JPS6221074Y2 - - Google Patents

Description

[Detailed description of the invention] The invention is based on, for example, a magnetic recording/reproducing device (hereinafter simply referred to as
VTR) and television receivers (hereinafter simply referred to as
It pertains to a simple television transmitter used as an interface between
An external board is formed extending outside the case, and by surrounding the terminal wiring pattern formed on the board with a ground pattern, various 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 adjacent terminals and is easy to assemble.

FIG. 1 shows a block diagram of a simple television transmitter. A dotted line 1 indicates a case in which each circuit block is incorporated. Tv and Ts are terminals to which video signals and audio signals are supplied, respectively, and Vcc
indicates the terminal to which power is supplied. After the video signal from the terminal Tv is amplified, the main carrier signal from the oscillator is amplitude-modulated, and the modulated wave signal is supplied to the sum circuit. The audio signal from the other terminal Ts is
A 4.5 MHz subcarrier is frequency modulated, its output amplitude modulates the main carrier signal from the oscillator, the output modulated wave signal is supplied to the sum circuit, and the output signal is output to the output terminal To. , and then connected to the antenna terminal of the TV (not shown).

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

1 is a simple television transmitter case, 3
Reference numeral 4 indicates a printed circuit board, 4 indicates an external terminal projecting outside the case through the case opening window H, and 6 indicates a male connector having a plug pin attached to the upper surface of the external board. The portions of the substrate 3 indicated by a satin pattern indicate the earth pattern G. The video signal supply terminal Tv, the power supply terminal Vcc, and the audio signal supply terminal Ts are each provided with wiring patterns on the external board 4 extending from the board 3 inside the case 1 at right angles to the case opening window H. A plug pin terminal of the connector 6 is soldered to the external board 4 by penetrating it from the surface thereof.

In addition, between terminals Vcc and Ts and between Ts and Tv, there are 11,
There are idle terminals soldered to the two ground patterns _G1 and _G2 shown at 12, 13, and 14, but this is to prevent signal interference between the terminals. . Pc, Ps and Pv are
This is a wiring pattern connected to each terminal of Vcc, Ts, and Tv. The ground patterns G ₁ and G ₂ are provided with protrusions 7 and 8 on the case 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 3 shown in a satin pattern through the case 1. S ₁ , S ₂ , and S ₃ are the parts where the earth pattern 3 and the case 1 are soldered.

In such a conventional simple television transmitter, in order to establish electrical continuity between the ground patterns G ₁ and G ₂ and the other ground pattern 3, protrusions 7 and 8 are provided on the case, and the protrusions 7 and 8 are connected to the ground patterns G ₁ and G 2 . There is a problem that it is necessary to solder 2 and ₂ , which increases the number of soldering steps. Furthermore, in order to project the external board 4 out of the case, it is necessary to pass through the case opening window H, but this opening window H has two protrusions 7 and 8 formed therein.
Since the width of the opening window H is very small in order to prevent external noise and unnecessary radiation from the oscillator, it is structurally very difficult to pass the external board 4 through the opening window H. The problem is that it takes time. 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 opening window H are at the same potential because they are at the ends. 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 eliminates the various problems mentioned above, and one embodiment thereof will be described with reference to the drawings shown below. Note that the same parts as in FIGS. 1 and 2 are given the same reference numerals, and the explanation thereof will be omitted.

FIG. 3 shows an embodiment of the present invention, in which a ground pattern shown in a satin pattern is arranged around the wiring patterns Pc, Ps, and Pv, and ground patterns G ₃ , _G4 is connected by the ground pattern around the wiring patterns Pc, Ps, and Pv, and their potentials are maintained at the same potential. In order to maintain this same potential, it is desirable that the ground pattern G ₆ between the ground patterns G ₃ and G ₄ is arranged at the shortest distance, so that the end of each wiring pattern on the board 4 side inside the case is 1 near the case opening 5, as shown in FIG.
The circuit element Q is inserted from the top surface of the board 3 in the same manner, and soldered on the back surface thereof. Therefore, the earth pattern
G ₆ is placed between the terminals of the circuit element Q on the back side of the substrate.

The ground patterns G ₁ and G ₂ arranged between the wiring patterns Pc and Ps and Ps and Pv are formed integrally with the ground patterns arranged around them, so that other There is no need to provide special grounding. Note that it is most optimal for the ground patterns G ₁ and G ₂ to be connected to the ground patterns G ₅ and G ₆ on both the tip side of the external board 4 and the case inner board 3 side, as in this embodiment. However, it is not limited to this, and the desired purpose can be sufficiently achieved even if the connection is made to either G ₅ or G ₆ .

