with a relatively small height and relatively small top and base radiuses. The third layer conical structure 403 may be, for example, a truncated cone with a base radius of approximately same as that of the first layer conical structure 401 (e.g., r=0.85 h/2). Further, the sum of the height of the first layer conical structure 401, the second layer conical structure 402, and the third layer conical structure 403 may approximately equal to h.
Accordingly, with respect to the conventional single-layer conical antenna shown in
Optionally, the first layer conical structure 401, the second layer conical structure 402, and the third layer conical structure 403 may have other shapes and structures. The present disclosure is not intended to be limiting. Different shapes and structures of the first layer conical structure 401, the second layer conical structure 402, and the third layer conical structure 403 may define and achieve different operating frequency bandwidths of the antenna. Further, based on the specific design of the first layer conical structure 401, the second layer conical structure 402, and the third layer conical structure 403, the overall size reduction in the cone-based multi-layer antenna 400 with respect to the single-layer conical antenna in
Further, the actual number of layers of conical structures in the cone-based member 400a is not limited to three, as long as the layer of conical structure closest to the ground plane 400b has antenna impedance of approximately 50 ohms. That is, the cone-based multi-layer antenna 400 may include a layer of conical structure configured to ensure desired impedance matching performance, and one or more additional layers of conical structures configured to increase the signal path length of the antenna to lower the operating frequency of the antenna. Further, radiuses or other dimensions of the one or more additional layers of conical structures may need to be controlled for an overall reduced size of the antenna.
As such, by occupying less space, the disclosed cone-based multi-layer antenna may be applied to applications where the space is limited, and the weight of the disclosed antenna and the material cost may be reduced. Further, by maintaining impedance of approximately 50 ohms, the impedance matching performance of the cone-based antenna may be ensured, such that energy transfer may be maximized and wideband matching with high return loss may be achieved. Further, because the cone-based member is designed to include a multi-layer structure, the signal path length of the disclosed antenna may be increased, thereby lowering the operating frequency of the antenna.
In practical implementations, a transmission line may have impedance other than 50 ohms (e.g., 35 ohms). Under these situations, the disclosed antenna may be correspondingly designed to have pre-determined impedance same as the impedance of the transmission line. For example, for the disclosed antenna 400 in which the first layer conical structure 401 is a full cone spanning 360 degrees, the height and the base radius of the first layer conical structure 401 may be designed to yield the pre-determined impedance that matches the impedance of a target transmission line.
Further, in some embodiments, the ground plane 400b may not have a continuous surface shown in
Further, a plurality of holes may be arranged in a certain pattern such that the corresponding pattern may be removed from the ground plane 1800 to further reduce the weight of the antenna. For example, each of the four groups of holes 1801a may be arranged in two small triangles which together forms a large triangle, and when a reduced weight is desired for the ground plane 1800, one or more of the large triangles may be relatively easily removed from the ground plane 1800 to reduce the weight thereof. Besides the reduction of the weight, the antenna parameter such as operating frequency may be tuned by removing certain portion of the ground plane. The removed portion may be made of dielectric material or conductive material.
The first layer conical structure 501 may be closest to the ground plane 500b, and may be designed to yield predetermined impedance (e.g., approximately 50 ohms) to ensure good impedance matching performance. The detailed design process of the first layer conical structure 501 to yield the predetermined impedance may refer to aforementioned descriptions, and is not repeated herein.
Further, the first layer conical structure 501, the second layer conical structure 502, the third layer conical structure 503, the fourth layer conical structure 504, and the fifth layer conical structure 505 may form a continuous shaped sidewall. For example, for the cone-based member 500a to have a continuous shaped sidewall, the first layer conical structure 501, the second layer conical structure 502, the third layer conical structure 503, the fourth layer conical structure 504, and the fifth layer conical structure 505 may each be a truncated cone with a shaped sidewall.
