An electronically tuneable inductance with extended frequency range
The extension of the usable frequency range of an electronically tuneable inductance circuit is investigated. By means of numerical and analytical studies, the transistor-internal reverse transfer capacitance can be identified as a frequency-limiting element, which must be minimised. This is achieved by circuitry-wise compensation of the capacitive effect by introducing an additional inductance. The concept is verified through measurements of the practical implementation and shows an extension of the frequency range by two octaves throughout the VHF range, which proves beneficial for applications such as broadband matched and tuneable transmission lines, amplifier circuits, oscillators, or filters.
Implementation of an Electronically Tuneable, Transistor-based, Passive, Symmetric RF Inductance
The concept of an electrically tuneable inductance based on a transistor circuit is introduced. Even though it incorporates an active circuit, passive, reciprocal behaviour is displayed at the output terminals. The resulting inductance value is tuneable through a variation of the biasing condition, constant for a wide frequency range, and it can be used in either series or parallel circuit configuration. Guidelines for the design of the circuit are presented and used to successfully simulate, build and measure the tuneable inductance. The inductance circuit is a promising approach to closing a long-existing gap, and thereby providing new possibilities of circuit design, e.g., in terms of miniaturisation through integrated circuits. It can prove beneficial for numerous applications, such as broadband matched and tuneable transmission lines, amplifier circuits, oscillators, or filters.
XV. Notes on the Geological Survey Memoir—“The Geology of the Glasgow District.”
Introductory. During the late summer the Geological Survey issued a map of the Glasgow district which will prove a boon not only to the members of this Society, but also to the increasing number of those who, although not members, still take an interest in geology as a branch of liberal education. The present map differs from its predecessors in that it is colour-printed, and the printing and general details are brought out more clearly than was possible in the hand-coloured maps. This fact has been taken advantage of to add an enormous amount of detail, which is often of such a minute character that after study one feels inclined to wish that he were gifted with microscopic eyes or that the map had been drawn to a larger scale. Not the least of its benefits is the low price at which it is sold (2s. on paper, and 3s. on cloth), the price of the previous maps having lately become prohibitive (19s. 3d. on paper). It will be observed that the long way of the map is from north to south. This has doubtless been adopted for good and sufficient reasons, if we only knew them; but I, at least, would have preferred that the long way should have been east and west, with Glasgow in the centre. The map is accompanied by an extensive memoir of the geology of the district, and the more one reads of it the more one is impressed with the This 250-word extract was created in the absence of an abstract