HK1149645B - Radio frequency power amplifier applicable for the use of different battery supply voltages and operation method thereof - Google Patents

Description

Radio frequency power amplifier capable of using different battery power supply voltages and operation method thereof

Technical Field

The present invention relates to wireless communication systems, and more particularly to a radio frequency power amplifier for use in a transmitter of a wireless device in such a wireless communication system.

Background

Known communication systems support wireless and/or wired communication between wireless communication devices and/or wired communication devices. Such communication systems encompass national and/or international cellular telephone systems, the internet, point-to-point indoor wireless networks. Any communication system is established in accordance with one or more communication standards and is operable thereby. For example, a wireless communication system may operate in accordance with one or more of the following listed standards (including but not limited to): ieee802.11x, bluetooth, wireless wide area network (e.g., WiMAX), Advanced Mobile Phone Service (AMPS), Digital Advanced Mobile Phone Service (DAMPS), global system for mobile communications (GSM), Code Division Multiple Access (CDMA), wideband CDMA, Local Multipoint Distribution Service (LMDS), multiple multipoint distribution technology (MMDS), Radio Frequency Identification (RFID), enhanced data rates for GSM evolution (EDGE), General Packet Radio Service (GPRS), and various other standards.

Depending on the type of wireless communication system, a wireless communication device (e.g., a cellular phone, a walkie-talkie, a personal digital assistant, a Personal Computer (PC), a laptop computer, or a home entertainment device) communicates directly or indirectly with other wireless communication devices. For direct communication, also referred to as point-to-point communication, the participating wireless communication devices tune their receivers and transmitters to the same channel or channels and communicate over the channels. Each channel may use one or more of a plurality of Radio Frequency (RF) carriers of the wireless communication system. For indirect wireless communication, each wireless communication device may communicate directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for indoor or in-building wireless networks) over the assigned channel or channels. To complete a communication connection between wireless communication devices, the associated base stations and/or associated access points communicate directly with each other through a system controller, a public switched telephone network, the internet, and/or other wide area networks.

Each wireless communication device participating in wireless communication has a built-in wireless transceiver (i.e., has a receiver and a transmitter) or is connected to an associated wireless transceiver (e.g., a base station of an indoor or in-building wireless communication network, a radio frequency modem, etc.). As is known, the receiver is connected to an antenna and comprises a low noise amplifier, one or more intermediate frequency stages, a filtering stage and a data recovery stage. The low noise amplifier receives an input radio frequency signal from the antenna and amplifies the signal. One or more intermediate frequency stages mix the amplified radio frequency signal with one or more local oscillations and convert the mixed signal to a baseband signal or an intermediate frequency signal. The filtering stage filters the baseband signal or the intermediate frequency signal to attenuate signals outside the undesired band, thus obtaining a filtered signal. The data recovery stage recovers the filtered signal into the original data in accordance with a particular wireless communication standard. The transmitter includes a data modulation stage, one or more intermediate frequency sections, and a power amplifier. The data modulation stage converts the raw data to a baseband signal in accordance with a particular wireless communication standard. One or more intermediate frequency sections mix the baseband signal with one or more local oscillations to obtain a radio frequency signal. The power amplifier amplifies the radio frequency signal and transmits the amplified radio frequency signal from the antenna.

Most, if not all, wireless communication standards place limits on transmit power levels. In addition, some wireless communication standards have reverse link power control that allows a remote device to control the transmit power of another wireless device, e.g., a base station controls the reverse link transmit power of a handset. Therefore, in most wireless devices, the power amplifier is effectively controlled, thereby controlling the transmission power. This presents drawbacks related to the efficiency of the power amplifier. When the power amplifier is well matched to the antenna, efficient transmission is obtained. However, if a mismatch occurs, the emission efficiency is low. Such inefficiency results in excessive power consumption (by the power amplifier) and reduced transmit power. This mismatch can occur for the following reasons: operational deviations of the antenna (e.g., changes in input impedance due to antenna configuration and/or location) and operational deviations of the power amplifier, as well as other radio frequency signal path components of the wireless device due to temperature fluctuations, power supply voltage deviations, and the like. In wireless communication devices, it is often desirable for a power amplifier to provide a high swing at its output. The power amplifier must also maintain a high degree of linearity in its operation and also function as a small power supply where possible. These competing goals are very difficult to meet, particularly in portable devices that are battery powered and operate at relatively low voltages.

Disclosure of Invention

The apparatus and method of operation of the present invention are further described in the accompanying drawings, the detailed description and the claims.

According to an aspect of the present invention, there is provided a Radio Frequency (RF) power amplifier that can use different battery supply voltages, the RF power amplifier including:

a transconductance stage having a transistor with a gate having a radio frequency signal input;

a cascode stage having at least two cascode transistors, the cascode stage and transconductance stage connected in series between a battery voltage node and ground, the cascode stage having a radio frequency signal output and at least two bias inputs to the at least two cascode transistors; and

a cascode bias feedback circuit to:

applying a fixed bias voltage to the at least two bias inputs for low battery voltages;

applying a feedback bias voltage to the at least two bias inputs for a high battery voltage, wherein the feedback bias voltage is based on a voltage of the battery voltage node.

