JPH0448025Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is applicable to, for example, a magnetic recording/reproducing device (hereinafter simply referred to as VTR) and a television receiver (hereinafter simply referred to as VTR).
This relates to a simple television transmitter used as an interface between a TV and a TV, in which an external board is formed extending outside the case, and wiring for multiple input signal terminals formed on the board. By forming a ground pattern near the pattern and providing a capacitor between these wiring patterns and the ground pattern, electrical characteristics such as oscillation of the oscillator and modulation of the modulator can be stabilized. It is an object of the present invention to provide a simple television transmitting device that reduces electrical interference between terminals and unnecessary radiation, and is easy to assemble.

FIG. 1 is a block diagram of a simple television transmitter. A broken line 1 indicates a case in which each circuit block is incorporated. Tv and Ts are respectively a video signal supply terminal and an audio signal supply terminal;
Vcc indicates a power supply terminal. The video signal from the terminal Tv is amplified by the amplifier 2 constituting the video signal processing circuit, and then the main carrier signal from the oscillator OSC is amplitude-modulated by the first amplitude modulator AM1, and the modulated wave signal is is supplied to the sum circuit SC.
On the other hand, the audio signal from terminal Ts is transmitted to the FM modulator FM, which constitutes the audio signal processing circuit, at 4.5M.
Frequency modulates the Hz subcarrier and its output is an oscillator
The main carrier signal from the OSC is transferred to the second amplitude modulator AM
2, the output of the modulated wave signal is supplied to the sum circuit SC. The output signal of the summation circuit SC is output to the output terminal To, and then connected to the antenna terminal of the TV (not shown).

FIG. 2 is a rear perspective view with the cover removed of a conventional simple television transmitter incorporating the circuit block described above.

Reference numeral 1 indicates a case, 3 a printed circuit board, 4 an external board protruding outside the case through the case opening window H, and 6 a male connector having plug pins attached to the upper surface of the external board 4. A portion of the printed circuit board 3 shown in a satin pattern indicates a ground pattern G. The video signal supply terminal Tv, the audio signal supply terminal Ts, and the power supply terminal Vcc are connected to wiring patterns Pv, Ps, and Connected to a PC. Plug pin terminals of the connector 6 penetrate from the surface of the external board 4 and are soldered to the ends of these patterns.

Furthermore, between the wiring pattern Pc for the power supply terminal Vcc and the wiring pattern Ps for the audio signal supply terminal Ts, and between the wiring pattern Ps for the audio signal supply terminal Ts and the wiring pattern Pv for the video signal supply terminal Tv. are provided with ground patterns G ₁ and G ₂ , respectively. In this way, a signal input terminal section is configured on the external board 4. Earth pattern G ₁ ,
G ₂ has two loose terminals 11, 12 and 13, 14 soldered to each G 2 to prevent signal interference between the terminals. The ground patterns G ₁ and G ₂ are provided with protrusions 7 and 8 on the case 1 at the case opening window H, and the protrusions 7 and 8 are connected to the ground patterns.
G ₁ and G ₂ are soldered and electrically connected to another ground pattern G shown in a matte pattern through the case 1. S ₁ , S ₂ , and S ₃ are respectively case 1
This is the location where the ground pattern G and the ground pattern G are soldered.

In such a conventional simple television transmitting device, there are an audio subcarrier and a main carrier, and these are connected to a video signal supply terminal Tv and an audio signal supply terminal.
There is a problem in that unnecessary radiation is emitted to the outside through Ts and interferes with other communications.

Further, in order to measure electrical continuity between the ground patterns G ₁ and G ₂ with other ground patterns G, the protrusions 7 and 8 of the case 1 are provided, and the ground patterns G ₁ and
There is a problem that it is necessary to solder G ₂ and the number of soldering steps increases. Moreover, the external board 4
In order to protrude outside the case 1, use the case opening window H.
It is necessary to pass. However, this case opening window H is formed with two protrusions 7 and 8, and the width of the case opening window H is very large in order to prevent external noise and unnecessary radiation from the oscillator OSC. It is formed small. Therefore, there is a problem in that the operation of passing the external board 4 through the case opening window H is structurally extremely difficult and time consuming.

Furthermore, another problem is that the ground pattern must have the same potential at all parts, but in this device, the ground patterns G ₃ and G ₄ near both ends of the case opening window H have the same potential at the ends. Therefore, it is difficult to reach the same potential, and as a result, there are problems in that the oscillation of the oscillator becomes unstable and the modulation of the modulator becomes unstable.

