一种圆锥形横电磁波传输室的分析

给出一种新型横电磁波传输室－圆锥菜横电磁波传输室,并在球坐标系下采用时域有限差分（FDTD）法对其场分布进行计算,分析了高阶模的影响,确定了传输室的上限工作频率范围。分析和计算结果表明,圆锥形横电磁波传输室的电场极化方向可任意改变,上限工作频率可达4GHz,具有广泛的应用前景。     

吉赫横电磁波传输室传输特性的宽频带分析

吉赫横电磁波传输室(GTEMcell)上限工作频率可达几个吉赫,因而在电磁兼容测量中得到越来越广泛的重视和应用。本文在非正交坐标系下采用FDTD(时域有限差分)法求解电磁波在GTEMcell中的传输特性,给出了GTEMcell中TEM模的横向分布和纵向分布,分析了高阶模对场分布均匀性的影响,由此确定了GTEMcell的上限工作频率范围。计算及分析结果对GTEMcell的设计和使用具有重要意义。     

宽频带GTEM传输室接头的优化设计

研制宽频带的吉赫横电磁波传输室,其高频输入接头的设计尤为关键.采用有限积分技术进行输入转接头的驻波比计算,利用软件建立仿真计算模型对内导体过渡段、介质垫片结构和圆形到方形处的结构进行优化,从而解决高频输入转接头的设计制作难题,保证了吉赫横电磁波传输室的整体性能.测试结果表明,采用此接头研制的传榆室工作频率上限达18GHz,电压驻波比小于1.5.     

吉赫横电磁波传输室传输特性的宽频带分析

吉赫横电磁波传输室（ＧＴＥＭ ｃｅｌｌ）上限工作频率可达几个吉赫,因而在电磁兼容测量中得到越来越广泛的重视和应用。本文在非正效坐标系下采用ＦＤＴＤ（时域有限差分）法求解电磁波在ＧＴＥＭ ｃｅｌｌ中的传输特性,给出了ＧＴＥＭ ｃｅｌｌ中ＴＥＭ模的模向分布和纵向分布,分析了高阶模对场分布均匀性的影响,由此确定了ＧＴＥＭ ｃｅｌｌ的上限工作频率范围。计算及分析结果对ＧＴＥＭ ｃｅｌｌ的设计和使用具有重要     

横电磁波传输室的三维FDTD法分析

本文运用时域有限差分（FDTD）法模拟电磁波在TEMcell（横电磁波传输室）中的传输，并对之进行了三维分析，给出了TEMcell中TEM模场的横截面分布及纵向分布；计算了TEM模与高阶模的谐振频率；分析了TEMcell的上限可用频率。此结果对横电波传输室的设计和使用具有重要意义。     

TEM传输室置入金属EUT后场分布的边界元分析

横电磁波传输室广泛应用于电磁兼容试验中，当置入受试设备后，其中的场分布会发生扰动。本文采用边界元法分析了横电磁波传输室中置入金属箱体的受试设备后场分布的规律，对受试设备所受暴露场的场强进行了计算，并提出了具体的估算方法。对空载时横电磁波传输室的场分布进行了测量，测量结果证实了计算方法的正确性。     

基于遗传算法的横电磁波传输室芯板优化设计

采用遗传算法,对横电磁波传输室(TEM CELL)内的芯板结构参数做了优化,优化结果增加了横电磁波传输室(TEM CELL)的测试区域,提高了传输室的效费比。同时也验证了遗传算法解决此类问题的有效性。     

大型吉赫横电磁波室的数值分析

为了解10m以上的大型GTEM（吉赫横电磁波）室的传输特性和场的均匀性,利用FDTD（时域有限差分）法对大型GTEM室进行了数值分析。选用了上升前沿为纳秒级的高空电磁脉冲波形和高频特性较好的高斯脉冲源作为激励源,计算结果表明对于10m长的GTEM室可以无失真地传输1．5GHz的电磁波,所以能够利用GTEM室传输上升前沿为纳秒级的快上升沿电磁脉冲。“三分之一”测试区域的场强不均匀性小于±2dB,可以用做精度较高的测量区域。     

非对称横电磁波传输室的工程设计

本文利用非对称横电磁波传输室(ATEM Cell)的特性分析公式,给出了一套ATEMCell的工程设计方法。该方法借助计算机,实现了对ATEM Cell的三大参数(特性阻抗、截止频率和横向场分布)的优化设计。该方法的特点是,计算准确度高,方便工程应用。文中提供的数据图表为工程人员提供了更便捷的设计途径。     

加载横电磁传输室中的电场分布计算

用“准静脉法”研究了当工作频率远低于截止频率时,放置于横电磁传输室中的被测物体中的电场分布。文中使用的是有限差分法,给出了在三维空间中不同介质交界面上拉普拉斯方程的差分格式。计算结果表明当把ＥＴＵ放入ＴＥＭＣｅｌｌ的中心时,ＥＵＴ横截面上的电场分布是均匀的。     

Proposal for a Tunable Millimeter Wave Molecular Oscillator and Amplifier

An atomic beam apparatus suitable for a millimeter wave generator is theoretically discussed. The beam consists of atoms having a net magnetic moment. The upper and lower Zeeman levels of the atomic beam in a magnetic field are spatially separated by an inhomogeneous magnetic field. The upper state atoms enter a cavity where transitions occur at a frequency determined by a static magnetic field. The resonant frequency of the cavity is set at the transition frequency. The positive feedback of the cavity allows operation as an oscillator. Some of the more important parameters for oscillator operation are evaluated.The upper frequency limit is determined primarily by the resonant structure design.     

