Patent Publication Number: US-2023163465-A1

Title: High gain and large bandwidth antenna incorporating a built-in differential feeding scheme

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY 
     This application is a continuation of U.S. patent application Ser. No. 17/444,986, filed Aug. 12, 2021, which is a continuation of U.S. patent application Ser. No. 17/195,401, filed Mar. 8, 2021, now U.S. Pat. No. 11,145,979, which is a continuation of U.S. patent application Ser. No. 16/949,878, filed Nov. 18, 2020, now U.S. Pat. No. 10,944,172, which is a continuation of U.S. patent application Ser. No. 16/410,981, filed May 13, 2019, now U.S. Pat. No. 10,931,014, which claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 62/724,175 filed Aug. 29, 2018 and U.S. Provisional Patent Application No. 62/732,070 filed Sep. 17, 2018, each of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to an antenna structure. More specifically, the present disclosure relates to an antenna structure that generates a moderate radiated gain over a large frequency range. 
     BACKGROUND 
     The concept of Massive Multi-Input Multi-Output (MIMO) is aimed at improving the coverage and spectral efficiency of the next generation of telecommunication systems. In the next generation of telecommunication systems, users are dedicated with one or multiple spatial directions for the intended communication purposes. Massive MIMO-based systems generate multiple beams and form beams subjectively for a user or a group of users in order to increase the desired radiation efficiency. Some Massive MIMO antenna systems have a large number of antenna elements. Therefore, the overall system&#39;s performance relies on the performance of individual elements which have a high gain and a reasonably small structure compared to the wavelength at the operating frequency. The operating frequency can range from 2.3-2.6 GHz and/or 3.4-3.6 GHz. 
     Because of the design frequency and resulting wavelength, difficulties arise in designing an antenna element with a gain of equal or better than ˜6 dB and a wideband radiation over a range of 3.2-3.9 GHz while maintaining a simple and cost-effective overall antenna structure that can be mass-produced. 
     Further, filtering masks in requested by Massive MIMO communication systems are generally realized by an external filter or filters such as cavity or surface acoustic wave filters in order to provide a high roll-off for out-of-band rejection. These filtering masks can result in losses associated with interconnects to the physical point of contacts, soldering, and mechanical restriction. These filtering masks are typically bulky and expensive. 
     SUMMARY 
     Embodiments of the present disclosure include an antenna and a base station including an antenna. 
     In one embodiment, an antenna includes a sub-array. The sub-array includes first and second unit cells and a feed network. The first unit cell includes a first patch. The second unit cell includes a second patch. Each of the first and second patches have a quadrilateral shape. The feed network comprises a first transmission line, a second transmission line, a third transmission line, and a fourth transmission line. The first transmission line terminates below a first corner of the first patch and a first corner of the second patch. The second transmission line terminates below a third corner of the first patch and a third corner of the second patch, wherein the first corners are opposite the third corners on the respective first and second patches. The third transmission line terminates below a second corner of the first patch and a fourth corner of the second patch. The fourth transmission line terminates below a fourth corner of the first patch and a second corner of the second patch, wherein the second corners are opposite the fourth corners on the respective first and second patches. 
     In another embodiment, a base station includes an antenna including a sub-array. The sub-array includes first and second unit cells and a feed network. The first unit cell includes a first patch. The second unit cell includes a second patch. Each of the first and second patches have a quadrilateral shape. The feed network comprises a first transmission line, a second transmission line, a third transmission line, and a fourth transmission line. The first transmission line terminates below a first corner of the first patch and a first corner of the second patch. The second transmission line terminates below a third corner of the first patch and a third corner of the second patch, wherein the first corners are opposite the third corners on the respective first and second patches. The third transmission line terminates below a second corner of the first patch and a fourth corner of the second patch. The fourth transmission line terminates below a fourth corner of the first patch and a second corner of the second patch, wherein the second corners are opposite the fourth corners on the respective first and second patches. 
     In another embodiment, an antenna includes a sub-array. The sub-array includes a first unit cell, a second unit cell, a feed network, and a pair of decoupling elements. The first unit comprises a first patch. The second unit cell comprises a second patch. The feed network includes a first transmission line and a second transmission line. The pair of decoupling elements comprises a first decoupling element corresponding to the first transmission line and a second decoupling element corresponding to the second transmission line. 
     In this disclosure, the terms antenna module, antenna array, beam, and beam steering are frequently used. An antenna module may include one or more arrays. One antenna array may include one or more antenna elements. Each antenna element may be able to provide one or more polarizations, for example vertical polarization, horizontal polarization or both vertical and horizontal polarizations at or around the same time. Vertical and horizontal polarizations at or around the same time can be refracted to an orthogonally polarized antenna. An antenna module radiates the accepted energy in a particular direction with a gain concentration. The radiation of energy in the particular direction is conceptually known as a beam. A beam may be a radiation pattern from one or more antenna elements or one or more antenna arrays. 
     Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims. 
     Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout the present disclosure. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “transmit,” “receive,” and “communicate,” as well as derivatives thereof, encompass both direct and indirect communication. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrase “associated with,” as well as derivatives thereof, means to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The term “controller” means any device, system or part thereof that controls at least one operation. Such a controller may be implemented in hardware or a combination of hardware and software and/or firmware. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C. 
     Moreover, various functions described below can be implemented or supported by one or more computer programs, each of which is formed from computer readable program code and embodied in a computer readable medium. The terms “application” and “program” refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer readable program code. The phrase “computer readable program code” includes any type of computer code, including source code, object code, and executable code. The phrase “computer readable medium” includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. A “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links that transport transitory electrical or other signals. A non-transitory computer readable medium includes media where data can be permanently stored and media where data can be stored and later overwritten, such as a rewritable optical disc or an erasable memory device. 
