Abstract:

Energy harvesting is a technique for extracting the ambient energy available in the environment and its transformation in a usable electrical energy. The harvested energy may be stored and used after conversion RF-dc for the supply of the electronic devices with low power, such as the feeding of Nano-sensors for short distances or other devices. This paper presents a design of equiangular spiral antenna capable of collecting and managing energy from RF electromagnetic waves. Two structures of spiral antennas will be proposed. These antennas were designed and optimized using CST MWS software. Simulated results like return loss, radiation pattern, gain, and axial ratio will be presented. They show that this type of antennas is suitable for applications of energy recovery.

Abstract:

The reactive impedance surfaces (RIS) were introduced by Sarabandy as a substrate for planar antennas. There provide performance superior to perfect electric conductor (PEC) and perfect magnetic conductor (PMC) when used as backing antenna in terms of miniaturization and high bandwidth. This is interpreted physically by the fact that RIS can cancel the reactive energy stored in the substrate, thus it minimizes the interaction between dipole and substrate. In this paper, an RIS based dipole antenna is introduced and simulated. Then, we try to apply the optical ray model in order to maximize the radiation of total structure formed by both dipole and RIS. We will demonstrate that the dipole with RIS can provide wider bandwidth and better miniaturization factor compared to a dipole over PEC, dipole over PMC and Sarabandy results. The electromagnetic simulation of the antenna using HFSS demonstrates a wide bandwidth of 8.9 % (6.4 % for Sarabandy) and a good size reduction with l/λ=0.33 at a frequency of 1.58 GHz (l/ λ=0.36 at 1.67 GHz for Sarabandy).

Abstract:

This paper presents two Directions of Arrival DoAs) estimation algorithms for Electronically Steerable Parasitic Array Radiator (ESPAR) antennas. The constraints on the proposed algorithms are the same as those imposed onto the classic subspace methods allowing superior high resolution and localization capabilities as compared with existing schemes even for correlated sources situations but with more reduced computations load and processing time. The low complexities as well as the possible adaptive implementation give both resulting algorithms a potential interest for real time applications. The asymptotic performances of the developed algorithms are studied and compared with conventional antenna arrays. The simulation results confirm that high-resolution DoAs estimation can be achieved by using both proposed algorithms and prove the validity of our approach.