JPS62141935A - Power line signal carrier transmission - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a power line signal transmission system, and when noise is generated on the power line, the amplification gain of the receiver is lowered to reduce the influence of the noise. Regarding the remote control device that can be used.

[Background of the invention]

In the power line signal transmission system, noise generated in the power line impairs the reliability of signal transmission. An example of a method for reducing the influence of noise is shown in Japanese Patent Application Laid-open No. 58-151130 and Japanese Patent Application Laid-Open No. 59-17828 Gin.

The former proposes a method of monitoring power line noise and not transmitting until the noise level falls below a certain value. The latter also proposes a method of transmitting signals after determining the stability of the power line using test signals. Both of these mean that transmission and reception cannot be performed until the noise on the power line falls below a certain value.

[Purpose of the invention]

An object of the present invention is to provide a power line system that detects noise in almost the same frequency band as the carrier signal, which has the most adverse effect on signal transmission, by distinguishing it from the carrier signal, adjusts the amplification gain of the receiver, and improves the noise immunity characteristics of reception. An object of the present invention is to provide a carrier type receiving device.

[Summary of the invention]

For the above purpose, a so-called Manchester code is used in which the presence of a carrier signal is a high level (H) and the absence of a carrier signal is a combination of a low level (L) to represent 0.1 of the data.

If the carrier signal continues to be H for a certain period of time in a case other than 1 (carrier signals are arranged in H and L), it indicates that noise is occurring on the power line or data transmission is colliding between devices. to decide. Both determinations will be described later, but when it is determined that noise has occurred, the gain of the variable gain circuit of the receiving circuit is gradually lowered to reduce the influence of noise before transmitting and receiving data. In addition, when it is determined that there is a collision between transmitted data, the commonly used C3MA type access method (for example, CS M
A/CD).

[Embodiments of the invention]

FIG. 1 is a circuit configuration diagram of a power line carrier system showing an embodiment of the present invention. In FIG. 6, 1 is a power line, 2 is a zero cross pulse generation circuit that detects the zero cross point of the power line, which is used as a synchronization signal, 3 is a transmitting circuit, 4 is a transformer that superimposes a signal on the power line, and 5 and 6 are a resonance capacitor and a coupling capacitor. The part surrounded by a broken line in the figure constitutes a receiving circuit. 7 is a coupling capacitor, 8 and 9 are bias resistors, 10 is an amplification transistor, 11, 12 and 13 are emitter resistors, 14.15 is a gain adjustment switch, and 16 and 17 are a resonant circuit made up of a coil and a capacitor. , tuned to the carrier signal frequency. 18 is the power supply,
19 is a comparator, and 20 and 21 are resistors that determine the threshold voltage of the comparator 19.

22 is a microcomputer that transmits and receives signals and analyzes data based on the zero cross pulse.

A control key (not shown) is imported, etc. The gain adjustment switches 14 and 15 are controlled by the P□p2 terminal of the microcomputer 22.

What is important in power line transmission systems is that power lines have more noise sources (e.g., televisions, mixers, vacuum cleaners, etc.) than other signal transmission lines, and a signal discrimination method that is resistant to these noises is required.

As an example of this, as shown in Figure 2, the number of carrier waves is counted within a certain period using the zero cross signal of the power line as a reference, and when the number is within a certain range, L
, and the true H.

There is a method of determining 1°0 of data using a combination of L, H, and H. The method of this determination will be explained with reference to FIG.

2S is a power supply waveform, 26 is a zero level, 27 is a zero cross pulse, 28 is a timing pulse for carrier wave counting, 29
is the carrier wave, 30 is the threshold level of the comparator,
31 is the ML sound.

Further, this figure shows a case where 2 bits of data are superimposed on one power cycle, and when the power line is 50)1z, the transmission speed is 100 bps. In other words, it represents one data transmission/reception every ``8 crosses.''

