GB982894A - Circuit arrangement for generating triggered oscillations - Google Patents

Abstract

982,894. Pulsing carrier frequencies; valve oscillator and pulse circuits; cathode ray oscilloscopes. ZENTRALINSTITUT FUR KERNPHYSIK. May 30, 1961, No. 19521/61. Headings H3F, H3P, H3R and H4T. A U.H.F. oscillator generates oscillations of phase demined by the leading edge of pulse and reaching a maximum limited amplitude during the first half cycle of oscillation and is used for generating calibrating marker pulses on a C.R.T. time base. Sharp positive pulses are applied to the grid of a pulse steepening valve 4 with small output capacitance Ca so that the Ia leading edge slope - is steep- Ca ened, and the negative going anode voltage applied to the cathode of an oscillator valve 6 whose tuned circuit is so highly damped by normally conductive forwardly biased diodes 10 that oscillations are not generated until the diode<SP>s</SP> 10 are blocked by the resulting negative excursion of the oscillator anode voltage. The #-network tuned L circuit 26, 27 being of high Q and - ratio, C oscillations build up immediately (within half a cycle) to a maximum amplitude limited by the diodes 10 (although feedback is small, for high stability). The oscillations are then fed to a Class C amplifier 13 so that " flat-topped " cycles are applied as marker pulses to the C.R.T. The output capacitance of valve 13 and input capacitance of the C.R.T. provide with the series inductor 22 a # circuit for the highest selected oscillator frequency (e.g. 1000 mc/s.) and, with the shunt inductor 23, a parallel resonant circuit, for the next lower frequency range. The tuned circuit 26, 27 is connected to the oscillator grid and anode by switch contacts 24, 25 so that a frequency range change may be made, and feedback is made independent of frequency by a large value of capacitor 9. The pulse sharpening valve 4 may be in parallel with a further valve fed with a differentiated trigger pulse, whose output is added to that of valve 4 to further steepen the output pulse leading edge.