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π/4-QPSK是一种线性调制技术,它是QPSK和OQPSK调制方式的修正形式.这些调制方式在静态条件下具有相同的频谱利用率、误码特性.而π/4-QPSK因其相位变化不经过原点,其调制包络变化比较小,因而功率放大器的非线性对其性能影响比较小.这种调制方式已被北美和日本的数字移动通信系统所采用.本文分析和比较了QPSK和π/4-QPSK不同调制、解调方式的特性,以延迟差分检测解调方案为例,分析了误码特性,并给出了在不同衰落条件下的计算机模拟性能.
π / 4-QPSK is a linear modulation technique that is a modified version of the QPSK and OQPSK modulation schemes that have the same spectral efficiency and error characteristics under static conditions, whereas π / 4-QPSK, The variation of the modulation envelope is small when the variation does not pass through the origin, and thus the nonlinearity of the power amplifier has a relatively small influence on the performance. This modulation method has been adopted by the digital mobile communication systems in North America and Japan. This paper analyzes and compares the QPSK and π / 4-QPSK modulation and demodulation methods. By taking the delay demodulation scheme as an example, the error characteristics are analyzed and the computer simulation performance under different fading conditions is given.