Self-biasing radio frequency circuitry

The present disclosure describes self-biasing radio frequency circuitry. In some aspects a radio frequency (RF) signal is amplified via a circuit having a first transistor configured to source current to an output of the circuit and a second transistor configured to sink current from the output of the circuit, and another signal is provided, without active circuitry, from the output of the circuit to a gate of the first transistor effective to bias a voltage at the output of the circuit. By so doing, the output of the circuit can be biased without active circuitry which can reduce design complexity of and substrate area consumed by the circuit.

BACKGROUND

Wireless communications between computing devices are often transmitted as radio frequency (RF) signals. Communications (e.g., data or medium control information) of a transmitting device are modulated to a radio frequency and amplified before being broadcast as RF signals via an antenna. These RF signals, often because they have a degraded signal strength due to antenna efficiencies or propagation, are typically amplified by a receiving device to enable demodulation of the RF signals and recovery of the communications. Circuitry associated with the amplification of RF signals, however, may have stability issues due to high-impedance nodes within the circuitry. While these stability issues can be resolved with negative feedback, circuitry capable of providing negative feedback is typically active circuitry (e.g., operational amplifiers). Adding active feedback circuitry to an amplifier circuit, however, increases design complexity and an amount of substrate area consumed by the amplifier circuit, which may result in increased design costs, fabrication costs, and/or amplifier power consumption.

SUMMARY

This summary is provided to introduce subject matter that is further described below in the Detailed Description and Drawings. Accordingly, this Summary should not be considered to describe essential features nor used to limit the scope of the claimed subject matter.

A method is described for amplifying a radio frequency (RF) signal via a circuit having a first transistor configured to source current from a power source to an output of the circuit based on the RF signal and a second transistor configured to sink current from the output of the circuit to a current sink based on the RF signal, and providing, without active circuitry, another signal from the output of the circuit to a gate of the first transistor effective to bias a voltage at the output of the circuit.

Another method is described for applying an RF signal to respective gates of a first and a second metal-oxide-semiconductor field-effect transistor (MOSFET) that are operatively connected in series between a power source and a current sink by their respective drains, sourcing current via the first MOSFET to an output formed at the drains, sinking current via the second MOSFET from the output formed at the drains, and biasing a voltage at the output without active circuitry operably connected between a gate of the first MOSFET and the output formed at the drains of the first and the second MOSFETs.

A circuit is described that includes two p-type metal-oxide-semiconductor field-effect transistors (pMOSFETs) operably connected in series and configured to source current from a current source to an output of the circuit, two n-type metal-oxide-semiconductor field-effect transistors (nMOSFETs) operably connected in series and configured to sink current from the output of the circuit to a current sink, and non-active biasing circuitry operably connected between the output of the circuit and a gate of one of the pMOSFETs configured to bias a voltage of the output of the circuit.

DETAILED DESCRIPTION

Conventional amplification circuits use active circuitry to maintain stability when amplifying radio frequency (RF) signals. This active circuitry (e.g., transistors, diodes, operational amplifiers) increases design complexity and an amount of substrate area consumed by the amplification circuit. This disclosure describes apparatuses and techniques for self-biasing that enable an amplification circuit to be implemented without active feedback circuitry. A signal can be provided from the output of an amplification circuit to a gain cell of the amplification circuit in such a way as to preserve stability during operation, thereby precluding a need to add active circuitry to the amplification circuit.

The following discussion describes an operating environment, techniques that may be employed in the operating environment, and a System-on-Chip (SoC) in which components of the operating environment can be embodied. In the discussion below, reference is made to the operating environment by way of example only.

Operating Environment

FIG. 1illustrates an example of an operating environment100having wireless computing devices102(wireless devices102) and a base station104, each of which are capable of communicating data, packets, and/or frames over a wireless connection106, such as a cellular, local-area, or short-range wireless network. The wireless network may operate in accordance with various standards, such as high-speed packet access (HSPA) or long-term evolution (LTE) cellular standards, or an Institute of Electrical and Electronics Engineers (IEEE) standard such as 802.11, 802.15, or 802.16. Wireless computing devices102include smart-phone108, tablet computer110, and laptop computer112. Although not shown, other configurations of wireless computing devices102are also contemplated, such as a desktop computer, a server, personal navigation device (PND), mobile-internet device (MID), network-attached-storage (NAS) drive, mobile gaming console, and so on.

