Linear compensation bias circuit

Abstract

The application discloses a linear compensation bias circuit, which comprises a linear regulation unit and a temperature compensation unit, the linear regulation unit is connected with a radio frequency amplifier and an external power supply respectively, the temperature compensation unit is connected with the linear regulation unit and another external power supply respectively, and the temperature compensation unit is adjacent to a power tube of the radio frequency amplifier; the linear regulation unit comprises a first resistor, a second resistor and a first transistor, one end of the first resistor is connected with a base of the power tube, the other end is connected with an emitter of the first transistor, a base of the first transistor is connected with one end of the second resistor, the other end of the second resistor is connected with an external power supply, and a collector of the first transistor is connected with the temperature compensation unit. The linear compensation bias circuit can compensate the radio frequency amplifier in temperature and large signal linearity, so that the temperature of the radio frequency amplifier is more stable, the linearity of the power tube is better, and the dynamic performance adjustment capability of the radio frequency amplifier circuit is improved.

Description

Technical Field

[0001] This invention relates to the field of radio frequency microwaves, and more specifically to a linear compensation bias circuit. Background Technology

[0002] With the continuous development of mobile communication technology, the new mobile communication system (5G) has put forward higher requirements for data transmission rate, requiring high-bandwidth modulation signals for data transmission, which increases the difficulty of designing linear radio frequency power amplifiers.

[0003] When an RF power amplifier is operating, its temperature gradually increases with the increase in operating time and RF input signal. Due to the physical characteristics of the power transistor die (as the PN junction temperature rises, electrons in the emitter region are excited by heat, and the total number of drift electrons increases with temperature), the amplifier current increases, affecting the amplifier's operating state and consequently its linearity (which gradually decreases with changes in the transistor's operating state). Therefore, additional current compensation is needed through a bias circuit to improve circuit linearity. Figure 1 This is a schematic diagram of the existing linear compensation bias circuit; such as... Figure 1 As shown, transistors HBT1, HBT2, and HBT3 form a current mirror. The current mirror and capacitor C1 form a linear bias circuit. Transistor HBT1, resistor R3, and capacitor C1 serve to linearize the circuit. When the input signal increases, the base static bias voltage V of power transistor HBT0 increases. BE(0) The voltage decreases, and there is radio frequency signal leakage to the bias circuit. The leakage signal passes through transistor HBT1 and grounding capacitor C1 to ground. Due to the rectification effect of the BE junction diode of transistor HBT1, the leakage signal will increase the static DC current of transistor HBT1, thereby increasing the junction voltage V. BE(1) The base bias voltage of power transistor HBT0 can be expressed as:

[0004] V BE(0) =V B(1) -V BE(1) -I B(0) R3 (1)

[0005] In equation (1) above, because the voltage V B(1) It is fixed, so the voltage V BE(1) The change will compensate for the voltage V BE(0) The change in impedance improves AM-AM / AM-PM distortion in the RF path. The impedance on the HBT2 side of the bias circuit is much smaller than that on the HBT1 side, therefore the current flowing through the left side is much greater than that on the right. The two transistors HBT2 and HBT3 on the left act as a voltage divider; when the current causes the transistor temperature to rise, the voltage V of transistor HBT1... BE(1)This will decrease, which will reduce the current I flowing into the power transistor HBT0 from the main path. B(0) The temperature increases. However, as the temperature rises, the junction voltages of transistors HBT2 and HBT3 decrease accordingly, which increases the current flowing through transistors HBT2 and HBT3, thereby increasing the voltage drop across resistor R1. Therefore, the base voltage V of transistor HBT1 increases. B(1) Decrease, causing current I B(0) reduce.

[0006] However, in the circuit described above, although transistor HBT3 has temperature compensation capability, when the bias current is large, for example, when the bias current at room temperature is 110mA, the difference between the bias current under low temperature and high temperature operating conditions is about 20mA. This deviation will still affect the operating performance and efficiency of the RF amplifier.

[0007] Therefore, it is necessary to provide an improved linear compensation bias circuit that can guarantee the operating performance of the RF amplifier to overcome the above-mentioned defects. Summary of the Invention

[0008] The purpose of this invention is to provide a linear compensation bias circuit adapted to radio frequency (RF) amplifiers. This linear compensation bias circuit can perform temperature compensation and large-signal linear compensation on the RF amplifier, making the temperature of the RF amplifier more stable, improving the linearity of the power transistor, and enhancing the dynamic performance adjustment capability of the RF amplifier circuit.

