KR100240306B1 - High frequency apparatus including an rf modulator and a tv tuner - Google Patents

Abstract

The present invention provides a high frequency device having an RF modulator and a TV tuner that reduce the number of crystal oscillators used, reduce manufacturing costs, and do not cause bit interference.

The RF modulator 1 and the TV tuner 2 are arranged separately from the shielding case 34 by the shielding plate 35, and are formed of the first reference oscillator 14 of the RF modulator 1 and the TV tuner 2. The oscillation frequency is set by the two reference oscillators 24 by one crystal oscillator 13 common to them. In the printed circuit board 38 on which the RF modulator 1 and the TV tuner 2 are arranged, a low pass filter 25 is arranged near the TV tuner side and the shielding plate 35, and the RF modulator side and the first filter. The crystal oscillator 13 is arranged near the reference oscillator 14 so that the crystal oscillator 13 is connected to the first reference oscillator 14 and the second reference oscillator 24 via the low pass filter 25. Is connected to.

Description

High frequency equipment with RF modulator and TV tuner

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency device in which an RF modulator and a TV tuner are housed in one shielding case and assembled in a VCR (video casset recorder).

A typical VCR includes an RF modulator for converting a video signal reproduced from the VCR into a high frequency signal and applying the same to a television receiver, and a TV tuner for selecting and receiving a TV signal and applying it to the recording circuit portion of the VCR.

FIG. 2 is a schematic diagram showing an example of the configuration of a high frequency device having a conventional RF modulator 1 and a TV tuner 2 incorporated in a VCR, and the RF modulator 1 and the TV tuner 2 each include one shield case. It is attached to the printed circuit board 38 which is common to 34. The distribution output terminal 19 of the signal distributor 5 of the RF modulator 1 is connected to the RF signal input terminal 31 of the TV tuner 2 in the shielding case 34.

The RF modulator 1 comprises a modulation stage 10, an antenna input terminal 15, a first RF amplifier, a signal divider 5, a second RF amplifier, a signal mixer 7, a TV output terminal 16, and a distribution. An output terminal 19 is provided. The modulation stage 10 includes a first phase locked loop (PLL) 12 including a first oscillator 11 and a first reference oscillator for generating a reference frequency signal stabilized by the crystal oscillator 13 ( 14, a video signal input terminal 17, and an audio signal input terminal 18, the first oscillator 11, the first PLL 12, the crystal oscillator 13 and the first reference oscillator ( 14 constitutes a first frequency synthesizer.

The TV tuner 2 has at least a tuning section 20 and an RF signal input terminal 31, wherein the tuning section 20 includes a second PLL 22 including a second oscillator 21, and a crystal. A second reference oscillator 24 and an IF signal output terminal 32 for generating a reference frequency signal stabilized by the oscillator 23 are provided. The second oscillator 21, the second PLL 22, and the crystal oscillator are provided. 23 and the second reference oscillator 24 constitute a second frequency synthesizer.

In addition, the crystal oscillator 13 is used to resonate at 4 MHz, for example, and the crystal oscillator 22 is used to resonate at 3.2 MHz, for example.

A high frequency device including the RF modulator 1 and the TV tuner 2 according to the above configuration operates schematically as follows.

First, when the RF modulator 1 operates, the first oscillator 11 generates a carrier wave, and the first reference oscillator 14 generates a reference frequency signal whose frequency is stabilized by the resonance frequency of the crystal oscillator 13. Occurs, these carriers and the reference frequency signal are compared in phase in the first PLL 12 to stabilize the frequency of the carrier. This carrier wave is modulated by the video signal supplied from the video signal input terminal 17 and the audio signal supplied from the audio signal input terminal 18 to generate an RF modulated signal. This RF modulated signal is input to the signal mixer 7 at the modulation stage 10 and mixed with the TV broadcast signal input at the signal mixer 7 via the second RF amplifier 6 at the signal distributor 5. Then, it is supplied to the antenna connection terminal of a television receiver (not shown) via the TV output terminal 16.

Next, when the TV tuner 2 operates, a TV broadcast signal is input from the distribution output terminal 19 of the RF modulator 1 to the RF signal input terminal 31 of the TV tuner 2. Further, the second oscillator 21 generates a local oscillation signal, and the reference oscillator 24 generates a reference frequency signal whose frequency is stabilized by the resonance frequency of the crystal oscillator 23, so that these local oscillation signals and the reference frequency are generated. The signal is compared in phase with the second PLL 22 to stabilize the frequency of the local oscillation signal. By selecting the TV broadcast signal desired to be received by the local oscillation signal, the selected TV broadcast signal is converted into an IF (middle frequency) signal, and the intermediate frequency circuit (not shown) of the rear end of the IF signal output terminal 32 is shown. Not supplied).

