RADIO FREQUENCY AMPLIFIERS WITH CAPACITANCE NEUTRALIZATION

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 400 MHz to about 7.125 GHz for Frequency Range 1 (FR1) of the Fifth Generation (5G) communication standard or in the range of about 24.250 GHz to about 71.000 GHz for Frequency Range 2 (FR2) of the 5G communication standard.

SUMMARY

In certain embodiments, the present disclosure relates to a radio frequency amplifier. The radio frequency amplifier includes a radio frequency input terminal, a radio frequency output terminal, a gain transistor including a control terminal configured to receive a radio frequency signal from the radio frequency input terminal, a cascode transistor connected in series with the gain transistor and configured to provide an amplified radio frequency signal to the radio frequency output terminal, and a neutralization capacitor connected in parallel with the cascode transistor.

In some embodiments, the neutralization capacitor has a controllable capacitance value.

In several embodiments, the neutralization capacitor includes a capacitor bank having a plurality of selectable capacitor branches each including a capacitor and a switch in series. According to a number of embodiments, the switch is implemented as a field-effect transistor. In accordance with various embodiments, the radio frequency amplifier further includes a DC blocking capacitor interposed between the switch and the cascode device.

In some embodiments the radio frequency amplifier further includes a load connected between a power supply voltage and the radio frequency output terminal. According to several embodiments, the load includes an inductor and a resistor in parallel.

In various embodiments, the gain transistor is a common source field-effect transistor having a gate connected to the radio frequency input terminal, and a source connected to a ground voltage. According to a number of embodiments, the cascode transistor is a cascode field-effect transistor having a gate biased by a cascode voltage, a source connected to a drain of the common source field-effect transistor and to a first end of the neutralization capacitor, and a drain connected to the radio frequency output terminal and to a second end of the neutralization capacitor.

In certain embodiments, the present disclosure relates to a mobile device including an antenna, and a front-end system including a radio frequency amplifier. The radio frequency amplifier includes a radio frequency input terminal connected to the antenna, a radio frequency output terminal, a gain transistor including a control terminal configured to receive a radio frequency signal from the radio frequency input terminal, a cascode transistor connected in series with the gain transistor and configured to provide an amplified radio frequency signal to the radio frequency output terminal, and a neutralization capacitor connected in parallel with the cascode transistor.

In several embodiments, the neutralization capacitor has a controllable capacitance value.

In some embodiments, the neutralization capacitor includes a capacitor bank having a plurality of selectable capacitor branches each including a capacitor and a switch in series. According to a number of embodiments, the switch is implemented as a field-effect transistor. In accordance with various embodiments, the radio frequency amplifier further includes a DC blocking capacitor interposed between the switch and the cascode device.

In several embodiments, the radio frequency amplifier further includes a load connected between a power supply voltage and the radio frequency output terminal. According to various embodiments, the load includes an inductor and a resistor in parallel.

In some embodiments, the gain transistor is a common source field-effect transistor having a gate connected to the radio frequency input terminal, and a source connected to a ground voltage. According to a number of embodiments, the cascode transistor is a cascode field-effect transistor having a gate biased by a cascode voltage, a source connected to a drain of the common source field-effect transistor and to a first end of the neutralization capacitor, and a drain connected to the radio frequency output terminal and to a second end of the neutralization capacitor.

In certain embodiments, the present disclosure relates to a method of radio frequency signal amplification. The method includes receiving a radio frequency signal from a radio frequency input terminal at a control terminal of a gain transistor of a radio frequency amplifier, providing an amplified radio frequency signal to the radio frequency output terminal from a cascode transistor of the radio frequency amplifier, the cascode transistor in series with the gain transistor, and providing a gain boost to the radio frequency amplifier using a neutralization capacitor that is connected in parallel with the cascode transistor.

In several embodiments, the gain transistor is a common source field-effect transistor having a gate connected to the radio frequency input terminal, and a source connected to a ground voltage. In accordance with various embodiments, the cascode transistor is a cascode field-effect transistor having a gate biased by a cascode voltage, a source connected to a drain of the common source field-effect transistor and to a first end of the neutralization capacitor, and a drain connected to the radio frequency output terminal and to a second end of the neutralization capacitor.