[0009] To achieve the above objectives, the present invention provides a linear compensation bias circuit adapted to an RF amplifier, comprising a linear adjustment unit and a temperature compensation unit. The linear adjustment unit is connected to the RF amplifier and an external power supply respectively to adjust the linearity of the RF amplifier. The temperature compensation unit is connected to the linear adjustment unit and another external power supply respectively, and is located adjacent to the power transistor of the RF amplifier to sense the temperature change of the power transistor and perform temperature compensation on the power transistor in real time according to the temperature change. The linear adjustment unit includes a first resistor, a second resistor, and a first transistor. One end of the first resistor is connected to the base of the power transistor, and the other end is connected to the emitter of the first transistor. The base of the first transistor is connected to one end of the second resistor, and the other end of the second resistor is connected to an external power supply. The collector of the first transistor is connected to the temperature compensation unit.

[0010] Preferably, the linear adjustment unit further includes an inductor connected between the first resistor and the emitter of the first transistor.

[0011] Preferably, the linear adjustment unit further includes a first capacitor and a second capacitor, one end of the first capacitor being connected to the base of the first transistor and the other end being grounded; one end of the second capacitor being connected to the other end of the second resistor and the other end of the second capacitor being grounded.

[0012] Preferably, the temperature compensation unit includes a second transistor, a third transistor, a third resistor, and a fourth resistor. The base of the second transistor is connected to the base of the first transistor, and the collector of the second transistor is connected to the collector of the first transistor. The emitter of the second transistor is connected to one end of the fourth resistor and the base of the third transistor, and the other end of the fourth resistor is grounded. The collector of the second transistor is connected to one end of the third resistor and the collector of the first transistor, and the other end of the third resistor is connected to another external power supply. The collector of the third transistor is connected to the emitter of the first transistor, and the emitter of the third transistor is grounded.

[0013] Preferably, the temperature compensation unit further includes a third capacitor, one end of which is connected to the other end of the third resistor, and the other end of the third capacitor is grounded.

[0014] Preferably, the third transistor is exactly the same size as the first transistor.

[0015] Compared with the prior art, the linear compensation bias circuit of the present invention can adjust the linearity of the power transistor of the RF amplifier under large signal input conditions through the linear adjustment unit, thereby performing linear compensation on the power transistor for large signals and adjusting and improving the linearity of the RF amplifier power transistor; at the same time, the temperature compensation unit senses the temperature change of the power transistor in real time and controls and adjusts the static current of the power transistor, thereby performing temperature compensation on the power transistor and improving the dynamic performance adjustment capability of the RF amplifier circuit.

[0016] The invention will become clearer from the following description, taken in conjunction with the accompanying drawings, which are used to explain embodiments of the invention. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the circuit structure of a linear compensation bias circuit in the prior art.

[0018] Figure 2 This is a schematic diagram of the linear compensation bias circuit of the present invention.

[0019] Figure 3 This is a schematic diagram of the application scenario structure of the linear compensation bias circuit of the present invention.

[0020] Figure 4 for Figure 3The graph shows a comparison of the DC output and temperature change curves between the application scenario shown and the application scenario of existing technologies.

[0021] Figure 5 The graph shows a comparison of the third-stage base voltage as a function of RF input in the application scenario shown in Figure 3 and the application scenario of existing technologies. Detailed Implementation

[0022] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which similar element reference numerals represent similar elements. As described above, the present invention provides a linear compensation bias circuit adapted to an RF amplifier. The linear compensation bias circuit of the present invention can perform temperature compensation and large-signal linear compensation on the RF amplifier, making the temperature of the RF amplifier more stable, improving the linearity of the power transistor, and enhancing the dynamic performance adjustment capability of the RF amplifier circuit.

[0023] Please refer to Figure 2 , Figure 2 This is a schematic diagram of the linear compensation bias circuit of the present invention. As shown in the figure, the linear compensation bias circuit of the present invention is adapted to an RF amplifier; the linear compensation bias circuit includes a linear adjustment unit and a temperature compensation unit. The linear adjustment unit is connected to the RF amplifier and an external power supply Vbb respectively, and is used to adjust the linearity of the RF amplifier; the temperature compensation unit is connected to the linear adjustment unit and another external power supply Vcc respectively, and the temperature compensation unit is adjacent to the power transistor HBT0 of the RF amplifier, and is used to accurately sense the temperature change of the power transistor HBT0 and perform temperature compensation on the power transistor HBT0 in real time according to the temperature change.

