JPH0129099B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a voice band communication current (including not only a voice current but also a measurement control signal and a data signal) and a frequency shift type ringer signal. The present invention relates to a multiplexed power line carrier telephone terminal equipment that transmits data using a carrier suppressed single sideband method.

[Conventional technology]

Conventionally, in this type of device, a part of the modulated and demodulated carrier wave on the transmitting side is sent to the receiving side as a pilot current, and on the receiving side, at least part of the demodulated carrier wave current is extracted by separating and extracting the pilot current in the demodulation stage. I am getting .

[Problem to be solved by the invention] Therefore, a narrow band filter, an amplifier, etc. are required to separate and extract this pilot current.
In addition, it has a negative effect on the communication current transmitted in the frequency band close to this pilot frequency.
It is necessary to provide a separate frequency band between this pilot frequency and the communication current band.

Pilot signals are also used to control the gain of receiving amplifiers and the like in response to variations in power line transmission loss. 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. For this reason, for example, a device transmitting six communication paths requires at least three pilot signals, and the insertion of the pilot signals widens the transmission band, which has the disadvantage that the band cannot be used effectively.

Furthermore, the frequency allocation at each modulation/demodulation stage is restricted due to pilot signal insertion, and usually the lower sideband of odd channels is placed on the lower side of 20KHz, and the upper band of even channels is placed on the upper side, and these are group modulated at intervals of 6KHz, for example. The basic group is modulated by a carrier wave, and this basic group is further modulated by a line modulated carrier wave and sent to the power line.

For this reason, for example, if the upper sideband waves of the odd channels are not sufficiently suppressed, the upper sideband waves are linearly added to the communication current of the even channels, causing crosstalk. Since this crosstalk is non-inverted crosstalk and is intelligible, unnecessary sideband waves must be sufficiently suppressed. Therefore, the above-mentioned even channel,
It is necessary to provide a separate frequency spacing between the odd channels, which increases the disadvantages mentioned above.

The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks and
An object of the present invention is to provide a power line carrier telephone terminal equipment that effectively utilizes a limited line frequency band by making the separation frequency interval narrower than that of conventional equipment.

[Means for solving problems]

The present invention provides a voltage-controlled crystal oscillator, a means for controlling the oscillation frequency of the crystal oscillator according to a deviation of the frequency of a demodulated ringer signal from a reference frequency, and a means for controlling the oscillation frequency of the crystal oscillator according to the deviation of the frequency of a demodulated ringer signal from a reference frequency, the frequency of the modulation/demodulation carrier current and the level of the reception signal, comprising: means for generating it in a phase lock loop circuit based on the oscillation frequency; and means for controlling the level of the received signal according to the magnitude of the demodulated ringer signal; is configured to be controlled by a received ringer signal.

[Effect]

In the present invention, the oscillation frequency of a voltage-controlled crystal oscillator, which is the main oscillator, is controlled by using a frequency-shifted ringer signal that is received together with the speech current in the voice band, and each carrier current and ringer signal is output from the main oscillator. By generating signal current in a phase lock loop circuit and controlling the level of the received signal, synchronization of transmitting and receiving frequencies between opposing devices and automatic gain control are achieved, eliminating the need for pilots in conventional devices. By eliminating the need for signal current, the separation frequency spacing between each telephone line is reduced.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing an apparatus according to an embodiment of the present invention. In this embodiment, a three-channel communication line is configured.

The transmitting speech current s of the first channel is sent to the modulator 2 via the terminal S and the low-band transmitter 1, and is modulated by a modulation carrier F of, for example, 100 KHz. only is sent to the transmit amplifier 4.

On the other hand, the oscillation frequency of the voltage controlled crystal oscillator 5 of, for example, 1 MHz is decreased by a phase lock loop circuit 6 and sent to the modulator 2 as the modulation carrier wave F of 100 KHz. Further, the oscillation frequency of 1MHz of this voltage controlled crystal oscillator 5 is supplied to a frequency shift modulator 7 whose input is connected to the signal transmission terminal SIG S, and is divided in this frequency range modulator 7, for example, 2560Hz and Two high and low frequency ringer signals f _H and f _L of 2550 Hz are formed. One of these ringer signals f _H and f _L is the signal transmission terminal.
It is selected in response to the presence or absence of grounding of SIG S, and is sent to the modulator 2 via the bandpass filter 8, where it is modulated by the modulation carrier F along with the communication current. Unnecessary sideband waves are removed from this modulated signal by the bandpass filter 3, and only the upper sideband wave is sent to the transmission amplifier 4.

That is, the communication current s and the ringer signal f _H or f _L are integrated and input to the transmission amplifier 4 . The output current from the transmission amplifier 4 is
The signal is supplied to the phase comparator circuit 10 via the bandpass filter 9, and is also sent to the power line via the hybrid circuit 11 and the line terminal L as a transmission signal. The phase comparator circuit 10 compares the phase and level values of the transmitted signal and a wraparound signal to the receiving side that occurs due to mismatch between the transmitted signal and the power line, using the oscillation frequency from the voltage controlled crystal oscillator 5 as a reference. do. Further, the phase comparator circuit 10 performs impedance matching with the power line by controlling the value of the balance resistor of the hybrid circuit 11 so that the wrap-around signal becomes the minimum value based on the comparison result, and the transmission signal is connected to the line terminal. Sent to L.

