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This paper presents simulation results for a 600 GHz micromachined waveguide mixer with integrated horn antenna, a hybrid-integrated planar Schottky diode and IF filter structures on a quartz substrate. In addition to the simulated electrical performance we show approaches for the manufacturing of the split-block mixer by both micro-mechanical milling and silicon etching technology.

We present a survey of the application of micromachining techniques for the fabrication of THz-components. Micro-machining of new THz- devices based on deep trench etching of silicon is discussed with respect to its capability to generate complex 3-dimensional geometries with high aspect ratios (ARs) and to meet the high mechanical requirements for THz-components. First results for the application of deep trench etching for the design of a branch-line coupler for 600 GHz is discussed. We emphasize the potential of silicon based microstructures for manufacturing new devices and focus on technological issues.

The paper reports on an octave-bandwidth double-balanced mixer which operates in the millimeter-wave range from 35 to 70 GHz. The design uses a low cost hybrid technology: A thin-film circuit is fabricated on an alumina substrate, and the diodes are flip-chip mounted. Balanced signals are provided by side coupled Marchand baluns. As a result the conversion loss averages out at 13 dB

The paper presents the development of a fast scanning W-Band (75-100 GHz) system and a suitable antenna concept for advanced imaging applications. The goal is to obtain a broadband frequency response from a large target area within a short time period. Two typical approaches for the design of a free space millimetre-wave imaging setup will be discussed. The first approach consists of a focused bistatic measurement setup that includes a combination of a conical horn and a dielectric lens in order to focus the beam. The basic idea of the second approach is to use an unfocused measurement setup employing Synthetic Aperture Radar (SAR) algorithms in order to focus the image numerically. Both measurement setups will be discussed with respect to the capability for fast scanning mm-wave imaging systems. Experimental results on planar test objects demonstrate the performance of the developed W-Band system compared to a commercial vector network analyzer (VNA).

In this paper we present measurement results of a micro-machined split-block waveguide mixer for 600 GHz. The mixer implements a planar GaAs Schottky diode on a quartz substrate. Two different diode designs used for this mixer design are compared. The overall performance of the waveguide mixer is demonstrated by measurements of the mixer in a quasi-optical setup at 600 GHz. In this setup we are able to measure single sideband conversion losses of 9-14 dB at 600 GHz and voltage responsivities of 421-1690 mV/mW.

Passive millimeter wave imaging can complement security measures in scenarios such as airports or checkpoints, due to the fact that these frequencies penetrate clothes and enable e.g. concealed weapon detection (CWD). Such a radiometric system has to meet several key requirements concerning its thermal and spacial resolution and the image acquisition time. The latter can be reduced significantly by scanning the scene with multiple beams simultaneously. The demonstrator system presented in this paper describes a multi-channel focal plane array (FPA) approach that cuts the overall scanning time down by a factor of four. Dielectric rod antennas are proposed as feed elements in high density arrays. The dielectric wide angle lens of the FPA is focused at a distance of 20 m for stand-off measurements. Besides addressing the design and characterization of both the antenna setup and the radiometric receivers, measurement results are presented to demonstrate the feasibility of the multi-channel concept.

The field of view of wide angle dielectric lens antennas for focal plane arrays is mainly limited due to astigmatic aberrations which are often not taken into consideration even in more complex coma-corrected lens designs with two aspheric surfaces. The paper describes an efficient compact range setup for the measurement of high-gain lens antennas in small antenna chambers and presents a thorough experimental study of the effects of astigmatism and feed displacement/misalignment on the pattern degradation for large scanning angles. An experimentally derived method to minimize these aberrations is explained, resulting in a fairly constant beam quality with a maximized gain over a large field of view of 40/spl deg/.

Dielectric rod antennas of rectangular cross section have a number of significant advantages over conventional waveguide or horn antennas when used as feed elements in focal plane arrays. They provide a broadband input matching, a much lower mutual coupling and an appreciable reduction of spillover losses even in densely packed feed arrays. The design, simulation, optimization and experimental investigation of feed arrays with waveguide- and slotline-fed dielectric rod antennas at millimeter-wave frequencies is presented.

A new class of frequency selective surfaces (FSSs), to be used as quasi-optical filters for harmonic suppression in sub-mm wave frequency multipliers, is proposed and experimentally verified. The FSSs consist of two-dimensional aperture arrays, and are made from microstructured aluminium on electrically thick, high-resistivity silicon substrates. This leads to a very good mechanical stability, low insertion loss, and permits the structure to be manufactured using standard processes available from the semiconductor industry. The paper presents the design, fabrication, and testing of two sets of prototypes, the former with a pass-band at 300 GHz and a stop-band at 450 GHz and the latter with a pass-band at 600 GHz and a stop-band at 750 GHz.

