Amplifier circuits and electronic devices

Abstract

The present application discloses a power amplifier circuit and an electronic device, which relate to the field of radio frequency and are used to improve the impedance of a junction point. The power amplifier circuit comprises: a first output end of a power divider is electrically connected to an input end of a first power amplifier, an output end of the first power amplifier is electrically connected to a first end of a first phase-shifting network, a second output end of the power divider, a first end of a second phase-shifting network, and a first end of a first switch are electrically connected, a second end of the second phase-shifting network, an input end of a second power amplifier, and a second end of the first switch are electrically connected, an output end of the second power amplifier, an input end of a third phase-shifting network, and a first end of a second switch are electrically connected, an output end of the third phase-shifting network, a second end of the second switch, and a second end of the first phase-shifting network are electrically connected; a third output end of the power divider is electrically connected to a switching circuit; and the switching circuit is used to control the first switch to close and the second switch to open according to the input power, or to control the first switch to open and the second switch to close.

Description

Technical Field

[0001] The present application relates to the field of radio frequency, and in particular to a power amplifier circuit and an electronic device. Background Art

[0002] Power amplifiers are used in the power amplifier circuits of electronic devices to amplify the power of radio frequency signals. In the linear region, the output power of the power amplifier increases linearly with the increase of input power. When the input power of the power amplifier increases further, the power amplifier enters the saturation region, and the output power of the power amplifier no longer increases with the increase of input power. The output power of the power amplifier reaches saturation, and the efficiency of the power amplifier is the highest at this time. The power amplifier works in the linear region most of the time, which means that the power amplifier cannot reach saturation most of the time, so the efficiency is not the highest most of the time.

[0003] In the prior art, the efficiency of power amplification is improved by using the power back-off technology of two power amplifiers. Specifically, the first power amplifier is load modulated by a frequency element so that the power amplifier is more likely to enter the saturation region in advance as the input power increases, thereby improving the efficiency of the power amplifier in amplifying small signals (i.e., the power of the RF signal is relatively small). The branch where the power amplifier is located is called the carrier branch. The second power amplifier is used to amplify large signals (i.e., the power of the RF signal is relatively large), thereby improving the efficiency of power amplification as a whole. The branch where the power amplifier is located is called the peak branch.

[0004] After the carrier branch and the peak branch are connected in parallel at the junction, they must go through the impedance transformation of the matching network so that the impedance at the output of the power amplifier circuit is the target impedance (for example, 50 ohms). If the impedance at the junction is small, the broadband impedance matching design of the matching network is more difficult. Summary of the invention

[0005] Embodiments of the present application provide a power amplifier circuit and an electronic device for improving the impedance of a combining point.

[0006] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0007] In a first aspect, a power amplifier circuit is provided, comprising: a power divider, a first power amplifier, a second power amplifier, a first phase-shifting network, a second phase-shifting network, a third phase-shifting network, a first switch, a second switch, and a switching circuit, wherein an input end of the power divider is used to input a radio frequency signal, a first output end of the power divider is electrically connected to an input end of the first power amplifier, an output end of the first power amplifier is electrically connected to a first end of the first phase-shifting network, a second output end of the power divider, a first end of the second phase-shifting network, and a first end of the first switch are electrically connected, a second end of the second phase-shifting network, an input end of the second power amplifier, and a second end of the first switch are electrically connected, an output end of the second power amplifier, a first end of the third phase-shifting network, and a first end of the second switch are electrically connected, and a second end of the third phase-shifting network, a second end of the second switch, and a second end of the first phase-shifting network are electrically connected to a junction point; the third output end of the power divider is electrically connected to the switching circuit; and the switching circuit is used to control the first switch to close and the second switch to open according to the input power, or to control the first switch to open and the second switch to close.

[0008] In the power amplifier circuit provided by the embodiment of the present application, the branch where the first power amplifier is located is called the carrier branch, and the branch where the second power amplifier is located is called the peak branch, and the two branches are electrically connected to the junction. A third phase-shifting network is added to the output end of the second power amplifier, the second phase-shifting network is connected in parallel with the first switch, and the third phase-shifting network is connected in parallel with the second switch. When the power is backed off, if the input power of the switching circuit is small, the switching circuit controls the first switch to be disconnected and the second switch to be closed, so that the second phase-shifting network is connected to the peak branch and the third phase-shifting network is not connected to the peak branch, so as to avoid the third phase-shifting network affecting the open circuit characteristics of the second power amplifier, resulting in current leakage in the peak branch. If the input power of the switching circuit is large, the switching circuit controls the first switch to be closed and the second switch to be disconnected, so that the third phase-shifting network is connected to the peak branch and the second phase-shifting network is not connected to the peak branch, and the third phase-shifting network performs impedance transformation on the load impedance of the second power amplifier, improves the impedance of the junction, reduces the difficulty of broadband impedance matching design and insertion loss of the matching network, and does not even need to electrically connect the matching network, and does not need to design broadband impedance matching of the matching network. It also avoids the second phase shifting network introducing an additional 90-degree phase shift to the peak branch, which causes the combining point to be unable to achieve in-phase combining.

[0009] In a possible implementation, the switching circuit is specifically used for: when the power is backed off, if the input power of the switching circuit is less than the power threshold, the first switch is controlled to be disconnected, and the second switch is controlled to be closed, so that the second phase-shifting network is connected to the peak branch and the third phase-shifting network is not connected to the peak branch, so as to avoid the third phase-shifting network affecting the open-circuit characteristics of the second power amplifier, resulting in current leakage in the peak branch; if the input power of the switching circuit is greater than the power threshold, the first switch is controlled to be closed, and the second switch is controlled to be disconnected, so that the third phase-shifting network is connected to the peak branch and the second phase-shifting network is not connected to the peak branch, and the third phase-shifting network performs impedance transformation on the load impedance of the second power amplifier, improves the impedance of the junction point, reduces the difficulty of broadband impedance matching design and insertion loss of the matching network, and even does not need to electrically connect the matching network, and does not need to design broadband impedance matching of the matching network. And avoid the second phase-shifting network introducing an additional 90-degree phase shift to the peak branch, resulting in the inability of the junction point to achieve in-phase merging.

[0010] In a possible implementation, the power threshold is the power outputted by the third output terminal of the power divider when the load impedance of the second power amplifier is equal to the characteristic impedance of the third phase-shifting network. At this time, assuming that the load impedance of the second power amplifier is R1, the characteristic impedance of the third phase-shifting network is R2, and the load impedance R1 of the second power amplifier is equal to the characteristic impedance R2 of the third phase-shifting network, if the first switch is closed and the second switch is opened, the load impedance R1 of the second power amplifier after the impedance transformation of the third phase-shifting network is R2*R2 / R1=R1, which is the same as the load impedance R1 of the second power amplifier before switching, so it will not affect the impedance of the peak branch.

[0011] In a possible implementation, the switching circuit includes a power voltage conversion module, a first comparator, and a second comparator. The input end of the power voltage conversion module is electrically connected to the third output end of the power divider; the output end of the power voltage conversion module is electrically connected to the first input end of the first comparator and the second input end of the second comparator, the second input end of the first comparator and the first input end of the second comparator input a reference voltage, the output end of the first comparator is electrically connected to the control end of the first switch, and the output end of the second comparator is electrically connected to the control end of the second switch; the power voltage conversion module is used to convert the input power into voltage; if the output voltage of the power voltage conversion module is less than the reference voltage, the first comparator controls the first switch to be disconnected, and the second comparator controls the second switch to be closed; if the output voltage of the power voltage conversion module is greater than the reference voltage, the first comparator controls the first switch to be closed, and the second comparator controls the second switch to be disconnected. This implementation is a possible structure of the switching circuit, the reference voltage is the voltage corresponding to the power threshold, and this implementation converts the power output of the power divider into voltage and compares it with the reference voltage, which is equivalent to comparing the power output of the power divider with the power threshold, thereby determining the switching timing of the first switch and the second switch.

