What is IQ modulation?

IQ modulation means that data is divided into two paths, which are modulated by carriers respectively, and the two paths of carriers are orthogonal to each other. I is in phase and q is orthogonal.

IQ modulation is a problem of vector direction, and in-phase is a signal with the same vector direction; Quadrature component means that the two signal vectors are orthogonal (90 degrees apart); The IQ signal has one path of 0 or 180 and the other path of 90 or 270, which is called I path and Q path. They are two orthogonal signals.

Because I and Q are orthogonal (uncorrelated) in phase, they can be regarded as two signals. Therefore, the spectrum utilization ratio is doubled compared with single-phase modulation. However, IQ needs more demodulation than single phase (it must be strictly different from I by an integer multiple of 90 degrees, otherwise the Q signal will be mixed with I, and I will also be mixed with Q).

Extended data modulation has three purposes:

1) facilitates wireless transmission and reduces antenna size;

2) Frequency division multiplexing to improve communication capacity;

3) Improve the signal anti-interference ability. In order to make full use of the channel capacity and meet the different needs of users, communication signals adopt different modulation methods. With the rapid development of electronic technology and the continuous improvement of users' requirements for information transmission, the modulation mode of communication signals has experienced a development process from analog to digital and from simple to complex.

Baidu encyclopedia-IQ modulation