Thermal compensation of radio frequency power amplifiers

Abstract

The present invention relates to techniques for amplifying radio frequency (RF) signals. An apparatus having an RF amplifier including a bias input. The RF amplifier is to receive a temperature dependent bias input and an RF signal. The RF amplifier is to amplify the RF signal in response to a transmit enable signal. The apparatus includes one or more bias transistors to generate the temperature dependent bias signal. The apparatus includes one or more heating transistors to heat the one or more bias transistors. The apparatus includes control circuitry to cause the one or more heating transistors to heat the one or more bias transistors when the RF amplifier is powered on.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to radio frequency (RF) power amplifiers. BACKGROUND

[0002] In wireless terminals such as cellular telephones, RF power amplifiers are one of the most critical components. The role of the RF power amplifier is to amplify the transmit power level of a modulated RF signal for transmission from an antenna. The RF power amplifier amplifies the modulated RF signal sufficiently to meet the RF signal transmit power requirements of the intended application scenario. In addition, the RF power amplifier needs to have low RF signal distortion. In performing its role, the RF power amplifier consumes a significant amount of power, which can be a problem for wireless communication devices that are powered by a battery. Therefore, it is desirable to reduce the power consumption of the RF power amplifier to extend battery life.

[0003] In certain architectures, the RF power amplifier is powered on and off in response to a transmit enable signal. For example, in Wi-Fi communications, the RF power amplifier can operate in a mode in which it is powered on and off in response to a transmit enable signal. The temperature of the RF power amplifier increases rapidly when it is powered on and decreases rapidly when it is powered off. At the same time, the gain of the RF power amplifier is dependent on temperature. Therefore, at least for a short time, the gain of the RF power amplifier can vary significantly as the ambient temperature of the RF power amplifier increases. After the ambient temperature of the RF power amplifier stabilizes, the gain typically enters a relatively stable phase. However, the RF power amplifier typically transmits data while the ambient temperature is increasing. Gain instability can cause RF signal distortion. RF signal distortion can result in data loss at the RF signal receiver. SUMMARY

[0004] According to one aspect of the present invention, an apparatus for amplifying a radio frequency (RF) signal is provided. The apparatus includes an RF amplifier for receiving a temperature dependent bias input and the RF signal. The RF amplifier is for amplifying the RF signal in response to a transmit enable signal. The apparatus includes one or more bias transistors for generating a temperature dependent bias signal. The apparatus includes one or more heating transistors for heating the one or more bias transistors. The apparatus includes a control circuit for causing the one or more heating transistors to heat the one or more bias transistors when the RF amplifier is powered on.

[0005] Optionally, in any of the above aspects, the control circuit is for generating a DC bias current that tracks the transmit enable signal. The circuit is for providing the DC bias current to the one or more heating transistors to cause the one or more heating transistors to heat the one or more bias transistors when the RF amplifier is powered on.

[0006] Optionally, in any of the above aspects, the control circuit is configured to provide heating to the one or more bias transistors in accordance with a received control signal generated by a processor in accordance with a specified parameter. The parameter specifies an amount of heating compensation for the one or more bias transistors. The control circuit is configured to generate a DC bias current based on the control signal. The heating transistors generate heat dependent on the magnitude of the DC bias current to heat the one or more bias transistors when the RF amplifier is powered on.

[0007] Optionally, in any of the above aspects, the control circuit is configured to determine the magnitude of the DC bias current in accordance with a target power of an amplified RF signal output by the RF amplifier.

[0008] Optionally, in any of the above aspects, the control circuit is configured to sample the amplified RF signal from the RF amplifier and provide the sampled amplified RF signal to the one or more heating transistors. The one or more heating transistors are configured to heat the one or more bias transistors in accordance with the magnitude of the amplified RF signal when the RF amplifier is powered on.

[0009] Optionally, in any of the above aspects, the one or more heating transistors comprise one or more bipolar junction transistors. The control circuit provides the DC bias current to a base of each of the one or more bipolar junction transistors. The control circuit provides the amplified RF signal to the base of each of the one or more bipolar junction transistors.

[0010] Optionally, in any of the above aspects, the one or more heating transistors comprise a first transistor positioned on a first side of the one or more bias transistors and a second transistor positioned on a second side of the one or more bias transistors. The second side is opposite the first side.

[0011] Optionally, in any of the above aspects, the RF amplifier comprises a preamplification stage having a first RF input, a bias input as a first bias input, and a first RF output. The RF amplifier comprises a power amplification stage having a second RF input coupled to the first RF output, a second bias input, and a second RF output. The one or more bias transistors are configured to provide a first bias signal to the first bias input of the preamplification stage and a second bias signal to the second bias input of the power amplification stage. The control circuit is configured to sample the amplified RF signal at the first RF output. The one or more heating transistors are configured to heat the one or more bias transistors in accordance with a magnitude of the amplified RF signal at the first RF output.

[0012] Optionally, in any of the above aspects, the RF amplifier includes a preamplification stage having a first RF input, a first bias input, and a first RF output. The RF amplifier includes a power amplification stage having a second RF input coupled to the first RF output, a second bias input, and a second RF output. The one or more bias transistors are to provide a first bias signal to the first bias input of the preamplification stage and a second bias signal to the second bias input of the power amplification stage. The control circuit is to sample the amplified RF signal at the second RF output. The one or more heating transistors are to heat the one or more bias transistors in accordance with an amplitude of the amplified RF signal at the second RF output.

[0013] Optionally, in any of the above aspects, the one or more bias transistors include a first group of one or more bias transistors to provide the first bias signal to the preamplification stage and a second group of one or more bias transistors to provide the second bias signal to the power amplification stage. The one or more heating transistors include a first heating transistor between the first group of one or more bias transistors and the second group of one or more bias transistors.

[0014] Optionally, in any of the above aspects, the one or more heating transistors further include a second heating transistor on a first side of the first group of one or more bias transistors, the second heating transistor opposing a second side of the first group of one or more bias transistors adjacent to the first heating transistor. The one or more heating transistors further include a third heating transistor on a first side of the second group of one or more bias transistors, the third heating transistor opposing a second side of the second group of one or more bias transistors adjacent to the first heating transistor.

[0015] Another aspect of the disclosure includes a method for amplifying a radio frequency (RF) signal. The method includes operating an RF amplifier in a mode in which the RF amplifier is powered on and off in response to a transmit enable signal. The method includes amplifying, by the RF amplifier, the RF signal when the RF amplifier is powered on. The method includes providing, from one or more bias transistors, a temperature-dependent bias signal to a bias input of the RF amplifier when the RF amplifier is powered on. The method includes heating, by one or more heating transistors, the one or more bias transistors when the RF amplifier is powered on.

[0016] According to another aspect of the present application, a radio frequency (RF) signal transmitter for transmitting an RF signal is provided. The RF transmitter includes a preamplification stage having an RF input, an RF output, and a first bias input. The preamplification stage is configured to receive the RF signal at the RF input of the preamplification stage and provide a preamplified RF signal to the RF output of the preamplification stage. The RF transmitter includes a power amplification stage having an RF input coupled to the RF output of the preamplification stage, an RF output, and a second bias input. The power amplification stage is configured to receive the preamplified RF signal at the RF input of the power amplification stage and provide a power amplified RF signal to the RF output of the power amplification stage. The preamplification stage and the power amplification stage are configured to amplify the RF signal in accordance with a transmit enable signal. The RF transmitter includes an antenna coupled to the RF output of the power amplification stage. The antenna is configured to transmit the power amplified RF signal. The RF transmitter includes one or more bias transistors configured to provide a first bias signal to the first bias input and a second bias signal to the second bias input. The RF transmitter includes one or more heating transistors configured to heat the one or more bias transistors. The RF transmitter includes control circuitry configured to cause the one or more heating transistors to heat the one or more bias transistors when the preamplification stage and the power amplification stage are powered on.

[0017] This summary introduces some concepts that will be further described in the detailed description. This summary is neither intended nor constitutes a feature of the claimed subject matter nor is it used in determining or limiting the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all of the problems presented in the background. BRIEF DESCRIPTION OF DRAWINGS

[0018] Various aspects of the application are illustrated by way of example, and not limitation, in the accompanying drawings, in which like references indicate similar elements, and in which:

[0019] Figure 1 A wireless network for data communications is shown.

[0020] Figure 2 Example details of a user equipment (UE) that can implement the methods and teachings in accordance with the present application are shown.

[0021] Figure 3 An example base station that can implement the methods and teachings in accordance with the present application is shown.

[0022] Figure 4 A block diagram of one embodiment of a direct conversion receiver (DCR) is shown.

[0023] Figure 5 Details of one example of a direct conversion transmitter are shown.

[0024] Figure 6 One embodiment of an apparatus for amplifying an RF signal is described.

[0025] Figure 7A and 7B An embodiment of an apparatus for amplifying an RF signal is described.

[0026] Figure 8 An example of a transmit enable signal (TX_EN) is described.

[0027] Figure 9 An example of a thermal compensation signal is described.

[0028] Figure 10 A current versus time of a DC bias current that tracks a transmit enable signal is described.

[0029] Figure 11 A circuit schematic of one embodiment of a circuit for amplifying an RF signal is described.

[0030] Figure 12 A flowchart of one embodiment of a process for amplifying an RF signal is described.

[0031] Figure 13 A flowchart of one embodiment of a process for biasing a heating transistor is described.

[0032] Figure 14 A flowchart of one embodiment of a process for providing an amplifier RF signal to a heating transistor is described.

[0033] Figure 15 The ambient temperature of an amplifier and biasing circuit if no thermal compensation is used is described.

[0034] Figure 16 The gain versus time of an RF amplifier if no thermal compensation is used is described.

[0035] Figure 17 The ambient temperature of an amplifier and biasing circuit if different levels of thermal compensation are used is described.

