JPS5950627A - Power line superposed communication device - Google Patents

Abstract

PURPOSE:To eliminate the effect on communication level even if a load impedance is fluctuated, by using the 1st and the 2nd envelope detecting circuit having a relatively large and small time constant. CONSTITUTION:When a signal of FSK modulation is applied to an input terminal 1, the signal is amplified at amplifiers 2, 3, 4 and transmitted to an indoor distribution network from an AC plug via capacitors C4, C5 for power frequency signal cut and a tank circuit 5. The noise component synchronized with a frequency twice the power frequency in the signal is detected at an envelope detecting circuit 8 and a high frequency signal is eliminated. If there exists fluctuation in an output signal due to the fluctuation in the power impedance, the signal level transmitted to the indoor distribution network is fed back via the tank circuit 5 and the high frequency component is eliminated at an envelope detecting circuit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of the Invention The present invention relates to a power superimposition communication device, and particularly to a power superimposition communication device having features in a transmitting circuit section.

(b) Prior art and its problems The power supply superimposition communication device uses an indoor power distribution network as one communication line, and performs communication by superimposing a high frequency signal based on the FSK or PSK modulation method on the indoor power distribution network.

Even in this type of communication device, the communication level often fluctuates due to various causes occurring on the transmitting side, the receiving side, or the indoor power distribution network, which may affect the quality of communication.

Conventionally, as a countermeasure against this, the receiving side detected the noise level near the signal frequency and performed automatic gain control (AGC). However, AGC alone on the receiving side cannot completely eliminate impedance fluctuations in the power supply line and the influence of noise components synchronized with the power supply frequency, for example, at a frequency twice the power supply frequency.

(C) Purpose of the Invention The purpose of the present invention is to eliminate the drawbacks of the conventional power supply superimposed communication device as described above, and to solve the problem of power supply impedance fluctuation due to fluctuations in the load connected to the power distribution network and on/off of multiple loads. It is an object of the present invention to provide a power supply superimposition communication device which is not affected by the communication level even when the power source frequency is doubled and which can remove noise components synchronized with twice the power frequency component.

(b) Structure and Effect of the Invention In order to achieve the above object, the power superimposition communication device of the present invention has a transmitting circuit that receives a signal sent from the transmitting circuit itself and performs envelope detection with a relatively large time constant. a first detection circuit for adjusting the level of the transmission signal using the output of the first detection circuit; and a second detection circuit that performs envelope detection on the extracted output signal with a relatively small time constant.

A second automatic level control circuit is provided for adjusting the level of the sending signal using the output of the second detection circuit.

According to the power superimposed communication device of the present invention, the feedback circuit formed by the first detection circuit that performs envelope detection with a relatively large time constant and the first automatic level control circuit generates a signal to be sent out due to fluctuations in power source impedance. means for suppressing and stabilizing fluctuations in the communication signal; a second detection circuit for performing envelope detection with a relatively small time constant; A feedback circuit formed by the level control circuit can cancel level fluctuations synchronized with integral multiples of the power supply frequency.

(E) Description of Embodiments The present invention will be described in detail below with reference to embodiments shown in the drawings.

FIG. 1 is a connection diagram of a transmitting circuit of a power superimposed communication device showing an embodiment of the present invention.

In FIG. 1, 1 is an input terminal to which a modulated wave Em is applied. The modulated wave Em is, for example, F S

It contains a frequency component of fC+fm (corresponding to logic tl 011). Reference numerals 2 and 3 designate amplifiers with an automatic level control function, each having a hexagonal terminal, an output terminal, and a control terminal for receiving a signal for controlling the amplification level. The internal circuits of these amplifiers 2 and 3 are already known. 4 is also an amplifier.

5 is the coil L1. This is a tank circuit consisting of capacitor C5. Its band characteristics are as shown by the dotted line A in FIG. T1 is an output transformer for sending the modulated wave Em to the indoor power distribution network, C4 and C5 are capacitors for cutting signal components of the power frequency, and 6 is an AC plug. This AC plug 6 is inserted and connected to an outlet provided in an indoor power distribution network.

In addition, the AC plug 6 is connected to the primary winding La of the power transformer T2.
is connected to the secondary winding Lb! /'i, connected to the bandpass filter. The band characteristics of the bandpass filter 7 are selected so that its center frequency fN is close to the communication signal frequencies f and c, as shown in FIG. 2B.

The bandpass filter 7 includes diodes D1. It is connected to an envelope detection circuit 8 consisting of a resistor R1 and a capacitor C1, and the detection output of the envelope detection circuit 8 is connected so as to be applied to the control terminal of the amplifier 2.

Note that the time constant τ1=KI R1C1 (K1: constant) of the resistor R1 and the capacitor C1 of the envelope detection circuit 8 is selected to be small so that it can sufficiently follow fast fluctuations at a frequency about twice the power supply frequency.

