Brother Joseph N. Streiff, S.M. 1918-1985

News release announces Brother Joseph M. Streiff, S.M., died at age 67 after suffering from leukemia

Microwave Liquid Crystal Enabling Technology for Electronically Steerable Antennas in SATCOM and 5G Millimeter-Wave Systems

Future satellite platforms and 5G millimeter wave systems require Electronically Steerable Antennas (ESAs), which can be enabled by Microwave Liquid Crystal (MLC) technology. This paper reviews some fundamentals and the progress of microwave LCs concerning its performance metric, and it also reviews the MLC technology to deploy phase shifters in different topologies, starting from well-known toward innovative concepts with the newest results. Two of these phase shifter topologies are dedicated for implementation in array antennas: (1) wideband, high-performance metallic waveguide phase shifters to plug into a waveguide horn array for a relay satellite in geostationary orbit to track low Earth orbit satellites with maximum phase change rates of 5.1°/s to 45.4°/s, depending on the applied voltages, and (2) low-profile planar delay-line phase shifter stacks with very thin integrated MLC varactors for fast tuning, which are assembled into a multi-stack, flat-panel, beam-steering phased array, being able to scan the beam from −60° to +60° in about 10 ms. The loaded-line phase shifters have an insertion loss of about 3 dB at 30 GHz for a 400° differential phase shift and a figure-of-merit (FoM) > 120°/dB over a bandwidth of about 2.5 GHz. The critical switch-off response time to change the orientation of the microwave LCs from parallel to perpendicular with respect to the RF field (worst case), which corresponds to the time for 90 to 10% decay in the differential phase shift, is in the range of 30 ms for a LC layer height of about 4 µm. These MLC phase shifter stacks are fabricated in a standard Liquid Crystal Display (LCD) process for manufacturing low-cost large-scale ESAs, featuring single- and multiple-beam steering with very low power consumption, high linearity, and high power-handling capability. With a modular concept and hybrid analog/digital architecture, these smart antennas are flexible in size to meet the specific requirements for operating in satellite ground and user terminals, but also in 5G mm-wave systems

To Kick Against the Pricks: An Examination of the Oresteia and the Acts of the Apostles

The major themes found in the Oresteia and the books of Luke and Acts of the Apostles are compared. By focusing on the similarities found in the themes of Justice, Religion, and New versus Old, the reader may determine if the phrase in question is being used as a literary allusion in the book of Acts of the Apostles to the Oresteia trilogy. The author believes this to be the case and believes that to arrive at a full understanding of the literary meaning of the phrase in question, an understanding of the major themes of the Oresteia is necessary

Radio wave propagation and single-cell coverage prediction of broadband radio access systems including passive reflectors, Journal of Telecommunications and Information Technology, 2001, nr 2

This paper presents the scheme of a software planing tool for single microcells of broadband radio access systems operating at millimeter waves, providing local multi- point distribution services (LMDS), particularly in urban or suburban areas. The aim of this planing tool is to provide operators with information, which supports the assessment of the profitability by calculating link budgets and the area coverage and by roughly estimating the maximum number of potential customers, i.e. the total number of households in a certain area, as well as the number of customers (house-holds) which will actually be covered from a site. A house-hold is here considered as a single apartment or flat, thus a building usually consists of several households. This novel household-estimation model is able to estimate the number of households based only on the 3D-data of buildings, without using residential data. Besides the optimization of line-of-sight (LOS) coverage, also the possibility is considered to enhance the coverage into shadowed areas by using optimized reflectors as passive repeaters up to distances of 1 km from the base station, depending on the system margin and the rain climate zone. All calculations are based on 3D-databases of both, buildings and vegetation

Network-Structured BST/MBO Composites Made from Core-Shell-Structured Granulates

A finite element method (FEM)-based simulation approach to predict the tunability in composite materials was developed and tested with analytical data. These tests showed good prediction capabilities of the simulation for the test data. The simulation model was then used to predict the tunability of a network-structured composite, where the dielectric phase formed clusters in a paraelectric network. This was achieved by simulating a reciprocal core-shell unit cell of said network. The simulation showed a high tunability for this network model, exceeding the tunability of the analytically evaluated layered, columnar, and particulate model. The simulation results were experimentally verified with a Ba0.6Sr0.4TiO3/Mg3B2O6 (BST/MBO) composite, where core-shell granulates were made with a two-step granulation process. These structured samples showed higher tunability and dielectric loss than the unstructured samples made for comparison. Overall, the structured samples showed higher tunability to loss ratios, indicating their potential for use in tunable radio frequency applications, since they may combine high performance with little energy loss

Intra- and inter-cell interference investigations for broadband radio access systems above 10 GHz, Journal of Telecommunications and Information Technology, 2001, nr 2

