Multifunctional high-quality digital-analog fusion radio player

Abstract

The utility model discloses a kind of multi-functional high sound quality digital analog fusion radio player, belong to audio electronic equipment technical field.It integrates FM radio, USB decoding, bluetooth dual-mode communication function, and three mode signal switching is realized by I2S switch dynamic strobe technology, complete digital-analog conversion by MCU control professional DAC chip, after the power amplifier circuit amplification of built-in low-frequency gain component, earphone single-end and loudspeaker balanced double output are realized by electronic switch.Key technologies include: support LDAC high-definition audio reception and SBC emission bluetooth module, high-strength radio frequency chip IC enhances signal stability, pull rod antenna design of impedance matching optimization.The equipment breaks through the bottleneck of traditional radio function single, sound quality rough, with functional diversification, sound quality high fidelity (signal-to-noise ratio is greater than or equal to 115dB), compact structure and cost advantage, applicable to vehicle, household, outdoor and other scenes, realize the depth of analog technology and digital audio fusion.

Description

Technical Field

[0001] This utility model relates to the field of audio electronic equipment technology, specifically to a radio player that integrates FM radio reception, USB digital decoding, and Bluetooth dual-mode communication functions, achieving high-fidelity sound output through a combination of professional audio chips and a digital-analog fusion architecture. Its innovation lies in solving the problems of traditional radios, such as limited functionality, poor sound quality, and unstable signal, through I2S switch dynamic gating technology, low-noise DAC digital-to-analog conversion, RF enhancement design, and low-frequency gain optimization circuitry. Background Technology

[0002] (a) Deficiencies in existing technology Traditional radios typically only have a single FM reception function, and their audio processing relies on simple analog circuits, resulting in the following significant drawbacks: Limited functionality: It is incompatible with modern digital audio signal sources (such as USB storage devices and high-definition audio transmitted via Bluetooth), requires additional adapters to expand its functionality, is cumbersome to operate, and suffers significant loss of sound quality.

[0003] Sound quality limitations: The use of low-cost analog power amplifier chips and MCU built-in digital-to-analog converters results in high noise levels, insufficient low-frequency response, and an inability to reproduce high-resolution audio details.

[0004] Insufficient signal stability: Traditional telescopic antennas paired with ordinary tuning chips are easily interfered with in complex electromagnetic environments, resulting in low signal reception sensitivity and frequent audio quality interruptions.

[0005] (ii) Deficiencies of existing improvement plans Although some multi-functional radios integrate Bluetooth modules, they only support basic audio encoding formats and have low transmission rates, which cannot meet the requirements of high-definition audio. Furthermore, they do not perform independent isolation processing for different signal sources, resulting in channel crosstalk and blurry sound quality. Utility Model Content

[0006] The purpose of this invention is to provide a multi-functional, high-quality digital-analog fusion radio player that seamlessly switches between FM radio, USB decoding, and Bluetooth transceiver modes to meet the audio needs of various scenarios such as in-vehicle, home, and outdoor use. It enhances sound quality through a combination of professional audio chips, significantly reduces noise and distortion, and improves low-frequency dynamic performance. The optimized RF receiving module improves signal stability and anti-interference capabilities. A compact modular design reduces circuit size and lowers costs.

[0007] To achieve the above objectives, this utility model is implemented through the following technical solution: a multifunctional high-quality digital-analog fusion radio player, comprising: The signal input module includes an FM radio module, a USB bridging module, and a Bluetooth module; The signal processing module includes an I2S switch, a DAC module, and an MCU. The signal output module includes a power amplifier circuit, electronic switches, headphone output, and speaker interface; The FM radio module, USB bridging module, and Bluetooth module are connected to the I2S switch input terminal via the I2S protocol. The I2S switch output terminal is connected to the DAC module. The DAC module is connected to the MCU via the I2C protocol. The DAC module output terminal is sequentially connected to the power amplifier circuit, electronic switch, and output interface.

[0008] As a further improvement to the technical solution of this utility model, the Bluetooth module is a dual-mode wireless communication module that supports LDAC high-definition audio reception and SBC audio transmission, and has a built-in radio frequency antenna matching circuit.

[0009] As a further improvement to the technical solution of this utility model, the DAC module adopts a professional digital-to-analog converter chip with low noise and low distortion characteristics, with a signal-to-noise ratio ≥120dB and total harmonic distortion ≤0.0003%.

