JPS629597Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an RF modulator for video tape recorders, video disks, etc., and aims to make it more compact.

Normally, in order to reproduce video and audio signals from a video tape recorder or the like on a general home television receiver, an RF modulator is used that modulates the video and audio signals into the same radio waves as those used in general television. This RF modulator reproduces video and audio signals using the empty channels of home television receivers. However, the channel that is not being used is switched and used.

An example of the circuit of this RF modulator is shown in FIG. 1 and will be explained. The input level of the video signal is adjusted and input to a clamp circuit 1, where the DC potential at the leading end of the synchronizing signal is clamped and output to a mixing circuit 2. In addition, the audio signal is input to the FM modulation circuit 4 via the buffer amplifier circuit 3, and is input to the FM modulation circuit 4 at 4.5MHz.
The signal is converted into an FM modulation signal, the oscillation level is adjusted, and the signal is output to the mixing circuit 2. On the other hand, the resonator 5 described later
A predetermined carrier wave f is obtained by the oscillation circuit 6 and the buffer amplifier circuit 7, and is amplitude-modulated by the amplitude modulation circuit 8 using the signal from the mixing circuit 2. Then, the level of the output of the amplitude modulation circuit 8 is adjusted and the RF output is taken out via the bandpass filter 9. The circuits surrounded by broken lines in Figure 1 are all one-chip IC10
be incorporated into. Although a crystal oscillator can also be used as the resonator 5, surface acoustic wave resonators (SAW resonators) have recently been widely used due to their advantages in terms of number of parts and cost. This SAW resonator 5 has two channels stored in a package, and has an external shape in which three leads 5c are led out from an outer case 5b with a flange 5a as shown in FIG. 2, for example.

By the way, the above-mentioned RF modulator has the above-mentioned IC 10 on one printed board 11 as shown in FIG.
The printed circuit board 11 is housed in a shield case 13 on which electrical components 12 such as the SAW resonator 5 and the SAW resonator 5 are assembled. The shield case 13 surrounds the printed circuit board 11 and has a frame shape from which protrusions 11', on which the RF output terminals of the printed circuit board 11 are printed, protrude. Covers 14 and 15 are fitted. However, all the components 1 of the RF modulator circuit are mounted on one printed circuit board 11 in this way.
2, the SAW resonator 5 in particular occupies a large space and the outer diameter of the printed circuit board 11 becomes large, making it difficult to downsize the RF modulator.

The present invention has been developed to improve and eliminate the above-mentioned structural problems.The structure of the present invention will be explained below with reference to embodiments shown in the drawings.

For example, when the present invention is applied to the RF modulator circuit shown in FIG. 1, and an example of the assembled structure is shown in FIGS. 4 and 5, 16 is a main printed board, 17 is a sub-printed board, 18 is a shield case, ,2
0 is a shield cover. Most of the components 16, such as the IC 10 and the bandpass filter 9, are attached to the main printed circuit board 16. The sub printed board 17 is fixed upright on one side of the main printed board 16.
The SAW resonator 5 and its switches are attached to the . Therefore, the main printed circuit board 16 does not require a mounting space for the relatively large diameter SAW resonator 5.
The vertical and horizontal outer diameters can be made smaller by at least the amount of this mounting space.

Further, a long hole 21 is formed in a part of the main printed circuit board 16 along the sub-printed circuit board 17, and a part of the flange 5a of the SAW resonator 5 is passed through this long hole 21 to attach the SAW resonator 5. . and
The lower end m of the flange 5a of the SAW resonator 5 protruding from the back surface of the main printed circuit board 16 is brought into elastic contact with the lower shield cover 20 by utilizing the elasticity of the shield cover 20. On the other hand, the upper end n of the flange 5a of the SAW resonator 5 is slightly projected from the upper end surface of the sub-printed board 17, and this upper end m is brought into elastic contact with the upper shield cover 19. In this way, the SAW resonator 5 has shield covers 19, 20
The height of the shield case 18 is closest to the outer diameter of the SAW resonator 5, and the increase in size in the height direction is minimized.

Although it is possible to attach the IC 10 to the sub-printed board 17, since the IC 10 has as many as ten or more terminals, electrical connection between the sub-printed board 17 and the main printed board 16 becomes complicated, which is not preferable.

As explained above, according to the present invention, the outer diameter of the main printed circuit board can be reduced, making it easier to downsize the RF modulator. In fact, while the length and width of conventional RF modulators were 50 x 60 x 22 (mm), the present invention has 40 x 45 x 20 mm.
(mm), resulting in an area reduction of approximately 50%.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of an RF modulator circuit, Fig. 2 is a perspective view showing an example of a resonator used in the circuit of Fig. 1, and Fig. 3 is a partially omitted perspective view of a conventional RF modulator. FIG. 4 is a partially omitted perspective view showing an embodiment of the RF modulator according to the present invention, and FIG. 5 is a sectional view taken along the - line in FIG. 4. 5...SAW resonator, 16...Main printed board, 17...Sub printed board.

Claims (1)

[Scope of utility model registration request] An RF modulator characterized in that a sub-print board is stood upright on a main print board, and an RF modulator resonator is assembled to the sub-print board with a part of its periphery penetrating the main print board.