Desarrollo de un modulador PSK para transmisión de telemetría satelital.

Abstract

Low-order digital modulations are the first choice in applications associated with satellite telemetry transmission. This preference stems from the ability of these schemes to provide link robustness, which is required to guarantee the controllability of the flight segment from the ground station. Furthermore, given the nature of the application, SWaP-C criteria also play a highly relevant role in the design of the systems that must implement these functionalities, which is even more important in the small satellite segment. The use of FPGAs is presented as an alternative to traditional digital systems, ensuring compliance with these criteria by resulting in less expensive, lighter, smaller, and lower-power solutions. Furthermore, this technology allows for implementation changes without requiring hardware modifications, which represents a significant advantage in terms of flexibility and adaptability for satellites once they have been launched into orbit. This work develops a configurable, FPGA-based digital PSK modulator for TT&C applications in satellite communications. In addition to the modulators, the design includes several auxiliary blocks typically used in this type of application, dedicated to data conditioning and formatting. These include randomization, convolutional coding, timing mark introduction, and storage structures. The data to be modulated, as well as some configuration parameters, are introduced into the design through standard AMBA, AHB, and APB interfaces, allowing easy integration of the modulator into more complex designs. Testbenches are implemented for the different modulation system configurations, allowing simulations to be run to verify their correct operation. In the analog field, LTSpice is used to perform circuit simulations that generate in-phase and quadrature signals from the modulated signals. These are used to obtain the constellation and vector diagrams for each of the modulations, thus providing another alternative for checking the operation of the modulators.