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
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
A high power density monolithic power amplifier operated at Ku band is presented utilizing a 0.3μm AlGaN/GaN HEMT production process on a 2-inch diameter semi-insulating（SI） 4H-SiC substrate by MOCVD. Over the 12-1...A high power density monolithic power amplifier operated at Ku band is presented utilizing a 0.3μm AlGaN/GaN HEMT production process on a 2-inch diameter semi-insulating（SI） 4H-SiC substrate by MOCVD. Over the 12-14 GHz frequency range,the single chip amplifier demonstrates a maximum power of 38 dBm（6.3 W）, a peak power added efficiency（PAE） of 24.2%and linear gain of 6.4 to 7.5 dB under a 10%duty pulse condition when operated at V_（ds） = 25 V and V_（gs） = -4 V.At these power levels,the amplifier exhibits a power density in excess of 5 W/mm.展开更多
Ku-band GaN power transistor with output power over 100 W under the pulsed operation mode is pre- sented. A high temperature A1N nucleation together with an Fe doped GaN buffer was introduced for the developed GaN HEM...Ku-band GaN power transistor with output power over 100 W under the pulsed operation mode is pre- sented. A high temperature A1N nucleation together with an Fe doped GaN buffer was introduced for the developed GaN HEMT. The A1GaN/GaN hetero-structure deposited on 3 inch SiC substrate exhibited a 2DEG hall mobility and density of -2100 cm2/（V.s） and 1.0 x 10^13 cm-2, respectively, at room temperature. Dual field plates were introduced to the designed 0.25μm GaN HEMT and the source connected field plate was optimized for minimizing the peak field plate near the drain side of the gate, while maintaining excellent power gain performance for Ku-band application. The load-pull measurement at 14 GHz showed a power density of 5.2 W/mm for the fabricated 400 μm gate periphery GaN HEMT operated at a drain bias of 28 V. A Ku-band internally matched GaN power transistor was developed with two 10.8 mm gate periphery GaN HEMT chips combined. The GaN power transistor exhibited an output power of 102 W at 13.3 GHz and 32 V operating voltage under pulsed operation mode with a pulse width of 100 μs and duty cycle of 10%. The associated power gain and power added efficiency were 9.2 dB and 48%, respectively. To the best of the authors＇ knowledge, the PAE is the highest for Ku-band GaN power transistor with over 100 W output power.展开更多
The preliminary design results of a 1-MW,Kuband gyrotron traveling wave amplifier(gyro-TWA)are presented.Operating at the second cyclotron harmonic of the TE11 mode,the amplifier characterizes good stability even in t...The preliminary design results of a 1-MW,Kuband gyrotron traveling wave amplifier(gyro-TWA)are presented.Operating at the second cyclotron harmonic of the TE11 mode,the amplifier characterizes good stability even in the case of no distributed losses loaded,which could potentially allow it to be operated at high average power.Large signal simulation shows that the amplifier can generate a saturated peak power of about 1MW with efficiency of 26.6%,gain of 31 dB,and 3-dB bandwidth of about 1 GHz when driven by a 100 kV,40 A electron beam with 5%axial velocity spread.展开更多
This paper describes the first domestic Ku-band power AlGaN/GaN HEMT fabricated on a sapphire substrate. The device with a gate width of 0.5 mm and a gate length of 0.35μm has exhibited an extrinsic current gain cuto...This paper describes the first domestic Ku-band power AlGaN/GaN HEMT fabricated on a sapphire substrate. The device with a gate width of 0.5 mm and a gate length of 0.35μm has exhibited an extrinsic current gain cutoff frequency of 20 GHz and an extrinsic maximum frequency of oscillation of 75 GHz.Under VDS=30 V,CW operating conditions at 14 GHz,the device exhibits a linear gain of 10.4 dB and a 3-dB-gain-compressed output power of 1.4 W with a power added efficiency of 41%.Under pulse operating conditions,the linear gain is 12.8 dB and the 3-dB-compressed output power is 1.7 W.The power density reaches 3.4 W/mm.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 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.
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A high power density monolithic power amplifier operated at Ku band is presented utilizing a 0.3μm AlGaN/GaN HEMT production process on a 2-inch diameter semi-insulating（SI） 4H-SiC substrate by MOCVD. Over the 12-14 GHz frequency range,the single chip amplifier demonstrates a maximum power of 38 dBm（6.3 W）, a peak power added efficiency（PAE） of 24.2%and linear gain of 6.4 to 7.5 dB under a 10%duty pulse condition when operated at V_（ds） = 25 V and V_（gs） = -4 V.At these power levels,the amplifier exhibits a power density in excess of 5 W/mm.
文摘Ku-band GaN power transistor with output power over 100 W under the pulsed operation mode is pre- sented. A high temperature A1N nucleation together with an Fe doped GaN buffer was introduced for the developed GaN HEMT. The A1GaN/GaN hetero-structure deposited on 3 inch SiC substrate exhibited a 2DEG hall mobility and density of -2100 cm2/（V.s） and 1.0 x 10^13 cm-2, respectively, at room temperature. Dual field plates were introduced to the designed 0.25μm GaN HEMT and the source connected field plate was optimized for minimizing the peak field plate near the drain side of the gate, while maintaining excellent power gain performance for Ku-band application. The load-pull measurement at 14 GHz showed a power density of 5.2 W/mm for the fabricated 400 μm gate periphery GaN HEMT operated at a drain bias of 28 V. A Ku-band internally matched GaN power transistor was developed with two 10.8 mm gate periphery GaN HEMT chips combined. The GaN power transistor exhibited an output power of 102 W at 13.3 GHz and 32 V operating voltage under pulsed operation mode with a pulse width of 100 μs and duty cycle of 10%. The associated power gain and power added efficiency were 9.2 dB and 48%, respectively. To the best of the authors＇ knowledge, the PAE is the highest for Ku-band GaN power transistor with over 100 W output power.
基金supported by the Funds for Doctor Degree Teacher of North China Electric Power University (Grant No.200822008).
文摘The preliminary design results of a 1-MW,Kuband gyrotron traveling wave amplifier(gyro-TWA)are presented.Operating at the second cyclotron harmonic of the TE11 mode,the amplifier characterizes good stability even in the case of no distributed losses loaded,which could potentially allow it to be operated at high average power.Large signal simulation shows that the amplifier can generate a saturated peak power of about 1MW with efficiency of 26.6%,gain of 31 dB,and 3-dB bandwidth of about 1 GHz when driven by a 100 kV,40 A electron beam with 5%axial velocity spread.
基金supported by the National Natural Science Foundation of China(No.60890191 )
文摘This paper describes the first domestic Ku-band power AlGaN/GaN HEMT fabricated on a sapphire substrate. The device with a gate width of 0.5 mm and a gate length of 0.35μm has exhibited an extrinsic current gain cutoff frequency of 20 GHz and an extrinsic maximum frequency of oscillation of 75 GHz.Under VDS=30 V,CW operating conditions at 14 GHz,the device exhibits a linear gain of 10.4 dB and a 3-dB-gain-compressed output power of 1.4 W with a power added efficiency of 41%.Under pulse operating conditions,the linear gain is 12.8 dB and the 3-dB-compressed output power is 1.7 W.The power density reaches 3.4 W/mm.
