An input protection circuit for a wideband radio frequency amplifier

Abstract

The application discloses an input protection circuit of a wideband radio frequency amplifier, and belongs to the field of radio frequency amplifier technology. IN VCC is a power input end, RF OUT is a radio frequency signal output end; the input end of the power detection circuit (203) is connected with the output end of the input matching (202) and the input end of the input pre-matching (204). The application has the characteristics of high integration and wafer area miniaturization, and can greatly reduce the cost of realizing high-precision input level limitation.

Description

Technical Field

[0001] This invention relates to the field of input protection circuits, and more particularly to an input protection circuit for a broadband radio frequency amplifier. Background Technology

[0002] With the rapid development of semiconductor technology, the transmission and processing of radio frequency (RF) signals have become increasingly complex. The application of new materials and processes, as well as the trend towards integration, have driven RF amplifiers to continuously evolve towards miniaturization, higher frequencies, and wider operating bandwidths, while simultaneously increasing the requirements for their reliability. Therefore, to ensure that RF amplifiers are not damaged by excessively strong RF signals, it is particularly necessary to add an overvoltage protection circuit to their input ports.

[0003] VCC represents the power input terminal, RFIN represents the RF signal input terminal, and RFOUT represents the RF signal output terminal. The RF signal input terminal of this power amplifier first passes through an input protection circuit, then through input matching, and is connected to the base of a single-cell transistor or multiple pairs of parallel single-cell transistors T1. The collector of the single-cell transistor or multiple pairs of parallel single-cell transistors T1 is connected to the signal output terminal through output matching. The bias circuit provides bias current, L1 is a choke inductor, and C1 is a decoupling capacitor. The input protection circuit typically uses a unidirectional or bidirectional limiting circuit with a PIN diode or Schottky diode for protection or control. The diode limiting circuit achieves clipping and limiting effects by utilizing the clamping effect of the diode; no additional bias is required, and it can be implemented on the transmission line.

[0004] Input protection circuits typically employ unidirectional or bidirectional limiting circuits using PIN diodes or Schottky diodes to protect or control the output voltage amplitude from excessive levels. Taking a forward limiting protection circuit with one or more diodes connected in series as an example, the diode threshold voltage is typically 0.7V. When the input signal level is high, the diode conducts, thus limiting the amplitude of the transmitted signal. Furthermore, in the design structure of broadband power amplifiers, there is a significant difference in gain between low and high frequencies, making it impossible for a diode limiting protection circuit without any bias to accurately limit the output voltage amplitude after signal amplification.

[0005] For diode-limiting circuits, a higher signal swing is required to limit the input signal. Typically, when the output power is 35dBm, the transistor area is relatively large, and its input impedance is 1~2 ohms. The input protection circuit of the RF amplifier is usually placed near the 50-ohm input port. In the design of broadband RF amplifiers using GaAsHBT technology, both the input protection circuit and input matching must be designed using gallium arsenide technology, which results in a larger wafer area and increases the cost of the broadband RF amplifier chip. However, gallium arsenide diodes are also prone to burnout when the input power is too high, leading to the failure of the entire circuit. Summary of the Invention

[0006] In view of the above problems, the present invention is proposed to provide an input protection circuit for a broadband radio frequency amplifier that overcomes or at least partially solves the above problems.

[0007] According to one aspect of the present invention, an input protection circuit for a broadband radio frequency amplifier is provided, the input protection circuit comprising: a power detection circuit (203), a gain control circuit (206), and a bias circuit module (201).

[0008] The overvoltage protection circuit is placed between the input matching (202) and the input pre-matching (204);

[0009] VCC is the power input terminal, RF IN For radio frequency signal input, RF OUT This is the radio frequency signal output terminal;

[0010] The input terminal of the power detection circuit (203) is connected to the output terminal of the input matching (202) and the input terminal of the input pre-matching (204).

[0011] Optionally, the input protection circuit further includes: the radio frequency signal input terminal is first connected to the base of transistor T2 via input matching (202), then via input pre-matching (204).

[0012] Optionally, the input protection circuit further includes:

[0013] The collector of transistor T2 is connected to the signal output terminal via output matching (205);

[0014] The bias circuit module (201) provides the bias current;

[0015] The output terminal of the power detection circuit (203) is connected to the input terminal of the gain control circuit (206), and the output terminal of the gain control circuit (206) is connected to the bias circuit module (201).