Dual-band dual polarised printed antenna element

A novel printed antenna element capable of providing dual polarised operation over two widely separated frequency bands is described. The element consists of a perforated proximity-fed microstrip patch antenna operating at the lower frequency, layered over a subarray of aperture coupled microstrip elements operating at the upper frequency. Results for a specific example operating at L and X bands (a frequency ratio of 8:1) are presented. The impedance bandwidth for both bands is >6%, with isolation within bands >20 dB and isolation between bands >40 dB. The element and feed network also has the advantage of being compact enough to be used in arrays, providing dual polarised dual-band operation from a single low-profile aperture     

Tunable magneto-dielectric resonator for W-band isolators

A magnetic field tunable barium hexaferrite (BaM) dielectric resonator that could potentially function as an isolator operating at 82?90 GHz has been designed and characterised. A 30 GHz increase in operating frequency was achieved by using dielectric resonances instead of the usual ferromagnetic resonance. The dielectric resonance and the operating frequency of the isolator can be tuned by 0.84 MHz/Oe almost linearly with an applied magnetic field.     

On the maximum rate of fluctuation in mode-stirred reverberation

Theoretical limits are derived for the maximum permissible rate of mechanical/electronic stirring or spatial/spectral scanning inside a reverberant cavity. These limits are based on upper bounds for the maximum rate of field fluctuations and are obtained by imposing the requirement of quasi-stationarity on the interior cavity field. For a sinusoidal excitation field, the interior field is represented as a narrowband random hybrid amplitude-plus-frequency modulation, as induced by the stirring or scanning process, and is based on an analytic field formulation. Distortion (nonlinearity) of the modal and effective field is quantified for first-order variations of amplitude and frequency. Its dependence on the random amplitude modulation index is demonstrated. The latter is estimated from macroscopic system parameters. The effect of compensation of net input power on the distortion and maximum stirring rate is analyzed. The maximum stirring rate exhibits an inverse power law dependence on the operating frequency. For a specified level of maximum distortion, maximum rates of electronic, mechanical, or electromechanical mode stirring are derived. The effect of the order of the EUT transfer function on the distortion, as well as the detuning, bandwidth, and amplitude distortion of the perceived test field caused by stirring or scanning are quantified and analyzed.     

Innovative test method for the shielding effectiveness measurement of conductive thin films in a wide frequency range

This paper presents an innovative test procedure for the prediction of the shielding effectiveness of small sample materials, consisting of a dielectric substrate coated with thin conducting film, in a wide frequency range up to 8 GHz. The proposed technique overcomes the limitations of the ASTM D4935 test method concerning the upper operating frequency and the required minimum specimen dimensions. A new high-order equivalent circuit model of the test fixture is developed. A correction factor is applied to the measured insertion loss to eliminate both the resonance peak below cutoff appearing in the high-frequency range and the low-frequency errors due to the weak capacitive coupling between the flanges of the coaxial cell. The accurate prediction of the shielding effectiveness of the test material against a plane wave is then derived from the insertion loss measurements.     

频率可调太赫兹回旋振荡管互作用电路的设计与研究

根据动态核极化核磁共振成像技术对回旋振荡管的要求,设计了130 GHz 回旋振荡管的注波互作用电路,基于线性理论对互作用电路进行了研究并选择了合适的工作点,分析了电路的频率调节特性。利用相对论电子回旋脉塞非线性理论对互作用系统进行了模拟和计算,优化了工作参数,计算了磁场及电子注参数对输出功率及效率的影响。最后,用粒子模拟方法进行了模拟并与非线性理论结果进行了比较,两者符合得很好。模拟结果显示,当电压为10 kV、电流为0.3 A、磁场强度由2.34 T 增加到2.41 T 时,输出功率由1310 W 减小到230 W,对应的效率分别为43.6%和7.7%,振荡管的频率可调范围约为2.7 GHz。     

Study of transmembrane potentials on cellular inner and outer membrane--frequency response model and its filter characteristic simulation

Based on the multilayer dielectric model for a spherical cell, a frequency response model of transmembrane potentials on cellular inner and outer membranes is established with a simulating method. The simulating results indicate that transmembrane potential on the inner membrane shows first-order bandpass filter characteristic, while transmembrane potential on the outer membrane shows first-order low-pass filter characteristic approximately. It could be found that the transmembrane potential on the inner membrane is greater than that on the outer membrane, and can keep a higher value in the range from a center frequency to an upper cutoff frequency, which is desirable to induce intracellular electromanipulation. Both a discussion about an equivalent RC model of the cell and the experimental result are in agreement with the aforementioned conclusion. Therefore, the frequency response model could help to choose reasonable window parameters for the application of a nanosecond pulsed electric field to tumor treatment.     

Nonresonant excitation and nonlinear suppression of parasitic transverse modes in free-electron masers

Excitation of transverse parasitic modes at the frequency of the operating mode in free-electron masers is considered. The influence of parasitic field on the starting current of the autooscillator with a low-quality cavity as well as the phenomenon of suppression of the total parasitic field by the operating one in the regime of its saturation are investigated.     

Performance of InP 3-level oscillators in K and Q bands: 18?40 GHz

Epitaxial InP of 5.4 ?m thickness has oscillated at frequencies up to 40 GHz and has yielded an efficiency of within 2% at 29.4 GHz. The optimum operating frequency for these 3-level oscillators appears to be determined by a defined transit velocity, and results have not suggested that an upper frequency limit has yet been encountered.