Experimental estimation of propagation impairments of a satellite-to-helicopter radio channel at Ku band

Results of a satellite-to-helicopter radio channel characterization experiment carried out at 14.25GHz are presented. A Sweep Time Delay Cross Correlation (STDCC) sounder using a Pseudo-Random Binary Sequence (PRBS) was used for the experiment. From the measurements, signal fading, delay and Doppler spread are estimated. Results show that delay spread will have no significant effect for 36 MHz and 72 MHz transponders, so no channel equalization would be required. However, a periodic signal fading exists, due to the blockage of the main radio signal by the rotor blades. Compensating this fading would require some kind of Automatic Gain Control or diversity technique at the helicopter.