A high power waveguide directional coupler was designed to measure the transmitted power and reflected power in the 4.6 GHz LHCD （lower hybrid current drive） launcher for the EAST tokamak. The design principle of th...A high power waveguide directional coupler was designed to measure the transmitted power and reflected power in the 4.6 GHz LHCD （lower hybrid current drive） launcher for the EAST tokamak. The design principle of the coupler is assessed. Further analysis is performed by CST （computer simulating test） and Ansoft HFSS （high frequency structure simulator） software and the optimal structural parameter is obtained. In addition, finite element code ANSYS is used to determine the temperature distribution in the coupler conductively cooled by forced water. The test results of a directional coupler manufactured according to the design are close to what is expected.展开更多
The nonideal effects in a quantum field-effect directional coupler where two quantum wires are coupled through a finite potential barrier are studied by adopting the lattice Green function method. The results show tha...The nonideal effects in a quantum field-effect directional coupler where two quantum wires are coupled through a finite potential barrier are studied by adopting the lattice Green function method. The results show that the electron energy distribution, asymmetric geometry and finite temperature all have obvious influence on the electron transfer of the coupler. Only for the electrons with energies in a certain region, can the complete periodic transfer between two quantum wires take place. The conductance of these electrons as a function of the barrier length and potential height exhibits a fine periodic or quasi-periodic pattern. For the electrons with energies beyond the region, however, the complete periodic transfer does not hold any more since many irregular oscillations are superimposed on the conductance profile. In addition, the finite temperature and asymmetric geometry both can reduce the electron transfer efficiency.展开更多
In this paper a compact polarization beam splitter based on a deformed photonic crystal directional coupler is designed and simulated. The transverse-electric （TE） guided mode and transverse-magnetic （TM） guided m...In this paper a compact polarization beam splitter based on a deformed photonic crystal directional coupler is designed and simulated. The transverse-electric （TE） guided mode and transverse-magnetic （TM） guided mode are split due to different guiding mechanisms. The effect of the shape deformation of the air holes on the coupler is studied. It discovered that the coupling strength of the coupled waveguldes is strongly enhanced by introducing elliptical airholes, which reduce the device length to less than 18.Sttm. A finite-difference tlme-domain simulation is performed to evaluate the performance of the device, and the extinction ratios for both TE and TM polarized light are higher than 20 dB.展开更多
An analysis of a 3 dB lumped-element directional coupler （LEDC） based on arbitrary terminal impedance is described numerically. To solve the conflicted requirement for broad bandwidth and small size in LEDC, a new s...An analysis of a 3 dB lumped-element directional coupler （LEDC） based on arbitrary terminal impedance is described numerically. To solve the conflicted requirement for broad bandwidth and small size in LEDC, a new structure of coupler is introduced, which can significantly improve bandwidth and whose size is only 3 cm×4 cm on the conditions of the frequency domain of 410 MHz to 490 MHz. The measure results are in good agreement with simulations despite the unexpected resistor loss.展开更多
Power measurement is necessary for an electron cyclotron resonance heating(ECRH)system.The directional coupler method has been put forward to monitor high-power microwave from gyrotrons in real time.A multi-hole direc...Power measurement is necessary for an electron cyclotron resonance heating(ECRH)system.The directional coupler method has been put forward to monitor high-power microwave from gyrotrons in real time.A multi-hole directional coupler has been designed and manufactured for the 105 GHz/500 kW ECRH system on the J-TEXT tokamak.During the design process,we established the relationships between hole parameters and coupling characteristics based on the multi-hole coupling method and small-hole coupling theory.High-power tests have been carried out.The results indicated the reasonability of the theoretical design and practicality of the fabricated directional coupler.Sources of test errors have been discussed in detail,and the influences of spurious modes on the directional couplers have been emphatically analyzed.展开更多
Characteristics of optical switching in a twin-core fibre coupler are numerically analysed under short pulse input by using supermode theory. The dynamic nonlinear coupled superlnode equations are derived, The numeric...Characteristics of optical switching in a twin-core fibre coupler are numerically analysed under short pulse input by using supermode theory. The dynamic nonlinear coupled superlnode equations are derived, The numerical results show that the input pulse width determines the power transfer and the pulse temporal profile in the output ports. The optimal switching characteristics can be obtained by selecting an appropriate initial pulse width. In addition, the switching characteristic curves are insensitive to the input pulse shape for either fundamental soliton pulse or Gaussian pulse input, but sensitive to pulse sharpness. A reduced switching power and a sharper switching transition can be obtained by using the sharp super-Gaussian pulse.展开更多
设计了一种结构紧凑、工作频带较宽、耦合平稳、高方向性的"十字形"多孔耦合的太赫兹波导定向耦合器。基于多孔耦合原理,利用HFSS软件对太赫兹波导定向耦合器进行了模型仿真和结构优化。仿真结果表明:在325~475 GHz带宽范围内...设计了一种结构紧凑、工作频带较宽、耦合平稳、高方向性的"十字形"多孔耦合的太赫兹波导定向耦合器。基于多孔耦合原理,利用HFSS软件对太赫兹波导定向耦合器进行了模型仿真和结构优化。仿真结果表明:在325~475 GHz带宽范围内,该多孔耦合太赫兹波导定向耦合器耦合度达到7.5±0.8 d B,隔离度达到30 d B,即方向性优于20 d B,各端口回波损耗小于-20 d B。通过对该波导定向耦合器进行高温高压模拟仿真,确定了使用负性光刻胶SU-8作为结构材料的可行性,提出应用MEMS工艺在硅衬底上进行加工,将牺牲层工艺应用到波导腔结构的制作中。利用光刻在直通波导和耦合波导公共宽壁上形成的"十字形"等间距排列耦合孔结构,可以实现较宽的带宽和良好的耦合平坦度。该方法提高了耦合孔尺寸和位置的精度,减小了反射损耗,为太赫兹波导结构的加工提供了新思路。展开更多
文摘A high power waveguide directional coupler was designed to measure the transmitted power and reflected power in the 4.6 GHz LHCD （lower hybrid current drive） launcher for the EAST tokamak. The design principle of the coupler is assessed. Further analysis is performed by CST （computer simulating test） and Ansoft HFSS （high frequency structure simulator） software and the optimal structural parameter is obtained. In addition, finite element code ANSYS is used to determine the temperature distribution in the coupler conductively cooled by forced water. The test results of a directional coupler manufactured according to the design are close to what is expected.
