KR19990042741A - Gain compensation circuit - Google Patents

Abstract

In the communication terminal, in order to compensate for the signal attenuated according to the environment of the communication line, the direct current voltage is rectified and output from the bridge circuit by connecting a resistor in series with the bridge circuit to rectify the AC power supplied from the exchanger in the primary power supply of the terminal. By detecting the current value flowing through the resistor according to the voltage drop generated when passing through the resistor, it is possible to recognize the amount of signal attenuation in the communication line, thereby automatically adjusting the gain according to the signal attenuation of the communication line.

Therefore, since the current amount of the communication line can be detected by adding a resistor to the primary power supply of the terminal, a separate echo signal for measuring the signal attenuation is not required, and the signal attenuation amount of the communication line is detected and compensated for. There is an advantage in that the gain can be adjusted.

Description

Gain compensation circuit

The present invention relates to a gain compensation circuit, and more particularly, in order to compensate for a signal attenuated according to the environment of a communication line during transmission and reception at a communication terminal, a voltage supplied from the communication line by adding a resistance to a primary power supply unit of the terminal. The present invention relates to a gain compensating circuit which detects a current value according to a voltage drop generated while passing through a resistor, thereby determining an amount of signal attenuation and automatically adjusting a gain to be compensated accordingly.

In general, a communication terminal such as a telephone is a device used for exchanging desired information with each other by performing voice or non-voice communication with a remote party, and in order to form a call path for exchanging such information, There is an exchanger that transmits an information signal between the receiver and the receiver and switches and amplifies the transmitted signal between the transmitter and the receiver, and these transmitters, receivers and exchanges are interconnected by a communication line.

Using these communication terminals, voice or non-voice signals are transmitted / received through a public telephone network, which is a communication line, while the signal transmitted from the transmitting side is transmitted along the communication line to the receiving side. The attenuation of the transmitted / received signal is caused by the external environment. Accordingly, when a communication path is formed to compensate the gain of the attenuated signal, a signal attenuation amount is detected on a communication line for transmission / reception, and a signal previously gain-compensated by the attenuation amount is transmitted / received.

In addition, for communication, most countries set communication standards such as transmission / reception frequency characteristics and sound pressure for normal communication, and the communication terminal must satisfy these standards. Thus, a signal for performing communication must be transmitted after gain compensation has been made. Here, when the terminal uses the power supplied from the exchange, it is possible to detect the amount of current in the communication line to perform communication by compensating the gain as prescribed by the detected current value, and supplying a speaker phone mode or a separate power source. When communicating using a cordless telephone or the like used, a method for detecting a signal attenuation amount is required because the power supplied from the exchange cannot be detected.

A general voice signal transmission / reception step will be described with reference to FIG. 1 as follows.

In the speaker phone mode, when a voice signal is input through a microphone, the signal is an analog signal and thus amplified and then converted into digital data and converted into digital data for recognition by the control unit 2 through the A / D converter 1. The data is converted into an analog signal by the D / A converter 3 again under the control of the control unit 2, and then through the 4-wire / 2-wire coupling 5 of the LIU (Line Interface Unit) 4, It is sent to the public telephone network. The signal transmitted to the exchange via the communication line is amplified and transmitted to the switched receiver according to the receiver identifier input from the transmitter. In addition, since the received signal is amplified at the exchange and received separately from the power supply by the 4-wire / 2-wire coupling 5 of the LIU 4, and the signal attenuation occurs during transmission through the communication line at the exchange, It is gain-compensated so as to be recognized and converted into digital so that it can be recognized by the control unit 2 through the D / A converter 3. Under the control of the control unit 2, the received voice signal, which is converted into analog again by the A / D converter 2, can be recognized by the user through the speaker.

In the conventional communication terminal, a method for detecting signal attenuation according to a communication line for gain compensation in order to normally perform communication is as follows.

In the above communication, in order to compensate for the attenuation of the signal before the information signal is transmitted, the signal attenuation amount of the communication line must be detected in advance and the gain-compensated signal is transmitted to the receiving side. In order to detect the amount of signal attenuation, the terminal sends out a predetermined echo signal which is fed back first before the signal for communication is transmitted. This signal is fed back to the receiving direction from the LIU through the transmitting step and input to the speaker. First, in order to detect the amount of signal attenuation according to the actual communication line, the amplifier gain inside the speakerphone is adjusted. For example, the target gain to be obtained in the feedback signal is set to 4 dB, and the echo signal for transmission adds 12 dB for detecting the attenuation amount to 4 dB, and a total signal of 16 dB is transmitted. 12 dB is adjusted by the amount of signal attenuation according to the power supplied from the primary side while passing through the LIU 4 according to the transmitting step of FIG. 1, and the adjusted gain value attenuated according to the state of the 4 dB and the communication line is received through the receiving step. When the gain value of the echo signal is detected by the received signal, the gain value adjusted in addition to the target gain can be recognized in comparison with the set signal, thereby detecting the amount of signal attenuation of the connected communication line.

