Voltage controlled attenuator circuit
By employing parallel stacked transistors and a microstrip line structure connected in parallel to ground in the voltage-controlled attenuator circuit, the problem of uneven frequency response at high frequencies is solved, and the power compression point and system performance are improved.
Patent Information
- Application Number
- CN202511742360.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-25
- Publication Date
- 2026-02-10
AI Technical Summary
Existing voltage-controlled attenuators have uneven frequency response, poor gain, and low power compression point at high frequencies, which leads to decreased system performance and increased debugging complexity.
By adopting a parallel stacked transistor structure and a microstrip line structure connected to ground, the matching state of the branch circuit is improved, the gate voltage swing of the transistor is reduced, and the power compression point is increased.
It improves the flatness of attenuation and raises the power compression point at high frequencies, simplifying the system debugging process.
Smart Images
Figure CN121508488A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of voltage-controlled attenuator chip technology, and in particular to a voltage-controlled attenuator circuit with a high power compression point and wide bandwidth with high flatness. Background Technology
[0002] A voltage-controlled attenuator (VCA) chip is a functional circuit that adjusts the amplitude (power) of a radio frequency signal by applying an external control voltage. Compared with fixed or digital attenuators, analog VCA attenuators have advantages such as wider operating bandwidth, continuously adjustable attenuation, smaller size, and easier integration. They are widely used in automatic gain control (AGC) systems, vector regulators, and phased array antenna systems.
[0003] With the continuous development of microwave radio frequency technology, the operating frequency of communication systems has been continuously increasing, rising from the traditional low-frequency microwave band to millimeter wave and even terahertz band, requiring the development of voltage-controlled attenuator chips for the corresponding frequency bands. Similar to the low-frequency band, most voltage-controlled attenuators in the current millimeter wave band use a balanced circuit topology. This circuit topology connects multiple transistors or diodes connected in parallel to ground between two orthogonal coupling circuits. The impedance of the transistors or diodes changes with the external control voltage, thereby generating a continuously changing transmission coefficient. The signal reflected by the transistors or diodes is absorbed by the load at the isolation end of the orthogonal coupling circuit. The main advantages of this circuit topology are: (1) The impedance variation range of the parallel transistors or diodes is large, enabling the voltage-controlled attenuator circuit to achieve a wide range of attenuation changes. (2) The return loss of the input and output ports can be kept below -10dB under different attenuation states, achieving good matching with the preceding and following stage circuits.
[0004] However, the parasitic parameters of semiconductor devices (transistors or diodes), such as parasitic capacitance and series inductance, have a more pronounced impact on circuit performance as the operating frequency increases. Specifically, the attenuation of a voltage-controlled attenuator (VCO) circuit exhibits a significant frequency response; that is, under a fixed control voltage, the attenuation is smaller at lower frequencies and larger at higher frequencies within the operating frequency range. This frequency response degrades the overall system gain flatness, affecting overall system performance. To improve the flatness of the VCO and the system, it is necessary to design a dedicated compensation circuit or write complex control power supply programs, increasing system complexity and cost.
[0005] On the other hand, the impedance of a semiconductor device changes significantly when it transitions from an off state to an on state, while the control voltage adjustment range for this transition state is very small. Therefore, traditional voltage-controlled attenuator circuits are highly sensitive to the control voltage when operating between the maximum and minimum attenuation states. Since the signal power input to the voltage-controlled attenuator circuit is related to the induced RF voltage on the semiconductor device, an increase in input signal power leads to a larger swing in the induced RF voltage on the semiconductor device, causing a change in the semiconductor device's impedance. At the circuit level, this manifests as a change in attenuation with the input signal power, i.e., power compression by the voltage-controlled attenuator. The problem of an excessively low power compression point in the intermediate attenuation state is common in traditional voltage-controlled attenuators. Once the input signal power changes, it is necessary to re-establish the correspondence between the control voltage and attenuation of the voltage-controlled attenuator circuit, significantly increasing the workload of system debugging. Summary of the Invention
[0006] The technical problem to be solved by the present invention is how to provide a balanced voltage-controlled attenuator circuit with a high power compression point and wide bandwidth and high flatness.