Base station104provides connectivity to Internet114or other networks via backhaul link116, which may be either wired or wireless (e.g., a T1 line, a fiber optic link, a wireless data relay). Although not shown, other configurations of base station104are also contemplated, such as an access point or cellular modem. Backhaul link116may include or connect with data networks operated by an internet service provider, such as a digital subscriber line (DSL) or broadband cable and may interface with base station104via an appropriately configured modem (not shown). While in communication with base station104, smart-phone108, tablet computer110, or laptop computer112has internet access and/or connectivity with other networks and services for which base station104acts as a gateway.

Each of wireless devices102include processor(s)118and computer-readable storage media120. Processor118can be any suitable type of processor, either single-core or multi-core, for executing instructions or code associated with applications and/or an operating system of the wireless device102. Processor118may be constructed with or fabricated from any suitable material such as silicon or other semiconductors. Computer-readable storage media120may include any type and/or combination of suitable storage media, such as electronic, magnetic, or optical media embodied as memory devices122and storage drive(s)124. Memory devices122may include memory components or modules such as random-access memory (RAM), non-volatile RAM (NVRAM), read-only memory (ROM), or Flash memory useful to store data of applications and/or an operating system of the wireless device102(not shown). Storage drive(s)124may include hard disk drives and/or solid-state drives (not shown) and are useful to store code or instructions associated with the applications and the operating system of wireless device102.

Wireless devices102may also each include I/O ports126, graphics engine128, and wireless interface130. I/O ports126allow a wireless device102to interact with other devices and/or users. Graphics engine128processes and renders graphics for wireless device102, including user interface elements of an operating system, applications, and the like. Wireless interface130provides one or more wireless connections, such as wireless connection106with base station104, and is described in greater detail below.

Base station104includes base station processor132(BS processor132) and base station computer-readable storage media134(BS computer-readable storage media134). BS computer-readable storage media134includes any suitable type and/or combination of storage media, such as electronic media embodied as ROM136, Flash138, or other memory devices (not shown). ROM136may store firmware (e.g., boot code) for base station104and Flash138may be useful to store code or instructions associated with an operating system of base station104.

Base station104also includes network interface140and base station wireless interface142(BS wireless interface142). Network interface140enables base station104to communicate via backhaul link116with the Internet or other networks. BS wireless142enables communication with wireless devices102or other wirelessly-enabled clients. BS wireless interface142may be similar in configuration to wireless interface130, having the same circuits or components, while featuring increased power output and/or robust routing abilities for communication with a number of wireless clients over greater distances.

FIG. 2illustrates a detailed example of wireless interface130, which is capable of communicating over various wireless networks, such as cellular, local-area, or short-range wireless networks. Wireless interface130includes medium access control (MAC) controller202, which facilitates communication of data between wireless interface130and wireless device102via a suitable internal bus (not shown), such as a serial bus, universal serial bus (USB), peripheral component interconnect (PCI) express bus, and the like. Wireless interface130also includes baseband processing block204and radio frequency block206(RF block206) for processing and communicating wireless data.

Baseband processing block204manages communication functions of wireless interface130and processes (e.g., encodes/decodes) un-modulated data communicated by wireless interface130. RF Block206includes RF mixer208for modulating data for transmission or demodulating received data. RF block206also includes low-noise amplifier210that amplifies received RF signals with push-pull circuitry212, which is described below in greater detail. Power amplifier214amplifies signals of wireless interface130prior to transmission to base station104or other wireless devices. Although not shown, power amplifier214may also implement push-pull circuitry212to amplify RF signals. RF Block206may also include filter216to isolate particular frequency bands of RF signals communicated by wireless interface130and antenna port(s)218that enable connections to one or more antennas configured for diversity or multiple-input multiple-output (MIMO) communication. Functionalities or portions of RF block206may be implemented separately as transmitter and receiver components (not shown) or combined as a transceiver (shown).

