A High-Side Wideband Current and Voltage Sensor for Radio-Frequency Power Amplifiers

The radio-frequency power amplifier (RF PA) is one of the critical elements within the wireless, as it is expected to provide a suitable output power with high efficiency and linearity. Improving the power efficiency of the RF power amplifier is a key challenge of the modern wireless communications, especially in the presence of wideband modulations signals. In fact, to achieve this goal, various techniques are investigated, including supply voltage modulation (e.g., envelope- tracking). In the supply-modulated Pas employed in modern telecom base stations, it is important to measure the dynamic current drained by the power amplifier and the dynamic voltage at the supply terminal. This thesis project is focused on the design and realization of a high-side wideband (frequency response from dc up to > 100 MHz) voltage and current sensor suitable for supply-modulated power amplifiers. In order to be used with Gallium Nitride (GaN) PAs, the sensor must be able to withstand dynamic supply voltages up to 80 V and dynamic drain currents up to 2 A. The proposed current sensor is based on a shunt resistor approach, where the voltage drops across the resistor is firstly attenuated, and then amplified by a balanced differential circuit consisting of two cascaded stages. The voltage sensor consists of an operational amplifier configured as a buffer. The first part of the project, developed at the DEI EDM Lab (UNIBO), was dedicated to the analysis of the sensing architecture, the simulation of the resulting circuit. The design of the board its characterization and board test were realized in at the Warsaw University of Technology in Poland.