CN114422030A - Half-duplex audio transmission device based on LIFI technology and implementation method - Google Patents
Half-duplex audio transmission device based on LIFI technology and implementation method Download PDFInfo
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Abstract
The invention relates to a half-duplex audio transmission device and method based on LIFI technology, comprising a transmitting part circuit, a receiving part circuit, a power supply part circuit and a core control circuit; the power supply voltage reduction circuit provides power supply for the transmitting circuit and the receiving circuit; the core control circuit is used for presetting working parameters of the gain-adjustable operational amplification circuit I, the audio coding circuit I, the operational amplification circuit II and the audio coding circuit II; the transmitting part circuit is used for processing an analog audio signal which is not suitable for being directly transmitted in a channel into a digital modulation signal which is suitable for being transmitted in the channel, and loading the modulation signal to the transmitting circuit for transmitting; the receiving part circuit is used for receiving the modulation signal transmitted by the transmitting circuit, processing the modulation signal into an analog audio signal suitable for being directly accessed to the playing equipment, and finally outputting the analog audio signal to the outside through the audio output interface circuit. The invention has the characteristics of lower cost, lower complexity, higher reliability and better stability.
Description
Technical Field
The invention belongs to the technical field of optical communication, and particularly relates to a half-duplex audio transmission device based on an LIFI technology and an implementation method.
Background
The electromagnetic spectrum is a precious and limited resource for human beings, and according to incomplete statistics, in 1995-2011, countries such as the United states, the English, the Germany and the French develop third-generation and fourth-generation mobile communication networks, and the total value of the auctioned spectrum reaches up to 1300 billion dollars. With the rapid development of the electronic communication industry in the beginning of the 21 st century, the global electromagnetic spectrum resource is in the forefront.
According to the ITU (International telecommunication Union) planning, the electromagnetic spectrum range available for human is 10 KHz-400 GHz, but limited by the current information technology level, the spectrum resource actually available for human development and use only accounts for 68% of the total resource amount. The frequency band range which is suitable for communication is below 3GHz, the application of frequency spectrum resources in the range tends to be saturated, the development space is limited, more than seven military and civil communication equipment working frequency bands are concentrated in the range in China, the development of the frequency band communication technology above 3GHz is limited by the aspects of chip technology, channel characteristic research and the like which cannot be broken through in a short time, the development of the visible light communication technology is promoted, the urgency of electromagnetic spectrum tension can be greatly relieved, the popularization of the LED lighting equipment lays a foundation for the implementation of the visible light communication technology.
According to the fact that the market structure of the current global main lighting application is continuously changed, the permeability of the global LED general lighting equipment reaches 45% only in 2017, under the action that the permeability is continuously and rapidly increased, the composite speed of the LED general lighting market is increased by 22% in 2014-2019, the total sales of the global LED market in 2019 reaches up to 648 billion dollars, and the traditional lighting rapidly drops to 398 billion dollars. Currently, several countries around the world, such as china, the united states, canada, japan, korea, the european union, the united kingdom, and australia, have been introduced and implemented elimination plans for conventional incandescent lighting fixtures. The occupancy of the LED in China in the lighting market is gradually increased from 1% in 2011 to 78% in 2020.
The LED has the characteristics of low power consumption, high brightness, response time and good modulation performance, and the modulation frequency of the white light LED reaches 50MHz with the continuous development of semiconductor manufacturing processes. In addition, the modulation frequency of the LED device made of the new material gallium arsenide can reach 2GHz theoretically, and the LED device is very suitable for being used for loading digital signals.
Compared with the traditional electromagnetic communication technology, the LIFI technology using the LED as a key device has the following characteristics:
1. the cost is low: the traditional communication technology depends on electromagnetic signal transmitting equipment and an antenna feed system, frequency bands above a very high frequency generally depend on communication base station equipment, the total number of mobile communication base stations in China is 931 ten thousand only in 2020, the number of mobile communication base stations is expected to be increased continuously by 100 ten thousand every year, the initial installation cost of each base station is up to only million RMB, and a large amount of maintenance cost is required to be invested subsequently; the LIFI technology can be reconstructed based on the existing LED lighting equipment in any form in any scene, each LED lighting equipment in the scene can be used as an antenna or a base station of the LIFI technology, the base station and electromagnetic signal transmitting equipment do not need to be purchased additionally, and the visible light communication in the scene can be realized only by installing a simple modulation and demodulation device on the basis of the original lighting equipment.
2. Low energy consumption: according to the analysis of the institution in 2020, the power consumption of the communication device in the mobile communication base station is only 32%, and up to 56% of the power consumption is used for heat dissipation of the communication device. According to conservative estimation, mobile communication operators in China need to pay 165-512 billion-element electricity charges each year, and in 2026 years, the total energy consumption of mobile communication base stations is estimated to reach 2.1% of the total electricity consumption of the society in China; the LIFI technology is based on the existing LED lighting equipment, and the communication requirement can be met without the cooperation of any other high-power electrical appliance.
3. High speed: at present, the international mainstream LIFI technical research team has preliminarily designed the transmission speed of data which can reach dozens of million to hundred million per second, and with the continuous development and maturity of the technology, the transmission speed of the optical fiber is possibly surpassed in the future.
4. The frequency spectrum resources are rich: according to the planning of ITU (International telecommunication Union), the range of electromagnetic spectrum available for human use is 10 KHz-400 GHz, and the total bandwidth is approximately equal to 400 GHz; the wavelength range of visible light is 380nm to 780nm, the frequency range is 3850000-7890000 GHz, the spectrum width is far larger than 4000000GHz, and the frequency spectrum is about thirty-thousand times of the electromagnetic spectrum.
5. Confidentiality: because the LIFI technology adopts light as a transmission signal, in some confidential places, the privacy of communication in the environment can be ensured by simply arranging shading facilities, and the cost of signal shielding in the confidential places is greatly increased.
Some preliminary technical achievements and demonstration devices have been developed for LIFI audio transmission in and out of the global industry at present, but there are few of mass production, popularization and practical deployment operability because devices with longer transmission distance and lower transmission loss generally have higher system complexity, manufacturing cost and larger volume weight, for example:
example 1, the invention patent with publication number CN 10509570B, orthogonal multi-carrier light source and PDM-QPSK signal transmitting device, the invention patent uses a highly reliable multi-carrier light source as a transmitting antenna at the transmitting end, a phase shifter is used between two groups of carrier light sources for phase shifting, a demodulator uses a phase to greatly improve redundancy and stability of modulation and demodulation, theoretically, almost lossless audio transmission can be realized, but such a transmitting device depends on a very stable radio frequency sinusoidal signal source, it is necessary to ensure that the temperature of the signal source is minimal, otherwise, temperature variation may cause phase confusion, phase confusion between the transmitter and the receiver may be caused in a short time, and the original signal input by the transmitter cannot be demodulated on the receiver; moreover, the cost of the radio frequency signal source with extremely low temperature drift is extremely high, and the cost is not suitable for the civil communication field.
