Switch adaptive biasing circuit

Abstract

The invention relates to a switch adaptive bias circuit, which belongs to the technical field of radio frequency integrated circuits, is used for adjusting the bias state of a power amplification circuit, and comprises a linear bias module, a temperature compensation module and a switch control module, the linear bias module, the temperature compensation module and the switch control module are connected in sequence; the bias current output end of the linear bias module is connected with the base electrode of a power transistor of the power amplification circuit, and the linear bias module is used for outputting bias current to adjust the linearity of the power transistor; the temperature compensation module is used for suppressing the temperature drift of the power amplification circuit so as to realize temperature compensation; and the switch control module is provided with a switch control transistor, and an emitter of the switch control transistor is used as a switch interface. According to the invention, the linear bias module, the temperature compensation module and the switch control module are integrated, so that the integration level of the self-adaptive bias circuit is improved; the on and off of the switch self-adaptive bias circuit are realized through the control voltage of the switch interface, and wide-range stable switch regulation and control are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency integrated circuits, and particularly relates to a switch adaptive bias circuit. Background Art

[0002] With the advent of the 5G era, the rapid development of modern communication technologies has promoted the rapid progress and application of radio frequency and microwave integration technologies. As a core component of radio frequency transceiver systems, radio frequency power amplifiers play an important role in many fields such as electronic devices and radars. They are crucial modules in high-speed communication systems and determine the performance of the entire radio frequency system. At the same time, the high-speed development of modern communication technologies has also posed challenges to circuit design, making the design of performance indicators such as the gain, additional efficiency, linearity, and bandwidth of radio frequency circuits increasingly difficult.

[0003] As a current supply unit of the power amplifier, the bias circuit provides a suitable static operating point for the transistor and determines the operating state of the entire circuit. The widely commercialized GaAs HBT (Heterojunction Bipolar Transistor) currently has the disadvantages of poor thermal conductivity and obvious temperature effects. Moreover, due to the sharp increase in temperature, it will lead to the deterioration of the transistor current, which has an adverse impact on the performance indicators of the entire circuit. In addition, when the input power of the radio frequency circuit increases, due to the rectifying effect of the diode, the base voltage of the transistor will drift, thereby reducing the circuit linearity. And the power amplifier does not work at the maximum power for a long time, which requires the radio frequency circuit to have high efficiency within a wide range of powers. To solve this problem, an adaptive bias circuit is often used to adjust the bias point of the transistor, thereby optimizing the performance of the overall circuit.

[0004] With the progress of semiconductor technology, radio frequency power amplifier chips are developing towards miniaturization and integration. Combining the switching function with the adaptive bias circuit helps to achieve the miniaturization and multi-functionality of the circuit. However, the fluctuation of the switching voltage in the switch adaptive bias circuit will cause the drift of the bias operating point, thereby leading to the fluctuation of the overall circuit performance. The switching current will also change with the change of the switching voltage, thereby affecting the circuit power consumption and efficiency and affecting the stability of the switching control. Therefore, an adaptive bias circuit capable of achieving stable wide-range switching control is needed. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a switch adaptive bias circuit. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0006] The present invention provides a switch adaptive bias circuit for adjusting the bias state of a power amplifier circuit, including: a linear bias module, a temperature compensation module, and a switch control module; wherein, the linear bias module, the temperature compensation module, and the switch control module are connected in sequence; the bias current output terminal of the linear bias module is connected to the base of the power transistor of the power amplifier circuit, and is used to output a bias current to adjust the linearity of the power transistor; the temperature compensation module is used to suppress the temperature drift of the power amplifier circuit to achieve temperature compensation; the switch control module is provided with a switch control transistor, and the emitter of the switch control transistor is used as a switch interface, and the on and off of the switch adaptive bias circuit is realized through the control voltage of the switch interface.

[0007] In an embodiment of the present invention, the linear bias module includes: transistor Q4, transistor Q5, capacitor C1, resistor R4, and resistor R5; wherein, the base of transistor Q4 is connected to the base of transistor Q5; the collector of transistor Q4 is connected to the collector of transistor Q5; the emitter of transistor Q4 is connected to the emitter of transistor Q5; the first plate of capacitor C1 is connected to the base of transistor Q4, and the second plate is connected to the ground terminal; the first end of resistor R4 is used as the bias voltage control terminal, and the second end is connected to the collector of transistor Q4; the first end of resistor R5 is connected to the emitter of transistor Q4, and the second end is used as the bias current output terminal to output a bias current.

