Switchable adaptive dynamic biasing circuit applied to power amplifier

Abstract

The invention discloses a switchable self-adaptive dynamic biasing circuit applied to a power amplifier, relates to a radio frequency integration technology, and provides a scheme aiming at the problems of inconvenience in dynamic adjustment and the like in the prior art. The self-adaptive linearization bias module is used for dynamically adjusting the linearity index of the power amplifier according to the quiescent current of the self-adaptive linearization bias module 3; the switch module is used for controlling the power amplifier to be turned on or turned off according to the voltage drop of the switch voltage on the corresponding trunk series resistor; and the quiescent current adjusting module is used for adjusting the quiescent circuit according to the voltage drop of the reference voltage on the corresponding trunk series resistor. The method has the advantages that the dynamic adjustment of the linearity index of the power amplifier can be realized, and the self-heating effect suppression, the linearity improvement and the like are balanced. The switch of the whole applied power amplifier can be controlled only by adjusting the voltage of the switch corresponding to the bias circuit. The quiescent current can be accurately adjusted by adjusting the resistor.

Description

Technical Field

[0001] The present invention relates to radio frequency integration technology, and in particular to a switchable adaptive dynamic biasing circuit applied to a power amplifier. Background Art

[0002] Traditional power amplifiers can use complementary metal oxide semiconductor (CMOS), gallium arsenide heterojunction bipolar transistor (GaAs HBT), gallium arsenide pseudomorphic high electron mobility transistor (GaAs pHEMT), etc. as power amplification elements. Among them, the radio frequency power amplifier implemented by CMOS devices has the advantages of good compatibility and low cost, but has the disadvantages of low linearity and low breakdown voltage; while GaAs pHEMT can provide good noise performance and is widely used in low-noise amplifiers and radio frequency switches. Its process cost is relatively high and it is more used in high-frequency power amplifiers such as microwave and millimeter wave bands. When designing a power amplifier in the Sub-6GHz band, GaAs HBT has advantages such as good material thermal stability, high output power, high linearity, and good device reliability.

[0003] The radio frequency power amplifier implemented by GaAs HBT devices generally uses load pulling to find the maximum output power point. In order to improve the average efficiency of the power amplifier, it is required that the power amplifier has high efficiency in a wide operating range. Therefore, the design consideration is generally a compromise between efficiency and linearity, resulting in the linearity of the amplifier not reaching the optimal design. For the monolithic integrated circuit of HBT, the biasing circuit, as an important part of the radio frequency amplifier, provides a DC biasing point for the circuit and directly affects the gain, efficiency, and linearity indexes of the power amplifier. When the GaAs HBT process has a high-power input, the voltage drop at the base-emitter junction and the self-heating effect of the process itself will both cause the change of the transistor operating point, resulting in the change of the overall circuit gain and linearity.

[0004] In order to improve the linearity of the amplifier and avoid the phenomena of gain compression and non-linear distortion of the signal, a biasing circuit structure that makes the biasing voltage or biasing current of the transistor change with the change of the input signal power is usually adopted, so that the amplifier works in a dynamic state. This kind of biasing circuit is called a dynamic biasing structure. The representative literatures are [1][2][3][4].

[0005] In the design of MMIC amplifiers, in order to improve the linearity of the amplifier while keeping the biasing point of the amplifier from fluctuating with the change of the ambient temperature, an active biasing circuit is often used to stabilize the biasing point of the amplifier, thereby improving the linearity of the amplifier. Moreover, the active biasing circuit structure can not only make the amplifier work stably and output stably, but also compensate for the change of the ambient temperature and the fluctuation of the power supply voltage, thereby improving the stability of the amplifier. The representative literatures in this regard are [5][6][7][8].

[0006] Conventional adaptive bias circuits usually compromise linearity and self-heating suppression through ballast resistors. And due to the need to turn off the power amplifier, an additional switch is generally added to turn off the power amplifier.

