JPS5899020A - High-frequency input device - Google Patents

Abstract

PURPOSE:To improve high frequency characteristics, by connecting an outer conductor of a coaxial cable to two side walls of a shield case via a capacitor and connecting an inner conductor of the coaxial cable to a transformer having 1:1 impedance ratio and an HPF. CONSTITUTION:Holes are drilled to two side walls of a box type shield case 1, one electrode of disc capacitors C2, 3 is connected to the case 1 and the other electrode of the C2, 3 is to an outer conductor of coaxial cables 4, 5. In the inside of the case 1, one end of a primary winding 6a of a transformer 6 having 1:1 impedance ratio is connected to the inner conductor of the coaxial cable 4, the other end of the winding 6a is to the outer conductor of the coaxial cable 4, and the inner conductor of the coaxial cable 5 is connected to an HPF7. The secondary winding 6b of the transformer 6 and the other end of the HPF coil 7 are connected to the case 1. The C2, and C3 show a low impedance at high frequencies, the coaxial cables 4, 5 and the case 1 are completely shielded and no external interference electromagnetic waves can be intruded. The transformer 6 and the HPF7 transmit desired freuencies of high frequency band with low loss and unnecessary radiation of low frequencies receives large attenuation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency input device that is effective for coupling between a transformerless television receiver and an antenna, and particularly to an input device that requires double insulation. It prevents the leakage of unnecessary radiation generated from inside the receiver, prevents the intrusion of interference waves from the outside, and improves high frequency characteristics.

The purpose is to

Conventionally, this type of high-frequency input device, whose main purpose was to prevent the outflow of unnecessary radiation generated from inside the receiver, had problems with the intrusion of interference waves from the outside and poor high-frequency characteristics.
On the other hand, those whose main purpose was to prevent the intrusion of interference waves from the outside and improve high-frequency characteristics had the disadvantage that a large amount of unnecessary radiation generated from inside the receiver leaked out.

The present invention improves the above-mentioned conventional drawbacks, and embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, holes are made in two side walls of a box-shaped shield case 1, and one electrode of each of the disk-shaped or cylindrical feed-through capacitors 2 and 3 is connected to the shield case 1. Coaxial cables or outer conductors of coaxial connectors 4 and 5 are connected to the other electrodes of the feedthrough capacitors 2 and 3, respectively. Inside the shield case 1,
The inner conductors of the coaxial cable or coaxial connector (hereinafter referred to as coaxial) 4 and 5 have an input/output impedance ratio of 1.
=1 transformer 6 and bypass filter 7. Here, one end of the primary winding 6a of the transformer 6 is connected to the inner conductor of the coaxial 4, and the other end is connected to the outer conductor of the coaxial 4.

Further, one end of the secondary winding 6b of the transformer 6 is connected to one terminal of the bypass filter 7, and the other end is connected to the shield case 1. ...The other terminal of the Ibus filter 7 is connected to the inner conductor of the coax 6. With this configuration, the outer conductors of coax 4 and coax 6 are connected to two feedthrough capacitors 2 and 3.
and the inner conductors of coax 4 and coax 5 are connected to transformer 6.
And... They are insulated by the series capacitor of the I-pass filter 7, and both the outer conductor and the inner conductor have a double insulation structure.

Next, the operation of the high frequency input device of the present invention will be explained.

In Fig. 1, the disk-shaped or cylindrical feed-through capacitors 2 and 3 are coupled with low impedance in high frequency bands, and are completely shielded by the coaxes 4, 5 and the shield case 1, so there is no interference from the outside. It can prevent the intrusion of radio waves. On the other hand, the feedthrough capacitors 2 and 3 have high impedance in a low frequency band, and no signal is transmitted from the outer conductor of the coax 4 to the coax 6 via the shield case 1.

Next, the transmission characteristics of the transformer 6 and bypass filter 7 are as follows:
Insertion loss is small in high frequency bands and large attenuation in low frequency bands. Therefore, the desired signal in the high frequency band is transmitted with low loss, and unnecessary radiation components of relatively low frequency generated inside the receiver are sufficiently attenuated and do not flow out from the receiver toward the antenna terminal. Furthermore, the transformer 6 has the effect of sufficiently attenuating the mode transmitted between the outside of the coaxial outer conductor and the ground, and has the effect of blocking unnecessary radiation components that try to flow out from inside the receiver in this mode. be.

Here, an example of the specific configuration of the transformer 6 is shown in FIG. 2(a).
, shown in (b). This is composed of ferrite cores sa and sb of the same cylindrical shape (a) or glasses shape (b), with the same number of input and output windings, and the ratio of input and output impedance is 1:1.
I am trying to make it so that As shown in Figure 1, the transformer 6
The capacitor 6C connected between the primary winding 6a and the secondary winding 6b is used to achieve impedance matching particularly in the high frequency region of the high frequency band and to reduce loss.

The bypass filter 7 can be a lumped constant type filter as shown in FIG.
An i-pass filter may also be used.

An example of the transmission characteristics of the high frequency input device according to the present invention is shown in FIG.
It is shown in FIGS. 4 and 5. Figure 3 shows the actual measured values of the high frequency band transmission characteristics from coax 4 to coax 5 in Figure 1.
It can be seen that the signal is transmitted with low loss over a frequency range of ~900 MHz. FIG. 4 shows actual measured values of the transmission characteristics in the low frequency band from the coax 4 to the coax 6 in FIG. 1, and it can be seen that the transmission characteristics are sufficiently attenuated over a range of 0 to 3 oMHz. Furthermore, Fig. 6 shows the measured values of the transmission characteristics in the low frequency band from coax 4 to coax 5 in the transmission mode between the outside of the outer conductor of the coax shown in Fig. It can be seen that it is attenuated.

As is clear from the above description, according to the present invention, it is possible to prevent unnecessary radiation of relatively low frequency components generated inside the receiver from flowing out, and to prevent interference radio waves from entering from outside.
It can improve signal transmission by reducing transmission loss in the high frequency band, and is particularly suitable as an antenna input device for transformerless television receivers that require double insulation.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a high frequency input device according to an embodiment of the present invention, FIGS. Figures 4 and 6
The figure is a transmission characteristic diagram of an embodiment of the present invention. 1-1-Shield case, 2, 3... Feedthrough capacitor, 4, 5... Coaxial cable or coaxial connector, 6... Transformer, 7... No. 1 pass filter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure/ Figure 2 Figure 3 1 West 1 Nno 1 12 Tarami ()'JH! J Fig. 4 Liquid ice (MHz Fig. 5 71 Wave R (tfptt)

Claims (1)

[Claims] One electrode of a disk-shaped or cylindrical feed-through capacitor is connected to each of the two side walls of the shield case, and the outer conductor of a coaxial cable or coaxial connector is connected to the other electrode, respectively, and the inside of the shield case is A high frequency input device characterized in that the inner conductors of each of the coaxial cables or coaxial connectors are connected via a transformer and a bypass filter having an input/output impedance ratio of 1:1.