用频率300HZ正弦波调制频率30KHZ的正弦波，采用同步解调，观察调制信号、已调信号、解调信号的波形、频谱以及解调器输入输出信噪比的关系。-300HZ frequency sine wave with a sine wave modulation frequency 30KHZ, using synchronous demodulation, the modulated signal was observed, modulated signal, the waveform of the demodulated signal, and the spectral output of the demodulator input signal to noise ratio relationship.