Preferably, the cascode bias feedback circuit selects the fixed bias voltage or the feedback bias voltage based on a DC voltage of a battery voltage node.

Preferably, the cascode bias voltage feedback circuit includes:

a switching network connected between the battery voltage node and ground, having a plurality of lumped (lumped) circuit elements and a plurality of switches, for generating a feedback bias voltage;

a fixed bias voltage source for generating a fixed bias voltage;

at least one switch for applying one of a fixed bias voltage and a feedback bias voltage to the at least one bias input.

Preferably, at least some of the centralized circuit elements in the switching network comprise variable resistors.

Preferably, the radio frequency power amplifier further includes:

at least one driver coupling an output of the at least one switch to the at least two bias voltage inputs, the at least one driver being controllably coupled to any of the at least two cascode transistors;

a corresponding bias input; or

A disabling voltage (disabling voltage).

Preferably, the different supply voltages comprise at least two different battery supply voltages.

Preferably, the different supply voltages comprise at least four different battery supply voltages.

According to an aspect of the present invention, there is provided a Radio Frequency (RF) power amplifier that can use different battery supply voltages, the RF power amplifier including:

a transconductance stage having a transconductance device with a radio frequency signal input;

a cascode stage having at least one cascode transistor, the cascode stage and transconductance stage connected in series between a battery voltage node and ground, the cascode stage having a radio frequency signal output and at least one bias voltage input to the at least one cascode transistor; and

a cascode bias feedback circuit to:

applying a fixed bias voltage to the at least one bias input for low battery voltages;

applying a feedback bias voltage to the at least one bias input for high battery voltages, wherein the feedback bias voltage is based on a voltage of the battery voltage node.

Preferably, the cascode bias feedback circuit selects the fixed bias voltage or the feedback bias voltage based on a DC voltage of a battery voltage node.

Preferably, the cascode bias voltage feedback circuit includes:

a switching network connected between the battery voltage node and ground, having a plurality of lumped circuit elements and a plurality of switches, for generating a feedback bias voltage;

a fixed bias voltage source for generating a fixed bias voltage;

at least one switch for applying one of a fixed bias voltage and a feedback bias voltage to the at least one bias input.

Preferably, at least some of the centralized circuit elements in the switching network comprise variable resistors.

Preferably, the radio frequency power amplifier further includes:

at least one driver coupling an output of the at least one switch to the at least one bias voltage input, the at least one driver being controllably coupled to any of the at least one cascode transistor;

the at least one bias input; or

A disabling voltage (disabling voltage).

As a preference, the first and second liquid crystal compositions are,

the transconductance stage includes a first transistor;

the cascode transistor includes second and third transistors; and

the source and drain of the first transistor, the source and drain of the second transistor, and the source and drain of the third transistor are connected in series between a power supply voltage node and ground.

Preferably, the different supply voltages comprise at least two different voltage levels.

Preferably, the different supply voltages comprise at least four different voltage levels.

According to an aspect of the invention, there is provided a method of operating a Radio Frequency (RF) cascode power amplifier powered by different battery supply voltage levels, comprising:

determining a battery supply voltage;

comparing the battery supply voltage to at least one voltage threshold;

applying a fixed bias voltage to at least one bias input of a cascode stage of the radio frequency cascode power amplifier for a first comparison result indicative of a relatively low battery voltage;

applying a feedback bias voltage to at least one bias input of the radio frequency cascode power amplifier for a second comparison result indicative of a relatively higher battery voltage, wherein the feedback bias voltage is based on an output voltage of the radio frequency cascode power amplifier.

Preferably, the method further comprises selecting one of the fixed bias voltage or the feedback bias voltage based on the DC battery supply voltage.

Preferably, the different supply voltages comprise at least two different voltage levels.

Preferably, the different supply voltages comprise at least four different voltage levels.

Various advantages, aspects and novel features of the invention, as well as details of an illustrated embodiment thereof, will be more fully described with reference to the following description and drawings.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

fig. 1 is a schematic illustration of a wireless communication system constructed and operative in accordance with one or more embodiments of the present invention;

FIG. 2 is a block diagram of the components of a wireless device constructed and operative in accordance with the present invention;

FIG. 3 is a schematic diagram of a wireless communication device including a master device and associated radios;

fig. 4 is a block diagram of a radio frequency cascode power amplifier constructed and operated in accordance with one or more embodiments of the invention;

fig. 5 is a block diagram of another radio frequency cascode power amplifier constructed and operated in accordance with one or more embodiments of the invention;

fig. 6 is a circuit diagram of a portion of a radio frequency power amplifier constructed in accordance with one or more embodiments of the invention;

fig. 7 is a block diagram of another different embodiment of a radio frequency power amplifier constructed in accordance with one or more embodiments of the invention;

fig. 8 is a flow diagram of the operation of a radio frequency cascode power amplifier powered by different battery supply voltage levels in accordance with one or more embodiments of the present invention.

