KR940008100Y1 - Wireless frequency modulating device - Google Patents

Abstract

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Description

Radio frequency modulator to prevent interference of channels

1 is a conventional apparatus.

2 is a schematic diagram showing an area of an output channel according to a transmission scheme.

3 is a device according to the present invention.

4 is a detailed circuit diagram of an operation control unit for operating FIG.

* Explanation of symbols for main parts of the drawings

1: antenna booster circuit 2: RF converter

AMP _{1 to} AMP ₂ : Amplifier 3,11: Splitter

MIX: Mixer RF MOD: RF Modulator

OSC: Oscillators D _{1 to} D ₄ : Diodes

Q _{1 to} Q ₄ : Transistor 21: MICOM

22: motion control unit

The present invention relates to a radio frequency (RF) modulator of a VCR (Video Cassette Recorder), and more particularly, to an RF modulator capable of preventing channel interference when outputting a predetermined UHF RF modulator. will be.

In general, unlike a NTSC RF modulator which outputs a modulated RF signal to one transmission channel alone, a predetermined UHF RF modulator outputs a mixed channel with another channel on an RF frequency, so that the image of the other channel Interference occurs when images overlap.

Accordingly, an object of the present invention for solving the above problems is to provide an RF modulator capable of preventing interference of a channel by separating an amplifier power supply of an RF modulator and operating each amplifier only when necessary.

A feature of the present invention for achieving the above object is a control for responding to a VCR / TV switched signal in an RF modulator having a VCR tuner for recording an RF signal applied through an antenna and a distributor for distributing to a TV. An operation control unit which receives a signal and driving power and outputs driving power of an amplifier and an RF modulator, is connected between the antenna and the divider, and in response to the driving power outputs of the amplifier and the RF modulator of the operation control unit, loss in distribution is generated. A first amplifier for compensating, a second amplifier connected between the distributor and the TV signal output terminal and receiving a signal distributed to the TV and outputting an RF signal without loss in response to only the amplifier driving power output of the operation controller; RF modulator of the operation control unit receives audio and video signals of broadcast signals and video tapes recorded through a tuner May includes a RF modulator capable of preventing interference of the channel characterized in that only in response to the power output including a RF modulator for modulating the output of a signal input and output without mixing of the second amplifier.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 1 is a circuit diagram of a conventional RF modulator. The apparatus of FIG. 1 is applied to an antenna booster circuit 1 and a video tape or tuner for distributing a signal input through an antenna ANT to a VCR tuner and a TV through a dedicated amplifier according to VHF UHF through a filter. It consists of an RF converter (2) which modulates video and audio signals into RF signals by selecting and recording the radio waves of a desired station among the radio waves. Looking in more detail, the output of the antenna booster circuit 1 includes a first amplifier (AMP ₁₎ and the first amplifier (AMP ₁₎ for amplifying the RF signal (Ri) received through the antenna (ANT) to a VCR tyuwoo Tu TV The distributor 3 includes a distribution amplifier 3, a second amplifier AMP ₂ for amplifying the signal distributed to the TV, and a mixer MIX. The RF converter 2 is divided into a tuner and recorded with a broadcast signal or video tape. It consists of RF modulator (RF MOD) that receives video and audio signals (Vi, Ai), and converts them into frequencies easily transmitted to the transmission channel, and oscillator (OSC) that determines the transmission channel of the RF modulator (RF MOD) .

In FIG. 1, the RF input signal Ri coming from the antenna ANT is divided into two and distributed to the tuner and the TV, respectively. In this case, the first amplifier AMP ₁ compensates for the loss caused by the distribution in advance. The signal distributed from the divider 3 to the tuner is converted and amplified at the video intermediate frequency, demodulated and separated from the video signal and the audio signal, and recorded on a tape. The signal distributed to the TV first compensates for the gain reduction in the RF band through the second amplifier AMP ₂ . When the oscillator (OSC) determines the RF channel, the RF modulator (RF MOD) converts the video and audio signals (Vi, Ai) of the broadcast signal or videotape recorded through the tuner to a frequency easily transmitted to the channel. The signal amplified by the second amplifier AMP ₂ and the signal modulated by the RF modulator RF MOD are mixed through the mixer MIX and output to the TV. At this time, since the two signals are mixed on the RF frequency, it affects the interference.

