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

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

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

Measuring method of loss for optical waveguides by use of a rectangular glass probe

The use of a glass-plate probe of rectangular shape is proposed for the measurement of transmission loss in thin-film optical waveguides. The light-collecting window is of a thin rectanglar shape perpendicular to the light streak, while the conventional fiber probe has a very small circular face. This transversely elongated form results in a great improvement of the mechanical tolerance for the probe movement in the vertical as well as the transverse direction. Theoretical investigation is also presented in reasonable agreement with the experiments

太陽フレアーにおける融合不安定

Double sub-peak structures in the quasi-periodic oscillations found in the time profiles of two solar flares on 1980 June 7 and 1982 November 26 are well explained in terms of the coalescence instability of two current loops. This interpretation is supported by the observations of two microwave sources and their interaction for the November 26 flare. The difference of both sub-peak structures and time scales between the two flares are discussed from the viewpoint of different plasma parameters in our computer simulations

ソーラーフレアーにおける電流ループのコアレッセンス

The nonlinear coalescence instability of current carrying solar loops can explain many of the characteristics of the solar flares such as their impulsive nature, heating and high energy particle acceleration, amplitude oscillations of electromagnetic emission as well as the characteristics of 2-D microwave images obtained during a solar flare. The physical characteristics of the explosive coalescence of currents are presented in detail through computer simulation and theory.Canonical characteristics of the explosive coalescence are: (1) a large amount of impulsive increase of kinetic energies of electrons and ions, (2) simultaneous heating and acceleration of electrons and ions in high and low energy spectra, (3) ensuing quasi-periodic amplitude oscillations in fields and particle quantities, (4) the double peak (or triple peak) structure in these profiles, and (5) characteristic break in energy spectra of electrons and ions. A single pair of currents as well as multiple currents may participate in the coalescence process, yielding varieties of phenomena. These physical properties seem to underlie in some of impulsive solar flares.In particular, double sub-peak structures in the quasi-periodic oscillations found in the time profiles of two solar flares on June 7, 1980 and November 26, 1982 are well explained in terms of the coalescence instability of two current loops. This interpretation is supported by the observations of two microwave sources and their interaction for the November 26, 1982 flare.Some more details as well as a generalization of the present model to solar flares with the coalescence as an elementary process in the flare phenomenon are presented

New 60-cm Radio Survey Telescope with the Sideband-Separating SIS Receiver for the 200 GHz Band

We have upgraded the 60-cm radio survey telescope located in Nobeyama, Japan. We developed a new waveguide-type sideband-separating SIS mixer for the telescope, which enables the simultaneous detection of distinct molecular emission lines both in the upper and lower sidebands. Over the RF frequency range of 205-240 GHz, the single-sideband receiver noise temperatures of the new mixer are 40-100 K for the 4.0-8.0 GHz IF frequency band. The image rejection ratios are greater than 10 dB over the same range. For the dual IF signals obtained by the receiver, we have developed two sets of acousto-optical spectrometers and a telescope control system. Using the new telescope system, we successfully detected the 12CO (J=2-1) and 13CO (J=2-1) emission lines simultaneously toward Orion KL in 2005 March. Using the waveguide-type sideband-separating SIS mixer for the 200 GHz band, we have initiated the first simultaneous 12CO (J=2-1) and 13CO (J=2-1) survey of the galactic plane as well as large-scale mapping observations of nearby molecular clouds.Comment: 15 pages, 15 figures, Accepted for publication in PASJ, version with high resolution figures is available via http://www.nro.nao.ac.jp/~nakajima/vst1_2sb.pd

VLBI Monitoring Observations of Water Masers Around the Semi-Regular Variable Star R Crateris

We monitored water-vapor masers around the semi-regular variable star R Crateris with the Japanese VLBI Network (J-Net) at the 22 GHz band during four epochs with intervals of one month. The relative proper motions and Doppler-velocity drifts of twelve maser features were measured. Most of them existed for longer than 80 days. The 3-D kinematics of the features indicates a bipolar expanding flow. The major axis of the asymmetric flow was estimated to be at P.A. = 136 degrees. The existence of a bipolar outflow suggests that a Mira variable star had already formed a bipolar outflow. The water masers are in a region of apparent minimum radii of 1.3 x 10^12 m and maximum radii of 2.6 x 10^12 m, between which the expansion velocity ranges from 4.3 to 7.4 km/s. These values suggest that the water masers are radially accelerated, but still gravitationally bound, in the water-maser region. The most positive and negative velocity-drifting features were found relatively close to the systemic velocity of the star. We found that the blue-shifted features are apparently accelerated and the red-shifted apparently decelerated. The acceleration of only the blue-shifted features seems to be consistent with that of the expanding flow from the star.Comment: 15 pages, 5 figures, Accepted for publication in PASJ (2001), preprint can be obtained via WWW on http://www.nro.nao.ac.jp/library/report/list.htm

Fine definition of the pedigree haplotypes of closely related rice cultivars by means of genome-wide discovery of single-nucleotide polymorphisms

<p>Abstract</p> <p>Background</p> <p>To create useful gene combinations in crop breeding, it is necessary to clarify the dynamics of the genome composition created by breeding practices. A large quantity of single-nucleotide polymorphism (SNP) data is required to permit discrimination of chromosome segments among modern cultivars, which are genetically related. Here, we used a high-throughput sequencer to conduct whole-genome sequencing of an elite Japanese rice cultivar, Koshihikari, which is closely related to Nipponbare, whose genome sequencing has been completed. Then we designed a high-throughput typing array based on the SNP information by comparison of the two sequences. Finally, we applied this array to analyze historical representative rice cultivars to understand the dynamics of their genome composition.</p> <p>Results</p> <p>The total 5.89-Gb sequence for Koshihikari, equivalent to 15.7× the entire rice genome, was mapped using the Pseudomolecules 4.0 database for Nipponbare. The resultant Koshihikari genome sequence corresponded to 80.1% of the Nipponbare sequence and led to the identification of 67 051 SNPs. A high-throughput typing array consisting of 1917 SNP sites distributed throughout the genome was designed to genotype 151 representative Japanese cultivars that have been grown during the past 150 years. We could identify the ancestral origin of the pedigree haplotypes in 60.9% of the Koshihikari genome and 18 consensus haplotype blocks which are inherited from traditional landraces to current improved varieties. Moreover, it was predicted that modern breeding practices have generally decreased genetic diversity</p> <p>Conclusions</p> <p>Detection of genome-wide SNPs by both high-throughput sequencer and typing array made it possible to evaluate genomic composition of genetically related rice varieties. With the aid of their pedigree information, we clarified the dynamics of chromosome recombination during the historical rice breeding process. We also found several genomic regions decreasing genetic diversity which might be caused by a recent human selection in rice breeding. The definition of pedigree haplotypes by means of genome-wide SNPs will facilitate next-generation breeding of rice and other crops.</p