Available at: https://digitalcommons.calpoly.edu/theses/3334
Date of Award
6-2026
Degree Name
MS in Electrical Engineering
Department/Program
Electrical Engineering
College
College of Engineering
Advisor
Payam Nayeri
Advisor Department
Electrical Engineering
Advisor College
College of Engineering
Abstract
In recent years, there has been growing interest in high-speed communication for small satellites. Achieving higher communication speeds will enable any experimental CubeSat to conduct experiments at higher rates and allow further research into SAR and deep-space exploration. At Cal Poly, the CubeSat Lab has mainly operated at 9600 baud and utilized the Ultra High Frequency (UHF) amateur radio band. While it has proven itself resilient, the UHF band lacks the infrastructure to support higher-bandwidth communication systems. To address this gap, this work presents a prototype space-side downlink RF front end comprising an upconverter, a power amplifier (PA), and a PLL. The proposed system takes in an IF of 2.4 GHz and outputs an RF of 10 GHz. The IF frequency was chosen to accommodate a second 2.4 GHz uplink channel. The goal of this work is to develop the background and some of the testing behind a 10 Mbps link at maximum elevation and a 1 Mbps link at minimum elevation. Each sub-system was tested individually. Gain and compression measurements were performed on the PA, while operational testing was performed on other components, such as the PLL, to confirm functionality. Bench testing the PA demonstrates functionality; however, with increased losses in the transmission lines, some discrepancies arise. Furthermore, the PLL exhibits leakage of the VCO’s fundamental and second harmonic; however, this issue is successfully mitigated by the band-pass filter after the PLL. Moreover, the upconverter testing yields similar discrepancies from the expected total insertion gain due to losses in the transmission line and unaccounted-for losses in the measuring cable at the spectrum analyzer input. Integrating the PLL and the upconverter with two SDRs, the system is fully capable of preserving data, as an image was transmitted and received with 0 bit errors at a 2.5 MHz channel bandwidth.