Theoretical Study of Millimeter Wave Harmonic Oscillator Stabilized with a Transmission Cavity

An equivalent circuit model of millimeter wave second harmonic oscillator stabilized with a transmission cavity has been proposed for constructing analytical formulations between performance parameters of the oscillator and parameters of the circuit. The model consists of an equivalent circuit of fundamental wave and that of second harmonic wave. Each of the circuits comprises circuit models of main cavity, transmission waveguide, and transmission cavity. Absorbing material placed between the transmission waveguide and the transmission cavity can suppress additional resonances originated from transmission cavity. The behavior of the second harmonic oscillator can be effectively described by the circuit model. Furthermore, based on this model, mechanical tuning characteristics have been studied at first, and then analytical formulas for quality factor and efficiency depending on circuit parameters have been derived. The circuit parameters can be conveniently extracted by electromagnetic field simulation. Hence the formulas exhibit both compact form and enough accuracy. Thereafter, general rules of performance parameters varying with circuit parameters have been deduced for the harmonic oscillators. Then some design considerations have been derived according to the corresponding analysis. The equivalent circuit model is useful for designing and adjusting millimeter wave second harmonic stabilizing oscillator with a transmission cavity.     

Theoretical Study for Folded Waveguide Traveling Wave Tube

A wideband folded waveguide traveling-wave tube (TWT) amplifier has advantages of simpler coupling structures and robust structure over the conventional helix TWT. The phase velocity of waves in folded waveguide is slowed down to the velocity of electron beam. Slow-wave interaction with the electron beam in folded waveguide is studied in a linear fashion. For a cold beam, the linear theory predicts a gain of 2 dB/cm and a bandwidth of 37% at the center frequency of 14 GHz. A closed algebraic dispersion relation for the frequency and the axial phase shift per period is obtained using an equivalent circuit model. Numerical solution calculated from the dispersion relation and three-dimensional electromagnetic code, HFSS simulations predict a mode coalescing in the folded waveguide. And a theoretical phase velocity prediction of the electromagnetic wave in this circuit is verified by HFSS simulations.     

脊波导在速调管输出组件中的应用

在新型L波段多注速调管的研制中,为了降低电磁聚焦系统的设计难度,需要减小输出波导的截面尺寸。为此,提出了在速调管输出组件中应用脊波导的方案。针对该型速调管的要求,设计了完整的脊波导输出组件并进行验证。计算结果表明,这种采用了脊波导的速调管输出组件,能够在10%的带宽内达到1.2以下的驻波比,理论功率容量达到490 MW。采用了该方案的组件尺寸紧凑,加工方便,调试容易。     

A scale mixer model for sis waveguide receivers

We report results from measurements of a scale mixer model, built to investigate the embedding impedance presented to a superconductor-insulator-superconductor (SIS) tunnel junction detector in a full height waveguide with two tuning elements. The embedding impedance is measured as a function of junction position across the waveguide channel. The results are compared to i) computer simulations of the embedding impedance using waveguide theory, ii) a lumped element circuit derived from the theory, iii) an SIS receiver operating between 200 and 280 GHz.     

谐振型Josephson隧道结与外加微波的磁耦合(Ⅰ)

谐振型Josephson隧道结在建立Josephson电压基准的工作中受到广泛的应用。本文从受迫振动的模型出发,运用磁耦合的边条件,对波导中的结作了处理,得到了和实验相符的结果。在实验中我们对波导系统的短路装置作了适当改进,减少了微波漏损并改善了短路条件。低温实验的结果表明这种改进是有效的。 关键词：     

All-optical flip-flop composed of a single nonlinear passive microring coupled to two straight waveguides

Microrings can have different hysteresis characteristics at their different resonance frequencies. They can be used as a multi-hysteresis optical component. In this paper an optical D-flip-flop circuit composed of a single nonlinear passive microring coupled to two straight waveguide based on the Kerr effect is proposed. The proposed circuit can operate as an optical digital circuit which synchronizes input DATA with the CLOCK of the circuit. A simple analytical model for hysteresis design and the transient analysis of the proposed D-flip-flop are presented. According to our model, the switching time of the flip-flop is in the order of 10 ps.     