     Definitions for other certain words and phrases are provided throughout the present disclosure. Those of ordinary skill in the art should understand that in many if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of this disclosure and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
         FIG.  1    illustrates a system of a network according to various embodiments of the present disclosure; 
         FIG.  2    illustrates a base station according to various embodiments of the present disclosure; 
         FIG.  3 A  illustrates a top perspective view of a sub-array according to various embodiments of the present disclosure; 
         FIG.  3 B  illustrates a side view of a sub-array according to various embodiments of the present disclosure; 
         FIG.  3 C  illustrates an exploded view of a sub-array according to various embodiments of the present disclosure; 
         FIGS.  4 A- 4 B  illustrate example feed networks according to various embodiments of the present disclosure; 
         FIG.  5 A  illustrates a top perspective view of a sub-array according to various embodiments of the present disclosure; 
         FIG.  5 B  illustrates a side view of a sub-array according to various embodiments of the present disclosure; 
         FIG.  5 C  illustrates an exploded view of a sub-array according to various embodiments of the present disclosure; and 
         FIG.  6    illustrates an example feed network of a sub-array according to various embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1  through  6   , discussed below, and the various embodiments used to describe the principles of the present disclosure are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless communication system. 
     To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a “beyond 4G network” or a “post LTE system.” 
     The 5G communication system is considered to be implemented in higher frequency (mmWave) bands and sub-6 GHz bands, e.g., 3.5 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission coverage, the beamforming, Massive MIMO, full dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques and the like are discussed in 5G communication systems. 
     In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul communication, moving network, cooperative communication, coordinated multi-points (CoMP) transmission and reception, interference mitigation and cancellation and the like. 
       FIG.  1    illustrates an example wireless network according to embodiments of the present disclosure. The embodiment of the wireless network shown in  FIG.  1    is for illustration only. Other embodiments of the wireless network  100  could be used without departing from the scope of this disclosure. 
     As shown in  FIG.  1   , the wireless network  100  includes a gNB  101 , a gNB  102 , and a gNB  103 . The gNB  101  communicates with the gNB  102  and the gNB  103 . The gNB  101  also communicates with at least one network  130 , such as the Internet, a proprietary Internet Protocol (IP) network, or other data network. 
     The gNB  102  provides wireless broadband access to the network  130  for a first plurality of UEs within a coverage area  120  of the gNB  102 . The first plurality of UEs includes a UE  111 , which may be located in a small business (SB); a UE  112 , which may be located in an enterprise (E); a UE  113 , which may be located in a WiFi hotspot (HS); a UE  114 , which may be located in a first residence (R); a UE  115 , which may be located in a second residence (R); and a UE  116 , which may be a mobile device (M), such as a cell phone, a wireless laptop, a wireless PDA, or the like. The gNB  103  provides wireless broadband access to the network  130  for a second plurality of UEs within a coverage area  125  of the gNB  103 . The second plurality of UEs includes the UE  115  and the UE  116 . In some embodiments, one or more of the gNBs  101 - 103  may communicate with each other and with the UEs  111 - 116  using 5G, LTE, LTE-A, WiMAX, WiFi, or other wireless communication techniques. 
     Depending on the network type, the term “base station” or “BS” can refer to any component (or collection of components) configured to provide wireless access to a network, such as transmit point (TP), transmit-receive point (TRP), an enhanced base station (eNodeB or gNB), a 5G base station (gNB), a macrocell, a femtocell, a WiFi access point (AP), or other wirelessly enabled devices. Base stations may provide wireless access in accordance with one or more wireless communication protocols, e.g., 5G 3GPP new radio interface/access (NR), long term evolution (LTE), LTE advanced (LTE-A), high speed packet access (HSPA), Wi-Fi 802.11a/b/g/n/ac, etc. For the sake of convenience, the terms “BS” and “TRP” are used interchangeably in the present disclosure to refer to network infrastructure components that provide wireless access to remote terminals. Also, depending on the network type, the term “user equipment” or “UE” can refer to any component such as “mobile station,” “subscriber station,” “remote terminal,” “wireless terminal,” “receive point,” or “user device.” For the sake of convenience, the terms “user equipment” and “UE” are used in the present disclosure to refer to remote wireless equipment that wirelessly accesses a BS, whether the UE is a mobile device (such as a mobile telephone or smartphone) or is normally considered a stationary device (such as a desktop computer or vending machine). 
     Dotted lines show the approximate extents of the coverage areas  120  and  125 , which are shown as approximately circular for the purposes of illustration and explanation only. It should be clearly understood that the coverage areas associated with gNBs, such as the coverage areas  120  and  125 , may have other shapes, including irregular shapes, depending upon the configuration of the gNBs and variations in the radio environment associated with natural and man-made obstructions. 
     Although  FIG.  1    illustrates one example of a wireless network, various changes may be made to  FIG.  1   . For example, the wireless network could include any number of gNBs and any number of UEs in any suitable arrangement. Also, the gNB  101  could communicate directly with any number of UEs and provide those UEs with wireless broadband access to the network  130 . Similarly, each gNB  102 - 103  could communicate directly with the network  130  and provide UEs with direct wireless broadband access to the network  130 . Further, the gNBs  101 ,  102 , and/or  103  could provide access to other or additional external networks, such as external telephone networks or other types of data networks. 
       FIG.  2    illustrates an example gNB  102  according to embodiments of the present disclosure. The embodiment of the gNB  102  illustrated in  FIG.  2    is for illustration only, and the gNBs  101  and  103  of  FIG.  1    could have the same or similar configuration. However, gNBs come in a wide variety of configurations, and  FIG.  2    does not limit the scope of this disclosure to any particular implementation of a gNB. 