[0008] In an embodiment of the present invention, several transistors are connected in parallel with transistor Q4 in the linear bias module to adjust the magnitude of the bias current.

[0009] In an embodiment of the present invention, the temperature compensation module includes: transistor Q1, transistor Q2, resistor R1, resistor R2, and resistor R3; wherein, the base of transistor Q2 is connected to the base of transistor Q4; the collector of transistor Q2 is connected to the collector of transistor Q5; the first end of resistor R2 is connected to the emitter of transistor Q2, and the second end is connected to the base of transistor Q1; the first end of resistor R1 is connected to the emitter of transistor Q1, and the second end is connected to the ground terminal; the first end of resistor R3 is connected to the collector of transistor Q1, and the second end is used as the voltage control terminal.

[0010] In one embodiment of the present invention, the switch control module includes a switch control transistor Q3, a resistor R6, and a resistor R7. Among them, the base of the switch control transistor Q3 is connected to the base of the transistor Q2. The first end of the resistor R6 is connected to the emitter of the switch control transistor Q3, and the second end serves as a switch voltage control terminal for inputting a control voltage. The first end of the resistor R7 is connected to the collector of the transistor Q3, and the second end is connected to the collector of the transistor Q1.

[0011] In one embodiment of the present invention, the second end of the resistor R6 serves as a switch voltage control terminal and is connected to the ground terminal.

[0012] In one embodiment of the present invention, the size of the switch control transistor Q3 is the same as the sizes of the other transistors in the switch adaptive bias circuit.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] The switch adaptive bias circuit of the present invention integrates a linear bias module, a temperature compensation module, and a switch control module, improving the integration degree of the adaptive bias circuit. At the same time, the emitter of the switch control transistor in the switch control module is used as a switch interface, and the on / off of the switch adaptive bias circuit is realized through the control voltage of the switch interface, achieving wide-range and stable switch control.

[0015] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of the present invention more obvious and understandable, the following specific preferred embodiments are given and described in detail in conjunction with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. is a schematic structural diagram of a switch adaptive bias circuit provided by an embodiment of the present invention;

[0017] Figure 2 FIG. is a schematic structural diagram of a multi-stage Doherty circuit for switch adaptive bias control provided by an embodiment of the present invention;

[0018] Figure 3 FIG. is a schematic structural diagram of a switch adaptive bias circuit at a class C operating bias point provided by an embodiment of the present invention;

[0019] Figure 4 FIG. is a schematic diagram showing the change of the base voltage Vbe of a power transistor with the control voltage Ven provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, a switch adaptive bias circuit proposed according to the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0021] The above and other technical contents, features and effects of the present invention are clearly presented in the following detailed description of the specific implementation modes in conjunction with the accompanying drawings. Through the description of the specific implementation modes, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and explanation purposes and are not used to limit the technical solutions of the present invention.

[0022] Embodiment 1

[0023] like Figure 1 As shown, the present invention provides a switch adaptive bias circuit for adjusting the bias state of a power amplifier circuit, comprising: a linear bias module 100, a temperature compensation module 200 and a switch control module 300; wherein the linear bias module 100, the temperature compensation module 200 and the switch control module 300 are connected in sequence; the bias current output end of the linear bias module 100 is connected to the base of the power transistor of the power amplifier circuit, and is used to output the bias current to adjust the linearity of the power transistor; the temperature compensation module 200 is used to suppress the temperature drift of the power amplifier circuit to achieve temperature compensation; the switch control module 300 is provided with a switch control transistor, and the emitter of the switch control transistor is used as a switch interface, and the switch adaptive bias circuit is turned on and off by the control voltage of the switch interface.

[0024] In the switch adaptive bias circuit of this embodiment, the principle of achieving stable wide-range switch regulation is that the bias current output end of the linear bias module 100 is connected to the base of the power transistor of the power amplifier circuit. When the control voltage of the switch interface (switch voltage control end) is low voltage, the switch control transistor is turned on, and the bias current is drained, so that its base voltage is less than the normal working voltage of the switch adaptive bias circuit, and finally the switch adaptive bias circuit is turned off; and when the control voltage of the switch interface is high voltage (but not enough to break down the switch control transistor), the switch control transistor does not work, and has no draining effect on the bias current. The change of the control voltage within the range greater than its voltage threshold has no effect on the switch adaptive bias circuit, that is, the working state of the switch adaptive bias circuit does not change with the change of the control voltage, so the switch adaptive bias circuit can maintain a normal working state. Therefore, by controlling the working state of the switch control transistor through the control voltage, a wide range and stable switch regulation of the switch adaptive bias circuit can be achieved.