However, since a high frequency device having a conventional RF modulator and a TV tuner has crystal oscillators 13 and 23 in the RF modulator 1 and the TV tuner 2, respectively, the high frequency device has a large number of components, There is a problem that the manufacturing cost is expensive.

In addition, since the crystal oscillator 13 and the crystal oscillator 23 use the thing of the resonant frequency slightly different from 4 MHz and 3.2 MHz as mentioned above, these two crystal oscillators 13 and 23 are used. ) Has a problem that bit interference occurs because the resonant frequencies of the antennas interfere with each other.

This problem can be solved by setting the resonant frequencies of the two quartz crystal oscillators 13 and 23 to be the same (for example, 4 MHz), but even if set as such, in practice, there is only a slight difference between them. However, because of the inevitable difference, bit interference cannot be prevented.

In order to solve the above problems, the first object of the present invention is to reduce the number of uses of the crystal oscillator to reduce the manufacturing cost and at the same time not to cause bit interference between the RF modulator 1 and the TV tuner 2, It is to provide a high frequency device having an RF modulator and a TV tuner.

A second object of the present invention is to provide a high frequency device having an RF modulator and a TV tuner such that the local oscillation signal of the TV tuner 2 is minimized from leaking to the RF modulator 1.

In order to achieve the first object, a high frequency device including an RF modulator and a TV tuner of the present application is provided in which a RF modulator and a TV tuner are divided into shield plates in a shielding case, and a first reference oscillator and a TV of the RF modulator. The second reference oscillator of the tuner is provided with a first means by which the oscillation frequency is set by one crystal oscillator shared by them.

In order to achieve the above first and second objects, a high frequency device having an RF modulator and a TV tuner of the present application includes an RF modulator and a TV tuner disposed on one printed circuit board with a shield plate sandwiched therebetween. On the printed circuit board, a low pass filter is disposed near the TV tuner side and the shielding plate, a crystal oscillator is disposed near the RF modulator side and the first reference oscillator, and the crystal oscillator is connected to the first reference oscillator. And second means connected to the second reference oscillator via the low pass filter.

According to the first means, since the first reference oscillator and the second reference oscillator share a single crystal oscillator, the number of crystal oscillators is reduced compared to the conventional high frequency apparatus, so that the high frequency apparatus having an RF modulator and a TV tuner is provided. The manufacturing cost of is reduced, and since the two reference oscillators share the resonance frequency of one crystal oscillator, no bit interference occurs between the two reference oscillators.

Further, according to the second means, since the quartz crystal oscillator disposed near the first reference oscillator and the second reference oscillator are connected via a low pass filter disposed near the shield plate, the local oscillation signal generated by the TV tuner is RF. The amount of leakage to the modulator is reduced. Therefore, the local oscillation signal is not transmitted externally at the antenna input terminal 15 or the TV output terminal 16.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing the configuration of an embodiment of a high frequency device having an RF modulator and a TV tuner according to the present invention.

2 is a schematic diagram showing a configuration of a high frequency device having a conventional RF modulator and a TV tuner.

Explanation of symbols on the main parts of the drawings

1: RF modulator 2: TV tuner

10 modulation stage 11: first oscillator

12: 1st PLL 13: crystal oscillator

14: first reference oscillator 15: antenna input terminal

16: TV output terminal 20: synchronization unit

21: second oscillator 22: second PLL

24: second reference oscillator 25: low pass filter

34 shielding case 35 shielding plate

38: printed circuit board

In an embodiment of the present invention, a high frequency device having an RF modulator and a TV tuner includes a first oscillator for generating a carrier wave, a first PLL for controlling the oscillation frequency of the first oscillator, and a reference frequency signal to the first PLL. An RF modulator having a first reference oscillator to impart, converting and outputting a video signal into an RF signal, a second oscillator for generating a local oscillation signal, a second PLL for controlling the oscillation frequency of the second oscillator, and a second A second reference oscillator for imparting a reference frequency signal to the PLL, and having a TV tuner for selecting and receiving a television signal, wherein the RF modulator and the TV tuner are arranged separately in a shielding case with a shielding plate; The second reference oscillator has its oscillation frequency set by one crystal oscillator shared by them.

