Patent Grant
10361490
This application is related to U.S. patent application Ser. No. 14/632,929, filed Feb. 26, 2015.
A large and growing population of users is enjoying entertainment through the consumption of digital media items, such as music, movies, images, electronic books, and so on. The users employ various electronic devices to consume such media items. Among these electronic devices (referred to herein as user devices) are electronic book readers, cellular telephones, personal digital assistants (PDAs), portable media players, tablet computers, netbooks, laptops and the like. These electronic devices wirelessly communicate with a communications infrastructure to enable the consumption of the digital media items. In order to wirelessly communicate with other devices, these electronic devices include one or more antennas.
The present inventions will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the present invention, which, however, should not be taken to limit the present invention to the specific embodiments, but are for explanation and understanding only.
Antenna structures and methods of operating the same of an electronic device are described. One apparatus includes a radio coupled to a RF feed and an RF switch, a first antenna element coupled to the RF feed, and a second antenna element coupled to the RF switch, the RF switch being coupled to a grounding point of a ground plane. The radio controls the RF switch between a first mode and a second mode. The radio causes the first antenna element to radiate electromagnetic energy in a first radiation pattern in the first mode and causes the second antenna element to radiate electromagnetic energy in a second radiation pattern in the second mode. The second radiation pattern is different than the first radiation pattern.
In a constrained radiation space (low and thin profiles for mobile devices) of user devices, antenna engineers face various challenges. One challenge is antenna selection diversity to ensure wireless connectivity over channel fading caused by multipath and null spots of the antenna radiation pattern. To achieve the benefit of antenna diversity, a low envelope correlation coefficient (ECC) is needed. ECC is an indication or a measurement of how independent two antennas' radiation patterns are. ECC takes into account the antennas' radiation patterns, including the shapes, polarizations and phases of the antennas. Traditionally, low ECC may be obtained by two or more antennas located in different orientations and/or locations. In such cases, more antenna space is needed to accommodate the additional antennas needed for a low ECC for antenna diversity. However, it is difficult to obtain low ECC with co-located antennas or closely coupled antennas.
The embodiments described herein are directed to pattern diversity assisted antennas. Some embodiments achieve low ECC for a single-input-single-output (SISO) antenna. Other embodiments achieve low ECC for a multiple-input-multiple-output (MIMO) antenna. Alternatively, the embodiments described herein may be used in various single-antenna or multi-antenna configurations. In one embodiment, a single antenna with two switchable modes is set forth for a pattern diversity assisted SISO antenna. The two modes of the antenna share the same antenna geometry but perform differently in terms of current flow and antenna radiation pattern, resulting in low ECC. Without requiring more space for multiple antennas, a single antenna element may be used and the single antenna element's current flow can be redirected in the two modes to effectively different radiation patterns.
In some cases, in order to achieve the best antenna diversity (low ECC), the antenna geometry of the antenna element should be designed to be self-resonant at two different frequencies. In another embodiment, two antennas with four modes are designed. In one embodiment, two antennas with four switchable modes are set forth for a pattern diversity assisted MIMO antenna. The four modes of the two antennas share the same antenna geometry but perform differently in terms of current flow and antenna radiation pattern, resulting in low ECC. Without requiring more space for multiple antennas (e.g., four antennas), existing two-by-two MIMO RF and antenna architecture and the two antenna elements' current flows can be redirected in the four modes to effectively different radiation patterns. In order to achieve the best antenna diversity, the antenna geometry of the antenna elements should be designed to meet the ECC requirement. Some pattern diversity assisted antenna systems include algorithms that utilized pattern diversity assistance. Some embodiments may include basic monopole mode and loop mode antennas.
