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This paper proposes a novel metal-graphene plasmonic antenna over a Si/SiO2 substrate, working in terahertz frequency band. Novelty of the work lies in the use of metal and graphene as a patch antenna, as this combination enhances the gain & the radiation efficiency of the whole structure. Besides the analysis provides detailing of graphene and its conductivity modelling using MATLAB. The antenna is analyzed using FDTD based CST software, conductivity of graphene used in CST is verified with the conductivity achieved using MATLAB. Further, a 3-element Multiple Input and Multiple Output (MIMO) antenna system using same single element antenna, is designed & analyzed. The metal-graphene hybrid patch antenna provides maximum directivity around 5.8 dBi, maximum gain around 5 dBi, and high radiation efficiency (approx. 80%) at resonant frequency of 1.8 THz. Besides, the 3-element MIMO antenna provides radiation efficiency around 77%, with directivity around 5 dB & diversity gain of around 10 dBi. The proposed metal-graphene hybrid MIMO patch antenna has the potential to be used in advanced THz communication systems.

This paper presents a Particle Swarm Optimization (PSO) based co-channel interference constrained efficient and low-complexity novel spectrum allocation scheme with simultaneous power and network capacity optimization for a Cognitive Radio Network (CRN) with a system model of multiple secondary user (SU) pairs and one primary user (PU) pair in a spectrum underlay fashion. A novel weighted fitness function is proposed subject to the constraint that all primary users and secondary users are supported with their target signal-tointerference-noise ratio (SINR). MATLAB simulation shows that total transmitted-power-per-node (TPPN) decreases while the network capacity remains almost constant for proper choice of weight ratio of the fitness function involved and hence, in the real-time situation, we can avoid the high computational burden of multi-objective optimization by predetermining the weight ratio through parametric study.

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