Self-adaptive linearization biasing circuit and radio frequency power amplifier

Abstract

The invention provides a self-adaptive linearization biasing circuit, which belongs to the field of radio frequency power amplifiers and comprises triodes Q1-Q4, a base ballast resistor R0, resistors R1-R2, a biasing resistor R3 and a linear capacitor C0. The base of a triode Q2 is connected to the base of the triode Q1, one end of the resistor R2 and one end of the linear capacitor C0. A base electrode and a collector electrode of the triode Q2 are connected and then connected to one end of the bias resistor R3, the other end of the resistor R3 is connected with reference voltage, an emitting electrode of the triode Q2 is connected to a collector electrode of the triode Q3, a base electrode of the triode Q3 is connected to the other end of the resistor R2, a collector electrode of the triode Q4 and a base electrode of the triode Q4 are connected to one end of the resistor R1, and a collector electrode of the triode Q1 is connected with bias voltage. The emitter of the triode Q1 is connected to one end of a base ballast resistor R0, and the other end of the base ballast resistor R0 is connected with the other end of the resistor R1 and then serves as the output end of the biasing circuit; a radio frequency power amplifier is also provided. The adjustable range of the bias resistor is widened, and the compensation effect of nonlinear distortion is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency power amplifiers, and particularly to an adaptive linearization bias circuit and a radio frequency power amplifier. Background Art

[0002] With the development of the fifth-generation mobile communication technology 5G, higher requirements are put forward for performance indicators such as the linearity and efficiency of radio frequency power amplifiers. In order to improve the signal transmission rate, 5G adopts a signal modulation technology with higher spectrum utilization rate. While the new modulation technology improves the transmission rate, it also increases the distortion of the signal, bringing serious signal nonlinear distortion to the radio frequency front end. Therefore, in order to avoid the distortion of the transmitted signal, the output power of the radio frequency power amplifier is usually backed off, sacrificing the working efficiency to provide linear amplification. Therefore, the linearity and output power of the radio frequency power amplifier restrict each other. When designing a radio frequency power amplifier, a certain trade-off needs to be made between the two indicators to obtain more balanced performance.

[0003] Currently, the widely used technical solution is to adopt a traditional adaptive linearization bias circuit, such as Figure 1 shown, a current mirror structure is constructed by transistors in the bias circuit. Through the clamping effect of the diode and connecting a capacitor C0 in parallel to the base of the transistor, the bias circuit can compensate for the radio frequency signal and improve the linearity of the output signal of the radio frequency power amplifier. However, this bias circuit is not sensitive to the temperature change of the power triode, and the temperature compensation effect is average. In addition, the capacitance value of the capacitor C0 in this bias circuit is usually large, so the layout area of the capacitor C0 is also large, making this bias circuit occupy a large layout area.

[0004] In the prior art, the Chinese patent application for invention "A Linearization Bias Circuit and a Radio Frequency Power Amplifier" with the publication number CN112543004A discloses a linearization bias circuit, including a first triode Q1, a second triode Q2, a third triode Q3, a first resistor R1, a base ballast resistor R0, a fourth resistor R4, a second capacitor C2, and an RC circuit. By introducing the structure of a current mirror, temperature compensation is performed for the problem of heat generation at high power. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to improve the temperature compensation effect when the radio frequency power amplifier works at high output power and reduce signal distortion.

[0006] The present invention solves the above technical problems through the following technical solutions: an adaptive linearization bias circuit, which includes transistors Q1-Q4, a base ballast resistor R0, resistors R1-R2, a bias resistor R3, and a linear capacitor C0. The base of transistor Q2 is connected to the base of transistor Q1, one end of resistor R2, and one end of linear capacitor C0. After the base and collector of transistor Q2 are connected, they are connected to one end of bias resistor R3. The other end of bias resistor R3 is connected to a reference voltage. The emitter of transistor Q2 is connected to the collector of transistor Q3. The base of transistor Q3 is connected to the other end of resistor R2 and the collector of transistor Q4. The emitters of transistors Q3 and Q4 and the other end of linear capacitor C0 are all grounded. The base of transistor Q4 is connected to one end of resistor R1. The collector of transistor Q1 is connected to a bias voltage. The emitter of transistor Q1 is connected to one end of base ballast resistor R0. The other end of base ballast resistor R0 is connected to the other end of resistor R1 and serves as the output terminal of the bias circuit.

