针对可见光链路发射源发光二极管调制带宽有限的问题, 提出了一种基于DCO(直流偏置)CAP(无载波幅度相位调制)的可见光通信系统设计方案(DCO-CAP)。该方案采用正交滤波器组进行基带脉冲成形来传输时域实信号, 并利用直流偏置实现信号单极化。基于希尔伯特变换原理, 给出两种正交滤波器组冲激响应形式, 推导了DCO-CAP系统误码率的闭式表达式并分析了系统误码性能。仿真结果表明, 不同滤波器组的抗限幅噪声性能相异, 抗信道噪声性能一致。直流偏置取值存在最优解, 能够使系统可靠性达到最佳。

In order to overcome the problem of limited bandwidth of LED devices used in a Visible Light Communication (VLC) system, a bandwidth efficiency scheme named DCO-CAP, employing Carrierless Amplitude and Phase (CAP) modulation, is proposed in this paper. In the proposed scheme, by utilizing orthogonal shaping filter bank and adding DC bias, a real and positive signal is transmitted in visible light link. Two kinds of Finite Impulse Response(FIR) of orthogonal shaping filter bank is proposed on the basis of Hilbert transform. The Bit Error Rate (BER) performance is derived for DCO-CAP system in VLC channel. The simulation results show that two types of filter bank have different capability in combating with the clipping noise jamming and identical capability in depressing channel noise jamming. It is proved that the optimal DC bias exists, which makes DCO-CAP system to obtain the best reliability performance.