KR20030050540A - RF-repeater having a function of oscillation protection in CDMA communication system - Google Patents

Abstract

PURPOSE: A wireless relay device having an oscillation preventing function for a CDMA(Code Division Multiple Access) mobile communication system is provided to prevent an oscillation state by detecting an initial oscillation state on the basis of an input time and a level of a signal provided from a base station-side antenna, adjusting an amplification gain of a relayed signal, and securing the isolation degree between the base station-side antenna and a terminal-side antenna. CONSTITUTION: The first antenna(10) communicates with a base station. The second antenna(70) communicates with a wireless communication terminal. The first and second amplifiers(50,100) amplify signals received from the first and second antennas(10,70). If an input signal provided from the base station through the first antenna(10) has a fog signal time which is quicker than the minimum fog signal time between the input signal and a previous input signal, and a level of the input signal is higher than a level of the previous input signal, an oscillation detecting unit(110) generates a certain oscillation detecting signal. A control unit(120) adjusts the amplification gains of the first and second amplifiers(50,100) on the basis of the oscillation detecting signal provided from the oscillation detecting unit(110).

Description

Radio repeater for CDA communication system with oscillation prevention function {RF-repeater having a function of oscillation protection in CDMA communication system}

The present invention relates to a wireless relay device for a CDM communication system, and in particular, an oscillation state is detected at the beginning of oscillation based on the input time of a signal applied from a base station antenna and its signal level. The present invention relates to a wireless relay device for a CD communication system having an oscillation prevention function to prevent an oscillation state by controlling the amplification gain of a signal to secure the isolation between the base station side antenna and the terminal side antenna.

With the rapid development of communication technology, wireless communication systems such as mobile communication system, wireless calling system, WLL, TRS, and IMT-2000 system have been developed and popularized. Recently, these wireless communication systems divide the frequency and time into communication channels. The trend is to use a CDMA communication method for allocating a CDMA.

In addition, the wireless communication system is configured to provide a communication service for a plurality of wireless communication terminals existing in its own control cell area in a plurality of base stations that control a predetermined communication cell area, wherein the control cell area of the base station In accordance with its location, a predetermined communication shaded area is formed due to a dense location such as a mountainous area or a large building.

In order to prevent the degradation of the communication service due to the formation of the communication shaded area, the wireless relay device amplifies the signal received from the base station and sends it to the wireless communication terminal, and amplifies the signal received from the wireless communication terminal and sends it to the base station. Has been developed and introduced.

That is, as shown in FIG. 1, the wireless relay apparatus selects a signal applied from a first antenna for communicating with a base station and a second antenna for performing communication with a wireless communication terminal, and first and second antennas. And amplifying means for outputting the level amplification.

In this case, since the forward link from the base station to the wireless communication terminal and the reverse link from the wireless communication terminal to the base station exist at the same time as described above, if the proper isolation between the links is not ensured, the signal between the links is lost. Will have a mutual influence on the oscillation phenomenon.

In addition, the oscillation phenomenon generated in the wireless repeater affects the input signal, resulting in the input signal being distorted and outputted, and the repeated oscillation phenomenon causes the problem of paralyzing the function of the wireless repeater.

Accordingly, the present invention has been made in view of the above circumstances, and based on the fact that a signal having a higher level than the previous input signal is applied from the base station within a predetermined time, the oscillation phenomenon is initially detected, and based on this, It is a technical object of the present invention to provide a wireless relay device for a CDMA communication system having an oscillation prevention function that prevents oscillation by controlling the amplification gain level so that minimum isolation between the base station antenna and the terminal antenna is maintained.

1 is a view for explaining the configuration of a general wireless relay device

Figure 2 is a block diagram showing the functional separation of the internal configuration of the radio relay apparatus according to the first embodiment of the present invention.

Figure 3 is a block diagram showing the functional separation of the internal configuration of the oscillation detection unit 110 shown in FIG.

Figure 4 is a block diagram showing the functional separation of the internal configuration of the radio relay apparatus according to the second embodiment of the present invention.

FIG. 5 is a block diagram showing functional separation of another internal configuration of the oscillation detection unit 110 shown in FIG.

Figure 6 is a block diagram showing the functional separation of the internal configuration of the radio relay apparatus according to the third embodiment of the present invention.

Figure 7 is a block diagram showing the functional separation of the internal configuration of the radio relay apparatus according to the fourth embodiment of the present invention.