Example 2, the invention patent with application publication No. CN 101945079 a, which is a device for generating and receiving high-order optical OFDM-NMSK signals, adopts a modulation and demodulation method of OFDM-NMSK, and cooperates with a continuous wave laser as a transmitting antenna, and can also achieve visible light signal transmission with high stability, the continuous wave laser has a characteristic of fast response, and is very suitable for loading high-frequency signals, and can greatly improve transmission bandwidth, but the light emitted by the continuous wave laser is parallel light and has a point-to-point fixed transmission path characteristic, which needs to ensure that the relative positions of a transmitter and a receiver are absolutely kept stable when the device works, obviously, the point is almost impossible to achieve in actual deployment, and the continuous wave laser has high cost and large heat productivity, generally needs to cooperate with an active heat dissipation system, and has high system complexity, and the volume and the weight of the device are not ideal, and the device is difficult to put into practical use.
Example 3, the invention patent with publication number CN 110830112 a, a method and apparatus for visible light communication, the invention is characterized in that a deep neural network is used to perform DNN equalization operation, i.e. a software equalizer, the DNN equalization technology can reduce transmission loss and nonlinear distortion of signals in a channel to the maximum extent, but since the software DNN equalization operation requires a faster operation speed, a general embedded operation system is difficult to meet the performance, and needs to be implemented by matching with a special computer with stronger operation performance, such computer cost can reach thousands of elements or even ten thousand elements, and the operation of the software DNN equalizer has different preset parameters under different illumination degrees and different illumination properties, so the workload for developing such a deep neural network is very large, and the cost in the development stage is directly increased.
However, a transmission device that reduces the cost and complexity of the system blindly would result in the disadvantages of shorter transmission distance and higher transmission loss, and can only be used as a principle prototype in an experimental stage, for example:
example 4, an invention patent with publication number CN 110739996 a is applied, based on LED visible light communication transmission equipment, and the invention patent adopts an extremely simple video baseband signal transmission model, which does not need the support of a complex hardware system, and only needs a simple logic circuit, a transmitting circuit and a receiving circuit to complete signal transmission, but in practical experiments, it is confirmed that the transmission distance of the transmission model is extremely unstable, and is greatly affected by ambient light disturbance, and a certain receiving signal-to-noise ratio can be reached only by gathering optical signals with a complex optical device, and almost no possibility of practical deployment and use exists.
Example 5, the invention patent with application publication No. CN 111510213 a, a supermarket audio transmission system based on visible light, the invention patent adopts a relatively simple audio baseband signal transmission model, only performs simple amplitude amplification on the input signal of the audio signal source at the transmitting end, the manufacturing cost of a single set of equipment can be controlled within 10 yuan, but the analog audio signal amplitude and the anti-interference capability are extremely low, the loss of direct transmission in the channel without modulation is large, experiments prove that the audio distortion of the signal sink compared with the signal source is much greater than 30%, and in practical use, such audio distortion cannot be tolerated at all.
Example 6, the invention patent with publication No. CN 113114360 a, an intelligent media player based on visible light communication, adopts a signal transmission model with a modulator/demodulator, and is low in cost, but its transmitting part circuit is not subjected to a/D conversion before the modem, as mentioned above, the amplitude and the anti-interference capability of the analog audio signal are extremely low, the analog signal is directly modulated, for example, low-order modulation is adopted, the anti-interference capability of the transmission in the channel is only higher than that of the baseband signal, the audio distortion data obtained in the practical experiment is about 20% -30%, and such distortion cannot be accepted in the practical use as well; the use of high-order modulation will also significantly increase the manufacturing cost and system complexity.
Therefore, balancing the advantages and disadvantages of such transmission devices to make them easily advanced to the practical mass production and deployment stage is a great urgency for the development of the LIFI technology, and therefore, a transmission device with low cost, low complexity, high transmission distance and transmission loss within the allowable range is urgently needed to solve the above problems.
Disclosure of Invention
The invention provides a half-duplex audio transmission device based on an LIFI technology and an implementation method thereof, which comprehensively consider the current situations of transmission stability, transmission loss, device cost and system complexity in the prior art, realize audio transmission with better stability and reliability by the combination of an audio coding circuit, an FSK modulation circuit, an audio decoding circuit, an FSK demodulation circuit, an audio operational amplification circuit with adjustable gain and other circuits, compress the manufacturing cost and the system complexity of the device as far as possible on the premise of ensuring that the audio distortion is less than 5 percent, and reduce the product volume as far as possible, so that the device is more easily put into mass production and practical deployment.
In order to solve the problems, the technical scheme adopted by the invention is as follows: a half-duplex audio transmission device based on LIFI technology comprises a transmitting part circuit formed by connecting an audio input interface circuit sequentially through an audio conditioning circuit I, a gain-adjustable operational amplification circuit I, an audio coding circuit, an FSK modulation circuit I, a pre-emphasis circuit and a transmitting circuit, a receiving part circuit formed by connecting a receiving circuit sequentially through a compensation circuit, an FSK demodulation circuit II, an audio decoding circuit, an audio conditioning circuit II, a gain-adjustable operational amplification circuit II, an audio power amplification circuit and an audio output interface circuit, a power part circuit formed by connecting a power supply voltage reduction circuit through a power supply decoupling circuit and a power supply filter circuit, and a core control circuit;
the core control circuit is respectively connected with the gain-adjustable operational amplification circuit I, the audio coding circuit, the gain-adjustable operational amplification circuit II, the audio decoding circuit and the compensation circuit;
the power supply voltage reduction circuit is used for providing power supply for the transmitting circuit and the receiving circuit;
the core control circuit is used for presetting working parameters for the gain-adjustable operational amplification circuit I, the audio coding circuit, the operational amplification circuit II and the audio decoding circuit;
the transmitting part circuit is used for converting the analog audio signal into a digital modulation signal and loading the modulation signal to the transmitting circuit for transmitting;
the receiving part circuit is used for receiving the modulation signal transmitted by the transmitting circuit, processing the digital modulation signal into an analog audio signal, and finally outputting the analog audio signal to the outside through the audio output interface circuit.
The gain-adjustable operational amplification circuit consists of a digital potentiometer N101, an operational amplifier N102A, a resistor R101, a resistor R102, a resistor R103, a resistor R104, a capacitor C101, a capacitor C102, a capacitor C103 and a capacitor C104; the digital potentiometer N101 is provided with an INC pin, a U/D pin, an RH pin, a VSS pin, a RW pin, a RL pin, a CS pin and a VCC pin, wherein the INC pin is connected to an incremental signal, the UD pin is connected to a direction signal, the CS pin is connected to a chip selection signal, the VSS pin is connected to an analog ground, the VCC pin is connected to a direct current 3.3V power supply, the RH pin is communicated with a capacitor C102 to access an audio signal to be amplified, and the RW pin is connected to one end of the R103;
the operational amplifier N102A has an OUTA pin, -an INA pin, + an INA pin, a GND pin and a V + pin, wherein the INA pin is connected to the other end of the resistor R103, the other end of the resistor R101 and one end of the capacitor C101, the OUTA pin is connected to the resistor R101, the other end of the capacitor C101 and one end of the capacitor C103, the other end of the capacitor C103 is an output end of the gain-adjustable operational amplifier circuit, + the INA pin is connected to one ends of the resistor R102, the resistor R104 and the capacitor C104 at the same time, the other end of the resistor R102 and the V + pin are connected to a dc 5V power supply, and the resistor R104, the other end of the capacitor C104 and the GND pin are connected to an analog ground.