The above power transformer T2 → band pass filter 7 → envelope detection circuit 8 → amplifier 2 forms a feedback circuit for removing fast fluctuation components such as frequencies that are an integral multiple (for example, twice) of the power supply frequency. There is.

The output end of the amplifier 4 is connected to ground via a capacitor C1 resistor R. The capacitor C is a capacitor for cutting a DC component, and the p resistor R is a resistor for generating a feedback voltage according to the output voltage. The connection point between capacitor C and resistor R is diode D2. It is connected to an envelope detection circuit 9 consisting of a resistor R2 and a capacitor C2. The output terminal of the envelope detection circuit 9 is connected to the control terminal of the amplifier B. Note that the time constant τ2 = 2 R2C2 (R2: constant) determined by the resistor R2 and capacitor C2 of the envelope detection circuit 9 responds to relatively slow changes such as fluctuations in the power supply impedance, and responds to the above-mentioned power supply frequency. It is set to a relatively large value (τ1<τ2) so as not to follow a fast change of about twice the frequency.

The above-described capacitor C, resistor R, envelope detection circuit 9, and amplifier 3 form a feedback circuit for removing slow fluctuations such as output fluctuations due to fluctuations in power supply impedance.

Next, the operation of the embodiment circuit configured as described above will be explained.

When the FSK-modulated modulated wave Em is applied to the input terminal 1, the signal (modulated wave) is amplified by the amplifiers 2.3 and 4, and then sent to the tank circuit 5. The signal is sent to the indoor power distribution network from the AC plug 6 via capacitors C4 and C5 for cutting the power frequency signal.

If, for example, a fluctuation (noise) synchronized with a component twice the power supply frequency occurs in this transmitted signal, an AC component is added to the bandpass filter 7 via the power transformer T2. Since the bandpass filter 7 has a center frequency fNk near the frequency fc of the communication signal, the signal shown in FIG. 3(a) is outputted.

This signal includes a noise component N synchronized with a frequency twice the power supply frequency. This signal containing the noise component N is detected by the envelope detection circuit 8, and a detected signal from which the high frequency signal has been removed is obtained as shown in FIG. Added.

The amplifier 2 performs level control by adjusting the gain so that the output increases when the voltage applied to the envelope detection circuit 8 is small, and outputs the modulated wave signal shown in Fig. 3 (03. Note that the power supply frequency Since the amplifier 3 does not follow the signal with a fast change in level and performs the level control action as described above, the signal shown in FIG. 3(C) is sent out as is through the amplifiers 3 and 4.As a result The level increase shown in FIG. 6(C) compensates for the small level N shown in FIG. 3(a), and the noise component synchronized with the component twice the power supply frequency is removed.

On the other hand, if the output signal fluctuates due to fluctuations in the power source impedance, etc., as shown by dotted line 2 in Figure 4, the signal level sent to the indoor power distribution network is fed back via the tank circuit 5 and generated at the resistor R. The feedback voltage changes. This feedback voltage is detected by the envelope detection circuit 9, the high frequency component is removed, and the detected signal is applied to the control terminal of the amplifier 3. The amplifier 6 is arranged so that when the voltage applied to the envelope detection circuit 9 is small, the output signal to be sent out becomes large.

On the other hand, when the applied voltage is large, level control is performed by adjusting the gain so that the transmitted output signal becomes small. Therefore, when automatic level control is performed by amplifier B, the signal shown by solid line M in FIG. 4 can be sent out despite fluctuations in power source impedance, etc.

[Brief explanation of drawings]

FIG. 1 is a connection diagram of a transmission circuit of a power supply superimposed communication device showing an embodiment of the present invention, FIG. 2 is a diagram showing band characteristics of a tank circuit and a bandpass filter of the embodiment circuit shown in FIG. Figure 3 is a signal waveform diagram for explaining the operation of removing noise components that occur in synchronization with a frequency twice the power supply frequency in the same example circuit, and Figure 4 shows fluctuations in power supply impedance, etc. in the same example circuit. FIG. 4 is a signal waveform diagram for explaining an operation for removing the influence caused by the noise. 2.3: Amplifier with automatic level adjustment function. 5: Tank circuit, 6: AC plug, 7: Band pass filter, 8/9: Envelope detection circuit. T2: Power transformer, C: DC cut capacitor, R: Feedback voltage generation resistor. Patent applicant Tateishi Electric Co., Ltd. Agent Patent attorney Shigeru Nakamura

Claims (1)

[Claims] (1) For transmitting circuits that send communication signals to indoor power distribution networks. a first detection circuit that receives a signal sent out from the transmission circuit itself and performs envelope detection with a relatively large time constant; and a first detection circuit that adjusts the level of the sent signal using the output of the first detection circuit. 1. an automatic level control circuit; ii. means for extracting a signal component having a frequency near the frequency of the communication signal; 2 detection circuit. The present invention is characterized by comprising a second automatic level control circuit that adjusts the level of the transmission signal using the output of the second detection circuit. Power superimposition communication device.