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, vendor
documented 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.