[0010] As a further improvement to the technical solution of this utility model, the FM radio module integrates a high-intensity radio frequency chip IC, wherein the receiving sensitivity of the radio frequency chip IC is ≤-105dBm and the image rejection ratio is ≥50dB.

[0011] As a further improvement to the technical solution of this utility model, the power amplifier circuit includes: The gain adjustment unit consists of gain resistors R1 and R2 connected in series, wherein the resistance ratio of R1 to R2 is 10:1 to 20:1. The low-frequency boosting unit consists of parallel R3 and C1, and series R4 and C2. The capacitance value of C1 is 10μF to 100μF, and the capacitance value of C2 is 100nF to 470nF.

[0012] As a further improvement to the technical solution of this utility model, the electronic switch is an N-channel MOS transistor array, whose gate is connected to the PWM control pin of the MCU, and whose drain is connected to the single-ended signal terminal of the 3.5mm headphone output port and the balanced signal terminal of the speaker interface, respectively.

[0013] As a further improvement to the technical solution of this utility model, the MCU writes sampling rate information to the DAC module through the I2C bus, supporting adaptive switching of multiple sampling rates of 44.1kHz, 48kHz, and 96kHz.

[0014] As a further improvement to the technical solution of this utility model, the USB bridge module integrates a high-speed USB digital audio controller, supports the USB 2.0 high-speed protocol, and is compatible with the UAC 2.0 audio streaming standard.

[0015] As a further improvement to the technical solution of this utility model, the I2S switch is a dual-channel analog switching chip, and its selection signal is controlled by the level signal output by the GPIO pin of the MCU to realize the time-division transmission of FM / USB / Bluetooth three-mode signals.

[0016] As a further improvement to the technical solution of this utility model, the speaker interface is a balanced output interface, adopts a differential signal transmission mode, has a common-mode rejection ratio ≥60dB, and an output power ≥5W@8Ω.

[0017] It should be noted that the hardware architecture and key modules of this utility model are described as follows: 1. Hardware architecture and connectivity This utility model includes a signal input module, a signal processing module, and a signal output module, and the modules are connected in the following way: Signal input module: FM radio module: Receives radio frequency signals via a telescopic antenna, which are then processed by a high-intensity radio frequency chip IC and converted into I2S format digital signals; USB bridging module: Receives external digital signals via the Type-C interface, parses them, outputs I2S signals, and transmits sampling rate information to the MCU; Bluetooth module: Supports LDAC high-definition audio reception and SBC signal transmission. After successful pairing, it outputs I2S format digital signals.

[0018] Signal processing module: I2S switch: Controlled by MCU, selectively transmits FM, USB, and Bluetooth signals to the DAC module; DAC module: Employs a professional digital-to-analog converter chip with low noise and high signal-to-noise ratio, which receives the sampling rate parameters configured by the MCU via the I2C protocol and converts the digital signal into an analog signal; MCU: As the control core, it implements functions such as mode switching logic, sampling rate adaptation, and mute control.

[0019] Signal output module: The power amplifier circuit includes gain resistors and low-frequency boosting components. The resistance ratio of the gain resistors determines the amplification factor, and the low-frequency boosting components enhance the bass effect through a combination of capacitors and resistors. Electronic switch: Integrated mute function, can control the single-ended output of analog signals to headphones or the balanced output to speakers, reducing switching interference.

[0020] 2. Detailed Design of Key Modules FM radio module: It adopts a high-performance RF chip IC, which significantly improves the receiving sensitivity and enhances the image rejection capability. Combined with a telescopic antenna and impedance matching circuit, it effectively improves the signal stability in complex environments.

[0021] USB Bridge Module: Integrates a high-speed USB digital audio controller, supports the USB 2.0 high-speed protocol and UAC2.0 audio stream standard, and can quickly parse external digital signals and transmit them to the processing module.

[0022] Bluetooth module: It uses a dual-mode Bluetooth chip that supports LDAC / SBC and has a built-in ceramic antenna matching circuit to achieve high-definition audio wireless transmission. It also supports transmitting radio signals to other devices via Bluetooth.

[0023] DAC module: It adopts a professional digital-to-analog converter chip, which has low noise and low distortion characteristics. Its signal-to-noise ratio and total harmonic distortion are significantly better than traditional solutions, ensuring high-fidelity sound reproduction.

[0024] Amplifier circuit: It adopts a low-noise audio power amplifier, and achieves gain adjustment and low-frequency enhancement through a combination of precision resistors and capacitors, making the bass performance fuller and the sound quality more layered.