In this paper, simulated Brillouin scattering in Raman fiber amplifier was numerically calculated. The theoretical results show that much more power could be transferred from the pump to the signal in Raman fiber amplifier with no SBS and Brillouin frequency shift in a given fiber depends on temperature and on mechanical strain. And spatially variable longitudinal strain distribution in standard fibers for SBS suppression in active devices was proposed.

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.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A broadband low cost millimeterwave slotline detector circuit is proposed that can efficiently be realized on a low permittivity substrate (/spl epsiv//sub r/= 2.2) which is required for the integration of an antenna. The experimentally approved design achieved a voltage sensitivity of 1660 mV/mW at 77 GHz, with more than 1000 mV/mW between 62 and 85 GHz, a tangential signal sensitivity below -45 dBm and a 1-dB-compression point at -14.8 dBm. The sensitivity is about the same as for commercially available waveguide detectors despite the unfavourably low substrate permittivity. The compact design and the low cost allow the integration of a larger number of such slotline detectors with antennas on a single substrate for a receiver array in a millimeterwave focal plane imaging system.

In der vorliegenden Arbeit wird die die Frage untersucht, wie eine Comicbibliothek in Berlin/Deutschland existieren kann. Ausgegangen wird von einer Analyse der seit 1992 existierenden Comicbibliothek mit einer Leserbefragung zur Zielgruppenbestimmung und einer Zusammenfassung der Potentiale und Hemmnisse einer Weiterentwicklung. Einrichtungen in Deutschland mit ähnlich randständigem Sammelgebiet und verschiedenen Trägerstrukturen werden vergleichend befragt. Europaweit werden außerdem Comicbibliotheken zum Vergleich herangezogen. Im dritten Teil der Arbeit legt der Autor eine strategische Vision vor und erläutert im Folgenden, wie diese in kleinen Schritten und mittels Nahzielen erreicht werden soll.

A new class of quasi-optical filters for harmonic suppression in sub-mm wave frequency multipliers with a pass-band at 300 GHz and a stop-band at 450 GHz was developed. The filters consist of 2-dimensional aperture arrays, and are made from microstructured aluminium on electrically thick, high-resistivity silicon substrates. This leads to a very good mechanical stability, low insertion loss, and permits to manufacture the structure by using standard processes available from the semiconductor industries. Two quasi-optical filters, the former with rectangular slots and the latter with dogbone-shaped holes, have been designed by using the MoM/BI-RME method. Several prototypes have been fabricated, and measured by THz-time-domain spectroscopy and CW-measurements, showing an insertion loss smaller than 1.6 dB at 300 GHz and a stop-band attenuation larger than 20 dB at 450 GHz. High reproducibility of the structures has also been proved. Moreover, it was shown that fine-tuning of the stop-band can be accomplished by small changes of the incidence angle.

This paper describes the design and experimental verification of frequency selective surfaces, to be used as quasi-optical filters in the sub-millimeter wave range. They consist of a thin metal layer perforated periodically with rectangular or dogbone-shaped holes, and supported by a thick silicon substrate. A set of filters with pass-band at 600 GHz and stop-band at 750 GHz have been designed and tested. The design procedure based on the MoM/BI-RME method, the manufacturing of prototypes by standard processes available from the semiconductor industries, and their measurement by CW and THz time-domain spectroscopy are reported in this work. This class of filters is mechanically robust, presents low losses (1.4 dB), exhibits good reproducibility, and permits a fine tuning of the stop-band frequency by slightly changing the incidence angle.

We present an overview on the latest results using micromachining techniques for the fabrication of THz-components. Different machining techniques was discussed with respect to their capability to generate complex 3-dimensional geometries with high aspect ratios and to meet the high mechanical requirements for THz-components. Exemplary results for the application of micromachining techniques for the design of new components were reviewed. We emphasizes the potential of silicon based microstructures for the manufacturing of new devices.

Dielectric rod antennas of rectangular cross section are of increasing interest at mm-wave frequencies. For many applications, like e.g. densely packaged feed arrays for reflector/lens systems or electromagnetic field probes, an exact knowledge of the phase center location is required. This work describes a simple experimental method to determine the phase center of antennas by means of a phase pattern measurement and a numerical least square fit procedure. For feed antennas, the method can be adopted to the numerical aperture of reflector or lens systems. Phase center locations of various dielectric rod antennas with rectangular cross section are presented and the influence of geometrical parameters and frequency on the phase center an analysed and interpreted in detail.

With the increasing interest in new artificial materials ranging from meta-materials to photonic bandgap materials there is a growing need for accurate models of artificial materials. We examine the design of a three-layer structure with an artificial dielectric as an anti-reflection-coating on both sides of a dielectric slab. We present a field-equivalent circuit theory to calculate the effective dielectric constant of the structured dielectric. The materials discussed in this paper have a lateral periodicity smaller than /spl lambda//10 and can easily be manufactured from high density polyethylene (HDPE) for frequencies up to 20 GHz. The field-analog circuit theory can also be used to calculate the polarization dependence of the artificial dielectric. Theoretical results of three geometrically different structures were compared with waveguide measurements at X-band and showed excellent agreement. Applications such as the design of new components at millimeter and submillimeter wave frequencies are discussed, considering the X-Band measurements as a scaled model.