[0012] In a possible implementation, the switching circuit includes a power-voltage conversion module, a first comparator, and an inverter. The input end of the power-voltage conversion module is electrically connected to the third output end of the power divider; the output end of the power-voltage conversion module is electrically connected to the first input end of the first comparator, and a reference voltage is input to the second input end of the first comparator; the output end of the first comparator, the control end of the first switch, and the input end of the inverter are electrically connected, and the output end of the inverter is electrically connected to the control end of the second switch; the power-voltage conversion module is used to convert the input power into a voltage; if the voltage output by the power-voltage conversion module is less than the reference voltage, the first comparator controls the first switch to open, and the inverter controls the second switch to close; if the voltage output by the power-voltage conversion module is greater than the reference voltage, the first comparator controls the first switch to close, and the inverter controls the second switch to open. This implementation is another possible structure of the switching circuit. The reference voltage is the voltage corresponding to the power threshold. This implementation converts the power output by the power divider into a voltage and compares it with the reference voltage, which is equivalent to comparing the power output by the power divider with the power threshold, so as to determine the switching timing of the first switch and the second switch.

[0013] In a possible implementation, the reference voltage is equal to P2 * F1 * F2, where P2 is the power output by the second output end of the power divider when the load impedance of the second power amplifier is equal to the characteristic impedance of the third phase-shifting network, F1 is the ratio of the power output by the third output end of the power divider to the power output by the second output end, and F2 is the conversion coefficient of the power-voltage conversion module to convert the input power into a voltage. P2 * F1 is the power threshold.

[0014] In a possible implementation, the characteristic impedance Z of the first phase-shifting network and the third phase-shifting network satisfies Ropt < Z < sqrt(2Rt * Ropt), where Ropt is the load impedance when the first power amplifier and the second power amplifier are saturated, sqrt is the square root, and Rt is the target impedance (such as 50 ohms) at the output end of the power amplifier circuit. The power amplifier circuit further includes a matching network. The first end of the matching network is electrically connected to the combining point, and the second end of the matching network is used to output a radio frequency signal. The third phase-shifting network increases the impedance of the combining point, which can reduce the impedance matching design difficulty and insertion loss of the broadband matching of the matching network. Moreover, the larger Z is, the larger the impedance of the combining point is, and the lower the impedance matching design difficulty and insertion loss of the broadband matching of the matching network are.

[0015] In a possible implementation, the characteristic impedance Z of the first phase-shifting network and the third phase-shifting network satisfies Z=sqrt(2Rt*Ropt), Ropt is the load impedance of the first power amplifier and the second power amplifier when they are saturated, sqrt is the square root, and Rt is the target impedance (e.g., 50 ohms) at the output end of the power amplifier circuit. The junction point is not connected to a matching network, and there is no need to design broadband impedance matching of the matching network, which can reduce the insertion loss of the junction point.

[0016] In a possible implementation, the first switch and the second switch are manufactured using a Silicon-On-Insulator (SOI) process, or a pseudomorphic high electron mobility transistor (pHEMT) process. Large-bandwidth RF signals require high-frequency switching of the first switch and the second switch, so high requirements are placed on the switching speed of the first switch and the second switch. If the first switch and the second switch are manufactured using the SOI process, the switching speed can reach microseconds. If the first switch and the second switch are manufactured using the pHEMT process, the switching speed can even reach nanoseconds.

[0017] In a second aspect, an electronic device is provided, comprising an antenna and a power amplifier circuit as described in the first aspect and any embodiment thereof, wherein the power amplifier circuit is used to output a power-amplified radio frequency signal to the antenna.

[0018] The technical effects of the second aspect refer to the technical effects of the first aspect and any of its embodiments, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the appearance of an electronic device provided in an embodiment of the present application;

[0020] Figure 2 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0021] Figure 3 A schematic diagram of the structure of a mobile communication module provided in an embodiment of the present application;

[0022] Figure 4 A schematic diagram of the structure of a power amplifier circuit provided in an embodiment of the present application;

[0023] Figure 5 Schematic diagram of the structures of several quarter-wavelength lines provided in the embodiments of the present application;

[0024] Figure 6 A schematic diagram of a load impedance change of a power amplifier provided in an embodiment of the present application;

[0025] Figure 7 A schematic diagram of the relationship between power back-off and efficiency provided in an embodiment of the present application;

[0026] Figure 8 A schematic diagram of the structure of another power amplifier circuit provided in an embodiment of the present application;

[0027] Fig. 9 A schematic diagram of the structure of another power amplifier circuit provided in an embodiment of the present application;

[0028] Fig.10 A schematic diagram of the structure of another power amplifier circuit provided in an embodiment of the present application;

[0029] Fig.11 A schematic diagram of the structure of another power amplifier circuit provided in an embodiment of the present application;

[0030] Fig.12 A schematic diagram of the structure of another power amplifier circuit provided in an embodiment of the present application;

[0031] Fig.13 A schematic diagram of the structure of another power amplifier circuit provided in an embodiment of the present application;

[0032] Fig.14 A schematic diagram of the structure of another power amplifier circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] First, some concepts involved in this application are described.

[0034] The terms "first", "second", etc. involved in the embodiments of the present application are only used to distinguish features of the same type and cannot be understood as indicating relative importance, quantity, order, etc.

[0035] The terms "exemplary" or "for example" and the like in the embodiments of the present application are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the terms "exemplary" or "for example" is intended to present the related concepts in a specific way.

[0036] The terms "coupling" and "connection" involved in the embodiments of the present application should be understood in a broad sense. For example, they may refer to a direct physical connection, or an indirect connection achieved through electronic devices, such as a connection achieved through resistors, inductors, capacitors or other electronic devices.

[0037] The saturation region and linear region of the power amplifier. In the linear region, the output power of the power amplifier increases linearly with the increase of the input power. When the input power of the power amplifier increases further until the power amplifier enters the saturation region, the output power of the power amplifier no longer increases with the increase of the input power, and the output power of the power amplifier reaches saturation.

[0038] Classification of power amplifiers: According to the current conduction angle of the RF signal, the power amplifier can be divided into Class A, Class B, Class C, and Class AB. Among them, the conduction angle of the Class A power amplifier is 360 degrees, that is, it is always on. The Class A power amplifier is suitable for scenarios where the RF signal is a small signal. The conduction angle of the Class B power amplifier is 180 degrees. The static bias point is the critical point between conduction and shutdown. The power amplifier is turned on when the power of the input RF signal is greater than the static critical point. The conduction angle of the Class C power amplifier is less than 180 degrees, and the static bias point is higher than that of the Class B power amplifier. It requires a higher power input RF signal to conduct. Class B power amplifiers and Class C power amplifiers are suitable for scenarios where the RF signal is a large signal. The conduction angle of the Class AB power amplifier is between 180 degrees and 360 degrees. When the RF signal is a small signal, it is equivalent to the Class A power amplifier, and when the RF signal is a large signal, it is equivalent to the Class B power amplifier. The small signal refers to that the power of the RF signal input to the power amplifier is less than the threshold, and the large signal refers to that the power of the RF signal input to the power amplifier is greater than the threshold.

[0039] The efficiency of a power amplifier refers to the ratio of the output power to the input power of the power amplifier.

[0040] Power back-off: Reduce the 1dB compression point of the power amplifier (i.e., the critical point where the linear region of the power amplifier ends) by a certain amount (e.g., 6dB-10dB), so that the power amplifier can more easily enter the saturation region earlier as the input power increases, thereby improving the efficiency of the power amplifier in amplifying small signals.

[0041] like Figure 1As shown, an embodiment of the present application provides an electronic device 101, which is an electronic device with a wireless communication function. The electronic device can be mobile or fixed. The electronic device can be deployed on land (for example, indoors or outdoors, handheld or vehicle-mounted, etc.), on the water (for example, ships, etc.), or in the air (for example, airplanes, balloons, and satellites, etc.). The electronic device can be called user equipment (UE), access terminal, terminal unit, subscriber unit, terminal station, mobile station (MS), mobile station, terminal agent or terminal device, etc. For example, the electronic device can be a mobile phone, a tablet computer, a laptop computer, a smart bracelet, a smart screen, a smart watch, a virtual reality (VR) device, an augmented reality (AR) device, a terminal in industrial control, a terminal in self-driving, a terminal in remote medical, a terminal in smart grid, a terminal in transportation safety, a terminal in smart city, a terminal in smart home, etc. The embodiments of the present application do not limit the specific type and structure of the electronic device. A possible structure of the electronic device is described below.

