CN112019272B

CN112019272B - Digital-analog signal hybrid transmission system based on OOK and FM

Info

Publication number: CN112019272B
Application number: CN202010771977.9A
Authority: CN
Inventors: 朱明�; 曹存曦; 潘进豪; 马艳华; 樊鑫; 王雷; 罗钟铉
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2020-08-04
Filing date: 2020-08-04
Publication date: 2021-07-06
Anticipated expiration: 2040-08-04
Also published as: CN112019272A

Abstract

A digital-analog signal hybrid transmission system based on OOK and FM belongs to the technical field of visible light communication. The system performs FM modulation on audio signals, performs OOK coding on digital signals, performs OOK modulation on the FM signals serving as carriers to generate secondary modulation signals, performs optical communication through an LED-PD, performs demodulation, linear filling and decoding, recovers original signals, and finally outputs audio and texts through audio output equipment and a liquid crystal display respectively. The transmission system of the invention can simultaneously transmit digital and analog signals, namely audio and text signals, by utilizing secondary modulation, and has high working efficiency; the audio signals are transmitted by using FM and OOK signals simultaneously, so that the smoothness of the signals is ensured as much as possible, the signal interruption is prevented, the communication quality is improved when the external conditions permit, and the method is suitable for various scenes and various environments; and the LED-PD is used for transmission by adopting an LED-based optical communication technology, so that the flow and the operation are simplified.

Description

Digital-analog signal hybrid transmission system based on OOK and FM

Technical Field

The invention relates to a visible light communication technology in the communication field, in particular to a communication system which adopts OOK and FM secondary modulation technology and can perform mixed transmission of audio analog signals and digital signals based on LED visible light communication.

Background

At present, most of the mature and widely used Visible Light Communication (VLC) systems in the market adopt separate digital signal transmission, and the digital transmission system cannot guarantee normal communication under the conditions of large environmental interference and low receiver received signal strength. In addition, the existing visible light communication only uses a digital modulation technology, and the carrier signal of the existing visible light communication is not fully utilized. The analog signal transmission has low requirement on signal strength, and can still transmit analog audio signals under the condition of poor communication conditions.

The invention patent with the application number of 201911200724.X provides a visible light real-time voice image communication coding method based on a single LED, but cannot realize the mixed transmission of a digital signal and an analog signal simultaneously in work, only can independently transmit voice or images, and in a modulation stage, the patent synthesizes a digital frame by inserting image data instead of performing secondary modulation to generate a digital-analog mixed signal; the invention patent with application number 201811442338.7 provides a method, a device and a DAS system for hybrid transmission of digital-analog signals, but the method still belongs to pure digital transmission, in which analog signals are converted into digital signals and then transmitted. Neither patent makes efficient use of the carrier signal.

Disclosure of Invention

To solve the problems of the background art, the present invention provides a system capable of simultaneously transmitting analog and digital signals. The system has good compatibility, can meet the visible light communication condition under the complex environment and improve the functional diversity of the communication system as much as possible.

The technical scheme of the invention is as follows:

a digital-analog signal mixed transmission system based on OOK and FM comprises a transmitter part and a receiver part;

the transmitter part comprises audio input equipment, a keyboard, a transmitter ADC, a transmitter singlechip, a modulation DSP, a transmitter amplifier and an LED;

the transmitter singlechip receives the text input by the keyboard, processes the text and sends the processed text to the modulation DSP;

the modulation DSP firstly performs FM modulation on an input audio signal, performs OOK coding on the input digital signal, and then performs OOK digital modulation by taking the FM signal as a carrier, wherein the OOK coding comprises text input information and audio information, the OOK modulation is performed after the FM modulation, and at least one OOK code element is delayed to form a secondary modulation signal;

the transmitter amplifier amplifies the power of the modulated signal to meet the transmission requirement;

the LED emits a signal in the form of an optical signal;

the receiver part comprises a PD, a receiver amplifier, a receiver ADC, a demodulation DSP, a receiver singlechip, audio output equipment, an audio DAC and a liquid crystal display;

the PD receives the optical signal emitted by the LED to complete the optical reception in the external environment;

the receiver amplifier amplifies the signal;

the receiver ADC restores the signals processed by the transmitter amplifier into digital-analog mixed signals;

the demodulation DSP firstly carries out OOK demodulation on the signal according to the carrier wave to obtain a lossy FM voice signal and OOK digital coding; linear filling of the lossy FM signal by an algorithm: if the frequency of the last complete carrier is f1 and the frequency of the next first complete carrier is f2, the frequencies from f1 to f2 are linearly filled between the two carriers to form a continuous FM signal, then FM demodulation is carried out, the original FM digital audio signal is recovered, and the FM digital audio signal enters an alternative electronic switch; decoding OOK digital, and sending to a receiver singlechip and an alternative electronic switch; the receiver singlechip is used for judging and controlling the state of the alternative electronic switch according to the quality of the OOK signal, when the OOK signal is good, the receiver singlechip controls the output of the alternative electronic switch to be the OOK signal, the audio DAC is used for carrying out digital-to-analog conversion on a digital audio signal in the OOK signal to obtain an audio signal, and meanwhile, the receiver singlechip is also used for extracting a text signal in the OOK signal and outputting the text signal on an LCD; when the OOK signal is poor, the receiver singlechip controls the output of the alternative electronic switch to be an FM digital audio signal, and the audio DAC performs digital-to-analog conversion to output the audio signal;

the audio DAC carries out digital-to-analog conversion on the audio digital code obtained by demodulation and restores the audio digital code into an analog signal;

the audio output device outputs an audio signal;

the receiver singlechip and the LCD are used for controlling the LCD to output texts and the output state of the alternative electronic switch.