Figure 8 is a block diagram showing the functional separation of the internal configuration of the radio relay apparatus according to the fifth embodiment of the present invention.

******* Brief description of the main parts of the drawing *******

10,70: antenna, 20,60: duplexer,

30,80: LNA, 40,90: filter,

50, 100: amplifier, 110: oscillation detection unit,

120: control unit.

A wireless relay device for a CD communication system having an oscillation prevention function according to the present invention for achieving the above object is amplified by a predetermined level of the signal from the base station and sent to the wireless communication terminal, and applied from the wireless communication terminal. A wireless relay apparatus for a CDMA communication system for amplifying a predetermined level of a signal to be transmitted to a base station, comprising: a first antenna for communicating with a base station, a second antenna for communicating with a wireless communication terminal, and a first antenna And first and second amplifiers for amplifying a signal received from the second antenna by a predetermined level, respectively, and an input signal applied from the base station through the first antenna has a no-signal time faster than a minimum no-signal time between the previous input signal and the signal. An oscillation detector for generating a predetermined oscillation detection signal when the signal level is greater than the previous signal level, the oscillation detection And a control unit for adjusting amplification gains of the first and second amplifiers based on the oscillation detection signal applied from the output unit.

That is, according to the above, the oscillation state is initially detected by comparing the input time of the current input signal and its signal level with the previous signal, and based on this, the isolation between the first antenna and the second antenna is not generated. By automatically adjusting, it is possible to provide a radio relay apparatus for a CDMA communication system having an oscillation prevention function that can smoothly provide relay processing between a base station and a radio communication terminal period.

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

First, the radio relay apparatus for a CDMA communication system according to the present invention is a general term for the radio relay apparatus applied to various radio communication systems using the CDMA communication system.

2 is a diagram showing a schematic configuration of a wireless relay apparatus for a CDMA communication system having an oscillation preventing function according to the present invention.

In FIG. 2, reference numeral 10 denotes a first antenna composed of, for example, a directional antenna for performing communication with a base station, and 20 denotes a first low noise, which will be described later, with a forward signal applied from the first antenna 10. The reverse signal provided to the amplifier 30 and applied from the second amplifier 100 to be described later is a first duplexer which is transmitted to the first antenna 10.

Reference numeral 30 denotes a first low noise amplifier (LNA) for low noise amplifying the forward signal applied from the first duplexer 20, and 40 denotes a forward signal output from a predetermined frequency band, that is, a base station. The first filter for filtering the frequency band, 50 is a first amplifier for amplifying and outputting a predetermined level of the frequency signal filtered through the first filter 40. At this time, the first amplifier 50 is configured as a variable amplifier to enable the amplification gain control through the control unit 120.

Reference numeral 60 denotes a forward signal applied from the first amplifier 50 to the second antenna 70, and a reverse signal applied from the second antenna 70 to the second low noise amplifier 80 to be described later. The second duplexer to output to.

In FIG. 2, reference numeral 70 denotes a second antenna for performing communication with the wireless communication terminal, which may be configured as an omnidirectional antenna.

Reference numeral 80 denotes a second low noise amplifier for low noise amplifying the reverse signal applied from the second duplexer 60, and 90 denotes a frequency band corresponding to the reverse signal applied from the second low noise amplifier 80. The second filter 100 is a second amplifier for amplifying and outputting a reverse signal applied from the second filter 90 by a predetermined level. At this time, the second amplifier 100 is configured as a variable amplifier to enable the amplification gain control through the control unit 120.

Also, reference numeral 110 denotes an oscillation detection unit generating a predetermined oscillation detection signal by determining whether the oscillation is based on the input time of the signal applied from the first filter 40 and its signal level. It is configured to judge whether the oscillation is based on whether the input signal of the level is applied within a predetermined time.

That is, the present invention is applied to a CDMA communication system that allocates a channel by dividing a frequency and time. In the case of a CDMA communication system, one base station can generally use up to seven channels. Only one channel is selectively filtered and received. In the case of the CDMA communication system, the transmission and reception signal levels are adjusted at intervals of 1.25 ms, for example, so that the change time interval of the signal levels is 1.25 ms. In other words, there is no signal time for at least 1.25ms after a predetermined signal is input from the base station in the normal state. Therefore, the wireless relay apparatus according to the present invention determines that the signal input within 1.25ms after the predetermined signal is inputted from the base station is larger than the previous signal as the oscillation signal fed back from the second antenna 70. .

