A Beam Focusing Antenna for the TE(0)n Mode High-Power Millimeter Wave

This paper describes a method to design an antenna to focus millimeter-wave beam generated by a gyrotron. The antenna, which has been proposed by the authors, consists of a stair-cut circular waveguide and two cylindrical reflectors; one is elliptic and the other is parabolic. Its principle is based on the geometrical optics though slightly modified to consider the diffraction effect. Results of low-power experiments agree well with the design on beam direction, beam width and the position of the focal point. At 35.5 GHz using TE(01) mode, a focused beam with half-power thickness of 13 mm x 10 mm was obtained. This type of antennas find applications to millimeter-wave scattering measurement in fusion plasma research and high- energy-density source for material heating

On the Modulation Characteristics of an Electrically-biased Branched-waveguide Light Intensity Modulator

This paper presents a simple but elegant analysis of an electrically-biased branched-waveguide light intensity modulator. The analysis considers a perfectly symmetrical structure of the modulator, and subsequently takes into account the effect of fabricational asymmetry of the branching region on the modulation process. It brings out the important role of the optical bias in the linearity of modulation

A High-Speed Numerical Analysis Technique for Millimetre Wave Aperture Antennae

By use of the geometrical theory of optics the radiation characteristics of a WGM antenna have already been investigated and designed. In order to improve the accuracy of the present calculation it was necessary to account for diffraction. Since the conventional method based on Kirchhoff-Huygens principle requires much computational time and memory, a numerical analysis method has been developed to overcome such a difficulty, i.e. the antenna aperture is subdivided into a series of subapertures of small area so that the field amplitude can be assumed uniform with the phase either uniform or linearly changing. The radiation fields from the subapertures are evaluated by use of an appropriate analytical solution. The radiated field pattern of the aperture is subsequently obtained by summing the radiation contributions from each of the subapertures in turn. Results from the most recent WGM calculations will be presented

Locking Equations for Microwave Circuits

By extending an ordinary admittance expression, the simplified equation for an oscillator has been obtained, which as yet is in the most general form within the first order approximation. Then, this equation has been transformed into the amplitude and the phase equations suitable for analyzing a microwave circuit involving oscillators. It has been found that the amplitude equation can be ignored when the oscillator is adjusted to produce the maximum output power. An example of application has also been given

Two-Stage Parametric Amplifier Coupled Through Idler Wave

It is described how a matched parametric amplifier can be obtained if two negative resistance type parametric amplifiers are cascaded so that their idler tanks are interconnected by a quarter wave length transmission line. The analysis of such an amplifier has been carried out and testified by experiment. This type of parametric amplifier has several features besides the matched characteristic at the input and the output terminal, that is, the gain is independent of the phase difference between the two parametric excitations, the sensitivity of gain vs. excitation power is very low and the bandwidth is wider than that of single ones, having a double peak characteristic

A Study on Nonreciprocal Parametric Amplifiers

Two or three methods are described to obtain a nonreciprocal parametric amplifier by use of two parametric elements in the frequency inverting case without using nonreciprocal elements such as a uniguide or a circulator. This kind of amplifier can be matched at the input terminal and/or at the output terminal. In a certain case the backward insertion loss can be made infinite. It was proved, however, in regard to the stability criterion that the two properties (matching and infinite backward insertion loss) can not be realized simultaneously. The other characteristics are almost the same as the usual negative resistance parametric amplifier. Some experimental results are presented with respect to one of the amplifiers. Though it has an electrical difficulty of construction, if once built, it may be convenient for low noise pre-amplifier

Membranous Fibrosis of the Lung

Membranous fibrosis of the lung depicts a morphological feature of the fibrous tissue which covers alveolar duct walls. Membranous sheets of fibrous tissue usually bridge and obstruct the mouths of alveoli, and attach only at the tips of the septa; i.e., the alveolar duct walls, and often provoke a collapse of alveolar spaces. There seem to be two types of membranous fibrosis. The first type is, in fact, a fibrous replacement of pre-existing hyaline membrane, while the second is a de novo formation of membranous fibrous tissue which has little or no preceding hyaline membrane. We consider that both of these changes result from damage to the alveolar duct walls and may constitute forms of the fibrosing alveolar ductitis syndrome. Recognition of this type of fibrosis gives us a better understanding of the morphogenesis of so-called diffuse alveolar damage

Sclerosing Mediastinitis of Pulmonary Hilar Type Report of a Case

A case of sclerosing mediastinitis of pulmonary hilar type is presented. Sclerosing mediastinitis is an unusual postinflammatory sclerotic reaction of the mediastinum which presents challenging diagnostic and therapeutic problems when it involves the major bronchi. The clinical, pathological and etiological aspects of this disease entity are summarized