Multi-stage electrostatic and overload protection circuit of IOT receiving LNA

Abstract

The utility model discloses a kind of multistage electrostatic and overload protection circuit of IOT receiving LNA, belong to internet of things technical field, comprising: setting radio frequency signal main link, high pass filter, amplitude limiter and coupler are connected in series on it;The input end of radio frequency switch is connected with coupler, its first output end connects LNA, second output end connects bypass channel;Dynamic control loop monitors the signal power of main link in real time through coupler, when power is over-limit, the micro control unit in this loop will output control signal, on the one hand drive radio frequency switch switch signal from LNA channel to bypass channel, on the other hand simultaneously shut off the power supply of LNA.The utility model realizes quick, comprehensive overload protection to LNA by the double synergistic action of signal channel switching and power off, and combines the innovative π type ESD protection network, under the premise of not affecting signal quality, greatly improve the reliability of IOT equipment in complex electromagnetic environment.

Description

Technical Field

[0001] This utility model relates to the field of Internet of Things (IoT) technology, and more specifically, to a multi-level electrostatic and overload protection circuit for an IoT receiver LNA. Background Technology

[0002] With the rapid development and widespread application of Internet of Things (IoT) technology, wireless communication has become an indispensable core support. From smart homes to industrial automation and smart cities, billions of IoT devices exchange data and sense information through radio frequency (RF) links. In the RF receiver front-end, the low-noise amplifier (LNA) plays a crucial role, effectively amplifying the weak signals received from the antenna. Its performance directly determines the sensitivity and communication distance of the entire receiver. However, IoT devices are typically deployed in complex and variable electromagnetic environments, inevitably suffering from high-power signal interference from other communication devices, industrial equipment, or natural phenomena. Simultaneously, electrostatic discharge (ESD) is extremely common during the production, transportation, installation, and use of these devices. As a high-gain, high-sensitivity semiconductor device, the LNA has a very precise internal structure and extremely low tolerance to overvoltage and overcurrent. Therefore, without proper protection measures, strong interference signals or ESD pulses can easily cause permanent damage, leading to communication interruptions or even device malfunction. Currently, many LNA protection circuits rely on fixed passive components, such as PIN diode limiters or gas discharge tubes, whose protection thresholds are fixed and cannot be adaptively adjusted according to real-time changes in the signal environment. This results in either insufficient protection when facing diverse interference, failing to effectively filter out strong signals, or overprotection, causing unnecessary attenuation of normal communication signals and lacking flexibility. Utility Model Content

[0003] The purpose of this invention is to provide a multi-level electrostatic discharge and overload protection circuit for an IoT receiver LNA. It achieves multi-level protection by real-time monitoring and switching of bypass and shutting off the LNA power supply. Its innovative π-type ESD discharge network topology effectively protects against electrostatic discharge while significantly reducing signal loss and optimizing the overall performance of the receiving link.

[0004] The embodiments of this utility model are achieved through the following technical solutions: A multi-level electrostatic discharge and overload protection circuit for an IoT receiver LNA includes: The main RF signal link has an input terminal for connecting to the antenna. The main RF signal link is connected in series with a high-pass filter, a limiter, and a coupler. The radio frequency switch includes an input terminal, a first output terminal, a second output terminal, and a control terminal. The input terminal of the radio frequency switch is connected to the main output terminal of the coupler. The input terminal of the LNA is connected to the first output terminal of the RF switch, and the LNA is equipped with a power enable terminal. Bypass channel, the bypass channel is connected to the second output terminal of the RF switch; The dynamic control loop includes a detector and a microcontroller unit. The input terminal of the detector is connected to the coupling terminal of the coupler. The signal input terminal of the microcontroller unit is connected to the output terminal of the detector. The control output terminal of the microcontroller unit is connected to the control terminal of the RF switch and the power enable terminal of the LNA.

[0005] Optionally, an ESD discharge inductor is also included; the high-pass filter and the ESD discharge inductor together form a π-type network topology, in which the ESD discharge inductor is connected between the ground terminal of the high-pass filter and the system ground.

[0006] Optionally, the high-pass filter consists of a series capacitor and an inductor connected in parallel to ground.

[0007] Optionally, a voltage follower may be provided between the output of the detector and the signal input of the microcontroller.