[0025] Electronic switch: It adopts a MOS transistor array design, with the gate controlled by MCU, which can quickly realize the mute function and support both single-ended headphone and balanced speaker output modes to meet the needs of different scenarios.

[0026] (III) Work Process FM radio mode: The radio frequency signal received by the antenna is processed into an I2S digital signal by the radio module. After being selected by the I2S switch, it is transmitted to the DAC module, converted into an analog signal, and then amplified by the power amplifier before being output to headphones or speakers.

[0027] USB decoding mode: After the USB device is inserted, the bridging module parses the audio stream and extracts the sampling rate information. The MCU configures the DAC parameters according to this information, and the digital signal is transmitted to the DAC for processing and output after passing through the I2S switch.

[0028] Bluetooth mode: After successful Bluetooth pairing, the received LDAC signal is converted into I2S format, and then output after being selected by a switch and processed by a DAC; in transmit mode, the audio signal is converted into a digital stream by a DAC and then transmitted via Bluetooth.

[0029] This utility model has the following beneficial effects: Multifunctional: It integrates three mainstream audio modes, supports Bluetooth transmission and reception and USB decoding, and can adapt to a variety of audio sources without additional devices, improving ease of use.

[0030] Significantly improved sound quality: Through a professional DAC chip and optimized power amplifier circuitry, noise and distortion are significantly reduced, low-frequency response is enhanced, and sound clarity and dynamic range are superior to traditional radios.

[0031] Enhanced signal stability: The matching design of the RF chip and antenna improves signal reception sensitivity and anti-interference ability, enabling stable sound reception even in complex environments.

[0032] Compact and efficient structure: Modular design reduces circuit size and costs while ensuring reliability, making it suitable for space-constrained scenarios such as portable devices and automotive applications. Attached Figure Description

[0033] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 is an overall circuit architecture diagram of a multifunctional high-quality digital-analog fusion radio player according to an embodiment of the present invention; Explanation: The FM radio module, USB bridge module, and Bluetooth module shown in the diagram are connected to the I2S switch via the I2S protocol. After passing through the DAC module and power amplifier circuit, the output is sent to the headphones or speakers. The MCU controls the DAC and switch module via the I2C bus.

[0034] Figure 2 is a schematic diagram of the power amplifier and output circuit of an embodiment of the utility model; Component Description: The illustrated power amplifier circuit includes gain resistors and low-frequency boost components. Electronic switches connect the headphone and speaker interfaces, and the signal output path is controlled by the MCU. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0036] It should be noted that all directional indicators (such as up, down, left, right, front, back, upper end, lower end, top, bottom, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0037] In this utility model, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0038] Furthermore, in this utility model, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination should be considered non-existent and not within the scope of protection claimed by this utility model.

[0039] The present invention will be further described in detail below with reference to the accompanying drawings.

[0040] Refer to Figure 1 and Figure 2 A multi-functional, high-quality digital-analog fusion radio player: 1. Modular layout design The FM radio module (such as the RDA5807M RF chip) is located next to the telescopic antenna interface. A π-type LC matching circuit (L=10μH, C=22pF) is set at the front end of the chip to match the antenna impedance (75Ω) to the chip input impedance (50Ω), thereby reducing high-frequency signal reflection loss and improving receiving sensitivity.

[0041] USB bridging modules (such as the SA9123 high-speed controller) should be placed close to the Type-C interface, with a 100μF filter capacitor soldered near the power input (VBUS1) to suppress the interference of USB power ripple on digital signals and ensure the stability of audio stream transmission.

[0042] Bluetooth modules (such as the CSR8675 dual-mode chip) have their built-in 2.4GHz ceramic antennas facing the non-metallic area of ​​the casing, maintaining a distance of ≥8mm from the metal components on the PCB board to avoid signal obstruction and improve wireless transmission efficiency.

[0043] DAC modules (such as the ES9038Q2M professional chip) are covered with independent metal shields to isolate electromagnetic interference. The I2S signal line width is designed to be more than 10mil, and 50Ω impedance control wiring is used to ensure the integrity of high-speed digital signals.

[0044] The power amplifier module (such as the TPA6120A2 low-noise audio chip) has a 300mm² aluminum heat sink soldered to the bottom of the chip, and is connected to the casing through thermal grease to keep the junction temperature below 65℃ and avoid sound quality distortion caused by high temperature.

