On the Importance of Electromagnetic Models in RFIC Design
Dušan N. Grujić, Pavle Jovanović, Milan Savić, Lazar Saranovac
In low frequency analog or digital design designers are mainly concerned about parasitic resistance and capacitance, while neglecting inductive and propagation effects. The designs are complex, both in terms of number of transistors and interconnect lines. To cope with this complexity, tools for parasitic extraction use precomputed capacitance tables and employ pattern matching algorithms. Pattern matching approach results in reasonable run time and accuracy better than 10%, which is acceptable for most low frequency designs. In contrast, high frequency RFIC designs have much smaller number of transistors and simpler interconnect, but require higher accuracy and modeling of inductive, skin and possibly propagation effects. In this paper we will discuss some of the problems and possible solutions for proper simulation of RF circuits and the importance of electromagnetic models. Conclusions will be demonstrated on the example of modeling the integrated voltage controlled oscillator.
Limits to Optical Chemical Sensing: Fluctuations Versus Ultimate Performance
Zoran Jakšić, Olga Jakšić
The role of chemical sensing in modern process industry cannot be overestimated, since they are encountered at different stages of process control, helping maintain product quality and at the same time keeping an eye on environmental issues and pollution problems. Numerous device families are currently in use, where optical chemical sensors are probably the fastest, the simplest and the most sensitive. Affinity sensors represent a class of these devices based on adsorption of chemical analytes. The prime example of these are plasmonic sensors, which are label-free, ultrasensitive and ultrafast. Literature usually defines only the ideal sensitivity of such devices and their performance is taken as granted. In reality there are many parasitic processes that decrease their performance and introduce significant measurement uncertainties. Noise and fluctuations in such sensors can be generated by both extrinsic or intrinsic sources and a significant part of them is a consequence of fundamental processes that at the same time ensure the very function of the devices. The main intrinsic mechanisms include adsorption-desorption, optical flicker and thermal noise, while the level of the extrinsic noise is related with the quality of the interrogating beam source and the photodetector. In this contribution we offer a possible systematization of different sources of noise in refractometric chemical sensors and analyze the influence of such fluctuations to the ultimate device performance.