A medium wave transmitter monitoring and control integrated system

Abstract

This application relates to an integrated monitoring and control system for a medium-wave transmitter. It mainly includes a core control unit and an industrial control computer, dual exciters, a rack interface board, an RF sampling module, and a directional coupler, all communicatively connected to the core control unit. The core control unit receives control commands from the industrial control computer via a first serial bus, and, combined with its own monitoring data, sends control commands to the dual exciters and the rack interface board via a second serial bus. Simultaneously, it receives sampling data from the dual exciters via a data stream bus to verify the control effect. The core control unit uses a multi-stage voltage regulation topology to convert a single input voltage into multiple stable voltages, providing adaptive power to each module. This application can effectively improve the transmitter's integration, interface simplicity, operational reliability, maintenance convenience, and intelligence level.

Description

Technical Field

[0001] This application relates to the field of broadcast transmitter technology, and in particular to an integrated monitoring and control system for a medium-wave transmitter. Background Technology

[0002] As a crucial core piece of equipment in radio stations, the medium-wave transmitter's primary function is to modulate audio signals onto the medium-wave frequency band and radiate them through antennas, achieving wide-coverage wireless broadcasting. With the development of broadcasting technology and the increase in the power of transmitting equipment, the reliability, stability, and intelligence level of transmitter systems have gradually become key concerns in the industry. In the broadcasting field, the stable operation of medium-wave transmitters is vital for the effective propagation of broadcast signals; it concerns the wide coverage and accurate transmission of information, and has a profound impact on social information dissemination and cultural exchange.

[0003] Traditional medium-wave transmitters often employ a discrete design, where monitoring, control, and signal distribution functions are performed independently by different modules or circuits. To achieve basic monitoring and protection functions, different functional modules operate independently, interconnected through complex interfaces. In terms of communication, each module may have its own communication methods and protocols, affecting the efficiency and accuracy of data exchange. Regarding signal processing, different modules use inconsistent processing methods and standards, increasing system complexity and instability. To achieve audio signal distribution and processing, multiple independent circuits are required, making the overall system architecture cumbersome.

[0004] This traditional discrete design suffers from low system integration, complex signal interfaces, and difficult maintenance. Because each functional module operates independently, system integration is difficult to improve, resulting in larger equipment size and greater space consumption. Complex signal interfaces increase the possibility of interference and errors during signal transmission, reducing system reliability. When a module fails, the system's complexity makes troubleshooting and repair difficult, increasing maintenance costs and time. In high-power transmission applications (e.g., medium-wave transmitters of 10 kW and above), the transmitter's operating status directly affects the continuity and security of the broadcast signal. If conditions such as excessively high forward power, excessively high reflected power, excessively high RF voltage, or excessively high RF current occur, traditional discrete designs struggle to respond quickly and effectively, potentially damaging the transmitter exciter or even causing safety accidents.

[0005] Given the above situation, how to solve the technical problems of low system integration, complex signal interfaces, and difficult maintenance of traditional medium-wave transmitters is a problem to be solved in this technical field. Summary of the Invention

[0006] In view of the above-mentioned defects or improvement needs of the existing technology, and in order to solve the technical problems of low integration, complex signal interface and difficult maintenance of traditional medium-wave transmitter systems, this application provides an integrated monitoring and control system for medium-wave transmitters. By introducing bus communication technology, power detection and protection circuits, audio signal distribution and other means, a unified integrated monitoring and control system is constructed, which can effectively improve the integration, interface simplicity, operational reliability, maintenance convenience and intelligence level of the transmitter.

[0007] The embodiments of this application adopt the following technical solutions: In a first aspect, this application provides an integrated monitoring and control system for a medium-wave transmitter, including a core control unit and an industrial control computer, a dual exciter, a rack interface board, a radio frequency sampling module, and a directional coupler that are respectively communicatively connected to the core control unit; The core control unit receives control commands from the industrial control computer via the first serial bus, combines its own monitoring data, and sends control commands to the dual exciter and rack interface board via the second serial bus. At the same time, it receives the sampling data of the dual exciter via the data stream bus to verify the control effect. The core control unit extracts baseband audio signals from radio frequency signals, processes them, and outputs stable audio signals for monitoring. It also distributes various signals to dual exciters. The core control unit uses a multi-stage voltage regulation topology to convert a single input voltage into multiple stable voltages, providing adaptive power to each module. The core control unit monitors the radio frequency voltage and current signals of the radio frequency sampling module, as well as the incident and reflected power signals of the directional coupler in real time. The reflected power signal is used to trigger an over-threshold protection shutdown mechanism, while the incident power signal, radio frequency voltage signal, and radio frequency current signal are used to evaluate the operating status and provide data support for power regulation. The core control unit receives the fast power reduction signal from the rack interface board and simultaneously outputs a PDM disable signal, an address signal, and an RF drive latch signal to the dual exciter.

[0008] By adopting the above technical solution, the core control unit is used as the system hub, integrating collaborative communication and data interaction with multiple modules such as the industrial control all-in-one computer, dual exciters, rack interface board, RF sampling module, and directional coupler. This achieves integrated monitoring, control, signal processing, and power supply management of the transmitter, improving the integration level and solving the problems of complex interfaces and difficult maintenance in traditional discrete systems. In addition, through comprehensive monitoring and hierarchical fault control of key RF parameters, rapid response protection is ensured under abnormal operating conditions such as excessive reflected power, while ensuring stable processing and distribution of audio signals, significantly improving the reliability, safety, and intelligence level of transmitter operation.

[0009] In some implementations, the first serial bus is an RS232 serial bus, through which the core control unit and the industrial control computer achieve bidirectional conversion between TTL and RS232 signals; the second serial bus is an RS485 serial bus, through which the core control unit, the dual exciter, and the rack interface board achieve bidirectional conversion between TTL and RS485 signals.