[0042] like Figure 1 As shown in Figure A, the electronic device 101 may include a front camera 2931 and a display screen 294. Figure 1 As shown in B, the electronic device 101 may include a rear camera 2932. The front camera 2931 and the rear camera 2932 are used to capture static images or dynamic videos (collectively referred to as images). The display screen 294 is used to display images or receive user touch operations.

[0043] Taking a mobile phone as an example, Figure 2A possible structure of the electronic device 101 is shown, including: a processor 210, an external memory interface 220, an internal memory 221, a universal serial bus (USB) interface 230, a charging management module 240, a power management module 241, a battery 242, an antenna 1, an antenna 2, a mobile communication module 250, a wireless communication module 260, an audio module 270, a speaker 270A, a receiver 270B, a microphone 270C, an earphone interface 270D, a sensor module 280, a button 290, an indicator 292, a camera 293, a display screen 294 and a subscriber identification module (SIM) card interface 295, etc.

[0044] It is to be understood that the structure illustrated in this embodiment does not constitute a specific limitation on the electronic device. In other embodiments, the electronic device may include more or fewer components than shown in the figure, or combine some components, or split some components, or arrange the components differently. The components shown in the figure may be implemented in hardware, software, or a combination of software and hardware.

[0045] The processor 210 may include one or more processing units, for example, the processor 210 may include a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a system on chip (SoC), a central processor unit (CPU), a network processor (NP), a microcontroller unit (MCU), a programmable logic device (PLD), an application processor (AP), a modem processor, a graphics processor (GPU), an image signal processor (ISP), a controller, a video codec, a digital signal processor (DSP), a baseband processor and / or a neural-network processing unit (NPU), etc. Different processing units may be independent devices or integrated in one or more processors.

[0046] The external memory interface 220 can be used to connect an external memory card, such as a Micro SD card, to expand the storage capacity of the electronic device. The external memory card communicates with the processor 210 through the external memory interface 220 to implement a data storage function. For example, files such as music and videos can be stored in the external memory card.

[0047] The internal memory 221 can be used to store computer executable program codes, which include computer instructions. The processor 210 executes various functional applications and data processing of the electronic device by running the computer instructions stored in the internal memory 221. The internal memory 221 may include a program storage area and a data storage area. Among them, the program storage area may store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc. The data storage area may store data created during the use of the electronic device (such as audio data, a phone book, etc.), etc. In addition, the internal memory 221 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, a universal flash storage (UFS), etc.

[0048] The memory involved in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), and direct RAM bus RAM (DR RAM).

[0049] The SIM card interface 295 is used to connect a SIM card. The SIM card can be connected to or disconnected from the electronic device by inserting the SIM card interface 295 or removing the SIM card from the SIM card interface 295. The electronic device can support 1 or N SIM card interfaces, where N is a positive integer greater than 1. The SIM card interface 295 can support Nano SIM cards, Micro SIM cards, SIM cards, etc.

[0050] The wireless communication function of the electronic device can be realized by antenna 1, antenna 2, mobile communication module 250, wireless communication module 260, modulation and demodulation processor and baseband processor. Mobile communication module 250 can perform mobile communication such as 2G / 3G / 4G / 5G. Wireless communication module 260 can perform Bluetooth (BT), wireless local area network (WLAN), global navigation satellite system (GNSS), near field communication technology (NFC), infrared technology (IR), frequency modulation (FM), etc.

[0051] like Figure 3 As shown, the mobile communication module 250 may include a baseband chip 31 , a radio frequency integrated circuit (RFIC) 32 and a power amplifier circuit 33 .

[0052] The baseband chip 31 is used to convert the data from the processor 210 into a baseband signal, including modulation and demodulation, digital filtering, equalization processing, etc. of the baseband signal. The RFIC 32 is used to convert the baseband signal from the baseband chip 31 into a radio frequency signal, which is transmitted through the power amplifier circuit 33 and the antenna 34. The power amplifier circuit 33 can improve the efficiency of power amplification of the radio frequency signal when the power is backed off. It should be noted that the baseband chip 31 and the RFIC 32 can also be integrated with the processor 210 in the SoC.

[0053] like Figure 4 As shown, the power amplifier circuit 33 includes: a first power amplifier (also called a carrier power amplifier) ​​3301, a second power amplifier (also called a peak power amplifier) ​​3302, a matching network 3303, a first phase shift network 3304, a power divider 3305 and a second phase shift network 3306.

[0054] The matching network 3303 is used to perform impedance transformation on the impedance of the combining point CON (eg, 10 ohms) to obtain a target impedance (eg, 50 ohms), thereby achieving impedance matching.

[0055] The input end of the power divider 3305 is used to Figure 3 The RFIC 32 shown is electrically connected to input a radio frequency signal. The first output end of the power divider 3305 is electrically connected to the input end of the first power amplifier 3301, and the second output end of the power divider 3305 is electrically connected to the first end of the second phase shift network 3306. The second end of the second phase shift network 3306 is electrically connected to the input end of the second power amplifier 3302. The output end of the first power amplifier 3301 is electrically connected to the first end of the first phase shift network 3304. The second end of the first phase shift network 3304, the output end of the second power amplifier 3302, and the first end of the matching network 3303 are electrically connected to the junction point CON. The second end of the matching network 3303 is used as the output end of the power amplifier circuit 33 to be connected to the power amplifier circuit 33. Figure 3 The antenna 34 is shown to be electrically connected to output a power-amplified radio frequency signal.

[0056] The power divider 3305 is used to evenly divide the RF signal inputted from the input end into a first RF signal and a second RF signal, and output the first RF signal through the first output end and output the second RF signal through the second output end. The power of the first RF signal and the second RF signal are both half of the power of the input RF signal.

[0057] The first power amplifier 3301 is used to power amplify the first RF signal. The first power amplifier 3301 is a class AB power amplifier, that is, the first power amplifier 3301 is equivalent to a class A power amplifier when the first RF signal is a small signal, and is equivalent to a class B power amplifier when the first RF signal is a large signal. The second power amplifier 3302 is used to power amplify the second RF signal. The second power amplifier 3302 is a class B power amplifier or a class C power amplifier, that is, the second power amplifier 3302 starts working when the second RF signal is a large signal. The first power amplifier 3301 and the second power amplifier 3302 have the same load impedance when saturated, for example, both are resistors Ropt, and the efficiency is highest at this time. The load impedance of a power amplifier refers to the output voltage / output current of the power amplifier.

[0058] The first phase-shift network 3304 and the second phase-shift network 3306 are both frequency elements, that is, the impedance and the phase shift angle change with the frequency of the RF signal. The first phase-shift network 3304 plays the role of impedance transformation. The impedance of the first phase-shift network 3304 after impedance transformation is equal to the square of the characteristic impedance of the first phase-shift network 3304 divided by the input impedance. The impedance of the first phase-shift network 3304 input can be the impedance of the first end, then the impedance of the first phase-shift network 3304 after impedance transformation is the impedance of the second end; or, the impedance of the first phase-shift network 3304 input can be the impedance of the second end, then the impedance of the first phase-shift network 3304 after impedance transformation is the impedance of the first end. For example, assuming that the characteristic impedance of the first phase-shift network 3304 is 2Ropt, and the load impedance of the first power amplifier 3301 when saturated is Ropt, the impedance of the first phase-shift network 3304 after impedance transformation is (2Ropt*2Ropt) / Ropt=4Ropt. For another example, assuming that the characteristic impedance of the first phase-shift network 3304 is Ropt, and the load impedance of the first power amplifier 3301 when the power is backed off is 2Ropt, then the impedance of the first phase-shift network 3304 after impedance transformation is (Ropt*Ropt) / (2Ropt)=Ropt / 2. For another example, assuming that the characteristic impedance of the first phase-shift network 3304 is Ropt, and the load impedance of the first power amplifier 3301 when saturated is Ropt, then the impedance of the first phase-shift network 3304 after impedance transformation is (Ropt*Ropt) / (Ropt)=Ropt. For another example, assuming that the characteristic impedance of the first phase-shift network 3304 is Ropt, and the impedance of the designed junction CON is Ropt / 2, then after the impedance transformation of the first phase-shift network 3304, the load impedance of the first power amplifier 3301 is (Ropt*Ropt) / (Ropt / 2)=2Ropt.

[0059] The first phase shift network 3304 or the second phase shift network 3306 can be a quarter wavelength line, which refers to the wavelength corresponding to the center frequency of the RF signal. The quarter wavelength line can also be called a 90-degree phase shift line, that is, at the center frequency of the RF signal, a 90-degree phase shift can be generated on the RF signal.

[0060] The first phase shift network 3304 performs a phase shift on the first RF signal, and the phase shift angle is related to the frequency of the RF signal. At the center frequency of the RF signal, the first phase shift network 3304 can produce a 90-degree phase shift on the first RF signal. The characteristic impedance of the first phase shift network 3304 can be equal to the load impedance Ropt of the first power amplifier 3301 when saturated, thereby achieving impedance matching with a reflection coefficient of 0.

[0061] The second phase shift network 3306 performs phase shifting on the second RF signal, and the phase shift angle is related to the frequency of the RF signal. The second phase shift network 3306 is used to adjust the phase shift angle of the peak branch so that at the center frequency of the RF signal, the carrier branch and the peak branch are phase-aligned at the junction CON, thereby improving the efficiency of the power amplifier circuit 33. Among them, at the center frequency of the RF signal, the second phase shift network 3306 can produce a 90-degree phase shift on the second RF signal, and the characteristic impedance of the second phase shift network 3306 can be equal to the load impedance of the first power amplifier 3301 when saturated. Under ideal conditions, for any frequency of the RF signal, the phase shift angle of the second phase shift network 3306 on the second RF signal is the same as the phase shift angle of the first phase shift network 3304 on the first RF signal, so that the first RF signal and the second RF signal are combined in phase at the junction CON to maximize the output power.

[0062] In the embodiment of the present application, the branch where the first power amplifier 3301 is located is called a carrier branch, and the branch where the second power amplifier 3302 is located is called a peak branch.

[0063] For example, Figure 5 As shown, the embodiments of the present application provide several implementation methods of quarter-wavelength lines. Figure 5 As shown in A, the quarter-wavelength line can be a microstrip line with an electrical length of 90 degrees. This quarter-wavelength line can achieve a -90 degree phase shift for the RF signal at the center frequency, and the phase shift angle will change linearly at other frequencies.

[0064] like Figure 5 As shown in B, the quarter-wavelength line can be a series inductor π-type network, including capacitor C1, capacitor C2, and inductor L1. The first end of the inductor L1 is electrically connected to the first end of the capacitor C1 and serves as the input end of the series inductor π-type network. The second end of the capacitor C1 is grounded. The second end of the inductor L1 is electrically connected to the first end of the capacitor C2 and serves as the output end of the series inductor π-type network. The second end of the capacitor C2 is grounded. This quarter-wavelength line can achieve a -90 degree phase shift for the RF signal at the center frequency, and the phase shift angle will change linearly at other frequencies.

[0065] like Figure 5 As shown in C, the quarter-wavelength line can be a series capacitor π-type network, including capacitor C1, inductor L1, and inductor L2. The first end of capacitor C1 is electrically connected to the first end of inductor L1 and serves as the input end of the series capacitor π-type network. The second end of inductor L1 is grounded. The second end of capacitor C1 is electrically connected to the first end of inductor L2 and serves as the output end of the series capacitor π-type network. The second end of inductor L2 is grounded. This quarter-wavelength line can achieve a 90-degree phase shift for the RF signal at the center frequency, and the phase shift angle will change linearly at other frequencies.

[0066] like Figure 5 As shown in D, the quarter-wavelength line can be a series inductor T-type network, including capacitor C1, inductor L1, and inductor L2, the first end of inductor L1 serves as the input end of the series inductor T-type network, the second end of inductor L1, the first end of inductor L2 and the first end of capacitor C1 are electrically connected, the second end of capacitor C1 is grounded, and the second end of inductor L2 serves as the output end of the series inductor T-type network. This quarter-wavelength line can achieve a -90 degree phase shift for the RF signal at the center frequency, and the phase shift angle will change linearly at other frequencies.

[0067] like Figure 5 As shown in Figure E, the quarter-wavelength line can be a series capacitor T-type network, including capacitor C1, capacitor C2, and inductor L1. The first end of capacitor C1 serves as the input end of the series capacitor T-type network, the second end of capacitor C1, the first end of capacitor C2, and the first end of inductor L1 are electrically connected, the second end of inductor L1 is grounded, and the second end of capacitor C2 serves as the output end of the series capacitor T-type network. This quarter-wavelength line can achieve a 90-degree phase shift for the RF signal at the center frequency, and the phase shift angle will change linearly at other frequencies.

[0068] Figure 5 The inductors in each network shown satisfy L=Ropt / (2πf), and the capacitors satisfy C=1 / (2πfRopt), where f is the center frequency of the RF signal, and Ropt is the load impedance when the first power amplifier 3301 and the second power amplifier 3302 are saturated.

[0069] Figure 4 The working principle of the power amplifier circuit 33 to achieve power back-off is as follows:

[0070] The load impedance of the power amplifier is equal to the output voltage / output current of the power amplifier, such as Figure 6 As shown in A, when the load impedance of the power amplifier remains unchanged (that is, the slope of the output voltage / output current remains unchanged), when the output current of the power amplifier is small, the output voltage is also small. At this time, the efficiency of the power amplifier is low. Figure 6 As shown in B, when the output current of the power amplifier is small, the efficiency of the power amplifier can be improved by increasing the load impedance of the power amplifier and then increasing the output voltage of the power amplifier, making it easier for the power amplifier to enter the saturation region in advance.

[0071] Therefore, if Figure 7As shown in the MN section of the "power amplifier circuit" in FIG. 1 , because the second power amplifier 3302 is a class B power amplifier or a class C power amplifier, when the input RF signal is a small signal, the power of the input RF signal is small and insufficient to trigger the second power amplifier 3302 to work, the second power amplifier 3302 is cut off and presents an open circuit state, and the load impedance of the second power amplifier 3302 is infinite (∞). Because the first power amplifier 3301 is a class AB power amplifier, when the input RF signal is a small signal, the first power amplifier 3301 starts to work, the first phase shift network 3304 transforms the load impedance of the first power amplifier 3301, increases the load impedance of the first power amplifier 3301, and increases the output voltage of the first power amplifier 3301, so that the first power amplifier 3301 enters the saturation state in advance, that is, the first power amplifier 3301 is more likely to enter the saturation zone in advance as the input power increases, thereby improving the efficiency of the first power amplifier 3301 in power amplification of small signals, thereby improving the overall power amplification efficiency of the power amplifier circuit 33. The output voltage of the first power amplifier 3301 increases as the power of the input radio frequency signal increases, and the output power of the first power amplifier 3301 also increases as the power of the input radio frequency signal increases.

[0072] like Figure 7 As shown at the mid-power back-off point N, because the second power amplifier 3302 is a class B power amplifier or a class C power amplifier, when the input RF signal is a small signal, the power of the input RF signal is small and insufficient to trigger the second power amplifier 3302 to work. The second power amplifier 3302 is cut off and presents an open circuit state, and the load impedance of the second power amplifier 3302 is infinite (∞). The characteristic impedance of the first phase-shifting network 3304 is Ropt, and the impedance of the designed junction CON is Ropt / 2. After the impedance transformation of the first phase-shifting network 3304, the load impedance of the first power amplifier 3301 is (Ropt*Ropt) / (Ropt / 2)=2Ropt, and the output power of the power amplifier circuit 33 is backed off by 6dB, that is, the output power of the power amplifier circuit 33 is one-fourth of the saturated output power, and the maximum efficiency under power back-off can be achieved.

[0073] like Figure 7As shown in the NP segment of the "power amplifier circuit" in FIG, the power of the RF signal input by the power amplifier circuit 33 is relatively large, triggering the second power amplifier 3302 to start working. As the power of the input RF signal continues to increase, the load impedance of the first power amplifier 3301 decreases from 2Ropt to Ropt, and the load impedance of the second power amplifier 3302 decreases from infinity (∞) to Ropt, thereby realizing the load modulation characteristic. The first power amplifier 3301 still maintains a pre-saturation state due to the high output voltage, the output voltage remains basically constant, and the output current increases with the increase of the power of the input RF signal. Therefore, the output power of the first power amplifier 3301 increases with the increase of the power of the input RF signal. The output voltage of the second power amplifier 3302 increases with the increase of the power of the input RF signal. Therefore, the output power of the second power amplifier 3302 increases with the increase of the power of the input RF signal. The overall power amplification efficiency of the power amplifier circuit 33 can still be maintained at a high level.

