Wireless communication has become ubiquitous in almost every sector, both in military and commercial systems. Communicating objects are getting smaller and smaller. Therefore, the antennae which are the fundamental elements of this circuit must meet the requirements of their integrating environment in terms of bandwidth, multiple frequencies, smaller size and affordability. Microstrip patch antenna (MPA), a priori, should have been the preferred candidate, but the narrowness of its bandwidth is a limitation. Therefore, many techniques have been explored including the use of fractal shapes for improving the performance of this type of antenna. Multiform fractal shapes have been used in various works to achieve the results expected in specific cases to effectively meet the requirements of wireless communication. In this paper, we will do an overview by highlighting the various kinds of fractal geometries which have been the most used in recent years by clearly specifying that the options of miniaturization of microstrip antennae by the theories of Sierpinski and Minkowski are ideal methods and therefore, will drive our future work on miniaturized antenna designs.
This article proposes a new engineering approach to detect targets using multi-static radars. It considers the aperture angle and the probability of false alarm of detection which allow to improve the performances of the radar system deployment. This proposed method is tested on three tomographic modes of multi-static radars: Single Input Multiple Output (SIMO), Multiple Input Multiple Output (MIMO), and Synthetic Aperture Radar (SAR). In this work, a calculation and estimation method for the parameters (spacing sensor and tilt angle of baseline) are developed using the deployment of the radar system based on geometrical arrangements. Employing these parameters, estimated by the proposed approach, and using them for the calculation of the tomographic resolution, the nearest ambiguity location, and the scan loss which are radar deployment performances. The results show that the spacing between sensors varies from 40 to 70% with an increment of aperture angle from 15° to 30° and the step of 10 −3 variation in the false alarm probability of detection. The length of the radar system deployment is also reduced by 6.66%. This approach improves the capabilities of distinction of the targets in a multistatic radar system and allows a reduction in deployment costs.
The objective of this paper is to design a parasitic antenna array capable of rejecting interfering signals and directing its main lobe towards the wanted signal. The designed antenna is a linear array consisting of an active monopole and fourteen parasitic monopoles. The method used is LMS, making it possible to calculate the values of the reactive loads to be connected to the ports of the parasitic elements so that the radiation patterns satisfies the fixed constraints. The simulation results in CST-MWS (Computer Simulation Tool Microwave Studio software) of the radiation patterns show an energy level of less than -0.71 dB in the direction of the interference and a gain greater than 5 dB in the direction of the wanted signal. Thus, this technique will make it possible to design directional antennas, with low energy consumption and interference rejection.
Our work is developed in context of studing Massive MIMO in a 5G context. The aim is to optimize spectral efficiency of several users hyper MIMO system during Uplink communication in a multi-cell contaminated pilot environment, using a new type of precoders called single cell-minimum mean square eroor (S-MMSE) and multicell-minimum mean square eroor (MMMSE). Indeed, we address two key and well-known issues of massive multiuser MIMO (MU-MIMO) environments in a test-driven development (TDD) operation scheme, namely acquisition of uplink channel state information (UL) and optimisation of the bit stream per unit frequency, the spectral efficiency (SE). From a practical point of view, these two notions are inclusively linked. Indeed, a very good channel estimation leads to a better spectral efficiency. In our approcah, we derive from the minimum mean square error estimator (MMSE) to two new types of precoders that can operate in a multicell environment with a contaminated pilot sequence, namely the SMMSE and the M-MMSE. A comparative study performance of these classical precoders such as regulated zero forcing (RZF), ZF (Zero Forcing) and MR (Minimum Ratio) encountered in multi-antenna processing shows an improvement of nearly 51% in terms of system gain and spectral efficiency.
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