Patent Publication Number: US-2023163728-A1

Title: Low noise amplifiers with low noise figure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 17/247,896, filed Dec. 29, 2020 and titled “LOW NOISE AMPLIFIERS WITH LOW NOISE FIGURE,” which claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Patent Application No. 62/959,011, filed Jan. 9, 2020 and titled “LOW NOISE AMPLIFIERS WITH LOW NOISE FIGURE,” each of which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Technical Field 
     Embodiments of the invention relate to electronic systems, and in particular, to radio frequency (RF) electronics. 
     Description of Related Technology 
     A low noise amplifier (LNA) can be used to boost the amplitude of a relatively weak radio frequency (RF) signal received via an antenna. Thereafter, the boosted RF signal can be used for a variety of purposes, including, for example, driving a switch, a mixer, and/or a filter in an RF communication system. 
     Examples of RF communication systems with one or more LNAs include, but are not limited to, mobile phones, tablets, base stations, network access points, customer-premises equipment (CPE), laptops, and wearable electronics. 
     LNAs can be included in RF communication systems to amplify signals of a wide range of frequencies. For example, an LNA can be used to provide low noise amplification to RF signals in a frequency range of about 30 kHz to 300 GHz, such as in the range of about 410 MHz to about 7.125 GHz for Fifth Generation (5G) cellular communications in Frequency Range 1 (FR1). 
     SUMMARY 
     In certain embodiments, the present disclosure relates to a mobile device. The mobile device includes an antenna configured to provide a single-ended input signal in response to receiving a radio wave, and a front-end system including a low noise amplifier having an input terminal electrically coupled to the antenna. The low noise amplifier includes a single-ended low noise amplifier stage configured to amplify the single-ended input signal to generate a single-ended amplified signal, an input balun configured to convert the single-ended amplified signal into a differential signal, and a first differential low noise amplifier stage configured to amplify the differential signal to generate a first differential amplified signal. 
     In various embodiments, the first differential low noise amplifier stage has variable gain. 
     In several embodiments, the low noise amplifier further includes an output balun configured to convert the first differential amplified signal into a single-ended output signal. 
     In some embodiments, the low noise amplifier further includes a second differential low noise amplifier stage configured to further amplify the first differential amplified signal to generate a second differential amplified signal. According to a number of embodiments, the low noise amplifier further includes an output balun configured to convert the second differential amplified signal into a single-ended output signal. In accordance with various embodiments, the low noise amplifier further includes a plurality of switches configured to selectively bypass the first differential low noise amplifier stage. According to several embodiments, the first differential low noise amplifier stage and the second differential low noise stage each have variable gain that is separately controllable. 
     In various embodiments, the single-ended low noise amplifier stage is a cascode field-effect transistor stage. According to several embodiments, the cascode field-effect transistor stage drives a first winding of the input balun, the first differential low noise amplifier stage being a differential cascode field-effect transistor stage configured to receive the differential signal from a second winding of the input balun. In accordance with some embodiments, the differential cascode field-effect transistor stage includes a first gain transistor, a first cascode transistor, a first inductor connected between the first gain transistor and the first cascode transistor, a second gain transistor, a second cascode transistor, and a second inductor connected between the second gain transistor and the second cascode transistor. 
     In a number of embodiments, the single-ended input signal has a frequency of 20 gigahertz or more. 
     In certain embodiments, the present disclosure relates to a low noise amplifier. The low noise amplifier includes a radio frequency input terminal configured to receive a single-ended input signal from an antenna, a single-ended low noise amplifier stage configured to amplify the single-ended input signal to generate a single-ended amplified signal, an input balun configured to convert the single-ended amplified signal into a differential signal, and a first differential low noise amplifier stage configured to amplify the differential signal to generate a first differential amplified signal. 
     In a number of embodiments, the first differential low noise amplifier stage has variable gain. 
     In several embodiments, the low noise amplifier further includes an output balun configured to convert the first differential amplified signal into a single-ended output signal. 
     In some embodiments, the low noise amplifier further includes a second differential low noise amplifier stage configured to further amplify the first differential amplified signal to generate a second differential amplified signal. According to a number of embodiments, the low noise amplifier further includes an output balun configured to convert the second differential amplified signal into a single-ended output signal. In accordance with several embodiments, the low noise amplifier further includes a plurality of switches configured to selectively bypass the first differential low noise amplifier stage. According to various embodiments, the first differential low noise amplifier stage and the second differential low noise stage each have variable gain that is separately controllable. 
     In several embodiments, the single-ended low noise amplifier stage is a cascode field-effect transistor stage. According to a number of embodiments, the cascode field-effect transistor stage drives a first winding of the input balun, the first differential low noise amplifier stage being a differential cascode field-effect transistor stage configured to receive the differential signal from a second winding of the input balun. In accordance with some embodiments, the differential cascode field-effect transistor stage includes a first gain transistor, a first cascode transistor, a first inductor connected between the first gain transistor and the first cascode transistor, a second gain transistor, a second cascode transistor, and a second inductor connected between the second gain transistor and the second cascode transistor. 
     In various embodiments, the single-ended input signal has a frequency of 20 gigahertz or more. 
     In certain embodiments, the present disclosure relates to a packaged module. The packaged module includes a package substrate, and a low noise amplifier die attached to the package substrate. The low noise amplifier die includes an input signal pin configured to receive a single-ended input signal, a single-ended low noise amplifier stage configured to amplify the single-ended input signal to generate a single-ended amplified signal, an input balun configured to convert the single-ended amplified signal into a differential signal, and a first differential low noise amplifier stage configured to amplify the differential signal to generate a first differential amplified signal. 
     In various embodiments, the first differential low noise amplifier stage has variable gain. 
     In several embodiments, the low noise amplifier die further includes an output balun configured to convert the first differential amplified signal into a single-ended output signal. 
     In some embodiments, the low noise amplifier die further includes a second differential low noise amplifier stage configured to further amplify the first differential amplified signal to generate a second differential amplified signal. According to various embodiments, the low noise amplifier die further includes an output balun configured to convert the second differential amplified signal into a single-ended output signal. In accordance with several embodiments, the low noise amplifier die further includes a plurality of switches configured to selectively bypass the first differential low noise amplifier stage. According to a number of embodiments, the first differential low noise amplifier stage and the second differential low noise stage each have variable gain that is separately controllable. 