The FSK modulation circuit is composed of a multiplexer N103, a phase-locked loop N104, a resistor R105, a resistor R106, a resistor R107, a resistor R108, a resistor R109, a resistor R110, a resistor R111, a resistor R112 and a capacitor C105;
the multiplexer N103 has an a _ IN pin, an a _ OUT pin, a B _ IN pin, a B _ OUT pin, a CTRL _ B pin, a CTRL _ C pin, a VSS pin, a C _ IN pin, a C _ OUT pin, a D _ IN pin, a CTRL _ D pin, a CTRL _ a pin, and a VDD pin, wherein the a _ IN pin is connected to one end of a resistor R110 and a digital ground, the a _ OUT pin is connected to one end of a resistor R105 and the other end of the resistor R110, the other end of the resistor R105 is connected to a direct current 5V power supply, the VSS pin is connected to a direct current-5V power supply, the CTRL _ a pin is connected to a baseband signal through a resistor R109, and the VDD pin is connected to a direct current 5V power supply;
the phase-locked loop N104 has a V1+ pin, an LGC pin, an IPV pin, an LF1 pin, an LF2 pin, an FI/RI pin, a BF pin, a GND pin, a VOT pin, a V2+ pin, a VO2 pin, an FSC1 pin, an FSC2 pin, an AO pin, an HS pin, and a TO pin, wherein the V1+ pin is connected TO one end of a resistor R106, a resistor R107, and a dc 5V power supply, the LGC pin is connected TO an a _ OUT pin of the multiplexer N103, the IPV pin, the FI/RI pin, and the GND pin are connected TO digital ground, the LF1 pin is connected TO the other end of the resistor R107, the LF2 pin is connected TO the other end of the resistor R106, the BF pin is connected TO digital ground through a resistor R111, the VOT pin is connected TO one end of the resistor R108 and outputs a modulated signal, the other end of the resistor R108 is connected TO the V2+ pin and the dc 5V power supply, and the FSC1 pin is connected TO the FSC2 pin through a capacitor C105.
The pre-emphasis circuit is composed of a resistor R113, a resistor R114, a resistor R115, a resistor R116, a capacitor C106 and an inductor L101, wherein one end of the resistor R114 is connected to a signal to be emphasized, one ends of the resistor R113 and the inductor L101 are connected at the same time, the other ends of the resistor R113 and the inductor L101 output an emphasized signal and are connected to one end of the resistor R115, the other ends of the resistor R114 and the resistor R115 are connected to one end of the resistor R116 at the same time, and the other end of the resistor R116 is connected to a digital ground through the capacitor C106.
The FSK demodulation circuit consists of a phase-locked loop N105, a resistor R117, a resistor R118, a resistor R119, a resistor R120, a resistor R121, a resistor R122, a capacitor C107, a capacitor C108, a capacitor C109, a capacitor C110, a capacitor C111 and a capacitor C112;
the phase-locked loop N105 has a V1+ pin, an LGC pin, an IPV pin, an LF1 pin, an LF2 pin, an FI/RI pin, a BF pin, a GND pin, a VOT pin, a V2+ pin, a VO2 pin, an FSC1 pin, an FSC2 pin, an AO pin, an HS pin, and a TO pin, wherein the V1+ pin is connected TO one end of a resistor R119 and a DC 5V power supply, the LGV pin is connected TO the other end of the resistor R119, the IPV pin is connected TO the VOT pin, a resistor R120, and one end of a resistor R122, the other end of the resistor R120 is connected TO the BF pin, a resistor R121, and one end of a capacitor C112, the other end of the capacitor C112 is connected TO digital ground, the other end of the resistor R121 is connected TO the FI/RI pin and a modulation signal is accessed through a capacitor C108, the other end of the resistor R122 is connected TO the VO2 pin, the LF1 pin is connected TO one end of a capacitor C109, the GND pin and the LF 110, and the LF 32 pin are connected TO 2, the V2+ pin is connected TO a resistor R117, one end of a resistor R118, and a dc 5V power supply, the other end of the resistor R117 is connected TO the TO pin and outputs a baseband signal, the other end of the resistor R118 is connected TO the HS pin, the FSC1 pin is connected TO the FSC2 pin through a capacitor C107, and the AO pin is connected TO digital ground through a capacitor C111.
A method for realizing a half-duplex audio transmission device based on an LIFI technology comprises the following steps:
when the system is powered on, the transmitting part circuit firstly enters a system initialization mode, the core control circuit presets gain parameters for the gain-adjustable operational amplifier circuit I through I/O, and simultaneously, the core control circuit presets sampling rate and frame length parameters for the audio coding circuit through an I2C bus; then entering a working mode, inputting an analog audio signal from an audio input interface circuit, filtering noise interference coupled in the audio transmission process by active filtering of an audio conditioning circuit I, performing operational amplification by an operational amplification circuit I with adjustable gain, sending the signal to an audio coding circuit for coding, sending the coded signal to an FSK modulation circuit I for modulating a baseband signal, performing pre-emphasis processing by a pre-emphasis circuit after modulation, enabling the immunity of the modulated signal in a transmission channel to be stronger, and finally loading the signal to a transmitting circuit for transmitting;
when the system is powered on, the receiving part circuit firstly enters a system initialization mode, a photoelectric detection diode of the receiving circuit detects the current ambient light disturbance intensity parameter and uploads the parameter to a core control circuit, the core control circuit presets a compensation voltage parameter for the compensation circuit through a DAC according to the parameter and presets a gain parameter for a gain-adjustable operational amplification circuit II, and meanwhile, the core control circuit presets a sampling rate and a frame length parameter for an audio coding circuit through an I2C bus;
the receiving circuit receives the signal transmitted to the free space channel from the transmitting circuit and then transmits the signal to the compensating circuit, the compensating circuit detects the current ambient light interference intensity and frequency band through the photodiode, and the information is uploaded to a core control circuit, the core control circuit adjusts the compensation waveform of the compensation circuit in real time according to the current ambient light interference degree, then the modulated signal is demodulated into a baseband signal by an FSK demodulation circuit II, then the baseband signal is sent into an audio decoding circuit for decoding to obtain an analog audio signal, the analog audio signal is sent into a gain-adjustable operational amplifier circuit II for amplitude amplification, a core control circuit adjusts the amplification factor in real time according to the optical disturbance degree detected by a preceding stage compensation circuit, then the signal is amplified in power by an audio power amplifier circuit II, the driving capability of the analog audio signal is enhanced, and finally the original analog audio signal is output through the audio output interface circuit.
The core control circuit in the transmitting part circuit presets a gain parameter range of 0.47 to 47 times for the gain-adjustable operational amplifier circuit I through I/O; meanwhile, the core control circuit presets a sampling rate parameter fixed value of 44.1KHz for the audio coding circuit through an I2C bus, and a frame length fixed value of 24 bits.