     As shown in  FIG.  2   , the gNB  102  includes multiple antennas  205   a - 205   n , multiple radiofrequency (RF) transceivers  210   a - 210   n , transmit (TX) processing circuitry  215 , and receive (RX) processing circuitry  220 . The gNB  102  also includes a controller/processor  225 , a memory  230 , and a backhaul or network interface  235 . In various embodiments, the antennas  205   a - 205   n  may be a high gain and large bandwidth antenna that may be designed based on a concept of multiple resonance modes and may incorporate a stacked or multiple patch antenna scheme. For example, in various embodiments, each of the multiple antennas  205   a - 205   n  can include one or more antenna panels that includes one or more sub-arrays (e.g., the sub-array  300  illustrated in  FIGS.  3 A-C  or the sub-array  500  illustrated in  FIGS.  5 A- 5 C ). 
     The RF transceivers  210   a - 210   n  receive, from the antennas  205   a - 205   n , incoming RF signals, such as signals transmitted by UEs in the wireless network  100 . The RF transceivers  210   a - 210   n  down-convert the incoming RF signals to generate IF or baseband signals. The IF or baseband signals are sent to the RX processing circuitry  220 , which generates processed baseband signals by filtering, decoding, and/or digitizing the baseband or IF signals. The RX processing circuitry  220  transmits the processed baseband signals to the controller/processor  225  for further processing. 
     The TX processing circuitry  215  receives analog or digital data (such as voice data, web data, e-mail, or interactive video game data) from the controller/processor  225 . The TX processing circuitry  215  encodes, multiplexes, and/or digitizes the outgoing baseband data to generate processed baseband or IF signals. The RF transceivers  210   a - 210   n  receive the outgoing processed baseband or IF signals from the TX processing circuitry  215  and up-converts the baseband or IF signals to RF signals that are transmitted via the antennas  205   a - 205   n.    
     The controller/processor  225  can include one or more processors or other processing devices that control the overall operation of the gNB  102 . For example, the controller/processor  225  could control the reception of forward channel signals and the transmission of reverse channel signals by the RF transceivers  210   a - 210   n , the RX processing circuitry  220 , and the TX processing circuitry  215  in accordance with well-known principles. The controller/processor  225  could support additional functions as well, such as more advanced wireless communication functions. For instance, the controller/processor  225  could support beam forming or directional routing operations in which outgoing/incoming signals from/to multiple antennas  205   a - 205   n  are weighted differently to effectively steer the outgoing signals in a desired direction. Any of a wide variety of other functions could be supported in the gNB  102  by the controller/processor  225 . 
     The controller/processor  225  is also capable of executing programs and other processes resident in the memory  230 , such as an OS. The controller/processor  225  can move data into or out of the memory  230  as required by an executing process. 
     The controller/processor  225  is also coupled to the backhaul or network interface  235 . The backhaul or network interface  235  allows the gNB  102  to communicate with other devices or systems over a backhaul connection or over a network. The interface  235  could support communications over any suitable wired or wireless connection(s). For example, when the gNB  102  is implemented as part of a cellular communication system (such as one supporting 5G, LTE, or LTE-A), the interface  235  could allow the gNB  102  to communicate with other gNBs over a wired or wireless backhaul connection. When the gNB  102  is implemented as an access point, the interface  235  could allow the gNB  102  to communicate over a wired or wireless local area network or over a wired or wireless connection to a larger network (such as the Internet). The interface  235  includes any suitable structure supporting communications over a wired or wireless connection, such as an Ethernet or RF transceiver. 
     The memory  230  is coupled to the controller/processor  225 . Part of the memory  230  could include a RAM, and another part of the memory  230  could include a Flash memory or other ROM. 
     Although  FIG.  2    illustrates one example of gNB  102 , various changes may be made to  FIG.  2   . For example, the gNB  102  could include any number of each component shown in  FIG.  2   . As a particular example, an access point could include a number of interfaces  235 , and the controller/processor  225  could support routing functions to route data between different network addresses. As another particular example, while shown as including a single instance of TX processing circuitry  215  and a single instance of RX processing circuitry  220 , the gNB  102  could include multiple instances of each (such as one per RF transceiver). In addition, various components in  FIG.  2    could be combined, further subdivided, or omitted and additional components could be added according to particular needs. 
       FIGS.  3 A- 3 C  illustrate a sub-array according to various embodiments of the present disclosure.  FIG.  3 A  illustrates a top perspective view of a sub-array according to various embodiments of the present disclosure.  FIG.  3 B  illustrates a side view of a sub-array according to various embodiments of the present disclosure.  FIG.  3 C  illustrates an exploded view of a sub-array according to various embodiments of the present disclosure. 
     The sub-array  300  includes a first unit cell and a second unit cell (for example, the first unit cell  401  and second unit cell  402  described in  FIGS.  4 A- 4 B ). The first unit cell includes a first patch  321  and the second unit cell includes a second patch  322 . A feed network  350  is provided that feeds each of the first unit cell and the second unit cell. The sub-array  300 , including the first unit cell and the second unit cell, comprises a ground plane  305 , a first layer  310 , a second layer  320 , a third layer  330 , and a fourth layer  340 . The ground plane  305  is comprised of metal and is positioned on the underside of the first layer  310 . 
     The first layer  310  is comprised of a substrate. The first layer  310  includes a feed network  350  positioned on the opposite side of the first layer  310  from the ground plane  305 . The feed network  350  transmits power to the first unit cell and the second unit cell of the sub-array  300 . The feed network  350  can be a series/corporate feed network. The feed network  350  includes a first transmission line  351 , a second transmission line  352 , a third transmission line  353 , a fourth transmission line  354 , a first excitation port  361 , and a second excitation port  362 . The feed network  350  is configured to correspond to the first patch  321  and the second patch  322  that are provided in the second layer  320 . 
     The second layer  320  is comprised of a substrate. For example, the second layer  320  can be a layer of electromagnetic (EM) or dielectric material. In some embodiments, a space is provided between the first layer  310  and the second layer  320 . The space includes the feed network  350  but otherwise is an absence of metallization elements. Although illustrated as an empty space filled with air, the space can include a dielectric material. The second layer  320  includes the first patch  321  and the second patch  322 . In some embodiments, the first patch  321  and the second patch  322  are positioned on top of the second layer  320 . For example, the first patch  321  and the second patch  322  can be stuck, staked, or grown on the second layer  320 . The dielectric material of the second layer  320  allows EM radiation to pass through the dielectric material of the second layer  320  to the hollow cavity of the third layer  330 . In other embodiments, when the second layer  320  is an EM material, the first patch  321  and the second patch  322  can comprise a dielectric material that allows EM radiation to pass through the first patch  321  and the second patch  322  to the hollow cavity of the third layer  330 . 
     Each of the first patch  321  and the second patch  322  are provided in a quadrilateral shape and include four corners. For example, the first patch  321  includes a first corner  321   a , a second corner  321   b , a third corner  321   c , and a fourth corner  321   d . The first corner  321   a  is arranged opposite of the third corner  321   c . The second corner  321   b  is arranged opposite of the fourth corner  321   d . This description should not be construed as limiting. In various embodiments, the first patch  321  can be a square, a rectangle, or any other shape where a first corner is opposite a third corner and a second corner is opposite a fourth corner. 
     The second patch  322  includes a first corner  322   a , a second corner  322   b , a third corner  322   c , and a fourth corner  322   d . The first corner  322   a  is arranged opposite of the third corner  322   c . The second corner  322   b  is arranged opposite of the fourth corner  322   d . This description should not be construed as limiting. In various embodiments, the second patch  322  can be a square, a rectangle, or any other shape where a first corner is opposite a third corner and a second corner is opposite a fourth corner. 
     The feed network  350  feeds both of the first unit cell and the second unit cell and is configured to correspond to the first patch  321  and the second patch  322  in the second layer  320 . For example, the first transmission line  351  includes the first excitation port  361  and terminates below the first corner  321   a  of the first patch  321  and the first corner  322   a  of the second patch  322 . The second transmission line  352  terminates below the third corner  321   c  of the first patch  321  and the third corner  322   c  of the second patch  322 . The third transmission line  353  includes the second excitation port  362  and terminates below the second corner  321   b  of the first patch  321  and the fourth corner  322   d  of the second patch  322 . The fourth transmission line  354  terminates below the fourth corner  321   d  of the first patch  321  and the second corner  322   b  of the second patch  322 . Although the term below is used to describe the termination points of the first transmission line, second transmission line, third transmission line, and fourth transmission line, this description is intended to be relative and should not be construed as a limitation on the orientation of the antennas or subarrays discussed herein. The termination point can be modified for perspective and is intended to encompass any position above, around, near, or to the side of any of the respective corners described above. For example, the term terminate below can be used to describe any of the first transmission line, second transmission line, third transmission line, and fourth transmission line terminating more closely to the corner than the center of the respective patch. 
     The third layer  330  is a hollow cavity formed by an enclosure. The enclosed portion comprises four sides and is open on each end. The openings on each end of the cavity enclosure provide an air gap  335  between the second layer  320  and the fourth layer  340 . The air gap  335  allows electromagnetic transmission from the first patch  321  and second patch  322  to flow through the hollow cavity to the fourth layer  340 . The third layer  330  improves the isolation and directivity of the sub-array  300 . 
     The fourth layer  340  is comprised of a substrate. For example, the fourth layer  340  can be a layer of EM or dielectric material. The fourth layer  340  includes a third patch  341  and a fourth patch  342 . In some embodiments, the third patch  341  and the fourth patch  342  are positioned on the underside of the fourth layer  340  proximate to the hollow cavity of the third layer  330 . For example, the third patch  341  and fourth patch  342  can be stuck, staked, or grown on the fourth layer  340 . The dielectric material of the fourth layer  340  allows EM radiation to pass through the fourth layer  340  to be radiated by the antenna  205   a - 205   n . In other embodiments, when the fourth layer  340  is an EM material, the third patch  341  and the fourth patch  342  can comprise a dielectric material that allows EM radiation to pass through the third patch  341  and the fourth patch  342  to be radiated by the antenna  205   a - 205   n.    
     The third patch  341  and the fourth patch  342  correspond to the first patch  321  and the second patch  322 , respectively, on the second layer  320 . The first unit cell includes the first patch  321  and the third patch  341 . The second unit cell includes the second patch  322  and the fourth patch  342 . Each of the third patch  341  and the fourth patch  342  are larger than each of the first patch  321  and second patch  322 , respectively. In other words, the third patch  341  of the first unit cell is larger than the first patch  321  of the first unit cell and the fourth patch  342  of the second unit cell is larger than the second patch  322  of the second unit cell. 
     In the sub-array  300 , the first patch  321  and the second patch  322  are positioned proximate to the feed network  350  and separated from the feed network  350  by the first layer  310 . The third patch  341  and the fourth patch  342  are separated from the first patch  321  and the second patch  322  by the air gap  335  provided by the third layer  330 . This configuration allows the sub-array  300  to achieve the desired radiation at a high gain and lower cross-polarization rejection ratio. 
     In some embodiments, one or more sub-arrays  300  can be included in an antenna, for example an antenna  205   a - 205   n . For example, one or more sub-arrays  300  can be developed into an antenna  205   n  comprising eight sub-arrays  300  arranged in a two by four arrangement while both the sub-array to sub-array and port-to-port isolations are maintained at high levels. In another example, one or more sub-arrays  300  can be developed into an antenna  205   n  comprising sixteen sub-arrays  300  arranged in one by sixteen, two by eight, or four by four arrangements while both the sub-array to sub-array and port-to-port isolations are maintained at high levels. These examples are not intended as limiting, and in some embodiments one or more sub-arrays  300  can be developed into antennas  205   n  comprising one hundred or more sub-arrays  300  while both the sub-array to sub-array and port-to-port isolations are maintained at high levels. In any of the above-examples, the sub-array  300  can propagate fields at the slanted +45 degree and −45 degree polarizations at or around the same time. Embodiments of the present disclosure, for example the embodiments described herein in  FIGS.  3 A- 3 C , can radiate orthogonal polarization with an advantageous level of cross-polarization rejection. 
     In various embodiments, the available area for each sub-array  300  arranged in the antenna  205   a - 205   n  can be less than 10,000 square millimeters. For example, the sub-array  300  arranged in the antenna  205   a - 205   n  can be arranged on a 62.5 mm by 132 mm area. This particular arrangement, when implemented in an antenna  205   a - 205   n , can be utilized to radiate the field at the highly isolated orthogonal polarizations including slanted +45 degree and −45 degree polarizations as previously described. In some embodiments where sixteen sub-arrays  300  are used to create an antenna  205   a - 205   n , the sub-arrays  300  can have a spacing of 0.74 λ toward the azimuth and a spacing of 1.48 λ toward the elevation direction. 
       FIGS.  4 A- 4 B  illustrate example feed networks of a sub-array according to various embodiments of the present disclosure. The sub-array  400  can be the sub-array  300 . The feed network  405  can be the feed network  350 . The feed network  405  can be a series/corporate feed network. 
     The feed network  405  can be the feed network  350  illustrated in  FIGS.  3 A- 3 C . The feed network  405  is deposited on a substrate. The feed network  405  includes a first transmission line  431 , a second transmission line  432 , a third transmission line  433 , and a fourth transmission line  434 . The first transmission line  431  includes a first excitation port  441 . The third transmission line  433  includes a second excitation port  442 . The first transmission line  431  can be the first transmission line  351 , the second transmission line  432  can be the second transmission line  352 , the third transmission line  433  can be the third transmission line  353 , the fourth transmission line  434  can be the fourth transmission line  354 , the first excitation port  441  can be the first excitation port  361 , and the second excitation port  442  can be the second excitation port  362 . 
       FIGS.  4 A- 4 B  also illustrate a first unit cell  401  and a second unit cell  402 . The first unit cell  401  includes a first patch  411  and a third patch  421 . The second unit cell  402  includes a second patch  412  and a fourth patch  422 . The first patch  411  can be the first patch  321 . The second patch  412  can be the second patch  322 . The third patch  421  can be the third patch  341 . The fourth patch  422  can be the fourth patch  342 . 
     The arrangement of the transmission lines  431 - 434  provides a differential feeding scheme that reduces cross-polarization of the sub-array  400  and phase-adjustment of both polarizations. For example, the first transmission line  431  is configured to provide a differential feeding scheme for a first polarization that is a +45 degree and −45 degree slanted polarization. The first transmission line  431  feeds the first corner  411   a  of the first patch  411  and the first corner  412   a  of the second patch  412 . The third transmission line  433  is configured to provide a differential feeding scheme for a second polarization that is a +45 degree and −45 degree slanted polarization. The third transmission line  433  feeds the second corner  411   b  of the first patch  411  and the fourth corner  412   d  of the second patch  412 . 
     The second transmission line  432  provides phase-adjustment for the first polarization that is fed by the first transmission line  431 . The second transmission line  432  feeds the third corner  411   c  of the first patch  411  and the third corner  412   c  of the second patch  412 . The fourth transmission line  434  provides phase adjustment for the second polarization that is fed by third transmission line  433 . The fourth transmission line  434  feeds the fourth corner  411   d  of the first patch  411  and the second corner  412   b  of the second patch  412 . 
     The transmission lines  431 - 434  are interconnected by the first patch  411  and the second patch  412 . In some embodiments, the feeding mechanism fed to each of the first unit cell  401  and the second unit cell  402  by the first transmission line  431  and the third transmission line  433  can be referred to as diagonal feeding. In some embodiments, the feeding mechanism fed to the sub-array  400  by the transmission lines  431 - 434  through the first patch  411  and the second patch  412  can be referred to as corner feeding or cross-corner feeding. For example, power can be introduced to the sub-array  400  by the first excitation port  441 . From the first excitation port  441 , the power is divided in half and fed through the first transmission line  431  to each of the first corner  411   a  of the first patch  411  and the first corner  412   a  of the second patch  412 . The power can be divided in half by a power divider (not pictured). The power can be transferred from the first transmission line  431  to the first patch  411  and the second patch  412  by proximity coupling excitation. Proximity coupling excitation allows the power to be transferred to the first patch  411  and the second patch  412  without physical contact. This enables the first transmission line  431  and the first patch  411  and the second patch  412  to be located on different layers of the sub-array  400 . 
     From the first corner  411   a , the power is fed through the first patch  411  and received by the second transmission line  432  at the third corner  411   c . The second transmission line  432  adjusts the phase of the power and cycles the power to the third corner  412   c . The power is then fed through the second patch  412  and received at the first corner  412   a . At or around the same time, the power introduced by the sub-array  400  is also fed through the first transmission line  431  to the first corner  412   a . From the first corner  412   a , the power is fed through the second patch  412  and received by the second transmission line  432  at the third corner  412   c . The second transmission line  432  adjusts the phase of the power and cycles the power to the third corner  411   c . The power is then fed through the first patch  411  and received at the first corner  411   a.    
