Patent GB-953331-A (GB)
Abstract: 953,331. Hall effect devices; electromagnetic waveguides. PHILIPS ELECTRICAL INDUSTRIES Ltd. April 6, 1960 [April 9, 1959], No. 12219/60. Headings H1K and H1W. A Hall effect device comprises a thin semiconductor body of high carrier mobility provided with a pair of input or output electrodes. At least one of the pair of electrodes is electrically anisotropic and attached to an anisotropic lead. Alternatively it is constituted by a plurality of separated electrode parts connected to separate lead parts to simulate an anisotropic electrode and lead assembly. Another pair of similarly constituted electrodes may be provided to form the input (or output) electrodes or a coil inductively coupled to the body may perform this function. In an arrangement of the former type both the Hall and current electrodes are bismuth telluride, the layered structure of which renders it anisotropically conductive, or tapes made up of mutually insulated bundles of wires. Alternatively a plurality of pairs of small area Hall and current electrodes and associated leads are used. In an amplifier, Figs. 4 and 5, using the former arrangement the current electrode tapes 2, 3 are joined to form the secondary windings of an input transformer and the Hall electrode tapes 4, 5 joined to form the primaries of an output transformer. When a plurality of pairs of electrodes are used the ourrent electrodes are connected to individual secondary windings of an input transformer and the Hall electrodes to primaries of an output transformer. In another arrangement, Fig. 9, adjacent electrodes are connected via inductors the centre taps of which are also connected via inductors. In an alternative arrangement where the current electrodes or both pairs of electrodes are in multiple they are connected to common leads via high resistances. A device suitable for the transmission of very high frequencies, Fig. 11, comprises a rectangular Hall plate 1 with electrodes in the form of tapes with comb-shaped ends. These ends are “ of the operating wavelength long so as to present an infinite impedance as viewed from the plate. If a Hall plate in the form of a parallelogram of obtuse angle 90 + α, where tan α=mobility X magnetic induction, is used in such a device it will completely block signals in one direction. An arrangement adapted for coupling a coaxial line to a parallel line comprises an annular disc of semi-conductor with segmented electrodes on its inner and outer peripheries connected to teeth of length #/4 cut in the ends of the inner and outer hollow conductors 2,3 (Fig. 14), respectively, of a coaxial line. The circulating currents generated in the disc are coupled to parallel lines by a loop in the plane of the annulus. In a simplified arrangement the annulus is replaced by a disc to the centre of which the inner conductor is directly connected. Another assembly suitable for this purpose, Fig. 16, comprises a hollow semi-conductor cylinder 1<SP>111</SP> with teeth cut in the conductors of a coaxial line connected to its opposite edges as shown, the cylinder being coupled to lines 4, 5 by loop 45. In a more easily manufactured equivalent of Fig. 16 individual Hall plates interconnected by anisotropically conductive tapes are disposed between the two sets of teeth. The coupling loop may be dispensed with in these arrangements by forming an axial slit in the cylinder of Fig. 16, or a radial slit in the annulus of Fig. 14 or disc and connecting the edges of the slit to the toothed ends of a pair of parallel tapes. Alternatively by using a spiral or helical slit of pitch angle α (tan α=mobility Î magnetic induction) an arrangement is produced which is blocking in one direction and therefore suitable for connecting an antenna to a transmitter or amplifier in a reaction free manner. If the coupling loop or its equivalent is omitted the device is useful as a line termination, the impedance of which is variable by the magnetic field. The efficiency of the above-described devices which is already greater than that of Hall plates with large area electrodes may be further increased by operating at low temperatures. The use of indium arsenide, indium antimonide, bismuth telluride and mercury selenide in Hall plates is suggested.