ABSTRACT
A beam scanning antenna based on an all-metal lens is presented for high-power microwave (HPM) application in this paper. This design includes a feed antenna and two layers of different all-metal lenses, whose prototypes operating at 14.25 GHz have been successfully designed and fabricated with an aperture radius of 300 mm. A full transmission phase range of 360° can be achieved with a transmission efficiency of over 99% by rotating the cross-slot on the lens elements. The results of the low-power tests depict that the designed antenna can realize a beam scanning range of 120° revolving cone angle with the side lobe below -10 dB and the reflection coefficient less than -16 dB. The high-power tests demonstrate that the power handling capacity of the antenna is higher than 350 MW in sulfur hexafluoride (SF6). In addition, both the designed lenses have a bandwidth of more than 100 MHz. All the merits show that our designed all-metal lens antenna has a great potential to be applied in HPM systems.
ABSTRACT
To solve the problem of the large axial size of high-power microwave (HPM) reflectarray antenna and difficulty in vacuum packaging, a dielectric is introduced in the design of the antenna element. On this basis, a dielectric embedded metasurface reflectarray antenna (DEMRA) with high power handling capacity and wide-range beam scanning capability is proposed and fabricated. Compared with traditional HPM antennas, the DEMRA does not need to be sealed and can work directly in open-air conditions. The DEMRA can realize free regulation of the radiation beam within a cone angle of 90° and has a power handling capacity of 1 GW/m2. As verification, a protype working at 10 GHz is fabricated and low-power experiments are carried out. Experimental results are consistent with the simulation, proving that the DEMRA has a bandwidth exceeding 600 MHz. During the scanning process, the aperture efficiency is always higher than 48.98%, and the side lobe level remains below -15 dB. At the same time, the cross-polarization component is less than -15 dB, while the main lobe-axis ratio remains within 4.5 dB, confirming its beam scanning capability.
ABSTRACT
The improved magnetically insulated transmission line oscillator (MILO) is a gigawatt-class L-band high power microwave tube. It has allowed us to generate 3.1 GW pulse of 40 ns duration in the single-pulse operation and 500 MW pulse of 25 ns duration in the repetition rate operation. However, because of the severe impedance mismatch, the power conversion efficiency is only about 4% in the repetition rate operation. In order to eliminate the impedance mismatch and obtain repetitive long-pulse high-power microwave (HPM), a series of experiments are carried out and the recent progress is presented in this paper. In the single-pulse operation, when the diode voltage is 466 kV and current is 41.6 kA, the radiated microwave power is above 2.2 GW, the pulse duration is above 102 ns, the microwave frequency is about 1.74 GHz, and the power conversion efficiency is about 11.5%. In the repetition rate operation, under the condition of the diode voltage about 400 kV, beam current about 38 kA, the radiated microwave power is about 1.0 GW, the pulse duration is about 85 ns. Moreover, the radiated microwave power and the pulse duration decline little by little when the shot numbers increase gradually. The experimental results show that the impedance matching is a vital factor for HPM systems and one of the major technical challenges is to improve the cathode for the repetition rate operation MILO.
ABSTRACT
The improved magnetically insulated transmission line oscillator (MILO) is a gigawatt-class L-band high power microwave tube driven by a 550 kV, 57 kA, 50 ns electron beam. It has allowed us to generate 2.4 GW pulse of 22 ns duration. The recent progress of the improved MILO is presented in this paper. First, a field shaper cathode is introduced into the improved MILO to avoid the cathode flares in the triple point region. The experimental results show that the cathode flares are avoided, so the lifetime of the velvet cathode is longer than that of the taper cathode. Furthermore, the shot-to-shot reproducibility is better than that of the taper cathode. Second, In order to prolong the pulse duration and increase the radiated microwave power, a self-built 600 kV, 10 Omega, 80 ns pulser: SPARK-03 is employed to drive the improved MILO. Simulation and experimental investigation are performed. In simulation, when the improved MILO is driven by a 600 kV, 57 kA electron beam, high-power microwave is generated with output power of 4.15 GW, frequency of 1.76 GHz, and relevant power conversion efficiency of 12.0%. In experiments, when the diode voltage is 550 kV and current is 54 kA, the measured results are that the radiated microwave power is above 3.1 GW, the pulse duration is above 40 ns, the microwave frequency is about 1.755 GHz, and the power conversion efficiency is about 10.4%.
ABSTRACT
In this study, we retrospectively analyzed 18 patients in whom antithyroid drug (ATD)-induced agranulocytosis developed during treatment of Graves' disease. All patients were more than 20 years of age, and we saw no correlation between age and the development of agranulocytosis. In 17 of 18 patients, ATD-induced agranulocytosis developed within 2 to 12 weeks of starting ATD treatment. Development of agranulocytosis was related to the dose of ATD. In some patients, agranulocytosis developed abruptly, and even weekly routine WBC and granulocyte counts failed to predict all case occurrences. Fever and sore throat were the earliest symptoms of agranulocytosis; patients who developed either of these symptoms were closely monitored immediately with WBC and granulocyte count examinations. In this series of patients, treatment with granulocyte-macrophage colony stimulating factor (GM-CSF) increased the granulocyte counts, whereas the effectiveness of glucocorticoid treatment was not confirmed.
