JP2607859Y2 - RF modulator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RF modulator, and more particularly to an RF modulator for a PAL video tape recorder. 2. Description of the Related Art R for a PAL video tape recorder
The F modulator amplifies the television signal coming into the antenna terminal by the amplifying unit and outputs the amplified signal from the video terminal to the channel selection circuit of the video tape recorder. On the other hand, a baseband video signal and a baseband audio signal from a video tape recorder are input to an input terminal, and these are RF-modulated by an RF modulator to be converted into a predetermined television signal. It is configured to output to a terminal. The RF modulator has an oscillation frequency of several hundred MHz.
It has an oscillating unit that can oscillate and output a video signal carrier that is arbitrarily variable in the band of the device and corresponds to an available channel for each region where the device is used. Is configured to be variably adjusted in accordance with The variable condenser is composed of a metal rotor and a stator, and as is well known, easily emits unnecessary radiation at a frequency of several hundred MHz. Therefore, an oscillation module is generally configured by magnetically shielding other circuits together with the inductance constituting the resonance circuit. [0005] However, in the above-mentioned conventional RF modulator, the signals input to the antenna terminal and the input terminal are extremely weak, and in order to prevent interference of the video signal carrier with each signal. There has been a problem that the above-mentioned oscillation module (oscillation unit) which is magnetically shielded is required. An object of the present invention is to provide an RF modulator in which a video signal carrier does not interfere with a television signal and a baseband video signal without magnetically shielding an oscillation section. [0007] In order to solve the above problems, the present invention is configured as follows. [0008] The present invention includes a shield case, the Ru is disposed in the shield case, and an antenna terminal for incoming television signal, a video terminal for outputting the video signal and,
A television terminal for outputting a television signal, an amplification unit for amplifying the television signal, an input terminal for inputting a baseband video signal from the outside, and an oscillation unit for oscillating and outputting a video signal carrier wave; The baseband video signal is RF-modulated based on the signal carrier, and
An RF modulating section for outputting to an external terminal, the amplifying section, the input terminal, and the RF modulating section being arranged inside the shield case, and at least first and second sides adjacent to each other; In an RF modulator including a printed circuit board having a third side facing the first side and a fourth side facing the second side, the shield case includes the third side. A claw protruding outward in a direction parallel to the first side and the third side and orthogonal to the fourth side, wherein the oscillating section has a frequency corresponding to a control signal from the outside; And the antenna terminal is located near the first side of the printed circuit board and near the second side, and the antenna terminal is near the third side. And protruding in the direction orthogonal to the printed circuit board near the fourth side. The video terminal is arranged so as to protrude from the printed circuit board in a direction parallel to the printed circuit board from the third side, and the input terminal is disposed on the first side of the fourth side of the printed circuit board. in a direction in which the claw portion is protruded in the shield case from the side near it has a configuration which protrudes in a direction parallel. According to the present invention having the above-described means, since the oscillating unit is configured to oscillate at a frequency corresponding to an external control signal, for example, a variable capacitance element such as a variable capacitor becomes unnecessary. The semiconductor device can be formed into a semiconductor, and an oscillating portion can be formed by the semiconductor device and an external tank circuit, so that unnecessary radiation is reduced. In addition, since the oscillating unit, the antenna terminal, and the input terminal are arranged at the above-described positions, the antenna terminal and the input terminal are separated from the oscillating unit by a predetermined distance.
The antenna terminal and the input terminal act so as to be hardly affected by unnecessary radiation from the oscillation unit . FIG. 1 is a perspective view showing an embodiment of the present invention, in which the inside of a shield case 1 is seen through. FIG. 2 shows the inside of the shield case 1 in FIG.
It is the top view rotated 90 degrees in the (theta) direction seen from the direction. FIG. 3 is a schematic block diagram of a modulator IC constituting a main part of the modulation unit 10. In the RF modulator according to the present invention, a printed circuit board 7 is disposed inside a metal shield case 1 in which an antenna terminal 2, a video terminal 3 and a TV terminal 4 are respectively protruded as shown in FIG. It becomes. The printed board 7 has a substantially square shape and a protruding portion 7a formed on one side thereof.
The input terminal 5 is provided at a. The input terminal 5 is provided so as to protrude from an opening (not shown) of the shield case 1 and is connected to a printed circuit board of the video tape recorder device so as to be electrically connectable to other circuits. Circuit parts of an amplifying part 8 and a modulating part 9 are respectively provided on the printed circuit board 7, and both circuit parts are separated by a shield plate (not shown) to prevent interference between signals on the board. Have been. Claw portions 6 are provided at the lower end portions on both sides of the shield case 1.
Are formed on the printed circuit board of the video tape recorder in the state shown in the figure, and are fixed to the claws 6 by soldering. FIG. 2 is a plan view in which the inside of the shield case 1 is rotated by 90 degrees in the θ direction as viewed from the direction A in FIG. A broadcast wave of a PAL television signal (hereinafter, referred to as a television signal) enters the antenna terminal 2, is amplified to a predetermined level by an amplifier 11, and is transmitted to a video terminal 3 via a distributor 13. Is output. Further, the signal is amplified by a predetermined level by the amplifier 12 and the TV terminal 4
Output to As described above, the amplification unit 8 on the printed circuit board 7
Are arranged such that the signal path is substantially straight and the shortest path. A video tape recorder supplies a baseband video signal, a baseband audio signal, a frequency control signal, a power supply, a ground, and the like to an input terminal 5 provided on the protruding portion 7a. Each of these signals is input to the modulation unit 10 disposed in the lower right portion of the printed circuit board 7 in FIG. 2 (in the vicinity of two adjacent sides), and is subjected to predetermined signal processing. . Then, the signal is output to the TV terminal 4 via the distributor 14 as an RF-modulated television signal. The modulation section 10 is generally constituted by a modulator IC 15 formed into one chip and a resonance circuit 16 externally attached to the modulator IC 15. The IFT circuit 17 and the changeover switch 18 are for variably setting the voice carrier frequency. As the modulator IC 15, for example, a one-chip IC (model TDA8720) manufactured by Philips can be used. Further, the resonance circuit 16 may use a general tank circuit including a capacitor and an inductance. Here, the modulator IC 15 (TDA8720) will be briefly described with reference to FIG. The modulator IC 15 (TDA8720) has a frequency synthesizer 20, and this frequency synthesizer 20 operates by inputting a reference clock (4 MHz) obtained from, for example, a crystal oscillator from the 10th pin. The frequency synthesizer 20 receives the serial clock SC from the video tape recorder via the input terminal 5 and the twelfth pin.
K is input, and a tuning voltage VT corresponding to the serial data SD similarly input via the 13th pin is output from the 8th pin. By inputting the tuning voltage VT to the sixth pin through an external circuit (not shown), the oscillation frequency of the UHF oscillator 21 for oscillating and outputting the video signal carrier is set to a predetermined frequency corresponding to the serial data SD. can do. The other parts of the IC have a well-known configuration as shown in the figure, and a baseband audio signal is input to pin 1 and a baseband video signal is input to pin 19, respectively. A television signal having a predetermined video signal carrier frequency is output to pins 15 and 16 in a balanced manner. Note that the frequency synthesizer 20
Is described in detail in the product specification of Philips, and therefore detailed description is omitted here. As described above, the oscillating unit 10 of this embodiment can variably set the video signal carrier frequency in accordance with an external control signal (serial data SD), and it is not necessary to use a variable condenser or the like as in the prior art. Since the oscillation unit 10 is made into a semiconductor and high-density mounting becomes possible, unnecessary radiation is less likely to be emitted as compared with the related art. Therefore, there is no need to provide a magnetic shield. In addition, in FIG. 2, the antenna terminal 2 is connected to the modulating unit 10 disposed in the lower right portion of the printed circuit board 7 (position near the two sides S ₁ and S ₂ adjacent to each other).
Are two adjacent sides S ₁ , S ₂ of the printed circuit board 7 which are different from the two adjacent sides S ₁ , S ₂ of the printed circuit board 7 on the surface of the shield case (1) which is substantially parallel to the board surface of the printed board 7.
_3, is disposed in the vicinity with respect to S _4, the input terminal 5, either one vicinity of S ₄ other mutually adjacent two sides S _3, S ₄ of the printed circuit board 7 (the protrusion 7a) The antenna terminal 2 and the input terminal 5 are respectively connected to the oscillation unit 1
0 and a predetermined distance. Therefore, since the antenna terminal 2 and the input terminal 5 are hardly affected by unnecessary radiation from the oscillating unit 10, the television signal through which the video signal carrier enters the antenna terminal 2 without shielding the oscillating unit 10. It does not interfere with the signal or interfere with the baseband video signal coming into the input terminal 5 to cause interference in the RF modulation signal, thereby deteriorating image quality and sound quality. The shape of the input terminal 5 and the shape of the printed circuit board 7 are not limited to those of the present embodiment, and the circuit section on the printed circuit board 7 and the external circuit are electrically connected via the input terminal 5. Any configuration can be used as long as the connection is possible. As described above, according to the present invention, unnecessary radiation of the video signal carrier from the oscillating unit is reduced as compared with using a variable condenser or the like, and the antenna terminal and the input terminal are connected to the oscillating unit, respectively. It is arranged at a predetermined distance and is less susceptible to unwanted radiation from the oscillating unit, so even if the oscillating unit is not shielded, the video signal carrier may interfere with the television signal entering the antenna terminal or There is a feature that image quality and sound quality are not impaired by interfering with an incoming baseband video signal and disturbing an RF modulation signal.

