Projeto de um circuito transceptor de frequências para integração em nanossatélites

Abstract

In this work, the design and characterization of a transceiver to operate at 401 MHz in the uplink (front-end) and at 2.26 GHz in the downlink (back-end) are discussed. The main goal is to use the developed transceiver for characterization of the uplink and downlink antennas installed onto the engineering model of a nanosatellite under development ate the Laboratory of Electromagnetics, Microwaves and Antennas (LEMA). The present work describes a theoretical study of a transceiver topology for the nanosatellite of the CONASAT project. The first part of the text presents a literature review covering the theoretical background related to electromagnetic wave propagation in free-space, the design of radio communication links, and the design of microstrip lines and coplanar waveguides (CPW). Also, a general review of the de_nitions and characteristics of communication components, such as transmitters, receivers and transceivers, is included. The characterization of the individual components has been done by measuring the Sparameters of ampli_ers, _lters and mixers. In a further step, all the components have been integrated into a single printed circuit board. The measurement setup used for this experimental characterization is also described. The overall measured gain of the constructed prototype was 44.25 dB, which is larger than the expected value estimated by considering the measured S-parameters of the individual components. The main reason for this is attributed to the absence of coaxial cables and conectors used for the measurements prior to the design of the _nal prototype. As a complementary part of this work, a study concerning the design and implementation of a low-pass _lter in microstrip technology to operate at 401 MHz is discussed. The design was developed as an alternative to LC-_lters, which are generally more compact than microstrip _lters at UHF frequencies.