KR20100051192A - Method for mitigating anti-jam and multipath interference signal in a global navigation satellite receiver - Google Patents

Abstract

PURPOSE: A jamming signal and multipath interference signal mitigating method in a global navigation receiver is provided to change a received signal received through a GNSS(Global Navigation Satellite System) receiver having multiple antenna into a positioning signal having a maximum signal to noise ratio. CONSTITUTION: A GPS(Global Positioning System) receiver projects the GPS received signal to a subspace to remove jamming signal(100). The GPS receiver projects the GPS signal from which the jamming signal is removed to subspace to remove the multipath interference signal(102). The GPS receiver changes the GPS received signal into the positioning signal having the maximum signal to noise ratio.

Description

METHODS FOR MITIGATING ANTI-JAM AND MULTIPATH INTERFERENCE SIGNAL IN A GLOBAL NAVIGATION SATELLITE RECEIVER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite navigation receiver for receiving location information from a satellite. In particular, the present invention relates to a subspace projection in a receiver of a global navigation satellite system (GNSS) having multiple antennas. The present invention relates to a method for removing radio interference signals and multipath interference signals in a satellite navigation receiver suitable for removing radio interference signals and multipath interference signals.

In general, GNSS is a system that provides a service that can accurately measure the current position, speed, and time using satellites anywhere in the world, including airplanes, ships, and cars. The GNSS receiver will determine the current position using signals received from at least three (eg four) satellites. Among them, Global Positioning System (hereinafter referred to as GPS) refers to a satellite navigation system developed in the United States. GPS was first developed for military purposes, but is now open to the public to provide services related to various location information.

The biggest obstacle in the service model using GPS is that GPS signals are very vulnerable to external interference signals and their multipath interference signals, so it is not easy to receive satellite GPS signals accurately from the receiver. GPS signals use spread spectrum to cope with external jamming signals, which protect the original signals from a certain level of jamming signals.

In the GPS system of the prior art satellite navigation receiver operating as described above, when the magnitude of the jamming signal exceeds 30dB, which is the gain of the spread spectrum code used in GPS, the receiver It is difficult to receive accurate information from. Therefore, the GPS receiver must be able to effectively recover signals from satellites from jamming signals. In addition to radio interference signals, multipath interference signals also cause difficulty in receiving accurate signals. Multipath interference signals are generated when GPS signals are reflected on various terrains around the receiver and enter the receiver at a certain time interval from the original signal. . These jamming signals and multipath interference signals prevent the GPS receiver from operating correctly, but there is no solution for this.

Accordingly, the present invention provides a method for removing a radio interference signal and a multipath interference signal in a satellite navigation receiver capable of effectively removing a radio interference signal and a multipath interference signal when using a location information related service using a satellite navigation system receiver.

In addition, the present invention, through the satellite navigation system receiver having a multi-antenna can effectively remove the jamming signal and the multipath interference signal by using subspace projection and beamforming when using the location information related service The present invention provides a method for removing radio interference signals and multipath interference signals in a satellite navigation receiver.

According to one embodiment of the present invention, a signal received by a GNSS receiver that receives a satellite navigation system (GNSS) signal from at least two satellites is projected to a subspace in which a jammer signal does not exist to remove the jammer signal. And removing the multipath interference signal by projecting the GNSS received signal from which the radio interference signal has been removed to a partial space in which the multipath interference signal does not exist.

In the present invention, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention has the effect of effectively removing the jamming signal and the multipath interference signal through the GNSS receiver having a multi-antenna and convert the received signal into a positioning signal having a maximum signal-to-noise ratio.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be made based on the contents throughout the specification.

The present invention effectively removes radio interference signals and multipath interference signals using subspace projection and beamforming when using location information related services through a satellite navigation system receiver having multiple antennas.

That is, the signal received by the satellite navigation system receiver is first projected into the space where no jamming signal exists, and the signal from which the jamming signal is removed is projected into the space where the multipath interference signal does not exist once again. The signal from which the jammer signal and the multipath interference signal are removed by using two subspaces is converted into an effective positioning signal having the maximum signal-to-noise ratio through beamforming.

Meanwhile, as a satellite navigation system receiver, a GPS receiver will be described. However, the present invention is not limited to a GPS receiver, but the present invention is applicable to all satellite navigation systems capable of providing a location interlocking service based on a signal received from a satellite. Of course.

1 is a flowchart illustrating a procedure of removing a radio interference signal and a multipath interference signal according to an embodiment of the present invention.

Referring to FIG. 1, in a GPS receiver receiving GPS signals from a plurality of satellites in step 100, first, a GPS reception signal is projected to a subspace in which a radio wave interference signal does not exist to remove radio wave interference signals. The GPS signal from which the signal is removed is projected to a subspace in which the multipath interference signal does not exist to remove the multipath interference signal. As described above, through the subspace projection of steps 100 and 102, the interference signal and the multipath interference signal are effectively removed, and in step 104, the GPS reception signal is converted into a positioning signal having the maximum signal-to-noise ratio and the GPS reception transmitted from the satellite Implement to correctly acquire the signal.

