Análise de desempenho de um oscilador colpitts com um sensor capacitivo na malha seletiva em frequência.

Abstract

This work presents the architecture and performance analysis of a Colpitts of a Colpitts oscillator with a capacitive sensor in its frequency-selective loop mesh. The components of the sinusoidal oscillator were selected for a for an oscillation frequency of 50 MHz and the capacitive sensor with planar geometry with an interdigitated transducer. The oscillator's performance was verified, simulations using the LTSpice software. The parameters analyzed were the amplitude and frequency of the oscillator's output signal. oscillator output signal in order to verify changes in these two parameters due to change in the sensor's capacitance when performing a detection. In the simulations the capacitive sensor was simulated as a simple capacitor with a reference capacitance of reference capacitance of 6 pF for the permittivity of air and 121 pF for the permittivity of water. permittivity of water, these values were obtained by analyzing the 𝑆11 parameters verified with the aid of a vector network analyzer. After verified that the circuit worked in the simulations, the next step was to physically physically build the oscillator on a printed circuit board and analyze its performance. The first step was to analyze the oscillator before adding the sensor to its frequency-selective loop. The second step was to see the changes in the oscillator's amplitude and frequency after adding the sensor, and finally to analyze its parameters after submerging the sensor completely in water. Analyzing the results obtained showed a considerable variation in both amplitude and frequency in the oscillator's output signal when comparing the oscillator working without the sensor with the oscillator working with the sensor, both for the sensor in the open air and for the sensor submerged in water. These variations in both frequency and amplitude occur as the capacitance of the sensor changes, showing that the oscillator performs well when acting in conjunction with the capacitive sensor and can be used as an alternative method to the vector network analyzer.