为了验证数字脉冲间隔调制(DPIM)在紫外光通信中应用的可行性, 设计了基于FPGA的DPIM调制和解调系统。调制过程在锁存器的控制下, 将串并转换后的数据输入比较器, 并与计数值相比较产生DPIM调制信号; 在解调端, 利用计数器检测相邻光脉冲间的空时隙数, 在锁存器的控制下, 恢复得到原始数据。以16-DPIM为例, 随机输入一组串行二进制数据, 经过调制系统得到了16-DPIM信号; 同样随机输入一个16-DPIM调制信号, 通过解调系统恢复得到了原始数据。并在此基础上提出了一种新型的双幅度、定长DPIM调制方式, 能更好地弥补DPIM符号长度不固定的缺陷。

In order to verify the feasibility of digital pulse interval modulation(DPIM)used in ultraviolet(UV) communication, a DPIM modulation and demodulation system was designed based on field programmable gate array (FPGA). The deserialized data was input into the comparator under the control of latch during modulation process, and the DPIM modulation signal was output through comparing with the count value. In the demodulator, the number of free slot between neighbor pulses was detected by counter, and the original data was acquired through recovering under the control of latch. In the case of 16-DPIM, we input a set of serial binary data randomly and output 16-DPIM signal in modulation system. In the same way, we input a 16-DPIM modulation signal randomly and recovered the original data in demodulation system. On the basis of this analysis, a new dual-amplitude fixed-length DPIM modulation which could make up the lack of the DPIM symbol length change was proposed.