[DESCRIPTION]

[invention Title]

INTERFERENCE CANCELLATION REPEATER

[Technical Field]

The present invention relates, in general, to an interference cancellation radio frequency repeater used in a radio communication system and, more particularly, to an interference cancellation radio frequency repeater, which uses adaptive filters to cancel interference signals from a received signal, or divides a received signal into a plurality of small bands or a plurality of channels and applies adaptive filters to respective signals when a received radio frequency signal is a wideband signal or a multi-channel signal, thus canceling interference signals.

[Background Art]

A repeater is a device that is disposed between a base station and a terminal station to amplify a low-level received signal to a level having excellent speech quality, and that is adapted to provide excellent speech quality to regions that radio waves cannot reach and have weak radio field intensity, that is, the inside buildings or outskirts. The types of repeaters may include an optical repeater, a microwave repeater, a frequency shifting

repeater, a Radio Frequency (RF) repeater, etc.

Of the above repeaters, the RF repeater is required to reduce a radio wave shadow area, which appears during the operation of a radio communication system, and to improve speech quality. The RF repeater denotes a repeater in which the frequency of a received signal and the frequency of a transmitted signal are operated in the same manner.

A typical RF repeater, shown in FIG. 1, is a repeater 10 using the same transmission/reception frequency, and has a forward link for receiving radio waves from a base station, amplifying the radio waves, and radiating the amplified radio waves to a service area, and a reverse link for receiving radio waves from the service area, amplifying the radio waves and transmitting the amplified radio waves to the base station. The forward link and the reverse link have the same structure, so only the operation of the forward link is described here.

First, if an RF signal to be repeated is received through a receiving antenna 100 and is input to a reception filter unit 110, the reception filter unit 110 performs band-pass filtering on the input signal, and transmits the filtered signal to an amplification unit 120. Then, the amplification unit 120 amplifies the filtered input signal and transmits the amplified signal to a service area through a transmitting antenna 130. However, as shown in

FIG. 1, the RF repeater 10, having only the function of amplifying and transmitting a received signal, has poor isolation between transmitting and receiving antennas. Accordingly, there is a problem in that a signal transmitted from the transmitting antenna 130 is fed back into the receiving antenna 100, and is amplified together with the original signal, and the amplified signal is transmitted again through the transmitting antenna, so that the repeater may oscillate. Such an oscillation causes more problems in a large-scale RF repeater having a strong transmitted signal at a transmitting antenna.

Therefore, in order to sufficiently cancel the signal that is fed back into the receiving antenna and causes the oscillation phenomenon, an RF repeater is constructed so that a transmitting antenna and a receiving antenna are separately installed in different locations to increase the isolation between the transmitting and receiving antennas, and a directional antenna having excellent directionality is used. However, there is a disadvantage in that, since the transmitting and receiving antennas must be installed far away from each other so that the isolation between the transmitting/receiving antennas overcomes the gain of the repeater, installation costs are increased. Further, there is a limitation in that the repeater must be designed to have reduced gain of the repeater so as to sufficiently reduce a feedback phenomenon for a transmitted signal .

In order to solve the above problems, a method of installing a shielding obstacle on transmitting and receiving antennas, or a method of utilizing phase signal processing for implementation of spatial isolation, frequency conversion repeating, and smart antenna technology has been used in the prior art to improve isolation between repeater base stations . However, there are problems in that the installation of a shielding obstacle is complicated, and an expensive signal processing device is required.

Further, various methods of canceling the above- described interference signal from a received signal using digital signal processing technology have recently been proposed. Most proposed methods are intended to predict respective reflected signals, obtained by reflecting a transmitted signal from an antenna and surrounding obstacles, and to cancel the reflected signals from a received signal. There are problems in that the precise prediction of reflected signals is difficult in an actual situation, and a long time is required for prediction, so it is almost impossible to cancel interference corresponding to variation in the surrounding environment in real time. Therefore, the methods proposed in the prior art are not suitable for actual usage from the standpoint of performance, and, consequently, the conventional methods are of very limited use in an actual field operation

environment .

