JPS59140718A - Automatic fine tuning circuit - Google Patents

Abstract

PURPOSE:To perform fine tuning automatically by counting noises by taking advantage of an increase in noise with a shift in tuning point and generating a tuning control voltage in such a direction that noises become less than before. CONSTITUTION:The output of an input circuit 1 is supplied to an AGC high- frequency amplifying circuit 3 through a tuning circuit 2, passed through a mixing circuit 4, and an IF amplifier 5 with AGC, and detected by a video detector 6, whose output is displayed on a cathode-ray tube 7 and also inputted to a level detector 11 to extract a signal lower than a blanking level; and a counter circuit 12 counts it for a specific period (controlled by a detection pulse generating circuit 16) and a decision making circuit 13 compares the counted value with the last counted value to sends a signal ''hold'' in case of a decrease, a signal ''reverse'' in case of >3 times successive increases, or a signal ''hold'' in case of <=3 times sucessive increases to a voltage control circuit 15. A voltage generating circuit 14 controls the tuning circuit 2 on the basis of said signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tuning circuit in communication equipment such as television receivers and radio receivers.

In the case of a conventional television, the rough circuit configuration is as shown in Figure 1. Such a circuit configuration has the disadvantage that even if it is tuned to a certain channel, if the tuning point shifts due to subsequent changes in temperature, location, etc., the tuning must be retuned from the beginning.

In order to solve these drawbacks, the present invention takes advantage of the fact that noise in the video signal increases when the tuning point shifts, counts this noise with a counter circuit, and uses a judgment circuit to calculate the increase in noise compared to the previous state. After determining whether the voltage has increased or decreased, the voltage generation control circuit is configured to increase the generated voltage if it has increased, or to maintain the same generated voltage direction if it has decreased in the opposite direction (increase or decrease). Control the generated voltage. This controlled voltage was applied to a tuning circuit to automatically find the tuning point, thereby eliminating manual tuning. (The initial direction of voltage generation is undefined.) As described above, the present invention counts noise and controls the tuning circuit using voltage so that the noise is reduced.

FIG. 2 is a block diagram of the present invention. A signal below the blanking level is extracted from the video signal from the video detection circuit 6 by a level detection circuit 11. (Figure 4 shows the output when the video signal shown in Figure 3 enters the level detection circuit.) Then, the 12 counter circuits output the synchronizing signal for a certain period (always constant) controlled by 16. The 13 judgment circuit judges whether the counted number increases or decreases compared to the previous number, and when it decreases, if the signal is "as is" and increases, the increase is 3 consecutive times. If it continues more than three times, a "reverse" signal is sent to the voltage control circuit 15, and if it is less than three times, a "no change" signal is sent to the voltage control circuit 15. In the voltage control circuit,
For the “as is” signal, an increase in the current generated voltage,
Alternatively, a command to "maintain" the direction of decrease is sent to the voltage generating circuit every certain period in synchronization with the 12 counter circuits in response to a "reverse" signal. In the voltage generation circuit No. 14, the voltage from the voltage control circuit is
When the command is "maintain", the current generated voltage is maintained in either direction of increase or decrease, and when the command is "opposite", the direction of the generated voltage is set to be opposite to the current direction. The voltage thus generated is applied to the tuning circuit for automatic tuning. However, there is a limit to the total generated voltage, and the voltage does not reach the level until the next channel is received, and the direction of the initial voltage generation is arbitrary.

As explained above, if you tune to a certain channel at the beginning, even if the tuning point shifts later, the tuning will be performed automatically. There is no need to do it manually every time. In addition, when performing tuning, you don't have to manually set the best tuning point, but if you get close to the tuning point to a certain extent, the best tuning point will be automatically set, making tuning very easy. This can be applied not only to televisions but also to other communication devices that require tuning, such as radios.

[Brief explanation of drawings]

Figure 1 is a rough circuit block diagram of a conventional television.
is the input circuit, 2 is the tuning circuit, 3 is the high priest circuit, 4 is the mixing circuit, 5 is the electronic amplifier, 6 is the video detection, 7 is the cathode ray tube, 8
9 is a local oscillation circuit, 9 is an ATT circuit, and 10 is an AGO circuit. FIG. 2 is a circuit block diagram according to the present invention.
11 is the level detection circuit, 1 is the same as that in Figure 1.
2 is a counter circuit, 13 is a determination circuit, 14 is a voltage generation circuit, 15 is a voltage generation control circuit, and 16 is a detection pulse generation circuit. Figure 3 shows a video signal which is a video detection output waveform, and 17
is a video signal, 18 is noise, and 19 is a horizontal synchronization signal. FIG. 4 shows the level detection circuit output waveform according to the waveform of FIG. 3, and 18.19 is the same as that of FIG. Applicant: Suwa Seikosha Co., Ltd.

Claims (1)

[Claims] An automatic fine tuning circuit that counts the noise in the video signal and applies a voltage that reduces the noise to the tuning circuit to gradually create the best reception condition with less noise.