STUDY OF THE REQUIRED CROSSPOLAR PROTECTION RATIO IN G-PAL TV FM SATELLITE TRANSMISSIONS PLANNING

An study including simulation and a measurement campaign using live TV broadcast satellite signals and receiving commercial equipment has be en carried out to investigate the required crosspolar protection ratio at the terrestrial receiving antenna for satellite transmissions plan ning. This experiment provides useful and realistic conclusions for ef ficient channels allocation of in the spectrum band of broadcast satel lite systems, as for example, frequency offset required between crossp olar channels depending on the crosspolar rejection at the receiving a ntenna, for a certain degree of video signal impairment due to the cro sspolar channel interference effect, and taken also into account the n oise contribution on the signal. A worst case in frequency offset valu e, i.e. larger subjective impairment on the picture at equal carrier t o noise ratio (CNR), has been detected around 5 MHz (near the chroma c arrier in G-PAL system 4.43 MHz) only for high values of CNR analyzed 21 dB and 18 dB. Also, different subjetive degradation on the image du e to crosspolar channel interference and noise has been observed and t heir particular contributions to impairment has been valued.