In addition, reference numeral 120 in FIG. 2 is a control unit for controlling the overall operation of the wireless repeater according to the present invention, which is based on the oscillation detection signal applied from the oscillation detection unit 110, the first and second amplifiers (50, 100) It is configured to adjust the amplification gain of.

That is, in general, the oscillation phenomenon gradually occurs when the isolation between the first antenna 10 and the second antenna 70 becomes "amplification gain + 15 dB or less," and the control unit 120 oscillates in consideration of this point. When the oscillation detection signal is applied from the detector 110, the amplification gains of the first and second amplifiers 50 and 100 are reduced. For example, the controller 120 adjusts the amplification gain of the first and second amplifiers 50 and 100 by 1 dBm whenever the oscillation detection signal is applied from the oscillation detection unit 110.

On the other hand, Figure 3 is a block diagram showing the functional separation of the internal configuration of the oscillation detection unit 110 shown in FIG.

In FIG. 3, reference numeral 111 is a rectifier for converting a signal applied from the first filter 40 shown in FIG. 2 into a voltage signal of a predetermined level, and 112 is signal level information for temporarily storing previous input signal level information. The storage unit 113 is input within the minimum no-signal time, and the abnormal signal recovery information storage unit for temporarily storing the input recovery information of the abnormal signal whose signal level is greater than the previous signal level, 114 is the current input after the previous input signal is input. A timer for counting the no-signal time until the signal is applied, 115 is an oscillation determination reference information storage unit for storing the minimum no-signal time information between input signals and the maximum input frequency information of the abnormal signal for recognizing the oscillation.

In addition, when a predetermined input signal is applied from the rectifying unit 111, 116 checks whether the non-signal time counted by the timer 114 is within the minimum no-signal time stored in the oscillation determination reference information storage unit 115 and presently. When the input signal level is greater than the previous input signal level stored in the signal level storage unit 112 and a signal having a level greater than the previous input signal level is input within the minimum no-signal time, the oscillation detection signal is generated by judging it as an abnormal signal. A signal comparison processing unit which sends a predetermined control signal to the unit 117. At this time, the signal comparison processing unit 116 increases the abnormal signal recovery information of the abnormal signal recovery information storage unit 113 when determining the abnormal signal, thereby storing the abnormal signal recovery information stored in the abnormal signal recovery information storage unit 113. When a match with the abnormal signal maximum input recovery information stored in the oscillation determination reference information storage unit 115 is configured to send a predetermined control signal to the oscillation detection signal generator 117.

In FIG. 3, reference numeral 117 denotes an oscillation detection signal generation unit for generating a predetermined oscillation detection signal based on the control signal applied from the signal comparison processing unit 116 and sending it to the control unit 120.

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

First, in the oscillation determination reference information storage unit 115 of the oscillation detection unit 110, reference information for determining an oscillation state, that is, minimum non-signal time information and abnormal signal maximum input recovery information is set and stored. The device may be configured to be stored in advance when the device is manufactured, or may be configured to be changed by the radio manager. In the case where the administrator of the wireless relay apparatus is set, the administrator directly operates the oscillation detection unit 110 to directly input the corresponding information, or via the control unit 120, the oscillation determination reference information storage unit of the oscillation detection unit 110. It is possible to configure it to be stored.

As described above, when a predetermined signal is applied from the base station to the wireless relay device while the oscillation determination reference information storage unit 115 stores the oscillation determination reference information, the input signal is transmitted through the first duplexer 20. 110).

In addition, the signal input to the oscillation detector 110 is converted into a voltage signal of a predetermined level through the rectifier 111 and applied to the signal comparison processor 116. The signal comparison processor 116 receives a timer when a predetermined signal is input. Through 114, the non-signal time with the previous input signal is checked, and it is checked whether the no-signal time is within the minimum no-signal time stored in the oscillation determination reference information storage 115.

Also, the signal comparison processing unit 116 compares the current input signal level with the previous signal level stored in the signal level storage unit 112 and determines that the current input signal is greater than the previous signal level while being input within the minimum no-signal time. The abnormal signal recovery information stored in the abnormal signal recovery information storage unit 113 as recognized by the signal is increased by "1". At this time, the signal comparison processing unit 116 does not clear the timer 114 and the signal level information storage unit 112 when it is determined that the abnormal signal.