[0010] By adopting the above technical solution, the first serial bus is defined as RS232 and the second serial bus as RS485, which ensures efficient compatibility and conversion between the TTL signal and the bus signal of the core control unit, reduces distortion and interference during signal transmission, ensures the accuracy and stability of control command issuance and operation status upload, and provides reliable communication support for the collaborative work of various modules in the system.

[0011] In some implementations, the dual actuators include a first actuator and a second actuator, each assigned a unique serial communication address. The core control unit enables independent addressing and bidirectional data communication between the first actuator and the second actuator via an RS485 serial bus, avoiding communication interference.

[0012] By adopting the above technical solution, a unique serial communication address is assigned to each of the two exciters, enabling the core control unit to independently address and communicate with the two exciters in parallel. This avoids command conflicts and interference when communicating with multiple devices, ensures accurate execution of control commands for each exciter and independent feedback of status data, improves the flexibility and reliability of the dual exciter operation control, and guarantees stable adjustment of the transmitter power output.

[0013] In some implementations, an opto-isolation circuit is provided between the data flow bus and the dual exciter. The opto-isolation circuit achieves signal level isolation and electromagnetic interference suppression through isolation devices, preventing circuit faults on the dual exciter side from being transmitted to the core control unit.

[0014] By adopting the above technical solution, an opto-isolation circuit is set between the data flow bus and the dual exciters. The isolation device is used to achieve signal level isolation and electromagnetic interference suppression, which not only ensures the accuracy of the exciter sampling data transmission, but also effectively blocks the transmission of circuit faults on the dual exciter side to the core control unit, avoids damage to the control center due to external faults, and improves the overall anti-interference capability and operational safety of the system.

[0015] In some implementations, the core control unit processes the radio frequency voltage signal, radio frequency current signal, incident power signal, and reflected power signal by performing rectification, filtering, amplification, and limiting in sequence. The processed signals are then converted from analog to digital and provided to the core control unit for analysis and decision-making. The limiting process is used to prevent damage to the analog-to-digital conversion port due to overvoltage.

[0016] By adopting the above technical solution, the four key radio frequency signals are rectified, filtered, amplified and limited in sequence, converting the AC radio frequency signal into a stable and compatible DC signal. At the same time, the limiting protection avoids overvoltage damage to the analog-to-digital conversion port, ensuring that the core control unit obtains accurate and safe monitoring data. This provides reliable data support for transmitter operation status assessment, power adjustment and fault diagnosis, and improves the accuracy of parameter monitoring and the security of system hardware.

[0017] In some implementations, the core control unit has a built-in reflected power over-threshold protection module. The reflected power over-threshold protection module includes a threshold setting unit and a signal comparison unit. The threshold setting unit outputs a dynamically adjustable safety threshold, and the signal comparison unit compares the processed reflected power signal with the safety threshold in real time. When the reflected power signal exceeds the safety threshold, a protection shutdown mechanism is triggered.

[0018] By adopting the above technical solution, a built-in reflected power over-threshold protection module is incorporated. Combined with a dynamically adjustable safety threshold and a real-time signal comparison mechanism, the system can quickly identify and trigger protection shutdown when the reflected power exceeds the limit. This avoids damage to the power amplifier components due to excessive reflected power, solves the equipment safety hazards in high-power transmission scenarios, and significantly improves the operational safety and timeliness of fault protection of the transmitter.

[0019] In some implementations, the processing of the baseband audio signal by the core control unit includes audio amplification, automatic gain control, and modulation detection. Automatic gain control is used to automatically attenuate the radio frequency carrier signal when the audio amplitude exceeds a preset threshold to maintain stable audio output. Modulation detection generates a DC signal that is linearly related to the audio modulation through active rectification and filtering, which is then sampled and monitored by the core control unit.

[0020] By adopting the above technical solution, the entire process of amplifying, automatically controlling, and detecting the modulation of the baseband audio signal is achieved. Automatic gain control can avoid abnormal fluctuations in audio amplitude, and modulation detection generates a linearly correlated DC signal for real-time monitoring. This not only ensures the stability and listening quality of the audio output, but also achieves precise control of the audio modulation, thereby improving the transmission quality of the broadcast signal.

[0021] In some implementations, the various signals allocated to the dual exciters by the core control unit include balanced audio signals, AES audio signals, and B+ voltage sampling signals. The core control unit filters, isolates, or buffers each type of signal before allocating the output, thereby improving the anti-interference and stability of signal transmission.

[0022] By adopting the above technical solution, the balanced audio, AES audio and B+ voltage sampling signals are processed and redistributed in a targeted manner, which effectively suppresses high-frequency interference, prevents overvoltage damage, improves signal driving capability, ensures the stability and reliability of various signals distributed to the dual exciter, ensures the consistency and accuracy of the exciter modulation process, and thus improves the stability of the transmitter output signal.

[0023] In some embodiments, the multi-stage voltage regulator topology is composed of a DC-DC conversion unit and a low-dropout linear regulator unit. The single input voltage is 15V, and the multiple stable output voltages after conversion include ±15V, ±12V, 5V and 3.3V. Each voltage conversion unit is equipped with a reverse current protection device and a filter network.

[0024] By adopting the above technical solution, a multi-stage voltage regulation topology is used to achieve stable conversion from a single 15V input to multiple voltages, adapting to the different power requirements of each module. At the same time, reverse current protection devices and filter networks prevent device damage, suppress ripple and noise, and balance power supply efficiency and stability. This provides clean and reliable power support for the coordinated operation of each module in the system, and improves the electromagnetic compatibility performance and overall operational stability of the system.

[0025] In some implementations, the fast power reduction signal received by the core control unit is a 5V level signal, which is converted into a logic level compatible with the core control unit after level conversion; the PDM disable signal and the RF drive latch signal are output from the digital port of the core control unit, and form an open collector structure through switching devices. They are kept at a high level during normal operation and pulled low to cut off the output of the corresponding exciter during faults.

