Experimental determination of propagation parameters of a microstrip line with tuning septums

The letter refers to the experimental determination of the propagation characteristics of a microstrip line with tuning septums. The purpose of this study is to measure with accuracy the (?, ?) diagram for the two fundamental modes of this line using a crossratio technique.     

Path integration in dogs

1. Desensitization of ET(A) endothelin receptor (ET(A)R) was compared between the rat and guinea-pig with regard to negative chronotropic response (NC) in the right atria (RA). 2. ET-1 (100 nM) produced distinct NC in the presence of BQ788 (300 nM), and positive chronotropic response (PC) in the presence of BQ123 (1 microM) in both species, showing that ETAR and ET(B) endothelin receptor (ET(B)R) mediate NC and PC, respectively. 3. Repetitive applications of ET-1 (50 nM) desensitized PC, and the second application only induced a strong NC in both species. Later applications of ET-1 produced virtually no response in the rat RA, whereas they produced BQ123-sensitive NCs repetitively in guinea-pig RA, exhibiting marked species difference in desensitization of ETAR-mediated NC. 4. Pretreatment with staurosporine (100 nM) prevented desensitization of ET(A)R in the rat RA altogether. However, phorbol 12-myristate 13-acetate (PMA, 300 nM) failed to induce, but rather hampered, desensitization of ET(A)R. 5. Partial amino acid sequencing of ET(A)Rs, spanning from the 2nd through the 4th intracellular loops, revealed that all the potential Ser/Thr phosphorylation sites, including a protein kinase C (PKC) site, are conserved among guinea-pigs, rats, rabbits, bovines and humans. 6. In guinea pig RA, pretreatment with okadaic acid (1 microg ml(-1)) and PMA did not facilitate desensitization of ET(A)R whereas these agents successfully desensitized ETAR during combined stimulation of beta-adrenoceptor and ET(A)R by isoproterenol (300 nM) and ET-1 (100 nM). 7. These results suggest that species differences in desensitization of ET(A)R are not caused by differences in the site(s) of, but caused by differences in the environment for phosphorylation of the receptor. Desensitization of ET(A)R appears to require phosphorylation of the receptor by PKC as well as a kinase stimulated by beta-adrenoceptor activation.     

Time-domain response of MIS coplanar waveguides for MMICs

An MIS coplanar waveguide propagating a slow-wave mode has been characterised in the time domain. The theoretical analysis proposed to obtain the time-domain response of the line gives results in good agreement with measurements. The circuit analysis used is suitable for the determination of spurious propagation effects, inherent to the use of miniature waveguides encountered in MMICs, such as Schottky contact coplanar lines and coupled microstrip lines laid on MIS substrates.     

Présentation de quelques modèles stochastiques de canal MIMO et comparaison expérimentale

Performances ofMimo systems are dependant on the propagation channel properties. These properties must be correctly introduced in theMimo channel propagation models. Several model families exist. We will particularly investigate those relying on the use of second order statistic parameters. No comparison of these models was found in a same propagation environment. As a result, this paper deals with a comparison of six different stochastic models in “indoor” and “outdoor” environments. The principle and the mathematical representation ofMimo systems are introduced. Then, we present the different models considered. The statistical parameters used in the models are computed using an experimental characterization of the two environments. The six models are then compared to measurements using the channel coefficient envelope distribution and the channel capacity. The ability of the models to express the correlation level in the channel is analysed and discussed.     

Performance of a radiation hard 128 channel analogue front-end chip for the readout of a silicon-based hybrid photon detector

The performance is described of a front-end chip, the SCT128A-LC chip, originally developed for the readout of a silicon based Hybrid Photon Detector (HPD), which is part of an RICH detector to be run in an LHC experimental environment. The relatively low signal charge from single photoelectrons, impinging on the silicon pad sensor, put very stringent requirements on the noise performance of the front-end chip. An absolute noise calibration using X-ray sources and a ²⁴¹Am γ source was performed. It is demonstrated that sufficiently good signal over noise ratio can be obtained to use this chip for the read-out of an HPD in LHC experiments.     

Systematic determination of the propagation characteristics ofcoplanar lines on semiconductor substrate

A method allowing the systematic determination of the propagation characteristics of micron-size waveguides and overcoming the influence of feeding access discontinuities is presented. The complex propagation constant and characteristic impedance of a slow-wave Schottky contact coplanar line are determined in the 1 to 26 GHz frequency range under different DC bias conditions. This method is successfully used to characterize the Schottky contact coplanar line of micron size under drastic conditions, that is, high value of slow-wave factor, significant attenuation, dispersive transmission line, and strong mismatches between feeding line and device under test. Comparisons with transmission line model theoretical results show very good agreement, despite the large slow-wave factor, attenuation, and dispersion of the waveguide. The electric schemes of the feeding access discontinuities are also presented     

The Time-Projection Ring Imaging Cherenkov (RICH) Counter ? New Experimental Results

A TPC-type RICH-counter with a 200 × 200 mm2 quartz window and a 1.27 mm wire pitch MWPC has been tested in a 10 GeV/c ?- beam. The MWPC is equipped with optical screens (called "cloisons") between the anode wires, with the purpose of absorbing the secondary UV-photons emitted from the charge avalanches around the wires. The test results show that the cloisons effectively suppress the noise caused by the photon reemission, without affecting the detection efficiency for single photoelectrons in the MWPC.     

The effects of a dielectric capacitor layer and metallization onthe propagation parameters of coplanar waveguide for MMIC

The study of coupling phenomena between lines laid on semiconductor substrates in monolithic microwave integrated circuit (MMIC) technologies and the determination of propagation effects on power FETs require the characterization of lines with micron transversal widths. For such lines, the influence of metallization thickness and dielectric cap layer on propagation properties can not be neglected. These effects are characterized for the case of coplanar lines laid on semiconductor substrates. The mathematical development used and the results obtained by a numerical technique are presented     

Desktop computer appraisal of potential slow-wave propagation characteristics for Schottky coplanar lines

An original analytical model of the Schottky coplanar line is presented. Determination of the potential slowing factor is made with good accuracy. In its present form the model does not give the slow-wave mode frequency limitation. However, it can be useful to initialise computer analyses using FEM or SDA techniques, and to explain the effect of varying DC bias and geometrical parameters on propagation characteristics.     

Accurate and efficient numerical method for the analysis ofmultimode waveguide discontinuities

This paper presents an original approach to analyze multimode waveguide discontinuities. The generalized scattering parameters are determined by a matrix pencil moment method associated with efficient numerically multimode matched loads placed at each physical port of the discontinuities. The analysis of both microstrip-coupled lines and coplanar lines asymmetric discontinuities is presented and successfully compared to experiments and available published results