A Hybrid Active-Passive Single-Order Equalizer for Visible Light Communication Systems

Although visible light communication (VLC) can provide high throughput and low latency, the inherent limited bandwidth of light-emitting diode (LED) remains its performance bottleneck. Thus, an effective equalizer with low complexity and good pervasiveness is indispensable to tackle this issue. In this letter, a hybrid active-passive single-order equalizer is proposed to expand LED bandwidth and support the design of resource-constrained transmitter front-end. Different from other active-passive equalizers, the active part of the proposed method can provide a lower output impedance for equalizer. Then, the effectiveness of the proposed equalizer is verified based on a practical experimental test-bed and it can extend the 3-dB bandwidth of the LED from 9 MHz to 181 MHz even with a trivial transistor. Moreover, the established red-blue-green-yellow (RGBY) LEDs-based VLC system is designed to verify the pervasiveness of the proposed equalizer. In particular, an achievable overall rate of 3.12 Gbps with a transmission distance of 4 m is obtained in the VLC system and the corresponding bit error ratio performance is below $1.2\times 10^{-6}$ .