[Disclosure] [Technical Problem]

An object of the present invention to solve the above problems is to provide an interference cancellation RF repeater, which can efficiently cancel an interference signal that is an output signal, transmitted from a transmitting antenna and received again through a receiving antenna, using adaptive filters. Another object of the present invention is to provide an interference cancellation RF repeater, which divides a received signal into a plurality of frequency bands or respective channels and applies adaptive filters to respective divided signals to cancel interference signals when a received RF signal is a wideband signal or a multi ^¬ channel signal, thus efficiently canceling interference signals having a long delay time, and efficiently implementing an adaptive filter having fast interference cancellation performance.

[Technical Solution]

In accordance with one aspect of the present invention to accomplish the above object, there is provided an interference cancellation Radio Frequency (RF) repeater, comprising a reception unit for controlling a gain of a

received signal from a receiving antenna, and transmitting a gain-controlled received signal, a frequency down converter for converting the received signal transmitted from the reception unit into an Intermediate Frequency (IF) signal, and outputting the IF signal, an interference cancellation signal processing unit for dividing the IF signal, received from the frequency down converter, into one or more bands or one or more channels, canceling interference signals from divided channel signals using adaptive filters, combining the divided channel signals into a single signal, and transmitting the signal, a frequency up converter for converting the signal received from the interference cancellation signal processing unit into a transmittable original frequency band signal, and outputting the original frequency band signal, an amplification unit for amplifying the signal received from the frequency up converter, and a transmitting antenna for transmitting the signal received from the amplification unit. Further, the interference cancellation signal processing unit may comprise an A/D converter for converting an analog received signal into a digital signal, one or more received signal digital down converters for receiving the signal transmitted from the A/D converter, converting the signal into a baseband signal, dividing the baseband signal into respective channels, converting

received signals of corresponding channels at preset sampling rates, and outputting the converted received signals, one or more interference control units for outputting corresponding channel signals, obtained by canceling interference signals from the received signals of the corresponding channels that are output from the received signal digital down converters, using predetermined reference signals, one or more digital up converters for increasing sampling rates of the corresponding channel signals, transmitted from the interference control units, converting the channel signals into IF signals, and outputting the IF signals, a combiner for combining the IF signals of all channels, output from the digital up converters, into a single signal, a D/A converter for converting the signal, output from the combiner, into an analog signal.

Further, each of the interference control units may comprise an adaptive filter unit for receiving a reference signal required to cancel an interference signal, predicting an interference signal from the reference signal using an adaptive filter algorithm, and outputting a predicted interference signal, and an adder for receiving a received signal, including the interference signal, through a non-inverting terminal, and the predicted interference signal, output from the adaptive filter unit, through an inverting terminal, and outputting an error signal obtained

by canceling the ^' predicted interference signal from the received signal.

Further, the adaptive filter unit may comprise a filter coefficient adjustment unit for inputting the reference signal and the error signal, output from the adder, and outputting a filter coefficient that is adjusted in real time for each signal sample using an adaptive filter algorithm, and a digital filter for inputting the reference signal, and the filter coefficient, output from the filter coefficient adjustment unit, and outputting the predicted interference signal that is generated by performing digital filtering on the reference signal.

In the above-described interference cancellation RF repeater, output signals of respective interference control units may be used as the reference signals input to the interference control units of the interference cancellation signal processing unit.

In accordance with another aspect of the present invention, the interference cancellation RF repeater may further comprise one or more reference signal digital down converters in the above-described RF repeater. The reference signal digital down converters may receive output signals of the digital up converters for corresponding channels, convert the received signals into baseband signals for respective channels, convert sampling rates into preset sampling rates, and output the baseband signals

at the preset sampling rates. The output signals of the reference signal digital down converters may be used as the reference signals input to the interference control units of the interference cancellation signal processing unit. In accordance with a further aspect of the present invention, there is provided an interference cancellation Radio Frequency (RF) repeater, comprising a reception unit for controlling a gain of a received signal from a receiving antenna and transmitting a gain-controlled received signal, a frequency down converter for converting the received signal, transmitted from the reception unit into an Intermediate Frequency (IF) signal and outputting the IF signal, an interference cancellation signal processing unit for inputting a predetermined reference signal and the IF received signal, dividing the IF received signal, output from the frequency down converter, into one or more channels, generating predicted interference signals, predicted from the reference signal, using adaptive filters, canceling predicted interference signals of corresponding channels from the divided received signals of respective channels, combining the divided channel signals into a single signal, and transmitting the signal, a frequency up converter for converting the signal received from the interference cancellation signal processing unit into a transmittable original frequency band signal, and outputting the original frequency band signal, an