[0007] Beneficial effects: The present invention utilizes Kirchhoff's law of transistor Q2. By adding resistor R2 between the base of transistor Q2 and the base of transistor Q3, when resistor R2 is increased, the collector-emitter voltage V of transistor Q2 be2 increases, causing the voltage shared by bias resistor R3 to decrease, expanding the selection range of bias resistor R3. Since bias resistor R3 is located at the total node of the bias current generated by the bias circuit, when the power amplifier operates at high power and causes nonlinear distortion, the increased current in the bias circuit causes the voltage drop across bias resistor R3 to increase, and the base voltage V of transistor Q1 b1 decreases, and this time the bias current decreases. It can be seen that the resistance value of bias resistor R3 is related to both the temperature compensation effect of the bias circuit and the magnitude of the bias current provided by the bias circuit. Therefore, increasing the adjustable range of bias resistor R3 can better select the appropriate resistance value of bias resistor R3, and thus can improve the compensation effect of the bias circuit on nonlinear distortion. The bias circuit of the present invention can maintain the stability of the static operating point when the temperature and the input signal power change, and improve the signal distortion problem in the high-power operating state of the power amplifier.

[0008] Preferably, transistors Q2-Q4, resistors R1-R2, and bias resistor R3 form a temperature feedback circuit structure.

[0009] Beneficial effects: Transistors Q2, Q3, Q4, resistors R1, R2, and bias resistor R3 form a temperature feedback circuit structure. When the input signal power increases, the temperature of power transistor Q0 rises, the base current of power transistor Q0 increases, and the static operating point shifts. At this time, the temperature of transistor Q4, which is relatively close to power transistor Q0, also rises. The B-E junction voltages V of power transistor Q0 and transistor Q4 beThe temperature change amount is the same. Due to the existence of resistor R1, the base voltage of triode Q4 drops significantly, so the collector current of triode Q4 increases significantly. At this time, the base current of triode Q3 increases, resulting in an increase in the collector current of triode Q3. Finally, the current fed back to bias resistor R3 increases, causing the voltage drop across bias resistor R3 to increase, thereby reducing the base voltage of triode Q1 and the emitter current of triode Q1. Therefore, the bias current flowing to power triode Q0 is reduced, preventing the static operating point from shifting, achieving more sensitive temperature compensation for the heating problem during high-output-power operation, suppressing the temperature drift of the static operating point, and simultaneously improving the distortion of the transmitted signal under the condition of high output power of the RF power amplifier.

[0010] The present invention also provides an RF power amplifier, including the adaptive linearization bias circuit described above. The amplifier further includes an RF amplification unit, which includes a power triode Q0 and an input matching circuit. The input end of the input matching circuit serves as the RF signal input end. The base of power triode Q0 is respectively connected to the output end of the bias circuit and the output end of the input matching circuit. The emitter of power triode Q0 is grounded, and the collector serves as the RF signal output end.

[0011] Beneficial effects: In the RF power amplifier of the present invention, when the input signal power increases, due to the parasitic resistance of the transistor, the base voltage V of power triode Q0 b0 decreases, and the base-emitter voltage V of triode Q1 be1 also decreases. Linear capacitor C0 keeps the base voltage V of triode Q1 b1 stable, making the emitter voltage V of triode Q1 e1 increase, compensating for the decrease in the base voltage V of power triode Q0 b0 , stabilizing the static operating point, playing a role of linear compensation, and reducing the distortion of the transmitted signal. Due to the existence of resistor R1 and triode Q4, a part of the RF signal coupled into the bias circuit is shared, and a part of the RF signal coupled into the bias circuit is leaked to the ground, thereby reducing the RF signal coupled into triode Q1 and linear capacitor C0. Since the RF signals coupled into triode Q1 and linear capacitor C0 are both leaked to the ground by linear capacitor C0, the requirement for the capacitance value of linear capacitor C0 can be reduced, and thus the area of the bias circuit can be reduced.

[0012] Preferably, the input matching circuit includes a capacitor C1. One end of capacitor C1 serves as the RF signal input end, and the other end is connected to the base of power triode Q0.

[0013] Preferably, the RF amplification unit further includes an output matching circuit. The collector of the power triode Q0 is connected to the input end of the output matching circuit, and the output end of the output matching circuit serves as the RF signal output end.

[0014] Preferably, the RF amplification unit further includes an RF choke L. One end of the RF choke L is connected to the collector of the power triode Q0, and the other end is connected to the DC supply voltage.

[0015] Preferably, the distance between the triode Q4 and the power triode Q0 is less than the distances between other components in the circuit and the power triode Q0.

[0016] Beneficial effects: By placing the triode Q4 beside the power triode Q0 in the present invention, the triode Q4 changes as the temperature of the power triode Q0 changes, improving the sensitivity of the RF power amplifier to temperature perception.

