A medium wave DRM digital amplitude modulation broadcast monitoring receiving device

Abstract

The utility model discloses a kind of medium wave DRM digital amplitude modulation broadcast monitoring receiving equipment, and it is designed specially for broadcast television transmitting station. The equipment core adopts high-integration DRM1000 module, is responsible for receiving and demodulating digital amplitude modulation broadcast signal. Supporting circuit includes: radio frequency front end module, for signal reception and coupling;Voltage stabilizing circuit module, provide stable 3.3V DC power supply, support equipment 7x24 hours uninterrupted operation;Audio processing module, the differential audio signal of DRM1000 output is handled in two ways: one way provides professional XLR balanced audio output interface after LC filtering, seamlessly docking station monitoring equipment;The other way is amplified by two-stage triode and drives local loudspeaker monitoring. Display circuit shows signal quality parameter in real time through I2C bus. The equipment significantly reduces hardware cost and complexity, solves the problem of interface incompatibility and inability to continuously monitor in traditional scheme, and improves broadcast safe broadcast guarantee capability.

Description

Technical Field

[0001] This utility model relates to the field of broadcast television signal monitoring technology, and in particular to a medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device. Background Technology

[0002] Medium wave digital amplitude modulation (AM) broadcasting, as a digital evolution of traditional analog amplitude modulation (AM) broadcasting, has shown broad application prospects in emergency broadcasting, long-distance coverage and professional communications due to its significant advantages such as sound quality close to FM broadcasting, strong anti-multipath interference capability, high spectrum utilization and ability to carry data services.

[0003] However, current monitoring methods for DRM broadcast systems still have several technical limitations, restricting their large-scale, high-reliability deployment at transmission stations: High hardware dependence and high cost: Most existing DRM monitoring systems rely on dedicated and complex receiving equipment. The internal circuit design of these devices is complicated, containing multiple discrete units such as independent radio frequency, intermediate frequency, demodulation, and decoding, resulting in high hardware costs and poor system scalability, making it difficult to meet the needs of parallel monitoring of multiple signals within a station.

[0004] The real-time audio monitoring function has shortcomings and cannot achieve continuous operation: Some DRM receiving solutions on the market are designed for portable applications and mainly rely on built-in batteries for power. Limited by battery capacity and power consumption, these devices cannot achieve continuous monitoring 24 / 7. During long-term operation, signal interruptions or device shutdowns may occur, making it impossible to detect nighttime or sudden broadcast failures in a timely manner, and failing to meet the monitoring requirements of unattended transmission stations.

[0005] Incompatible equipment interfaces hinder integration into existing monitoring systems: Traditional portable receivers typically use a 3.5mm unbalanced stereo headphone jack for audio output. However, professional signal monitoring cabinets at broadcast television stations generally use the XLR balanced audio interface standard. This interface mismatch prevents portable receivers from directly interfacing with existing professional equipment such as audio distributors, matrices, and silent alarms at the station, requiring additional complex audio interface conversion equipment, increasing system complexity and potential points of failure.

[0006] As a mainstream, highly integrated DRM demodulation chip solution in the industry, the DRM1000 module integrates a complete link from RF signal input to audio signal output, possessing advantages such as high integration, low power consumption, and stable performance. Although the module technology is mature, existing technologies have not fully utilized its hardware characteristics to design a lightweight, intelligent, and low-cost dedicated monitoring system that perfectly matches the professional application scenarios of transmitter stations and effectively solves the three major pain points mentioned above.

[0007] Therefore, there is an urgent need in this field for a dedicated monitoring device based on the DRM1000 module to achieve low-cost, high-reliability, and uninterrupted monitoring of medium-wave DRM broadcast signals, thereby effectively improving the ability to ensure the safe broadcasting of television programs. Utility Model Content

[0008] In view of the above situation, it is necessary to provide a medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device that solves at least one of the above problems, comprising: The DRM1000 system module is used to receive and demodulate digital amplitude modulation broadcast signals. The radio frequency front-end module is electrically connected to the radio frequency signal input terminal of the DRM1000 system module. The voltage regulator circuit module is used to provide a stable DC operating voltage for the DRM1000 system module and other circuit modules. An audio processing module is electrically connected to the differential audio signal output terminal of the DRM1000 system module. The audio processing module includes a balanced audio output interface for connecting to monitoring equipment of broadcast television transmission stations. The system also includes a display circuit, which is electrically connected to the I2C interface of the DRM1000 system module via an I2C bus to display signal quality parameters.