That is, the signal comparison processing unit 116 clears the timer 114 and updates the signal level information storage unit 112 when the current input signal is a normal signal input after a minimum no-signal time. In other words, the input time and signal level of the previous signal compared to the current input signal are limited to those for the normal signal.

In addition, the signal comparison processing unit 115 checks whether the abnormal signal recovery stored in the abnormal signal recovery information storage unit 113 is the same as the abnormal signal maximum input recovery information stored in the oscillation determination reference information storage unit 115, and in the same case, the oscillation detection signal. The generator 117 transmits a predetermined control signal for generating the oscillation detection signal. Then, the abnormal signal recovery information storage unit 113 is cleared. In addition, the signal comparison processing unit 115 determines that the current state is a normal state when the abnormal signal is continuously input a predetermined number of times while the abnormal signal count is less than the maximum input frequency of the abnormal signal. Will be cleared.

On the other hand, when a predetermined control signal is sent from the signal comparison processing unit 116 to the oscillation detection signal generation unit 117, the oscillation detection signal generation unit 117 generates a predetermined oscillation detection signal and sends it to the control unit 120. The controller 120 adjusts the amplification gain of the first amplifier 50 and the second amplifier 100 based on this.

For example, the controller 120 controls to reduce the amplification gain of the first amplifier 50 and the second amplifier 100 by 1 dBm each time the oscillation detection signal is applied from the oscillation detection signal generator 117. .

Meanwhile, in the first embodiment, the oscillation detection unit 110 is installed directly in front of the first amplifier 50, but as shown in FIG. 4, the oscillation detection unit 110 is provided in front of the first low noise amplifier 30. It is also possible to implement to perform the oscillation detection operation as described above in conjunction with

In addition, when implementing the wireless relay device with the configuration as shown in Figure 4, the oscillation detection unit 110 may be configured at the front end of the low noise amplifier as shown in FIG. In this case, the oscillation detection unit 110 may be configured to be coupled to the front end of the first duplexer 20.

That is, as shown in FIG. 5, the oscillation detector 110 includes a reference level information storage unit 118 for storing reference level information on a signal applied from a base station antenna, and for generating a predetermined over input detection signal. An over-input detection signal generation unit 119 is further provided, and the signal comparison processing unit 116 of the oscillation detection unit 110 performs the oscillation detection operation as described above based on the signal applied from the rectifier 111. In addition, when the input signal level is greater than the signal level stored in the reference level information storage unit 118, the over-input detection signal generator 119 is controlled to generate a predetermined over-input detection signal.

Then, the controller 120 controls to cut off the power supply of the first and second low noise amplifiers 30 and 80 based on the over-input detection signal applied from the oscillation detector 110 as shown in FIG. 5. do. As a result, it is possible to protect the radio relay from being damaged by the over-input signal through the antenna.

In addition, the oscillation detector 110 continuously checks the signal level of the input signal from the antenna while the power supply to the first and second low noise amplifiers 30 and 80 is blocked, and thus the input signal level is referred to as reference level information. When it is smaller than the signal level stored in the storage unit 118, it transmits a predetermined steady state detection signal to the control unit 120, the control unit 120 to the first and second low noise amplifiers (30, 80) based on this It may be configured to perform an auto reset operation to control to provide a predetermined power.

6 illustrates a configuration of a wireless relay apparatus according to a third embodiment of the present invention, in which an input terminal is coupled to a rear end of a first amplifier 50 and an amplified output level applied from the first amplifier 50. And compare the result value corresponding to the difference between the signal level applied from the first oscillation detector 110 and the amplification degree of the first amplifier 50, and if the result value is a difference between the amplification degree and the predetermined level or more, A second oscillation detection unit 210 for transmitting the oscillation detection signal to the control unit 220 is further provided. The controller 220 controls the amplification gains of the first and second amplifiers 50 and 100 to be reduced based on the oscillation detection signal applied from the first oscillation detection unit 110 or the second oscillation detection unit 210. do. In this case, the control unit 220 generates a first oscillation to prevent the amplification gain reduction from being repeatedly performed due to the redundant oscillation detection from the second oscillation detection unit 210 for the abnormal signal detected by the first oscillation detection unit 110. The oscillation detection signal applied from the second oscillation detection unit 210 within a predetermined time after the oscillation detection signal is applied from the detection unit 110 may be implemented so as not to adjust the amplification gain.

