KR100853746B1 - A Repeater for Cancellating Interference by Estimating Doppler Frequency and Method thereof - Google Patents

Abstract

The present invention relates to a repeater and method for eliminating oscillation using Doppler frequency estimation.

To this end, the present invention, in the co-band amplified wireless repeater for eliminating the oscillation due to the feedback signal, the wireless signal received through the receiving antenna, wherein the wireless signal contains a feedback signal to the Doppler frequency Doppler frequency measuring unit for measuring and estimating the correlation length; And a feedback signal removal unit for removing a feedback signal from the wireless signal and transmitting the transmission signal through a transmission antenna using the correlation length estimated by the Doppler frequency measurement unit as an input value.

According to the present invention, by removing the feedback signal flowing into the repeater through the Doppler frequency estimation from the received signal including the feedback signal to prevent the oscillation by the feedback signal to improve the performance of the repeater, outdoor type of co-band amplified wireless repeater It is possible to increase the reliability of mobile communication service by enabling high power service.

Repeater, Oscillator, Feedback, Doppler Frequency, Correlation

Description

A repeater for canceling oscillation using Doppler frequency estimation and its method {A Repeater for Cancellating Interference by Estimating Doppler Frequency and Method

1 is a view schematically showing the configuration of a conventional co-band amplified wireless repeater.

2 is a view schematically showing the configuration of a repeater according to an embodiment of the present invention.

3 is a flowchart illustrating an operation process of a repeater according to an embodiment of the present invention.

The present invention relates to an oscillation rejection repeater using Doppler frequency estimation and a method thereof. More specifically, the present invention relates to a repeater for removing a feedback signal by Doppler frequency estimation and a feedback signal cancellation method used at this time.

With the development of communication technology, mobile communication system has been developed and popularized, and the service business using it is expanding. Such a mobile communication system is capable of providing one-way or two-way communication service from a predetermined transmission medium to a reception medium in a jurisdiction. However, such a mobile communication system has difficulty in providing a communication service when a predetermined communication shadow area is formed, such as a location of a transmission medium and a reception medium, for example, a mountain area, a dense area of a large building, or a basement.

In order to prevent the degradation of the communication service due to the formation of the communication shadow area, a radio frequency (RF) repeater that amplifies and transmits a signal received from a transmission medium has been developed and operated. Therefore, the wireless repeater plays a role of amplifying a signal between a transmission medium and a reception medium, and is a device for providing a good quality of service by reaching an electric wave in a sound region covered by a distant space or a building. .

1 is a view schematically showing the configuration of a conventional co-band amplified wireless repeater.

Referring to FIG. 1, the wireless repeater 100 may receive a signal applied from a reception antenna 110 for communicating with a transmission medium, a transmission antenna 150 for performing communication with a reception medium, and a reception antenna 110. And an amplifier 130 that amplifies to a predetermined level and outputs it to the transmission antenna 150. When the wireless repeater 100 configured as described above does not sufficiently secure the separation distance between the antennas during installation, a feedback phenomenon in which the amplified signal amplified and output through the amplifier 130 is applied to the input of the wireless repeater 100 again occurs. Therefore, the amplified signal output through the amplifier 130 is repeatedly oscillated.

In more detail, the signal transmitted from the transmission medium to the reception medium is input to the reception antenna 110, and the signal is amplified by the gain G by the amplifier 130 and radiated by the transmission antenna 150. . Here, some of the signals radiated by the transmitting antenna 150 is introduced into the receiving antenna 110, amplified by the gain G again, and the oscillation phenomenon occurs as this process is repeated.

Therefore, the conventional co-band amplified wireless repeater was forced to operate by reducing the repeater gain due to the above-mentioned oscillation phenomenon, and is used only at low power in limited places such as underground buildings to avoid oscillation phenomenon.

In order to solve this problem, the present invention quantitatively detects a change in radio channel through Doppler frequency estimation from a received signal including a feedback signal, and removes the feedback signal by applying a correlation length in real time. And to provide a method.

