Patent Publication Number: US-2022239383-A1

Title: Three-dimensional wafer-stacked optical and radio frequency phased array transceiver system

Description:
BACKGROUND 
     The present disclosure relates to communication systems and, in particular, to a system and device for communicating over optical and radio frequency wavelengths. 
     Aircraft generally communicate with ground control operations over a selected communication medium. During general flight operations, aircraft can communicate with ground systems using optical communications. However, during selected moments of flight operations, optical noise is introduced, making optical communication unreliable. For example, during take-off and landing, dirt and particles can be kicked up into the air, interfering with optical signals. As a result, aircraft can select to communicate over multiple communication frequencies. However, doing so requires additional communication equipment, which adds additional weight to the aircraft. Therefore, there is a need to provide additional communication channels without significantly adding weight to the aircraft. 
     SUMMARY 
     According to one embodiment of the present disclosure, an antenna assembly for a communication system is disclosed. The antenna assembly includes an optical communication layer including a plurality of electro-optical (DO) antennas, and a radio-frequency communication layer including a plurality of radio frequency (RF) antennas. 
     According to another embodiment of the present disclosure, a communication system is disclosed. The communication system includes an antenna assembly and a processor. The antenna assembly includes an optical communication layer including a plurality of electro-optical (EO) antennas for communicating via an EO signal and a radio-frequency communication layer including a plurality of radio frequency (RF) antennas for communicating via an RF signal. The processor operates the antenna assembly to communicate via one of the EO signals and/or one of the RF signals. 
     Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The subject matter which is regarded as the disclosure is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The forgoing and other features, and advantages of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  shows a communication system  100  in an illustrative embodiment; 
         FIG. 2  shows a schematic diagram of a communication device used in the communication system of  FIG. 1 ; 
         FIG. 3  shows a schematic side view of an antenna assembly of the communication device, in an embodiment; 
         FIG. 4  shows an exploded perspective view of the antenna assembly; and 
         FIG. 5  shows a photonic vertical interconnect between an electro-optic communication layer and a radio frequency communication layer of the antenna assembly. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a communication system  100  in an illustrative embodiment. The communication system  100  includes communication devices conveyed on various vehicles. Aircraft  102 , for example, includes a communication device  110  that is capable of communicating with ground-based devices within a selected range  104 . Illustrative ground-based devices can include one or more mobile communication stations  106  which are in communication with each other. The mobile communication stations  106  can be mobile vehicles and/or portable hand-held communication devices, in various embodiments. One or more of the mobile communication stations  106  can include a communication device  110  such as used in aircraft  102 . The communication device  110  is capable of both electro-optical (EO) communication, such as with signals with wavelengths in the visible or infrared bands, and radio frequency (RF) communication which also includes millimeter wavelength signals. Thus, the aircraft  102  and ground-based communication devices  106  can communicate using either EO communication signals and/or RF communication signals, based on various conditions of the communication media and quality of signals. 
       FIG. 2  shows a schematic diagram  200  of the communication device  110  used in the communication system  100  of  FIG. 1 . The communication device  110  includes an antenna assembly  202  operated by a processor  204 . The processor  204  sends signals to the antenna assembly  202  in order to transmit a suitable signal (EO and/or RF). Incoming signals (EO and/or RF) received at the respective antenna assembly  202  are sent to the processor  204  for processing in order to read the received signals. In various embodiments, the antenna assembly  202  includes a plurality of antennas forming at least one phased array. The processor  204  sends communication signals to each of the plurality of antennas with a selected phase delay in order to steer the communication signal in a selected direction using a process known as beam steering. Additionally, the processor  204  is able to determine a direction from which an incoming communication signal is received based on a phase delay between signals received at the antenna assembly  202 . 