[0045] 2. Key Circuit Parameters In the I2S signal link, the clock signal (BCLK) frequency is dynamically generated according to the sampling rate (e.g., a sampling rate of 44.1kHz corresponds to a clock of 22.5792MHz), and the data signal (DATA) adopts a left-aligned format; the FM / USB / Bluetooth I2S signal lines follow the principle of "equal length and equal spacing" in the wiring, with a line spacing of ≥2mm to reduce crosstalk.

[0046] The power amplifier gain network uses a standard configuration: gain resistors R1=10kΩ and R2=1kΩ, achieving a 10x voltage gain (20dB). Users can switch to R1=20kΩ via jumper caps to obtain a 20x gain. In the low-frequency boost component, C1=47μF and R3=10kΩ are combined to boost the gain by 3dB at 30Hz, while C2=220nF and R4=22kΩ set the 50Hz cutoff frequency to optimize bass performance.

[0047] Electronic switches (such as AO3400 MOS transistor arrays) have a gate drive voltage of 0V (cutoff, mute) or 3.3V (conduction, normal output); a 100Ω resistor (R5) is connected in series in the headphone output path to adapt to 16-32Ω headphone loads and avoid sound quality degradation caused by impedance mismatch.

[0048] (II) System Initialization and Mode Switching Process 1. Power-on initialization After power-on, the MCU (such as STM32F103C8T6) performs the following operations: First, it configures the I2C bus rate to 400kHz and writes default parameters (sampling rate 44.1kHz, quantization precision 16bit) to the DAC module through this bus; then, it outputs a GPIO level signal to control the I2S switch to select the FM channel and puts the electronic switch into mute mode; finally, it starts the automatic station search algorithm of the FM radio module, scans the 87-108MHz frequency band, and stores the list of valid radio station frequencies.

[0049] 2. Mode switching control When a USB device is plugged in, the VBUS1 voltage rises to 5V, triggering an MCU interrupt. The MCU reads the sampling rate information transmitted by the USB bridge module via the I2C bus; then it controls the I2S switch to switch to the USB channel, and at the same time sends a new sampling rate configuration command to the DAC module. After completing the parameter update, it delays for 100ms to turn off the mute function of the electronic switch, achieving a smooth switching.

[0050] When switching Bluetooth modes, the user presses and holds the function key to put the Bluetooth module into broadcast mode (LED flashes quickly). After successful pairing with an external device (LED flashes slowly), the MCU reads the encoding format (LDAC or SBC) transmitted by the Bluetooth chip and automatically adjusts the input format of the DAC module to adapt to different encodings, ensuring that the audio signal is correctly decoded.

[0051] (III) Typical Application Scenarios and Examples 1. In-vehicle audio system integration In a vehicle setting, this device is fixed to the center console via a magnetic base and powered by a 5V / 2A USB power supply via a Type-C interface. When using Bluetooth transmission mode, the device transmits the FM radio signal to the vehicle's Bluetooth speaker via SBC encoding, replacing the traditional FM transmitter adapter and avoiding the use of the cigarette lighter socket. A 4-pin balanced output terminal connects to the differential input of the vehicle's amplifier, effectively reducing the interference of vehicle power supply noise on sound quality by utilizing a common-mode rejection ratio (CMRR) of ≥60dB.

[0052] 2. Application of outdoor emergency equipment Designed for outdoor use, the device features a built-in 2000mAh lithium battery, supporting 5V / 1A fast charging, while the PCB area is compressed to 60×40mm² to improve portability. In weak signal environments, the MCU controls the RF chip to enter narrowband reception mode (200kHz bandwidth) to improve the decoding stability of FM signals; non-working modules (such as the USB bridge module) cut off power through an independent electronic switch, keeping standby power consumption ≤0.1mW and extending battery life.

[0053] The working principle of this utility model: Overall working logic architecture This invention uses an MCU (Microcontroller Unit) as the core control hub to coordinate the collaborative work of the signal input module (FM / USB / Bluetooth), the signal processing module (I2S switch / DAC), and the signal output module (power amplifier / electronic switch) to realize a complete audio link of "digital signal gating → digital-to-analog conversion → analog amplification → mute control → multi-terminal output".

[0054] II. Detailed Explanation of the Working Principle of Different Modes 1. FM radio mode Signal input stage: The telescopic antenna receives 87-108MHz radio frequency signals, which are demodulated into I2S format digital audio signals by a high-intensity radio frequency chip IC (such as RDA5807M). This chip optimizes signal stability through built-in automatic gain control (AGC) circuit, with a receiving sensitivity ≤-105dBm and an image rejection ratio ≥50dB.

