GB417564A - Improvements in devices for generating electromagnetic fields oscillating with quasi-optical frequencies - Google Patents

Abstract

<PICT:0417564/III/1> Electromagnetic fields of quasi-optical frequencies are generated in the space between two oppositely-placed electrodes which are excited at one or more of their natural frequencies by an external high-frequency source. The electrodes are the seat of electromagnetic waves, after the manner of Lecher wires, but in two dimensions instead of one. The apparatus is applied for various purposes, including the chemical, physical, and biological processes referred to in Specification 417,501. The distribution of electric stress in the dielectric may be made visible by a polarized-light projection system. Fig. 1 shows a resonator comprising parallel circular plates 1, 2 excited by high-frequency voltages applied by the conductors 3, 4. The plates may be of square or rectangular form, and may be inclined to each other. One or both may be concave or convex on its inner surface. Current and voltage waves are propagated along the plates in the same manner as along Lecher wires. With circular plates excited at their centres and with their rims free, the fundamental <PICT:0417564/III/2> <PICT:0417564/III/3> <PICT:0417564/III/4> <PICT:0417564/III/5> oscillation gives a voltage peak and a current node at the rim. If the rims are short-circuited by added capacity, as for instance by inserting the resonator in a metal cylinder 9, Fig. 24, the voltage peak and current node are at the centre. The plates also resonate at higher frequencies, with nodal diameters and nodal concentric circles. With rectangular plates, nodal lines parallel or oblique to the edges are created. The positions of the nodal lines may be predetermined by metal blocks 10, Fig. 24, fixed to the external cylinder 9, or to one of the plates 1, 2. The plates may be of good conducting metal, or of poorly-conductive metal with or without a coating of good conductivity; or the plates may be in the form of containers filled with an electrolyte. The plates may be light-permeable, consisting of glass with a very thin coating of precious metal on their inner or outer faces. One or both plates may also be in the form of wire grids stretched across rings of insulating material and electro-plated with copper or silver to provide good conductivity where the wires cross. The resonator plates are excited by separate generators of damped or undamped waves. Fig. 25 shows a valve generator 54 with Lecher-wire output circuit 45, 46 tuned by a condenser bridge 53, and with the resonator 51, 52 loosely coupled thereto by two air gaps between small spheres 47--50. The coupling condensers may take the form of a ball and ring, or of small parallel plates at adjustable distance. The couplings may be slidable along the wires 45, 46, and along the resonator plates. The Lecher wires may be in the form of a wire and concentric tube, and they may be provided with knot extremities for coupling to the edge of the resonator plates. By inserting the Lecher wires between the resonator plates, an inductive coupling may be provided. In Fig. 32, the concentric-tube Lecher system 99 is adjusted in length by a trombone slide 108 and is tuned by reflection bridges 102, 103 placed in the divided branches 100, 100. The coupling conductors 104, 105 of the resonator 106, 107 project into the interior of the conduits. When liquid to be treated is contained in a glass envelope 128, Fig. 40, placed between the plates 120, 121 of the resonator, the dielectric is composed of layers of air glass and liquid. The Specification discusses the effect of the composite dielectric on the natural frequencies and the damping of the resonator. The distribution of electric stress in the liquid may be rendered visible by the apparatus of Fig. 40. The resonator plates are coupled by rods 122, 123 to Lecher wires 124, 125 fed by a valve generator 126. Temperature may be regulated by heating-coils 129 within the casing 130. Light from a source 137 which may be a mercury vapour lamp is projected through lens 131<a>, polarizing-prism 133, mica plates 135 and lens 132<a>, and after passage through the treated liquid 128 emerges through similar devices to the screen 138, giving thereon a picture of the field distribution within the resonator. If the exciting oscillation is modulated, a complex varying pattern is produced. Glass or liquid lenses 142, 143, Fig. 41, may be arranged between the container 144 for the liquid under treatment and the resonator plates 140, 141. If convex as shown the lenses tend to equalize the field over the whole area whilst concave lenses concentrate the field in the centre. The lenses may be attached to the container 144 or the plates 140, 141. The resonator may be housed in a double-walled cylindrical casing with external knobs and dials for screw adjustment of the plate gap. Heating coils and coils for spraying cooling liquids into the casing are provided. Lecher wires of the concentric type are led through the container walls to excite the resonator, and high tension may be applied through chokes. The resonator plates may take the form of shelves 231--233, Fig. 49, separated by insulating posts 234, the material to be treated, for example foodstuffs, being placed upon the shelves. Energy may be led to the shelves by Lecher wire systems terminating in knobs adjacent to the edges of the shelves.