[0016] The collector of transistor T2 is also connected to one end of choke inductor L2, and the other end of choke inductor L2 is connected to the power input terminal VCC and one end of decoupling capacitor C2, respectively. The other end of decoupling capacitor C2 is grounded.

[0017] Optionally, the input matching (202) provides a network in the second harmonic range with low impedance and low conversion ratio.

[0018] Optionally, the transistor T2 is a single-cell transistor or multiple pairs of single-cell transistors T2 connected in parallel.

[0019] Optionally, the input protection circuit is loaded with an active bias.

[0020] This invention provides an input protection circuit for a broadband radio frequency amplifier, comprising: a power detection circuit (203), a gain control circuit (206), and a bias circuit module (201); the overvoltage protection circuit is placed between input matching (202) and input pre-matching (204); VCC is the power input terminal, and RF... IN For radio frequency signal input, RF OUT It serves as the output terminal for radio frequency signals; the input terminal of the power detection circuit (203) is connected to the output terminal of the input matching (202) and the input terminal of the input pre-matching (204). It features high integration and miniaturized wafer area, significantly reducing the cost of achieving high-precision input level limits.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A circuit diagram of an input protection circuit for a broadband radio frequency amplifier provided in an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of the input overvoltage protection circuit structure of a broadband radio frequency amplifier provided in an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the implementation structure of the broadband radio frequency amplifier provided in an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram illustrating the control accuracy of input / output power provided in an embodiment of the present invention. Detailed Implementation

[0027] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0028] The terms "comprising" and "having," and any variations thereof, in the specification, embodiments, claims, and drawings of this invention are intended to cover non-exclusive inclusion, such as including a series of steps or units.

[0029] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] An input overvoltage protection circuit suitable for broadband RF power amplifiers is provided, comprising: a power detection circuit 203, a gain control circuit 206, and a bias circuit module 201. The overvoltage protection circuit is positioned between the input matching 202 and the input pre-matching 204. The circuit requires an active bias to achieve more precise gain limiting, enabling input and output level limiting of the broadband RF power amplifier at different gains and protecting the transistors. Due to its high integration and miniaturized wafer area, this solution significantly reduces the cost of achieving high-precision input level limiting.

[0031] Figure 1 An input overvoltage protection circuit scheme for a broadband radio frequency amplifier according to an embodiment of this application is shown.

[0032] exist Figure 1 In this diagram, VCC represents the power input, RFIN represents the RF signal input, and RFOUT represents the RF signal output. The RF signal input of the power amplifier first passes through input matching 202, then through input pre-matching 204, and finally connects to the base of a single-cell transistor or multiple pairs of parallel single-cell transistors T2. The collector of the single-cell transistor or multiple pairs of parallel single-cell transistors T2 is connected to the signal output through output matching 205. The bias circuit module 201 provides the bias current, the power detection circuit 203, the gain control circuit 206, L2 is a choke inductor, and C2 is a decoupling capacitor. The power detection circuit 203 is placed between input matching 202 and input pre-matching 204. Input matching 202 provides a good network in the second harmonic range under low impedance and low conversion ratio conditions.

[0033] In one implementation, transistor T2 is a heterojunction bipolar transistor.

[0034] (Heterojunction bipolar transistor, HBT) is composed of a single-cell transistor or multiple pairs of single-cell transistors connected in parallel, depending on the specific situation.

[0035] Figure 2 An input overvoltage protection circuit for a broadband radio frequency amplifier according to an embodiment of the application is shown.

[0036] like Figure 2 As shown, VDD represents the power input terminal, Vbias represents the enable terminal of the bias circuit, Vcc represents the power input terminal of the gain control circuit, input represents the input terminal of the power detection circuit, and Ibias represents the bias current output terminal.

[0037] Among them, the input access node is Figure 1 Between input match 202 and input pre-match 204, the Ibias access node is... Figure 1 The base of a single-cell transistor or multiple pairs of parallel single-cell transistors T2 in a mid-frequency amplifier.

[0038] The power detection circuit 203 includes a rectifier unit consisting of capacitor C3, resistor R5 and diode D1; a bias unit consisting of resistor R3 and resistor R4; an amplification unit consisting of transistor T3 and diode D2; and a matching unit consisting of resistor R7, capacitor C4, resistor R8 and resistor R10.