A core control circuit in the receiving part circuit presets a compensation voltage parameter range of-20 mV to +20mV for the compensation circuit through a DAC; the core control circuit presets a gain parameter range of 0.47 to 47 times for the gain-adjustable operational amplifier circuit II through the I/O; meanwhile, the core control circuit presets a sampling rate parameter fixed value of 44.1KHz for the audio decoding circuit through an I2C bus, and a frame length fixed value of 24 bits.
The power supply voltage reduction circuit, the power supply decoupling circuit and the power supply filter circuit supply power to the power device of the transmitting part circuit after processing the power supply and make precise bias voltage for the receiving device of the receiving part circuit.
The transmitting circuit is provided with a transmitting LED and is compatible with an external LED module.
The invention has the following beneficial effects: in the transmission distance, if the LED carried by the device is used for communication, the transmission distance is slightly short, but the anti-interference performance is better under the condition of lighting, under the normal illumination (no lighting illumination) in a daytime room, the communication distance can reach more than 1000mm (the total distortion degree under 1K audio excitation is less than 5%), and under the condition of indoor lighting at night, the communication distance can reach more than 650mm (the total distortion degree under 1K audio excitation is less than 5%); if the device is used as an LED driver to drive an external LED lamp strip (a 32W high-brightness LED lamp strip is adopted in the test), the communication distance can reach more than 3200mm (the total distortion degree is less than 5% under 1K audio excitation) under normal illumination (no lamplight illumination) in a daytime room, and the communication distance can reach more than 800mm under the indoor lamp strip condition at night. In addition, a large number of tests prove that the communication distance can be greatly increased by further increasing the power of the LED light source, for example, when a 64W high-brightness LED lamp strip is used, the daytime communication distance is as high as 4500mm or more (the total distortion under 1K audio excitation is less than 5%). In the transmission system realized by other debugging modes, the communication distance under normal illumination in the daytime and the indoor is mostly more than 2000mm, but the effective communication distance can only reach about 250mm under the indoor light condition at night.
In terms of cost, the manufacturing cost of the transmission device with actual deployment possibility in the prior art is more than thousands of yuan per device, even can reach ten thousand yuan per device; the manufacturing cost of the transmission device in the mass production stage is only 200 and 300 yuan/set, and the cost is reduced by several times or even dozens of times.
The invention utilizes LIFI technology to realize wireless transmission of analog audio signals, namely, the analog audio signals are loaded into one transmission device to be processed and transmitted, and then are transmitted through free space signals, and the other transmission device receives and processes the transmission signals, thus outputting the original analog audio signals.
Drawings
The contents expressed in the drawings of the present specification and the reference numerals in the drawings are briefly explained as follows:
FIG. 1 is a block diagram of the circuit connections of the present invention;
FIG. 2 is a schematic diagram of an operational amplifier circuit with adjustable gain according to the present invention;
FIG. 3 is a schematic diagram of an FSK modulation circuit of the present invention;
FIG. 4 is a schematic diagram of a pre-emphasis circuit of the present invention;
FIG. 5 is a schematic diagram of an FSK demodulation circuit of the present invention;
FIG. 6 is a diagram showing a concrete connection relation of example 1 of the present invention;
FIG. 7 is a diagram showing a detailed connection relationship of example 2 of the present invention;
FIG. 8 is a diagram showing a specific connection relationship in example 3 of the present invention.
Detailed Description
The following embodiments are provided to describe the embodiments of the present invention, and to further describe the details of the embodiments, such as the shapes, configurations, mutual positions and connection relationships of the components, the functions and working principles of the components, the manufacturing processes and the operation methods, etc., so as to help those skilled in the art to have a more complete, accurate and deep understanding of the inventive concept and technical solutions of the present invention.
As shown in fig. 1, a half-duplex audio transmission apparatus based on the LIFI technology is composed of a transmitting part circuit, a receiving part circuit, a power supply part circuit, and a core control circuit;
the transmitting part circuit consists of an audio input interface circuit, an audio conditioning circuit I, an operational amplifier circuit I with adjustable gain, an audio coding circuit, an FSK modulation circuit I, a pre-emphasis circuit and a transmitting circuit;
the receiving part circuit consists of a receiving circuit, a compensating circuit, an FSK demodulating circuit II, an audio decoding circuit, an audio conditioning circuit II, an operational amplifying circuit II with adjustable gain, an audio power amplifying circuit and an audio output interface circuit;
the power supply part is composed of a power supply voltage reduction circuit, a power supply decoupling circuit and a power supply filter circuit.
The transmitting circuit is used for converting the electric signal into an optical signal and transmitting the optical signal to a channel, and the receiving circuit is used for receiving the optical signal from the channel and converting the optical signal into the electric signal.
The audio conditioning circuit uses an ultra-low noise audio operational amplifier of the "OPA 1652aid r" type manufactured by "TI (texas instruments)" company as a core element.
The audio encoding circuit and the audio decoding circuit both use "TLV 320AIC 3106" type audio codec chips manufactured by "TI (texas instruments)" company as core elements.
As shown in fig. 2, the gain-adjustable operational amplification circuit is composed of a digital potentiometer N101, an operational amplifier N102A, a resistor R101, a resistor R102, a resistor R103, a resistor R104, a capacitor C101, a capacitor C102, a capacitor C103, and a capacitor C104;
the audio signal processed by the audio conditioning circuit realizes the gain adjustment of the preceding-stage signal through a digital potentiometer N101 and an operational amplifier N102A in the operational amplification circuit with adjustable gain.
The digital potentiometer N101 is a model of CAT5113VI-00-GT3 of ON (Anson), and the operational amplifier N102A is a model of NJM2094M of JRC (Japan radio corporation).
As shown in fig. 3, the FSK modulation circuit is composed of a multiplexer N103, a phase-locked loop N104, a resistor R105, a resistor R106, a resistor R107, a resistor R108, a resistor R109, a resistor R110, a resistor R111, a resistor R112, and a capacitor C105;
the audio signal is gated by a bidirectional analog switch chip N103 and then subjected to signal modulation by a frequency synthesis chip N104 to obtain a modulation signal;
the multiplexer N103 is a model of TI (texas instruments) CD4016BM96, and the frequency synthesis chip N104 is a model of NXP (enzima instruments) NE 564D.
As shown in fig. 4, the pre-emphasis circuit is composed of a resistor R113, a resistor R114, a resistor R115, a resistor R116, a capacitor C106, and an inductor L101;
the pre-emphasis circuit compensates according to the attenuation characteristic of the signal in the channel, so that the attenuation of the signal in the channel is smaller and the distortion degree is lower;
inductor L101 is selected from the AlRD-01-120K products of ABRACON.
As shown in fig. 5, the modulated signal received by the FSK demodulation circuit is signal-demodulated by the frequency synthesis chip N105 to obtain a digital audio signal.
Example 1, as shown in fig. 6, the present device can be used in indoor audio distribution scenarios of a privacy nature, such as hearing tests in educational system examinations.
