JPS61107832A - Connecting cord between av television set and its peripheral device - Google Patents

Abstract

PURPOSE:To reduce the electric field strength of an interference radio wave irradiated from an outer conductor by connecting an impedance suppressing a disturbing current flowing to the outer conductor of a cord connecting an AV television set and its peripheral device in series with the outer conductor. CONSTITUTION:A personal computer 1 as a peripheral equipment and the AV television set 2 are connected by the connecting cord 3. The cord 3 is formed by surrounding the grounding outer conductor 4 around a conductive core wire 6 via an insulator. A terminal 5 of output terminals 5, 9 from which a video signal of the personal computer 1 is connected to the core wire 6 and the terminal 9 being the grounding terminal is connected to the outer conductor 4 of the cord 3, and the core wire 6 is connected to a terminal 7 and the outer conductor 4 is connected to the grounding terminal 8 via an impedance element Z at the AV television set 2. An unnecessary current such as harmonic of the personal computer signal is superimposed on the personal computer signal and irradiated externally as an interference wave 10 from the outer conductor 4 through the core wire 6, a load of the AV television 2 and the outer conductor 4, but the unnecessary current is reduced by inserting the impedance element Z to reduce the radiated electric field strength of the wave 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Fields] The present invention relates to peripheral devices such as video discs, video tape recorders, character multiplex adapters, and personal computers, as well as monitor televisions with RGB terminals used as video terminals thereof.
The invention relates to a connection cord for transmitting signals to an AV television (hereinafter simply referred to as an AV television).

[Prior Art] In general, television receivers and personal computers are required to minimize electromagnetic interference (EM) to nearby electronic devices. For example, the US FCC (
According to the Federal Communications Commission (Federal Communications Commission) 315, Cl.
The unnecessary radiated electric field strength at a point m away must be less than or equal to the value shown in A in Figure 17 for television receivers, and must be less than the value shown in A in Figure 17 for class B computer equipment (home computer equipment, e.g. personal computers). Must be less than or equal to the value shown above. On the other hand, even if an AV TV or a personal computer satisfies the FCC regulations for F and CC regulated television receivers and class B computer equipment, when the two are connected with a connection cord, unnecessary radiation from the AV TV Although the electric field strength as a system is required to satisfy the FCC regulation (B in FIG. 17) for class B computer equipment, it has been difficult to satisfy this FCC regulation.

This type of connection cord has a structure in which the core wire is surrounded by an external conductor for grounding via an insulator.
There have been some attempts to reduce unnecessary radiation of interference waves by inserting a filter into the core wire of this type of connection cord.

[Problems to be solved by the invention] However, with the conventional connection cord in which a filter is inserted, the electric field strength of unnecessary radiated interference waves cannot be suppressed at all, and the F
CC regulations could not be satisfied.

The present invention has been made in view of the above-mentioned problems, and provides a connection cord that reduces the electric field strength of unwanted radiated interference waves (for example, satisfies FCC regulations for class B computer equipment). The purpose is to

[Means for solving the problem] The applicant has conducted various studies on unnecessary radiation of interference waves in the conventional case shown in FIG. ) and A
The outer conductor (4) of the connection cord (3) that connects the V-TV (2) acts as a kind of antenna element, and a disturbance wave current flows through this outer conductor (4), which causes unnecessary radiated interference. We realized that the electric field strength of the waves is increasing. That is, in FIG. 13 showing the equivalent circuit of FIG. 12, a PC signal sent from the PC signal source Ep of the PC (1) passes through the output internal resistance Rp for the PC signal and the non-grounded output terminal (5). , to the AV television (2) via the core wire (6) of the connection cord (3) and the non-grounded input terminal (7). On the other hand, if the interference wave signal source induced inside the personal computer (1) is Ei, then this Ei
The interference wave signal sent from the is superimposed on the PC signal via the output internal resistance Ri for the interference wave signal and the non-ground side output terminal (5), and is superimposed on the PC signal and sent to the core wire (6) of the connection cord (3) and the non-ground side input. It passes through the terminal (7) to the AV TV (2), and then connects the AV TV (2) to the PC signal.
Through the side load resistance RL, the ground side input terminal (8) and the external conductor (4) of the connection cord (3), the ground side output terminal (9)
and back to the disturbance signal source Ei via ground.

