Submillimeter-wave InP Gunn devices

Recent advances in design and technology signifi- cantly improved the performance of low-noise InP Gunn devices in oscillators first at -band (110–170 GHz) and then at -band (75–110 GHz) frequencies. More importantly, they next resulted in orders of magnitude higher RF output power levels above -band and operation in a second harmonic mode up to at least 325 GHz. Examples of the state-of-the-art performance are continuous-wave RF power levels of more than 30 mW at 193 GHz, more than 3.5 mW at 300 GHz, and more than 2 mW at 315 GHz. The dc power requirements of these oscillators compare favorably with those of RF sources driving frequency multiplier chains to reach the same output RF power levels and frequencies. Two different types of doping profiles, a graded profile and one with a doping notch at the cathode, are prime candidates for operation at submillimeter- wave frequencies. Generation of significant RF power levels from InP Gunn devices with these optimized doping profiles is predicted up to at least 500 GHz and the performance predictions for the two different types of doping profiles are compared

High-performance GaAs/AlAs superlattice electronic devices in oscillators at frequencies 100–320 GHz

Negative differential resistance devices were fabricated from two epitaxial wafers with very similar GaAs/AlAs super-lattices and evaluated in resonant-cap full-height waveguide cavities. These devices yielded output powers in the fun-damental mode between 105 GHz and 175 GHz, with 14 mW generated at 127.1 GHz and 9.2 mW at 133.2 GHz. The output power of 4.2 mW recorded at 145.3 GHz constitutes a 50-fold improvement over previous results in the funda-mental mode. The highest confirmed fundamental-mode oscillation frequency was 175.1 GHz. In a second-harmonic mode, the best devices yielded 0.92 mW at 249.6 GHz, 0.7 mW at 253.4 GHz, 0.61 mW at 272.0 GHz, and 0.54 mW at 280.7 GHz. These powers exceed those extracted previously from higher harmonic modes by orders of magnitude. The power of 0.92 mW constitutes an improvement by 77% around 250 GHz. The second-harmonic frequency of 317.4 GHz is the highest to date for superlattice electronic devices and is an increase by 25% over previous results

Transit-time devices as local oscillators for frequencies above 100 GHz

Very promising preliminary experimental results have been obtained from GaAs IMPATT diodes at F-band frequencies (75 mW, 3.5 percent at 111.1 GHz and 20 mW, 1.4 percent at 120.6 GHz) and from GaAs TUNNETT diodes at W-band frequencies (26 mW, 1.6 percent at 87.2 GHz and 32 mW, 2.6 percent at 93.5 GHz). These results indicate that IMPATT, MITATT and TUNNETT diodes have the highest potential of delivering significant amounts of power at Terahertz frequencies. As shown recently, the noise performance of GaAs W-band IMPATT diodes can compete with that of Gunn devices. Since TUNNETT diodes take advantage of the quieter tunnel injection, they are expected to be especially suited for low-noise local oscillators. This paper will focus on the two different design principles for IMPATT and TUNNETT diodes, the material parameters involved in the design and some aspects of the present device technology. Single-drift flat-profile GaAs D-band IMPATT diodes had oscillations up to 129 GHz with 9 mW, 0.9 percent at 128.4 GHz. Single-drift GaAs TUNNETT diodes had oscillations up to 112.5 GHz with 16 mW and output power levels up to 33 mW and efficiencies up to 3.4 percent around 102 GHz. These results are the best reported so far from GaAs IMPATT and TUNNETT diodes

Impact of edge shape on the functionalities of graphene-based single-molecule electronics devices

We present an ab-initio analysis of the impact of edge shape and graphene-molecule anchor coupling on the electronic and transport functionalities of graphene-based molecular electronics devices. We analyze how Fano-like resonances, spin filtering and negative differential resistance effects may or may not arise by modifying suitably the edge shapes and the terminating groups of simple organic molecules. We show that the spin filtering effect is a consequence of the magnetic behavior of zigzag-terminated edges, which is enhanced by furnishing these with a wedge shape. The negative differential resistance effect is originated by the presence of two degenerate electronic states localized at each of the atoms coupling the molecule to graphene which are strongly affected by a bias voltage. The effect could thus be tailored by a suitable choice of the molecule and contact atoms if edge shape could be controlled with atomic precision.Comment: 11 pages, 20 figure

On the Cost-of-Capital Rate under Incomplete Market Valuation

In this paper we discuss the concept of the cost-of-capital (CoC) rate for an insurance company as an equilibrium in the economic triangle of policyholders, shareholders, and the regulator. This provides a possible rationalization and an economic foundation for a quantity that is widely used in practice but whose value is typically neither technically nor economically well justified. We show how it can be well founded in such a triangular equilibrium. Under a simple one-period model and a valuation procedure of a two-price economy for illiquid assets we provide a corresponding economic-theoretical quantification for the CoC rate. The resulting rates are illustrated by a number of concrete numerical examples.ISSN:0022-4367ISSN:1539-697

Baryon stopping and strange baryon/antibaryon production at SPS energies

The amount of proton stopping in central Pb+Pb collisions from 20-160 AGeV as well as hyperon and antihyperon rapidity distributions are calculated within the UrQMD model in comparison to experimental data at 40, 80 and 160 AGeV taken recently from the NA49 collaboration. Furthermore, the amount of baryon stopping at 160 AGeV for Pb+Pb collisions is studied as a function of centrality in comparison to the NA49 data. We find that the strange baryon yield is reasonably described for central collisions, however, the rapidity distributions are somewhat more narrow than the data. Moreover, the experimental antihyperon rapidity distributions at 40, 80 and 160 AGeV are underestimated by up to factors of 3 - depending on the annihilation cross section employed - which might be addressed to missing multi-meson fusion channels in the UrQMD model.Comment: 18 pages, including 7 eps figures, to be published in Phys. Rev.

2.45 GHz Passive Wireless Temperature Monitoring System Featuring Parallel Sensor Interrogation and Resolution Evaluation

IEEE SENSORS 2006, EXCO, Daegu, Korea / October 22-25, 200