Part A: Digital F. M. Demodulation Using Frequency Counting Techniques ; Part B: Resistivity- Temperature Behaviour of SnO(2):B:Sb Resistor Species

Abstract

Part A abstract: The demodulation of analogue F.M. signals using frequency counting techniques is examined and implemented through the use of modern high speed T.T.L. integrated circuit technology. The entire demodulation unit was derived from exclusively digital components particularly compatible to frequency counting methods. The device was tested with carrier frequencies up to 2MHz and signal frequencies over the entire audio range with varying degrees of modulation. The main limitations appear to lay not in the hardware but in the actual counting technique itself which required quite large frequency deviations to resolve the higher audio frequency signals employed.

Part B abstract: Investigation of SnO(2):B:Sb semiconductor species over the temperature range -60°C to +175°C reveals that electrical resistivity in this region is determined by the complex superposition of stable thin film scattering phenomena. Transient effects due to lattice imperfections inherent in the fabrication process start to "anneal” out at temperatures greater than 50°c and can be characterized by an activation energy of the order of .013 eV. Uncompensated samples doped heavily with boron illustrate a trend toward ionized impurity scattering at lower temperatures but mainly the species exhibits a complicated interplay of acoustical and optical phonon scattering modulated by doping level in such a manner as to lower T.C.R. An empirical expression relating resistivity-temperature behaviour to doping is developed.