The initial procedure is:
ich 1=ich。 * kmod
qch 1=qch。 * kmod
x = ich 1+qch 1 * sqrt(- 1)； ? Using this program, you will find that the generated constellation points are not standard constellation points.
The constellation points are as follows:
The reason is that when performing QPSK modulation, there should be alternate sign inversion. In the program, the original sequence is converted into bipolar, that is, this code.
ich0=ich。 *2- 1;
qch0=qch。 *2- 1; But it is not used. The way to correct it is to use bipolar code for modulation, that is, to change it to
ich 1=ich0。 * kmod
qch 1=qch0。 * After KMOD correction, the constellation points are normal, so there will be no problem in demodulation.