Most modern wideband Direction of Arrival (DOA) estimation methods report reasonable resolution at the expenses of high computational complexity. In this paper, an enhanced approach for wideband DOA estimation with high resolution and low computational requirements is introduced. The suggested approach is based on combining the Incoherent Signal Subspace Method (ISSM) with Compressive Sensing (CS). The CS is employed using deterministic chaotic sensing matrices to decrease the dimension of the measurement vector, and hence reduce the software complexity. The efficiency of the introduced technique in enhancing the DOA estimation efficiency is studied for Uniform Linear Antenna Array (ULA). Several evaluation metrics, including the spatial spectrum, the consumed time, and the Root Mean Square Error (RMSE) between estimated and actual DOAs when varying the Signal to Noise Ratio (SNR) and number of elements, are investigated to assess the performance of the proposed approach. Results reveal that the proposed ISSM with CS succeeds not only to achieve high DOA resolution for separating very closely spaced sources, but also to significantly reduce the computational complexity while keeping nearly the same estimation resolution. This demonstrates the effectiveness of the proposed DOA estimation approach in wideband real-time wireless systems.
Organic inorganic hybrid perovskite solar cells (PSC) showed high performance since their use in photovoltaic industry. Recently, mixed cation perovskites are being studied by many researchers to reach the best composition and efficiency. Triple cation perovskites are characterized by their large band gap tunability which help them be modeled for single and tandem solar cells. In this paper we present solar cell characteristics of Cesium Formamidinium Methylammonium Lead Iodide Bromide Cs0.05 FA0.8 MA 0.15 Pb (I 1-x Br x ) 3 by tunning the band gap absorber layer from (1.54-2.11 eV) at different bromide concentrations using a computational 2D optical and electrical model. The conduction band offset of Electron Transport Layer (ETL) as well as the metal work function of the Contact/Hole Transport Layer (HTL) interface were optimized to reach the best performance. The structure ITO/TiO 2 /CsFAMAPbIBr/CuSCN/Au results in a short circuit current (J sc ) 20.789 mA/cm 2 an open circuit voltage V oc 1.14 V and power conversion efficiency (PCE) of 17.830%.
This paper presents a new type of phased array antenna (PAA) that uses plasma material to achieve circular polarization characteristics. The plasma controls the phase shift of individual elements without the need for conventional phase shifters feeding network. The PAA is made up of 64 plasma dipole elements arranged into $4\times 4$ sub-arrays, each consisting of $2\times 2$ sequentially rotated plasma dipole elements with different plasma ionization frequencies. The PAA is designed to radiate either right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP). Two different sub-array arrangements are designed with plasma frequencies distribution of $(\omega_{\mathrm{p}1},\omega_{\mathrm{p}2},\omega_{\mathrm{p}1},\omega_{\mathrm{p}2})$ for arrangement (I), and $(\omega_{\mathrm{p}1},\omega_{\mathrm{p}2},\omega_{\mathrm{p}^3},\omega_{\mathrm{p}4})$ for arrangement (II). The frequency for minimum axialratio is controlled by selecting $\omega_{\mathrm{p}1}$ , and $\omega_{\mathrm{p}2}$ . PAA is designed to radiate right-hand circular polarization (RHCP) with peak gain of 20.9 dBi, and the 3-dB bandwidth $(\text{AR} < 3\text{dB})$ is 200 MHz. In arrangement (II), PAA radiates left-hand circular polarization (LHCP) with peak gain 19.1 dBi and AR bandwidth of 440 MHz. The NF-focused array focuses the field on a spot width of 4.4 cm compared to 6.6 cm for the non-focused array. A near-field focused PAA is also designed using one of the sub-array arrangements (I). This array focuses the field on a narrower spot compared to the non-focused array.
This research presents a reconfigurable Multi-Beam Directional of Yagi-Uda array for terahertz communications. The structure consists of planar dipole antenna surrounded by rows of metallic patches with graphene sector rings printed on silicon oxide substrate. Controlling the chemical potential of the graphene sectors switch, a single beam in two, four or eight directions. OFF-state $(\mu_{c1}=0eV)$ acts as director and ON-state $(\mu_{c2}=2eV)$ acts as reflector. A parametric study on the influence of adjusting the distance between the driven dipole and the patch sectors and the radius of the copper patches is studied. Adjusting of number of graphene sector rings on the the resonance frequency and peak gain has been investigated. It produces good impedance matching at 2.29 THz with peak gain of 8.19 dBi.
Compressed sensing enables sparse signals recovery from few linear measurements. For many types of signals, such as those which exhibit sparsity in the wavelet domain, the non-zero elements occur in blocks. Signals of this type are referred to as block-sparse signals. This paper proposes a block-sparse signal reconstruction algorithm, block adaptive matching pursuit (BAMP), which is characterized by high speed and accuracy. In this algorithm, a number of blocks is selected in each iteration, which is adapted according to the average correlation between the signal and blocks of the measurement matrix. Moreover, in each iteration, the support is refined, or pruned, to exclude blocks that do not contribute to the signal. We apply BAMP to ECG signal recovery from compressed measurements. Simulations illustrate significant improvements in accuracy and speed in comparison to other related block-sparse recovery algorithms for random and ECG signals.
