ELECTRONIC INDUSTRIES
Year:2011 | Volume:2 | Issue:1|Papers Count:8

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.

This paper presents a rigorous and comprehensive method for retrieving the electromagnetic constitutive parameters of a slab of meta material from the measurement or numerically calculation of scattering parameters. The main problem in this process is the doubtfulness exists in the phase of the transmitted field or the correct branch of logarithmic function appears in relevant equations. The novelty introduced here is on applying the Kramers-Kronig (K-K) relation to the imaginary part of refractive index and therefore obtaining its real part with less ambiguity. In Addition, by means of the mentioned approach one can obtain full retrieval results even where the imaginary part of electric permittivity or magnetic permeability becomes negative. Indeed, this method can be applied to an extensive range of materials independent of their operational frequency.

Quantum Cellular Automata (QCA) represents an emerging technology at the nanotechnology level. Nowadays, many applications of QCA technology are introduced and cryptography can be an interesting application of QCA technology. The original encryption algorithm for GSM was A5/1. Here, we have implemented the A5/1 stream cipher using QCA technology. Simulation results are obtained from software of QCA Designer.

An important problem for the WiMAX networks is how to provide a guaranteed quality of service for applications. A key aspect of this problem is how BSs should share bandwidth capacity between different classes of traffic. This decision needs to be made for each incoming packet, and is known as the packet scheduling problem.A major challenge in packet scheduling is that the behavior of each traffic class may not be known in advance, and can vary dynamically.In this paper, we describe how we have modeled the packet scheduling problem as an application for reinforcement learning (RL). We demonstrate how our RL approach can learn scheduling policies that satisfy the quality of service requirements of multiple traffic classes under a variety of conditions. 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. 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.

The sinuous antennas have a numerous applications in military and civil systems such as direction finding, research and measurement laboratories and reflector feeds; which are due to their superior broadband characteristics and simultaneous right and left hand circular polarization. These capabilities are most required in radars and aerospace applications. Although, the sinuous antenna size, bandwidth, and radiation parameters are the same as spiral antenna, due to complex structure and complicated feeding network, the sinuous parameters do not investigated accurately.In this paper, a comprehensive survey on the antenna parameters has been proposed. Based on these studies, design, construction and measurements of an optimized planar sinuous antenna for 1–5 GHz frequency range have been presented.

In this paper, according to the size of the transistors and the feedback gain of the oscillator, a design point in which the gain of the active core of the oscillator is maximum, is derived. In order to realize the feedback gain, we utilize a transformer. This transformer is employed in such a way that it could be able to provide the feedback gain for the oscillator and also eliminate the large portion of parasitic capacitance, simultaneously. By using this technique, the phase noise at 1MHz offset and the tuning range in comparison with the general transformer oscillator is improved by 5dB and 70% respectively.Furthermore, we show that with linearization of the oscillator in millimeter-wave frequencies, phase noise of the oscillator can also be reduced even more. Regarding this criteria we linearize the oscillator as much as possible. Post-simulation results show that the circuit designed in 0.18-mm CMOS technology, consumes 43mW while showing -89dBc/Hz phase noise at 1MHz offset with 1.9GHz tuning range around 57GHz.

In this paper, a new feeding structure is applied in the patch antenna design to overcome undesirable features of the earlier multilayer feeding structures while maintaining their interesting features.To more readily understand the operation mechanism of proposed feeding structure, an efficient circuit model has been also presented.It is known that proximity and aperture coupled feeding structures are sensitive to the transverse feed point location. In contrast, the proposed feeding architecture is very easy to fabricate and it overcomes the alignment difficulties arising from the proximity and aperture coupled feeding structures. The CST simulation results, analytic results and measurement ones show good agreement with each other. Moreover, a new miniaturization technique which is based on using High Impedance Wire (HIW) structures has been introduced. Due to their artificial high permeability properties, using proposed method, someone may miniaturize conventional patch antenna without bandwidth and efficiency corruption. Applying suggested method to the proposed antenna structure, two different feeding structures have been designed and compared. Finally, by using AMC structures to load HIW, more miniaturization factor has been achieved.