     As another example, power can be introduced the sub-array  400  by the second excitation port  442 . From the second excitation port  442 , the power is divided in half and fed through the third transmission line  433  to each of the second corner  411   b  of the first patch  411  and the fourth corner  412   d  of the second patch  412 . The power can be divided in half by a power divider (not pictured). The power can be transferred from the third transmission line  433  to the first patch  411  and the second patch  412  by proximity coupling excitation. From the second corner  411   b , the power is fed through the first patch  411  and received by the fourth transmission line  434  at the fourth corner  411   d . The fourth transmission line  434  adjusts the phase of the power and cycles the power to the second corner  412   b . The power is then fed through the second patch  412  and received at the fourth corner  412   d . At or around the same time, the power introduced by the sub-array  400  is also fed through the third transmission line  433  to the fourth corner  412   d . From the fourth corner  412   d , the power is fed through the second patch  412  and received by the fourth transmission line  434  at the second corner  412   b . The fourth transmission line  434  adjusts the phase of the power and cycles the power to the fourth corner  411   d . The power is then fed through the first patch  411  and received at the second corner  411   b.    
     In some embodiments, power can be introduced to the sub-array  400  by the first excitation port  441  and the second excitation port  442  at or around the same time, resulting in each corner of the first patch  411  and second patch  412  being fed power that is balanced by equal power from another corner. For example, the power introduced at the first corner  411   a  is balanced by the power introduced at the third corner  411   c . Similarly, the power introduced at the second corner  411   b  is balanced by the power introduced at the fourth corner  411   d . In addition, the power introduced at the first corner  411   a  is balanced by the power introduced at the first corner  412   a  and the power introduced at the second corner  411   b  is balanced by the power introduced at the fourth corner  412   d.    
     As described above, the second transmission line  432  adjusts the phase of the power as it flows between the first patch  411  and second patch  412 . The phase adjusting performed by the second transmission line  432  ensures the power phases at each end of the second transmission line  432  are equal. Similarly, the fourth transmission line  434  adjusts the phase of the power as it flows between the first patch  411  and second patch  412 . The phase adjusting performed by the fourth transmission line  434  ensures the power phases at each end of the fourth transmission line  434  are equal. By utilizing two separate transmission lines to adjust the phase between the first unit cell  401  and the second unit cell  402 , the radiation pattern of the sub-array  400  and differential feeding of the sub-array  400  between the first unit cell  401  and the second unit cell  402  is stabilized. The differential feeding to the first patch  411  and second patch  412  can be provided by the first transmission line  431  and the third transmission line  433 . In addition, the phase adjusting between the first unit cell  401  and second unit cell  402  improves the efficiency of the sub-array  400  and controls the cross-polarization rejection ratio. 
     In embodiments utilizing the cross-corner feeding described above, each of the first unit cell  401  and second unit cell  402  are differentially excited with weighted excitation to control the side lobe level below 18 dB. In embodiments where the power is introduced to the sub-array  400  by both the first excitation port  441  and the second excitation port  442  at or around the same time, the side lobes can be canceled. By introducing the power through both the first excitation port  441  and the second excitation port  442  at or around the same time and reducing the side lobes level, the efficiency of the overall ratio of gain to physical area is improved. When the sub-array  400  is included in a target array antenna, the target array antenna may not have the optimal spacing between sub-arrays  400  based on the canceled side lobes. This can reduce the system implementation cost at the expense of limited beam steering capability. However, the system implementation cost can be overcome at the system level by algorithms executed by a processor, for example the controller/processor  225 , throughout the optimization process. 
     For example, the sub-array  400  illustrated in  FIG.  4 A , which includes the isolated first unit cell  401  and second unit cell  402 , is differentially excited with weighted excitation to control the side lobe level below 18 dB due to the nature of the feed network  405 . The sub-array  400  can exhibit a radiated gain of approximately 11.5 dB while the orthogonal polarization—cross polarization that can exhibit a radiated gain of greater than 20 dB. 
     Current iterations of Massive MIMO array antennas utilize external filtering masks, such as cavity or surface acoustic wave filters, to provide a high roll-off for out-of-band rejection. The filtering masks are large structures, comparable in size to the antenna itself, that suffer from losses associated with the interconnects to the physical point of contacts, soldering, and mechanical restriction. The losses associated with the interconnects result in a reduced coverage range. Other drawbacks to the filtering masks are emissions and interference from co-designed filters with the antenna radiation. The necessary filtering masks are a significant obstacle to achieving desired efficiency in terms of the generated equivalent isotropically radiated power (EIRP) and the radiated gain. Embodiments of the present disclosure, as illustrated in  FIG.  4 B , aim to overcome this obstacle by including one or more filtering structures  450  built into the feed network  405  of the sub-array  400 . 
     For example,  FIG.  4 B  illustrates a pair of filtering structures  450  incorporated into each of the first transmission line  431  and the third transmission line  433 . Each of the one or more filtering structures  450  can include various filtering structures for a RF network such as SMD filters, commercially off the shelf (COTS) components, parasitic elements, shorting pins, or enclosure cavities to meet the requirements for filtering elements traditionally found on external filters. By incorporating the one or more filtering structures  450  within the feed network  405 , it is possible to improve the gain of a sub-array  400  to equal to or better than 11.5 dB, improve the isolation between sub-arrays  400  when multiple sub-arrays  400  are arranged in close proximity in an antenna array, maintain low port-to-port coupling, and provide a design free of external filters that are often bulky and expensive. More specifically, the one or more filtering structures  450  help to prevent out-of-band radiation by associated antenna systems and therefore fully or partially achieve the desired frequency mask(s). 
