engleski

Voltage-controlled capacitor for large signals

The thesis explores the possibility of using micro-transformers, in the 10-1000MHz range, for the purpose of reducing voltage amplitude for components that require a constant working point, specifically varactor diodes. Varactor diodes are considered for use as voltage-controlled capacitors in tuning circuits for large signal power amplifiers. Normally this is impossible as the signal power (1-3W) in these circuits produces deviations from the varactor diode working point turning it into a large source of nonlinearity. An equivalent microwave transformer model was developed that accurately predicts behavior before the first s21 resonance frequency. An efficient method for characterization of this model was developed that uses S- parameter measurements. The method includes determining the inductance of the primary and secondary coil, coupling factor and the parasitic capacitance that causes the first resonant frequency in the measured s21 parameter, beyond which the transformer no longer functions as required.

transformers, varactor diodes, high-frequency electronics, wide-band electronics, scattering parameters

Bachelor's Thesis No. 5973