A circuit system for preventing radar wave interference based on RS485 chip

Abstract

The application discloses a circuit system for preventing radar wave interference based on an RS485 chip, and relates to the technical field of communication circuits.The circuit system takes an RS485 communication chip as a core, and integrates a shielding protection module, a filtering module, a signal isolation module and a grounding module.The shielding protection module adopts a metal shielding shell to cover the RS485 communication chip, and adopts an RS485 communication cable with double shielding layers to block the radiation interference of radar waves.The filtering module is composed of a high-pass filter and a low-pass filter, and is connected in series between the RS485 communication chip and the communication cable, and is used for filtering high-frequency and low-frequency stray interference in the communication link.The signal isolation module adopts a magnetic coupling isolation device, is connected in series between a microcontroller and the RS485 communication chip, realizes electrical isolation to block the interference conduction path, and adopts a low-resistance grounding collection row to construct an equipotential grounding system, so that the data transmission is stable and reliable, and the modular structure is convenient for integrated application in various electric control designs.

Description

Technical Field

[0001] This invention relates to the field of communication circuit technology, specifically to a circuit system based on an RS485 chip to prevent radar wave interference. Background Technology

[0002] RS485 communication interfaces are widely used in industrial control, logistics scheduling, and site equipment interconnection due to their advantages such as long transmission distance, strong common-mode interference resistance, and low networking cost, enabling serial data transmission between multiple devices. In scenarios such as airport perimeter facilities, base equipment systems, and port logistics scheduling systems, a large number of electrical control devices rely on RS485 buses to complete data interaction and command transmission.

[0003] The aforementioned scenarios typically involve the deployment of radar detection equipment. The high-frequency electromagnetic waves emitted by radar are characterized by high intensity, wide bandwidth, and broad radiation range, which can cause strong electromagnetic interference to surrounding RS485 communication circuits. On one hand, radar waves can penetrate RS485 chips and communication cables through radiative coupling, causing signal amplitude distortion and level shift. On the other hand, they can enter the communication link through power and grounding paths via conductive coupling, leading to data transmission errors and packet loss. In severe cases, this can even cause communication interruptions and equipment malfunctions, significantly impacting the reliability and stability of the system.

[0004] Currently, conventional RS485 communication circuits rely solely on the chip's own common-mode protection capability to cope with ordinary industrial interference. They lack specialized protection designs for strong electromagnetic radiation from radar waves and cannot simultaneously form coordinated protection from multiple dimensions such as radiation shielding, conduction filtering, electrical isolation, and equipotential grounding. This makes it difficult to meet the needs of long-term stable communication in radar wave environments. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a circuit system based on an RS485 chip to prevent radar wave interference. Through the coordinated action of four modules—shielding protection, filtering and noise reduction, electrical isolation, and equipotential grounding—radar wave interference is suppressed simultaneously through both radiative and conductive coupling paths, ensuring stable and accurate data transmission of the RS485 communication link in strong electromagnetic environments.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A circuit system based on an RS485 chip to prevent radar wave interference is applied to an electronic control board equipped with a microcontroller, including an RS485 communication chip, a shielding protection module, a filtering module, a signal isolation module, and a grounding module. The shielding module is placed over the RS485 communication chip and wraps around the RS485 communication cable; the filtering module is connected in series between the differential signal pin of the RS485 communication chip and the RS485 communication cable; the signal isolation module is connected in series between the microcontroller and the TTL signal pin of the RS485 communication chip; the grounding module is electrically connected to the grounding terminals of the RS485 communication chip, the shielding module, the filtering module, and the signal isolation module, respectively.

[0007] Furthermore, the RS485 communication chip is a MAX485 chip.

[0008] Furthermore, the shielding protection module includes a metal shielding shell and a cable shielding structure; The metal shielding shell completely covers the outside of the RS485 communication chip; the RS485 communication cable is provided with differential signal core pairs, aluminum foil shielding layer and copper braided mesh shielding layer from the inside to the outside. The aluminum foil shielding layer and the copper braided mesh shielding layer constitute the cable shielding structure, and both ends of the two are connected to the grounding module.

[0009] Furthermore, the filtering module includes a high-pass filter and a low-pass filter; the high-pass filter is used to filter out low-frequency interference signals below the RS485 communication signal frequency, and the low-pass filter is used to filter out high-frequency interference signals above the RS485 communication signal frequency; the high-pass filter and the low-pass filter are cascaded along the differential signal transmission path.

[0010] Furthermore, the high-pass filter is a π-type high-pass filter circuit, consisting of a capacitor C1 and an inductor L1; one end of the capacitor C1 is connected to the differential signal pin of the RS485 communication chip, and the other end is connected to one end of the inductor L1. The other end of the inductor L1 is connected to the corresponding signal core of the RS485 communication cable, and the connection node of the capacitor C1 and the inductor L1 is connected to the grounding module; the high-pass filter is provided on both the A and B differential signal lines of the RS485 communication.

[0011] Furthermore, the capacitance of capacitor C1 is 0.1μF, and the inductance of inductor L1 is 100μH.

[0012] Furthermore, the low-pass filter is a π-type low-pass filter circuit, consisting of capacitor C2 and resistor R1; one end of capacitor C2 is connected to the corresponding signal core of the RS485 communication cable, and the other end is connected to one end of resistor R1. The other end of resistor R1 is connected to the differential signal pin of the RS485 communication chip, and the connection node of capacitor C2 and resistor R1 is connected to the grounding module; the low-pass filter is provided on both the A and B differential signal lines of the RS485 communication.

[0013] Furthermore, the capacitance of capacitor C2 is 100pF, and the resistance of resistor R1 is 100Ω.

[0014] Furthermore, the signal isolation module employs an ADuM1201 magnetic coupling isolator, with its first-side pin connected to the microcontroller and its second-side pin connected to the RS485 communication chip, thereby achieving electrically isolated signal transmission between the microcontroller and the RS485 communication chip. The RO pin of the RS485 communication chip is connected to the input pin of the second side of the ADuM1201 magnetic coupling isolator, the DI pin is connected to the output pin of the second side of the ADuM1201 magnetic coupling isolator, and the RE pin is shorted to the DE pin and then connected to the control output pin of the second side of the ADuM1201 magnetic coupling isolator. The corresponding pins on the first side of the ADuM1201 magnetic coupling isolator are respectively connected to the signal receiving pin, signal transmitting pin, and transceiver control pin of the microcontroller.

[0015] Furthermore, the grounding module includes a grounding busbar made of copper plate, and the grounding resistance of the grounding busbar is less than 1Ω; the grounding pins of the RS485 communication chip, the shielding layer of the shielding protection module, the grounding node of the filtering module, and the grounding pins on both sides of the signal isolation module are all connected to the grounding busbar to form an equipotential grounding system.

[0016] This circuit system simultaneously suppresses radar wave interference through both radiative and conductive coupling, with each module working together to form a complete protection system. When radar wave radiation is present in the environment, the shielding protection module first acts as the first line of defense: the metal shielding shell encloses the RS485 communication chip and surrounding circuits, directly weakening the radiative coupling of radar waves to the chip itself; the double-layer shielded cable, through the composite structure of the inner aluminum foil and the outer copper braided mesh, simultaneously shields both electric and magnetic field components, significantly reducing the amount of radar wave radiation intrusion along the transmission cable, and the shielding layer forms an interference discharge path through the grounding module, diverting the interference energy intercepted by the shielding to the ground.

[0017] A small amount of conducted interference coupled into the signal link via cables is then filtered and protected by a second layer of filtering: cascaded high-pass and low-pass filters together form a bandpass characteristic that matches the RS485 communication frequency band, respectively filtering out low-frequency spurious components and high-frequency harmonic components in the radar wave, allowing only the effective communication differential signal to pass through, and filtering out out-of-band interference energy without affecting the normal communication rate and signal integrity.

[0018] Even after filtering, common-mode interference may still remain in the signal link. At this time, the third signal isolation module comes into play: the magnetic coupler uses a magnetic field as a medium to realize non-electrical contact transmission of signals, completely cutting off the direct electrical connection between the microcontroller and the RS485 bus side, blocking the path of interference to the main control side through the ground wire and power line, while completely transmitting communication data and receiving and transmitting control signals, ensuring the normal operation of communication control logic.

[0019] The grounding module serves as the common reference for the entire system. Through a low-resistance copper grounding busbar, it connects the chips, shielding layer, filter nodes, and the ground terminals on both sides of the isolator into an equipotential body. This provides a low-impedance interference discharge path for the shielding layer and filter circuits, while also preventing additional common-mode interference currents from being generated by ground potential differences in various parts of the system, further strengthening the protection effect. The four levels of protection work in tandem, suppressing radar wave interference from multiple dimensions, including the interference source coupling path, signal link conduction path, and system grounding reference, ultimately ensuring accurate data transmission and stable link operation of RS485 communication in strong radiation environments.

[0020] Compared with the prior art, the beneficial effects of the present invention are: 1. Comprehensive radiation shielding: By combining a chip-level metal shielding shell with a cable-level double-layer shielding structure, the radiation coupling of radar waves is completely blocked from the chip to the transmission link, significantly reducing the amount of radiation interference intrusion.

[0021] 2. Highly targeted conducted filtering: It adopts a cascaded filter structure combining high-pass and low-pass filters, which can simultaneously filter out low-frequency spurious interference and high-frequency harmonic interference of radar waves, retain the effective communication signal frequency band, and balance the filtering effect and signal compatibility.

[0022] 3. Electrical isolation to block conduction: A magnetic coupler is used to achieve electrical isolation between the microcontroller and the RS485 chip, cutting off the ground conduction path of interference, while not affecting the high-speed communication rate, adapting to high real-time communication requirements.

[0023] 4. Equipotential grounding to suppress common-mode interference: A unified equipotential body is constructed by using a low-resistance copper plate grounding busbar to eliminate potential differences between different parts of the system and suppress the impact of common-mode interference on communication signals.

[0024] 5. Modular design facilitates integration: Each functional module has an independent structure and a clear connection relationship. It can be directly integrated into the RS485 communication interface of various electronic control boards, making installation, debugging and maintenance convenient and applicable to a wide range of scenarios. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the circuit structure of the circuit system described in this invention; Figure 2 This is a block diagram illustrating the control principle of the circuit system described in this invention. Detailed Implementation

[0026] The technical solutions of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] like Figure 1-2 As shown, a circuit system based on an RS485 chip to prevent radar wave interference is applied to an electronic control board equipped with a microcontroller, including an RS485 communication chip, a shielding protection module, a filtering module, a signal isolation module, and a grounding module. The shielding module is placed over the RS485 communication chip and wraps around the RS485 communication cable; the filtering module is connected in series between the differential signal pin of the RS485 communication chip and the RS485 communication cable; the signal isolation module is connected in series between the microcontroller and the TTL signal pin of the RS485 communication chip; the grounding module is electrically connected to the grounding terminals of the RS485 communication chip, the shielding module, the filtering module, and the signal isolation module, respectively.

[0028] Furthermore, the RS485 communication chip is a MAX485 chip.

[0029] Furthermore, the shielding protection module includes a metal shielding shell and a cable shielding structure; The metal shielding shell completely covers the outside of the RS485 communication chip; the RS485 communication cable is provided with differential signal core pairs, aluminum foil shielding layer and copper braided mesh shielding layer from the inside to the outside. The aluminum foil shielding layer and the copper braided mesh shielding layer constitute the cable shielding structure, and both ends of the two are connected to the grounding module.

[0030] Furthermore, the filtering module includes a high-pass filter and a low-pass filter; the high-pass filter is used to filter out low-frequency interference signals below the RS485 communication signal frequency, and the low-pass filter is used to filter out high-frequency interference signals above the RS485 communication signal frequency; the high-pass filter and the low-pass filter are cascaded along the differential signal transmission path.

[0031] Furthermore, the high-pass filter is a π-type high-pass filter circuit, consisting of a capacitor C1 and an inductor L1; one end of the capacitor C1 is connected to the differential signal pin of the RS485 communication chip, and the other end is connected to one end of the inductor L1. The other end of the inductor L1 is connected to the corresponding signal core of the RS485 communication cable, and the connection node of the capacitor C1 and the inductor L1 is connected to the grounding module; the high-pass filter is provided on both the A and B differential signal lines of the RS485 communication.

[0032] Furthermore, the capacitance of capacitor C1 is 0.1μF, and the inductance of inductor L1 is 100μH.

[0033] Furthermore, the low-pass filter is a π-type low-pass filter circuit, consisting of capacitor C2 and resistor R1; one end of capacitor C2 is connected to the corresponding signal core of the RS485 communication cable, and the other end is connected to one end of resistor R1. The other end of resistor R1 is connected to the differential signal pin of the RS485 communication chip, and the connection node of capacitor C2 and resistor R1 is connected to the grounding module; the low-pass filter is provided on both the A and B differential signal lines of the RS485 communication.

[0034] Furthermore, the capacitance of capacitor C2 is 100pF, and the resistance of resistor R1 is 100Ω.

[0035] Furthermore, the signal isolation module employs an ADuM1201 magnetic coupling isolator, with its first-side pin connected to the microcontroller and its second-side pin connected to the RS485 communication chip, thereby achieving electrically isolated signal transmission between the microcontroller and the RS485 communication chip. The RO pin of the RS485 communication chip is connected to the input pin of the second side of the ADuM1201 magnetic coupling isolator, the DI pin is connected to the output pin of the second side of the ADuM1201 magnetic coupling isolator, and the RE pin is shorted to the DE pin and then connected to the control output pin of the second side of the ADuM1201 magnetic coupling isolator. The corresponding pins on the first side of the ADuM1201 magnetic coupling isolator are respectively connected to the signal receiving pin, signal transmitting pin, and transceiver control pin of the microcontroller.

[0036] Furthermore, the grounding module includes a grounding busbar made of copper plate, and the grounding resistance of the grounding busbar is less than 1Ω; the grounding pins of the RS485 communication chip, the shielding layer of the shielding protection module, the grounding node of the filtering module, and the grounding pins on both sides of the signal isolation module are all connected to the grounding busbar to form an equipotential grounding system.

[0037] In this embodiment, the RS485 communication chip selected is the MAX485 chip, which operates at a voltage range of 3.0V to 5.5V, has a maximum data transmission rate of 2.5Mbps, a common-mode input voltage range of -7V to +12V, and possesses basic electromagnetic protection capabilities, making it adaptable to complex electrical environments. The VCC pin of the MAX485 chip is connected to a 3.3V power supply, and the GND pin is connected to the grounding module; pins A and B are differential signal pins, connected to the filtering module; RO, DI, RE, and DE are TTL-side pins, connected to the signal isolation module.

[0038] The shielding protection module consists of two parts: chip shielding and cable shielding. At the PCB level, a metal shielding shell completely covers the MAX485 chip and its surrounding matching circuitry. The metal shell is connected to the grounding busbar of the grounding module via conductive posts, forming a closed shielding cavity to block radar waves from directly radiating to the chip. On the cable side, the RS485 communication cable adopts a double-layer shielding structure, consisting of, from the inside out, A and B differential signal core pairs, an aluminum foil shielding layer, and a copper braided mesh shielding layer. The aluminum foil shielding layer longitudinally wraps the core wires throughout, and the copper braided mesh shielding layer has a coverage rate of no less than 85%. At both ends of the cable, both the aluminum foil shielding layer and the copper braided mesh shielding layer are reliably connected to the grounding busbar on the equipment side via crimp terminals, forming a complete shielded grounding loop and effectively suppressing radar wave radiation interference to the transmission cable.