[0036] Figure 18 The gain versus time of an RF amplifier if different levels of thermal compensation are used is described. DETAILED DESCRIPTION

[0037] The present application will now be described with reference to the drawings, which generally relate to thermal compensation in RF power amplifiers. In one embodiment, an RF amplifier is operated in a mode where the RF amplifier is powered on and off in response to a transmit enable signal. One or more bias transistors are used to provide a bias signal to a bias input of the RF amplifier. The one or more bias transistors can also be powered on and off when the RF amplifier is powered on and off. The temperature of the RF amplifier can quickly rise when powered on and quickly drop when powered off. Without thermal compensation, the one or more bias transistors can warm up more slowly when the RF amplifier is powered on. This can cause the RF amplifier gain to be unstable and the RF signal to be distorted. In one embodiment, the addition of thermal compensation can allow the RF power amplifier to maintain a constant and stable gain. As a result, the RF signal distortion can be reduced or eliminated. At the same time, data loss in the received RF signal is also reduced or eliminated.

[0038] In one embodiment, thermal compensation is provided by one or more heating transistors that are used to heat the one or more bias transistors when the RF amplifier is powered on. In one embodiment, a control circuit is used to generate a DC bias current that tracks the transmit enable signal. The control circuit provides the DC bias current to the one or more heating transistors to cause the one or more heating transistors to heat the one or more bias transistors when the RF amplifier is powered on. In one embodiment, the control circuit is used to sample an amplified RF signal from the RF amplifier and provide the sampled amplified RF signal to the one or more heating transistors. As a result, the one or more heating transistors are used to heat the one or more bias transistors through thermal coupling based on the amplitude of the amplified RF signal when the RF amplifier is powered on. In this way, the heating transistors provide heat to allow the bias transistors to warm up in proportion to the RF power amplifier, thereby reducing thermal mismatch and stabilizing the gain response of the RF amplifier. Ultimately, the RF signal distortion can be reduced or eliminated. At the same time, data loss in the received RF signal is also reduced or eliminated.

[0039] It should be understood that the present embodiments of the application can be carried out by many different forms of what is broadly described herein without restricting the scope of the claims presenting the following embodiments. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concepts to those skilled in the art. Indeed, the scope of the application is intended to cover alternatives, modifications and equivalents of these embodiments, which are included in the spirit and scope of the application as defined by the following claims. Furthermore, in the following detailed description of the present embodiments of the application, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one of ordinary skill in the art that the present embodiments of the application can be practiced without these specific details.

[0040] Figure 1 A wireless network for communication is shown. The communication system 100 includes user equipment 110A, user equipment 110B, user equipment 110C, a radio access network (RAN) 120A, a RAN 120B, a core network 130, a public switched telephone network (PSTN) 140, the Internet 150, and other networks 160, among others. Other or alternative networks include private and public data packet networks, including corporate intranets. Although Figure 1 A certain number of these components or elements are shown in FIG. 1 to facilitate explanation of concepts. Any number of these components and elements can be utilized in the system 100.

[0041] In one embodiment, the wireless network can be a fifth generation (5G) network that includes at least one 5G base station. The 5G base station communicates with communication devices using orthogonal frequency-division multiplexing (OFDM) and / or non-OFDM and transmission time intervals (TTIs) of less than 1 millisecond (e.g., 100 microseconds or 200 microseconds). Generally, a base station can also refer to either an eNB and a 5G BS (gNB) interchangeably. In addition, the wireless network can also include a network server that is configured to process information received from the communication devices via the at least one eNB or gNB.

[0042] The communication system 100 enables multiple wireless users to send and receive data and other content. The communication system 100 can implement one or more channel access methods, including but not limited to code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), or single-carrier FDMA (SC-FDMA).

[0043] User equipment (UE) 110A, UE 110B, and UE 110C can each be referred to as a UE 110 or collectively as UEs 110 and can be configured to operate and / or communicate in the system 100. For example, the UEs 110 can be configured to transmit and / or receive wireless signals or wired signals. Each UE 110 can represent any suitable end-user device and can include (or be referred to as) a user equipment (UE), a wireless transmit / receive unit, a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop computer, a computer, a touchpad, a wireless sensor, a wearable device, a consumer electronics device, or the like. In some embodiments, the UEs 110 communicate with the RAN 120 using the IEEE 802.11 standard.

[0044] In the present embodiment, the RAN 120A and the RAN 120B include one or more base stations (BSs) 170A and BSs 170B, respectively. The RAN 120A and the RAN 120B can be referred to collectively as a RAN 120 or collectively as RANs 120. Similarly, the base stations (BSs) 170A and the BSs 170B can be referred to collectively as a base station (BS) 170 or collectively as BSs 170. Each BS 170 can be configured to wirelessly interface with one or more of the UEs 110 to enable access to the core network 130, the PSTN 140, the Internet 150, and / or the other networks 160. The base stations (BSs) 170 can include, for example, one or more base station transceiver stations (BTSs), NodeBs, evolved NodeBs (eNBs), next generation (fifth generation (5G)) NodeBs (gNBs), Home NodeBs (Home eNodeBs), site controllers, access points (APs), or wireless routers, or servers, routers, switches, or other processing entities with wired or wireless networks.

[0045] In one embodiment, the BS 170A is a part of the RAN 120A, which can include one or more other BSs 170, one or more elements, and / or one or more devices. Similarly, the BS 170B is a part of the RAN 120B, which can include one or more other BSs 170, one or more elements, and / or one or more devices. Each BS 170 operates to transmit and / or receive wireless signals within a particular geographic region or area, sometimes referred to as a "cell." In some embodiments, multiple-input multiple-output (MIMO) techniques can be used if each cell has multiple transceivers.

[0046] The BSs 170 communicate with one or more of the UEs 110 using wireless communication links over one or more air interfaces. These air interfaces can use any suitable wireless communication techniques.

[0047] The system 100 can use multi-channel access functionality, including a number of schemes for BSs 170 and UEs 110 to implement Long Term Evolution (LTE), LTE-Advanced (LTE-A), and / or LTE Multimedia Broadcast Multicast Service (MBMS) standards, for example. In other embodiments, the base stations 170, user devices 110A-110C are used to implement UMTS, HSPA, or HSPA+ standards and protocols. Of course, other multiple access schemes and wireless protocols can be used as well.

[0048] The RAN 120 is in communication with the core network 130 to provide the UEs 110 with access to voice, data, applications, Voice over Internet Protocol (VoIP), or other services. It will be appreciated that the RAN 120 and / or the core network 130 can be in direct or indirect communication with one or more other RANs (not shown). The core network 130 can also serve as a gateway for the UEs 110 to access other networks (e.g., the PSTN 140, the Internet 150, and other networks 160). In addition, some or all UEs 110 can communicate with each other directly through a peer-to-peer communication link.

[0049] The multiple RANs 120 can also include millimeter wave and / or microwave access points (APs). These APs can be part of the multiple BSs 170 or can be remote from the multiple BSs 170. The APs can include, but are not limited to, connection points (e.g., millimeter wave (mmW) connection points) or BSs 170 capable of mmW communications (e.g., mmW base stations). The millimeter wave APs can transmit and receive signals in the frequency range of 24 GHz to 100 GHz, among other frequency ranges, but are not required to operate in this entire range. The RAN 120 can also transmit and receive signals in a frequency range, for example, from 900 MHz to 6 GHz. The term “base station” is used herein to refer to base stations and / or wireless access points.

[0050] The RAN 120 can communicate with the UE 110 using time division multiplexing (TDM), where the same frequency band is used for uplink and downlink. When using time division multiplexing (TDM), there is no continuous wireless link between the RAN 120 and the UE 110. Instead, the system constantly switches between the UE 110 being in transmit mode (when the RAN 120 is in receive mode) and the UE 110 being in receive mode (when the RAN 120 is in transmit mode). In this mode, the transmitter in the UE 110 can repeatedly turn on and off.

[0051] While Figure 1 Various changes can be made to the communication system Figure 1 illustrated. For example, the communication system 100 can include any number of user devices, base stations, networks, or other components in any suitable configuration. It should also be understood that the term “user device” can refer to any type of wireless device that communicates with a wireless network node in a cellular or mobile communication system. Non-limiting examples of user devices include target devices, device-to-device (D2D) user devices, machine-type user devices or user devices capable of machine-to-machine (M2M) communication, laptops, PDAs, iPads, tablet PCs, mobile terminals, smart phones, laptop embedded equipment (LEE), laptop mounted equipment (LME), and USB dongles.

[0052] Figure 2Example details of a UE 110 that can implement the methods and teachings in accordance with this disclosure are shown. The UE 110 can be a mobile telephone, or other device such as a desktop computer, notebook computer, tablet computer, handheld computing device, automobile computing device, and / or other computing device. As shown, the example UE 110 includes at least one transmitter 202, at least one receiver 204, a memory 206, at least one processor 208, and at least one input / output device 212. The processor 208 can implement various processing operations for the UE 110. For example, the processor 208 can execute a signal coding, data processing, power control, input / output processing, or any other functionality enabling the UE 110 to operate in the system 100 Figure 1 ) in accordance with this disclosure. The processor 208 can include any suitable processing or computing device. For example, the processor 208 can include a microprocessor, microcontroller, digital signal processor, field programmable gate array, or application specific integrated circuit.

[0053] The transmitter 202 is configured to modulate data or other content for transmission by at least one antenna 210. The transmitter 202 can further be configured to amplify, filter, and frequency convert RF signals before providing the RF signals to the antenna 210 for transmission. The transmitter 202 can include any suitable structure for generating signals for wireless transmission.

[0054] The receiver 204 can be configured to demodulate data or other content received by at least one antenna 210. The receiver 204 can further be configured to amplify, filter, and frequency convert RF signals received by the antenna 210. In some embodiments, the receiver 204 is an RF signal receiver. The receiver 204 can include any suitable structure for processing signals received wirelessly. The antenna 210 includes any suitable structure for transmitting and / or receiving wireless signals. The same antenna 210 can be used for transmitting and receiving RF signals, or alternatively, different antennas 210 can be used for transmitting and receiving signals.

[0055] In some embodiments, the UE 110 is configured to operate the transmitter 202 in a pulsed mode. In one embodiment, the processor 208 issues a transmit enable signal (TX EN) to the transmitter 202 to cause the transmitter 202 to operate in the pulsed mode. In one embodiment of the pulsed mode, the transmitter 202 switches between an active (powered on and transmitting state) and an inactive (powered off) state. Turning off power to the transmitter 202 while not transmitting can save a considerable amount of power. However, the transmitter 202 can therefore experience considerable temperature variations. These temperature variations can increase distortion of the transmitted RF signal. Embodiments of the UE 110 have thermal compensation to reduce or eliminate such signal distortion.

[0056] It is to be understood that one or more transmitters 202 can be used in the UE 110, one or more receivers 204 can be used in the UE 110, and one or more antennas 210 can be used in the UE 110. While shown as separate blocks or components, at least one transmitter 202 and at least one receiver 204 can be combined into a transceiver. Thus, a single block shows a transceiver, rather than a separate block for the transmitter 202 and a separate block for the receiver 204 in Figure 2

[0057] The UE 110 also includes one or more input / output devices 212. The input / output devices 212 facilitate interaction with a user. Each input / output device 212 comprises any suitable structure for providing information to or receiving information from a user, including a speaker, microphone, keypad, keyboard, display, or touch screen.

[0058] ​Further, the UE 110 includes at least one memory 206. The memory 206 stores instructions and data used, generated, or collected by the UE 110. For example, the memory 206 could store software or firmware instructions executed by the one or more processors 208 and data used to reduce or eliminate interference in an input signal. In one embodiment, the memory 206 stores software or firmware instructions executed by the processor 208 and data used to provide thermal compensation for an RF power amplifier, as described herein. In one embodiment, the memory 206 stores one or more parameters that specify an amplitude of a thermal compensation signal. In one embodiment, the memory 206 stores a table that specifies different amplitudes for a thermal compensation signal based on a target power of an RF signal output from the RF power amplifier. The target power output can be determined by factors such as a signal strength and / or quality of an RF signal received from a device that the UE 110 is transmitting to. The thermal compensation signal can be used to control a size of a DC bias current provided to a heating transistor, as described herein. Thus, the size of the DC bias current can depend on a target power of an RF signal amplified by the RF amplifier. Each memory 206 includes one or more of any suitable volatile and / or non-volatile storage and retrieval devices. Any suitable type of memory can be used, for example, random access memory (RAM), read only memory (ROM), hard disk, optical disk, subscriber identity module (SIM) card, memory stick, secure digital (SD) memory card, and the like.

[0059] Figure 3 An exemplary BS 170 that can implement the methods and teachings provided in accordance with this disclosure is shown. As shown, the BS 170 includes at least one processor 308, at least one transmitter 302, at least one receiver 304, one or more antennas 310, and at least one memory 306. The processor(s) 308 implement various processing operations of the BS 170, such as signal coding, data processing, power control, input / output processing, or any other functionality. Each processor 308 includes any suitable processing or computing device configured to perform one or more operations. For example, each processor 308 can include a microprocessor, a microcontroller, a digital signal processor, a field programmable gate array, or application specific integrated circuit.

[0060] Each transmitter 302 includes any suitable structure for generating signals for wireless transmission to one or more UEs 110 or other devices. Each receiver 304 includes any suitable structure for processing signals wirelessly received from one or more UEs 110 or other devices. Although shown as separate blocks or components, at least one transmitter 302 and at least one receiver 304 may be combined into a transceiver. Each antenna 310 includes any suitable structure for transmitting and / or receiving wireless signals. Although a common antenna 310 is shown coupled to the transmitter 302 and the receiver 304, one or more antennas 310 may be coupled to one or more of the transmitters 302, and one or more individual antennas 310 may be coupled to one or more of the receivers 304. Each memory 306 includes one or more of any suitable volatile and / or non-volatile storage and retrieval devices.

[0061] In some embodiments, base station 170 is configured to operate transmitter 302 in pulse mode. In one embodiment, processor 308 sends a transmit enable signal (TX_EN) to transmitter 302 to enable transmitter 302 to operate in pulse mode. In one embodiment of pulse mode, transmitter 302 switches between an active (transmitting state) and an inactive (power-off) state. Powering off transmitter 302 while it is not transmitting can save considerable power. However, transmitter 302 may therefore experience significant temperature variations. These temperature variations can increase distortion of the transmitted RF signal. Embodiments of base station 170 have thermal compensation to reduce or eliminate this signal distortion. In one embodiment, memory 306 stores software or firmware instructions executed by processor 308 and data for providing thermal compensation to the RF power amplifier, as described herein. In one embodiment, memory 306 stores one or more parameters specifying the amplitude of a thermal compensation signal. The thermal compensation signal can be used to control the magnitude of the DC bias current supplied to the heating transistor, as described herein.

[0062] Figure 4 A block diagram of one embodiment of a direct conversion receiver (DCR) 404 is shown, which may be included in UE 110 (e.g., Figure 2 Receiver 204 in (as shown) or included in BS 170 (such as Figure 3The receiver 404 can be, but is not limited to, a DCR 404 as shown in FIG. 4, but is not limited thereto. The DCR 404 can also be referred to as a homodyne receiver or a zero intermediate frequency (IF) receiver. The DCR 404 uses synchronous detection to demodulate an input radio frequency (RF) signal. The DCR 404 can also be referred to as an RF signal receiver.

[0063] Referring to Figure 4 The receiver 404 is shown as including an input 406 at which a radio frequency (RF) signal is received, and thus the input 406 can also be referred to as an RF input 406. The RF input 406 can be coupled to an antenna or a coupler, but is not limited thereto. The RF signal received by the RF input 406 is provided to a low noise amplifier (LNA) 408, which can have an adjustable gain. The LNA 408 amplifies the relatively low power RF signal that it receives without significantly degrading the signal-to-noise ratio (SNR) of the signal.

[0064] The amplified RF signal output by the LNA 408 is provided to a mixer 410. The mixer 410 can input two signals at frequencies f1, f2 and mix them to produce two new signals, one at sum f1+f2 and the other at difference f1-f2. Typically, only one of these new signals is used. The mixer 410 receives the amplifier RF signal from the LNA 408 and an oscillator signal from a local oscillator (LO) as the two input signals. Thus, the mixer 410 can use the amplifier RF signal and the oscillator signal to produce a new signal. The mixer 410 can use the frequency of the oscillator signal to change (e.g., reduce) the frequency of the amplifier RF signal to produce the new signal. The amplifier RF signal can occupy a range of frequencies, and in this case, the mixer 410 can use the frequency of the oscillator signal to change the range of frequencies of the amplifier RF signal. In one embodiment, the mixer 410 is a down-mixer (DN MIX) that down-converts the amplified RF signal from a relatively high frequency to a baseband frequency. Figure 4 The mixer 410 in

[0065] Still referring to Figure 4The frequency-down-converted signal output from mixer 410 is shown to be provided to trans-impedance amplifier (TIA) 412. TIA 412 acts as a current buffer to isolate the multi-feedback (MFB) filter 414 downstream of TIA 412 from mixer 410 upstream of TIA 412. MFB filter 414 low-pass filters the frequency-down-converted signal to filter out unwanted high-frequency signal components, such as HF noise. The filtered signal output from MFB filter 414 is provided to variable gain amplifier (VGA) 416, which amplifies the filtered signal, and then provides the filtered signal to analog-to-digital (A / D) converter 418, which converts the signal from analog to digital. The digital signal output from A / D 418 is then provided to digital filter 420, which performs additional filtering to remove out-of-band signal components and attenuate the quantization energy from A / D 418. The filtered digital signal output by digital filter 420 is then provided to other digital circuits downstream of digital filter 420. Such digital circuits may include, but are not limited to, a digital signal processor (DSP). The same DSP or different DSPs may be used to implement digital filter 420.

[0066] The local oscillator 431 may include a voltage-controlled oscillator (VCO), a digitally controlled oscillator (DCO), or other circuitry providing the LO signal. In one embodiment, the local oscillator 431 includes a phase-locked loop (PLL) containing the VCO. The LO signal is provided to the mixer 410 for the down-conversion process. Although shown external to the receiver 404, according to an embodiment, the local oscillator 431 may be integrated with... Figure 4 On one or more other components on the same integrated circuit.

[0067] Receiver 204 in UE 110 (e.g.) Figure 2 (As shown) and receiver 304 included in BS 170, it is not limited to a direct conversion receiver. For example, receivers 204 and 304 may be superheterodyne receivers having a mixer that converts the input radio signal to an intermediate frequency (IF). After processing the IF signal, the superheterodyne receiver may have a mixer that downconverts the processed IF signal to a baseband signal.

[0068] Figure 5Details of one example of a direct conversion transmitter 502, which can be the transmitter 202 included in the UE 110 (as shown in FIG. 2) or the transmitter 302 included in the BS 170 (as shown in FIG. 3), but is not limited thereto, are shown. The direct conversion transmitter 502 can also be referred to as a direct modulation transmitter. Referring to FIG. 5, Figure 2 Details of one example of a direct conversion transmitter 502, which can be the transmitter 202 included in the UE 110 (as shown in FIG. 2) or the transmitter 302 included in the BS 170 (as shown in FIG. 3), but is not limited thereto, are shown. The direct conversion transmitter 502 can also be referred to as a direct modulation transmitter. Referring to FIG. 5, Figure 3 Details of one example of a direct conversion transmitter 502, which can be the transmitter 202 included in the UE 110 (as shown in FIG. 2) or the transmitter 302 included in the BS 170 (as shown in FIG. 3), but is not limited thereto, are shown. The direct conversion transmitter 502 can also be referred to as a direct modulation transmitter. Referring to FIG. 5, Figure 5 The transmitter 502 is shown as including an output 518 at which a radio frequency (RF) signal is provided, and thus the output 518 can also be referred to as an RF output 518. The RF output 518 can be coupled to an antenna or a coupler, but is not limited thereto. The RF signal provided by the RF output 518 is provided from a power amplifier PA 514 through a bandpass or notch filter 516. The filter 516 can be a duplex / SAW filter and is used to remove unwanted frequency components above and below a desired RF frequency range from the amplified RF output signal generated from the PA 514. The power amp (PA) 514 receives its input from a power pre-amplifier (PPA) 512, which in turn receives an upconverted signal to be transmitted from a mixer 510. The PPA 512 can be referred to as a pre-amplification stage. The PA 514 can be referred to as a power amplification stage.

