中文摘要：

由于非线性和功率受限问题，深空通信中需要采用恒包络调制方式。FQPSK作为一种准恒包络调制技术受到广泛关注，但其信号包络仍有波动。文章在简要介绍FQPSK和增强型FQPSK基本原理的基础上，提出了一种恒包络改进型FQPSK，通过理论分析和计算机仿真证明了该调制方式具有完全恒定的包络，能够显著提高功率放大器的功率效率，频谱性能优于FQPSK；当采用OQPSK接收机接收时，其误码率性能比FQPSK提高ldB左右。

英文摘要：

The high power efficiency is more important for deep space communication than others communication systems. FQPSK is a new quasi constant envelope modulation and can be used for deep space communication. Firstly, the basic principle of FQPSK and Enhanced FQPSK was introduced. Then, a new constant envelope enhanced FQPSK was presented. Lastly, the per- formance of the new modulation was justified by analysis and computer simulation. It outperforms conventional FQPSK in both frequency efficiency and end to end bit error ratio performance.