Yazar "Gozel, Mahmut Ahmet" seçeneğine göre listele

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    Application of ultra wideband RF energy harvesting by using multisection Wilkinson power combiner
    (Wiley, 2019) Kasar, Ömer; Kahriman, Mesud; Gozel, Mahmut Ahmet
    In this study, an ultra-wide band (UWB) energy harvesting circuit was proposed using the Greinacher rectifier circuit. The circuit was designed with Wilkinson power combiner (WPC) for use at two different radio frequency signal inputs. To enable broadband operation, the multisection Chebyshev impedance matching technique was applied in the branches of the WPC circuit. The center frequency was selected 2.2GHz in the design. In terms of the parameters of reflection, transmission and isolation, the WPC circuit operates in the 0.4 GHz-3.4 GHz range and the percentage bandwidth has been calculated as 136%. In the designed Greinacher rectifier circuit, power conversion efficiency (PCE) was analyzed for different input powers. When load resistor selected as R=1500, the PCE for the input power of 9 dBm was about 70%. The proposed circuit, where WPC and Greinacher rectifier circuits was used together for energy harvesting; was operated in the frequency ranges BW1=0.4-0.81GHz, BW2=1.54-1.84GHz, and BW3=2.2 GHz-2.89GHz. As a power combining application, dual power inputs were applied to the WPC circuit with frequencies of 540MHz-1800MHz, 540MHz-2450MHz, 540MHz-2700MHz, 800MHz-1800MHz, 800MHz-2450MHz and 800MHz-2700MHz. Eventually, approximately 70.5% PCE and 1.65V output voltage were obtained.
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    Design of an efficiency-enhanced Greinacher rectifier operating in the GSM 1800 band by using rat-race coupler for RF energy harvesting applications
    (Wiley, 2019) Gozel, Mahmut Ahmet; Kahriman, Mesud; Kasar, Ömer
    Radio frequency energy harvesting (RFEH) circuits can convert the power of communication signals from radio frequencies (RF) in the environment into direct current and voltage (DC power). In this study, the Greinacher full-wave rectifier circuit topology was combined with a 180 hybrid ring (rat-race) coupler which was a passive RF/microwave circuit. Thus, higher RF-DC conversion efficiency was obtained. First, using the Greinacher rectifier topology, RFEH circuit operating at the center frequency of 1850 MHz was designed. Then, at this frequency, designing of the rat-race coupler having 1000 MHz bandwidth was made. The S-parameter measurements and simulation data of the designed coupler circuit were compared. Finally, the high efficiency rectifier circuit where these two circuits were used together was designed. The proposed rectifier circuit was constructed on 70 × 70 × 1.6 mm3 FR4 substrate material with a permittivity of 4.3 (?r = 4.3). The power conversion efficiency (PCE) of the rectifier circuit, which had 125 MHz bandwidth at the center frequency of 1850 MHz and was developed with rat-race coupler, was calculated as 71% at 4.7 dBm input power. In addition, with this study, at ?15 dBm input power, which was a relatively low power level, 40% PCE value was obtained.