In other cases, as described in various embodiments described herein, the antenna geometry is designed to serve the same purpose of having the same geometry and two de-correlated modes. These embodiments may include additional geometries, including geometries that can be used in digital media devices, such as a TV dongle or the like. The digital media device may be a microconsole, HDMI-port plug-in devices, or the like. The embodiments described herein are directed to antenna geometries with two de-correlated modes that share the same antenna geometry, but perform differently in terms of current flow and antenna radiation pattern, resulting in low ECC. Without requiring more space for multiple antennas, using a single-fed antenna structure, the embodiments described herein re-direct current flow to achieve different antenna radiation patterns. The antenna geometries described herein have been designed to achieve antenna diversity (low ECC or de-correlated) and impedance matching. In some cases, the antenna's impedance can be matched with different matching components to focus on low ECC first. For example, three RF switches for one antenna may be used; two switches for separate matching components and one switch for switching between the different modes. In other cases, a parasitic radiating element is designed to change the antenna pattern, trading off ECC and impedance matching. For example, a single RF switch can be used between the different modes. This may simplify the antenna design.
Various embodiments described herein are directed to a TV dongle with radio circuitry that communicates over a wireless local area network (WLAN) using the Wi-Fi® technology in the 2.4 GHz frequency band. It should be noted that in other embodiments, the antenna structures described herein can be used for Long Term Evolution (LTE) frequency bands, third generation (3G) frequency bands, personal area network (PAN) frequency band (e.g., using the Bluetooth® technology or Zigbee® technology), wide area network (WAN) frequency bands, global navigation satellite system (GNSS) frequency bands (e.g., positioning system (GPS) frequency bands, other WLAN frequency bands, or the like.
In one embodiment, the RF switch 104 is a single-pole-single-throw (SPST) switch coupled between parasitic ground element 103 and the grounding point 108. The RF chipset 140 is operable to control the SPST switch between a closed state and an open state. The RF switch 104 redirects the current flow applied on the pattern diversity assisted antenna structure 101 by the single RF feed 106. For example, the RF chipset 140 can apply a RF signal to the single RF feed 106 that causes a first current flow on the antenna element 102 to achieve a first radiation pattern of electromagnetic energy in a first resonant mode when the SPST switch is in the open state. The RF chipset 140 can apply a separate RF signal to the single RF feed 106 that causes a second current flow on the antenna element 102 to achieve a first radiation pattern of electromagnetic energy in a second resonant mode when the SPST switch is in the closed state. Alternatively, the RF chipset 140 can apply the RF signal to the single RF feed 106 that causes a redirection of the first current flow to generate a second current flow on the first antenna element and on the second antenna element to radiate the electromagnetic energy in the second radiation pattern. Also, when the SPST is in the closed state, the second current flow on the parasitic ground element 103 parasitically induces a third current on the parasitic ground element 103. The second current flow and the third current flow collectively generate a second radiation pattern of electromagnetic energy in a second resonant mode. The second radiation pattern is different than the first radiation pattern. In one embodiment, the antenna element is self-resonant at approximately 2.4 GHz when the SPST switch is in the open state, and the antenna element 102 and the parasitic ground element 103 are self-resonant at approximately 2.4 GHz when the SPST switch is in the closed state. Alternatively, the antenna is self-resonant at a frequency between approximately 5.0 GHz and approximately 6.0 GHz.
In one embodiment, the antenna element 102 operates as a monopole antenna when the SPST switch is in the open state and the antenna element 102 and the parasitic ground element 103 together operate as a coupled mode antenna when the SPST switch is in the closed state, as described herein. In another embodiment, the antenna element 102 operates as a monopole antenna when the SPST switch is in the open state and the antenna element 102 and the parasitic ground element 103 together operate as a parasitic mode antenna when the SPST switch is in the closed state, as described herein.
