Patent GB-1432745-A (GB)
Title: Device for observing waveform of microwave signal
IPC: H01J31/00
Filed: 1974-03-08
Abstract: 1432745 Voltage measuring OSAKA UNIVERSITY 8 March 1974 [18 April 1973 26 May 1973] 10515/74 Heading G1U [Also in Division H1] In a device for observing the waveform of a micro-wave signal, an electron beam is deflected by a micro-wave voltage synchronized with the signal, whereby a subsequent shutter selectively passes the beam only when deflected through a specific angle to form a pulsed beam, which pulsed beam is deflected by the micro-wave signal, the phase of the pulsed beam with respect to the micro-wave deflecting signal being shifted at a low frequency, and the magnitude of the pulsed beam deflection  being displayed as a function of the phase shift. In Fig. 1, the micro-wave signal P i  to be displayed is applied, with a phase shift # introduced by phase shifter 3, to a pair of parallel electrodes 20 to deflect an electron beam which thereafter passes through a drift tube 40 and, in pulses corresponding to the zero voltage of the waveform, through a pin-hole 51, to be thereafter deflected by the  conductors 60 to which the signal P; is applied, to yield a point on the phosphor screen 90 corresponding to the waveform voltage at phase # from a zero voltage point; the sawtooth generator 4 applies a low frequency signal both to the phase shifter and to the deflection plates 70 orthogonally arranged with respect to electrodes 60, whereby the complete waveform is traced out on the screen. The phase shift may alternatively be produced by application of the sawtooth voltage to the drift tube 40. In another embodiment, Fig. 3, which avoids distortion due to difference of magnification between the centre and the periphery of the phosphor screen, the parallel conductors 60 are replaced by a slow-wave helix producing axial velocity modulation; the deflection plates 70 are replaced by two pairs of orthogonally disposed conductors fed to produce a rotational electric field; and the electron beam after passing through the drift tube 120 enters a retarding field between electrodes 130 and 131  where it is deflected transversely through an angle inversely proportional to its speed, to impact a phosphor screen 151 formed on the curved wall of the envelope, the annular electrodes 141 and 142 focusing the beam. Electrodes 20 or 60 may be replaced by a pair of parallel meandering electrodes Fig. 7 (1) (not shown), or by a helix surrounded by a coaxial or parallel earthed cylinder, the electron beam being directed axially, through the intermediate space Fig. 7 (2) (not shown). In a further embodiment Fig. 4, (not shown) the phosphor screen is replaced by a pair of spaced electrodes (171, 172) providing a central slit (170) in front of a collector electrode (160), the spaced electrodes, which the beam impacts for other than its undeflected path, being connected to earth via resistors (173, 174), the voltage across one or other of which is fed back to an additional pair of deflecting plates (181; 182) to return the beam to the undeflected path; the voltage - which corresponds to the positive or negative half, respectively, of the signal P i  is also fed to a cathode ray tube (210) for display. In an alternative arrangement of this type Fig. 6, (not shown), the additional deflecting plates are replaced by a slow-wave helix (100) producing axial velocity  modulation; and the signal derived from the impacted plate (171 or 172) is fed back to the centre member 82 of the final eccentric lens assembly 80.