Note that the case opening 5 is a back cover (not shown).
Because it is covered by a hakama, there are no problems with external noise or unnecessary radiation.

Next, Cc, Cs, and Cv represent chip-shaped capacitors, and as mentioned above, the audio subcarrier frequency of 4.5MHz and the main carrier frequency of 600MHz exist within the case, and these are externally transmitted through the terminals Tv and Ts. There is a problem that unnecessary radiation is caused by the FM transmitter, which may harm other communications. To prevent this, a capacitor is installed on the input side of the amplifier and FM modulator. Furthermore, a capacitor is connected from the power supply terminal Vcc to prevent external noise from entering the case. Chip capacitors Cv, Cc, and Cs are connected between the wiring patterns Pv, Pc, and Ps, which are connected to the terminals of Tv, Vcc, and Ts, and the ground pattern, respectively. The closer these capacitors are to the case opening, the better in order to improve the effectiveness of removing unnecessary radiation and external noise.

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

Figures 4A and B show equivalent circuits of the terminals Tv and Ts, Zvs and Zss indicate the impedance on the input signal source side connected to the terminals Tv and Ts, and Zvo and
Zso indicates the input impedance of the amplifier 2 and the FM modulator. Then, if the highest frequencies on the input side input to terminals Tv and Ts are respectively v and s, and the oscillation frequencies in the simple television transmitter are vo and so, respectively, unnecessary radiation and external noise removal characteristics are improved. capacitor to
When determining Cv and Cs, the following relationship must be satisfied.

1/2πvCv＞Zvo, 1/2πvoCv≪Zvo 1/2πsCs＞Zso, 1/2πsoCs≪Zso Incidentally, in this invention, for the video signal terminal Tv, v:Vo=5MHz:600MHz Zvo=75Ω, Cv=100PF Set, 1/2πvCv=318Ω, 1/2πvoCv=2.7
Ω.

On the other hand, for the audio signal terminal, set s:so=15KHz:4.5MHz Zso=100KΩ, Cs=50PF, 1/2πsCs=212KΩ, 1/2πsoCs=58
It is set to 0Ω.

Since the power supply terminal Vcc is a DC component and there is no signal that passes through it, the larger the capacitance of the capacitor Cc, the better.
It is set at 1000PF.

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

The use of chip-shaped capacitors as shown in FIG. 5 has the advantage that the dead space on the lower surface of the external board 4 to which the connector 6 is attached can be used more effectively.

As described above, in the present invention, the external board is formed to extend outside the case, and the terminal wiring pattern formed on the board is surrounded by the ground pattern, so that the ground patterns G ₃ , G at both ends of the opening 5 ₄ 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 also become stable. Since the ground patterns G ₁ and G ₂ are printed using the same pattern material as the other ground patterns, a stable ground pattern layer can be formed reliably, and Vcc-Ts and Ts-Tv between the input terminals can be maintained. It can be shielded and prevent signal interference between these terminals. Further, unlike the conventional example, it is not necessary to provide the protrusions 7 and 8 on the case corresponding to the ground patterns G ₁ and G ₂ and to solder them, thereby reducing the number of assembly steps. Since the opening 5 is not a window type like in the conventional example, but is open at the top (as viewed in the drawing), it has various effects such that insertion and fixation of 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 perspective view of a transmitter according to the present invention. Figures 4A and B are electrical equivalent circuit diagrams at terminals Tv and Ts.
The figure is a partially cutaway side view of the transmitter shown in Figure 3.
FIG. 6 shows a side view of a case where a discrete capacitor is used as the capacitor C. 1...Case, 3...Case internal board, 4...External board, 5...Case opening, 6...Connector, 7, 8...Protrusion, Tv...Video signal supply terminal, Ts... Audio signal supply terminal, Vcc...power supply terminal, To...output terminal, Pv, Pc, Ps...
Wiring pattern, G _1~4 ...Earth pattern, H...
...Case opening window, Cc, Cs, Cv...Capacitor.

Claims (1)

[Scope of utility model registration request] 1. A simple television transmitting device characterized in that an external board is formed to extend outside the case, and a terminal wiring pattern formed on the board is surrounded by a ground pattern.