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一、问题的提出 PSK相干检测最佳接收机,要求本地相干参考除了在相位上与输入信号是相干之外,包络函数也要相同。然而在工程上遇到信道信号与相干参考包络函数不一致的情况。例如在对流层散射信道上进行数据传输,带内频率分集常常是用来克服快衰落的手段,然而数据率较高时,为了使带内分集的多频率的信号在时间域或频率域上都不重迭,信道信号的包络就不能采用理想的矩形包络信号,而要采用占据带宽较窄的其它包络波形。如升余弦包络调制
First, the issue put forward PSK coherent detection of the best receiver, requiring the local coherent reference in addition to the input signal in the phase is coherent, the envelope function must be the same. However, in the project encountered channel signal and coherent reference envelope function inconsistencies. For example, data is transmitted on a troposcatter channel. In-band frequency diversity is often used to overcome fast fading. However, at high data rates, in order to make in-band, multi-frequency signals in time domain or frequency domain Overlapping, the envelope of the channel signal can not adopt the ideal rectangular envelope signal, but adopt other enveloping waveforms that take up the narrower bandwidth. Such as raised cosine envelope modulation