Further, a transmission signal from the other end station is input to a demodulator 15 via a hybrid circuit 11, a bandpass converter 12, a receiving amplifier 13, and a bandpass converter 14. This demodulator 15 demodulates the oscillation frequency from the voltage controlled crystal oscillator 5 by a demodulated wave F' of, for example, 110 KHz, which is reduced by a phase lock loop circuit 16. Of this demodulated signal, the communication current r
is taken out by the low frequency filter 17 and sent to the terminal R. Further, among the demodulated signals, the ringer signal f _H or f _L is separated from the speech current r by the bandpass converter 18 and input to the frequency shift demodulator 19, and then subjected to frequency discrimination, and based on the discrimination result, the signal receiving terminal SIG Ground or unground R. The amplitude of the ringer signal f _H or f _L is compared with a predetermined voltage, and the gain of the receiving amplifier 13 is controlled based on the comparison result to bring the amplitude of the ringer signal f _H or f _L closer to the predetermined voltage. The level of the communication current r is thereby controlled.

The above configuration and operation are the same for the second and third channels, so repeated explanation will be omitted.

On the other hand, the above ringer signal f _H of any one channel
Alternatively, f _L is converted into a voltage corresponding to the difference from the reference frequency, and by controlling the oscillation frequency of the voltage-controlled crystal oscillator 5, the oscillation frequency of the voltage-controlled crystal oscillator 5 is synchronized with the received ringer signal frequency.

FIG. 2 is a detailed block diagram of this voltage controlled crystal oscillator 5. In FIG. 2, the ringer signal f _H or f _L sent out from the bandpass filter 18 is guided to a frequency discrimination circuit 21 via a terminal 20. In FIG.
This frequency discrimination circuit 21 selects the ringer signal f _H or
Convert f _L to the corresponding voltage (V _H ) or (V _L ). The output of this frequency discrimination circuit 21 is led to a comparison input of a comparator 22. A reference voltage is applied to the reference input of this comparator 22.

The comparator 22 outputs a voltage (+V) when the comparison voltage is lower than the reference voltage, and outputs a voltage (-V) when the comparison voltage is higher than the reference voltage. The comparison output of this comparator 22 is guided to a voltage mixing circuit 23. This voltage mixing circuit 23 adds the comparison output and the output of the frequency discrimination circuit 21, and the added output is amplified by the voltage amplifier 24 of the mixing circuit 23. The output of this voltage amplifier 24 is led as a control input to an oscillation circuit 25 to control the oscillation frequency of this oscillation circuit 25.

If there is a frequency deviation (Δf) in the ringer signal f _H or f _L , the voltage converted by the frequency discrimination circuit 21 becomes (V _H +ΔV) or (f _L +ΔV), respectively. This voltage (V _H +ΔV) or (V _L +ΔV) is compared with the reference voltage by the comparator 22, and when the comparison input is the voltage (V _H +ΔV), the voltage (-V) is output, and the voltage (V _L +ΔV )
When , voltage (+V) is output.

If the setting conditions of the voltage mixing circuit 23 are selected so that V _H −V=0, V _L +V=0, the output of the voltage mixing circuit 23 will be as follows when the ringer signal (f _H +Δf) is input to the terminal 20. (V _H + ΔV) + (-V) = ΔV, and when the ringer signal (f _L + Δf) is input to terminal 20, (V _L + ΔV) + (+V) = ΔV, and in either case the ringer signal The addition output becomes a voltage (ΔV) proportional to the frequency deviation Δf of the ringer signal.

Thereby, the oscillation frequency of the voltage controlled crystal oscillator 5 is synchronized with the received ringer signal frequency.

〔Effect of the invention〕

As is clear from the above explanation, by using the ringer signal that is transmitted and received along with the communication current to synchronize the frequencies between opposing devices and by automatically controlling the received signal level, the pilot This eliminates the need for a signal and the frequency band required for the pilot signal.
Further, since the pilot signal is not required, the frequency arrangement at each modulation/demodulation stage can be freely arranged, and the separation frequency interval between each communication channel can be made small.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. FIG. 2 is a detailed block diagram of the voltage controlled crystal oscillator shown in FIG. 1. 1...Low band generator, 2...Modulator, 3...Band band generator, 4...Transmission amplifier, 5...Voltage controlled crystal oscillator,
6... Phase lock loop circuit, 7... Frequency shift modulator, 8, 9... Bandwidth wave generator, 10... Phase comparator circuit,
11...hybrid circuit, 12...bandwidth wave generator, 1
3... Reception amplifier, 14... Bandwidth wave generator, 15... Demodulator, 16... Phase lock loop circuit, 17... Low frequency wave generator, 18... Bandwidth wave generator, 19... Frequency shift demodulator, 20... Terminal, 21... Frequency Discrimination circuit, 22...
Comparator, 23... Voltage mixing circuit, 24... Voltage amplifier, 25... Oscillation circuit.

Claims (1)

[Scope of Claims] 1. In a multiplexed power line carrier telephone terminal equipment for transmitting a voice band speech current and a frequency-shifted ringer signal by a carrier-suppressed single sideband method, comprising: a voltage-controlled crystal oscillator; means for controlling the oscillation frequency of the crystal oscillator according to the deviation of the frequency of the ringer signal from the reference frequency, and generating a carrier current for modulation/demodulation and the ringer signal in a phase lock loop circuit based on the oscillation frequency of the crystal oscillator. A power line carrier telephone terminal apparatus, comprising: means for controlling the level of a received signal according to the level of the demodulated ringer signal.