Large Frequency Ratio Vivaldi Antenna System with Low Frequency Gain Enhancement Utilizing Dual-function Taper Slot

Author(s):  
Jian Ren ◽  
Miaomiao Zuo ◽  
Bing Zhang ◽  
Xiaoyu Du ◽  
Zhe Chen ◽  
...  
Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 5988
Author(s):  
Jungwoo Seo ◽  
Jae Hee Kim ◽  
Jungsuek Oh

A microstrip-to-slot line-fed miniaturized Vivaldi antenna using semicircular patch embedment is proposed in this study. The conventional Vivaldi antenna has ultrawide bandwidth, but suffers from low gain in the low-frequency band. The proposed antenna topology incorporates the embedment of semicircular patch elements into the side edge of the antenna. This enables the phases of electric fields at both ends of the antenna to be out of phase. Since the distance between the two ends are λL/2 where λL is the wavelength at a low operating frequency, this antenna topology can achieve the constructive addition of electrical fields at the radiating end, leading to gain enhancement at the chosen low frequency. In comparison with the conventional Vivaldi antenna, the proposed antenna has a wider bandwidth from 2.84 to 9.83 GHz. Moreover, the simulated result shows a gain enhancement of 5 dB at low frequency. This cannot be realized by the conventional low-band impedance matching techniques only relying on slotted topologies. The measured results of this proposed antenna with a size of 45 × 40 × 0.8 mm3 are in good agreement with the simulated results.


Author(s):  
Xu-Jun Yang ◽  
Lei Ge ◽  
Yuan Ji ◽  
Xie-Rong Zeng ◽  
Yu-Jian Li ◽  
...  

Author(s):  
Д.В. БОСОМЫКИН ◽  
А.П. ВОРОНЦОВ ◽  
И.В. ПРИЩЕПА ◽  
А.А. ГАВРИЛОВ ◽  
А.В. ПРОРЕШКИН ◽  
...  

Предложен широкополосный излучатель со стабильным фазовым центром (ФЦ) для использования в составе облучателя зеркальной антенны. Излу ортогональных поляризациях и круговой поляризации при использовании квадратурного питания. Рабочая полоса по уровню КстU ≤ 2 обеспечивается при коэффициенте перекрытия по частоте более 1:16. Исследованы характеристики направленности облучателя зеркальной антенны на базе антенны типа Вивальди, представлены результаты расчетов и измерений его параметров. Обоснована пригодность для использования в составе облучателя сверхширокополосной зеркальной антенной системы в режиме суммарного и разностного формирования диаграммы направленности (ДН). It is presented the wideband irradiator with a stable phase center for use in a reflector antenna irradiator. The irradiator is based on a smoothly expanding slot. It has two coaxial feeds to form dual linear orthogonal polarization. Circular polarization radiation can be achieved with an additional hybrid coupler. The VSWR≤2 bandwidth is obtained for a frequency ratio of more than 1:16. The directional characteristics of the irradiator of a reflector antenna based on a Vivaldi antenna are investigated, the results of calculations and measurements of its parameters are presented. The suitability of the irradiator for use as a part of the irradiator of the ultra-wideband reflector antenna system is justified.


Author(s):  
Kun He ◽  
Jian Li ◽  
Lifan Xiao ◽  
Yongqian Xiong ◽  
Linghao Wu

2015 ◽  
Vol 22 (8) ◽  
pp. 1080-1085 ◽  
Author(s):  
Sakari Simula ◽  
Tomi Laitinen ◽  
Tiina M Laitinen ◽  
Tuula Tarkiainen ◽  
Päivi Hartikainen ◽  
...  

Background: Fingolimod modulates sphingosine-1-phosphate receptors that are also found in cardiovascular tissue. Objective: To investigate the effects of fingolimod on cardiac autonomic regulation prospectively. Methods: Twenty-seven relapsing–remitting multiple sclerosis patients underwent 24-hour electrocardiogram recording before, at the first day of fingolimod treatment (1d) and after three months of continuous dosing (3mo). The time interval between two consecutive R-peaks (RR-interval) was measured. Cardiac autonomic regulation was assessed by the various parameters of heart rate variability. Parasympathetic stimulation prolongs the RR-interval and increases heart rate variability while the effects of sympathetic stimulation are mainly the opposite. The low frequency/high frequency ratio reflects sympathovagal balance. Results: From baseline to 1d, a prolongation of the RR-interval ( P<0.001), an increase in the values of various heart rate variability parameters ( P<0.05 to P<0.001) and a decrease in the low frequency/high frequency ratio ( P<0.05) were demonstrated. At 3mo, although the RR-interval remained longer ( P<0.01), the values of various heart rate variability parameters were lower ( P<0.01 to P<0.001) as compared to baseline. At 3mo, the low frequency/high frequency ratio ( P<0.05) was higher in men than in women although no such difference was found at baseline or at 1d. Conclusions: After an initial increase in parasympathetic regulation, continuous fingolimod dosing shifts cardiac autonomic regulation towards sympathetic predominance, especially in men. Careful follow-up of fingolimod-treated relapsing–remitting multiple sclerosis patients is warranted as sympathetic predominance associates generally with impaired outcome. ClinicalTrials.cov: NCT01704183


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