The present invention includes a video signal processing circuit for processing a video signal from a video signal supply terminal and an audio signal processing circuit for processing an audio signal from an audio signal supply terminal. In a simple television transmitter used as an interface with a television receiver, each of the terminals is placed on an external board formed by extending a part of the printed wiring board outside the case through a case opening formed by a notch. At the same time, a wiring pattern for each of these terminals is formed extending from a printed wiring board inside the case onto the external board, and a ground pattern is formed near each wiring pattern, A capacitor is connected near the case opening and at least one of between the wiring pattern for the audio signal supply terminal and the ground pattern, and between the wiring pattern for the audio signal supply terminal and the ground pattern. If it is between the wiring pattern for the supply terminal and the ground pattern, the capacitance Cv of the capacitor is within the range of 1/2πvZvo＞Cv≫1/2πvoZvo (however,
v is the highest frequency on the input side input to the video signal supply terminal, vo is the oscillation frequency for the video signal in the device, Zvo is the impedance on the video signal processing circuit side), and the wiring pattern for the audio signal supply terminal and the above If between the ground pattern, the capacitance Cs of the capacitor is within the range of 1/2πsZso＞Cs≫1/2πsoZso (however, s
is the highest frequency on the input side input to the audio signal supply terminal, so is the oscillation frequency for the audio signal in the device,
Zso is the impedance on the audio signal processing circuit side).

Embodiments of the present invention will be described below with reference to FIGS. 3 to 6. Note that the same parts as in FIGS. 1 and 2 are denoted by the same reference numerals, and explanations thereof will be omitted.

In FIG. 3, the signal input terminal section on the external board 4 is different from that shown in FIG. 2 in that a ground pattern shown in a satin pattern is arranged around the wiring patterns Pv, Ps, and Pc. The ground patterns G ₃ and G ₄ at both ends of the case opening 5 formed by the notch are connected by the ground patterns around the wiring patterns Pv, Ps, and Pc, and their potentials are maintained at the same potential. In order to maintain the same potential in this way, the ground pattern between ground patterns G ₃ and G ₄ must be
It is desirable that G ₆ be placed at the shortest distance. In order to do this, the end of each wiring pattern located inside the case must be placed closer to the case opening 5 in the case 1, and the end portion of each wiring pattern located inside the case must be placed close to the case opening 5 in the case 1, and the end portion of each wiring pattern must be placed as shown in FIG. The circuit element Q is inserted from the top surface of the printed circuit board 3 and soldered on the back surface thereof. Therefore, the ground pattern _G6 is placed between the terminals of the circuit element Q on the back side of the substrate.

Between wiring patterns Pc and Ps and wiring pattern
Earth pattern G ₁ placed between Ps and Pv,
Since G ₂ is formed integrally with the ground pattern arranged around them, there is no need for special grounding by other means as in the conventional example. It is best to connect the ground patterns G ₁ and G ₂ to both the ground patterns G ₅ and G ₆ on the tip of the external board 4 and on the printed circuit board 3 side inside the case as in this embodiment. However, the present invention is not limited to this, and the initial purpose can be sufficiently achieved even if the ground pattern is connected to either one of the ground patterns G ₅ and G ₆ .

Note that since the case opening 5 is covered with the hakama of the back cover (not shown), there is no problem with external noise and unnecessary radiation.

Next, Cv, Cs, and Cc are chip-shaped capacitors. As mentioned above, in Case 1, there are the 4.5 MHz audio subcarrier and the 600 MHz main carrier frequency, and these are unnecessarily radiated to the outside through the video signal supply terminal Tv and the audio signal supply terminal Ts, causing other interference. There is a problem in that it interferes with communication.
To prevent this, as shown in FIG. 1, capacitors are provided on the input sides of the amplifier 2 and the FM modulator FM. Furthermore, a capacitor is also connected to prevent external noise from entering the case from the power supply terminal Vcc. Specifically, chip-shaped capacitors are installed between each of the wiring patterns Pv, Ps, and Pc connected to the video signal supply terminal Tv, audio signal supply terminal Ts, and power supply terminal Vcc, respectively, and the ground pattern. Cv, Cs,
Cc is connected. These capacitors are
In order to improve the effect of removing unnecessary radiation and external noise, the closer the sensor is to the case opening 5, the better.

The capacitances of capacitors Cv, Cs, and Cc are determined as follows.

Figure 4 A and B are video signal supply terminals, respectively.
Tv shows the equivalent circuit of the audio signal supply terminal Ts part, Zvs and Zss show the impedance of the input signal source side connected to the video signal supply terminal Tv and the audio signal supply terminal Ts, and Zvo and Zso show the impedance of the amplifier 2 and the audio signal supply terminal Ts. The input impedance of the FM modulator FM is shown. Video signal supply terminal Tv and audio signal supply terminal
The highest frequency on the input side input to Ts is
If the oscillation frequencies in the simple television transmitter are vo and so, respectively, then in order to improve the unnecessary radiation and external noise removal characteristics, capacitors Cv and Cs should be determined. It is necessary to satisfy the following relationship.

