RF circuit

Abstract

The present invention provides a radio frequency circuit, comprising a target radio frequency switch circuit and a radio frequency switch protection circuit. The target radio frequency switch circuit comprises a first transistor; the radio frequency switch protection circuit comprises a protection diode and a protection switch. When the target radio frequency switch circuit is turned on, the first transistor is turned on, the protection switch is turned on, and the protection diode is turned off to protect the target radio frequency switch circuit. When the target radio frequency switch circuit is turned off, the first transistor is turned off, the protection switch is turned off, and the protection diode is turned off to protect the target radio frequency switch circuit. Thus, the radio frequency switch protection circuit can protect the target radio frequency switch circuit both when the target radio frequency switch circuit is turned on or off, preventing charge accumulation from affecting the target radio frequency switch circuit, reducing the performance degradation rate of components in the target radio frequency switch circuit, and thereby improving the reliability and circuit performance of the target radio frequency switch circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency switches, and in particular to a radio frequency circuit. Background Art

[0002] Radio frequency (RF) switches play a key role in wireless communication systems. They are used to switch signals between different circuit paths, such as switching between receive and transmit modes, or distributing signals between different antenna and receiver circuits. Switching is typically controlled by transistors, and to ensure optimal functioning of the transistors, diodes are often connected to protect them.

[0003] With the advancement of wireless communication technology, the performance requirements for RF switches are becoming increasingly stringent, especially in terms of switching speed. Fast switching is crucial for improving communication efficiency, reducing power consumption, and enhancing user experience. Researchers have found that in high-frequency, fast-switching applications, charge accumulation can lead to diode performance degradation, resulting in reduced reliability and impacting the performance of the entire switch. Summary of the Invention

[0004] Embodiments of the present invention provide a new radio frequency circuit, including a new radio frequency switch protection circuit, which can effectively improve the problem of diode performance degradation in existing radio frequency switch protection circuits, thereby affecting the performance of the switch protection circuit.

[0005] An embodiment of the present invention provides a radio frequency circuit, including:

[0006] a plurality of cascaded radio frequency switch circuits, wherein the plurality of cascaded radio frequency switch circuits include a target radio frequency switch circuit, and the target radio frequency switch circuit includes a first transistor;

[0007] a radio frequency switch protection circuit, the radio frequency switch protection circuit comprising a protection diode and a protection switch, the radio frequency switch protection circuit comprising a protection diode and a protection switch, the cathode of the protection diode being coupled to the control terminal of the first transistor, the anode of the protection diode being coupled to the first terminal of the protection switch, the second terminal of the protection switch being grounded, and the control terminal of the protection switch being coupled to the first transistor;

[0008] When the target RF switch circuit is turned on, the first transistor is turned on, the protection switch is turned on, and the protection diode is turned off to protect the target RF switch circuit; when the target RF switch circuit is turned off, the first transistor is turned off, the protection switch is turned off, and the protection diode is turned off to protect the target RF switch circuit.

[0009] In some possible embodiments, the protection switch is a protection transistor, and the protection transistor and the first transistor are transistors of the same type;

[0010] The first transistor includes a source, a drain and a gate, and the gate of the first transistor serves as a control terminal of the first transistor;

[0011] The protection transistor includes a source, a drain and a gate, and the gate of the protection transistor serves as a control terminal of the protection switch.

[0012] In some possible embodiments, the carrier type of the conductive channel of the first transistor is the first conductivity type, the source and drain of the first transistor are doped with the first conductivity type, the drain of the protection transistor serves as the first end of the protection switch, and the source of the protection transistor serves as the second end of the protection switch;

[0013] The gate of the protection transistor is connected to the gate of the first transistor, and the source of the protection transistor is connected to the substrate of the first transistor.

[0014] In some possible embodiments, when the first transistor is turned off, both the first transistor and the protection transistor are turned off, the substrate ripple voltage of the first transistor is less than the forward conduction voltage of the protection diode, and the protection diode is forward cutoff.

