GB1429401A - Device for observing waveform repeated at high frequency - Google Patents

Abstract

1429401 Cathode-ray tubes; velocity-modulated tubes UNIVERSITY OSAKA 8 March 1974 [25 June 1973] 10516/74 Heading H1D [Also in Divisions G1 and H4] The invention provides a system for displaying a repetitive short duration pulse (e.g. one picosecond); the pulse may be optical or microwave. In Fig. 1 the pulse is optical, and strikes a photocathode 1 in an evacuated housing E so that an electron beam is emitted having a density waveform corresponding to the optical pulse waveform. The beam passes via anode 2, lens electrodes 3, 4, 5, drift tube 6, cavity resonator 7 having pin-holes 9, 10, screen 13 have a slit or pin-hole 14 to a collector 15. A microwave signal is applied along waveguide 8 to deflect the beam; only at one particular value of the microwave signal will the beam deflection be such that it falls on the collector electrode 15. Fig. 2 shows how this system displays the electron density waveform B corresponding to the incoming optical pulses; the microwave waveform P 1 is synchronized with the incoming pulses, but has a higher frequency as shown, and only when the microwave voltage is V 1 will the beam strike the collector. The microwave voltage is supplied by an oscillator 16, Fig. 1, and phase shifter 17, and by altering the phase shifter the time t 2 in Fig. 2 at which the microwave voltage becomes V 1 is altered so as to scan across the optical pulse B. The phase shift is connected to the X axis of an oscilloscope 23, and the electron beam density is connected to the Y axis to reproduce the optical waveform. Instead of varying the phase shift in Fig. 1, switch 19 can be positioned so that a signal from sawtooth generator 18 is connected to drift tube 6 via transformer 20; this modulates the beam velocity which in effect displaces the waveform B relative to the microwave waveform to produce the time scan. To measure incoming microwave signals the photocathode is replaced by a suitable microwave/electron beam converter.