[0039] The filtering module is connected in series between the differential pins of the MAX485 chip and the RS485 communication cable. Each differential line is cascaded with a high-pass filter and a low-pass filter. The high-pass filter is a π-type structure, consisting of capacitor C1 and inductor L1. Taking channel A as an example, one end of capacitor C1 is connected to pin A of the MAX485, and the other end is connected to one end of inductor L1. The other end of inductor L1 is connected to the A core of the RS485 cable. The common node of capacitor C1 and inductor L1 is connected to the ground busbar. In this embodiment, C1 is 0.1μF and L1 is 100μH, which can effectively filter out low-frequency radar spurious interference below the communication frequency band. Channel B uses the same high-pass filter circuit and parameters. The low-pass filter is also a π-type structure, consisting of capacitor C2 and resistor R1. Taking path A as an example, one end of capacitor C2 is connected to the A core of the RS485 cable, and the other end is connected to one end of resistor R1. The other end of resistor R1 is connected to pin A of the MAX485. The common node of capacitor C2 and resistor R1 is connected to the ground busbar. In this embodiment, C2 is 100pF and R1 is 100Ω, which can effectively filter out high-frequency radar harmonic interference above the communication frequency band. Path B uses the exact same low-pass filter circuit and parameters. When laying out components, the filter elements are placed as close as possible to the differential pins of the MAX485 chip to shorten the trace length and reduce interference introduced by the traces themselves.

[0040] The signal isolation module uses the ADuM1201 magnetic coupler isolator, with an isolation voltage of up to 2.5kVrms and a maximum data transmission rate of up to 50Mbps, fully meeting the speed requirements of RS485 communication. The ADuM1201 is divided into left and right sides: the left side is the microcontroller side, and the right side is the RS485 chip side. The two sides have independent power supplies and independent ground planes. The pin connections are as follows: the left side signal input pins connect to the microcontroller's transmit data pins, the left side signal output pins connect to the microcontroller's receive data pins, and the left side control output pins connect to the microcontroller's transmit / receive control pins; the right side signal output pins connect to the DI pin of the MAX485, the right side signal input pins connect to the RO pin of the MAX485, and the right side control output pins connect to the shorted RE and DE pins of the MAX485. The control signals output by the microcontroller are transmitted through the isolator to control the MAX485 to switch between receive and transmit modes; communication data is also transmitted bidirectionally through the isolator, achieving complete electrical isolation between the microcontroller and the RS485 bus side, blocking the transmission path of radar interference.

[0041] The grounding module uses a copper plate grounding busbar as its core, with the overall grounding resistance controlled within 1Ω. The GND pin of the MAX485 chip, the metal shielding shell, the double-layer shielding of the cables, the grounding nodes of the high-pass filter circuit and the low-pass filter circuit, and the grounding pins on both sides of the ADuM1201 isolator are all connected to this grounding busbar via the shortest path, forming a unified equipotential body for the entire circuit system. When radar interference causes ground potential fluctuations, the potentials of all parts within the system change synchronously, avoiding interference currents driven by potential differences and further enhancing anti-interference capabilities.

[0042] The working principle of this circuit system is as follows: When in a radar wave interference environment, the metal shielding shell and double-shielded cable first block most of the radar radiation waves, reducing direct coupling of interference into the circuit; the small amount of conducted interference coupled in through the cable is filtered out by the high-pass and low-pass combined filter circuit, removing spurious components in the high and low frequency bands and retaining only the effective communication signal; the signal isolation module completely isolates the interference on the bus side from the microcontroller side, preventing interference from being conducted to the main control circuit; at the same time, the low-resistance equipotential grounding system suppresses common-mode interference, ensuring the integrity of the differential signal. Through the synergistic effect of shielding, filtering, isolation, and grounding, RS485 communication can still transmit data stably and accurately even in a strong radar wave environment.

[0043] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. These embodiments are merely descriptions of preferred embodiments and are not intended to limit the scope or concept of the invention. The specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. Such combinations, as long as they do not violate the spirit of the present invention, should also be considered as part of this disclosure. To avoid unnecessary repetition, the present invention will not further describe the various possible combinations.

[0044] This invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this invention and without departing from the design idea of ​​this invention, all modifications and improvements made by those skilled in the art to the technical solutions of this invention should fall within the protection scope of this invention. The technical content for which protection is sought in this invention has been fully described in the claims.

Claims

1. A circuit system for preventing radar wave interference based on an RS485 chip, applied to an electronic control board equipped with a microcontroller, characterized in that, Includes RS485 communication chip, shielding and protection module, filtering module, signal isolation module and grounding module; The shielding module is placed over the RS485 communication chip and wraps around the RS485 communication cable; the filtering module is connected in series between the differential signal pin of the RS485 communication chip and the RS485 communication cable; the signal isolation module is connected in series between the microcontroller and the TTL signal pin of the RS485 communication chip; the grounding module is electrically connected to the grounding terminals of the RS485 communication chip, the shielding module, the filtering module, and the signal isolation module, respectively.