     In various embodiments, the single-ended low noise amplifier stage is a cascode field-effect transistor stage. According to a number of embodiments, the cascode field-effect transistor stage drives a first winding of the input balun, the first differential low noise amplifier stage being a differential cascode field-effect transistor stage configured to receive the differential signal from a second winding of the input balun. In accordance with some embodiments, the differential cascode field-effect transistor stage includes a first gain transistor, a first cascode transistor, a first inductor connected between the first gain transistor and the first cascode transistor, a second gain transistor, a second cascode transistor, and a second inductor connected between the second gain transistor and the second cascode transistor. 
     In several embodiments, the single-ended input signal has a frequency of 20 gigahertz or more. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of this disclosure will now be described, by way of non-limiting example, with reference to the accompanying drawings. 
         FIG.  1    is a schematic diagram of one example of a communication network. 
         FIG.  2 A  is a schematic diagram of one example of a communication link using carrier aggregation. 
         FIG.  2 B  illustrates various examples of uplink carrier aggregation for the communication link of  FIG.  2 A . 
         FIG.  2 C  illustrates various examples of downlink carrier aggregation for the communication link of  FIG.  2 A . 
         FIG.  3 A  is a schematic diagram of one example of a downlink channel using multi-input and multi-output (MIMO) communications. 
         FIG.  3 B  is schematic diagram of one example of an uplink channel using MIMO communications. 
         FIG.  3 C  is schematic diagram of another example of an uplink channel using MIMO communications. 
         FIG.  4 A  is a schematic diagram of one example of a communication system that operates with beamforming. 
         FIG.  4 B  is a schematic diagram of one example of beamforming to provide a transmit beam. 
         FIG.  4 C  is a schematic diagram of one example of beamforming to provide a receive beam. 
         FIG.  5 A  is a schematic diagram of one embodiment of a low noise amplifier (LNA). 
         FIG.  5 B  is a schematic diagram of another embodiment of an LNA. 
         FIG.  5 C  is a schematic diagram of another embodiment of an LNA. 
         FIG.  6    is a schematic diagram of another embodiment of an LNA. 
         FIG.  7 A  is a graph of one example of noise figure versus frequency. 
         FIG.  7 B  is a graph of one example of the s-parameter S 11  versus frequency. 
         FIG.  7 C  is a graph of one example of the s-parameter S 21  versus frequency. 
         FIG.  7 D  is a graph of one example of the s-parameter S 22  versus frequency. 
         FIG.  7 E  is a graph of one example of load stability factor versus frequency. 
         FIG.  7 F  is a graph of one example of source stability factor versus frequency. 
         FIG.  8    is a schematic diagram of one embodiment of a mobile device. 
         FIG.  9 A  is a schematic diagram of one embodiment of a packaged module. 
         FIG.  9 B  is a schematic diagram of a cross-section of the packaged module of  FIG.  9 A  taken along the lines  9 B- 9 B. 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS 
     The following detailed description of certain embodiments presents various descriptions of specific embodiments. However, the innovations described herein can be embodied in a multitude of different ways, for example, as defined and covered by the claims. In this description, reference is made to the drawings where like reference numerals can indicate identical or functionally similar elements. It will be understood that elements illustrated in the figures are not necessarily drawn to scale. Moreover, it will be understood that certain embodiments can include more elements than illustrated in a drawing and/or a subset of the elements illustrated in a drawing. Further, some embodiments can incorporate any suitable combination of features from two or more drawings. 
     The International Telecommunication Union (ITU) is a specialized agency of the United Nations (UN) responsible for global issues concerning information and communication technologies, including the shared global use of radio spectrum. 
     The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications standard bodies across the world, such as the Association of Radio Industries and Businesses (ARM), the Telecommunications Technology Committee (TTC), the China Communications Standards Association (CCSA), the Alliance for Telecommunications Industry Solutions (ATIS), the Telecommunications Technology Association (TTA), the European Telecommunications Standards Institute (ETSI), and the Telecommunications Standards Development Society, India (TSDSI). 
     Working within the scope of the ITU, 3GPP develops and maintains technical specifications for a variety of mobile communication technologies, including, for example, second generation (2G) technology (for instance, Global System for Mobile Communications (GSM) and Enhanced Data Rates for GSM Evolution (EDGE)), third generation (3G) technology (for instance, Universal Mobile Telecommunications System (UMTS) and High Speed Packet Access (HSPA)), and fourth generation (4G) technology (for instance, Long Term Evolution (LTE) and LTE-Advanced). 
     The technical specifications controlled by 3GPP can be expanded and revised by specification releases, which can span multiple years and specify a breadth of new features and evolutions. 
     In one example, 3GPP introduced carrier aggregation (CA) for LTE in Release 10. Although initially introduced with two downlink carriers, 3GPP expanded carrier aggregation in Release 14 to include up to five downlink carriers and up to three uplink carriers. Other examples of new features and evolutions provided by 3GPP releases include, but are not limited to, License Assisted Access (LAA), enhanced LAA (eLAA), Narrowband Internet of things (NB-IOT), Vehicle-to-Everything (V2X), and High Power User Equipment (HPUE). 
     3GPP introduced Phase 1 of fifth generation (5G) technology in Release 15, and plans to introduce Phase 2 of 5G technology in Release 16 (targeted for 2019). Subsequent 3GPP releases will further evolve and expand 5G technology. 5G technology is also referred to herein as 5G New Radio (NR). 
     5G NR supports or plans to support a variety of features, such as communications over millimeter wave spectrum, beamforming capability, high spectral efficiency waveforms, low latency communications, multiple radio numerology, and/or non-orthogonal multiple access (NOMA). Although such RF functionalities offer flexibility to networks and enhance user data rates, supporting such features can pose a number of technical challenges. 
     The teachings herein are applicable to a wide variety of communication systems, including, but not limited to, communication systems using advanced cellular technologies, such as LTE-Advanced, LTE-Advanced Pro, and/or 5G NR. 
       FIG.  1    is a schematic diagram of one example of a communication network  10 . The communication network  10  includes a macro cell base station  1 , a small cell base station  3 , and various examples of user equipment (UE), including a first mobile device  2   a , a wireless-connected car  2   b , a laptop  2   c , a stationary wireless device  2   d , a wireless-connected train  2   e , a second mobile device  2   f , and a third mobile device  2   g.    