[0026] By adopting the above technical solution, the level conversion of the fast power reduction signal is performed to ensure compatibility with the core control unit. At the same time, the PDM disable signal and the RF drive latch signal are generated with an open collector structure to realize the rapid cut-off of the exciter output in case of failure. This not only ensures the adaptability and safety of the control signal, but also realizes the hierarchical rapid response under fault conditions, avoids the expansion of the fault, and further improves the fault protection reliability and safety of the transmitter.

[0027] In summary, this application includes at least the following beneficial technical effects: 1. By using the core control unit as the system hub, it integrates collaborative communication and data interaction with multiple modules such as the industrial control all-in-one computer, dual exciters, rack interface board, RF sampling module, and directional coupler. This achieves integrated monitoring, control, signal processing, and power supply management of the transmitter, improving integration and solving the problems of complex interfaces and difficult maintenance in traditional discrete systems. In addition, through comprehensive monitoring and hierarchical fault control of key RF parameters, it ensures rapid response protection under abnormal conditions such as excessive reflected power, while ensuring stable processing and distribution of audio signals, significantly improving the reliability, safety, and intelligence level of transmitter operation. 2. A multi-stage voltage regulation topology is used to achieve stable conversion from a single 15V input to multiple voltages, adapting to the different power requirements of each module. At the same time, reverse current protection devices and filtering networks prevent device damage, suppress ripple and noise, and balance power supply efficiency and stability. This provides clean and reliable power support for the coordinated operation of each module in the system, and improves the electromagnetic compatibility performance and overall operational stability of the system. 3. The rapid power reduction signal is level-converted to ensure compatibility with the core control unit. At the same time, the PDM disable signal and RF drive latch signal are generated with an open collector structure to quickly cut off the exciter output in case of failure. This not only ensures the adaptability and safety of the control signal, but also realizes a graded rapid response in the fault state, avoids the fault from escalating, and further improves the fault protection reliability and safety of the transmitter. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the architecture of an integrated monitoring and control system for a medium-wave transmitter provided in this application embodiment; Figure 2 This is a schematic diagram of four-channel radio frequency signal processing provided in an embodiment of this application; Figure 3 This is a schematic diagram of audio demodulation and modulation detection provided in an embodiment of this application. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. Furthermore, the technical features involved in the various embodiments described below can be combined with each other as long as they do not conflict with each other.

[0031] The present application will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] like Figure 1 As shown, this application provides an integrated monitoring and control system for a medium-wave transmitter. The core design breaks away from the functional fragmentation of traditional discrete systems, constructing an integrated architecture centered on the transmitter control board (i.e., the core control unit), achieving integrated coordination across the entire process of communication management, signal sampling, audio processing, power monitoring, fault control, and power supply management. Figure 1 As shown, the system mainly includes a core control unit, an industrial control all-in-one computer, dual exciters (exciter A and exciter B), a rack interface board, an RF sampling module (including RF voltage and current sampling boards), and a directional coupler. Each module establishes stable communication and signal interaction through a specific bus or signal line, forming a complete closed-loop control system of "signal acquisition-processing-decision-execution-feedback".

[0033] The core control unit includes an embedded core board, whose core processor is an embedded STM32 microcontroller. This processor features high performance, low power consumption, and rich peripheral interfaces, enabling it to efficiently handle critical tasks such as communication management, signal sampling, audio processing, and security protection. As the core hub of the entire system, the core control unit is responsible for coordinating the orderly operation of all subsystems. Integrating multiple functions, it is a key guarantee for achieving stable transmitter operation, automatic control, and fault protection.

[0034] The core functions of the core control unit revolve around three dimensions: communication interaction, signal processing, and control logic. The various functional modules work together to ensure the overall efficient operation of the system.

[0035] In terms of communication and interaction, the core control unit achieves precise data interaction with each subsystem through a combination of multiple buses: it transmits data to the industrial control computer via an RS232 serial bus to upload transmitter operating status and issue control commands; it establishes bidirectional data communication with exciter A and exciter B via an RS485 bus, and simultaneously receives sampling data from the two exciters via a data stream bus; in addition, it communicates with the rack interface board via an RS485 bus to receive RF power module status information and analog sampling data, as well as transmit main control commands such as power adjustment and start / stop control.

[0036] In terms of signal processing, the core control unit possesses dual capabilities for audio extraction and distribution, and key parameter monitoring. On one hand, it extracts low-frequency audio components from the radio frequency (RF) signal, converting audio amplitude changes into DC modulation signals for real-time monitoring of modulation changes. Simultaneously, the core control unit forwards the incident power signal to exciters A and B, and distributes audio signals such as BALANCEDAUDIO, ANALOG AES1, and DIGITAL AES2, along with the B+ voltage sampling signal, to the two exciters, ensuring modulation signal consistency. On the other hand, the core control unit provides ±15V operating power to the RF voltage and current sampling board and directional coupler, while simultaneously monitoring key parameters such as RF voltage, RF current, incident power, and reflected power in real time. When the reflected power exceeds a set threshold, it automatically triggers a protection shutdown mechanism to prevent equipment damage and ensure safe operation.

[0037] In terms of control logic, the core control unit has a hierarchical fault response capability: it can read the rapid power reduction signal sent by the rack interface board, and at the same time independently output PDM disable signal, address signal and RF drive latch signal to exciters A and B, so as to realize precise independent control and fault protection of the two exciters, and ensure rapid response and risk isolation in fault conditions.

[0038] Based on the above setup, the core control unit, as the core hub of the entire system, integrates communication management, signal processing, and safety control, and is a key guarantee for achieving stable operation, automatic control, and fault protection of the transmitter.

[0039] Furthermore, the specific implementation of the communication interface of this application will be described in detail below.

