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RISS 인기검색어
- 검색키워드
- 저자 : Md. Najmul Hossain (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Nonlinear Characteristics of DFT-Spread WR-OFDM System for Spectrum-efficient Communications
Md. Najmul Hossain,Tetsuya Shimamura,Heung-Gyoon Ryu 대한전자공학회 2019 IEIE Transactions on Smart Processing & Computing Vol.8 No.6
Since frequency resources are limited, and power saving is also a vital issue, a more spectrum-efficient and power-saving communications system design is the most important research goal. In this paper, we propose an improved, spectrally efficient new discrete Fourier transform (DFT)-Spread Windowing and Restructuring (WR)-Orthogonal Frequency Division Multiplexing (DFT-Spread WR-OFDM) communications system, in thought of various strengths of high-power amplifier (HPA) nonlinearity for a reasonably allowable peak-to-average power ratio (PAPR) and out-of-band (OOB) power emission reduction. Compensation for HPA nonlinearity becomes a difficult task when properly designing efficient multicarrier schemes and fifth generation (5G)-beyond 5G candidate waveforms for cellular wireless communications systems. In practical communications systems, spectral efficiency and power are highly affected by HPA nonlinearity features, and bit error rate (BER) performance also deteriorates. We implemented a time domain window named Tukey (tapered cosine) and localized subcarrier mapping, and the impact of HPA nonlinearity on BER performance and spectral characteristics is comprehensively analyzed. Simulation results demonstrate that the proposed system reduces PAPR and OOB power emissions by 3.176 ㏈ and -81 ㏈, respectively. Additionally, compared to conventional systems, the communication quality of the proposed scheme clearly demonstrates better performance even inHPA nonlinear environments.
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Multiband Slotted Crescent-shaped Patch Antenna for K-band Satellite and mmWave Communications
Md. Najmul Hossain,Liton Chandra Paul,Md. Abdur Rahim,Jungpil Shin 대한전자공학회 2022 IEIE Transactions on Smart Processing & Computing Vol.11 No.3
In this paper, a multiband miniaturized crescent-shaped patch antenna with circular slots is presented for ultra-wideband applications. The proposed antenna is constructed on a Flame Retardant 4 (FR-4) dielectric substrate. Next-generation wireless communication systems, such as beyond 5G (B5G) and 6G mobile communication systems require a wider bandwidth and higher data rates. The overall size of the proposed antenna is 11×9×2.4 mm3 operating in the frequency range of 17.73 GHz to 26.04 GHz and 29.6 GHz to 31.02 GHz for satellite communications and radar systems, respectively, as well as 35.40 GHz to 38.65 GHz for future mmWave B5G mobile applications. These frequency ranges usually fall into the K-band and mmWave frequency spectrums. Simulation results demonstrate that the peak gain of the proposed antenna is 4.68 dB, which is obtained at 25 GHz.
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Design and Analysis of a UWB Slotted Vivaldi Antenna for Microwave Imaging Applications
Liton Chandra Paul,Akash Majumder,Tithi Rani,Md. Najmul Hossain,Md. Abdur Rahim,Jungpil Shin,Keun Soo Yun 대한전자공학회 2023 IEIE Transactions on Smart Processing & Computing Vol.12 No.4
An ultra-wideband (UWB) slotted compact Vivaldi antenna with a microstrip line feed was evaluated for microwave imaging (MI) applications. The recommended FR4 substrate-based Vivaldi antenna is 50×50×1.5 mm3 in size. The proposed compact Vivaldi antenna showed good radiation characteristics and spanned an ultra-wide bandwidth of 10 GHz, ranging from 3.6 to 13.6 GHz, using a microstrip line feed with a radial stub, tapered slots, and resonant cavities. After analyzing the simulation findings, the proposed compact slotted UWB Vivaldi antenna was compared with the basic Vivaldi antenna. The maximum gain and efficiency were 7.35 dB and 82%, respectively. The antenna was simulated in the time domain using the computer simulation technology (CST) microwave studio. The frequency domain solver was also used for cross-validation, and the results were equally good. In conclusion, the proposed compact Vivaldi antenna is a good option for microwave imaging applications.
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