As one suitable example in the above embodiment, the RF modulator and the TV tuner are disposed on one printed circuit board with a shield plate sandwiched therebetween, the printed circuit board having a low pass filter near the TV tuner side and the shield plate. The crystal oscillator is arranged near the RF modulator side and the first reference oscillator, and the crystal oscillator is connected to the first reference oscillator and to the second reference oscillator via the low pass filter.

In addition, as a specific example in the embodiment of the present invention, the first PLL and the second PLL each constitute a frequency synthesizer.

Example

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing the configuration of an embodiment of a high frequency device having an RF modulator and a TV tuner according to the present invention. In Fig. 1, the same components as those shown in Fig. 2 are denoted by the same reference numerals. .

As shown in Fig. 1, in the high frequency device having the RF modulator and the TV tuner of the present embodiment, each installation area of the RF modulator 1 and the TV tuner 2 is separated in one shielding case 34. A shielding plate 35 is provided, and a low pass filter 25 is disposed near the TV tuner 2 side and the shielding plate 35, and the RF modulator 1 side and the first reference oscillator 14 are disposed. The crystal oscillator 13 is disposed near the crystal oscillator, and the second oscillator 24 on the TV tuner 2 side is disposed on the TV tuner 2 side via the low pass filter 25. ) Is different from the conventional high frequency equipment shown in Fig. 2, except that it is the same as the conventional high frequency equipment.

The low pass filter 25 is a π-type low pass filter composed of one series inductor 26 and two parallel capacitors 27 and 28 respectively connected between both ends and the ground point, and one end of the series inductor 26 is The second reference oscillator 24 is connected via the capacitor 29, and the other end of the series inductor 26 is connected to the crystal oscillator 13 via the capacitor 30.

For this reason, the shielding plate 35 is a portion where the low pass filter 25 is disposed, and a portion connecting the distribution output terminal 19 of the RF modulator 1 and the RF signal input terminal 31 of the TV tuner 2. Openings 36 and 37 are formed in the recesses, respectively.

The operation of the high frequency device provided with the RF modulator and the TV tuner of the above embodiment according to the present invention is such that when the TV tuner 2 is operated, the second reference oscillator 24 is frequencyd by the resonance frequency of the crystal oscillator 13. In operation of generating a stabilized reference frequency signal, the operation is different from that of the conventional high frequency device shown in FIG. 2, but other operations are the same as the operation of the conventional high frequency device. Therefore, the description of the configuration and operation of the high frequency device including the RF modulator and the TV tuner of the present embodiment will be omitted.

As described above, according to the invention of claim 1, since the first reference oscillator of the RF modulator and the second reference oscillator of the TV tuner share a single crystal oscillator, the use of a crystal oscillator as compared to the conventional high frequency device. The number is reduced, and the effect of reducing the manufacturing cost of such a high frequency device can be obtained.

In addition, since two reference oscillators share the resonance frequency of one crystal oscillator, there is a problem that bit interference occurs due to the difference in the resonance frequencies of two crystal oscillators between the first reference oscillator and the second reference oscillator. Do not.

Further, according to the invention of claim 2, since the second reference oscillator is connected to the crystal oscillator disposed on the RF modulator side via a low pass filter disposed near the TV tuner side and the shielding plate, The oscillation signal is prevented by the low pass filter, so that the amount of leakage to the RF modulator side is very small, and the transmission from the antenna input terminal or TV output terminal formed on the RF modulator side is eliminated.

Claims (3)

A first oscillator for generating a carrier wave, A first PLL for controlling the oscillation frequency of the first oscillator; Has a first reference oscillator for applying a reference frequency signal to the first PLL, An RF modulator for converting and outputting a video signal into an RF signal; A second oscillator for generating a local oscillation signal, A second PLL for controlling the oscillation frequency of the second oscillator, A second reference oscillator for imparting a reference frequency signal to the second PLL, A TV tuner for selecting and receiving a television signal, RF modulator and TV tuner are separated by shielding plate in one shielding case, The first and second reference oscillator is a high frequency device, characterized in that the oscillation frequency is set by a common crystal oscillator. The method of claim 1, The RF modulator and the TV tuner are placed on one printed circuit board with a shield between them. On the printed circuit board, a low pass filter is disposed near the TV tuner side and the shielding plate. The crystal oscillator is disposed near the RF modulator side and the first reference oscillator, And the crystal oscillator is connected to the first reference oscillator and connected to the second reference oscillator via a low pass filter. The high frequency device according to claim 1, wherein the first PLL and the second PLL each constitute a frequency synthesizer.

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