Detailed Description

Fig. 1 is a schematic illustration of a wireless communication system constructed and operative in accordance with one or more embodiments of the present invention. The wireless communication system 100 shown in fig. 1 includes a communication infrastructure and a plurality of wireless devices. The communication infrastructure includes one or more cellular networks 104, one or more Wireless Local Area Networks (WLANs) 106, and one or more Wireless Wide Area Networks (WWANs) 108. The cellular network 104, WLAN 106, WWAN108 are typically connected to one or more backbone networks. Backbone network 102 can comprise the internet, the world wide web, one or more public switched telephone network backbones, one or more cellular network backbones, one or more proprietary network backbones, and/or other types of backbones that support communication with the various wireless network infrastructures 104, 106, and 108. Server computers are connected to these different network infrastructures. For example, server computer 110 is connected to cellular network 104, web server 112 is connected to the internet/WWW/PSTN/cellular network 102, and server 114 is connected to WWAN network 108. Other devices may also be connected to these networks through various other arrangements.

Cellular network 104, WLAN 106, and WWAN108 each support communication with wireless devices in accordance with various different wireless protocol standards within various different wireless spectrums. For example, the cellular network 104 supports wireless communications with wireless devices in the 800MHz band and the 1900MHz band, and/or other radio frequency bands allocated for cellular network communications. The cellular network 104 may support GSM, EDGE, GPRS, 3G, CDMA, TDMA, and/or various other standardized communications. Of course, these are merely examples and are not considered limiting of the spectrum or operation used by such cellular networks. WLAN 106 typically operates within the industrial, scientific, and medical (ISM) frequency bands, including the 2.4GHz and 5.8GHz frequency bands. The ISM band also includes other frequency bands, supporting other types of wireless communications, including the 6.78MHz, 13.56MHz, 27.12MHz, 40.68MHz, 433.92MHz, 915MHz, 24.125GHz, 61.25GHz, 122.5GHz and 245GHz bands. WWAN network 108 may operate in different radio frequency spectrum based on what is allocated for operation in any particular situation. Device-to-device communication is also served by one of these frequency bands.

The wireless network infrastructures 104, 106 and 108 support communication to and from wireless devices 116, 118, 122, 124, 126, 128, 130, 132 and/or 136. Various types of wireless devices are shown. These wireless devices include laptop computers 116 and 118, desktop computers 122 and 124, cellular telephones 126 and 128, and portable beta terminals 130, 132, and 136. Of course, different types of devices are considered wireless devices within the scope of the present invention. For example, an automobile with a cellular interface is also considered a wireless device according to the present invention. Further, any device having a bidirectional or unidirectional wireless communication interface is considered a wireless device according to the present invention. For example, the wireless device has GPS receiving capability to receive positioning signals from a plurality of GPS satellites 150.

The wireless device 116 and 136 may also support point-to-point communications that do not require the support of the wireless network infrastructure. For example, the devices may communicate with each other in the 60GHz band, may use point-to-point communication in the WLAN spectrum, for example, or may use other types of point-to-point communication. For example, within the ISM spectrum, wireless devices may be in accordance with the Bluetooth protocol or any of the various available WLAN protocols supported by IEEE802.11 x.

As will be described later in connection with fig. 2-8, each wireless device 116 and 136 shown in fig. 1 includes baseband processing circuitry, a radio frequency transceiver, and at least one antenna. In accordance with the present invention, a radio frequency transceiver includes a radio frequency power amplifier constructed and operative in accordance with the present invention. The rf power amplifiers of these devices are energy efficient and can operate at multiple battery voltages without requiring a voltage regulator.

Fig. 2 is a block diagram of the components of a wireless device constructed and operative in accordance with the present invention. The wireless device includes a main circuit 204, a radio frequency transceiver 202, an antenna interface 206, and a plurality of antenna assemblies 208A, 208B, 208C, and 208N. In some embodiments of the wireless device shown in fig. 2, the antenna may have only a single antenna component. However, as shown, in fig. 2, the antenna may have multiple antenna components 208A-208N, configured by the antenna interface 206. Configurability through antenna interface 206 includes directional operation, MIMO, or other multiple antenna configurations.