     Although specific examples of base stations and user equipment are illustrated in  FIG.  1   , a communication network can include base stations and user equipment of a wide variety of types and/or numbers. 
     For instance, in the example shown, the communication network  10  includes the macro cell base station  1  and the small cell base station  3 . The small cell base station  3  can operate with relatively lower power, shorter range, and/or with fewer concurrent users relative to the macro cell base station  1 . The small cell base station  3  can also be referred to as a femtocell, a picocell, or a microcell. Although the communication network  10  is illustrated as including two base stations, the communication network  10  can be implemented to include more or fewer base stations and/or base stations of other types. 
     Although various examples of user equipment are shown, the teachings herein are applicable to a wide variety of user equipment, including, but not limited to, mobile phones, tablets, laptops, IoT devices, wearable electronics, customer premises equipment (CPE), wireless-connected vehicles, wireless relays, and/or a wide variety of other communication devices. Furthermore, user equipment includes not only currently available communication devices that operate in a cellular network, but also subsequently developed communication devices that will be readily implementable with the inventive systems, processes, methods, and devices as described and claimed herein. 
     The illustrated communication network  10  of  FIG.  1    supports communications using a variety of cellular technologies, including, for example, 4G LTE and 5G NR. In certain implementations, the communication network  10  is further adapted to provide a wireless local area network (WLAN), such as WiFi. Although various examples of communication technologies have been provided, the communication network  10  can be adapted to support a wide variety of communication technologies. 
     Various communication links of the communication network  10  have been depicted in  FIG.  1   . The communication links can be duplexed in a wide variety of ways, including, for example, using frequency-division duplexing (FDD) and/or time-division duplexing (TDD). FDD is a type of radio frequency communications that uses different frequencies for transmitting and receiving signals. FDD can provide a number of advantages, such as high data rates and low latency. In contrast, TDD is a type of radio frequency communications that uses about the same frequency for transmitting and receiving signals, and in which transmit and receive communications are switched in time. TDD can provide a number of advantages, such as efficient use of spectrum and variable allocation of throughput between transmit and receive directions. 
     In certain implementations, user equipment can communicate with a base station using one or more of 4G LTE, 5G NR, and WiFi technologies. In certain implementations, enhanced license assisted access (eLAA) is used to aggregate one or more licensed frequency carriers (for instance, licensed 4G LTE and/or 5G NR frequencies), with one or more unlicensed carriers (for instance, unlicensed WiFi frequencies). 
     As shown in  FIG.  1   , the communication links include not only communication links between UE and base stations, but also UE to UE communications and base station to base station communications. For example, the communication network  10  can be implemented to support self-fronthaul and/or self-backhaul (for instance, as between mobile device  2   g  and mobile device  2   f ). 
     The communication links can operate over a wide variety of frequencies. In certain implementations, communications are supported using 5G NR technology over one or more frequency bands that are less than 6 Gigahertz (GHz) and/or over one or more frequency bands that are greater than 6 GHz. For example, the communication links can serve Frequency Range 1 (FR1), Frequency Range 2 (FR2), or a combination thereof. In one embodiment, one or more of the mobile devices support a HPUE power class specification. 
     In certain implementations, a base station and/or user equipment communicates using beamforming. For example, beamforming can be used to focus signal strength to overcome path losses, such as high loss associated with communicating over high signal frequencies. In certain embodiments, user equipment, such as one or more mobile phones, communicate using beamforming on millimeter wave frequency bands in the range of 30 GHz to 300 GHz and/or upper centimeter wave frequencies in the range of 6 GHz to 30 GHz, or more particularly, 24 GHz to 30 GHz. 
     Different users of the communication network  10  can share available network resources, such as available frequency spectrum, in a wide variety of ways. 
     In one example, frequency division multiple access (FDMA) is used to divide a frequency band into multiple frequency carriers. Additionally, one or more carriers are allocated to a particular user. Examples of FDMA include, but are not limited to, single carrier FDMA (SC-FDMA) and orthogonal FDMA (OFDMA). OFDMA is a multicarrier technology that subdivides the available bandwidth into multiple mutually orthogonal narrowband subcarriers, which can be separately assigned to different users. 
     Other examples of shared access include, but are not limited to, time division multiple access (TDMA) in which a user is allocated particular time slots for using a frequency resource, code division multiple access (CDMA) in which a frequency resource is shared amongst different users by assigning each user a unique code, space-divisional multiple access (SDMA) in which beamforming is used to provide shared access by spatial division, and non-orthogonal multiple access (NOMA) in which the power domain is used for multiple access. For example, NOMA can be used to serve multiple users at the same frequency, time, and/or code, but with different power levels. 
     Enhanced mobile broadband (eMBB) refers to technology for growing system capacity of LTE networks. For example, eMBB can refer to communications with a peak data rate of at least 10 Gbps and a minimum of 100 Mbps for each user. Ultra-reliable low latency communications (uRLLC) refers to technology for communication with very low latency, for instance, less than 2 milliseconds. uRLLC can be used for mission-critical communications such as for autonomous driving and/or remote surgery applications. Massive machine-type communications (mMTC) refers to low cost and low data rate communications associated with wireless connections to everyday objects, such as those associated with Internet of Things (IoT) applications. 
     The communication network  10  of  FIG.  1    can be used to support a wide variety of advanced communication features, including, but not limited to, eMBB, uRLLC, and/or mMTC. 
       FIG.  2 A  is a schematic diagram of one example of a communication link using carrier aggregation. Carrier aggregation can be used to widen bandwidth of the communication link by supporting communications over multiple frequency carriers, thereby increasing user data rates and enhancing network capacity by utilizing fragmented spectrum allocations. 
     In the illustrated example, the communication link is provided between a base station  21  and a mobile device  22 . As shown in  FIG.  2 A , the communications link includes a downlink channel used for RF communications from the base station  21  to the mobile device  22 , and an uplink channel used for RF communications from the mobile device  22  to the base station  21 . 
     Although  FIG.  2 A  illustrates carrier aggregation in the context of FDD communications, carrier aggregation can also be used for TDD communications. 