[0069] Still referring to Figure 5 The signal to be transmitted is received from the processor 208 of the UE 110 in Figure 2 or the processor 308 of the BS 170 in Figure 3 At the digital-to-analog converter 506, the digitized signal is filtered by a low pass filter 508 to remove any high frequency noise before being upconverted at the mixer 510.

[0070] The mixer 510 can input two frequencies, fl, f2, and mix them to produce two new signals, one at the sum fl+f2 and the other at the difference fl-f2. Typically, only one of these new signals is used. An analog version of the signal (an "analog signal") is provided as one input signal to the mixer 510. The mixer 510 also receives an oscillator signal from a local oscillator (LO) as another input signal. Thus, the mixer 510 can use the analog signal and the oscillator signal to produce a new signal. The mixer 510 can use the frequency of the oscillator signal to change (e.g., increase) the frequency of the analog signal to produce the new signal. In one embodiment, the analog signal is a baseband signal. In one embodiment, the oscillator signal is used as a carrier wave. In one embodiment, the mixer 510 modulates the oscillator signal (e.g., carrier wave) with the baseband signal to produce a radio frequency signal.

[0071] Analog signals can occupy a frequency range, in which case the mixer 510 can use the frequency of the oscillator signal to change the frequency range of the analog signal. Figure 5 The mixer 510 is an up-mixer (UP MIX) used to up-convert the frequency of an analog signal. In one embodiment, the mixer 510 is an up-mixer (UP MIX) that up-converts an analog signal to an RF signal.

[0072] Figure 5 The local oscillator (LO) signal can be provided by local oscillator 531. Local oscillator 531 may include a VCO, DCO, or other circuitry providing the LO signal. In one embodiment, local oscillator 531 includes a PLL containing a VCO. The LO signal is provided to mixer 510 for the up-conversion process. Although shown external to transmitter 502, according to an embodiment, local oscillator 531 can be integrated with... Figure 5 On one or more other components on the same integrated circuit.

[0073] Transmitter 202 in UE 110 (e.g.) Figure 2 As shown, transmitter 302 included in BS 170 is not limited to a direct conversion transmitter. For example, transmitters 202 and 302 may be superheterodyne transmitters having a mixer that converts an analog signal into an intermediate frequency (IF) signal. In one embodiment, the mixer modulates an oscillator signal with an analog signal to generate an IF signal. After processing the IF signal, the superheterodyne transmitter may have a mixer that upconverts the processed IF signal into a radio frequency (RF) signal.

[0074] In some embodiments, the transmitter 502 operates in a pulsed mode. In one embodiment of the pulsed mode, the transmitter 502 is powered on and off in response to a transmit enable signal (e.g., TX EN). The transmit enable signal can be provided by a processor (e.g., 208, 308). In some embodiments, the pulsed mode is used to transmit Wi-Fi signals. When the transmitter is not used to transmit signals, powering off the transmitter 502 can save a considerable amount of power. However, due to this on / off cycling, at least some components in the transmitter 502 can experience significant temperature variations. When the transmitter 502 is enabled due to high power consumption of these components, the power pre-amplifier PPA 512 and / or the power amplifier PA 514 can heat up quickly. For example, the ambient temperature of the PPA 512 and / or the PA 514 can increase by about 150 degrees Celsius within a few microseconds. However, other components in the transmitter 502 heat up much more slowly. For example, if no thermal compensation is used, the components that provide the bias current to the PPA 512 and / or the PA 514 can heat up much more slowly than the PPA 512 and / or the PA 514. These differences in temperature profiles can cause the gain of the PPA 512 and / or the PA 514 to be unstable. Thus, the differences in temperature profiles can cause the transmitted RF signals to be distorted. This signal distortion can be quantified in terms of dynamic error vector magnitude (EVM). Dynamic EVM for RF transmitters includes, but is not limited to, Wi-Fi, which is one of the biggest challenges faced by RF PA front-end modules. Without proper thermal compensation, the transmitted signals will have significant signal distortion, resulting in data loss.

[0075] The thermal compensation bias 540 is used to provide a thermal compensation bias signal to the power pre-amplifier PPA 512 and also to the power amplifier PA 514. The bias signal can be a bias voltage or a bias current. In some embodiments, the thermal compensation bias 540 has a bias circuit to provide the bias signal and a heating circuit to provide thermal compensation. The thermal compensation can be used to compensate for the temperature difference between the PPA 512 and / or the PA 514 and the bias circuit. Without thermal compensation for the bias signal, there can be signal distortion in the transmitted RF signals.

[0076] The thermal compensation bias 540 can be located far enough away from the PPA 512 and the PA 514 to avoid RF interference. However, due to the distance, the heat from the PPA 512 and the PA 514 does not have a significant impact on the temperature of the bias circuit in the thermal compensation bias 540. The thermal compensation bias 540 provides temperature compensation for the bias signal provided to the PPA 512 and the PA 514. Thus, the temperature difference between the bias circuit and the PPA 512 and / or the PA 514 is compensated for. At the same time, distortion of the transmitted RF signals is also reduced or eliminated.

[0077] Figure 6 One embodiment of an apparatus for amplifying an RF signal is described. The apparatus can be used in an RF transmitter, such as any of the transmitters 202, 302, or 502, but is not limited thereto. The apparatus includes an RF amplifier 602 and a thermal compensation bias 540. In one embodiment, the RF amplifier 602 includes a PPA 512 and a PA 514. However, the RF amplifier 602 need not include both a preamplifier and a power amplifier. For example, the RF amplifier 602 can include one of the PPA 512 or the PA 514, but not both.

[0078] The RF amplifier 602 has an RF input for receiving an RF signal. The RF amplifier 602 is used to amplify the received RF signal and provide the amplified RF signal at an RF output. The RF amplifier 602 has at least one bias input for receiving a bias signal. The RF amplifier 602 can have multiple bias inputs. The bias signal can be a bias current or a bias voltage.

[0079] In some embodiments, the RF amplifier 602 operates in a pulsed mode. In one embodiment of the pulsed mode, the RF amplifier 602 is powered on / off in response to a transmit enable signal (TX EN). The transmit enable signal can be provided by the processor 208 or the processor 308. Powering off the RF amplifier 602 when it is not used to transmit a signal can save a considerable amount of power. However, the ambient temperature of the RF amplifier 602 can increase rapidly when powered on. If not properly compensated, the increase in ambient temperature can cause the gain of the RF amplifier 602 to vary and the RF signal to distort.

[0080] The thermal compensation bias 540 includes a bias circuit 610 and a heating circuit 620. The bias circuit 610 is used to generate a bias signal and provide the bias signal to a bias input of the RF amplifier 602. The bias circuit 610 can generate more than one bias signal, each of which is provided to a different bias input of the RF amplifier 602. The bias signal is temperature dependent, by which it is meant that the magnitude of the bias signal depends on the ambient temperature of the bias circuit 610. In one embodiment, the bias circuit 610 includes one or more sets of bias transistors. Here, a “bias transistor” is defined as a transistor that provides a bias signal (e.g., a bias current, a bias voltage). Each set of bias transistors has one or more transistors and is used to generate a bias signal. In one embodiment, the bias circuit 610 transistors include bipolar junction transistors (BJTs).

[0081] The biasing circuit 610 can be enabled by the same transmit enable signal used to power on / off the RF amplifier 602. With proper thermal compensation, the biasing circuit 610 can warm up more slowly than the RF amplifier 602 when the RF amplifier 602 and the biasing circuit 610 are enabled. The heating circuit 620 in the thermally compensated bias 540 is thermally coupled to the biasing circuit 610 and heats the biasing circuit 610 to compensate for the temperature difference between the RF amplifier 602 and the biasing circuit 610. In one embodiment, the heating circuit 620 compensates for the temperature difference between the RF amplifier 602 and the biasing circuit 610 when the RF amplifier 602 and the biasing circuit 610 are first enabled during the pulsed mode of operation. For example, the heating circuit 620 can compensate the biasing circuit 610 to warm up more slowly than the RF amplifier 602. The amount of heating can be predetermined based on test or empirical data.

[0082] Accordingly, the thermal compensation adjusts the biasing signal provided to the RF amplifier 602. For example, the thermal compensation adjusts the magnitude of the DC bias current provided by the biasing circuit 610 to the bias input of the RF amplifier 602. Accordingly, the thermal compensation helps stabilize the gain of the RF amplifier 602. For example, the thermal compensation enables the RF amplifier 602 to achieve a more constant gain when the RF is turned on during the pulsed mode of operation. Stabilizing the gain of the RF amplifier 602 can reduce or eliminate distortion in the transmitted RF signal. Ultimately, the dynamic EVM is improved.

[0083] Figure 7A One embodiment of an apparatus for amplifying an RF signal is described. Figure 7A More details of one embodiment of the apparatus are described. Figure 6 The apparatus can be used in an RF transmitter, such as any of the RF transmitters 202, 302, or 502, but is not limited thereto. The RF amplifier 602 includes the PPA 512 and the PA 514. The biasing circuit 610 is split into biasing circuits 610a and 610b. The biasing circuit 610a is used to generate a biasing signal that is provided to the bias input of the PPA 512. The biasing circuit 610b is used to generate a biasing signal that is provided to the bias input of the PA 514.