[0040] 1. Communication between RS232 serial bus and industrial control computer: The core control unit communicates with the industrial control all-in-one computer (model EM156-X86-4125) via an RS232 standard serial bus. This facilitates command interaction, status feedback, and system monitoring between the core control unit and the host computer. The industrial control all-in-one computer is installed on the front panel of the transmitter control cabinet and features a touchscreen interface for convenient local parameter setting, status monitoring, and control command issuance. The system also supports Ethernet remote control, allowing users to access the system remotely via computer and web browser to perform real-time equipment status monitoring, parameter setting, alarm information query, log export, and report viewing, adapting to various scenarios requiring both local maintenance and remote management.

[0041] To ensure the reliability and compatibility of signal transmission, the core control unit can use the SIT3232E chip as an RS232 transceiver driver. This chip can realize bidirectional conversion between 3.3VTTL signals and RS232 signals, effectively suppressing signal distortion during transmission and ensuring accurate interaction between control commands and status data.

[0042] 2. RS485 bus communication with exciters A and B: The core control unit communicates with exciters A and B via an RS485 bus. The system assigns a unique serial communication address to each exciter, enabling independent addressing and data exchange between exciters A and B, ensuring uninterrupted communication and stable, reliable operation. The core functions of the serial communication include control command transmission, exciter status information feedback, and operating parameter exchange, thereby achieving real-time control and operational status monitoring of the two exciters.

[0043] The core control unit can use the SIT3491E chip as an RS485 transceiver driver. This chip has strong anti-interference capabilities and signal conversion stability, and can realize bidirectional conversion between 3.3VTTL signals and RS485 signals, providing a guarantee for long-distance and highly reliable communication between the exciter and the control board.

[0044] 3. Communication between the data flow bus and actuators A and B: Exciters A and B transmit their sampled data to the core control unit in real time via a data stream bus. To prevent circuit faults on the exciter side from being transmitted to the core control unit and to suppress the influence of external electromagnetic interference on the sampled data, an opto-isolation circuit is installed between the data stream bus and the exciter on the transmitter control board. The isolation device in the opto-isolation circuit can be an ELD3H7 dual-channel optocoupler. The input side of the optocoupler is connected to the data bus terminal of the exciter through a current-limiting resistor to limit the input current and prevent damage from overcurrent. The output side is connected to the main control MCU (STM32 microcontroller) port through a pull-up resistor to achieve logic level isolation and reliable signal transmission, ensuring the accuracy of sampled data transmission and the safe operation of the core control unit.

[0045] 4. RS485 bus communication with rack interface board: The core control unit communicates with the rack interface board via an RS485 bus, employing a multi-device bus topology for data exchange. Each RF power module is pre-loaded with a unique serial number. When a module is inserted into the transmitter, the rack interface board automatically assigns it a serial communication address, thereby enabling unified management and communication among multiple RF power modules.

[0046] In terms of communication functionality, the rack interface board feeds back the operating status and analog sampling data of the RF power module to the core control unit, specifically including the temperature information and phase loss indication of the silicon controlled rectifier. The core control unit sends control commands to the rack interface board, including power adjustment commands and start / stop control commands, forming a closed-loop control of the RF power module. The core control unit also uses the SIT3491E chip as an RS485 transceiver driver to achieve bidirectional conversion between 3.3VTTL and RS485 signals, ensuring stability and reliability in multi-device communication scenarios.

[0047] Furthermore, the specific implementation of signal sampling and monitoring in this application will be described in detail below.

[0048] refer to Figure 1 and Figure 2 As shown, the core function of this circuit is to sample and monitor the key operating parameters of the transmitter's RF power system in real time, providing accurate basic data support for transmitter operating status analysis, power control, and protection logic. The sampling objects include the incident power and reflected power signals from the directional coupler, as well as the RF voltage and RF current signals output by the RF voltage and current sampling board.

[0049] 1. Sampling system composition: The sampling system consists of four radio frequency signal sampling and amplification modules and a set of reflected power over-threshold shutdown protection circuits. The four sampling and amplification modules correspond to four physical quantities: incident power, reflected power, radio frequency voltage, and radio frequency current. Each module works independently to ensure the independence and accuracy of parameter acquisition and avoid cross-interference.

[0050] 2. Radio frequency signal sampling and amplification process: The signal processing for each sampling channel follows a standardized process of "rectification-filtering-amplification-clamping". Rectification stage: Each sampling channel uses a TL074 series high-speed operational amplifier and diodes (model: 1N4607) to form a half-wave rectifier circuit, converting the AC RF signal into a unidirectional pulsating DC signal. Filtering stage: The rectified signal is filtered by a multi-stage RC network to effectively remove high-frequency interference components and obtain a stable DC sampling voltage. Amplification stage: The filtered signal enters an amplification circuit composed of a second-stage TL074 operational amplifier. The required gain is set by adjusting the feedback resistor value, while simultaneously improving the output impedance to make the signal amplitude match the ADC sampling range of the main control system (embedded core board). Clamping protection stage: Each final output terminal is equipped with a 3.3V Zener diode clamping circuit (e.g., model: BZX384C3V3) to limit the output signal peak value and prevent overvoltage damage to the ADC sampling port under abnormal conditions. After being processed by the above process, the four stable DC signals are finally sent to the ADC port of the main control system to realize the real-time acquisition of key parameters and calculation of operating status.

[0051] 3. Reflection power over-threshold protection is implemented: In the sampling and amplification channel corresponding to the reflected power, in addition to the conventional sampling and amplification functions, a reflected power over-threshold protection module is integrated to achieve rapid protection against reflected power exceeding limits. When the reflected power exceeds the set safety threshold, the protection circuit must act immediately to prevent excessive reflected power from damaging the power amplifier components. This module uses a comparator composed of a TLV2370 operational amplifier as its core. Its non-inverting input receives the dynamically adjustable threshold signal output from the DAC, while its inverting input receives the rectified, filtered, and amplified reflected power monitoring signal.