Dynamics of an optical signal in a multimode waveguide structure

A mathematical model of linear dynamic distortions of average signal power in a planar optical waveguide stemming from the intermodal coupling and dispersion of waveguide modes caused by macroscopic bends and irregularities of the optical waveguide surface has been developed on the basis of pulse intermodal scattering matrix. It is shown that the elements of this matrix are determined at a waveguide segment whose length greatly exceeds the correlation scale of the field of irregularities but is much smaller than the normalization length of waveguide modes and are described by rectangular functions with a duration proportional to the relative velocity of the corresponding modes. The dependences of the pulse intermodal scattering matrix on the intensities of absorption, Rayleigh scattering, and optical signal scattering from waveguide irregularities have been established. It is shown that, at waveguide lengths exceeding the normalization length, the optical signal shape becomes almost stable and can be expressed in terms of the pulse characteristic of an integrating circuit. It has been established that irregularities of the film in a bent optical waveguide lead not only to additional attenuation but also to enhancement of multimode distortion. A matrix method is proposed for taking into account these distortions, which is based on the effect of equalization (scrambling) of the signal energy over the spectrum of the bent waveguide modes. The model developed was used to process the experimental data on the dynamics of a signal in a weakly guiding multimode polymer optical fiber in order to estimate the parameters of attenuation and irregularities of the waveguide surface.     

220 GHz 折叠波导慢波结构

 优化设计了一种220 GHz的折叠波导慢波结构的尺寸,对其冷测特性如色散、耦合阻抗和衰减进行了分析。理论分析和软件仿真结果表明设计的折叠波导慢波结构在中心频率处具有较平缓的色散关系,较高的耦合阻抗和较低的电路衰减。互作用模拟表明,在电子注电压为20 kV,电流为10 mA时,27 mm（50个周期）的折叠波导慢波结构在220 GHz具有14.5 dB的增益,3 dB带宽为16.3 GHz（211.9～228.2 GHz）。     

Folded waveguide circuit for broadband MM wave TWTs

In millimeter wave band, the folded waveguide circuit exists some advantages such as wide operating frequency band, high mechanism strength, better heat disspation, easy fabrication and lower cost. It is expected that contradictory between broadband and high power in millimeter wave range can be solved by using the folded waveguide circuit. Computational results of dispersion character and coupling impedance of the folded waveguide are given. It is shown that the folded waveguide has wide bandwidth character in millimeter wave band.     

A siloxane polymer lightwave circuit on ceramic substrate applicable to ultrafast optoelectronic multi-chip-modules

Technique for integrating optical waveguide circuits on electrical circuits is developed toward the application to opto-electronic multi-chip modules (O/E-MCM), which enables one to handle ultrafast lightwave pulses and electrical signals on a common circuit board. We use ceramic material as the substrate of O/E-MCM having a multi-layer structure. A siloxane polymer is utilized to form low loss optical waveguides on ceramic substrates by low temperature processes. The waveguide has shown high transparency around 1310 nm. The group velocity dispersion has been measured and shown to become almost zero at wavelength of 1310 nm and about 0.4 fs/cm nm at 1550 nm. An optical circuit has been formed on simple electrical circuit consisting of a thermometer film resistance layer. A Mach–Zehnder interferometer optical switch exhibiting the waveguide extinction ratio of 30 dB, control power of 5 mW, and switching speed of 6 ms has been demonstrated. Thermal management characteristics also have been demonstrated successfully. This single-mode optical waveguide can thus be formed readily on ceramic substrates involving electrical circuit layers; this result confirms its applicability to O/E-MCM.     

