JPS625487B2 - - Google Patents

Description

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

Conventional narrowband filter (hereinafter abbreviated as BPF)
When configuring an oscillator circuit using a 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 will be distorted by that amount. There was a drawback that it was difficult to use. Furthermore, if the gain of the positive feedback loop is increased too much, the oscillation waveform becomes a rectangular wave or overshoots, causing oscillation.

The present invention aims to improve the rise characteristics of oscillation by controlling the gain of the positive feedback loop by the output level of the detection device and always controlling the loop gain to the optimum value.

FIG. 1 shows an embodiment of the present invention, in which 1 is an input terminal from the outside when operating as a detection device, 2 is a narrow band filter (hereinafter referred to as BPF).
) 3 is a detector that detects the output output from the BPF 2, 4 is an oscillation output terminal when operating as an oscillator, 5 is a digital output terminal when operating as a detector, 6 is an external control signal input terminal when operating as an oscillator, 7 is an ON/OFF switch controlled by the signal from input terminal 6, 8 is an analog detection output terminal of the detector 3, and 9 is, for example, A variable resistance element made of semiconductor or the like, 10 is an inverting amplifier, 11
is an amplifier. In this configuration, when operating as a detection device, the input to input terminal 6 is kept at "0" and the switch is therefore in the OFF state, so a positive feedback loop is formed at 2, 9, 11, and 7. There is no oscillation. Further, the signal of the target frequency waveformed by the BPF 2 is applied to the detector 3, and an output of "1" is outputted to the output terminal 5.

Next, when operating as an oscillator, a signal having the waveform shown in FIG. 2a is applied from the outside to the terminal 6, and the switch 7 is immediately turned on as shown in FIG. 2b.

On the other hand, the analog output of the detector 3 obtained from the terminal 8 is "0" because there is no output from the BPF2 yet at this time, and therefore the output of the inverting amplifier 10 is in the "1" state. , the variable resistor 9 has a very small conduction resistance, the loop gain of 2, 9, 11, and 7 is large, and oscillation starts.

Note that the BPF2 has an output rise delay as shown in FIG. 2c, and the detector 3 also has a rise delay, so its detected output level is as shown in FIG. 2D. Therefore, the output of the inverting amplifier 10 becomes as shown in FIG. Since it increases proportionally, the loop gain also changes from large to small.

Therefore, the oscillation waveform becomes as shown in g, and has good oscillation start-up characteristics with no start-up delay or overshoot as shown by the broken line.

As explained above, the present invention detects the rise of oscillation with a detection device and feeds back changes in the rise level to the loop gain, thereby making it possible to always keep the loop gain at an optimum level, thereby improving the rise characteristics of oscillation. I can do it.

[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...
...Detector digital output terminal, 6...Oscillation control input terminal, 7...Switch, 8...Detector analog output terminal, 9...Variable resistance element, 10...Inverting amplifier, 11...Amplifier.

Claims (1)

[Claims] 1. A narrowband filter device, a detector that detects the output of this filter device, a switch that operates with an oscillation control signal from the outside, and is inserted into a feedback loop consisting of this switch and the filter device, and detects the output of the detector. An oscillation/detection device comprising: control means for controlling the loop gain of the loop according to a level.