[0052] The comparator compares the two input signals in real time. When the reflected power monitoring signal exceeds the set safety threshold, the comparator output jumps to a low level. This signal is then converted to a logic level compatible with the core control unit by a 74LVC1T45 logic level converter and sent to the main control system interface. The main control system immediately triggers the subsequent shutdown control circuit to achieve protective power-off or power suppression of the RF power amplifier, preventing excessive reflected power from damaging the power amplifier components.

[0053] Furthermore, the specific implementation of audio signal processing and signal allocation will be described in detail below.

[0054] refer to Figure 1 and Figure 3As shown, the core control unit includes an audio demodulation module. The core function of this module is to extract baseband audio from the RF amplitude-modulated signal, detect the audio amplitude envelope, and output a DC voltage proportional to the modulation level. After envelope detection of the amplitude-modulated signal, it can simultaneously obtain a stable audio output signal and a DC voltage proportional to the modulation level. This module circuit mainly consists of a detection unit, an audio amplification unit, an audio power amplifier driver unit, an automatic gain control (AGC) loop, an audio amplitude envelope detection unit, and a buffer and protection unit for modulation level monitoring.

[0055] The specific workflow is as follows: Signal Input and Drive: The amplitude-modulated radio frequency signal is input from the interface and then sent to a high-speed unity-gain buffer (model: LH0002CN) through a series resistor. This buffer can drive the radio frequency signal without distortion, ensuring the signal quality of subsequent processing. Detection and Demodulation: The RF amplitude-modulated signal driven by LH0002CN is fed into a dual-diode detector network via a coupling transformer. The diodes alternately conduct the positive and negative envelopes of the amplitude-modulated RF signal to achieve full-wave rectification of the RF carrier. The rectified envelope signal is filtered by a multi-stage RC network to remove the carrier frequency component, retaining only the 0.3~3kHz audio modulation signal, thus completing the baseband demodulation of the amplitude-modulated signal. Audio amplification: The baseband audio signal is fed into an audio amplification circuit constructed by an operational amplifier. The feedback resistor and the compensation capacitor form a low-pass characteristic, which enables the circuit to provide sufficient gain and effectively suppress high-frequency noise in the demodulation process. Automatic Gain Control (AGC): The amplified audio signal is introduced into the AGC control loop. First, it enters the active low-pass filter circuit composed of resistors, capacitors, and operational amplifiers to extract the DC envelope signal that reflects the average amplitude of the audio. The subsequent comparator is composed of operational amplifiers. When the envelope voltage exceeds the preset threshold (set by an adjustable resistor), it drives the transistor to conduct, causing the LED inside the optocoupler variable resistor (model: VTL5C4) to light up. The resistance of its photoresistor decreases. This resistance change achieves automatic attenuation of the RF carrier signal through the voltage divider network at the front end, thereby maintaining the stability of the audio amplitude. Modulation detection: The amplified audio signal enters the audio amplitude envelope detection unit, where it is amplified and buffered again by an operational amplifier. It is then fed into an active full-wave rectifier composed of multiple operational amplifiers, and subsequently filtered by an RC filter to form a smooth DC voltage. This DC voltage is linearly related to the modulation. The DC envelope then enters the modulation monitoring buffer circuit, where it is further filtered and buffered by a two-stage voltage follower structure and a multi-stage RC smoothing network. A 3.3V Zener diode (e.g., model BZX384C3V3) is set at the output to provide clamping protection. The final output is a steady-state DC voltage proportional to the audio modulation, which can be sampled in real time by the controller and used for modulation display. Audio monitoring: The last branch of the amplified audio signal enters the audio driver circuit composed of LM384, which can directly drive monitoring headphones, speakers or external monitoring devices to realize real-time audio monitoring function, making it convenient for operators to verify audio quality.

[0056] For BALANCED AUDIO / AES1 / AES2 / B+ signal distribution: Considering the characteristics of the four types of signals, namely BALANCED AUDIO (balanced audio), ANALOG AES1 (analog AES1), IQ AES2 (digital AES2), and B+Sample (B+ voltage sampling), the system is designed with a highly reliable and highly anti-interference independent signal distribution and isolation structure to ensure stable transmission and accurate distribution of various signals.

[0057] The BALANCED AUDIO signal distribution module receives external balanced audio input signals. The input employs a precision RC matching network and an RC filter to form a low-pass filter structure, effectively suppressing high-frequency interference and RF noise. The signal then passes through a multi-stage clamping protection network composed of TVS diodes and fast diodes to prevent input overvoltage or electrostatic discharge. The protected signal then enters a low-noise audio operational amplifier (model: OP275) to enhance the driving capability of the balanced audio signal, ensuring stable signal transmission to the target device.

[0058] The ANALOG AES1 / IQ AES2 signal distribution module adopts a dual-channel structure, with each channel consisting of an input isolation transformer, a differential receiver, and a logic switching circuit. The input side uses a broadband audio isolation transformer (model: ADT1-6T+) to achieve electrical isolation of the signal and reduce interference conduction. The signal is then connected to a differential signal receiver chip (model: DS26C32ATM) to achieve highly reliable AES signal reception. The subsequent stage uses a multiplexing logic chip (model: SN74LVC257A) to flexibly switch and distribute output between the ANALOG AES1 and IQ AES2 channels according to control signals, adapting to the signal input requirements of dual exciters.

[0059] B+ signal distribution module: Used to distribute B+ voltage signal. The input adopts a precision voltage divider network to scale the high-voltage power supply signal to about 1 / 11 of its original size. At the same time, it forms a first-order low-pass filter with a 10nF capacitor to filter out voltage noise. The filtered signal is input to the operational amplifier buffer and outputs a stable, low-impedance voltage signal to provide accurate voltage samples for the system's control or monitoring modules, supporting power regulation and status monitoring logic.