In order to achieve the above technical problem, the present invention provides a repeater for eliminating oscillation caused by a feedback signal, wherein the Doppler frequency is adjusted using a wireless signal received through a reception antenna, wherein the wireless signal includes a feedback signal. Doppler frequency measuring unit for measuring and estimating the correlation length; And a feedback signal removing unit for removing a feedback signal from the radio signal by using the correlation length estimated by the Doppler frequency measuring unit as an input value and transmitting the feedback signal through a transmission antenna.

The present invention also provides a method of eliminating oscillation by a feedback signal in a repeater comprising the steps of: a) measuring a Doppler frequency using a received wireless signal, wherein the wireless signal comprises a feedback signal; b) estimating a correlation length using the measured Doppler frequency; And c) removing a feedback signal from the wireless signal and transmitting the received correlation length as an input value.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

In addition, the term module described herein refers to a unit for processing a specific function or operation, which may be implemented in hardware or software, or a combination of hardware and software.

2 is a view schematically showing the configuration of a repeater according to an embodiment of the present invention.

An oscillation elimination repeater using Doppler frequency estimation according to an embodiment of the present invention includes a receiving antenna 210, a mixer 220, an A / D converter 230, a Doppler frequency measuring unit 240, and a local frequency generator ( 250, a feedback signal removing unit 260, a D / A converter 270, an amplifier 280, and a transmission antenna 290.

를 수신하는 안테나이다. 또한, 본 발명의 실시예의 수신안테나(210)는 중계기의 송신안테나(290)로부터 무선 채널을 통해 수신되는 피드백 신호

도 함께 수신한다. The receiving antenna 210 receives the original received signal from the base station

To receive the antenna. In addition, the receiving antenna 210 of the embodiment of the present invention is a feedback signal received via a wireless channel from the transmitting antenna 290 of the repeater

Also receives with.

와 피드백 신호

의 합이 되며, 총입력신호는

로 나타낸다.Here, in the embodiment of the present invention, the total input signal received by the reception antenna 210 is a raw reception signal.

With feedback signal

And the total input signal is

Represented by

를 믹싱하여 저주파 형태로 주파수를 변환한다.The mixer 220 is a local frequency and the total input signal generated from the local frequency generator 250

Mixing to convert the frequency into the low frequency form.

로 나타낸다.The A / D converter 230 converts an analog signal, which is a frequency-converted signal from the mixer 220, into a digital signal, and converts the generated digital signal.

Represented by

The feedback signal remover 260 includes a feedback signal detector 261 and a feedback signal cancel filter 263.

The Doppler frequency measurement unit 240 includes a cell searcher 241, a pilot channel detector 242, an AFC (Automatic Frequency Control) 243, and a Doppler frequency detector 244.

The Doppler frequency measuring unit 240 should be operated after the operation of the feedback signal removing unit is basically stabilized, and after that, the feedback signal removing unit 260 is linked / operated to reflect the estimated Doppler frequency in real time to improve the feedback removing performance. Improve.

Here, the cell searcher 241 detects the timing and code of the base station signal from the digital signal received from the A / D converter 230 using the cell search technique and transmits it to the pilot channel detector 243.

를 이용하여 기준 채널을 복조하고, 복조한 파일럿 채널 심볼을 도플러 주파수 측정기(244) 및 AFC(243)로 송신한다.The pilot channel detector 243 is a phase of the initial code received from the cell searcher 241, information on the type of code, and a digital signal received from the A / D converter 230.

The demodulated reference channel is demodulated by using and the demodulated pilot channel symbols are transmitted to the Doppler frequency measurer 244 and the AFC 243.

The AFC 243 generates a stable local frequency through the local frequency generator 250 using the pilot channel symbols for the reference channel received from the pilot channel detector 243.

The Doppler frequency measurer 244 measures the Doppler frequency by using a correlation value of a pilot channel symbol and a zero cross rate method for the reference channel received from the pilot channel detector 243.

In this case, the Doppler frequency estimated by the Doppler frequency measurer 244 becomes a function for generating a correlation length M which is an input value for the correlation calculation in the feedback signal detector 261 to be described below.

Here, a method of calculating the correlation length M using the Doppler frequency will be described in detail below.

를 저주파 형태로 바꿔주기 위한 로컬주파수를 생성한다.The local frequency generator 250 is controlled by the AFC 243, which is a high frequency.

Create a local frequency to change to low frequency form.

