Amplifier circuit topological structure based on active bias

Abstract

The invention discloses an active bias-based amplifier circuit topological structure, which comprises an active bias circuit unit and a radio frequency amplification circuit unit, and is characterized in that the active bias circuit unit comprises a bias circuit I, a bias circuit II and a transistor I, and the radio frequency amplification circuit unit comprises an input matching network, an output matching network and a transistor II; an input signal sequentially passes through the input matching network, the transistor II and the output matching network to amplify an output signal. According to the circuit topological structure, when the second transistor is in saturation rollback, the first transistor gradually compensates the bias voltage, so that the grid bias voltage of the first transistor changes, in the process, the linearity of a signal becomes better along with the decrease of injection power, and due to the change of the grid bias voltage, the power is reduced slowly, and the linearity of the signal becomes better. The efficiency of the power amplifier in the rollback state can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of monolithic microwave integrated circuits, and in particular to an amplifier circuit topology structure based on active bias. Background Art

[0002] With the rapid development of wireless communication technology, microwave and millimeter wave monolithic integrated power amplifiers, which are core components in the system, have higher requirements for efficiency, linearity and other indicators. Since the essential properties of various processes determine the output power, linearity and other characteristics of the power amplifiers that can be developed by each process, it is necessary to improve the linearity and efficiency of the circuit from the perspective of circuit design.

[0003] In order to improve the efficiency of the power amplifier back-off zone, existing solutions include: envelope elimination and recovery technology, envelope tracking technology, polar coordinate technology, out-of-phase technology and Doherty technology. These technologies are relatively complex in design and difficult to implement. Traditional methods to improve linearity include the simpler Sweet Spot technology, which uses the phase cancellation produced by different gate voltages of the front and rear stages to improve linearity. Although it will improve the linearity when the saturation back-off is about 3dB, it will deteriorate the linearity in the linear region.

[0004] Therefore, designing a relatively simple active bias circuit structure to improve the efficiency and linearity of the power amplifier during saturation and back-off has important practical significance. Summary of the invention

[0005] The problem to be solved by the present invention is to provide an amplifier circuit topology structure based on active bias, which is used to achieve different bias states at different injection powers and effectively improve the efficiency and linearity of the power amplifier in the back-off state.

[0006] The present invention adopts the following technical solution: an amplifier circuit topology structure based on active bias, including an active bias circuit unit and a radio frequency amplification circuit unit;

[0007] The active bias circuit unit consists of a transistor 1, a bias circuit 1 and a bias circuit 2. An external Vg' DC voltage source is connected to the gate of the transistor 1 through the bias circuit 1; an external Vd' DC voltage source is connected to the drain of the transistor 1 through the bias circuit 2, and the source of the transistor 1 is connected to the input matching network at an appropriate position.

[0008] Preferably, bias circuit 1 is composed of a bias first inductor, a bias second inductor, a bias first capacitor and a bias first resistor, an external Vg' DC voltage source is connected from the bias first resistor, and is connected to the gate of transistor 1 through the bias second inductor and the bias first inductor in sequence, and the bias first capacitor is connected between the bias first inductor and the bias second inductor.

[0009] Preferably, bias circuit 2 is composed of bias circuit 2 first inductor, bias circuit 2 second inductor, bias circuit 2 first capacitor and bias circuit 2 first resistor. An external Vd' DC voltage source is connected to the bias circuit 2 first resistor, and is connected to the drain of transistor 1 through bias circuit 2 second inductor and bias circuit 2 first inductor in sequence. Bias circuit 2 first capacitor is connected between bias circuit 2 first inductor and bias circuit 2 second inductor.

[0010] The RF amplifier circuit unit is composed of transistor 2, an input matching circuit and an output matching circuit; an external Vg DC voltage source is connected to the gate of transistor 2 through an input matching network; an external Vd DC voltage source is connected to the drain of transistor 2 through an output matching network, and the source of transistor 2 is appropriately grounded.

[0011] The RF amplification circuit unit is used to amplify the RF signal. The input signal RFin is sequentially passed through the input matching network, transistor 2, and the output matching network to amplify the output signal RFout.

[0012] Preferably, the input matching network is composed of a first inductor of the input network, a second inductor of the input network, a third inductor of the input network, a first capacitor of the input network, a second capacitor of the input network and a first resistor of the input network. The input signal RFin is input from the first inductor of the input network, passes through the second inductor of the input network, and is connected to the gate of the transistor 2.

[0013] Preferably, the output matching network is composed of an output network first inductor, an output network second inductor, an output network third inductor, an output network first capacitor and an output network second capacitor. The output network first inductor is connected to the drain of transistor 2, and the output signal RFout is obtained through the output network second capacitor and the output network third inductor in sequence.

