This work presents the development of a prototype of a microwave oscillator with a fixed frequency, around 3 GHz, with microstrip lines, using a high frequency and low noise bipolar transistor, through the scattering parameters S, with the aim of support the practical activities developed in the RF laboratory of the electrical engineering course at IFSUL. Computational tools are used to develop the equations for the conversion of the scattering parameters, for the impedance matching calculations, for the fabrication of the microstrip lines and for the transistor polarization. Finally, two prototypes are built and the results are presented. The prototypes worked properly, highlighting the one designed with the aid of a computational tool.