로부터 피드백 신호를 제거한다. 여기서, 피드백 신호 제거부(260)에서 피드백 신호를 제거한 신호는 피드백 신호 제거 신호

로 나타낼 수 있으며, 이 피드백 신호 제거 신호

는 새로운 총입력신호가 피드백 신호 제거 필터(263)에 의해서 피드백 신호가 제거될 때마다 새로 갱신된다.The feedback signal remover 260 includes a feedback signal detector 261 and a feedback signal remover filter 263, and uses the correlation length M value received from the Doppler frequency measurer 244 of the Doppler frequency measurer 240. Digital signaled total input signal

Remove the feedback signal from the Here, the signal from which the feedback signal is removed by the feedback signal removing unit 260 is a feedback signal removing signal.

Can be represented by this feedback signal removal signal

The new total input signal is refreshed every time the feedback signal is removed by the feedback signal cancellation filter 263.

와 이전에 생성된 피드백 신호 제거 신호

와의 상관관계를 이용하여 상관도를 계산하고, 상관값을 통해 변화하는 피드백 신호의 시간 지연, 진폭 및 위상을 추정한다. 이때, 상관도를 계산하기 위하여 도플러 주파수 측정기(244)에서 계산된 상관 길이 M이 이용된다. 좀 더 상세한 계산 방법은 아래에서 설명하기로 한다.The feedback signal detector 261 is a total received signal converted to baseband

And previously generated feedback signal rejection signals

The correlation is calculated using the correlation with, and the time delay, amplitude, and phase of the feedback signal varying through the correlation value are estimated. In this case, the correlation length M calculated by the Doppler frequency meter 244 is used to calculate the correlation. More detailed calculation methods will be described below.

The feedback signal rejection filter 263 generates an antiphase signal of the feedback signal using the time delay, amplitude, and phase estimated by the feedback signal detector 261, and applies the generated antiphase signal to the total input signal to thereby input the total input signal. It consists of a digital adaptive filter that removes the feedback signal from the signal.

을 아날로그 신호 형태인

로 변환한다.The D / A converter 270 is a digital signal generated by the feedback signal remover 260.

To form an analog signal

Convert to

를 이득 G만큼 증폭한다. 이때, 증폭부(280)에서 증폭된 신호는

로 나타낼 수 있다.The amplifier 280 is a signal converted by the D / A converter 270

Amplify by G. At this time, the signal amplified by the amplifier 280 is

It can be represented as.

를 이동통신 단말기로 송신하는 안테나이다.The transmission antenna 290 is a signal amplified by the amplifier 280

Is an antenna for transmitting to a mobile communication terminal.

3 is a flowchart illustrating an operation process of a repeater according to an embodiment of the present invention.

및 송신안테나(290)로부터 수신되는 피드백 신호

를 포함하는 총입력신호

를 수신한다(S310). 여기서, 피드백 신호

는 피드백 신호

와 함께 수신되는 원수신신호

의 이전에 수신된 원수신신호가 피드백 신호 제거 과정을 거쳐 출력된 신호이다.First, the original reception signal received from the base station in the reception antenna 210

And a feedback signal received from the transmitting antenna 290

Total input signal including

Receive (S310). Where feedback signal

Feedback signal

Received signal received with

The previously received original received signal of is a signal output through the feedback signal removal process.

In this case, the total input signal may be represented by the sum of the original reception signal and the feedback signal, and may be represented by Equation 1 below.

는 기지국에서 수신되는 원수신신호이며,

는 피드백 신호를 의미한다. 또한

는 열잡음 항이다.here,

Is the original received signal from the base station,

Denotes a feedback signal. Also

Is the thermal noise term.

은 아래의 [수학식 2]로 나타낼 수 있다.In addition, a wireless channel between the transmitting antenna 290 and the receiving antenna 210 can be modeled as a time-varying multi-path channel having L multipaths, and according to the modeled time-varying multipath channel. Impulse response

Can be represented by Equation 2 below.

