Power amplifier linearization circuit

Abstract

The utility model relates to the technical field of radio frequency and microwave, in particular to a linearization circuit of a power amplifier, which comprises the power amplifier used for amplifying an input signal and providing required output power; the bias circuit is used for providing bias voltage for the power amplifier and controlling the change characteristic of a quiescent operating point of the power amplifier along with the temperature and the power; the active feedback circuit comprises a first connection point P1, a second connection point P2 and a third connection point P3, the active feedback circuit effectively reduces nonlinear distortion of the power amplifier through a negative feedback mechanism, and the nonlinear distortion of the power amplifier is effectively reduced by adjusting a first resistor R5, a second resistor R4, a third resistor R1 and a fourth resistor R3. The feedback circuit can be controlled to work in a critical region of a saturation region and a linear region, so that the linearity of the power amplifier can be optimized.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of radio frequency and microwave technology, concretely is power amplifier linearization circuit. BACKGROUND

[0002] With the continuous development of science and technology, the application scenarios of wireless communication systems are becoming more and more rich, from traditional handheld terminals, base stations to star chains, unmanned aerial vehicles and other continuous expansion. Power amplifier is a key device in wireless communication system, responsible for amplifying signals without distortion to expand the capacity and coverage of wireless communication system. With the continuous increase of communication system bandwidth and the complication of modulation mode, the linearity requirement of power amplifier is also higher and higher.

[0003] In practical application, the nonlinear characteristics of power amplifier will cause signal distortion, especially intermodulation distortion (IM3), which will seriously affect the performance of communication system. In order to improve the linearity of power amplifier, one of the commonly used methods is to make power amplifier work in deep backoff state. However, this method will significantly reduce the efficiency of the system, because the power amplifier cannot work at its maximum output power. Therefore, how to improve the linearity of power amplifier while maintaining high efficiency has become a problem to be solved.

[0004] Some existing linearization technologies mainly include pre-distortion, feedforward and auxiliary circuit methods. Among them, Chinese patents CN202310065475.8 and CN202410275267.5 propose a method of generating counter-phase intermodulation product (IM3) through auxiliary circuit to offset the IM3 of power amplifier itself, so as to improve its linearity. Although this method can effectively reduce IM3, it needs additional complex auxiliary circuit to generate counter-phase IM3 signal. This not only increases the cost of the system, but also prolongs the design cycle, making it more difficult to realize. UTILITY MODEL CONTENT

[0005] (I) Technical problem solved

[0006] In view of the deficiencies of the prior art, the utility model provides a power amplifier linearization circuit.

[0007] (II) Technical scheme

[0008] In order to achieve the above purpose, the utility model provides the following technical scheme: the power amplifier linearization circuit of the utility model, comprising:

[0009] A power amplifier for amplifying input signals and providing required output power;

[0010] a bias circuit, which provides a bias voltage for the power amplifier and controls the static working point of the power amplifier with the variation characteristics of temperature and power;

[0011] an active feedback circuit, which comprises a first connection point P1, a second connection point P2 and a third connection point P3, the active feedback circuit is connected with the output of the power amplifier through the first connection point P1, the active feedback circuit is connected with the input of the power amplifier through the second connection point P2, and the active feedback circuit is connected with the bias circuit through the third connection point P3, for adjusting the linearity of the power amplifier.

[0012] Preferably, the active feedback circuit comprises:

[0013] at least one transistor as a core element;

[0014] a first resistor R5 and a second resistor R4, which are connected in series between the base of the transistor and the bias circuit, for controlling the base voltage of the transistor;

[0015] a third resistor R1 and a fourth resistor R3, which are connected in series between the emitter of the transistor and the ground, for adjusting the working area of the transistor;

[0016] adjusting R5, R4, R1 and R3 so that the transistor works in the critical region between the saturation region and the linear region;

[0017] a first capacitor C1 and a second capacitor C2, which are connected between the base and the emitter of the transistor and the ground respectively, as DC blocking capacitors;

[0018] a third capacitor C3, which is connected between the collector of the transistor and the ground, as a RF bypass capacitor;

[0019] a fifth resistor R2, which is connected between the collector of the transistor and the input of the power amplifier, for changing the depth of feedback.

[0020] Further preferably, by adjusting the ratio of the third resistor R1 and the fourth resistor R3, the transistor works in the critical region between the saturation region and the linear region.

