研究目的
To design a voltage reference comparator circuit for the receiver circuit in a visible light communication (VLC) system to detect data signals transmitted via white LEDs.
研究成果
The designed voltage reference comparator circuit effectively detects data signals in the VLC system at frequencies around 9.615 kHz and distances up to 100 cm. The comparator allows for adjustable voltage reference to achieve a 50% duty cycle in output signals, enabling reliable data communication. Future work could focus on extending the range and improving resistance to environmental interference.
研究不足
The VLC system is limited to indoor use with constant transmission distances due to interference from sunlight and low-frequency noise. The communication distance is restricted to 50-100 cm, and the system may not perform well in environments with high ambient light or varying conditions. Optimization is needed for longer distances and better noise immunity.
1：Experimental Design and Method Selection:
The experiment involves designing and testing a VLC system with a transmitter circuit using an LED driver and a receiver circuit with a photodiode, amplifier, and comparator. Manchester encoding and decoding are implemented using an FPGA board for data modulation and demodulation. The UART protocol is used for serial communication at a frequency of
2：615 kHz. Sample Selection and Data Sources:
Data signals are generated using MATLAB on a computer and transmitted over distances of 50 to 100 cm in an indoor environment. Luminous intensity is measured using a luxmeter.
3：List of Experimental Equipment and Materials:
Includes FPGA board, white LEDs (3W and 5W), photodiode, operational amplifiers (OPA134PA), buffer circuits (SN7407N), LED driver (ULN2560N), resistors, adjustable resistors, power supplies (
4：3V, 5V, 22V), and a luxmeter. Experimental Procedures and Operational Workflow:
Steps include setting up the transmitter circuit to send Manchester-encoded data via LEDs, receiving light signals with a photodiode, amplifying the voltage signals, comparing them with a reference voltage using a comparator circuit, and decoding the data back to the computer via FPGA. Measurements are taken at various distances.
5：Data Analysis Methods:
Analysis involves measuring luminous intensity, voltage levels, duty cycles of output signals, and comparing transmitted and received data bits using oscilloscope waveforms and calculations of mode values for voltage reference adjustments.
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