Full CMOS continuous time filters for GSM applications

This paper describes full cmoscontinuous time filter design techniques which can meet the specifications commonly set for gsmapplications. First several cmosfilter design techniques are overviewed. The ota-ctechnique is discussed to some more detail. To overcome the main drawback of the lower total harmonic distortion in ota-ctechniques very linear operational transconductance amplifiers (ota)are required. Such an ota,together with the applied linearisation techniques is discussed. To fulfil high accuracy in cut- off frequencies of the filter an active tuning system is necessary. A new on- chip tuning system is presented. The paper concludes with a practical design example for the gsmsystem. Therein the different ota-ctechniques discussed are illustrated.     

Algorithmen zur Pulsweitenmodulation für Wechselrichter mit in Echtzeit berechnetem Pulsmuster

Übersicht Mit Hinblick auf die zunehmend Verbreitung findende Pulsmusterberechnung in Echtzeit werden in dem Aufsatz Gesichtspunkte diskutiert, die sich aus den Eigenschaften des leistungselektronischen Stellgliedes, des Pulswechselrichters, ergeben. Die bei Abtastregelungen für die Dauer einer Abtastperiode konstante Stellgröße muß bei ihm durch Pulsweitenmodulation in ein Pulsmuster mit konstanter Amplitude und Pulsen variabler Breite umgesetzt werden. Durch ein neues Verfahren mit versetzter Abtastung haben dabei Rechentotzeiten bis zur Dauer einer halben Abtastperiode keinen Einfluß mehr auf das Pulsmuster.

---

Algorithms for pulswidth modulation of inverters with online calculated pulse patterns

Contents Online calculation of pulse patterns will be employed more intensively in the future. Aspects concerning the powereleotronic circuit, the pulsewidth-modulated inverter, are to be discussed. The set value being constant for the duration of a sampling interval, has to be converted by a modulation algorithm into a pulse pattern with constant amplitude and pulses of variable width. Calculation dead-times up to half of sampling interval have no influence on the pulse pattern when using a new algorthm with shifted sampling instants.

---

---

Herrn Prof. Dr.-Ing. Klemens Heumann zum 60. Geburtstag gewidmet     

Rate of adsorption to and desorption from a langmuir surface: The case of zero activation barrier to adsorption without dissociation

Many rate constants of elementary steps on single crystals have been measured. Their pre-exponential factors can now be compared to those calculated by transition state theory. Such a calculation is presented in this Letter with due attention to microscopic reversibility, standard states, and configurational entropy.     

Les télécommunications par câbles sous-marins: l’avènement des fibres optiques

This paper explains why the new generation of the submarine transmission systems by optical fibres has come into existence, ensuing from the telegraphic cables and coaxial cable systems. The author expounds how the main characteristics of this new system have been selected and describes its different elements such as its optical fibre, repeaters, branching units and the equipment of the terminal stations. The French program of study and development of the system is indicated and some thoughts are given to what the future in this particular field could be.     

Analyse théorique d’un canal de propagation en présence de trajets multiples

Frequency representation of multipath fading on line-of-sight microwave paths is revisited together with a general point of view and with the aim of giving sound foundations of medium bandwidth modelling. Moreover some typical laws of variation of the selectivity according to the frequency and the hop length are derived.     

Statistiques de la fonction de transfert par trajets multiples pour des largeurs de bande moyennes. Application à la prévision de la qualité

It is shown, from data gathered on three different test links, that multipath transfer functions on a medium bandwidth can be modelled with three parameters. Moreover, the model parameters follow similar probability laws on the three links, thus leading to a universalstatistical model. This statistical model depends on two independent parameters. When the two statistical parameters are known, the outage time of the link can be deduced from the model. A first estimation of these parameters can be inferred from the distribution law of the levels at fixed frequency. The application of the method to two particular cases is presented.     

La réception hétérodyne en microondes et en optique: analogies et différences

The introduction of the heterodyne reception in radio technique many years ago, allows a better sensitivity of the receiver and then an increase of the range of the transmission system, when compared to the direct detection. The same improvement can be expected for optical systems and this is the reason why this technique is now being investigated in several laboratories and could be applied to transmission over single mode fibres. This paper tries to exhibit the analogies which can exist between the microwaves and optical techniques and are sometimes not very evident because the words are different, although describing identical or at least comparable concepts. Some key functions of a system are compared (amplification mixing, oscillation).     

Rayonnement en ondes métriques et décimétriques des orages

This article presents the result of the current knowledge on the very high frequency electromagnetic radiation of lightning. A phenomenology analysis of the new results obtained from the study of triggered lightning in New Mexico (TRIP 82) and at Saint-Privat-d’ Allier in Haute-Loire, France (1983) is first described. The authors then present the spectral and temporal characteristics of the VHF/UHF radiation which can be applied to the electromagnetic compatibility of systems. From a synthesis of the experimental and theoretical contributions, they propose a reflection on the lightning initiation process and on the mechanisms generating lightning radiation.