KR0179599B1 - If frequency mixing apparatus in satellite communication system - Google Patents

Abstract

The present invention relates to a transmission intermediate frequency combination apparatus of a satellite communication system that can cope with multiplexing of a transmission apparatus by combining a plurality of intermediate frequencies to be transmitted in a satellite communication system. Frequency combining means for combining one frequency signal into a frequency signal, first attenuating means for attenuating the intermediate frequency signal output from said frequency combining means to a level suitable for a system, and amplifying means for amplifying the signal attenuated by said attenuation means; And second attenuating means for attenuating the intermediate frequency signal amplified by the amplifying means to a level suitable for a later system.

Description

Transmission intermediate frequency combination device of satellite communication system

1 is a general system configuration for explaining the outline of a general satellite communication system.

FIG. 2 is a block diagram showing the configuration of the central control station 2 in FIG.

3 is a circuit diagram illustrating a transmission intermediate frequency combination apparatus of a satellite communication system according to an embodiment of the present invention.

4 is a block diagram showing a case where the transmission intermediate frequency combination apparatus shown in FIG. 3 is actually applied.

* Explanation of symbols for main parts of the drawings

1: satellite 2: central control station

3A, 3B: base station 11A, 11B: switchboard

12A, 12B: Telephone 13A, 13B: Data Terminal

14A, 14B: Facsimile 21: Antenna

22: orthogonal mode converter 23: low noise amplifier

24: frequency down converter 25, 26: SCPC channel unit

27: frequency up converter 28: high power amplifier

29: network control unit 30: network management system

40: transmission intermediate frequency combination device 41: combiner

42, 44: Attenuator 43: Amplifier

45 regulator 46 current detector

RY1: Relay CP1, CP2: Comparator

VR1, VR2: Variable resistor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system using satellites, and more particularly, to a transmission intermediate frequency combination apparatus of a satellite communication system that can cope with multiplexing of a transmission apparatus by combining a plurality of intermediate frequency signals to be transmitted.

Recently, with the rapid development of communication technology, satellite communication, which enables subscribers who are located at remote sites to make calls through satellites, has become increasingly common. Since such satellite communication does not require a separate signal line for a call, It is mainly used as a long distance communication between countries or as a communication method in a mountainous country such as Korea.

In the above-mentioned satellite communication, there are two types of PAMA (Pre Assignment Multiple Access) method for allocating communication channels for each subscriber according to the channel allocation method and Demand Assignment Multiful Access (DAMA) method for allocating communication channels according to the subscriber's request. In general, in the satellite communication system for communication between subscribers, many DAMA methods are adopted in consideration of the cost and the effectiveness of the communication channel.

1 is a block diagram showing the overall system configuration of a general satellite communication system according to the DAMA method.

In Fig. 1, reference numeral 1 is a satellite having a plurality of communication channels, 2 is a central control station for controlling the entire satellite communication system, and 3 (3A, 3B) is an exchanger (11A, 11B) or a telephone (12A, 12B). Communication function between the various terminals through data transmission and reception with the central control station 2 as well as an interface function for terminals such as data terminals 13A and 13B and facsimile 14A and 14B, such as a computer. The base station that provides.

In FIG. 1, reference numeral S denotes a service channel for transmitting and receiving control data, and T denotes a traffic channel for transmitting and receiving data or voice.

In the above-described configuration, the central control station 2 transmits a control message through a service channel in a normal state and then communicates the state of each base station 3 based on a response message transmitted from the base station 3. It performs the polling function to check the available capacity or the communication channel. When there is a call request from a specific base station, for example, the base station 3A to a terminal having jurisdiction over the base station 3B, it is determined whether the base station 3B is in a state in which communication is possible based on the information obtained in the polling process. In the case of the communicable state, the available traffic channel T of the satellite is allocated to both base stations 3A and 3B so that both base stations 3A and 3B can directly communicate with each other.

Subsequently, when the communication between the base stations 3A and 3B is terminated and the communication termination signal is applied through the service channel S from the base station 3A, which has been requested for communication, the central control station 2 is applied to both base stations. By executing the communication termination process, the traffic channel T which has been provided to both base stations 3A and 3B is released.

2 is a block diagram showing the configuration of the central control station 2 described above.

In FIG. 2, reference numeral 21 is an antenna for transmitting / receiving an satellite 1, an uplink signal, and a downlink signal, and 22 is an antenna 22 using frequency polarization characteristics. Orthogonal Mode Transducer (OMT), 23 for separating and transmitting and receiving signals transmitted and received through a low noise amplifier for low noise amplifying downlink frequency signals of LNA: Low Noise Amplifier (24), 24 is a frequency down converter (DC: Down Converter) for converting a frequency signal applied through the low noise amplifier 23 into an intermediate frequency signal IF of 70 MHz, for example, 25 is the frequency down converter. SCPC (Single Channel Per Carrier) channel unit that demodulates, decodes and outputs the intermediate frequency signal (IF) applied from (24).

