JPH0245827Y2 - - Google Patents

Description

[Detailed explanation of the invention] The invention is based on the transmission trigger signal of radar equipment.
This is a radar trigger playback device that processes signals for playback after recording on a VTR.

Generally, when recording a pulse signal asynchronous to the rotation of the video head on the video track of a VTR, switching noise generated when switching the video head mixes with the reproduced pulse signal and becomes a disturbance. In the case of a radar trigger signal, the pulse repetition period is usually known in advance, so conventionally, the number of trigger noise mask gate generation circuits 15 to 17 corresponding to the pulse repetition period is provided as shown in FIG. A selection switch 18 is used to select the head, and an AND gate circuit 13 takes the input trigger signal from the input terminal 1 and the output of the selection switch to obtain a trigger signal at the output terminal 14 to eliminate head switching noise. However, it still had the following drawbacks.

(1) The period of the trigger signal may change depending on the range of the radar, and the number of trigger noise mask gate generation circuits corresponding to the repetition period of each pulse is required, which increases the size of the device.

(2) Even in a radar range with a constant cycle, it is difficult to use the radar because the trigger noise mask gate generation cannot be followed for radars whose trigger signal cycle varies within a certain range.

(3) There is a method of displaying the radar trigger cycle on a recorded tape case, etc., and matching it to the cycle of the trigger noise mask gate generation circuit during playback, but this method requires considerable care and handling. That's true.

In order to eliminate these drawbacks, the present invention measures the period of the playback trigger signal using two counters, and by comparing these periods, automatically extracts the repetition period of the playback trigger signal and takes measures accordingly. The noise mask gate is generated at a period equal to 100 nm, and will be explained in detail below with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention, in which 1 is a playback trigger signal input terminal, 2 is a timing control circuit, 3, 4 and 5 are gates, 6 is an original pulse generation circuit, and 7 and 8 are counter, 9 is a comparison circuit, 10 is a latch circuit, 11 is a down counter,
12 is a gate flip-flop, 13 is an AND gate, and 14 is a trigger signal output terminal.

The operation of this circuit is divided between the AND gate 13 and the timing control circuit 2 when a reproduction trigger signal is applied to the input terminal 1. The timing control circuit 2 generates a 60Hz signal as shown in Figure 3, and the first four playback trigger signals within the 16.7mS period are extracted and the period is measured for each two. Ru. Further, as shown in FIG. 4A to D, the timing control circuit 2 includes gates 3, 4, and
and outputs timing pulses necessary to operate the counters 7 and 8. On the other hand, the original pulse generation circuit 6 generates a pulse f ₁ (1MHz; 1μS) with an accurate frequency.
is generated and output to gates 3, 4 and 5. The gate 3 opens with the first playback trigger signal and closes with the next playback trigger signal, and the counter 7 counts the number of passages of the original pulse.
Figure 4. Similarly, in the next reproduction trigger cycle, the gate 4 is opened and the counter 8 counts the number of original pulses. Go to Figure 4. In this case, if the previous and subsequent reproduction trigger cycles are the same, the counts of both counters 7 and 8 will almost match. When the difference in the counted values of the regeneration trigger cycles falls within a predetermined range, the comparator circuit 9 applies a pulse for latching to the latch circuit 10 and transfers the contents of the counter 8 to the latch circuit 10 as shown in FIG.
Move to 0. On the other hand, AND gate 13 remains open until gate flip-flop 12 is reset.

Now, the reproduction trigger signal from the input terminal 1 applied to the AND gate 13 passes through the AND gate 13 and is output to the trigger signal output terminal 14, and at the same time, the gate flip-flop 12 is reset and the AND gate is output. 13 is closed, and the contents of the latch circuit are read into the down counter 11. The down counter 11 subtracts the original oscillation pulse that passed through the gate 5, and when the content becomes zero, it outputs a borrow pulse, closes the regate 5 in FIG. 4, and sets the gate flip-flop 12. Then, the AND gate 13 is opened until the reproduction trigger signal shown in FIG. 4 passes through.

In practice, the AND gate 13 needs to be open for the reproduction trigger signal to pass through, so the repetition period of the original pulse is made shorter than _f1 .
It is given as f ₂ . Although the number of pulses subtracted by the down counter 11 is the same, it reaches zero earlier due to the shorter period, and a borrow pulse is output. In addition,
The gate 5 is controlled by the timing control circuit 2,
It is also possible to have f ₂ pass for a short period at the beginning, followed by f ₁ . Furthermore, instead of using _f2 , the down counter 11 may be preset to a certain value, thereby ensuring the time required for the reproduction trigger signal to pass. Thereafter, by repeating the above operation, the gate period is automatically set, unnecessary pulses are prevented from being output as a trigger signal, and the AND gate 13
While the is open, send one pulse as a trigger signal.
Output only one. The right side of FIG. 4 shows how noise is masked. The period of the trigger signal is
In the case of T ₁ ′≠T ₂ ′, if the difference between the count values of counter 7 and counter 8 is greater than a predetermined range, the latch pulse is not output from the comparator circuit 9, and as a result, the contents of the latch circuit 10 are updated. Not done. Therefore, the latch circuit 10 only holds values with the correct period, and the down counter 11 always outputs borrow pulses with the correct period, so that the present invention performs a stable noise mask operation. In addition, when the period of the trigger signal changes slightly within a certain range, if the difference between the count values of counter 7 and counter 8 is within a predetermined range, a latch pulse is output from comparison circuit 9 and sent to down counter 11. The data also follows the period, and the gate period can change in accordance with the period of the reproduction trigger signal.

As explained above, the present invention can automatically open and close the gate in accordance with the cycle of the input pulse of the playback trigger signal, so the transmission trigger signal that is asynchronous to the rotation of the video head is recorded and played back on the video track of the VTR. This is a suitable device for Also,
It goes without saying that the present invention can be applied to sonar, medical recording equipment, etc. in addition to radar. Moreover, the switching noise generated when switching the video head does not mix into the reproduced trigger signal and cause a disturbance, which is highly effective in practical use.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional radar trigger reproducing device, Fig. 2 is a block diagram of an embodiment of the present invention,
3 and 4 are timing diagrams for explaining the operation of the device of the present invention. 1...Reproduction trigger signal input terminal, 2...Timing control circuit, 3-5...Gate, 6...Original pulse generation circuit, 7, 8...Counter, 9...Comparison circuit, 10...Latch circuit , 11...down counter, 12...gate flip-flop, 13...
...And gate, 14...Trigger signal output terminal.

Claims (1)

[Scope of utility model registration request] an AND gate that controls the opening and closing of a trigger signal output that reproduces the transmission trigger signal of the radar device recorded in the recording device; and a first gate that measures the time interval from the previous reproduction trigger signal output to the next reproduction trigger signal output. and a second counter for measuring the time interval from the next reproduction trigger signal output of the next reproduction trigger signal output to the next reproduction trigger signal output.
a comparator circuit that outputs a match signal when the difference between the count values of both counters is within a predetermined range, a latch circuit that receives the match signal and holds the count value of the first counter; a down counter that counts the held count value using an original oscillation pulse having a slightly shorter period than the original oscillation pulse that drives the first and second counters; and a gate flip-flop that outputs a signal that opens the AND gate until the reproduction trigger signal output passes, and automatically extracts the cycle of the reproduction trigger signal output and sends out only the reproduction trigger signal output. A radar trigger playback device characterized by: