Farzad Khajeh-Khalili

Bio: Farzad Khajeh-Khalili is an academic researcher from Islamic Azad University. The author has contributed to research in topics: Antenna (radio) & Metamaterial. The author has an hindex of 6, co-authored 16 publications receiving 71 citations.

Compact Tri-band Wilkinson Power Divider Based on Metamaterial Structure for Bluetooth, WiMAX, and WLAN Applications

Abstract: A novel Wilkinson power divider is presented in this paper for triple band operation. It comprises a Π-shaped transmission-line coupled to a rectangular split ring resonator metamaterial structure....

Design investigation of a dual-band wearable antenna for tele-monitoring applications

Abstract: This paper presents a novel dual-band wearable antenna using Rectangular Parasitic Elements (RPEs) and Defected Ground Structure (DGS) methods in telemedicine applications. The dual-band ranges covered by this antenna are in 890–960 MHz and 1710–1885 MHz which are used in Global System for Mobile communications (GSM) applications. Wearable and flexible material that is used as the substrate is a standard rubber with dielectric constant er = 3, thickness = 1.57 mm, and tan (δ) = 0.0095. The dimensions of the proposed wearable antenna are 70 × 85 × 1.64 mm3 or 0.0007λg3 at 900 MHz. The measured maximum gain is achieved at 900 MHz and 1800 MHz, which are equal to 7.46 dB and 8.13 dB, respectively. A good agreement between simulation and experimental results are obtained by a fabricated prototype of the antenna. Therefore, the results represent this antenna is a promising candidate in biomedical technology such as tele-monitoring at the GSM bands.

A design of triple lines Wilkinson power divider for application in wireless communication systems

Abstract: In this article, a novel microstrip Wilkinson power divider (WPD) has been analyzed, simulated, and fabricated, using the proposed triple lines (TLs) in place of the common quarter-wavelength transmission-line. The proposed structure has the high ability of selectivity for designing dimensions. In this direction with the use of PSO algorithm, optimized options will be obtained for the electrical lengths of the TLs. The characteristic admittances, with the intention of fabricating a structure with compact dimensions are also obtained. Besides, three coupled lines theory is used to reach a wideband performance. The proposed triple lines Wilkinson power divider (TLWPD) operates from 0.5 to 4.5 GHz with S11 < −10 dB, which include several wireless communication standards such as GSM, GPS, DCS, PCS, UMTS, WLAN, and WiMAX. The overall size of the TLWPD is 23.5 × 8.3 mm2 or 0.23 λg × 0.08 λg. The results of investigations taken in this article show the fact that the TLWPD, in addition to the small struct...

Compact Tri-band Wilkinson Power Divider Based on Metamaterial Structure for Bluetooth, WiMAX, and WLAN Applications

Abstract: A novel Wilkinson power divider is presented in this paper for triple band operation. It comprises a Π-shaped transmission-line coupled to a rectangular split ring resonator metamaterial structure....

Planar antenna beam deflection using low‐loss metamaterial for future 5G applications

Abstract: A method to tilt the beam of a planar antenna in the E-plane is demonstrated by implementing a metamaterial (MM) structure onto the antenna substrate at the fifth-generation (5G) band of 3.5 GHz. The beam tilting is achieved due to the phase change that occurs when the electromagnetic (EM) wave traverses through two media with different refractive indices. A new adjacent square-shaped resonator (ASSR) structure is proposed to achieve the beam tilting in a dipole antenna. This structure provides a very low loss of −0.2 dB at 3.17 GHz. The simulation and measurement results illustrate that the radiation beam of the dipole antenna is tilted by +25° and −24° depending on the position of the ASSR array onto the dipole antenna substrate. In addition, no degradation in the gain is observed as in the conventional beam-tilting methods; in fact, gain enhancement values of 3 dB (positive deflection) and 2.7 dB (negative deflection) are obtained compared with that of a dipole antenna with no ASSR array. The reflection coefficient of the dipole antenna with ASSR array has a good agreement with that of the dipole antenna with no ASSR array. The measured results agree well with the simulated ones.

Improving medical communication process using recurrent networks and wearable antenna s11 variation with harmonic suppressions

Abstract: In medical applications, most of the patients are remotely monitored to eliminate the risk of being infected from the healthcare facilities. The process of remotely monitoring patients involves placing several body sensor networks on the patient’s body to collect their health details. The collected information is transmitted via the wireless communication process that must be of a high quality. Hence, this paper investigated antenna S11 variation (AS11V) with harmonic suppression to improve the communication process in medical applications. In this research, the antenna was placed on a 2- to 4-mm thickness belt, 15 to 300 mm body thickness, and 40 to 50 dielectric constants. In addition, 3-short pin resonators were used in the harmonic suppression process aid in reducing the unnecessary harmonics in the communication process. Optimized recurrent neural networks (ORNN) were then used to process the wearable antenna–based collected devices. This in return helped in determining how effectively the gathered data helps in the medical analysis. The efficiency of the wireless antenna–based communication process was then evaluated using simulation results, and the ORNN approach showed 99.17% accuracy using the collected and validated data.