JPS6364929B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention converts voice band communication current (including not only voice current but also measurement control signals, data signals, etc.) and frequency-shifted ringer signals into a carrier-suppressed single sideband system. The present invention relates to a power line carrier device for transmitting data.

Conventionally, in this type of device, modulation/demodulation carrier currents for the transmitting side device and receiving side device are supplied by independent oscillators, or a part of the modulating/demodulating carrier wave on the transmitting side is supplied as a pilot current to the receiving side. On the sending and receiving sides, at least a part of the demodulated carrier current is obtained by separating and extracting the pilot current in the demodulation stage. With all independent oscillators, each oscillator is required to be very accurate and highly stable. On the other hand, if part of the signal is derived from the pilot current, a narrowband filter and amplifier are required to separate and extract the pilot current, and this may have an adverse effect on the speech current transmitted in a frequency band close to the pilot frequency. It has the disadvantage of causing The pilot signal is also used to control the gain of the receiving amplifier etc. in response to fluctuations in transmission loss of the power line. Transmission loss in power lines has poor frequency characteristics, and one pilot current is not sufficient for the gain control described above, so one pilot signal is required for at least two channels. As a result, for example, in a device transmitting six communication paths, at least three pilot signals are required, which not only increases the above-mentioned drawbacks but also increases the load on line amplifiers etc. by sending pilot signals, causing overload. This causes adverse effects such as an increase in nonlinear distortion due to Another drawback is that the transmission band is widened due to pilot signal insertion, making it impossible to utilize the band effectively. Furthermore, the frequency allocation at each modulation/demodulation stage is constrained due to pilot signal insertion, and usually the lower sideband waves of odd channels are placed below 20kHz, and the upper sideband waves of even channels are placed above 20kHz, and these are separated by, for example, 6kHz. The basic group is modulated by a group modulated carrier wave, and the basic group is further modulated by a line modulated carrier wave and sent to the power line. For this reason, the frequency conversion process and communication path configuration of the device differ depending on the number of required communication paths, and therefore the device also differs. In other words, there is no compatibility or commonality of devices. In addition, in the above-mentioned frequency arrangement, for example, if the upper sideband waves of odd-numbered channels are not sufficiently suppressed,
The upper sideband wave is added linearly to the communication current of the even channels, resulting in crosstalk. Since this crosstalk is non-inverting crosstalk and is predictable, unnecessary sideband waves must be sufficiently suppressed by a bandpass filter with a large amount of attenuation.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional power line and to provide a power line transport device having a simple structure and requiring no pilot signal.

The terminal device of the present invention includes a voltage controlled crystal oscillator,
means for controlling the oscillation frequency of the crystal oscillator according to the deviation of the frequency of the demodulated ringer signal from a reference frequency; and means for controlling the level of the received signal according to the magnitude of the level of the demodulated ringer signal. and means for dividing and transmitting the output of the voltage controlled oscillator to generate a modulation/demodulation carrier current of an arbitrary frequency, the frequency of the modulation/demodulation carrier current and the level of the received signal being controlled by the reception ringer signal. It is characterized by being made to do.