Further, reference numeral 26 denotes an SCPC channel unit for encoding, modulating and outputting a message output from the network controller 29 to be described later, and 27 denotes an IF signal of 70 MHz output from the SCPC channel unit 26, for example, from 14.0 to A frequency up converter (UC) for converting microwaves to 14.5 GHz to generate an uplink frequency signal, and a high power amplifier (HPA) for amplifying an uplink frequency signal output from the frequency up converter 27. Amplifier.

In addition, reference numeral 29 is a polling function that checks the state of each base station 3 based on a response message transmitted from the base station 3 after transmitting a control message to each base station 3 through the SCPC channel unit 25. If there is a call request from a specific base station, the other base station determines whether the other base station can communicate with each other based on the information obtained during the polling process. ) Is a network control unit that performs system control such that both base stations directly communicate with each other by allocating the "

In addition, reference numeral 30 denotes a network management system for managing the overall network of the satellite communication system by the system administrator to manage the network control unit 29.

That is, in the above configuration, when the network control unit 29 generates a message for each base station and outputs the message to the SCPC channel unit 26, the SCPC channel unit 26 encodes and modulates the message, such as 70 MHz. The intermediate frequency signal is converted and output, and the intermediate frequency signal is converted into an uplink frequency signal of, for example, 14.5 GHz by the frequency increase converter 27. The uplink frequency signal is output through the high power amplifier 28, the quadrature mode converter 22, and the antenna 21, and then transmitted to each base station 3 through the satellite 1 in FIG. .

Meanwhile, the response message received from the base station 3 through the satellite 1 to the antenna 21, that is, the downlink frequency signal of 12.25 GHz is transmitted through the quadrature mode converter 22 and the low noise amplifier 23 to the frequency down converter. It is applied to (24) is converted into an intermediate frequency signal of 70MHz, then applied to the SCPC channel unit 25, demodulated and decoded is applied to the network control unit 29.

Then, the network control unit 29 controls the entire communication system by controlling the status detection and call processing of each base station based on the message information from the SCPC channel unit 25.

However, in the above-described apparatus, since the central control station 2 controls the plurality of base stations 3 to provide communication functions for various subscribers coupled to each base station 3, the central control station 2 ), The problem occurs that the whole communication system is paralyzed.

In addition, since the central control station 2 manages a plurality of base stations 3, it is often necessary to transmit and receive a plurality of intermediate frequencies to demodulate or modulate.

Therefore, in the conventional satellite communication system, the SCPC channel for modulating or demodulating the data transmitted and received by the central control station 2 to the base station 3 or the data transmitted and received by the base station 3 to the central control station 2. Multiplexing of units has also been considered to deal with any abnormal conditions.

However, when the SCPC channel units are multiplexed as described above, the modulated intermediate frequency signals outputted from the multiplexed SCPC channel units multiplexed in FIG. 2 are converted into one intermediate frequency signal, and then converted into one intermediate frequency signal. If such a frequency combination is realized only through parallel connection of signal lines, the level of the transmitted frequency signal becomes unstable due to deterioration of signal level and the like. If the amplification means outputs through the amplification means, when the level of the frequency signal outputted by the amplification means is changed, the frequency detection operation of another system that receives the signal may become insufficient or the receiver may be damaged. .

Accordingly, the present invention has been made in view of the above circumstances, and combines a plurality of intermediate frequency signals into one intermediate frequency signal and stabilizes the level of the combined intermediate frequency signals to expand and stability the entire satellite communication system. It is an object of the present invention to provide a lifetime intermediate frequency combination device of the satellite communication system that can be achieved.

A transmission intermediate frequency combining device of a satellite communication system according to the present invention for realizing the above object comprises: frequency combining means for combining a plurality of input intermediate frequency signals into a predetermined frequency signal, and an intermediate outputted from the frequency combining means; First attenuation means for attenuating the frequency signal to a level suitable for the system, amplifying means for amplifying the signal attenuated by the attenuation means, and attenuating the intermediate frequency signal amplified by the amplifying means to a level suitable for subsequent systems. It characterized in that it comprises a second attenuating means to make.

In addition, the present invention is characterized in that it further comprises a current detecting means for detecting the abnormal state of the operating power supplied to the amplifying means and automatically shuts off the operating power supplied to the amplifying means when an abnormality occurs.

In addition, the current detecting means is characterized in that configured to output an abnormal signal indicating an abnormal state of the operating power supply.