[0025] In other words, through the control of the control voltage Ven of the switch interface formed at the emitter of the transistor Q3, a wide-range stable switch regulation of the adaptive bias circuit is achieved. In addition, by combining the adaptive bias circuit with the switch regulation, on the one hand, the integration degree of the circuit is improved, and on the other hand, an adaptive bias with stable wide-range switch regulation can be realized.

[0026] In an alternative embodiment, the linear bias module 100 includes: a transistor Q4, a transistor Q5, a capacitor C1, a resistor R4, and a resistor R5; wherein, the base of the transistor Q4 is connected to the base of the transistor Q5; the collector of the transistor Q4 is connected to the collector of the transistor Q5; the emitter of the transistor Q4 is connected to the emitter of the transistor Q5; the first plate of the capacitor C1 is connected to the base of the transistor Q4, and the second plate is connected to the ground terminal; the first end of the resistor R4 serves as a bias voltage control terminal, and the second end is connected to the collector of the transistor Q4; the first end of the resistor R5 is connected to the emitter of the transistor Q4, and the second end serves as a bias current output terminal to output a bias current.

[0027] It should be noted that the magnitude of the bias current can also be flexibly adjusted by adjusting the number of transistors connected in parallel in the linear bias module; for example, in the linear bias module 100, in addition to the transistors Q4 and Q5 connected in parallel, several other transistors are also connected in parallel to flexibly adjust the magnitude of the bias current.

[0028] In an alternative embodiment, the temperature compensation module 200 includes: a transistor Q1, a transistor Q2, a resistor R1, a resistor R2, and a resistor R3; wherein, the base of the transistor Q2 is connected to the base of the transistor Q4; the collector of the transistor Q2 is connected to the collector of the transistor Q5; the first end of the resistor R2 is connected to the emitter of the transistor Q2, and the second end is connected to the base of the transistor Q1; the first end of the resistor R1 is connected to the emitter of the transistor Q1, and the second end is connected to the ground terminal; the first end of the resistor R3 is connected to the collector of the transistor Q1, and the second end serves as a voltage control terminal.

[0029] In an alternative embodiment, the switch control module 300 includes: a switch control transistor Q3, a resistor R6, and a resistor R7; wherein, the base of the switch control transistor Q3 is connected to the base of the transistor Q2; the first end of the resistor R6 is connected to the emitter of the switch control transistor Q3, and the second end serves as a switch voltage control terminal to input a control voltage; the first end of the resistor R7 is connected to the collector of the transistor Q3, and the second end is connected to the collector of the transistor Q1.

[0030] The working principle of the switch adaptive bias circuit in this embodiment is that when the RF input power of the power amplifier circuit increases, due to the rectifying effect of the power transistor, the DC current increases, but the base voltage of the power transistor (not shown in the figure) connected to the bias current terminal Ib is limited. When the RF signal enters the linear bias module, due to the rectifying effect, the voltage between the base and emitter of transistor Q4 decreases and the current increases. Capacitor C1 conducts the RF signal to ground, thereby compensating the base voltage of the power transistor and keeping its bias operating point stable at high input power, thus achieving adaptive adjustment. At the same time, the addition-emitter biasing effect formed by transistor Q2 and transistor Q4 reduces the shunting of the base current to the reference current; and by adjusting the number of transistors connected in parallel with transistor Q4, the bias current can be flexibly adjusted. For example, when 4 transistors are connected in parallel compared with the case of 2 transistors connected in parallel, the bias current will be significantly increased.

[0031] Since the switch adaptive bias circuit has the same temperature characteristics as the power transistor, it maximally suppresses the temperature drift when the temperature rises. At the same time, resistor R5 also suppresses the current collapse effect of the transistor, further improving the temperature stability of the circuit.

[0032] Taking the emitter terminal of the switch control transistor Q3 as the switch interface, when the control voltage Ven of the switch interface is low voltage (such as 0 to 0.3V), the switch control transistor Q3 conducts, and the current of the bias control terminal Vctrl flows into the switch control transistor Q3, making its base voltage less than the normal operating voltage of the switch adaptive bias circuit, and the other transistors in the switch adaptive bias circuit do not work, and the switch adaptive bias circuit is turned off. When the control voltage Ven is high voltage (such as 2.05 to 6V) and does not break down the transistor, the switch control transistor Q3 does not work and has no diversion effect on the bias current. The change of the control voltage within the range greater than its voltage threshold has no influence on the switch adaptive bias circuit, and the switch adaptive bias circuit can work normally. At the same time, resistors R6 and R7 limit the current of the switch control transistor Q3 to protect the transistor from being broken down.