[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a voltage-controlled attenuator circuit, comprising: an input circuit, a branch circuit, and an output circuit. Two branch circuits with identical structures are provided between the input circuit and the output circuit. The first output quadrature coupling circuit port of the input circuit is connected to the input terminal of the first branch circuit, and the output terminal of the first branch circuit is connected to the first input quadrature coupling circuit port of the output circuit. The second output quadrature coupling circuit port of the input circuit is connected to the input terminal of the second branch circuit, and the output terminal of the second branch circuit is connected to the second input quadrature coupling circuit port of the output circuit. The first branch circuit and the second branch circuit include several multi-stage parallel stacked transistor structures. A microstrip line structure connected in parallel to ground is provided inside the series capacitor in the first branch circuit and the second branch circuit to improve the matching state of the branch.
[0008] A further technical solution is that the input circuit includes an input quadrature coupling circuit and a load resistor R. 01 The input terminal of the input quadrature coupling circuit is the radio frequency input port RF. IN The load resistor R 01 The first output quadrature coupling circuit port and the second output quadrature coupling circuit port of the input quadrature coupling circuit are connected to the isolation terminal of the input quadrature coupling circuit, respectively, and are connected to the matching microstrip line L0 of the first branch circuit and the second branch circuit.
[0009] A further technical solution is that the output circuit includes an output quadrature coupling circuit and a load resistor R. 02The output terminal of the output quadrature coupling circuit is a radio frequency output port (RF). OUT The load resistor R 02 The output quadrature coupling circuit is connected to the isolation terminal of the output quadrature coupling circuit. The first input quadrature coupling circuit port and the second input quadrature coupling circuit port of the output quadrature coupling circuit are respectively connected to the matching microstrip line L of the first branch circuit and the second branch circuit. N+2 connect.
[0010] A further technical solution is that the first branch circuit and the second branch circuit have the same structure, including a multi-stage parallel stacked transistor structure and a microstrip line structure connected to ground. Each branch circuit includes matching microstrip lines L0~L1. N+2 Series capacitors C1 and C2, stacked transistor M 11 ~M 1N and stacked transistor M 21 ~M 2N Gate bias resistor R 11 ~R 1N Gate resistance R 21 ~R 2N , connected in parallel to ground microstrip line L A ~L B and control voltage port V C ; One end of the branch circuit is connected to the series capacitor C1 via the matching microstrip line L0, and the other end is connected to the matching microstrip line L... N+2 Connect capacitor C2 in series; capacitors C1 and C2 are connected by matching microstrip lines L1~L2. N+1 They are connected in series, with stacked transistors connected in parallel to ground between two adjacent matching microstrip lines; Among them, transistor M 11 The drain of transistor M is connected to the junction between matching microstrip line L1 and matching microstrip line L2. 11 The source of the transistor M 21 The drain connection of transistor M 21 The source of the transistor M is grounded through a via. 11 The gate is connected to resistor R 11 With control voltage port V C Connection, at the same time, M 11 The gate is connected to resistor R 21 With transistor M 21 The gates of the two transistors are connected, which allows the control voltage to be applied to the gates of the two transistors, while avoiding crosstalk caused by the direct connection of the gates of the two transistors. Transistor M 12 The drain of transistor M is connected to the junction between matching microstrip line L2 and matching microstrip line L3. 12 The source of the transistor M 22The drain connection of transistor M 22 The source of the transistor M is grounded through a via. 12 The gate is connected to resistor R 12 With control voltage port V C Connection, at the same time, M 12 The gate is connected to resistor R 22 With transistor M 22 The gates of the two transistors are connected, which allows the control voltage to be applied to the gates of the two transistors, while avoiding crosstalk caused by the direct connection of the gates of the two transistors. Similarly, transistor M... 1N Drain-matched microstrip line L N Matching microstrip line L N+1 The junction between them, transistor M 1N The source of the transistor M 2N The drain connection of transistor M 2N The source of the transistor M is grounded through a via. 1N The gate is connected to resistor R 1N With control voltage port V C Connection, at the same time, M 1N The gate is connected to resistor R 2N With transistor M 2N The gates of the two transistors are connected, which allows the control voltage to be applied to the gates of the two transistors, while avoiding crosstalk caused by the direct connection of the gates of the two transistors. microstrip line L A One end of the microstrip line L1 is connected to the junction between the series capacitor C1 and the microstrip line L1, and the ground microstrip line L1 is connected to the junction between the series capacitor C1 and the microstrip line L1. A The other end is grounded; microstrip line L to ground B One end is connected in series with capacitor C2 and microstrip line L N+1 At the junction between them, the other end of the microstrip line LB is grounded and connected in parallel to the microstrip line L. A and L B Used to improve the frequency response of branch circuits at the high end of the operating frequency band.
