Patent Application
20170117625
This disclosure relates to the field of phased-array antennas, and in particular, to mitigating electromagnetic (EM) radiation effects that arises when multiple phased-array antennas are integrated together.
Satellite communication systems may include both a receive antenna and a transmit antenna in order to provide bi-directional communication capabilities to a platform. The receive antenna and the transmit antenna are separated from each other to prevent the receive antenna from being overwhelmed by the EM transmissions generated by the transmit antenna. The antennas are also located along a portion of the platform that has a direct line of sight to the satellite(s).
However, providing a separation between the receive antenna and the transmit antenna can be difficult when the physical real estate onboard the platform for the antennas is limited. For instance, on a small aircraft such as a drone, the antennas would ideally be located along a top surface of the fuselage of the drone at a sufficient separation from each other in order to preclude the transmit antenna from generating Radio Frequency (RF) interference at the receive antenna. Yet, there may not be enough physical area on the fuselage to provide such separation. Further, utilizing multiple antennas, even when they are sufficiently separated from each other, involves the use of two separate enclosures that are each subjected to the environment and therefore, provide the possibility of multiple points of failure for the communication system. Further still, there is an ongoing desire to provide bi-directional communication systems that are of a light weight and compact design.
Embodiments described herein provide for integrating a pair of phased-array antennas onto a common electrically-conductive plate, with groves fabricated into a top surface of the plate that operate as an RF choke. The RF choke providing an attenuation of the EM radiation induced on a receive antenna formed on the plate by a transmit antenna formed on the plate
One embodiment comprises an apparatus that includes an electrically-conductive plate that has a top surface and an opposing bottom surface, a transmit phased-array antenna comprising a first plurality of holes through the plate from the top surface to the bottom surface that include RF transmit elements, and a receive phased-array antenna comprising a second plurality of holes through the plate from the top surface to the bottom surface that include RF receive elements. The apparatus further includes a plurality of grooves fabricated on the top surface of the plate that attenuate EM radiation induced on the receive phased-array antenna by the transmit phased-array antenna by a pre-defined amount.
Another embodiment comprises a method of fabricating a pair of phased-array antennas that are integrated on a common electrically-conductive plate. The method comprises forming a transmit phased-array antenna utilizing a first plurality of holes through an electrically-conductive plate that include RF transmit elements. The method further comprises forming a receive phased-array antenna utilizing a second plurality of holes through the plate that include RF receive elements. The method further comprises fabricating a plurality of grooves on a top surface of the plate that attenuate EM radiation induced on the receive phased-array antenna by the transmit phased-array antenna by a pre-defined amount.
Another embodiment comprises an apparatus that includes an electrically-conductive aperture plate that has a top surface, a first antenna aperture formed from a first plurality of holes through the aperture plate, and a second antenna aperture formed from a second plurality of holes through the aperture plate. The apparatus further comprises a plurality of grooves fabricated on the top surface of the aperture plate that are configured to attenuate EM radiation induced on a receive antenna formed from the first antenna aperture by a transmit antenna formed from the second antenna aperture by a pre-defined amount.
The above summary provides a basic understanding of some aspects of the specification. This summary is not an extensive overview of the specification. It is intended to neither identify key or critical elements of the specification nor delineate any scope particular embodiments of the specification, or any scope of the claims. Its sole purpose is to present some concepts of the specification in a simplified form as a prelude to the more detailed description that is presented later.
Some embodiments are now described, by way of example only, and with reference to the accompanying drawings. The same reference number represents the same element or the same type of element on all drawings.
The figures and the following description illustrate specific exemplary embodiments. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the embodiments and are included within the scope of the embodiments. Furthermore, any examples described herein are intended to aid in understanding the principles of the embodiments, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the inventive concept(s) is not limited to the specific embodiments or examples described below, but by the claims and their equivalents.
In this embodiment, mobile platform 100 communicates with one or more satellites 104 using an antenna device 102, although in other embodiments antenna device 102 may be used to communicate with other entities that utilize Common Data Link (CDL) protocols. In this embodiment, antenna device 102 provides a bi-directional communication link between mobile platform 100 and satellite(s) 104. For example, antenna device 102 may communicate with satellite(s) 104 to provide high speed bi-directional data services to mobile platform 100 over the Ka-band, which covers frequencies from 26.5 GHz to 40 GHz. One example of a Ka-band data service that may be provided by satellite(s) 104 includes the Inmarsat Global Xpress (GX) program.
Receive antenna 208 is formed from a second plurality of holes 209 that are disposed away from holes 207, and traverse through plate 202 between top surface 204 and bottom surface 205. Holes 209 include RF receive elements 211 that are used to receive RF signals.
Plate 202 may be referred to as an aperture plate in some embodiments. One example of the material that plate 202 may be formed from is aluminum, although plate 202 may be formed from any material that is electrically-conductive as desired.
In this embodiment, plate 202 is illustrated having surfaces 204-205 that are planar, although in other embodiments, surfaces 204-205 may be include non-planar features that allow antenna device 202 to conform to an outer surface of mobile platform 100.