However, according to the method for gain compensation of signal attenuation according to a communication line in the conventional communication terminal as mentioned above, the following problems occur.

(1) In order to grasp the signal attenuation of the communication line, it is impossible to directly detect the amount of current supplied from the exchange in the terminal using the speaker phone mode or a separate power source such as a cordless telephone. A step of transmitting a separate signal for a predetermined time for detecting a signal attenuation amount of the communication line is required for gain compensation for reception.

(2) If the amount of signal attenuation of the communication line is unknown at the primary power supply, further circuit and method configurations are needed to control the communication standard for normal communication at the secondary.

Accordingly, the present invention is to solve the above problems, the first object of the present invention is the amount of signal attenuation detected by adding a circuit for detecting the amount of signal attenuation in the primary side power supply unit directly connected to the exchange through a public telephone network in the terminal; It is to provide a gain control circuit to compensate for this according to.

In addition, the second object of the present invention is to control the gain by automatically adjusting the gain according to the detected signal attenuation amount, and transmitting a compensated signal to the secondary side by the switched communication loop to add a separate circuit to satisfy the requirements of the communication standard. It is another object of the present invention to provide a gain control circuit that enables normal communication without the need.

1 is a circuit diagram for detecting a signal attenuation amount according to the prior art;

2 is a circuit diagram for automatically adjusting gain compensation according to the current amount detection according to the present invention.

<Description of the code | symbol about the principal part of drawing>

6: bridge circuit 7: voltage detector

8: A / D converter 9: control unit

10: gain compensation section 11: signal processing section

12: handset interface unit 13: speakerphone interface unit

14: DSP interface 15: photo coupler

16: switch

A feature of the present invention for achieving the above objects is that, in a communication terminal, when a signal is transmitted / received on a communication line connecting the exchange and the communication terminal, the signal is gain-compensated according to the amount of signal attenuation generated. A circuit for receiving, the circuit comprising: a bridge circuit for rectifying power supplied from the exchange; A voltage detector connected in series with an output portion of the bridge circuit to detect a voltage drop generated when a DC voltage output from the bridge circuit passes; An analog / digital converter for converting a digital value to be recognized in the communication terminal by inputting a current value proportional to the voltage drop detected by the voltage detector; A control unit which receives data according to the amount of current converted into digital by the analog / digital converter and controls a gain compensation value of a signal attenuated during transmission / reception; A gain compensator for gain compensating and outputting the information signal input from the exchange under the control of the controller, and receiving and gain compensating the input information signal according to the user's selection; And a signal for processing the gain-compensated received signal input from the gain compensator so as to be recognized by the user, and gain-compensating the input signal selected by the user and outputting the gain signal to the gain compensator for transmission to the receiver through the exchange. The gain compensation circuit includes a processing unit.

Hereinafter, a gain compensation control circuit according to signal attenuation detection according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram for automatically controlling gain compensation in accordance with the signal attenuation detection of a communication line according to the present invention.

In order to carry out the present invention, a voltage drop generated by passing a DC voltage output from the bridge circuit 6 through a bridge circuit 6 and a bridge circuit 6 for rectifying the DC power supplied from the exchanger is passed. A / D converter 8 and A / D converter 8, which converts the current amount in proportion to the value and converts it to digital, to the voltage drop detected by the voltage detector 7 and the voltage detector 7, When the inputted data is input, the controller 9 adjusts the gain compensation value of the input / output information signal from the terminal, and outputs the gain compensation of the information signal input from the exchange under the control of the controller 9. The user may recognize a gain compensator 10 for receiving an input information signal according to a selection and gain compensating the output signal to the exchange, and a gain compensated received signal input from the gain compensator 10. And a signal processor 11 for outputting to the gain compensator 10 for transmitting the input signal selected by the user to the receiver through the exchange.

Here, the voltage detector 7 preferably uses a resistor to easily detect the voltage value of the voltage drop.

In addition, the power supply unit of the terminal separates the power supply portion using the power supplied from the exchanger to the primary side power supply portion, and the power supply portion that is converted into direct current by receiving a separate AC power source and used as a secondary power supply portion. The primary side and the secondary side power supply units may be divided based on the porter coupler 15.