[0007] References

[0008] [1] Zheng R.Q., Zhang G.h., Yu K, et al. A 5.7-6.4GHz GaAs HBT power amplifier with a gain enhanced bias circuit[J]. Chinese Journal of Electronics, 2017, 26(3):502-507.

[0009] [2] Peng Yanjun, Song Jiayou, Wang Zhigong. Adaptive linearization bias technology for HBT MMIC power amplifiers[J]. China Integrated Circuit, 2006, (11):32-37.

[0010] [3] Y.S. Noh, Ji.H. Kim, MMIC power amplifier with on-chip bias current controlling circuit for W-CDMA mobile handset[J], Electronics Letters 2002, 38(25):1686-1688.

[0011] [4] Y.S. Noh, C.S. Park, An Intelligent Power Amplifier MMIC Using a New Adaptive Bias Control Circuit for W-CDMA Applications[J], IEEE J. Solid State Circuits, 2004, 39(6):967-970.

[0012] [5] Xu Shiyi, Wang Chao'er, Huang Jianhua, et al. Design of broadband low-noise amplifier based on negative feedback and active bias[J]. Journal of Zhejiang University (Engineering Science), 2018, 52(6):1081-1087.

[0013] [6]Y.S. Noh and C.S. Park, PCS / W-CDMA dual band MMIC power amplifier with a newly proposed linearizing bias circuit[J], IEEE J. Solid-State Circuits, 2002, 37(9): 1096 - 1099

[0014] [7]K. Fujita, K. Shirakawa, et al. A 5GHz high efficiency and low distortion InGaP / GaAs HBT power amplifier MMIC[A], IEEE MTT-S Microwave Symp. Dig.[C], 2003: 871 - 874.

[0015] [8]Joon H. Kim, Ji H. Kim, et al. High linear HBT MMIC power amplifier with partial RF coupling to bias circuit for W-CDMA portable application[A], Proc. 3rd Int. Conf. Microwave and Millimeter Wave Technology[C], 2002: 809 - 812. Summary of the Invention

[0016] The object of the present invention is to provide a switchable adaptive dynamic bias circuit applied to a power amplifier to solve the problems existing in the above-mentioned prior art.

[0017] The switchable adaptive dynamic bias circuit applied to a power amplifier in the present invention includes an adaptive linearization bias module, a switch module, and a static current adjustment module;

[0018] The adaptive linearization bias module is used to dynamically adjust the linearity index of the power amplifier according to the static current of the adaptive linearization bias module 3;

[0019] The switch module is used to control the turn-on or turn-off of the power amplifier according to the voltage drop of the switch voltage across the corresponding series resistor in the main circuit;

[0020] The static current adjustment module is used to adjust the static circuit according to the voltage drop of the reference voltage across the corresponding series resistor in the main circuit.

[0021] The advantages of the switchable adaptive dynamic biasing circuit applied to a power amplifier in the present invention are as follows:

[0022] (1) The integrated adaptive linearization biasing module can dynamically adjust the linearity index of the power amplifier, and there is also a choke resistor, achieving a balance in suppressing self-heating effects and improving linearity.

[0023] (2) The switch module is integrated into the biasing circuit. Instead of using a traditional additional CMOS switch to control the power amplifier's on-off, only by adjusting the voltage of the corresponding switch in the biasing circuit can the on-off of the entire power amplifier applied be controlled.

[0024] (3) The static current regulation module can accurately adjust the static current by adjusting the resistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of the switchable adaptive dynamic biasing circuit described in the present invention.

[0026] Figure 2 is a schematic structural diagram of the simulation circuit in which the switchable adaptive dynamic biasing circuit described in the present invention is applied.

[0027] Figure 3 is a waveform diagram of the bias voltage Vbias of the switchable adaptive dynamic biasing circuit described in the present invention varying with the input power Pin.

[0028] Figure 4 is a waveform diagram of the bias voltage Vbias of the switchable adaptive dynamic biasing circuit described in the present invention varying with the output power Pout.

[0029] Figure 5 is a waveform diagram of the gain Gain of the switchable adaptive dynamic biasing circuit described in the present invention varying with the output power Pout.