[0084] The heating circuit 620 is located in close physical proximity to the biasing circuit 610 such that heat generated by the heating circuit 620 will heat the biasing circuit 610. In one embodiment, the heating circuit 620 will heat the biasing circuit 610 to compensate for a temperature difference between the biasing circuit 610 and the RF amplifier 602. In one embodiment, the heating circuit 620 will heat the biasing circuit 610 to compensate for different heating rates between the biasing circuit 610 and the RF amplifier 602. In one embodiment, the heating circuit 620 includes one or more heating transistors. Here, a heating transistor is defined as a transistor that generates heat and provides at least a portion of that heat to a biasing transistor. In one embodiment, the heating circuit 620 transistors include one or more bipolar junction transistors (BJTs).

[0085] The heating circuit 620 is divided into three sections, 620a, 620b, 620c. In one embodiment, each section 620a, 620b, 620c has one or more heating transistors. Here, the three sections can be referred to as heating circuit 620a, heating circuit 620b, and heating circuit 620c. The heating circuit 620a is located in close physical proximity to the biasing circuit 610a such that heat generated by the heating circuit 620a will heat the biasing circuit 610a. The heating circuit 620b is located between the biasing circuits 610a, 610b and in close physical proximity to both the biasing circuit 610a and the biasing circuit 610b such that heat generated by the heating circuit 620b will heat both the biasing circuit 610a and the biasing circuit 610b. The heating circuit 620c is located in close physical proximity to the biasing circuit 610b such that heat generated by the heating circuit 620c will heat the biasing circuit 610b. In another embodiment, the heating circuit 620 includes section 620b but not sections 620a or 620c. In another embodiment, the heating circuit 620 includes sections 620a and 620c but not section 620b.

[0086] The thermal compensation bias 540 has a heating circuit bias 630 for providing a bias signal to the heating circuit 620. In one embodiment, the heating circuit bias 630 provides a DC bias current to the heating circuit 620. The heating circuit bias 630 can be referred to herein as a control circuit, or as a portion of a control circuit. In one embodiment, the DC bias current tracks the transmit enable signal such that the heating circuit 620 begins heating when the RF amplifier 602 begins heating. Thus, the heating circuit 620 will heat the biasing circuit 610 such that the bias signal is thermally compensated.

[0087] The heat compensation control signal is used to control the heat generated by the heating transistor when the RF amplifier 602 is powered on. In one embodiment, the heat compensation control signal controls the magnitude of the DC bias current provided by the heating circuit bias 630 to the heating transistor. In one embodiment, the magnitude of the DC bias current is at least one factor that controls the heat generated by the heating transistor. The heat compensation control signal can be a digital signal or an analog signal. In some embodiments, the magnitude of the heat compensation control signal depends on the target power of the RF signal output from the RF amplifier 602. Thus, in some embodiments, the magnitude of the DC bias current provided to the heating circuit 620 depends on the target power of the RF signal output from the RF amplifier 602 and is a function of the target power. The target power output can be determined by the processor 208 / 308 and provided to the RF amplifier 602.

[0088] The heat compensation bias 540 samples the amplified RF signal (labeled as RF signal sample) from the output of the PPA 512. The sample can be a small fraction of the amplitude of the amplified RF signal. That is, the amplitude of the sampled RF signal is proportional to the amplitude of the amplified RF signal, but the amplitude can be smaller. The sampled RF signal is provided as an input to the heating circuit 620. The heating circuit 620 generates heat in response to the amplitude of the sampled RF signal. The amplitude of the sampled RF signal depends on the ambient temperature of the RF amplifier 602. Thus, the heating circuit 620 will heat the biasing circuit 610 such that the bias signal is thermally compensated.

[0089] Figure 7B One embodiment of an apparatus for amplifying an RF signal is described. Figure 7B More details of one embodiment of the apparatus are described. Figure 6 The apparatus can be used in an RF transmitter, such as any of the RF transmitters 202, 302, or 502, but is not limited thereto. Figure 7B The apparatus shown is similar to Figure 7A The apparatus in the apparatus. However, the heat compensation bias 540 samples the amplified RF signal (labeled as RF signal sample) from the output of the PA 514. The amplified RF signal is provided to the heating circuit. The heating circuit 620 heats the biasing circuits 610a, 610b based on the amplitude of the amplified RF signal from the PA 514.

[0090] Figure 7A And 7B The RF amplifier 602 in the and the RF amplifier 602 each receive a transmit enable signal, which is provided by a processor (e.g., 208, 308). Figure 8 An example of a transmit enable signal (TX EN) 800 is described. Figure 8The voltage versus time relationship of the transmit enable signal 800 is described. The transmit enable signal 800 has a pulsed shape with rising edges at times tl, t3, and t5. The transmit enable signal 800 has falling edges at times t2, t4, and t6. The transmit enable signal can be provided by a processor (e.g., 208, 308) to the RF amplifier 602. The transmit enable signal is used to operate the RF amplifier in a pulsed mode. In one embodiment, the RF amplifier 602 is powered on when the transmit enable signal 800 is at a high level and powered off when the transmit enable signal 800 is at a low level (as shown by the voltage axis in Figure 8 One example of a high level is 1.5 V. One example of a low level is 0 V. In one embodiment, the transmit enable signal 800 has a duty cycle, which is defined as the percentage of each cycle that the transmit enable signal 800 is at a high level. Thus, the duty cycle corresponds to the percentage of time that the RF amplifier 602 in the transmitter is powered on each cycle. The duty cycle need not be the same each cycle.

[0091] Figure 7A and 7B The thermal compensation bias 540 in each of FIGS. 6 and 7 receives a thermal compensation signal. The thermal compensation signal is provided to the heating circuit bias 630. Figure 9 An example of the thermal compensation signal 900 is described. The thermal compensation signal 900 tracks the transmit enable signal 800, by which it is meant that it has the same duty cycle, i.e., the pulses of the two signals rise and fall at the same times. For example, the thermal compensation signal 900 has a pulsed shape with rising edges at times tl, t3, and t5. The thermal compensation signal 900 has falling edges at times t2, t4, and t6. Note that these times correspond to the times described in Figure 8

[0092] The thermal compensation signal 900 is provided to the heating circuit bias 630, which generates a bias signal based thereon. In one embodiment, the bias signal is a DC current. Figure 10 A current versus time relationship of the DC bias current 1000 generated by the heating circuit bias 630 is described. The DC bias current 1000 tracks the transmit enable signal 800, by which it is meant that it has the same duty cycle, i.e., the pulses of the two signals rise and fall at the same times. For example, the DC bias current 1000 has a pulsed shape with rising edges at times tl, t3, and t5. The DC bias current 1000 has falling edges at times t2, t4, and t6. Note that these times correspond to the times described in Figure 8 ​At the time described in the middle, the transmit enable signal 800 is asserted. The DC bias current 1000 has a maximum value of "DC bias," which is the size of the DC bias current provided to the heating transistor. In one embodiment, the heating bias circuit 630 generates the DC bias current 1000 based on the thermal compensation signal 900. In some embodiments, the thermal compensation control signal 900 depends on the target power of the RF signal output by the RF amplifier 602. Thus, in some embodiments, the size of the DC bias current 1000 depends on the target power of the RF signal output by the RF amplifier 602. For example, the target power of the RF signal can have several ranges, such that different DC bias currents 1000 can be used for each target power range. In one embodiment, the size of the DC bias current 1000 is larger for higher target RF power.

[0093] Figure 11 is a circuit schematic of one embodiment of a circuit for amplifying an RF signal. The circuit 1100 describes more details of one embodiment of the PPA 512, the PA 514, and the thermal compensation bias 540. The circuit 1100 is consistent with the example of Figure 7A , where the RF signal is sampled from the output of the PPA 512.

[0094] The PPA 512 includes transistors Q5 and Q8, resistor R5, and capacitor C4. Transistor Q5 can function as a current buffer. The base of Q5 functions as a bias input for the PPA 512. Current from transistor Q5 enters the base of transistor Q6. Capacitor C4 is connected to the RF input for input impedance matching. Transistor Q6 amplifies the RF signal. The collector of Q6 is the RF output of the PPA 512. The RF signal at the collector of Q6 can be referred to herein as the "pre-amp RF signal."

[0095] The PA 514 includes transistors Q1, Q2, Q3, and Q4. The PA 514 includes resistors R1, R2, R3, and R4. The PA 514 also includes capacitors C1, C2, and C3. Capacitors C1, C2, and C3 are the RF signal inputs to the PA 514. Capacitors C1, C2, and C3 can perform at least some of the input impedance matching for the PA 514. Note that there can be additional impedance matching circuitry between the RF output of the PPA 512 and the RF input of the PA 514. Transistor Q1 can function as a current buffer. The base of Q1 functions as a bias input for the PA 514. Transistors Q2, Q3, and Q4 amplify the RF signal and provide the amplified RF signal to the RF output (RF OUT). There can be more of these "amplification transistors" in the PA 514. The RF signal at the collectors of Q2, Q3, and Q4 can be referred to herein as the "power-amp RF signal."

[0096] The thermal compensation bias 540 has transistors Q7, Q8, Q9, Q10, Q11, Q12, and Q13. The thermal compensation bias 540 also has capacitors C5, C6, C7, and resistor R6.

[0097] Biasing transistors Q8 and Q9 produce a bias signal (e.g., bias current) that is provided to the base of transistor Q5 in PPA 512. Thus, biasing transistors Q8 and Q9 provide a bias signal to the bias input of PPA 512. DC bias current source 1102 provides a DC bias current to Q9. Transistors Q8 and Q9 and capacitor C6 are one embodiment of bias circuit 610a.