Next, the present invention will be explained in detail with reference to the drawings.
FIG. 1 is a block diagram showing one embodiment of the present invention, and the portion surrounded by a dashed line shows the configuration related to each channel. In this embodiment, a six-channel communication line is configured. The transmission speech current S of the first channel is sent to the channel modulator 2 via the wave reducer 1, and is modulated by a channel modulation/demodulation carrier F of, for example, 128kHz.
Accordingly, only the upper sideband wave is sent to the group modulator 4. On the other hand, for example, the oscillation frequency of the voltage controlled crystal oscillator OSC of 8192 kHz is divided by 1/64, and the 128 kHz channel modulation/demodulation carrier wave F is output to the channel modulator 2.
sent to. In addition, this frequency-divided output is supplied to a frequency shift modulator 5, where the frequency is further divided, for example, 2650kHz and 2550kHz.
Ringer signals _H and _L having high and low frequencies of Hz are formed. Either one of these ringer signals _H and _L is selected in response to the presence or absence of grounding of the signal transmission terminal SIGS, and is sent to the channel modulator 2 via the low frequency filter 6, where the ringer signal is selected along with the talking current S. It is modulated by a channel modulation/demodulation carrier F. Unwanted sidebands are removed from this modulated signal by the band modulator 3, and only the upper sideband is removed by the group modulator 4.
sent to. That is, the talking current S and the ringer signal current _H or _L are input into the group modulator 4 in an integrated manner. On the other hand, the channel modulation/demodulation carrier wave F was further divided into 1/128 to form a
Phase lock loop circuit (PLL)7 for 1kHz signal
, to form a group modulated/demodulated carrier wave C ₁ , and this carrier wave C ₁ is supplied to the modulator/demodulator 4 . The output of the group modulator 4 is combined and arranged with the outputs of the group modulators 4 of all other channels to form a group band signal, which is sent to the band waver 8, where it is modulated again by the line modulator 9, and then a low frequency signal is generated. The signal is sent to the power line via the transmitter 10, the transmission amplifier 11, the bandpass amplifier 12 and the hybrid network HYB. A line modulation/demodulation carrier CS is supplied to the line modulator 9 from a phase lock loop circuit 13. A signal current modulated by the line modulation/demodulation carrier wave CR is sent from the opposite end station and input to the receiving line waver 14 via the hybrid circuit network HYB. Thereafter, the signal is sent to all channels in parallel via a line demodulator 15 and a bandpass filter 16. A line modulation/demodulation carrier wave CR is supplied to the line demodulator 15 from a phase lock loop circuit 17. The output current of the bandpass converter 16 is demodulated by the group modulation/demodulation carrier C ₁ via the automatic gain control amplifier AGC and the group demodulator 18 of the first channel, and is then combined with the signal of the other channel via the bandpass converter 19. The signal is separated and sent to the channel demodulator 20. The signal is demodulated by the channel modulation/demodulation carrier F. Of the demodulated signals, the speech current is extracted by the low frequency wave generator 21, and the ringer signal _H or _L is separated from the speech current by the band wave generator 22 and sent to the frequency shift demodulator 2.
3, the frequency is discriminated, and the signal receiving terminal SIGR is grounded or ungrounded depending on the discrimination result. The amplitude of the ringer signal _H or _L is compared with a predetermined voltage, and based on the comparison result, the gain of the automatic gain control amplifier AGC is controlled to control the level so that the amplitude of the ringer signal _H or _L approaches the predetermined voltage. This controls the level of the talking current. As a result, a pilot signal for level control becomes unnecessary. The above configuration operation is the same for each channel. However, the output current of the phase lock loop circuit 7, that is, the group modulation/demodulation carrier wave
C ₁ is the group modulation/demodulation carrier C ₂ in the second channel
Similarly, the third and subsequent channels are group modulated and demodulated carrier waves C ₃ to _{C 6} . The group modulation/demodulation carrier waves C ₁ to _{C 6} are arranged at constant frequency intervals, for example, at 2.5 kHz intervals, and the outputs of the group modulator 4 of each channel are arranged at constant frequency intervals to form a group band signal. Furthermore, in at least one channel, for example the second channel, the frequency shift demodulator 23' is provided with means for generating a control voltage for the voltage controlled crystal oscillator OSC as shown _{in FIG.} or the voltage controlled crystal oscillator OSC by _L
control the oscillation frequency. The voltage controlled crystal oscillator
The output of the OSC is frequency-divided as described above to be the channel modulation/demodulation carrier wave F, and further frequency-divided to a reference frequency of, for example, 1 kHz, which is sent to each modulation/demodulation device via the respective phase lock loop circuits.

_{FIG .} 2 is a block diagram showing an example of a configuration for generating the aforementioned oscillation frequency control _voltage .
(center frequency of _L and H) is converted into a voltage corresponding to the difference between the center frequencies of L and _H. This voltage is compared with a reference voltage (a voltage corresponding to _H − _N when there is no frequency shift in the ringer signal) in the comparator circuit 25, and the output voltage of the comparator circuit 25 is set to be negative or negative depending on the polarity with respect to the reference voltage. Or use a positive reference voltage. The output voltage of the comparator 25 and the output voltage of the frequency discrimination circuit 24 are each connected to a resistor R ₁
and added via R ₂ . This added voltage is applied to the voltage controlled crystal oscillator via the voltage amplifier 26.
It is supplied to the OSC, which controls the oscillation frequency. The output voltage of the amplifier 26 is a positive voltage when the ringer signal _L or _H is shifted toward a higher frequency due to the "shift" of each modulation/demodulation carrier wave, and a negative voltage when the frequency is shifted toward a lower frequency. becomes.
That is, regardless of whether the input ringer signal is _L or _H , a control voltage corresponding to the shift in carrier frequency is generated. As a result, a pilot signal for synchronization becomes unnecessary.

As is clear from the above description, in this embodiment, the synchronization control of the modulation/demodulation carrier wave and the level control of the received signal are performed without using the pilot signal. As a result, it is possible to eliminate the above-mentioned drawbacks of the conventional device that occur with the use of pilot signals. Further, since the level control of the received signal by the above-mentioned level adjustment means is performed for each channel, fine control corresponding to each channel can be performed even if the variation of the amount of attenuation of the power line due to the frequency characteristics is large. Note that for lines that do not require transmission and reception of ringer signals, the level may be controlled by the ringer signal of an adjacent channel.