[0055] Signal processing stage: An I2S switch (such as CD74HC4052) selects the FM signal channel under the control of the MCU, transmitting digital audio to the DAC module (such as ES9038Q2M). The MCU writes the default sampling rate information (such as 44.1kHz) to the DAC via the I2C bus. The DAC then initiates digital-to-analog conversion, converting the digital signal into an analog audio signal. During this process, it utilizes its low noise (signal-to-noise ratio ≥120dB) and low distortion (total harmonic distortion ≤0.0003%) characteristics to optimize the sound quality.

[0056] Signal output stage: The analog signal enters the power amplifier circuit, where the gain resistors R1 and R2 (resistance ratio 10:1 to 20:1) determine the amplification factor. The larger the R1 / R2 ratio, the higher the gain. The low-frequency boosting components (R3, R4, R5, C1, C2) provide gain compensation for the 20-200Hz frequency band. The C1 capacitor value (10μF~100μF) adjusts the gain amplitude, and the C2 capacitor value (100nF~470nF) adjusts the gain frequency point to enhance bass fullness. When the signal passes through an electronic switch (such as an AO3400 MOS transistor), the MCU can trigger the MUTE mute function by controlling the gate level to avoid switching interference. Finally, the single-ended signal is output to the headphones, and the balanced signal is output to the speaker.

[0057] 2. USB Decoding Mode Signal input stage: External USB devices (such as USB flash drives and PCs) are connected via USB bridging modules (such as the SA9123 high-speed controller). The module parses the digital audio stream, extracts the sampling rate information (such as 44.1kHz, 48kHz, and 96kHz), and transmits it to the MCU via the I2C bus.

[0058] Signal processing stage: The MCU reconfigures the DAC module parameters based on the sampling rate information to ensure that the digital-to-analog conversion matches the input signal specifications; The USB bridging module converts digital signals into I2S format, which are then transmitted to the DAC after the USB channel is selected by the I2S switch.

[0059] Signal output stage: The subsequent process is the same as in FM mode, achieving high-fidelity audio output through power amplifier circuit gain adjustment, low-frequency boost, and electronic switch mute control.

[0060] 3. Bluetooth mode Signal input stage (receiver mode): After a Bluetooth module (such as CSR8675) is paired with a mobile phone, tablet or other device, it receives LDAC high-definition audio signals (transmission rate 990kbps) or SBC basic signals (328kbps) and converts them into I2S format digital streams.

[0061] Signal processing and output stage: The I2S switch selects the Bluetooth channel. The digital signal is output after being converted from digital to analog by a DAC, amplified by a power amplifier, and controlled by an electronic switch. The process is the same as the previous two modes. In transmit mode, the FM radio signal or USB decoded signal is converted into a digital stream by the DAC, encoded into SBC format by the Bluetooth module, and transmitted in reverse to the Bluetooth headset / speaker to realize the "wireless radio signal relay" function.

[0062] III. Key Collaboration Mechanisms Mode switching logic: The MCU outputs a level signal through the GPIO pin to control the A / B selection terminal of the I2S switch, realizing the switching between FM / USB / Bluetooth modes with a switching delay of ≤10ms; During switching, the MCU first triggers the electronic switch mute function (cuts off the output), completes the channel switching and reconfigures the DAC parameters, and then cancels the mute to avoid popping noise interference.

[0063] Sound quality optimization technology: Digital signal isolation: I2S switches independently select signals for each mode, avoiding interference from the mixing of FM analog tuning signals and USB / Bluetooth digital signals, with channel crosstalk ≤-60dB; Analog circuit noise reduction: The DAC module uses an independent shield, and the power amplifier circuit integrates an LC filter network (L=10μH, C=100μF) at the power supply end to suppress power supply ripple from polluting the audio.

[0064] RF enhancement design: The FM radio module integrates a π-type LC matching network (L=10μH, C=22pF) between the telescopic antenna and the RF chip IC to match the antenna impedance (75Ω) and the chip input impedance (50Ω), reducing signal reflection loss and improving high-frequency reception efficiency.

[0065] IV. Core Technological Advantages Multi-mode compatibility: By unifying the digital signal format through the I2S protocol, it achieves seamless integration of analog (FM) and digital (USB / Bluetooth) signals, breaking through the functional boundaries of traditional radios; High-fidelity audio link: Professional DAC + power amplifier chip combination (such as ES9038Q2M+TPA6120A2) builds a full-chain optimization from digital decoding to analog amplification, improving the signal-to-noise ratio by more than 35% and extending the low-frequency response to 20Hz; Intelligent control: The MCU automatically identifies the signal source type and adapts the sampling rate, eliminating the need for manual settings by the user. Combined with the electronic switch mute function, the operation experience is smoother.

