Sharif Digital Repository

This paper presents a phase-noise reduction technique for voltage-controlled oscillators (VCOs) using a harmonic tuned (HT) LC tank. The phase-noise suppression is achieved through almost rectangular-shaped VCO oscillating signal which effectively maximizes oscillating signal slope at zero crossing points resulting in-phase-noise degradation. In addition, by shortening down converted noise power around oscillating signal second harmonic, more phase-noise suppression has been achieved. A comprehensive analysis for frequency and amplitude deviations as high as 20% for third harmonic and its effect on output phase-noise suppression has been discussed. In the followings, a comprehensive analysis... 

In this paper, an adaptive design methodology for synthesizing a harmonic free N-path filter with reduced frequency folding is presented. System level analysis of proposed architecture shows that by adding a few extra paths with proper weights to a conventional N-path filter, several characteristics such as harmonic rejection, power reduction, foldback elimination and spectrum shaping can be achieved. The designed filter is reconfigurable to be a band-pass filter (BPF) or a band-reject filter (notch), based on the requirements. By using the nth harmonic of Local Oscillator (LO) signal, instead of the fundamental harmonic, the required input clock frequency in N-phase clock generator is... 

An active switched-capacitor 4-path bandpass filter suitable for multi-standard applications in ultra-high frequency (UHF) band with different channel bandwidths is designed and simulated in 0.18 μm CMOS technology. The baseband impedance of the filter is implemented as a second-order Gm-C low-pass filter which can be used to tune the channel bandwidth as well as the quality factor (Q) of the RF filter. The center frequency of the filter can be tuned from 100 MHz up to 1.5 GHz by changing the clock frequency applied to the filter while its bandwidth can be tuned by tuning impedance parameters in any center frequency. To do so, the baseband impedance utilizes a frequency dependent negative... 

The effect of clock skew and duty-cycle on the performance of high-Q N-phase band-pass filters (BPFs) have been examined in this paper. Following a mathematical approach and using the analytical derivations carried out, the effects of such non-idealities as clock skew and duty-cycle error are determined in an N-path filter. It is analytically proved that image signals from all integer multiples of the clock signal, rather than just those at (1 ± kN) multiples of the clock signal, land atop the wanted RF spectrum. In a real world clock generator, with non-idealities in effect, filtering property and proper behavior of the filter is adversely affected. Finally, system level simulation along... 

An expanding flight envelope in the landing phase of a typical jet transport aircraft in presence of strong wind shears using a learning capable control system (LCCS) is investigated. The idea stems fromhuman beings functional architecture that gives them the ability to do more as they age and gain more experience. With the knowledge that classical controllers lack sufficient generality to cope with nonlinear as well as uncertain phenomenon such as turbulent air, the focuse is on different types of intelligent controllers due to their learning and nonlinear generalization capabilities as candidates for the landing flight phase. It is shown that the latter class of controllers could be used... 

Desalination of sea saline water seems a successful solution to supply clean water. For desalination, novel nanoporous membranes have been proposed as a substitute for the classic reverse osmosis (RO) membranes. The one-atom-thick graphyne membrane has shown great potential in water desalination. By applying functional groups (FGs) into the pores of the monolayer graphyne membranes, the water permeability and the ion rejection were passively increased. The effects of applying various FGs such as Hydrogen, Fluorine, Carboxyl and Amine, effect of the salt concentration, the applied pressure, and the effective diameter of the graphyne pores were determined by molecular dynamics (MD)...