Avalanche Diode Noise Sources at Short Centimeter and Millimeter Wavelengths (Short Papers)

Semiconductor noise sources for microwave frequencies have been constructed using commercial avalanche diodes in waveguide mounts. For the diodes and waveguide configurations reported here the upper usable frequency is approximately 40 GHz. The measurements are in limited agreement with previous predictions. It is possible that a reduction in package and diode parasitic would improve this agreement, and raise appreciably the upper usable frequency of such noise sources.     

Highly Stabilized IMPATT Oscillators at Millimeter Wavelengths (Short Papers)

Highly stabilized IMPATT oscillators at millimeter wavelengths have been developed. The IMPATT diode is mounted in the coaxial-waveguide circuit at the detuned open position, and is series-resonant at the design frequency. The frequency stability and power output of /spl plusmn/5x10/sup -5/ / /spl plusmn/20/spl deg/C and 50 mW,, respectively, have been obtained at 80 GHz.     

Attenuation Characteristics of Circular Dielectric Waveguide at Millimeter Wavelengths

Experiments were done to determine the practicality of using circular dielectric waveguide for a low-loss transmission line at millimeter wavelengths. The lowest order mode on a circular dielectric guide will propagate regardless of how small the guide diameter is. Thus it is possible to make the attenuation factor of a circular dielectric guide arbitrarily small by reducing its diameter. Loss measurements for several different diameters of polystyrene and Teflon rods were made at 72.70 GHz. The measurements were made by directly probing long sections of dielectric guide and plotting the average power as a function of length on an X-Y plotter. Dielectric constants were measured from the standing wave patterns of polystyrene Teflon, and fused quartz rods at 71.0 GHz. Teflon rods exhibited attenuation factors from 0.8 dB/m to 2.2 dB/m depending on the diameter. This is an improvement over silver waveguide at this frequency. Polystyrene rods were found to have attenuation factors ranging from 3.9 dB/m to 12.5 dB/m, again depending on the diameter of the rod. The measured dielectric constants are consistent with previously published data. The various attenuation factors are related to the intrinsic loss tangent of the dielectric using the theory of the HE/sub 11/ mode. Values of tan delta derived from measurements of different rods are consistent indicating that the experimental results are valid. The problem of radiation from dielectric rods is discussed. The experimental results are not conclusive but it appears likely that radiation loss is negligible.     

A Design of Flattop-beam Shaper at Millimeter Wavelengths

Beam shaping technique for generating flattop beam has long been used in optics, and there are many methods to design flattop-beam shapers in optics. Flattop beam is also important in some applications at millimeter wavelengths such as in the quasi-optical power divider, however, there are few design method for the flattop-beam shaper used at millimeter wave frequencies and the design method of optics are not suitable to the beam shaper at millimeter wave frequencies, so a design method for the flattop-beam shaper at millimeter wave frequencies is presented in this paper. Several flattop-beam shapers in the form of diffractive element have been designed and simulation results are presented.     

Some Characteristics of Dielectric Image Lines at Millimeter Wavelengths

The attenuation characteristics of several dielectric image lines have been calculated for the frequency range extending from 24 to 100 kmc and have been checked experimentally at 35 and 70 kmc. To obtain low attenuation at these high frequencies, dielectric materials with little loss and small size of cross section are required, while low values of the dielectric constant are also desirable. The effects of the size and shape of the dielectric cross section and of low dielectric constant are treated separately. To find proper materials with low dielectric constants several new foam plastics were investigated. Three types were found suitable for image line use, and in fact, these plastics have such good electrical and physical properties that they should be useful in many microwave applications. A qualitative measure of field extent is given for several image lines at 35 or 70 kmc, and various image lines and associated components are discussed. A new type of image line, called the tape line, is described.     