amplification unit for amplifying the signal received from the frequency up converter, and a transmitting antenna for transmitting the signal received from the amplification unit. Further, the interference cancellation signal processing unit may comprise a first A/D converter for converting an analog received signal into a digital signal, a second A/D converter for converting an analog reference signal into a digital signal, one or more received signal digital down converters for receiving the signal transmitted from the first A/D converter, converting the signal into a baseband signal, dividing the baseband signal into respective channels, converting received signals of corresponding channels at preset sampling rates, and outputting the converted received signals, one or more reference signal digital down converters for receiving the signal transmitted from the second A/D converter, converting the signal into a baseband signal, dividing the baseband signal into respective channels, converting reference signals of corresponding channels at preset sampling rates, and outputting the converted reference signals, one or more interference control units for outputting corresponding channel signals, obtained by canceling interference signals from the received signals of corresponding channels that are output from the received signal digital down converters, using the reference signals

of the corresponding channels that are received from the reference signal digital down converters, one or more digital up converters for increasing sampling rates of the corresponding channel signals, transmitted from the interference control units, converting the channel signals into IF signals, and outputting the IF signals, a combiner for combining the IF signals of all channels, output from the digital up converters into a single signal, and a D/A converter for converting the signal output from the combiner into an analog signal.

In the above-described interference cancellation RF repeater, an output signal of the interference cancellation signal processing unit is used as the reference signal input to the interference cancellation signal processing unit.

In accordance with yet another aspect of the present invention, an output signal of the frequency up converter is used as the reference signal input to the interference cancellation signal processing unit, the interference cancellation RF repeater further comprises a frequency down converter disposed between the frequency up converter and the interference cancellation signal processing unit, and the frequency down converter converts the output signal of the frequency up converter into an IF signal and transmits the IF signal to the interference cancellation signal processing unit.

In accordance with still another aspect of the present invention, an output signal of the amplification unit is used as the reference signal input to the interference cancellation signal processing unit, the interference cancellation RF repeater further comprises a frequency down converter disposed between the amplification unit and the interference cancellation signal processing unit, and the frequency down converter converts the output signal of the amplification unit into an IF signal and transmits the IF signal to the interference cancellation signal processing unit.

[Advantageous Effects]

Unlike a conventional repeater for tracking feedback signals for respective paths, the repeater according to the present invention can not only simultaneously cancel all feedback interference signals, but also cancel interference signals in real time, through an adaptive filter algorithm that uses a transmitted signal as a reference signal.

Accordingly, the present invention processes a received signal by dividing the received signal into a plurality of bands or channels, thus reducing interference cancellation time. In this case, the term "interference cancellation time" means the time required to cancel the interference signals of the system and to achieve stable signal quality when variation in an external channel occurs

and the status of interference signals varies.

Further, the present invention can process a received signal by dividing the received signal into respective channels, thus easily implementing the adaptive filters of an interference control unit.

Further, the present invention can process a received signal, implemented with a multi-channel signal, by- dividing the received signal into respective channels, so that on/off control of signals for respective channels is possible, and the control of gain is also possible.

[Description of Drawings]

FIG. 1 is a block diagram schematically showing a conventional RF repeater using the same transmission/reception frequency; FIG. 2 is a block diagram schematically showing the overall construction of an interference cancellation RF repeater according to a first embodiment of the present invention; FIG. 3 is a block diagram schematically showing the construction of the interference cancellation signal processing unit of the interference cancellation RF repeater of FIG. 2; and FIG. 4 is a block diagram schematically showing the construction of the interference control unit of the interference cancellation signal processing unit of FIG. 3; FIG. 5 illustrates spectral diagrams showing the

input and output signals of a digital down converter; and FIG. 6 illustrates spectral diagrams showing the input and output signals of a digital up converter;

FIG. 7 is a block diagram schematically showing the overall construction of an interference cancellation RF repeater according to a third embodiment of the present invention;

FIG. 8 is a block diagram schematically showing an interference cancellation RF repeater according to a fourth embodiment of the present invention, and FIG. 9 is a block diagram schematically showing the construction of the interference cancellation signal processing unit of the interference cancellation RF repeater according to the fourth embodiment of the present invention; and FIG. 10 is a block diagram schematically showing the construction of the interference cancellation signal processing unit of an interference cancellation RF repeater according to a fifth embodiment of the present invention.