[0015] In some possible embodiments, when the gate-source voltage of the first transistor is greater than or equal to the forward conduction voltage of the protection transistor and less than the reverse breakdown voltage of the protection diode, the first transistor and the protection transistor are both forward-conducted, and the protection diode is reverse-cutoff;

[0016] When the first transistor is overloaded, both the first transistor and the protection transistor are forward-conducted, the gate-source voltage of the first transistor is greater than the reverse breakdown voltage of the protection diode, and the protection diode reversely breaks down.

[0017] In some possible embodiments, the source and drain of the first transistor are doped with the second conductivity type, the carrier type of the conductive channel of the protection transistor is the second conductivity type, the source of the protection transistor serves as the first end of the protection switch, and the drain of the protection transistor serves as the second end of the protection switch;

[0018] A gate of the protection transistor is connected to the substrate of the first transistor, and a drain of the protection transistor is connected to the substrate of the first transistor.

[0019] In some possible embodiments, when the gate-source voltage of the first transistor is greater than the forward conduction voltage of the first transistor and greater than the forward conduction voltage of the protection transistor, the first transistor is forward-conducted, the protection transistor is in a normally-on state, and the protection diode is in a reverse state to protect the target RF circuit;

[0020] When the gate-source voltage of the first transistor is less than the forward conduction voltage of the protection transistor, the first transistor is turned off, the protection transistor is reversely cut off, and the protection diode is turned off to protect the target RF circuit.

[0021] In some possible embodiments, both the first transistor and the protection transistor are enhancement-mode transistors.

[0022] In some possible embodiments, the target RF switch circuit further includes: an impedance matching circuit and a capacitive reactance matching circuit;

[0023] The impedance matching circuit includes a first resistance circuit and a second resistance circuit, the first resistance circuit is coupled to the gate of the first transistor, and the second resistance circuit is coupled to the source and drain of the first transistor;

[0024] The capacitive reactance matching circuit includes a capacitor circuit, and the capacitor circuit is connected in parallel with the second resistor circuit.

[0025] In some possible embodiments, there are multiple RF switch protection circuits, and the multiple RF switch protection circuits are respectively connected to the multiple RF switch circuits.

[0026] Beneficial effects of the embodiments of the present invention:

[0027] An embodiment of the present invention provides a radio frequency circuit comprising a plurality of cascaded radio frequency switch circuits, wherein the plurality of cascaded radio frequency switch circuits include a target radio frequency switch circuit, wherein the target radio frequency switch circuit includes a first transistor; and a radio frequency switch protection circuit, wherein the radio frequency switch protection circuit includes a protection diode and a protection switch. When the target radio frequency switch circuit is turned on, the first transistor is turned on, the protection switch is turned on, and the protection diode is turned off to protect the target radio frequency switch circuit; when the target radio frequency switch circuit is turned off, the first transistor is turned off, the protection switch is turned off, and the protection diode is turned off to protect the target radio frequency switch circuit. Thus, by coupling the radio frequency switch protection circuit provided with the protection diode and the protection switch to the target radio frequency switch circuit, the radio frequency switch protection circuit can protect the target radio frequency switch circuit when the target radio frequency switch circuit is turned on or off, preventing charge accumulation from affecting the target radio frequency switch circuit, reducing the performance degradation rate of components in the target radio frequency switch circuit, and thereby improving the reliability and circuit performance of the target radio frequency switch circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 work.

[0029] Figure 1 is a schematic diagram of an embodiment of a radio frequency circuit provided by an embodiment of the present invention;

[0030] Figure 2 FIG. 1 is a schematic diagram of another embodiment of a radio frequency circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. In the present invention, unless otherwise specified, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; while "inside" and "outside" refer to the outline of the device.