[0074] It should be noted that at the power back-off point N, the output power of the power amplifier circuit 33 is one-fourth of the saturated output power. This is because, relative to the saturation of the first power amplifier 3301 and the second power amplifier 3302, at the power back-off point N, only the first power amplifier 3301 is working, so the output power of the entire power amplifier circuit 33 is halved. Since the load impedance of the first power amplifier 3301 is 2Ropt, which is twice the load impedance Ropt at saturation, the output power of the first power amplifier 3301 is half of the saturated output power. The corresponding ratio of the output power of the first power amplifier at the power back-off point N is 0.5, which further halves the output power of the power amplifier circuit 33.

[0075] like Figure 7 As shown in the power saturation point P of the "power amplifier circuit", when the power of the input RF signal continues to increase, so that the first power amplifier 3301 and the second power amplifier 3302 are both saturated, the characteristic impedance of the first phase shift network 3304 is Ropt, and the load impedance of the first power amplifier 3301 when saturated is Ropt, then the impedance of the first phase shift network 3304 after impedance transformation is (Ropt*Ropt) / (Ropt)=Ropt, and the load impedance of the second power amplifier 3302 when saturated is also Ropt. Since the carrier branch and the peak branch have the same phase shift network, the RF signals of the two branches are phase-aligned at the junction CON, and the impedance of the junction CON is still Ropt / 2, and the overall power amplification efficiency of the power amplifier circuit 33 reaches the highest.

[0076] for Figure 7Although the class B power amplifier or class AB power amplifier shown has the highest efficiency at the power saturation point P, when the power is backed off, the efficiency will drop significantly as the power back-off increases. Figure 4 Compared with the class B power amplifier and the class AB power amplifier, the power amplifier circuit shown not only has the highest efficiency at the power saturation point P, but also has higher efficiency in power amplification in the entire MP section.

[0077] Assuming that under ideal conditions, the impedance of the output end of the power amplifier circuit 33 (i.e., the second end of the matching network 3303) is the target impedance (e.g., 50 ohms), and in order to adapt to a wider frequency, it is necessary to design a broadband impedance matching of the matching network 3303 so that the impedance of the combining point CON of the power amplifier circuit is Ropt / 2 when the power is backed off and saturated. After the impedance transformation of the matching network 3303, the impedance of the second end of the matching network 3303 is as close to the target impedance (e.g., 50 ohms) as possible.

[0078] Assuming that the saturation power P of the power amplifier circuit 33 is 35dBm and the operating voltage V is 5V, according to P=V*V / 2Ropt, Ropt=4 ohms, Ropt / 2=2 ohms, which is far from the target impedance (e.g., 50 ohms). Therefore, the broadband impedance matching design of the matching network 3303 is difficult, that is, it is difficult to keep the impedance stable within the preset range in all frequency bands, and the insertion loss of the matching network 3303 is also large.

[0079] To solve this problem, Figure 8 As shown, the impedance of the junction CON when the power amplifier circuit is powered off can be increased, for example, the impedance of the junction CON when the power amplifier circuit is powered off can be designed from Ropt / 2 to 2Ropt, so as to reduce the difficulty of broadband impedance matching design of the matching network 3303 and reduce the insertion loss of the matching network 3303. Accordingly, the characteristic impedance of the first phase shift network 3304 needs to be redesigned to 2Ropt. When the power is backed off, the load impedance of the first power amplifier 3301 when the power is backed off is 2Ropt, and the impedance of the first phase shift network 3304 after impedance transformation is (2Ropt*2Ropt) / (2Ropt)=2Ropt, which can meet the requirement that the impedance of the junction CON is 2Ropt. However, when saturated, the load impedance of the first power amplifier 3301 is Ropt, and the impedance of the first phase shift network 3304 after impedance transformation is (2Ropt*2Ropt) / (Ropt)=4Ropt. The load impedance of the second power amplifier 3302 is Ropt when saturated, and the impedance of the combining point CON is 4Ropt / 5, which cannot meet the requirement that the impedance of the combining point CON is also 2Ropt.

[0080] Therefore, an embodiment of the present application provides another power amplifier circuit 33, which adds a phase-shifting network at the output end of the second power amplifier 3302 to transform the load impedance of the second power amplifier 3302, thereby increasing the impedance of the combining point CON, reducing the difficulty of broadband impedance matching design and insertion loss of the matching network, and even eliminating the matching network 3303, so there is no need to design broadband impedance matching of the matching network.

[0081] like Fig. 9 As shown, the embodiment of the present application provides another power amplifier circuit 33, including: a first power amplifier (also called a carrier power amplifier) ​​3301, a second power amplifier (also called a peak power amplifier) ​​3302, a first phase shift network 3304, a power divider 3305, a second phase shift network 3306, a third phase shift network 3307, a first switch K1, a second switch K2, and a switching circuit 3308. Optionally, it also includes a matching network 3303. For the functions of the first power amplifier 3301, the second power amplifier 3302, the first phase shift network 3304, and the second phase shift network 3306, refer to Figure 4 The relevant description in will not be repeated here.

[0082] The RF signal with large bandwidth requires the first switch K1 and the second switch K2 to switch at high frequency, so the switching speed of the first switch K1 and the second switch K2 is relatively high. If the first switch K1 and the second switch K2 are made by SOI process, the switching speed can reach microsecond level. If the first switch K1 and the second switch K2 are made by pHEMT process, the switching speed can even reach nanosecond level.

[0083] The input end of the power divider 3305 is used to Figure 3 The RFIC 32 shown is electrically connected to input a radio frequency signal. The first output terminal of the power divider 3305 is electrically connected to the input terminal of the first power amplifier 3301, and the output terminal of the first power amplifier 3301 is electrically connected to the first terminal of the first phase shift network 3304. The second output terminal of the power divider 3305, the first terminal of the second phase shift network 3306, and the first terminal of the first switch K1 are electrically connected. The second terminal of the second phase shift network 3306, the input terminal of the second power amplifier 3302, and the second terminal of the first switch K1 are electrically connected. The output terminal of the second power amplifier 3302, the first terminal of the third phase shift network 3307, and the first terminal of the second switch K2 are electrically connected, and the output terminal of the third phase shift network 3307, the second terminal of the second switch K2, and the second terminal of the first phase shift network 3304 are electrically connected to the junction point CON. The third output terminal of the power divider 3305 is electrically connected to the switching circuit 3308. The junction point CON serves as the output terminal of the power amplifier circuit 33 and is used to Figure 3The antenna 34 shown is electrically connected to output the power-amplified RF signal; or, the junction point CON is electrically connected to the first end of the matching network 3303, and the second end of the matching network 3303 serves as the output end of the power amplifier circuit 33, and is used to Figure 3 The antenna 34 is shown to be electrically connected to output a power-amplified radio frequency signal.

[0084] The power divider 3305 is used to divide the RF signal inputted from the input end into a first RF signal, a second RF signal, and a third RF signal, and output the first RF signal through the first output end, output the second RF signal through the second output end, and output the third RF signal through the third output end. The power of the first RF signal is equal to the power of the second RF signal, and the ratio of the power of the third RF signal to the power of the second RF signal (or the first RF signal) is F1, and F1>0. Optionally, since the first RF signal and the second RF signal need to be transmitted eventually, the third RF signal is used for power detection, so F1 is less than 1 so that more power can be transmitted, thereby improving the efficiency of the power amplifier circuit 33. The smaller F1 is, the higher the power transmitted is, and the higher the efficiency of the power amplifier circuit 33 is.

[0085] The third phase shift network 3307 can be a quarter-wavelength line, where the wavelength refers to the wavelength corresponding to the center frequency of the RF signal. The quarter-wavelength line can also be called a 90-degree phase shift line, that is, at the center frequency of the RF signal, a 90-degree phase shift can be generated on the RF signal. For several implementation methods of the quarter-wavelength line, please refer to Figure 5 The third phase shift network 3307 is a frequency element, that is, the impedance and phase shift angle vary with the frequency of the RF signal.