[0009] Furthermore, the radio frequency front-end module includes: Loop antenna interface; The primary coil of the radio frequency transformer is electrically connected to the loop antenna interface, and the differential output terminal of the secondary coil serves as the signal output terminal of the radio frequency front-end module. A bidirectional transient voltage suppression diode is connected in parallel across the primary coil of the radio frequency transformer.

[0010] Furthermore, the voltage regulator circuit module includes: Power input interface; A linear regulator whose output provides the DC operating voltage; A bidirectional Zener diode, a first filter capacitor bank, and a second filter capacitor bank are connected sequentially between the power input interface and the input terminal of the linear regulator.

[0011] Furthermore, in the audio processing module, an LC filter circuit is provided on the circuit connected to the balanced audio output interface; the LC filter circuit includes: A first inductor and a second inductor are connected in series in the two signal paths from the differential audio signal output terminal, respectively. And a first filter capacitor and a second filter capacitor respectively connected between the two signal paths and ground.

[0012] Furthermore, the audio processing module also includes a speaker amplifier circuit, the signal input terminal of which is taken from one of the signals of the differential audio signal output terminal, and its output terminal is connected to a local speaker; the speaker amplifier circuit includes a two-stage amplifier circuit composed of a first transistor and a second transistor.

[0013] Furthermore, in the speaker amplifier circuit, the first transistor is an NPN transistor, whose base receives audio signals through a coupling capacitor; the second transistor is a PNP transistor, whose base is electrically connected to the collector of the first transistor, and whose emitter is connected to the local speaker through an output capacitor.

[0014] Furthermore, the display circuit includes a display module, and the I2C_SCL pin and I2C_SDA pin of the DRM1000 system module are connected to the serial clock input terminal and serial data input terminal of the display module through pull-up resistors, respectively.

[0015] Furthermore, it also includes a keyboard circuit, which is a matrix keyboard. The row scan lines of the matrix keyboard are connected to the first general-purpose input / output pin group of the DRM1000 system module, and the column detection lines of the matrix keyboard are connected to the second general-purpose input / output pin group of the DRM1000 system module.

[0016] Furthermore, each row scan line is connected in series with a current-limiting resistor and an RC filter circuit for eliminating jitter.

[0017] Furthermore, the RF power amplifier power pin of the DRM1000 system module is connected to a π-type filter circuit consisting of an inductor and a first capacitor and a second capacitor that are grounded to the input and output terminals of the inductor, respectively. Beneficial effects

[0018] Compared with the prior art, this utility model has the following significant innovative advantages and beneficial effects: High hardware integration, significantly reduced cost and complexity: This solution is based on the DRM1000 module, which natively supports multiple standards such as DRM30 / DRM+ and integrates a complete receiver demodulation link. By designing a simplified and efficient peripheral circuit, the complex discrete demodulation circuits of traditional solutions are eliminated, greatly reducing hardware complexity and production costs, while also reducing the number of components, thereby lowering the potential failure rate.

[0019] Achieving 24 / 7 real-time uninterrupted monitoring: This device features a specially designed onboard voltage regulator circuit, allowing it to be directly powered by an external adapter, completely eliminating the battery life limitations of portable devices. Combined with the DRM1000 module's low standby power consumption of less than 1W, this device can be deployed unattended at transmitting stations for extended periods, achieving millisecond-level response to broadcast signals and continuous monitoring around the clock.

[0020] High interface compatibility and seamless integration into existing station systems: This solution innovatively features dual audio outputs. One output is a balanced audio output with professional LC filtering, whose interface can directly connect to the XLR input of audio distributors, silent alarms, and other equipment in the transmitter station's monitoring cabinet, resolving the industry pain point of interface incompatibility. The other output drives a local speaker, facilitating real-time monitoring by on-site personnel.