[0032] The present invention provides a radio frequency circuit, including a radio frequency switching circuit and a radio frequency switch protection circuit. The radio frequency switching circuit is primarily used to switch signals between different circuit paths, while the radio frequency switching circuit protection circuit protects the radio frequency switching circuit to ensure the signal switching capability and communication efficiency of the radio frequency switching circuit. The radio frequency circuit provided by the present invention is described in detail below.

[0033] like Figure 1 FIG. 1 is a schematic diagram of an embodiment of a radio frequency circuit provided by the present invention. Figure 1In some embodiments, the RF circuit includes multiple cascaded RF switch circuits, which can switch signals to switch between receive or transmit modes, or distribute signals between different antennas and receiver circuits. The RF circuit also includes an RF switch protection circuit, which is typically electrically connected to the RF switch circuit to protect the RF switch circuit. In some embodiments, the multiple cascaded RF switch circuits include a target RF switch circuit, which in turn includes a first transistor 10. The RF switch protection circuit may include a protection diode 20 and a protection switch 30, both of which are connected to the first transistor 10 in the RF switch circuit to protect the first transistor 10.

[0034] Specifically, the protection diode 20 in the present application may include an anode and a cathode. The cathode of the protection diode 20 is coupled to the control terminal of the first transistor 10, and the anode of the protection diode 20 is coupled to the first terminal of the protection switch 30. The second terminal of the protection switch 30 is grounded, and the control terminal of the protection switch 30 is coupled to the first transistor 10. When the gate-source voltage of the first transistor 10 turns on the first transistor 10, that is, the target RF switch circuit is turned on and the target RF switch circuit operates normally; at this time, the protection switch is also turned on accordingly, and the cathode of the protection diode 20 is connected to the gate of the first transistor 10, so that the cathode of the protection diode 20 is connected to a high potential. At this time, the protection diode 20 is reverse-blocked, thereby protecting the RF circuit. The protection switch 30 in the turned-on state does not affect the protection effect of the protection diode 20 on the RF circuit. In other embodiments, when the gate-source voltage of the first transistor 10 turns on the first transistor 10, the protection switch 30 is also turned on accordingly; if the first transistor 10 is overloaded, the gate-source voltage of the first transistor 10 is greater than the reverse breakdown voltage of the protection diode 20, and the protection diode is reversely broken down, which can also play a role in protecting the RF switch circuit. When the gate-source voltage of the first transistor is unable to turn on the first transistor, the first transistor and the protection switch are both turned off. At this time, the protection diode is also turned off to protect the target RF switch circuit. The principle of the RF switch protection circuit protecting the RF switch circuit is described in detail in subsequent embodiments and is not limited here.

[0035] Continue to refer Figure 1 The first transistor 10 may include a source, a drain and a gate, and the gate of the first transistor 10 may serve as a control terminal of the first transistor 10 .

[0036] In this embodiment, the protection switch 30 may be a protection transistor 30 , which may also include a source, a drain, and a gate. The gate of the protection transistor 30 may serve as a control terminal of the protection switch 30 .

[0037] In this embodiment, the source and drain of the first transistor 10 both have the first conductivity type doping, and the source and drain of the protection transistor 30 also have the first conductivity type doping. The drain of the protection transistor 30 serves as the first terminal of the protection switch 30, and the source of the protection transistor 30 serves as the second terminal of the protection switch 30. In this case, the gate of the protection transistor 30 is connected to the gate of the first transistor 10, and the source of the protection transistor 30 is connected to the substrate of the first transistor 10.

[0038] Specifically, when the protection switch 30 is a protection transistor 30, if the gate-source voltage of the first transistor 10 is greater than the forward conduction voltage of the first transistor 10 itself, the first transistor 10 is forward-conducted, and the gate-source voltage of the first transistor 10 is greater than or equal to the forward conduction voltage of the protection transistor 30; when the gate of the protection transistor 30 is connected to the gate of the first transistor 10, so that the gate of the protection transistor 30 is connected to a high-voltage signal, the protection transistor 30 will also be forward-conducted. The anode of the protection diode 20 is connected to the drain of the protection transistor 30, and the cathode of the protection diode 20 is connected to the gate of the first transistor 10, so that the anode potential of the protection diode 20 is the same as the drain potential of the protection transistor 30, and is a low potential, and the cathode potential of the protection diode 20 is the same as the gate potential of the first transistor 10, and is a high potential. At this time, since the anode potential of the protection diode 20 is lower than the cathode potential of the protection diode, the protection diode is in a reverse working state.

