Multi-node passive coupling communication system and method for a sealed metal cavity

Abstract

This invention discloses a multi-node passive coupling communication system and method for sealed metal cavities. The system includes a master node, a passive distributed coupling feeder, and several slave nodes. Each node is equipped with a radio frequency (RF) transceiver antenna. The feeder uses parallel double-wire transmission conductors with total reflection boundaries at both ends. The total length of the parallel double-wire is an integer multiple of half the wavelength of the RF wireless protocol's operating frequency band. After the RF signal is reflected by the boundaries, it forms a standing wave magnetic field distributed along the line. RF interaction between the RF transceiver antenna and the parallel double-wire is achieved only through spatial standing wave magnetic coupling. The communication employs TDMA (Time Division Multiplexing) polling, node sleep mode, CRC check, ACK acknowledgment, adaptive frequency hopping, and data packet retransmission mechanisms. This addresses the shortcomings of complex wiring, large node signal differences, and severe co-channel interference in shielded environments with metal and carbon fiber conductive cavities. The system features low transmission loss, excellent communication consistency among nodes, and low overall power consumption, making it suitable for devices such as power battery packs and energy storage metal cabinets.

Description

Technical Field

[0001] This invention relates to the field of multi-node radio frequency wireless communication technology, specifically to a multi-node passive coupling communication system and method for sealed metal cavities, which is particularly suitable for multi-node data acquisition and communication scenarios inside conductive sealed cavities such as electric vehicle power battery packs, energy storage battery cabinets, and industrial metal shielded cabinets. Background Technology

[0002] Achieving master-slave distributed data communication within a conductive, sealed cavity (such as a power battery pack metal casing, an energy storage box with a continuous carbon fiber conductive cover, or a metal industrial cabinet) has been a long-standing engineering challenge in the industry. Existing communication solutions fall into three categories: wired point-to-point harness communication, independent radio frequency wireless communication, and single-line closed-loop coupling communication. All of these solutions have inherent and insurmountable drawbacks.

[0003] 1. Traditional wired sampling harness solution: As the number of battery cells / sampling nodes increases, the number of harnesses increases exponentially. Vibration inside the cavity and thermal expansion and contraction at high and low temperatures can easily cause fatigue fractures of wires and solder joints. Assembly and maintenance costs are high. A large number of connectors occupy cavity space and pose a short circuit and fire safety hazard.

[0004] 2. Independent RF wireless module solution: The conductive cavity forms a Faraday shield, resulting in severe RF signal attenuation. Simultaneous transmission and reception by multiple nodes generates severe co-channel interference. The broadband noise of the switching power supply and power devices further increases the packet loss rate.

[0005] 3. Existing single-wire closed-loop coupled communication: The transmission of high-frequency radio frequency signals through a single wire is affected by the skin effect and ground loop coupling, resulting in extremely uneven magnetic field distribution along the line. The signal is strong at the near-end node, but communication is almost impossible at the far-end node. Furthermore, the single-wire loop is highly sensitive to the contact resistance of the connector. Oxidation or loosening of any connector will lead to impedance mismatch in the entire loop, resulting in a complete interruption of communication.

[0006] Existing technologies lack a multi-node passive coupling communication scheme that can achieve uniform magnetic field throughout the entire line, low loss, and simple wiring within a conductive shielded cavity. Summary of the Invention

[0007] To address the shortcomings of existing technologies, such as cumbersome wiring, uneven signal distribution, poor communication stability in shielded environments, and severe interference from multiple nodes, this invention collaboratively designs a parallel dual-line transmission conductor standing wave resonant structure and a time-division radio frequency protocol to achieve low-loss, high-signal-consistency, low-power, multi-node passive magnetic coupling communication within a conductive sealed cavity.