[Brief description of the drawings] FIG. 1 is an external perspective view of an embodiment of the present invention. FIG. 2 is a plan view of a main part of one embodiment of the present invention. FIG. 3 is a block diagram of a main part of one embodiment of the present invention. [Explanation of symbols] 1 shield case 2 Antenna terminal 3 Video terminal 4 TV terminal 5 Input terminal 7 Printed circuit board 8 Amplifier 9 RF modulator 10 Oscillator 20 frequency synthesizer 21 UHF oscillator

Claims (1)

(57) [range claims as] and [Claim 1] shield case, Ru is disposed on the shield case, and an antenna terminal for incoming television signal, a video terminal for outputting the video signal and, Television
A television terminal for outputting a television signal, an amplifying unit for amplifying the television signal, an input terminal for inputting a baseband video signal from outside, and an oscillating unit for oscillating and outputting a video signal carrier. The baseband video signal is RF-modulated based on the signal carrier and transmitted to the television terminal.
An output RF modulator, the amplifier, the input terminal, and the RF
A modulating unit disposed inside the shield case, and at least first and second sides adjacent to each other;
A third side facing the second side and a fourth side facing the second side.
And a printed circuit board having a shape having the following sides: wherein the shield case is parallel to the first side and the third side and orthogonal to the fourth side. The oscillating portion is configured to oscillate at a frequency corresponding to a control signal from the outside, and is near the first side of the printed circuit board; The antenna terminal is disposed near the second side, and is disposed near the third side and protrudes near the fourth side in a direction orthogonal to the printed circuit board. The video terminal is arranged so as to protrude from the printed circuit board in a direction parallel to the printed circuit board from the third side, and the input terminal is the first side of the fourth side of the printed circuit board. before from the vicinity of the shield case RF modulator which protrudes in a direction parallel to a direction in which the claw portion is protruded.