Plate 202 includes a plurality of grooves 212 on top surface 204. Grooves 212 operate as an RF choke to attenuate EM radiation induced upon receive antenna 208 when transmit antenna 206 is operating (e.g., when RF transmit elements 210 are generating RF signals). Grooves 212 are located between transmit antenna 206 and receive antenna 208, and traverse across plate 202.
Grooves 212 in this embodiment are spaced apart, and have a period 304 and a width 306. Period 304, width 306, and/or depth 302 may be selected to provide a desired RF attenuation performance of grooves 212.
During RF transmissions, transmit antenna 206 has the potential to induce EM radiation on receive antenna 208 due to the close proximity of receive antenna 208 to transmit antenna 206. During RF transmission, RF transmit elements 210 within transmit antenna 206 induce a surface current 308 at plate 202, which can interfere with the RF performance of RF receive elements 211 within receive antenna 208. Grooves 212 operate as an RF choke by cancelling out a portion of surface current 308. Grooves 212 present a different path length to a current 309 that travels within grooves 212, and a 180 degree phase shift is imparted onto current 309. When surface current 308 and current 309 re-combine, a portion of surface current 308 is cancelled by current 309. The amount of attenuation of surface current 308 can be controlled based on the number of grooves 212 that are included on top surface 204 of plate 202.
The distance that current 309 takes through grooves 212 is based on the surface path length within each of grooves 212, so the performance of grooves 212 as an RF choke is sensitive to the center frequency of transmit antenna 206. The performance of grooves 212 as an RF choke can be improved by varying depth 302 for grooves 212.
In
Prior to the actual fabrication of an integrated pair of phased-array antennas, an RF designer starts with a number of design parameters that constrain some of the physical parameters of an integrated phased-array antenna. For instance, the physical size of the antenna device may be limited on smaller mobile platforms, the number of grooves in the plate may be constrained by the available surface area that may be used as an RF choke, the aperture sizes of the transmit and/or the receive antenna may have both RF constraints and physical constraints. From an RF perspective, the aperture size of the transmit antenna may have a lower limit based on the effective radiated power of the transmit antenna, the sensitivity of the intended receiver of the transmit antenna, etc. The aperture size of the receive antenna may have a lower limit based on a corresponding RF sensitivity of the receive antenna, the transmit power of the RF source for the receive antenna, etc.
To fabricate antenna device 102 (see
To fabricate the RF choke for antenna device 102, grooves 212 are fabricated on top surface 204 of plate 202 (see
The particular placement of grooves 212 on plate 202 is subject to design considerations, with some options including circumscribing transmit antenna 206 and/or receive antenna 208 (see step 902 of
As discussed previously, the depth may vary around the idealized ¼ wavelength to attenuate frequencies slightly above and/or below the operating frequencies. For example, the depth may increase (see step 906 of
Other fabrication steps for antenna device 102 may include forming dielectric material 602 in grooves 212 (see step 1002 of
In this embodiment, transmit antenna aperture 1104 comprises 2048 separate holes 1112, forming an area that is 17.625 inches by 17.625inches on each side 1114. The designed frequency of a transmit phased-array antenna formed from transmit antenna aperture 1104 (e.g., utilizing active RF elements within holes 1112) is 14 GHz to 14.5 GHz in this embodiment.
Receive antenna aperture 1106 comprises 2880 separate holes 1116, forming an area that is 23.925 inches by 23.925 inches on each side 1118. The designed frequency of a receive phased-array antenna formed from receive antenna aperture 1106 (e.g., utilizing passive RF elements within holes 1116) is 10.7 GHz to 12.75 GHz. A center of transmit antenna aperture 1104 and a center of receive antenna aperture 1106 are separated by a distance 1120 in this embodiment that is 25.23 inches.
Utilizing the embodiments described herein allows for the integration of both transmit phased-array and receive phased-array antennas together on the same electrically-conductive plate, which eliminates the use of two separate enclosures that house separate antenna assemblies. Further, the embodiments described herein provide bi-directional communication systems that are of a light weight and compact design.
Any of the various elements shown in the figures or described herein may be implemented as hardware, software, firmware, or some combination of these. For example, an element may be implemented as dedicated hardware. Dedicated hardware elements may be referred to as “processors”, “controllers”, or some similar terminology. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, a network processor, application specific integrated circuit (ASIC) or other circuitry, field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), non-volatile storage, logic, or some other physical hardware component or module.
Also, an element may be implemented as instructions executable by a processor or a computer to perform the functions of the element. Some examples of instructions are software, program code, and firmware. The instructions are operational when executed by the processor to direct the processor to perform the functions of the element. The instructions may be stored on storage devices that are readable by the processor. Some examples of the storage devices are digital or solid-state memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media.
Although specific embodiments were described herein, the scope is not limited to those specific embodiments. Rather, the scope is defined by the following claims and any equivalents thereof.
