Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 5 Articles
A dual-band SiGe HBT frequency-tunable and phase-shifting differential amplifier has been developed for the future active phased\r\narray antennas with a multiband, multibeam, and multitarget tracking operation. The amplifier uses varactor-loaded, stacked\r\nLC resonators in the design of the output circuit in order to provide frequency-tunable and phase-shifting capabilities for dual\r\nfrequencies. By utilizing the varactor-loaded LC resonator, which has a variable resonant frequency and a large insertion phase\r\nvariation, frequency-tunable and phase-shifting performances become available. Moreover, by using the stacked configuration,\r\nthe frequency and insertion phase can be varied independently for dual frequencies. A dual-band SiGe HBT differential amplifier\r\nhas achieved a lower-frequency tuning range of 0.56 to 0.7 GHz for a higher fixed frequency of 0.97 GHz as well as a higherfrequency\r\ntuning range of 0.92 to 1.01 GHz for a lower fixed frequency of 0.63 GHz. A lower-frequency phase variation of 99? and\r\na higher-frequency phase variation of 90.3? have been accomplished at 0.63 and 0.97 GHz, respectively. This is the first report on\r\nthe dual-band differential amplifier with frequency-tunable and phase-shifting capabilities....
Rain attenuation at Ka-band is a severe phenomenon that drastically impairs satellite communications at these frequencies. Several\r\nadaptive compensation techniques have been elaborated to counteract its effects and most often applied one at a time. The present\r\npaper proposes the contemporary exploitation of different techniques in a combined approach. Such an integrated approach is\r\nthoroughly analyzed in a simplified scenario and will be shown to achieve a very effective solution, making the Ka-band spectrum\r\nfully available for broadband satellite applications and network-centric systems....
Thefourth mobile generation requires ofmultistandard operating handsets of small physical size aswell as has an increasing demand\r\nfor higher data rates. Compact multiband printed inverted-F antennas (IFAs) for available wireless communications are proposed\r\nin this paper. A new design of a printed IFA based on a uniplanar compact EBG concept is proposed. An L-loaded printed IFA\r\nshaped over an artificial ground plane is designed as the main antenna to cover the GSM, LTE, UMTS, bluetooth, andWLAN. The\r\nmulti-band is created by means of an electromagnetic band-gap (EBG) structure that is used as a ground plane. Different shapes\r\nof uniplanar EBG as ring, split ring resonator, and a spiral rather than mushroom-like structure are investigated. The proposed\r\nantenna is built on the uniplanar EBG ground plane with a size of 35 Ã?â?? 45mm2, which is suitable for most of the mobile devices....
Microwave-osmotic dehydration of cranberries was evaluated under continuous flow medium spray (MWODS) conditions after some pretreatments. A central composite rotatable design was used with three input variables at five levels (temperature, 33Ã?°Cââ?¬â??67Ã?°C; sucrose concentration, 33Ã?°Bââ?¬â??67Ã?°B; and contact time, 5ââ?¬â??55?min). Responses were moisture loss (ML), solids gain (SG), and weight reduction (WR) as well as color and texture parameters. The responses were related to process variables using response surface methodology and statistical analysis: each model was tested for lack of fit to assure nonsignificance (p<0.05) and each process variable was tested for significance (p < 0.05 or p < 0.0001).Temperature was found to have the most prominent effect as it was significant with all drying (ML, SG, and WR) and quality (hardness and chewiness) parameters, while contact time was found to be significant with ML and WR. Concentration wasnââ?¬â?¢t found to be significant for any response. Increasing skin pretreatment severity generally promoted SG but had little effect on ML. The exception was chemical peeling, which favored ML but had no effect on SG. Overall, MWODS enables food dehydration in a much faster period of time than conventional osmotic dehydration (COD), while specifically promoting moisture loss over solids gain....
Swarm intelligence denotes a class of new stochastic algorithms inspired by the collective social behavior of natural entities (e.g.,\r\nbirds, ants, etc.). Such approaches have been proven to be quite effective in several applicative fields, ranging from intelligent\r\nrouting to image processing. In the last years, they have also been successfully applied in electromagnetics, especially for antenna\r\nsynthesis, component design, and microwave imaging. In this paper, the application of swarmoptimization methods to microwave\r\nimaging is discussed, and some recent imaging approaches based on such methods are critically reviewed....
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