Hans Brand

Simulation and Measurement of Dielectric Antennas at 150 GHz

Based on the development of a flexible, dielectric waveguide system for frequencies in the region of 150 GHz [1], the antenna characteristics of various tapered ends of dielectric waveguides have been studied. The flexible waveguide consists of a rectangular, dielectric fibre made of polyethylene. The paper describes the simulation and optimization of different tapers using 3D electromagnetic field computation, the precise fabrication of the antennas and the verification of the simulated data by field measurements at 150 GHz.

Flexible low-loss dielectric waveguides for THz frequencies with transitions to metal waveguides

A flexible low-loss dielectric waveguide system for sub-millimetre wave frequencies up to 600 GHz is presented, with measured attenuation values shown at 300 GHz. Mode transformers for an accurate and reproducible transition to metal waveguides have been investigated and improved.

Microwave Technology in the Terahertz Region

Electromagnetic waves with frequencies between 0.1 THz and some 10 THz cover the gap from the millimeter wave bands to the infrared optical region. Coherent microwave technology concerning signal generation and detection has been introduced in this THz-region to a steadily growing extent in the past, mainly forced by applications in radioastronomy and remote sensing. The paper tries to review the state of the art of this submillimeter wave technology with emphasis on molecular gas lasers as sources and quasi-optical waveguiding for signal processing.

Lineselective CO2-lasers with variable line-spacing and variable reflectivity silicon gratings

A lineselective CO2-laser with an unstable resonator is presented. The CO2-laser is realised with an rf-excited slab geometry to get a compact design with high output power. As lineselective element a grating in Littrow mount is used. The gratings are manufactured by anisotropic etching of silicon. The grating has a variable duty cycle to obtain a variable reflectivity. Furthermore, gratings are presented that have focusing propteries by a variation of the grating periodicity.

MEMSTIC - eine neue Schaltungskonzeption für den Submillimeter- Wellenlängenbereich

The acronym MEMSTIC is the short form of MM Bement MM Substrate Terahertz /ntegrated Circuit and is for a new, for some years developed circuit concept, in which different circuit functions (e.g. oscillations producing, filtering or amplifying) are performed by different substrates which are only connected by the field of a beam waveguide. In the plain of a substrate many items (10 bis 10) at the same function operate synchronously in phase. They are not coupled among themselves but by their antenna elements with the electromagnetic field before and behind the substrate. The paper wants to give an overview over the background for this concept, over the circuit connection and the possible multi-element components as well as the measurement problems. Für die Dokumentation Quasi-Optik / Strahlwellenleiter-Schaltungen / Integration bei THz-Frequenzen / Multi-Element Systeme

Overall Final Report on NATO-ARW-IMEI-1983

This was a very stimulating and successful week of work. The field of imaging by inverse processing is important and fruitful; its rapid development gained impetus from the activities of the workshop. The foresight shown by Wolfgang-M. Boerner in conceiving and by NATO in supporting this Advanced Research Workshop was shown to be fully justified.

Final Report of Working Discussion Group W-C on Polarization Utilization in High Resolution Imaging

There is good evidence from particular problem areas that target detection and classification can be considerably improved by use of polarization information. However, the general usefulness of this technique in target detection and classification still involves many unresolved issues. Many of these issues have been identified at this ARW and initial recommendations were made for futher research.

Final Report of Working Discussion Groups

The working discussion groups are to work on isolating unresolved problems and providing recommendations for potential future research projects which will require active interaction of engineering scientists of all NATO-member countries. The five questions (W-A to W-E) chosen define issues for which immediate answers are required. The composition of the chosen speakers, senior research scientists/engineers is well suited to tackle these problems and we do expect clear-cut resolutions and recommendations for additional near-future NATO Advanced Study Institutes and/or NATO Advanced Research Workshops.

Final Report of Working Discussion Group W-F on Enhancement of Interaction Between Active R & D Labs Within Nato-Member Countries on the Subject of Electromagnetic Imaging

The present ARW-IMEI has successfully brought together key experts and observers from a majority of NATO-mem- ber countries allowing them to judge the current level of interaction. In this report we attempt to summarize the existing interaction paths, Substantiate why enhancement of interaction is desireable and to suggest mechanisms for achieving these goals.

Final Report of Working Discussion Group W-E on Holographic and Tomographic Imaging and Related Phase Problems

The phase retrieval problem occurs in electromagnetic inverse scattering, optical and x-ray applications. The phase unwrapping problem is of importance in signal processing applications, ultrasound, and geophysical diffraction tomography. This working group identified problem areas and made general recommendations.