Uydu haberleşmesi için anten ve RF ön uç devre tasarımı

Satellite communication is an indispensable technology due to its wide range of applications and usage scenarios. Frequent bands such as S, C, X, Ku, and Ka are typically preferred in the design of ground stations for satellite communication. This dissertation aims to design an antenna with circular polarization in the X-band frequency range, a low-noise amplifier with high gain, and a frequency downconverter with low image rejection. Ground station designs require large-scale reflective antenna systems based on the usage scenario and the G/T value. In this design, subsystems including an X-band feed antenna capable of generating the tracking signal from an electromagnetic perspective for a ground station with a diameter of 7.3 meters, a low-noise amplifier with high gain that minimally alters the noise value of the received signal, and a frequency downconverter that downconverts the high-frequency signal to the IF frequency band without compromising signal quality were designed. The X-band feed antenna consists of a septum polarizer, a quadruple tracking antenna, and a corrugated antenna. The feed antenna achieves a gain above 19.3 dBi with a variation of ±0.3 dB across the band. The impedance match (S11) is less than -15 dB. First, the septum polarizer structure was designed. A corrugated antenna structure was created and combined with the septum polarizer structure to increase antenna gain. Once the desired antenna aperture was achieved, a quadruple antenna structure with tracking capability and suitable dimensions was added to the system. Another subsystem in the ground station system is the low-noise amplifier, which is designed with four stages. The first two stages were designed using transistors to ensure low noise performance. In comparison, the final two stages were designed using amplifiers to achieve both gain and the desired output P1dB value. The low-noise amplifier has a gain exceeding 50 dB, a noise value below 0.7 dB, and input and output impedance match below -15 dB. The subsequent subsystem in the system is the frequency downconverter unit. The frequency downconverter was designed using a single-conversion superheterodyne architecture. The RF signal received at the X-band frequency is designed to provide an IF signal output with a center frequency of 720 MHz and a bandwidth of 400 MHz. In conclusion, the developed subsystem structures are suitable for use in ground stations.