[0098] Biasing transistors Q11 and Q12 produce a bias signal (e.g., bias current) that is provided to the base of transistor Q1 in PA 514. Thus, biasing transistors Q11 and Q12 provide a bias signal to the bias input of PA 514. DC bias current source 1104 provides a DC bias current to Q12. Transistors Q11 and Q12 and capacitor C7 are one embodiment of bias circuit 610b.

[0099] In one embodiment, the positions of transistors Q7 through Q13 in the schematic diagram represent their relative physical positions. Heating transistor Q7 is located in physical proximity to the group of biasing transistors Q8 and Q9, such that the heat generated by heating transistor Q7 will heat transistors Q8 and Q9. In other words, heating transistor Q7 is adjacent to the group of biasing transistors Q8 and Q9, such that the heat generated by heating transistor Q7 will heat biasing transistors Q8 and Q9. Heating transistor Q7 is one embodiment of heating circuit 620a.

[0100] Heating transistor Q10 is located between the group of biasing transistors Q8 and Q9 and the group of biasing transistors Q11 and Q12. Heating transistor Q10 is also in physical proximity to both the group of biasing transistors Q8 and Q9 and the group of biasing transistors Q11 and Q12. Thus, the heat generated by heating transistor Q10 will heat both the group of biasing transistors Q8 and Q9 and the group of biasing transistors Q11 and Q12. In other words, heating transistor Q10 is adjacent to both the group of biasing transistors Q8 and Q9 and the group of biasing transistors Q11 and Q12, such that the heat generated by heating transistor Q10 will heat both biasing transistors Q8 and Q9 and biasing transistors Q11 and Q12. Transistor Q10 is one embodiment of heating circuit 620b.

[0101] The heating transistor Q13 is located in close physical proximity to the set of bias transistors Q11 and Q12 such that heat generated by the heating transistor Q13 will heat the set of bias transistors Q11 and Q12. In other words, the heating transistor Q13 is adjacent to the set of bias transistors Q11 and Q12 such that heat generated by the heating transistor Q13 will heat the set of bias transistors Q11 and Q12. The transistor Q13 is one embodiment of the heating circuit 620c.

[0102] In one embodiment, the heating transistors Q7 and Q10 work in conjunction to heat the bias transistors Q8 and Q9. The heating transistor Q7 is located on one side of the pair of Q8 and Q9, and the heating transistor Q10 is located on the other side of the pair of Q8 and Q9. In one embodiment, the heating transistors Q13 and Q10 work in conjunction to heat the bias transistors Q11 and Q12. The heating transistor Q13 is located on one side of the pair of Q11 and Q12, and the heating transistor Q10 is located on the other side of the pair of Q11 and Q12.

[0103] The thermal compensation bias 540 includes a heating circuit bias 630 that is used to provide a bias signal (e.g., a bias current) to the base terminal of the heating transistors Q7, Q10, and Q13. In one embodiment, the heating circuit bias 630 provides a DC bias current to the base terminal of Q7, Q10, and Q13. The DC bias current tracks the transmit enable signal. Thus, when the PPA 512 and the PA 514 are enabled (turned on), Q7, Q10, and Q13 receive the bias current from the heating circuit bias 630. However, when the PPA 512 and the PA 514 are not enabled (turned off), Q7, Q10, and Q13 do not receive the DC bias current from the heating circuit bias 630. The heating circuit bias 630 inputs a thermal compensation control signal that indicates when the heating circuit bias 630 should and should not provide the DC bias current to Q7, Q10, and Q13.

[0104] The thermal compensation bias 540 samples the RF signal at the output of the PPA 512. In one embodiment, the thermal compensation bias 540 samples a small portion of the RF signal power. Note that sampling of the RF signal does not have a significant impact on the overall power consumption of the circuit 1100. For example, by sampling a small portion of the RF signal power, the impact on overall power consumption can be minimized. To sample the RF signal, the resistor R6 is connected to the collector of the transistor Q6. The capacitor C5 is connected between the resistor R6 and the base terminals of the transistors Q7, Q10, and Q13. Thus, the sampled RF signal, which can be a small portion of the RF signal amplitude, is provided to the base terminals of the transistors Q7, Q10, and Q13. Thus, heating the transistors Q7, Q10, and Q13 will heat in response to the amplitude of the sampled RF signal. The amount of heat generated can be adjusted by the DC bias current received from the heating circuit bias 630. In one embodiment, the thermal compensation control signal 900 specifies the magnitude of the DC bias current 1000 provided to the heating circuit bias 630.

[0105] As described herein, when the PPA 512 and / or PA 514 are powered on (e.g., enabled), the ambient temperature of the PPA 512 and / or PA 514 can quickly rise. The ambient temperature of the PPA 512 and / or PA 514 affects the base emitter on voltage. In some embodiments, when the ambient temperature is low, the base emitter on voltage of the transistors in the PPA 512 and / or PA 514 is relatively high and decreases as the ambient temperature increases. Even without thermal compensation, the transistors in the bias circuit (e.g., Q8, Q9, Q11, Q12) can experience a similar impact in the base emitter on voltage, but at a different rate due to the slower rise in ambient temperature of the bias circuit. Without thermal compensation, this difference can cause the gain of the PPA 512 and / or PA 514 to be unstable. For example, the gain starts relatively low and then quickly rises. The gain of the PPA 512 and / or PA 514 can then asymptotically stabilize (decrease). However, heating the transistors Q7, Q10, Q13 provides thermal compensation that compensates for the temperature difference between the transistors in the bias circuit (e.g., Q8, Q9, Q11, Q12) and the transistors in the PPA 512 and / or PA 514. Thus, heating the transistors Q7, Q10, Q13 helps stabilize the gain in the PPA 512 and / or PA 514. Ultimately, RF signal distortion can be reduced or eliminated.

[0106] There are many variations of the circuit 1100. In one embodiment, additional heating transistors can be added. For example, one or more additional heating transistors can be added next to Q10, such that there are two or more heating transistors between the Q8 and Q9 pair and the Q11 and Q12 pair. Similarly, one or more additional heating transistors can be added next to Q7 or Q13. It is not required that all of Q7, Q10, and Q13 be used. Any subset of Q7, Q10, and Q13 can be used. In one embodiment, there is one or more heating transistors between the Q8 and Q9 pair and the Q11 and Q12 pair; however, transistors Q7 and Q13 are optional.

[0107] It is not required that the bias signals provided to both the PPA 512 and the PA 514 be thermally compensated. In one embodiment, the bias signals from the Q8 and Q9 pair are thermally compensated, but it is optional that the bias signals from the Q11 and Q12 pair be thermally compensated. In one embodiment, the bias signals from the Q11 and Q12 pair are thermally compensated, but it is optional that the bias signals from the Q8 and Q9 pair be thermally compensated.

[0108] Another possible variation of the circuit 1100 is to sample the RF signal from the RF output of the PA 514, rather than from the RF output of the PPA 512. Thus, the sampled RF signal from the PA 514 can be provided to the base terminals of transistors Q7, Q10, and Q13 (rather than the RF signal from the RF output of the PPA 512).

[0109] Another possible variation of the circuit 1100 is to replace some or all of the bipolar junction transistors with another type of transistor, such as a MOSFET.

[0110] Figure 12 A flowchart of one embodiment of a process of amplifying an RF signal is described. The process 1200 can be implemented by an RF transmitter, such as 202, 302, 502. In one embodiment, the process 1200 is implemented by a UE 110. In one embodiment, the process 1200 is implemented by a base station 170. The base station 170 can comprise a wireless access point. The process can be implemented by an apparatus in Figure 6 、 7A or 7B, but is not limited thereto. In one embodiment, the process 1200 is implemented by the circuit 1100. In one embodiment, the RF signal transmits in compliance with an IEEE 802.11 protocol. For example, the process 1200 can be used to transmit a Wi-Fi signal.

[0111] Step 1202 includes operating the RF amplifier 602 in a pulsed mode in response to a transmit enable signal (TX_EN). In the pulsed mode, the RF amplifier 602 is powered on and off in response to the transmit enable signal. The transmit enable signal can be provided by a processor (e.g., the processor 208, 308).

[0112] Step 1204 includes providing a temperature dependent bias signal from one or more bias transistors to a bias input of the RF amplifier 602. In one embodiment, the bias circuit 610a provides a bias signal to the RF input of the PPA 512. Reference is made to Figure 11 In one embodiment, the bias transistors Q8 and Q9 provide a bias signal to the base of the transistor Q5 in the PPA 512. In one embodiment, the bias circuit 610b provides a bias signal to the RF input of the PA 514. Reference is made to Figure 11 In one embodiment, the bias transistors Q11 and Q12 provide a bias signal to the base of the transistor Q1 in the PA 514. The temperature dependent factor in the bias signal is that the bias circuit 610a includes one or more bias transistors that operate in dependence on temperature.

[0113] Step 1206 includes heating one or more bias transistors with one or more heating transistors when the RF amplifier 602 is powered on. The one or more heating transistors can be physically proximate to the one or more bias transistors so as to heat the one or more bias transistors. Heating the one or more bias transistors helps to compensate for a temperature difference between the RF amplifier 602 and the one or more bias transistors. Heating the one or more bias transistors helps to compensate for different heating rates of the RF amplifier 602 and the one or more bias transistors. As a result, the thermal compensation helps to stabilize the gain of the RF amplifier 602. For example, the thermal compensation enables a more constant gain of the RF amplifier 602 for the duration of the duty cycle during the pulsed mode of operation. Stabilizing the gain of the RF amplifier 602 can reduce or eliminate distortion in the transmitted RF signal. Ultimately, the dynamic EVM is improved.