     In certain implementations, a communication link can provide asymmetrical data rates for a downlink channel and an uplink channel. For example, a communication link can be used to support a relatively high downlink data rate to enable high speed streaming of multimedia content to a mobile device, while providing a relatively slower data rate for uploading data from the mobile device to the cloud. 
     In the illustrated example, the base station  21  and the mobile device  22  communicate via carrier aggregation, which can be used to selectively increase bandwidth of the communication link. Carrier aggregation includes contiguous aggregation, in which contiguous carriers within the same operating frequency band are aggregated. Carrier aggregation can also be non-contiguous, and can include carriers separated in frequency within a common band or in different bands. 
     In the example shown in  FIG.  2 A , the uplink channel includes three aggregated component carriers f UL1 , f UL2 , and f UL3 . Additionally, the downlink channel includes five aggregated component carriers f DL1 , f DL2 , f DL3 , f DL4 , and f DL5 . Although one example of component carrier aggregation is shown, more or fewer carriers can be aggregated for uplink and/or downlink. Moreover, a number of aggregated carriers can be varied over time to achieve desired uplink and downlink data rates. 
     For example, a number of aggregated carriers for uplink and/or downlink communications with respect to a particular mobile device can change over time. For example, the number of aggregated carriers can change as the device moves through the communication network and/or as network usage changes over time. 
       FIG.  2 B  illustrates various examples of uplink carrier aggregation for the communication link of  FIG.  2 A .  FIG.  2 B  includes a first carrier aggregation scenario  31 , a second carrier aggregation scenario  32 , and a third carrier aggregation scenario  33 , which schematically depict three types of carrier aggregation. 
     The carrier aggregation scenarios  31 - 33  illustrate different spectrum allocations for a first component carrier f UL1 , a second component carrier f UL2 , and a third component carrier f UL3 . Although  FIG.  2 B  is illustrated in the context of aggregating three component carriers, carrier aggregation can be used to aggregate more or fewer carriers. Moreover, although illustrated in the context of uplink, the aggregation scenarios are also applicable to downlink. 
     The first carrier aggregation scenario  31  illustrates intra-band contiguous carrier aggregation, in which component carriers that are adjacent in frequency and in a common frequency band are aggregated. For example, the first carrier aggregation scenario  31  depicts aggregation of component carriers f UL1 , f UL2 , and f UL3  that are contiguous and located within a first frequency band BAND 1 . 
     With continuing reference to  FIG.  2 B , the second carrier aggregation scenario  32  illustrates intra-band non-continuous carrier aggregation, in which two or more components carriers that are non-adjacent in frequency and within a common frequency band are aggregated. For example, the second carrier aggregation scenario  32  depicts aggregation of component carriers f UL1 , fuzz, and f UL3  that are non-contiguous, but located within a first frequency band BAND 1 . 
     The third carrier aggregation scenario  33  illustrates inter-band non-contiguous carrier aggregation, in which component carriers that are non-adjacent in frequency and in multiple frequency bands are aggregated. For example, the third carrier aggregation scenario  33  depicts aggregation of component carriers f UL1  and f UL2  of a first frequency band BAND 1  with component carrier f UL3  of a second frequency band BAND 2 . 
       FIG.  2 C  illustrates various examples of downlink carrier aggregation for the communication link of  FIG.  2 A . The examples depict various carrier aggregation scenarios  34 - 38  for different spectrum allocations of a first component carrier f DL1 , a second component carrier f DL2 , a third component carrier f DL3 , a fourth component carrier f DL4 , and a fifth component carrier f DL5 . Although  FIG.  2 C  is illustrated in the context of aggregating five component carriers, carrier aggregation can be used to aggregate more or fewer carriers. Moreover, although illustrated in the context of downlink, the aggregation scenarios are also applicable to uplink. 
     The first carrier aggregation scenario  34  depicts aggregation of component carriers that are contiguous and located within the same frequency band. Additionally, the second carrier aggregation scenario  35  and the third carrier aggregation scenario  36  illustrates two examples of aggregation that are non-contiguous, but located within the same frequency band. Furthermore, the fourth carrier aggregation scenario  37  and the fifth carrier aggregation scenario  38  illustrates two examples of aggregation in which component carriers that are non-adjacent in frequency and in multiple frequency bands are aggregated. As a number of aggregated component carriers increases, a complexity of possible carrier aggregation scenarios also increases. 
     With reference to  FIGS.  2 A- 2 C , the individual component carriers used in carrier aggregation can be of a variety of frequencies, including, for example, frequency carriers in the same band or in multiple bands. Additionally, carrier aggregation is applicable to implementations in which the individual component carriers are of about the same bandwidth as well as to implementations in which the individual component carriers have different bandwidths. 
     Certain communication networks allocate a particular user device with a primary component carrier (PCC) or anchor carrier for uplink and a PCC for downlink. Additionally, when the mobile device communicates using a single frequency carrier for uplink or downlink, the user device communicates using the PCC. To enhance bandwidth for uplink communications, the uplink PCC can be aggregated with one or more uplink secondary component carriers (SCCs). Additionally, to enhance bandwidth for downlink communications, the downlink PCC can be aggregated with one or more downlink SCCs. 
     In certain implementations, a communication network provides a network cell for each component carrier. Additionally, a primary cell can operate using a PCC, while a secondary cell can operate using a SCC. The primary and secondary cells may have different coverage areas, for instance, due to differences in frequencies of carriers and/or network environment. 
     License assisted access (LAA) refers to downlink carrier aggregation in which a licensed frequency carrier associated with a mobile operator is aggregated with a frequency carrier in unlicensed spectrum, such as WiFi. LAA employs a downlink PCC in the licensed spectrum that carries control and signaling information associated with the communication link, while unlicensed spectrum is aggregated for wider downlink bandwidth when available. LAA can operate with dynamic adjustment of secondary carriers to avoid WiFi users and/or to coexist with WiFi users. Enhanced license assisted access (eLAA) refers to an evolution of LAA that aggregates licensed and unlicensed spectrum for both downlink and uplink. 
       FIG.  3 A  is a schematic diagram of one example of a downlink channel using multi-input and multi-output (MIMO) communications.  FIG.  3 B  is schematic diagram of one example of an uplink channel using MIMO communications. 