[0039] In this embodiment, if the gate-source voltage of the first transistor 10 is less than the reverse breakdown voltage of the protection diode 20, that is, the voltage across the protection diode 20 is less than its own reverse breakdown voltage, then the protection diode 20 is in a reverse cutoff state. However, if the first transistor 10 is overloaded, that is, the gate-source voltage of the first transistor 10 is much greater than its own forward conduction voltage and much greater than the forward conduction voltage of the protection transistor 30, both the first transistor 10 and the protection transistor 30 are normally turned on. At this time, the gate-source voltage of the first transistor 10 is greater than the reverse breakdown voltage of the protection diode 20, and the protection diode 20 is reversely broken down.

[0040] In summary, when the first transistor 10 and the protection transistor 30 are forward-conducted, no matter whether the protection diode 20 is in the reverse cutoff state or the reverse breakdown state, the protection diode 20 is not forward-conducted, so it can play a certain voltage dividing role, thereby protecting the RF circuit.

[0041] In other embodiments, when the gate-source voltage of the first transistor 10 is 0 or a negative voltage, the first transistor 10 is turned off, and the gate-source voltage of the protection transistor 30 also becomes 0 or a negative voltage. Both cannot be forward-conducted and are in a cut-off or off state. At this time, the cathode of the protection diode 20 is connected to the gate of the first transistor 10, and the cathode of the protection diode 20 is 0 or a negative voltage; the anode of the protection diode 20 is connected to the drain of the protection transistor, and the first transistor 10 in the present application will generate a substrate ripple voltage, so that the drain of the protection transistor 30 is at a high potential, and then the anode of the protection diode 20 connected to the drain of the protection transistor 30 is at a high potential. At this time, the anode potential of the protection diode 20 is greater than the cathode potential of the protection diode 20, and the two ends of the protection diode are forward voltages. The protection diode may be forward-cut off or forward-conducted. However, in the embodiment of the present application, the substrate ripple voltage of the first transistor is generally required to be less than the forward conduction voltage of the protection diode 20, so that the protection diode 20 cannot conduct forward, thereby isolating the substrate ripple voltage of the first transistor, preventing the substrate ripple voltage from affecting the first transistor 10, and protecting the RF switching circuit. In other words, when the voltage across the first transistor 10 and the protection transistor 30 is at zero or negative, the protection diode 20 can effectively isolate the substrate ripple voltage, thereby protecting the RF switching circuit.

[0042] In actual RF circuits, since the ripple substrate voltage fluctuates, the forward voltage of the protection diode 20 generally needs to be greater than the maximum value of the ripple substrate voltage. In other embodiments, the forward voltage of the protection diode 20 can be an adjustable voltage; that is, the forward voltage of the protection diode 20 can be adjustable.

[0043] In the embodiment of the present application, the doping ranges of the first conductive type doping region and the second conductive type doping region in the protection diode 20 can be adjusted, that is, the doping ranges of the anode and cathode in the protection diode 20 can be adjusted, thereby adjusting the forward conduction voltage of the protection diode 20 to adapt to RF circuits of different powers.

[0044] In the embodiment of the present application, the first transistor 10 and the protection transistor 30 in the radio frequency circuit are transistors of the same type. For example, the first transistor 10 and the protection transistor 30 are both enhancement-mode transistors.