[0017] Preferably, the power triode Q0 and the triodes Q1 - Q4 are all heterojunction bipolar transistors made of gallium arsenide material.

[0018] Preferably, the linear capacitor C0 and the capacitor C1 are both parallel - plate capacitors made of gallium arsenide material.

[0019] Preferably, the base ballast resistor R0, the resistors R1, R2, and the bias resistor R3 are all thin - film resistors made by gallium arsenide process. Description of the Drawings

[0020] Figure 1 It is the circuit diagram of an RF power amplifier using a traditional linearization bias circuit;

[0021] Figure 2 It is the circuit diagram of the RF power amplifier provided by the embodiment of the present invention;

[0022] Figure 3 It is the effect diagram of the improvement of the signal distortion problem by the adaptive linearization bias circuit provided by the embodiment of the present invention. Detailed Embodiments

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the following combines specific embodiments and refers to the drawings to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] Figure 1The circuit diagram of a radio frequency power amplifier using a traditional linearized bias circuit. The bias circuit includes two transistors Q2 and Q3 connected in the form of diodes, a linear capacitor C0, and a driving transistor Q1. Transistors Q1 and Q2 form a mirror current source to provide a bias current for the power amplifier transistor Q0. As the radio frequency power increases, the DC current of the power amplifier transistor Q0 increases. Due to the self-heating effect of the transistor and the rectification effect of the B-E diode of the power amplifier transistor Q0, the base potential of the power amplifier transistor Q0 will decrease. At the same time, a small part of the radio frequency power will leak into the bias circuit. After passing through the transistor Q1, it is bypassed to the ground by the linear capacitor C0. Therefore, the base potential of the transistor Q1 will remain unchanged. The leaked power causes the DC current of the transistor Q1 to increase, and the DC rectification of the transistor Q1 causes the DC component of the B-E junction voltage to decrease. Since the base potential of the transistor Q1 remains unchanged, the emitter potential of the transistor Q1 is raised, and the base potential of the power amplifier transistor Q0 is compensated. However, the problems of this bias circuit are: it is not sensitive to the temperature change of the power amplifier transistor Q0, the temperature compensation effect is average, and the capacitance value of the linear capacitor C0 in this bias circuit is usually large, resulting in a large layout area for the linear capacitor C0, and further causing this bias circuit to occupy a large layout area.

[0025] To solve the problems that the bias circuit in the existing radio frequency power amplifier is not sensitive to the temperature change of the power amplifier transistor and the temperature compensation effect is average, the present invention provides an adaptive linearized bias circuit and a circuit of a radio frequency power amplifier including this bias circuit. The circuit setting and working principle of the present invention will be introduced in detail below: Figure 2 As shown, the following will introduce the circuit setting and working principle of the present invention in detail:

[0026] Refer to Figure 2 , the radio frequency power amplifier includes an adaptive linearized bias circuit and a radio frequency amplification unit. Among them, the adaptive linearized bias circuit includes: a triode Q1, a triode Q2, a triode Q3, a triode Q4, a base ballast resistor R0, a resistor R1, a resistor R2, a bias resistor R3, and a linear capacitor C0. The base of the triode Q2 is respectively connected to the base of the triode Q1, one end of the resistor R2, and one end of the linear capacitor C0. After the base and the collector of the triode Q2 are connected, they are connected to one end of the bias resistor R3. The other end of the resistor R3 is connected to the reference voltage V reb , the emitter of the triode Q2 is connected to the collector of the triode Q3. The base of the triode Q3 is respectively connected to the other end of the resistor R2 and the collector of the triode Q4. The emitters of the triodes Q3 and Q4 and the other end of the linear capacitor C0 are all grounded. The base of the triode Q4 is connected to one end of the resistor R1. The collector of the triode Q1 is connected to the bias voltage V bat, the emitter of the triode Q1 is connected to one end of the base ballast resistor R0, and the other end of the base ballast resistor R0 is connected to the other end of the resistor R1 and then used as the output end of the bias circuit. The RF amplification unit includes a power triode Q0, an input matching circuit, an output matching circuit, and an RF choke coil L. The input matching circuit is a capacitor C1. One end of the capacitor C1 is used as the RF signal input end. The base of the power triode Q0 is connected to the output end of the bias circuit and the other end of the capacitor C1 respectively. The emitter of the power triode Q0 is grounded. The collector of the power triode Q0 is connected to the input end of the output matching circuit. The output end of the output matching circuit is used as the RF signal output end. One end of the RF choke coil L is connected to the collector of the power triode Q0, and the other end is connected to the DC supply voltage. Among them, the distance between the triode Q4 and the power triode Q0 is less than the distance between other components in the circuit and the power triode Q0.