2 is a schematic diagram showing an area of an output channel according to a transmission method, in which a predetermined NTSC RF modulator is compared with a UHF RF modulator.

FIG. 2a is an NTSC method for independently outputting a modulated RF output channel, and (b) is a UHF method for outputting a modulated RF output channel mixed with other RF channels on an RF frequency. As shown, since NTSC uses single channel, there is no effect of interference. However, in the PAL and SECAM UHF bands, which are mainly used in Europe, RF channels of strong electric fields exist around output channels due to RF mixing. . The interference of the RF output channel is caused by the second amplifier AMP ₂ supplying the RF channel in FIG. Conversely, a strong RF modulator output can interfere with other channels.

For this reason, the oscillator OSC that determines the RF channel of FIG. 1 can variably convert the output channel between 30 and 40 channels. In practice, however, RF channels are intensively distributed in the UHF band, especially between 30 and 40 channels (in the case of PAL and SECAM). Interference of outputs in which images of other channels overlap with images of a receiving channel cannot be avoided. Good and poor output quality of the RF modulator is important as a criterion for evaluating the performance of the VCR.

3 is a circuit diagram of an RF modulator capable of preventing interference of a channel according to the present invention. As shown in FIG. There is a difference in that the power source of the first and second amplifiers AMP ₁ and AMP ₂ are separated and used. Before describing the operation of FIG. 3, FIG. 4 will be described first.

FIG. 4 is a detailed circuit diagram of an operation control unit for operating the circuit of FIG. 3, wherein the first NPN transistor having a base B connected to the micom is driven on / off according to a control signal output from the microcomputer 21 of the VCR. Q ₁₎ and, connected to the emitter (E) to the transistor drive voltage V and the 1PNP transistor (Q ₂₎ and the NPN transistor connected to the base (B) to the collector (C) of said NPN transistor (Q ₁₎ the 2NPN transistor connecting the base to the collector (C) of the (Q ₁₎ (Q ₃₎ and, connected to the base (B) to the collector (C) of the first 2NPN transistor (Q ₃₎ and the emitter in the transistor drive voltage V It consists of a second PNP transistor (Q ₄ ) for connecting the emitter. Here, the transistor driving voltage V is used at 5 volts. In FIG. 4, when the user sets the VCR to the VCR mode, the microcomputer 21 applies a high signal to the first NPN transistor Q ₁ . At this time, the first NPN transistor Q ₁ is turned on because the voltage using the bias voltage is high. Therefore, the state of the output terminal becomes low, and applies a low signal to the base B of the first PNP transistor Q ₂ and the _second NPN transistor Q ₃ .

At this time, since the voltage used as the bias voltage is low, the first NPN transistor Q ₂ is turned on and the _second NPN transistor Q ₃ is turned off. Therefore, RF modulator driving power source (V ₂₎ being supplied to the 2NPN transistor (Q ₃₎ of claim 2NPN transistor (Q ₄₎ is connected to the output terminal and the base (B) of are open (OPEN) state amplifier driving power ( V ₁ ) is not supplied. On the contrary, when the user sets the VCR to the TV mode, the microcomputer 21 applies a low signal to the first NPN transistor Q ₁ .

At this time, since the voltage used as the bias voltage is low, the first NPN transistor Q ₁ is turned off. Therefore, the first PNP transistor Q ₂ is in an open state and cannot supply the RF modulator driving power V ₂ . However, the first PNP transistor Q ₂ connects the base B between the transistor driving voltage V and the emitter E to apply a high signal to the base B of the second NPN transistor Q ₃ . do. At this time, since the voltage used as the bias voltage is high, the second NPN transistor Q ₃ is turned on to apply a low signal to the second PNP transistor Q ₄ . Therefore, the second PNP transistor Q ₄ is turned on to supply the amplifier driving power supply V ₁ .