In actual deployment, firstly slightly modifying the existing LED lighting equipment in an examination room, firstly removing an LED driver in the original LED lighting equipment, directly connecting an original lighting power line into an LED lamp strip, disconnecting all lighting power lines from the lighting power supply at a central control room or a switch box, respectively connecting a + binding post and a-binding post which are reserved in a transmitting circuit of the device and externally connected with an LED lamp strip interface to the + binding post and the-binding post of the LED lamp strip, and connecting an N line and an L line of the original lighting power supply to the N binding post and the L binding post of an alternating current power supply interface of the device to supply power to the device, so that the N line and the L line are used as transmitting terminals of an audio distribution system in the examination room;
in the aspect of a receiving terminal, the original headset special for hearing test can be slightly modified, specifically, firstly, a frequency modulation broadcast receiving circuit of the original headset is removed, the device is installed in the headset, the receiving circuit of the device is ensured to be exposed during installation and can effectively receive optical signals, a + terminal and a-terminal of a battery box of the headset are connected to a + terminal and a-terminal of a direct-current power supply interface of the device to supply power for the device, and an audio terminal of an audio output interface circuit of the device, namely the + terminal and a GND terminal, are respectively connected to a left sound channel, a right sound channel and a GND contact of the headset.
When the device is used, audio output equipment is connected with an audio input interface circuit of the device of the transmitting terminal, a power switch positioned in a central control room or a switch box is firstly jointed to supply power to the transmitting terminal and the receiving terminal, after the device is started successfully, a core control circuit firstly detects current ambient light interference intensity parameters according to a photoelectric detection diode of a receiving circuit and uploads the parameters to the core control circuit, after the core control circuit analyzes and calculates the ambient light interference intensity parameters, the core control circuit presets a gain parameter range of 0.47 to 47 times for an operational amplification circuit I with adjustable gain through I/O according to a calculation result, and simultaneously, the core control circuit presets a sampling rate parameter fixed value of 44.1KHz and a frame length fixed value of 24 bits for an audio coding circuit through an I2C bus. Then, using audio output equipment such as a recorder or a computer to transmit analog audio signals to a transmitting terminal through a 3.5mm audio interface, processing the analog audio signals at the transmitting terminal to form pre-emphasis modulation signals, transmitting the pre-emphasis modulation signals to the LED lamp belts of each examination room through an original illumination power line, converting the pre-emphasis modulation signals into optical signals through the LED lamp belts, and transmitting the optical signals; in summary, the core functions of the transmitting terminal are: the analog audio baseband signal with large distortion and attenuation transmitted in free space in the field of view is converted into a digital code modulation signal with small distortion and attenuation.
When the device is started successfully, the core control circuit firstly detects current ambient light interference intensity parameters according to a photoelectric detection diode of the receiving circuit and uploads the parameters to the core control circuit, the core control circuit presets a compensation voltage parameter range from-20 mV to +20mV for the compensation circuit through a DAC after analyzing and calculating the ambient light interference intensity parameters, the core control circuit presets a gain parameter range from 0.47 to 47 times for an operational amplification circuit II with adjustable gain through I/O according to a calculation result, meanwhile, the core control circuit presets a sampling rate parameter fixed value for an audio decoding circuit through an I2C bus to be 44.1KHz, and the frame length fixed value is 24 bits. Then the photoelectric detection diode receives the optical signal transmitted by the transmitting terminal, converts the optical signal into an electric signal, and restores the electric signal after processing to obtain an analog audio signal and sends the analog audio signal to the left and right sound channels of the headset so as to realize audio signal transmission based on the LIFI technology; in summary, since the digital code modulation signal cannot be directly input to the headset as an audio signal source of the headset, the core functions of the receiving terminal are: the digital coding modulation signal transmitted by the transmitting terminal is reduced into an analog audio baseband signal which can be directly played by the headset.
In a traditional frequency modulation broadcast transmission mode, a professional frequency modulation broadcast radio transmitting system needs to be arranged near one or more examination room areas in advance, the radio transmitting system at least comprises a radio transmitter, a radio frequency power amplifier and an omnidirectional transmitting antenna with certain gain, and in actual deployment, in order to ensure a signal coverage range, the transmitting antenna is usually installed on a signal tower with a certain height, so that the installation and deployment work is very complicated; and the hearing test is carried out by adopting a frequency modulation broadcast transmission mode, the signal transmission is more easily interfered by some illegal equipment, so that signal distortion or audio interruption is caused, and a radio monitoring vehicle is usually required to be arranged near an examination room in advance by a radio management department to ensure the transmission of examination broadcast signals.
In addition, the traditional FM broadcast transmission mode is very easy to be eavesdropped by personnel outside the examination room, and the examination personnel is very likely to cheat with the personnel outside the examination room by utilizing the leak, so the confidentiality is poor. If the frequency modulation broadcasting mode is used to improve the security, the coverage of the signal needs to be accurately controlled, which requires accurately calculating the radio frequency parameters such as the gain, the transmitting angle, the standing wave ratio, the transmitting power and the like of the transmitting antenna, which is difficult to realize in practical operation.
The LIFI technology-based indoor audio distribution system does not need to add an additional complicated transmitting device and an antenna, and as described above, the audio distribution in the examination room can be realized only by slightly modifying the existing lighting circuit in the examination room; compared with frequency modulation broadcasting, the LIFI technology has the great advantage in confidentiality, because visible light cannot penetrate opaque objects, signal coverage can be flexibly controlled in an examination room through simple curtain shading measures, the actual effect that people outside the signal coverage cannot receive signals is achieved, and theoretically, the confidentiality of an indoor audio distribution system based on the LIFI technology is higher than 99% of that of the existing wireless communication technology.
In actual deployment, firstly slightly modifying the existing LED street lamps on two sides of a road, firstly removing an LED driver in the original LED street lamps, directly connecting original lighting power lines into an LED lamp strip, disconnecting all the lighting power lines from a lighting power supply in a central control room, reserving a + binding post and a-binding post of an external LED lamp strip interface in a transmitting circuit of the device, respectively connecting the + binding post and the-binding post of the LED lamp strip interface, and connecting an N line and an L line of the original lighting power supply to an N binding post and an L binding post of an alternating current power supply interface of the device to supply power to the device, so that the device is used as a transmitting terminal in the central control room of the internet of vehicles; in summary, the core functions of the transmitting terminal are: the analog audio baseband signal with large distortion and attenuation transmitted in the free space near the urban road is converted into a digital code modulation signal with small distortion and attenuation.
In the aspect of a receiving terminal, the device can be preset in a sound system of a vehicle, specifically, the device is firstly installed in a center console of the vehicle, a receiving circuit of the device is ensured to be exposed during installation and can effectively receive optical signals, a + terminal and a-terminal of a vehicle-mounted power supply are connected to a + terminal and a-terminal of a direct-current power supply interface of the device to supply power to the device, and an audio terminal of an audio output interface circuit of the device is respectively connected to a left sound channel contact, a right sound channel contact and a GND terminal of the vehicle-mounted sound; in summary, since the digital code modulation signal cannot be directly input to the car audio as the audio signal source of the car audio, the core functions of the receiving terminal are: the digital coding modulation signal transmitted by the transmitting terminal is restored into an analog audio baseband signal which can be directly played by the vehicle-mounted sound box.
