A switchable adaptive dynamic bias circuit for power amplifier

Abstract

The present invention discloses a switchable adaptive dynamic bias circuit for a power amplifier, which relates to radio frequency integration technology. This solution addresses the inconvenience of dynamic adjustment in existing technologies. An adaptive linearization bias module is used to dynamically adjust the linearity index of the power amplifier based on the quiescent current of the adaptive linearization bias module 3; a switch module is used to control the power amplifier on or off based on the voltage drop across the corresponding trunk series resistor caused by the switch voltage; and a quiescent current adjustment module is used to adjust the quiescent current based on the voltage drop across the corresponding trunk series resistor caused by the reference voltage. Advantages of the invention include: dynamic adjustment of the linearity index of the power amplifier can be achieved, achieving a balance between suppressing self-heating effects and improving linearity. Simply adjusting the voltage of the corresponding switch in the bias circuit controls the switching of the entire power amplifier. Precise adjustment of the quiescent current can be achieved 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 bias circuit applied to a power amplifier. Background Art

[0002] Traditional power amplifiers can use complementary metal oxide semiconductors (CMOS), gallium arsenide heterojunction bipolar transistors (GaAs HBTs), and gallium arsenide pseudomorphic high electron mobility transistors (GaAs pHEMTs) as power amplifier components. RF power amplifiers implemented using CMOS devices, while offering good compatibility and low cost, suffer from low linearity and low withstand voltage. GaAs pHEMTs, on the other hand, offer superior noise performance and are widely used in low-noise amplifiers and RF switches. However, their process costs are relatively high, and they are more commonly used in high-frequency power amplifiers, such as microwave and millimeter-wave amplifiers. When designing power amplifiers for the sub-6 GHz band, GaAs HBTs offer advantages such as excellent material thermal stability, high output power, high linearity, and excellent device reliability.

[0003] RF power amplifiers implemented using GaAs HBT devices generally use load pull to find the maximum output power point. To improve the average efficiency of the power amplifier, it is required to have high efficiency over a wide operating range. Therefore, design considerations generally compromise between efficiency and linearity, resulting in the amplifier's linearity not reaching the optimal design. For HBT monolithic integrated circuits, the bias circuit, as an important component of the RF amplifier, provides a DC bias point for the circuit, directly affecting the power amplifier's gain, efficiency, and linearity specifications. When the GaAs HBT process is used with high power input, the voltage drop at the base-emitter junction and the self-heating effect of the process itself will cause the transistor operating point to change, resulting in changes in the overall circuit gain and linearity.

[0004] In order to improve the linearity of the amplifier and avoid gain compression and nonlinear distortion of the signal, a bias circuit structure is usually used to change the bias voltage or bias current of the transistor with the change of the input signal power, so that the amplifier operates in a dynamic state. This bias circuit is called a dynamic bias structure. Representative literature includes [1][2][3][4].

[0005] In the design of MMIC amplifiers, in order to improve the linearity of the amplifier while preventing the bias point of the amplifier from fluctuating with changes in ambient temperature, an active bias circuit is often used to stabilize the bias point of the amplifier, thereby improving the linearity of the amplifier. Moreover, the active bias circuit structure not only enables the amplifier to operate stably and output stably, but also compensates for changes in ambient temperature and fluctuations in power supply voltage, thereby improving the stability of the amplifier. Representative literature in this regard includes [5][6][7][8].

[0006] Previous adaptive bias circuits usually compromise linearity and suppress self-heating effects through ballast resistors, and due to the need to shut down the power amplifier, an external switch is generally added to shut down the power amplifier.

[0007] References

[0008] [1]Zheng RQ, Zhang Gh, Yu K, et al.A 5.7-6.4GHz GaAs HBT poweramplifier 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 amplifier[J]. China Integrated Circuits, 2006, (11): 32-37.

[0010] [3]YSNoh,Ji.H.Kim,MMIC power amplifier with on-chip bias currentcontrolling circuit for W-CDMA mobile handset[J], Electronics Letters2002,38(25):1686-1688.

[0011] [4]YSNoh,CSPark,An Intelligent Power Amplifier MMIC Using a NewAdaptive Bias Control Circuit for W-CDMA Applications[J], IEEE J.Solid StateCircuits,2004,39(6):967-970.