For example, referring to
Further, the second layer conical structure 502 may be a truncated cone with its half-cone angle much greater than the preset angle θ0, and the sidewall of the second layer conical structure 502 may have a slightly convex shape. The third layer conical structure 503 may be an inverted truncated cone with relatively large half-cone angle(>θ0), and the sidewall of the third layer conical structure 503 may be a slightly convex shape. The fourth layer conical structure 504 may be a truncated cone with a relatively large half-cone angle (>θ0), and the sidewall of the fourth layer conical structure 504 may have a concave shape. The fifth layer conical structure 505 may be an inverted truncated cone with a relatively small half-cone angle (<θ0), and the sidewall of the fifth layer conical structure 505 may have a slightly convex shape.
Further, the thickness of the first layer conical structure 501, the second layer conical structure 502, the third layer conical structure 503, the fourth layer conical structure 504, and the fifth layer conical structure 505 may be different from each other. The present disclosure is not intended to be limiting.
As a result, a cross-sectional shape of the cone-based member 500a may show large scale curvature both at the left side and at the right side. The large scale curvature herein may be, for example, a portion of a complex waveform. Further, the distance between two adjacent troughs (e.g., points A and A′ in
The aforementioned large scale curvature increases the side length of the cross-sectional shape of the disclosed cone-based member 500a and broadens the antenna bandwidth. That is, the large scale curvature formed by the multi-layer structure of the cone-based antenna may enable the disclosed antenna 500 to have a longer electrical length than the conical antenna indicated by dashed line of
Further, the top-loaded plate 500c may be disposed on top of the cone-based member 500a. In some embodiments, the top-loaded plate 500c may be a circular disc loaded on top of the cone-based member 500a. The top-loaded plate 500c may improve the impedance matching performance of the antenna.
In some embodiments, the ground plane 500b may have a continuous surface or a non-continuous surface. For example, the ground plane 500b may include a plurality of holes, such that the weight of the ground plane 500b is reduced to further save the overall weight of the disclosed antenna 500. Further, due to the existence of holes, the position of the cone-based member 500a with respect to the ground plane 500b may be more flexibly adjusted. In some other examples, the ground plane 500b may be meandered or slotted to reduce the overall weight of the disclosed antenna 500. Some embodiments of a meandered ground plane may be found in aforementioned descriptions.
As such, the impedance of the antenna may be maintained to be a desired or predetermined value (e.g., approximately 50 ohms), such that the impedance matching performance of the cone-based antenna is ensured, which maximizes energy transfer and achieves wide band matching with high return loss. Further, because the cone-based member is designed to include a multi-layer structure, the signal path length of the disclosed antenna may be increased, thereby lowering the operating frequency of the antenna.
To further extend the electrical length to lower the operating frequency of the cone-based multi-layer antenna, the meander line is introduced as a solution. A meander line structure is designed by folding a straight wire or straight strip back and forth, thus reducing the length of the meander line structure with respect to the length of the original straight wire or straight strip. Such design enables the meander line structure to include a plurality of vertical segments and horizontal segments which form multiple turns. The presence of the meander line structure reduces the operating frequency of the antenna.
As shown in
The plurality of disc structures may each be a circular plate. Further, the plurality of disc structures may have same or different small thickness. The radius of the circular disc in different layers may be different from each other or may be the same as each other, depending on practical demands. The order of the plurality of disc structures may be so arranged that the cross-sectional shape of the cone-based member 600a displays a left-side meander line and a right-side meander line along the large scale curvatures shown in
Further, from the flattened cross-sectional shape of antenna in
Further, the top-loaded plate 600c may be disposed on top of the cone-based member 600a. In some embodiments, the top-loaded plate 600c may be a circular disc loaded on top of the cone-based member 600a. The top-loaded plate 600c may improve the impedance matching performance of the antenna.
In some embodiments, the ground plane 600b may have a continuous surface or a non-continuous surface. For example, the ground plane 600b may include a plurality of holes, such that the weight of the ground plane 600b is reduced to further save the overall weight of the disclosed antenna 600. Further, due to the existence of holes, the position of the cone-based member 600a with respect to the ground plane 600b may be more flexibly adjusted. In some other examples, the ground plane 600b may be meandered or slotted to reduce the overall weight of the disclosed antenna 600.