[0024] Specifically, the linear adjustment unit includes a first resistor R1, a second resistor R2, and a first transistor HBT1. One end of the first resistor R1 is connected to the base of the power transistor HBT0, and the other end is connected to the emitter of the first transistor HBT1. The base of the first transistor HBT1 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is connected to an external power supply Vbb. The external power supply Vbb provides input current to the first transistor HBT1 through the second resistor R2, and the resistance value of the second resistor R2 is used to control the magnitude of the input current. The collector of the first transistor HBT1 is connected to the temperature compensation unit. In a preferred embodiment of the present invention, the linear adjustment unit further includes a first capacitor C1 and a second capacitor C2. One end of the first capacitor C1 is connected to the base of the first transistor HBT1, and the other end is grounded. When an RF signal leaks into the bias circuit, the leaked signal can be directly grounded through the first capacitor C1, reducing the impact on the bias circuit. One end of the second capacitor C2 is connected to the other end of the second resistor R2, and the other end of the second capacitor C2 is grounded. The second capacitor C2 is a decoupling capacitor connected in parallel to the power supply Vbb.

[0025] Additionally, the temperature compensation unit includes a second transistor HBT2, a third transistor HBT3, a third resistor R3, and a fourth resistor R4. The base of the second transistor HBT2 is connected to the base of the first transistor HBT1, and its collector is connected to the collector of the first transistor HBT1. The emitter of the second transistor HBT2 is connected to one end of the fourth resistor R4 and the base of the third transistor HBT3, while the other end of the fourth resistor R4 is grounded. The collector of the second transistor HBT2 is connected to one end of the third resistor R3 and the collector of the first transistor HBT1, while the other end of the third resistor R3 is connected to another external power supply Vcc. The external power supply Vcc provides collector current to the first transistor HBT1 and the second transistor HBT2 through the third resistor R3. The collector of the third transistor HBT3 is connected to the emitter of the first transistor HBT1, and the emitter of the third transistor HBT3 is grounded. In a preferred embodiment of the present invention, the temperature compensation unit further includes a third capacitor C3, one end of which is connected to the other end of the third resistor R3, the other end of which is grounded, and the third capacitor C32 is a decoupling capacitor connected in parallel to the power supply Vcc.

[0026] Furthermore, in this invention, the third transistor HBT3 is exactly the same size as the first transistor HBT1, so that the current on the third transistor HBT3 and the first transistor HBT1 can change synchronously.

[0027] Furthermore, the linear adjustment unit also includes an inductor L1, which is connected between the first resistor R1 and the emitter of the first transistor HBT1. In this invention, when the feedback network is built using the third transistor HBT3, the impedance of the bias circuit viewed from the RF path direction will be smaller, which will make the leakage of the RF signal more serious. However, by adding the inductor L1, the leakage of the RF signal can be suppressed, ensuring the stability of the entire circuit operation.

[0028] Please refer to the following: Figure 2 The working principle of the linear compensation bias circuit of the present invention is described as follows:

[0029] When the input RF signal INPUT increases, the base static bias voltage V of the power transistor HBT0 increases. BE(0) The signal is reduced, and there is radio frequency signal leakage to the bias circuit. ； The leakage signal reaches ground through the first transistor HBT1 and the first capacitor C1. Furthermore, due to the rectification effect of the BE junction diode of the first transistor HBT1, the leakage signal will increase the static DC current of the first transistor HBT1, thereby increasing the junction voltage V. BE(1) Reduce the static bias voltage V at the base of the power transistor HBT0. BE(0) The changes improve the AM-AM / AM-PM distortion of the RF amplifier, enhance the linearity of the power transistor HBT0, and improve the dynamic performance adjustment capability of the RF amplifier circuit. At the same time, it enables the adjustment of the linearity of the power transistor HBT0 of the RF amplifier under large signal input conditions.

[0030] The third transistor HBT3 of the temperature compensation unit is positioned as close as possible to the power transistor HBT0 to sense temperature changes in HBT0 in real time. The second transistor HBT2 provides DC input current to the third transistor HBT3, and the fourth resistor R4 controls the magnitude of the current input to the third transistor HBT3. In this invention, since the dimensions of the third transistor HBT3 are identical to those of the first transistor HBT1, when the temperature of the power transistor HBT0 rises, the BE junction diode of the first transistor HBT1 decreases, resulting in a decrease in the output DC current I of the first transistor HBT1. CE(1) The current increases. Meanwhile, the output current I of the third transistor HBT3... CE(3) It will also increase. The third transistor HBT3 will reduce the current I of the first transistor HBT1. CE(1) The current is shunted, and the DC current I flowing into the base of the power transistor HBT0 is... B(0) and ICE(3) I CE(1) The relationship is shown in the following formula:

[0031] I B(0) =I CE(1) -ICE(3)

[0032] Therefore, when the temperature changes, the current changes of the first transistor HBT1 and the third transistor HBT3 are the same, ensuring that the base DC current I of the power transistor HBT0 is maintained. B(0) Unaffected by temperature, temperature compensation for the power transistor HBT0 is achieved.