[Best Mode] First embodiment

Hereinafter, the construction and operation of an interference cancellation RF repeater according to a first embodiment of the present invention are described in detail with reference to the attached drawings. FIG. 2 is a block diagram schematically showing the

overall internal construction of an interference cancellation RF repeater 20 according to a first embodiment of the present invention, FIG. 3 is a block diagram schematically showing the internal construction of an interference cancellation signal processing unit 220 of FIG. 2, and FIG. 4 is a block diagram schematically showing the internal construction of the first channel interference control unit 330 of FIG. 3.

Referring to FIG. 2, the interference cancellation RF repeater 20 according to the first embodiment of the present invention includes a receiving antenna 200, a transmitting antenna 242, a reception unit 202, a first frequency down converter 210, an interference cancellation signal processing unit 220, a frequency up converter 230, an amplification unit 240, a second frequency down converter 250, and a gain control unit 260. Hereinafter, the components of the interference cancellation RF repeater 20 are described in detail.

The reception unit 202 receives an RF signal from the receiving antenna 200, controls the gain of the RF signal to a certain level, and transmits the gain-controlled RF signal to the first frequency down converter 210.

The first frequency down converter 210 converts the RF signal, received from the reception unit 202, into an Intermediate Frequency (IF) signal, and transmits the IF signal to the interference cancellation signal processing

unit 220. In this case, the signal, transmitted from the first frequency down converter 210 to the interference cancellation signal processing unit 220, is a signal, in which an interference signal, indicating the output signal of the repeater transmitted from the transmitting antenna and received again through the receiving antenna, is added to the signal received from the original signal source, and which includes interference before the cancellation of interference. The second frequency down converter 250 receives a signal, output from and fed back by the amplification unit 240, converts the received signal into an IF signal, and transmits the IF signal to the interference cancellation signal processing unit 220. In this case, the signal input to the second frequency down converter 250 is a signal corresponding to the signal source of an interference signal component that indicates the output signal of the repeater received again through the receiving antenna. The signal is a reference signal used by the interference cancellation signal processing unit 220 to cancel the interference signal included in the original RF signal.

The gain control unit 260 controls the gain of the signal output from the amplification unit 240 to a suitable level, and transmits the gain-controlled signal to the second frequency down converter 250.

The interference cancellation signal processing unit

220 cancels an interference signal from the IF signal that is received from the first frequency down converter, using the reference signal that is received from the second frequency down converter 250, and transmits the interference-free IF signal to the frequency up converter 230.

The frequency up converter 230 converts the IF signal, received from the interference cancellation signal processing unit 220, into an original RF signal, and transmits the RF signal to the amplification unit 240. The amplification unit 240 amplifies the received signal, and transmits the amplified signal to the outside of the repeater through the transmitting antenna 242.

Hereinafter, with reference to FIGS. 3 and 4, the construction and operation of the interference cancellation signal processing unit 220 are described in detail.

Referring to FIG. 3, the interference cancellation signal processing unit 220 includes a first Analog/Digital (A/D) converter 300, a second A/D converter 302, one or more received signal digital down converters (hereinafter referred to as ^λ DDCs' ) 310, 312 to 314, one or more reference signal DDCs 320, 322 to 324, one or more interference control units 330, 332 to 334, one or more digital up converters (hereinafter referred to as ^v DUCs' ) 340, 342 to 344, a combiner 350, and a D/A converter 360. The interference cancellation signal processing unit 220

having the above construction inputs a received signal and a reference signal from the first frequency down converter and the second frequency down converter, respectively, cancels an interference signal from the received signal, using the reference signal, and transmits the interference- free received signal to the frequency up converter. Hereinafter, the procedure of the interference cancellation signal processing unit 220 removing interference signals from the received signal using the reference signal is described.

