In this article, we apply a novel fractal in arms of an antipodal dipole for antenna miniaturization that uses the Chu's sphere very effectively to keep antenna efficiency very high in comparison with its counterparts like Koch dipole/monopole. Then, a formula is extracted to determine the first resonance of the dipole. We used this method to design a mobile antenna at LTE13 band (746–787 MHz) which is well known for leading the size of a common dipole antenna to be very large for a handheld mobile. The proposed design shows 40% size reduction in comparison with a common dipole while antenna efficiency is better than 79.28% with S11 greater than 10 dB. It also covers LTE band2 (1850–1990 MHz) with S11 and efficiency better than 6 dB and 78.91%, respectively. The overall size of the printed antenna is 62 × 115 × 1.6 mm3. The simulation and measurement results verify the presented calculations very well. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2429–2434, 2015

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In this article a novel feeding system for BST Multiband Antennas is presented. This system is based on a 4 × 4 Butler matrix that uses a novel triple band hybrid. This hybrid operates on GSM900, DCS1800 and UMTS2100 bands. The presented novel implementation technique in the triple band hybrid can also be used in other application. The Butler matrix network is fabricated on FR4 substrate and the simulated and measured results are presented.

Background: As a soccer referee or an assistant referee, having perfect visual skills is mandatory, which will help make quick and accurate decisions in the field of the play and during matches; however, this skill is not well studied among referrers. This study aimed to assess the visual skills of referees and assistant referees. Methods: Men’s professional referees and assistant referees working for the Iran football federation were investigated in 2019. The visual skill investigation consists of the evaluation of static visual acuity, color vision, stereoacuity, intraocular pressure, confrontation test, and eye anatomical assessment with slit lamp. The statistical analysis was performed using the SPSS software Version 18. Results : In this study, 159 men’s professional referees and assistant referees with a mean age of 35.52±5.39 were selected. The results of this study showed that 1.88% of the referees and assistant referees had color blindness dyschromatopsia) and 3.14% of them needed more follow-up examinations. The mean spherical equivalent of examined eyes was -0.42D in the right eye and -0.16 D in the left eye. Conclusion: Our results showed that referees and assistant referees both had some kind of visual skill deficiencies. As visual skills are among the fundamental skills for success in referees in dynamic sports such as soccer, all of them must undergo visual skill assessments during the precompetition period to avoid any errors in judgment due to visual disturbances.