In this way, the interference wave signal is superimposed on the computer signal and is transmitted to the AV TV (2) via the connection cord (3), including harmonic components of the clock signal in the computer (1), so the interference wave signal is For a signal, its output internal resistance can be considered equal to Rp.

Considering this, FIG. 13 can be replaced with the equivalent circuit of FIG. 14. In this figure, Eia is
This figure shows an interference signal source based on replacing the equivalent circuit. 1st
Figure 15 shows an equivalent circuit assuming that the impedance of the connection cord (3) in Figure 4 is matched.
In Figure 5, the outer conductor (4) of the connection cord (3) is connected to the interference wave (
Fig. 16 shows an equivalent circuit when considering that 10) is working as a radiating antenna element.

In FIG. 16, Zr indicates the radiation impedance of the outer conductor (4) of the connection cord (3).

Based on the above recognition, the present invention inserts the impedance element 2 shown by the dotted line in FIG. The present invention is characterized in that the electric field strength of unnecessary radiated interference waves is reduced.

[Operation] When the impedance element Z specific to the present invention shown by the dotted line in Fig. 16 is inserted, the interference wave current is Ii,
To simplify the explanation, this patent features Zr and Z.

On the other hand, in FIG. 16, the interference wave current I imax in the conventional example in which no impedance element Z is inserted is as follows.

According to the above equations (1) and (2), It is smaller than the conventional Iimax. Generally, Rp = 75Ω, RL = 75Ω, and Zr = 70Ω, so if Z = Rr (approximately resistive) 220Ω, then formula (3) is obtained, and Ii becomes 1/2 of Iimax. Since the electric field strength of the electromagnetic waves radiated from the antenna element is proportional to the current flowing through the antenna element, if the interference wave current is reduced to 1/2, the electric field strength of the unnecessary radiated interference waves is also reduced to 1/2. Therefore, when Z=440Ω, the electric field strength of the interference wave is reduced to 1/3.

[Embodiment] FIG. 1 shows an embodiment of the present invention, and the same parts as in FIGS. 12 to 16 are given the same reference numerals. In Figure 1,
(1) is a personal computer as a peripheral device, (2) is an AV television, and (3) is a connection cord that connects the two. This connection cord (3) is formed by surrounding a conductive core wire (6) with an external conductor (4) for grounding via an insulator, and this external conductor (4) is made of a braided or annealed copper wire. It consists of a continuous uniform conductor wrapped with amminium tape. Output terminal (5) for outputting the video signal of the personal computer (1)
The non-grounded output terminal (5) of (9) is connected to the negative end bundle of the core wire (6) of the connection cord (3), and the grounded output terminal (9) is connected to the negative end bundle of the core wire (6) of the connection cord (3). Outer conductor (4
) is connected to the - side end bundle. The connection code (3)
The other end of the core wire (6) is connected to the non-grounded input terminal (7) of the AV television (2), and the other end of the outer conductor (4) of the connection cord (3) is connected to the non-grounded input terminal (7) of the AV television (2). It is connected to the ground side input terminal (8) of the AV television (2) via an impedance element Z. Note that this impedance element Z is not limited to being inserted at the terminal of the external conductor (4), but may also be inserted in series with the external conductor (4), for example, inserted in the middle of the external conductor (4). That's fine. (10) is an interference wave unnecessarily radiated from the connection cord (3).

Specifically, the impedance element Z is constructed as shown in FIGS. 2 to 4. Among these, the impedance element Z shown in FIG. 2(a) is attached to the bobbin (15).
Wrap the conductive wire (16) around the coating material (1
7), and the frequency characteristics of the insertion loss (75Ω system) when the inductance is 1°5 μH are as shown in FIG. 7(b).