[0021] High monitoring efficiency and reliable, durable equipment: Through its built-in DSP core, the DRM1000 can acquire and display key signal quality indicators such as MER, BER, and SNR in real time, providing accurate data for signal quality assessment. Its modular design and streamlined circuit structure enhance stability and extend lifespan, providing solid technical support for ensuring safe broadcasting. Attached Figure Description

[0022] Figure 1 This is a block diagram of the overall structure of the audio monitoring device provided in this embodiment of the utility model.

[0023] Figure 2 This is a schematic diagram of the DRM1000 system module and reset circuit in an embodiment of this utility model.

[0024] Figure 3 This is a circuit diagram of the radio frequency front-end module in an embodiment of this utility model.

[0025] Figure 4 This is a circuit diagram of the voltage regulator circuit module in an embodiment of this utility model.

[0026] Figure 5 This is a circuit diagram of the balanced audio output section of the audio processing module in this embodiment of the present invention.

[0027] Figure 6 This is a circuit diagram of the speaker amplifier circuit of the audio processing module in this embodiment of the present invention.

[0028] Figure 7 This is a circuit diagram of the keyboard circuit in an embodiment of this utility model.

[0029] Figure 8This is a circuit diagram of the display circuit in an embodiment of this utility model. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this utility model clearer, the medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining this utility model and are not intended to limit this utility model.

[0031] In the description of this utility model, unless otherwise stated, "a plurality of" means two or more; the terms "center," "longitudinal," "lateral," "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 communication between two components. Those skilled in the art will be able to understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0033] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0034] Please see Figure 1 The present invention provides a medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device, the overall structure of which mainly includes: a radio frequency front-end module 100, a DRM1000 system module 200, a voltage regulator circuit module 300, an audio processing module 400, a keyboard circuit 500, and a display circuit 600.

[0035] During operation, the DRM RF signal from the loop antenna ANT is first received, impedance matched, and preliminarily filtered by the RF front-end module 100. The processed differential RF signal is then sent to the DRM1000 system module 200. As the core of the device, the DRM1000 system module 200 performs a series of processes on the input RF signal, including amplification, downconversion, demodulation, channel decoding, and audio decoding, ultimately outputting a digital audio stream and a series of key parameters characterizing signal quality.

[0036] The audio processing module 400 receives the differential audio signal from the DRM1000 system module 200 and splits it into two paths: one path is processed by an LC filter network to form a balanced audio signal, which is output through a balanced audio output interface (such as an XLR connector) for connection to the station's professional monitoring system; the other path is amplified by a two-stage transistor amplifier circuit to drive a local speaker for on-site personnel to listen to.

[0037] The display circuit 600 acquires data from the DRM1000 system module 200 via the I2C bus and displays information such as frequency, mode, signal strength, SNR, MER, and BER on the OLED screen in real time. Users can interact with the DRM1000 system module 200 via the keyboard circuit 500 to perform operations such as frequency adjustment, volume control, mode switching, and station access. The entire device is provided with a stable and clean 3.3V DC power supply by the voltage regulator circuit module 300, which efficiently converts externally supplied 5V DC power, ensuring the device's ability to operate uninterrupted 24 / 7.

[0038] Detailed descriptions of each module 1. DRM1000 System Module 200 (see...) Figure 2 ) This module is the core of the entire device, and its core component is the DRM1000 chip U2. The U2 is a highly integrated DRM / AM / FM receiver chip that integrates a low-noise amplifier (LNA), mixer, ADC, digital signal processor (DSP), and microcontroller interface.

[0039] Power Supply and Filtering: Chip U2 requires multiple power supplies. VDD_3V1 provides the main power supply for both the digital and analog sections, at 3.3V. VDD_PA supplies power to the internal RF power amplifier module. To ensure RF performance, the power supply to the VDD_PA pin (pin 41) passes through a π-type filter circuit consisting of inductor L1 (220nH), capacitor C11 (100nF), and capacitor C12 (47uF). This circuit effectively filters out high-frequency noise from the power supply, providing an extremely clean power supply for the internal LNA, which is crucial for ensuring receiver sensitivity. Simultaneously, the main power supply VCC also passes through a filter network consisting of C8, C10, C9, and R2 before entering the VDD_3V1 pin (pin 7), further enhancing power supply stability.