[0014] Furthermore, transistor 1 and transistor 2 form a variable resistor controlled by a bias voltage difference, and as the injected DC voltage source increases, the gate voltage of the active bias circuit unit increases. When the input signal RFin power is close to the saturated injected signal of transistor 2, transistor 1 is in an open circuit state; when the injected signal decreases from large to small and transistor 2 saturates and retreats, the linearity of the signal becomes better as the injected power decreases.

[0015] Preferably, the transistor 1 and the transistor 2 are HEMT devices based on GaAs or GaN technology, or other microwave power transistor devices, and the number is one or more, determined according to the output power value and transistor power density.

[0016] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0017] 1. The present invention is based on an active bias amplifier circuit topology structure, has a simple structure, and is suitable for the design of power amplifiers of various types and frequency bands.

[0018] 2. The present invention is based on an amplifier circuit topology structure with active bias. When the input signal power is close to the saturation injection signal of transistor 2, transistor 1 is in an open circuit state, thereby achieving saturation power and efficiency performance that is substantially unchanged compared to when there is no transistor 1.

[0019] 3. The present invention is based on an amplifier circuit topology structure with active bias. In the process of the injected signal changing from large to small, that is, the transistor second saturation back-off, the linearity of the signal will become better as the injected power decreases. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The topological structure block diagram of the amplifier circuit based on active bias of the present invention;

[0021] Figure 2 The topological structure principle diagram of the amplifier circuit based on active bias of the present invention;

[0022] Figure 3 It is the schematic diagram of variable resistor;

[0023] Figure 4 This is a circuit topology block diagram of an embodiment of the present invention;

[0024] Figure 5 It is a partial circuit schematic diagram of an embodiment of the present invention;

[0025] Explanation of the numbers in the figures:

[0026] 101-active bias circuit unit; 102-RF amplifier circuit unit; 103-bias circuit 1; 104-bias circuit 2; 105-input matching network; 106-output matching network; 111-transistor 1; 211-transistor 2;

[0027] 321-biased first inductor; 322-biased second inductor; 331-biased first capacitor; 341-biased first resistor; 421-biased second first inductor; 422-biased second second inductor; 431-biased second first capacitor; 441-biased second first resistor;

[0028] 521-the first inductor of the input network; 522-the second inductor of the input network; 523-the third inductor of the input network; 531-the first capacitor of the input network; 532-the second capacitor of the input network; 541-the first resistor of the input network; 621-the first inductor of the output network; 622-the second inductor of the output network; 623-the third inductor of the output network; 631-the first capacitor of the output network; 632-the second capacitor of the output network. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Unless otherwise defined, the technical terms or scientific terms of the present disclosure shall have the usual meanings understood by persons with ordinary skills in the field described in the present disclosure. The words "include" or "comprises" and the like in the present disclosure mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but do not exclude other elements or objects. The positional relationship of various elements in the drawings of the present disclosure is only used to indicate their relative positional relationship. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0031] The present invention provides an amplifier circuit topology based on active bias, such as Figure 1 As shown, it includes: an active bias circuit unit 101 and a radio frequency amplification circuit unit 102; the structure adopts an active bias structure as a dynamic bias of the radio frequency amplification transistor, which can be applied to microwave and millimeter wave monolithic integrated power amplifier circuits, especially in the design of high linearity and high efficiency circuits.

[0032] Among them, the active bias circuit unit 101 is composed of a transistor 111, a bias circuit 103 and a bias circuit 2 104. The external Vg' DC voltage source is connected to the gate of the transistor 111 through the bias circuit 103; the external Vd' DC voltage source is connected to the drain of the transistor 111 through the bias circuit 2 104, and the source of the transistor 1 is connected to the input matching network 105 at an appropriate position.

[0033] The RF amplifier circuit unit 102 is composed of a transistor 211, an input matching circuit 105 and an output matching circuit 106; an external Vg DC voltage source is connected to the gate of the transistor 211 through the input matching network 105; an external Vd DC voltage source is connected to the drain of the transistor 211 through the output matching network 105, and the source of the transistor 211 is appropriately grounded.

[0034] The input signal RFin passes through the input matching network 105, the transistor 211, and the output matching network 106 in sequence to amplify the output signal RFout.

[0035] Preferably, Figure 2As shown, bias circuit 1 103 is composed of bias first inductor 321, bias second inductor 322, bias first capacitor 331 and bias first resistor 341, and bias circuit 2 104 is composed of bias second first inductor 421, bias second second inductor 422, bias second first capacitor 431 and bias second first resistor 441.