[0033] The switch adaptive bias circuit of the present invention integrates the linear bias module, the temperature compensation module and the switch control module into one body, improving the integration degree of the adaptive bias circuit; at the same time, taking the emitter of the switch control transistor in the switch control module as the switch interface, and realizing the opening and closing of the switch adaptive bias circuit through the control voltage of the switch interface, achieving wide-range stable switch control.

[0034] Embodiment 2

[0035] On the basis of Embodiment 1, this embodiment provides an application embodiment of a novel switch adaptive bias circuit in a multi-stage Doherty circuit, and the circuit structure is asFigure 2 As shown, it includes input matching, a first-stage power amplifier, a second-stage power amplifier, a power divider, a carrier power amplifier, a peak power amplifier, and output matching. Each power amplifier is connected with a switch adaptive bias circuit;

[0036] Among them, the input end of the input matching is connected to the radio frequency signal to be amplified, and its output end is connected to the input end of the first-stage power amplifier; the output end of the first-stage power amplifier is connected to the input end of the second-stage power amplifier; the output end of the second-stage power amplifier is connected to the input end of the power divider; the two output ends of the power divider are respectively connected to the input ends of the carrier power amplifier and the peak power amplifier; the carrier power amplifier and the peak power amplifier are in parallel, and their output ends are both connected to the output matching; the output end of the output matching outputs the amplified radio frequency signal.

[0037] In this embodiment, the structures of the switch adaptive bias circuits of the first-stage power amplifier, the second-stage power amplifier, and the carrier power amplifier are the same, as Figure 3 shown, Figure 3 which is a schematic diagram of the structure of the switch adaptive bias circuit of the class-C operating bias point provided by the embodiment of the present invention.

[0038] Specifically, the bias current output ends of each switch adaptive bias circuit are respectively connected to the bases of each power amplifier. By adjusting the number of transistors connected in parallel with the transistor Q4, and by adjusting the magnitudes of the resistor R2, the resistor R3, and the resistor R4, the magnitude of the bias current Ib can be flexibly controlled. The voltage control end Vctrl and the bias voltage control end Vbias of each switch adaptive bias circuit are both connected to the VBIAS end, and the switch voltage control end is connected to the VEN end.

[0039] It can be understood that according to the different magnitudes of the required current, in the switch adaptive bias circuits of the first-stage power amplifier, the second-stage power amplifier, and the carrier power amplifier, the resistance values of the respective resistors and the sizes of the transistors can be correspondingly selected and adjusted.

[0040] Furthermore, the structural diagram of the switch adaptive bias circuit of the peak power amplifier is as Figure 3 shown. Due to the structural characteristics of the Doherty circuit, the peak power amplifier needs to operate in the class-C bias state. Therefore, by grounding the switch control end, the switch control transistor Q3 is always turned on, and the size and various parameters of the switch control transistor Q3 are selected to be the same as those of the other transistors in the switch adaptive bias circuit, so as to provide a class-C static operating point for the peak power amplifier.

[0041] In other words, the second end of the resistor R6 is used as the switch voltage control end and is connected to the ground end; at the same time, the size of the switch control transistor Q3 is set to be the same as the size of the other transistors in the switch adaptive bias circuit.

[0042] The switch control terminals of each switch adaptive bias circuit are all connected to the VEN terminal (the end where the bias circuit is connected to the outside). When the VEN terminal is connected to a high voltage and the transistor is not broken down, the switch control transistor Q3 does not work and has no drainage effect on the bias current. When the switch voltage changes within the range greater than its voltage threshold, it has no effect on the bias circuit, and the adaptive bias circuit can work normally. When the VEN terminal is connected to a low voltage, the switch control transistor Q3 conducts, which has a drainage effect on the bias current, and the other transistors in the switch adaptive bias circuit do not work, and the switch adaptive bias circuit is turned off. In a multi-stage power amplifier circuit, the switch adaptive bias circuit turns off each stage of the power amplifier step by step, and finally completely turns off the entire Doherty power amplifier circuit.

