利用matlab软件设计并仿真下面的无线通信系统。模拟信源为单音频信号。模拟调制方式为DSB。信道为多径信道（仿真中2径），信道中噪声为加性高斯白噪声。采用相干解调接收。画出了解调器输出端性能曲线与点信噪比SNR的关系。

-Software design and simulation using matlab the following wireless communication systems. A single analog audio signal source. Analog modulation of DSB. Channel multi-path channel (simulation 2 diameter), channel noise is additive white Gaussian noise. The use of coherent demodulation receiver. Draw the output of the demodulation performance curve and the point of the relationship between signal to noise ratio SNR.