[0011] The beneficial effects of the above technical solution are as follows: the radio frequency (RF) signal transmitted in the branch circuit of the attenuator circuit will induce a change in the gate voltage of the parallel transistor. When the swing of the gate-induced voltage is too large, it will cause the operating state of the transistor to deviate from the static bias point, resulting in an impedance change. In traditional voltage-controlled attenuators, the gate voltage swing of a single parallel transistor is usually half of the RF signal voltage. However, by using the stacked structure of two transistors in this application, the gate voltage swing of each transistor will be reduced to one-quarter of the RF signal voltage. A higher power RF signal is required to cause an impedance change in the stacked parallel transistors, thereby increasing the power compression point of the voltage-controlled attenuator circuit. The parallel microstrip line structure added to the branch circuit is simple, easy to design and implement, and does not increase the design difficulty of the overall voltage-controlled attenuator circuit.
[0012] The improvements in power compression point and flatness of the voltage-controlled attenuator circuit are mainly due to the parallel stacked transistor structure, the inter-gate resistance of the stacked transistors, and the parallel-to-ground microstrip line structure used in the branch circuit, regardless of the semiconductor substrate material and devices used. It is applicable to voltage-controlled attenuator circuit designs with different semiconductor substrate materials, devices, and operating frequencies. Attached Figure Description
[0013] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0014] Figure 1 This is a schematic diagram of the voltage-controlled attenuator circuit described in an embodiment of the present invention; Figure 2 This is a circuit topology diagram of a balanced voltage-controlled attenuator in the prior art, as shown in the embodiments of the present invention. Figure 3a This refers to the frequency response of the attenuation amount of the voltage-controlled attenuator circuit described in this embodiment of the invention under different control voltages; Figure 3b This refers to the frequency response of attenuation in existing voltage-controlled attenuator circuits under different control voltages. Figure 4 This is a comparison chart of the attenuation of two voltage-controlled attenuator circuits as a function of the input signal power (power compression) under a fixed control voltage. Detailed Implementation
[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0016] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.
[0017] like Figure 1 As shown, this embodiment of the invention discloses a voltage-controlled attenuator circuit. The attenuator circuit includes an input circuit, two structurally identical branch circuits, and an output circuit. Two structurally identical branch circuits are arranged between the input circuit and the output circuit. The first output quadrature coupling circuit port of the input circuit is connected to the input terminal of the first branch circuit, and the output terminal of the first branch circuit is connected to the first input quadrature coupling circuit port of the output circuit. The second output quadrature coupling circuit port of the input circuit is connected to the input terminal of the second branch circuit, and the output terminal of the second branch circuit is connected to the second input quadrature coupling circuit port of the output circuit. The first and second branch circuits include several multi-stage parallel stacked transistor structures. A microstrip line structure connected in parallel to ground is arranged inside the series capacitor in the first and second branch circuits to improve the matching state of the branch circuits.
[0018] Connecting the source and drain of two (or more) transistors sequentially creates a stacked transistor structure. The first and second branch circuits utilize a multi-stage parallel stacked transistor structure, reducing the RF voltage across a single transistor and thus increasing the power compression point of the overall voltage-controlled attenuator circuit. Furthermore, a microstrip line structure connected in parallel to ground is incorporated within the series capacitors in both the first and second branch circuits, improving the branch matching and resulting in a flatter frequency response for the voltage-controlled attenuator circuit.
[0019] Furthermore, such as Figure 1 As shown, the input circuit includes an input quadrature coupling circuit and a load resistor R. 01 The input terminal of the input quadrature coupling circuit is the radio frequency input port RF. IN The load resistor R 01 The first output quadrature coupling circuit port and the second output quadrature coupling circuit port of the input quadrature coupling circuit are connected to the isolation terminal of the input quadrature coupling circuit, respectively, and are connected to the matching microstrip line L0 of the first branch circuit and the second branch circuit.