     MIMO communications use multiple antennas for simultaneously communicating multiple data streams over common frequency spectrum. In certain implementations, the data streams operate with different reference signals to enhance data reception at the receiver. MIMO communications benefit from higher SNR, improved coding, and/or reduced signal interference due to spatial multiplexing differences of the radio environment. 
     MIMO order refers to a number of separate data streams sent or received. For instance, MIMO order for downlink communications can be described by a number of transmit antennas of a base station and a number of receive antennas for UE, such as a mobile device. For example, two-by-two (2×2) DL MIMO refers to MIMO downlink communications using two base station antennas and two UE antennas. Additionally, four-by-four (4×4) DL MIMO refers to MIMO downlink communications using four base station antennas and four UE antennas. 
     In the example shown in  FIG.  3 A , downlink MIMO communications are provided by transmitting using M antennas  43   a ,  43   b ,  43   c , . . .  43   m  of the base station  41  and receiving using N antennas  44   a ,  44   b ,  44   c , . . .  44   n  of the mobile device  42 . Accordingly,  FIG.  3 A  illustrates an example of m×n DL MIMO. 
     Likewise, MIMO order for uplink communications can be described by a number of transmit antennas of UE, such as a mobile device, and a number of receive antennas of a base station. For example, 2×2 UL MIMO refers to MIMO uplink communications using two UE antennas and two base station antennas. Additionally, 4×4 UL MIMO refers to MIMO uplink communications using four UE antennas and four base station antennas. 
     In the example shown in  FIG.  3 B , uplink MIMO communications are provided by transmitting using N antennas  44   a ,  44   b ,  44   c , . . .  44   n  of the mobile device  42  and receiving using M antennas  43   a ,  43   b ,  43   c , . . .  43   m  of the base station  41 . Accordingly,  FIG.  3 B  illustrates an example of n×m UL MIMO. 
     By increasing the level or order of MIMO, bandwidth of an uplink channel and/or a downlink channel can be increased. 
     MIMO communications are applicable to communication links of a variety of types, such as FDD communication links and TDD communication links. 
       FIG.  3 C  is schematic diagram of another example of an uplink channel using MIMO communications. In the example shown in  FIG.  3 C , uplink MIMO communications are provided by transmitting using N antennas  44   a ,  44   b ,  44   c , . . .  44   n  of the mobile device  42 . Additional a first portion of the uplink transmissions are received using M antennas  43   a   1 ,  43   b   1 ,  43   c   1 ,  43   m   1  of a first base station  41   a , while a second portion of the uplink transmissions are received using M antennas  43   a   2 ,  43   b   2 ,  43   c   2 ,  43   m   2  of a second base station  41   b . Additionally, the first base station  41   a  and the second base station  41   b  communication with one another over wired, optical, and/or wireless links. 
     The MIMO scenario of  FIG.  3 C  illustrates an example in which multiple base stations cooperate to facilitate MIMO communications. 
       FIG.  4 A  is a schematic diagram of one example of a communication system  110  that operates with beamforming. The communication system  110  includes a transceiver  105 , signal conditioning circuits  104   a   1 ,  104   a   2  . . .  104   an ,  104   b   1 ,  104   b   2  . . .  104   bn ,  104   m   1 ,  104   m   2  . . .  104   mn , and an antenna array  102  that includes antenna elements  103   a   1 ,  103   a   2  . . .  103   an ,  103   b   1 ,  103   b   2  . . .  103   bn ,  103   m   1 ,  103   m   2  . . .  103   mn.    
     Communications systems that communicate using millimeter wave carriers (for instance, 30 GHz to 300 GHz), centimeter wave carriers (for instance, 3 GHz to 30 GHz), and/or other frequency carriers can employ an antenna array to provide beam formation and directivity for transmission and/or reception of signals. 
     For example, in the illustrated embodiment, the communication system  110  includes an array  102  of m×n antenna elements, which are each controlled by a separate signal conditioning circuit, in this embodiment. As indicated by the ellipses, the communication system  110  can be implemented with any suitable number of antenna elements and signal conditioning circuits. 
     With respect to signal transmission, the signal conditioning circuits can provide transmit signals to the antenna array  102  such that signals radiated from the antenna elements combine using constructive and destructive interference to generate an aggregate transmit signal exhibiting beam-like qualities with more signal strength propagating in a given direction away from the antenna array  102 . 
     In the context of signal reception, the signal conditioning circuits process the received signals (for instance, by separately controlling received signal phases) such that more signal energy is received when the signal is arriving at the antenna array  102  from a particular direction. Accordingly, the communication system  110  also provides directivity for reception of signals. 
     The relative concentration of signal energy into a transmit beam or a receive beam can be enhanced by increasing the size of the array. For example, with more signal energy focused into a transmit beam, the signal is able to propagate for a longer range while providing sufficient signal level for RF communications. For instance, a signal with a large proportion of signal energy focused into the transmit beam can exhibit high effective isotropic radiated power (EIRP). 
     In the illustrated embodiment, the transceiver  105  provides transmit signals to the signal conditioning circuits and processes signals received from the signal conditioning circuits. As shown in  FIG.  4 A , the transceiver  105  generates control signals for the signal conditioning circuits. The control signals can be used for a variety of functions, such as controlling the gain and phase of transmitted and/or received signals to control beamforming. 
       FIG.  4 B  is a schematic diagram of one example of beamforming to provide a transmit beam.  FIG.  4 B  illustrates a portion of a communication system including a first signal conditioning circuit  114   a , a second signal conditioning circuit  114   b , a first antenna element  113   a , and a second antenna element  113   b.    
     Although illustrated as included two antenna elements and two signal conditioning circuits, a communication system can include additional antenna elements and/or signal conditioning circuits. For example,  FIG.  4 B  illustrates one embodiment of a portion of the communication system  110  of  FIG.  4 A . 
     The first signal conditioning circuit  114   a  includes a first phase shifter  130   a , a first power amplifier  131   a , a first low noise amplifier (LNA)  132   a , and switches for controlling selection of the power amplifier  131   a  or LNA  132   a . Additionally, the second signal conditioning circuit  114   b  includes a second phase shifter  130   b , a second power amplifier  131   b , a second LNA  132   b , and switches for controlling selection of the power amplifier  131   b  or LNA  132   b.    
