KR980012979A - High Frequency Equipment (Video Equipment) with RF Modulator and 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 shielding plate 35 is disposed separately from the shielding case 34 of the RF modulator 1 and the TV tuner 2. The oscillation frequency of the first reference oscillator 14 of the RF modulator 1 and the second reference oscillator 24 of the TV tuner 2 are set by one crystal oscillator 13 common to them. In the printed circuit board 38 on which the RF modulator 1 TV tuner 2 is arranged, a low pass filter 25 is arranged near the TV tuner side and the shield plate 35, and the RF modulator side and the first reference. The crystal oscillator 13 is disposed near the oscillator 14, and the crystal oscillator 13 is connected to the first reference oscillator 14 and is connected to the second reference oscillator 24 via the low pass filter 25. Connected.

Description

[Brief Description of Drawings]

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 for the main parts of the drawings

1: RF modulator 2: TV tuner

10: modulated 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: shield plate

38: printed circuit board

Detailed description of the invention

[Purpose of invention]

[Technical Field to which the Invention belongs and Prior Art in the Field]

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 inside a video casset recorder (VCR) or the like.

In a typical VCR, 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 are assembled.

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 have one shield case. It is attached to the printed circuit board 38 which is common to 34. In the shielding case 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. As shown in FIG.

The RF modulator 1 comprises a modulation stage 10, an antenna input terminal 15, an IRF amplifier, a signal divider 5, a second RF amplifier, a signal mixer 7, a TV output terminal 16, and a distribution output terminal. (19) is provided. The modulation stage 10 includes a first phase locked loop (IPLL) 12 including a first oscillator 11 and a first reference oscillator 14 generating a reference frequency signal stabilized by the crystal oscillator 13. ), 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 includes at least a tuning unit 27 and an RF signal input terminal 31. Among them, the slave unit 20 includes a second PLL 22 including a second oscillator 21, a second reference oscillator 24 and an IF signal output terminal for generating a reference frequency signal stabilized by the crystal oscillator 23. (32), the second oscillator 21, the second PLL 22, the crystal oscillator 23, and the second reference oscillator 24 constitute a second frequency synthesizer.

In addition, the crystal oscillator 13 uses a resonance at 47 MHz, for example, and the crystal oscillator 22 uses a resonance 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 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. The carrier frequency and the reference frequency signal are compared with each other in the IPLL 12 to stabilize the frequency of the carrier wave. The 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. The RF modulated signal is input to the signal combiner 7 at the modulation stage 10 and, in the signal combiner 7, the TV broadcast signal inputted via the second RF amplifier 6 at the signal divider 5. They are mixed and supplied to the antenna connection terminal of the television receiver (not shown) via the TV output terminal 16.

Next, when the TV tuner 2 is operated, 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 modulated 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. Is supplied).

[Technical task to achieve the invention]

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 and is manufactured. There is a problem that the cost is expensive.

As described above, the crystal oscillator 13 and the crystal oscillator 23 have a resonance frequency of slightly different at 4 MHz and 3.5 MHz, so that these crystal oscillators 13 and 23 can be used. The resonance frequencies interfere with each other, causing a problem of bit interference.

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). There is an inevitable difference that prevents bit interference.

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

In order to achieve the above first and second purposes, a high frequency device including the RF modulator and the TV tuner of the present application is disposed on one printed circuit board with a shield plate between the RF modulator and the TV tuner. Being. On the printed circuit board, a low pass filter is arranged near the TV tuner side and the shielding plate, and a 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. A second means connected to the second reference oscillator is provided via a 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 the antenna is reduced, and the two reference oscillators share one resonant frequency with one crystal oscillator, so that bit interference does not occur 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 externally transmitted from the antenna input terminal 15 or the TV output terminal 16.

[Configuration and Function of Invention]

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; and a first PLL for controlling an oscillation frequency of the first oscillator. An RF modulator for converting a video signal into an RF signal, a second oscillator for generating a local oscillation signal, and an oscillation frequency of the second oscillator; And a second reference oscillator for controlling and a second reference oscillator for giving a reference frequency signal to the second PLL, the TV tuner for selecting and receiving a television signal. The RF modulator and the TV tuner are divided into shield plates in one shielding case, and the first and second reference oscillators are set in oscillation frequency 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 disposed near the RF modulator side and the first reference oscillator. The crystal oscillator is connected to the first reference oscillator and is connected 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 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. have. As shown in Fig. 1, in the high frequency device including the RF modulator and the TV tuner of the present embodiment, the installation area ratios of the RF modulator 1 and the TV tuner 2 are separated in one shielding case 34. The shield plate 35 is provided, the low pass filter 25 is disposed near the TV tuner 2 side and the shield plate 35, and the RF modulator 1 side and the first reference oscillator 14 are disposed. The crystal oscillator 130 is disposed near the crystal oscillator 130, and the second oscillator 24 on the TV tuner 2 side is a low frequency filter 25, and the crystal oscillator is disposed on the TV tuner 2 side. Although the configuration is different from that of the conventional high frequency equipment shown in Fig. 2 in that it is connected to (13), it is the same as the structure of 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 2 is connected via the capacitor 29, and the other end of the series inductor 27 is connected to the quartz crystal oscillation 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.

The operation of the high frequency device including the RF modulator and the TV tuner of the embodiment according to the present invention is such that when the TV tuner 2 is operated, the second reference oscillator 24 causes the frequency 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.

[Effects of the Invention]

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 one crystal oscillator. Compared with the conventional high frequency device, the number of crystal oscillators used is reduced, so that the manufacturing cost of the high frequency device can be reduced.

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 seven crystal oscillators between the first reference oscillator and the second reference oscillator. Do not.

Further, according to the invention of claim 2, the second reference oscillator is connected to the crystal oscillator arranged on the RF modulator side via the low pass filter rate arranged near the TV tuner side and the shield plate. Local oscillation signals from the TV tuner are blocked by the low pass filter. The effect is that the amount of leakage to the RF modulator side is very small and no transmission is made externally from the antenna input terminal or the TV output terminal formed on the RF modulator side.

Claims (3)

A first oscillator for generating a carrier, an IPLL for controlling the oscillation frequency of the first oscillator, and a first reference oscillator for applying a reference frequency signal to the IPLL. 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, and a second reference for giving a reference frequency signal to the second PLL One crystal oscillator having an oscillator and having a TV tuner for selecting and receiving a television signal, wherein the RF modulator and the TV tuner are divided into shield plates in one shielding case, and the first and second reference oscillators are shared. High frequency equipment characterized in that the oscillation frequency is set by, 713. The RF modulator and TV tuner of claim 711, wherein the RF modulator and the TV tuner are disposed on one printed circuit board with a shield plate interposed therebetween, wherein a low pass filter is disposed near the TV tuner, i.e., the shield plate in the printed circuit board. And the crystal oscillator in the vicinity of the first reference oscillator. And the crystal oscillator is connected to the first reference oscillator. A high frequency device that taps connected to a second reference oscillator via a low pass filter. The high frequency device according to claim 1, wherein each of said IPLL and said 2 PM.on constitutes a frequency synthesizer. ※ Note: The disclosure is based on the initial application.