[0027] The present invention utilizes Kirchhoff's law of the triode Q2. By adding a resistor R2 between the base of the triode Q2 and the base of the triode Q3, when the resistor R2 is increased, the collector-emitter voltage V of the triode Q2 be2 increases, so that the voltage shared by the bias resistor R3 decreases, expanding the selection range of the bias resistor R3. Since the bias resistor R3 is located at the total node of the bias current generated by the bias circuit, when the power amplifier operates at high power and causes nonlinear distortion, the increased current in the bias circuit causes the voltage drop on the bias resistor R3 to increase, and the base voltage V of the triode Q1 b1 decreases, and this time the bias current decreases. It can be seen that the resistance value of the bias resistor R3 is related to both the temperature compensation effect of the bias circuit and the magnitude of the bias current provided by the bias circuit. Therefore, increasing the adjustable range of the bias resistor R3 can better select the appropriate resistance value of the bias resistor R3, and thus can improve the compensation effect of the bias circuit on nonlinear distortion. Compared with the traditional linearized bias circuit, the bias circuit of the present invention can maintain the stability of the static operating point when the temperature and the input signal power change, and improve the signal distortion problem in the high-power operating state of the power amplifier.

[0028] In the adaptive linearized bias circuit of the present invention, the triode Q2, the triode Q3, the triode Q4, the resistor R1, the resistor R2, and the bias resistor R3 form a temperature feedback circuit structure. When the input signal power increases, the temperature of the power triode Q0 increases, the base current of the power triode Q0 increases, and the static operating point shifts. At this time, the temperature of the triode Q4, which is relatively close to the power triode Q0, also increases. The B-E junction voltages V of the power triode Q0 and the triode Q4 beThe change amount is the same with temperature. Due to the existence of resistor R1, the base voltage of triode Q4 drops significantly, so the collector current of triode Q4 increases significantly. At this time, the base current of triode Q3 increases, resulting in an increase in the collector current of triode Q3. Finally, the current fed back to bias resistor R3 increases, causing the voltage drop across bias resistor R3 to increase, thereby reducing the base voltage of triode Q1 and the emitter current of triode Q1. Therefore, the bias current flowing to power triode Q0 is reduced, which will not cause the static operating point to shift, achieving more sensitive temperature compensation for the heating problem in high-output-power operation, suppressing the temperature drift of the static operating point, and at the same time improving the distortion degree of the transmitted signal under the condition of high output power of the RF power amplifier. The present invention selects the values of linear capacitor C0, resistor R2, and bias resistor R3 according to the magnitude of the output power and the operating frequency, which can improve the linearity of the circuit and reduce the distortion of the transmitted signal.

[0029] In the circuit of the RF power amplifier of the present invention, triode Q4 is placed beside power triode Q0, such that triode Q4 changes with the temperature change of power triode Q0. That is, when actually arranging the circuit structure, the distance between triode Q4 and power triode Q0 is less than the distance between other components in the circuit and power triode Q0. To further improve the sensitivity of the RF power amplifier to temperature perception, the present invention can also place both triode Q3 and triode Q4 beside power triode Q0.

[0030] In addition, due to the existence of resistor R1 and triode Q4, a part of the RF signal coupled into the bias circuit is shared, and a part of the RF signal coupled into the bias circuit is leaked to the ground, thereby reducing the RF signal coupled into triode Q1 and linear capacitor C0. Since the RF signals coupled into triode Q1 and linear capacitor C0 are both leaked to the ground by linear capacitor C0 (the existence of linear capacitor C0 stabilizes the base voltage V of triode Q1, compensates for the reduction of the base-emitter voltage of triode Q0, and stabilizes the static operating point), it is possible to reduce the requirement for the capacitance value of linear capacitor C0. Also, because the capacitance value of a capacitor is positively correlated with its area, and the capacitor is the component with the largest area ratio in the bias circuit, the area of the bias circuit can be reduced. b1 ,compensates for the reduction of the base-emitter voltage of triode Q0, and stabilizes the static operating point), so it is possible to reduce the requirement for the capacitance value of linear capacitor C0. Also, because the capacitance value of a capacitor is positively correlated with its area, and the capacitor is the component with the largest area ratio in the bias circuit, the area of the bias circuit can be reduced.

[0031] The output impedance matching circuit (OutputMatch) adopts the maximum output power configuration to enable the RF power amplifier to obtain the maximum output power. Power triode Q0, triode Q1, triode Q2, triode Q3, and triode Q4 all adopt heterojunction bipolar transistors made of gallium arsenide material. Linear capacitor C0 and capacitor C1 both adopt parallel plate capacitors made of gallium arsenide material. Base ballast resistor R0, resistor R1, resistor R2, and bias resistor R3 all adopt thin film resistors made by gallium arsenide process.