[0008] This was achieved through the following technical solutions:

[0009] First, a multi-node passive coupling communication system for a sealed metal cavity is proposed, including a master node, a passive distributed coupling feeder and at least one slave node; the master node and each slave node are equipped with radio frequency transceiver antennas, and the nodes transmit radio frequency signals through a radio frequency wireless protocol.

[0010] The passive distributed coupling feeder is a set of parallel double-wire transmission conductors that extend through the master node and each slave node.

[0011] The parallel bi-line transmission conductor has total reflection boundaries at both ends to reflect radio frequency signals;

[0012] The radio frequency signals transmitted by the master node and each slave node are transmitted in the parallel double-line transmission conductor and reflected by the total reflection boundary to form a standing wave magnetic field that is uniformly distributed along the line on the parallel double-line transmission conductor.

[0013] The master node and each slave node complete the radio frequency signal interaction and transmission through their own radio frequency transceiver antennas and standing wave magnetic fields in the air-to-air magnetic coupling. There is no electrical conductive connection between the master and slave radio frequency transceiver antennas and the parallel double-line transmission conductors.

[0014] Alternatively, the total reflection boundary may include at least one of the following implementations:

[0015] Form 1: Electrical short circuit at the ends of the two wires; when the parallel two-wire transmission conductor is a double-strand flexible wire, the short circuit is achieved by soldering the wire ends or shorting with a connector; when the parallel two-wire transmission conductor is a PCB differential trace, the short circuit is achieved by bridging with PCB metal pads.

[0016] Form 2: The ends of the two wires are open and suspended, without external electrical load, forming an open-circuit total reflection boundary;

[0017] Form 3: Connect the ends of the two wires to a short stub of a pure inductor or pure capacitor reactance to form a reactive total reflection boundary.

[0018] Optionally, the length of the parallel bi-line transmission conductor is an integer multiple of half the wavelength of the operating frequency band of the radio frequency wireless communication protocol.

[0019] Optionally, the radio frequency wireless communication protocol uses the 2.4 GHz ISM common band.

[0020] Optionally, the parallel bi-line transmission conductor is a pure copper flexible wire, with the wire size matched to the corresponding radio frequency band, so that its characteristic impedance matches the impedance of the radio frequency operating band.

[0021] Optionally, when the radio frequency operating band is the 2.4GHz ISM band, the cross-sectional area of ​​a single conductor in the parallel double-wire transmission conductor is 0.5mm²±0.1mm², the center-to-center distance between the two wires is 2.0mm~3.3mm, and the insulation layer thickness of the conductor is 0.2mm~0.5mm.

[0022] Optionally, all slave nodes are arranged inside the conductive sealed cavity; master nodes can be arranged inside or outside the conductive sealed cavity.

[0023] Optionally, the RF transceiver antennas of the master node and each slave node are arranged in parallel with the passive distributed coupling feed line; each RF transceiver antenna is an on-board antenna.

[0024] Optionally, the master node and each slave node communicate using a TDMA time-division multiplexing polling method, and each slave node enters a sleep state during non-polling periods; the radio frequency wireless communication protocol includes CRC check, ACK confirmation, adaptive frequency hopping, and data packet retransmission mechanisms.

[0025] Secondly, a multi-node passive coupling radio frequency communication method is proposed, which uses the above-mentioned multi-node passive coupling communication system to perform communication, including the following steps:

[0026] S1. Lay a passive distributed coupling feeder along the path of the master node and all slave nodes, and set a total reflection boundary at both ends of the parallel double-line transmission conductor;

[0027] S2. The master node transmits radio frequency signals. The radio frequency energy is fed into the passive distributed coupling feeder through spatial near-field magnetic coupling. The radio frequency transceiver antenna has no electrical contact with the parallel double-line transmission conductor, forming a stable and uniform standing wave magnetic field on the feeder.

[0028] S3. Each slave node receives the signal sent by the master node through its own radio frequency transceiver antenna coupled with the standing wave magnetic field, and uploads the radio frequency signal to the feeder magnetically according to the preset timing. The antenna and the two-wire conductor have no conductive connection throughout the entire process.

[0029] S4. The master node receives data uploaded by the slave node through its own radio frequency transceiver antenna coupled with the standing wave magnetic field, and performs verification and acknowledgment on the data packets; if no valid ACK acknowledgment is received, adaptive frequency hopping or data packet retransmission operation is performed.

[0030] The beneficial effects of this invention compared to the prior art are:

[0031] 1) Parallel double lines combined with multiple types of total reflection boundaries form a uniform standing wave magnetic field, solving the problems of uneven magnetic field distribution and communication failure at remote nodes caused by single-line coupling.

[0032] 2) The RF transceiver antenna and the feeder have no electrical connection, which completely avoids the safety hazards of wire harness and solder joint breakage due to temperature and vibration, greatly simplifies the internal wiring of the cavity, and reduces the material and labor costs of assembly and maintenance.

[0033] 3) The TDMA time-division multiplexing polling mechanism combined with the slave node sleep mechanism is used to eliminate interference between multiple nodes on the same frequency, and the whole machine operates with low power consumption. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the cross-sectional structure of a passive distributed coupled feeder.

[0035] Figure 2 A schematic diagram of a passive distributed coupled feeder with short-circuit welding structure at both ends;

[0036] Figure 3 This is a diagram of the overall architecture of a multi-node passively coupled radio frequency communication system with a conductive sealed cavity. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0038] This invention provides a multi-node passive coupling communication system and method for sealed metal cavities, which is particularly suitable for multi-node data acquisition and communication scenarios inside conductive sealed cavities such as electric vehicle power battery packs, energy storage battery cabinets, and industrial metal shielded cabinets.

[0039] Combination Figure 3 The system architecture diagram shown primarily comprises a master node, a passive distributed coupling feeder, and at least one slave node. Both the master node and each slave node are equipped with RF transceiver antennas, and RF signals are transmitted between nodes via a radio frequency (RF) wireless protocol. The core innovation lies in the use of a set of parallel dual-line transmission conductors as the passive distributed coupling feeder. This feeder extends through the antennas of both the master node and each slave node. Total reflection boundaries are set at both ends of the feeder, causing the RF signals to be reflected and superimposed within the feeder to form a uniformly distributed standing wave magnetic field along the line. Each node interacts with the standing wave magnetic field through its own antenna, achieving signal exchange without any electrical connection between the antenna and the feeder.

[0040] The master node can be integrated into the battery pack BMS motherboard or made into an independent wireless transceiver module, connecting to an external main control MCU via interfaces such as SPI, UART, I2C, or CAN. The master node can be located inside or outside a conductive sealed cavity, while all slave nodes are located inside the conductive sealed cavity (e.g., each slave node corresponds to a single battery cell, directly powered by the cell). Each slave node is equipped with a radio frequency transceiver antenna, which can be of various forms such as a PCB-onboard antenna, an external ceramic antenna, or a spring dipole antenna, as long as it can generate near-field magnetic coupling with the parallel bipolar transmission conductor. In a preferred embodiment of the invention, each node uses a PCB-onboard antenna to reduce cost and simplify assembly.

[0041] The passive distributed coupling feeder is a set of parallel two-wire transmission conductors, and its cross-sectional structure is as follows: Figure 1As shown. The feeder can be constructed from double-strand pure copper stranded wire (each strand consisting of multiple strands of fine copper wire to improve flexibility and reduce skin effect), or from PCB differential copper foil traces or parallel metal conductive strips. The feeder is routed along the path of the master node and all slave nodes, maintaining a straight line in the magnetic coupling region and being arranged parallel to the RF transceiver antennas of each node to achieve the maximum magnetic coupling coefficient. Total reflection boundaries are set at both ends of the feeder to reflect the RF signals transmitted to the ends back to the feeder, forming standing waves.

[0042] Since the core condition for a transmission line to generate a standing wave is a total reflection boundary, which satisfies |Γ|=1, where Γ is the reflection coefficient; in engineering implementation, there are three types of structures: short circuit, open circuit, and purely reactive load. This invention preferably uses the short circuit scheme for battery pack vibration environments, while the open circuit / reactive scheme can be used as an equivalent alternative wiring scheme. The three methods are referenced below:

[0043] Form 1 (Short-Circuit Total Reflection): Electrical short circuit at both ends of the two wires. When the parallel two-wire transmission conductors are double-strand flexible wires, the short circuit is achieved by soldering the wire ends or shorting with a connector; when the parallel two-wire transmission conductors are PCB differential traces, the short circuit is achieved by bridging with PCB metal pads. The short-circuit ends form current antinodes and voltage nodes, with a reflection coefficient close to -1, resulting in almost total energy reflection. This form has a simple structure and high reliability, and is particularly suitable for vibration environments such as battery packs, making it a preferred solution for mass production (e.g., ...). Figure 2 (As shown).

[0044] Type 2 (Open-Circuit Total Reflection): The two wires are left open at both ends, without any external electrical load. The open ends form voltage antinodes and current nodes, with a reflection coefficient close to +1, thus achieving total reflection. This type requires no soldering and is suitable for wiring scenarios where soldering is not allowed or inconvenient.

[0045] Form 3 (Reactive Total Reflection): Matching pure inductance or pure capacitance reactance (surface mount inductor) stubs are connected to the ends of the two wires to form the reactive total reflection boundary. This is suitable for phase compensation when the feeder length cannot precisely meet integer multiples of half-wavelength, or for scenarios requiring flexible wiring within confined cavities.

[0046] All three forms meet the total internal reflection condition and can be flexibly selected according to specific application scenarios. In the preferred embodiment of the present invention, form one (short circuit) can be preferred because it is the most stable and has the lowest cost.

[0047] To achieve consistent communication among slave nodes, the standing wave magnetic field must be distributed as uniformly as possible along the feed line, ensuring that the magnetic field amplitude at each slave node's location is approximately equal. This invention achieves this by precisely designing the total length of the parallel two-wire transmission conductor. Specifically, the total length of the parallel two-wire transmission conductor is set to an integer multiple of the half-wavelength of the guided wave within the operating frequency band of the radio frequency wireless communication protocol; under this condition, the incident wave and the reflected wave superimpose to form a stable standing wave along the line. The magnetic field amplitude of the standing wave exhibits a periodic distribution of antinodes and nodes, but by arranging all slave nodes in the gently sloping magnetic field region between adjacent antinodes and nodes (i.e., the interval with a small rate of amplitude change), it can be ensured that the induced signal intensity picked up by each node is basically consistent.

[0048] In a preferred embodiment of the present invention, the radio frequency wireless communication protocol uses the 2.4 GHz ISM common frequency band. Accordingly, the dimensions of the parallel twin-wire transmission conductors need to be matched to the 2.4 GHz frequency band to ensure good impedance matching with the RF front-end. When using twin-strand pure copper stranded wire, the cross-sectional area of ​​a single conductor is preferably 0.5 mm² ± 0.1 mm², the center-to-center spacing between the twin wires is 2.0 mm to 3.3 mm, and the insulation layer thickness is 0.2 mm to 0.5 mm. Within this size range, the characteristic impedance of the twin wires is approximately 80 to 100 Ω, which can be matched to a 50 Ω RF port through an appropriate matching network. It should be noted that these dimensions are examples for the 2.4 GHz frequency band. If other frequency bands (such as 433 MHz, 868 MHz, 5.8 GHz, etc.) are used, the conductor cross-sectional area and spacing should be adjusted accordingly to meet impedance matching and standing wave conditions.

[0049] It is important to emphasize that one of the most significant features of this invention is the "passive" magnetic coupling method between the antenna and the feed line. The RF transceiver antennas of both the master node and each slave node are arranged parallel to the parallel bi-line transmission conductor, but there are no conductive connections such as wires, solder pads, or metal contacts between the antenna and the feed line. Signal transmission relies entirely on spatial near-field magnetic coupling: when the master node transmits RF signals, the alternating magnetic field generated by its antenna is coupled to the feed line through space, inducing a differential-mode current in the feed line; this current propagates along the feed line and forms a standing-wave magnetic field under the action of the total reflection boundaries at both ends; the antennas of each slave node are located in this standing-wave magnetic field, and through magnetic coupling, they induce corresponding RF signals, thereby receiving data transmitted from the master node. Conversely, when a slave node uploads data, it also couples RF energy to the feed line through its antenna, which is then received by the master node antenna. Throughout the entire process, there is no conductive contact between the antenna and the feed line, completely eliminating reliability risks such as contact resistance, solder fatigue, and insulation damage caused by wired connections.

[0050] Because multiple slave nodes transmitting simultaneously within a conductive, sealed cavity can cause severe co-channel interference, and the cavity also contains broadband noise from switching power supplies and power devices. To address this, this invention integrates a multi-layered anti-interference mechanism into the radio frequency wireless protocol: the master node communicates with each slave node using a TDMA (Time Division Multiplexing) polling method; each slave node responds only within its allocated time slot and enters a sleep state the rest of the time, avoiding collisions and reducing power consumption. The protocol includes CRC checksums for error detection, an ACK (Acknowledgment) mechanism to ensure reliable transmission, adaptive frequency hopping to avoid fixed-frequency interference, and a packet retransmission mechanism (up to 3 retransmissions if no ACK is received) to improve communication success rate. These mechanisms work together to maintain a low packet loss rate even in harsh electromagnetic environments.

[0051] Furthermore, based on the above system, the present invention also provides a multi-node passive coupling radio frequency communication method, comprising the following steps:

[0052] S1. Lay a passive distributed coupling feeder (parallel double-wire transmission conductor) along the arrangement path of the master node and all slave nodes, and set total reflection boundaries (short-circuit, open-circuit, or reactive type, short-circuit preferred) at both ends. When laying the feeder, ensure that it remains straight in the coupling area and parallel to the antennas of each node.

[0053] S2. The master node transmits radio frequency (RF) signals via an RF transceiver antenna. The RF energy is fed into a passive distributed coupled feeder via near-field magnetic coupling. There is no electrical conductive contact between the antenna and the feeder. The fed signal is transmitted within the feeder and, after being reflected by the total internal reflection boundaries at both ends, the incident wave and the reflected wave are superimposed to form a stable and uniform standing wave magnetic field on the feeder.

[0054] S3. Each slave node receives command signals from the master node by air-coupled standing wave magnetic field through its own RF transceiver antenna, and magnetically uploads data (such as voltage, temperature, etc.) to the feeder through its own antenna within its allocated time slot according to the preset TDMA timing. Throughout the entire process, the antenna and the feeder remain non-conductively connected.

[0055] S4. The master node receives data packets uploaded by slave nodes by coupling the standing wave magnetic field through its own antenna, performs CRC check on the data packets, and replies with ACK confirmation if the check passes; if no valid ACK response is received (or the check fails), it performs adaptive frequency hopping (switching the working channel) or data packet retransmission operation until communication is successful or the maximum number of retries is reached.

[0056] The following examples illustrate several possible implementation schemes of this solution:

[0057] Example 1 (Preferred Mass Production Solution): The master node is integrated into the battery pack BMS motherboard and located outside the battery pack cavity. 92 slave nodes are deployed inside the cavity, with both the master and slave nodes integrating onboard antennas on a PCB. The passive distributed coupling feeder uses pure copper stranded wire with a single-wire cross-sectional area of ​​0.5mm²±0.1mm², a center-to-center spacing of 2.0mm~3.3mm, and an insulation layer thickness of 0.2mm~0.5mm. The total length of the two wires is an integer multiple of the 2.4GHz in-conductor half-wavelength (approximately 6.15cm). The ends of the two wires are short-circuited to serve as total reflection boundaries. The feeder is routed along the onboard antennas of each slave node and extends through the cavity wall to the vicinity of the onboard antenna of the master node, parallel and close to each antenna but without any conductive connection, relying on air-to-ground magnetic coupling for signal transmission. Communication uses the 2.4GHz ISM band, TDMA time-division polling, with a maximum of 3 retransmissions if no ACK is received, and automatic frequency hopping in case of interference.

[0058] Example 2 (PCB Differential Trace Replacement): The passive distributed coupling feeder is replaced with parallel differential copper foil traces on the PCB. The pads at both ends of the PCB are shorted to achieve short-circuit total reflection. Each slave node is equipped with an external ceramic antenna, which is arranged parallel to the differential traces. The rest of the system architecture, VSWR communication principle, and time-division protocol are completely consistent with Example 1, achieving the same communication performance.

[0059] Example 3 (Open-Circuit Total Reflection Boundary): The passive distributed coupling feeder uses pure copper stranded wire, with no short-circuit welding at the ends of the two wires, leaving them directly suspended and open. The open-circuit boundary also achieves total reflection of the 2.4GHz RF signal. The total length of the feeder remains an integer multiple of half the wavelength, forming a stable standing wave magnetic field along the line. The remaining communication process is the same as in Example 1.

[0060] Example 4 (Reactive Stubbed Total Reflection Boundary): A matching patch inductor is soldered to the end of the differential dual-line PCB to serve as a reactive load, forming a reactive total reflection boundary. The incident wave undergoes total reflection and superposition to generate a standing wave, suitable for scenarios where it is inconvenient to solder short circuits in narrow cavities. There is no conductive connection between the antenna and the feed line, and the communication principle remains unchanged.

[0061] It should be noted that the parallel dual-line transmission conductor of this invention is not limited to double-strand soft copper wire. PCB differential copper foil, parallel metal conductive strips, etc., are all dual-line transmission structures composed of two parallel conductors, and can all achieve the same standing wave magnetic coupling function, and all fall within the scope of protection of this invention. The RF transceiver antenna is not limited to PCB-mounted antennas; external ceramic and spring dipole antennas are also compatible. Changing only the feed carrier, antenna type, or RF frequency band does not depart from the core technical essence of the dual-line standing wave magnetic coupling scheme of this invention.

[0062] In summary, this invention employs a design with two parallel lines and preferably electrical short-circuiting at both ends, enabling uniform signal distribution and low transmission loss in standing wave resonance. The master node position is flexible, supporting both inside and outside the cavity, and the standing wave magnetic field is unaffected by the internal structural materials of the equipment cavity or fillers such as electrolyte and insulation cotton within the battery pack cavity. Furthermore, the combination of TDMA to resolve multi-node co-frequency interference and the implementation of a sleep mechanism for multiple slave nodes effectively reduce power consumption, demonstrating significant advancements.

[0063] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A multi-node passive coupling communication system for a sealed metal cavity, comprising a master node, a passive distributed coupling feeder, and at least one slave node; wherein the master node and each slave node are equipped with radio frequency transceiver antennas, and the nodes transmit radio frequency signals to each other via a radio frequency wireless protocol; characterized in that: The passive distributed coupling feeder is a set of parallel double-wire transmission conductors, which extend through the master node and each slave node. The first and last ends of the parallel bilinear transmission conductor are provided with total reflection boundaries to reflect radio frequency signals; The radio frequency signals transmitted by the master node and each slave node are transmitted in the parallel double-line transmission conductor and reflected by the total reflection boundary to form a standing wave magnetic field that is uniformly distributed along the line on the parallel double-line transmission conductor. The master node and each slave node complete the radio frequency signal interaction and transmission through their own radio frequency transceiver antennas and the standing wave magnetic field in the air-isolated magnetic coupling. There is no electrical conductive connection between the master and slave radio frequency transceiver antennas and the parallel double-line transmission conductor.

2. The multi-node passive coupling communication system according to claim 1, characterized in that, The total reflection boundary includes at least one of the following implementations: Form 1: Electrical short circuit at the ends of the two wires; when the parallel two-wire transmission conductor is a double-strand flexible wire, the short circuit is achieved by soldering the wire ends or shorting with a connector; when the parallel two-wire transmission conductor is a PCB differential trace, the short circuit is achieved by bridging with PCB metal pads. Form 2: The ends of the two wires are open and suspended, without external electrical load, forming an open-circuit total reflection boundary; Form 3: Connect the ends of the two wires to a short stub of pure inductance or pure capacitance reactance to form a reactive total reflection boundary.

3. The multi-node passive coupling communication system according to claim 1, characterized in that, The length of the parallel bi-line transmission conductor is an integer multiple of half the wavelength of the operating frequency band of the radio frequency wireless communication protocol.

4. The multi-node passive coupling communication system according to claim 1, characterized in that, The radio frequency wireless communication protocol uses the 2.4GHz ISM common frequency band.

5. The multi-node passive coupling communication system according to claim 1, characterized in that, The parallel bi-line transmission conductor is a pure copper flexible wire, and the wire size is matched to the corresponding radio frequency band so that its characteristic impedance is matched with the impedance of the radio frequency operating band.

6. The multi-node passive coupling communication system according to claim 4, characterized in that, When the radio frequency operating frequency band is 2.4GHz ISM band, the cross-sectional area of ​​the single conductor of the parallel double-wire transmission conductor is 0.5mm²±0.1mm², the center-to-center distance between the two wires is 2.0mm~3.3mm, and the insulation layer thickness of the conductor is 0.2mm~0.5mm.

7. The multi-node passive coupling communication system according to claim 1, characterized in that, All slave nodes are arranged inside the conductive sealed cavity; the master node can be arranged inside or outside the conductive sealed cavity.

8. The multi-node passive coupling communication system according to claim 1, characterized in that, The RF transceiver antennas of the master node and each slave node are arranged in parallel with the passive distributed coupling feed line; each RF transceiver antenna is an onboard antenna.

9. The multi-node passive coupling communication system according to claim 1, characterized in that, The master node and each slave node communicate using a TDMA time-division multiplexing polling method, and each slave node enters a sleep state during non-polling periods; the radio frequency wireless communication protocol includes CRC check, ACK confirmation, adaptive frequency hopping, and data packet retransmission mechanisms.

10. A multi-node passive coupling radio frequency communication method, characterized in that, The multi-node passive coupling communication system as described in any one of claims 1 to 9 is used to perform communication, comprising the following steps: S1. Lay a passive distributed coupling feeder along the path of the master node and all slave nodes, and set a total reflection boundary at both ends of the parallel double-line transmission conductor; S2. The master node transmits radio frequency signals. The radio frequency energy is fed into the passive distributed coupling feeder through spatial near-field magnetic coupling. The radio frequency transceiver antenna has no electrical contact with the parallel double-line transmission conductor, forming a stable and uniform standing wave magnetic field on the feeder. S3. Each slave node receives the signal sent by the master node through its own radio frequency transceiver antenna coupled with the standing wave magnetic field, and uploads the radio frequency signal to the feeder magnetically according to the preset timing. The antenna and the two-wire conductor have no conductive connection throughout the entire process. S4. The master node receives data uploaded by the slave node through its own radio frequency transceiver antenna coupled with the standing wave magnetic field, and performs verification and acknowledgment on the data packets; if no valid ACK acknowledgment is received, adaptive frequency hopping or data packet retransmission operation is performed.

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