The invention has the following beneficial effects: FM and OOK technologies are utilized to perform FM modulation on an audio signal, OOK secondary modulation is utilized to form a digital-analog mixed signal with a text signal for transmission, voice and digital signals can be transmitted simultaneously, and the method is efficient, flexible and high in adaptability. The LED and the PD are adopted for optical communication, so that the structure of the transmitter and the processes of signal modulation, transmission and reception are greatly simplified. The system has wide application range and reliable communication quality, and is suitable for various environments and conditions;

drawings

Fig. 1 is a structural framework of the transmission system.

Fig. 2 is a schematic diagram of the modulation DSP performing secondary modulation on an FM signal.

Fig. 3 is a demodulation schematic diagram of the demodulation DSP.

Fig. 4 is a switching flow chart of the receiver single chip microcomputer.

FIG. 5 is a schematic of the output of the system.

Detailed Description

The following further describes the specific embodiments of the present invention with reference to the technical solutions and the drawings of the specification.

A digital-analog signal mixed transmission system based on OOK and FM is shown in figure 1, the transmitter part of the invention comprises an audio input device and a text input keyboard, a transmitter ADC, a transmitter singlechip, a modulation DSP, a transmitter amplifier and an LED transmitting circuit;

the receiver part comprises a PD, a receiver amplifier, a receiver ADC, a demodulation DSP, a voice output device, a receiver singlechip and a liquid crystal display.

The working steps of the digital-analog hybrid transmission system are as follows:

firstly, as shown in fig. 1, a user inputs a text through a keyboard, the text is converted into a digital signal after being processed by a single chip of a transmitter, and the digital signal is sent to a modulation DSP;

the input audio signal is first FM-modulated by the transmitter ADC and DSP and converted to an FM signal. Then the signal is used as OOK carrier signal, simultaneously the audio signal digitized by ADC and digital signal sent by single chip are OOK coded together to become OOK digital signal, FM carrier is modulated to form secondary modulation signal of FM and OOK, OOK at least delays one OOK code element when modulating FM. Converting the audio and text signals into digital-analog mixed signals by the above means;

the secondary modulation signal is subjected to power amplification on the signal through a transmitter amplifier, so that the power of the signal meets the emission requirement and is emitted by an LED;

after the receiver PD finishes receiving, the receiver amplifier amplifies the signals, and the receiver ADC and the demodulation DSP perform OOK demodulation on the secondarily modulated signals according to the carrier waves to obtain lossy FM audio signals and OOK digital codes. For the lost part of the FM signal, linear filling is carried out through an algorithm: if the frequency of the last complete carrier is f1 and the frequency of the next first complete carrier is f2, the frequencies from f1 to f2 are linearly filled between the two carriers to realize lossy complementary restoration, and the signals are restored to continuous FM signals and then subjected to FM demodulation to restore the signals to digital voice signals; after the digital voice signal passes through the audio DAC, the digital voice signal is output to a system through audio output equipment such as a loudspeaker; OOK digital code passes through the singlechip, and FM digital voice signals or OOK digital voice signals are selected by the singlechip to be used and are restored into original text signals and another path of digital voice signals through audio signals, and the original text signals and the other path of digital voice signals are output to the system through a liquid crystal display screen under the control of the singlechip. By now it should be appreciated by those skilled in the art that while various exemplary embodiments of the present invention have been shown and described herein in detail. Many other variations and modifications in keeping with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope thereof. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.

Claims

1. A digital-analog signal hybrid transmission system based on OOK and FM is characterized in that the digital-analog signal hybrid transmission system based on OOK and FM comprises a transmitter part and a receiver part;

the modulation DSP firstly digitizes an audio signal input into the transmitter ADC to obtain an audio digital signal, the audio digital signal is input into the modulation DSP to be subjected to FM modulation to obtain an original FM digital audio signal, simultaneously OOK coding is carried out on the audio digital signal and a text digital signal sent by the singlechip to obtain an OOK coding signal, the OOK coding signal comprises text input information and audio information, then OOK digital modulation is carried out on the original FM digital audio signal by the OOK coding signal, the OOK modulation is carried out after the FM modulation, and at least one OOK code element is delayed to form a secondary modulation signal;

the LED emits a signal in the form of an optical signal;

the receiver amplifier amplifies the signal;

the demodulation DSP firstly carries out OOK demodulation on the signals according to the carrier waves to obtain damaged FM voice signals and OOK digital coding signals; linear filling of the lossy FM signal by an algorithm: if the frequency of the last complete carrier is f1 and the frequency of the next first complete carrier is f2, the frequencies from f1 to f2 are linearly filled between the two carriers to form a continuous FM signal, and then FM demodulation is carried out to recover the continuous FM digital audio signal, and the continuous FM digital audio signal enters an alternative electronic switch; decoding the OOK digital coding signals, and sending the decoded signals to a receiver singlechip and an alternative electronic switch; the receiver singlechip is used for judging and controlling the state of the alternative electronic switch according to the quality of the OOK signal, when the OOK signal is good, the receiver singlechip controls the output of the alternative electronic switch to be the OOK signal, the audio DAC is used for carrying out digital-to-analog conversion on a digital audio signal in the OOK signal to obtain an audio signal, and meanwhile, the receiver singlechip is also used for extracting a text signal in the OOK signal and outputting the text signal on an LCD; when the OOK signal is poor, the receiver singlechip controls the output of the alternative electronic switch to be an FM digital audio signal, and the audio DAC performs digital-to-analog conversion to output the audio signal;

the audio output device outputs an audio signal;