The present application relates to the structure of a radiating element, specifically to radio frequency (RF) connections between planar-to-planar and planar-to-inclined surfaces. Furthermore, the application also relates to the configuration of an array of radiating elements of a hybrid steerable beam antenna integrating receive and transmit capabilities in the same aperture.
Many existing and future broadband satellite services require small, lightweight and low-cost antennas to be mounted on mobile platforms, such as vehicles, trains, and airplanes, or antennas integrated on portable systems or installed in fixed positions on buildings. In order to minimize the size and/or the thickness of the antenna and to provide beam steering capabilities, array antennas are often applied for wall-mount applications, portable applications and mobile front-end applications.
Satellite services with large capacity and fast connection speed often apply high frequency bands (e.g. Ku, Ka and Q-band) which typically have large frequency ranges for downlink and uplink channels. These services also typically have large spacing between transmit and receive bands in order to avoid interferences between uplink and downlink signals. The large bandwidths and the large spacing between bands make it difficult to design antenna arrays using the same aperture for both uplink and downlink functions. One solution used in many products is to split the antenna aperture in two parts, one aperture for receiving signals and another aperture for transmitting signals.
An advantageous approach is to use the same surface and volume of the antenna for both transmit and receive functionalities. This is generally achieved in reflector antennas through the design of wideband feeds which integrate diplexers to separate transmit and receive signals. However, using the same surface is difficult in array antennas where wideband elements tend to loose radiation efficiency in the required bands and where the integration of active components (e.g. for beam steering) includes a separation of transmit and receive signals at each element, generally resulting in an increase in costs and integration issues.
Additionally, integrating two types of elements, one for transmit and one for receive, in the same surface, may result in a high coupling between elements that affects quality of the radiation of the antenna. Typically, the antenna design is very challenging because the spacing between radiating elements is very small and field couplings very high. The high couplings between the two types of elements can cause problems on the generation of the beam forming and power isolation between the transmit and receive chain. Overall, designing the receive function and the transmit function onto a single aperture may result in inefficiencies, increased complexity and cost, and high coupling between the radiating elements.
Thus, it is desirable to have an antenna architecture having both transmit and receive elements on a single aperture, and where the antenna architecture is configured to operate efficiently and with reduced coupling between the elements.
In an exemplary embodiment, an antenna architecture comprises a single aperture having both receive elements and transmit elements. Furthermore, in an exemplary embodiment, the array beam forming network and active circuitry are integrated into a low-profile structure, thus making it suitable for integration on vehicles for communications on the move.
Furthermore, in an exemplary method, an antenna array is designed to take advantage of the entire surface of the aperture for both transmit and receive functions. The application of original design concepts allows building an antenna having the performances of a dual-aperture joined in a single aperture having about half the size.
In the exemplary embodiment, the shape of the receiving and transmitting patches is designed to integrate both receive and transmit elements in the antenna aperture while minimizing the coupling between the two types of elements. Moreover, different shapes of the apertures in the ground plane can have different effects on the performance of an antenna. For example, an H-shaped slot or a dual-C slot have the advantage to make the slot smaller compared to linear slots, thus reducing back radiation and increasing antenna efficiency.
Moreover, in the case of an array with inclined elements, there is the need to interconnect a planar substrate, such as a printed circuit board (PCB) with an inclined substrate at an angle. In an exemplary embodiment, a planar PCB interconnects with an inclined PCB using a thick slot transition. A thick slot transition is a connecting hole through a core, where the planar PCB is located on one side of the core and the inclined PCB is located on the other side of the core. A benefit of implementing the cut-through interconnection of the two PCBs is the reduction of mechanical assembling, such as a reduction in the amount of soldering used to form a connection.
A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the Figures, where like reference numbers refer to similar elements throughout the Figures, and:
While exemplary embodiments are described herein in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that logical material, electrical, and mechanical changes may be made without departing from the spirit and scope of the invention. Thus, the following detailed description is presented for purposes of illustration only.