[0032] Figure 3 This is the effect diagram of the improvement of the signal distortion problem by the adaptive linearization bias circuit of the present invention, comparing the variation trend of the signal phase distortion (AMPM) of the adaptive linearization bias circuit with different capacitance values with the output power. It can be seen from the figure that first, under the condition of the same capacitance value, the phase distortion AMPM of the transmitted signal of the bias circuit of the present invention is reduced by 0.3° compared with the traditional bias circuit, and the AMPM value is limited within 1.5°. Generally, the technical specifications of radio frequency power amplifiers require that the AMPM value should be within 1.5°. Therefore, the bias circuit of the present invention reduces the signal distortion better than the traditional bias circuit under the same capacitance value and is more likely to meet the performance indicators of radio frequency power amplifiers. Secondly, comparing the effects before and after the improvement of the bias circuit under different capacitance values, for the traditional bias circuit to achieve the same effect of reducing signal distortion as the circuit of the present invention, the capacitance needs to be increased from 2 pF to 8 pF, that is, the capacitance area is enlarged by 3 times. Therefore, for the bias circuit of the present invention to achieve the same effect of reducing signal distortion, the capacitance value of the linear capacitance C0 required is smaller and the capacitance area is smaller than that of the traditional bias circuit.

[0033] The above embodiments are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adaptive linearization bias circuit, characterized in that: The circuit includes transistors Q1-Q4, base ballast resistor R0, resistors R1-R2, bias resistor R3, and linear capacitor C0. The base of transistor Q2 is connected to the base of transistor Q1, one end of resistor R2, and one end of linear capacitor C0. The base of transistor Q2 is connected to the collector and then connected to one end of bias resistor R3. The other end of resistor R3 is connected to a reference voltage. The emitter of transistor Q2 is connected to the collector of transistor Q3. The base of transistor Q3 is connected to the other end of resistor R2 and the collector of transistor Q4. The emitters of transistors Q3 and Q4 and the other end of linear capacitor C0 are all grounded. The base of transistor Q4 is connected to one end of resistor R1. The collector of transistor Q1 is connected to the bias voltage. The emitter of transistor Q1 is connected to one end of base ballast resistor R0. The other end of base ballast resistor R0 is connected to the other end of resistor R1 and serves as the output end of the bias circuit.

2. The adaptive linearization bias circuit according to claim 1, characterized in that: Transistors Q2-Q4, resistors R1-R2, and bias resistor R3 form a temperature feedback circuit structure.

3. A radio frequency power amplifier, characterized in that: The invention comprises the adaptive linearization bias circuit as described in any one of claims 1 to 2, and the amplifier further comprises an RF amplification unit, the RF amplification unit comprises a power transistor Q0 and an input matching circuit, the input end of the input matching circuit serves as an RF signal input end, the base of the power transistor Q0 is respectively connected to the output end of the bias circuit and the output end of the input matching circuit, the emitter of the power transistor Q0 is grounded, and the collector serves as an RF signal output end.

4. The radio frequency power amplifier according to claim 3, characterized in that: The input matching circuit includes a capacitor C1, one end of the capacitor C1 is used as a radio frequency signal input end, and the other end is connected to the base of the power transistor Q0.

5. The radio frequency power amplifier according to claim 3, characterized in that: The radio frequency amplification unit also includes an output matching circuit. The collector of the power transistor Q0 is connected to the input end of the output matching circuit. The output end of the output matching circuit serves as the radio frequency signal output end.

6. The radio frequency power amplifier according to claim 3, characterized in that: The radio frequency amplification unit further includes a radio frequency choke L, one end of the radio frequency choke L is connected to the collector of the power transistor Q0, and the other end is connected to a DC power supply voltage.

7. The radio frequency power amplifier according to claim 3, characterized in that: The distance between the transistor Q4 and the power transistor Q0 is smaller than the distance between other components in the circuit and the power transistor Q0.

8. The radio frequency power amplifier according to claim 3, characterized in that: The power transistor Q0 and transistors Q1-Q4 are all heterojunction bipolar transistors made of gallium arsenide material.

9. The radio frequency power amplifier according to claim 3, characterized in that: The linear capacitor C0 and the capacitor C1 are both parallel plate capacitors made of gallium arsenide material.

10. The radio frequency power amplifier according to claim 3, characterized in that: The base ballast resistor R0, the resistor R1, the resistor R2, and the bias resistor R3 are all thin film resistors made using gallium arsenide technology.

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