[0060] Furthermore, the specific implementation of fault shutdown and logic control in this application will be described in detail below.

[0061] This application system is equipped with multi-level fault shutdown and logic control circuits. The core objective is to quickly and reliably limit or cut off the power output of the exciter when an abnormal state is detected, so as to protect the safe operation of the RF power module and the whole system. Specifically, it includes four parts: PDM disable control, RF drive disable control, exciter address selection control, and FastShuntback feedback control.

[0062] 1. PDM disable and RF driver disable control: The core control unit generates independent PDM disable signals and RF drive disable signals for exciter A and exciter B respectively, ensuring independent protection and control of the two exciters. These signals are all output from the digital control port of the MCU (STM32 microcontroller), and after passing through a current-limiting resistor, drive an NPN transistor to form an open collector structure, which is then connected to a 3.3V power supply via a pull-up resistor.

[0063] Under normal operating conditions, the transistor is cut off, the corresponding disable signal remains high, and the exciter is in normal operating condition. When an alarm or fault condition is detected, the MCU outputs a valid control signal to turn on the transistor and pull the corresponding disable signal low, thereby quickly disabling the PDM drive output and / or RF drive output of the specified exciter.

[0064] The exciter has two core signal generation functions during operation: First, it generates a digital PDM signal, which consists of six PDM sub-signals with a phase difference of 60 electrical degrees. These sub-signals collectively determine the transmitter's output power level and modulation level. Each RF power module receives three PDM signals with a phase difference of 120 electrical degrees (e.g., phases 1, 3, and 5), while adjacent modules receive three other phase difference signals (e.g., phases 2, 4, and 6) to achieve optimal harmonic cancellation. Second, it synthesizes a carrier frequency RF drive signal, which is output in pulse form to drive subsequent RF power modules. By setting independent PDM disable and RF drive disable signals, the system can selectively disable the corresponding outputs of the exciter under different levels of faults, achieving flexible power control and fault isolation.

[0065] 2. Exciter address signal and logic selection control: The PDM signals from exciter A and exciter B are switched and output through a 2x2 Ethernet port. The selection of exciter A and B and the switching of the PDM signals are controlled by address signals. The address control signal is also generated using an "MCU output + transistor open collector" structure. By using address signals with different level combinations, precise switching of the two exciter PDM signal output channels is achieved, ensuring the coordinated operation and independent control of single or dual exciters.

[0066] 3. Fast Shuntback Feedback Control: To achieve higher priority system protection, a Fast Shuntback signal channel is introduced. When the rack interface board detects an abnormal condition requiring immediate reduction of transmitter output power (such as thyristor overheating or severe phase loss), it outputs a Fast Shuntback signal. This signal is 5V; to ensure electrical safety and logic compatibility of the MCU input port, it needs to be converted from 5V to 3.3V using a level conversion chip before being input to the MCU.

[0067] Upon detecting a valid Fast Shuntback signal, the MCU immediately enters a power limiting or power reduction control process: on the one hand, it communicates with the rack main controller via the RS485 serial communication interface to send power adjustment or start / stop commands; on the other hand, based on the fault level and system configuration, it coordinates with the aforementioned PDM disable signal and RF drive disable signal to quickly adjust the output state of the exciter, achieving multiple collaborative protections to prevent the fault from escalating.

[0068] Furthermore, the specific implementation of the power management in this application will be described in detail below.

[0069] The power management system of this application adopts a multi-stage voltage regulation topology. Its core function is to simultaneously generate multiple stable voltages of ±15V, ±12V, 5V, and 3.3V from a single 15V input power supply. The overall design follows the principles of high efficiency, low ripple, high isolation, and low noise to ensure the reliability of the system power supply and electromagnetic compatibility performance. The power management module consists of five independent and collaboratively operating sub-power supply units, specifically implemented as follows: 1. 15V to –15V conversion unit: This unit uses the LT3580 boost / inverting DC / DC converter chip, forming an inverting Buck-Boost topology through inductors, fast rectifier diodes, and filter capacitors, and utilizes a feedback voltage divider network to achieve precise regulation of the -15V output voltage. This -15V power supply mainly provides a stable input for the subsequent -12V regulator module, laying the foundation for the negative voltage power supply link.

[0070] 2. 15V to 5V conversion unit: This section uses the TPS54527 synchronous buck DC / DC chip, which forms a buck structure with inductors and filter capacitors, and achieves precise control of the 5V output through a feedback resistor network. The generated 5V power supply provides a stable input to the subsequent 3.3V regulator module, and also powers some intermediate stage circuits.

[0071] 3. 5V to 3.3V conversion unit: This unit uses the SGM2212-3.3 low dropout linear regulator, which has a protection diode at its input to prevent reverse current from damaging the device when the system is powered off. The output uses an LC filter network to effectively suppress ripple and high-frequency interference, thereby obtaining a stable, low-noise 3.3V power supply, which mainly powers the STM32 microcontroller and related digital circuits of the core control unit.

[0072] 4. 15V to 12V conversion unit: This unit uses a CJ7812 linear regulator for voltage regulation and conversion. A protection diode is installed at the input to prevent reverse current flow during power outages, and an LC filter at the output reduces output ripple. This 12V power supply is primarily used for relay drives and analog circuits with high power quality requirements.

[0073] 5. –15V to –12V conversion unit: This unit employs a CJ7912 negative voltage linear regulator, whose structure is symmetrical to the positive 12V voltage regulator unit. It also features a reverse protection diode at the input and an LC filter network at the output to reduce ripple and noise. This unit, together with the positive 12V power supply, constitutes the system's bipolar regulated power supply system, providing a suitable power source for analog circuits such as audio processing and signal amplification.

