Clipped diversity combining for channels with partial-bandinterference. II. Ratio-statistic combining

For pt.I see ibid., vol.COM-3, no.12, p.1320 (1987). Ratio-statistic combining is proposed for mitigating partial-band interference in systems with diversity transmission and frequency-hop signaling. Systems with noncoherent demodulation and binary orthogonal signaling are covered. The partial-band interference is Gaussian, and Gaussian quiescent noise is included in the analysis to account for wideband noise sources. The exact probability of error is found for a receiver using ratio-statistic combining, and this is compared to the exact error probabilities for receivers with optimum combining with perfect side information, clipped-linear combining, the ratio-threshold test with majority-logic decoding, and self-normalization diversity combining. Numerical results are also given for a frequency-hop system which uses ratio-statistic combining for channels with Rayleigh fading and partial-band interference. It is determined that ratio-statistic combining is an excellent diversity combining scheme for systems with partial-band interference and fading     

Pyrolyse-gas-chromatographische und pyrolyse-massenspektrometrische Untersuchungen an polymeren Kronenethern

Zusammenfassung Pyrolyse-Gas-Chromatographie und Pyrolyse-Massenspektrometrie dienen zur Charakterisierung erstmalig hergestellter Polymeren mit Polyethern als Ankergruppen. Zu den untersuchten Polymeren gehören: mit cyclischen Polyethern und nichtcyclischen Ethern substituiertes Polystyrol, mit cyclischen Polyethern substituiertes Kieselgel und Polykondensate, hergestellt aus cyclischen Polyethern und Vernetzern. Die Pyrolyse-Gas-Chromatogramme zeigen für den jeweiligen Polymertyp charakteristische Spektren und gestatten eine eindeutige Zuordnung der Art der Matrix und Ankergruppen sowie der Verknüpfung von Ankergruppe und Matrix. Die Pyrolyse-Massenspektren liefern schnelle qualitative Aussagen über Zusammensetzung und pyrolytisches Abbauverhalten der Polymeren. Mit den vorliegenden Ergebnissen kann der Syntheseweg von Polymeren mit cyclischen Polyethern als Ankergruppen beurteilt und gegebenenfalls modifiziert werden. Auch eine einfache Identifizierung unbekannter Polymeren ist möglich.

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Pyrolysis gas-chromatographic and pyrolysis mass-spectrometric examinations of polymeric crown ethers

Summary Pyrolysis gas-chromatography and pyrolysis mass-spectrometry are useful to characterize polymers with polyethers as anchor groups, which are synthesized for the first time. The analysed polymers are: polystyrene substituted with cyclic polyethers and non-cyclic ethers, silica gel substituted with cyclic polyethers and polycondensates synthesized from cyclic polyethers and cross-linking reagents. The pyrolysis gas-chromatograms show characteristic spectra for the respective type of polymer and make possible a definite classification of the type of the matrix and anchor groups as well as of the cross-linking of anchor group and matrix. Pyrolysis mass-spectra provide rapid qualitative information on composition and thermal breakdown mechanism of the polymers.The results given allow the evaluation of the efficiency of the synthesis way used for polymers with cyclic polyethers as anchor groups and may be used to modify the syntheses. They also allow a simple identification of unknown polymers.

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Für finanzielle Unterstützung danken wir der Deutschen Forschungsgemeinschaft, Bonn-Bad Godesberg.     

Superconducting diode as high-frequency sound detector

The properties of a broadband sound detector utilising microwave-phonon-assisted tunnelling in superconductors are described. Using Al?Pb tunnel diodes at 1.3°K, the sensitivity of the detector to 9.3 × 109 c/s sound waves was found to be approximately 2 × 10?4 V/W cm?2. At high frequencies the sensitivity is expected to increase as the square of the sound frequency.     

Papierchromatographie

Ohne Zusammenfassung     

Design and fabrication of double-chirped mirrors

We present an analytic design method for the reproducible fabrication of double-chirped mirrors to achieve simultaneously a high reflectivity and dispersion compensation over an extended bandwidth compared with those of standard quarter-wave Bragg mirrors. The mirrors are fabricated by ion beam sputtering. Use of these mirrors in a Ti:sapphire laser leads to 6.5-fs pulses directly out of the laser. The method can also be applied to the design of chirped-fiber gratings and general optical filters.     

Passively Q-switched 1.34- mum Nd:YVO(4) microchip laser with semiconductor saturable-absorber mirrors

We demonstrate a passively Q -switched diode-pumped 1.34- microm Nd:YVO(4) microchip laser. We achieved single-frequency, 230-ps pulses by using an InGaAsP semiconductor saturable-absorber mirror. We can vary the pulse width and the repetition rate from 230ps to 12ns and from 30 kHz to 4 MHz, respectively, by changing the design parameters of the saturable absorber, the thickness of the crystal, and the pump power.