Determining the number of sources from observed data, is a fundamental problem in array signal processing. In this paper, first we focus on two popular estimators based on information theoretic criteria, AIC and MDL. Then another algorith m based on eigenvalue grads, namely EGM is presented. The co mputer simu lation results prove the effective performance of the EGM for non-coherent signals but in the small differences between the incident angles of non-coherent sources, MDL and AIC have a much better detection performance than EGM . These methods can detect only non-coherent signals, and the performance of them will be sharply declined even signals are coherent and/or correlated. So, first forward/backward spatial s moothing (FBSS) method is used as a pre-processing step to solve the coherency/correlation, and then MDL, AIC and EGM algorithms are run to estimate the number of signals. Nu merical results show that FBSS-based EGM offers higher detection probability rather than FBSS-based MDL and AIC in the case of coherent sources as well as correlated ones. Also, the higher detection probability can be achieved for correlated case compared to coherent one.
Black phosphorus (BP), a new elemental 2D material, is a suitable candidate for broadband photodetection from the visible to the infrared (IR) range of the spectrum because of its tunable bandgap and high carrier mobility. Herein, the electrical and optical properties of pristine and Se‐doped BP have been investigated, using the density functional theory (DFT) method. The results show that the Se‐doped BP has an indirect bandgap of 0.4 eV which is smaller than that of the pristine monolayer BP. Moreover, the Se‐doped BP exhibits higher optical absorption compared with pristine BP in the low energy regions. Furthermore, the simulation results of designed (12 nm thick) field‐effect transistors, based on Se doped BP, show excellent optoelectronic properties in the mid‐IR photodetector applications. The responsivity of this device reaches up to about 0.75 μA W−1 in a mid‐IR region of 4 μm with an excitation intensity of 0.0001 W cm−2 and bias voltage and drain voltage of 1 and 0.5 V, respectively. Finally, the results demonstrate that doping BP with Se improves device performance by increasing optical properties and enhances responsivity of the mid‐IR photodetector.
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