Microeletronics and systems
High-efficiency transmitters for 4G mobile communication systems
The fourth generation of mobile communications systems (4G) promises competitive performance with current cable modems in a scenario of complete mobility. However, the current rate of growth of wireless applications has dramatically increased the power consumed by these systems. This brings undesirable consequences for the base stations, whose transmitters are responsible for over 60% of its energy consumption, and also to the user, since the advances in battery technology for portable devices do not follow the same pace. As a result, the transmitter design for 4G systems has been guided by the search for high energy efficiency. This implies practically abandoning the classical linear amplification based on the operation of the transistors in linear classes (A, AB and B) and low power levels. This research line aims to search for new transmitter architectures, capable of keeping the transmitter operating at a high efficiency over a wide output power range, and the digital implementation (FPGAs or ASICs) of baseband linearizers, to exploit the operation of transmitters in high efficiency while meeting the stringent linearity requirements.
Development of behavioral models for wireless functional blocks
In modern wireless communication systems, different functional blocks (ADC, DAC, filters, amplifiers, mixers) act on a signal bearing information, contributing both to perform a predetermined task and to the degradation of the signal over the system. When transmitting, the information modulates an RF carrier in both amplitude and phase, in order to improve spectral efficiency. However, since the envelope can be variable, there must be a tradeoff between linearity and efficiency. Unless a linearization scheme is implemented in the transmission chain, the power amplifier should operate at low power levels in order to meet the stringent linearity requirements, degrading the energy efficiency. At the reception, the signal goes through consecutive gain stages, frequency translation, filtering and demodulation. The compromise in this case is to get the highest sensitivity and most useful signal robustness to interference with the lowest possible energy consumption. For the computer aided design of modern mobile communication systems, behavioral models that have low computational complexity are required to represent the functional blocks. These models must accurately represent the complex information signals at the input and output. In this context, this research line aims to develop behavioral models of functional blocks for mobile communication systems.on.
RF switched receivers for multistandard software-defined radio applications