Simulated performance and model measurements of an SIS waveguide mixer using integrated tuning structures

A three-port approximation of the quantum mixer theory is employed to perform mixer gain calculations at 230 GHz for SIS junctions with integrated tuning structures. In addition, the embedding impedance range of a waveguide mixer mount has been obtained from model measurements and has been included in the gain calculations. The results show that even moderately small junctions can perform well in a waveguide environment when an integrated tuning structure is used. A three-element tuning circuit is presented that would allow broad band operation with a fixed embedding impedance which is important for applications using a planar antenna structure.     

Instability of traveling waves in an optical waveguide

Instability of traveling IR waves within a waveguide structure is discussed. A practical model of a traveling wave amplifier of a solid state is proposed, utilizing an optical waveguide. The mechanism of instability is interpreted in terms of an interaction between a plasmon wave and a circuit one under a constraining boundary condition. Properties of the traveling amplification and related problems are discussed, with appropriately suggested semiconductor materials and device designs. The features of the amplifier are a simple structure, a low DC biasing power dissipation for room-temperature operation, unidirectionality, and a wide wavelength range from IR or submillimeter order, suited to various applications.     

Loss in a rectangular optical waveguide induced by the crossover of a second waveguide

We calculate the loss induced in a single-mode rectangular optical waveguide by the presence of a second waveguide, perpendicular to the first, which crosses over the first waveguide at a variable distance d. Our calculation is applied to the analysis of several doped silica waveguides of practical importance for optical circuit design.     

Analytical expression for the input impedance of a microstrip probe in waveguide

We present a closed-form expression for the the input impedance of a microstrip probe in a rectangular waveguide. The probe extends only part way across the waveguide and is therefore compatible with RF components that require an open circuit at low frequencies. Our analysis is based on the spectral-domain method and is able to take into account the orientation of the antenna with respect to the direction of propagation. We have examined the validity of our model by carrying out extensive impedance measurements at 5GHz. In those cases where the probe did not extend more than half way across the waveguide, excellent agreement was obtained. We show that the bandwidth of a probe that stretches only part way cross the waveguide is very much greater than the bandwidth of a probe that stretches all of the way across the waveguide and that is earthed at both ends. Moreover, the input resistance is lower and more suited to submillimetre-wave detectors such as SIS tunnel junctions. Our expression suggests that it should be possible to develop low-impedance, wideband probes for nearlydouble-height waveguide, and this implies that the upper frequency limit to which probes and waveguides can be manufactured can be extended well into the THz frequency range. A related, and often neglected consideration, is that the ohmic loss associated with an oversized waveguide is very much smaller than the ohmic loss associated with a reduced-height waveguide.     

一种基于热离子二极管的大功率微波探测器

 主要给出了波导型的X波段大功率微波探测器的结构、标定方法和标定结果。该新型大功率微波探测器具有承受微波峰值功率高（可达100 kW），时间响应快（响应时间小于2.0 ns），不需要同步信号，抗干扰能力强等特点。根据不同的需要，可以制作成波导型和同轴型的大功率微波探测器。波导型探测器由热离子二极管、标准波导、滤波器和外电路组成，其工作频率范围为波导的工作频率范围；而同轴型探测器由热离子二极管、同轴波导，滤波器和外电路组成，可以宽带使用。标定结果表明该探测器很适合高功率微波峰值功率测量，尤其是在强电磁干扰环境和高重频微波脉冲条件下的测量，为解决功率测量不准的技术难题提供一种有效的技术手段。     

Analytical Modeling of Metal-Insulator-Semiconductor Interconnects Using the Energy Based Approach

Simple formulae for calculating circuit parameters of metal-insulator-semiconductor (MIS) interconnects are obtained using the energy based approach. The energy based approach results in a new consistent equivalent transmission line model that exhibits power equivalence to the original MIS waveguide. This new model has solid physical foundation and is valid for a wide range of frequency and impurity doping rate. At the quasi-TEM limit, this new model reduces to the existing model that was obtained using the contour integral based approach.     

