Improved design of a wide-band reconfigurable reflectarray unit with loaded SPP structure

This paper proposes an improved design of a pulse-based radar. An improved design of a pulse generator is presented using step recovery diodes and a signal mixer for the received signal. Two-step recovery diodes produce pulses of 120 ps in duration. A pulse generator is improved by removing the negative power supply, resulting in a reduced number of electronic pulses. A sampling mixer at the receiver’s site receives the generated signal and stretches it from picoseconds into microseconds. The improved pulse generator is also used in the sampling mixer as a strobe pulse generator, which makes the sampling mixer much simpler. The stretched signal is then sampled by a low sample rate using an analog to digital converter. The proposed radar design achieves up to 8 GHz bandwidth and an equivalent receiving sample rate of about 100 GSa/s. The radar is controlled using a software-defined radio called Red Pitaya, which is also used for data acquisition. The proposed radar design uses widely available commercial components, which makes radar design widely available with low cost implementation.

Download Full-text

Improved Design of Microstrip-to-Slotline Transition

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.668-669.844 ◽

2014 ◽

Vol 668-669 ◽

pp. 844-847

Author(s):

Yuan Zhao ◽

Bing Liang Hu ◽

Chao Deng ◽

Hong Wei Wang ◽

Lei Li ◽

...

Keyword(s):

Wide Band ◽

Ultra Wide Band ◽

Equivalent Circuits ◽

Commercial Software ◽

High Impedance ◽

Measurement Results ◽

Improved Design ◽

Traditional Structures ◽

Better Than

A novel compact Ultra-Wide Band (UWB) microstrip-slotline transition utilizing high impedance chip resistor is proposed and analyzed. The reactance introduced by the microstrip open end and slotline short end, which is the main limitation to the bandwidth in the traditional structures, is minimized in the design. The model is analyzed with the method of equivalent circuits and simulated by the commercial software HFSS. To test the performance of this transition a back-to-back structure is fabricated. The measurement results show that the bandwidth of 45 octaves can be obtained while the insert loss is better than 0.7dB within the band.

Download Full-text

Seven-colour photometry at the Geneva Observatory

Symposium - International Astronomical Union ◽

10.1017/s0074180900053535 ◽

1966 ◽

Vol 24 ◽

pp. 262-266 ◽

Cited By ~ 1

Author(s):

M. Golay

Keyword(s):

Wide Band ◽

Electric System ◽

Band Type

During the last 5 years, we have developed a seven-colour photometry at the Geneva Observatory. Our multicolour photo-electric system is of a wide-band type; the bandwidth being about 500Å for four filters. The three others are similar to theUBVsystem. In Table 1 we give the filter combinations used in our photometry (1).

Download Full-text

TEM and cathodoluminescence of precipitates in II-VI semiconductors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104509 ◽

1988 ◽

Vol 46 ◽

pp. 488-489

Author(s):

Joanna L. Batstone

Keyword(s):

Crystal Growth ◽

Band Gap ◽

Local Strain ◽

Wide Band ◽

Optoelectronic Device ◽

Wide Band Gap ◽

Bulk Crystal Growth ◽

Transmission Electron ◽

Device Applications ◽

Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

Download Full-text

An improved design for an Scanning Tunnelling Microscope (STM) for use in a Transmission Electron Microscope (TEM)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100086222 ◽

1991 ◽

Vol 49 ◽

pp. 384-385

Author(s):

W.K. Lo ◽

J.C.H. Spence

Keyword(s):

Electron Microscope ◽

Transmission Electron Microscope ◽

Mechanical Stability ◽

Scanning Tunnelling Microscope ◽

Reflection Mode ◽

Specimen Holder ◽

Transmission Electron ◽

Scanning Tunnelling ◽

Improved Design

An improved design for a combination Scanning Tunnelling Microscope/TEM specimen holder is presented. It is based on earlier versions which have been used to test the usefulness of such a device. As with the earlier versions, this holder is meant to replace the standard double-tilt specimen holder of an unmodified Philips 400T TEM. It allows the sample to be imaged simultaneously by both the STM and the TEM when the TEM is operated in the reflection mode (see figure 1).The resolution of a STM is determined by its tip radii as well as its stability. This places strict limitations on the mechanical stability of the tip with respect to the sample. In this STM the piezoelectric tube scanner is rigidly mounted inside the endcap of the STM holder. The tip coarse approach to the sample (z-direction) is provided by an Inchworm which is located outside the TEM vacuum.

Download Full-text

Electron microscopic characterization of diamond thin films and substrates for diamond heteroepitaxial growth

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154937 ◽

1989 ◽

Vol 47 ◽

pp. 592-593

Author(s):

J.B. Posthill ◽

R.P. Burns ◽

R.A. Rudder ◽

Y.H. Lee ◽

R.J. Markunas ◽

...

Keyword(s):

Thin Films ◽

Wide Band ◽

Deposition Process ◽

Heteroepitaxial Growth ◽

Electron Microscopic ◽

Wide Band Gap ◽

Lattice Matching ◽

Different Types ◽

Diamond Thin Films

Because of diamond’s wide band gap, high thermal conductivity, high breakdown voltage and high radiation resistance, there is a growing interest in developing diamond-based devices for several new and demanding electronic applications. In developing this technology, there are several new challenges to be overcome. Much of our effort has been directed at developing a diamond deposition process that will permit controlled, epitaxial growth. Also, because of cost and size considerations, it is mandatory that a non-native substrate be developed for heteroepitaxial nucleation and growth of diamond thin films. To this end, we are currently investigating the use of Ni single crystals on which different types of epitaxial metals are grown by molecular beam epitaxy (MBE) for lattice matching to diamond as well as surface chemistry modification. This contribution reports briefly on our microscopic observations that are integral to these endeavors.

Download Full-text