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Measurement and Explanation of DC/RF Power Loci of an Active Patch Antenna
Neil J. McEwan,Nazar T. Ali,Kahtan A. Mezher,Elmahdi A. El-Khazmi,Raed A. Abd-Alhameed 한국전자통신연구원 2011 ETRI Journal Vol.33 No.1
A case study of an active transmitting patch antenna revealed a characteristic loop locus of DC power versus RF output power as drive frequency was varied, with an operational bandwidth substantially smaller than the impedance bandwidth of the radiator. An approximate simulation technique, based on separation of the output capacitance of the power transistor, yielded easily visualized plots of power dependence on internal load impedance, and a simple interpretation of the experimental results in terms of a near-resonance condition between the output capacitance and output packaging inductance.
Adaptive threshold and optimal frame duration for multi-taper spectrum sensing in cognitive radio
Ahmed O. Abdul Salam,Ray E. Sheriff,Saleh R. Al-Araji,Kahtan Mezher,Qassim Nasir 한국통신학회 2019 ICT Express Vol.5 No.1
This paper delivers an accurate approximation for adaptive threshold and optimal frame detection algorithms based on the robust multi-taper method aiming at an efficient spectrum sensing in cognitive radio systems. An appropriate adaptive thresholding allows for seamless vacation of unlicensed secondary users from certain bands upon primary users’ requests, while arbitrary optimal frame detection contributes to the computational and throughput demands. Simulation exercises corroborate the given analysis over Rayleigh channel and multiple-input multiple-output configuration and emphasize the critical role of adopting applicable adaptive threshold and optimal frame detection policies.
Novel Approach for Modeling Wireless Fading Channels Using a Finite State Markov Chain
Ahmed Abdul Salam,Ray Sheriff,Saleh Al-Araji,Kahtan Mezher,Qassim Nasir 한국전자통신연구원 2017 ETRI Journal Vol.39 No.5
Empirical modeling of wireless fading channels using common schemes such as autoregression and the finite state Markov chain (FSMC) is investigated. The conceptual background of both channel structures and the establishment of their mutual dependence in a confined manner are presented. The novel contribution lies in the proposal of a new approach for deriving the state transition probabilities borrowed from economic disciplines, which has not been studied so far with respect to the modeling of FSMC wireless fading channels. The proposed approach is based on equal portioning of the received signal-to-noise ratio, realized by using an alternative probability construction that was initially highlighted by Tauchen. The associated statistical procedure shows that a first-order FSMC with a limited number of channel states can satisfactorily approximate fading. The computational overheads of the proposed technique are analyzed and proven to be less demanding compared to the conventional FSMC approach based on the level crossing rate. Simulations confirm the analytical results and promising performance of the new channel model based on the Tauchen approach without extra complexity costs.