     In some embodiments, additional filters can be introduced into the feed network  405 . For example, although illustrated in  FIG.  4 B  as including a pair of filtering structures  450  incorporated into each of the first transmission line  431  and the third transmission line  433 , some embodiments may include two pairs of filtering structures  450  incorporated into each of the first transmission line  431  and the third transmission line  433 . In these embodiments, including additional filtering structures  450  can result in achieving a higher order filtering feature. This description should not be construed as limiting. Any suitable number of filtering structures  450  can be incorporated into any of the first transmission line  431 , second transmission line  432 , third transmission line  433 , and fourth transmission line  434  to achieve the desirable filtering requirements. 
       FIGS.  5 A- 5 C  illustrate a sub-array according to various embodiments of the present disclosure.  FIG.  5 A  illustrates a top perspective view of a sub-array according to various embodiments of the present disclosure.  FIG.  5 B  illustrates a side view of a sub-array according to various embodiments of the present disclosure.  FIG.  5 C  illustrates an exploded view of a sub-array according to various embodiments of the present disclosure. 
     The sub-array  500  includes a first unit cell and a second unit cell (for example, the first unit cell  601  and second unit cell  602  described in  FIG.  6   ). The first unit cell includes a first patch  531  and a plurality of vertical feeds  556 . The second unit cell includes a second patch  532  and a plurality of vertical feeds  556 . The sub-array  500 , including the first unit cell and the second unit cell, is arranged in a first layer  510 , a second layer  520 , and a third layer  530 . 
     The first layer  510  comprises a substrate and includes a feed network  550 , a first excitation port  561 , and a second excitation port  562 . The feed network  550  transmits power to the first unit cell and the second unit cell of the sub-array  500 . The feed network  550  can be a series/corporate feed network. The feed network  550  includes a first transmission line  551 , a second transmission line  552 , phase-shifting portions  553 , hybrid couplers  554 , and a plurality of vertical feeds  556 . The first transmission line  551  is coupled to the first excitation port  561 . The second transmission line  552  is coupled to the second excitation port  562 . 
     The second layer  520  is a hollow cavity formed by an enclosure. The enclosed portion comprises four sides but the second layer  520  is open on each end. The openings on each end of the cavity enclosure provide an air gap  525  between the feed network  550  on the first layer  510  and the first patch  531  and the second patch  532  of the third layer  530 . The air gap  525  allows electromagnetic transmission to flow through the hollow cavity in the second layer  520 . The air gap  525  further provides an enclosed area for the plurality of vertical feeds  556  extending from the feed network  550  on the first layer  510  to connect to the horizontal feeds  542  on the third layer  530 . 
     The third layer  530  is comprised of a substrate. For example, the third layer  530  can be a layer of EM material. The third layer  530  includes decoupling elements  535   a ,  535   b , the first patch  531 , and the second patch  532 . The decoupling elements  535   a ,  535   b  are located between the first patch  531  and the second patch  532  to improve the cross-polarization rejection ratio. The decoupling element  535   a  performs a decoupling function on the first transmission line  551  and the decoupling element  535   b  performs a decoupling function on the second transmission line  552 . 
     In some embodiments, the first patch  531  and the second patch  532  can comprise a dielectric material. The dielectric material of the first patch  531  and the second patch  532  allows EM radiation to pass through to the EM material to be radiated by the antenna  205   a - 205   n . Each of the first patch  531  and the second patch  532  includes horizontal feeds  542  and openings  544 . Each of the openings  544  corresponds to both a horizontal feed  542  and a vertical feed  556 . For example, each of the openings  544  are configured to allow one of the plurality of vertical feeds  556  to pass through the third layer  530  and couple to a horizontal feed  542 . 
     The first transmission line  551  and second transmission line  552  transfer power through the sub-array  500 . In one embodiment, power can be introduced to the sub-array  500  by one or both of the first excitation port  561  and the second excitation port  562 . From the first excitation port  561 , the power is divided in half and fed through the first transmission line  551  to vertical feeds  556  of both the first unit cell and the second unit cell. The power can be divided in half by a power divider (not pictured). For example, as illustrated in  FIG.  5 C , the first transmission line  551  feeds two vertical feeds  556  that correspond to the first patch  531  and two vertical feeds  556  that correspond to the second patch  532 . 
     From the second excitation port  562 , the power divided in half and is fed through the second transmission line  552  to vertical feeds  556  of both the first unit cell and the second unit cell. The power can be divided in half by a power divider (not pictured). For example, as illustrated in  FIG.  5 C , the second transmission line  552  feeds two vertical feeds  556  that correspond to the first patch  531  and two vertical feeds  556  that correspond to the second patch  532 . The second transmission line  552  forms a built-in 180 degree hybrid coupler. 
     The vertical feeds  556  transfer the power, which is received from the first excitation port  561  and the second excitation port  562  and fed through the first transmission line  551  and second transmission line  552 , through the hollow cavity formed by the second layer  520 . The vertical feeds  556  pass through the openings  544  and transfer the power to the horizontal feeds  542  coupled to the vertical feeds  556 , respectively. The horizontal feeds  542  transfer the power from a perimeter of the first patch  531  and the second patch  532  toward the interior of each of the first patch  531  and the second patch  532 , respectively, where the horizontal feeds  542  terminate. From the termination point, the power can be radiated from the sub-array  500  in the form of a transmission. 