[0040] RF signal input: The differential signal processed by the RF front-end module is input to the chip internally through LF_IN_P (pin 21) and LF_IN_N (pin 23). This design is mainly for medium wave / short wave, therefore the LF (low frequency) input port is used. The VHF_IN and HF_IN ports can be used for other frequency bands.

[0041] Audio signal output: The U2 integrates a Class D audio amplifier, outputting differential PWM (Pulse Width Modulation) audio signals through SPEAKER_P (pin 4) and SPEAKER_N (pin 3). This differential output method has a high common-mode noise rejection ratio and strong anti-interference capability.

[0042] Reset Circuit: To ensure that U2 reliably resets to its initial state upon each power-on, a reset circuit consisting of resistor R3 (100KΩ), capacitor C13 (470nF), and resistor R11 (10R) was designed. Upon power-on, VCC charges C13 through R3, keeping the RESETN pin (pin 5) low. When the charging voltage of C13 reaches the threshold, the RESETN pin goes high, the chip is de-reset, and it begins normal operation. This power-on reset process ensures stable system startup.

[0043] Communication and Control Interfaces: U2 interacts with peripheral circuits through multiple interfaces. I2C_CLK (pin 35) and I2C_SDA (pin 34) form an I2C bus for communication with the display circuit 600. UART_RX (pin 33) and UART_TX (pin 32) form a UART serial port, which can be used for communication with an external host MCU or for firmware upgrades. Multiple GPIO pins (GPIO0-GPIO7) are used to connect to the keyboard circuit 500, enabling human-machine interaction.

[0044] 2. RF front-end module 100 (see...) Figure 3 ) The function of this module is to efficiently and with low noise couple the weak DRM signal received by the antenna to the DRM1000 chip.

[0045] Antenna Interface and Transformer: The signal is input via a loop ant interface. The RF transformer T1 is the core of this module. Its primary coil (pins 4, 6) connects to the antenna interface to achieve impedance matching with the antenna. More importantly, it converts the single-ended unbalanced signal from the antenna input into a differential balanced signal output by the secondary coil (pins 1, 3) through electromagnetic induction. This differential signal has strong common-mode interference immunity, effectively suppressing noise picked up from the antenna and transmission path, providing a cleaner signal for subsequent processing.

[0046] Electrostatic Discharge Protection: Diodes D7 and D8 are transient voltage suppressor diodes, connected in parallel across the primary winding of transformer T1 and grounded. When a high-voltage transient pulse occurs at the antenna end due to lightning strike induction or electrostatic discharge, D7 and D8 will quickly conduct, discharging the surge current to ground, thereby protecting the downstream DRM1000 chip from damage.

[0047] Coupling capacitors: Capacitors C22 and C23 (both 1uF) are DC blocking coupling capacitors. They couple the AC RF signal output from the transformer secondary to the input of the DRM1000, while isolating the DC potential between the front and rear stages, ensuring the stability of the operating point of each circuit.

[0048] 3. Voltage regulator circuit module 300 (see...) Figure 4 ) This module is key to the device's ability to operate stably 24 / 7.

[0049] Input and Protection: Power is input through interface H1, typically a 5V DC power adapter. Following this is a transient voltage suppressor D2, used to absorb surge voltages at the input.

[0050] Multi-stage filtering: Before entering the regulator, the input power supply undergoes two stages of LC or RC filtering. The first stage, consisting of C7 and C4 (both 100uF), filters out low-frequency ripple on the power lines. The second stage, consisting of C5 and C6 (both 100nF), filters out high-frequency noise. This multi-stage filtering design ensures that the voltage fed into the linear regulator is relatively smooth and clean.

[0051] Linear regulation: The core component is the low-dropout linear regulator U1. It can accurately stabilize the filtered input voltage at an output of 3.3V. The advantage of using an LDO (low-dropout) regulator is its high efficiency and extremely low noise, making it ideal for powering RF and analog circuits.

[0052] Output filtering and indication: The output terminal of U1 is connected to a capacitor network consisting of C1 (10uF), C2 (100nF), and C3 (1nF), which are used to stabilize the output voltage, filter out high-frequency noise, and improve transient response, respectively. An LED D30 and a current-limiting resistor R30 form a power indicator light to visually show whether the device is powered on normally.