[0030] Figure 6 is a waveform diagram of the AMAM curve of the switchable adaptive dynamic biasing circuit described in the present invention varying with the output power Pout.

[0031] REFERENCE MARKS:

[0032] Adaptive linearization biasing module Module1, switch module Module2, static current regulation module Module3;

[0033] First resistor R1, second resistor R2, third resistor R3, fourth resistor R4, fifth resistor R5, sixth resistor R6, seventh resistor R7, ballast resistor Rb;

[0034] Cbias bias capacitor, Cb base capacitor, decoupling capacitor Cc, choke inductor Lc;

[0035] Power amplifier HBT0, first transistor HBT1, second transistor HBT2, third transistor HBT3, fourth transistor HBT4, fifth transistor HBT5, sixth transistor HBT6, seventh transistor HBT7;

[0036] Reference voltage Vref, switching voltage Vcon, power supply voltage Vdd. Detailed implementation

[0037] In the present invention, a switchable adaptive dynamic bias circuit applied to a power amplifier is as Figure 1 shown, including an adaptive linearization bias module Module1, a switch module Module2, and a static current regulation module Module3.

[0038] The adaptive linearization bias module Module1 is used to dynamically adjust the linearity index of the power amplifier HBT0 according to the static current of the adaptive linearization bias module Module13.

[0039] The switch module Module2 is used to control the turn-on or turn-off of the power amplifier HBT0 according to the voltage drop of the switching voltage Vcon across the corresponding series resistor in the main circuit.

[0040] The static current regulation module Module3 is used to adjust the static circuit according to the voltage drop of the reference voltage Vref across the corresponding series resistor in the main circuit.

[0041] The structure of the adaptive linearization bias module Module1 is as follows: The collector of the first transistor HBT1 is connected to the power supply voltage Vdd through the first resistor R1, the emitter of the first transistor HBT1 is connected to the base of the power amplifier HBT0 through the ballast resistor Rb, and the base of the first transistor HBT1 is connected to the output end of the switch module Module2 and grounded through the bias capacitor Cbias.

[0042] The structure of the switch module Module2 is as follows: The switching voltage Vcon is used as the output end of the switch module Module2 through the second resistor R2, and is respectively connected to the base and collector of the second transistor HBT2, the base and collector of the third transistor HBT3. The emitter of the second transistor HBT2 is connected to the base of the fourth transistor HBT4 through the third resistor R3. The emitter of the third transistor HBT3 is respectively connected to the output end of the static current regulation module Module3 and the collector of the fourth transistor HBT4. The emitter of the fourth transistor HBT4 is grounded through the fourth resistor R4.

[0043] The structure of the static current regulation module Module3 is as follows: The collector of the fifth transistor HBT5 serves as the output terminal of the static current regulation module Module3 and is connected to the switching voltage Vcon through the fifth resistor R5. The base of the fifth transistor HBT5 is connected to the base and the collector of the sixth transistor HBT6. The emitter of the fifth transistor HBT5 is connected to the base of the seventh transistor HBT7 through the sixth resistor R6. The collector of the sixth transistor HBT6 is connected to the reference voltage Vref through the seventh resistor R7. The emitter of the sixth transistor HBT6 is connected to the collector of the seventh transistor HBT7. The emitter of the seventh transistor HBT7 is grounded.

[0044] In the present invention, the switchable adaptive dynamic biasing circuit applied to a power amplifier is specifically applied as Figure 2 shown, and the specific working principle is analyzed in combination with Figure 1 the structure shown as follows:

[0045] Adaptive linearization biasing module Module1: When the input power of the power amplifier HBT0 increases, its base current Ib0 increases accordingly, causing the collector current Ic0 to increase, and further resulting in a decrease in the base-emitter junction voltage Vbe0. On the other hand, part of the radio frequency signal leaks to the first transistor HBT1 through the ballast resistor Rb. Due to the rectifying effect of the base-emitter junction of the first transistor HBT1, the emitter current Ie1 increases, and the base-emitter junction voltage of the first transistor HBT1 decreases. At the same time, the collector current Ic0 of the power amplifier HBT0 increases. Due to the existence of the biasing capacitor Cbias, point B is maintained at a constant voltage, and the voltage drop across the ballast resistor Rb is very small, so Vel≥Iel*Rb. It should be noted that although the voltage drop across the ballast resistor Rb is very small, it has a thermal stabilization effect and can effectively suppress the self-heating effect naturally existing in HBT. The selection of the biasing capacitor Cbias mainly depends on the equivalent impedance ZB seen from point B; within the working frequency band, the impedance value of the biasing capacitor Cbias needs to be less than ZB to ensure that all radio frequency signals from the first transistor HBT1 are short-circuited to ground without affecting the normal operation of other circuits.

[0046] Switching module Module2: In addition to providing appropriate operating voltage and current to the static current regulation module Module3, it also acts as a switch for the power amplifier HBT0. The turn-on voltage of the base-emitter junction of a conventional HBT is approximately 1.24V. The second transistor HBT2 and the third transistor HBT3 are connected in a diode configuration, which has a voltage clamping effect, maintaining the voltage across the collector-emitter terminals of the second transistor HBT2 and the third transistor HBT3 at 1.24V. The third resistor R3 is connected in series to limit the current. Due to the influence of the adaptive linearization bias module Module1, the potential across the collector-emitter terminals of the fourth transistor HBT4 is also limited to the base-emitter junction turn-on voltage. Therefore, the voltage drop at point B is the sum of the voltages across two base-emitter junctions and the voltage drop across the fourth resistor R4. On the other hand, the voltage drop at point B is also the sum of the base-emitter junction voltage of the first transistor HBT1, the base-emitter junction voltage of the power amplifier HBT0, and the voltage drop across the ballast resistor Rb. Thus, by controlling the magnitude of the switching voltage Vcon and the voltage division of the second resistor R2, the power amplifier HBT0 can be turned on or off.

[0047] Static current regulation module Module3: Its main function is to precisely regulate the static current, facilitating later debugging. The seventh resistor R7 serves as a negative feedback resistor. By adjusting the resistance value of the seventh resistor R7 for voltage division, the seventh resistor R7 can change the common-base voltage drop of the sixth transistor HBT6. At the same time, the fifth transistor HBT5 and the sixth transistor HBT6 form a mirror current source structure, thereby controlling the collector current Ic5 of the fifth transistor HBT5. Similar to the switching module Module2, the connection methods of the three HBT transistors in the static current regulation module Module3 also have a voltage clamping effect, and the sixth resistor R6 connected in series also serves to limit the current. The clamping effect of the static current regulation module Module3 is mainly for its own static current regulation and does not affect the switching of the adaptive linearization bias module Module1, the switching module Module2, and the power amplifier HBT0. The function of the fifth resistor R5 is to ensure that when the resistance value of the seventh resistor R7 changes, the corresponding change in the collector current Ic5 of the fifth transistor HBT5 can smoothly flow into the switching module Module2, acting as a current limiting function.

[0048] Analysis of the control process of the seventh resistor R7 affecting the operating point static current is as follows:

[0049] The current IR7 flowing through the seventh resistor R7 can be expressed as:

[0050]

[0051] The current IR4 flowing through the fourth resistor R4 can be expressed as:

[0052]

[0053] The potential at point B can be expressed as:

[0054] V B = V be2 + V be4 + I E4 R 4

[0055] = 2V be + I E4 R 4

[0056] = V be1 + V be0 + I b R b

[0057] = 2V be + I b R b 。

[0058] Then the expression of Ib0 can be obtained:

[0059]

[0060] When the parameters except the seventh resistor R7 are fixed, increasing the resistance value of the seventh resistor R7 can increase both the base current and the collector current of the power amplifier HBT0, and vice versa, thus realizing the control of the static current.

