提出了一种非限幅四相相移键控(QPSK)类正弦调制技术，并将其运用到大气激光通信系统中。介绍了大气激光通信信道模型，给出了非限幅QPSK类正弦调制的大气激光通信系统模型。在此基础上，对采用非限幅QPSK类正弦调制和采用直流偏置副载波强度调制的大气激光通信系统在无湍流和弱湍流信道下的功率利用率、误码率、中断概率和信道容量进行了分析和比较。结果表明，非限幅QPSK类正弦调制具有更好的抗噪声性能、更高的功率利用率、较低的中断概率及较高的信道容量，提高了大气激光通信系统的性能，可满足大气激光通信系统的需要。

A non-clipped quadrature phase shift keying (QPSK) sine-like modulation technology is proposed in this paper and applied to the atmospheric laser communication system. The atmospheric laser communication channel model is introduced and the atmospheric laser communication system model of non-clipped QPSK sine-like modulation is given. Based on there, the power efficiency, bit error rate (BER), outage probability and channel capacity of atmospheric laser communication systems which adopt non-clipped QPSK sine-like modulation and direct current bias sub-carrier intensity modulation are compared and analyzed. The results demonstrate that the proposed scheme has better anti-noise performance, higher power utilization, lower outage probability and higher channel capacity, and improves the performance of atmospheric laser communication system. The scheme can satisfy the requirements of atmospheric laser communication system.