JPS59202741A - Power line carrier signal receiving device - Google Patents

Abstract

PURPOSE:To erase completely a noise component even in case a noise level exceeds by far a carrier wave level by providing a limiter for limiting a carrier wave receiving signal level, and a tuning circuit which tunes with frequency of a carrier wave, on its post-stage. CONSTITUTION:However high a noise level may be, a waveform drawing of a point B of the collector of a TRQ3 is clamped to a degree which is a little higher than a peak value of a carrier wave by a limiter 8. An amplifying circuit 9 having a wide band characteristic amplifies a carrier wave and a noise in the same way, and the carrier wave and the noise in a point C become the same level by a limiter 10. A resonance circuit 11 amplifies the carrier wave and attenuates other frequency component, therefore, as for waveform of a point D of the collector of a TRQ4, a peak value of the noise becomes much smaller than a peak value of the carrier wave. As a result, in an output point E of a Schmitt circuit 13, a noise component is erased completely.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a signal receiving device for a system that transmits signals to a remote location using a power line.

<Problem to be solved> When controlling power, etc. in power line transmission, there is a large amount of noise on the power line (and the noise level may be very high. Also, the carrier wave signal received by power transmission has a long transmission distance). When the impedance is low or the impedance is small, the attenuation is considerable.For this reason, the noise level is often much higher than the received level of the carrier signal.In some cases, the noise level is several thousand times the carrier wave level. Therefore, if the received carrier signal level is amplified by a wideband amplifier to a level that can be processed by the subsequent digital circuit, the carrier signal and noise will be amplified together, making it impossible to distinguish or separate them.

<Prior art> In the conventional example shown in FIG. This is a circuit in which only signals or noise greater than a threshold are output.

In addition, in the conventional example shown in FIG. 2, the signal and noise on the power line are amplified by an amplifier circuit 5 mainly composed of a transistor Q2 after passing through a tuning circuit 4, and a signal and noise larger than a threshold value are amplified by a Schmint circuit 6. This circuit outputs only

FIG. 3 shows waveform diagrams of various parts according to the above-mentioned conventional examples. (a
) is a waveform diagram in which noise is superimposed on the input signal carried to point A on the power line. The carrier wave signal az% to be received is superimposed on the positive half cycle or negative half cycle of the sine waveform a1 of the commercial AC power supply, but irregular noise a3
is on board.

The frequency component of this commercial AC power supply is removed by a coupling capacitor, the carrier wave component and noise are amplified and taken into the receiving circuit, and a separate zero-cross detection circuit distinguishes between a positive half cycle or a negative half cycle of the commercial AC power supply. It is assumed that it is detected in which half cycle the carrier signal is input.

Since this part is not particularly related to the gist of the present invention, its explanation will be omitted. Note that other signals can be used as the synchronization signal instead of the commercial AC power supply.

According to the conventional example shown in FIG. 1, the waveform at the output point B of the transistor Q1 is one in which both the carrier wave and the noise are amplified as shown in FIG. 3(b), and the waveform at the output point C of the Schmitt circuit 3 is As shown in FIG. 3(C), noise with the same peak value as the carrier wave remains, making it impossible to identify and separate the carrier signal and the noise.

According to the conventional example shown in FIG. 2, since there are four tuning circuits, the waveform at the output point of the amplifier circuit 5 has the tuning frequency of the tuning circuit ( The waveform at the output point E of the Schmitt circuit 6 is such that a pulse with a certain time width is generated for noise larger than the threshold value, as shown in FIG. 3(e). As a result, it is still necessary to distinguish between carrier waves and noise.
Cannot be separated.

<Object of the Invention> An object of the present invention is to provide a power line carrier signal receiving apparatus that can completely eliminate noise components even when the noise level far exceeds the carrier wave level.

<Configuration of the Invention> The present invention provides a limiter that limits the level of a carrier superimposed signal in a receiving device of a system that transmits a signal modulated with a carrier wave of a predetermined frequency to a remote location using a power line, and a It is characterized by the provision of a tuning circuit tuned to a predetermined frequency.

<Example> FIG. 4 shows a circuit diagram of an embodiment of the present invention.

Signals and noise on the power line are input to the coupling transformer 7 via the coupling capacitor Co. The secondary output of the transformer 7 passes through a first stage limiter 8 consisting of diodes DI and D2, and is amplified by an amplification transistor Q3. The signal and noise amplified by the amplifier circuit 9 pass through the second stage limiter 10', and are connected to the coil L1 and the capacitor C.
Only the frequency components of the carrier wave are taken out by a tuning circuit 11 consisting of a series connection of transistors Q4, amplified again by an amplifier circuit 12 mainly composed of a transistor Q4, and only those exceeding the threshold level are outputted by a Schmitt circuit 13. be done. The frequency characteristic of the amplifier circuit 9 is a broadband characteristic in which both the shadow transmission signal and the noise component are amplified.
The frequency characteristic of the amplifier circuit 12 may be such that only the carrier signal is amplified.

Further, the clamp level of the first stage limiter 8 is higher than the peak value of the carrier wave.

Next, the operation of the above embodiment will be explained according to the waveform diagram in FIG.

The input waveform carried to point A on the power line is the same as that described for the conventional example, in which carrier signal a2 and noise a3 are superimposed on commercial AC power supply a1. No matter how high the noise level is, the first stage limiter 8
As a result, the waveform diagram at three points on the collector of transistor Q3 is clamped to a level slightly higher than the peak value of carrier wave b2, as shown in FIG. 5(b). The amplifier circuit 9 with broadband characteristics amplifies the carrier wave and noise in the same way, and the second stage limiter 10 amplifies the carrier wave C2 and noise C3 at the 0 point.
are at the same level as shown in FIG. 5(C). Since the resonant circuit 11 amplifies the carrier wave and attenuates other frequency components, the waveform at the collector 0 point of the transistor Q4 is a wave of the noise d3 relative to the peak value of the carrier wave d2, as shown in FIG. 5(d). The highs will be much smaller. As a result, at the output point E of the Schmint circuit 13, the noise component is completely eliminated and only the carrier wave component e2 remains.

<Effects of the Invention> According to the present invention, by providing a limiter, the carrier wave peak value and the noise peak value are kept the same no matter how high the noise level is, and then the noise is reduced by passing the carrier wave through a tuned circuit tuned to the carrier wave. The level can be attenuated much lower than the carrier wave level, and by providing a Schmitt circuit at the subsequent stage, noise can be completely eliminated.

[Brief explanation of the drawing]

Figures 1 and 2 are circuit diagrams showing conventional examples;
The figure is an explanatory diagram of the operation of these conventional examples. FIG. 4 is a circuit diagram showing an embodiment of the present invention, and FIG. 5 is an explanatory diagram of its operation. 8.10--Clamp circuit 11-Series resonant circuit9.12-Amplifier circuit 13-Schmitt circuit

Claims (1)

[Claims] In a receiving device for a system that transmits a signal modulated with a carrier wave of a predetermined frequency to a remote location using a power line, a limiter that limits the level of the carrier wave reception signal is provided, and a tuning circuit tuned to the predetermined frequency is provided after the limiter. A power line carrier signal device characterized by: