Patent GB-645473-A (GB)
Title: Improvements in or relating to radar and other installations
Inventor: COLCHESTER CHRISTOPHER DERING
IPC: G01S1/02
Filed: 1946-07-16
Abstract: 645,473. Cathode-ray oscillographs. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. July 16, 1946, No. 21317. [Class 37] [Also in Groups XXXVIII and XL (c)] Relates to a system in which the radial time-base of a cathode-ray tube is rotated synchronously with a rotating mechanical member by means of a rotary transformer of the Magslip type comprising a rotor and a stator, one having a singlephase winding and the other a polyphase winding, and the rotor being driven synchronously with the mechanical member. According to the invention the singlephase winding is energized by an A.C. voltage and the output from each polyphase winding is combined with the A.C. voltage and rectified, the D.C. component of the resultant voltage being removed by subtracting a D.C. voltage produced by rectifying said A.C. voltage and the resultant voltages thus obtained being applied to control the amplitudes of the time-base voltages or currents applied to fixed angularly-disposed deflection members of the cathode-ray tube. The Figure shows one embodiment applied to a radar P.P.I. system with a rotating aerial and a Magslip 1 having a single-phase rotor mechanically coupled to the aerial and a deltawound three-phase stator, a 500 c/s. singlephase A.C. voltage being applied to the rotor terminals P1, P2 from the secondary 3 of a transformer T. The outputs from the stators which are developed across corresponding resistances R1-R3 comprise two side bands 500 Œ# c/s., where f is the rotation frequency and a 500 c/s. carrier component is added to each output by connecting the lower ends of resistances R1-R3 to one end of the secondary winding 5 of transformer T, the other end being connected to earth through the parallel RC circuit R5, C1. The resultant modulated carrier developed across R1 and secondary 5 is applied to a diode rectifier V1 which produces across its load circuit C4, R8 a negative voltage varying sinusoidally at the rotation frequency f and in order to balance out the D.C. component, the auxiliary diode V4 is provided which produces across its load circuit C1, R5 a positive voltage proportional to the injected 500 c/s. carrier so that the output voltage between the anode of V1 and earth comprises a pure A.C. voltage of frequency f. Similar A.C. voltages are produced between earth and the anodes of the diodes V2 and V3, the three outputs having a three-phase relationship. Each output voltage is applied through corresponding resistances R9-R11 to change condensers C5-C7 in a linear manner during intervals determined by scan timing waves WF applied to a bank of clamping diodes 10 to produce trains of sawtooth waveforms, the amplitudes of which vary sinusoidally at the rotation frequency, and these are applied through amplifiers A1-A3 to the three-phase electromagnetic or electrostatic deflector system DC1-DC3 of the cathode-ray tube to produce a radial scan which rotates synchronously with the aerial. Fig. 2 (not shown) illustrates a modification employing a Magslip with a two-phase stator in which a push-pull output is obtained from each stator by using two reversely-connected diode rectifiers for each stator and two auxiliary diodes, the outputs being applied to Miller time-base valves which are directly coupled to the X and Y plates of the cathode-ray tube, the scan timing waves being applied to the suppressor grids of the Miller valves.