The main mission of OTM(On-The-Move) satellite communication system is to provide satellite communication service while its platforms are moving. So it should have a capability to maintain a reliable communication channel when it travels at high speeds or in a severe fluctuation region. In addition, it needs to be small size and light weight to be installed on various vehicles.
In order to keep a reliable link, first, this paper proposes a simple multi-mode monopulse tracking system.
Conventionally, multi-mode monopulse tracking systems are applicable to large antenna systems such as fixed satellite earth stations due to their complexities in spite of their precision tracking performance.
This thesis presents a small multi-mode monopulse system applicable to the OTM satellite communication system which has only one mode coupler with a pair of slots using a feature of circular polarized received signal. Here, a tracking error signal is defined using fundamental and high-order modes before azimuth and elevation errors are derived from the amplitude and phase of the tracking error signal.
Also, in this thesis, a double-input single-output architecture of an LNA(Low Noise Amplifier) is presented to realize a light weight and small system suitable to be mounted on vehicles. In spite of advantages of the double-input single-output architecture of an LNA such as the reduction of the number of physical channels, it results in a time-varying phase error between a fundamental mode path and a high-order mode path. This dissertation shows that the error can be corrected by adding pilot signals to the LNA and using signal processing, and also gives the measured data on the phase error correction.
An OTM terminal for the satellite communication uses an OTM satellite communication system mounted on a vehicle and offers satellite communication service while moving via the Ka band GEO(Geostationary Earth Orbit) satellite. Hence, it is necessary to measure channel characteristics of an OTM terminal in the operating areas and throughly analyze the measured data for improving the link availability of the system.
This dissertation describes channel characteristics in the operating areas of OTM terminals, which are kinds of slow fading from blockage environments. In order to analyze the channel characteristics, the communication channel between the Koreasat-5 and an OTM terminal is measured and recorded in downtown areas of Daejeon city, highway and national road environments, using the beacon signal of the Koreasat-5, and the measured data are statistically analyzed and then compared with one another.
The statistical evaluations of the satellite channel have been performed by using a probability density function and the Markov model and then average connection duration(ACD), average fade duration(AFD), and level crossing rate(LCR) of each environment are presented.
At last, an M&S(Modeling & Simulation) method using three dimensional geographic information is proposed as an alternative method of channel characterization.