[0074] Each voltage conversion unit operates independently yet works in concert. Through reverse current protection devices and filtering networks, it balances power supply efficiency, stability, and electromagnetic compatibility performance, providing precise and reliable power support for all modules in the system.

[0075] Based on the above settings, the system workflow includes: Power-on initialization: After the system is powered on, the power management module first completes the stable output of multiple voltages of ±15V, ±12V, 5V, and 3.3V to power each module; the STM32 microcontroller of the transmitter control board (core control unit) starts the initialization program, establishes communication connections with the industrial control all-in-one computer, dual exciter, rack interface board, etc. through various communication buses, completes the equipment status self-check, and confirms whether each module is normal and ready.

[0076] During normal operation: The transmitter control board collects key parameters such as incident power, reflected power, RF voltage, and RF current in real time through the RF sampling module and directional coupler. After rectification, filtering, amplification, and clamping, the data is sampled by the ADC for real-time monitoring, and the monitoring data is uploaded to the industrial control computer for display. At the same time, it receives control commands from the industrial control computer and sends power adjustment, start / stop commands to the dual exciters and rack interface board through the RS485 bus, combined with the monitoring data. It also receives the sampled data from the exciters through the data stream bus to verify the control effect. The audio processing module continuously extracts the baseband audio signal, and after AGC control and modulation detection, outputs stable audio for listening, while feeding back the modulation data to the industrial control computer.

[0077] Fault handling phase: When the reflected power exceeds the threshold, the reflected power protection circuit quickly triggers the transmitter control board to start protection shutdown; when the rack interface board detects an emergency abnormality, it triggers the control board to perform a rapid power reduction operation through the Fast Shuntback signal; the control board selectively outputs PDM disable signal and RF drive disable signal according to the fault level, cuts off the abnormal exciter output, and displays alarm information on the industrial control computer to facilitate users to troubleshoot the fault in a timely manner.

[0078] Through the implementation of the above technical solutions in the embodiments of this application, the intelligence level, operational reliability, safety protection capability, and maintenance convenience of the 10kW medium-wave transmitter monitoring and control system are significantly improved in all aspects, specifically in the following aspects: 1. Significantly enhanced integration and a simpler, more reliable system architecture: Through the integrated architecture design of the transmitter control board, core functions such as communication management, signal sampling, audio processing, power monitoring, and protection control are highly integrated onto a single control board, completely overcoming the drawbacks of traditional discrete systems with fragmented functions and complex interfaces. The number of system interfaces is significantly reduced, and the structural complexity is greatly reduced. This not only reduces interference and fault points in signal transmission between modules but also improves the stability of the entire system. Furthermore, it makes equipment installation, inspection, and daily maintenance more convenient and efficient, reducing operation and maintenance costs and difficulties.

[0079] 2. Highly efficient and stable communication transmission, and accurate and error-free data interaction: The construction of a multi-bus combined communication system enables precise communication adaptation in different scenarios. The RS232 bus ensures reliable transmission of commands and status feedback between the control board and the industrial control computer. Combined with the local touch screen operation and Ethernet remote access function of the industrial control computer, operators can flexibly perform operations such as real-time equipment monitoring, parameter setting, alarm query, and export of operation logs. The multi-channel RS485 bus, through independent addressing design, ensures stable communication and unified management of dual exciters and multiple RF power modules, avoiding communication interference between multiple devices. The data stream bus enables high-speed, real-time transmission of exciter sampling data. Combined with opto-isolation protection, it further improves the accuracy and security of data transmission, providing reliable data support for precise system control.

[0080] 3. Precise RF parameter monitoring and timely and effective safety protection: The application of a multi-parameter synchronous sampling and protection mechanism for RF power enables comprehensive real-time monitoring of key parameters such as incident power, reflected power, RF voltage, and RF current. Through rectification, filtering, amplification, and limiting processing, the stability and accuracy of the sampled data are ensured, providing a reliable basis for transmitter operation status analysis and precise power adjustment. The design of an adjustable threshold comparison circuit in the reflected power channel can quickly determine the reflected power over-limit state and trigger the protection shutdown mechanism, effectively preventing excessive reflected power from damaging power amplifier devices and eliminating equipment failures or safety accidents caused by abnormal parameters, significantly improving system safety and operational reliability in high-power transmission scenarios.

[0081] 4. Excellent audio processing quality and strong anti-interference capability in signal distribution: The comprehensive audio signal processing solution ensures stable output and controllable quality of broadcast audio. Stable extraction of the baseband audio signal is achieved through envelope detection and multi-stage filtering. The AGC automatic gain control mechanism automatically attenuates the RF carrier signal when the audio amplitude exceeds a set threshold, effectively preventing audio fluctuations and ensuring stable audio output. The modulation monitoring function generates a DC monitoring quantity proportional to the modulation through active rectification and RC smoothing, allowing operators to monitor audio modulation quality in real time. Combined with the real-time monitoring function implemented by the audio driver circuit, audio anomalies can be detected and troubleshooted promptly. Simultaneously, the independent optimized distribution structure for balanced audio, AES signals, and B+ voltage sampling signals, through filtering, isolation, and buffering designs, significantly improves the anti-interference capability and stability of signal transmission, ensuring accurate distribution of various signals to the target module and guaranteeing the consistency and reliability of the transmitter modulation process.

[0082] 5. Multi-level fault protection with enhanced equipment safety: A multi-level fault shutdown and rapid power reduction control mechanism constructs a comprehensive safety protection system. The independent design of the PDM disable signal and the RF drive disable signal allows for selective disconnection of the corresponding exciter output based on the fault level, achieving flexible power control and fault isolation. The introduction of the rapid power reduction signal channel enables the rack interface board to trigger the system to immediately execute power limiting or power reduction operations when it detects an emergency anomaly. Combined with PDM disable, RF drive disable, and other control logics, this forms multiple layers of collaborative protection, achieving rapid response and risk blocking under fault conditions, preventing the fault from escalating and spreading, maximizing the protection of the RF power module and the entire system, and significantly improving the transmitter's operational reliability and service life.

[0083] 6. Stable and adaptable power supply system with excellent electromagnetic compatibility: The multi-voltage coordinated power management structure, through the combination of multi-stage DC / DC converters and linear regulators, stably outputs ±15V, ±12V, 5V, and 3.3V from a single 15V input, accurately adapting to the differentiated power requirements of various modules such as RF sampling modules, analog circuits, digital circuits, and relay drivers. The reverse protection diodes and LC filter networks in each sub-power supply unit effectively prevent damage to components from reverse current, significantly suppressing output ripple and high-frequency noise. It balances power efficiency, low ripple, high isolation, and low noise characteristics, providing a clean and reliable power supply for the stable operation of each module in the system, improving the overall electromagnetic compatibility performance, and reducing interference to peripheral equipment.

[0084] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An integrated monitoring and control system for a medium-wave transmitter, characterized in that, It includes a core control unit and an industrial control all-in-one computer, dual exciters, a rack interface board, an RF sampling module, and a directional coupler, all of which are communicatively connected to the core control unit. The core control unit receives control commands from the industrial control computer via the first serial bus, combines its own monitoring data, and sends control commands to the dual exciter and rack interface board via the second serial bus. At the same time, it receives the sampling data of the dual exciter via the data stream bus to verify the control effect. The core control unit extracts baseband audio signals from radio frequency signals, processes them, and outputs stable audio signals for monitoring. It also distributes various signals to dual exciters. The core control unit uses a multi-stage voltage regulation topology to convert a single input voltage into multiple stable voltages, providing adaptive power to each module. The core control unit monitors the radio frequency voltage and current signals of the radio frequency sampling module, as well as the incident and reflected power signals of the directional coupler in real time. The reflected power signal is used to trigger an over-threshold protection shutdown mechanism, while the incident power signal, radio frequency voltage signal, and radio frequency current signal are used to evaluate the operating status and provide data support for power regulation. The core control unit receives the fast power reduction signal from the rack interface board and simultaneously outputs a PDM disable signal, an address signal, and an RF drive latch signal to the dual exciter.

2. The integrated monitoring and control system for a medium-wave transmitter according to claim 1, characterized in that, The first serial bus is an RS232 serial bus, through which the core control unit and the industrial control all-in-one computer achieve bidirectional conversion between TTL and RS232 signals; the second serial bus is an RS485 serial bus, through which the core control unit, the dual exciter, and the rack interface board achieve bidirectional conversion between TTL and RS485 signals.

3. The integrated monitoring and control system for a medium-wave transmitter according to claim 2, characterized in that, The dual exciter includes a first exciter and a second exciter, each assigned a unique serial communication address. The core control unit enables independent addressing and bidirectional data communication between the first exciter and the second exciter via an RS485 serial bus, avoiding communication interference.

4. The integrated monitoring and control system for a medium-wave transmitter according to claim 1, characterized in that, An opto-isolation circuit is provided between the data stream bus and the dual exciter. The opto-isolation circuit achieves signal level isolation and electromagnetic interference suppression through isolation devices, preventing circuit faults on the dual exciter side from being transmitted to the core control unit.

5. The integrated monitoring and control system for a medium-wave transmitter according to claim 1, characterized in that, The core control unit processes the radio frequency voltage signal, radio frequency current signal, incident power signal, and reflected power signal in sequence, including rectification, filtering, amplification, and limiting. The processed signals are then converted from analog to digital and provided to the core control unit for analysis and decision-making. The limiting process is used to prevent damage to the analog-to-digital conversion port due to overvoltage.

6. The integrated monitoring and control system for a medium-wave transmitter according to claim 5, characterized in that, The core control unit has a built-in reflection power over-threshold protection module. The reflection power over-threshold protection module includes a threshold setting unit and a signal comparison unit. The threshold setting unit outputs a dynamically adjustable safety threshold. The signal comparison unit compares the processed reflection power signal with the safety threshold in real time. When the reflection power signal exceeds the safety threshold, the protection shutdown mechanism is triggered.

7. The integrated monitoring and control system for a medium-wave transmitter according to claim 1, characterized in that, The core control unit processes the baseband audio signal, including audio amplification, automatic gain control, and modulation detection. Automatic gain control is used to automatically attenuate the radio frequency carrier signal when the audio amplitude exceeds a preset threshold, so as to maintain stable audio output. Modulation detection generates a DC signal that is linearly related to the audio modulation through active rectification and filtering, which is then sampled and monitored by the core control unit.

8. The integrated monitoring and control system for a medium-wave transmitter according to claim 1, characterized in that, The core control unit distributes various signals to the dual exciters, including balanced audio signals, AES audio signals, and B+ voltage sampling signals. The core control unit filters, isolates, or buffers each type of signal before distributing it to the output, thereby improving the anti-interference and stability of signal transmission.

9. The integrated monitoring and control system for a medium-wave transmitter according to claim 1, characterized in that, The multi-stage voltage regulator topology is composed of a DC-DC conversion unit and a low-dropout linear regulator unit. The single input voltage is 15V, and the multiple stable output voltages after conversion include ±15V, ±12V, 5V and 3.3V. Each voltage conversion unit is equipped with a reverse current protection device and a filter network.

10. The integrated monitoring and control system for a medium-wave transmitter according to claim 1, characterized in that, The fast power reduction signal received by the core control unit is a 5V level signal, which is converted into a logic level compatible with the core control unit after level conversion. The PDM disable signal and the RF drive latch signal are output from the digital port of the core control unit and form an open collector structure through switching devices. They are kept at a high level during normal operation and pulled low to cut off the output of the corresponding exciter during faults.

Images