FIG. 3illustrates a detailed example of push-pull circuitry212, which is capable of amplifying RF signals for transmission or signal recover. Push-pull circuitry212includes input302at which a signal (e.g. RF signal) is received, and output304that provides an amplified signal (e.g. an amplified RF signal). Power can be supplied to push-pull circuitry212via voltage drain306(VDD306) or another suitable power source. Current from push-pull circuitry212can be sank to ground308(GND308) or another node having a potential lower than VDD306.

Push-pull circuitry212may also include Direct Current (DC) blocking capacitors310and312, which block DC or low frequency components of signals received at input302. Transistors314and316are configured to source current from VDD306to output304. Transistors318and320are configured to sink current from output304to GND308. Transistors316and318, functioning as additional gain cells, increase a gain of push-pull circuitry212or enable a similar gain at lower power supply potentials.

In this example, transistors314and316are illustrated as p-type metal-oxide-semiconductor field-effect transistors (pMOSFETs or pMOS) and transistors318and320are illustrated as n-type metal-oxide-semiconductor field-effect transistors (nMOSFETs or nMOS). Although shown as a single-ended or common-mode circuit, push-pull circuitry212may be implemented as a differential circuit by essentially mirroring the design shown. It should also be noted, that the push and pull sections of push-pull circuitry may be implemented with any suitable combination of transistors, such as with fewer transistors (e.g., without transistors316and318) or with transistors of a different type or structure.

Push-pull circuitry212also includes self-biasing circuitry322, which biases DC and/or low frequency voltages at output304. Although current is sourced to and sank from output304at RF frequencies, biasing or setting a DC voltage at output304can enable proper circuit function. Self-biasing circuitry includes bias resistor324, which provides a feedback signal from output304to a gate of transistor314. By so doing, a DC voltage at output304can be biased or set based on bias resistor324and an amount of current flowing through transistor314. Self-biasing circuitry322may also include compensation capacitor326for stability, such as when an impedance of input302and output304are similar. Depending on a value of compensation capacitor326, self-biasing circuitry may include isolation resistor328to prevent compensation capacitor326from conducting RF signals.

As described above, wireless interface130and BS wireless interface142may be configured in a similar fashion, with BS wireless interface142having one or more of the components described above (e.g., push-pull circuitry212). As such, apparatuses or techniques described herein may equally apply to a BS wireless interface142. Additionally, although described with respect to a wireless networks, these techniques may be implemented in association with any wired or wireless communication system (e.g., microwave, optical) that implement push-pull amplification circuitry.

Techniques of Self-Biasing RF Circuitry

The following discussion describes techniques of self-biasing RF circuitry. These techniques can be implemented using the previously described environments, such as self-biasing circuitry322ofFIG. 3embodied on a wireless interface130of wireless device102and/or BS wireless interface142of base station104. These techniques include methods illustrated inFIGS. 4 and 5, each of which is shown as a set of operations performed by one or more entities. These methods are not necessarily limited to the orders shown for performing the operations. Further, these methods may be used in conjunction with one another, in whole or in part, whether performed by the same entity, separate entities, or any combination thereof In portions of the following discussion, reference will be made to operating environment100ofFIG. 1and entities ofFIG. 2and/orFIG. 3by way of example. Such reference is not to be taken as limited to operating environment100but rather as illustrative of one of a variety of examples.

At402, an RF signal is received. The RF signal may range in frequency from about 3 kHz to about 300 Ghz and may include encoded and/or modulated data. The RF signal may be received from any suitable source, such as a component in an RF circuit including a filter, switch, multiplexor, mixer, and the like. In some cases, the RF signal is a signal received via an antenna or an RF signal to be transmitted via an antenna.

As an example, consider smart-phone108in the context ofFIG. 1, which shows smart-phone108communicating with base station104over wireless connection106. Assume here that wireless interface130of smart-phone108is communicating over an LTE cellular network and is receiving RF signals from base station104. Here, low-noise amplifier receives an RF signal from filter216for amplification.