The microcomputer 22 in FIG. 1 performs various processes based on the zero cross pulse 27, and the reception status will be described below. The microcomputer 22 receives the carrier signal 2 input to the comparator 19.
9, the threshold voltage Vs1 (30 is exceeded) is counted while the timing pulse 28 is LOW. Based on the count number at this time, it is determined whether it is an H level or an L level.
For example, the waveform ``■'' in FIG. 1 is shown in FIG. 2(d), and in the interval ``■'' (during the power supply cycle), the first half is H and the second half is L, so the data is determined to be 1. Similarly ■
In the section , the data is determined to be O due to the combination of I(. Because it is short, it is determined to be r4 by determining the count number.As a result, the data is determined to be O due to the combination of H in this section, and the influence of noise is reduced.■
In the first half of the section, there are lip sounds and signals that can send the threshold level 30 over the entire area.
The latter half becomes I(, and the data is neither 1.0 nor undefined. When it becomes undefined like this, it is due to a collision between transmitted data or when noise occurs in the same band as the carrier frequency. The former is extremely rare. Since this is a state that occurs in By determining the number, the data is determined to be 1, and the influence of noise disappears.

In this way, the carrier signal 29 is counted for a certain period of time.

By determining H and L based on that number, and determining 0.1 of the data based on the combination of H and L.

The influence of qt seizure noise can be reduced. However, the second
In the @ section of Figure (d), the influence of continuity noise as shown by 31 cannot be eliminated.

Below, methods for reducing the effects of continuity noise will be described. Now, suppose that noise with the same frequency as the signal occurs.

Figure 3 shows the waveform at point ■ in Figure 1.9(a)
When the noise level is small, (b) is when the noise level is large, and (C) is in the state of (b), the variable gain adjustment switches 14 and 15 of the receiving circuit shown in FIG.
2 and shows a state in which the gain is lowered.

As shown in (a), when the noise level is small and does not exceed the threshold level 30, only the signal 29 is at VSll.
The microcomputer 22 recognizes the combination of H, L, or H as shown in the figure, and the data string exceeds 1100.
It is judged as 1001.

(b) shows a case where the noise level increases and exceeds VsI (30).At this time, the microcomputer 22 recognizes that H is consecutive, and since it is not a combination of H, L or H, ”.

"Undefined" includes cases where noise 29 (same frequency as the signal, 4F) exceeding the threshold level of the comparator vslf 30 occurs on the transmission line (power line), and when multiple other slave units transmit at the same time. In other words, this is a signal collision in the power line transport system.

Various CSMA-based access methods have been devised for processing when a collision occurs, and the most commonly used method among these is CSMA/CD. In this method, when a collision is detected, it is retransmitted after a certain period of time, and the time until retransmission is individually set using random numbers. Therefore, if "undefined" is due to signal collision.

According to the CSMA/CD described above, signal transmission ends after a certain period of time. However, if the cause of "inconsistency" is noise, signal transmission will not take place as long as the noise as shown in FIG. 3(b) exists.

Now, as shown in FIG. 3(b), when the signal level 29 is higher than the noise level 31 and the noise level 31 exceeds the threshold level VSI[3Q, as described above, the microcomputer 22 is judged to be "indeterminate", but at this time, the first
By switching the gain adjustment switches 14 and 15 shown in the figure, the gain of the receiving circuit is lowered. FIG. 3(c) shows the waveform at this time.

According to this, the noise level 31 is the threshold level V
In order not to exceed SIT 30, the microcomputer 22
Signal data can be recognized by the combination of As a result, it can be determined that the data string is l 1.001001.

Note that for the gain adjustment shown in FIG.
2.13 are respectively R□, R2, and R3, and switch 1
Four types of combined resistance values can be obtained depending on the open/closed state of 4.15. The normal state is when the switches 14 and 15 are closed, and at this time the emitter resistance of the transistor 10 is set to R.
I: is the maximum. When only switch 15 is opened, L
EE K, go down.

The above is a case where the gain of the amplification transistor 10 is controlled to change the amplitude of the input signal (or noise) to the comparator 19, but the same result can be obtained by changing the level of the comparator threshold level Vs+t 30. You can get the effect.