[0045] In one embodiment, both the first transistor 10 and the protection transistor 30 are NMOS transistors. In this solution, by using an NMOS transistor as the protection transistor 30, the protection transistor 30 can quickly conduct overload voltage during reverse cutoff or reverse breakdown, thereby avoiding damage to the RF switching circuit, thereby meeting the speed requirements of the RF switching circuit for the transistor.

[0046] In some other embodiments, the first transistor and the protection transistor may both be PMOS transistors.

[0047] Figure 2 This is a schematic diagram of another embodiment of the radio frequency circuit provided in the embodiment of the present application. Figure 1 and Figure 2 ,exist Figure 2 In the embodiment shown, the RF circuit also includes multiple cascaded RF switch circuits, the multiple cascaded RF switch circuits include a target RF switch circuit, and the target RF switch circuit includes a first transistor 10; the RF switch protection circuit includes a protection diode 20 and a protection switch 30, and the protection diode 20 and the protection switch 30 are both connected to the first transistor in the RF switch circuit to protect the first transistor.

[0048] In this embodiment, Figure 1 The difference between the RF circuit shown is that Figure 2 In the circuit shown, although the protection diode 20 and the protection switch 30 are both connected to the first transistor 10 in the RF switch circuit, the connection relationship is different; when the protection switch 30 is a protection transistor 30, the types of the first transistor 10 and the protection transistor 30 are also different. Figure 1 The first transistor 10 and the protection transistor 30 are of different types.

[0049] Specifically, the carrier type of the conductive channel of the first transistor 10 of the RF switch circuit is the second conductive type, and the source and drain of the first transistor 10 both have the second conductive type doping; when the protection switch 30 is a protection transistor 30, the carrier type of the conductive channel of the protection transistor 30 is also the second conductive type, and the source and drain of the protection transistor 30 both have the second conductive type doping. For example, the second conductive type and the second conductive type doping are both P-type, and both are PMOS transistors. In this case, the source of the protection transistor 30 serves as the first end of the protection switch 30, and the drain of the protection transistor 30 serves as the second end of the protection switch 30. The gate of the protection transistor 30 is connected to the substrate of the first transistor 10, and the drain of the protection transistor 30 is also connected to the substrate of the first transistor 10. The source of the protection transistor 30 is connected to the second conductive type doping region of the protection diode 20 (i.e., the anode of the protection diode); the first conductive type doping region of the protection diode 20 (i.e., the cathode of the protection diode) is connected to the gate of the first transistor 10.

[0050] In this embodiment, when the gate-source voltage of the first transistor 10 is greater than the forward conduction voltage of the first transistor 10, the first transistor 10 is forward-conducted; the gate and drain of the protection transistor 30 are connected to the substrate of the first transistor 10, and the substrate of the first transistor 10 is usually at zero potential, so the gate and drain of the protection transistor 30 are also at zero potential (the influence of the ripple substrate voltage is not considered at this time); the source of the protection transistor 30 and the anode of the protection diode 20 are connected to a negative potential, so the gate-source voltage of the protection transistor 30 is negative and less than the threshold voltage of the protection transistor 30, and the protection transistor 30 is in the on state and is in the normally-on state. The cathode of the protection diode 20 is connected to the gate of the first transistor 10 and is at a high potential, and the anode of the protection diode 20 is connected to the drain of the first transistor 10 and is at a low potential; therefore, the cathode potential of the protection diode 20 is greater than the anode potential of the protection diode 20, and the protection diode 20 is in the reverse state. If the voltage difference across the protection diode 20 is greater than the reverse cutoff voltage of the protection diode 20, the protection diode 20 is reverse cutoff; if the voltage difference across the protection diode 20 is further greater than the reverse breakdown voltage of the protection diode 20, the protection diode 20 is reversely broken down. Whether the protection diode 20 is reverse cutoff or reverse breakdown, it does not affect the protective effect of the protection diode 20. Since the protection transistor 30 is in the normally open state and the protection diode 20 is in the reverse state, the protection transistor 30 and the protection diode 20 can both play a voltage divider role, thereby protecting the RF switch circuit.