As such, the impedance of the antenna may be maintained to be a desired or predetermined value (e.g., approximately 50 ohms), such that the impedance matching performance of the cone-based antenna is ensured, which maximizes energy transfer and achieves wide band matching with high return loss. Further, because the cone-based member is designed to include a multi-layer structure, the signal path length of the disclosed antenna may be increased, thereby lowering the operating frequency of the antenna.
Referring to the antenna 700 shown in
Different from the antenna 600 in
Optionally, the 3D-version cone-based member 700a and top-loaded plate 700c may be translated into a two-dimensional (2D) member, i.e., a cone-based planar member, with meander lines on the top side and at the two sides. The translation process may be implemented, for example, by slicing the 3D-version antenna 700 into different thin planes.
For example, the coned-based planar member may include a top-loaded meander line structure, a left-side meander line structure, a right-side meander line structure, and a first layer planar structure. The top-loaded meander line structure may be translated from the 3D-version top-loaded plate 700c, and the first layer planar structure may be translated from the 3D-version first layer conical structure 701. The first layer planar structure may help maintain a cross-sectional shape of cone or truncated cone, and may be so designed to ensure desired impedance matching.
Further, the top-loaded meander line structure may have a shape of slotted meander line including a plurality of turns (e.g., seven turns in
Further, the left-side meander line structure and the right-side meander line structure may respectively have a shape of left-side slotted meander line and right-side slotted meander line. The left-side slotted meander line may be symmetric to the right-side slotted meander line, and the left-side slotted meander line and/or the right-side slotted meander line may be arranged along the large scale curvature shown in
Optionally, the aforementioned cone-based planar member may be solid or hollow, depending on specific situations. In some embodiments, the cone-based planar member may have a solid structure, and the solid structure includes a supporting member (not shown) and a thin conductive strip covering certain exterior surface of the supporting member. The supporting member may be configured to allow the thin conductive strip to maintain a structure and shape disclosed in
Optionally, to simplify the design of the antenna, instead of the top-loaded meander line structure disclosed in
Further, by spinning the coned-based planar member disclosed in
The structure and features of the cone-based member 800a and the ground plane 800b may be similar to the cone-based member 600a and the ground plane 600b shown in
Further, the top-loaded plate 1000c and the upper cone-based member 1000d in
The bottom-loaded plate 1000b may be the same as or different from the top-loaded plate 1000c. For example, the bottom-loaded plate 1000b may be a circular disc having a flat surface, or may include a plurality of concentric annuli. Further, the bottom-loaded plate 1000b may have a meandered surface (not shown in
The two crossed cone-based planar members 1100a and 1100c may or may not be perpendicular to each other. Further, the cone-based planar member 1100c may be the same as or different from the cone-based planar member 1100a. For example, the cone-based planar member 1100c may have similar shape as the cone-based planar member 1100a but a smaller size. Further, in some embodiments, more than two cone-based planar members may be configured to form the cone-based wide band antenna 1100, and the present disclosure is not limiting the number, shape and size of cone-based planar members (1100a, 1100c . . . ) included in the disclosed antenna 1100.
Further, the two crossed cone-based planar member 1100a and 1100c may each be perpendicular to the ground plane 1100b. In some embodiments, the ground plane 1100b may not have a continuous surface. For example, the ground plane 1100b may include a plurality of holes, such that the weight of the ground plane 1100b may be reduced to reduce the overall weight of the disclosed antenna 1100. Further, due to the existence of holes, the position of the cone-based member 400a with respect to the ground plane 1100b may be more flexibly adjusted. For example, the cone-based planar member 1100a may be relocated or changed even after being manufactured. In some other examples, the ground plane 1100b may be meandered or slotted to reduce the overall weight of the disclosed antenna 1100 and fine tune the operating bandwidth of the antenna.
Whether the supporting member is hollow or solid may be designed based on practical situations. For example, when a light-weighted antenna is desired, the supporting member may be designed to be hollow, and when a relatively simple antenna fabrication process is desired, the supporting member may be designed to be solid.