Low-loss, compact waveguiding with TE mode in metal/dielectric waveguides for planar lightwave circuit

We propose a low-loss metal/dielectric waveguide for compact planar lightwave circuit. The basic waveguide structure is a metal-defined high-index-contrast strip waveguide based on silicon/silica. As the guide is designed for TE single mode waveguiding, extremely low propagation loss (e.g. <0.04 dB/cm), very low bend loss (e.g. 0.0043 dB/90°-turn) and small waveguide pitch of zero-crosstalk are theoretically achievable, and can be further improved by compromising with component size and density. Examples of multi-bends and device integration are demonstrated with numerical simulations. The proposal is compatible with silicon technology and appealing for development of silicon-based planar lightwave circuit.     

Coupling of waveguide and resonator by inductive and capacitive irises for EPR spectroscopy

An analytic circuit model for slot coupling from a waveguide to a loop-gap resonator (LGR) in a context of electron paramagnetic resonance (EPR) spectroscopy is presented. The physical dimensions of the waveguide, iris, LGR, and aqueous sample are transformed into circuit values of inductance, capacitance, and resistance. These values are used in a solution of circuit equations that results in a prediction of the radio frequency (rf) currents, magnitude and phase, frequency, and magnetic and electric stored energies near the critical coupling. The circuit geometry reflects magnetic flux conservation between the iris and LGR as well as modification of the outer loop LGR currents by the iris. Unlike conventional models, coupling is not explicitly based on a mutual inductance between the iris and LGR. Instead, the conducting wall high-frequency rf boundary condition is used to define surface currents, regions, and circuit topology with lumped-circuit values of self-inductance, capacitance, and resistance. Match is produced by a combination of self-inductive and capacitive circuit coupling. Two conditions must be met to achieve match. First, the equivalent resistance of the LGR as seen by the iris must be transformed into the waveguide characteristic impedance. This transformation is met at a particular frequency relative to the natural LGR resonance frequency. The frequency shift magnitude is largely determined by the LGR properties, weakly dependent on the iris length and placement, and independent of other iris dimensions. The second condition for match is that the iris reactance at this frequency shift must cancel the residual reactance of the LGR. This second condition is sensitive to the iris dimensions. If both conditions are not simultaneously satisfied, overcoupling or undercoupling results. A slotted iris with a length equal to the size of the large dimension of the waveguide is found to have many properties opposite to a conventional iris with shorter length. Notably, the magnetic field near the iris tends to reinforce rather than oppose the magnetic field in the resonator. The long iris improves the LGR EPR performance by providing increased rf magnetic field homogeneity at the sample, higher signal, and reduced total frequency shift since the shifts due to sample and iris tend to cancel. Investigations reveal that the first match condition can be adjusted by LGR dimensional changes and such adjustment can eliminate the frequency shift. Results are consistent with Ansoft High Frequency Structure Simulator (Version 10.1, Ansoft Corporation, Pittsburgh, PA) simulations and can be extended to cavity resonators.     

The Analysis of Hole-Gap Helical Groove Waveguide

The hole-gap helical groove waveguide, as a all-metal slow-wave circuit, has advantages of good heat dissipation and great size, and thus is suitable for use of mm TWT. By means of an approximate field theory, the expressions of the dispersion equation and the coupling impedance of the hole-gap helical groove waveguide is obtained in this paper. The influence of various circuit dimensions on the dispersion relation and the coupling impedance is discussed by the numerical computation.     

Ka波段波导滤波器的设计

采用高精度三维电磁场分析软件对电感膜片建模,并与等效电路相结合设计波导带通滤波器。实验结果表明,样品测试结果与仿真结果基本吻合,该方法不仅适合波导滤波器设计,也适合其它谐振器耦合结构滤波器的设计。