[0008] Optionally, it also includes an LNA power module, the input of which is connected to the main power supply, the output of which supplies power to the LNA, and the enable control terminal of which is connected to the control output terminal of the microcontroller.

[0009] Optionally, the coupler in the dynamic control loop is a microstrip PCB coupler fabricated on a circuit board. After the detector detects the coupled radio frequency signal, it is processed by a first-stage voltage follower and then input to the microcontroller unit.

[0010] Optionally, the RF switch includes a single-pole double-throw switch circuit, with its common terminal forming the input terminal, its first throw forming the first output terminal, and its second throw forming the second output terminal. The control output terminal of the microcontroller unit is connected to the control port of the RF switch to selectively establish a conduction path between the common terminal and the first throw, or between the common terminal and the second throw.

[0011] Optionally, the microcontroller unit can be replaced by a control signal generation circuit, which includes a voltage comparator. The signal input terminal of the voltage comparator is connected to the output terminal of the detector, and the output terminal of the voltage comparator serves as the output terminal of the control signal generation circuit, which is connected to the control terminal of the RF switch and the power enable terminal of the LNA.

[0012] The technical solution of this utility model embodiment has at least the following advantages and beneficial effects: This invention enables real-time monitoring of the input power at the antenna port through the coordinated operation of a coupler, detector, and microcontroller unit. Upon detecting an overload signal exceeding the safety threshold, the system responds at microsecond speeds, controlling the RF switch to transfer the signal to a safe bypass channel and simultaneously shutting off the LNA's power supply. This provides dual protection from both signal and power perspectives, preventing LNA saturation and damage. Furthermore, this invention cleverly removes the ESD inductor, which was originally connected in series in the main signal path and degraded performance, and moves it to the ground terminal of the high-pass filter, forming a π-type resonant network together with the filter. While providing an effective discharge path for electrostatic pulses, the inductance of this inductor cancels out parasitic capacitance in the link, significantly reducing insertion loss and optimizing overall performance. Attached Figure Description

[0013] Figure 1 A schematic diagram of the principle of a multi-level electrostatic and overload protection circuit for an IOT receiving LNA provided by this utility model; Figure 2 A schematic diagram illustrating the principle of an alternative solution for a multi-level electrostatic and overload protection circuit for an IOT receiving LNA provided by this utility model. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0015] See Figure 1 This utility model provides an embodiment: a multi-level electrostatic discharge and overload protection circuit for an IoT receiver LNA. The overall structure of the protection circuit includes a radio frequency signal main link, a radio frequency switch, a low noise amplifier (LNA), a bypass channel, and a dynamic control loop.

[0016] Specifically, the main RF signal link is the primary transmission path of the RF signal after it enters from the antenna port. In this embodiment, the input end of the main RF signal link is used to connect to the antenna, and a high-pass filter, a limiter, and a coupler are sequentially connected in series along this link.

[0017] A high-pass filter is constructed to perform initial frequency selection on the input signal to filter out unwanted low-frequency interference signals. A high-pass filter consists of at least one capacitor connected in series in the circuit and at least one inductor connected in parallel to the circuit ground, forming an LC high-pass network that can effectively prevent low-frequency or DC components such as electrostatic discharge (ESD) energy from entering subsequent circuits.

[0018] The limiter, connected in series after the high-pass filter, incorporates a PIN diode. Its function is to rapidly reduce its impedance when the instantaneous power of the input signal exceeds a preset threshold, diverting the excessive energy to ground and thus providing first-stage transient high-voltage protection for subsequent circuits.

[0019] The coupler is connected in series after the limiter. Its configuration is used to extract a small portion of the signal energy from the main link at a set ratio (set to -20dB in this embodiment) for power detection by the dynamic control loop. Understandably, in this embodiment, the coupler is a microstrip PCB coupler formed by direct wiring on the circuit board (PCB). The integrated construction reduces costs and improves product consistency.

[0020] Specifically, this embodiment employs a particular ESD protection structure. The ESD protection structure includes an ESD bleed inductor. Unlike the traditional practice of directly connecting inductors in series or parallel in the main signal path, in this embodiment, the high-pass filter and the ESD bleed inductor together form a π-type network topology. In the specific connection relationship of this topology, one end of the ESD bleed inductor is connected to a ground terminal of the high-pass filter (e.g., the ground terminal of its parallel inductor), and the other end is connected to system ground (GND). This ensures that the ESD bleed inductor is not on the main transmission path of the high-frequency signal, avoiding insertion loss to the signal; simultaneously, it provides a low-impedance discharge path directly to system ground for ESD pulses. Furthermore, the ESD bleed inductor can resonate with parasitic capacitances in the circuit, thereby optimizing the transmission performance of high-frequency signals.

