Sharif Digital Repository

The state-of-art technologies keep generating new ways of improving on remote sensing and Earth monitoring like Synthetic Aperture Radars that is widely used in military applications such as reconnaissance and espionage especially on military and industrial sensitive and strategic areas. In order to protection of strategic fields and being aware of hostile activities and also do sufficient countermeasure action, in this research a simple SAR satellite detection and tracking is proposed by using a reliable fast search and tracking antenna considering the limitation of radio visibility duration of SAR satellites. The tracking antenna is a DBF phased array antenna with circular polarized patch... 

Genetic algorithm for optimization of beam forming in spiral array antenna is used. The goal is to achieve a -20 dB in null over the wide frequency band. Our simulation shows -20 dB over 75 MHz Null Band width, in VHF band. © 2006 IEEE  

Network-on-Chip (NoC) as a promising design approach for on-chip interconnect fabrics could overcome the energy as well as synchronization challenges of the conventional interconnects in the gigascale System-on-Chips (SoC); The advantages of communication performance of traditional wired NoC will no longer be continued by the future technology scaling. Packets that travel between distant nodes of a large scale wired on-chip network significantly suffer from energy dissipation and latency due to the routing overhead at each hop. According to the International Technology Roadmap for Semiconductors annual report, the RFCMOS characteristics will be steadily improved by technology scaling. As the... 

Weighting elements to achieve radiation patterns with desired characteristics is a classical work in phased array antennas. These characteristics can be low sidelobe level, narrow beamwidth, high directivity, pattern nulling in special angle and etc. For each of these characteristics, different methods have been introduced. Most of methods have been presented for uniform arrays, however there are lots of methods to obtain a desired pattern for antennas with non-uniform element distances. The problem with these methods is complexity or not very good results. In this paper, fast and easy methods based on Least Square Error that leads to good results are presented. In addition, weighting of... 

The continued migration to smaller nanometer geometries brought fundamental limits to traditional on-chip hard wires performance. According to the International Technology Roadmap for Semiconductor (ITRS), feature size shrinking leads an increase in the operating frequency of RFCMOS devices. Thus, new interconnect methodologies such as radio frequency (RF) wireless can be employed on future chips projected for intra-chip wireless data communications. The size of Si integrated antenna in these frequencies will be several millimetres and the antenna length will be decrease by frequency increasing. In this paper, we have proposed an optimum radiation pattern achieved by a phased array (PA)... 

A fiber Bragg grating (FBG)-based delay line (or phase shifter) has been developed for microwave over fiber and phased array antenna (PAA) applications. The scheme uses band edge time delay of tunable fiber gratings to provide a continuously controllable microwave time delay or phase shift. Following the formulation and analysis of the device behavior, simulations of amplitude and phase responses are conducted. The results confirm the validity of theoretical predictions  

In this paper, a closed-form two-dimensional reconstruction technique for hybrid frequency and mechanical scanning millimeter-wave (MMW) imaging systems is proposed. Although being commercially implemented in many imaging systems as a low-cost real-time solution, the results of frequency scanning systems have been reconstructed numerically or have been reported as the captured raw data with no clear details. Furthermore, this paper proposes a new framework to utilize the captured data of different frequencies for three-dimensional (3D) reconstruction based on novel proposed closed-form relations. The hybrid frequency and mechanical scanning structure, together with the proposed... 

Usually the digital phase shifters are used to steer the beam of a phased array antenna, and the accuracy of beam steering and other properties of the radiation pattern is dependent on the number of bits of the phase shifter and its resolution. In this paper the results of simulations, accomplished using a number of phase feeding methods in order to reduce the phase quantization error effects are presented and three new methods are introduced and compared with the previous works. Copyright 2006 IEICE