2. The circuit system for preventing radar wave interference based on an RS485 chip according to claim 1, characterized in that, The RS485 communication chip is the MAX485 chip.

3. The circuit system for preventing radar wave interference based on an RS485 chip according to claim 1, characterized in that, The shielding protection module includes a metal shielding shell and a cable shielding structure; The metal shielding shell completely covers the outside of the RS485 communication chip; the RS485 communication cable is provided with differential signal core pairs, aluminum foil shielding layer and copper braided mesh shielding layer from the inside to the outside. The aluminum foil shielding layer and the copper braided mesh shielding layer constitute the cable shielding structure, and both ends of the two are connected to the grounding module.

4. The circuit system for preventing radar wave interference based on an RS485 chip according to claim 1, characterized in that, The filtering module includes a high-pass filter and a low-pass filter; the high-pass filter is used to filter out low-frequency interference signals below the RS485 communication signal frequency, and the low-pass filter is used to filter out high-frequency interference signals above the RS485 communication signal frequency; the high-pass filter and the low-pass filter are cascaded along the differential signal transmission path.

5. The circuit system for preventing radar wave interference based on an RS485 chip according to claim 4, characterized in that, The high-pass filter is a π-type high-pass filter circuit, consisting of a capacitor C1 and an inductor L1. One end of the capacitor C1 is connected to the differential signal pin of the RS485 communication chip, and the other end is connected to one end of the inductor L1. The other end of the inductor L1 is connected to the corresponding signal core of the RS485 communication cable. The connection node between the capacitor C1 and the inductor L1 is connected to the grounding module. The high-pass filter is installed on both the A and B differential signal lines of the RS485 communication.

6. The circuit system for preventing radar wave interference based on an RS485 chip according to claim 5, characterized in that, The capacitance of capacitor C1 is 0.1μF, and the inductance of inductor L1 is 100μH.

7. The circuit system for preventing radar wave interference based on an RS485 chip according to claim 4, characterized in that, The low-pass filter is a π-type low-pass filter circuit, consisting of capacitor C2 and resistor R1. One end of capacitor C2 is connected to the corresponding signal core of the RS485 communication cable, and the other end is connected to one end of resistor R1. The other end of resistor R1 is connected to the differential signal pin of the RS485 communication chip. The connection node between capacitor C2 and resistor R1 is connected to the grounding module. The low-pass filter is provided on both the A and B differential signal lines of the RS485 communication.

8. The circuit system for preventing radar wave interference based on an RS485 chip according to claim 7, characterized in that, The capacitance of capacitor C2 is 100pF, and the resistance of resistor R1 is 100Ω.

9. The circuit system for preventing radar wave interference based on an RS485 chip according to claim 1, characterized in that, The signal isolation module uses an ADuM1201 magnetic coupler isolator. Its first-side pins are connected to the microcontroller, and its second-side pins are connected to the RS485 communication chip, enabling electrically isolated signal transmission between the microcontroller and the RS485 communication chip. The RO pin of the RS485 communication chip is connected to the input pin of the second side of the ADuM1201 magnetic coupler isolator, the DI pin is connected to the output pin of the second side of the ADuM1201 magnetic coupler isolator, and the RE pin is shorted to the DE pin and then connected to the control output pin of the second side of the ADuM1201 magnetic coupler isolator. The corresponding pins on the first side of the ADuM1201 magnetic coupler isolator are respectively connected to the signal receiving pin, signal transmitting pin, and transceiver control pin of the microcontroller.

10. The circuit system for preventing radar wave interference based on an RS485 chip according to claim 1, characterized in that, The grounding module includes a grounding busbar made of copper plate, and the grounding resistance of the grounding busbar is less than 1Ω; the grounding pins of the RS485 communication chip, the shielding layer of the shielding protection module, the grounding node of the filtering module, and the grounding pins on both sides of the signal isolation module are all connected to the grounding busbar to form an equipotential grounding system.

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