Harmonics at Millimeter Wavelengths

Two techniques for obtaining millimeter waves with sufficient power to make physical measurements have been investigated at the Columbia Radiation Laboratory. The first in point of time was to use the harmonics of the fundamental frequency directly emitted by a magnetron when it is in oscillation. Harmonics up to wavelengths of 1.25 mm have been observed. The only advantage of the magnetron is in the ease of adjustment. An operator of moderate experience should be able to produce 1.5 mm radiation within a few hours using this technique. The other method in use is to frequency multiply the power emitted by a klystron by means of a silicon-tungsten contact used as a non-linear device. This method ps produced 1.5mm wavelength radiation at Columbia and wavelengths up to 0.77 mm at Duke University. It has the advantages that the radiation is stable in power and frequency, is monochromatic, and also is tuneable. The price paid is in a considerably greater time of adjustment and alignment, a few weeks being not at all uncommon.     

Some Applications and Characteristics of Ferrite at Wavelengths of 0.87 Cm and 1.9 Cms

This paper describes the use of ferrites in waveguide to produce Faraday rotations at 0.87 cm and 1.9 cms wavelengths. The Dicke radiometric receiver is briefly reviewed and its improvement by the use of ferrite waveguide components is described. Experimental equipment for securing data on the behavior of ferrites is discussed. Details are given for the construction of a unidirectional waveguide transmission line for 0.87 cm wavelength.     

Rain Attenuation at Millimeter Wavelengths

A method of determining the rationality for raindrop size distribution is first presented. The relative volume occupied by raindrops is derived. The attenuation and cross-polar discrimination induced by rainfall at millimeter waves are investigated with the incoming expression and a brief analysis is presented.     

A Design of High-Power Beam Combiner at Millimeter Wavelengths Utilizing Wire Grids

A beam combiner, which can combine multiple Gaussian beams into a single one, has many important applications, such as high-power radar and weapon. In this paper, we propose a new scheme of the design of high-power beam combiner at millimeter wavelengths by using wire grids. The design tool is to combine a genetic algorithm (GA) for global optimization and an Ansoft HFSS for rigorous electromagnetic computation. The design method is described in detail and the optimized results are presented. Finally, a brief summary is given.     

Rain Attenuation at Millimeter and Submillimeter Wavelengths

The rain attenuation was calculated by using the Marshall-Palmer, Best, Joss-Thomas-Waldvogel and Weibull distributions for raindrop-size. The results were compared with the recent measurements from 8 to 312.5 GHz at the rain rate R = 50mm/hr. Especially, the Weibull distribution has a good agreement with the measurements at 312.5 GHz (0.96 mm) in the submillimeter wavelength. Specific attenuation values from 1 to 1000 GHz were calculated for a rain temperature of ?10°C, 0°C and 20°C by using the Weibull distribution.     

Multiple Quantum Effects at Millimeter Wavelengths

When a quantum mechanical system interacts with a radiation field it may do so by multiple as well as single quantum processes. These multiple quantum processes give rise to nonlinear effects such as harmonic generation and parametric amplification and oscillation. The density matrix formulation is used to describe these multiple quantum processes. Two- and three-level systems are considered as forms of harmonic generators and some of the desired properties of the materials to be used are described. Two methods of generating submillimeter radiation starting with optical signals are also discussed.     

Millimetric V-groove guide and components

A characteristic equation of single V-groove guide has been derived using the transverse resonance technique. This equation is much less complex and tedious to solve when compared with that obtained by the conformal mapping technique. The computed results are within 1% of the published experimental values for the cut-off wavelengths at X-band and 100 GHz. The present analytical approach is to approximate the central groove region by a large number of rectangular steps and the previously derived analytical solution for the rectangular-groove guide are applied to predict the propagation characteristics of single V-groove guide. A number of components in V-groove guide which have very similar characteristics to those of the rectangular-groove counter-part have been reviewed. It is noted that both the E-plane and H-plane cylindrical bends in both rectangular-groove and V-groove guides had unacceptably high-loss and a satisfactory solution have yet to be reached.     

Modified H Guide for Millimeter and Submillimeter Wavelengths (Short Papers)

A theoretical and experimental investigation is being made of a modified form of H guide as a possible guided wave structure for millimeter and submilliieter wavelengths. The effects of channels in the conducting planes to support a dielectric film has been studied by scaled-up models at 3-cm wavelength. Low losses, even at the shorter wavelengths, are predicted. The channels may be used to filter unwanted higher order modes, and the use of high-permittivity dielectric is suggested to further reduce the guide attenuation.     