The first A/D converter 300 converts an analog received signal into a digital signal, and transmits the digital signal to one or more received signal DDCs . The second A/D converter 302 converts an analog reference signal into a digital signal, and transmits the digital signal to one or more reference signal DDCs.

Each of the received signal DDCs converts a wideband received signal or a multi-channel received signal, composed of a plurality of channels, into a baseband signal, separates a specific band or specific channel signal from the baseband signal using a digital filter, converts the sampling rate of the separated signal into the lowest sampling rate (for example, a Nyquist rate) for a corresponding single band or corresponding channel, and outputs the separated signal at the lowest sampling rate. Therefore, received signal DDCs of the interference

cancellation RF repeater according to the present invention are provided in a number corresponding to the number of bands or channels constituting the received signal . The received signal DDCs include the first channel received signal DDC 310, the second channel received signal DDC 310, ^••• , the n-th channel received signal DDC 314. The first channel received signal DDC 310 transmits a digital first channel received signal to the first channel interference control unit 330, the second channel received signal DDC 312 transmits a digital second channel received signal to the second channel interference control unit 332, and the n-th channel received signal DDC 314 transmits a digital n- th channel received signal to the n-th channel interference control unit 334. FIG. 5 illustrates spectral diagrams showing the operation of a DDC module, in which FIG. 5 (a) is a spectral diagram showing the input signal of the DDC module, and FIG. 5(b) is a spectral diagram showing the output signal of the DDC module. In FIG. 5, f _si is the sampling rate of the input signal of DDC, and f _f2 is the sampling rate of the output signal of DDC. Referring to FIGS. 5 (a) and (b) , it can be seen that a multi-channel signal, composed of a plurality of channels, is input to the DDC, an i-th channel signal, which is a specific channel signal, is separated from the multi-channel signal, and the separated signal is output in such a way that the sampling rate decreases from

fa _l tO f _s2 .

Meanwhile, each of the reference signal DDCs converts a reference signal composed of a plurality of channels into a baseband signal, separates a specific channel signal from the baseband signal, converts the sampling rate of the separated signal into a sampling rate equal to that of the received signal DDC, and outputs the separated signal at the converted sampling rate. Therefore, the number of reference signal DDCs of the interference cancellation RF repeater provided according to the present invention corresponds to the number of received signal DDCs, and includes the first channel reference signal DDC 320, the second channel reference signal DDC 322, ^••• , the n-th channel reference signal DDC 324. The reference signal DDCs are operated in the same manner as the above-described received signal DDCs, so a detailed description thereof is omitted. The first channel reference signal DDC 320 transmits a digital first channel reference signal to the first channel interference control unit 330, the second channel reference signal DDC 322 transmits a digital second channel received signal to the second channel interference control unit 332, and the n-th channel reference signal DDC 324 transmits a digital n-th channel reference signal to the n-th channel interference control unit 334. The interference control units are required to cancel predicted interference signals of respective channels,

predicted from the reference signals, from received signals of corresponding channels, using adaptive filters, and output the predicted interference signal-free signals. The interference control units include the first channel interference control unit 330, the second channel interference control unit 332, ^••• , the n-th channel interference control unit 334. FIG. 4 is a block diagram schematically showing the construction of the first channel interference control unit 330. Referring to FIG. 4, the first channel interference control unit 330 includes an adaptive filter unit 400 and an adder 410. The adaptive filter unit 400 includes a digital filter 402 and a filter coefficient adjustment unit 404.

The digital filter 402 is implemented in the form of a Finite Impulse Response Filter (hereinafter referred to as an ^λ FIR filter' ) , and inputs the first channel reference signal, output from the first channel reference signal DDC, and a filter coefficient, output from the filter coefficient adjustment unit 404. The output signal of the digital filter 402 is input to the inverting terminal of the adder 410. The output signal of the digital filter 402 is a predicted interference signal obtained by predicting a feedback interference signal indicating the output signal of a corresponding channel of the RF repeater, having passed through several paths and received again through a receiving antenna .

