Sharif Digital Repository

An efficient ray tracing technique for channel modeling of an ultrawideband signal in 60 GHz band is introduced. In the usual method, field calculations at many frequencies must be done where has a high computational cost. We have introduced a novel method using Chebyshev polynomials interpolation to reduce the computational cost. Some propagation parameters such as gain and root mean square (RMS) delay spread are obtained and compared to the other method  

Interfering electromagnetic energy could be a very powerful pulse which is generated and incident onto communication system such as linear wire antenna through direct radiation. In this paper, the transient responses of the linear wire antenna such as dipole antenna under the impact of the early-time (E1) high-altitude electromagnetic pulse (HEMP) are investigated using the equivalent circuit due to a primary element used in the modeling of systems for HEMP vulnerability is the linear wire antenna such as dipole antenna. Based on the equivalence concept of HEMP radiation source and linear wire antennas, the response at receiving antenna port is calculated efficiently with an uncomplicated... 

In most applications of antenna arrays, side lobe levels (SLLs) are commonly unwanted. Especially, the first side lobe level which determines maximum SLL is the main source of electromagnetic interference (EMI), and hence, it should be lowered. A procedure of finding the optimum side lobe-minimizing weights for an arbitrary linear equally spaced array is derived, which holds for any scan direction, beam width, and type of antenna element used. In this science article, the use of convolution procedure and the time scaling property reduces the side lobe level for any type of linear equally spaced array. Results show that by this procedure, the side lobe level is reduced about two times or even... 

In this paper a closed-form expression is introduced to calculate slot shape of long slot leaky wave waveguide antennas at its fundamental mode of operation with minimum side lobe level (SLL). The derived equation is a function of geometrical parameters of the structure. This is an advantage because they show a clear relationship between geometrical parameters of the antenna and radiated field that allows intelligent modification of the pattern. The Gaussian slot is used to obtain the best radiation pattern with lowest SLL. The results obtained by introduced formula are compared with the full wave commercial simulator such as HFSS software which confirms the accuracy of the introduced... 

This paper is a counterfactual analysis investigating the consequences of the formation of a currency union for Canada and the USA: whether outputs increase and prices decrease if these countries form a currency union. We use a two-country cointegrated model to conduct the counterfactual analysis, where the conditional forecasts are generated based on the Gaussian assumption. To deal with structural breaks and model uncertainty, conditional forecasts are generated from different models/estimation windows and the model-averaging technique is used to combine the forecasts. We also examine the robustness of our results to parameter uncertainty using the wild bootstrap method. The results show...