Study of Rain Attenuation using Ka and Ku-band frequency beacons at Delhi Earth Station

Abstract- Quantitative analysis and prediction of radio signal attenuation is necessary in order to improve the reliability of satellite -earth communication links and for economically efficient design. Ka band suffers large attenuation due to rain and India being a tropical region, the impact of rain on Ka band propagation is more severe. None of the existing ITU -R models is validated for prediction of rain attenuation for tropical region and hence it calls for a propagation experiment to validate the existing models.  In this paper, study on the effect of rain attenuation on the propagation of satellite signals in Ka band has been carried out by receiving signal of frequency 20.199827 GHz from the IPSTAR (Thaicom-4 Satellite) and a Ku band beacon signal of frequency 11.6985 GHz from GSAT-8 satellite at Delhi Earth Station of ISRO. It has been observed that the difference between the ITU-R predicted rain attenuations and the observed rain attenuations for Ka band varies from 1.5 dB to 4.5 dB and that for Ku band varies from 2.1 dB to 3.7 dB.  The long-term probability distribution of fade slope for any definite base value of attenuation is symmetric on both positive and negative sides and this feature is independent of frequency. This observation corroborates earlier findings.

Ionospheric scintillation characteristics in IRNSS L5 and S-band signals

Ionospheric scintillation is a common phenomenon observed over the low latitude Indian region. It occurs due to the rapid fluctuations in phase and amplitude of the signal and affects Global Navigation Satellite Systems (GNSS) very severely, especially in L-band. Severe scintillation leads to loss of lock at the receiver, which affects user position accuracy. Ionospheric scintillation mainly depends on solar cycle, user latitude, local time, season and elevation angle of the satellite. It also depends on the frequency of the transmitted signal. Usually, lower frequencies experience higher scintillation at ionosphere. In this paper, ionospheric amplitude scintillation effect on Indian Regional Navigation Satellite System (IRNSS) L5 and S-band frequencies is studied on the basis of computed S4 index from Carrier to Noise (C/No) ratio measurements from IRNSS receivers installed at New Delhi and Ahmedabad. A comparison of L5 and S-band scintillation is done. A confirmation of scintillation phenomenon is also carried out using co-located GPS Septentrio (PolarRxS REO) receiver at frequency L1. It is, further, found that the scintillation occurrence is mostly in post sunset periods and may result in frequent loss of lock at L5 band during these periods

Ionospheric scintillation characteristics in IRNSS L5 and S-band signals

15-19Ionospheric scintillation is a common phenomenon observed over the low latitude Indian region. It occurs due to the rapid fluctuations in phase and amplitude of the signal and affects Global Navigation Satellite Systems (GNSS) very severely, especially in L-band. Severe scintillation leads to loss of lock at the receiver, which affects user position accuracy. Ionospheric scintillation mainly depends on solar cycle, user latitude, local time, season and elevation angle of the satellite. It also depends on the frequency of the transmitted signal. Usually, lower frequencies experience higher scintillation at ionosphere. In this paper, ionospheric amplitude scintillation effect on Indian Regional Navigation Satellite System (IRNSS) L5 and S-band frequencies is studied on the basis of computed S4 index from Carrier to Noise (C/No) ratio measurements from IRNSS receivers installed at New Delhi and Ahmedabad. A comparison of L5 and S-band scintillation is done. A confirmation of scintillation phenomenon is also carried out using co-located GPS Septentrio (PolarRxS REO) receiver at frequency L1. It is, further, found that the scintillation occurrence is mostly in post sunset periods and may result in frequent loss of lock at L5 band during these periods

Rain attenuation using Ka and Ku band frequency beacons at Delhi Earth Station

45-50Quantitative analysis and prediction of radio signal attenuation is necessary in order to improve the reliability of satellite-earth communication links and for economically efficient design. The Ka band suffers large attenuation due to rain and as most of the parts of India are situated in the tropical region, the impact of rain on Ka band propagation is severe. None of the existing ITU-R models is validated for prediction of rain attenuation over India and only a few over the tropical region and hence, it calls for a propagation experiment to validate the existing models. In this paper, study on the effect of rain attenuation on the propagation of satellite signals in Ka band has been carried out by receiving signal of frequency 20.199 GHz from the IPSTAR (Thaicom-4 Satellite) and a Ku band beacon signal of frequency 11.698 GHz from GSAT-8 satellite at Delhi Earth Station of ISRO. It has been observed that the difference between the ITU-R predicted rain attenuations and the observed rain attenuations for Ka band varies from 1.5 to 4.5 dB and that for Ku band from 2.1 to 3.7 dB. The long-term probability distribution of fade slope for any definite base value of attenuation is symmetric on both positive and negative sides and this feature is independent of frequency. This observation corroborates earlier findings