[0021] Specifically, the RF switch is the actuator that performs protection switching actions. It has an input terminal, a first output terminal, a second output terminal, and a control terminal. The input terminal of the RF switch is connected to the output terminal of the coupler. The first output terminal of the RF switch is connected to the input terminal of the low-noise amplifier (LNA), forming the normal operating path. The second output terminal of the RF switch is connected to the bypass channel, forming the protection path. The control terminal of the RF switch is used to receive control signals from the dynamic control loop. It can be understood that the RF switch in this embodiment is physically a single-pole double-throw (SPDT) switch circuit. The common terminal of the SPDT circuit is the input terminal of the RF switch; the first throw is the first output terminal; and the second throw is the second output terminal.

[0022] More specifically, the low-noise amplifier (LNA) is the core protected component. It is an active amplification device whose input is connected to the first output of the RF switch. The LNA also has a power enable terminal (EN), which receives control signals from the dynamic control loop to turn its power on or off.

[0023] In this embodiment, the bypass channel is a passive radio frequency transmission path, which can be constructed as a microstrip line with a 50-ohm characteristic impedance, used to bypass the LNA to transmit signals in protection mode. The dynamic control loop is the core structure for implementing the protection function of this embodiment. The dynamic control loop includes a detector and a microcontroller unit (MCU).

[0024] In this specific application, the input terminal of the detector is connected to the signal terminal coupled from the coupler. Its configuration converts the coupled high-frequency radio frequency signal into a DC voltage signal, the amplitude of which is proportional to the power of the radio frequency signal. To improve the quality of the detected signal, a voltage follower is also provided between the output terminal of the detector and the input terminal of the MCU. This voltage follower is built from an operational amplifier and its configuration provides impedance buffering, ensuring that the MCU can accurately acquire the voltage signal output by the detector. The microcontroller unit (MCU) integrates an analog-to-digital converter (ADC) and general-purpose input / output (GPIO) ports. The signal input terminal (ADC port) of the microcontroller unit is connected to the output terminal of the preceding detector (via the voltage follower). The control output terminal (GPIO port) of the microcontroller unit is connected to the control terminal of the radio frequency switch and the power enable terminal of the LNA, respectively.

[0025] Furthermore, this embodiment also includes an LNA power supply module. The LNA power supply module is constructed as an independent regulated power supply. Its input terminal is connected to the system's main power supply, its output terminal is dedicated to powering the LNA, and its enable control terminal is connected to the control output terminal of the MCU. This effectively isolates the power noise interference generated by the MCU and other digital circuits on the LNA, and allows the MCU to independently control the power supply of the LNA.

[0026] Based on the above structure, the working process of this embodiment is as follows: Normal operating condition: When the input signal power is within a safe range, the DC voltage output by the detector is lower than the threshold set internally by the MCU. The MCU outputs a control signal to connect the input terminal to the first output terminal (LNA path) via the RF switch, and simultaneously enables the LNA power module to supply power to the LNA. The signal is amplified normally along the main link.

[0027] Overload Protection: When the input signal power exceeds the safe range, the DC voltage output by the detector rises and exceeds the threshold set internally by the MCU. The MCU is configured to perform the following coordinated actions: it immediately changes the level of its control output terminal. This signal controls the RF switch to switch the input terminal to the second output terminal (bypass channel), allowing the strong signal to bypass the LNA; simultaneously, this signal acts on the power enable terminal of the LNA (or the enable terminal of the LNA power module), completely shutting off its power. This dual protection structure of signal path switching and power shutdown provides rapid and comprehensive protection for the LNA. When the MCU detects that the input power has fallen back to a safe level, it can automatically return to normal operation.

[0028] like Figure 2 As shown, this utility model also provides another alternative embodiment. The main difference between this embodiment and the above embodiment lies in the specific construction of the dynamic control loop.