[0114] Figure 13 A flowchart of one embodiment of a process 1300 to describe the process of biasing the heating transistors in the thermal compensation bias 540 is described. The process 1300 can be implemented in one embodiment of the step 1206 of the process 1200. Reference is made to Figure 11 the circuit 1100 in FIG. 11, Figure 13Process 1300 of FIG. 13 can be used to bias heating transistors Q7, Q10, and Q13. Process 1300 can be implemented by an RF transmitter (e.g., 202, 302, 502). In one embodiment, process 1300 is implemented by UE 110. In one embodiment, process 1300 is implemented by base station 170. The process can be implemented by Figure 6 , 7A or the apparatus in 7B, but is not limited thereto. In one embodiment, process 1400 is implemented by circuit 1100.

[0115] Step 1302 includes accessing a transmitter enable signal. Figure 8 One embodiment of a transmitter enable signal 800 is described. The transmitter enable signal can be provided by a processor (e.g., 208, 308).

[0116] Step 1304 includes generating a DC bias current that tracks the transmitter enable signal. Heating circuit bias 630 can generate the DC bias current. Figure 10 An example of a DC bias current 1000 is described. Figure 10 A current versus time relationship of DC bias current 1000 is described. DC bias current 1000 tracks transmitter enable signal 800. In one embodiment, the low level of DC bias current 1000 is 0 amperes. In one embodiment, the high level of DC bias current 1000 is between 1 milliampere and 10 milliampere; however, the high level of DC bias current 1000 can be less than 1 milliampere or greater than 10 milliampere. In one embodiment, the magnitude of DC bias current 1000 is used to adjust the amount of heat generated by heating circuit 620 (e.g., heating transistors Q7, Q10, Q13). In some embodiments, the magnitude of DC bias current 1000 can be determined experimentally.

[0117] In some embodiments, the magnitude of DC bias current 1000 depends on the target power of the RF signal output by RF amplifier 602. In one embodiment, a processor (e.g., 208, 308) determines the magnitude of DC bias current 1000 based on the target power. In one embodiment, the processor accesses a table stored in a memory (e.g., 206, 306) to determine the magnitude of DC bias current 1000. The table can directly indicate the magnitude of DC bias current 1000 for two or more target power ranges, or indirectly indicate the magnitude of DC bias current 1000 by specifying the value of a thermal compensation control signal for two or more target power ranges. Determining the magnitude of DC bias current 1000 based on the target power output of the RF signal output by RF amplifier 602 is not limited to the table approach.

[0118] Step 1306 includes providing a DC bias current to one or more heating transistors. In one embodiment, the heating circuit bias 630 provides a DC bias current to the heating transistors Q7, Q10, and Q13. The DC bias current can be provided to the respective base terminals of Q7, Q10, and Q13. In one embodiment, the magnitude of the DC bias current is a factor that controls the amount of heat provided by the heating transistors Q7, Q10, and Q13. Thus, adjusting the magnitude of the DC bias current can be used to control the amount of heat provided by the heating transistors Q7, Q10, and Q13.

[0119] Figure 14 A flowchart of one embodiment of a process of providing an amplified RF signal to one or more heating transistors is described. The process 1400 can be implemented in one embodiment of step 1206 of the process 1200. The process 1400 can be implemented by an RF transmitter (e.g., 202, 302, 502). In one embodiment, the process 1400 is implemented by the UE 110. In one embodiment, the process 1400 is implemented by the base station 170. The base station 170 can include a wireless access point. The process can be implemented by an apparatus in Figure 6 、 7A or 7B, but is not limited thereto. In one embodiment, the process 1400 is implemented by the circuit 1100.

[0120] Step 1402 includes sampling the RF signal from the RF amplifier 602. In one embodiment, the RF signal is sampled from the output of the PPA 512. In one embodiment, the RF signal is sampled from the output of the PA 514. In one embodiment, the RF signal is sampled by the sampling circuit in the thermal compensation bias 540. Referring to Figure 11 , the sampling circuit can include R6 and C5. The sampling circuit can be referred to herein as a control circuit, or as part of a control circuit.

[0121] Step 1404 includes providing the sampled RF signal to a heating transistor. Referring to Figure 11 , the sampled RF signal is provided to the respective base terminals of the transistors Q7, Q10, and Q13. Thus, each heating transistor Q7, Q10, and Q13 will respond to the sampled RF signal. For example, the collector-to-emitter current of each transistor Q7, Q10, and Q13 can respond to the sampled RF signal. Thus, each transistor Q7, Q10, and Q13 will generate heat that depends on the magnitude of the sampled RF signal.

[0122] Step 1406 includes the heating transistor heating the biasing transistor based on the sampled RF signal. The heating transistor can be physically proximate to the biasing transistor so as to heat the biasing transistor.

[0123] Figure 15The ambient temperature of the RF amplifier 602 and the biasing circuit 610 if no thermal compensation is used is described. The plot 1510 describes the ambient temperature of the amplifier 602 versus time. The plot 1520 describes the ambient temperature of the biasing circuit 610 versus time if no thermal compensation is used. The RF amplifier 602 will be enabled at time tl, at which point the amplifier will be powered on and begin to heat up. When the RF amplifier 602 is enabled, the biasing circuit 610 will also be powered on. The ambient temperature of the amplifier 602 rises much faster than the ambient temperature of the biasing circuit 610.

[0124] Figure 16 The gain of the RF amplifier versus time if no thermal compensation is used is described. The plot 1610 describes the gain of the RF amplifier versus time if no thermal compensation is used. The RF amplifier will be enabled at time tl, at which point the amplifier will be powered on and begin to heat up. Over time, the gain will change considerably. As the RF amplifier warms up, the RF amplifier gain rises significantly and eventually levels off. This change in gain can cause distortion in the RF signal. However, the RF amplifier needs to transmit the RF signal immediately after enabling transmission. Therefore, Figure 16 The gain curve in the plot 1610 can result in poor dynamic EVM for RF signal transmission, including but not limited to Wi-Fi signal transmission.

[0125] Figure 17 The ambient temperature of the RF amplifier 602 and the biasing circuit 610 if different levels of thermal compensation are used is described. The plot 1720 describes the temperature of the RF amplifier 602 versus time. The plots 1702 through 1718 describe the temperature of the biasing circuit 610 versus time if different levels of thermal compensation are used. If more thermal compensation is used, the biasing circuit 610 will heat up to a higher temperature. In one embodiment, the amount of thermal compensation depends on the size of the DC bias current provided to the heating transistor by the heating circuit bias 630, and a small fraction of the RF power sampled from the RF amplifier 602. The fraction of the RF power sampled from the RF amplifier 602 can be adjusted based on factors such as the values of the resistor R6 and the capacitor C5 (see circuit 1100).

[0126] Figure 18 The gain of the RF amplifier 602 versus time if different levels of thermal compensation are used is described. The plots 1802 through 1818 describe the gain of the RF amplifier versus time if different levels of thermal compensation are used in the plot 1700. The plot 1802 corresponds to the plot 1702, and is for Figure 17 The gain of the RF amplifier versus time if different levels of thermal compensation are used in the plot 1700 is described. The plot 1802 corresponds to the plot 1702, and is for Figure 17The minimum heat compensation amount in the curve graph 1804. The curve graph 1804 corresponds to the curve graph 1704; the curve graph 1806 corresponds to the curve graph 1706; the curve graph 1808 corresponds to the curve graph 1708; the curve graph 1810 corresponds to the curve graph 1710; the curve graph 1812 corresponds to the curve graph 1712; the curve graph 1814 corresponds to the curve graph 1714; the curve graph 1816 corresponds to the curve graph 1716; and the curve graph 1818 corresponds to the curve graph 1718.

[0127] The gain of the curve graph 1810 tends to be relatively constant over time. Thus, the heat compensation associated with the curve graph 1710 can be selected to provide a relatively constant gain in the RF amplifier 602. Figure 17 and 18 The curve graphs of FIGS. 17A and 17B can be experimentally determined by applying different amounts of heat compensation. The magnitude of the DC bias current generated by the heating circuit bias 630 can be selected based on an analysis of the curve graphs of FIGS. 17A and 17B. Figure 17 and 18 The appropriate values of the resistor R6 and / or the capacitor C5 can be selected based on an analysis of the curve graphs of FIGS. 17A and 17B. Figure 17 and 18 The appropriate values of the resistor R6 and / or the capacitor C5 can be selected based on an analysis of the curve graphs of FIGS. 17A and 17B.

[0128] In some embodiments, the techniques described herein can be implemented using hardware, software, or a combination of both hardware and software. The software used is stored in one or more processor readable storage devices, as described above, to program one or more processors to implement the functions described herein. The processor readable storage devices can include computer readable media such as volatile and non-volatile media, removable and non-removable media. By way of example, and not limitation, computer readable media can comprise computer readable storage media and communication media. Computer readable storage media can be implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer readable storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. Computer readable media do not include propagating signals, modulated signals or transient signals.

[0129] Communication media typically embodies computer-readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term "modulated data signal" refers to a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as RF and other wireless media. Combinations of the any of the above can also be included within the scope of computer-readable media.

[0130] In alternative embodiments, some or all of the software can be replaced by dedicated hardware logic components. Illustrative types of hardware logic components that can be used include, but are not limited to, Field-programmable Gate Arrays (FPGAs), Application-specific Integrated Circuits (ASICs), Application-specific Standard Products (ASSPs), System-on-a-chip (SOCs), Complex Programmable Logic Devices (CPLDs), dedicated computer chips, etc. In one embodiment, software implementing one or more embodiments (stored in storage) is used to program one or more processors. The one or more processors can be in communication with one or more computer-readable media / stores, peripheral devices, and / or communication interfaces.

[0131] It should be understood that the subject matter of the present invention can be embodied in many different ways and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the subject matter of the invention to those skilled in the art. In fact, the subject matter of the present invention is intended to encompass alternatives, modifications, and equivalents of these embodiments, including those that are now known or which become known in the future, which include within their scope the spirit and the principles of the present invention. Moreover, in the following detailed description of the subject matter of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be clear to those of ordinary skill in the art that the present invention can be practiced without these specific details.

