Estimation of diversity improvement for satellite-to-helicopter radio channel at Ku-Band

This contribution introduces the results obtained for the satellite-to-helicopter radio channel characterization in the Ku-Band. For the wideband sounding, the results show that, in terms of wideband radio channel characterization, the root mean square delay spread was small enough to allow using 32 or 72 MHz satellite transponders with no need of equalization. Regarding the narrowband radio channel analysis, we observed two important propagation phenomena due to the rotor blades: average power attenuation related to the obstruction of the direct ray, and power level oscillation dependent on the amplitude of the received multipath components. The signal fading related to both narrowband impairments could be compensated by using the spatial diversity technique. Additionally, we also analysed the signal obtained using polarization diversity in the receiver end in a setup simulating a satellite located behind the helicopter so totally blocking the direct ray. Generally speaking, we concluded that it is possible to implement an Automatic Gain Control or time diversity to compensate the both multipath and level fading.