JPH08213903A - Vfo automatic adjustment device - Google Patents

Abstract

PURPOSE: To allow the VFO automatic adjustment device to be locked to a received synchronizing signal by oscillating a waveform whose peak voltage is made constant. CONSTITUTION: The VFO automatic adjustment device is made up of an oscillation unit 1 to which an oscillation capacitor 11 is connected, whose oscillating frequency is controlled by varying a DC voltage applied to a control input terminal (c), and providing an output of a signal synchronized with a synchronizing signal, up of an oscillation frequency detection section 2, an oscillated peak voltage detection section 3, an oscillating frequency setting section 4, a setting table 5, a control voltage decision means 6, and a D/A converter 7. An oscillated frequency from the oscillating frequency detection section 2 and a setting frequency output of the table 5 with respect to a setting frequency from the oscillating frequency setting section 4, and an oscillated peak voltage from the oscillated peak voltage detection section 3 and setting peak voltage of the table 5 with respect to the setting frequency from the oscillating frequency setting section 4 are compared respectively to set DC voltage data to be applied to the control input terminal (c). The DC voltage data are converted into an analog signal by the D/A converter 7 and the analog signal is given to the control input terminal (c).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic VFO adjusting device, and more particularly to a device for accurately locking a set frequency.

[0002]

2. Description of the Related Art A conventional VFO adjustment is as shown in FIG.
The oscillation frequency is controlled by connecting an oscillation capacitor to the outside and changing the DC voltage applied to the control input terminal.
In an oscillating unit that oscillates and outputs a signal synchronized with an input synchronizing signal, an oscillating frequency setting unit and a control voltage adjusting unit are provided to determine the DC voltage applied to the control input terminal. The waveform at both ends was monitored and the DC control voltage was manually adjusted. However, in this method, even if the frequency at both ends of the oscillation capacitor matches the frequency set by the frequency setting unit due to variations in the oscillation unit, the oscillation cycle is not constant, and as shown in FIG. There is a problem that the peak voltage of the wave may be locked to the synchronization signal in a state where it is not constant, the period is constant, and a stable oscillation signal cannot be obtained.

[0003]

SUMMARY OF THE INVENTION The present invention solves the problems described above, and automatically oscillates as a waveform with a constant peak voltage at the frequency set by the frequency setting unit and locks to the input synchronizing signal. It is an object of the present invention to provide a VFO automatic adjustment device that can be adjusted and can obtain a stable oscillation signal of a constant cycle.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention connects an oscillation capacitor to the outside and controls the oscillation frequency by changing the DC voltage applied to the control input terminal. In an oscillating unit that oscillates and outputs a signal synchronized with the signal, the DC voltage applied to the control input terminal is an oscillating frequency detector that detects the wake-up frequency from the wake-up waveform across the oscillating capacitor An oscillation peak voltage detection unit that detects a voltage, an oscillation frequency setting unit, a setting table that stores the setting frequency and the setting peak voltage for the setting frequency set by the oscillation frequency setting unit, a control voltage setting unit, and D /
An A converter, which compares the oscillation frequency from the oscillation frequency detection unit and the oscillation peak voltage from the oscillation peak voltage detection unit with the set frequency and the set peak voltage with respect to the set frequency from the oscillation frequency setting unit, respectively. By doing so, the DC voltage data applied to the control input terminal is set, the DC voltage data is converted into an analog signal, and the analog signal is applied to the control input terminal.

Further, the oscillation frequency detecting section includes a high impedance buffer circuit that receives and outputs signals at both ends of the oscillation capacitor with high impedance, and a frequency counter that counts the frequency of the signal from the high impedance buffer circuit. It consists of.

Further, the oscillation peak voltage detection section includes a peak hold circuit that holds the peak voltage of the signal across the oscillation capacitor, and an A / D converter that converts the signal from the peak hold circuit into a digital signal. It consists of.

The control voltage setting means includes a frequency comparing section for comparing the set frequency and the set peak voltage with respect to the frequency from the frequency setting section with the oscillation frequency data from the frequency detecting section, and an A / D converter. A peak voltage comparison unit that compares the peak voltage data with the oscillation peak voltage, a correction table that stores in advance control voltage correction data for the frequency difference data and the peak voltage difference data, and a DC control voltage setting unit. Based on the difference data from the comparison unit and the difference data from the peak voltage comparison unit, the control voltage is corrected by referring to the correction table, and the DC control voltage setting unit sets the DC control voltage.

