| 摘要 |
586,098. Pulse modulation. STANDARD TELEPHONES & CABLES, Ltd. Dec. 1, 1944, No. 24103. Convention date, Dec. 6, 1943. [Class 40 (v)] In a full-wave rectifier circuit adapted to produce time-modulated pulses, an A.C. voltage wave is fed to the grid of a valve, out-of-phase versions thereof being derived from the anode and cathode circuits and applied through individual cathode follower stages to two rectifiers whose outputs are combined. This produces a wave with spaced peaks, the timing of which is modulated by the amplitude modulation, in push-pull, of the rectifier inputs. In one embodiment, Fig. 1, the output of a sine-wave oscillator 14a is fed to triode 14b which produces the rectangular waveform 20 by saturating on positive half-cycles and cut-off on the negative. The rectangular waveform becomes triangular, 12, in the integrating network R3, R4, C1, the output from which is fed to the grid of valve 32. Out-of-phase waves from the anode and cathode circuits of this valve are fed through cathode-follower stages 41, 42 and the secondaries 72, 73 of a modulation transformer 70 to diode rectifiers 37, 38 having a common load resistance. Referring to Fig. 2, the rectification " axis " for the wave 12 is set at a predetermined place such as 48 by the grid bias potentiometer 46, Fig. 1, and modulation applied from the primary of transformer 70 shifts this axis between the limits 76a, 77a for example. The rectified output, in the absence of modulation, is shown as curve 50 and this is modulated between the limiting forms 76, 77. The clipper and shaper circuits 60, Fig. 1, clip the rectifier output at level 62 to select the peaks 51, 52 ; 53, 54 ; 55, 56 and convert them into pairs of narrow pulses 51a, 52a, &c. modulated between the limits 78, 79 towards and away from each other. It is stated that the wave applied to valve 33 may be sinusoidal if the modulating swing is limited to the approximately linear portion of the wave near the axis. In a modification, Fig. 3 (not shown), the transformer 70 is connected in the grid circuits of valves 41, 42. Alternatively, the modulation may be applied to separate grids of mixer valves substituted for valves 41, 42. |
