چكيده به لاتين
Todays the various applications of satellite positioning systems, especially GPS, are not hidden. These are from everyday applications to very sensitive applications in various industries such as Mapping, Geodesy, Military industries and so on. Despite the need for accurate positioning in these industries, there are always various factors such as receiver accuracy, processor accuracy, error correction algorithms, positioning data analysis software, satellite receiver antenna performance, etc., that can influence the overall accuracy of positioning. In designing GNSS receiver antennas, along with all the necessary parameters, knowing the exact point of the phase center as well as having a stable phase pattern, means that the changes of the phase center according to all dimensions and angles of space are zero, are very important. It can have a significant impact on millimeter performance and accurate satellite positioning.
There are two main goals in this thesis; The first goal is to analyze the theory and explain the way to find the phase center of an antenna according to the phase pattern information of its electrical field in all angles of space and introduce a method to optimize the changes of the phase center of an antenna, which are discussed in the third chapter. Using the MATLAB code and genetic algorithm, and considering the phase of the right hand electrical field of the array antenna in all angles, the phase center of the antenna can be obtained, and after that to stabilize the phase center of the antenna and reduce the phase changes, with the new MATLAB code and genetic algorithm, we find the phases applied to the array antenna elements, and the new phase center of the phased array antenna are obtained. The second goal is to introduce a new method of phase center measurement of an unknown antenna (without having valid phase information), which will be described in the fourth chapter in an operational way, and we will see that with considering the value of the length that is obtained from Differential GPS with using commercial and known antennas and receivers, and comparing with the same value that is obtained with an unknown antenna, we can reach the value of the length with an error less than 0.25% over three x,y,z directions of the length and an error less than 1 cm in calculated phase center of the unknown antenna (the theoretical and practical difference of the phase center), which is less than the computational error of the reference commercial antenna according to its datasheet.