[0051] Similarly, if the first transistor 10 is overloaded, the first transistor 10 is forward-conducted; the gate and drain of the protection transistor 30 are connected to the substrate of the first transistor 10 and are in a 0 potential state, and the source of the protection transistor 30 is connected to the anode of the protection diode 20 and is in a negative potential. Therefore, the gate-source voltage of the protection transistor 30 is negative and less than the threshold voltage of the protection transistor 30, and the protection transistor 30 is in a forward-conducting state. The cathode potential of the protection diode 20 is greater than the anode potential of the protection diode 20, and the protection diode 20 is in a reverse state. The forward-conducting protection transistor 30 can quickly conduct the overloaded voltage, and the protection diode 20 can also be reverse-cutoff or reverse-breakdown to avoid the overloaded voltage from flowing. At this time, the protection transistor 30 and the protection diode 20 can also play a role in protecting the RF switching circuit.

[0052] In this embodiment, when the gate-source voltage of the first transistor 10 is positive and less than the threshold voltage of the first transistor 10, the first transistor 10 is forward-cut off and cannot be turned on; at this time, the gate and drain of the protection transistor 30 are both connected to the substrate of the first transistor 10, and the substrate of the first transistor 10 generates a ripple voltage so that the gate and drain of the protection transistor 30 are at a high potential, while the source of the protection transistor 30 is at a low potential state. At this time, the gate voltage of the protection transistor 30 is greater than the source voltage of the protection transistor, so that the protection transistor 30 cannot be forward-conducted and is in the off state. The ripple voltage cannot pass through the protection transistor 30 and cannot reach the protection diode 20. At this time, there is no voltage or voltage difference between the two ends of the protection diode 20; therefore, the protection transistor 30 can effectively isolate the impact of the ripple voltage on the RF switch circuit and play a role in protecting the RF switch circuit.

[0053] It should be noted that in the above embodiment, the opening or closing of the first transistor 10, the protection transistor 30 and the protection diode 20 include but are not limited to: forward / reverse conduction, forward / reverse breakdown, forward / reverse cutoff caused by a voltage difference between the two ends but the voltage difference is less than the threshold voltage, and cutoff caused by the absence of voltage at both ends, etc.

[0054] Please refer to Figure 1 and Figure 2 In the RF circuit provided in the present application, the target RF switch circuit may further include an impedance matching circuit and a capacitive reactance matching circuit. The impedance matching circuit includes a first resistor circuit and a second resistor circuit, wherein the first resistor circuit is coupled to the gate of the first transistor 10, and the second resistor circuit is coupled to the source and drain of the first transistor 10. The capacitive reactance matching circuit includes a capacitor circuit, which is connected in parallel with the second resistor circuit and coupled to the source and drain of the first transistor 10.

[0055] In this embodiment, the first resistance circuit and the second resistance circuit may each include one or more resistors or resistance devices, and the capacitor circuit may include one or more capacitors or capacitance devices, which is not limited in this application.

[0056] In the embodiment of the present application, there is one RF switch protection circuit and it is connected to the target RF switch circuit. In other embodiments, there may be multiple RF switch protection circuits, and the multiple RF switch protection circuits are electrically connected to multiple cascaded RF switch circuits respectively. The connection relationship between the RF switch protection circuit and the RF switch circuit and the specific structure of the RF switch protection circuit can be referred to the content of the above embodiments and will not be repeated here.