The impedance element Z shown in FIG. 3(a) has a coil (
18) (19) and a capacitor (20) of constant type, P, F, (low pass filter) are shown, and the coils (18) and (19) each have a resistance of 0.6 μH.
, the frequency characteristic of insertion loss (75Ω system) when the capacitor (20) is 220PF is as shown in FIG. 2(b).

The impedance element Z shown in FIG. 4(a) has a coil (
21) (22) (23) and a capacitor (24), P, F, (low-pass filter) are used. Insertion loss (75
The frequency characteristics of the Ω system) are as shown in FIG. 2(b).

Next, the operation of the embodiment described above will be explained using the drawings from FIG. 5 to FIG. 8. FIG. 5 is an equivalent circuit of FIG. 1.

In Fig. 5, EP is a personal computer signal source as a transmission signal source, and Rp is an output internal resistance (
Ei is the interference signal source, Ri is the output internal resistance to the interference signal, and RL is the AV television (2) unbalanced load resistance (usually 75Ω). The interference signal source Ei
is spatially or conductively induced inside the personal computer (1), and includes harmonic components of the clock signal of the personal computer (1). In FIG. 5, the PC signal sent from the PC signal source E'p (usually 0 to 10 MHz) is connected to the output internal resistance Rp and the non-grounded output terminal (5
) to the AV child television 2) via the core wire (6) of the connection cord (3) and the non-grounded input terminal (7).

On the other hand, the interference signal sent from the interference signal source Ei (frequency band where unnecessary radiation is a problem is 30 to 100MHz) is superimposed on the PC signal via the output internal resistance Ri and the non-grounded output terminal (5). and the core wire of the connection cord (3) (
6) and the non-grounded side input terminal (7) to the AV child TV 2), and then the AV child TV 2) unbalanced load resistor RL.
, the ground side input terminal (8), the impedance element Z and the external conductor (4) of the connection cord (3), and returns to the interference wave signal source Ei via the ground side output terminal (9).

As mentioned above, the interference wave signal is superimposed on the PC signal and is transmitted to the AV child TV 2) via the connection cord (3), including the harmonic components of the computer's clock signal. Therefore, its output internal resistance can be considered to be equal to RP. Considering this, FIG. 5 can be replaced with the equivalent circuit of FIG. 6. In FIG. 6, Eia indicates an interference signal source based on the replacement of the equivalent circuit. Figure 7 shows an equivalent circuit assuming that the impedance of the connection cord (3) is matched in Figure 6. In Figure 7, the external conductor (4) of the connection cord (3) FIG. 8 shows an equivalent circuit when considering that (10) constitutes an antenna element that radiates.

In FIG. 8, Zr indicates the radiation impedance of the external conductor (4) of the connection cord (3).

In Fig. 8, the interference current flowing through the outer conductor (4) of the connection cord (3) is designated as Ii, and for simplicity of explanation, Z
If r and Z are resistances, then `` is obtained in the same way as the above equation (1).

On the other hand, in FIG. 8, if the interference current in the conventional example in which the impedance element Z is not inserted is Iimax, then the equation is similar to the above equation (2).

From the above formula (la) (2a) Therefore, Ii is smaller than the conventional Ii+*ax.

Generally, the radiation impedance of a transmitting antenna that is erected perpendicularly to the ground and has a length of λ/4 (λ: wavelength) is approximately 70Ω. On the other hand, the connection cord (3), which is thought to form a radiation antenna element for interference waves, connects the PC (1) and the AV.
Approximately 1.5 m is required to connect the child TV 2). If we take this 1.5m as λ/4.

The relevant frequency is 50MHz. Furthermore, in actual measurement examples, the frequency band in which interference wave radiation caused by personal computers becomes a problem is 30 to 100 MHz.

Based on the above, consider the case where the length of the connection cord (3) is 1.5 m and the frequency of the interference wave is 50 MHz. Note that the installation conditions for the connection cord (3) are different from the installation conditions for the actual transmitting antenna, so the radiation impedance Zr
Although the value of the radiation impedance of the transmitting antenna cannot be directly applied to the value of the radiation impedance (
≠radiation resistance) Zr is considered as 70Ω. Also, normally Rp = 75Ω.