In one embodiment, the RF chipset 140 includes a wireless local area network (WLAN) is operable to cause the antenna element 102 to radiate electromagnetic energy in a frequency range (e.g., approximately 2.4 GHz and approximately 2.5 GHz) in the first resonant mode and cause the antenna element 102 and the parasitic ground element 103 to radiate electromagnetic energy in the same frequency range in the second resonant mode. The first resonant mode and the second resonant mode are de-correlated modes. In one embodiment, the first resonant mode is a monopole mode and the second resonant mode is a coupled mode. In another embodiment, the first resonant mode is a monopole mode and the second resonant mode is a parasitic mode. These modes can be further matched to desired working bands of interest. For example, in dual-band Wi-Fi® networks, the antenna element 102 can be matched in the two modes to cover the 2.4 GHz band and the 5 GHz band. For example, the WLAN module may include a WLAN RF transceiver for communications on one or more Wi-Fi® bands (e.g., 2.4 GHz and 5 GHz). It should be noted that the Wi-Fi® technology is the industry name for wireless local area network communication technology related to the IEEE 802.11 family of wireless networking standards by Wi-Fi Alliance. For example, a dual-band WLAN RF transceiver allows an electronic device to exchange data or connection to the Internet wireless using radio waves in two WLAN bands (2.4 GHz band, 5 GHz band) via one or multiple antennas. For example, a dual-band WLAN RF transceiver includes a 5 GHz WLAN channel and a 2.4 GHz WLAN channel. In other embodiments, the antenna architecture may include additional RF modules and/or other communication modules, such as a WLAN module, a GPS receiver, a near field communication (NFC) module, a PAN modules that implements the Bluetooth® or Zigbee® technologies, an amplitude modulation (AM) radio receiver, a frequency modulation (FM) radio receiver, a Global Navigation Satellite System (GNSS) receiver, or the like. The RF chipset 140 may include one or multiple RFFE (also referred to as RF circuitry). The RFFEs may include receivers and/or transceivers, filters, amplifiers, mixers, switches, and/or other electrical components. In another embodiment, the radio is a WLAN radio.
The RF chipset 140 may be coupled to a modem that allows the user device 100 to handle both voice and non-voice communications (such as communications for text messages, multimedia messages, media downloads, web browsing, etc.) with a wireless communication system. The modem may provide network connectivity using any type of digital mobile network technology including, for example, LTE, LTE advanced (4G), CDPD, GPRS, EDGE, UMTS, 1×RTT, EVDO, HSDPA, WLAN (e.g., Wi-Fi® network), etc. In the depicted embodiment, the modem can use the RF chipset 140 to radiate or receive electromagnetic energy on the antennas to communication data to and from the user device 100 in the respective frequency ranges. In other embodiments, the modem may communicate according to different communication types (e.g., WCDMA, GSM, LTE, CDMA, WiMAX, etc.) in different cellular networks.
The user device 100 (also referred to herein as an electronic device) may be any content rendering device that includes a modem for connecting the user device to a network. Examples of such electronic devices include electronic book readers, portable digital assistants, mobile phones, laptop computers, portable media players, tablet computers, cameras, video cameras, netbooks, notebooks, desktop computers, gaming consoles, Blu-ray® or DVD players, media centers, drones, and the like. The user device may connect to a network to obtain content from a server computing system (e.g., an item providing system) or to perform other activities. The user device may connect to one or more different types of cellular networks.
As described above, a diversity antenna, or a MIMO antenna, is a secondary antenna that may be used along with the one or more primary antennas to improve the quality and reliability of a wireless link. There may be no clear line-of-sight between a transmitter and a receiver. Instead, a signal may undergo multiple reflections between transmission and reception. Each reflection may introduce time delays, phase shifts, distortions, attenuations, etc. that can degrade a signal quality. The diversity antennas have a different location and/or configuration than the primary antennas on the user device, and may therefore experience different phase shifts, time delays, attenuations, distortions, etc. Accordingly, signals at the diversity antenna can be compared to signals at the primary antenna to determine and mitigate such effects. Using the embodiments described herein, a single antenna structure can be used in two resonant modes to create two radiation patterns to achieve a diversity pattern assisted antenna. That is, the RF chipset 140 can use the same antenna structure for two different radiation patterns to achieve diversity.