Local multipoint distribution systems (LMDS) operating above 10 GHz have a large bandwidth (2–3 GHz) but a very limited range. These systems can provide coverage to a few kilometers only. The size of the macro cells illuminated by the base stations, where line of sight (LOS) exists, is 1 to 6 km. To provide coverage to customers where LOS is not possible, repeaters or passive reflectors may be used. In this paper we present first results of reflection measurements at 42 GHz, and based on that, simple multipath studies, taking into account the beam width of the antennas of both, transmitter and receiver. Secondly, LOS cochannel and adjacent channel interference are assessed for cellular LMDS networks. As suggested in the CRABS report, the maximal spectral efficiency can be obtained with a dual frequency and polarization reuse plan. This frequency and polarization reuse leads to interference. In this paper we have first calculated the cochannel interference (CCI) and the adjacent channel interference (ACI) due to the frequency/polarization reuse schemes suggested in the CRABS report. The effects of the variation of the half power beam width (HPBW) of the receiver, the time percentage parameter p, and the cell radius on C/I are also reported. In the latter part of the paper we propose a simple interference reduction technique based on re-orientation of the receiver antennas. We have also explored the possibility of using trellis coded modulation (TCM) for reducing interference levels. Initial results have been found to be quite encouraging

Evaluation of GaN-HEMT power amplifiers using BST-based components for load modulation

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.In this paper, the concept of load-modulated power amplifiers (PAs) is studied. Two GaN-HEMT power amplifiers (PAs), targeted for high efficiency at maximum and output back-off (OBO) power levels, are designed, implemented, and tested across 1.8–2.2 GHz. The load modulation in the first design is realized by tuning the shunt capacitors in the output matching network. A novel method is employed in the second design, where barium–stronrium–titante is used for the realization of load modulation. The large-signal measurement results across the desired band show 59–70% drain efficiency at 44–44.5 dBm output power for both designs. Using the available tunable technique, the drain efficiency of the PAs is enhanced by 4–20% at 6 dB OBO across the bandwidth

Wideband evaluation of two types of slow‐wave microstrip lines

The design, characterization and comparison of two widely used approaches in realizing slow-wave effect on microstrip transmission lines, that is stub loaded and defected ground structure loaded microstrip lines are presented in a wide bandwidth (10–67 GHz) for the first time. Transparent substrate and dielectric material are chosen to ease the alignment of electrode and ground plane. Thin dielectric layer are applied to make the comparison prominent. The results indicate that defected ground structure loaded microstrip line has better RF performance in terms of compactness and insertion loss than stub loaded method within the whole band especially in thin film applications

Electromagnetic modeling of tunability of Barium Strontium Titanate and Magnesium Borate composites

A complete tunability electromagnetic simulation model for the Ba$_{0.6}$Sr$_{0.4}$TiO$_3$ (BST), with ≈ 2000, and Mg$_2$B$_2$O$_6$ (MBO), with ≈ 7, composites is proposed here. The model is based on electrostatics, to simulate the effects of bias fields distribution in the composite varactor at the unbiased state to create the biased state for all volumetric mixture compositions. A bulk-ceramic varactor approach is chosen for the fabricated varactors. Varactors are fabricated with different volume compositions of BST and MBO, ranging from 10 to 100 vol-% of BST. Simulated results of the varactor model are then verified with the measured results of the varactor. The simulated and measured tunability shows considerable discrepancy at room temperature, which leads to Curie temperature _ investigation of the fabricated varactors. It has been observed that a shift in _ is directly proportional to the discrepancies in the simulated and measured tunability. After incorporating the _ shifts in the model, the results show close proximity between measured and _ -shifted simulated tunabilities with differences being reduced from around 32% to 2% for 80 vol-% BST varactor

Numerical Optimization of an Open-Ended Coaxial Slot Applicator for the Detection and Microwave Ablation of Tumors

A multiobjective optimization method for a dual-mode microwave applicator is proposed. Dual-modality means that microwaves are used apart from the treatment, and also for the monitoring of the microwave ablation intervention. (1) The use of computational models to develop and improve microwave ablation applicator geometries is essential for further advances in this field. (2) Numerical electromagnetic–thermal coupled simulation models are used to analyze the performance of the dual-mode applicator in liver tissue; the sensitivity evaluation of the dual-mode applicator’s sensing mode constrains the set of optimal solutions. (3) Three Pareto-optimal design parameter sets are derived that are optimal in terms of applicator efficiency as well as volume and sphericity of the ablation zone. The resulting designs of the dual-mode applicator provide a suitable sensitivity to distinguish between healthy and tumorous liver tissue. (4) The optimized designs are presented and numerically characterized. An improvement on the performance of previously proposed dual-mode applicator designs is achieved. The multiphysical simulation model of electromagnetic and thermal properties of the applicator is applicable for future comprehensive design procedures