The primary circuitry 204 includes processing circuitry, memory, a user interface, a wired interface, and/or other circuitry associated with the wireless device. For example, wireless devices typically have a display, a keyboard, and/or a plurality of other user interface devices. In addition, the wireless device includes one or more batteries to power it. The radio frequency transceiver 202 includes baseband processing circuitry 210 and radio frequency circuitry 212. Baseband processing circuit 210 generates an output baseband signal 220 to transmitter portion 216 of radio frequency circuit 212. The receiver portion 214 of the rf circuitry 212 generates an input baseband signal 218 to the baseband processing circuitry 210. The rf circuit 212 generates an output rf signal from the transmitter portion 216 to the antenna interface 206. Antenna interface 206 couples the output radio frequency signal to one or more antenna assemblies 208A-208N. The receiver portion 214 of the rf circuitry 212 receives an input rf signal from the antenna interface 206 and converts the input rf signal to an input baseband signal 218. Likewise, the transmitter portion 216 converts the output baseband signal 220 to an output radio frequency signal that is provided by the transmitter portion 216 to the antenna interface 206.

According to the invention, the transmitter section comprises at least one radio frequency power amplifier operable at a plurality of battery voltages. In some embodiments, the radio frequency power amplifier has a cascode configuration and has a cascode bias voltage feedback circuit to provide at least one bias voltage to the cascode stage of the amplifier. Various embodiments according to the present invention will be described later in connection with fig. 3-8.

Fig. 3 is a block diagram of a wireless communication device having a master device and associated radios in accordance with an embodiment of the present invention. The radio is a built-in component to the cellular telephone host. For a personal digital assistant, laptop computer, and/or personal computer host, the wireless transceiving means 360 may be built-in, or may be an externally connected component, connected to the host device 302 through a communication link, such as a PCI interface, PCMCIA interface, USB interface, or other type of interface.

As shown, master device 302 includes processing module 350, memory 352, wireless interface 354, output interface 356, and input interface 358. The processing module 350 and memory 352 may execute corresponding instructions that are typically executed by a host device. For example, for a cellular telephone device, the processing module 350 may perform the corresponding communication function operations in accordance with a particular cellular telephone standard.

Wireless interface 354 may receive data from wireless transceiver device 360 and may transmit data to wireless transceiver device 360. For data received from radio 360, e.g., inbound data, wireless interface 354 communicates it to processing module 530 for further processing and/or routing to output interface 356. Output interface 356 may provide a connection to an output display device, such as a display, monitor, or speaker, for outputting the received data. The wireless interface 354 also transmits outbound data from the processing module 350 to the wireless transceiver 360. The processing module 350 may receive outbound data from an input device, which may be a keyboard, keypad, microphone, or the like, through the input interface 358. The processing module 350 may also generate data itself. For data received via the input interface 358, the processing module 350 may perform corresponding functional operations on the data and/or route it to the wireless transceiving means 360 via the wireless interface 354.

The wireless transceiver device 360 may include a main interface 362, a baseband processing circuit/baseband processing module 364, an analog-to-digital converter (ADC)366, a filtering/gain/attenuation module 368, an intermediate frequency mixing downconversion module 370, a receiver filter 371, a Low Noise Amplifier (LNA)372, a transmitter/receiver switching module 373, a local oscillation module 374, a memory 375, a digital-to-analog converter 378, a filtering/gain/attenuation module 380, an intermediate frequency mixing upconversion module 382, a Power Amplifier (PA)384, a transmitter filtering module 385, and one or more antennas 386. The antenna 386 may be a single antenna shared by both the transmitter and the receiver, switched by the antenna switching module 373, or the antenna 386 includes separate antennas for the transmit path and the receive path. The specific implementation of the antenna may depend on the particular standard to which the wireless communication device is to be subjected and the particular design of the device.

The baseband processing module 364, in conjunction with operating instructions stored within memory 375, performs digital receiver functions and digital transmitter functions. Digital receiver functions include, but are not limited to: digital intermediate frequency to baseband conversion, demodulation, constellation (constellation) demapping, decoding and/or descrambling. Digital transmitter functions include, but are not limited to: scrambling, encoding, cluster mapping, modulation, and/or digital baseband to intermediate frequency conversion. The baseband processing circuit 364 may be implemented using a shared processing device, a single processing device, or multiple processing devices. Such a processing device may be a microprocessor, microcontroller, Digital Signal Processor (DSP), microcomputer, central processing unit, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC), Programmable Logic Device (PLD), state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that may process analog and/or digital signals according to operational instructions. Memory 375 may be a single memory device or a plurality of memory devices. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, and/or any device that may store digital information. It is noted that if the baseband processing circuit 364 performs one or more functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory storing the corresponding operational instructions may be embedded within the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Memory 375 stores and executes operational instructions by baseband processing circuit 364 to implement the functionality of the device.

In operation, the wireless transceiving means 360 may receive outbound data 394 from a host device through the host interface 362. The host interface 362 routes the outbound data 394 to the baseband processing module 364, which processes the outbound data 394 in accordance with a particular wireless communication standard, such as cellular, WiMAX, IEEE802.11 a, IEEE802.11 b, IEEE802.11g, IEEE802.11 n, or Bluetooth, to generate a data/output baseband signal 396 in a digital transmission format. The data 396 in digital transmission format may be a digital baseband signal or a digital low intermediate frequency signal, the low intermediate frequency of which typically ranges from one hundred kilohertz to several megahertz.

