Browsing by Author "Youssouf, Abdouraouf Said"

In this dissertation, a characterization and comparison between the effects of Electron irradiation on low noise amplifiers (LNAs) implemented in a Silicon-Germanium (SiGe) Heterojunction Bipolar Transistor (HBT) and Gallium-Arsenide (GaAs) HBT technologies, respectively, was carried out. Nowadays, commercial on the shelves (COTS) LNAs have been used in CubeSat communication system lunched in Low and Medium Earth Orbits. It therefore believed that the electron radiation in space may degrade the LNAs performance and lead to it failure. This is shows the importance of such investigation in evaluating and comparing the performance of the GaAs and SiGe LNAs which represent an important module in the front end of the communication receiver system. Two samples of GaAs and SiGe have been selected: the SiGe BFU730F and the ADL 5523 GaAs LNAs which are respectively cover a frequency range of 2.3 to 2.7 GHz and 400MHz to 4 GHz. The SiGe BFU730F achieves a peak gain of 21.5 dB and a peak of 0.8 dB noise figure within the frequency range before radiation. While the ADL 5523 GaAs LNA achieves a peak gain of 21.5 at 900 MHz; and it achieves approximately 15 GHz of gain, with a noise figure (NF) of 0.9 dB in the interested band of 2.3 GHz. Samples were irradiated with 3 MeV Electron doses ranging from 50 kGy to 250 kGy. The results show the increase of the NF and the drop of the gain of both LNAs which indicate that both SiGe and GaAs HBT technologies have been affected by the electron Irradiation. However, the GaAs LNA exhibits to be robust with a minimal degradation compare with the SiGe LNA, where it can still achieve a peak gain of 12 dB and a mean of Noise figure below 3 dB. However, the SiGe degraded with a drop of the gain down up to 7 dB and an increase of the Noise Figure above 3 dB within the frequency range.

To improve performance and reduce the cost of the inter-satellite communication systems, academia and industry are active in discovering adequate solutions. Both satellite industry and communication start to work on a new paradigm in integrating the space, aerial, and terrestrial networks to form the three-dimensional of the 5G. Low Earth Orbit presents a niche for such projects. However, spacecraft, space stations, satellites, and astronauts are exposed to an increased level of radiation when in space, so it is crucial to evaluate the risks and performance effects associated with extended radiation exposures in missions and space travel in general. This thesis focuses on the LEO, especially in the near-equatorial radiation environment, and how the particles interact with materials in general and with inter-satellite optical wireless communication systems, in particular. The exposed dosage due to the LEO space environment radiation sources, as a function of orbital altitude, orbital inclination, and duration of the inter-satellite Optical Wireless Communication system under radiation, is investigated using existing empirical models. Radiation experiments supported with simulations have made it possible to obtain and evaluate the electron and neutron radiation impact on the optoelectronic components, namely the laser diode at the transmitter and the photodiodes at the receiver subsystems the optical link performance while onboard. Results have shown the degradation of the optoelectronics devices' performance under both radtions, which is affected the performance of the link at the system level. Results show as well the sensitivity of the transmitter subsystems compared to the receiver subsystem. The neutron radiation has been induced a system degradation up to 85% while the electron radiation up to 80%. This shows the importance of such an investigation to predict and take necessary and suitable reliable quality service for future space missions.