Sharif Digital Repository

In this thesis we focus on the extraction of resonance modes in photonic crystal resonators. This work could be divided in two different parts: in the first part we apply the Galerkin’s method effectively to the two and three dimensional structures, in the second part that constitutes the main part of this thesis we derive transmission line models for these structures. Fist we derive transmission line models for resonators based on the point defect and line defect in two-dimensional photonic crystals. Then we generalize this model to the three-dimensional photonic crystals. Finally we apply the same approach to the coupled resonators and analyze the coupled resonator optical waveguide. In... 

In today’s microwave communication, oscillators play a very important role as signal sources, so, the design of an oscillator with suitable parameters can affect the final performance of a communication system. Among different parameters, phase noise is of utmost importance since this parameter can lead to interference in multi-frequency channel systems and thus its estimation and measurement is vital. In an oscillator, in addition to measurement, the most important problem is to reduce phase noise. In fact, for improving the performance of a transmitter-receiver ( e.g. receiver sensitivity ), one of the solutions is using a local oscillator with low phase noise. Our purpose in this project... 

In this thesis, we intend to explore the application of active inductors in high-performance radio receivers. The proposed active inductor uses a feed-forward path to improve the noise performance. This is done without sacrificing the quality factor and the power consumption. The proposed active inductor is designed and implemented in a standard 0.18μm CMOS technology. The measurement results show an almost three fold improvement in the noise performance, comparing to the typical existing structures. The resonance frequency of the inductor can be tuned from 1.8 GHz to 5.5 GHz, while the quality factor can be adjusted up to 30. The total current consumption of the active inductor is 4.8... 

Ultra-sensitive magnetometers based on Radio Frequency Superconducting Quantum Interference Device (rf SQUID), have wide applications in Non-destructive Evaluation (NDE), geophysical measurements and biomagnetic measurements, especially in magnetocardiography (MCG) systems. A superconducting module coupled to rf SQUID is designed to provide a resonance frequency in GHz range (according to the electronic system frequency), as well as concentrating the magnetic flux in the effective area of SQUID. The signal can be measured through a port pumping AC power to the module. The resonator has been also implemented by lumped element tank circuits, but the quality factor of these circuits are usually... 

Structures with time-varying electromagnetic properties can potentially yield non-reciprocity, amplification, harmonic generation, and other interesting wave propagation phenomena. To date, some studies have dealt with time-varying media and circuits, including time-varying optical ring resonators having degenerate travelling wave resonances. In time-varying ring resonators, the clockwise and counter clockwise resonances lose their degeneracy, and non-reciprocity is observed. One of the main challenges of such research is the need to induce time-variations in the entirety of the resonator or structure, which makes their implementation very limited or impossible in practice. The purpose of... 

Noise pollution is one of the major issues in automative industry. Many of these noises are caused by the internal combustion engine. Using reactive mufflers in the car's exhaust path can effectively reduce this annoying noises. Imposed pressure drop caused by installation this mufflers must be within an acceptable range for the car engine. Resonators, despite having a much lower pressure drop than other components of the exhaust system, can be used to cover the weaknesses of the muffler in the acoustic performance of the noise reduction set. One of the most common methods for designing a resonator is to use perforated plates. In this study the effect of various geometric parameters of a...