GB666624A - Pulse generating circuits - Google Patents

Abstract

666,624. Wave-form changing circuits. BRITISH THOMSON-HOUSTON CO., Ltd., and MELVILLE, W. S. Dec. 2, 1949, No. 31042/49. Class 38 (ii). A pulse generating electric circuit, as for radar pulse modulators, nuclear particle accelerators, impulse-testing generators and pulse and initiating circuits, wherein the load R is series connected with a saturable cored reactor P whose saturated and unsaturated impedances are respectively low and high compared with the load impedance, and the load R and reactor P form a discharge circuit for a capacitative element C2 series connected with a gridcontrolled valve V and an inductance L across a capacitor C1. The latter, when charged from an A.C. supply D, such as is described in Specification 666,575, in turn charges, when the valve is made to conduct, through the current limiting inductance L, the capacitative element C2, no current flowing in the load circuit due to the high unsaturated reactor impedance, but when the voltage has risen such as to fully charge the element C2 the reactor P saturates, its impedance drops, and a pulse flows through the load. The element C2 may be a pulseforming network of the artificial transmission line type. The reactor P, which has a polarizing winding W carrying the charging current of capacitor C1, or alternatively is connected to a separate D.C. supply or a decoupling circuit, has a core, such as of 50-50 coldrolled nickel-iron, giving a high ratio, of up to 1000, of unsaturated to saturated impedance. The grids of the rectifying valve V, preferably a " thyratron, " are controlled by valves or peaking transformers (not shown). In a modification, a step-up transformer is interposed between the valve V and element C2 should the voltage of the required pulse be in excess of that suitable for the valve, the transformer having sufficient inductance to replace the inductance L. In another modification, providing for rate of rise of load currents greater than that suitable for the valve V, capacitative elements and reactors are connected in the discharge circuit as described in Specification 666,574, the impedances of each reactor varying in a particular manner described in the Specification. In a further modification, two valves in opposition are parallel connected for fullwave operation, another load comprises two ignitron valves connected through rectifiers to oppositely wound transformer secondary windings.