[0057] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A radio frequency circuit, characterized in that: include: A plurality of cascaded radio frequency switching circuits, configured to perform signal switching to switch between a receive or transmit mode, or to distribute signals between different antennas and receiver circuits; the plurality of cascaded radio frequency switching circuits including a target radio frequency switching circuit, the target radio frequency switching circuit including a first transistor; a radio frequency switch protection circuit, the radio frequency switch protection circuit comprising a protection diode and a protection switch, wherein a cathode of the protection diode is coupled to the control terminal of the first transistor, an anode of the protection diode is coupled to the first terminal of the protection switch, a second terminal of the protection switch is grounded, and the control terminal of the protection switch is coupled to the first transistor; When the target RF switch circuit is turned on, the first transistor is turned on, the protection switch is turned on, and the protection diode is turned off to protect the target RF switch circuit; When the target RF switch circuit is turned off, the first transistor is turned off, the protection switch is turned off, and the protection diode is turned off to protect the target RF switch circuit.

2. The radio frequency circuit according to claim 1, wherein: The protection switch is a protection transistor, and the protection transistor and the first transistor are transistors of the same type; The first transistor includes a source, a drain and a gate, and the gate of the first transistor serves as a control terminal of the first transistor; The protection transistor includes a source, a drain and a gate, and the gate of the protection transistor serves as a control terminal of the protection switch.

3. The radio frequency circuit according to claim 2, characterized in that: The source and drain of the first transistor are doped with the first conductivity type, the source and drain of the protection transistor are doped with the first conductivity type, the drain of the protection transistor serves as the first terminal of the protection switch, and the source of the protection transistor serves as the second terminal of the protection switch; The gate of the protection transistor is connected to the gate of the first transistor, and the source of the protection transistor is connected to the substrate of the first transistor.

4. The radio frequency circuit according to claim 3, characterized in that: When the first transistor is turned off, both the first transistor and the protection transistor are turned off, the substrate ripple voltage of the first transistor is less than the forward conduction voltage of the protection diode, and the protection diode is forward-cut off.

5. The radio frequency circuit according to claim 3, characterized in that: When the gate-source voltage of the first transistor is greater than or equal to the forward conduction voltage of the protection transistor and less than the reverse breakdown voltage of the protection diode, the first transistor and the protection transistor are both forward-conducted, and the protection diode is reverse-cutoff; When the first transistor is overloaded, both the first transistor and the protection transistor are forward-conducted, the gate-source voltage of the first transistor is greater than the reverse breakdown voltage of the protection diode, and the protection diode reversely breaks down.

6. The radio frequency circuit according to claim 2, characterized in that: The source and drain of the first transistor are doped with the second conductivity type, the source and drain of the protection transistor are doped with the second conductivity type, the source of the protection transistor serves as the first terminal of the protection switch, and the drain of the protection transistor serves as the second terminal of the protection switch; A gate of the protection transistor is connected to the substrate of the first transistor, and a drain of the protection transistor is connected to the substrate of the first transistor.

7. The radio frequency circuit according to claim 6, characterized in that: When the gate-source voltage of the first transistor is greater than the forward conduction voltage of the first transistor and greater than the forward conduction voltage of the protection transistor, the first transistor is forward-conducted, the protection transistor is in a normally-on state, and the protection diode is in a reverse state to protect the target RF circuit; When the gate-source voltage of the first transistor is less than the forward conduction voltage of the protection transistor, the first transistor is turned off, the protection transistor is reversely cut off, and the protection diode is turned off to protect the target RF circuit.

8. The radio frequency circuit according to claim 2, characterized in that: The first transistor and the protection transistor are both enhancement-mode transistors.

9. The radio frequency circuit according to claim 2, characterized in that: The target radio frequency switch circuit further includes: an impedance matching circuit and a capacitive reactance matching circuit; The impedance matching circuit includes a first resistance circuit and a second resistance circuit, the first resistance circuit is coupled to the gate of the first transistor, and the second resistance circuit is coupled to the source and drain of the first transistor; The capacitive reactance matching circuit includes a capacitor circuit, and the capacitor circuit is connected in parallel with the second resistor circuit.

10. The radio frequency circuit according to claim 1, characterized in that: There are multiple radio frequency switch protection circuits, and the multiple radio frequency switch protection circuits are respectively connected to the multiple radio frequency switch circuits.

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