[0053] 4. Audio processing module 400 (see...) Figure 5 and Figure 6 ) It contains two parallel audio processing paths.

[0054] Path 1: Balanced audio output ( Figure 5 This path is designed specifically for connecting professional broadcast equipment. The SPEAKER_P and SPEAKER_N differential PWM signals from U2 first pass through a second-order LC low-pass filter network. This network consists of inductors L2 and L3 (both 33uH) connected in series in the signal path and capacitors C19 and C21 (both 100nF) connected in parallel to ground. The function of this LC network is to restore the audio components carried in the PWM square wave signal, while filtering out the high-frequency components of the PWM carrier itself and other high-frequency noise generated by the Class D amplifier, outputting a smooth analog audio signal. Capacitor C20 (470nF) further enhances the filtering effect. The filtered, clean differential audio signal is sent to interface J7. This J7 interface can be designed as a three-pin XLR connector, with pin 2 connected to the inverting signal (from the SPEAKER_P path), pin 3 connected to the inverting signal (from the SPEAKER_N path), and pin 1 grounded. The balanced output signal can be directly input to professional equipment such as mixing consoles and audio distributors, achieving perfect interface compatibility and high-quality signal transmission. D10 and D11 are TVS diodes used to protect the output ports.

[0055] Path 2: Speaker Amplification Circuit Figure 6This path is used to drive the local monitoring speaker. It takes the audio signal from one of the differential signals (e.g., IN in the diagram, which can be taken from the filtered signal of SPEAKER_P or SPEAKER_N). The circuit consists of two directly coupled transistor amplifier stages. The first stage is a common-emitter voltage amplifier stage composed of NPN transistor Q1 (2N3904) and its peripheral components (R41, R42, C51). The input signal is sent to the base of Q1 through coupling capacitor C51, and the amplified signal is output from the collector of Q1. The second stage is a common-collector current amplifier stage (emitter follower) composed of PNP transistor Q2 and its emitter resistor R43. The base of Q2 is directly connected to the collector of Q1, achieving direct coupling between stages, simplifying the circuit and widening the bandwidth. Q2 is responsible for providing sufficient current to drive speaker spk1. The amplified audio signal is sent to the speaker through output coupling capacitor C52 to produce sound. This dual-channel audio design caters to both professional applications and local monitoring needs, and is a major highlight of this solution.

[0056] 5. Keyboard circuit 500 (see...) Figure 7 ) This module provides the physical interface for human-computer interaction.

[0057] Matrix Structure: The circuit adopts a 3x4 matrix keyboard structure, using only 7 GPIO ports (3 outputs + 4 inputs) to scan 12 keys. Row scan lines are connected to GPIO0, GPIO1, and GPIO2 configured for output mode. Column detection lines are connected to GPIO3, GPIO4, GPIO5, and GPIO6 configured for internal pull-up input mode.

[0058] Scanning principle: The software sequentially sets GPIO0, GPIO1, and GPIO2 to low level while simultaneously detecting the status of GPIO3-GPIO6. For example, if GPIO0 is low and GPIO3 is also detected to be low, it means that button SW3 in the first row and first column has been pressed.

[0059] Hardware Debouncing: Key presses generate mechanical bounce during the pressing and releasing motions, leading to signal instability. To address this issue, an RC filter circuit is designed for each row of the scan line. Taking the first row as an example, R4 (220Ω) is a current-limiting resistor, and C16 (68pF) and R5 (10KΩ) form a low-pass filter. This filter can filter out high-frequency glitches caused by key bounce, making the level signal detected by the MCU more stable and reliable, greatly simplifying the complexity of software debouncing.

[0060] 6. Display circuit 600 (see...) Figure 8 ) This module is used to visually present the working status of the device.

[0061] I2C Communication: This embodiment uses an OLED display driven by an SD1306 chip. This display is connected to the DRM1000 module U2 via an I2C bus. The I2C_SCL (clock) and I2C_SDA (data) pins of U2 are connected to the SCK and SDA pins of the display module, respectively. Figure 2 As shown, pull-up resistors R36 and R37 are connected to these two buses respectively, which is required by the I2C bus specification.

