| 摘要 |
1,192,706. Staircase wave generators, tuning radio receivers. C.I.T. COMPAGNIE INDUSTRIELLE DES TELECOMMUNICATIONS. 29 Aug., 1968 [4 Sept., 1967], No. 41288/68. Headings H3P and H3Q. [Also in Division G4] A circuit for generating a voltage variable stepwise to selectable values comprises means for producing a preselected number of pulses, each pulse occupying a time period ito in a pulse repetition period Nto, where i has a maximum value of N, means for averaging the pulses so as to produce a smooth D.C. output signal of value proportional to i and means for changing the integer i so as to vary stepwise the output signal. High frequency pulses from 21 step-up a counter 13 (of capacity N) until it reaches the value i set into a similar counter 11 whereupon a coincidence detector 12 produces a pulse which switches over a bi-stable circuit 16 to terminate the output at its upper terminal and via its lower terminal to close the gate 22. A similar counter 14 of capacity N operating in parallel with 13 continues to count and when it is full its output resets counter 13 and bi-stable 16 so that the gate 22 reopens and the count in 13 restarts. The pulses thus produced at the upper output of the bi-stable circuit have a width proportional to the count i set in counter 11. Averaging at 17 the output provides a D.C. output having an amplitude proportional to i. The output of counter 14 steps up a further counter 15 and when this counter is full it produces a pulse which steps on the reference counter 11 by one. Accordingly the pulse width and D.C. output increase correspondingly in steps. This continues, producing a staircase output wave at 18, until counter 11 is full whereupon a circuit 24 discharges the averaging circuit and the staircase wave returns to zero and restarts. By applying appropriate voltages to A the output wave can be held at any step and voltage at B can cause the counter to reverse so that the output steps downwards. The voltage may be applied to a varicap diode tuning an oscillator so as to cause the frequency to vary stepwise. |