는 p번째 다중경로의 실수 진폭(Real Amplitude), δ는 디락 델타(Dirak Delta) 함수, j는 복소수,

는 p번째 다중경로의 지연시간(Delay),

는 p번째 다중경로의 위상(Phase) 및

는 p번째 다중경로의 도플러천이(Doppler Shift)를 의미한다. 송신안테나와 수신안테나 간의 피드백 신호 변화 정도가

로 모델링 된다. 여기서 디락 델타 함수 δ는 연속함수로서의 임펄스를 수학적으로 표현한 함수이며, 당업자들에게 널리 알려진 함수이므로 본 발명의 실시예에서는 상세한 설명을 생략하기로 한다.here,

Is the real amplitude of the pth multipath, δ is the Dirak Delta function, j is the complex number,

Is the delay of the pth multipath (Delay),

Is the phase of the pth multipath, and

Is the Doppler shift of the p-th multipath. The degree of change in the feedback signal between the transmitting and receiving antennas

Is modeled as: Here, the dirac delta function δ is a mathematical expression of an impulse as a continuous function, and since the function is well known to those skilled in the art, detailed descriptions thereof will be omitted.

로 정의하고 p번째 경로의 채널에 따른 임펄스 응답을 디지털 신호화된 기저대역으로 표현하면 [수학식 3]으로 나타낼 수 있다.In this case, the impulse response is

If the impulse response according to the channel of the p-th path is expressed as a digital signal baseband, it can be represented by Equation 3.

라고 하면, 중계기 이득 G 및 다중경로 채널을 통과한 피드백된 피드백 신호

는 [수학식 4]와 같이 나타낼 수 있다. Here, the signal after the previous feedback signal removal process

The feedback gain signal passed through the repeater gain G and the multipath channel.

Can be expressed as shown in [Equation 4].

를 저주파로 변경한 후 A/D 컨버터(230)를 통해 디지털 신호화하여 기저대역 형식으로 변환한다(S320). 이때, 기저대역 형식으로 변환된 총입력신호

는

로 나타낼 수 있다.Subsequently, the mixer 220 uses the local frequency received by the local frequency generator 250 to output the total input signal.

After converting the signal to a low frequency, the A / D converter 230 converts the signal into a baseband format (S320). At this time, the total input signal converted to the baseband format

Is

It can be represented as.

를 디지털 신호화한 기저대역으로 표현하면 [수학식 5]와 같이 나타낼 수 있다.Where feedback signal

When expressed as a digital signal baseband can be expressed as shown in [Equation 5].

Here, for convenience of calculation, the delay time of the system itself is omitted in the equation.

를 고려한 중계기의 총입력신호

를 기저대역으로 표현하면 [수학식 6]과 같이 나타낼 수 있다.Thus, the feedback signal fed back

Total input signal of repeater

When expressed as the baseband can be expressed as shown in [Equation 6].

과

의 상관값 또는

의 자기 상관값을 이용하여 피드백 신호 특성을 검출할 수 있으며, 검출 시 상관값 길이 M의 최초값은 기본 설정값이며, 도플러 주파수 측정부(240)가 동작한 이후에는 측정된 도플러 주파수를 이용하여 최적의 값으로 갱신한다(S330).

and

Correlation value of or

The feedback signal characteristic can be detected by using the autocorrelation value of. The initial value of the correlation value length M is a default setting value when the detection is performed. After the Doppler frequency measurement unit 240 operates, the measured Doppler frequency is used. Update to an optimal value (S330).

)이라고 한다.

는 도플러 주파수

의 함수이며 [수학식 7]과 같이 나타낼 수 있다.The characteristics of a wireless channel change with time, and the maximum time that a channel characteristic remains unchanged is Coherent Time (

It is called).

Doppler Frequency

It can be expressed as [Equation 7].

)의 1/4 내지 1/10 정도가 적합하며, 이 조건에서 피드백채널의 특성을 안정적으로 추정할 수 있다. 이때, 측정된 도플러 주파수를

라고 할 때, 상관 길이를 시간으로 나타낸

는 [수학식 8]과 같이 나타낼 수 있다(상관 길이 M을 Coherent Time(

)의 1/10 이라고 가정한 경우).In this case, the correlation length M is approximately Coherent Time (

1/4 to 1/10 of) is suitable, and it is possible to stably estimate the characteristics of the feedback channel under these conditions. At this time, the measured Doppler frequency

, The correlation length in hours

Can be expressed as [Equation 8] (correlation length M is represented by Coherent Time (

Assuming 1/10 of).