FIG. 5 shows the operating procedure of the present invention, and procedures related to the present invention are shown with double frames. FIG. 4 is an auxiliary diagram for explanation, and numeral 27 indicates the zero cross pulse of the power supply, as in FIG. 2. (2) Figure 2 shows the position where the carrier wave exists, which corresponds to the signal 29 or noise 31 in Figure 2. Further, this figure shows that if the power supply frequency is 501 Tz, the transmission speed is 100 bρS. A series of operations will be explained below with reference to FIG.

(A) in FIG. 5 detects that a signal or noise is generated in a signal transmission path (power line). Now, assuming that 1 is H and 2 is L in Figure 4, the determination in (A) is N, the reception status is determined to be normal, and the process jumps to the data processing routine in (h). .

Next, if both the country and (2) are ■■, the judgment for (A) will be Y. In this case, either noise is generated or a collision occurs, so the collision avoidance process (B) is performed first. After this again (C
), it is determined whether both ■ and (2) are H. At this time, if either l or the figure is L, it passes through branch N and performs the data processing in (h).

In the judgment (C), if (2) both times are H, it is judged that noise is occurring in the transmission path, and the 1st branch Y is selected, and the gain of the receiver is lowered by one step as shown in d).

At this time, the gain adjustment is performed by P□p of the microcomputer 22 shown in Figure 1.
5W14 and 15 are switched by two terminals. In this example, four types of gain adjustment can be performed. In (e), check again whether both the signal and (2) are H. If the branch is N, go to data processing in (h), and if it is Y, the receiver gain is the minimum value of the predetermined variable width. (In Figure 1, 5W14.
15 are both open). If it is the minimum value at this time, it is determined that communication is impossible. If the gain of the receiver is not the minimum, return to (A) again and perform the same operation as described above.

Improvements made when the gain of the receiver is changed will be explained using FIG. Assume that the waveform shown in FIG. 3(b) is applied to the input terminal of the comparator 19 in FIG. At this time, both the signal 29 and the noise 31 exceed the threshold level 30, so the texture in FIG.
In the input waveform of the comparator 19 described above, the amplitude of both the signal 29 and the noise 31 decreases, as shown in FIG. 3(C).

As is clear from this figure, the signal 29 exceeds the threshold level 30, the noise 31 becomes below the threshold level, and signal transmission becomes possible.

FIG. 6 is a characteristic diagram showing signal levels and communicable noise levels, where the broken line is the conventional (constant gain) characteristic and the solid line is the one according to the present invention. In contrast to the conventional example where the noise level remains constant even when the signal level increases, the present invention shows that transmission is possible even if the noise level increases by one level as the signal level increases.

〔Effect of the invention〕

According to the present invention, noise generated in a signal transmission path and a signal or collision between signals can be detected using the characteristics of Manchester code and the W
A signal transmitting/receiving device with excellent noise resistance characteristics can be provided by separating the signals by the f-bump avoidance process and the gain adjustment of the receiver.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, FIG.
3 and 4 are operation explanatory diagrams, FIG. 5 is a flowchart of the present invention, and FIG. 6 is a comparative explanatory diagram of the conventional example and the present invention. 1...power line, 3...transmission circuit, 4...transformer. 10...Amplification transistor, 22...Microcomputer.

Claims (1)

[Claims] 1. In a power line carrier system that uses power lines as signal transmission paths, the signal transmission method is a combination of the presence and absence of a carrier signal, and in a system that uses Manchester codes to represent data 0 or 1, at least the zero cross of the power line is A zero cross pulse generation circuit for detecting, a power supply circuit and a reset circuit, a coupling circuit between a power line and a transmitter/receiver circuit, a transmitter circuit and a microcomputer, and a receiver circuit that changes the gain of an amplifier circuit under the control of the microcomputer. and among the combinations of presence and absence of carrier signals,
When a carrier wave is detected at a value other than 0 or 1, collision avoidance is performed, and when a carrier wave is detected at a value other than 0 or 1 again,
A power line signal transmission system characterized in that the gain of the receiving circuit is gradually lowered.