The filter coefficient adjustment unit 404 inputs the reference signal of the corresponding channel and an error signal e, output from the adder 410, and outputs a filter coefficient, which is adjusted in real time through an adaptive filter algorithm, to the digital filter 402. The filter coefficient is a numerical value adjusted in real time to minimize an error component through the adaptive filter algorithm. The convergence speed of the adaptive filter algorithm increases as the number of taps is small. The number of taps N _tap of the FIR filter is determined by an eliminable signal delay time td _e iay and the sampling rate of a signal f _sa i _r pi _e - As a result, the interference cancellation time of the adaptive filter unit becomes shorter as the eliminable signal delay time gets shorter, and as the sampling rate gets lower. The adaptive filter algorithm required to adjust the coefficient of the FIR filter must be operated for each signal sample. Accordingly, there is a problem in that, when the time interval between samples is short, the time required to process the adaptive filter algorithm is limited, so that it is difficult to actually implement the filter. In order to solve the above problem, the interference cancellation RF repeater of the present invention employs a method of dividing a signal into respective channels, decreasing the sampling rates of the signals, and applying adaptive filters to respective channels while utilizing the adaptive filter, thus enabling

the FIR filter to be actually implemented.

Meanwhile, the first channel received signal output from the first channel received signal DDC is input to the non-inverting terminal of the adder 410, and the predicted interference signal, which is the output signal of the adaptive filter unit, is input to the inverting terminal of the adder 410. The adder 410 outputs the error signal e that is obtained by canceling the predicted interference signal from the first channel received signal. The error signal e, output from the adder, is input to the filter coefficient adjustment unit 404, and is used as a signal for adjusting the coefficients of respective taps of the digital filter in real time through the adaptive filter algorithm. The filter coefficient adjustment unit 404 is operated to vary the coefficients of the taps of the digital filter so that the power of the error signal e is minimized.

Therefore, the error signal, output from the adder, is a signal obtained by canceling the predicted interference signal from the first channel received signal, and is the first channel signal that is the output signal of the first interference control unit 330. Through such a procedure, the first channel signal output from the adder is transmitted to the first channel digital up converter (hereinafter referred to as a ^λ DUC ) 340.

The digital up converters DUCs are required in order

to increase the sampling rate of the signal processed in a baseband, and to convert the frequency of the processed signal into the carrier frequency at an intermediate frequency. Since the interference cancellation RF repeater of the present invention processes the received signal by dividing the received signal into respective channels, the DUCs include the first channel DUC 340, the second channel DUC 342, ^••• , the n-th channel DUC 344. FIGS. 6 (a) and (b) are spectral diagrams of the input signal and output signal of each DUC. In this case, f _s2 is the sampling rate of the input signal of the DUC, and f _s i is the sampling rate of the output signal of the DUC. The first channel DUC 340 inputs the first channel signal, which is the output signal of the first channel interference control unit 330, and outputs a first channel signal, the sampling rate of which is increased and which is converted into the carrier frequency signal at an intermediate frequency. The first channel signal, the second channel signal, ^••• , the n-th channel signal, output from the first channel DUC, the second channel DUC, ^••• , the n-th channel DUC, respectively, are input to the combiner 350 and are combined into a single signal. The combined signal is converted into an analog signal by the D/A converter 360, and the analog signal is output . The interference cancellation RF repeater of the present invention having the above construction processes

the received signal by dividing the received signal into respective channels, so that the frequency bandwidth is reduced and, as a result, the sampling rate is decreased due to the DDC. Accordingly, the number of taps of the adaptive filter is decreased with respect to the same eliminable interference delay time. As a result, since the convergence speed of the adaptive filter algorithm is increased, not only an interference cancellation time is decreased, but also the time interval between respective signal samples is increased, thus the implementation of the algorithm is facilitated. Further, the interference cancellation RF repeater according to the present invention can not only perform on-off control on each channel, but also control gain, so the measurement of power for each channel is possible, thereby enabling a plurality of supplementary functions to be implemented through the operation of equipment.