Digital to analog converter 378 is used to convert digital transmission format data 396 from the digital domain to the analog domain. The filter/gain/attenuation block 380 filters and/or adjusts the gain of the analog signal before passing it to the if mixing stage 382. The intermediate frequency mixing stage 382 converts the analog baseband or low IF signal to an RF signal, either directly or through multiple conversion steps, based on a transmitter local oscillator signal 383 provided by the local oscillator module 374. The power amplifier 384 may amplify the RF signal to produce the outbound RF signal 398, and the transmitter filtering module 385 will then filter the outbound signal 398. The antenna 386 transmits the outbound RF signal 398 to a destination device, such as a base station, an access point, and/or another wireless communication device.

The radio 360 may receive an inbound RF signal 388 transmitted from a base station, access point, or another wireless communication device via an antenna 386. The antenna 386 may transmit the inbound RF signal 388 to the receiver filter module 371 through the transmitter/receiver switching module 373. The receive filter 371 band pass filters the inbound RF signal 388 and passes the filtered RF signal to a Low Noise Amplifier (LNA) 372. The low noise amplifier 372 amplifies the signal 388 to produce an amplified inbound RF signal. The low noise amplifier 372 passes the amplified inbound RF signal to the intermediate frequency mixing module 370. The intermediate frequency mixing down conversion module 370 directly converts the amplified inbound RF signal to an inbound low IF signal or baseband signal based on the receiver local oscillation signal 381 provided by the local oscillation module 374. The down-conversion module 370 passes the inbound low-IF signal or baseband signal to the filtering/gain/attenuation module 368. The filtering/gain/attenuation module 368 may be implemented in accordance with the teachings of the present invention to filter and/or attenuate an inbound low-IF signal or an inbound baseband signal to generate a filtered inbound signal.

The analog-to-digital converter 366 may convert the filtered inbound signal from the analog domain to the digital domain to produce a digital receive format data/input baseband signal 390. The baseband processing circuit 364 may decode, descramble, demap, and/or demodulate the digital receive format data 390 to recover the inbound data 392 in accordance with the particular wireless communication standard to which the wireless transceiver 360 is compliant. The host interface 362 communicates the retrieved inbound data 392 to the host devices 18-32 via the wireless interface 354.

Those skilled in the art will appreciate that the wireless communication device shown in fig. 3 may be implemented using one or more integrated circuits. For example, the host device may be implemented on one integrated circuit, the baseband processing circuit 364 and the memory 375 may be implemented on a second integrated circuit, and the remaining components of the radio 360, excluding the antenna 386, may be implemented on a third integrated circuit. As another alternative, the radios 360 may be implemented on a single integrated circuit. In another example, the processing module 350 and the baseband processing circuit 364 of the master device may be a common processing device implemented on a single integrated circuit. Further, memory 352 and memory 357 may be implemented on a single integrated circuit and/or on the same integrated circuit as the processing module 350 and a common processing module for baseband processing circuit 354.

According to various aspects of the invention, the power amplifier 384 (radio frequency power amplifier) may operate using multiple supply voltages without the need for a voltage regulator. Various embodiments of the radio frequency power amplifier will be described later in connection with fig. 4-8.

Fig. 4 is a block diagram of a radio frequency cascode power amplifier constructed and operated in accordance with one or more embodiments of the invention. The radio frequency power amplifier comprises an amplifier section 402 having a transconductance stage 408 and a cascode stage 410. The transconductance stage 408 has a transconductance device with an rf input capable of receiving an rf input signal P_in. Cascode stage 410 has at least one cascode transistor and is connected in series with transconductance stage 408 between battery voltage node 404 and ground 406. Cascode stage 410 has an rf signal output, generating signal P_out. In addition, the cascode stage 410 has at least one bias voltage input applied to the gate of the at least one cascode transistor. As shown in fig. 4, the at least one bias input receives one or more bias voltages, the number of which depends on the number of cascode transistors included in cascode stage 410.