The pattern diversity assisted antenna structure 101 of
The embodiments of the pattern diversity assisted antenna structures of
In this embodiment, the multi-antenna system includes two pattern diversity assisted antenna structures 400, 700. The first pattern diversity assisted antenna structure 400 is illustrated and described in more detail with respect to
In one embodiment, the pattern diversity assisted antenna structure 400 is approximately 20 mm wide and approximately 9 mm tall as disposed on the antenna carrier 407. Alternatively, the pattern diversity assisted antenna structure 400 may be other dimensions. In one embodiment, as illustrated in
RF circuitry 440 is operable to control the RF switch 404 to switch the pattern diversity assisted antenna structure 400 between the first mode and the second mode. The RF circuitry 440 may control the RF switch 404 using a switch control signal (not illustrated in
In one embodiment, the pattern diversity assisted antenna structure is a two arm structure that includes two modes: monopole mode and loop mode. The monopole arm is the antenna main radiation element. A wide ground arm provides RF current return path back to the ground plane and change return current direction. The RF switch provides an RF open or short circuit to modulate the current flow. The RF feed provides RF excitation to the antenna structure.
In one embodiment, the antenna element 702 includes a first arm having a first effective length between a first end coupled to the RF feed 706 and a second end at a distal end of the first arm. The parasitic ground element 708 includes a second arm having a second effective length between a first end and a second end of the second arm, the first end of the second arm being coupled to the ground plane 305 at the grounding point 718. The first arm and the second arm are coplanar. In the depicted embodiment, a segment 712 of the first arm extends in a first direction such that the second end of the first arm is disposed in a first gap formed between a first segment 714 and a second segment 716 of the second arm, the second segment 716 extending in a second direction beyond the second end of the first arm to form a second gap between a portion of the second segment 716 and the segment 712 of the first arm. The first arm may also include another segment 710 that couples the segment 712 to the RF feed 706.
In a further embodiment, the parasitic ground element includes an additional arm 720 that extends in the first direction and folds towards the ground plane 305 in a third direction. The additional arm 720 may be used for impedance matching, resulting in an increased bandwidth.
In one embodiment, the pattern diversity assisted antenna structure is a two arm structure that includes two modes: monopole mode and coupled mode. The monopole arm is the antenna main radiation element. A long ground arm provides RF current return path back to the ground plane and provides low band resonance. The RF switch provides an RF open or short circuit to modulate the current flow. The RF feed provides RF excitation to the antenna structure.
In some embodiments, the antenna mode impedance is very different in the first and second modes. The two modes can be matched to desired working bands of interest (e.g., 2.4 GHz). In one embodiment, the first mode is matched using a first impedance matching circuit and the second modes is matched using a second impedance matching circuit. In another embodiment, a single impedance matching circuit can be used to match both the first mode and the second mode. The impedance matching circuits operate to match an impedance of a respective antenna to an impedance of a RF circuit coupled to the respective antenna to radiate or receive electromagnetic energy in a specified frequency range.
In one embodiment, the antenna element 1302 includes a first arm 1310 and the parasitic ground element 1308 includes a second arm 1312. The first arm 1310 and the second arm 1312 are coplanar. A segment of the first arm 1310 extends in a first direction and a segment of the second arm 1312 extends in the first direction to form a gap between the segment of the first arm 1310 and the segment of the second arm 1312. The first arm 1310 and the second arm 1312 are symmetrical about an axis 1320 defined along a length of the gap between the segment of the first arm 1310 and the segment of the second arm 1312.
In one embodiment, the pattern diversity assisted antenna structure is a two arm structure that includes two modes: monopole mode and parasitic mode. The monopole arm is the antenna main radiation element. A symmetrical ground arm provides RF current return path back to the ground plane and provides low band resonance. The RF switch provides an RF open or short circuit to modulate the current flow. The RF feed provides RF excitation to the antenna structure.
In some embodiments, the antenna mode impedance is very different in the first and second modes. The two modes can be matched to desired working bands of interest (e.g., 2.4 GHz). In one embodiment, the first mode is matched using a first impedance matching circuit and the second modes is matched using a second impedance matching circuit. In another embodiment, a single impedance matching circuit can be used to match both the first mode and the second mode. The impedance matching circuits operate to match an impedance of a respective antenna to an impedance of a RF circuit coupled to the respective antenna to radiate or receive electromagnetic energy in a specified frequency range.