[0033] Please refer to the references. Figures 3 to 5 This describes the differences between the linear compensation bias circuit of the present invention and the prior art in the same application scenario. For example... Figure 3 As shown, the linear compensation bias circuit of the present invention is applied to a three-stage amplifier circuit, where BIAS1, BIAS2, and BIAS3 are all linear compensation bias circuits described in the present invention. In the same three-stage amplifier circuit, a comparison of the ADS simulation curves of the DC output of the third stage of the RF amplifier circuit as a function of temperature is obtained through simulation, showing the difference between the present invention's solution and the prior art's solution. Figure 4 As shown, curve a represents the current generated by applying the present invention, while curve b represents the current generated by the prior art. Clearly, the current generated by applying the present invention exhibits the smallest variation with temperature, thus achieving better temperature compensation for the RF amplifier. Additionally, please refer to... Figure 5 ,exist Figure 5 In the diagram, curve d represents the curve generated by applying the present invention, while curve c represents the curve generated by the prior art. Figure 5 As can be seen from the data, within the range of -30dBm to 5dBm of the input RF signal, the voltage value of curve c decreases from 1.3V to 1.18V, indicating that the change in the input signal has a significant impact on the circuit; while for curve d, within the range of -30dBm to 5dBm of the input RF signal, the voltage value remains basically at 1.3V, with only a slight decrease and very little fluctuation.

[0034] In summary, the linear compensation bias circuit of the present invention can adjust the linearity of the power transistor of the RF amplifier under large signal input conditions through the linear adjustment unit, thereby performing linear compensation on the power transistor for large signals and improving the linearity of the RF amplifier power transistor; at the same time, the temperature compensation unit senses the temperature change of the power transistor in real time and controls and adjusts the quiescent current of the power transistor, thereby performing temperature compensation on the power transistor and improving the dynamic performance adjustment capability of the RF amplifier circuit.

[0035] The present invention has been described above in conjunction with the preferred embodiments, but the present invention is not limited to the embodiments disclosed above, but should cover various modifications and equivalent combinations made in accordance with the essence of the present invention.

Claims

1. A linear compensating bias circuit adapted for a radio frequency amplifier, characterized by, The linear regulation unit is connected with the radio frequency amplifier and an external power source respectively, and is used to adjust the linearity of the radio frequency amplifier. The temperature compensation unit is connected with the linear regulation unit and another external power source respectively, and is adjacent to the power tube of the radio frequency amplifier, and is used to sense the temperature change of the power tube and compensate the temperature of the power tube in real time according to the temperature change. The linear regulation unit comprises a first resistor, a second resistor and a first transistor. One end of the first resistor is connected with the base of the power tube, and the other end is connected with the emitter of the first transistor. The base of the first transistor is connected with one end of the second resistor, and the other end of the second resistor is connected with an external power source. The collector of the first transistor is connected with the temperature compensation unit. The temperature compensation unit comprises a second transistor, a third transistor, a third resistor and a fourth resistor. The base of the second transistor is connected with the base of the first transistor, and the collector is connected with the collector of the first transistor. The emitter of the second transistor is connected with one end of the fourth resistor and the base of the third transistor. The other end of the fourth resistor is grounded. The collector of the second transistor is connected with one end of the third resistor and the collector of the first transistor. The other end of the third resistor is connected with another external power source. The collector of the third transistor is connected with the emitter of the first transistor, and the emitter is grounded.

2. The linearly compensating biasing circuit of claim 1, wherein, The linear regulation unit further comprises an inductor connected between the first resistor and the emitter of the first transistor.

3. The linearly compensating biasing circuit of claim 1, wherein, The linear regulation unit further comprises a first capacitor and a second capacitor. One end of the first capacitor is connected with the base of the first transistor, and the other end is grounded. One end of the second capacitor is connected with the other end of the second resistor, and the other end is grounded.

4. The linearly compensating biasing circuit of Claim 1, wherein, The temperature compensation unit further comprises a third capacitor. One end of the third capacitor is connected with the other end of the third resistor, and the other end is grounded.

5. The linearly compensating biasing circuit of claim 1, wherein, The third transistor and the first transistor are completely the same in size.

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