Patent GB-857612-A (GB)
Title: Improvements in or relating to signal wave responsive and measuring circuit arrangements
Inventor: KOLLANYI MIKLOS
IPC: G01R27/06
Filed: 1958-02-04
Abstract: 857,612. Voltage measurements; measuring short time intervals. MARCONI INSTRUMENTS Ltd. Nov. 4, 1958 [Feb. 4, 1958], No. 3605/58. Class 37 An arrangement responsive to the ratio of the maximum and minimum values of a voltage comprising two, initially equally charged, condensers, a circuit including a rectifier between the voltage source and to each condenser, the rectifier being oppositely directed and means giving an indication of the ratio of the final voltages stored on the condensers when the voltage of the source has been varied from minimum to maximum or vice versa. A voltage standing wave ratio measuring apparatus comprises a probe 2 which is moved along the transmission line 1, the signals picked up by the probe being fed through a detector 3, amplifier 4, and demodulator 5 through oppositely poled crystal rectifiers 6, 7 to initially equally charged condensers 8, 9 so that, if switch 1S1 is open (as shown), the charges stored on the condensers 8, 9 will correspond to the maximum and minimum signals respectively picked up by the probe as it moves along the line. The voltages across the condensers 8, 9 are applied to the grids of valves 101, 102 respectively, the difference of the output signals from said valves being converted into A.C. by a chopper switch having an armature 13 actuated by a mains relay coil 131 which also drives a second chopper switch 132. The A.C. difference signal is amplified at 15, the output being then taken through a further valve 16, the armatures of choppers 13, 132 at the same instant being as shown if amplifier 15 has an even number of stages and armature 132 will be in its other position if amplifier 15 has an odd number of stages. If the voltages stored in the condensers are unequal (corresponding to maximum and minimum signals), the difference A.C. voltage will energize relay 19 thus connecting the grid of valve 101 to earth and therefore causing condenser 8 to discharge to earth through resistance 20 until the voltages on condensers 8 and 9 are equal when there will be no A.C. difference signal and relay 19 will no longer be energized so that armature 191 will move to the position shown, so shortcircuiting a relay 21 which, until the short circuit holds switch 121 closed. The opening of switch 121 terminates the operation of a time measuring circuit comprising a double triode 22, having earthed cathodes and similar condensers 25, 26 in their grid circuits. While switch 121 is closed condenser 25 (condensers 25, 26 are equally charged, before the measurement is made, by closing switches IS2, 1S3) discharges through resistance 121 so that the initially equal voltages on the cathode of valve 22 will become more unequal, the inequality being dependent on the time switch 121 is closed and therefore on the ratio of the original voltages across condensers 8, 9. The voltage inequality is measured by a double triode 28 and a meter 29 which may be calibrated to read to V.S.W.R. directly. Switches S1, S2 are ganged and are moved to their other positions after the measurement has been made and condensers 8, 9 are charged to prevent backward currents through the rectifiers altering the charges and to connect the meter 29 to the measuring circuit. In modifications (Figs. 2 and 3 not shown) the ratio of voltages on condensers 8 and 9 are read directly by a ratiometer, either of the electrostatic or electromagnetic type). In a further embodiment (Fig. 4, not shown) the condenser 8 is discharged in small steps through a further chopper switch and measurement is made by a counter. A modification of the apparatus for measuring modulation depth or noise in an amplifier or receiver where continuous indication of the ratio of the maximum and minimum of an incoming signal is provided by replacing switch 1S1 by a resistance (Fig. 5, not shown).