A fast computational technique for RF window in millimeter wave tubes

RF Window of millimeter wave tubes becomes very thin because of extreme high frequency, so that power capacity of the window is limited, manufacturing is difficult and it easy leaks. The equivalent circuit and computation are given for a type of ceramic block RF window with compensating irises. This RF window has higher power capacity, compact mechanical strength, easy manufacturing and airtight welding. The testing results show that the design method is fast and useful accuracy.     

A model based technique for recognizing targets by using millimeter wave radar signatures

A technique for recognizing real targets by millimeter wave (MMW) radar at 35 GHz and 94 GHz is presented. The recognition is performed by a model based technique in which real targets are represented by their high range resolution (HRR) profiles in hierarchical fashion.The unknown signal is classified by a model matching method and a coarse-fine searching technique. The advantages of this model based method are in low storage capacity, fast processing time and high recognition performance. Moreover this technique is very easily modifiable to incorporate multi sensor processing.We will present the results of the several experiments that we have conducted.     

A RF window for broadband millimeter wave tubes

The equivalent circuit and design method for a RF window in millimeter wave band are presented. Computation and experiment show that matching band of the RF window is wider. It can be used as output window for broadband millimeter wave tubes.     

A study of millimeter wave cusptron

The interaction between electron beam and RF fields of H₈₁₁ -mode in an eighth harmonic cusptron at f₀=35GH_z is studied numerically. The finite thickness and eccentricity of a rotating annular electron beam and the cusp magnetic field in the imbalance case (B_c–B₀) are considered in the mumerical calculation. The results show that these pratical factors have a great influence upon the electron efficieency.     

A millimeter wave dielectric waveguide antenna

This paper describes the theoretical and experimental results of a novel leaky-wave antenna incorporating a homogeneous dielectric transmission line and radiating aperture into a single structure. The primary objective of this investigation is to demonstrate the ability to control aperture radiation by simply cutting slots into a metal-free dielectric transmission line. Experimental line source antennas with identical periodic slots were designed to operate in the 35 GHz frequency region. The successful performance of these antennas resulted in the design of a dielectric line source antenna with a symmetrical amplitude taper which provided a lower sidelobe level. The design represents a significant breakthrough in achieving affordable, low-loss, lightweight antennas in the millimeter wave region. The most significant applications for this type of antenna include radar surveillance and tactical missile-seeker terminal guidance.     

Spectral technique for measuring phase retardation of a wave plate

We present a technique and algorithm for measuring the phase retardation of a wave plate based on spectral transmission curve. Through accurately extracting the intersection points' wavelengths from the spectral transmission curve, the effective phase retardation, absolute phase retardation, order, and physical thickness of the wave plate can be measured simultaneously in a wide spectral range. Experimental results show that the proposed technique has many advantages, such as higher data utilization, simpler extraction algorithm, and no strict requirement for the directions of transmission axes of the polarizer and analyzer, and the fast axis of the wave plate.     

A fast algorithm for DC design of millimeter wave impatts

Computation of steady state I-V characteristics combined with the expression of dc to rf conversion efficiency in terms of voltages across avalanche and drift regions can be used for profile optimisation of mm-wave Impatts. This provides a faster design when compared to using comprehensive simulation programmes for the same purpose. The algorithm developed for faster computation of dc I-V characteristics of Impatts is described here with some specific example where the results of the present computation are compared with those obtained by other method. A good agreement, within ±0.2%, has been observed. Since the method involved here does not require large computer memory, a desk top computer with modest capabilities is good enough for designing the profiles for Impatts efficiently. The method is general in nature and can easily be adopted for device designs for lower frequencies as well.     

A broadband Ka-band microstrip circulator for integrated millimeter wave systems

A Ka-band microstrip circulator, using ferrite with 4 M=5000 G, have been developed. By optimizing the circulator configuration, broadband n=2 Chebyshev response performance are obtained over 7 GHz bandwidth. The circulator have isolation of greater than 15 dB, and insertion loss of less than 1.0 dB.     

Study on the millimeter wave double-strip H-waveguide sensor

In this paper, we present a new kind of millimeter wave sensor which is constituted by double-strip H-wave-guide. This sensor has some major advantages such as big size, simple structure and good measurement performance. It is particularly suitable for measuring humidities of pellet materials at microwave band.     

Shielded rectangular dielectric wave guides for millimeter wave integrated circuits

The dispersion characteristics of Insulated non-radiative dielectric guides are computed using mode matching technique. From the dispersion characteristics the dielectric loss conductor loss and wave impedances are derived. Effect of metallic walls on trapped insulated image guide are also discussed. The dimensions of Insulated non radiative dielectric guide are same as that of rectangular metallic wave guide at ka band.     

Seven matched bolometers for millimeter wave observations

We have fabricated a millimeter wave observation system using an array of bolometric detectors. The performance of the system depends largely on obtaining identical performance from each bolometer. We achieved a variance in the responsivity of less than 4% except for one of the seven elements. The bolometers had an electrical NEP of 1.3×10^–16 W/Hz under radiation background loading of 30pW. We used an AC bridge readout circuit to significantly improve the stability of the array and showed that observations can be done without a mechanical beam switch. The bolometer array is now in use on the Nobeyama 45-m telescope for 150GHz observations.H. Matsuo thanks those who helped him work on bolometers during his stay in Berkeley, especially to T. Wilbanks, M. Devlin and C. Inman. The authors are also grateful to S. Sato and T. Watabe at Nagoya University for their advice on the AC bridge circuit. This work is partly supported by the Shimazdu Science Foundation.     