At404, the RF signal is amplified via a circuit having transistors configured to source current to or sink current from an output of the circuit. The circuit may be configured with a push-pull topology, such as push-pull circuitry212ofFIGS. 2 and 3. The transistors of the circuit may be any suitable type of transistors, such as single or stacked pMOSFETs or nMOSFETs, configured to source or sink current respectively.

In the context of the present example, the RF signal is amplified by push-pull circuitry212, which sources current from VDD306with transistors314and316to output304and sinks current from output304to GND308with transistors318and320. This current sourced to and sank from output304forms an amplified RF signal at output304suitable for transmission to another stage of RF block206, such as RF mixer208.

At406, another signal is provided from the output of the circuit to the gate of one of the transistors without active circuitry. This active circuitry may include any active circuit component or structure such as diodes, triodes, transistors, or operational amplifiers. The other signal may be provided via a resistor connected between the output of the circuit to the gate of one of the transistors. This other signal is effective to bias or set a voltage (DC or low frequency) at the output of the circuit.

Additionally, this signal may be compensated and/or isolated with additional passive circuitry, such as a capacitor and an additional resistor. In some cases, a compensation capacitor may be connected in parallel with the resistor conducting the other signal for compensation or stabilization purposes. In such a case, a resistor may be connected in series with this capacitor to prevent the capacitor from conducting or leaking an RF signal or noise.

Concluding the present example, a feedback signal is provided by bias resistor324or self-biasing circuitry322. Assume here that impedances of input302and output304of push-pull circuitry212are similar and may cause stability issues. Compensation capacitor326provides compensation for these stability issues and isolation resistor328prevents compensation capacitor326from conducting an RF signal from output304to the gate of transistor314. Note that this is but one example of self-biasing, and that a feedback signal may be provided using any suitable passive circuitry without departing from the spirit of the present disclosure.

FIG. 5depicts a method500of biasing a voltage of an output formed by gates of two transistors, including operations performed by self-biasing circuitry322ofFIG. 3.

At502, an RF signal is received. The RF signal may range in frequency from about 3 kHz to about 300 Ghz and may include encoded and/or modulated data. The RF signal may be received from any suitable source, such as a component in an RF circuit including a filter, switch, multiplexor, mixer, and the like. In some cases, the RF signal is a signal received via an antenna or an RF signal to be transmitted via an antenna.

As an example, consider RF block206ofFIG. 2, which shows RF mixer208, low-noise amplifier210, power amplifier214, filter216, and antenna ports218. Assume here that wireless interface130is receiving an RF signal from BS wireless interface142via wireless connection106. Here antenna ports218receive the signal from antennas (not shown) and filter216mitigates signals of various undesirable frequency bands.

At504, the RF signal is applied to respective gates of a first and a second metal-oxide-semiconductor field-effect transistor (MOSFET). The respective MOSFETs may be configured as single or stacked gain cells (cascode configurations), such as p-type MOSFETs and n-type MOSFETs connected by their respective gates (e.g., push-pull topology). Configuring MOSFETs as stacked gain cells can increase an effective gain of the gain cells or enable a similar gain to be obtained from the gain cells with reduced power consumption. In the context of the present example, the RF signal from filter216is applied to gates of transistors314and320of push-pull circuitry212.

At506, current is sourced via the first transistor to an output formed by the drains of the first and the second transistor. The current may be sourced from a higher potential node, such as a power supply or rail to which the first transistor is connected. An amount and/or frequency of the current sourced to the output may be based on the RF signal applied to the gates of the first transistor.

At508, current is sank via the second transistor from the output formed by the drains of the first and the second transistor. The current may be sank from the output to a node of lower potential, such as a power or digital ground to which the second transistor is connected. An amount and/or frequency of the current sank from the output may be based on the RF signal applied to the gates of the second transistor.

In the context of the ongoing example and with reference to operations506and508, transistors314and316source current from VDD306to output304, which is formed by the drains of transistors316and318. Transistors318and320sink to GND308from output304, which is formed by the drains of transistors316and318. The current sourced to or sank from output304forms an amplified RF signal based on the RF signal applied to the gates of transistors314and320.