[0132] The computer program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other processing device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other processing device to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart diagrams and / or block diagrams.

[0133] The description of the application thus far only illustrates and describes the aspects of the present application and is not intended to be exhaustive or to limit the application to any disclosed implementations. Numerous modifications and adaptations thereof will be apparent to those skilled in the art without departing from the scope and spirit of the application. Various aspects of the application are selected and described for the purpose of explanation and understanding of the principles of the application and its practical application, and to enable others skilled in the art to understand the application and various modifications that are suited to specific uses.

[0134] For purposes of this document, each process associated with the disclosed technology can be performed continuously by one or more computing devices. Each step in a process can be performed by the same or different computing devices used in other steps, and each step need not be performed by a single computing device.

[0135] While the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A device for amplifying radio frequency (RF) signals, characterized in that, The device includes: An RF amplifier is used to receive a temperature-dependent bias input and an RF signal, and the RF amplifier is used to amplify the RF signal according to a transmit enable signal; One or more bias transistors are used to generate the temperature-dependent bias signal; One or more heating transistors for heating the one or more bias transistors; A control circuit is configured to generate a DC bias current that tracks the transmit enable signal; and to provide the DC bias current to the one or more heating transistors so that the one or more heating transistors heat the one or more bias transistors when the RF amplifier is powered on.

2. The apparatus according to claim 1, characterized in that, The control circuit is used for; Heating compensation is provided for the one or more bias transistors based on the control signal generated by the processor based on specified parameters received from the processor. The DC bias current is generated according to the control signal, wherein the magnitude of the DC bias current controls the heat generated by the heating transistor to heat the one or more bias transistors when the RF amplifier is powered on.

3. The apparatus according to claim 2, characterized in that, The control circuit is used for: The magnitude of the DC bias current is determined based on the target power of the amplified RF signal output by the RF amplifier.

4. The apparatus according to any one of claims 1 to 3, characterized in that, The control circuit is used to sample the amplified RF signal from the RF amplifier and provide the sampled amplified RF signal to the one or more heating transistors; The one or more heating transistors are used to heat the one or more bias transistors according to the amplitude of the amplified RF signal when the RF amplifier is powered on.

5. The apparatus according to any one of claims 1 to 3, characterized in that, The one or more heating transistors include one or more bipolar junction transistors; The control circuit provides the DC bias current to the base of each of the one or more bipolar junction transistors; The control circuit provides an amplified RF signal to the base of each of one or more bipolar junction transistors.

6. The apparatus according to any one of claims 1 to 3, characterized in that, The one or more heating transistors include a first transistor located on a first side of the one or more bias transistors and a second transistor located on a second side of the one or more bias transistors, wherein the second side is opposite to the first side.

7. The apparatus according to claim 1, characterized in that, The RF amplifier includes a preamplifier stage having a first RF input, a bias input as a first bias input, and a first RF output; The RF amplifier includes a power amplification stage having a second RF input coupled to the first RF output, a second bias input, and a second RF output. The one or more bias transistors are configured to provide a first bias signal to the first bias input of the preamplifier stage and a second bias signal to the second bias input of the power amplifier stage. The control circuit is used to sample the amplified RF signal at the first RF output, wherein the one or more heating transistors are used to heat the one or more bias transistors according to the amplitude of the amplified RF signal at the first RF output.

8. The apparatus according to claim 1, characterized in that, The RF amplifier includes a preamplifier stage having a first RF input, a first bias input, and a first RF output; The RF amplifier includes a power amplification stage having a second RF input coupled to the first RF output, a second bias input, and a second RF output. The one or more bias transistors are configured to provide a first bias signal to the first bias input of the preamplifier stage and a second bias signal to the second bias input of the power amplifier stage. The control circuit is used to sample the amplified RF signal at the second RF output, wherein the one or more heating transistors are used to heat the one or more bias transistors according to the amplitude of the amplified RF signal at the second RF output.

9. The apparatus according to claim 7 or 8, characterized in that, The one or more bias transistors include a first group of one or more bias transistors for providing the first bias signal to the preamplifier stage and a second group of one or more bias transistors for providing the second bias signal to the power amplifier stage; The one or more heating transistors include a first heating transistor between a first group of the one or more bias transistors and a second group of the one or more bias transistors.

10. The apparatus according to claim 7 or 8, characterized in that, The one or more heating transistors also include: A second heating transistor on a first side of a first group of one or more bias transistors, the second heating transistor being opposite to a second side of a first group of one or more bias transistors adjacent to the first heating transistor; A third heating transistor is located on the first side of the second group of the one or more bias transistors, the third heating transistor being opposite to the second side of the second group of the one or more bias transistors adjacent to the first heating transistor.

11. A method for amplifying radio frequency (RF) signals, characterized in that, The method includes: The RF amplifier operates in a mode where it is powered on and off in response to a transmit enable signal; When the RF amplifier is powered on, the RF signal is amplified by the RF amplifier; When the RF amplifier is powered on, a temperature-dependent bias signal is provided from one or more bias transistors to the bias input of the RF amplifier; and A DC bias current is generated to track the transmit enable signal; when the RF amplifier is powered on, the DC bias current is provided to the one or more heating transistors to heat the one or more bias transistors.

12. The method according to claim 11, characterized in that, The method further includes: Access the parameters upon which the heating compensation amount of the one or more bias transistors is based; and The DC bias current is generated according to the parameters, wherein the magnitude of the DC bias current controls the heat generated by the heating transistor to heat the one or more bias transistors when the RF amplifier is powered on.

13. The method according to claim 11, characterized in that, The method further includes: Provide the target power of the amplified RF signal to the RF amplifier; and The magnitude of the DC bias current is determined based on the target power of the amplified RF signal.

14. The method according to any one of claims 11 to 13, characterized in that, The method further includes: The amplified RF signal from the RF amplifier is sampled; and While the RF amplifier is powered on, the sampled and amplified RF signal is provided to the one or more heating transistors.

15. The method according to claim 14, characterized in that, Sampling the amplified RF signal from the RF amplifier includes sampling the output of the preamplifier stage in the RF amplifier; as well as Providing a temperature-dependent bias signal from one or more bias transistors to the bias input of an RF amplifier includes providing a temperature-dependent bias signal to the bias input of a preamplifier stage.

16. The method according to claim 14, characterized in that, Sampling the amplified RF signal from the RF amplifier includes sampling the output of the power amplification stage in the RF amplifier; Providing a temperature-dependent bias signal from one or more bias transistors to the bias input of an RF amplifier includes providing a temperature-dependent bias signal to the bias input of a power amplifier stage.

17. A radio frequency (RF) transmitter for transmitting RF signals, characterized in that, include: A preamplifier stage has an RF input, an RF output, and a first bias input. The preamplifier stage is used to receive the RF signal at the RF input of the preamplifier stage and provide a preamplified RF signal to the RF output of the preamplifier stage. A power amplifier stage has an RF input, an RF output, and a second bias input coupled to the RF output of the preamplifier stage, wherein the power amplifier stage is configured to receive the preamplified RF signal at the RF input of the power amplifier stage and provide a power-amplified RF signal to the RF output of the power amplifier stage, and the preamplifier stage and the power amplifier stage are configured to amplify the RF signal according to a transmit enable signal; An antenna coupled to the RF output of the power amplifier stage, the antenna being used to transmit the RF signal amplified by the power amplifier; One or more bias transistors are used to provide a first bias signal to the first bias input and a second bias signal to the second bias input; One or more heating transistors for heating the one or more bias transistors; A control circuit is configured to generate a DC bias current that tracks the transmit enable signal; and to provide the DC bias current to the one or more heating transistors so that the one or more heating transistors heat the one or more bias transistors when the preamplifier stage and the power amplifier stage are energized.

18. The radio frequency (RF) transmitter according to claim 17, characterized in that, The control circuit is used for: Access the parameter that specifies the amount of heating compensation for the one or more bias transistors; as well as The DC bias current is generated according to the parameters, wherein the magnitude of the DC bias current controls the heat generated by the heating transistor to heat the one or more bias transistors when the preamplifier stage and the power amplifier stage are energized.

19. The radio frequency (RF) transmitter according to claim 17 or 18, characterized in that, The control circuit is used for: The magnitude of the DC bias current is determined based on the target power of the power amplified RF signal.

20. The radio frequency (RF) transmitter according to claim 17 or 18, characterized in that, The control circuit is used for: The preamplified RF signal is sampled; as well as When the preamplifier stage and power amplifier stage are powered on, the sampled preamplified RF signal is provided to the corresponding base terminals of one or more heating transistors.

21. The radio frequency (RF) transmitter according to claim 17 or 18, characterized in that, The control circuit is used for: The power amplified RF signal is sampled; and When the preamplifier stage and power amplifier stage are powered on, the sampled power amplified RF signal is provided to the corresponding base terminals of one or more heating transistors.

22. The radio frequency (RF) transmitter according to claim 17 or 18, characterized in that, The one or more bias transistors include a first group of one or more bias transistors for providing a first DC bias current to the first bias input and a second group of one or more bias transistors for providing a second DC bias current to the second bias input; The one or more heating transistors include a first heating transistor located between the first group of one or more bias transistors and the second group of one or more bias transistors, wherein the first heating transistor is used to heat the first group of one or more bias transistors and the second group of one or more bias transistors.

23. The radio frequency (RF) transmitter according to claim 22, characterized in that, The one or more heating transistors also include: A second heating transistor is located on a first side of a first group of one or more bias transistors, the second heating transistor being opposite to a second side of a first group of one or more bias transistors adjacent to the first heating transistor, wherein the second heating transistor is used to heat the first group of one or more bias transistors; A third heating transistor is located on a first side of a second group of one or more bias transistors, the third heating transistor being opposite a second side of a second group of one or more bias transistors adjacent to the first heating transistor, wherein the third heating transistor is used to heat one or more bias transistors in the second group.

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