     Although one embodiment of signal conditioning circuits is shown, other implementations of signal conditioning circuits are possible. For instance, in one example, a signal conditioning circuit includes one or more band filters, duplexers, and/or other components. 
     In the illustrated embodiment, the first antenna element  113   a  and the second antenna element  113   b  are separated by a distance d. Additionally,  FIG.  4 B  has been annotated with an angle θ, which in this example has a value of about 90° when the transmit beam direction is substantially perpendicular to a plane of the antenna array and a value of about 0° when the transmit beam direction is substantially parallel to the plane of the antenna array. 
     By controlling the relative phase of the transmit signals provided to the antenna elements  113   a ,  113   b , a desired transmit beam angle θ can be achieved. For example, when the first phase shifter  130   a  has a reference value of 0°, the second phase shifter  130   b  can be controlled to provide a phase shift of about −2πf(d/ν)cos θ radians, where f is the fundamental frequency of the transmit signal, d is the distance between the antenna elements, ν is the velocity of the radiated wave, and π is the mathematic constant pi. 
     In certain implementations, the distance d is implemented to be about ½λ, where λ is the wavelength of the fundamental component of the transmit signal. In such implementations, the second phase shifter  130   b  can be controlled to provide a phase shift of about −π cos θ radians to achieve a transmit beam angle θ. 
     Accordingly, the relative phase of the phase shifters  130   a ,  130   b  can be controlled to provide transmit beamforming. In certain implementations, a baseband processor and/or a transceiver (for example, the transceiver  105  of  FIG.  4 A ) controls phase values of one or more phase shifters and gain values of one or more controllable amplifiers to control beamforming. 
       FIG.  4 C  is a schematic diagram of one example of beamforming to provide a receive beam.  FIG.  4 C  is similar to  FIG.  4 B , except that  FIG.  4 C  illustrates beamforming in the context of a receive beam rather than a transmit beam. 
     As shown in  FIG.  4 C , a relative phase difference between the first phase shifter  130   a  and the second phase shifter  130   b  can be selected to about equal to −2πf(d/ν)cos θ radians to achieve a desired receive beam angle θ. In implementations in which the distance d corresponds to about ½λ, the phase difference can be selected to about equal to −π cos θ radians to achieve a receive beam angle θ. 
     Although various equations for phase values to provide beamforming have been provided, other phase selection values are possible, such as phase values selected based on implementation of an antenna array, implementation of signal conditioning circuits, and/or a radio environment. 
     Examples of LNAs with Low Noise Figure 
     A low noise amplifier (LNA) is the first active circuit in a receiver chain. The position of LNA renders it as one of the most important components of a receiver. However, LNA designs are compromised by relatively low gain and relatively high noise figure (NF) due to parasitic capacitances and Miller effect. Consequently, in the design of an LNA, decisive trade-offs must be made between parameters such as gain, NF, linearity and power. 
     Apparatus and methods for LNAs with low noise figure are provided herein. In certain embodiments, an LNA includes a single-ended LNA stage including an input for receiving a single-ended input signal from an antenna and an output for providing a single-ended amplified signal. The LNA further includes a balun for converting the single-ended amplified signal to a differential signal. 
     By implementing the LNA in this manner, low noise figure is achieved. For example, in comparison to an LNA that includes a cascade of a balun and a differential LNA stage, using the single-ended LNA stage as a first stage provides higher noise figure, lower DC power consumption, and avoids insertion loss arising from using the balun prior to amplification. Moreover, the LNAs herein exhibit improvement in stability and/or immunity to noise effects. 
     In certain implementations, the LNA further includes a variable gain differential amplification stage for amplifying the differential signal from the balun. Implementing the LNA in this manner provides higher gain, flexibility in controlling gain, and less sensitivity to ground/supply impedance. 
       FIG.  5 A  is a schematic diagram of one embodiment of an LNA  210 . The LNA  210  includes an input terminal RF IN , a single-ended LNA stage  201 , an input balun  202 , a differential LNA stage  203 , an output balun  206 , and an output terminal RF OUT  connected to a load  207 . 
     The input terminal RF IN  receives a single-ended input signal from an antenna (not shown in  FIG.  5 A ). The single-ended input signal is a radio frequency signal, and in certain implementations has a frequency of 20 GHz or more. The single-ended LNA stage  201  amplifies the single-ended input signal to generate a single-ended amplified signal that is provided to a first winding of the input balun  202 . The second winding of the input balun  202  generates a differential signal that serves as an input to the differential LNA stage  203 . 
     As shown in  FIG.  5 A , the differential LNA stage  203  amplifies the differential signal to generate a differential amplified signal that is provided to a first winding of the output balun  206 . The output balun  206  operates to convert the differential amplified signal received at the first winding to a single-ended output signal that is outputted from a second winding. As shown in  FIG.  5 A , the output balun  206  provides the single-ended output signal to the output terminal RF OUT . 
     In the illustrated embodiment, the differential LNA stage  203  is a variable gain stage. For instance, the differential LNA stage  203  can have a gain that is programmable or otherwise controllable, for instance, by adjusting the bias and/or load of the differential LNA stage  203  to provide gain steps. In certain implementations, a gain setting of the differential LNA stage  203  is programmable via data received over a serial interface or bus. 
     As shown in  FIG.  5 A , the LNA  210  is depicted as driving the resistive load  207 . However, the LNA  210  can drive any suitable load impedance. 
       FIG.  5 B  is a schematic diagram of another embodiment of an LNA  220 . The LNA  220  includes an input terminal RF IN , a single-ended LNA stage  201 , an input balun  202 , a first differential LNA stage  203 , a second differential LNA stage  204 , an output balun  206 , and an output terminal RF OUT  connected to a load  207 . 
     In comparison to the LNA  210  of  FIG.  5 A , the LNA  220  of  FIG.  5 B  further includes the second differential LNA stage  204 , which is in cascade with the first differential LNA stage  203 . In the illustrated embodiment, both the first differential LNA stage  203  and the second differential LNA stage have variable gain, which can be separately controlled. 
       FIG.  5 C  is a schematic diagram of another embodiment of an LNA  230 . The LNA  230  includes an input terminal RF IN , a single-ended LNA stage  201 , an input balun  202 , a first differential LNA stage  203 , a second differential LNA stage  204 , an output balun  206 , a first gain control switch  221 , a second gain control switch  222 , a third gain control switch  223 , a fourth gain control switch  224 , a fifth gain control switch  225 , a sixth gain control switch  226 , and an output terminal RF OUT  connected to a load  207 . 