For capacitor Cv, 1/2πvCv＞Zvo, 1/2πvoCv≪Zvo, so, 1/2πvZvo＞Cv≫1/2πvoZvo, while for capacitor Cs, 1/2πsCs＞Zso, 1/2πsoCs≪Zso, so Therefore, 1/2πsZso＞Cs≫1/2πsoZso, Usually the frequency v is 4.5MHz to 6MHz, vo is maximum 885.25MHz, and the input impedance Zvo=
For 75Ω, the capacitance of capacitor Cv is 2.4 to 471PF.

On the other hand, for capacitor Cs, the frequency fs is
7.5 to 15kHz, frequency so is maximum 6.5MHz, impedance Zso is 10kΩ to several tens of kΩ, so 0.25
~1061PF.

Incidentally, in this invention, the video signal supply terminal Tv is v:vo=5MHz:600MHz, Zvo=75Ω, Cv=
It is set to 100PF, 1/2πvCv=318Ω, 1/2πvoCv=2.7Ω.

On the other hand, for the audio signal supply terminal Ts, s:so=15kHz:4.5MHz, Zso=100kΩ, Cs=
It is set to 50PF, 1/2πsCs = 212kΩ, 1/2πsoCs = 580Ω.

Since the power supply terminal Vcc is a DC component and there is no signal passing through it, the capacitance of the capacitor Cc should be large, preferably about 1000PF.

5 and 6 show side views of a simple television transmitter, and the capacitor C in FIG.
(Cv, Cs, Cc) shows an example using discrete type capacitors.

Note that, as shown in FIG.
It has the advantage that the dead space on the bottom surface can be used effectively.

As mentioned above, in the present invention, the external board is formed to extend outside the case, and the ground pattern connected to the ground pattern on the printed circuit board is provided near the terminal wiring pattern formed on this external board. The ground potentials of the ground patterns can be kept at the same potential, and as a result, the oscillation of the oscillator becomes stable, and the modulation characteristics of the modulator become stable.

Further, by connecting a capacitor near the case opening between the input terminal of the modulator and the ground pattern and between the input terminal of the amplifier and the ground pattern, unnecessary radiation to the outside can be prevented.

In addition, since the earth patterns G ₁ and G ₂ are printed with the same material as the other earth patterns, a stable earth pattern layer can be formed reliably.
Moreover, as a result, Vcc−Ts and Ts−Tv between the terminals
can be shielded, and signal interference between these terminals can be prevented.

Furthermore, as in the conventional example, the ground patterns G ₁ and G ₂
Since there is no need to provide protrusions on the corresponding case or solder them, the number of assembly steps is reduced. The case opening is not a window type like in the conventional example, but is open at the top (as viewed in the drawing), so that it has various effects such that inserting and fixing the board is much easier than in the conventional example.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a simple television transmitter, FIG. 2 is a rear perspective view of a conventional simple television transmitter, and FIG. 3 is a rear view of a simple television transmitter according to the present invention. Perspective view, 4th
Figures A and B are electrical equivalent circuit diagrams of the terminals Tv and Ts, Figure 5 is a partially cutaway side view of the simple television transmitter shown in Figure 3, and Figure 6 is a discrete circuit diagram of the capacitor C. A side view when using a capacitor is shown. 1 is a case, 3 is a printed circuit board, 4 is an external board, 5 is a case opening, 6 is a connector, Tv is a video signal supply terminal, Ts is an audio signal supply terminal, Vcc
is the power supply terminal, To is the output terminal, Pv, Ps, Pc are the wiring patterns, G, G ₁ , G ₆ are the ground patterns,
5.H is the case opening window, and Cv, Cs, and Cc are the capacitors.

Claims (1)

[Claims for Utility Model Registration] Includes a video signal processing circuit for processing a video signal from a video signal supply terminal and an audio signal processing circuit for processing an audio signal from an audio signal supply terminal. In a simple television transmitting device used as an interface between the device and a television receiver, a part of the printed wiring board is led out of the case through a case opening formed by a cutout, and placed on an external board formed by extending it. In addition to providing each of the terminals, a wiring pattern for each of these terminals is formed extending from a printed wiring board inside the case onto the external board, and a ground pattern is formed near each wiring pattern. A capacitor is connected near the case opening at least one of between the wiring pattern for the signal supply terminal and the ground pattern and between the wiring pattern for the audio signal supply terminal and the ground pattern. , if it is between the wiring pattern for the video signal supply terminal and the ground pattern, the capacitance Cv of the capacitor is within the range of 1/2πvZvo＞Cv≫1/2πvoZvo (however,
v is the highest frequency on the input side input to the video signal supply terminal, vo is the oscillation frequency for the video signal in the device, Zvo is the impedance on the video signal processing circuit side), and the wiring pattern for the audio signal supply terminal and the above If between the ground pattern, the capacitance Cs of the capacitor is within the range of 1/2πsZso＞Cs≫1/2πsoZso (however, s
is the highest frequency on the input side input to the audio signal supply terminal, so is the oscillation frequency for the audio signal in the device,
A simple television transmitter characterized in that Zso is the impedance on the audio signal processing circuit side.