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. 2A is a schematic diagram of one example of a communication link using carrier aggregation.

FIG. 2B illustrates various examples of uplink carrier aggregation for the communication link of FIG. 2A.

FIG. 2C illustrates various examples of downlink carrier aggregation for the communication link of FIG. 2A.

FIG. 3A is a schematic diagram of one example of a downlink channel using multi-input and multi-output (MIMO) communications.

FIG. 3B is schematic diagram of one example of an uplink channel using MIMO communications.

FIG. 3C is schematic diagram of another example of an uplink channel using MIMO communications.

FIG. 4A is a schematic diagram of one example of a communication system that operates with beamforming.

FIG. 4B is a schematic diagram of one example of beamforming to provide a transmit beam.

FIG. 4C is a schematic diagram of one example of beamforming to provide a receive beam.

FIG. 5A is a schematic diagram of one embodiment of a radio frequency (RF) amplifier.

FIG. 5B is a schematic diagram of another embodiment of an RF amplifier.

FIG. 5C is a schematic diagram of another embodiment of an RF amplifier.

FIG. 6A is a schematic diagram of another embodiment of an RF amplifier.

FIG. 6B is a schematic diagram of a model of the RF amplifier of FIG. 6A.

FIG. 7A is a schematic diagram of another embodiment of an RF amplifier.

FIG. 7B is a schematic diagram of another embodiment of an RF amplifier.

FIG. 8 is a graph of one example of s-parameter versus frequency for various capacitance values.

FIG. 9 is a graph of another example of s-parameter versus frequency for two capacitance values.

FIG. 10 is a graph of another example of s-parameter versus frequency.

FIG. 11 is a schematic diagram of one embodiment of a mobile device.

FIG. 12A is a schematic diagram of one embodiment of a packaged module.

FIG. 12B is a schematic diagram of a cross-section of the packaged module of FIG. 12A taken along the lines 12B-12B.

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 (ARIB), 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 introduced Phase 2 of 5G technology in Release 16. 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 2a, a wireless-connected car 2b, a laptop 2c, a stationary wireless device 2d, a wireless-connected train 2e, a second mobile device 2f, and a third mobile device 2g.

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 2g and mobile device 2f).

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. Cellular user equipment can communicate using beamforming and/or other techniques over a wide range of frequencies, including, for example, FR2-1 (24 GHz to 52 GHz), FR2-2 (52 GHz to 71 GHz), and/or FR1 (400 MHz to 7125 MHz).

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. 2A 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. 2A, 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. 2A 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. 2A, 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. 2B illustrates various examples of uplink carrier aggregation for the communication link of FIG. 2A. FIG. 2B 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 full, a second component carrier f_UL2, and a third component carrier f_UL3. Although FIG. 2B 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_UL3that are contiguous and located within a first frequency band BAND1.

With continuing reference to FIG. 2B, 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, f_UL2, and f_UL3that are non-contiguous, but located within a first frequency band BAND1.

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_UL1and f_UL2of a first frequency band BAND1 with component carrier f_UL3of a second frequency band BAND2.

FIG. 2C illustrates various examples of downlink carrier aggregation for the communication link of FIG. 2A. 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. 2C 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. 2A-2C, 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. Furthermore, NR-U can operate on top of LAA/eLAA over a 5 GHz band (5150 to 5925 MHz) and/or a 6 GHz band (5925 MHz to 7125 MHz).