[0066] In summary, this utility model has the following beneficial effects: Multifunctional: It integrates three mainstream audio modes, supports Bluetooth transmission and reception and USB decoding, and can adapt to a variety of audio sources without additional devices, improving ease of use.

[0067] Significantly improved sound quality: Through a professional DAC chip and optimized power amplifier circuitry, noise and distortion are significantly reduced, low-frequency response is enhanced, and sound clarity and dynamic range are superior to traditional radios.

[0068] Enhanced signal stability: The matching design of the RF chip and antenna improves signal reception sensitivity and anti-interference ability, enabling stable sound reception even in complex environments.

[0069] Compact and efficient structure: Modular design reduces circuit size and costs while ensuring reliability, making it suitable for space-constrained scenarios such as portable devices and automotive applications.

[0070] The technical solutions provided by the embodiments of this utility model have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of this utility model. The description of the above embodiments is only for helping to understand the principles of the embodiments of this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of this utility model. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A multifunctional high-quality digital-analog fusion radio player, characterized in that, include: The signal input module includes an FM radio module, a USB bridging module, and a Bluetooth module; The signal processing module includes an I2S switch, a DAC module, and an MCU. The signal output module includes a power amplifier circuit, electronic switches, headphone output, and speaker interface; The FM radio module, USB bridging module, and Bluetooth module are connected to the I2S switch input terminal via the I2S protocol. The I2S switch output terminal is connected to the DAC module. The DAC module is connected to the MCU via the I2C protocol. The DAC module output terminal is sequentially connected to the power amplifier circuit, electronic switch, and output interface.

2. The multifunctional high-quality digital-analog fusion radio player according to claim 1, characterized in that, The Bluetooth module is a dual-mode wireless communication module that supports LDAC high-definition audio reception and SBC audio transmission, and it has a built-in radio frequency antenna matching circuit.

3. The multifunctional high-quality digital-analog fusion radio player according to claim 1, characterized in that: The DAC module uses a professional digital-to-analog converter chip with low noise and low distortion characteristics, with a signal-to-noise ratio ≥120dB and total harmonic distortion ≤0.0003%.

4. A multifunctional high-quality digital-analog fusion radio player according to claim 1, characterized in that: The FM radio module integrates a high-intensity radio frequency chip IC, which has a receiving sensitivity of ≤-105dBm and an image rejection ratio of ≥50dB.

5. A multifunctional high-quality digital-analog fusion radio player according to claim 1, characterized in that: The power amplifier circuit includes: The gain adjustment unit consists of gain resistors R1 and R2 connected in series, wherein the resistance ratio of R1 to R2 is 10:1 to 20:

1. The low-frequency boosting unit consists of parallel R3 and C1, and series R4 and C2. The capacitance value of C1 is 10μF to 100μF, and the capacitance value of C2 is 100nF to 470nF.

6. A multifunctional high-quality digital-analog fusion radio player according to claim 1, characterized in that: The electronic switch is an N-channel MOS transistor array, with its gate connected to the PWM control pin of the MCU and its drain connected to the single-ended signal terminal of the 3.5mm headphone output jack and the balanced signal terminal of the speaker interface, respectively.

7. A multifunctional high-quality digital-analog fusion radio player according to claim 1, characterized in that: The MCU writes sampling rate information to the DAC module via the I2C bus, supporting adaptive switching of multiple sampling rates of 44.1kHz, 48kHz, and 96kHz.

8. A multifunctional high-quality digital-analog fusion radio player according to claim 1, characterized in that: The USB bridging module integrates a high-speed USB digital audio controller, supports the USB 2.0 high-speed protocol, and is compatible with the UAC2.0 audio streaming standard.

9. A multifunctional high-quality digital-analog fusion radio player according to claim 1, characterized in that: The I2S switch is a dual-channel analog switching chip. Its selection signal is controlled by the level signal output from the GPIO pin of the MCU, realizing time-division transmission of FM / USB / Bluetooth signals.

10. A multifunctional high-quality digital-analog fusion radio player according to claim 1, characterized in that: The speaker interface is a balanced output interface, which adopts differential signal transmission mode, with a common-mode rejection ratio ≥60dB and an output power ≥5W@8Ω.

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