When the device is used, audio output equipment is connected with an audio input interface circuit of the device of the transmitting terminal, a power switch positioned in a central control room is firstly jointed to supply power to the transmitting terminal and the receiving terminal, after the device is started successfully, a core control circuit firstly detects current ambient light interference intensity parameters according to a photoelectric detection diode of a receiving circuit and uploads the parameters to the core control circuit, after the core control circuit analyzes and calculates the ambient light interference intensity parameters, the range of a gain parameter is preset to be 0.47-47 times through an I/O (input/output) gain-adjustable operational amplification circuit I according to a calculation result, meanwhile, the core control circuit presets a sampling rate parameter fixed value to be 44.1 for an audio coding circuit through an I2C bus, and a frame length fixed value is 24 bits. Then, using audio output equipment such as a recorder or a computer to transmit the analog audio signals to a transmitting terminal through a 3.5mm audio interface, processing the analog audio signals at the transmitting terminal to be pre-emphasis modulation signals, transmitting the pre-emphasis modulation signals to LED lamp belts in each street lamp of a target road section through an original illumination power line, converting the pre-emphasis modulation signals into optical signals through the LED lamp belts, and transmitting the optical signals; the method comprises the steps that a vehicle-mounted receiving terminal in a street lamp illumination coverage range starts to supply power along with the start of a vehicle-mounted power supply system, after the device is successfully started, a core control circuit detects current ambient light interference intensity parameters according to a photoelectric detection diode of a receiving circuit and uploads the parameters to the core control circuit, the core control circuit analyzes and calculates the ambient light interference intensity parameters, a compensation voltage parameter range is preset for the compensation circuit through a DAC (digital-to-analog converter) to be-20 mV to +20mV according to a calculation result, the core control circuit presets a gain parameter range to be 0.47 to 47 times for an operational amplification circuit II with adjustable gain through I/O, meanwhile, the core control circuit presets a sampling rate parameter fixed value to be 44.1KHz for an audio decoding circuit through an I2C bus, and a frame length fixed value is 24 bits. The photoelectric detection diode receives the optical signal transmitted by the transmitting terminal, converts the optical signal into an electric signal, and restores the electric signal into an analog audio signal after processing and sends the analog audio signal to the left and right sound channels of the headset, so that the intelligent road condition early warning system based on the LIFI technology is realized.
At present, the road condition early warning usually adopts a frequency modulation broadcast timing broadcast mode, and the mode has the defects of lacking flexibility and accuracy, and a road traffic management department cannot accurately and independently distribute early warning information for each road section, and can only broadcast the early warning information uniformly in a city range, so that the difficulty of knowing the road condition information by a driver in the driving process is greatly improved; if the flexibility and accuracy of road condition information broadcast are to be improved by using a frequency modulation broadcast mode, radio frequency parameters such as gain, transmission angle, standing-wave ratio and transmission power of a transmitting antenna need to be accurately calculated, which is difficult to realize in actual operation.
The intelligent road condition early warning system based on the LIFI technology only needs to slightly reform transform the existing street lamps at two sides of the road, can realize the early warning of road condition information in the road section, and because the attenuation of light in the free space is very big, can utilize this characteristic, broadcasts different early warning information at two adjacent road sections, need not worry the problem of signal aliasing. In the driving process of a driver, different broadcast contents can be automatically switched in different road sections without human intervention, and the intelligent broadcasting system has strong flexibility.
Generally, when the transmission distance is greater than 1000mm, the transmission of the visible light carrying the signal in the free space is affected by the ambient interference light, and the attenuation and distortion are large, so that a method similar to that of embodiment 1 and embodiment 2 can be adopted, and the power of the transmitting antenna is increased by externally connecting the LED module with larger power, so that the signal-to-noise ratio of the receiving end is improved, and the attenuation and distortion of the transmitting signal caused by long-distance transmission in the free space are reduced.
The existing mainstream wireless intercom equipment in the market adopts traditional communication modes such as UHF/VHF and the like, the communication mode uses electromagnetic waves as signal carriers, all electromagnetic transmitting devices are prevented from working in mines, at the present stage, communication and intercom equipment in global mines mainly use wired explosion-proof telephones, the manufacturing cost of the wired explosion-proof telephones is high, the wired explosion-proof telephones are difficult to be deployed in a roadway in large quantities, mine workers need to use telephones to contact a dispatching center or other regional personnel, the explosion-proof telephones need to be used at specified positions after leaving behind, the flexibility is greatly reduced compared with a movable intercom device, and therefore the problem can be solved by adopting the transmission device.
In the actual fixed terminal deployment work, a large number of devices, named as fixed terminals 1, fixed terminals 2 and the like, can be deployed on the mine roadway wall, the audio terminals '+' of the audio input interface circuit and the audio terminals '+' of the audio output interface circuit of the devices in a plurality of fixed terminals deployed on the roadway wall are respectively connected in series to be used as a downlink audio bus and an uplink audio bus, the audio input interface circuit and the '-' terminals of the audio output interface circuit of the devices in all the fixed terminals in the area are connected in series to be used as common GND of all the fixed terminals and a dispatching center, the direct current supply terminals '+' and '-' of the devices in all the fixed terminals are respectively connected in series and then led out, five lines are laid in parallel to the dispatching center, the direct current supply '+' and '-' are respectively connected to the '+' terminals and '-' terminals of a direct current power supply, then connecting the downlink audio bus to an MIC binding post of the microphone, connecting the uplink audio bus to an SPK binding post of the wired sound, and respectively connecting the public GND line to the microphone and the GND binding post of the wired sound; in the aspect of mobile terminal, the traditional wired portable headset can be slightly modified, firstly, the signal wire of the original headset is removed to change the signal wire into a wireless headset, the device and a small battery box are arranged in the headset, the transmitting circuit and the receiving circuit of the device are ensured to be exposed during installation, so that the transmitting and receiving optical signals are conveniently transmitted and received, the audio terminals '+' and '-' of the audio output interface circuit of the device in the mobile terminal are respectively connected to the SPK _ LR and GND contacts of a headset receiver, the audio terminals '+' and '-' of the audio input interface circuit of the device in the mobile terminal are respectively connected to the MIC and GND contacts of the headset microphone, and finally the '+' and '-' terminals of the small battery box are connected to the '+' and '-' terminals of the direct-current power supply interface of the device in the mobile terminal to supply power for the mobile terminal.
