Usually, microwave signals are not used for ionospheric propagation. The reason is

The microwave frequency range lies between 300 MHz to 300GHz.

Beyond 40 MHz, frequency doesn’t get reflected back by the ionosphere, it can pass through the ionosphere, due to this microwave frequencies are not suitable for ionospheric propagation. Microwave frequencies are used in Satellite communication.

Important Points

IONSPHERIC PROPAGATION:

In radio communication, skywave or skip refers to the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere.

Since it is not limited by the curvature of the Earth, skywave propagation can be used to communicate beyond the horizon, at intercontinental distances. It is mostly used in the shortwave frequency bands.

We can understand ionospheric propagation by the given figure.