جستجوی مقالات مرتبط با کلیدواژه « پترن تشعشعی » در نشریات گروه « برق »

Radio Telecommunication between satellites and ground stations is considered as one of the key parts of space missions. Since controlling a satellite is carried out using Telemetry-Telecommand (TT&C) and positioning links, these two satellite links are crucial. Unlike  ground antennas, there are many requirements in designing space antennas depending on the type of communication. Due to the rotation of the satellite around the Earth and the need to maintain the communication with the satellite, one of the most important requirements in designing TT&C and positioning links antennas is to create a relatively omnidirectional radiation pattern with circular polarization to cover at least 300 degrees of space. On the other hand, the location of antennas on the satellite, type of satellite structure and dimension considering mass budget constraints are other important challenges  which determine the antenna layout and location, as well as the antenna type.In this paper, the challenges in designing the TT&C and positioning links antennas for a remote sensing satellite in VHF and UHF frequency bands are investigated, then the designed antennas are fabricated. Finally, the simulation and test results are compared.

In this work the inverse transfer function of the measurement room is obtained using a linear and RLS (recursive least-squares algorithm) adaptive filter. At first, an antenna with known pattern (reference antenna) is placed in the test zone to obtain the optimal tap weights of the adaptive filter. Once the filter converges, the learning stage finishes. After that the reference antenna is replaced with the test antenna and its pattern is measured and the data of the measurement is filtered by the optimal tap weights adaptive filter. The filter cancels the stray signals (reflected and scattered signal) and produces the radiation pattern of the test antenna. This technique is superior to that of others because it has better accuracy and it is less costly.