When DC power is supplied from the exchange to the terminal through the public telephone network, it is output along the power supply loop and rectified in the bridge circuit 6. As the rectified DC voltage passes through the resistor 7 connected in series with the output of the bridge circuit 6, the voltage value due to the voltage drop generated in the resistor 7 can be known and the amount of current is detected by the resistance value and the voltage value. do. The detected amount of current is input to the A / D converter 8, converted into digital so that the analog signal can be recognized in the terminal, and then transmitted to the control unit 9. The control unit 9 adjusts the gain of the information signal to be input / output at the terminal by recognizing the signal attenuation amount of the communication line connected to the exchange according to the digitally converted and input data of the detected current amount. In other words, when the low current value is input, the gain of the amplifier is increased, and when the high current value is input, the gain of the amplifier is reduced to compensate for the gain due to the attenuation of the transmitted / received information signal. When the gain value is adjusted under the control of the controller 9 and transmitted to the gain compensator 10, the gain compensator 10 gain-compensates the information signal received from the exchange so that the user can recognize the signal. 11), and when the information signal input by the user is transmitted to the signal processing unit 11 and input, the signal is compensated for gain and transmitted to the public circuit network through the LIU (not shown) so that the signal can be transmitted to the receiving side through the exchange. Output

In addition, the signal processor 11 in which the gain-compensated signal is input and the input signal selected by the user is transmitted in the configuration of detecting and compensating for the signal attenuation as described above is switched to the handset communication loop according to the user's communication method selection. Interfacing the handset interface unit 12, the speakerphone interface unit 13 to be switched and interfaced with the communication rope in the speakerphone mode, the DSP interface unit 14 for processing digital signals input and output in the speakerphone mode, DSP interface unit Input / output according to the operation of the photocoupler 15 and the photocoupler 15 which operate according to a control signal for setting the speakerphone mode transmitted from 14 and divide the power supply unit into a primary side power supply unit and a secondary side power supply unit. The switch 16 is configured to switch the signal to the handset and speakerphone modes to form a communication loop.

Here, the switch 16 is basically switched to the handset interface 12 to form a communication loop for use of the handset. When the user picks up the handset and is in the hook-off state, since the control signal for setting the speakerphone mode is not transmitted, the switching unit 16 maintains the switching state in the handset communication loop because the photocoupler 15 does not operate. . When the speakerphone mode is set, the speakerphone control signal is transmitted to the photocoupler 15 through the DSP interface central processing unit 14 on the secondary side. The current flows through the photocoupler 15 in accordance with the transmitted control signal, and the communication loop is switched from the switching unit 16 to the speakerphone interface unit 13 according to the operation of the photocoupler 15. When the communication loop is formed according to the signal transmitted from the photocoupler 15 in the switching unit 16, the signal compensated for gain through the input / output unit 11 is transmitted to the secondary side through the switching unit 16. In the above-described method, in the case of a circuit for automatically controlling gain compensation according to signal attenuation according to the present invention, since the signal compensated for all voice frequency bands can be supplied to the secondary side, the circuit itself does not need to be considered separately. Can control normal communication performance.

Therefore, when the DC power supplied from the exchanger is rectified while passing through the bridge circuit and the rectified DC voltage passes through the resistor connected in series with the bridge circuit, the current value flowing through the resistor is detected and transmitted to the controller. The signal attenuation of the communication line can be known according to the current value, and the gain compensation value can be adjusted accordingly, and the gain-compensated signal information signal is transmitted to the signal processor which is switched to the handset or speakerphone mode according to the user's selection to form a communication loop. Since the signal processing unit can be controlled so that normal communication can be made without a separate control of the communication standard.

As a result, according to the circuit for detecting the communication line signal attenuation amount according to the present invention and adjusting the gain compensation accordingly, there are advantages as follows.

(1) The terminal does not require a gain detection step of transmitting a separate echo signal for measuring the amount of signal attenuation, and adds a resistor in series to the output terminal of the bridge circuit for rectifying the power to detect the amount of current in the communication line. Since the amount of signal attenuation can be known, the amount of signal attenuation of the communication line can be detected and the gain to compensate for this can be adjusted.

(2) When the information signal is transmitted to the signal processing unit, the switching unit is configured to form a communication rope by switching to a handset or speakerphone mode according to a user's communication method selection, and a gain-compensated signal when switching to an interface unit to form a communication loop. Since the signal is transmitted from the signal processor, the burden of circuit and method operation on the primary signal change using the power supplied to the exchange is reduced.

Claims (1)

In a communication terminal, when a signal is transmitted / received on a communication line connecting the exchange and the communication terminal, a circuit for gain-compensating and transmitting / receiving a signal according to a signal attenuation amount generated at the time of transmitting / receiving an information signal. : A bridge circuit for rectifying power supplied from the exchanger; A voltage detector connected in series with an output portion of the bridge circuit to detect a voltage drop generated when a DC voltage output from the bridge circuit passes; An analog / digital converter for converting a digital value to be recognized in the communication terminal by inputting a current value proportional to the voltage drop detected by the voltage detector; A control unit which receives data according to the amount of current converted into digital by the analog / digital converter and controls a gain compensation value of a signal attenuated during transmission / reception; A gain compensator for gain compensating and outputting the information signal input from the exchange under the control of the controller, and receiving and gain compensating the input information signal according to the user's selection; And, A signal processor which processes a gain-compensated received signal input from the gain compensator so as to be recognized by a user, and outputs the gain-compensated input signal selected by the user to the gain compensator for transmission to the receiver through the exchange A gain compensation circuit comprising.