RL=75Ω. Therefore, the above formula (3a) becomes as follows.

Therefore, if the impedance Z specific to the present invention is set to 220Ω, the interference current Ii is reduced to 172 of the conventional interference current Iimax according to equation (3b).

Since the electric field strength of the electromagnetic waves radiated from the antenna element is proportional to the current flowing through the antenna element, the interference wave current can be reduced by 17
If it is set to 2, the electric field strength of unnecessary radiated interference waves will also be reduced to 1/2. Further, if 2 is set to 440Ω, the electric field strength of the interference wave is also reduced to 1/3.

From the above point, in order to reduce the electric field strength of the interference wave to 172, the insertion impedance Z specific to the present invention must be Z≧220 in the interference frequency band (30~loOMHz).
:F3 RL...It is desirable to satisfy (4), but in practice it varies from 0.3RL to 2 depending on the combination of equipment.
It may be up to 0RL.

However, even if the value of Z is increased more than necessary, the computer (
1) It is desirable that the interference waves radiated from the main body have no direct effect, and that the insertion loss in the frequency band of the transmission signal is extremely small compared to the load resistance RL. That is, it is desirable that Z((RL(=75Ω)...(5) be satisfied in the frequency band (0 to 10 MHz) of the PC signal.

In the above embodiment, the connection cord has a structure in which a single core wire is surrounded by an external conductor for grounding via an insulator; however, the present invention is not limited to this; The structure may be one in which the conductor is surrounded by an external conductor for grounding via an insulator.

For example, an individually shielded multicore connection cord (3a) as shown in FIG. 9 may be used. This individually shielded multicore connection cord (3a) consists of five core wires (6a) to (6a) for video signal transmission, and these core wires (6a) to (6a).
It consists of external conductors (4a) to (4a) consisting of shielded wires wrapped around each of a) via an insulator, and a ground wire (4b) connected to these shielded wires, The five core wires (4a) of the connection cord (3a)
) ~ (4a) - side end bundle is connected to the ground wire (4) via the pin terminals (26a) ~ (26a) of the DIN plug (25).
The negative end bundle of b) is connected to the output terminal (1a) of each video signal such as R, G, B, horizontal sync, vertical sync, etc. of the personal computer (1) via the pin terminal (26b) of the DIN plug (25).
) to (1a) and the ground side output terminal (1b). The five core wires (6a) of the connection cord (3a)
(6a) The other side terminal connects to the AV TV (2) via the pin terminals (27a) to (27a) of the square 8-bin plug (27).
It is connected to the input terminals (2a) to (2a) of each video signal such as R, G, B, horizontal sync, vertical sync, etc., and the ground wire (
4b) The other terminal is connected to the pin terminal (2) of the square 8-pin club (27) through an impedance element Z specific to the present invention.
7b) (27b) is coupled to the ground side input terminal (2b) (2b) of the AV television (2).

Further, as shown in FIG. 10, the entire circumference of the individually shielded multicore connection cord (3a) is surrounded by a full-face shield (28), and a ground wire (4b) is connected to this full-face shield (28). It may be configured to connect. In this case, since the entire surface shield body (28) is added, the shielding performance against external interference is further improved. Furthermore, as shown in FIG.
The AV TV (2) side of 8a) is connected directly to the ground wire (4b).
After passing through the impedance Z specific to the present invention without connecting to the ground wire (4b) and the external conductors (4a) to (4
It may be connected to a).

In this case, the influence of the inserted impedance element Z on the transmission signal (0 to IOM) lz) is extremely small, so
The frequency characteristics of insertion loss due to insertion of the impedance element 2 are improved, and the selection range of impedance values of the inserted impedance element 2 is widened.