Therefore, if the Doppler transition is about 5 ms, it means that it should be correlated with a length of about 1.9 ms.

In addition, the correlation length M value is determined according to the sampling rate in the A / D converter 230, and if M is applied to a WCDMA system sampled at a chip rate of 3.84 MHz, M is about 7300 samples. Becomes

과 피드백 신호 제거 신호

과의 상관관계를 이용하여 상관도

을 계산하면 [수학식 9]와 같이 나타낼 수 있다. 이때, 상관도를 계산하는 M 샘플 구간 내에서는 채널 특성 변화가 크지 않아야 하며, [수학식 8]을 적용하여 상관 길이 M을 선정하는 것이 바람직하다.Subsequently, the feedback signal detector 261 receives the total received signal.

And feedback signal rejection signal

Correlation using correlation with

Calculate Equation 9 can be expressed as [Equation 9]. At this time, the channel characteristic change should not be large within the M sample interval for calculating the correlation, and it is preferable to select the correlation length M by applying Equation 8.

이

일 때, 상관값이 나타남을 알 수 있으며, 이때 나타난 상관값의 진폭과 위상은 피드백 채널의 특성을 반영한다.Here, looking at Equation 9, the index of the correlation

this

When the correlation value appears, the amplitude and phase of the correlation value reflected here reflect the characteristics of the feedback channel.

Subsequently, the feedback signal detector 261 estimates the time delay, amplitude, and phase of the feedback signal using a complex correlation value (S350), and this value is reflected as a coefficient of the feedback cancellation filter 263.

The feedback signal rejection filter 263 coefficients are implemented in the form of a digital adaptive filter using an antiphase signal sequence of correlation values as shown in [Equation 10], and the reflection component of the feedback path is transformed into a filter coefficient w (n). As it is reflected, the time-varying characteristics of the feedback channel can be removed in real time.

The feedback signal removal filter 263 removes the feedback signal from the total input signal (S370), converts the total input signal from which the feedback signal is removed into an analog signal through the D / A converter 270, and then gains the gain to the amplifier 280. Amplified by G and transmitted through the transmission antenna (290) (S380).

The embodiments of the present invention described above are not implemented only through the apparatus and the method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Implementation may be easily implemented by those skilled in the art from the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, according to the present invention, by removing the feedback signal flowing into the repeater through the Doppler frequency estimation from the received signal including the feedback signal to prevent the oscillation by the feedback signal to improve the performance of the repeater, the same-band amplification It is possible to increase the reliability of the mobile communication service by enabling the outdoor high power service of the wireless repeater.

Claims (18)