As illustrated in
The user device 1805 includes one or more processor(s) 1830, such as one or more CPUs, microcontrollers, field programmable gate arrays, or other types of processors. The user device 1805 also includes system memory 1806, which may correspond to any combination of volatile and/or non-volatile storage mechanisms. The system memory 1806 stores information that provides operating system component 1808, various program modules 1810, program data 1812, and/or other components. In one embodiment, the system memory 1806 stores instructions of methods to control operation of the user device 1805. The user device 1805 performs functions by using the processor(s) 1830 to execute instructions provided by the system memory 1806.
The user device 1805 also includes a data storage device 1814 that may be composed of one or more types of removable storage and/or one or more types of non-removable storage. The data storage device 1814 includes a computer-readable storage medium 1816 on which is stored one or more sets of instructions embodying any of the methodologies or functions described herein. Instructions for the program modules 1810 may reside, completely or at least partially, within the computer-readable storage medium 1816, system memory 1806 and/or within the processor(s) 1830 during execution thereof by the user device 1805, the system memory 1806 and the processor(s) 1830 also constituting computer-readable media. The user device 1805 may also include one or more input devices 1818 (keyboard, mouse device, specialized selection keys, etc.) and one or more output devices 1820 (displays, printers, audio output mechanisms, etc.).
The user device 1805 further includes a modem 1822 to allow the user device 1805 to communicate via a wireless network (e.g., such as provided by the wireless communication system) with other computing devices, such as remote computers, an item providing system, and so forth. The modem 1822 can be connected to RF circuitry 1883 and zero or more RF modules 1886. The RF circuitry 1883 may be a WLAN module, a WAN module, PAN module, or the like. Antennas 1888 are coupled to the RF circuitry 1883, which is coupled to the modem 1822. Zero or more antennas 1884 can be coupled to one or more RF modules 1886, which are also connected to the modem 1822. The zero or more antennas 1884 may be GPS antennas, NFC antennas, other WAN antennas, WLAN or PAN antennas, or the like. The modem 1822 allows the user device 1805 to handle both voice and non-voice communications (such as communications for text messages, multimedia messages, media downloads, web browsing, etc.) with a wireless communication system. The modem 1822 may provide network connectivity using any type of mobile network technology including, for example, cellular digital packet data (CDPD), general packet radio service (GPRS), EDGE, universal mobile telecommunications system (UMTS), 1 times radio transmission technology (1×RTT), evaluation data optimized (EVDO), high-speed down-link packet access (HSDPA), Wi-Fi®, Long Term Evolution (LTE) and LTE Advanced (sometimes generally referred to as 4G), etc.
The modem 1822 may generate signals and send these signals to pattern diversity antennas 1888, and 1884 via RF circuitry 1883, and RF module(s) 1886 as descried herein. User device 1805 may additionally include a WLAN module, a GPS receiver, a PAN transceiver and/or other RF modules. These RF modules may additionally or alternatively be connected to one or more of antennas 1884, 1888. Antennas 1884, 1888 may be configured to transmit in different frequency bands and/or using different wireless communication protocols. The antennas 1884, 1888 may be directional, omnidirectional, or non-directional antennas. In addition to sending data, antennas 1884, 1888 may also receive data, which is sent to appropriate RF modules connected to the antennas. One of the antennas 1884 may be any combination of the pattern diversity assisted antenna structures 400, 700, 1300 as described herein.