[0021] Preferably, by adjusting the resistance value of the fifth resistor R2, the feedback depth of the active feedback circuit is changed, increasing the resistance value of the fifth resistor R2, for reducing the influence of the active feedback circuit on the gain and output power of the power amplifier.

[0022] Further preferably, the active feedback circuit is used to reduce the IM3 of the power amplifier, and the values of the first resistor R5, the second resistor R4, the third resistor R1 and the fourth resistor R3 are adjusted according to the IM3 simulation results, and the static working point of the transistor is adjusted.

[0023] (III) Advantages

[0024] Compared with the prior art, the power amplifier linearization circuit provided by the utility model has the following

[0025] Advantages:

[0026] Improved linearity:

[0027] Reduced intermodulation distortion (IM3): The active feedback circuit effectively reduces the nonlinear distortion of the power amplifier, especially the IM3, through a negative feedback mechanism, which enables the power amplifier to maintain high linearity even at high power output.

[0028] Optimized feedback circuit transistor working point: By adjusting the ratio of the first resistor R5 and the second resistor R4, and the ratio of the third resistor R1 and the fourth resistor R3, the feedback circuit transistor works in the critical region between the saturation region and the linear region, which can maximize the optimization of the linearity of the power amplifier.

[0029] Flexible adjustment:

[0030] Adjustable feedback depth: The fifth resistor R2 is connected between the collector of the transistor and the input of the power amplifier, which is used to change the depth of feedback. By adjusting the resistance value of R2, the linearity can be improved while minimizing the impact on the gain and output power of the power amplifier.

[0031] Static working point adjustment: According to the IM3 simulation results, the static working point of the transistor can be optimized by adjusting the values of R5, R4, R1 and R3, thereby achieving the best linearization effect.

[0032] Simple and reliable:

[0033] Simple structure: The active feedback circuit mainly consists of several basic elements, including transistors, resistors and capacitors, which has a simple structure and is easy to implement.

[0034] DC blocking capacitor and RF bypass capacitor: The first capacitor C1 and the second capacitor C2 are connected between the base and the emitter of the transistor and the ground, respectively, as DC blocking capacitors to prevent the influence of DC signals on the feedback circuit. The third capacitor C3 is connected between the collector of the transistor and the ground as an RF bypass capacitor to prevent high-frequency signals from interfering with the feedback circuit. These capacitors ensure that the feedback circuit only processes AC signals, improving the stability and reliability of the circuit.

[0035] No impact on gain and output power:

[0036] Maintain gain: By reasonably designing the feedback circuit, especially when increasing the resistance value of the fifth resistor R2, the impact on the gain of the power amplifier can be minimized while improving linearity.

[0037] Maintain output power: Similarly, by adjusting the parameters of the feedback circuit, the output power of the power amplifier can be maintained without significant impact while improving linearity.

[0038] Temperature and power adaptability:

[0039] Bias circuit: The bias circuit provides a stable bias voltage for the power amplifier and controls the static working point with temperature and power variation characteristics. This enables the power amplifier to maintain good performance under different temperature and power conditions.

[0040] Feedback circuit stability: The bias circuit also provides a bias voltage for the active feedback circuit to ensure stable operation of the feedback circuit under different conditions.

[0041] Wide application prospects:

[0042] Multi-field application: The circuit is suitable for various occasions requiring high linearity power amplifiers, such as wireless communication, radar systems, satellite communication, etc.

[0043] Cost-effective: Compared with traditional linearization methods (such as pre-distortion, feedforward, etc.), the circuit structure of the invention is simple, the implementation cost is low, and it has high cost performance. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 The overall circuit structure of the present application is shown in the figure;

[0045] Figure 2 The active feedback circuit structure of the present application is shown in the figure;

[0046] Figure 3 The third-order intermodulation (IM3) performance structure of the present application is shown in the figure;

[0047] Figure 4 The output end third-order intermodulation point (OIP3) performance structure of the present application is shown in the figure;

[0048] Figure 5 The power amplifier gain vs. output power curve structure of the present application is shown in the figure; DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the utility model.

[0050] Please refer to Figures 1-5 The utility model relates to a power amplifier linearization circuit, through adding active feedback circuit at the input and output end of power amplifier, improve the linearity of power amplifier. The circuit includes a power amplifier, a bias circuit and an active feedback circuit. Active feedback circuit is connected with the output end of power amplifier through first connecting point P1, is connected with the input end of power amplifier through second connecting point P2, is connected with bias circuit through third connecting point P3, for adjusting the linearity of power amplifier.