[0020] Furthermore, such as Figure 1 As shown, the output circuit includes an output quadrature coupling circuit and a load resistor R. 02 The output terminal of the output quadrature coupling circuit is a radio frequency output port (RF). OUT The load resistor R02 The output quadrature coupling circuit is connected to the isolation terminal of the output quadrature coupling circuit. The first input quadrature coupling circuit port and the second input quadrature coupling circuit port of the output quadrature coupling circuit are respectively connected to the matching microstrip line L of the first branch circuit and the second branch circuit. N+2 connect.
[0021] Furthermore, such as Figure 1 As shown, the first branch circuit has the same structure as the second branch circuit, including a multi-stage parallel stacked transistor structure and a microstrip line structure connected to ground. Each branch circuit includes matching microstrip lines L0~L1. N+2 Series capacitors C1 and C2, stacked transistor M 11 ~M 1N and stacked transistor M 21 ~M 2N Gate bias resistor R 11 ~R 1N Gate resistance R 21 ~R 2N , connected in parallel to ground microstrip line L A ~L B and control voltage port V C ; One end of the branch circuit is connected to the series capacitor C1 via the matching microstrip line L0, and the other end is connected to the matching microstrip line L... N+2 Connect capacitor C2 in series; capacitors C1 and C2 are connected by matching microstrip lines L1~L2. N+1 They are connected in series, with stacked transistors connected in parallel to ground between two adjacent matching microstrip lines; Among them, transistor M 11 The drain of transistor M is connected to the junction between matching microstrip line L1 and matching microstrip line L2. 11 The source of the transistor M 21 The drain connection of transistor M 21 The source of the transistor M is grounded through a via. 11 The gate is connected to resistor R 11 With control voltage port V C Connection, at the same time, M 11 The gate is connected to resistor R 21 With transistor M 21 The gates of the two transistors are connected, which allows the control voltage to be applied to the gates of the two transistors, while avoiding crosstalk caused by the direct connection of the gates of the two transistors. Transistor M 12 The drain of transistor M is connected to the junction between matching microstrip line L2 and matching microstrip line L3. 12 The source of the transistor M 22 The drain connection of transistor M 22The source of the transistor M is grounded through a via. 12 The gate is connected to resistor R 12 With control voltage port V C Connection, at the same time, M 12 The gate is connected to resistor R 22 With transistor M 22 The gates of the two transistors are connected, which allows the control voltage to be applied to the gates of the two transistors, while avoiding crosstalk caused by the direct connection of the gates of the two transistors. Similarly, transistor M... 1N Drain-matched microstrip line L N Matching microstrip line L N+1 The junction between them, transistor M 1N The source of the transistor M 2N The drain connection of transistor M 2N The source of the transistor M is grounded through a via. 1N The gate is connected to resistor R 1N With control voltage port V C Connection, at the same time, M 1N The gate is connected to resistor R 2N With transistor M 2N The gates of the two transistors are connected, which allows the control voltage to be applied to the gates of the two transistors, while avoiding crosstalk caused by the direct connection of the gates of the two transistors. microstrip line L A One end of the microstrip line L1 is connected to the junction between the series capacitor C1 and the microstrip line L1, and the ground microstrip line L1 is connected to the junction between the series capacitor C1 and the microstrip line L1. A The other end is grounded; microstrip line L to ground B One end is connected in series with capacitor C2 and microstrip line L N+1 The nodes between them, the microstrip line L B The other end is grounded and connected in parallel to the ground microstrip line L. A and L B It is used to improve the frequency response of branch circuits at the high end of the operating frequency band and avoid the phenomenon of increased transmission loss at the high end of the operating frequency band caused by the parasitic capacitance of the stacked transistor structure.
[0022] The branch circuit structure in the voltage-controlled attenuator circuit can be used to improve the circuit performance of a balanced voltage-controlled attenuator circuit based on an orthogonal coupling circuit structure. The voltage-controlled attenuator circuit can be implemented using semiconductor substrates made of materials including, but not limited to, silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), and indium phosphide (InP).