[0043] The switch adaptive bias circuit is designed using a 0.1μm GaAs HBT process. The sizes of the transistors in the bias circuit are all selected as 4-finger HBT devices with an emitter width of 2μm and an emitter length of 12μm. The current-limiting resistors R1, R4, R6, and R7 are all selected as 10Ω. The magnitude of the required current is achieved by adjusting the values of the remaining resistors. As Figure 4 shown, Figure 4 is a schematic diagram of the change of the base voltage Vbe of the power transistor with the control voltage Ven provided by the embodiment of the present invention. The switch voltage Ven is connected to the VEN terminal. When the switch voltage Ven is less than the threshold Voff = 0.3V, the circuit is turned off and does not work; when the switch voltage Ven is greater than the threshold Von = 2.05V, the circuit is turned on and works normally; the intermediate transition state is an abnormal working state.

[0044] When the control voltage Ven is less than Voff, the switch adaptive bias circuit is turned off and the overall circuit does not work; when the control voltage Ven is greater than Von, the switch adaptive bias circuit is turned on and the overall circuit works normally, and the working state of the circuit is not affected by the change of the switch voltage. By controlling the emitter voltage of the switch control transistor Q3, a wide-range and stable switch control of the switch adaptive bias circuit can be achieved.

[0045] It should be noted that through the switch adaptive bias circuit of this embodiment, a stable wide-range switch control can be achieved, that is, a stable wide-range adjustment is achieved during the switch control process.

[0046] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant is intended to cover non-exclusive inclusion, so that an article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the article or device comprising said element. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The orientation or positional relationship indicated by "above", "below", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention.

[0047] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A switch adaptive bias circuit for adjusting the bias state of a power amplifier circuit, characterized in that: include: A linear bias module (100), a temperature compensation module (200) and a switch control module (300); Wherein, the linear bias module (100), the temperature compensation module (200) and the switch control module (300) are connected in sequence; The bias current output end of the linear bias module (100) is connected to the base of the power transistor of the power amplifier circuit, and is used to output the bias current to adjust the linearity of the power transistor; The temperature compensation module (200) is used to suppress the temperature drift of the power amplifier circuit to achieve temperature compensation; The switch control module (300) is provided with a switch control transistor, the emitter of the switch control transistor is used as a switch interface, and the switch adaptive bias circuit is turned on and off through the control voltage of the switch interface.

2. The switch adaptive bias circuit according to claim 1, characterized in that: The linear bias module (100) comprises: a transistor Q4, a transistor Q5, a capacitor C1, a resistor R4 and a resistor R5; wherein the base of the transistor Q4 is connected to the base of the transistor Q5; the collector of the transistor Q4 is connected to the collector of the transistor Q5; the emitter of the transistor Q4 is connected to the emitter of the transistor Q5; the first plate of the capacitor C1 is connected to the base of the transistor Q4, and the second plate is connected to the ground; the first end of the resistor R4 serves as a bias voltage control end, and the second end is connected to the collector of the transistor Q4; the first end of the resistor R5 is connected to the emitter of the transistor Q4, and the second end serves as a bias current output end to output the bias current.

3. The switch adaptive bias circuit according to claim 2, characterized in that: In the linear bias module (100), the transistor Q4 is also connected in parallel with a plurality of transistors to adjust the magnitude of the bias current.

4. The switch adaptive bias circuit according to claim 2, characterized in that: The temperature compensation module (200) comprises: a transistor Q1, a transistor Q2, a resistor R1, a resistor R2 and a resistor R3; wherein the base of the transistor Q2 is connected to the base of the transistor Q4; the collector of the transistor Q2 is connected to the collector of the transistor Q5; the first end of the resistor R2 is connected to the emitter of the transistor Q2, and the second end is connected to the base of the transistor Q1; the first end of the resistor R1 is connected to the emitter of the transistor Q1, and the second end is connected to the ground end; the first end of the resistor R3 is connected to the collector of the transistor Q1, and the second end serves as a voltage control end.

5. The switch adaptive bias circuit according to claim 4, characterized in that: The switch control module (300) comprises: a switch control transistor Q3, a resistor R6 and a resistor R7; wherein the base of the switch control transistor Q3 is connected to the base of the transistor Q2; the first end of the resistor R6 is connected to the emitter of the switch control transistor Q3, and the second end serves as a switch voltage control end to input a control voltage; the first end of the resistor R7 is connected to the collector of the transistor Q3, and the second end is connected to the collector of the transistor Q1.

6. The switch adaptive bias circuit according to claim 5, characterized in that: The second end of the resistor R6 serves as a switch voltage control end and is connected to the ground end.

7. The switch adaptive bias circuit according to claim 5, characterized in that: The size of the switch control transistor Q3 is the same as the size of the remaining transistors in the switch adaptive bias circuit.

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