FIG. 3A is a schematic diagram of one example of a downlink channel using multi-input and multi-output (MIMO) communications. FIG. 3B 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. 3A, downlink MIMO communications are provided by transmitting using M antennas 43a, 43b, 43c, . . . 43m of the base station 41 and receiving using N antennas 44a, 44b, 44c, . . . 44n of the mobile device 42. Accordingly, FIG. 3A 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. 3B, uplink MIMO communications are provided by transmitting using N antennas 44a, 44b, 44c, . . . 44n of the mobile device 42 and receiving using M antennas 43a, 43b, 43c, . . . 43m of the base station 41. Accordingly, FIG. 3B 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. 3C is schematic diagram of another example of an uplink channel using MIMO communications. In the example shown in FIG. 3C, uplink MIMO communications are provided by transmitting using N antennas 44a, 44b, 44c, . . . 44n of the mobile device 42. Additional a first portion of the uplink transmissions are received using M antennas 43a1, 43b1, 43c1, . . . 43m1 of a first base station 41a, while a second portion of the uplink transmissions are received using M antennas 43a2, 43b2, 43c2, . . . 43m2 of a second base station 41b. Additionally, the first base station 41a and the second base station 41b communication with one another over wired, optical, and/or wireless links.

The MIMO scenario of FIG. 3C illustrates an example in which multiple base stations cooperate to facilitate MIMO communications.

FIG. 4A 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 104a1, 104a2 . . . 104an, 104b1, 104b2 . . . 104bn, 104m1, 104m2 . . . 104mn, and an antenna array 102 that includes antenna elements 103a1, 103a2 . . . 103an, 103b1, 103b2 . . . 103bn, 103m1, 103m2 . . . 103mn.

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. 4A, 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. 4B is a schematic diagram of one example of beamforming to provide a transmit beam. FIG. 4B illustrates a portion of a communication system including a first signal conditioning circuit 114a, a second signal conditioning circuit 114b, a first antenna element 113a, and a second antenna element 113b.

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. 4B illustrates one embodiment of a portion of the communication system 110 of FIG. 4A.

The first signal conditioning circuit 114a includes a first phase shifter 130a, a first power amplifier 131a, a first low noise amplifier (LNA) 132a, and switches for controlling selection of the power amplifier 131a or LNA 132a. Additionally, the second signal conditioning circuit 114b includes a second phase shifter 130b, a second power amplifier 131b, a second LNA 132b, and switches for controlling selection of the power amplifier 131b or LNA 132b.

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 113a and the second antenna element 113b are separated by a distance d. Additionally, FIG. 4B 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 113a, 113b, a desired transmit beam angle Θ can be achieved. For example, when the first phase shifter 130a has a reference value of 0°, the second phase shifter 130b can be controlled to provide a phase shift of about −2πf(d/v)cos Θ radians, where f is the fundamental frequency of the transmit signal, d is the distance between the antenna elements, v 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 130b 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 130a, 130b can be controlled to provide transmit beamforming. In certain implementations, a baseband processor and/or a transceiver (for example, the transceiver 105 of FIG. 4A) controls phase values of one or more phase shifters and gain values of one or more controllable amplifiers to control beamforming.

FIG. 4C is a schematic diagram of one example of beamforming to provide a receive beam. FIG. 4C is similar to FIG. 4B, except that FIG. 4C illustrates beamforming in the context of a receive beam rather than a transmit beam.

As shown in FIG. 4C, a relative phase difference between the first phase shifter 130a and the second phase shifter 130b can be selected to about equal to −2πf(d/v)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.

RF amplifiers with capacitance neutralization are provided. In certain embodiments, an RF amplifier includes an RF input terminal, an RF output terminal, a gain transistor including a control terminal that receives an RF signal from the RF input terminal, a cascode transistor connected in series with the gain transistor and that provides an amplified RF signal to the RF output terminal, and a neutralization capacitor connected in parallel with the cascode transistor.

By including the neutralization capacitor, a number of benefits can be achieved. For example, the neutralization capacitor provides a gain and noise figure (NF) improvement to the RF amplifier. For example, a transconductance of the cascode transistor can operate in combination with the neutralization capacitor to create a strong internal circulation for noise that leads to an NF improvement, while positive feedback can lead to phase conversion and capacitance neutralization. Furthermore, the neutralization capacitor can limit leakage of the cascode transistor to improve gain while the Miller effect at the gain transistor can be low to provide gain enhancement.

The RF amplifiers herein can be used in a wide variety of applications, including, for example, to operate as a low noise amplifier in a mobile device.

FIG. 5A is a schematic diagram of one embodiment of an RF amplifier 160. The RF amplifier 160 includes a gain transistor 151, a cascode transistor 152, a load 153, and a neutralization capacitor 154.

As shown in FIG. 5A, the gain transistor 151 includes a control terminal that receives an RF input signal from an RF input terminal RF_IN. In certain implementations, the control terminal of the gain transistor 151 is also biased by a bias circuit (not shown in FIG. 5A). The cascode transistor 152 is connected in series with the gain transistor 151 between an RF output terminal RF_OUTand a ground voltage. The cascode transistor 152 includes a control terminal that receives a cascode bias voltage V_CAS. The load 153 is connected between a power supply voltage V_CCand the RF output terminal RF_OUT.

The RF amplifier 160 includes the neutralization capacitor 154, which is connected in parallel with the cascode transistor 152. In particular, the neutralization capacitor 154 includes a first end connected to a first signal terminal of the cascode transistor 152 and a second end connected to a second signal terminal of the cascode transistor 152.

The neutralization capacitor 154 provides a gain and noise figure (NF) improvement to the RF amplifier 160. For example, the neutralization capacitor 154 can boost gain by 1 dB or more, while a transconductance of the cascode transistor 152 can lead to strong internal circulation for noise that leads to a NF improvement. For example, positive feedback can lead to phase conversion and capacitance neutralization. Furthermore, the neutralization capacitor 154 can limit leakage of the cascode transistor 152 to improve gain while the Miller effect at the gain transistor 151 can be low to provide gain enhancement.

FIG. 5B is a schematic diagram of another embodiment of an RF amplifier 170. The RF amplifier 170 of FIG. 5B is similar to the RF amplifier 160 of FIG. 5A, except that the RF amplifier 170 includes a controllable neutralization capacitor 164 having a controllable capacitance value.

Including the controllable neutralization capacitor 164 provides flexibility in adjusting gain and/or NF.

FIG. 5C is a schematic diagram of another embodiment of an RF amplifier 180. The RF amplifier 180 of FIG. 5C is similar to the RF amplifier 170 of FIG. 5B, except that the RF amplifier 180 includes a controllable neutralization capacitor that is implemented as a neutralization capacitor bank 174. In the illustrated embodiment, the neutralization capacitor bank 174 includes switches 176a, 176b, . . . 176n each in series with a corresponding one of the capacitors 175a, 175b, . . . 175n, respectively. Any number n capacitors and switches can be included.

Including the neutralization capacitor bank 174 provides flexibility in adjusting gain and/or NF by providing multiple neutralization states, which can be digitally selected or controlled by setting the states (opened or closed) of the switches 176a, 176b, . . . 176n.

FIG. 6A is a schematic diagram of another embodiment of an RF amplifier 210. The RF amplifier 210 includes a common source field-effect transistor (FET) 201, a cascode FET 202, a neutralization capacitor 203, a load inductor 204, and a load resistor 205.

As shown in FIG. 6A, a gate of the common source FET 201 is connected to an RF input terminal RF_IN, and a source connected to a ground voltage. Additionally, the cascode FET 202 includes a gate connected to a cascode voltage V_CAS, a source connected to a drain of the common source FET 201, and a drain connected to the RF output terminal RF_OUT. Furthermore, the neutralization capacitor 203 has a capacitance value Cx, and includes a first end connected to the source of the cascode FET 202 and a second end connected to the drain of the cascode FET 202 (and thus is in parallel with the cascode FET 202). Additionally, the load inductor 204 and the load resistor 205 are connected in parallel with one another between a power supply voltage V_CCand the RF output terminal RF_OUT.