In addition, the wireless relay apparatus according to the present invention may be configured by additionally installing a predetermined oscillation detecting means on the reverse link as shown in Figs.

That is, as shown in FIG. 7, the oscillator is coupled to the front end of the second amplifier 100 in the configuration of FIG. 3 and detects the oscillation based on a signal input from the front end of the second amplifier 100 to detect a predetermined oscillation. The eleventh oscillation detector 310 may be further configured to transmit a signal to the controller 120.

At this time, the eleventh oscillation detection unit 310 is configured in the same manner as the first oscillation detection unit 110, and determines whether the input signal is input within the minimum no-signal time and the input signal level is larger than the previous input signal level. And to output a predetermined oscillation detection signal.

The controller 320 adjusts the amplification gain of the first amplifier 50 based on the oscillation detection signal applied from the oscillation detection unit 110 and based on the oscillation detection signal applied from the eleventh oscillation detection unit 310. To adjust the amplification gain of the second amplifier 100.

In addition, in FIG. 7, the eleventh oscillation detector 310 may be coupled to the front end of the second amplifier 100, in particular, coupled to the front end of the second low noise amplifier 80.

In addition, as shown in FIG. 8, the wireless relay apparatus according to the present invention couples the eleventh oscillation detector 310 to the front end of the second amplifier 100 in the configuration of FIG. 5 and the second amplifier 100. The twenty-first oscillation detection unit 410 may be configured to be further coupled to the rear end.

At this time, the eleventh oscillation detector 310 is configured to transmit a predetermined oscillation detection signal when the input signal is input within a minimum no-signal time and the input signal level is larger than the previous input signal level, and the twenty-first oscillation detection unit ( In operation 410, a result value corresponding to the difference between the amplified output signal level applied from the output terminal of the second amplifier 100 and the signal level applied from the eleventh oscillation detector 310 coincides with the amplification of the second amplifier 100. And generate a predetermined oscillation detection signal when the difference is more than a predetermined level.

The controller 420 adjusts the amplification gain of the first amplifier 50 based on the oscillation detection signals applied from the first and second oscillation detectors 110 and 210, and the eleventh and 21st oscillation detectors. It is configured to adjust the amplification gain of the second amplifier 100 based on the oscillation detection signal applied from (310,410).

That is, according to the embodiment, in the CDMA communication system, a signal applied from a base station or a wireless communication terminal is input within a signal input minimum no-signal time, and the current input signal is oscillated when the input signal level is larger than the previous input signal level. It is determined that the signal, based on this control to reduce the amplification gain of the radio relay apparatus can maintain the isolation between the first antenna and the second antenna.

In addition, when the signal level in front of the low noise amplifier is above a predetermined level, the supply of power to the low noise amplifier is interrupted to temporarily suspend the relay processing operation of the wireless repeater, thereby preventing damage to the wireless repeater due to an over input signal. .

Therefore, according to the present invention, the oscillation state is initially detected, and the isolation degree between the first antenna and the second antenna is automatically adjusted to the state where no oscillation occurs, thereby smoothly relaying the base station and the wireless communication terminal period. To be able to provide.

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

As described above, according to the present invention, the oscillation state is initially detected by comparing the input time and the signal level of the current input signal with the previous signal, and based on this, the oscillation degree between the first antenna and the second antenna is not generated. By automatically adjusting to a state, it is possible to provide a wireless relay device for a CDMA communication system having an oscillation prevention function that can smoothly provide relay processing between a base station and a wireless communication terminal period.

Claims (10)