[0039] The gain control circuit 206 includes resistors R9, R11, and R12, and transistor T4.

[0040] The bias circuit module 201 includes a resistor R6, a diode D3, a diode D4, a capacitor C5, and a transistor T5.

[0041] In this embodiment, the power detection circuit 203 rectifies and amplifies the signal, converting it into a stable voltage that flows into its matching unit and provides to the base of transistor T4 in the gain control circuit 206. Resistors R9, R11, and R12 provide pre-bias to transistor T4, thereby controlling the output current of the emitter stage of transistor T5 in the bias circuit module 201.

[0042] Figure 3 A schematic diagram of the implementation structure of the broadband radio frequency amplifier according to the embodiment of the application is shown;

[0043] exist Figure 3In this diagram, VCC represents the power input, RFIN represents the RF signal input, and RFOUT represents the RF signal output. The RF signal input of this power amplifier is first connected to the base of a single-cell transistor or multiple pairs of parallel single-cell transistors T6 via input matching 212, then to input pre-matching 214. The collector of the single-cell transistor or multiple pairs of parallel single-cell transistors T6 is connected to the signal output via output matching 215. 211 provides bias current for the bias circuit, 213 is the power detection circuit, 216 is the gain control circuit, L3 is the choke inductor, C3 is the decoupling capacitor, and R13 is the bias resistor.

[0044] in, Figure 2 The input access node is located between the matching circuit 212 and the pre-matching circuit 214. Figure 2 The Ibias access node is the base of a single-cell transistor of an RF amplifier or multiple pairs of parallel single-cell transistors T6. Figure 2 The Vcc access point is the base collector of the RF amplifier's single-cell transistor or multiple pairs of parallel single-cell transistors T6. In the design structure of the embodiment of this application, cell 210 represents the design and implementation by GaAs HBT wafer process, while other input matching 212, output matching 213, resistor R13, and capacitor C3 are implemented by substrate process or IPD process, and inductor L3 is also implemented by substrate process or IPD process.

[0045] Figure 4 The diagram illustrates an embodiment of the present invention, showing the control precision of the input / output power. By adjusting the bias current in the gain control circuit, a good power dynamic range is achieved, which can accurately limit the output voltage amplitude after signal amplification under different gains.

[0046] Beneficial effects: Active biasing enables more precise gain limiting, thereby limiting the input and output levels of broadband RF power amplifiers at different gains and protecting their transistors. Due to its high integration and miniaturized wafer size, this solution significantly reduces the cost of achieving high-precision input level limiting.

[0047] This package structure is suitable for broadband RF power amplifiers. The circuit features excellent power dynamic range, accurately limiting the output voltage amplitude after signal amplification. Protection circuitry is placed at the low-impedance end of the input transmission line's characteristic impedance, effectively reducing the design cost of the power amplifier.

[0048] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An input protection circuit for a broadband radio frequency amplifier, characterized in that, The input protection circuit includes: a power detection circuit (203), a gain control circuit (206), and a bias circuit module (201). The input protection circuit is placed between the input matching (202) and the input pre-matching (204); VCC is the power input terminal, RF IN is the radio frequency signal input terminal, RF OUT is the radio frequency signal output terminal; The input terminal of the power detection circuit (203) is connected to the output terminal of the input matching (202) and the input terminal of the input pre-matching (204); The RF signal input terminal is first connected to the base of transistor T2 via input matching (202), then via input pre-matching (204); The collector of transistor T2 is connected to the signal output terminal via output matching (205); The bias circuit module (201) provides the bias current; The output terminal of the power detection circuit (203) is connected to the input terminal of the gain control circuit (206), and the output terminal of the gain control circuit (206) is connected to the bias circuit module (201). The collector of transistor T2 is also connected to one end of choke inductor L2, and the other end of choke inductor L2 is connected to the power input terminal VCC and one end of decoupling capacitor C2, respectively. The other end of decoupling capacitor C2 is grounded.

2. A wideband radio frequency amplifier input protection circuit according to claim 1, wherein, The input matching (202) provides a network in the second harmonic range with low impedance and low conversion ratio.

3. A wideband RF amplifier input protection circuit according to claim 1, wherein, The transistor T2 is a single-cell transistor or multiple pairs of single-cell transistors T2 connected in parallel.

4. A wideband RF amplifier input protection circuit according to claim 1, wherein, The input protection circuit is loaded with an active bias.

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