When the mobile terminal is used, a mine worker can wirelessly talk with a dispatching center at any position in an LIFI system deployment area only by wearing the mobile terminal; in the aspect of uplink call, firstly, a power switch of the mobile terminal is turned on, after the device is started successfully, the core control circuit detects current ambient light interference intensity parameters according to a photoelectric detection diode of the receiving circuit and uploads the parameters to the core control circuit, after the core control circuit analyzes and calculates the ambient light interference intensity parameters, the core control circuit presets a gain parameter range of 0.47-47 times for an operational amplification circuit I with adjustable gain through I/O according to a calculation result, meanwhile, the core control circuit presets a sampling rate parameter fixed value of 44.1KHz for an audio coding circuit through an I2C bus, and a frame length fixed value is 24 bits. When a worker speaks, a microphone of the headset picks up an audio signal, then the analog audio signal is transmitted to a transmitting part circuit of the mobile terminal through a wire, the analog audio signal is processed and changed into a pre-emphasis modulation signal, and the pre-emphasis modulation signal is converted into an optical signal through an LED of the headset and transmitted. The fixed terminal of the roadway wall is also required to be turned on, after the device is started successfully, the core control circuit detects the current ambient light interference intensity parameter according to the photoelectric detection diode of the receiving circuit and uploads the parameter to the core control circuit, the core control circuit analyzes and calculates the ambient light interference intensity parameter, according to the calculation result, the DAC is used for presetting the compensation voltage parameter range for the compensation circuit to be-20 mV to +20mV, the core control circuit is used for presetting the gain parameter range for the gain-adjustable operational amplification circuit II to be 0.47 to 47 times through I/O, meanwhile, the core control circuit is used for presetting the sampling rate parameter fixed value for the audio decoding circuit to be 44.1KHz through an I2C bus, and the frame length fixed value is 24 bits. Then the photoelectric detection diode receives the optical signal transmitted by the transmitting terminal, converts the optical signal into an electric signal, restores an analog audio signal after processing, and transmits the analog audio signal to a sound box of a dispatching center through an uplink audio bus for playing; in summary, the core functions of the circuit of the transmitting part of the mobile terminal or the fixed terminal are as follows: the analog audio baseband signal with larger distortion and attenuation is directly transmitted in the free space in the mine is converted into a digital coding modulation signal with smaller distortion and attenuation; since the digital modulation signal can not be directly input to the earphone or the wired sound as the audio signal source, the core function of the receiving part circuit is as follows: the digital coding modulation signal transmitted by the transmitting part circuit is reduced into an analog audio baseband signal which can be directly played by a headset and a wired sound.
In the aspect of downlink communication, when a dispatcher in a dispatching center speaks, a microphone picks up an audio signal, then the audio signal is transmitted to a transmitting circuit of a fixed terminal of a roadway wall through a downlink audio bus, an analog audio signal is processed to be a pre-emphasis modulation signal, and the pre-emphasis modulation signal is converted into an optical signal through an LED (light emitting diode) arranged on the device and transmitted. The photoelectric detection diode of the receiving circuit of the mobile terminal receives the optical signal transmitted by the transmitting terminal and converts the optical signal into an electric signal, and the electric signal is processed to restore an analog audio signal and played by a headset.
Most of work types in the mine belong to high-risk operation, mechanical and electrical facilities in a roadway all need workers and safety personnel to work under gapless supervision, serious potential safety hazards are caused by leaving off-post call making, the LIFI-based mine wireless communication system can greatly improve the current situation of 'difficult call' in the current mine, and the workers can complete voice call with a dispatching center without leaving the work post.
When the distance between the transmitting terminal and the receiving terminal is less than 1000mm, attenuation and distortion caused by the influence of environmental interference fibers on the propagation of the visible fibers carrying signals in free space are relatively small, particularly after the visible fibers are matched with a coding, modulation and pre-emphasis circuit in the device, the adverse influence of the environment on the optical signals can be almost ignored, an LED module is not needed to increase transmitting power, and an LED carried by the device is used.
The invention has been described in an illustrative manner, and it is to be understood that the invention is not limited to the precise form disclosed, and that various insubstantial modifications of the inventive concepts and solutions, or their direct application to other applications without such modifications, are intended to be covered by the scope of the invention. The protection scope of the present invention shall be subject to the protection scope defined by the claims.
Claims (10)
1. A half-duplex audio transmission device based on LIFI technology is characterized in that: the device comprises an audio input interface circuit, a transmitting part circuit, a receiving part circuit, a power supply part circuit and a core control circuit, wherein the transmitting part circuit is formed by connecting an audio input interface circuit, an audio conditioning circuit I, a gain-adjustable operational amplification circuit I, an audio coding circuit, an FSK modulation circuit I, a pre-emphasis circuit and a transmitting circuit in sequence;
the core control circuit is respectively connected with the gain-adjustable operational amplification circuit I, the audio coding circuit, the gain-adjustable operational amplification circuit II, the audio decoding circuit and the compensation circuit;
the power supply voltage reduction circuit is used for providing power supply for the transmitting circuit and the receiving circuit;
the core control circuit is used for presetting working parameters for the gain-adjustable operational amplification circuit I, the audio coding circuit, the gain-adjustable operational amplification circuit II and the audio decoding circuit;
the transmitting part circuit is used for converting the analog audio signal into a digital modulation signal and loading the modulation signal to the transmitting circuit for transmitting;
the receiving part circuit is used for receiving the modulation signal transmitted by the transmitting circuit, processing the digital modulation signal into an analog audio signal, and finally outputting the analog audio signal to the outside through the audio output interface circuit.
2. The apparatus for half-duplex audio transmission based on LIFI technology as claimed in claim 1, wherein: the gain-adjustable operational amplification circuit consists of a digital potentiometer N101, an operational amplifier N102A, a resistor R101, a resistor R102, a resistor R103, a resistor R104, a capacitor C101, a capacitor C102, a capacitor C103 and a capacitor C104; the digital potentiometer N101 is provided with an INC pin, a U/D pin, an RH pin, a VSS pin, a RW pin, a RL pin, a CS pin and a VCC pin, wherein the INC pin is connected to an incremental signal, the UD pin is connected to a direction signal, the CS pin is connected to a chip selection signal, the VSS pin is connected to an analog ground, the VCC pin is connected to a direct current 3.3V power supply, the RH pin is communicated with a capacitor C102 to access an audio signal to be amplified, and the RW pin is connected to one end of the R103;
the operational amplifier N102A has an OUTA pin, -an INA pin, + an INA pin, a GND pin and a V + pin, wherein the INA pin is connected to the other end of the resistor R103, the other end of the resistor R101 and one end of the capacitor C101, the OUTA pin is connected to the resistor R101, the other end of the capacitor C101 and one end of the capacitor C103, the other end of the capacitor C103 is an output end of the gain-adjustable operational amplifier circuit, + the INA pin is connected to one ends of the resistor R102, the resistor R104 and the capacitor C104 at the same time, the other end of the resistor R102 and the V + pin are connected to a dc 5V power supply, and the resistor R104, the other end of the capacitor C104 and the GND pin are connected to an analog ground.
3. The apparatus for half-duplex audio transmission based on LIFI technology as claimed in claim 1, wherein: the FSK modulation circuit is composed of a multiplexer N103, a phase-locked loop N104, a resistor R105, a resistor R106, a resistor R107, a resistor R108, a resistor R109, a resistor R110, a resistor R111, a resistor R112 and a capacitor C105;
the multiplexer N103 has an a _ IN pin, an a _ OUT pin, a B _ IN pin, a B _ OUT pin, a CTRL _ B pin, a CTRL _ C pin, a VSS pin, a C _ IN pin, a C _ OUT pin, a D _ IN pin, a CTRL _ D pin, a CTRL _ a pin, and a VDD pin, wherein the a _ IN pin is connected to one end of a resistor R110 and a digital ground, the a _ OUT pin is connected to one end of a resistor R105 and the other end of the resistor R110, the other end of the resistor R105 is connected to a direct current 5V power supply, the VSS pin is connected to a direct current-5V power supply, the CTRL _ a pin is connected to a baseband signal through a resistor R109, and the VDD pin is connected to a direct current 5V power supply;
the phase-locked loop N104 has a V1+ pin, an LGC pin, an IPV pin, an LF1 pin, an LF2 pin, an FI/RI pin, a BF pin, a GND pin, a VOT pin, a V2+ pin, a VO2 pin, an FSC1 pin, an FSC2 pin, an AO pin, an HS pin, and a TO pin, wherein the V1+ pin is connected TO one end of a resistor R106, a resistor R107, and a dc 5V power supply, the LGC pin is connected TO an a _ OUT pin of the multiplexer N103, the IPV pin, the FI/RI pin, and the GND pin are connected TO digital ground, the LF1 pin is connected TO the other end of the resistor R107, the LF2 pin is connected TO the other end of the resistor R106, the BF pin is connected TO digital ground through a resistor R111, the VOT pin is connected TO one end of the resistor R108 and outputs a modulated signal, the other end of the resistor R108 is connected TO the V2+ pin and the dc 5V power supply, and the FSC1 pin is connected TO the FSC2 pin through a capacitor C105.
