JPS6210041B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oscillation/detection device using a narrowband filter, and aims to improve the rise of oscillation.

Conventionally, when configuring an oscillation circuit using a narrowband filter, positive feedback is applied to the circuit to cause oscillation, but generally there is always a delay time in the filter, so the rising waveform of the oscillation is limited by that amount. , it had the disadvantage of becoming stale. Increasing the gain of the positive feedback loop speeds up the rise, but has the disadvantage that the oscillation waveform is clipped and becomes a rectangular wave.

The present invention aims to improve the oscillation rise characteristics by increasing the gain of the positive feedback loop only at the rise of oscillation, and after making the rise early, return the loop gain to a value for normal sine wave oscillation. An example will be explained in detail using the following.

FIG. 1 shows an embodiment of the present invention, in which 1 is an input terminal from the outside when operating as a wave detection device, 2 is a narrow band filter (hereinafter abbreviated as BPF), and 3 is a signal input by BPF 2. A detector that detects the output output, 4 is an oscillation output terminal when operating as an oscillator, 5 is a detection output terminal when operating as a detector, 6 is an external terminal when operating as an oscillator. Control signal input terminals, 7 and 9 are control devices that determine the gain of the positive feedback loop of the oscillator, 8 is a switch that turns on the positive feedback loop by input from terminal 6, 10 is an inverter, 11 is an AND gate, and 12 is a This is a switch operated by the output of AND gate 11.

In this configuration, when operating as a detection device, the input of terminal 6 is held at "0" and switches 8 and 12 are turned off, so BPF 2 receives positive feedback in the loop including switch 8 or 12. It does not work as an oscillator. Here, when an external input is applied to terminal 1, the BPF
Only the input that matches the center frequency of 2 passes through the BPF 2 and is applied to the detection device 3, and an output of "1" appears at the terminal 5, resulting in a detected output. Next, when operating as an oscillator, when a signal "1" is applied as an oscillation control signal from the outside to terminal 6, switch 8 is turned on and oscillation is started by the loop gain determined by control device 7 to ensure stable oscillation. It begins.

However, if it is only this feedback loop, BPF2
The rise will be delayed due to the delay.

Therefore, in order to improve this point, the present invention
In addition to the positive feedback loop of 9 and 12, a second loop with a high loop gain is constructed.

That is, when an oscillation control signal such as a in Fig. 2 is applied from the outside, switch 8 in Fig. 1 is turned on as shown in Fig. 2 b, and 2, 7, and 8 form a positive feedback loop. , the oscillation waveform at this time rises with a delay as shown in FIG. 2c. On the other hand, since the detector 3 in FIG. 1 usually has some delay in rising, when a signal with the waveform shown in FIG. 2 c is applied, the detector 3 rises with a delay as shown in FIG. 2 d.

Therefore, the output of the AND gate 11 in FIG.
As shown in Figure 2, it remains ON for a while, and only during this period, 12 and 9 form a loop with a large loop gain, and the oscillation waveform starts to overshoot and rise as shown in Figure 2, f. . As a result, the input of the detector 3 in FIG. 1 is inputted quickly, so the output from the terminal 5 rises quickly,
The ON period of the AND gate 11 becomes shorter, and at the stable point of this repetition, the AND gate 11 turns OFF.

As explained above, according to the present invention, the gain of the positive feedback loop can be increased at the time of oscillation rise, so that the oscillation rise characteristic can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an oscillation/detection device according to an embodiment of the present invention, and FIG. 2 is a waveform diagram showing its operation. 1...Detection input terminal, 2...Narrowband filter,
3...Detection device, 4...Oscillation device output terminal, 5...
...Detection output terminal, 6...Oscillation control input terminal, 7...
...Oscillation loop gain device, 8...Switch, 9...
...Oscillation loop gain device, 10...Inverter,
11...and gate, 12...switch.

Claims (1)

[Claims] 1. A narrowband filter device, a detector that detects the output of this filter device, a first switch operated by an external oscillation control signal, and a control that determines the gain of the feedback loop formed by this switch and the narrowband filter. a second switch controlled by the output of the detector and the oscillation control signal;
An oscillation/detection device comprising a control device that determines the gain of a second feedback loop formed by the second switch and the narrowband filter.