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A Configuration of Power Divided Diplexer for Satellite Onboard Application in Ku-Band
Ohmine, Hiroyuki,Yabushita, Takeshi,Yamato, Masao,Yoneda, Naofumi,Konishi, Yoshihiko 통신위성우주산업연구회 2004 Joint Conference on Satellite Communications Vol.2004 No.-
In designing of high power satellite communication antenna, the high precise design is necessary to avoid multipactor generation under the condition of high vacuum space environment. Especially, realizing high power-handling diplexer, which separates transmitting and receiving power, os required for antenna feed circuit. This paper proposes a new configuration of high power handling diplexer for satellite onboard application and test results in Ku-band. For surviving high power handling, two methods are applied. One is input power to band pass filter (BPF) is divided into half power using hybrid coupler, and the other is input power of stub of BPF is divided into half power using double sided stub configuration. This configuration can decrease to a quarter power of input to avoid power concentration. And design method of stub filter with optimized procedure to obtain good isolation performance in receiving band is described. Drastic improvement can be achieved by introducing this technique. Further, electric field is also calculated using simulator and power limitation to multipactor is estimated. A diplexer has been designed and manufactured in the Ku-band and its design effectiveness has been confirmed through test results.
Kojima Tsukasa,Yamasaki Yuzo,Kamitani Takeshi,Yabuuchi Hidetake,Shirasaka Takashi,Shimomiya Yamato,Kondo Masatoshi,Hamasaki Hiroshi,Kato Toyoyuki,Nagao Michinobu,Honda Hiroshi 아시아심장혈관영상의학회 2019 Cardiovascular Imaging Asia Vol.3 No.1
Objective: The smallest diagnostically sufficient amount of contrast media (CM) should be used for coronary computed tomography angiography (CCTA) to minimize the risk of contrast- induced nephrotoxicity in elderly patients with coronary artery disease. The purpose of this study was to propose dynamic-CCTA using a low dose of CM and temporal maximum intensity projection (TMIP) and to investigate its image quality compared to standard-CCTA. Materials and Methods: Participants comprised 30 patients with coronary artery disease who underwent dynamic-CCTA and standard-CCTA using 320-row CT. Dynamic-CCTA was continuously performed at mid-diastole throughout 15–25 cardiac cycles after bolus injection of CM [103 mg iodine/kg body weight (mgI/kg)]. TMIP-CCTA was reconstructed from three-phase dynamic-CCTA data, including a phase with peak enhancement of the ascending aorta. Standard-CCTA was performed using a standard CM dose (259 mgI/kg). Image quality of both TMIP-CCTA and standard-CCTA was analyzed. Results: The amount of CM used in TMIP-CCTA and standard-CCTA was 16.2±2.6 mL and 40.1±7.3 mL, respectively. The mean effective radiation dose was not significantly different between the two methods. Mean coronary attenuation was significantly lower for TMIP-CCTA than standard-CCTA [346.9±82.8 Hounsfield units (HU) vs. 455.4±75.3 HU, p<0.05]. Image noise was significantly lower for TMIP-CCTA than standard-CCTA (20.0±3.2 HU vs. 28.1± 3.6 HU, p<0.05). There were no differences in signal-to-noise ratio and visual assessment scores between the two methods. Conclusion: TMIP-CCTA can be performed using more than 50% less CM with the same image quality as standard-CCTA.