Dual-Frequencies Diffractive Lenses at Millimeter Wavelengths

Diffractive lens have many advantages over refractive lens at millimeter waves band, such as thin, light and low dielectric loss and so on. However, diffractive lens have chromatic aberration, that is, focusing performance of diffractive lens is frequency dependent. In this report, a dual frequencies diffractive lens is developed, which can work at 8mm band and 3mm band, based on the harmonic diffractive lens techniques. Experiments show it has almost same focusing performance at 8mm band and 3mm band.     

近红外波段的金属纳米腔激光器

无论是从科研视角来研究激光器和腔体还是为了实现低功率应用的小型优质激光器．纳米腔激光器都引起了人们极大的兴趣。目前,利用光子晶体纳米腔将光局限在波长尺度范围内的研究已有报道。在金属腔体中甚至还可以将光局限在体积尺寸小于波长尺度的范围内。然而,普遍认为,金属纳米腔抑制了激光工作时的高损耗。最近,我们报道了填充有电激励半导体的金属纳米腔的受激辐射现象。重要的是,这些装置的制作方法能够使激光器更加小型化。特别是,利用我们的工艺技术可以实现尺寸远小于衍射极限的金属一绝缘体一金属（MIM）波导结构。本文给出了MIM波导的实验结果。理论上存在可以将MIM波导结构的半导体增益介质的尺寸减小到几十纳米的可能性。最后,验证了最新的制作MIM波导结构的结果。     

A Technique for Measuring Phase at Millimeter Wavelengths

A technique for measuring the phase of millimeter signals in free space is described that uses a reference signal of varying phase. The phase of the reference signal is measured independently and subtracted from the total phase measured to determine the desired phase. The use of a varying reference phase is necessary because flexible or movable waveguide whose phase characteristics can readily be measured are not available at millimeter wavelengths. The theory of the technique described is based upon the interference pattern of slowly varying electric fields.     

Hollow-Cylinder Waveguide Isolators for Use at Millimeter Wavelengths

The device considered in this study is a semiconductor waveguide isolator consisting of a hollow column of a semiconductor mounted coaxially in a circular waveguide in a longitudinal dc magnetic field. An elementary and physical analysis based on the excitation of plane waves in the guide and a more rigorous mode-matching analysis (MMA) are presented. These theoretical predictions are compared with experimental results for an InSb isolator at 94 GHz and 7.5 K.     

毫米波椭偏测量法的数值模拟研究

介绍了一种新型的毫米波椭偏法,可以用来测量介质材料的介电常数和厚度.通过分析入射波波长和入射角的不同取值对实验结果的影响,给出了入射波波长和入射角的取值范围,同时对介电常数、厚度与椭偏参数之间的关系进行了数值模拟研究.研究结果表明,由椭偏参数经数值计算反演出的介电常数、厚度通常会出现多值的情况.但对大多数的介质薄膜而言,却可以通过该方法求出唯一确定的介电常数与厚度,表明了毫米波椭偏法在介质参数测量上的可行性.     

Experimental Attenuation of Rectangular Waveguides at Millimeter Wavelengths

The experimental values of attenuation of commercially available rectangular waveguides were determined at frequencies between 25 and 200 GHz with emphasis on high accuracy. They were compared with the theoretical values computed from the dc conductivities, taking into consideration temperature effects, work hardening, size effects, surface roughness, and a room-temperature anomaly of the skin effect. A new way to express the excess attenuation due to these effects was fomulated. Excess ratios of attenuation of coin-silver waveguides were found to be well below the values used in engineering in the past. They can satisfactorily be explained by surface roughness. The normalized excess attenuations of copper guides are higher than those of guides made of silver but lower than cited in the literature.     

A Calorimeter for Power Measurements at Millimeter Wavelengths

A calorimeter for measuring low-level power at millimeter wavelengths is described. This is a broadband device capable of measuring power levels of the order of one milliwatt with an estimated accuracy of plus or minus 1/4 db. The calorimeter utilizes the substitution principle by matching the temperature rises of two identical power absorbers, in one of which is dissipated the unknown high frequency power while the other is heated by a measured amount of direct current power.