JPS63131665A - Rf modulator - Google Patents

Abstract

PURPOSE:To obtain a receiver with resulting low cost, by providing a mixing device in which an RF signal and a voice signal are mixed. CONSTITUTION:When the receiver receives a video signal and the voice signal of prescribed channel, they are inputted to an RF modulator, and the RF signal is outputted from a first mixing circuit 7, and a required signal is passed through at a high-pass filter 8a as the RF signal, and an unrequired low-pass frequency is attenuated. Meanwhile, out of the voice signals inputted to the RF modulator at a low-pass filter 8b, for example, a frequency impossible to be listened by human ears is attenuated. Therefore, the RF signal and the voice signal passing the high-pass filter 8a and the low-pass filter 8b are mixed without being mixed at a second mixing circuit 8c, and the voice signal of a monitor television and an ordinary RF signal are outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an RF modulator, and more particularly to an RF modulator that mixes an RF multiplied signal and an audio signal.

[Conventional Example] Conventionally, a VTR or CATV receiver is provided with an RF modulator as shown in FIG. This RF modulator is
For example, it is intended to enable connection even to a television receiver without a video/audio terminal, and modulates the video equalization signal and audio signal obtained by the satellite receiver into, for example, a US VHF channel 3 or channel 4 signal. Output. Therefore, the RF modulation circuit includes a clamp circuit that extracts a signal at a predetermined level from the obtained video signal, and a video AM modulation circuit that performs AM modulation and amplification of the video signal that has passed through the clamp circuit 1 based on the frequency of the video carrier oscillation circuit 2. A circuit 3, an audio amplification circuit 4 that amplifies the obtained audio signal to a predetermined level, a frequency conversion circuit 6 that converts the frequency of the amplified audio signal based on the frequency of the resonant image carrier oscillation circuit 2 of the tank circuit 5a, and a video AM circuit. A mixing circuit 7 that mixes the video signal output from the modulation circuit 3 and the audio signal converted by the frequency conversion section 6 is provided. As a result, the RF multiplied signal obtained by this mixing circuit 7 is output from the RF terminal.

[Problems to be Solved by the Invention] Generally, this type of receiver is provided with a video terminal for outputting a video signal and an audio terminal for outputting an audio signal, in addition to the above-mentioned RF terminal. That is, this receiver is capable of outputting video and audio signals to either a monitor television or an ordinary television receiver. However, when using a monitor television receiver, the RF terminal is not used, and when using an ordinary television receiver, the video terminal and audio terminal are not used.

In a receiver, either an RF terminal or an audio or video terminal is usually used. and,
This terminal is expensive.

This resulted in an increase in the cost of the receiver. In particular, nowadays, receivers that are as low in cost as possible are desired.

This invention was made in view of the above points.

The purpose is to provide an RF modulator for a receiver that can reduce the cost of the receiver.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an RF modulator of a receiver that outputs an RF multiplied signal modulated by a video signal and an audio signal. It is equipped with a mixing device for mixing.

[Function] The mixing device of the invention having the above configuration passes the mixed RF signal of the video signal and the audio signal in the receiver through the high-pass filter, and passes the audio signal through the low-pass filter, and the high-pass filter and the low-pass filter pass the audio signal through the high-pass filter. To mix signals that have passed through a filter without causing interference. The RF multiplied audio signal of this mixed signal is output from the same terminal.

[Example] Hereinafter, an embodiment of the present invention will be described based on FIG. 1.

In the figure, the same parts and parts corresponding to the same parts as in FIG. 2 are denoted by the same reference numerals, and redundant explanation will be omitted.

In FIG. 1, reference numeral 8 denotes a mixing device that mixes the RF multiplied signal output from the mixing circuit 7 (referred to as the first mixing circuit in this embodiment) described above and the audio signal input to this RF modulator. It is. This mixing device 8 includes a first mixing circuit 7
A high-pass filter 8a that passes a predetermined frequency, e.g., 30 MHz or more, of the RF multiplied signal from the input audio signal, a low-pass filter 8b, which passes a predetermined frequency, e.g., 10011z or less, of the input audio signal, and the high-pass filter 8a and the low-pass filter 8.
It consists of a second mixing circuit 8c which mixes the signals that have passed through b and outputs the RF multiplied signal.

Next, the operation of the RF modulator having the above configuration will be explained.

First, the receiver receives a video signal and an audio signal of a predetermined channel. Then, this video signal and audio signal are input to this RF modulator, and are outputted from the RF multiplied signal first mixing circuit 7, which has undergone processing similar to the conventional one. Then, the high-pass filter 8a multiplies the RF signal and passes necessary signals, while unnecessary low frequencies are attenuated. On the other hand, among the audio signals input to the RF modulator, the low-pass filter 8b attenuates, for example, frequencies higher than those that cannot be heard by the human ear. Therefore, the RF multiplied signal (30 MHz or higher) that has passed through the high-pass filter 8a and the low-pass filter 8b) and the audio signal (100 kHz or lower) are mixed in the second mixing circuit 8c without interference. That is, by this mixing, the second mixing circuit 8C outputs the monitor television audio signal and the normal RF signal.

Therefore, a receiver equipped with this RF modulator only needs to be provided with a video terminal for outputting the video signal of the monitor television and an RF signal terminal, and an audio terminal is not required. It can be configured at lower cost. Furthermore, the distribution circuit that conventionally outputs audio signals to audio terminals can be omitted.

[Effects of the Invention] As explained above, according to the receiver RF modulator of the present invention, the device dio signal and the R
Since a mixing device for mixing F-fold signals is provided, the audio terminal provided on the receiver can be omitted, and since this mixing device is cheaper than the audio terminal,
The cost of the receiver can be further reduced.

[Brief explanation of the drawing]

Fig. 1 is a circuit block diagram of an RF modulator of a receiver showing an embodiment of the present invention, and Fig. 2 is a circuit block diagram of a conventional RF modulator of a receiver.
8a is a high-pass filter, 8C'J Patent applicant: Fujitsu General Co., Ltd. Patent attorney Takuya Ohara lh-mer

Claims (2)

[Claims] (1) An RF modulator that outputs an RF signal modulated by a video signal and an audio signal, further comprising a mixing device that mixes the audio signal with the RF signal. (2) In claim (1), the mixing device includes: a high-pass filter that attenuates low frequency components of the RF signal; a low-pass filter that attenuates high frequency components of the audio signal; An RF modulator comprising a mixing circuit that mixes an RF signal that has passed through a high-pass filter and an audio signal that has passed through the low-pass filter, and the output of the mixing circuit is used as the output of the RF modulator. .