Emergency communication equipment using tunnel metal pipe waveguide coupling

Abstract

The application discloses an emergency communication device utilizing tunnel metal pipeline waveguide coupling, which can utilize existing metal air ducts and water pipes in the tunnel as waveguide media, utilize the surface current waveguide characteristics of the metal pipeline in the medium and low frequency band, realize signal injection and reception through the near-field magnetic coupling mode of an induction antenna, realize long-distance emergency voice communication in the tunnel without relying on existing communication infrastructure, establish an emergency communication link under the condition that the tunnel communication infrastructure is completely disabled, improve rescue efficiency, realize precise rescue, and guarantee personnel safety; through the cooperation of units in the device, the communication stability of the device in the complex electromagnetic environment of the tunnel can be ensured, harmonics can be effectively suppressed, different waveguide line lengths and coupling conditions can be adapted, high-sensitivity reception can be realized, and out-of-band interference in the complex electromagnetic environment of the tunnel can be effectively suppressed.

Description

Technical Field

[0001] This invention relates to the field of railway emergency communication technology, and in particular to an emergency communication device that utilizes waveguide coupling in a tunnel metal pipe. Background Technology

[0002] Currently, some railway tunnels pass through active fault zones, and the potential threats of natural disasters such as earthquakes and debris flows are becoming increasingly prominent, posing a severe challenge to the structural safety and operational stability of the tunnels.

[0003] When a tunnel collapses, communication infrastructure such as fiber optic cables, electrical cables, and base stations within the tunnel are often damaged. Traditional communication methods are blocked by the collapsed material, preventing trapped personnel from effectively communicating with the outside world, severely hindering emergency rescue efforts. Existing emergency communication methods mainly rely on existing communication infrastructure, which cannot be quickly restored when communication systems are damaged. There is a lack of a tunnel emergency communication method that does not rely on existing communication lines and has rapid deployment capabilities.

[0004] Magnetic induction communication technology utilizes alternating magnetic fields to achieve signal coupling and transmission. Operating in the low-to-mid frequency band, its electromagnetic waves exhibit a low attenuation constant in conductive media, resulting in strong diffraction and penetration capabilities. Metal ducts and water pipes commonly laid within tunnels possess excellent waveguide characteristics and can serve as waveguide transmission media for induction communication, enabling long-distance signal propagation along the pipe's direction. Utilizing this characteristic, an effective voice communication link can still be established even under extreme conditions where tunnel communication infrastructure fails; however, a perfect solution is currently lacking.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide an emergency communication device that utilizes waveguide coupling in a tunnel metal pipe. This device can provide a basic command channel for emergency rescue under extreme conditions where tunnel communication infrastructure fails, thereby improving rescue efficiency and ensuring personnel safety.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] An emergency communication device utilizing waveguide coupling in a tunnel metal pipe includes: a human-machine interface unit, a main control unit, an FPGA RF modulation and demodulation unit, an RF transceiver unit, an inductive antenna, a transmit power control and detection unit, and a temperature detection unit; wherein: The human-machine interface unit is used to enable interaction between the user and the emergency communication equipment; The main control unit communicates with the human-machine interface unit and the FPGA radio frequency modulation and demodulation unit. It is used to receive digital signals input from the human-machine interface unit, encode them, and transmit them to the FPGA radio frequency modulation and demodulation unit. It also decodes digital signals from the FPGA radio frequency modulation and demodulation unit and transmits them to the human-machine interface unit. It is also used to read the monitoring information from the transmit power control detection unit and the temperature detection unit to determine whether to activate the stop transmission protection. The FPGA RF modulation and demodulation unit is used to modulate the information transmitted by the main control unit and then transmit it to the RF transceiver unit. It is also used to demodulate the signal sent by the RF transceiver unit to obtain the corresponding digital information and then transmit it to the main control unit. The radio frequency transceiver unit is used to convert the signal modulated by the FPGA radio frequency modulation and demodulation unit into an analog radio frequency signal that meets the requirements of inductive coupling transmission; it is also used to convert the radio frequency signal obtained by the inductive antenna coupling and transmit it to the FPGA radio frequency modulation and demodulation unit. Inductive antennas are used to transmit and receive signals via magnetic coupling through tunnel metal pipes. The transmit power control and detection unit communicates with the RF transceiver unit and the main control unit to monitor the status of the RF transceiver unit. Temperature detection unit is used to monitor the temperature of relevant components in emergency communication equipment.

[0009] As can be seen from the technical solution provided by the present invention, by using existing metal air ducts and water pipes in the tunnel as waveguide media, there is no need to lay additional dedicated induction lines or leaky cables. Signal injection and reception are achieved on the pipes through inductive coupling. This can establish an emergency communication link even when the tunnel communication infrastructure is completely unusable, thereby improving rescue efficiency, enabling precise rescue, and ensuring personnel safety. Through the cooperation of each unit in the emergency communication equipment, the communication stability of the emergency communication equipment in the complex electromagnetic environment of the tunnel can be guaranteed, effectively suppressing harmonics and adapting to different waveguide lengths and coupling conditions, achieving high-sensitivity reception, and effectively suppressing out-of-band interference in the complex electromagnetic environment of the tunnel. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of an emergency communication device using waveguide coupling in a tunnel metal pipe, provided as an embodiment of the present invention.

