Resumen de Methods and tools for the design of RFICs
Tomas Carrasco Carrillo
Ambient intelligence is going to focus the next advances in wireless technologies. Hence, the increasing demand on radio frequency (RF) devices and applications represents, not only a challenge for technological industries to improve its roadmaps, but also for RF engineers to design more robust, low-power, small-size and low-cost devices. Regarding to communication robustness, in the latest years, differential topologies have acquired an important relevance because of its natural noise and interference immunity. Within this framework, a differential n-port device can still be treated with the classical analysis circuit theory by means of Z-,Y-, h-parameters or the most suitable S-parameters in the radio frequency field. Despite of it, Bockelman introduced the mixed-mode scattering parameters, which more properly express the differential and common-mode behavior of symmetrical devices. Since then, such parameters have been used with a varying degree of success, as it will be shown, mainly because of a misinterpretation. Thereby, this thesis is devoted to extend the theory of mixed-mode scattering parameters and proposes the methodology to analyze such devices. For this proposal, the simplest case of a two-port device is developed. By solving this simple case, most of the lacks of the current theory are filled up. As instance, it allows the characterization and comparison of symmetric and spiral inductors, which have remained a controversy point until now. After solving this case, the theory is extended to a n-port device. Another key point on the fast and inexpensive development of radio frequency devices is the advance on fast CAD tools for the analysis and synthesis of passive devices. In the case of silicon technologies, planar inductors have become the most popular shapes because of its integrability. However, the design of inductors entails a deep experience and acknowledge not only on the behavior of such devices but on the use of electromagnetic (EM) simulators. Unfortunately, the use of EM simulators consumes an important quantity of time and resources. Thereby, this thesis is devoted to improve some of the aspects that slow down the synthesis process of inductors. Therefore, an ‘ab initio’ technique for the meshing of planar radio frequency and microwave circuits is described. The technique presented can evaluate the losses in the component with a high accuracy just in few seconds where an electromagnetic simulator would normally last hours. Likewise, a simple bisection algorithm for the synthesis of compact planar inductors is presented. It is based on a set of heuristic rules obtained from the study of the electromagnetic behavior of these planar devices. Additionally, design of a single-ended to differential low noise amplifier (LNA) in a CMOS technology is performed by using the methods and tools described.