The above is summarized in Table 1.

TABLE 1

The operation of FIG. 3 will be described through the above description. When the amplifier driving power supply V ₁ is supplied in the TV mode, the first and second amplifiers AMP ₁ and AMP ₂ are operated through the third and fourth diodes D ₃ and D ₄ . After the RF input signal Ri sent from the antenna ANT is amplified by the first amplifier AMP ₁ to compensate for the loss caused by the distribution, the divider 11 is divided into a VCR tuner and a TV. The signal distributed to the TV is outputted without loss by the second amplifier AMP ₂ . At this time, the RF modulator driving power supply (V ₂ ) is not supplied and does not operate. This allows you to watch one pro on television while simultaneously receiving and recording other pros on a video built-in tuner. In the VCR mode, the RF modulator driving power supply V ₂ is supplied to operate the first amplifier AMP ₁ and the RF modulator RE MOD through the first and second diodes D ₁ and D ₂ . The RF input signal Ri transmitted from the antenna ANT is amplified by the first amplifier AMP ₁ that compensates for the loss in distribution, and is divided into a VCR tuner and a TV through the distributor 11. The mutual distribution to the tuner operates normally. The RF modulator (RF MOD) receives the video and audio signals (Vi, Ai) of the broadcast program recorded through the video tape or the tuner and transmits them to the transmission channel. Modulated output. At this time, the second amplifier AMP ₂ does not operate. The channel can be selected and viewed, and the signal distributed to the TV does not affect the output signal of the RF modulator (RF MOD) because the second amplifier AMP ₂ does not operate. In addition, in order to reduce interference, an attenuator is inserted at the RF antenna input side to attenuate the input signal.

As described above, the RF modulation apparatus capable of preventing interference of the channel according to the present invention is separated from the driving power of each of the amplifiers AMP ₁ and AMP ₂ and the RF modulator RF MOD by the operation control unit, and the power is supplied to each of them only when necessary. It can prevent the interference of the output channel by supplying. By preventing channel interference, good image quality can be obtained. Especially, it is suitable for VCR in Europe using PAL or SECAM.

Claims (3)

An RF modulator having a VCR tuner for recording an RF signal applied through an antenna and a divider for distributing it to a TV. The RF modulator receives a control signal and driving power in response to a VCR / TV switching signal. An operation control unit for outputting driving power; A first amplifier connected between the antenna and the divider, the first amplifier compensating for losses in distribution in response to the driving power outputs of the amplifier and the RF modulator of the operation control unit; A second amplifier connected between the distributor and the TV signal output terminal to receive a signal distributed to the TV and output an RF signal without loss in response to only the amplifier driving power output of the operation control unit; Receiving the audio and video signals of the broadcast signal and video tape recorded through the VCR tuner in response to only the RF modulator driving power output of the operation control unit to modulate and output the input signal without being mixed with the output of the second amplifier RF modulator capable of preventing interference of the channel, characterized in that it comprises an RF modulator According to claim 1, wherein the operation control unit is connected to the first NPN transistor connected to the base to be turned on / off according to the control signal, the base connected to the output terminal of the first NPN transistor to be turned on / off according to the first NPN transistor, An amplifier driving power supply unit having a first PNP transistor configured by connecting an output terminal to an amplifier driving power supply output terminal; And a first NPN transistor connected to a base to be turned on / off according to the control signal, and a base connected to an output terminal of the first NPN transistor and to an emitter and a base of the first PNP transistor to be turned on / off according to the first NPN transistor. An RF modulator having a second PNP transistor configured to be connected between the second NPN transistor and a second PNP transistor configured by connecting a base to an output terminal of the second NPN transistor so as to be turned on and off according to the second NPN transistor, and an output terminal to an RF modulator driving power output output terminal. RF modulator comprising a drive power supply. The RF modulator of claim 1, further comprising a diode at a power supply terminal supplied to the first and second amplifiers and the RF modulator such that a reverse current does not flow by the power supplied through the operation control unit.