[0023] The attenuator structure can be used to design voltage-controlled attenuator circuits with different operating frequencies, including but not limited to microwave, millimeter-wave, and even higher terahertz bands. Depending on the operating frequency, the capacitors, inductors, resistors, and transistors in the circuit structure can be implemented in different ways. The microstrip line elements in the circuit structure can also be implemented in various ways depending on the designed operating frequency, ranging from low to high frequencies, and can be implemented using various forms including but not limited to lumped inductors, spiral inductors composed of microstrip transmission lines, and microstrip transmission lines with high characteristic impedance.
[0024] Figure 1 Each parallel stacked transistor structure in the voltage-controlled attenuator circuit described herein comprises two transistors, serving as an example to illustrate the practical effects of the invention. Depending on the actual needs of the voltage-controlled attenuator circuit design, three or more transistors can be used to form a stacked transistor structure. The orthogonal coupling circuit in the voltage-controlled attenuator circuit structure can be a Lange structure orthogonal coupling circuit, or other structures can also be used. Each of the two branch circuits in the voltage-controlled attenuator circuit has a control voltage port Vc, clearly demonstrating the circuit topology of the invention. In actual circuit design and layout, the control voltage ports Vc of the two branches can be interconnected and merged into one port as needed. The RF performance and operating state of the voltage-controlled attenuator are independent of whether the control voltage ports are merged.
[0025] Figure 2 It is a traditional balanced voltage-controlled attenuator circuit topology, through with Figure 1 Compared to the circuit topology of this invention, the main difference lies in the branch circuit structure: such as Figure 2 As shown, the microstrip lines L1~L are matched in the branch circuit. N+1 Transistors M1~M1 connected in parallel N It is a single transistor, and a stacked transistor structure consisting of multiple transistors with their sources and drains connected together is not used. Furthermore, the junction between matching microstrip line L0 and matching microstrip line L1 is not designed to be connected in parallel to ground microstrip line L. A In matching microstrip line L N+1 and matching microstrip line L N+2 The nodes between them were not designed to be connected in parallel to the ground microstrip line L. B .
[0026] like Figure 3a To measure the attenuation of the voltage-controlled attenuator circuit designed using this invention under different control voltage conditions, Figure 3b This represents the attenuation of a traditional balanced voltage-controlled attenuator under different control voltage conditions. By comparison, the voltage-controlled attenuator circuit designed in this invention exhibits lower attenuation at higher operating frequencies, approaching the attenuation at lower operating frequencies, thus achieving high flatness of attenuation across the entire operating frequency range.
[0027] like Figure 4 As shown, the power compression curves of the voltage-controlled attenuator circuit designed in this invention and the traditional balanced voltage-controlled attenuator are compared under a fixed control voltage. It can be seen that the input P-1dB compression point of the traditional balanced voltage-controlled attenuator circuit is 15.5dBm, while the input P-1dB compression point of the voltage-controlled attenuator circuit designed in this invention is 19.5dBm. This invention can improve the power compression point of the voltage-controlled attenuator circuit and enhance its power tolerance.
Claims
1. A voltage-controlled attenuator circuit, characterized in that... include: The circuit includes an input circuit, a branch circuit, and an output circuit. Two branch circuits with identical structures are provided between the input circuit and the output circuit. The first output quadrature coupling circuit port of the input circuit is connected to the input terminal of the first branch circuit, and the output terminal of the first branch circuit is connected to the first input quadrature coupling circuit port of the output circuit. The second output quadrature coupling circuit port of the input terminal circuit is connected to the input terminal of the second branch circuit, and the output terminal of the second branch circuit is connected to the second input quadrature coupling circuit port of the output terminal circuit. The first branch circuit and the second branch circuit include several multi-stage parallel stacked transistor structures. A microstrip line structure connected in parallel to ground is set inside the series capacitor in the first branch circuit and the second branch circuit to improve the matching state of the branch.
2. The voltage-controlled attenuator circuit as described in claim 1, characterized in that: The input circuit includes an input quadrature coupling circuit and a load resistor R. 01 The input terminal of the input quadrature coupling circuit is the radio frequency input port RF. IN The load resistor R 01 The first output quadrature coupling circuit port and the second output quadrature coupling circuit port of the input quadrature coupling circuit are connected to the isolation terminal of the input quadrature coupling circuit, respectively, and are connected to the matching microstrip line L0 of the first branch circuit and the second branch circuit.
