ETD

• distributed-element filters
• low noise amplifier
• noise figure
• RF chain

In the contemporary technological landscape, characterized by the widespread predominance of digital systems, the radio-frequency (RF) domain remains a notable exception, as analog circuitry is required to interface directly with the inherently analog nature of physical phenomena. RF modules, which are predominantly analog, perform a central function within spacecraft communication systems.
This thesis examines the radio-frequency reception chain integrated into a spacecraft receiver board developed by engineers at IngeniArs, utilized as Electrical Ground Support Equipment (EGSE) to receive signals transmitted by a spacecraft during ground-based operations in the UHF, L, and portions of the S band. These bands support applications including meteorology, climatology, telemetry, defense and security, global navigation satellite systems such as GPS and Galileo, and broadband communication services in regions lacking reliable terrestrial infrastructure.
A fundamental challenge in receiver design, and thus in the built hardware, is the severe attenuation of the input signal power due to long propagation distances, as predicted by link budget analysis.
Addressing this challenge requires the integration of RF, analog, and digital hardware subsystems as discrete components on a printed circuit board, resulting in a hybrid architecture for signal amplification, filtering, and demodulation.
Additionally, the wide dynamic range of the received signal power complicates signal integrity. This variability arises from the spacecraft’s motion relative to the ground station, causing rapid changes in received signal power, ranging from very weak levels at the edges of visibility to significantly stronger levels under optimal alignment conditions. Moreover, the limited and time-varying visibility window above the horizon imposes stringent constraints on signal acquisition time.
As a result, achieving an adequate signal-to-noise ratio (SNR) at the antenna input alone is insufficient unless the signal can traverse the entire reception chain without significant degradation. For this reason, particular attention must be devoted to the RF front-end stages to minimize noise figure, nonlinear distortion, and insertion losses.
Within this context, the thesis presents a detailed analysis of the assigned portion of the RF chain, corresponding to a section of the schematic of the complete receiver system provided by the company as the initial reference document.
The schematic is based on the interconnection of commercially available, vendordocumented RF components, whose selection and combination determine the overall receiver hardware. Based on the specified part numbers, a thorough examination of the corresponding datasheets was executed, succeeded by an assessment of each component’s role within the RF chain. Subsequently, S-parameter models were implemented in the Advanced Design System (ADS) environment to carry out circuit-level electrical simulations, allowing the behavior of both individual RF blocks and of the complete designated RF chain to be analyzed in terms of power losses, amplifier stability and noise figure.
Insights gained from the analyses and simulations motivated design improvements aimed at optimizing the existing RF chain.
These enhancements include the replacement of selected RF components with higher efficiency alternatives, the evaluation of the optimal placement of an RF component and the investigation of an alternative PCB stack-up.
Among these improvements, the design of custom distributed RF filters represents a significant contribution within the scope of this thesis. They were designed and implemented for use within the receiver’s frequency band, ensuring adequate isolation from external satellite and terrestrial interference without reliance on commercial filtering solutions.
The effectiveness of this filtering methodology was validated through electromagnetic simulations, entailing non-negligible computational effort.