The rf power amplifier shown in fig. 4 further includes a cascode bias feedback circuit 412. Cascode bias feedback circuit 412 is coupled between battery voltage node 404 and ground 406. In its operation (described later in connection with fig. 5-8), the cascode bias feedback circuit 412 applies a fixed bias voltage to at least one bias input for a relatively low battery voltage and at least one bias voltage for at least one relatively high battery voltageA feedback bias voltage is applied to the at least one bias input of cascode stage 410. The battery voltage upon which cascode bias voltage feedback circuit 412 determines and sets the bias voltage is determined by V appearing at battery voltage node 404_battAs indicated. As will be described subsequently in connection with FIGS. 5-8, the feedback bias voltage is based on the voltage V at the battery voltage node 404_battAlso serving as a signal output node for generating the signal P_out。

In its various operations, the cascode bias feedback circuit 412 selects one of the fixed bias voltage or the feedback bias voltage based on the DC voltage at the battery voltage node 404. In a specific embodiment of the present invention, the supply voltages supported by the inventive radio frequency power amplifier are 2.5V, 3.3V, 4.3V, and 5.5V. Based on one of these battery voltages appearing at the battery voltage node at a particular point and at a particular time, the cascode bias feedback circuit 412 selects a feedback bias voltage or a fixed bias voltage to apply at the bias input of the cascode stage 410. Further, the values of the fixed bias voltage and/or the feedback bias voltage may be different based on the battery supply voltage level.

Fig. 5 is a block diagram of another radio frequency cascode power amplifier constructed and operated in accordance with one or more embodiments of the invention. In contrast to the architecture shown in fig. 4, the architecture shown in fig. 5 does not show the cascode power amplifier 502 in detail, but rather shows an embodiment of the cascode bias feedback circuit in detail according to one particular architecture. Cascode power amplifier 502 and V_BIASThe circuit 506 is connected between the battery voltage node 404 and ground 406. The cascode power amplifier 502 receives its input from a Power Amplifier Driver (PAD)504, the power amplifier driver 504 receiving an input voltage signal P_in. Cascode power amplifier 502 generates an amplified radio frequency output signal P_out。V_BIASThe circuit 506 determines the voltage level (V) of the battery voltage node 404_LEVEL)。V_BIASThe circuit 506 further generates V_LOWAnd V_HIGHThe level is given to a level shifter 510. V_LEVELSignalFrom V_BIASThe circuit 506 is provided to voltage logic 508, which generates a logic output 0 or 1 to a level shifter 510. Level shifter 510 generates V_LOWAnd V_HIGHOutputs a signal to the bias enable circuit 512. The bias enable circuit 512 also receives the enable signal and generates one or more Vts_BIASThe signal is provided to cascode power amplifier 502. These V_BIASThe signal is provided to one or more gates of the cascode transistors of cascode power amplifier 502.

The operation of the structure shown in fig. 5 will be described in conjunction with fig. 8. A specific example of the structure shown in fig. 5 will be described in conjunction with fig. 6. A different configuration of a radio frequency power amplifier according to one or more embodiments of the invention is shown in fig. 7.

Fig. 6 is a circuit diagram of a portion of a radio frequency power amplifier constructed in accordance with one or more embodiments of the invention. The radio frequency power amplifier includes a transconductance stage, a cascode stage, and a cascode bias feedback circuit. The transconductance stage has a transistor Mb 602 (with a smaller feature size, in this embodiment a thin gate device) and receives a radio frequency signal at its gate. The cascode stage includes two cascode transistors Mt 606 and Mm604 (both having larger feature sizes, in this embodiment thick gate devices). Cascode amplifier generating an output signal V_outp. The choke inductor 608 is used to block signal flow to the battery voltage node 404, and the capacitor 620 is used to block the signal V_outpOf the DC component of (a). In other embodiments, the AC blocking device (inductor) and the DC blocking device (capacitor) may be configured differently for the radio frequency power amplifier. Furthermore, an output balun is used to couple the different radio frequency signal outputs to the antenna.

The cascode transistors Mm604 and Mt 606 of the cascode stage each have a bias voltage input at their respective gates. The cascode feedback circuit provides a fixed bias voltage or feedback bias voltage to the gates of transistors 604 and 606. The cascode feedback circuit includes a switching network connected between the battery voltage node 404 and ground. The switching network comprises a plurality of concentrated circuit devices R1, R2. R3, R4, and R5, and a plurality of switches swm1, swm2, swb1, and swb 2. The cascode bias feedback circuit also has a fixed bias voltage node V_C1And V_C2Which receives corresponding bias voltages from other circuitry (not shown). For relatively high battery voltages, switch swhv is closed and at least some of switches swm1, swm2, swb1, and swb2 are closed. Note that at least some of the plurality of concentrator circuit devices in the switching network of cascode bias feedback circuits may be variable resistors.

The switch position and resistor resistance of the cascode bias voltage feedback circuit may be selected based on the particular implementation of the radio frequency power amplifier and the voltage level at the battery voltage node 404. For example, in one particular embodiment, the radio frequency power amplifier supports battery voltage levels of 2.5V, 3.3V, 4.3V, and 5.5V. At two lower battery voltage levels of 2.5V and 3.3V, the bias voltage V is fixed_C1And V_C2Are applied to the gates of cascode transistors Mm604 and Mt 606, respectively (switch swlv closed and switch swhw open). Fixed bias voltage V_C1And V_C2The 2.5V and 3.3V supply voltages may be different for different batteries. At the two higher battery voltage levels of 4.3V and 5.5V, a feedback bias voltage is applied to the gates of cascode transistors Mm604 and Mt 606, which is generated by the feedback switching network based on the voltage present at the battery voltage node 404 (switch swhw closed, switch swlv open). The positions of the switches swm1, swm2, swb1, and swb2 and/or the resistance values of the variable resistors R2, R3, R4, and R5 may be different for different battery supply voltages of 4.3V and 5.5V.