Furthermore, in this embodiment, the channel modulation/demodulation carrier wave
A basic group arrangement is obtained by setting C ₁ to C ₆ at constant frequency intervals. Therefore, the configuration of each channel can be the same, resulting in compatibility, which is extremely convenient in manufacturing, construction, maintenance, etc. Even devices with different numbers of communication paths can have the same configuration. It goes without saying that the bandpass filters 3 and 19 may have the same pass band for all channels. In the conventional device, as mentioned above, for example, odd channels and even channels are arranged above and below 20 kHz, so many types of band wavers are required. As a result, in the conventional device, intelligible straight-line crosstalk occurs if unnecessary sideband waves in adjacent channels are not suppressed sufficiently, but in this embodiment, crosstalk due to unnecessary sideband waves in adjacent channels is not intelligible. There is also the effect that it can be inverted crosstalk. As a result, the design of the bandpass filters 3 and 19 becomes easy, and the transmission loss at the end of the passband can be reduced. Moreover, instead of the above-mentioned frequency arrangement, it is also possible to have a configuration in which the group modulation/demodulation carrier waves C ₁ to C ₆ are the same for each channel, and the channel modulation/demodulation carrier F is changed for each channel, but in this case, It is necessary to make the band wave transmitters 3 and 19 different for each channel.

Furthermore, in this embodiment, the group modulation/demodulation carrier wave
C ₁ to C ₆ and the line modulation and demodulation carriers CS and CR
are supplied by phase lock loop circuits 7, 13 and 17, respectively. The phase lock loop circuit can easily oscillate at any frequency that is an integral multiple of the input reference frequency by changing the frequency division ratio of the loop circuit using a switch.
can have the same configuration, and
Line modulation/demodulation carrier waves CS and CR can be easily changed. That is, the devices are compatible.
Further, by controlling the oscillation frequency of the voltage controlled crystal oscillator OSC by the aforementioned control means, the frequencies of all modulation/demodulation carrier waves can be controlled at once. There is no need to provide individual accurate oscillators as in conventional devices. It is of course possible to supply each carrier current by a separate multiplier circuit without using a phase-locked loop circuit.

As described above, in the present invention, the oscillation frequency of the voltage-controlled crystal oscillator and the level of the received signal are controlled by the received ringer signal, so the pilot signal is no longer necessary, and the pilot signal transmission and reception are simplified. All the drawbacks of the conventional method can be eliminated. That is, the transmission band can be narrowed and the band can be used effectively. Also, the overload point of the device can be raised. Furthermore, since a pilot is not required, the frequency arrangement can be simplified, and along with this, linear crosstalk can be eliminated, and equipment can be simplified and shared. Devices with different numbers of calls can also have the same call path configuration. Of course, there is no deterioration in transmission characteristics due to insertion and extraction of pilot signals.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a block diagram showing an example of means for controlling the oscillation frequency of a voltage controlled crystal oscillator. In the figure, 1...Low band modulator, 2...Channel modulator, 3...Band band modulator, 4...Group modulator,
5...Frequency shift modulator, 6...Low frequency generator, 7
...Phase lock loop circuit, 8... Bandwidth wave generator,
9...Line modulator, 10...Low frequency device, 11...
...Transmission amplifier, 12... Bandwidth wave generator, 13... Phase lock loop circuit, 14... Low band wave generator, 15
... Line demodulator, 16 ... Bandwidth wave device, 17 ...
Phase lock loop circuit, 18...Group demodulator, 19
... Bandwidth wave generator, 20 ... Channel demodulator, 21
...Low frequency device, 22... Bandwidth device, 23,2
3'...Frequency shift demodulator, 24...Frequency discrimination circuit, 25...Comparator, 26...Amplifier,
OSC...Voltage controlled crystal oscillator, F...Call modulation/demodulation carrier wave, _C1 to _C6 ...Group modulation/demodulation carrier wave, CS,
CR...Line modulation/demodulation carrier wave, AGC...Automatic gain control amplifier, VAGC...Gain control voltage, HYB...
...hybrid circuit network.

Claims (1)

[Scope of Claims] 1. In a power line carrier telephone terminal equipment that transmits a voice band speech current and a frequency-shifted ringer signal using a carrier suppression single sideband method, a voltage-controlled crystal oscillator and a demodulated ringer signal are used. means for controlling the oscillation frequency of the crystal oscillator according to the deviation of the frequency of the signal from the reference frequency; means for controlling the level of the received signal according to the magnitude of the level of the demodulated ringer signal; and the voltage means for dividing and multiplying the output of the controlled oscillator to generate a modulation/demodulation carrier current of an arbitrary frequency, and the frequency of the modulation/demodulation carrier current and the level of the received signal are controlled by the reception ringer signal. A power line carrier telephone terminal equipment characterized by the following. 2. The power line carrier telephone terminal equipment according to claim 1, characterized in that modulation and demodulation is performed using a channel modulation and demodulation carrier wave, and modulation and demodulation is performed using a different group modulation and demodulation carrier wave. 3. The power line carrier telephone terminal equipment according to claim 1, wherein the carrier current generating means for modulation and demodulation is constituted by a phase lock loop circuit.