       FIG. 3  shows a schematic side view of the antenna assembly  202  of  FIG. 2  in an embodiment. The antenna assembly  202  is a two-dimensional thin-film device that includes an electro-optical (EO) communication layer  302  capable of transmitting and receiving EO signals and a radio frequency (RF) communication layer  304  capable of transmitting and receiving RF signals. Signals are transmitted from and received through an interface  320  of the antenna assembly  202 . In various embodiments, interface  320  is an outer surface of the EO communication layer  302  and the RF communication layer  304  is beneath the EO communication layer  304 , however this particular order is not meant as a limitation of the disclosure. In various, the RF communication layer  304  can be coincident or above the EO communication layer  304 . The RF communication layer  304  passes RF signals via interface  320  by first traversing the EO communication layer  302 . The EO communication layer  302  includes a plurality of EO antennas forming an optical phased array. The RF communication layer  304  includes a plurality of RF antennas forming a radio frequency phased array. 
     The EO communication layer  302  includes a plurality of EO antennas  306   a - 306   n  and  308   a - 308   n . In one embodiment, the plurality of EO antennas  306   a - 306   n  can form a first EO antenna group  310  and the plurality of EO antennas  308   a - 308   n  can form a second EO antenna group  312 . One or more of the plurality of EO antennas  306   a - 306   n  and  308   a - 308   n  can be implemented as a grating coupler. The EO antennas  306   a - 306   n  can form a one-dimensional phase array as shown in  FIG. 3  or a two-dimensional phase array. Similarly, the EO antennas  308   a - 308   n  can form a one-dimensional phased array or a two-dimensional phased array. 
     Within each EO antenna group, each EO antenna is separated from a nearest neighbor EO antenna by an EO antenna spacing ‘4:1’. To achieve maximum or substantially maximum efficiency, the EO antenna spacing is about half the operating wavelength of an EO signal at the EO communication layer  302 . In one embodiment, an optical wavelength of the EO signal is about 2 micrometers (μm), and consequently the EO antenna spacing is selected to be about d=1 μm. 
     The RF communication layer  302  includes RF antennas  314   a - 314   c . Although the RF communication layer  302  is shown having only three RF antennas for illustrative purposes, it is to be understood that more RF antennas can be included in the RF communication layer  302  and additional groups of EO antenna can be formed in the EO communication layer continuing the antenna sequence shown in  FIG. 2 . The RF antennas  314   a - 314   c  can form a one-dimensional phase array as shown in  FIG. 3  or a two-dimensional phase array. Each RF antenna  314   a - 314   c  is separated from its nearest neighbor RF antenna by an RF antenna spacing ‘D’. The RF antenna spacing is about half the wavelength of the RF signal though other spacings can be used to achieve maximum or substantially maximum efficiency. In one embodiment, an RF wavelength of a RF signal at the RF communication layer  304  is about 10 millimeters (mm), and consequently the RF antenna spacing is about 5 mm, corresponding to a frequency of about 30 Gigahertz (GHz). 
     The plurality of RF antenna includes a first RF antenna  314   a  and a second RF antenna  314   b . The plurality of EO antennas  306   a - 306   n  in the first EO antenna group  310  can be arranged to form a line between the first RF antenna  314   a  and a second RF antenna  314   b . In other words, a plane perpendicular to the interface  320  and containing both the first RF antenna  314   a  and the second RF antenna  314   b  also contains the plurality of EO antennas  306   a - 306   n . Similarly, the plurality of EO antenna  308   a - 308   n  in the second EO antenna group  312  form a line between the second RF antenna  314   b  and the third RF antenna  314   c . As shown in  FIG. 2 , the first group  310  and the second group  312  can be separated by a gap at the location an RF antenna (e.g., RF antenna  314   b ), thereby reducing interference of any RF signals by an otherwise overlying EO antenna. 
     In various embodiments, the plurality of EO antennas can form a two-dimensional array and the plurality of RF antennas of the RF communication layer can form a two-dimensional array. The two-dimensional array of the EO antennas can include a void at the location of an underlying RF antenna in order to facilitate RF communications. 