[0012] Figure 2This is a schematic diagram illustrating the device application scenarios and deployment schemes provided in the embodiments of the present invention.

[0013] Figure 3 This is a schematic diagram of an FPGA radio frequency modulation module provided in an embodiment of the present invention.

[0014] Figure 4 This is a schematic diagram of an FPGA radio frequency demodulation module provided in an embodiment of the present invention.

[0015] Figure 5 This is a schematic diagram of the transmission link provided in an embodiment of the present invention.

[0016] Figure 6 This is a schematic diagram of the receiving link provided in an embodiment of the present invention.

[0017] Figure 7 This is a schematic diagram of a software layered architecture provided for an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0019] First, the following explanations are provided for the terms that may be used in this article: The terms "comprising," "including," "containing," "having," or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.) should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0020] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.

[0021] Unless otherwise explicitly specified or limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this document according to the specific circumstances.

[0022] The following is a detailed description of an emergency communication device utilizing waveguide coupling in a tunnel metal pipe, provided by this invention. Contents not described in detail in the embodiments of this invention are prior art known to those skilled in the art. Where specific conditions are not specified in the embodiments of this invention, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Instruments used in the embodiments of this invention, unless otherwise specified by the manufacturer, are all conventional products that can be purchased commercially.

[0023] Example 1 like Figure 1 The diagram shown is a schematic of an emergency communication device using waveguide coupling in a tunnel metal pipe, provided by an embodiment of the present invention. It mainly includes: a human-machine interface unit, a main control unit, an FPGA (Field Programmable Gate Array) RF modulation and demodulation unit, an RF transceiver unit, an inductive antenna, a transmit power control and detection unit, and a temperature detection unit. Furthermore, it includes a power supply unit, which uses a built-in battery or an external power input to provide operating power to each unit in the emergency communication device.

[0024] 1. Human-machine interface unit, used to enable interaction between users and emergency communication equipment.

[0025] 2. The main control unit communicates with the human-machine interface unit and the FPGA radio frequency modulation and demodulation unit to receive digital signals input from the human-machine interface unit, encode them, and transmit them to the FPGA radio frequency modulation and demodulation unit, as well as to decode digital signals from the FPGA radio frequency modulation and demodulation unit and transmit them to the human-machine interface unit; it is also used to read the monitoring information from the transmit power control detection unit and the temperature detection unit to determine whether to activate the stop transmission protection.

[0026] The main control unit includes a universal asynchronous transceiver, a universal input / output interface, an audio processing module, a power monitoring module, and a temperature monitoring module. Each module works together during the transmission and reception processes.

[0027] During transmission, the general purpose input / output interface responds to the user's press of the PTT button, switches the operating mode to transmit mode, and generates a sub-audio signal; the general purpose asynchronous transceiver receives voice data from the human-machine interface unit; the audio processing module compresses and encodes the voice data, generates MSK (Minimum Shift Keying) digital control data according to the current communication status, and then encapsulates the encoded voice data, sub-audio signal, and MSK data into a frame; the general purpose asynchronous transceiver transmits the encapsulated data to the FPGA RF modulation and demodulation unit, which performs modulation processing before transmitting it through the RF transceiver unit.

[0028] During reception, the FPGA RF modulation and demodulation unit demodulates the data and receives it via a universal asynchronous transceiver. The audio processing module deframes the demodulated data and decompresses the voice data, decodes the sub-audio signal, and decodes the MSK data. The decompressed voice data is sent to the human-machine interface unit via the universal asynchronous transceiver and outputs through a speaker. The decoded sub-audio signal is transmitted to the universal input / output interface to determine whether to enable squelch and control the switching of the receiving mode. The decoded MSK data is transmitted to the protocol layer for call control, channel access control, and other communication process processing.

[0029] During transmission and reception, the power monitoring module continuously reads the monitoring information from the transmit power control detection unit. When the transmit power is abnormal, it notifies the general input / output interface to activate the transmit stop protection. The temperature monitoring module continuously reads the monitoring information from the temperature detection unit. When the temperature exceeds the threshold, it also activates the transmit stop protection.

[0030] 3. FPGA RF modulation and demodulation unit, used to modulate the information transmitted by the main control unit and then transmit it to the RF transceiver unit, and also used to demodulate the signal sent by the RF transceiver unit to obtain the corresponding digital information and transmit it to the main control unit.

[0031] The FPGA radio frequency modulation and demodulation unit includes: an FPGA radio frequency modulation module, used to modulate the information transmitted by the main control unit and then transmit it to the radio frequency transceiver unit; and an FPGA radio frequency demodulation module, used to demodulate the signal sent by the radio frequency transceiver unit.

[0032] (1) The FPGA RF modulation module includes: (1.1) Differential coding module, used to perform differential coding processing on the information transmitted by the main control unit to obtain a serial data stream.

[0033] (1.2) Serial-to-parallel conversion and IQ mapping module, used to convert the serial data stream into serial and parallel data to obtain IQ two-channel data symbol sequences, and to alternately assign values ​​to the I and Q channels so that the data symbols can be loaded onto the orthogonal carrier components to form IQ modulated baseband signals.

[0034] (1.3) Numerical control oscillator, used to generate two orthogonal sine and cosine carrier waves in real time.

[0035] (1.4) MSK modulation module, used to multiply the IQ modulation baseband signal with the quadrature carrier respectively, that is, the I-channel modulation baseband signal is multiplied with the cosine carrier, and the Q-channel modulation baseband signal is multiplied with the sine carrier and vector synthesized to obtain the modulated quadrature carrier signal.

[0036] (2) The FPGA RF demodulation module includes: (2.1) The NCO digital downconversion module is used to generate two orthogonal sine and cosine carriers and multiply them with the output signal of the radio frequency transceiver unit to realize digital downconversion and IQ demodulation, and output the downconverted IQ signal.

[0037] (2.2) Equiripple decimation filter, used to compress bandwidth and downsample the downconverted IQ signal, and output downsampled IQ signal.

[0038] (2.3) Digital channel filter, used to perform channel filtering on downsampled signals and output the channel-filtered IQ signal.

[0039] (2.4) Integrator, used to determine the symbol state in the IQ signal after channel filtering by using the symbol period integral decision method, realize the XOR combination of I and Q signals, and output the demodulated digital signal.

[0040] The FPGA RF demodulation module is also equipped with a phase detector and a loop filter; wherein: the phase detector is used to compare the decision result of the integrator with the phase of the actual received signal and output a phase error signal; the loop filter is used to filter the phase error signal, output a control signal, and input it to the NCO digital downconverter module to control the frequency and phase of the carrier in the NCO digital downconverter module.

[0041] 4. Radio frequency transceiver unit, used to convert the signal modulated by the FPGA radio frequency modulation and demodulation unit into an analog radio frequency signal that meets the requirements of inductive coupling transmission; it is also used to convert the radio frequency signal obtained by the inductive antenna coupling and transmit it to the FPGA radio frequency modulation and demodulation unit.

[0042] The radio frequency transceiver unit includes: a transmit link for converting the signal modulated by the FPGA radio frequency modulation and demodulation unit into an analog radio frequency signal that meets the requirements of inductive coupling transmission; and a receive link for converting the radio frequency signal obtained by the inductive antenna coupling and transmitting it to the FPGA radio frequency modulation and demodulation unit.

[0043] (1) The transmission link includes: (1.1) Digital-to-analog converter, used to convert the orthogonal carrier signal generated by the FPGA RF demodulation module into digital and analog signals.

[0044] (1.2) Power drive amplifier circuit, used to drive and amplify the modulated signal.

[0045] (1.3) Radio frequency power amplifier (Class D power amplifier may be used) is used to further amplify the output of the power drive amplifier circuit to the power level required by the induction antenna.

[0046] (1.4) Low-pass filter, used to perform low-pass filtering on the output signal of the RF power amplifier.

[0047] (1.5) Induction antenna interface, used to transmit the low-pass filtered signal to the induction antenna.

[0048] (2) The receiving link includes: (2.1) Induction antenna interface, used to obtain electrical signals from the induction antenna.

[0049] (2.2) Frequency selective filter, which adopts an LC resonant circuit structure, is used to achieve preliminary frequency band limitation at the radio frequency front end.

[0050] (2.3) Low noise amplifier, used to amplify the output signal of the frequency selective filter.

[0051] (2.4) LC bandpass filter, used to filter the amplified signal.

[0052] (2.5) Analog-to-digital converter, used to convert the filtered signal into digital signals and transmit it to the FPGA RF modulation and demodulation unit.

[0053] In this embodiment of the invention, the transmit link and the receive link share the same frequency band and antenna interface, and adopt a time-division duplex mechanism. Through time slot division and high-speed transmit / receive switching mechanism, the transmit and receive work alternately. The transmit / receive switching is uniformly scheduled by the FPGA RF modulation and demodulation unit. In addition, the receive link protection measures are set to automatically turn off the power supply of the low-noise amplifier of the receive link during the transmit time slot.

[0054] 5. Inductive antenna, used to transmit and receive signals via magnetic coupling using the metal pipes in the tunnel.

[0055] In this embodiment of the invention, the inductive antenna is a loop magnetic core inductive antenna, which serves as a coupling device to achieve energy coupling with the tunnel metal pipe through an alternating magnetic field; the magnetic core material is manganese-zinc ferrite with a rectangular cross section, and the magnetic core is composed of multiple arc-shaped magnetic core lobes spliced ​​together, with magnetic adhesive applied between the lobes; the winding wire is made of Litz wire.

[0056] 6. Transmit power control and detection unit, which communicates with the radio frequency transceiver unit and the main control unit, is used to monitor the status of the radio frequency transceiver unit.

[0057] 7. Temperature detection unit, used to monitor the temperature of relevant components in emergency communication equipment.

[0058] The components monitored by the temperature detection unit include: an FPGA radio frequency modulation and demodulation unit, a main control unit, and a power supply unit.

[0059] The above-mentioned solutions provided by the embodiments of the present invention are as follows: (1) A 400 kHz inductive communication scheme using existing metal air ducts and water pipes in the tunnel as waveguide media is used. The surface current conduction characteristics of metal pipes in the mid-to-low frequency band are utilized to achieve signal injection and reception through near-field magnetic coupling of the inductive antenna. Long-distance emergency voice communication in the tunnel is achieved without relying on existing communication infrastructure. (2) A digital orthogonal modulation and demodulation architecture based on FPGA is used. Differential coding, IQ mapping, NCO digital carrier generation, MSK modulation and multi-level decimation filtering are adopted to achieve high-precision modulation and stable demodulation of 400 kHz inductive carrier signals. A digital phase-locked loop is introduced to achieve carrier dynamic tracking and synchronous recovery, which improves the communication stability in the complex electromagnetic environment of the tunnel. (3) A complete radio frequency transceiver link scheme is designed. The transmitting link can adopt a structure combining a Class D power amplifier and an LC low-pass filter to effectively suppress harmonics and adapt to different waveguide lengths and coupling conditions. The receiving link can adopt a cascaded structure of LC pre-selection filtering, low-noise amplification and two-stage bandpass filtering to achieve high-sensitivity reception and effectively suppress out-of-band interference in the complex electromagnetic environment of the tunnel.

[0060] To more clearly demonstrate the technical solution and its effects provided by the present invention, the emergency communication equipment provided by the embodiments of the present invention will be described in detail below with reference to specific examples.

[0061] I. Overall Overview of the Plan

[0062] This invention provides an emergency communication device that utilizes waveguide coupling in a tunnel's metal pipes. It can use 400 kHz inductive communication technology and employs commonly found metal ventilation ducts and water pipes in tunnels as waveguide media to enable intercom communication in disaster scenarios such as landslides, providing emergency voice communication support.

[0063] like Figure 2 As shown, the emergency communication equipment is mainly used for emergency rescue communication scenarios within tunnels. The communication link consists of 400kHz inductive communication equipment hosts at both ends, inductive antennas, and a middle waveguide channel. The transmitting end generates an alternating magnetic field, injecting the signal into the duct waveguide structure through near-field magnetic induction coupling. The signal is then transmitted along the duct to the far end and picked up by the receiving end's inductive antenna, enabling cross-regional emergency communication.

[0064] The ventilation ducts (or water pipes) inside the tunnel are typically circular metal pipes, mostly made of galvanized steel or stainless steel. Signals propagate along the metal walls of the ducts as surface currents and couple with external induction antennas via electromagnetic induction. The ducts are usually laid along the entire length of the tunnel, covering a coverage area equal to the tunnel's length. By using the ducts as waveguides, there is no need to lay additional dedicated induction lines or leaky cables, resulting in high signal transmission efficiency and significant savings in engineering costs.

[0065] Emergency communication equipment mainly includes: human-machine interface unit, main control unit, FPGA radio frequency modulation and demodulation unit, radio frequency transceiver unit, transmit power control and detection unit, temperature detection unit, power supply unit, and antenna interface.

[0066] 1) The main control unit is the core control module of the emergency communication equipment. It is responsible for the business management and process scheduling of the emergency communication equipment. Its main functions include user voice / data encoding and frame encapsulation, transmit and receive working mode control, power control, temperature protection and abnormal alarm.

[0067] 2) The FPGA RF modulation and demodulation unit realizes functions such as digital-to-analog / analog-to-digital conversion, digital baseband processing and modulation and demodulation, modulating audio, sub-audio, and MSK digital signals to a 400KHz carrier frequency and demodulating them.

[0068] 3) The radio frequency transceiver unit realizes analog front-end processing of 400 kHz signals, and realizes functions such as signal filtering, low noise amplification, and magnetic field excitation output.

[0069] 4) The transmit power control and detection unit monitors the transmit current, voltage and output power in real time to prevent overcurrent and overvoltage from damaging the power amplifier.

[0070] 5) The temperature detection unit collects the temperature of the power amplifier and key components in real time to realize over-temperature alarm and automatic power reduction protection.

[0071] 6) The power supply unit provides stable power to all units of the emergency communication equipment and supports battery power or external power input.

[0072] 7) The human-machine interface unit is used to realize the interaction between the device and the user, and supports functions such as voice input and output and status display.

[0073] The communication device provided in this embodiment of the invention can realize voice intercom and low-speed data transmission functions, adopts a TDMA time-division multiplexing frame structure, and supports concurrent transmission of multiple voice and data services. Furthermore, it can adopt a portable, handheld structure with a built-in replaceable lithium battery to meet the needs of long-term operations in tunnel emergency rescue.

[0074] II. Detailed introduction of the plan.

[0075] This section provides a detailed introduction to each unit in the application communication equipment.

[0076] 1. Main control unit.

[0077] The main control unit can use an ARM processor and mainly performs the following functions: 1) UART (Universal Asynchronous Receiver / Transmitter) serial communication: communicates with the human-machine interface unit to realize MSK data transmission and reception, parameter query and setting, and software upgrade functions.

[0078] 2) GPIO (General Purpose Input / Output) control: controls transmit / receive switching, generates sub-audio signals, and controls peripheral status.

[0079] 3) Audio processing: Sub-audio signal decoding is achieved based on the Goretzel algorithm, and MSK signal decoding is achieved based on 1-bit differential MSK signal software decoding technology, realizing speech compression encoding and decoding processing.

[0080] 4) Communication with FPGA RF modulation and demodulation unit: Communicates with FPGA RF modulation and demodulation unit via UART to transmit digital signals such as audio, sub-audio, and MSK data.

[0081] 5) I 2 C (Inter-Integrated Circuit) power monitoring: Real-time reading of transmit power detection unit data, and protection to stop transmission when transmit power is abnormal.

[0082] 6) Temperature monitoring: Reads temperature sensor data in real time and stops transmission when the temperature exceeds the limit.

[0083] 2. FPGA RF modulation and demodulation unit.

[0084] (1) FPGA radio frequency modulation module.

[0085] like Figure 3 As shown, this is the main working process of the FPGA RF modulation module, which is responsible for mapping baseband information to a 400kHz inductive carrier.

[0086] 1) The input digital signal is first processed by differential encoding, and the data sequence is remapped by the XOR relationship between the current bit and the previous bit.

[0087] 2) The serial data stream after differential encoding is further converted from serial to parallel and mapped to two symbol sequences, I (in-phase) and Q (quadrature). In each sampling period, the I and Q channels are alternately assigned values ​​so that the data symbols can be loaded onto the quadrature carrier components respectively, thereby forming the IQ modulated baseband signal.

[0088] 3) The carrier signal is digitally generated by the NCO (Numerically Controlled Oscillator). The NCO generates two strictly orthogonal sine and cosine carriers in real time based on the phase accumulator and the CORDIC algorithm. Then, the I and Q baseband signals are multiplied with the orthogonal carriers respectively and vector synthesized to obtain the modulated output.

[0089] 4) The MSK (Minimum Frequency Shift Keying) continuous phase modulation method is used to load voice, sub-audio and data service information, and output modulated quadrature carrier signals. The baseband input sampling rate is 48kHz, the modulation index is 1.67, and the NCO sampling rate is 1536kHz.

[0090] (2) FPGA RF demodulation module.

[0091] like Figure 4 The diagram shows the main working process of the FPGA RF demodulation module, which is responsible for digital down-conversion and baseband recovery of the induced carrier signal acquired by the receiving end, and extracting audio, sub-audio control signals and MSK digital data.

[0092] 1) An NCO is used to generate a digital local oscillator signal with a center frequency of 425 kHz. The input signal is multiplied by the quadrature cosine and sine local oscillators respectively to achieve digital down-conversion and IQ demodulation, shifting the modulation signal from the carrier frequency to near the zero intermediate frequency for subsequent baseband recovery.

[0093] 2) The down-converted I / Q signal is subjected to bandwidth compression and downsampling using an Equiripple FIR digital low-pass filter with a two-stage decimation filter structure: the first stage has a decimation factor of 8 and the second stage has a decimation factor of 4.

[0094] 3) To further improve the signal-to-noise ratio, a digital channel filter is configured to filter out out-of-band noise and adjacent channel interference, while retaining the effective spectral components required for audio and MSK data.

[0095] 4) For MSK digital signals, a symbol period integration decision method is adopted, where each data bit is accumulated and integrated within a complete sampling period to enhance the noise immunity of the decision. The decision unit uses zero-crossing detection to determine the symbol state, and the Q-channel and I-channel signals are XORed and combined to output the final digital bit stream.

[0096] 5) To ensure carrier phase and frequency synchronization during demodulation, a loop filter (PLL) is used to implement dynamic balance control, which is used to suppress the error accumulation caused by local oscillator frequency deviation and phase noise, maintain stable convergence of the demodulation loop, and thus achieve reliable carrier tracking and synchronous output.

[0097] 3. Radio frequency signal transceiver unit.

[0098] (1) Transmit link (RF radio frequency transmission unit).

[0099] like Figure 5 As shown, this is the main working process of the transmission link, which is responsible for converting the modulated digital signal into a 400 kHz analog radio frequency signal that meets the requirements of inductive coupling transmission, and driving the inductive antenna to achieve magnetic field radiation coupling after power amplification and filtering.

[0100] 1) The digital modulation signal generated by the FPGA RF modulation module is converted from digital to analog by a high-speed DAC, and the output carrier center frequency is 425 kHz, with a sampling rate ≥1.536 MSPS and a resolution of 14 bits.

[0101] 2) The power drive amplifier circuit provides voltage gain and power gain, achieves impedance matching and signal buffering, and amplifies the received signal to drive the RF power amplifier.

[0102] 3) The RF power amplifier uses a Class D high-efficiency power amplifier module to further amplify the output signal of the driver stage to the transmit power level required by the induction antenna.

[0103] 4) The low-pass filter adopts an LC passive low-pass filter structure with a cutoff frequency of 500 kHz, which is used to reduce out-of-band radiation and improve the purity of the transmitted signal spectrum.

[0104] 5) The transmitter connects to the induction antenna via a standardized RF interface with a 50 Ω BNC connector, which maximizes the power amplifier output power coupled to the loop magnetic core induction antenna to achieve stable magnetic field radiation output.

[0105] (2) Receive link (RF radio frequency receiver unit).

[0106] like Figure 6The receiving link is responsible for the main working process of the receiving link. It is responsible for frequency selection, low-noise amplification, out-of-band interference suppression, and analog-to-digital conversion of the weak radio frequency signal obtained by the induction antenna coupling, and finally outputting it to the FPGA radio frequency modulation and demodulation unit.

[0107] 1) The receiving link is equipped with a frequency selective filter, which adopts an LC resonant circuit structure to achieve preliminary frequency band limitation at the RF front end and prevent strong out-of-band signals from entering the amplifier and causing blocking or intermodulation distortion.

[0108] 2) Set up a low-noise amplifier to increase the signal amplitude to reach the sampling range of the ADC (Analog-to-digital Converter) while minimizing the introduction of front-end noise.

[0109] 3) An LC bandpass filter is used to suppress out-of-band interference, reduce adjacent-frequency and broadband noise components, and improve digital demodulation performance. The passband range is 412.5 kHz to 437.5 kHz.

[0110] 4) The filtered and amplified analog RF signal needs to be converted into a digital signal by a high-speed ADC and input to the FPGA RF modulation and demodulation unit to realize digital down-conversion, decimation filtering and demodulation processing, with a sampling rate of 1536KHz.

[0111] Figure 5 The transmitting antenna in Figure 6 The receiving antennas in the above are all considered to be inductive antennas.

[0112] (3) Send and receive switching and duplex.

[0113] The transmit and receive links share the same frequency band and antenna interface, employing a time-division duplex mechanism based on TDMA (Time Division Multiple Access). Through strict time slot division and a high-speed transmit / receive switching mechanism, alternating operation of transmit and receive is achieved. Transmit and receive alternate within different time slots. The transmit slot sends voice / data modulated signals, while the receive slot receives and demodulates the return signal from the other end. The transmit / receive switching is uniformly scheduled by the FPGA, and the antenna port rapidly switches between Tx / Rx (transmit / receive) paths via a high-speed RF switch.

[0114] Since power signals may enter the receiver through coupling during transmission, emergency communication equipment is designed with receiver front-end protection measures to automatically shut off the power supply of the receiver link LNA (low noise amplifier) ​​during the transmission time slot. This mechanism can effectively prevent large signal impacts from damaging the LNA and avoid the front-end from entering the nonlinear region and generating intermodulation interference.

[0115] 4. Transmit power control and detection unit.

[0116] The transmit power control and detection unit uses a logarithmic detector to achieve a large dynamic range power measurement, used for precise monitoring and control of transmit power. Its main functions include: 1) Real-time acquisition of forward and reflected power at the output of the RF power amplifier.

[0117] 2) Calculate VSWR (Voltage Standing Wave Ratio) based on real-time data to evaluate the antenna matching status; when VSWR>3.0 or the output power deviation exceeds ±3dB, notify the main control unit to shut down the transmission to prevent device damage.

[0118] 3) Supports the main control unit to set the transmit power level (5 W / 10 W / 15 W / 20 W) via I²C command.

[0119] 5. Temperature detection unit.

[0120] The temperature detection unit sets measurement points in the main control unit, FPGA RF modulation and demodulation unit, and power supply unit. It uses digital temperature sensors to monitor the temperature in real time. When the temperature exceeds the safety threshold, it notifies the main control unit to stop transmission to prevent the power amplifier and other components from being damaged due to overheating.

[0121] 6. Induction antenna.

[0122] A ring magnetic core induction antenna is used as a coupling device. During installation, it is placed near the outer wall of the duct and energy coupling with the duct waveguide is achieved through an alternating magnetic field.

[0123] The magnetic core material is manganese-zinc ferrite, with a rectangular cross-section, 30mm wide and 20mm high. The core is composed of multiple arc-shaped core segments, bonded together with magnetic adhesive. The winding wire is made of Litz wire, with a specification of 60 strands × 0.1mm monofilament. The winding is evenly distributed on the entire circumference of the core ring to ensure uniform coupling of current to the duct surface.

[0124] 7. Software architecture of emergency communication equipment.

[0125] The main control unit software architecture adopts a four-layer layered design, consisting of the hardware driver layer, middleware layer, protocol layer, and application layer from bottom to top. Figure 7As shown. The hardware driver layer provides low-level drivers for UART, GPIO, I²C, SPI (Serial Peripheral Interface), ADC / DAC, timers, FLASH, etc.; the middleware layer provides voice codec libraries, digital processing algorithm libraries, and RS error correction codec libraries; the protocol layer implements time-division frame management, channel access control, synchronization processing, call control protocols, and network routing protocols; the application layer provides functions such as intercom control, data transmission management, device status monitoring, parameter configuration management, and remote maintenance interfaces.

[0126] The FPGA firmware implements digital signal processing functions, mainly including: differential coding, serial-to-parallel conversion, NCO carrier generation, MSK modulation and phase accumulation in the modulation module; digital down-conversion, multi-stage decimation filtering, channel filtering, integral decision and loop filtering (PLL carrier synchronization) in the demodulation module; and clock management and UART interface for communication with the main control unit.

[0127] Those skilled in the art will understand that, for the sake of convenience and brevity, the above-described division of functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the system can be divided into different functional modules to complete all or part of the functions described above.

[0128] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. An emergency communication device utilizing waveguide coupling in a tunnel metal pipe, characterized in that, include: The system comprises a human-machine interface unit, a main control unit, an FPGA RF modulation and demodulation unit, an RF transceiver unit, an inductive antenna, a transmit power control and detection unit, and a temperature detection unit; among which: The human-machine interface unit is used to enable interaction between the user and the emergency communication equipment; The main control unit communicates with the human-machine interface unit and the FPGA radio frequency modulation and demodulation unit. It is used to receive digital signals input from the human-machine interface unit, encode them, and transmit them to the FPGA radio frequency modulation and demodulation unit. It also decodes digital signals from the FPGA radio frequency modulation and demodulation unit and transmits them to the human-machine interface unit. It is also used to read the monitoring information from the transmit power control detection unit and the temperature detection unit to determine whether to activate the stop transmission protection. The FPGA RF modulation and demodulation unit is used to modulate the information transmitted by the main control unit and then transmit it to the RF transceiver unit. It is also used to demodulate the signal sent by the RF transceiver unit to obtain the corresponding digital information and then transmit it to the main control unit. The radio frequency transceiver unit is used to convert the signal modulated by the FPGA radio frequency modulation and demodulation unit into an analog radio frequency signal that meets the requirements of inductive coupling transmission; it is also used to convert the radio frequency signal obtained by the inductive antenna coupling and transmit it to the FPGA radio frequency modulation and demodulation unit. Inductive antennas are used to transmit and receive signals via magnetic coupling through tunnel metal pipes. The transmit power control and detection unit communicates with the RF transceiver unit and the main control unit to monitor the status of the RF transceiver unit. Temperature detection unit is used to monitor the temperature of relevant components in emergency communication equipment.

2. An emergency communication device utilizing waveguide coupling in a tunnel metal pipe according to claim 1, characterized in that, The main control unit includes: a universal asynchronous transceiver, a universal input / output interface, an audio processing module, a power monitoring module, and a temperature monitoring module. Each module works together during the transmission and reception processes. During transmission, the general purpose input / output (GPIO) interface responds to the user pressing the PTT button, switching the operating mode to transmit mode and generating a sub-audio signal; the GPIO receives voice data from the human-machine interface unit; the audio processing module compresses and encodes the voice data, generates MSK digital control data according to the current communication status, and then encapsulates the encoded voice data, sub-audio signal, and MSK data into a frame; the GPIO transmits the encapsulated data to the FPGA RF modulation and demodulation unit, which performs modulation processing before transmitting it through the RF transceiver unit; During reception, the FPGA RF modulation and demodulation unit demodulates the data and receives it via a universal asynchronous transceiver. The audio processing module deframes the demodulated data and decompresses the voice data, decodes the sub-audio signal, and decodes the MSK data. The decompressed voice data is sent to the human-machine interface unit via the universal asynchronous transceiver and outputs through a speaker. The decoded sub-audio signal is transmitted to the universal input / output interface to determine whether squelch is enabled and to control the switching of the receiving mode. The decoded MSK data is transmitted to the protocol layer for communication process processing. During transmission and reception, the power monitoring module continuously reads the monitoring information from the transmit power control detection unit. When the transmit power is abnormal, it notifies the general input / output port interface to activate the transmit stop protection. The temperature monitoring module continuously reads the monitoring information from the temperature detection unit. When the temperature exceeds the threshold, it also activates the transmit stop protection.