[0086] On the one hand, the third phase-shift network 3307 can play the role of impedance transformation. The impedance of the third phase-shift network 3307 after impedance transformation is equal to the square of the characteristic impedance of the third phase-shift network 3307 divided by the input impedance. The input impedance of the third phase-shift network 3307 can be the impedance of the first end, and the impedance of the third phase-shift network 3307 after impedance transformation is the impedance of the second end; or, the input impedance of the third phase-shift network 3307 can be the impedance of the second end, and the impedance of the third phase-shift network 3307 after impedance transformation is the impedance of the first end. Figure 10-12 The characteristic impedance transformation function of the third phase shift network 3307 is described.

[0087] On the other hand, the third phase shift network 3307 performs phase shifting on the second RF signal, and the phase shift angle is related to the frequency of the RF signal. The third phase shift network 3307 can adjust the phase shift angle of the peak branch so that at the center frequency of the RF signal, the carrier branch and the peak branch are phase-aligned at the junction CON, thereby improving the efficiency of the power amplifier circuit 33. Under ideal conditions, for any frequency of the RF signal, the phase shift angle of the second RF signal by the third phase shift network 3307 is the same as the phase shift angle of the first RF signal by the first phase shift network 3304, so that the first RF signal and the second RF signal are combined in phase at the junction CON to maximize the output power.

[0088] The switching circuit 3308 is used to control the first switch K1 to close and the second switch K2 to open according to the input power (i.e., the power of the third RF signal output by the third output terminal of the power divider 3305); or to control the first switch K1 to open and the second switch K2 to close. The input power can be the real-time input power or the average input power within a preset time.

[0089] In practical applications, when the performance of the first switch K1 and the second switch K2 is not sufficient to support high-frequency switching, the power-to-voltage conversion module 33081 can convert the input power into voltage in real time, or convert the average input power over a period of time into voltage, that is, the switching circuit 3308 controls the first switch K1 to close and the second switch K2 to open according to the average input power, or controls the first switch K1 to open and the second switch K2 to close. The specific method is described in the previous text and will not be repeated here.

[0090] During power fallback, if the input power of the switching circuit 3308 is less than the power threshold, the switching circuit 3308 controls the first switch K1 to be disconnected and the second switch K2 to be closed, thereby short-circuiting the third phase-shifting network 3307 and connecting the second phase-shifting network 3306 to the peak branch. The second phase-shifting network 3306 is connected to the peak branch while the third phase-shifting network 3307 is not connected to the peak branch, so as to avoid the third phase-shifting network 3307 affecting the open-circuit characteristic of the second power amplifier 3302, resulting in current leakage in the peak branch. The power threshold is the power output from the third output terminal of the power divider 3305 when the load impedance of the second power amplifier 3302 is equal to the characteristic impedance of the third phase-shifting network 3307.

[0091] If the input power of the switching circuit 3308 is greater than the power threshold, the switching circuit 3308 controls the first switch K1 to close and controls the second switch K2 to open, thereby short-circuiting the second phase-shifting network 3306 and connecting the third phase-shifting network 3307 to the peak branch. The third phase-shifting network 3307 is connected to the peak branch while the second phase-shifting network 3306 is not connected to the peak branch. The third phase-shifting network 3307 performs impedance transformation on the load impedance of the second power amplifier 3302, improves the impedance of the junction CON, reduces the difficulty of broadband impedance matching design and insertion loss of the matching network 3303, and can even cancel the matching network 3303, without having to design broadband impedance matching of the matching network.

[0092] Assuming that the load impedance of the second power amplifier 3302 is R1, and the characteristic impedance of the third phase-shift network 3307 is R2, the load impedance R1 of the second power amplifier 3302 is equal to the characteristic impedance R2 of the third phase-shift network 3307. If the first switch K1 is closed and the second switch K2 is opened, the load impedance R1 of the second power amplifier 3302 after the impedance transformation of the third phase-shift network 3307 is R2*R2 / R1=R1, which is the same as the load impedance R1 of the second power amplifier 3302 before switching, so it will not affect the impedance of the peak branch.

[0093] In addition, the purpose of short-circuiting the second phase shift network 3306 is that after the third phase shift network 3307 is connected to the peak branch, a 90-degree phase shift has been generated on the second RF signal, and the phases of the first RF signal and the second RF signal at the junction CON are already the same, so there is no need for the second phase shift network 3306 to generate a 90-degree phase shift. That is, it is prevented that the second phase shift network 3306 introduces an additional 90-degree phase shift to the peak branch, resulting in the junction CON being unable to achieve in-phase merging.

[0094] Fig. 9 The working principle of the power amplifier circuit 33 to achieve power back-off is as follows:

[0095] like Figure 7 As shown in the MN section of the "power amplifier circuit" in FIG. 3 , because the second power amplifier 3302 is a class B power amplifier or a class C power amplifier, when the input RF signal is a small signal, the power of the input RF signal is small and insufficient to trigger the second power amplifier 3302 to work, and the second power amplifier 3302 is cut off and presents an open circuit state, and the load impedance of the second power amplifier 3302 is infinite (∞). When the input power of the switching circuit 3308 is less than the power threshold, the switching circuit 3308 controls the first switch K1 to be disconnected and controls the second switch K2 to be closed, thereby short-circuiting the third phase shift network 3307 and connecting the second phase shift network 3306 to the peak branch.

[0096] Because the first power amplifier 3301 is a class AB power amplifier, when the input RF signal is a small signal, the first power amplifier 3301 starts to work, and the first phase shift network 3304 transforms the load impedance of the first power amplifier 3301, thereby increasing the load impedance of the first power amplifier 3301, and the output voltage of the first power amplifier 3301 increases, so that the first power amplifier 3301 enters the saturation state in advance, that is, the first power amplifier 3301 is more likely to enter the saturation zone in advance as the input power increases, thereby improving the efficiency of the first power amplifier 3301 in power amplification of small signals, thereby improving the overall power amplification efficiency of the power amplifier circuit 33. The output voltage of the first power amplifier 3301 increases as the power of the input RF signal increases, and the output power of the first power amplifier 3301 also increases as the power of the input RF signal increases.

[0097] like Figure 7 As shown in the middle power back-off point N, because the second power amplifier 3302 is a class B power amplifier or a class C power amplifier, when the input RF signal is a small signal, the power of the input RF signal is small and insufficient to trigger the second power amplifier 3302 to work, and the second power amplifier 3302 is cut off and presents an open circuit state, and the load impedance of the second power amplifier 3302 is infinite (∞). The output power of the power amplifier circuit 33 is backed off by 6dB, that is, the output power of the power amplifier circuit 33 is one-fourth of the saturated output power, and the maximum efficiency under power back-off can be achieved.

[0098] like Figure 7 As shown in the NQ section of the "power amplifier circuit" in FIG. 3 , the power of the RF signal input by the power amplifier circuit 33 is relatively large, triggering the second power amplifier 3302 to start working. As the power of the input RF signal continues to increase, the load impedance of the first power amplifier 3301 decreases from 2Ropt to Ropt, and the load impedance of the second power amplifier 3302 decreases from infinity (∞) to Ropt, thereby realizing the load modulation characteristic. When the load impedance of the second power amplifier 3302 is equal to the characteristic impedance of the third phase shift network 3307, the switch switching point Q is reached. The first power amplifier 3301 still maintains a pre-saturation state due to the high output voltage, the output voltage remains basically constant, and the output current increases with the increase of the power of the input RF signal. Therefore, the output power of the first power amplifier 3301 increases with the increase of the power of the input RF signal. The output voltage of the second power amplifier 3302 increases with the increase of the power of the input RF signal. Therefore, the output power of the second power amplifier 3302 increases with the increase of the power of the input RF signal. The overall power amplification efficiency of the power amplifier circuit 33 can still be maintained at a high level.