3. The voltage-controlled attenuator circuit as described in claim 1, characterized in that: The output circuit includes an output quadrature coupling circuit and a load resistor R. 02 The output terminal of the output quadrature coupling circuit is a radio frequency output port (RF). OUT The load resistor R 02 The output quadrature coupling circuit is connected to the isolation terminal of the output quadrature coupling circuit. The first input quadrature coupling circuit port and the second input quadrature coupling circuit port of the output quadrature coupling circuit are respectively connected to the matching microstrip line L of the first branch circuit and the second branch circuit. N+2 connect.
4. The voltage-controlled attenuator circuit as described in claim 1, characterized in that: The first branch circuit has the same structure as the second branch circuit, including a multi-stage parallel stacked transistor structure and a microstrip line structure connected to ground. Each branch circuit includes matching microstrip lines L0~L1. N+2 Series capacitors C1 and C2, stacked transistor M 11 ~M 1N and stacked transistor M 21 ~M 2N Gate bias resistor R 11 ~R 1N Gate resistance R 21 ~R 2N , connected in parallel to ground microstrip line L A ~L B and control voltage port V C ; One end of the branch circuit is connected to the series capacitor C1 via the matching microstrip line L0, and the other end is connected to the matching microstrip line L... N+2 Connect capacitor C2 in series; capacitors C1 and C2 are connected by matching microstrip lines L1~L2. N+1 They are connected in series, with stacked transistors connected in parallel to ground between two adjacent matching microstrip lines; Among them, transistor M 11 The drain of transistor M is connected to the junction between matching microstrip line L1 and matching microstrip line L2. 11 The source of the transistor M 21 The drain connection of transistor M 21 The source of the transistor M is grounded through a via. 11 The gate is connected to resistor R 11 With control voltage port V C Connection, at the same time, M 11 The gate is connected to resistor R 21 With transistor M 21 The gate is connected; Transistor M 12 The drain of transistor M is connected to the junction between matching microstrip line L2 and matching microstrip line L3. 12 The source of the transistor M 22 The drain connection of transistor M 22 The source of the transistor M is grounded through a via. 12 The gate is connected to resistor R 12 With control voltage port V C Connection, at the same time, M 12 The gate is connected to resistor R 22 With transistor M 22 The gate is connected; Similarly, transistor M... 1N Drain-matched microstrip line L N Matching microstrip line L N+1 The junction between them, transistor M 1N The source of the transistor M 2N The drain connection of transistor M 2N The source of the transistor M is grounded through a via. 1N The gate is connected to resistor R 1N With control voltage port V C Connection, at the same time, M 1N The gate is connected to resistor R 2N With transistor M 2N The gate is connected; microstrip line L A One end of the microstrip line L1 is connected to the junction between the series capacitor C1 and the microstrip line L1, and the ground microstrip line L1 is connected to the junction between the series capacitor C1 and the microstrip line L1. A The other end is grounded; microstrip line L to ground B One end is connected in series with capacitor C2 and microstrip line L N+1 The nodes between them, the microstrip line L B The other end is grounded and connected in parallel to the ground microstrip line L. A and L B Used to improve the frequency response of branch circuits at the high end of the operating frequency band.
5. The voltage-controlled attenuator circuit as described in claim 1, characterized in that: The voltage-controlled attenuator chip is implemented using a semiconductor substrate made of silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), or indium phosphide (InP).
6. The voltage-controlled attenuator circuit as described in claim 1, characterized in that: The voltage-controlled attenuator operates in the microwave, millimeter-wave, or terahertz frequency bands.
7. The voltage-controlled attenuator circuit as described in claim 1, characterized in that: The stacked transistor structure includes two or more transistors connected in parallel.
8. The voltage-controlled attenuator circuit as described in claim 1, characterized in that: The orthogonal coupling circuits in the input and output circuits are orthogonal coupling circuits with a Lange structure.
9. The voltage-controlled attenuator circuit as described in claim 1, characterized in that: In the voltage-controlled attenuator circuit, each of the two branch circuits has a control voltage port Vc, and the two control voltage ports Vc are connected to each other and merged into one port.