使用matlab自带的fsk调制解调函数进行4fsk的调制解调，对比原二进制码流和解调后二进制码流完全正确，可以作为对4fsk的初步学习(Using the FSK modulation and demodulation function carried by MATLAB to modulate and demodulate 4FSK, compare the original binary stream and demodulation binary stream exactly right, can be used as the primary learning of 4FSK.)