Patent GB-1158590-A (GB)
Title: Cross-Field Discharge Device Arrangement and Microwave Circuits Incorporating the Same
IPC: H01J25/50
Filed: 1966-08-04
Abstract: 1,158,590. Transit-time tubes. GENERAL ELECTRIC CO. 4 Aug., 1966 [30 Aug., 1965], No. 35034/66. Heading H1D. In a crossed-field device for generating or amplifying axially directed waves at a frequency for which the maintenance of radially directed waves is precluded by the radial dimensions of the device, generally of the form disclosed in Specification 1,158,589, but in which there is no conductive connection, within the device envelope, between the rods and the annular anode member, a transmission line is coupled to at least two of the annular anode members, the assembly of rods, and the cathode, to form with the transmission line constituted by the device either an open-ended transmission line, or a resonator. The crossed-field device 110, Fig. 3, having cathode 140, recessed anode block 111, rods 130 insulated from the anode block, and polepieces 120 for the production of a unidirectional magnetic field and the support of the rods, may be employed as an oscillator by mounting between short-circuited coaxial lines 180B and 185B, Fig. 14, each of which is coupled between the anode and the rod assembly, the frequency of the oscillator being determined by the resonant system formed by the two coaxial lines and the transmission line constituted by the anode block together with the rod assembly. This frequency may be adjusted by varying the effective length of the line 185B by the use of the plunger-operated movable shorting bar 189B. The output coaxial line 64 is coupled between the anode and the cathode. In an alternative oscillator arrangement (Figs. 15 to 17, not shown) the shortcircuited coaxial lines are coupled between the anode block and the cathode, a conductive connection being provided, outside the device envelope, between the anode block and the rod assembly. When the crossed-field device is employed as an amplifier (Figs. 27 and 28, not shown) the anode block and the rod assembly together act as an open-ended transmission line, input and output coaxial lines being coupled to their ends; it is stated that satisfactory amplification may be achieved with an anode length only 1/10th the wavelength of the amplified signal. In a modified form of the crossed-field device. Fig. 31, the assembly of rods is supported, by polepiece 620 and conductor 623, at the top end only, the cathode being mounted and aligned within the assembly by one of the heater leads 602 and by ceramic wedges 627 mounted on a ring 626 connecting the lower ends of the rods, a heat shield 645 being mounted at the top of the cathode. In a further modified device (Fig. 29, not shown), the cathode is in the form of a truncated cone rather than a cylinder; it is stated that increased output or amplification, respectively, may be obtained by the use of this form of cathode in the oscillator or amplifier arrangement, if the output is taken from that end of the device at which the base of the cathode cone is located. The excitation of radial modes of oscillation in the device is prevented by ensuring that the radial distance between the cathode surface and the outermost walls of the anode recesses is less than that required to support a radial standing wave of a frequency corresponding to that of an axially directed wave of a wavelength equal to twice the length of the anode block, i.e. to the minimum wavelength of the axial wave, which occurs for zero length of the short-circuited coaxial line(s) coupled to the anode; circumferentially propagating modes may, in principle, be excited, but have not been observed during operation. Details of dimensions, mode of operation, and of operating characteristics, are given.