4. The apparatus for half-duplex audio transmission based on LIFI technology as claimed in claim 1, wherein: the pre-emphasis circuit is composed of a resistor R113, a resistor R114, a resistor R115, a resistor R116, a capacitor C106 and an inductor L101, wherein one end of the resistor R114 is connected to a signal to be emphasized, one ends of the resistor R113 and the inductor L101 are connected at the same time, the other ends of the resistor R113 and the inductor L101 output an emphasized signal and are connected to one end of the resistor R115, the other ends of the resistor R114 and the resistor R115 are connected to one end of the resistor R116 at the same time, and the other end of the resistor R116 is connected to a digital ground through the capacitor C106.
5. The apparatus for half-duplex audio transmission based on LIFI technology as claimed in claim 1, wherein: the FSK demodulation circuit consists of a phase-locked loop N105, a resistor R117, a resistor R118, a resistor R119, a resistor R120, a resistor R121, a resistor R122, a capacitor C107, a capacitor C108, a capacitor C109, a capacitor C110, a capacitor C111 and a capacitor C112;
the phase-locked loop N105 has a V1+ pin, an LGC pin, an IPV pin, an LF1 pin, an LF2 pin, an FI/RI pin, a BF pin, a GND pin, a VOT pin, a V2+ pin, a VO2 pin, an FSC1 pin, an FSC2 pin, an AO pin, an HS pin, and a TO pin, wherein the V1+ pin is connected TO one end of a resistor R119 and a DC 5V power supply, the LGV pin is connected TO the other end of the resistor R119, the IPV pin is connected TO the VOT pin, a resistor R120, and one end of a resistor R122, the other end of the resistor R120 is connected TO the BF pin, a resistor R121, and one end of a capacitor C112, the other end of the capacitor C112 is connected TO digital ground, the other end of the resistor R121 is connected TO the FI/RI pin and a modulation signal is accessed through a capacitor C108, the other end of the resistor R122 is connected TO the VO2 pin, the LF1 pin is connected TO one end of a capacitor C109, the GND pin and the LF 110, and the LF 32 pin are connected TO 2, the V2+ pin is connected TO a resistor R117, one end of a resistor R118, and a dc 5V power supply, the other end of the resistor R117 is connected TO the TO pin and outputs a baseband signal, the other end of the resistor R118 is connected TO the HS pin, the FSC1 pin is connected TO the FSC2 pin through a capacitor C107, and the AO pin is connected TO digital ground through a capacitor C111.
6. A method for implementing the half-duplex audio transmission apparatus based on the LIFI technology as claimed in claim 1, comprising the steps of:
when the system is powered on, the transmitting part circuit firstly enters a system initialization mode, the core control circuit presets gain parameters for the gain-adjustable operational amplifier circuit I through I/O, and simultaneously, the core control circuit presets sampling rate and frame length parameters for the audio coding circuit through an I2C bus; then entering a working mode, inputting an analog audio signal from an audio input interface circuit, filtering noise interference coupled in the audio transmission process by active filtering of an audio conditioning circuit I, performing operational amplification by an operational amplification circuit I with adjustable gain, sending the signal to an audio coding circuit for coding, sending the coded signal to an FSK modulation circuit I for modulating a baseband signal, performing pre-emphasis processing by a pre-emphasis circuit after modulation, enabling the immunity of the modulated signal in a transmission channel to be stronger, and finally loading the signal to a transmitting circuit for transmitting;
when the system is powered on, the receiving part circuit firstly enters a system initialization mode, a photoelectric detection diode of the receiving circuit detects the current ambient light disturbance intensity parameter and uploads the parameter to a core control circuit, the core control circuit presets a compensation voltage parameter for the compensation circuit through a DAC according to the parameter and presets a gain parameter for a gain-adjustable operational amplification circuit II, and meanwhile, the core control circuit presets a sampling rate and a frame length parameter for an audio coding circuit through an I2C bus;
the receiving circuit receives the signal transmitted to the free space channel from the transmitting circuit and then transmits the signal to the compensating circuit, the compensating circuit detects the current ambient light interference intensity and frequency band through the photodiode, and the information is uploaded to a core control circuit, the core control circuit adjusts the compensation waveform of the compensation circuit in real time according to the current ambient light interference degree, then the modulated signal is demodulated into a baseband signal by an FSK demodulation circuit II, then the baseband signal is sent into an audio decoding circuit for decoding to obtain an analog audio signal, the analog audio signal is sent into a gain-adjustable operational amplifier circuit II for amplitude amplification, a core control circuit adjusts the amplification factor in real time according to the optical disturbance degree detected by a preceding stage compensation circuit, then the signal is amplified in power by an audio power amplifier circuit II, the driving capability of the analog audio signal is enhanced, and finally the original analog audio signal is output through the audio output interface circuit.
7. The method of claim 6, wherein the LIFI technology-based half-duplex audio transmission apparatus comprises: the core control circuit in the transmitting part circuit presets a gain parameter range of 0.47 to 47 times for the gain-adjustable operational amplifier circuit I through I/O; meanwhile, the core control circuit presets a sampling rate parameter fixed value of 44.1KHz for the audio coding circuit through an I2C bus, and a frame length fixed value of 24 bits.
8. The method of claim 6, wherein the LIFI technology-based half-duplex audio transmission apparatus comprises: a core control circuit in the receiving part circuit presets a compensation voltage parameter range of-20 mV to +20mV for the compensation circuit through a DAC; the core control circuit presets a gain parameter range of 0.47 to 47 times for the gain-adjustable operational amplifier circuit II through the I/O; meanwhile, the core control circuit presets a sampling rate parameter fixed value of 44.1KHz for the audio decoding circuit through an I2C bus, and a frame length fixed value of 24 bits.
9. The method of claim 6, wherein the LIFI technology-based half-duplex audio transmission apparatus comprises: the power supply voltage reduction circuit, the power supply decoupling circuit and the power supply filter circuit supply power to the power device of the transmitting part circuit after processing the power supply and make precise bias voltage for the receiving device of the receiving part circuit.
10. The method of claim 6, wherein the LIFI technology-based half-duplex audio transmission apparatus comprises: the transmitting circuit is provided with a transmitting LED and is compatible with an external LED module.
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