[0062] Display Content: Through I2C communication, the microcontroller inside the U2 can send various demodulated information to the display screen. This information is crucial for the staff at the transmitting station, including: current receiving frequency, broadcast mode (DRM30 / DRM+), signal strength indicator (RSSI), signal-to-noise ratio (SNR), modulation error rate (MER), bit error rate (BER), and audio decoding status. The real-time display of these parameters transforms the monitoring of broadcast signal quality from a subjective "listening" to an objective "seeing," achieving quantitative management.

[0063] In summary, this invention combines a highly integrated DRM1000 chip with meticulously designed peripheral circuits (especially those for power supply stability and audio interface compatibility) to create an audio monitoring device that meets the professional monitoring needs of broadcast television transmission stations. It not only solves many pain points of existing technologies but also achieves significant progress in cost, reliability, and ease of use, possessing high promotional value and broad application prospects.

[0064] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device, characterized in that, include: The DRM1000 system module is used to receive and demodulate digital amplitude modulation broadcast signals. The radio frequency front-end module is electrically connected to the radio frequency signal input terminal of the DRM1000 system module. The voltage regulator module is used to provide a stable DC operating voltage for the DRM1000 system module and other circuit modules. An audio processing module is electrically connected to the differential audio signal output terminal of the DRM1000 system module. The audio processing module includes a balanced audio output interface for connecting to monitoring equipment of broadcast television transmission stations. The system also includes a display circuit, which is electrically connected to the I2C interface of the DRM1000 system module via an I2C bus to display signal quality parameters.

2. The medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device according to claim 1, characterized in that, The radio frequency front-end module includes: Loop antenna interface; The primary coil of the radio frequency transformer is electrically connected to the loop antenna interface, and the differential output terminal of the secondary coil serves as the signal output terminal of the radio frequency front-end module. A bidirectional transient voltage suppression diode is connected in parallel across the primary coil of the radio frequency transformer.

3. The medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device according to claim 1, characterized in that, The voltage regulator circuit module includes: Power input interface; A linear regulator whose output provides the DC operating voltage; A bidirectional Zener diode, a first filter capacitor bank, and a second filter capacitor bank are connected sequentially between the power input interface and the input terminal of the linear regulator.

4. The medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device according to claim 1, characterized in that, In the audio processing module, an LC filter circuit is provided on the circuit connected to the balanced audio output interface; The LC filter circuit includes: A first inductor and a second inductor are connected in series in the two signal paths from the differential audio signal output terminal, respectively. And a first filter capacitor and a second filter capacitor respectively connected between the two signal paths and ground.

5. A medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device according to claim 1 or 4, characterized in that, The audio processing module further includes a speaker amplifier circuit. The signal input terminal of the speaker amplifier circuit is taken from one of the signals from the differential audio signal output terminal, and its output terminal is connected to a local speaker. The speaker amplifier circuit includes a two-stage amplifier circuit composed of a first transistor and a second transistor.

6. A medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device according to claim 5, characterized in that, In the loudspeaker amplifier circuit, the first transistor is an NPN transistor, whose base receives audio signals through a coupling capacitor; the second transistor is a PNP transistor, whose base is electrically connected to the collector of the first transistor, and whose emitter is connected to the local loudspeaker through an output capacitor.

7. A medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device according to claim 1, characterized in that, The display circuit includes a display module. The I2C_SCL pin and I2C_SDA pin of the DRM1000 system module are connected to the serial clock input terminal and serial data input terminal of the display module through pull-up resistors, respectively.

8. A medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device according to claim 1, characterized in that, It also includes a keyboard circuit, which is a matrix keyboard. The row scan lines of the matrix keyboard are connected to the first general-purpose input / output pin group of the DRM1000 system module, and the column detection lines of the matrix keyboard are connected to the second general-purpose input / output pin group of the DRM1000 system module.

9. A medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device according to claim 8, characterized in that, Each line of the scan line is connected in series with a current-limiting resistor and an RC filter circuit for eliminating jitter.

10. A medium-wave DRM digital amplitude modulation broadcast monitoring and receiving device according to claim 1, characterized in that, The DRM1000 system module has a π-type filter circuit connected to the RF power amplifier power pin, consisting of an inductor and a first capacitor and a second capacitor grounded to the inductor's input and output terminals, respectively.

Images