As illustrated in
In a typical antenna, a transmit radiating element and a receive radiating element are coupled to a diplexer to form a combined transmit and receive chain. However, the diplexer is generally a bulky component with high insertion loss. In contrast, in an exemplary embodiment, and with reference to
In an exemplary embodiment and with reference to
In an exemplary embodiment, the radiating elements are based on microstrip patch antennas. In the exemplary embodiment, the shape of the receiving and transmitting patches is designed to integrate both receive and transmit elements in the antenna aperture while minimizing the coupling between the two types of elements. In an exemplary embodiment, the radiating element is coupled by at least one of a coaxial probe, microstrip line, proximity coupling, aperture coupling, and other suitable devices. Electromagnetically coupling a microstrip line through an aperture on the ground plane of the element has several advantages in terms of bandwidth, polarization purity, and isolation between feed lines and radiating elements. Moreover, different shapes of the apertures in the ground plane can have different effects on the performance of an antenna. For example, and as illustrated in
In another exemplary embodiment, one or more stacked radiating elements comprising a T-shaped patch has increased efficiency and bandwidth compared to a prior art single patch. Furthermore, the patch may be suitable shapes other than the T-shape, such as the H-shape, triangular shape, and the like. Additionally, the T-shaped antenna has good radiation characteristics and low inter-element coupling. Therefore, in an exemplary embodiment, the T-shaped antenna is well suited to build arrays, specifically arrays with electronic beam scanning capabilities, where the low coupling between adjacent elements allows achieving easily large scanning ranges without having to compensate for mutual coupling effects due to beam scanning.
In an exemplary embodiment and with reference to
In accordance with an exemplary embodiment and with reference to
As previously discussed, in an exemplary embodiment, an antenna comprises a single aperture having both receive and transmit radiating elements. The transmit and receive functions operate at two different frequency bands and are isolated between the radiating elements. In an exemplary embodiment and with reference to
In addition to the difficulty of radiating element proximity, the design of a combined transmit/receive array antenna with beam and polarization control also has a high complexity in the integration of several components. The several components include feed networks and special interconnections between separated printed circuit boards. The components include RF feed networks plus DC and logic circuits for power supply of electronics and for control of beam and polarization. For example, in the case of a dual-linear transmit/receive antenna, four separated feed networks are integrated in the antenna structure.
Moreover, in the case of an array with inclined elements, there is the need to interconnect a planar PCB with an inclined PCB at an angle. The inclined PCB may be at an angle of 45 degrees from the planar PCB. In another embodiment, the inclined PCB is within the range of 15-65 degrees from the planar PCB, though there are other suitable angles. In an exemplary embodiment, a planar PCB interconnects with an inclined PCB using a slot transition. A slot transition is a connecting hole through a core, where the planar PCB is located on one side of the core and the inclined PCB is located on the other side of the core.
A benefit of implementing the cut-through interconnecting the two PCBs is the reduction of mechanical assembling, such as a reduction in the amount of soldering used to form a connection. This benefit provides an advantage in that it allows testing of the antenna sub-arrays with little or no damage or stress to the array. Additionally, in an exemplary embodiment, replacement of arrays takes place with little or no damage to the whole antenna, and the replacement may be accomplished in a cost effective manner.
Planar Thick Slot Transition
In an exemplary embodiment, an array comprises a first interconnection designed to facilitate RF connectivity between two planar multilayer circuit boards without any direct physical contact between the two boards. In one embodiment, soldering is not used in the connection between the planar boards. In a specific exemplary embodiment and with reference to
For example,
In an exemplary embodiment, the slot length is below the first resonant propagating mode to avoid spurious radiation. In other words, in an exemplary embodiment, the length of the slot is less than the half-wavelength at the frequency of interest. Accordingly, the RF transmission is obtained through proximity coupling. This facilitates having slots (or holes) much smaller than the size of a propagating waveguide. On the other hand, using an aperture under the cut-off frequency is limited in that the transition is inefficient for large thicknesses of the metal core. In one embodiment, the thickness of the metal core is 5 millimeters. In another embodiment, the core thickness is 12 millimeters. In yet another embodiment, the core thickness is greater than 12 millimeters, but transmission efficiency will decrease as the thickness increases.
In an exemplary embodiment, the shape of the slot can be designed depending on specific needs of surface occupation and thickness of the metal core. Typical shapes are circular, rectangular, H-shaped, and the like.
Inclined Thick Slot Transition
Similar to the planar thick slot transition, a first PCB inclined with respect to a second PCB may be interconnected in a contactless transition based on an aperture coupling effect. In an exemplary embodiment and with reference to
In an exemplary embodiment and with reference to
In an exemplary embodiment, manufacturing the connecting hole perpendicular to the bisector of the angle of inclination of the two planes is advantageous in that the transition in the faces of the structure is symmetrical and hence simplifies the design. In an exemplary embodiment, the design is also simplified in part as a result of the same microstrip-to-slot transition (i.e., the length of the microstrip open stub) being applied on both sides of the thick slot.