According to the present invention having the above-described configuration, by combining a plurality of intermediate frequency signals into one intermediate frequency signal and stabilizing the level of the combined intermediate frequency signals, the stability of the entire satellite communication system can be achieved.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.

3 is a block diagram showing a transmission intermediate frequency combination apparatus of a satellite communication system according to an embodiment of the present invention.

In Fig. 3, reference numeral 41 denotes a frequency combiner which combines a plurality of intermediate frequency signals (five in this embodiment) IF1 to IF5 as one intermediate frequency signal, and 42 denotes this frequency combiner 41. A first attenuator for attenuating the level of the intermediate frequency signal output from the attenuator 42 to a level suitable for the system according to the selection signals S1 to S3, 43 is an amplifier for amplifying the level of the intermediate frequency signal output from the attenuator 42; Is a second attenuator for attenuating the intermediate frequency signal output from the amplifier 43 according to the selection signals S4 to S6 to a level suitable for the device to which the intermediate frequency signal is applied.

Here, the first attenuators 42 perform attenuation operations of 0.5 dB, 1 dB, and 2 dB, respectively, in accordance with the selection signals S1 to S3, and the second attenuators 44 respectively according to the selection signals S4 to S6. Attenuation of 4dB, 8dB and 16dB is achieved.

Reference numeral 45 is a regulator for applying a constant voltage to the amplifier 43, and C1 and C2 are smoothing capacitors.

In FIG. 3, reference numeral RY1 is a relay provided to the power supply line applied from the regulator 45 to the amplifier 43 to interrupt the operating power supplied to the amplifier 43. The relay RY1 Is to control the operating voltage applied to the amplifier 43 according to the detection signal from the current detector 46 to be described later.

In addition, reference numeral 46 denotes a current detector for detecting an abnormal state of the current applied to the amplifier 43. The first comparator CP1 detects that the supply current supplied to the amplifier 43 falls below a predetermined level. ) And a second comparator (CP2) for detecting that the supply current rises above a certain level.

In the first and second comparators CP1 and CP2, the voltage supplied to the amplifier 43 is coupled to the inverting terminal (−) and the non-inverting terminal (+), respectively. In addition, the resistors R5 and R6 and the variable resistor VR1 are connected in series between the power supply line to the amplifier 43 and the ground for supplying the reference voltage of the first comparator CP1, and the resistor R5. A connection point of R6 is coupled to the non-inverting terminal (+) of the first comparator CP1, and is connected between a power supply line to the amplifier 43 and a ground for supplying a reference voltage of the second comparator CP2. (R7, R8) and the variable resistor VR2 are connected in series, and the connection points of the resistors R7 and R8 are coupled to the inverting terminal (-) of the second comparator CP2.

In addition, a resistor R4 is provided between the connection point of the resistors R5 and R7 to the power supply line to the amplifier 43 and the connection point of the first and second comparators CP1 and CP2. The drop voltage of the resistor R4 changes according to the amount of current flowing through the power supply line. Accordingly, the first and second comparators CP1 and CP2 can detect a variation range of the amount of current supplied to the amplifier 43 based on the voltage difference between the both ends of the resistor R4.

In addition, in the above configuration, the variable resistors VR1 and VR2 are used to appropriately adjust the reference voltages for the first and second comparators CP1 and CP2, wherein the first and second comparators CP1 and CP2. Denotes reference voltages set by the variable resistors VR1 and VR2, that is, reference voltages applied to the non-inverting terminal (+) of the first comparator CP1 and the inverting terminal (-) of the second comparator CP2, respectively. When V1 and V2 are supplied and the supply voltage to the amplifier 43 is Vo, a low level voltage is output in the case of V1VoV2 and a high level voltage is output in the case of VoV1 or VoV2.

The output signals of the first and second CP1 and CP2 are applied to the relay RY1 side through the AND gate AND1 and coupled to the anode side of the reverse current preventing diode D1.

In addition, the power supply voltage Vcc is coupled to the output terminals of the first and second comparators CP1 and CP2 through a resistor R9, and an abnormal signal FAIL indicating an abnormal state of the power supply from the coupling node is provided. It is supposed to be output.

In addition, the power supply voltage Vcc applied to the combined node of the diode D1 and the relay RY1 is for preventing the relay RY1 from being turned off due to an instantaneous voltage abnormality of the present circuit.

Next, the operation of the device having the above configuration will be described.

In the above configuration, when a plurality of intermediate frequency signals are inputted from a plurality of SCPC channel units, first, the frequency combiner 41 combines the signals into one intermediate frequency signal and the level of the signal is increased by the first attenuator 42. It will be attenuated to a signal level suitable for the system.