[0036] The input matching network is composed of a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor and a first resistor. The output matching network is composed of a first inductor, a second inductor, a third inductor, a first capacitor and a second capacitor.

[0037] The principle of the present invention is as follows:

[0038] When the amplifier is working, as the injected power increases, the power gain first maintains a stable value and then gradually decreases. This process is called gain compression. When the linearizer is working, as the injected power increases, the power gain gradually increases from a stable value. After adding the linearizer, the total gain of the amplifier and the linearizer will undergo a gain expansion process, thereby improving the linearity of the amplifier.

[0039] Therefore, it is necessary to design an equivalent circuit in which the gate voltage increases with the increase of injection. The present invention utilizes the deep triode region of the HEMT device to design a variable resistor controlled by the bias voltage difference, thus realizing an active bias circuit in which the gate voltage increases with the increase of injection.

[0040] When the HEMT device works in the deep triode region, Ids is a linear function of Vds. This linear function shows that the channel between the source and the drain can be represented by a linear resistor, and the resistance value R on for:

[0041]

[0042] Among them, μ n represents the electron mobility, C ox represents the capacitance per unit area of ​​the gate oxide layer, w represents the thickness of the epitaxial layer, L represents the channel length, and v GS represents the gate-source voltage, v TH Represents the threshold voltage.

[0043] The drain, gate and source of the HEMT device in the active bias circuit are defined as d', g' and s' respectively. When it works in the deep triode region, the relationship between the resistance of the variable resistor and the drain-source voltage and the gate-source voltage can be obtained by combining the formula: Rd's'=(Vd'-Vs') / Id's'.

[0044] With the basic model of variable resistors, it is also necessary to add variable resistors to amplifier design to qualitatively analyze the basic principles of variable resistors in amplifier circuit design.

[0045] like Figure 3 As shown, in the DC path from the external Vd' DC voltage source to Vg, there are three resistors, R1, Rd's', and R2. Considering Ig's', the potential of Vs' can be calculated by the following formula:

[0046]

[0047] When Rd's' is infinite, Vs'=Vg+Ig's'·R2; when Rd's'+R1 approaches 0, Vs'=Vd'+Ig's'·R2. If the influence of Ig's' is ignored, it can be obtained that when Rd's' is infinite, Vs'=Vg; when Rd's'+R1 approaches 0, Vs'=Vd'.

[0048] When Vs' is connected to the RF terminal, the voltage at Vs' will change between Vd' and Vg as Rd's' changes. The value of Rd's' is a function of Vd's' and Vg's', and the potential at Vs' changes with RF injection. This is a basic model of active bias that changes with injection.

[0049] In one embodiment of the present invention, based on the development of a GaAs power amplifier with an operating frequency of 19 GHz-21 GHz and a saturated output power of 24 dBm, the active bias amplifier circuit topology structure proposed in the present invention is further described in detail.

[0050] like Figure 4 As shown, the power amplifier of this embodiment can be divided into a radio frequency amplification circuit unit and an active bias circuit unit. The radio frequency amplification circuit unit is designed with a matching network according to the required electrical performance, and is a three-stage amplification topology with an independent gate bias network and a drain bias network. The radio frequency signal can still be amplified without an active bias circuit unit.

[0051] This embodiment further includes two active bias circuit units, each unit is composed of a bias transistor, a bias circuit 1 and a bias circuit 2, and the two identical bias circuits are connected in parallel and then connected to a Vg DC voltage source.

[0052] To further illustrate this embodiment, a partial circuit schematic diagram is shown in FIG. Figure 5 As shown, the circuit topology structure includes: an active bias circuit unit, a second-stage inter-stage matching network of a radio frequency amplifier circuit unit, a third-stage transistor and a gate bias network.

[0053] Furthermore, the gate bias network is composed of an independent gate bias circuit structure, and each gate bias circuit supplies power to each transistor. Both the third-stage transistor and the bias transistor use HEMT devices. The gate of the third-stage transistor is connected to the second inter-stage matching network; the drain of the third-stage transistor is connected to the output matching network; and the source of the third-stage transistor is grounded at a suitable position.

[0054] The external Vg DC voltage source is divided and connected to the gate of the bias transistor through the bias circuit 1; the external Vg DC voltage source is divided and connected to the drain of the bias transistor through the bias circuit 2; the source of the bias transistor is connected to the inter-stage matching network 2 at a suitable position.

[0055] The working process of this embodiment is as follows: as the RF power increases, under the action of the bias transistor, the third-stage transistor gradually changes from a relatively linear bias state to a bias state of Vd and Vg, so that the power and efficiency performance of the amplifier in the saturation state are almost the same as when there is no active bias; and when the amplifier retreats from the saturation state, due to the change in bias, the change in linearity will be faster than the decrease in efficiency, thereby improving the efficiency and linearity performance of the amplifier when retreating.

[0056] It should be noted that, taking into account the operating frequency, bandwidth, power, efficiency, linearity, consistency, and yield rate, transistor 1 and transistor 2 in this embodiment are manufactured using appropriate semiconductor technology, and use GaAs or GaN materials as substrates, but are not limited to this.

[0057] It can be seen that the amplifier circuit topology structure based on active bias in the present invention can achieve different bias states at different injection powers, thereby improving the efficiency and linearity in the back-off state.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An amplifier circuit topology based on active bias, characterized in that: include: An active bias circuit unit (101) and a radio frequency amplification circuit unit (102); The radio frequency amplification circuit unit (102) is composed of a transistor 2 (211), an input matching circuit (105) and an output matching circuit (106); the input signal RFin is sequentially passed through the input matching network (105), the transistor 2 (211) and the output matching network (106) to amplify the output signal RFout; The active bias circuit unit (101) is composed of a transistor one (111), a bias circuit one (103) and a bias circuit two (104); an external Vg' DC voltage source is connected to the gate of the transistor one (111) through the bias circuit one (103), an external Vd' DC voltage source is connected to the drain of the transistor one (111) through the bias circuit two (104), and the source of the transistor one (111) is connected to the input matching network (105).

2. The active bias based amplifier circuit topology according to claim 2, characterized in that: The external Vg DC voltage source is connected to the gate of transistor 2 (211) through the input matching network (105); the external Vd DC voltage source is connected to the drain of transistor 2 (211) through the output matching network (106); and the source of transistor 2 (211) is grounded.

3. The active bias based amplifier circuit topology according to claim 1, characterized in that: The bias circuit 1 (103) comprises: a biased first inductor (321), a biased second inductor (322), a biased first capacitor (331) and a biased first resistor (341); The external Vg' DC voltage source is connected from a bias first resistor (341), and is connected to the gate of a transistor (111) through a bias second inductor (322) and a bias first inductor (321) in sequence; the bias first capacitor (331) is connected between the bias first inductor (321) and the bias second inductor (322).

4. The active bias based amplifier circuit topology according to claim 3, characterized in that: The bias circuit 2 (104) comprises: a bias second first inductor (421), a bias second second inductor (422), a bias second first capacitor (431) and a bias second first resistor (441); The external Vd' DC voltage source is connected from the bias second first resistor (441), and is connected to the drain of the transistor one (111) through the bias second second inductor (422) and the bias second first inductor (421) in sequence, and the bias second first capacitor (431) is connected between the bias second first inductor (421) and the bias second second inductor (422).

5. The active bias based amplifier circuit topology according to claim 1, characterized in that: The input matching network (105) comprises: an input network first inductor (521), an input network second inductor (522), an input network third inductor (523), an input network first capacitor (531), an input network second capacitor (532) and an input network first resistor (541); The input signal RFin is input from the first inductor (521) of the input network, passes through the second inductor (522) of the input network, and is connected to the gate of the transistor 2 (211).

6. The active bias based amplifier circuit topology according to claim 5, characterized in that: The output matching network (106) comprises: an output network first inductor (621), an output network second inductor (622), an output network third inductor (623), an output network first capacitor (631) and an output network second capacitor (632); The first inductor (621) of the output network is connected to the drain of the second transistor (211), and the output signal RFout is obtained by sequentially passing through the second capacitor (632) of the output network and the third inductor (623) of the output network.

7. The active bias based amplifier circuit topology according to claim 1, characterized in that: The transistor 1 (111) and the transistor 2 (211) form a variable resistor controlled by a bias voltage difference. As the injected DC voltage source increases, the gate voltage of the active bias circuit unit (101) increases.

8. The active bias based amplifier circuit topology according to claim 7, characterized in that: When the power of the input signal RFin is close to the saturated injection signal of transistor 2 (211), transistor 1 (111) is in an open circuit state; when the injection signal decreases from large to small and transistor 2 (211) saturates and retreats, the linearity of the signal becomes better as the injection power decreases.

9. The active bias based amplifier circuit topology according to claim 1, characterized in that: The transistor one (111) and the transistor two (211) are HEMT devices or microwave power transistor devices, and the number is one or more, which is determined according to the output power value and the transistor power density.

10. The active bias based amplifier circuit topology according to claim 9, characterized in that: The HEMT device uses GaAs or GaN material as a substrate.

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