[0099] like Figure 7As shown in the QP section of the "power amplifier circuit", as the power of the input radio frequency signal continues to increase, the load impedance of the first power amplifier 3301 continues to decrease towards Ropt, and the load impedance of the second power amplifier 3302 continues to decrease towards Ropt, thereby realizing the load modulation characteristic. After exceeding the switch switching point Q, when the input power of the switching circuit 3308 is greater than the power threshold, the switching circuit 3308 controls the first switch K1 to close and the second switch K2 to open, thereby short-circuiting the second phase-shifting network 3306 and connecting the third phase-shifting network 3307 to the peak branch. Since the output voltage of the first power amplifier 3301 is relatively high, it remains in the pre-saturated state, the output voltage remains basically constant, and the output current increases with the increase of the power of the input radio frequency signal. Therefore, the output power of the first power amplifier 3301 increases with the increase of the power of the input radio frequency signal. The output voltage of the second power amplifier 3302 increases with the increase of the power of the input radio frequency signal. Therefore, the output power of the second power amplifier 3302 increases with the increase of the power of the input radio frequency signal. The overall power amplification efficiency of the power amplifier circuit 33 can still be maintained at a high level.

[0100] The following combines Figure 10-12 to illustrate the possible impedances of the first phase-shifting network 3304, the third phase-shifting network 3307, and the matching network 3303.

[0101] The characteristic impedance Z of the first phase-shifting network 3304 and the third phase-shifting network 3307 satisfies Ropt < Z ≤ sqrt(2Rt * Ropt), where Ropt is the load impedance when the first power amplifier 3301 and the second power amplifier 3302 are saturated, sqrt is the square root, and Rt is the target impedance at the output end of the power amplifier circuit 33, and Rt > Ropt / 2. If Ropt < Z < sqrt(2Rt * Ropt), the third phase-shifting network 3307 increases the impedance of the combining point CON, which can reduce the impedance matching design difficulty and insertion loss of the broadband matching of the matching network 3303, and the larger Z is, the larger the impedance of the combining point CON is, and the lower the impedance matching design difficulty and insertion loss of the broadband matching of the matching network 3303 are. If Z = sqrt(2Rt * Ropt), the power amplifier circuit 33 does not even need the matching network 3303, that is, the combining point CON is not connected to the matching network 3303, and there is no need to design the broadband impedance matching of the matching network 3303, which can reduce the insertion loss of the combining point CON.

[0102] Exemplarily, as Fig.10 shown, the characteristic impedance of the first phase-shifting network 3304 and the third phase-shifting network 3307 is 2Ropt.

[0103] When the power is backed off, the load impedance of the first power amplifier 3301 when the power is backed off is 2Ropt, then the impedance after the impedance transformation of the first phase shift network 3304 is (2Ropt*2Ropt) / (2Ropt)=2Ropt, the load impedance of the first power amplifier 3301 is infinite, equivalent to an open circuit, and the impedance of the junction CON is 2Ropt. When saturated, the load impedance of the first power amplifier 3301 when saturated is Ropt, and the impedance after the impedance transformation of the first phase shift network 3304 is (2Ropt*2Ropt) / (Ropt)=4Ropt, the load impedance of the second power amplifier 3302 when saturated is Ropt, and the impedance after the impedance transformation of the third phase shift network 3307 is (2Ropt*2Ropt) / (Ropt)=4Ropt, and the impedance of the junction CON is also 2Ropt. The impedance of the output end of the power amplifier circuit 33 is the target impedance (for example, 50 ohms).

[0104] For example, Fig.11 As shown, the characteristic impedance of the first phase-shifting network 3304 and the third phase-shifting network 3307 is sqrt(2n)*Ropt, where n is greater than 1 / 2.

[0105] When the power is backed off, the load impedance of the first power amplifier 3301 is 2Ropt, and the impedance after the impedance transformation by the first phase shift network 3304 is (sqrt(2n)*Ropt*sqrt(2n)*Ropt) / (2Ropt)=nRopt. The load impedance of the first power amplifier 3301 is infinite, which is equivalent to an open circuit, and the impedance of the junction CON is nRopt. When saturated, the load impedance of the first power amplifier 3301 is Ropt, and the impedance after the impedance transformation by the first phase shift network 3304 is (sqrt(2n)*Ropt*sqrt(2n)*Ropt) / (Ropt)=2nRopt. The load impedance of the second power amplifier 3302 is Ropt when saturated, and the impedance after the impedance transformation by the third phase shift network 3307 is (sqrt(2n)*Ropt*sqrt(2n)*Ropt) / (Ropt)=2nRopt, and the impedance of the junction CON is also nRopt. The impedance of the output end of the power amplifier circuit 33 is the target impedance (for example, 50 ohms). If n is greater than 1 / 2, the impedance of the junction point CON is greater than Ropt / 2 when the power is backed off and when it is saturated. Figure 4The impedance of the junction CON shown is larger. The difficulty of broadband impedance matching design and insertion loss of the matching network 3303 can be reduced, and the larger n is, the larger the impedance of the junction CON is, and the difficulty of broadband impedance matching design and insertion loss of the matching network 3303 are reduced. By designing the value of n, the impedance of the junction CON can be flexibly designed when the power is backed off and when it is saturated.

[0106] For example, Fig.12 As shown, the characteristic impedance of the first phase shift network 3304 and the third phase shift network 3307 is sqrt(2Rt*Ropt). In this case, the matching network described above may not be required.

[0107] When power is reduced, the load impedance of the first power amplifier 3301 is 2Ropt, and the impedance of the first phase shift network 3304 after impedance transformation is (sqrt(2Rt*Ropt)*sqrt(2Rt*Ropt)) / (2Ropt)=Rt. The load impedance of the first power amplifier 3301 is infinite, which is equivalent to an open circuit, and the impedance of the junction CON is Rt. When saturated, the load impedance of the first power amplifier 3301 is Ropt, and the impedance after impedance transformation by the first phase shift network 3304 is (sqrt(2Rt*Ropt)*sqrt(2Rt*Ropt)) / (Ropt)=2Rt. The load impedance of the second power amplifier 3302 is Ropt, and the impedance after impedance transformation by the third phase shift network 3307 is (sqrt(2Rt*Ropt)*sqrt(2Rt*Ropt)) / (Ropt)=2Rt. The impedance of the junction CON is also Rt. That is, the impedance of the output end of the power amplifier circuit 33 is the target impedance Rt (e.g., 50 ohms).

[0108] In summary, by increasing the characteristic impedance of the first phase-shifting network 3304 and the third phase-shifting network 3307, the impedance of the combining point CON is closer to the target impedance (e.g., 50 ohms), or even equal to the target impedance (e.g., 50 ohms), the difficulty of broadband impedance matching design and insertion loss of the matching network 3303 will gradually decrease, and even a matching network will not be needed, and there is no need to design broadband impedance matching of the matching network.

[0109] Combine the following Fig.13 and Fig.14 A possible structure of the switching circuit 3308 is described.

[0110] like Fig.13 As shown, in a possible implementation, the switching circuit 3308 includes a power-to-voltage conversion module 33081 , a first comparator 33082 , and a second comparator 33083 .

[0111] The input end of the power voltage conversion module 33081 is electrically connected to the third output end of the power divider 3305; the output end of the power voltage conversion module 33081 is electrically connected to the first input end (for example, the non-inverting input end) of the first comparator 33082 and the second input end (for example, the inverting input end) of the second comparator 33083, the second input end (for example, the inverting input end) of the first comparator 33082 and the first input end (for example, the non-inverting input end) of the second comparator 33083 are input with a reference voltage Vref, the output end of the first comparator 33082 is electrically connected to the control end of the first switch K1, and the output end of the second comparator 33083 is electrically connected to the control end of the second switch K2.

[0112] The power-to-voltage conversion module 33081 is used to convert input power (i.e., the power of the third RF signal outputted from the third output terminal of the power divider 3305) into voltage. If the output voltage of the power-to-voltage conversion module 33081 is less than the reference voltage Vref, the output terminal of the first comparator 33082 outputs a low level, controls the first switch K1 to be disconnected, and the output terminal of the second comparator 33083 outputs a high level, controls the second switch K2 to be closed; if the output voltage of the power-to-voltage conversion module 33081 is greater than the reference voltage Vref, the output terminal of the first comparator 33082 outputs a high level, controls the first switch K1 to be closed, and the output terminal of the second comparator 33083 outputs a low level, controls the second switch K2 to be disconnected.