In the repeater to remove the oscillation by the feedback signal, A Doppler frequency measurement unit for measuring a Doppler frequency and estimating a correlation length using a wireless signal received through a reception antenna, wherein the wireless signal includes a feedback signal; And A feedback signal removing unit for removing a feedback signal from the radio signal and transmitting it through a transmission antenna using the correlation length estimated by the Doppler frequency measuring unit as an input value Repeater comprising a. The method of claim 1, The Doppler frequency measuring unit A cell searcher that finds a base station reference timing, a phase of an initial code, and a type of a code by using a cell searching method using the radio signal; A pilot channel detector for demodulating a reference channel and a pilot channel symbol for the reference channel using the phase of the initial code found in the cell searcher and the type of code; And Doppler frequency detector for measuring Doppler frequency and estimating correlation length using pilot channel symbols for the reference channel received from the pilot channel detector Repeater comprising a. The method of claim 2, The repeater A mixer for converting the wireless signal into a low frequency form; An A / D converter converting a signal converted into a low frequency from the mixer into a digital signal and providing the converted signal to the Doppler frequency measuring unit; A local frequency generator for generating a local frequency for converting the radio signal into a low frequency in the mixer; A D / A converter converting the radio signal from which the feedback signal is removed by the feedback signal removing unit into an analog signal; And An amplifier for amplifying the signal converted into the analog signal by a predetermined gain and transmitting the same through the transmission antenna Repeater further comprising. The method of claim 3, wherein The Doppler frequency measuring unit Automatic frequency control (AFC) for generating a stable local frequency in the local frequency generator using a pilot channel symbol for the reference channel received from the pilot channel detector Repeater, characterized in that it further comprises. The method according to any one of claims 1 to 4, The feedback signal removing unit The correlation length estimated by the Doppler frequency measuring unit is an input value, and the wireless signal and the previous feedback signal removing signal, wherein the previous feedback signal removing signal is obtained from the wireless signal inputted before the wireless signal through the feedback signal removing unit. A feedback signal detector for estimating the time delay, amplitude, and phase of the feedback signal using correlation with the feedback signal removed signal; And Generating an antiphase signal of the feedback signal by using the time delay, amplitude, and phase of the feedback signal estimated by the feedback signal detector, and applying the generated antiphase signal to the radio signal to remove the feedback signal Signal rejection filter Repeater comprising a. The method of claim 5, wherein And a Doppler frequency measured by the Doppler frequency measuring unit is a function for estimating a correlation length which is an input value for calculating a correlation in the feedback signal detector. In the method for removing the oscillation by the feedback signal in the repeater, a) measuring the Doppler frequency using the received wireless signal, wherein the wireless signal comprises a feedback signal; b) estimating a correlation length using the measured Doppler frequency; And c) removing a feedback signal from the wireless signal and transmitting it to the outside using the estimated correlation length as an input value; Oscillation removal method comprising a. The method of claim 7, wherein Step a) is Finding a phase of an initial code and a type of a code by using a cell search technique using the radio signal; Finding a reference channel and a pilot channel symbol for the reference channel using the phase of the initial code and the type of code; And Measuring a Doppler frequency using a pilot channel symbol for the reference channel Oscillation removal method comprising a. The method of claim 8, Step c) is Calculating a correlation using the estimated correlation length as an input value; Estimating time delay, amplitude, and phase of the feedback signal from the calculated correlation; Generating an antiphase signal of the feedback signal using the estimated time delay, amplitude, and phase of the feedback signal; And Generating a signal obtained by removing the feedback signal from the wireless signal by using the generated antiphase signal Oscillation removal method further comprising. The method of claim 9, The wireless signal is

(here,

The wireless signal,

Is the original received signal received from the base station,

Means the feedback signal and

Is a thermal noise signal.) Represented by The feedback signal

Is the feedback signal

The signal from which the feedback signal has been removed from the previously received wireless signal of the original received signal through the steps a), b) and c) is transmitted to the repeater and then fed back through the wireless channel. Characterized by the rash removal method. The method of claim 10, The wireless channel is When modeled as a time-varying multi-path channel with L multipaths, expressed as an impulse response,

(here,

Is the real amplitude of the pth multipath, δ is the Dirak Delta function, j is the complex number,

Is the delay of the pth multipath (Delay),

Is the phase of the pth multipath, and

Is the Doppler Shift of the pth multipath.) Oscillation removal method characterized in that represented by. The method of claim 11, When the impulse response according to the channel of the p-th path of the radio channel to baseband,

(here,

To be defined.) Oscillation removal method characterized in that represented by. The method of claim 12, The feedback signal received over the wireless channel

Is,

(here,

Is the repeater output signal, and G is the repeater gain.) Oscillation removal method characterized in that represented by. The method of claim 13, remind

Converting to baseband,

Oscillation removal method characterized in that represented by. The method of claim 14, When converting the radio signal to baseband,

Oscillation removal method characterized in that represented by. The method of claim 15, In step c), The estimated Doppler frequency

And the maximum time the channel remains unchanged is Coherent Time (

Doppler frequency

And Coherent Time (

) Relationship with

Represented by the correlation length

When defined as, the correlation length

Is the Coherent Time (

Oscillation removal method characterized in that between 1/10 to 1/4 of. The method of claim 16, The correlation

(here,

Means the correlation, M means the correlation length,

Means the radio signal converted to baseband,

Is the output signal converted to baseband.) Oscillation removal method characterized in that represented by. The method of claim 17, The estimated correlation value

The antiphase signal sequence of the feedback signal generated using the time delay, amplitude and phase of

And the anti-phase signal sequence is reflected by the digital feedback signal cancellation adaptive filter coefficient.

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