Capacitors 614 and 616 filter out the bias signal V_BIAStAnd V_BIASmThe high frequency part of (2). As such, the feedback bias voltage applied to transistors 604 and 606 is substantially a DC voltage level. When the rf power amplifier is in operation (during transmit operation, calibration operation, etc.), a bias voltage is applied to the cascode transistors through drivers 610 and 612. Drivers 610 and 612 operate by appropriate enable signals (EN) to enable and disable the bias voltages at transistors 604 and 606, respectively. By means ofAppropriate signal levels EN disable the drivers 610 and 612 to achieve power saving operation by disabling the power amplifiers.

Fig. 7 is a block diagram of another different embodiment of a radio frequency power amplifier constructed in accordance with one or more embodiments of the invention. The different radio frequency power amplifiers include single-ended cascode amplifiers 702 and 704. Cascode power amplifier 702 includes a transconductance stage 706 and a cascode stage 708. Cascode power amplifier 704 includes a transconductance stage 710 and a cascode stage 712. Bias feedback circuit 714 applies a bias voltage to one or more bias inputs of cascode stages 708 and 712. Different signal inputs Pin1, Pin2 are input to the transconductance stages 710 and 706. Different transconductance stage outputs appear at respective battery voltage node 404 output points.

Fig. 8 is a flow diagram of the operation of a radio frequency cascode power amplifier powered by different battery supply voltage levels in accordance with one or more embodiments of the present invention. Operation 800 of fig. 8 begins at step 802 where a battery voltage level is determined. Using the structure described above in connection with fig. 4-7, the cascode bias feedback circuit determines the battery voltage level at the battery voltage node. The cascode bias voltage feedback circuit then compares the battery voltage level to at least one voltage threshold in step 804. Since the method of the present invention supports multiple (i.e., more than two) different battery voltage levels, in some embodiments, at least two thresholds are required for comparison. Then, in step 806, the cascode bias voltage feedback circuit selects the cascode bias voltage input based on the comparison of step 804. When a relatively low battery voltage is determined, the result of step 806 will be to select a fixed bias voltage to apply to the cascode transistors of the cascode radio frequency power amplifier. However, when the determination in step 806 indicates a relatively high level at the battery voltage node, the cascode bias feedback circuit decides to apply the feedback bias voltage to the cascode transistors of the cascode radio frequency power amplifier.

However, in step 808, the cascode stage applies one or more selected cascode bias inputs to the cascode stage of the radio frequency power amplifier. These operations continue until such time as the device determines that a different bias voltage is not required. For example, referring to fig. 6, if the rf power amplifier does not need to immediately pass or amplify the transmitted signal, the cascode transistors of the cascode stage will be disabled in order to reduce power consumption. Additionally, if the device enters a timeout condition, as determined in step 812, it returns to step 802. In addition, if the device is reset, operation will also return to step 802.

In another embodiment, the cascode bias voltage feedback circuit continuously or periodically monitors the battery voltage level at the battery voltage node. In this case, the cascode bias voltage feedback circuit may detect a change in the battery voltage in step 810. In this case, if the battery voltage changes, the operation proceeds to step 802 again.

The terms "circuit" and "circuitry" as used herein may refer to either individual circuits or portions of a multi-function circuit that may perform multiple potential functions. For example, the processing circuit may be implemented as a single-chip processor or as a plurality of processing chips, depending on the embodiment. Likewise, the first circuit and the second circuit may be combined into one circuit in one embodiment, or may be operated independently in different chips in another embodiment. The term "chip" as used herein refers to an integrated circuit. Circuits and circuitry may comprise general purpose or special purpose hardware, and may comprise a combination of such hardware and associated software, such as firmware or object code.

The present invention demonstrates the specific functionality and relationship thereof through the use of method steps. The scope and order of the method steps have been arbitrarily defined for convenience of description. Other boundaries and sequences may be applicable as long as the specified functions and sequences are performed. Any such stated or selected limits or sequences therefore fall within the scope and spirit of the invention.

The invention has also been described above with the aid of functional blocks illustrating some important functions. For convenience of description, the boundaries of these functional building blocks have been defined specifically herein. When these important functions are implemented properly, varying their boundaries is permissible. Similarly, flow diagram blocks may be specifically defined herein to illustrate certain important functions, and the boundaries and sequence of the flow diagram blocks may be otherwise defined for general application so long as the important functions are still achieved. Variations in the boundaries and sequence of the above described functional blocks, flowchart functional blocks, and steps may be considered within the scope of the following claims. Those skilled in the art will also appreciate that the functional blocks described herein, and other illustrative blocks, modules, and components, may be implemented as discrete components, special purpose integrated circuits, processors with appropriate software, and the like.

