This article presents a planar monopole antenna with reduced radiation hazard toward human head using thin-wire mesh which is needed in smart phone (mobile) for less crowded 801.11ac (5 GHz Wi-Fi) applications. The antenna consists of a rectangular radiating element with a particular rectangular part being removed from it to increase the electrical length of the antenna for miniaturization. CPW-feed and radiating element are printed on the topside of the double sided PCB. Radiation hazards toward human head has been reduced using a metallic thinwire mesh in the backside of the PCB. Orientation of metallic thin wire mesh play a vital role. It has been placed in such a way to disturb the fringing field coupled toward head direction (positive X direction). The proposed antenna offers an impedance bandwidth of 1.47 GHz from 4.35 GHz to 5.82 GHz with resonant frequency 5.18 GHz when it printed on an FR4-epoxy substrate with dielectric constant (e r ) of 4.4. It is over all in dimension of 21.7 3 25.5 3 1.6 mm 3 . It has been designed and optimized using parametric study on the geometrical dimensions are investigated using electromagnetic simulation software HFSS 13.0 (High Frequency Structure Simulator).
To overcome the multipath fading effect in wireless communications an efficient multicarrier modulation technique OFDM (Orthogonal frequency division multiplexing) is used. The OFDM system has high spectral efficiency and support high data rate wireless transmission without any additional requirement of equalization.So, it is an attractive technology formodern wireless communication systems. One major drawback of OFDM system is high peak -to-average power ratio (PAPR) of transmit signal.There are many methods to reduce PAPR in OFDM system, in which selected mapping (SLM) is one of the best distortion less method.However, it requires a bank of inverse Fast Fourier Transforms (IFFTs).Therefore, the system has more computational complexity. In this paper, we proposed a modified selected mapping (M-SLM) scheme using a perfect sequence /conversion vectors.In this method,the data sequences are equally divided then for the first half of the data sequence IFFT is taken then circular convolutionis performed with perfect sequences.conventional SLM is applied for the second half section to reduce the complexity and PAPR. Finally, the number of candidate signals are doubled from the same IFFT blocks. From the simulation results, the proposed method slightly reducesPAPR.Moreover, the computational complexity of the proposed method reduces much than C-SLM.
IndexTerms---Orthogonalfrequency division multiplexing (OFDM), peak-to-average power ratio (PAPR), selective mapping (SLM), partial transmit sequence (PTS), high power amplifier (HPA).I.
Orthogonal Frequency Division Multiplexing (OFDM) is a digital transmission method developed to meet the increasing demand for higher data rates in communications which can be used in both wired and wireless environments this paper presents a hybrid Peak-to-Average Power Ratio (PAPR) reduction technique, which combines a selective mapping method with the clipping method. Clipping is one of the simplest PAPR reduction techniques, but this introduces Distortion to the transmitted signal .Selective Mapping (SLM) is the Distortion less Method of PAPR reduction. Our proposed method is less complex and having advantages of both SLM and Clipping method.
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