     In comparison to the LNA  220  of  FIG.  5 B , the LNA  230  of  FIG.  5 C  further includes the gain control switches  221 - 226  which can be used to selectively bypass the first differential LNA stage  203  to provide gain control and widen dynamic range. For example, the LNA  230  is operable in a bypass mode in which the first to fourth gain control switches  221 - 224  are closed and the fifth and sixth gain control switches  225 - 226  are opened, and a gain mode in which the first to fourth gain control switches  221 - 224  are opened and the fifth and sixth gain control switches  225 - 226  are closed. 
       FIG.  6    is a schematic diagram of another embodiment of an LNA  340 . The LNA  340  includes a single-ended input terminal V in , an input stage series input capacitor  301 , an input stage series input inductor  302 , an input stage shunt input capacitor  303 , an input stage bias resistor  304  (for receiving a bias voltage from a gate bias terminal V GB ), an input stage gain transistor  305 , an input stage cascode transistor  306 , an input stage degeneration inductor  307 , an input stage series inductor  308 , an input stage cascode capacitor  309 , an input stage output shunt capacitor  310 , an input balun  311 , an output stage input capacitor  312 , a first output stage gain transistor  321 , a second output stage gain transistor  322 , a first output stage cascode transistor  323 , a second output stage cascode transistor  324 , a first output stage degeneration inductor  325 , a second output stage degeneration inductor  326 , a first output stage series inductor  327 , a second output stage series inductor  328 , a first output stage cascode capacitor  329 , a second output stage cascode capacitor  330 , an output stage output capacitor  331 , an output balun  332 , an output capacitor  333 , and a single-ended output terminal V out . 
     The LNA  340  of  FIG.  6    illustrates one embodiment of the LNA  210  of  FIG.  5 A . However, the teachings herein are applicable to LNA circuitry implemented in a wide variety of ways. 
     Although not shown in  FIG.  6   , in certain implementations, the gain of the depicted LNA circuitry is adjustable or otherwise controllable. In one example, a bias of the first output stage gain transistor  321  and the second output stage gain transistor  322  is adjustable by a bias circuit (not shown in  FIG.  6   ) to provide gain control. 
     The depicted LNA circuitry is implemented using field-effect transistors (FETs), such as silicon-on-insulator (SOI) metal-oxide-semiconductor (MOS) transistors, arranged as cascode amplifier stages. In particular, the LNA  340  includes a cascade of a single-ended cascode stage, the input balun  311 , a differential cascode stage, and the output balun  332 . Using cascode stages aids in moderating Miller effects, resulting in improved LNA performance. Moreover, the cascode configuration improves reverse isolation (S 12 ), enhances rejection of common mode input noise, and improves gain since the differential cascode stage offers reduced sensitivity to parasitic ground impedance. 
     The design of the single-ended cascode stage achieves low noise figure (NF), and is coupled to the differential cascode stage by way of the passive balun-transformer  311 . Such a single to differential topology provides high immunity to noise effects, and as a result the inclusion of the differential cascode stage causes little to no degradation of NF. A balun is also used in order to export a single-ended output from the differential cascode stage. In certain implementations, either or both of the baluns can be tuned (for instance, using one or more tunable impedances connected thereto) at a particular frequency or frequency range (for instance, millimeter wave frequencies) to reduce loss. 
       FIGS.  7 A- 7 F  illustrates simulation results for one example of an LNA circuitry implemented in accordance with the LNA  340  of  FIG.  6   . Although one example of simulation results are depicted, simulation results can vary based on a wide variety of factors, including, but not limited to, simulation parameters, circuit models, simulation tools, circuit topology, and/or a wide variety of other factors. 
       FIG.  7 A  is a graph of one example of noise figure versus frequency. 
     As shown in  FIG.  7 A , the LNA exhibits low NF of approximately 3.5˜4.5 dB over frequency from 30 GHz to 48 GHz. 
       FIG.  7 B  is a graph of one example of the s-parameter S 11  versus frequency. 
       FIG.  7 C  is a graph of one example of the s-parameter S 21  versus frequency. 
       FIG.  7 D  is a graph of one example of the s-parameter S 22  versus frequency. 
     As shown by the graphs of s-parameters, the LNA exhibits robust operational performance, including excellent reverse isolation (S 12 ). 
       FIG.  7 E  is a graph of one example of load stability factor versus frequency. 
       FIG.  7 F  is a graph of one example of source stability factor versus frequency. 
     As shown by  FIGS.  7 E and  7 F , the LNA exhibits robust operating stability over frequency from 30 GHz to 48 GHz. 
       FIG.  8    is a schematic diagram of one embodiment of a mobile device  800 . The mobile device  800  includes a baseband system  801 , a transceiver  802 , a front end system  803 , antennas  804 , a power management system  805 , a memory  806 , a user interface  807 , and a battery  808 . 
     The mobile device  800  can be used communicate using a wide variety of communications technologies, including, but not limited to, 2G, 3G, 4G (including LTE, LTE-Advanced, and LTE-Advanced Pro), 5G NR, WLAN (for instance, WiFi), WPAN (for instance, Bluetooth and ZigBee), WMAN (for instance, WiMax), and/or GPS technologies. 
     The transceiver  802  generates RF signals for transmission and processes incoming RF signals received from the antennas  804 . It will be understood that various functionalities associated with the transmission and receiving of RF signals can be achieved by one or more components that are collectively represented in  FIG.  8    as the transceiver  802 . In one example, separate components (for instance, separate circuits or dies) can be provided for handling certain types of RF signals. 
     The front end system  803  aids in conditioning signals transmitted to and/or received from the antennas  804 . In the illustrated embodiment, the front end system  803  includes antenna tuning circuitry  810 , power amplifiers (PAs)  811 , low noise amplifiers (LNAs)  812 , filters  813 , switches  814 , and signal splitting/combining circuitry  815 . However, other implementations are possible. 
     For example, the front end system  803  can provide a number of functionalities, including, but not limited to, amplifying signals for transmission, amplifying received signals, filtering signals, switching between different bands, switching between different power modes, switching between transmission and receiving modes, duplexing of signals, multiplexing of signals (for instance, diplexing or triplexing), or some combination thereof. 
