In this paper, a time-varying rain characterization and diurnal variation in the Ku-band satellite systems simulated with synthetic storm techniques (SST) over a tropical location in Nigeria have been presented. Three...In this paper, a time-varying rain characterization and diurnal variation in the Ku-band satellite systems simulated with synthetic storm techniques (SST) over a tropical location in Nigeria have been presented. Three years’ rain rate time-series data measured by a raingauge located inside the Federal University of Technology Akure, Nigeria were utilized for the purpose of this work. The analysis is based on the CDF of one-minute rain rate;time-series simulated annual/seasonal and diurnal rain rate, rain attenuation statistics and fade margins observed over four time intervals: 00:00-06:00, 06:00-12:00, 12:00-18:00 and 18:00-24:00. In addition, comparison was also made between the synthesized values and rain attenuation statistics, at 12.245 GHz for a hypothetical downlink from EUTELSAT W4/W7 satellite in the area. It could be observed that at 99.99% link availability, the fade margin as high as ~20 dB may be required at Ku band uplink frequency bands in this area. We also observed that the communication downlinks working in the early morning and early to late in the evening hours must be compensated with an appropriate Down-Link Power Control (DLPC) for optimum performances during severe atmospheric influences in the region.展开更多
We report a high power Ku band internally matched power amplifier （IMPA） with high power added efficiency （PAE） using 0.3 μm A1GaN/GaN high electron mobility transistors （HEMTs） on 6H-SiC substrate. The intemal...We report a high power Ku band internally matched power amplifier （IMPA） with high power added efficiency （PAE） using 0.3 μm A1GaN/GaN high electron mobility transistors （HEMTs） on 6H-SiC substrate. The intemal matching circuit is designed to achieve high power output for the developed devices with a gate width of 4 mm. To improve the bandwidth of the amplifier, a T type pre-matching network is used at the input and output circuits, respectively. After optimization by a three-dimensional electromagnetic （3D-EM） simulator, the amplifier demonstrates a maximum output power of 42.5 dBm （17.8 W）, PAE of 30% to 36.4% and linear gain of 7 to 9.3 dB over 13.8-14.3 GHz under a 10% duty cycle pulse condition when operated at Vas = 30 V and Vgs = -4 V. At such a power level and PAE, the amplifier exhibits a power density of 4.45 W/mm.展开更多
Due to the good performance of tracking low elevation target as compared to microwave and the superiority in penetrating smoke, dust, fog, and dry snow as compared to infrared, a Ku and Ka dual band experimental radar...Due to the good performance of tracking low elevation target as compared to microwave and the superiority in penetrating smoke, dust, fog, and dry snow as compared to infrared, a Ku and Ka dual band experimental radar was designed and developed. This Ku and Ka dual band experimental radar is an arnplitute-comparison monopulse tracking and guiding radar. The constitution and parameters of this radar is described in paragraph 2. Paragraph 3 deals with two experiments for testing the tracking performances against low elevation target, and gives the important results. Both Ku and Ka band have high tracking precision when they track high elevation targets, while Ka band has much better tracking performance than Ku band when they track low elevation targets. Ka band can track a helicopter, whose radar cross section is about 6 square meters, at 40m, 20m, 10m, and even 5m above sea. Ku band can only track the same helicopter at 160m and higher above sea.展开更多
In order to enhance the power capacity, an improved Ku-band magnetically insulated transmission line oscillator （MILO） with overmoded slow-wave-structure （SWS） is proposed and investigated numerically and experime...In order to enhance the power capacity, an improved Ku-band magnetically insulated transmission line oscillator （MILO） with overmoded slow-wave-structure （SWS） is proposed and investigated numerically and experimentally. The analysis of the dispersion relationship and the resonant curve of the cold test indicate that the devine can operate at the near π mode of the TM01 mode, which is useful for mode selection and control. In the particle simulation, the improved Ku-band MILO generates a microwave with a power of 1.5 GW and a frequency of 12.3 GHz under an input voltage of 480 kV and input current of 42 kA. Finally, experimental investigation of the improved Ku-band MILO is carried out. A high-power microwave （HPM） with an average power of 800 MW, a frequency of 12.35 GHz, and pulse width of 35 ns is generated under a diode voltage of 500 kV and beam current of 43 kA. The consistency between the experimental and simulated far-field radiation pattern confirms that the operating mode of the improved Ku-band MILO is well controlled in zc mode of the TM01 mode.展开更多
