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Shaharil Mohd Shah
Universiti Tun Hussein Onn Malaysia (UTHM)

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Comparative analysis of sokal’s equations versus load-pull implementation of class E low-pass network Boodhoo Kirish; Farid Zubir; Mohamad Kamal A. Rahim; Shaharil Mohd Shah
Indonesian Journal of Electrical Engineering and Computer Science Vol 19, No 3: September 2020
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijeecs.v19.i3.pp1348-1357

Abstract

In this paper, class E power amplifiers (PA) aimed at frequency bandwidth of 3.4 GHz to 3.6 GHz (LTE 42) and 3.6 GHz to 3.8 GHz (LTE 43) respectively are designed with objective of attaining high efficiency. The viability of Sokal’s equations for present communication systems aimed at GHz are analyzed for high efficiency using HEMT (high-electron-mobility transistor) on Nitronex NPTB00004 as opposed to the Bipolar Junction Transistor used by Sokal in 1975. Load-pull configuration techniques aimed at the drain is implemented at the output matching network (OMN) and benchmarked against Sokal’s equation. At the OMN, to suppress harmonics, band-pass filters are employed for the LTE 42 and 43 respectively. Sokal’s equation shows that the drain must be conjugately matched before his equations are applied at the OMN. The efficiency at 3.4 GHz obtained for Sokal’s circuit is at 67 % and gain of 9.3 dB. More than 65% efficiency is obtained from load-pull network at 3.4 GHz to 3.76 GHz before filter implementation while showing gain above 7.8 dB. After filter addition at OMN, the efficiency is above 65% and gain above 8 dB for dual - band having bandwidth of 3.4389 GHz - 3.542GHz and 3.6569GHz - 3.8GHz.
A wearable antenna based on fabric materials with circular polarization for Body-centric wireless communications Adel Y. I. Ashyap; Z. Z. Abidin; Samsul Haimi Dahlan; Shaharil Mohd Shah; Huda A. Majid; Yee See Khee; Norun Abdul Malek
Indonesian Journal of Electrical Engineering and Computer Science Vol 18, No 1: April 2020
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijeecs.v18.i1.pp335-342

Abstract

A compact and simple structure antenna for wearable application at 2.4 GHz is presented and studied. The felt fabric material is used in this paper due to its suitable thickness and dielectric constant. This material provides high flexibility which can be easily worn on a body and incorporated into our daily clothes. In view of the fact that the design will work on a moving person, therefore a circularly polarized antenna is desired to optimize the off-body communication link. The Cicular Polarization (CP) is achieved by introducing truncated corners on the patch. The antenna size is 60 × 60 × 2 mm3. The Axial Ratio (AR), the Front to Back Ratio (FRB) and the realized gain are 0.96 dB, 10.5 dB, and 4.62 dB, respectively indicating a good performance of the antenna at the desired frequency. Furthermore, the antenna was investigated when operating near the body. The obtained result shows that the design has performance similar to the case of free space. This is due to the present of the full ground plane that acts as a shielding between the antenna and body. Finally, the Specific Absorption Rate (SAR) is carried out and showed that the antenna has a level less than the limits fixed by the FCC standard. Therefore, the antenna could be useful for wearable applications.
Co-Authors Adel Y. I. Ashyap Boodhoo Kirish Farid Zubir Huda A. Majid Mohamad Kamal A. Rahim Norun Abdul Malek Samsul Haimi Dahlan Yee See Khee Z. Z. Abidin