[0029] The microcontroller unit (MCU) in the dynamic control loop can be replaced by a simpler control signal generation circuit. This control signal generation circuit can mainly consist of a voltage comparator, with the following connections: the non-inverting input (+) of the voltage comparator is connected to the output of the detector; its inverting input (-) is connected to a reference voltage source that provides a fixed reference voltage, the value of which is the trigger threshold for protection action; the output of the voltage comparator serves as the output of this control signal generation circuit, and is also connected to the control terminal of the RF switch and the power enable terminal of the LNA.

[0030] In practice, when the detector output voltage is lower than the reference voltage, the comparator outputs a logic level (such as a low level), and the circuit is in normal operation. When the detector output voltage exceeds the reference voltage, the comparator output level immediately flips (becomes high level). The flipped signal directly drives the RF switch to bypass and shuts off the LNA power supply, achieving protection. It has a fast response speed and lower cost.

[0031] In summary, this utility model, through the specific construction and connection of components such as high-pass filter, ESD discharge inductor, limiter, coupler, RF switch, LNA, bypass channel and dynamic control circuit, forms a circuit structure that can realize multi-level, dynamic and intelligent protection. It effectively solves the problems of single protection capability and performance trade-off, and greatly improves the reliability and durability of the RF receiving front end of IoT equipment.

[0032] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A multi-level electrostatic discharge and overload protection circuit for an IoT receiver LNA, characterized in that, include: The main RF signal link has an input terminal for connecting to the antenna. The main RF signal link is connected in series with a high-pass filter, a limiter, and a coupler. The radio frequency switch includes an input terminal, a first output terminal, a second output terminal, and a control terminal. The input terminal of the radio frequency switch is connected to the main output terminal of the coupler. The input terminal of the LNA is connected to the first output terminal of the RF switch, and the LNA is equipped with a power enable terminal. Bypass channel, the bypass channel is connected to the second output terminal of the RF switch; The dynamic control loop includes a detector and a microcontroller unit. The input terminal of the detector is connected to the coupling terminal of the coupler. The signal input terminal of the microcontroller unit is connected to the output terminal of the detector. The control output terminal of the microcontroller unit is connected to the control terminal of the RF switch and the power enable terminal of the LNA.

2. The multi-level electrostatic discharge and overload protection circuit for the IOT receiving LNA according to claim 1, characterized in that, It also includes an ESD discharge inductor; the high-pass filter and the ESD discharge inductor together form a π-type network topology. In the π-type network topology, the ESD discharge inductor is connected between the ground terminal of the high-pass filter and the system ground.

3. The multi-level electrostatic discharge and overload protection circuit for the IOT receiving LNA according to claim 2, characterized in that, A high-pass filter consists of a series capacitor and an inductor connected in parallel to ground.

4. The multi-level electrostatic discharge and overload protection circuit for the IOT receiving LNA according to claim 1, characterized in that, A voltage follower is also provided between the output of the detector and the signal input of the microcontroller.

5. The multi-level electrostatic discharge and overload protection circuit for the IOT receiving LNA according to claim 1, characterized in that, It also includes an LNA power module. The input of the LNA power module is connected to the main power supply, the output of the LNA power module supplies power to the LNA, and the enable control terminal of the LNA power module is connected to the control output terminal of the microcontroller unit.

6. The multi-level electrostatic discharge and overload protection circuit for the IOT receiving LNA according to claim 1, characterized in that, The coupler in the dynamic control loop is a microstrip PCB coupler fabricated on a circuit board. The detector detects the coupled radio frequency signal, processes it through a first-stage voltage follower, and then inputs it to the microcontroller unit.

7. The multi-level electrostatic discharge and overload protection circuit for the IOT receiving LNA according to claim 1, characterized in that, The radio frequency switch includes a single-pole double-throw switch circuit, with its common terminal forming the input terminal, its first throw forming the first output terminal, and its second throw forming the second output terminal. The control output terminal of the microcontroller unit is connected to the control port of the radio frequency switch to selectively establish a conduction path between the common terminal and the first throw, or between the common terminal and the second throw.

8. The multi-level electrostatic discharge and overload protection circuit for the IOT receiving LNA according to claim 1, characterized in that, The microcontroller unit can be replaced by a control signal generation circuit, which includes a voltage comparator. The signal input terminal of the voltage comparator is connected to the output terminal of the detector, and the output terminal of the voltage comparator serves as the output terminal of the control signal generation circuit, which is connected to the control terminal of the RF switch and the power enable terminal of the LNA.

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