[0008]

With the above-described structure, in the VFO automatic adjustment apparatus of the present invention, the oscillation frequency and the peak voltage are detected from the oscillation waveform at both ends of the oscillation capacitor of the oscillation unit, and the oscillation frequency is set to the frequency. The control voltage is set so that it matches the frequency set in the section and the peak voltage of the oscillation waveform has a predetermined constant value, so that a stable oscillation signal with a constant cycle is obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A VFO automatic adjusting device according to the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a VF according to the present invention.
It is a circuit block diagram which shows one Example of the O automatic adjustment apparatus. In the figure, 1 is an oscillation unit, and an oscillation capacitor 11 is connected to the oscillation capacitor connection terminals b1 and b2,
The oscillating frequency is controlled by the DC voltage input to the control input terminal c, and the vertical signal oscillated in synchronization with the vertical synchronizing signal input from the synchronizing input terminal a is output from the output terminal d. Reference numeral 2 is a frequency detection unit, which is a high impedance buffer 2 connected between the oscillation capacitor connection terminals b1 and b2.
1 and a frequency counter 22 to detect the oscillation frequency of the signal across the oscillation capacitor 11. Three
Is an oscillation peak voltage detector, which is a peak hold circuit 31 connected between the oscillation capacitor connection terminals b1 and b2;
The A / D converter 32 converts the peak voltage from the peak hold circuit 31 into a digital signal, and detects the oscillation peak voltage of the oscillation waveform across the oscillation capacitor 11. A frequency setting unit 4 sets the frequency of the oscillating vertical signal in accordance with the input vertical synchronizing signal. Reference numeral 5 denotes a setting table which stores in advance the oscillation frequency and the set peak voltage corresponding to the frequency set by the frequency setting unit. Reference numeral 6 is a control voltage setting means, which is a frequency comparison section 61 for comparing the oscillation frequency detected by the frequency detection section 2 with the set frequency set by the frequency setting section 4.
And a peak voltage comparison unit 62 that compares the oscillation peak voltage from the A / D converter 32 with the set peak voltage from the setting table 5, frequency difference data from the frequency comparison unit 61, and the peak voltage comparison. A correction table 63 in which control voltage correction data for the peak voltage difference data from the unit 62 is stored in advance, and a DC control voltage setting unit 64 for correcting and setting the DC control voltage based on the control voltage correction data from the correction table 63. And the DC control voltage data to be input to the control input terminal c is set. A D / A converter 7 converts the DC control voltage data from the control voltage setting unit 6 into an analog signal.

The operation of the above arrangement will be described below. FIG. 2 shows an example of the signal waveform of each part of FIG.
The frequency detecting section 2 counts the frequency from the oscillation waveform Sosc across the oscillation capacitor 11 and inputs the frequency data fosc to the control voltage setting means 6. Further, the oscillation peak voltage detection unit 3 detects the oscillation peak voltage from the oscillation waveform Sosc across the oscillation capacitor 11 and inputs the oscillation peak voltage data Epo to the control voltage setting means 6. On the other hand, the frequency setting unit 4
The setting frequency fs and the setting peak voltage Eps corresponding to the setting frequency are input to the control voltage setting means 6 by referring to the setting table 5 based on the setting frequency set in step 3. In the control voltage setting means 6, the frequency comparison unit 61 compares the frequency data fosc detected by the frequency comparison unit 61 with the set frequency data fs to be set, and the frequency difference data Df (= fs-f).
osc), and the peak voltage comparison unit 62 compares the detected peak voltage data Epo with the set peak voltage Eps corresponding to the set frequency to be set, and calculates the peak voltage difference data Dep (= Eps-Epo). Based on the frequency difference data Df and the peak voltage difference data Dep, the DC control voltage setting section 64 refers to the correction data ΔDcc of the correction table 63 to set the DC control voltage Ddcc. The DC control voltage Ddcc set by the control voltage setting means 6 is converted into an analog voltage dcc by a D / A converter and input to the control input terminal c of the oscillation unit 1. The oscillation unit 1 oscillates the frequency set by the frequency setting unit 4 based on the DC control voltage dcc input to the control input terminal c, and outputs the vertical oscillation signal synchronized with the input vertical synchronization signal from the output terminal d. There is. 3 shows an example of data stored in the setting table 5, and FIG. 4 shows an example of data stored in the correction table 63.