[Mode for Invention]

Second embodiment An interference cancellation RF repeater according to a second embodiment of the present invention uses a signal extracted from location B in FIG. 2 as a reference signal input to the interference cancellation signal processing unit. Accordingly, the signal extracted from the location B of FIG. 2 is input to the second frequency down converter

through the gain control unit. The signal input to the second frequency down converter is converted into an IF signal, and is then transmitted to the interference cancellation signal processing unit. Third embodiment

Hereinafter, with reference to FIG. 7, the construction and operation of an interference cancellation RF repeater according to a third embodiment of the present invention are described in detail. Referring to FIG. 7, an interference cancellation RF repeater 70 according to a third embodiment of the present invention includes a reception unit 702, a frequency down converter 710, an interference cancellation signal processing unit 720, a frequency up converter 730, an amplification unit 740, a transmitting antenna, and a receiving antenna. The interference cancellation RF repeater 70 according to the third embodiment of the present invention controls the gain of the signal, output from the interference cancellation signal processing unit 720, and uses the gain-controlled signal as the reference signal of the interference cancellation signal processing unit 720. The remainder of the construction and operation of the interference cancellation RF repeater 70 according to the third embodiment of the present invention is the same as in the first embodiment of the present invention, so repetitive descriptions are omitted.

Fourth embodiment

Hereinafter, with reference to FIGS. 8 and 9, the construction and operation of an interference cancellation RF repeater 80 according to a fourth embodiment of the present invention are described in detail. FIG. 8 is a block diagram schematically showing the overall construction of the interference cancellation RF repeater 80 according to the fourth embodiment of the present invention, and FIG. 9 is a block diagram schematically showing the internal construction of the interference cancellation signal processing unit 820 of the interference cancellation RF repeater 80 according to the fourth embodiment of the present invention.

Referring to FIG. 8, the interference cancellation RF repeater 80 according to the fourth embodiment of the present invention includes a receiving antenna 800, a reception unit 802, a frequency down converter 810, an interference cancellation signal processing unit 820, a frequency up converter 830, an amplification unit 840, and a transmitting antenna 842. The construction and operation of components other than the interference cancellation signal processing unit 820 are the same as in the first embodiment of the present invention, so repetitive descriptions are omitted. Referring to FIG. 9, the interference cancellation signal processing unit 820 of the interference cancellation

RF repeater 80 according to the fourth embodiment of the present invention includes an A/D converter 900, first and second to n-th channel received signal DDCs 910, 912 to 914, first and second to n-th channel reference signal DDCs 920, 922 to 924, first and second to n-th channel interference control units 930, 932 to 934, first and second to n-th channel DUCs 940, 942 to 944, a combiner 950, and a D/A converter 960. The interference cancellation signal processing unit 820 of the interference cancellation RF repeater 80 uses the output signals of the first and second to n-th channel DUCs 940, 942 to 944 as reference signals required to cancel interference. Therefore, unlike the interference cancellation RF repeaters according to the first to third embodiments, the interference cancellation RF repeater 80 according to the fourth embodiment of the present invention does not need to perform separate A/D conversion on the reference signals of the interference control unit 930.

Fifth embodiment Hereinafter, the construction and operation of an interference cancellation RF repeater according to a fifth embodiment of the present invention are described. The overall construction of the interference cancellation RF repeater according to the fifth embodiment of the present invention is almost the same as for the interference cancellation RF repeater according to the fourth embodiment

of the present invention. Only the construction of the interference cancellation signal processing unit differs. FIG. 10 is a block diagram schematically showing the construction of the interference cancellation signal processing unit of the interference cancellation RF repeater according to the fifth embodiment of the present invention. Referring to FIG. 10, the interference cancellation signal processing unit according to the embodiment of the present invention includes an A/D converter 1000, first and second to n-th channel received signal DDCs 1010, 1012 to 1014, first and second to n-th channel interference control units 1030, 1032, to 1034, first and second to n-th channel DUCs 1040, 1042, to 1044, a combiner 1050, and a D/A converter 1060. The first and second to n-th channel interference control units 1030, 1032 to 1034 of the interference cancellation signal processing unit according to the embodiment of the present invention use the output signals of the first and second to n-th channel interference control units as reference signals required to cancel interference signals, without change .

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention

as disclosed in the accompanying claims. For example, in embodiments of the present invention, the location at which a reference signal, required to cancel an interference signal from a received signal, is detected can be variously modified and implemented to improve the performance of an RF repeater and the performance of an adaptive filter. Further, differences related to the modifications and applications should be interpreted as being included in the scope of the present invention defined by the accompanying claims.

[industrial Applicability]

The interference cancellation RF repeater according to the present invention can be widely used in radio communication systems .

[Sequence List Text]