Next, as a connection cord (3), a multi-core connection cord (3a) as shown in FIG.
The results actually measured using the 3m unnecessary radiation measurement method according to A will be explained. Here, the impedance element Z inserted in series with the external conductor (4) of the connection cord (3) was a 1.5 μH reactance element, and the electric field strength of the interference wave showed a peak value when the interference wave frequency was 40 MHz. According to the actual measurement results, when the interference signal frequency band is 35 to 45 MHz, as shown in (a) and (b) of Table 1 below, the impedance element Z
The present invention with the insertion of
It can be seen that it has also decreased. This shows that the present invention has an extremely superior effect compared to the conventional example in which a filter was inserted into the core wire of the connection cord, which could hardly reduce the field strength of the interference wave.

Table 1 In Table 1 above, is the measured value of (a) 40 dB the first? Corresponds to an electric field strength of 100 μV/m in the figure. Also, (c)
1 shows a case where a glasses core (the number of turns of the conducting wire is 2.5 turns) is used as the impedance element Z, and (d) shows a case where the same glasses core (the number of turns of the conducting wire is 4.5 turns) is used.

[Effects of the Invention] As described above, the present invention suppresses unnecessary interference radiated from the external conductor by inserting an impedance element in series in the external conductor for suppressing the interference current flowing through the external conductor of the connection cord. Since the configuration is configured to reduce the electric field strength of the waves, electromagnetic interference (EMI) to electronic equipment placed close to the connection cord can be suppressed as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a connection cord for an AV child television and peripheral equipment according to the present invention, and FIGS. 2 to 4 each show a specific example of the impedance element 2 in FIG. 1. , In these figures, (a) shows a configuration diagram or an electric circuit diagram of the impedance element 2,
(b) shows a frequency characteristic diagram of insertion loss of impedance element Z, Fig. 5 is an equivalent circuit diagram of Fig. 1, and Fig. 6 is an equivalent circuit diagram of Fig. 5.
Figure 7 is an equivalent circuit diagram for the interference signal shown in Figure 6, and Figure 8 is an equivalent circuit diagram when the impedance of the connecting cord is matched in Figure 6. Fig. 9 is a block diagram showing the second embodiment of the present invention, Fig. 1O is a block diagram showing the third embodiment of the present invention, and Fig. 11 is a block diagram showing the fourth embodiment of the present invention. FIG. 12 is a configuration diagram showing a conventional example, FIG. 13 is an equivalent circuit diagram of FIG. 12, FIG. 14 is an equivalent circuit diagram of the interference signal in FIG. 13, and FIG. 15 Fig. 14 is an equivalent circuit diagram when the impedance of the connection cord is matched, Fig. 16 is an equivalent circuit diagram when the external conductor of the connection cord is considered as an antenna element in Fig. 15, and Fig. 17 is an FCC diagram. FIG. 3 is a diagram showing the regulation value of unnecessary radiated electric field strength according to the above. (1)...PC (peripheral equipment), (2)...A
V child TV (3) (3a) - connection cord, (4) (4
a) (4b) ・=Outer conductor, (6) (6a)...
Core wire, (10)...Interference wave, Z...Impedance element, Ei, Eia...Interference wave signal source, Eρ...PC signal source, R...AV child TV 2) side load resistance , Zr... Radiation impedance of the external conductor of the connection cord, Ii... Interference wave current. Applicant: Showa Musen Kogyo Co., Ltd. Figure 2 (Q) Figure 3 (b) Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17) ηEIv number (MHz)

Claims (3)

[Claims] (1) Connecting the AV TV to this
In a device that connects a peripheral device that transmits signals to a V-TV, an impedance element is inserted in series into the external conductor to suppress interference current flowing through the external conductor, and unnecessary radiation from the external conductor is prevented. A connection cord between an AV television and its peripheral equipment, characterized in that the electric field strength of interference waves is reduced. (2) The AV television set forth in claim 1, wherein the impedance element for suppressing the interference current is inserted between the ground side of the AV television side plug portion of the connection cord and the external conductor. Connection cord for peripheral devices. (3) The impedance of the impedance element for suppressing the interference current has a value approximately 0.3 to 20 times the load resistance on the AV TV side in the frequency band of the interference current, and in the frequency band of the transmission signal. In the above AV
A connection cord between an AV television and its peripheral equipment according to claim 1 or 2, which has a value extremely smaller than a load resistance on the television side.