SU789847A1 - Frequency discrimination digital apparatus - Google Patents

Description

The invention relates to information-measuring technology and is intended for automatic comparison of the frequencies of highly stable oscillators with the output of the comparison result in a digital code suitable for input into a digital computer. A device comprising a serially connected reference frequency generator, a pulse reference frequency generator, a switch and a counter, a pulse generator measuring the frequency, a second switch and a second counter, a control trigger and a coincidence circuit, the inputs of which are connected to the outputs of the driver, and the output of the coincidence circuit through the control trigger is connected to the control inputs of both keys Ij. A disadvantage of the known devices is the dependence of the measurement accuracy on the duration spine T coincident pulses. For example, when the measured frequency f is close to the reference f, the output of the coincidence circuit is a packet of coincidence pulses that interferes with the normal operation of the device and increases the measurement error. For elimination of matching packets duration. pulses must be reduced to the value of T: LT, which is not always easy to implement. The purpose of the invention is to improve the measurement accuracy. The goal is achieved by the fact that in a device comprising a generator connected in series, the first driver, a key and a counter, a second driver in series, a switch and a counter, a trigger, the output of which is connected to the second inputs of the keys and a matching element, inputs connected to the driver outputs, additionally introduced two trigger, the first delay line and connected in series the second delay line, the third and fourth keys, and the output of the second delay line through the first delay line and n rvy additional trigger is connected to the second input of the third switch, the inverse output of the first flip-flop through an additional optional second trigger coupled to a second input of the fourth switch, whose output is connected to the input of the flip-flop and to a second input of the second

the additional trigger, the output of the coincidence element is connected to the second input of the first additional trigger, and the output of the first driver is connected to the input of the second delay line,

FIG. 1 shows a block diagram of the device; in fig. 2 time diagrams for his work.

The device for comparison of frequencies contains a coincidence element 1, impulse-potential keys 2 and 3, shapers 4 and 5, a reference frequency generator 6, triggers 7-9, impulse-potential keys 10 and 11, delay lines 12 and 13, and counters 14 and 15 .

FIG. 2 is indicated: a - pulses of the reference number of stotos; b - measured frequency pulses; impulses at the inputs; c - match element; d - delay lines 13; d - line 12 delay; and - key 11; to - key 10; W - input pulses; Setting zero for trigger 8; stress diagrams; e - output 1 trigger 7; 3 - Output About Trigger 8.

The device works as follows.

The coincidence element 1 and the potential pulse switches 2 and 3 are supplied with two pulse sequences, one from the former 4, which converts the input voltage frequency f into a sequence of pulses with a repetition period Tu Z, the other from the generator 6 of the reference frequency fg close to to f and a driver 5, which converts the voltage of this frequency into a sequence of pulses with a period. Let the device turn on at the moment t. In this case, the operation of the device proceeds as follows. The impulse from the output of the coincidence element 1 transfers the trigger 7, which results in closing the normally open impulse-potential key 10. Therefore, the reference impulse, frequency f of duration T, delayed by delay line 13 by time t T + tcp. where is the reset time of the trigger 7, will not pass through the key 10.

The positive impulse that forms when the flip-flop 7 is thrown overturns the flip-flop 8. As a result, the normally closed impulse-potential key 11 is opened.

The impulse of the reference frequency fg passes through the delay line 12 (which it delays by time C; but a pulse width) returns the trigger 7 to its original position and the key 10 opens again. In subsequent matches of the pulse sequences, only a flip-flop trigger occurs.

7, locking and unlocking the key 8.

But as soon as the coincidence stops and the flip-flop of the trigger 7 does not occur, the pulse of the reference frequency passes through the delay line 13, the keys 10 and 11, overturns the control trigger 9. The keys 2 and 3 open and the frequency pulses go to counters 14 and 15, respectively fy and fg. The impulse from the output of the key 11 also throws the trigger

8, which leads to closing the key 11. The first pulse of the second packet of matches, knocking over the trigger 7, leads to unlocking the key 11, and after the end of the packet the pulse of the reference frequency passes the delay line 13, keys 10 and 11, flips the control trigger 9 and keys 2 and 3 are closed.

Q When the device is switched on at the moment tjj, the reference frequency pulses passed the delay line 13 and the open key 10 will not pass through the normally closed key 11, which will open only when the first pulse of the coincidence packet arrives on the trigger 8.

Let the number of pulses counted in counter 15 be equal to m, and the number of pulses be measured

0 frequency, recorded in the counter (16-p).

Then the value of fy can be found as f P. f. SL m

The accuracy of this result does not depend on the duration of the pulses T. It contains only errors determined by the instability of the reference frequency generator and the quality of the matching element.

Claims (1)

1. USSR author's certificate No. 360167, cl. B 23 B 51/02, 197P. Phie.