[0113] The reference voltage Vref is equal to P2*F1*F2, where P2 is the power output from the second output end of the power divider 3305 when the load impedance of the second power amplifier 3302 is equal to the characteristic impedance of the third phase shift network 3307, F1 is the ratio of the output power of the third output end to the second output end of the power divider 3305, and P2*F1 is the power threshold mentioned above. F2 is the conversion coefficient of the power voltage conversion module 33081 to convert the input power into voltage. The reference voltage is the voltage corresponding to the power threshold. By converting the power output of the power divider into a voltage and comparing it with the reference voltage, which is equivalent to comparing the power output of the power divider with the power threshold, the switching timing of the first switch and the second switch is determined.

[0114] like Fig.14As shown, in another possible implementation, the switching circuit 3308 includes a power voltage conversion module 33081, a first comparator 33082, and an inverter 33084. The input end of the power voltage conversion module 33081 is electrically connected to the third output end of the power divider 3305; the output end of the power voltage conversion module 33081 is electrically connected to the first input end (e.g., the positive input end) of the first comparator 33082, and the second input end (e.g., the negative input end) of the first comparator 33082 inputs a reference voltage Vref. The output end of the first comparator 33082, the control end of the first switch K1, and the input end of the inverter 33084 are electrically connected, and the output end of the inverter 33084 is electrically connected to the control end of the second switch K2. The power voltage conversion module 33081 is used to convert input power into voltage. If the output voltage of the power voltage conversion module 33081 is less than the reference voltage Vref, the output end of the first comparator 33082 outputs a low level, controls the first switch K1 to be disconnected, and the output end of the inverter 33084 outputs a high level, controls the second switch K2 to be closed; if the output voltage of the power voltage conversion module 33081 is greater than the reference voltage Vref, the output end of the first comparator 33082 outputs a high level, controls the first switch K1 to be closed, and the output end of the inverter 33084 outputs a low level, controls the second switch K2 to be disconnected.

[0115] About reference voltage Vref Fig.13 The relevant description will not be repeated here.

[0116] In the power amplifier circuit and electronic device provided by the embodiment of the present application, the branch where the first power amplifier is located is called the carrier branch, and the branch where the second power amplifier is located is called the peak branch, and the two branches are electrically connected to the junction. A third phase-shifting network is added to the output end of the second power amplifier, the second phase-shifting network is connected in parallel with the first switch, and the third phase-shifting network is connected in parallel with the second switch. When the power is backed off, if the input power of the switching circuit is small, the switching circuit controls the first switch to be disconnected and the second switch to be closed, so that the second phase-shifting network is connected to the peak branch and the third phase-shifting network is not connected to the peak branch, so as to avoid the third phase-shifting network affecting the open circuit characteristics of the second power amplifier, resulting in current leakage in the peak branch. If the input power of the switching circuit is large, the switching circuit controls the first switch to be closed and the second switch to be disconnected, so that the third phase-shifting network is connected to the peak branch and the second phase-shifting network is not connected to the peak branch, and the third phase-shifting network performs impedance transformation on the load impedance of the second power amplifier, improves the impedance of the junction, reduces the difficulty of broadband impedance matching design and insertion loss of the matching network, and does not even need to electrically connect the matching network, and does not need to design broadband impedance matching of the matching network. It also avoids the second phase shifting network introducing an additional 90-degree phase shift to the peak branch, which causes the combining point to be unable to achieve in-phase combining.

[0117] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A power amplifier circuit, characterized in that: include: A power divider, a first power amplifier, a second power amplifier, a first phase shift network, a second phase shift network, a third phase shift network, a first switch, a second switch, and a switching circuit. The input end of the power divider is used to input a radio frequency signal, the first output end of the power divider is electrically connected to the input end of the first power amplifier, the output end of the first power amplifier is electrically connected to the first end of the first phase-shifting network, the second output end of the power divider, the first end of the second phase-shifting network, and the first end of the first switch are electrically connected, the second end of the second phase-shifting network, the input end of the second power amplifier, and the second end of the first switch are electrically connected, the output end of the second power amplifier, the first end of the third phase-shifting network, and the first end of the second switch are electrically connected, and the second end of the third phase-shifting network, the second end of the second switch, and the second end of the first phase-shifting network are electrically connected to a junction point; the third output end of the power divider is electrically connected to the switching circuit; The switching circuit is used for controlling the first switch to be opened and the second switch to be closed if the input power is less than the power threshold; If the input power is greater than the power threshold, controlling the first switch to be closed and controlling the second switch to be opened; The third phase shift network is used to perform impedance transformation on the load impedance of the second power amplifier to increase the impedance of the combining point.

2. The circuit according to claim 1, characterized in that The power threshold is the power output from the third output end of the power divider when the load impedance of the second power amplifier is equal to the characteristic impedance of the third phase shift network.

3. The circuit according to any one of claims 1 to 2, characterized in that: The switching circuit includes a power voltage conversion module, a first comparator, and a second comparator. The input end of the power voltage conversion module is electrically connected to the third output end of the power divider; the output end of the power voltage conversion module is electrically connected to the first input end of the first comparator and the second input end of the second comparator, the second input end of the first comparator and the first input end of the second comparator input a reference voltage, the output end of the first comparator is electrically connected to the control end of the first switch, and the output end of the second comparator is electrically connected to the control end of the second switch; the power voltage conversion module is used to convert input power into voltage; if the output voltage of the power voltage conversion module is less than the reference voltage, the first comparator controls the first switch to be disconnected, and the second comparator controls the second switch to be closed; if the output voltage of the power voltage conversion module is greater than the reference voltage, the first comparator controls the first switch to be closed, and the second comparator controls the second switch to be disconnected.

4. The circuit according to any one of claims 1 to 2, characterized in that: The switching circuit includes a power voltage conversion module, a first comparator, and an inverter. The input end of the power voltage conversion module is electrically connected to the third output end of the power splitter; the output end of the power voltage conversion module is electrically connected to the first input end of the first comparator, and a reference voltage is input to the second input end of the first comparator; the output end of the first comparator, the control end of the first switch, and the input end of the inverter are electrically connected, and the output end of the inverter is electrically connected to the control end of the second switch; the power voltage conversion module is used to convert the input power into voltage; if the voltage output by the power voltage conversion module is less than the reference voltage, the first comparator controls the first switch to disconnect, and the inverter controls the second switch to close; if the voltage output by the power voltage conversion module is greater than the reference voltage, the first comparator controls the first switch to close, and the inverter controls the second switch to disconnect.

5. The circuit according to claim 3, characterized in that The reference voltage is equal to P2*F1*F2, where P2 is the power output by the second output end of the power splitter when the load impedance of the second power amplifier is equal to the characteristic impedance of the third phase shifter network, F1 is the ratio of the power output by the third output end of the power splitter to the power output by the second output end, and F2 is the conversion coefficient of the power voltage conversion module to convert the input power into voltage.

6. The circuit according to any one of claims 1 to 2, characterized in that: The characteristic impedance Z of the first phase shifter network and the third phase shifter network satisfies Ropt < Z < sqrt(2Rt*Ropt), where Ropt is the load impedance when the first power amplifier and the second power amplifier are saturated, sqrt is the square root, and Rt is the target impedance of the output end of the power amplifier circuit; the power amplifier circuit further includes a matching network, the first end of the matching network is electrically connected to the combining point, and the second end of the matching network is used to output a radio frequency signal.

7. The circuit according to any one of claims 1 to 2, characterized in that: The characteristic impedance Z of the first phase shifter network and the third phase shifter network satisfies Z = sqrt(2Rt*Ropt), where Ropt is the load impedance when the first power amplifier and the second power amplifier are saturated, sqrt is the square root, and Rt is the target impedance of the output end of the power amplifier circuit, and the combining point is not connected to the matching network.

8. The circuit according to any one of claims 1 to 2, characterized in that: The first switch and the second switch are fabricated using silicon-on-insulator technology or pseudomorphic high electron mobility transistor technology.

9. An electronic device, characterized in that: It includes an antenna and the power amplifier circuit according to any one of claims 1-8, and the power amplifier circuit is used to output a power-amplified radio frequency signal to the antenna.

Images