[0011]

As described above, the VF according to the present invention
According to the O automatic adjustment device, the oscillation frequency and the peak voltage are detected from the oscillation waveforms at both ends of the oscillation capacitor of the oscillation unit, and the oscillation frequency matches the frequency set by the frequency setting unit. Since the control voltage is set so that the peak voltage of is a predetermined value, it is automatically adjusted so that it will oscillate as a waveform with a constant peak voltage at the frequency set by the frequency setting section and lock to the input synchronization signal. However, it is possible to provide a VFO automatic adjustment device that can obtain a stable oscillation signal of a constant cycle.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of a VFO automatic adjustment device according to the present invention.

FIG. 2 shows an example of a signal waveform of each part in FIG.

FIG. 3 shows an example of data in a setting table.

FIG. 4 shows an example of data in a lookup table.

FIG. 5 shows an example of signal waveforms of respective parts in FIG.

FIG. 6 is a circuit block diagram showing a conventional VFO automatic adjustment device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oscillation unit 2 Frequency detection part 3 Peak voltage detection part 4 Frequency setting part 5 Setting table 6 Control voltage setting means 7 D / A converter 11 Oscillation capacitor 21 High impedance buffer 22 Frequency counter 31 Peak hold circuit 32 A / D converter 61 Frequency comparison unit 62 Peak voltage comparison unit 63 Correction table 64 DC control voltage setting unit a Synchronization input terminal b1 Oscillation capacitor connection terminal b2 Oscillation capacitor connection terminal c Control input terminal d Output terminal

Claims (4)

[Claims] 1. An oscillation unit for connecting an oscillation capacitor to the outside and controlling an oscillation frequency by changing a DC voltage applied to a control input terminal to oscillate and output a signal synchronized with an input synchronization signal, The DC voltage applied to the control input terminal is an oscillation frequency detection unit that detects the starting frequency from the starting waveform at both ends of the oscillation capacitor, an oscillation peak voltage detection unit that detects the oscillation peak voltage, and an oscillation frequency setting unit. A setting table for storing the set frequency and the set peak voltage with respect to the set frequency set by the oscillation frequency setting unit, control voltage setting means, and D /
An A converter, which compares the oscillation frequency from the oscillation frequency detection unit and the oscillation peak voltage from the oscillation peak voltage detection unit with the set frequency and the set peak voltage with respect to the set frequency from the oscillation frequency setting unit, respectively. By doing so, the DC voltage data to be applied to the control input terminal is set, the DC voltage data is converted into an analog signal, and the analog signal is applied to the control input terminal. 2. The oscillation frequency detection unit includes a high impedance buffer circuit that receives and outputs signals at both ends of the oscillation capacitor with high impedance, and a frequency counter that counts the frequency of the signal from the high impedance buffer circuit. 2. The VFO automatic adjustment device according to claim 1, wherein 3. The oscillation peak voltage detection section includes a peak hold circuit that holds the peak voltage of a signal across the oscillation capacitor, and an A / D converter that converts the signal from the peak hold circuit into a digital signal. 2. The VFO automatic adjustment device according to claim 1, wherein 4. The control voltage setting means includes a frequency comparing section for comparing a set frequency and a set peak voltage with respect to the frequency from the frequency setting section with oscillation frequency data from the frequency detecting section, and an A / D converter. A peak voltage comparison unit that compares the peak voltage data with the oscillation peak voltage, a correction table that stores in advance control voltage correction data for the frequency difference data and the peak voltage difference data, and a DC control voltage setting unit. The control voltage is corrected by referring to the correction table based on the difference data from the comparison unit and the difference data from the peak voltage comparison unit, and the DC control voltage setting unit sets the DC control voltage. The VFO automatic adjustment device according to claim 1.