At510, a voltage at the output formed by drains of the transistors is biased without active circuitry. The voltage may be a DC or low frequency voltage at the output. Biasing the voltage may implement a passive component, such as a resistor connected between the output formed by the drains of the transistors and a gate of the first transistor. Additionally, the output may be stabilized with additional passive components, such as a capacitor connected in parallel with the resistor. In such a case, another resistor may be connected in series with the capacitor to prevent the capacitor from conducting other RF signals or noise from the output to the gate of the first transistor.

Continuing the ongoing example, a DC voltage at output304is biased with bias resistor324, which provides a feedback signal to a gate of transistor314. Assume here that impedances of input302and output304of push-pull circuitry212are similar and may cause stability issues. Compensation capacitor326provides compensation for these stability issues and has a capacitance value that sufficiently prevents other RF signals or noise from conducting from output304to the gate of transistor314. Thus, in this case, an additional isolation resistor is not needed for stability or operation of push-pull circuitry212. Note that this is but one example of self-biasing, and that a feedback signal may be provided using any suitable passive circuitry without departing from the spirit or intent of the present disclosure.

At512, an amplified RF signal formed by the current sourced and sank by the transistors is transmitted. The amplified signal may be transmitted to any suitable component, such as an RF mixer, filter, switch, multiplexor, and the like. In some cases, the amplified RF signal may be transmitted to another amplification stage for further amplification.

Concluding the present example, low-noise amplifier210transmits an amplified signal of push-pull circuitry212to RF mixer208for further processing, such as demodulation. It should be noted that by implementing self-biasing circuitry, design of push-pull circuitry can be simplified which may result in design cost savings and a reduced amount of substrate consumed by the push-pull circuit.

FIG. 6illustrates a System-on-Chip (SoC)600, which can implement various embodiments described above. An SoC can be implemented in any suitable device, such as a smart-phone, cellular phone, video game console, IP enabled television, desktop computer, laptop computer, tablet computer, server, base station, wireless router, network-enabled printer, set-top box, printer, scanner, camera, picture frame, and/or any other type of device that may implement wireless connective technology.

SoC600can be integrated with electronic circuitry, a microprocessor, memory, input-output (I/O) logic control, communication interfaces and components, other hardware, firmware, and/or software needed to provide communicative coupling for a device, such as any of the above-listed devices or as an application specific integrated circuit (ASIC) for integration within any of the above-listed devices. SoC600can also include an integrated data bus (not shown) that couples the various components of the SoC for data communication between the components. A wireless communication device that includes SoC600can also be implemented with many combinations of differing components. In some cases, these differing components may be configured to implement concepts described herein over a wireless connection or interface.

In this example, SoC600includes various components such as an input-output (I/O) logic control602(e.g., to include electronic circuitry) and a microprocessor604(e.g., any of a microcontroller, application processor, or digital signal processor). SoC600also includes a memory606, which can be any type of RAM, low-latency nonvolatile memory (e.g., flash memory), ROM, and/or other suitable electronic data storage. SoC600can also include various firmware and/or software, such as an operating system608, which can be computer-executable instructions maintained by memory606and executed by microprocessor604. SoC600can also include other various communication interfaces and components, communication components, other hardware, firmware, and/or software.

SoC600includes MAC Controller202, baseband processing block204, RF mixer208, low-noise amplifier210, push-pull circuitry212, and self-biasing circuitry322, which may be embodied as disparate or combined components, as described in relation to various aspects presented herein. Examples of these various components, functions, and/or entities, and their corresponding functionality, are described with reference to the respective components of the environment100shown inFIGS. 1-3.

Self-biasing circuitry322, either independently or in combination with other entities, can be implemented with any suitable combination of passive components to implement various embodiments and/or features described herein. Self-biasing circuitry322may also be provided integral with other entities of the SoC, such as integrated with one or both of low-noise amplifier210, push-pull circuitry212, or any RF section within SoC600. Alternately or additionally, self-biasing circuitry322and the other components can be implemented as hardware, firmware, fixed logic circuitry, or any combination thereof that is implemented in connection with the I/O logic control602and/or other signal processing and control circuits of SoC600.

Although the subject matter has been described in language specific to structural features and/or methodological operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or operations described above, including orders in which they are performed.