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

[0013] [6]YSNoh and CSPark, PCS / W-CDMA dual band MMIC power amplifier with a newly proposed linearizing bias circuit[J], IEEE J.Solid-StateCircuits, 2002, 37(9):1096-1099

[0014] [7] K.Fujita, K.Shirakawa, et al.A 5GHz high efficiency and lowdistortion InGaP / GaAs HBT power amplifier MMIC[A], IEEE MTT-S MicrowaveSymp.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 present invention aims to provide a switchable adaptive dynamic bias circuit for a power amplifier to solve the above problems in the prior art.

[0017] The present invention provides a switchable adaptive dynamic bias circuit for a power amplifier, comprising an adaptive linearization bias module, a switch module, and a quiescent current regulation module.

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

[0019] The switch module is used to control the power amplifier to be turned on or off according to the voltage drop of the switch voltage on the corresponding trunk series resistor;

[0020] The static current regulating module is used to regulate the static current according to the voltage drop of the reference voltage on the corresponding main circuit series resistor.

[0021] The switchable adaptive dynamic bias circuit for a power amplifier described in the present invention has the following advantages:

[0022] (1) The integrated adaptive linearization bias module can realize dynamic adjustment of the linearity index of the power amplifier, and there is also a choke resistor, which achieves a balance between suppressing the self-heating effect and improving the linearity.

[0023] (2) The switch module is integrated into the bias circuit, eliminating the need for a traditional additional CMOS switch to control the on / off of the power amplifier. Instead, the entire power amplifier can be controlled by simply adjusting the voltage of the corresponding switch in the bias circuit.

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

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

[0026] Figure 2 It is a schematic diagram of the structure of a simulation circuit used in the switchable adaptive dynamic bias circuit described in the present invention.

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

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

[0029] Figure 5 This is a waveform diagram showing how the gain Gain of the switchable adaptive dynamic bias circuit described in the present invention changes with the output power Pout.

[0030] Figure 6 This is a waveform diagram showing how the AMAM curve of the switchable adaptive dynamic bias circuit described in the present invention changes with the output power Pout.

[0031] Reference numerals:

[0032] Adaptive linearization bias module Module1, switch module Module2, quiescent current regulation module Module3;

[0033] A first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and a 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, switch voltage Vcon, power supply voltage Vdd. DETAILED DESCRIPTION

[0037] The switchable adaptive dynamic bias circuit for a power amplifier described in the present invention is as follows Figure 1 As shown, it includes 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 quiescent current of the adaptive linearization bias module Module13.

[0039] The switch module Module2 is used to control the power amplifier HBT0 to be turned on or off according to the voltage drop of the switch voltage Vcon on the corresponding trunk series resistor.

[0040] 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 series resistor.

[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 to ground through the bias capacitor Cbias.

[0042] The structure of the switch module Module2 is as follows: the switching voltage Vcon is connected to the output terminal 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 terminal 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 end 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 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.

[0044] The switchable adaptive dynamic bias circuit for a power amplifier described in the present invention is specifically applied as follows: Figure 2 As shown, combined Figure 1 The specific working principle of the structural analysis shown is as follows:

[0045] Adaptive linearization bias 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, which in turn causes the base-emitter junction voltage Vbe0 to decrease. On the other hand, part of the RF signal leaks to the first transistor HBT1 through the ballast resistor Rb. Due to the rectification 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 presence of the bias capacitor Cbias, the voltage at point B remains constant, and the voltage drop across the ballast resistor Rb is very small, so Vel ≥ Iel*Rb. It is worth noting that although the voltage drop across the ballast resistor Rb is very small, it has a thermal stabilization effect and can effectively suppress the natural self-heating effect of the HBT. The selection of bias capacitor Cbias mainly depends on the equivalent impedance ZB seen from point B. Within the operating frequency band, the impedance value of bias capacitor Cbias needs to be smaller than ZB to ensure that all RF signals from the first transistor HBT1 are short-circuited to ground without affecting the normal operation of other circuits.