文摘The nonideal effects in a quantum field-effect directional coupler where two quantum wires are coupled through a finite potential barrier are studied by adopting the lattice Green function method. The results show that the electron energy distribution, asymmetric geometry and finite temperature all have obvious influence on the electron transfer of the coupler. Only for the electrons with energies in a certain region, can the complete periodic transfer between two quantum wires take place. The conductance of these electrons as a function of the barrier length and potential height exhibits a fine periodic or quasi-periodic pattern. For the electrons with energies beyond the region, however, the complete periodic transfer does not hold any more since many irregular oscillations are superimposed on the conductance profile. In addition, the finite temperature and asymmetric geometry both can reduce the electron transfer efficiency.
基金supported by National Key Basic Research Special Fund of China (Grand No 2006CB921701-705)
文摘In this paper a compact polarization beam splitter based on a deformed photonic crystal directional coupler is designed and simulated. The transverse-electric （TE） guided mode and transverse-magnetic （TM） guided mode are split due to different guiding mechanisms. The effect of the shape deformation of the air holes on the coupler is studied. It discovered that the coupling strength of the coupled waveguldes is strongly enhanced by introducing elliptical airholes, which reduce the device length to less than 18.Sttm. A finite-difference tlme-domain simulation is performed to evaluate the performance of the device, and the extinction ratios for both TE and TM polarized light are higher than 20 dB.
文摘An analysis of a 3 dB lumped-element directional coupler （LEDC） based on arbitrary terminal impedance is described numerically. To solve the conflicted requirement for broad bandwidth and small size in LEDC, a new structure of coupler is introduced, which can significantly improve bandwidth and whose size is only 3 cm×4 cm on the conditions of the frequency domain of 410 MHz to 490 MHz. The measure results are in good agreement with simulations despite the unexpected resistor loss.
基金supported by the National Key Research and Development Program of China (Nos.2017YFE0300200 and 2017YFE0300204)in part by National Natural Science Foundation of China(No.51821005).
文摘Power measurement is necessary for an electron cyclotron resonance heating(ECRH)system.The directional coupler method has been put forward to monitor high-power microwave from gyrotrons in real time.A multi-hole directional coupler has been designed and manufactured for the 105 GHz/500 kW ECRH system on the J-TEXT tokamak.During the design process,we established the relationships between hole parameters and coupling characteristics based on the multi-hole coupling method and small-hole coupling theory.High-power tests have been carried out.The results indicated the reasonability of the theoretical design and practicality of the fabricated directional coupler.Sources of test errors have been discussed in detail,and the influences of spurious modes on the directional couplers have been emphatically analyzed.
基金Supported by the Natural Science Foundation of Guangdong Province （04010397）, and the Excellent Teacher Foundation of Guangdong Province （Q02084）.
文摘Characteristics of optical switching in a twin-core fibre coupler are numerically analysed under short pulse input by using supermode theory. The dynamic nonlinear coupled superlnode equations are derived, The numerical results show that the input pulse width determines the power transfer and the pulse temporal profile in the output ports. The optimal switching characteristics can be obtained by selecting an appropriate initial pulse width. In addition, the switching characteristic curves are insensitive to the input pulse shape for either fundamental soliton pulse or Gaussian pulse input, but sensitive to pulse sharpness. A reduced switching power and a sharper switching transition can be obtained by using the sharp super-Gaussian pulse.
文摘设计了一种结构紧凑、工作频带较宽、耦合平稳、高方向性的"十字形"多孔耦合的太赫兹波导定向耦合器。基于多孔耦合原理,利用HFSS软件对太赫兹波导定向耦合器进行了模型仿真和结构优化。仿真结果表明:在325~475 GHz带宽范围内,该多孔耦合太赫兹波导定向耦合器耦合度达到7.5±0.8 d B,隔离度达到30 d B,即方向性优于20 d B,各端口回波损耗小于-20 d B。通过对该波导定向耦合器进行高温高压模拟仿真,确定了使用负性光刻胶SU-8作为结构材料的可行性,提出应用MEMS工艺在硅衬底上进行加工,将牺牲层工艺应用到波导腔结构的制作中。利用光刻在直通波导和耦合波导公共宽壁上形成的"十字形"等间距排列耦合孔结构,可以实现较宽的带宽和良好的耦合平坦度。该方法提高了耦合孔尺寸和位置的精度,减小了反射损耗,为太赫兹波导结构的加工提供了新思路。
