The medium frequency radar uses the circular polarization echoes to retrieve the wind fields and the electron density in the middle and upper atmosphere. To transmit and receive circular polarization echoes, a spaced antenna system, composed of a series of cross-dipoles, is used. Different demands are imposed for the circular characteristics in the echoes to retrieving the wind fields and the electron density, consequently, the receiver should be able to keep and remove the circular characteristics in the echoes. In most medium frequency radars, a hardware solution is adopted to remove the circular characteristics by making a phase adjustment to one of the two sets of signals associated with a cross dipole unit and then overlapping it with the other. Adjusting the phase at a medium frequency requires extra devices and a complicated system, what is more, the reliability of the device might be influenced by the environment. In this paper, the 4 I/Q components of a cross dipole unit are employed to compose the I/Q components of the signals associated with the circular polarization echoes. This method is very simple, and it only involves some basic calculations and judgments at each point. Theoretical analyses and numeral simulations show that this method is effective in removing the polarization characteristics.

medium frequency radar  /  receiving polarization echoes  /  I/Q decomposition