     Referring back to  FIG. 2 , the processor  204  can select to communicate using either an EO signal or an RF signal based on a parameter of an EO signal. For example, when a quality of an EO signal drops below a selected threshold, then the processor  204  can switch over to transmitting and receiving RF signals. When the quality of an EO signal is above the selected threshold, the processor  204  can switch back to transmitting and receiving EO signals. When the quality of the EO signal is above the selected threshold, the EO signals can be of higher resolution or higher data rate than the RF signals. 
       FIG. 4  shows an exploded perspective view  400  of the antenna assembly. The assembly includes a Silicon-Germanium (SiGe) and Complementary Metal Oxide Semiconductor (CMOS) layer  402 , a direct bond hybridization layer  404 , a silicon photonics layer  406  and a cooling layer  408 . The SiGe/CMOS layer  402  includes one or more EO antennas (such as Bragg reflectors), EO amplifiers, RF antennas and RF phase shifters. The silicon photonics (SiPho) layer  406  includes light waveguides and phase shifters for implementing optical beam steering along with optical gratings or similar devices for transmitting the light from the SiPho layer  406  to the SiGe/CMOS layer  402  (also shown in the interposer wafer). The cooling layer  408  includes various microfluid cooling devices therein for maintaining a temperature of the antenna assembly  202 . 
     In is to be understood that the order of the layers is not meant as a limitation to the disclosure. In  FIG. 4 , the SiGe/CMOS layer  402  includes EO amplifiers and amplifiers along with RF phase shifters and antennas, and the SiPho layer  406  has waveguides and photonic (EO) phase shifters and other photonic integrated circuit (PIC) components. In various embodiments, the SiPho or other photonic components and SiGe/CMOS components are fabricated into a single wafer or layer. Also, in various embodiments, the SiPho layer  406  can includes photonic materials made of material other than Silicon, such as Gallium Nitride (GaN) and Indium Phosphide (InP). 
       FIG. 5  shows a photonic vertical interconnect  500  between the EO communication layer  302  and RF communication layer  304 , in an embodiment. The photonic vertical interconnect  500  can be used to communicate optical signal between the EO communication layer  302  and the RF communication layer  304 . In various embodiments, the photonic vertical interconnect  500  can include a Bragg grating coupler, coupled waveguides, lensed waveguides, detector/transmitter pairs or through-silicon waveguides, etc. 
     The photonic vertical interconnect  500  includes a first optical communication layer  502  and a second optical communication layer  504  which transfer optical signal  506  between them. The first optical communication layer  502  can be the EO communication layer  302  and the second optical communication layer  504  can be the RF communication layer  304 , in various embodiments. The first optical communication layer  502  includes a first waveguide  508  and a first SiO 2  layer  510  adjacent the first waveguide  508 . The first SiO 2  layer  510  includes a first Bragg grating  510  therein. Light  520  passing through the first waveguide  508  at the interface between the first waveguide  508  and the first SiO 2  layer  510  is coupled out of the first waveguide  508  and diverted toward the second optical communication layer  504 . In addition, light received from the second optical communication layer  504  via the first Bragg grating  510  is coupled into the first waveguide  408  in order to be transmitted along the first waveguide  508 . 
     Similarly, the second optical communication layer  404  includes a second waveguide  514  and a second SiO 2  layer  516  adjacent the second waveguide  514 . The second SiO 2  layer  516  includes a second Bragg grating  518  therein. Light  520  passing through the second waveguide  514  at the interface between the second waveguide  514  and the second SiO 2  layer  516  is coupled out of the second waveguide  514  and diverted toward the first optical communication layer  502 . In addition, light received from the first optical communication layer  502  via the second Bragg grating  518  is coupled into the second waveguide  514  in order to be transmitted along the second waveguide  514 . 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one more other features, integers, steps, operations, element components, and/or groups thereof. 
     The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for exemplary embodiments with various modifications as are suited to the particular use contemplated. 
     While the exemplary embodiment to the disclosure had been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the disclosure first described.