[0061] In Figure 2 the structure shown for simulation, Figure 3 、 Figure 4 the curves of the bias voltage of the bias circuit varying with the input power and the output power are shown. It can be seen that its bias voltage can increase slowly with the increase of the input power, so as to dynamically adjust the bias point under high-power conditions and optimize indexes such as linearity and 1dB compression point. Figure 5 、 Figure 6 The curves of the simulation gain curve and the AMAM curve varying with the output power are shown. It can be seen that the adaptive bias circuit can effectively suppress the gain compression problem, expand the 1dB compression point and optimize indexes such as linearity.

[0062] For the switching function, the switching voltage Vcon is conventionally set to 3V, and at this time the power amplifier is in the on state, and the static current is shown in Table 1 below. And when the switching voltage Vcon is set to 2V, the power amplifier is off, as shown in Table 2 below.

[0063] Table 1

[0064] Icq_total_mA Iref_mA Icon_mA Idd_mA Icc_mA 172.054 10.295 23.962 0.957 136.840

[0065] Table 2

[0066] Icq_total_mA Iref_mA Icon_mA Idd_mA Icc_mA 10.599 10.521 0.071 9.644E-5 0.008

[0067] As can be seen from the above table, except that there is still part of the Iref current in the static current regulation module Module3, the currents of the other modules are all turned off, and the entire power amplifier is turned off accordingly.

[0068] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all such changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A switchable adaptive dynamic bias circuit for a power amplifier, characterized in that: It includes an adaptive linearization bias module (Module1), a switch module (Module2) and a static current regulation module (Module3); The adaptive linearization bias module (Module1) is used to dynamically adjust the linearity index of the power amplifier (HBT0) according to the static current of the adaptive linearization bias module (Module1) 3; The switch module (Module2) is used to control the power amplifier (HBT0) to turn on or off according to the voltage drop of the switch voltage (Vcon) on the corresponding trunk series resistor; The static current regulating module (Module3) is used to regulate the static current according to the voltage drop of the reference voltage (Vref) on the corresponding main circuit series resistor.

2. A switchable adaptive dynamic bias circuit for a power amplifier according to claim 1, characterized in that: The structure of the adaptive linearization bias module (Module1) is as follows: the collector of the first transistor (HBT1) is connected to the power supply voltage (Vdd) through the first resistor (R1), the emitter of the first transistor (HBT1) is connected to the base of the power amplifier (HBT0) through the ballast resistor (Rb), and the base of the first transistor (HBT1) is connected to the output end of the switch module (Module2) and is grounded through a bias capacitor (Cbias).

3. A switchable adaptive dynamic bias circuit for a power amplifier according to claim 2, characterized in that: The structure of the switch module (Module2) is as follows: the switch voltage (Vcon) is used as the output end of the switch module (Module2) through the second resistor (R2), and is respectively connected to the base of the second transistor (HBT2), the collector of the second transistor (HBT2), the base of the third transistor (HBT3) and the collector of the third transistor (HBT3); the emitter of the second transistor (HBT2) is connected to the base of the fourth transistor (HBT4) through the third resistor (R3); the emitter of the third transistor (HBT3) is respectively connected to the output end of the static current regulation module (Module3) and the collector of the fourth transistor (HBT4); the emitter of the fourth transistor (HBT4) is grounded through the fourth resistor (R4).

4. A switchable adaptive dynamic bias circuit for a power amplifier according to claim 3, characterized in that: The structure of the static current regulation module (Module3) is as follows: the collector of the fifth transistor (HBT5) as the output end of the static current regulation module (Module3) is connected to the switching voltage (Vcon) through the fifth resistor (R5), the base of the fifth transistor (HBT5) is connected to the base of the sixth transistor (HBT6) and the collector of the sixth transistor (HBT6), the emitter of the fifth transistor (HBT5) is connected to the base of the seventh transistor (HBT7) through the sixth resistor (R6), the collector of the sixth transistor (HBT6) is connected to the reference voltage (Vref) through the seventh resistor (R7), the emitter of the sixth transistor (HBT6) is connected to the collector of the seventh transistor (HBT7), and the emitter of the seventh transistor (HBT7) is grounded.

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