[0051] Main structure composition

[0052] Power amplifier:

[0053] For amplifying input signal and providing required output power.

[0054] Bias circuit:

[0055] Provide bias voltage for power amplifier, and control the static working point of power amplifier with the change characteristic of temperature and power.

[0056] Also provide bias voltage for active feedback circuit.

[0057] Active feedback circuit:

[0058] Connected with the output end of power amplifier through first connecting point P1.

[0059] Connected with the input end of power amplifier through second connecting point P2.

[0060] Connected with bias circuit through third connecting point P3.

[0061] For adjusting the linearity of power amplifier.

[0062] Including the following components:

[0063] Transistor: as core element.

[0064] First resistance R5 and second resistance R4: in series between the base of transistor and bias circuit, for controlling the base voltage of transistor.

[0065] Third resistor R1 and fourth resistor R3: connected in series between the emitter of the transistor and ground, used to adjust the operating region of the transistor, making it work in the critical region between saturation and linear regions.

[0066] First capacitor C1 and second capacitor C2: connected between the base and emitter of the transistor and ground respectively, as a DC blocking capacitor.

[0067] Third capacitor C3: connected between the collector of the transistor and ground, as a RF bypass capacitor.

[0068] Fifth resistor R2: connected between the collector of the transistor and the input of the power amplifier, used to change the depth of feedback.

[0069] Basic working principle

[0070] Power amplifier:

[0071] The power amplifier receives the input signal and amplifies it, providing the required output power.

[0072] The amplified signal is transmitted to the active feedback circuit through the first connection point P1.

[0073] Bias circuit:

[0074] The bias circuit provides a stable bias voltage for the power amplifier, ensuring its normal operation under different temperature and power conditions.

[0075] The bias circuit also provides a bias voltage for the active feedback circuit, ensuring the normal operation of the feedback circuit.

[0076] Active feedback circuit:

[0077] The active feedback circuit receives the output signal of the power amplifier through the first connection point P1.

[0078] The transistor is the core component of the feedback circuit, and by adjusting its base voltage and operating region, the performance of the feedback circuit can be adjusted.

[0079] The processed signal of the feedback circuit is fed back to the input of the power amplifier through the second connection point P2, forming a negative feedback loop.

[0080] Through the negative feedback mechanism, the nonlinear distortion (such as IM3) of the power amplifier can be reduced, and its linearity can be improved.

[0081] Working principle of each preferred technical solution

[0082] Transistor and its base voltage control

[0083] Transistor: As the core component of the active feedback circuit, the working state of the transistor directly affects the performance of the feedback circuit.

[0084] First resistor R5 and second resistor R4: connected in series between the base of the transistor and the bias circuit, used to control the base voltage of the transistor. By adjusting the ratio of R5 and R4, the base voltage of the transistor can be precisely controlled, thereby adjusting the operating point of the transistor.

[0085] Adjustment method: through simulation and experiment, the values of R5 and R4 are optimized to make the base voltage of the transistor at a suitable level to achieve the best feedback effect.

[0086] Transistor operating region adjustment

[0087] Third resistor R1 and fourth resistor R3: connected in series between the emitter of the transistor and ground, used to adjust the operating region of the transistor, making it work in the critical region between saturation and linear regions.

[0088] Adjustment method: by adjusting the ratio of R1 and R3, the transistor can work in the critical region between saturation and linear regions, which can ensure the linearity of the transistor and maintain sufficient gain and output power.

[0089] Optimization goal: according to the IM3 simulation results, adjust the values of R1 and R3 to make the operating point of the transistor in the best state, thereby minimizing IM3.

[0090] Direct current blocking capacitor and radio frequency bypass capacitor

[0091] First capacitor C1 and second capacitor C2: connected between the base and emitter of the transistor and ground respectively, as direct current blocking capacitors, used to isolate direct current components and prevent direct current signals from affecting the feedback circuit.

[0092] Third capacitor C3: connected between the collector of the transistor and ground, as a radio frequency bypass capacitor, used to bypass high frequency signals and prevent them from interfering with the feedback circuit.

[0093] Effect: these capacitors ensure that the feedback circuit only processes alternating current signals, improving the stability and reliability of the feedback circuit.

[0094] Feedback depth adjustment

[0095] Fifth resistor R2: connected between the collector of the transistor and the input of the power amplifier, used to change the depth of feedback.

[0096] Adjustment method: by adjusting the resistance of R2, the feedback depth of the feedback circuit can be changed. Increasing the resistance of R2 can reduce the impact of the feedback circuit on the gain and output power of the power amplifier, while still effectively reducing IM3.