In yet another exemplary embodiment and with reference to
Planar Thick Coaxial Transition
A second type of structure used to interconnect two planar or inclined PCBs is also based on a metal core with a drilled circular aperture. In an exemplary embodiment, an array comprises a first PCB and a second PCB substantially parallel to one another. Likewise, a microstrip of the first PCB is substantially parallel to a microstrip of the second PCB. In an exemplary embodiment, and with reference to
In an exemplary embodiment, the first and second PCBs to be connected together are mounted on two sides of the metal core. The metal core comprises at least one hole connecting the two sides, and the microstrip lines are attached so that one end of each microstrip is at the hole. The metal core may further comprise one or more grounding pins placed around the hole in the metal core and connecting the pad on top of the first PCB with the ground of the second PCB. The circular aperture can be empty (air) or filled with a dielectric material to reduce the size of the hole.
In another exemplary embodiment, a metallic wire is surrounded by a cylinder of plastic material that fits within the diameter of the hole in the metal core. The metal wire can be first inserted in the metal core and will remain in place supported by the plastic cylinder. Then the first and second PCBs are placed and the contacts soldered.
In an exemplary method of assembly, an interconnection is formed by inserting a metallic wire in a hole of one of two PCBs at the edge of the microstrip of the one PCB and soldered in place. The PCB is mounted on one side of the metal core and the metallic wire slides through the hole in the metal core. In one embodiment, the metallic pins coming out of the metal core are inserted in the grounded metalized via holes in the PCB. The metallic pins can eventually be soldered with the circular pads on the external side of the PCB. The second PCB on the other face of the metal core is then set in place in a similar way inserting the wire in the hole at the edge of the PCB and soldered completing the connection between the two PCB.
Inclined Thick Coaxial Transition
Similar to the planar thick coaxial transition, a first PCB inclined with respect to a second PCB may be interconnected based on a coaxial section. In an exemplary embodiment and with reference to
In an exemplary embodiment and with reference to
In an exemplary method of assembly, the PCB interconnection is assembled by manufacturing a metal core with the desired inclined plane and drilling a connecting hole either perpendicular to one of the metal surfaces, or perpendicular to the bisector angle. A section of a dielectric cylinder with a metallic wire in the center is inserted in the connecting hole. The metallic wire is cut at the level of the metal surface. Additionally, the metallic wire is bent until perpendicular, or substantially perpendicular, to the surfaces of the metal core. Furthermore, in the exemplary method, a first PCB and a second PCB are placed on the metallic surfaces, and the metallic wire is threaded through the via-hole in the first and second PCBs and soldered to the microstrip lines.
In one exemplary method, ground planes of the first and second PCBs are grounded to the metal core. This may be facilitated by manufacturing at least one metallic pin around the coaxial aperture and soldering the metallic pins to grounded pads on the exposed surfaces of the first and second PCBs. Advantageously, the coaxial pin and the grounded pins can be soldered in a single process, thus reducing the complexity and cost of assembly. Similarly, a PCB may be replaced by disassembling the PCB interconnection in case of component failure.
Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of any or all the claims. As used herein, the terms “includes,” “including,” “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, no element described herein is required for the practice of the invention unless expressly described as “essential” or “critical.”
This application is a non-provisional of U.S. Provisional Application No. 61/221,504, entitled “HYBRID SINGLE APERTURE INCLINED ANTENNA,” which was filed on Jun. 29, 2009. This application is also a non-provisional of U.S. Provisional Application No. 61/250,775, entitled “HYBRID SINGLE APERTURE INCLINED ANTENNA,” which was filed on Oct. 12, 2009. This application is also a non-provisional of U.S. Provisional Application No. 61/323,285, entitled “DESIGN AND PROTOTYPING OF A MICROSTRIP TRANSMIT-RECEIVE ARRAY ANTENNA FOR MOBILE KU-BAND SATELLITE TERMINALS,” which was filed on Apr. 12, 2010. All of the contents of the previously identified applications are hereby incorporated by reference for any purpose in their entirety.
Number | Date | Country | |
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61221504 | Jun 2009 | US | |
61250775 | Oct 2009 | US | |
61323285 | Apr 2010 | US |