In one embodiment, the user device 1805 establishes a first connection using a first wireless communication protocol, and a second connection using a different wireless communication protocol. The first wireless connection and second wireless connection may be active concurrently, for example, if a user device is downloading a media item from a server (e.g., via the first connection) and transferring a file to another user device (e.g., via the second connection) at the same time. Alternatively, the two connections may be active concurrently during a handoff between wireless connections to maintain an active session (e.g., for a telephone conversation). Such a handoff may be performed, for example, between a connection to a WLAN hotspot and a connection to a wireless carrier system. In one embodiment, the first wireless connection is associated with a first resonant mode of an antenna structure that operates at a first frequency band and the second wireless connection is associated with a second resonant mode of the antenna structure that operates at a second frequency band. In another embodiment, the first wireless connection is associated with a first antenna element and the second wireless connection is associated with a second antenna element. In other embodiments, the first wireless connection may be associated with a media purchase application (e.g., for downloading electronic books), while the second wireless connection may be associated with a wireless ad hoc network application. Other applications that may be associated with one of the wireless connections include, for example, a game, a telephony application, an Internet browsing application, a file transfer application, a global positioning system (GPS) application, and so forth.
Though a modem 1822 is shown to control transmission and reception via antenna (1884, 1888), the user device 1805 may alternatively include multiple modems, each of which is configured to transmit/receive data via a different antenna and/or wireless transmission protocol.
The user device 1805 delivers and/or receives items, upgrades, and/or other information via the network. For example, the user device 1805 may download or receive items from an item providing system. The item providing system receives various requests, instructions and other data from the user device 1805 via the network. The item providing system may include one or more machines (e.g., one or more server computer systems, routers, gateways, etc.) that have processing and storage capabilities to provide the above functionality. Communication between the item providing system and the user device 1805 may be enabled via any communication infrastructure. One example of such an infrastructure includes a combination of a WAN and wireless infrastructure, which allows a user to use the user device 1805 to purchase items and consume items without being tethered to the item providing system via hardwired links. The wireless infrastructure may be provided by one or multiple wireless communications systems, such as one or more wireless communications systems. One of the wireless communication systems may be a WLAN hotspot connected with the network. The WLAN hotspots can be created by Wi-Fi® products based on IEEE 802.11x standards by Wi-Fi Alliance. Another of the wireless communication systems may be a wireless carrier system that can be implemented using various data processing equipment, communication towers, etc. Alternatively, or in addition, the wireless carrier system may rely on satellite technology to exchange information with the user device 1805.
The communication infrastructure may also include a communication-enabling system that serves as an intermediary in passing information between the item providing system and the wireless communication system. The communication-enabling system may communicate with the wireless communication system (e.g., a wireless carrier) via a dedicated channel, and may communicate with the item providing system via a non-dedicated communication mechanism, e.g., a public WAN such as the Internet.
The user devices 1805 are variously configured with different functionality to enable consumption of one or more types of media items. The media items may be any type of format of digital content, including, for example, electronic texts (e.g., eBooks, electronic magazines, digital newspapers, etc.), digital audio (e.g., music, audible books, etc.), digital video (e.g., movies, television, short clips, etc.), images (e.g., art, photographs, etc.), and multi-media content. The user devices 1805 may include any type of content rendering devices such as electronic book readers, portable digital assistants, mobile phones, laptop computers, portable media players, tablet computers, cameras, video cameras, netbooks, notebooks, desktop computers, gaming consoles, DVD players, media centers, and the like.
In the above description, numerous details are set forth. It will be apparent, however, to one of ordinary skill in the art having the benefit of this disclosure, that embodiments may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the description.
Some portions of the detailed description are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the above discussion, it is appreciated that throughout the description, discussions utilizing terms such as “inducing,” “parasitically inducing,” “radiating,” “detecting,” determining,” “generating,” “communicating,” “receiving,” “disabling,” or the like, refer to the actions and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (e.g., electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
Embodiments also relate to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but not limited to, any type of disk including floppy disks, optical disks, CD-ROMs and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions.
The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct a more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description below. In addition, the present embodiments are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the present invention as described herein. It should also be noted that the terms “when” or the phrase “in response to,” as used herein, should be understood to indicate that there may be intervening time, intervening events, or both before the identified operation is performed.
It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the present embodiments should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
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