A wireless relay apparatus for a CDMA communication system which amplifies a signal applied from a base station by a predetermined level and sends the signal to a wireless communication terminal, and amplifies a signal applied from the wireless communication terminal by a predetermined level and sends the signal to a base station. A first antenna for performing communication with the base station, A second antenna for communicating with a wireless communication terminal, First and second amplifiers for a predetermined level amplifying the signals received from the first and second antennas, respectively, An oscillation detector for generating a predetermined oscillation detection signal when the input signal applied from the base station through the first antenna has a non-signal time earlier than the minimum input signal time between the previous input signal and the signal and its signal level is greater than the previous signal level; And a control unit for controlling amplification gains of the first and second amplifiers based on the oscillation detection signal applied from the oscillation detection unit. The method of claim 1, The oscillation detection unit is a signal level information storage unit for temporarily storing the previous input signal level information, a timer for counting the time from when the previous input signal is applied to the current input signal, and after the previous input signal is input. An oscillation judgment reference information storage unit for storing the minimum no-signal time information until a current input signal is input, an oscillation detection signal generator for generating a predetermined oscillation detection signal, and counting through the timer when a predetermined signal is applied. If the time information is within the minimum no-signal time information stored in the oscillation judgment reference information storage unit, and if the signal level is greater than the previous signal level, it is determined to be within the minimum no-signal time and larger than the previous signal level. A signal comparison processor for transmitting a predetermined control signal for generating an oscillation detection signal to the oscillation detection signal generator; Wireless relay apparatus for a CDMA communication system having an oscillation preventing function being configured to include. The method of claim 2, The oscillation detection unit comprises an abnormal signal recovery information storage unit for temporarily storing the detection frequency of the abnormal signal whose signal level is greater than the previous signal level while being input within the minimum no-signal time, and the oscillation judgment reference information storage unit is configured to oscillate. The abnormal signal maximum input frequency information for determining is additionally stored. If the input signal is determined to be an abnormal signal, the abnormal signal recovery information is increased by "1" and the abnormal signal frequency information is increased. CDMA communication with oscillation prevention function characterized in that the predetermined signal is sent to the oscillation detection signal generator when the abnormal signal recovery information stored in the storage unit matches the maximum input recovery information of the abnormal signal stored in the oscillation determination reference information storage unit. Wireless repeater system. The method of claim 1, The control unit controls to reduce the amplification gain of the first and second amplifiers by a predetermined level every time the oscillation detection signal is applied from the oscillation detection unit. . The method of claim 1, And a first low noise amplification processing unit configured to low noise amplify a forward signal applied from the first antenna, And the oscillation detector is coupled to the front end of the low noise amplifier and generates a predetermined oscillation detection signal based on a signal applied from the first antenna. The method of claim 5, The oscillation detector is configured to store predetermined reference signal level information to transmit a predetermined over-input detection signal to the controller when the signal level of the front end of the low noise amplifier is greater than the reference signal level. The control unit is a wireless relay device for a CDMA communication system having an oscillation prevention function characterized in that the control to cut off the power to the low noise amplifier based on the over-input detection signal applied from the oscillation detector. The method of claim 6, The oscillation detector transmits a predetermined steady state detection signal to the controller when the signal level input from the antenna is smaller than the reference signal level after the over-input detection signal is sent. And the control unit controls to provide power supply to the low noise amplifier based on the steady state detection signal applied from the oscillation detection unit. The method of claim 1, The difference between the output level of the amplified signal output from the first amplifier and the signal level applied from the first oscillation detector coupled to the rear end of the first amplifier and the output terminal of the oscillation detector is greater than or equal to the amplification degree of the first amplifier. If the difference is configured to further include a second oscillation detection unit for transmitting a predetermined oscillation detection signal to the control unit, The control unit controls the amplification level of the first and second amplifiers on the basis of the oscillation detection signal applied from the first and the second oscillation detection unit, the wireless relay device having a oscillation prevention function . The method of claim 1, A second oscillator generating a predetermined oscillation detection signal when the input signal applied from the wireless communication terminal through the second antenna has a no-signal time faster than the minimum no-signal time between the previous input signal and the signal and the signal level is larger than the previous signal level. 11 is further provided with an oscillation detection unit, The control unit adjusts the amplification gain of the first amplifier based on the oscillation detection signal applied from the first oscillation detection unit, and adjusts the amplification gain of the second amplifier based on the oscillation detection signal applied from the eleventh oscillation detection unit. A wireless relay device for a CDMA communication system having an oscillation prevention function, characterized in that for controlling. The method of claim 9, The difference between the output level of the amplified signal output from the second amplifier coupled to the rear end of the second amplifier and the eleventh oscillation detector and the signal level applied from the eleventh oscillation detector is greater than or equal to the amplification degree of the second amplifier. The difference is further provided with a twenty-first oscillation detection unit for transmitting a predetermined oscillation detection signal to the control unit, The control unit adjusts the amplification level of the first amplifier based on the oscillation detection signals applied from the first and second oscillation detection units, and the second amplifier based on the oscillation detection signals applied from the eleventh and 21th oscillation detection units. A wireless relay device for a CDMA communication system having an oscillation prevention function, characterized by controlling to adjust the amplification level of the oscillator.