Transmission device of DCO-OFDM visible light communication system

Abstract

The invention provides a transmission device of a DCO-OFDM visible light communication system. The transmission device comprises a pre-emphasis module, a digital-to-analog conversion module, a protection module, a filter, an amplitude attenuator, a power amplifier, a Bias-Tee and a constant current source module which are connected in sequence; a quantized digital signal is transmitted to the pre-emphasis module for digital pre-emphasis compensation operation; after that, the quantized digital signal is transmitted to the digital-to-analog conversion module to generate an analog signal; the overload pulse of the analog signal is absorbed by the protection module, the analog signal is filtered by a filter module, adjusted by an amplitude attenuator module, and subjected to power amplification by a power amplifier module; and a Bias-Tee module couples a bias current from the constant current source module and a signal from the power amplifier module, and then uses the coupled signal to drive an LED lamp to emit an optical signal. According to the transmission device of the DCO-OFDM visible light communication system provided by the invention, digital pre-emphasis compensation can becarried out on transmitted signals, LED frequency response characteristics can be optimized, and noises in DCO-OFDM baseband signals can be reduced.

Description

technical field [0001] The present invention relates to the technical field of wireless optical communication, in particular to a transmitting device of a DCO-OFDM visible light communication system, comprising a sequentially connected pre-emphasis module, a digital-to-analog conversion module, a protection module, a filter, an amplitude attenuator, a power amplifier, and a Bias -Tee bias and constant current source module. Background technique [0002] In a visible light communication system, an optical signal transmitting device is an important component. For optical signal transmission devices, what needs to be solved most is how to expand the available bandwidth of LEDs and reduce the noise in OFDM baseband signals. For expanding the available bandwidth of LEDs, most of the past used equalizing circuits or resonant circuits to increase the signal power, which is equivalent to extending the bandwidth of LEDs, but the following problems will occur: On the one hand, due to...

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Problems solved by technology

For expanding the available bandwidth of LEDs, most of the past used equalizing circuits or resonant circuits to increase the signal power, which is equivalent to extending the bandwidth of LEDs, but the following problems will occur: On the one hand, due to the limitations of hardware circuits, It cannot compensate the bandwidth of the LED well; on the other hand, since the frequency response of the LED is also related to the magnitude of the bias current of the LED, compensation purely from the signal power may not be able to achieve the desired effect

For reducing the noise in the OFDM baseband signal, the previous circuit design has not considered this factor, but the interference of the noise to the baseband signal cannot be ignored in the implementation

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