3. An emergency communication device utilizing waveguide coupling in a tunnel metal pipe according to claim 1, characterized in that, The FPGA radio frequency modulation and demodulation unit includes: an FPGA radio frequency modulation module, used to modulate the information transmitted by the main control unit and then transmit it to the radio frequency transceiver unit; The FPGA radio frequency modulation module includes: The differential encoding module is used to perform differential encoding processing on the information transmitted by the main control unit to obtain a serial data stream; The serial-to-parallel conversion and IQ mapping module is used to convert the serial data stream into a serial-to-parallel format to obtain two data symbol sequences, I and Q. The I and Q channels are alternately assigned values ​​so that the data symbols can be loaded onto the quadrature carrier components to form an IQ modulated baseband signal. A numerically controlled oscillator is used to generate two orthogonal sine and cosine carrier waves in real time. The MSK modulation module is used to multiply the IQ modulated baseband signal with the quadrature carrier, that is, the I-channel modulated baseband signal is multiplied with the cosine carrier and the Q-channel modulated baseband signal is multiplied with the sine carrier and then vector synthesized to obtain the modulated quadrature carrier signal.

4. An emergency communication device utilizing waveguide coupling in a tunnel metal pipe according to claim 1, characterized in that, The FPGA radio frequency modulation and demodulation unit includes: an FPGA radio frequency demodulation module, used to demodulate the signal transmitted by the radio frequency transceiver unit; The FPGA RF demodulation module includes: The NCO digital downconversion module is used to generate two orthogonal sine and cosine carriers, and multiply them with the output signal of the RF transceiver unit to achieve digital downconversion and IQ demodulation, and output the downconverted IQ signal. The Equiripple decimation filter is used to compress the bandwidth and downsample the downconverted IQ signal, and output the downsampled IQ signal. A digital channel filter is used to perform channel filtering on a downsampled signal and output the filtered IQ signal. The integrator discriminator is used to determine the symbol state in the channel-filtered IQ signal by employing the symbol period integration decision method, thereby realizing the XOR combination of the I and Q signals and outputting the demodulated digital signal.

5. An emergency communication device utilizing waveguide coupling in a tunnel metal pipe according to claim 4, characterized in that, The FPGA RF demodulation module is also equipped with a phase detector and a loop filter; wherein: A phase detector is used to compare the decision result of the integrator with the phase of the actual received signal and output a phase error signal. The loop filter is used to filter the phase error signal, output a control signal, and input it to the NCO digital downconverter module to control the frequency and phase of the carrier in the NCO digital downconverter module.

6. An emergency communication device utilizing waveguide coupling in a tunnel metal pipe according to claim 1, characterized in that, The radio frequency transceiver unit includes: a transmit link for converting the signal modulated by the FPGA radio frequency modulation and demodulation unit into an analog radio frequency signal that meets the requirements of inductive coupling transmission; and a receive link for converting the radio frequency signal obtained by the inductive antenna coupling and transmitting it to the FPGA radio frequency modulation and demodulation unit. The transmit link includes: a digital-to-analog converter for converting the modulated quadrature carrier signal into an analog signal and outputting an induced carrier signal to the radio frequency transceiver unit; a power drive amplifier circuit for amplifying the modulated signal; a radio frequency power amplifier for further amplifying the output of the power drive amplifier circuit to the power level required by the inductive antenna; a low-pass filter for low-pass filtering the output signal of the radio frequency power amplifier; and an inductive antenna interface for transmitting the low-pass filtered signal to the inductive antenna. The receiving link includes: an inductive antenna interface, which is also used to acquire electrical signals from the inductive antenna; a frequency selective filter, which adopts an LC resonant circuit structure, for implementing preliminary frequency band limitation at the RF front end; a low-noise amplifier, for amplifying the output signal of the frequency selective filter; an LC bandpass filter, for filtering the amplified signal; and an analog-to-digital converter, for performing analog-to-digital conversion on the filtered signal and transmitting it to the FPGA RF modulation and demodulation unit.

7. An emergency communication device utilizing waveguide coupling in a tunnel metal pipe according to claim 6, characterized in that, The transmit and receive links share the same frequency band and antenna interface, and adopt a time-division duplex mechanism based on time-division multiple access. Through time slot division and high-speed transmit / receive switching mechanism, the transmit and receive operations are alternately operated. The transmit / receive switching is uniformly scheduled by the FPGA RF modulation and demodulation unit. Furthermore, the receive link protection measures are set up to automatically shut down the power supply of the low-noise amplifier in the receive link during the transmit time slot.

8. An emergency communication device utilizing waveguide coupling in a tunnel metal pipe according to claim 1, characterized in that, The emergency communication equipment also includes a power supply unit, which uses a built-in battery or an external power input to provide operating power to each unit in the emergency communication equipment.

9. An emergency communication device utilizing waveguide coupling in a tunnel metal pipe according to claim 1, characterized in that, The components monitored by the temperature detection unit include: an FPGA radio frequency modulation and demodulation unit, a main control unit, and a power supply unit.

10. An emergency communication device utilizing waveguide coupling in a tunnel metal pipe according to claim 1, characterized in that, The inductive antenna is a loop magnetic core inductive antenna, which serves as a coupling device to achieve energy coupling with the tunnel metal pipe through an alternating magnetic field. The magnetic core material is manganese-zinc ferrite with a rectangular cross-section. The magnetic core is composed of multiple arc-shaped magnetic core segments, which are bonded together with magnetic adhesive. The winding wire is made of Litz wire.

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