文摘In this paper, a time-varying rain characterization and diurnal variation in the Ku-band satellite systems simulated with synthetic storm techniques (SST) over a tropical location in Nigeria have been presented. Three years’ rain rate time-series data measured by a raingauge located inside the Federal University of Technology Akure, Nigeria were utilized for the purpose of this work. The analysis is based on the CDF of one-minute rain rate;time-series simulated annual/seasonal and diurnal rain rate, rain attenuation statistics and fade margins observed over four time intervals: 00:00-06:00, 06:00-12:00, 12:00-18:00 and 18:00-24:00. In addition, comparison was also made between the synthesized values and rain attenuation statistics, at 12.245 GHz for a hypothetical downlink from EUTELSAT W4/W7 satellite in the area. It could be observed that at 99.99% link availability, the fade margin as high as ~20 dB may be required at Ku band uplink frequency bands in this area. We also observed that the communication downlinks working in the early morning and early to late in the evening hours must be compensated with an appropriate Down-Link Power Control (DLPC) for optimum performances during severe atmospheric influences in the region.
基金Project supported by the National Basic Research Program of China(No.2010CB327503)the National Natural Science Foundation of China(No.60890191)
文摘We report a high power Ku band internally matched power amplifier （IMPA） with high power added efficiency （PAE） using 0.3 μm A1GaN/GaN high electron mobility transistors （HEMTs） on 6H-SiC substrate. The intemal matching circuit is designed to achieve high power output for the developed devices with a gate width of 4 mm. To improve the bandwidth of the amplifier, a T type pre-matching network is used at the input and output circuits, respectively. After optimization by a three-dimensional electromagnetic （3D-EM） simulator, the amplifier demonstrates a maximum output power of 42.5 dBm （17.8 W）, PAE of 30% to 36.4% and linear gain of 7 to 9.3 dB over 13.8-14.3 GHz under a 10% duty cycle pulse condition when operated at Vas = 30 V and Vgs = -4 V. At such a power level and PAE, the amplifier exhibits a power density of 4.45 W/mm.
文摘Due to the good performance of tracking low elevation target as compared to microwave and the superiority in penetrating smoke, dust, fog, and dry snow as compared to infrared, a Ku and Ka dual band experimental radar was designed and developed. This Ku and Ka dual band experimental radar is an arnplitute-comparison monopulse tracking and guiding radar. The constitution and parameters of this radar is described in paragraph 2. Paragraph 3 deals with two experiments for testing the tracking performances against low elevation target, and gives the important results. Both Ku and Ka band have high tracking precision when they track high elevation targets, while Ka band has much better tracking performance than Ku band when they track low elevation targets. Ka band can track a helicopter, whose radar cross section is about 6 square meters, at 40m, 20m, 10m, and even 5m above sea. Ku band can only track the same helicopter at 160m and higher above sea.
基金Project supported partly by the National Natural Science Foundation of China(Grant No.61171021)
文摘In order to enhance the power capacity, an improved Ku-band magnetically insulated transmission line oscillator （MILO） with overmoded slow-wave-structure （SWS） is proposed and investigated numerically and experimentally. The analysis of the dispersion relationship and the resonant curve of the cold test indicate that the devine can operate at the near π mode of the TM01 mode, which is useful for mode selection and control. In the particle simulation, the improved Ku-band MILO generates a microwave with a power of 1.5 GW and a frequency of 12.3 GHz under an input voltage of 480 kV and input current of 42 kA. Finally, experimental investigation of the improved Ku-band MILO is carried out. A high-power microwave （HPM） with an average power of 800 MW, a frequency of 12.35 GHz, and pulse width of 35 ns is generated under a diode voltage of 500 kV and beam current of 43 kA. The consistency between the experimental and simulated far-field radiation pattern confirms that the operating mode of the improved Ku-band MILO is well controlled in zc mode of the TM01 mode.
