"8.8 FSK调制原理及电路设计"

8 FSK调制是一种通过使用不同频率的载波来传输数字信号的调制技术。在二进制频移键控（FSK）中，使用两个不同频率的载波来代表数字信号的两种电平，接收端通过解调将不同频率的载波信号转换为数字信号，从而完成信息传输过程。FSK信号的产生有两种方法，一种是直接调频法，即通过数字基带信号来直接控制载波振荡器的频率；另一种是频率键控法，通过控制转换开关选择不同频率的高频信号来实现FSK调制。频率键控法产生的FSK信号具有很高的频率稳定度和转换速度，波形也较为优秀，但在频率转换瞬间会出现相位不连续的现象。频率键控法的原理电路通常包括两个独立的振荡器和分频器，通过控制转换开关实现FSK调制。Overall, FSK modulation is a modulation technique that uses different frequencies of carrier waves to transmit digital signals. In binary frequency shift keying (FSK), two different frequencies of carrier waves are used to represent two digital signal levels, and the receiving end demodulates the different frequency carrier signals into digital signals to achieve the information transmission process. FSK signal generation can be done by direct frequency modulation or frequency keying. Direct frequency modulation involves using the digital baseband signal to directly control the frequency of the carrier oscillator, while frequency keying involves using a control switch to select different frequencies of high frequency signals for FSK modulation. The FSK signal generated by frequency keying has high frequency stability and fast conversion speed, and produces high quality waveforms. However, there may be phase discontinuities at the moment of frequency switching. The principle circuit of frequency keying method typically includes two independent oscillators and dividers, and utilizes a control switch to achieve FSK modulation.