It will be understood by those within the art that the term "substantially" or "about," as may be used herein, provides an industry-accepted tolerance to the corresponding term. Such an industry-accepted tolerance ranges from less than 1% to 15% and corresponds to, but is not limited to, component values, integrated circuit process fluctuations, temperature fluctuations, rise and fall times, and/or thermal noise. It will be further understood by those within the art that the term "operably coupled", as may be used herein, includes direct coupling and indirect coupling via another component, element, circuit, or module where, for indirect coupling, the intervening component, element, circuit, or module does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As one of ordinary skill in the art will appreciate, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two elements in the same manner as "operably coupled". One of ordinary skill in the art will also recognize that the term "compares favorably", as may be used herein, indicates that a comparison between two or more elements, items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater amplitude than signal 2, favorable comparison results may be obtained when the amplitude of signal 1 is greater than the amplitude of signal 2 or the amplitude of signal 2 is less than the amplitude of signal 1.

The present invention demonstrates the specific functionality and relationship thereof through the use of method steps. The scope and order of the method steps have been arbitrarily defined for convenience of description. Other boundaries and sequences may be applicable as long as the specified functions and sequences are performed. Any such stated or selected limits or sequences therefore fall within the scope and spirit of the invention.

Furthermore, although the present invention has been described in terms of several embodiments, it will be understood by those skilled in the art that the present invention is not limited to these embodiments, and various changes or equivalent substitutions may be made in these features and embodiments without departing from the spirit and scope of the invention. The scope of the invention is only limited by the claims of the present application.

Claims (10)

1. A radio frequency power amplifier that can use different battery supply voltages, the radio frequency power amplifier comprising:

a transconductance stage having a transconductance device with a radio frequency signal input;

a cascode stage having at least one cascode transistor, the cascode stage and transconductance stage connected in series between a battery voltage node and ground, the cascode stage having a radio frequency signal output and at least one bias voltage input to the at least one cascode transistor; and

a cascode bias feedback circuit to:

applying a fixed bias voltage to the at least one bias input for low battery voltages;

applying a feedback bias voltage to the at least one bias input for high battery voltages, wherein the feedback bias voltage is based on a voltage of the battery voltage node.

2. The radio frequency power amplifier of claim 1, wherein the cascode bias feedback circuit selects either a fixed bias voltage or a feedback bias voltage based on a DC voltage of a battery voltage node.

3. The radio frequency power amplifier of claim 1, wherein the cascode bias feedback circuit comprises:

a switching network connected between the battery voltage node and ground, having a plurality of lumped circuit elements and a plurality of switches, for generating a feedback bias voltage;

a fixed bias voltage source for generating a fixed bias voltage;

at least one switch for applying one of a fixed bias voltage and a feedback bias voltage to the at least one bias input.

4. A radio frequency power amplifier as claimed in claim 3, wherein at least some of the lumped circuit elements in the switching network comprise variable resistors.

5. The rf power amplifier of claim 3, wherein the rf power amplifier further comprises:

at least one driver coupling an output of the at least one switch to the at least one bias voltage input, the at least one driver being controllably coupled to any of the at least one cascode transistor;

the at least one bias input; or

The voltage is disabled.

6. A radio frequency power amplifier as claimed in claim 3, wherein the power amplifier is capable of using different battery supply voltages:

the transconductance stage includes a first transistor;

the cascode transistor includes second and third transistors; and

the source of the first transistor is connected to a battery voltage node, the drain of the first transistor is connected to the source of the second transistor, the drain of the second transistor is connected to the source of the third transistor, and the drain of the third transistor is connected to ground.

7. A radio frequency power amplifier as claimed in claim 3, wherein the different battery supply voltages comprise at least two different voltage levels.

8. A radio frequency power amplifier as claimed in claim 3 which can use different battery supply voltages, wherein the different battery supply voltages include at least four different voltage levels.

9. A method of operating a radio frequency cascode power amplifier powered by different battery supply voltage levels, comprising:

determining a battery supply voltage;

comparing the battery supply voltage to at least one voltage threshold;

applying a fixed bias voltage to at least one bias input of a cascode stage of the radio frequency cascode power amplifier for a first comparison result indicative of a relatively low battery voltage;

applying a feedback bias voltage to at least one bias input of the radio frequency cascode power amplifier for a second comparison result indicative of a relatively higher battery voltage, wherein the feedback bias voltage is based on a battery supply voltage of the radio frequency cascode power amplifier.

10. The method of operating a radio frequency cascode power amplifier circuit powered by different battery supply voltage levels according to claim 9, characterized in that the method further comprises selecting one of a fixed bias voltage or a feedback bias voltage based on a DC battery supply voltage.