Response of a Polarimetric Antenna to Ionospherically Propagated Signals

Abstract

The Earth's magnetic field causes the ionosphere to be birefringent at radio frequencies, which means that any system using ionospherically propagated radio waves, such as long distance broadcasting, high frequency (HF) skywave communications, over-the-horizon radar and oblique incidence sounders (OIS), will receive pairs of waves with different polarizations. In this paper we develop a model for the polarization of ionospherically propagated radio waves; the polarization is dependent only upon the strength and direction of the magnetic field at the location where the radio wave exits the ionosphere. This leads to the hemisphere of possible incoming directions of arrival to any particular receiver being divided into three distinct regions. We then use this model to predict the response of a polarimetric antenna to a transmitted OIS signal, and validate the model against real ionograms, including cases where all three polarization regions can be clearly observed.

Polarization Characteristics Distortion for L-Band Fully Polarimetric Radar Subject to Magnetized Plasma Sheath

“…The positive and negative signs correspond to the left-and right-handed circularly polarized waves, respectively. According to the angle between the applied geomagnetic field and the direction of EM wave propagation, the types of propagation can be quasi-transverse and quasi-longitudinal [32]. For the Very-High-Frequency (VHF) band and above, the propagation of radar waves in the plasma sheath can be regarded as quasi-longitudinal propagation [13].…”