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.

Presents an overview on established source and detector technologies as well as an outlook on emerging technologies for the frequency range between 0.3 and 10 THz. Applications for spectroscopy, radiometry, imaging and the examination of biological samples are reviewed. Continuous wave and time-domain THz technologies are contrasted in order to demonstrate the broad variety of measurement systems, their strengths and current limitations of THz technologies.

The LHFT is currently working on a broadband heterodyne receiver for stratospheric measurements at 2.5 THz. Many molecules and radicals such as OH, H/sub 2/O and O/sub 3/ which are involved in the stratospheric ozone chemistry exhibit characteristic emissions in this spectral range. In order to measure these spectra and extract concentration data of the single components, a platform operating at high altitudes is necessary to overcome atmospheric absorption due to water vapor. Research at the LHFT includes the construction of a stable and compact local oscillator (LO) as well as the development of the receiver front end. In the LO subsystem an RF excited grating tunable sealed off CO/sub 2/ laser with an apodized out-coupling element will be used as a pump source. The compact and rugged design is realized by a slab discharge geometry and a metal tube housing. Long term stable gas composition for sealed off operation is optimized during the design phase of the laser by making use of tunable diode laser absorption spectroscopy (TDLAS). A methanol ring-laser with an output power of up to 49 mW at 2522.8 GHz (pump power 20 W) has been developed and is available as a very powerful FIR source. The optimization of the front end concentrates upon broadband and low noise performance. A mixer with newly developed substrate-less Schottky diodes followed by a broadband, noise matched IF-amplifier allow for low noise operation over a frequency range from 6 to about 13 GHz, thus covering emission lines of at least the three species mentioned above.

A number of applications of microwave and, in particular, millimeter-wave MMICs (monolithic microwave integrated circuits) in automotive systems are under development. The authors review these applications and give the current status of some of these developments. The applications considered are sensors (both radar and radiometric), communication systems, and traffic control systems. MMICs for the following specific systems are considered: speed sensors, electronic toll collection, and collision avoidance radar. >

A variety of transitions between rectangular dielectric waveguides and planar waveguides like microstrip or slotline have been designed to combine the advantages of dielectric wave-guides at millimeterwaves with the excellent hybrid integration capabilities of planar circuits. FDTD field simulations have been applied to analyze and optimize the designed transitions with respect to low insertion and return losses as well as minimized mutual coupling between adjacent transitions. Experimental investigations between 60 and 90 GHz proved the promising results of the simulations with insertion losses between 0.5 and 1.5 dB over the full waveguide band (WR-12). The transitions can well be used for the integration of planar circuits into dielectric waveguides or rod antennas and the designed structures are scalable up to frequencies beyond 100 GHz.

An X-band microwave/photonic phased-array radar demonstrator is described. The critical components associated with the microwave/photonic beamforming network have been experimentally studied. Measured parameters of a DFB (distributed feedback) laser and an EDFA (erbium-doped fiber amplifier) for analog modulation are in good agreement with theory. Using a simplified analytical system model with incorporation of an EDFA, it is shown that for a system bandwidth of 100 MHz and a modulation index of 46% the maximum attainable SNR is approximately 40 dB. >

In the millimeter wave region several communication and sensor systems are emerging which presently are served only by III/V based technologies. First sensor systems of relevant volume market are tested at 76 GHz for automotive sensors, with other systems operating at 60 GHz and 94 GHz. For mm-wave communication systems volume applications arise at 38 GHz for the interconnection of PCN cells. This paper describes GaAs based technologies and components which are available to serve the requirements of mm-wave communication sensor systems up to 80 GHz.

The paper describes the design and realization of a heterodyne vector field measurement system. The system is designed to work in a frequency range from 148 GHz to 152 GHz with a dynamic range of about 75 dB and a phase uncertainty better than 3 degrees. It uses two channels for the measurement of the magnitude as well as the phase characteristics of an electromagnetic field. Two fundamental mixers at 150 GHz have been installed, which are both pumped by a 150 GHz phase locked solid-state oscillator unit. The system can be extended to the 300 GHz and 450 GHz frequency range by replacing these mixers by subharmonically pumped mixers. The mixers and two dielectric antennas, used as distortion minimized field probes, are mounted on a high precision 3D scanning platform. At the IF frequency of 160 MHz the vector analysis of the measured signals is done by an IF processing unit with considerably enhanced measurement accuracy by software corrections with a personal computer.

As Schottky diodes still remain the most frequently used devices in THz mixers, precise evaluation of their DC and noise performance is essential for the improvement of mixers in the sub-millimeter wave regime. We present first results from a measurement system which is able to measure the DC characteristics and the noise for Schottky diodes as a function of frequency and bias current. The automated system is capable of contacting many diodes consecutively.