[0097] Optimization goal: under the premise of ensuring the power amplifier gain and output power are not obviously affected, by adjusting the resistance value of R2, the optimal feedback depth is found to achieve the best linearization effect.

[0098] Summary

[0099] The power amplifier linearization circuit of the utility model, through adding active feedback circuit in the input and output end of power amplifier, effectively reduces the intermodulation distortion (IM3) of power amplifier, improves its linearity. Specifically includes:

[0100] High efficiency linearization: through active feedback circuit, effectively reduce IM3, improve the linearity of power amplifier.

[0101] Flexible adjustment: by adjusting the proportion of resistance R5 / R4 and R1 / R3, the base voltage and working area of feedback circuit transistor can be accurately controlled, the performance of feedback circuit is optimized, and the linearity of power amplifier is further optimized.

[0102] Simple and reliable: the circuit structure is simple, easy to realize, and through the blocking capacitor and RF bypass capacitor, the stability and reliability of the feedback circuit are improved.

[0103] Without affecting gain and output power: by adjusting the resistance value of the fifth resistor R2, the influence on the gain and output power of the power amplifier can be minimized while improving the linearity.

[0104] Through the above design and technical scheme, the circuit not only improves the linearity of the power amplifier, but also maintains its original gain and output power characteristics, and has wide application prospect.

[0105] As shown in Figure 3 , Figure 4 and Figure 5 : red is the performance without feedback circuit, blue is the performance with feedback circuit, the feedback circuit can improve the IM3 and OIP3 of the power amplifier in a wide power range, and has basically no effect on the gain and output power of the power amplifier. Among them, Figure 3 The third-order intermodulation (IM3) performance is shown in the figure, the horizontal axis represents the output power of the power amplifier, and the vertical axis represents IM3, Figure 4 The output end third-order intermodulation point (OIP3) performance is shown in the figure, the horizontal axis represents the output power of the power amplifier, and the vertical axis represents OIP3, Figure 5 The power amplifier gain vs output power curve (AMAM) is shown in the figure, the horizontal axis represents the output power, and the vertical axis represents the gain.

[0106] Although the embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A power amplifier linearization circuit, characterized by, The application relates to a power amplifier circuit, comprising: a power amplifier for amplifying an input signal and providing required output power; a bias circuit for providing a bias voltage for the power amplifier and controlling the static working point of the power amplifier to change with temperature and power; an active feedback circuit comprising a first connection point P1, a second connection point P2 and a third connection point P3, the active feedback circuit being connected with the output of the power amplifier through the first connection point P1, the active feedback circuit being connected with the input of the power amplifier through the second connection point P2, and the active feedback circuit being connected with the bias circuit through the third connection point P3, for adjusting the linearity of the power amplifier.

2. The power amplifier linearization circuit of claim 1, wherein, The active feedback circuit comprises: at least one transistor as a core element; a first resistor R5 and a second resistor R4 connected in series between the base of the transistor and the bias circuit, for controlling the base voltage of the transistor; a third resistor R1 and a fourth resistor R3 connected in series between the emitter of the transistor and the ground, for adjusting the working area of the transistor; adjusting R5, R4, R1 and R3 so that the transistor works in the critical area between the saturation area and the linear area; a first capacitor C1 and a second capacitor C2 connected between the base and the emitter of the transistor and the ground respectively, as DC blocking capacitors; a third capacitor C3 connected between the collector of the transistor and the ground, as a radio frequency bypass capacitor; a fifth resistor R2 connected between the collector of the transistor and the input of the power amplifier, for changing the feedback depth.

3. The power amplifier linearization circuit of claim 2, wherein, The first resistor R5, the second resistor R4, the third resistor R1 and the fourth resistor R3 are adjusted so that the transistor works in the critical area between the saturation area and the linear area.

4. The power amplifier linearization circuit of claim 3, wherein, The resistance value of the fifth resistor R2 is adjusted to change the feedback depth of the active feedback circuit, and increasing the resistance value of the fifth resistor R2 is used to reduce the influence of the active feedback circuit on the gain and output power of the power amplifier.

5. The power amplifier linearization circuit of claim 4, wherein, The active feedback circuit is used to reduce the IM3 of the power amplifier, the values of the first resistor R5, the second resistor R4, the third resistor R1 and the fourth resistor R3 are adjusted according to the IM3 simulation result, and the static working point of the feedback circuit transistor is adjusted.

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