     The decoupling elements  535   a ,  535   b  assist in isolating the radiation from the sub-array  500  by reducing the coupling between the first patch  531  and the second patch  532 . In combination, the functions of the decoupling elements  535   a ,  535   b  isolate the resulting radiation and improve the cross-polarization rejection ratio of the sub-array  500  to reduce or cancel the side lobes of the radiation. 
     Several advantages can be obtained in antennas, for example antennas  205   a - 205   n , that utilize the design described in  FIGS.  5 A- 5 C . For example, the radiated gain can be measured at greater than 11.5 dB. A cross-polarization rejection ratio can be measured at greater than 18 dB. A return loss can be measured at greater than 20 dB. Port-to-port isolation of the sub-array  500  can be measured at greater than 20 dB. In-plane can be measured at better than 25 dB. Cross-coupling can be measured at better than 30 dB. Bandwidth can be measured at 200 MHz. 
       FIG.  6    illustrates an example feed network of a sub-array according to various embodiments of the present disclosure. The sub-array  600  can be the sub-array  500  described in  FIGS.  5 A- 5 C . The feed network  605  can be the feed network  550  described in  FIGS.  5 A- 5 C . 
     As illustrated in  FIG.  6   , the sub-array  600  includes the feed network  605 , decoupling elements  610   a ,  610   b , a first unit cell  601 , and a second unit cell  602 . The first unit cell  601  includes a first patch  611 , horizontal feeds  622 , a plurality of openings  624 , and a plurality of vertical feeds (not pictured, for example the vertical feeds  556  illustrated in  FIGS.  5 A- 5 C ). The second unit cell  602  includes a second patch  612 , horizontal feeds  622 , a plurality of openings  624 , and a plurality of vertical feeds (not pictured, for example the vertical feeds  556  illustrated in  FIGS.  5 A- 5 C ). The decoupling elements  610   a ,  610   b  can be the decoupling elements  535   a ,  535   b . The first patch  611  can be the first patch  531 . The second patch  612  can be the second patch  532 . 
     The feed network  605  includes a first transmission line  630 , a first excitation port  632 , a second transmission line  640 , a second excitation port  642 , horizontal feeds  622 , a plurality of vertical feeds (not pictured), and a plurality of openings  624 . The first transmission line  630  can be the first transmission line  551 . The second transmission line  640  can be the second transmission line  552 . The horizontal feeds  622  can be the horizontal feeds  542 . The plurality of vertical feeds can be the plurality of vertical feeds  556 . The plurality of openings  624  can be the plurality of openings  544 . The first excitation port  632  can be the first excitation port  561 . The second excitation port  642  can be the second excitation port  562 . 
       FIG.  6    illustrates the relationship between the feed network  605 , decoupling elements  610   a ,  610   b , first unit cell  601 , and second unit cell  602 . More specifically,  FIG.  6    illustrates that the termination points of the first transmission line  630  and the second transmission line  640  correspond to the openings  624  to connect the first transmission line  630  and the second transmission line  640  with the horizontal feeds  622  via the plurality of vertical feeds (not pictured).  FIG.  6    further illustrates that the decoupling element  610   a  is arranged to correspond to the first transmission line  630  and that the decoupling element  610   b  is arranged to correspond to the second transmission line  640 . This arrangement allows the decoupling element  610   a  to perform a decoupling function on the first transmission line  630  and the decoupling element  610   b  to perform an equivalent decoupling function on the second transmission line  640 . The decoupling functions performed by the decoupling elements  610   a ,  610   b  can combine to isolate the resulting radiation and improve the cross-polarization rejection ratio of the sub-array  600 . In some embodiments, the decoupling elements  610   a ,  610   b  can reduce or cancel the side lobes of the radiation from the sub-array  600 . 
     In some embodiments, the gradual progression of the phase of the electromagnetic waves is the result of the progression of a phase shift in the feed networks of the antenna panel. For example, the beam can be steered by manipulating the cross-polarization of the feed networks by using the RF currents received through the excitation ports. 
     This disclosure should not be construed as limiting. Various embodiments are possible. 
     In some embodiments, the feed network is configured to provide cross-corner feeding to the sub-array. 
     In some embodiments, the first and third transmission lines are configured to provide a cross-polarization of the first unit cell and the second unit cell via the cross-corner feeding. In some embodiments, the cross-polarization includes a difference of +45 and −45 degrees. 
     In some embodiments, the feed network further comprises a filter provided on at least one of the first transmission line, second transmission line, third transmission line, or fourth transmission line. 
     In some embodiments, the first transmission line results in a first polarization of the sub-array and the third transmission line results in a second polarization of the sub-array, the first transmission line and the third transmission line provide cross-polarization of the sub-array, the second transmission line is configured to provide phase-adjusting for the second polarization; and the fourth transmission line is configured to provide phase-adjusting for the first polarization. 
     In some embodiments, the sub-array further comprises a first layer including the feed network, a second layer including the first patch and the second patch, a third layer comprising a hollow cavity formed by an enclosure, and a fourth layer including a third patch and a fourth patch. 
     In some embodiments, the first unit cell further comprises the third patch, the second unit further comprises the fourth patch, the third patch is larger than the first patch, and the fourth patch is larger than the second patch. 
     In some embodiments, the third patch is located directly above the first patch and the fourth patch is located directly above the second patch. 
     In some embodiments, the hollow cavity provides an air gap between (i) the first patch and the third patch, and (ii) the second patch and the fourth patch. 
     In some embodiments, the feed network is configured to provide differential feeding to the sub-array. 
     None of the description in this application should be read as implying that any particular element, step, or function is an essential element that must be included in the claim scope. Moreover, none of the claims is intended to invoke 35 U.S.C. § 112(f) unless the exact words “means for” are followed by a participle.