     In certain implementations, the mobile device  800  supports carrier aggregation, thereby providing flexibility to increase peak data rates. Carrier aggregation can be used for both Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD), and may be used to aggregate a plurality of carriers or channels. Carrier aggregation includes contiguous aggregation, in which contiguous carriers within the same operating frequency band are aggregated. Carrier aggregation can also be non-contiguous, and can include carriers separated in frequency within a common band or in different bands. 
     The antennas  804  can include antennas used for a wide variety of types of communications. For example, the antennas  804  can include antennas for transmitting and/or receiving signals associated with a wide variety of frequencies and communications standards. 
     In certain implementations, the antennas  804  support MIMO communications and/or switched diversity communications. For example, MIMO communications use multiple antennas for communicating multiple data streams over a single radio frequency channel. MIMO communications benefit from higher signal to noise ratio, improved coding, and/or reduced signal interference due to spatial multiplexing differences of the radio environment. Switched diversity refers to communications in which a particular antenna is selected for operation at a particular time. For example, a switch can be used to select a particular antenna from a group of antennas based on a variety of factors, such as an observed bit error rate and/or a signal strength indicator. 
     The mobile device  800  can operate with beamforming in certain implementations. For example, the front end system  803  can include amplifiers having controllable gain and phase shifters having controllable phase to provide beam formation and directivity for transmission and/or reception of signals using the antennas  804 . For example, in the context of signal transmission, the amplitude and phases of the transmit signals provided to the antennas  804  are controlled such that radiated signals from the antennas  804  combine using constructive and destructive interference to generate an aggregate transmit signal exhibiting beam-like qualities with more signal strength propagating in a given direction. In the context of signal reception, the amplitude and phases are controlled such that more signal energy is received when the signal is arriving to the antennas  804  from a particular direction. In certain implementations, the antennas  804  include one or more arrays of antenna elements to enhance beamforming. 
     The baseband system  801  is coupled to the user interface  807  to facilitate processing of various user input and output (I/O), such as voice and data. The baseband system  801  provides the transceiver  802  with digital representations of transmit signals, which the transceiver  802  processes to generate RF signals for transmission. The baseband system  801  also processes digital representations of received signals provided by the transceiver  802 . As shown in  FIG.  8   , the baseband system  801  is coupled to the memory  806  of facilitate operation of the mobile device  800 . 
     The memory  806  can be used for a wide variety of purposes, such as storing data and/or instructions to facilitate the operation of the mobile device  800  and/or to provide storage of user information. 
     The power management system  805  provides a number of power management functions of the mobile device  800 . In certain implementations, the power management system  805  includes a PA supply control circuit that controls the supply voltages of the power amplifiers  811 . For example, the power management system  805  can be configured to change the supply voltage(s) provided to one or more of the power amplifiers  811  to improve efficiency, such as power added efficiency (PAE). 
     As shown in  FIG.  8   , the power management system  805  receives a battery voltage from the battery  808 . The battery  808  can be any suitable battery for use in the mobile device  800 , including, for example, a lithium-ion battery. 
       FIG.  9 A  is a schematic diagram of one embodiment of a packaged module  900 .  FIG.  9 B  is a schematic diagram of a cross-section of the packaged module  900  of  FIG.  9 A  taken along the lines  9 B- 9 B. 
     The packaged module  900  includes radio frequency components  901 , a semiconductor die  902 , surface mount devices  903 , wirebonds  908 , a package substrate  920 , and an encapsulation structure  940 . The package substrate  920  includes pads  906  formed from conductors disposed therein. Additionally, the semiconductor die  902  includes pins or pads  904 , and the wirebonds  908  have been used to connect the pads  904  of the die  902  to the pads  906  of the package substrate  920 . 
     The semiconductor die  902  includes a low noise amplifier  945 , which can be implemented in accordance with one or more features disclosed herein. 
     The packaging substrate  920  can be configured to receive a plurality of components such as radio frequency components  901 , the semiconductor die  902  and the surface mount devices  903 , which can include, for example, surface mount capacitors and/or inductors. In one implementation, the radio frequency components  901  include integrated passive devices (IPDs). 
     As shown in  FIG.  9 B , the packaged module  900  is shown to include a plurality of contact pads  932  disposed on the side of the packaged module  900  opposite the side used to mount the semiconductor die  902 . Configuring the packaged module  900  in this manner can aid in connecting the packaged module  900  to a circuit board, such as a phone board of a mobile device. The example contact pads  932  can be configured to provide radio frequency signals, bias signals, and/or power (for example, a power supply voltage and ground) to the semiconductor die  902  and/or other components. As shown in  FIG.  9 B , the electrical connections between the contact pads  932  and the semiconductor die  902  can be facilitated by connections  933  through the package substrate  920 . The connections  933  can represent electrical paths formed through the package substrate  920 , such as connections associated with vias and conductors of a multilayer laminated package substrate. 
     In some embodiments, the packaged module  900  can also include one or more packaging structures to, for example, provide protection and/or facilitate handling. Such a packaging structure can include overmold or encapsulation structure  940  formed over the packaging substrate  920  and the components and die(s) disposed thereon. 
     It will be understood that although the packaged module  900  is described in the context of electrical connections based on wirebonds, one or more features of the present disclosure can also be implemented in other packaging configurations, including, for example, flip-chip configurations. 
     Applications 
     The principles and advantages of the embodiments herein can be used for any other systems or apparatus that have needs for low noise amplification. Examples of such apparatus include RF communication systems. RF communications systems include, but are not limited to, mobile phones, tablets, base stations, network access points, customer-premises equipment (CPE), laptops, and wearable electronics. Thus, the low noise amplifiers herein can be included in various electronic devices, including, but not limited to, consumer electronic products. 
     CONCLUSION 
     Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The word “coupled”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Likewise, the word “connected”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. 
     Moreover, conditional language used herein, such as, among others, “may,” “could,” “might,” “can,” “e.g.,” “for example,” “such as” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment. 
     The above detailed description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. For example, while processes or blocks are presented in a given order, alternative embodiments may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, or may be performed at different times. 
     The teachings of the invention provided herein can be applied to other systems, not necessarily the system described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments. 
     While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.