A SIMO System of Digital Transmission Through the Ionospheric Channel

This paper presents a SIMO system of trans horizon transmission through the ionospheric channel in the HF band (3- 30 MHz). The technical challenge is to increase significantly the data transfer rate if compared with standard modems (typically 4.8 kbits/s in a 3 kHz bandwidth). A multi channel receiving system is connected to an original array of collocated antennas : this device appears as polarization sensitive and, consequently, makes the separation of the incident multi paths efficient though there is no spatial diversity. A blind spatio temporal equalization, based on the Constant Modulus Algorithm (CMA), balances the distortions of the spectrum in an extended bandwidth of 9 kHz. An experimental radio link has been tested with a range of 1300 km. The corresponding results underline the improvement of the bit transfer rate which attains 30 kbits/s in a 9 kHz bandwidth resorting to a 16 QAM waveform.