Optionally,
Further, modeling of an existing conical antenna and a cone-based multi-layer antenna according to the present disclosure are described hereinafter, and input matching bandwidths of these antenna are provided, respectively.
As shown in
The S-parameter S11 is parameter indicating how much power is reflected back at an antenna port due to mismatching between the antenna and the transmission line. When connected to a network analyzer, S11 measures the amount of energy returning to the analyzer, and the amount of energy returned to the analyzer is directly affected by how well the antenna is matched to the transmission line. S11 value is measure in dB and is negative. When made positive, S11 is also referred to as return loss (i.e., return loss=−S11). Since the impedance of the antenna varies with frequency, the antenna is matched to the transmission line within a limited frequency range (bandwidth). In this example, a bandwidth of approximately 107 MHz is obtained.
As shown in
Further,
As such, a cone-based multi-layer antenna is provided to maintain 50 ohm antenna impedance, a compact size, and low operating frequencies. The actual number of layers included in the multi-layer structure can be application specific and determined based on practical needs. Further, the weight and cost of the disclosed antenna maybe controlled to be relatively low, which enables the disclosed antenna to be applicable in many applications where the space is limited or a low cost is desired.
More specifically, according to the present disclosure, the first layer cone-based structure (e.g., the first layer conical structure and the first layer planar structure) included in the multi-layer structure of the disclosed antenna (i.e., the layer that is closest to the ground plane) is used for desired impedance matching. By controlling the height and base radius of the first layer cone-based structure, the slope of the conical antenna can be controlled to achieve desired or predetermined impedance (e.g., approximately 50 ohm).
To further improve the antenna performance at lower frequency, additional features such as scale curvature, meander lines along the large scale curvature, top-loaded plate, and ground plane with drilled holes are introduced into the disclosed antenna. The large scale (or global) curvature expends the signal path length and lowers the frequency coverage of the disclosed antenna. Further, the small scale (or local) meander line riding on the large curvature line further lowers the lower frequency coverage of the antenna. The top-loaded plate (e.g., meander surface) may additionally extend the lower frequency coverage of the antenna.
Accordingly, the present disclosure provides a large degree of the freedom to modify the dimension of the first layer conical structure dimension and adjust the antenna impedance. The matching performance of antenna impedance is enhanced, and the bandwidth is broadened. Further, the surface area (looking from the top) may be reduced significantly.
Further, the aforementioned 3D cone-based antenna can be sliced into a number of planes for re-arrangement to form antennas with reduced weight and cost. If mounted on an autonomous vehicle such as a UAV (unmanned aerial vehicle) or other flying objects, the disclosed antenna can reduce the drag coefficient and the weight.
The present disclosure further presents a communication system including a cone-based multi-layer antenna. The cone-based multi-layer antenna may be any of aforementioned antennas according to embodiments of the present disclosure. The disclosed communication system may further include a transmitter that supplies an electrical signal to the antenna, a receiver that receives an electrical signal from the antenna, and/or a processor to process signals received or transmitted by the antenna. There are other components or devices possibly included in the communication system, and the present disclosure is not intended to be limiting.
Aforementioned descriptions are preferred embodiments of the present disclosure, but are not intended to limit the present disclosure. For those skilled in the art, various alterations and variations can be made in the present disclosure. Without departing from the spirit and scope of the present disclosure, any modifications, equivalent replacements, and improvements, etc. shall fall within the protection scope of the present disclosure.
This invention was made with Government support under Contract No. W31P4Q12C0128, awarded by the DARPA. The U.S. Government has certain rights in this invention.
Number | Name | Date | Kind |
---|---|---|---|
5534880 | Button | Jul 1996 | A |
20030058181 | Sasaki | Mar 2003 | A1 |
20050248499 | Park | Nov 2005 | A1 |
20150244077 | Sanford | Aug 2015 | A1 |
20150255874 | Hung | Sep 2015 | A1 |
20170294714 | Lindenmeier | Oct 2017 | A1 |
Number | Date | Country | |
---|---|---|---|
20190356053 A1 | Nov 2019 | US |