[0046] Switch module Module 2: In addition to providing appropriate operating voltage and current to the quiescent current regulation module Module 3, it also acts as a switch for the power amplifier HBT0. The base-emitter junction of a conventional HBT is approximately 1.24V. The diode-connected second and third transistors HBT2 and HBT3 clamp the voltage, maintaining the collector-emitter voltage at 1.24V. A third resistor R3 is connected in series to provide current limiting. Due to the influence of the adaptive linearization bias module Module 1, the collector-emitter potential of the fourth transistor HBT4 is also limited to the base-emitter junction conduction voltage. Therefore, the voltage drop at point B is the sum of the two base-emitter junction voltages plus the voltage drop across the fourth resistor R4. Conversely, the voltage drop at point B is also the sum of the base-emitter junction voltage of the first transistor HBT1 plus the base-emitter junction voltage of the power amplifier HBT0, plus the voltage drop across the ballast resistor Rb. Therefore, by controlling the switching voltage Vcon and the voltage divider of the second resistor R2, the power amplifier HBT0 can be turned on or off.

[0047] Quiescent Current Regulation Module 3: Its primary function is to precisely regulate the quiescent current, facilitating later debugging. The seventh resistor R7 acts as a negative feedback resistor. By adjusting its resistance, it divides the voltage. This resistor modifies the common-base voltage drop of the sixth transistor HBT6. Simultaneously, the fifth and sixth transistors HBT5 and HBT6 form a mirrored current source structure, thereby controlling the collector current Ic5 of the fifth transistor HBT5. Similar to the switch module Module 2, the connection of the three HBT transistors in the quiescent current regulation module Module 3 also clamps the voltage, while the series connection of the sixth resistor R6 also provides current limiting. The clamping function of the quiescent current regulation module Module 3 primarily regulates its own quiescent current and does not affect the switching of the adaptive linearization bias module Module 1, the switch module Module 2, or the power amplifier HBT0. The fifth resistor R5 ensures that changes in the collector current Ic5 of the fifth transistor HBT5, corresponding to changes in the resistance of the seventh resistor R7, allow the current to flow smoothly into the switch module Module 2, thus providing current limiting.

[0048] The control process of the seventh resistor R7 affecting the quiescent current at the operating point is analyzed 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 R4

[0055] =2V be +I E4 R4

[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] All parameters except the seventh resistor R7 are fixed. Increasing the resistance of the seventh resistor R7 can increase the base current and collector current of the power amplifier HBT0, and vice versa, thereby achieving control of the quiescent current.

[0061] exist Figure 2 The simulation is performed on the structure shown. Figure 3 、 Figure 4 The figure shows the bias voltage of the bias circuit as a function of input power and output power. It can be seen that the bias voltage can slowly increase as the input power increases, thereby dynamically adjusting the bias point under high-power conditions and optimizing indicators such as linearity and 1dB compression point. Figure 5 、 Figure 6 The graph of the simulated gain curve and AMAM curve changing with output power shows that the adaptive bias circuit can effectively suppress the gain compression problem, extend the 1dB compression point, and optimize linearity and other indicators.

[0062] For the switch function, the switch voltage Vcon is generally set to 3V, at which point the amplifier is turned on, and the quiescent current is shown in Table 1. However, when the switch voltage Vcon is set to 2V, the amplifier is turned off, as shown in Table 2.

[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 for the quiescent current regulation module Module3, which still has some Iref current, the currents of other modules are all turned off, and the entire power amplifier is turned off accordingly.

[0068] Those skilled in the art can make various other corresponding changes and deformations based on the technical solutions and concepts described above, and all of these changes and deformations should fall within the scope of protection 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 quiescent 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 be turned 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; 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 the bias capacitor (Cbias); The switch module (Module2) has a structure as follows: a switch voltage (Vcon) is used as an output terminal of the switch module (Module2) through a second resistor (R2), and is respectively connected to a base of a second transistor (HBT2), a collector of a second transistor (HBT2), a base of a third transistor (HBT3), and a collector of a third transistor (HBT3); an emitter of the second transistor (HBT2) is connected to a base of a fourth transistor (HBT4) through a third resistor (R3); an emitter of the third transistor (HBT3) is respectively connected to an output terminal of a static current regulation module (Module3) and a collector of a fourth transistor (HBT4); and an emitter of the fourth transistor (HBT4) is grounded through a fourth resistor (R4); The structure of the static current regulation module (Module3) is as follows: the collector of the fifth transistor (HBT5) is connected to the switching voltage (Vcon) through the fifth resistor (R5) as the output end of the static current regulation module (Module3); 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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