JPH03178273A - Specific channel automatic video detection stage peaking circuit - Google Patents

Abstract

PURPOSE:To correct the frequency characteristic of a video detection output automatically at channel selection by providing a video detection stage peaking circuit and varying a voltage by a signal relating to the channel selection so as to vary the frequency characteristic of the video detection stage. CONSTITUTION:When a specific channel desiring to operate a trap or filter 3 is selected, a signal from a microcomputer 5 is outputted to a band switch IC 4, a voltage to select the band switch by the switch IC 4 is fed to a tuner 2 and a voltage operating the trap or filter 3 is fed to the tuner 2 and a video detection stage peaking circuit 7. An RF signal inputted from an antenna input section 1 of the tuner 2 is converted into an IF signal and outputted and the IF signal enters the video detection circuit 6 and the video signal is outputted. In this case, since the frequency characteristic of the detection output is varied with the trap or filter 3, the signal is switched on/off by the video detection stage peaking circuit 7. Thus, the frequency characteristic of the detection output is changed automatically.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a device capable of receiving TV signals, which automatically changes the frequency characteristics of the video detection output when a specific channel is selected. This invention relates to a specific channel automatic video detection stage peaking circuit.

[Conventional technology]

FIG. 2 is a block diagram from the antenna input section of the tuner to the video detection output in a conventional device capable of receiving TV signals. Reference numeral 1 in FIG. 2 is an antenna input section of the tuner 2, and this antenna input section 1 is connected to a trap or filter 3 built in the tuner 2.

4 is a band switch integrated circuit (hereinafter referred to as band switch I)
It is controlled by a microcomputer (hereinafter referred to as microcomputer) to switch a band switch (not shown) of the tuner 2.

Further, the IF (intermediate frequency) signal output from the tuner 2 is subjected to video detection by a video detection circuit 6.

Next, the operation will be explained. When you select a specific channel on which you want to activate trap or filter 3,
The signal related to channel selection from the microcomputer 5 is sent to the band switch IC.
4, and the band switch IC4 that received the signal,
The voltage for switching the band switch of the tuner 2 and the voltage for operating the trap or filter 3 are set in the tuner 2.
Add to.

As a result, the RF multiplied signal coming from the antenna input section 1 of the tuner 2 passes through the trap or filter 3, is converted into an IF multiplied signal, and is output from the tuner 2.

The IF multiplied signal from the tuner 2 enters the video detection circuit, is detected, and is output as a video signal.

[Problem to be solved by the invention]

Since the conventional equipment capable of receiving TV signals is configured as described above, in a certain channel in which the trap or filter 3 is operated, the frequency characteristics of the detection output of the video detection circuit 6 are different from the trap or filter 3. There was a problem that this was different from other channels that were not activated.

This invention was made to solve the above-mentioned problems, and when a certain channel is selected in a device capable of receiving TV signals, the frequency characteristics of the detection output of the video detection circuit are automatically adjusted. The purpose of the present invention is to obtain a specific channel automatic video detection stage peaking circuit that can be changed to a specific channel.

(Means for Solving the Problems) A specific channel video detection stage peaking circuit according to the present invention is added to a video detection circuit, and when a certain specific channel is selected, a channel selection related signal output from a microcomputer is used to The video detection circuit has a circuit whose voltage changes, and is provided with a video detection circuit peaking circuit that uses the voltage change to change the frequency characteristics of the video detection output.

[For production]

The video detection circuit peaking circuit in the present invention converts a signal related to channel selection output from a microcomputer into a change in voltage, changes the frequency characteristic of the video detection output, and corrects this frequency characteristic.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a specific channel automatic video detection stage peaking circuit according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of one embodiment.
In FIG. 1, parts that are the same as those in FIG. 2 are given the same reference numerals to avoid redundant explanation, and the parts that are different from those in FIG. 2 will be mainly described.

As is clear from comparing Figure 1 with Figure 2,
In the figure, a video detection stage peaking circuit 7 is newly added to the configuration shown in FIG. The frequency characteristics of the video detection circuit 6 are changed by the change in . The other configurations are the same as in FIG. 2.

Next, the operation will be explained. Trap or filter 3
When you select a specific channel that you want to operate, a signal related to the channel selection is sent from the microcomputer 5 to the band switch IC 4.
The band switch IC 4 receiving the signal applies a voltage for switching the band switch of the tuner 2 to the tuner 2, and a voltage for operating the trap or filter 3 to the tuner 2 and the video detection stage peaking circuit 7.

The RF multiplied signal input from the antenna input section 1 of the tuner 2 passes through the trap or filter 3, is converted into an IF multiplied signal, and is output from the tuner 2. The IF multiplied signal output from the tuner 2 enters the video detection circuit 6, is detected, and is output as a video signal.

Therefore, when the trap or filter 3 operates, the frequency characteristics of the detection output change due to the trap or filter 3, so a part of the video detection stage is equipped with a video detector that can be turned on/off by the voltage from the band switch IC4. It can be turned on/off by the wave stage peaking circuit 7.

For channels where trap or filter 3 operates,
The video detection stage peaking circuit is turned on, and the frequency characteristics from the antenna to the detection output can be made similar to other channels in which the trap or filter 3 does not operate.

[Effects of the Invention] As described above, according to the present invention, when a particular channel is selected, the video detection stage peaking circuit
Since the frequency characteristics of the video detection stage are changed by changing the voltage according to the channel selection signal from the microcomputer, it is possible to automatically correct the frequency characteristics of the video detection output when selecting a channel.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a specific channel automatic detection stage peaking circuit according to an embodiment of the present invention, and FIG. 2 is a circuit configuration from a tuner antenna input section to a video detection output in a conventional TV signal receiving device. FIG. 1... Antenna input section, 2... Tuner, 3...
Trap or filter, 4...Band switch IC
. 5...Microcomputer, 6...Video detection circuit, 7...Video detection stage peaking circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A tuner having a trap or filter, capable of receiving television signals, and capable of switching a band switch; and a voltage for switching the band switch in the tuner upon receiving a signal related to channel selection from a microcomputer, and operating the trap or filter. A band switch integrated circuit that outputs voltage to the tuner, a video detection circuit that performs video detection of the intermediate frequency signal output from the tuner, and a video detection circuit that turns on and off according to the voltage output from the band switch integrated circuit. and a video detection stage peaking circuit that corrects the output frequency characteristic of the video detection circuit by changing the output frequency characteristic of the video detection circuit.