Then, the intermediate frequency signal output from the first attenuator 42 is amplified to a predetermined level by the amplifier 43 and level compensated, and then by the second attenuator 44 to the level of the device to which the intermediate frequency signal is applied. The output will be attenuated properly.

In addition, in the normal state as described above, the outputs of the first and second comparators CP1 and CP2 of the current detector 46 are maintained at a high level. Therefore, in this case, the cathode side of the diode D1 and the output level of the AND gate AND1 are set to a high level so that no current flows through the coil of the relay RY1, thereby allowing the regulator 45 to the amplifier 43. Normal operating power is supplied.

At this time, the power supply voltage Vcc is outputted to the abnormal signal output terminal FAIL through the resistor R9, thereby outputting a high level normal signal.

On the other hand, when the supply current value supplied from the regulator 45 to the amplifier 43 falls below a certain value due to an abnormality occurring in the amplifier 43 or the like in the above-described operating state, the resistance of the current detector 46 is reduced. As the voltage drop by R4 is lowered, the voltage applied to the non-inverting terminal (+) of the first comparator CP1 is lower than the voltage applied to the inverting terminal (-) side, thereby lowering the voltage from the first comparator CP1. The voltage of the level is output. That is, the output terminal of the first comparator CP1 is set at the low level.

Accordingly, the power supply voltage Vcc applied through the resistor R9 is lowered to the ground level by the output of the first comparator CP1, thereby outputting the low level abnormal signal through the abnormal signal output terminal FAIL. . Then, the output of the AND gate AND1 is lowered to the low level, so that the power supply voltage Vcc flows to the output terminal side of the AND gate AND1 through the coil of the relay RY1, whereby the relay RY1 is turned off and the amplifier As the operating power supplied to the 43 is cut off, the malfunction state of the amplifier 43 is prevented.

In the normal operation state, when the supply current value supplied from the regulator 45 to the amplifier 43 rises above the predetermined value due to an abnormality in the amplifier 43 or the like, the resistance R4 of the current detector 46 As the voltage drop due to) increases, the voltage applied to the inverting terminal (-) side of the second comparator CP2 becomes higher than the voltage applied to the non-inverting terminal (+) side, thereby lowering the voltage of the second comparator CP2. Will be output.

Accordingly, the power supply voltage Vcc applied through the resistor R9 is lowered to the ground level by the output of the second comparator CP2, thereby outputting the low level abnormal signal through the abnormal signal output terminal FAIL. . Then, the output of the AND gate AND1 is lowered to the low level, so that the power supply voltage Vcc flows to the output terminal side of the AND gate AND1 through the coil of the relay RY1, whereby the relay RY1 is turned off and the amplifier As the operating power supplied to the 43 is cut off, the malfunction state of the amplifier 43 is prevented.

4 is a block diagram showing a case in which the above-described transmission intermediate frequency combination apparatus is actually applied, and thus, a single intermediate frequency signal can be generated through the intermediate frequency combination apparatus 40 as described above, thereby providing a plurality of SCPC channel units. It can be used to effectively deal with the case of using the system to expand the capacity.

Therefore, according to the above embodiment, one intermediate frequency signal is generated by combining a plurality of intermediate frequencies, and the combined signal is converted into a signal suitable for a later circuit by using a selection signal from the outside and output. This allows for increased scalability of system capacity.

In addition, when an error occurs in the amplifier used in the frequency combining process and a change occurs in the operating power applied to the amplifier, the supply of the operating power to the amplifier is automatically shut off and the abnormal state signal is output to the outside. Therefore, the system administrator can easily recognize the abnormal state and can prevent other systems from being damaged by the abnormal operation of the amplifier.

In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the technical scope of the present invention.

As described above, according to the present invention, satellite communication is designed to stabilize the overall satellite communication system by combining a plurality of intermediate frequency signals into one intermediate frequency signal and stabilizing the level of the combined intermediate frequency signals. The transmission intermediate frequency combination device of the system can be realized.

Claims (3)

Frequency combining means for combining a plurality of intermediate frequency signals input into a predetermined frequency signal, first attenuation means for attenuating the intermediate frequency signal output from the frequency combining means to a level suitable for a system, and the attenuation means Amplifying means for amplifying the attenuated signal, and second attenuating means for attenuating the intermediate frequency signal amplified by the amplifying means to a level suitable for a later system. Combination device. The satellite according to claim 1, further comprising a current detecting means for detecting an abnormal state of the operating power supplied to the amplifying means and automatically shutting off the operating power supplied to the amplifying means when an abnormality occurs. Transmission intermediate frequency combination device of communication system. The apparatus of claim 2, wherein the current detecting means outputs an abnormal signal indicating an abnormal state of an operating power source.