نشریه صنایع الکترونیک
پیاپی 3 (پاییز 1389)

Always antenna structures with low sidelobe levels are a main goal during antenna design. In this paper, a new method for reduction of radiation patter sidelobe level in phased array antenna with uniform and non-uniform weighting is presented. In this method, by change of array elements weight or adding several elements, such as SLC technique, the pattern with low side lobe level can be achieved. According to the design, in an array with uniform weighting value of SLL in third sidelobe to next more than -10 dB can be reduced so that main beam-width changes less than %3 and variations of gain is negligible. Since in applications use non-uniform weighting so, here a new method for sidelobe level reduction in phased array antennas radiation pattern by Taylor weighting is presented. In this method, by use of uniform weighting results, the weight vector of array modify so that sidelobe reduction in resultant pattern is perceptible. In this method, the value of SLL in third sidelobe to next, ratio to primary Taylor weighting can be reduced so that main beam-width approximately %1 to %2 changes and variation of array gain is negligible. Since in phased array antennas, location of main-lobe can be set electronically by applied proper phase in arbitrary angle, performance of this method in pattern scanning is considered and shown in both way that this method is independent from main-lobe location.

Recent developments on the wireless communication technology have brought much innovativeness to make wireless access networks, e.g. WiMAX systems, to be able to compete with the wired access networks with much more bandwidth. QoS service provisioning is an important issue for deploying such networks. The IEEE 802.16d standard has specified the services should be provided at the medium access control (MAC) layer in WiMAX networks. However, it has left a wide space for research to develop and implement those specified services. In this paper, the issue of differentiated service provisioning will be addressed with the non-real-time polling service in WiMAX systems. The proposed solution has been designed to have an ability to accommodate integrated traffic in the networks with effective scheduling schemes. A series of simulation experiments have been carried out to evaluate the performance of the proposed scheduling algorithm. In our algorithm we introduce a two-phase Learning Automaton queuing (2PLAQ) algorithm tailored for uplink scheduling in the WiMAX network. It aims to strike the balance between delay requirement and fair bandwidth allocation. The results reveal that the proposed solution performs effectively to the integrated traffic composed of messages with or without time constraints and achieves proportional fairness among different types of traffic.

Quantum Cellular Automata (QCA) represents an emerging technology at the nanotechnology level. There are various faults which may occur in QCA cells. One of these faults is the Single Electron Fault (SEF) that can happen during manufacturing or operation of QCA circuits. A detailed simulation based logic level modeling of Single Electron Fault for QCA binary wire is represented in this paper.

In this paper study and obtain allowable threshold area for switching between missile guidance systems. Missile defence (without back turn) consisting of vertical, midcourse and terminal guidance phases that interceptor engages the target successfully. the yoal of this paper Detrominy the suitable time for threshold area of switching system whit missile trajectory near to optimal trajectory and increase speed of operation with minimum calculation.

Present work evaluates the application of artificial neural networks for weld beads pattern recognition using pulse-echo ultrasonic techniques. In this study pattern classifier is an MLP artificial neural network implemented in MATLAB. The ultrasonic signals, acquired from pulse-echo, are separately introduced to the neural network with and without preprocessing. The preprocessing objective is smoothing the signal that improves the classification. Five conditions of weld beads are evaluated: lack of fusion (LOF), lack of penetration (LOP), excess penetration (EX.P), slag inclusion (SL) and non-defect (ND). The defects are intentionally inserted in a weld bead of AISI 1020 steel plates of 20 mm thickness and confirmed using radiographic test. The results obtained show that it is possible to classify ultrasonic signals of weld joints by the pulse-echo techniques using artificial neural networks and the success rate of 78.82% can be achieved. The preprocessing role is significant in this respect.

In this paper, we investigated the antenna applications of EBG materials, especially for two Mushroom and UC-EBG structures. Based on EBG technology and reactive impedance substrate (RIS), someone achieves unidirectional radiation pattern for a conventional spiral and sinuous antennas. For a better comparison, a metamaterial cover is used. Using metamaterial cover, one does not need to design and fabricate the cavity backed, whereas, the losses of the absorber material have been cancelled. Such metamaterial cover, although modified the radiation pattern, the antenna bandwidth is decreased and AR is degraded. So as an alternative approach, mushroomlike EBG incorporate with RIS structure, have been used. The last suggestion is a low profile structure which is provides antenna gain and FBR modification. Mutual coupling reduction is one of the main topics in array antenna applications. The use of electromagnetic band gap structures built by microstrip technology is an attractive way to mitigate the mutual coupling problem. This paper describes a novel configuration of uniplanar compact electromagnetic band gap (UC-EBG) structures to reduce mutual coupling between the radiating elements. The idea is to use the UC-EBG structures built on a separated layer placed on the top of the patch antennas which reduces mutual coupling between the elements efficiently. The main objective is to reduce both the element separation and the mutual coupling between the patch antennas which in turn increases antenna directivity. For this purpose, a circuit model for the proposed array of antennas and EBG structure has been derived. Numerical simulations have good agreement with circuit model analysis.

Satellites have important role in technology development. In correct communication with satellite should have precise attitude control. In this paper study mathematic preliminary of orbit ballistic and different algorithm of determination and attitude control of satellite same as thruster control, momentum wheel control, magnitude control, and also algebraic & q & geometric satellite attitude determination. There are also considered their design constrains.