A compound high power millimeter wave waveguide circulator

In this paper, a high power millimeter wave waveguide Y-junction circulator, which is compound in structure, has been analyzed and developed. Its enduring power attains 60 W CW-power and the temperature of the waveguide surface does not exceed 25 degree centigrade under natural coolness.     

Modelling a millimeter wave harmonic power combiner by a hybrid field analysis technique

A dual-diode millimeter wave harmonic power combiner in which two radial line transformers are used is modelled by a field analysis technique based on Galerkin's method combined with collocation technique. The external circuit impedances looking outside from each of two active devices are computed at both fundamental frequencies and the second harmonic frequencies. Numerical results of the impedances with respect to various structural parameters are presented. Some important characteristics of the harmonic power combiner are revealed. A number of useful conclusions have been deduced for practical design and adjustment.     

In situ technique for measuring the orthogonality of a plane wave to a substrate

A new compact in situ method of measuring the perpendicularity of a plane wave to a substrate is proposed. Off-axis cylindrical Fresnel lenses are used to focus a portion of the incident plane wave onto target lines. The displacement of the focal line from the targets is determined by the degree of angular misalignment. The proposed design has been incorporated into a 10-mm-thick fused-silica module, which enables us to obtain an alignment precision of better than 0.0083 degrees. This method is designed for use in optical assembly procedures that require an incident collimated beam that is normal to the alignment features. Experimental results are presented.     

Numerical analysis for millimeter wave slot type coupler

The numerical analysis for millimeter wave slot type coupler of overmode waveguide cavity is studied by mode-matching taking account of the thickness of the plate on which the slot is cut. It is found that the higher modes in cavity can be suppressed by proper thickness of the plat and proper dimension of the output waveguide.     

A millimeter wave radio spectrometer for material analysis below T<1 K

A radio spectrometer set suggesting wide fuctional possibilities and operating in the shortwave part of the millimeter band at temperatures below 1 K is described. The set is intended for analyzing materials of polarized nuclear targets under the conditions close to actual operation, with the use of magnetic resonance methods. The potential of spectrometer allows employing it in semiconductor physics, physics of disordered media, biology, et.c.     

Investigation of cross-polarized heterodyne technique for measuring refractive index and thickness of glass panels

A new mathematical model of cross-polarized heterodyning is proposed for measuring glass panels. An optical system is presented for obtaining relative thickness variation and difference distribution of refractive indices simultaneously, and the dual-balanced coherent demodulation technique is used. The experiment results show that the transmittance of light beam can be less than 0.5% when the vibration amplitude of the glass panels is equal to 5 mm. It takes about 200 s to scan the whole glass sample with size of 1430 × 1360 mm². The resolution of the thickness variation is 0.3 μm, and the lateral sampling resolution is 1 mm.     

A simulation of the thermal behaviour of the UK-NL millimeter wave telescope

To keep the thermally induced average telescope deformations within 15 m, a thermal design goal has been set which limits the temperature difference between all locations in the panels, backing structure and subframe to 1°C. Temperature gradients are caused by non-homogeneous exposure and by difference in response to a changing exposure for elements with different time constants.Thermal model simulations are used to identify the critical elements in the thermal design of telescope and enclosure. It is shown that an enclosure with a highly reflective paint with high infrared emissivity on the outside surface and an inside zinc coating with low infrared emissivity works as a highly effective radiation shield. A sprayed aluminium coating on the telescope makes free convection the dominant heat transfer mechanism. An enclosure with louvres works as a chimney forcing the inside air temperature to follow the ambient temperature to within a few degrees. The resulting temperature stratification in the area where the telescope reflector is located does not exceed 1.5°C. Structural analysis shows that temperature gradients in the subframe cause reflector surface deformations with a regular pattern, like gravitational deformations, which means that an error budget summation based on independent rms values is not necessarily valid. Knowing the structural analysis coefficients for differential thermal expansion one can decide which time constants in backing structure and subframe have to be matched to achieve optimal performance.     

Electromagnetic method for measuring glacier thickness

Summary Complex permittivities of ice and snow are used as a basis for defining the design parameters of a radar capable of mapping the thickness of a glacier covering the rock mantel which lies above Mont Blanc underground stations.

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Riassunto Le permittività complesse del ghiaccio e della neve sono utilizzate per definire i parametri di progetto di un radar capace di dare una topografia dello spessore del ghiaccio che ricopre il mantello roccioso sovrastante i laboratori del Monte Bianco.

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Резюме Комплексные диэлектрические проницаемости льда и снега представляют основу для определения параметров конструкции радара, способного давать отображение толщины ледника, покрывающего скалы над подземными станциями под Монбланом.

     

毫米波折叠波导行波管输入输出过渡波导设计

折叠波导以其宽频带、加工方便而成为一类重要的毫米波与太赫兹波段行波管慢波线。针对折叠波导慢波系统与标准波导的匹配过渡连接,通过等效电路分析与电磁计算软件模拟,设计出了直渐变波导、双曲圆弧渐变波导、切比雪夫阶梯渐变波导3种输入输出过渡波导结构,分析了各种过渡波导的优缺点及结构尺寸对性能的影响。计算表明,经过合理优化的设计,3种过渡结构均可以使反射系数在28~40 GHz波段小于0.05。