FIG. 6B is a schematic diagram of a model 220 of the RF amplifier 210 of FIG. 6A. The model 220 includes a gate-to-source capacitance Cgs of the cascode FET 202. The model 220 also includes a capacitance —Cx*gm*R*L at a source of the common-source FET 202, where gm is the FET transconductance, R is a resistance of the load resistor 205, and L is an inductance of the load inductance 204. The model 220 also includes a capacitance of about Cx at a drain of the common-source FET 202.

With reference to the model 220, v2=Av*v1, where Av is about equal to gm*R*L when R*L is much less than an output resistance (ro) of the RF amplifier 210. Therefore, the capacitance value Cx1 at the source of the common-source FET 202 is about equal to Cx(1−Av) due to the Miller effect, and thus is approximately —Cx*gm*R*L as indicated by annotation in FIG. 6B. The negative capacitance value present at the source of the common-source FET 202 can lead to gain boosting due to negative resistance generation. In particular an output impedance looking into the RF output terminal RF_OUTcan be amount equal to −gm*(1/ωCx)*(1/ωCgs), where w is angular frequency.

In certain implementations, a capacitance value Cx of the neutralization capacitor 203 is selected such that Cx*gm*R*L is between 0.5 and 1.5 times (or more particularly, between 0.8 and 1.2 times) a value of the gate-to-source capacitance Cgs of the cascode transistor to aid in providing neutralization.

FIG. 7A is a schematic diagram of another embodiment of an RF amplifier 230. The RF amplifier 230 includes a common source FET 201, a cascode FET 202, a neutralization capacitor bank 223, a load inductor 204, and a load resistor 205.

The RF amplifier 230 of FIG. 7A is similar to the RF amplifier 210 of FIG. 6A, except that the RF amplifier 230 implements the neutralization capacitor as the neutralization capacitor bank 223.

The neutralization capacitor bank 223 includes FET switches 224a, 224b, . . . 224n each in series with one of the capacitors 225a, 225b, . . . 225n. Any number n (where n is an integer of at least 1, or more particularly 2 or more) capacitors and switches can be included. The capacitors 225a, 225b, . . . 225n have capacitance values Cxa, Cxb, . . . Cxn, which can be weighted with any desired capacitance weighting scheme. The gates of the FET switches 224a, 224b, . . . 224n receive control signals ctrla, ctrlb, . . . ctrln, which can be individually controlled to achieve a desired capacitance setting.

FIG. 7B is a schematic diagram of another embodiment of an RF amplifier 240. The RF amplifier 240 includes a common source FET 201, a cascode FET 202, a neutralization capacitor bank 233, a load inductor 204, and a load resistor 205.

The RF amplifier 240 of FIG. 7B is similar to the RF amplifier 230 of FIG. 7A, except that the neutralization capacitor bank 233 further includes a DC blocking capacitor 241 interposed between the FET switches 224a, 224b, . . . 224n and the cascode FET 202. The DC blocking capacitor 241 provides DC voltage blocking that aids in biasing the FET switches 224a, 224b, . . . 224n.

FIG. 8 is a graph of one example of s-parameter versus frequency for various capacitance values. The s-parameter represents gain in this example, with Cx swept from 1 fF to 500 fF. As shown in FIG. 8, the capacitor neutralization and corresponding negative resistance generation leads to a gain improvement.

FIG. 9 is a graph of another example of s-parameter versus frequency for two capacitance values. The s-parameter represents gain in this example, with Cx set to two different values by using a FET switch.

FIG. 10 is a graph of another example of s-parameter versus frequency. The s-parameter represents NF in this example. As shown in FIG. 10, low NF is achieved over the frequency range of interest, for example, between about 3 GHz and about 6 GHz in this example.

FIG. 11 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. 11 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. The LNAs 812 can include one or more LNAs implemented in accordance with the teachings herein.

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. 11, 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. 11, 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. 12A is a schematic diagram of one embodiment of a packaged module 900. FIG. 12B is a schematic diagram of a cross-section of the packaged module 900 of FIG. 12A taken along the lines 12B-12B.

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. 12B, 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. 12B, 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.

RADIO FREQUENCY AMPLIFIERS WITH CAPACITANCE NEUTRALIZATION

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