Specifically, the GPS receiver is composed of M spatial array antennas. The signal coming into the antenna array consists of GPS signal, multipath interference signal and jamming signal. The signal received by the antenna may be represented by Equation 1 in the form of a baseband signal sampled at chip intervals.

는 나이퀴스트 샘플링 간격(Nyquist sampling interval),

는 다중경로 간섭신호의 개수,

는

번째 다중경로 간섭신호의 신호 요소,

는

번째 다중경로 간섭신호의 C/A-code 샘플,

는

번째 다중경로 간섭신호의 C/A-code 샘플의 시간지연,

는

번째 다중경로 간섭신호의 공간 표지(spatial signature),

은 전파방해신호의 개수,

는

번째 전파방해신호,

는

번째 전파방해신호의 공간 표지(spatial signature),

는 백색 가우시안 잡음(AWGN) 벡터를 나타낸다.At this time,

Is the Nyquist sampling interval,

Is the number of multipath interference signals,

Is

Signal element of the first multipath interference signal,

Is

C / A-code sample of the first multipath interference signal,

Is

Time delay of the C / A-code samples of the first multipath interference signal,

Is

Spatial signature of the first multipath interference signal,

Is the number of jammer signals,

Is

Th jamming signal,

Is

Spatial signature of the first jamming signal,

Denotes a white Gaussian noise (AWGN) vector.

Since signals from multiple satellites are easily distinguished due to the cross-correlation characteristics of C / A-code, Equation 1 above assumes only one satellite signal. The subscript '0' in each variable represents the signal component transmitted directly from the satellite to the receiver. Therefore, if the signal transmitted directly to the antenna array is expressed as a vector equation as shown in Equation 2 below,

<Equation 1> can be represented by the following vector equation.

은

개의 다중경로 간섭신호의 성분을 나타내며

는 전파방해신호의 성분을 나타낸다.

및

각각의 신호 성분에 대한 식은 다시 아래의 <수학식4>와 같이 나타낼 수 있다.At this time,

silver

Components of the multipath interference signal

Denotes the component of the jamming signal.

And

The equation for each signal component may be expressed as in Equation 4 below.

Under the assumption that the GPS signal, the jammer signal, and the noise are independent of each other, the covariance matrix of the received signal can be expressed as follows.

는 기대값을 나타내고

는 복소수 벡터의 공액전치(conjugate transpose)를 의미하며,

,

,

는 각각 GPS 신호와 전파방해신호, 노이즈의 공분산 행렬을 의미한다. 각각의 공분산 행렬을 살펴보면,At this time,

Indicates the expected value

Is the conjugate transpose of a complex vector,

,

,

Denotes the covariance matrix of the GPS signal, the jammer signal, and the noise, respectively. Looking at each covariance matrix,

는 MxM 단위행렬을 의미한다.Equations 6 to 8 may be represented. At this time,

Means MxM unit matrix.

는 다음과 같이 근사화 된다.Jamming cancellation by subspace projection is based on the fact that the GPS signal has a relatively very low signal size (typically 20 to 30 dB lower than AWGN) compared to noise and jamming. do. Therefore, it can be seen that almost all of the signals received by the receiver are composed of jamming signals. In this case, the covariance matrix

Is approximated as

에 대한 특이값 분해(SVD:singular value decomposition)를 통하여 우리는 효과적으로 수신된 신호를 <수학식10>과 같이 2개의 부분 공간(subspace)으로 분리 할 수 있다.

Through singular value decomposition (SVD), we can effectively separate the received signal into two subspaces as shown in Equation 10.

로서, 가장 큰

개의 고유값(eigenvalue)으로 구성된 LxL 대각 행렬이다.

는 가장 큰

개의 고유값(eigenvalue)과 대응하는 고유벡터(eigenvector) 열들로 구성된

행렬이며 이 행렬은 전파방해신호의 부분 공간을 나타낸다.

로서, 나머지

고유값들(eigenvalues)로 구성되며 이 때, 각각의 값은

과 같다고 가정한다. 그리고

는

의 각각의 고유값들(eigenvalues)에 대응하는 고유값(eigenvalue) 열들로 구성된

행렬이며, 이 행렬은 노이즈 부분 공간 을 나타낸다. 전파방해신호의 부분 공간이 위와 같은 방식으로 표현될 때, 노이즈 부분 공간은 아래 <수학식11>로 표현되는 전파방해신호 부분 공간의 직교 투영 매트릭스(orthogonal projection matrix)를 통해 얻을 수 있다.At this time,

As, the largest

L x L diagonal matrix of eigenvalues.

Is the biggest

Of eigenvalues and corresponding eigenvector columns

Matrix, which represents the subspace of the jamming signal.

As the rest

Consisting of eigenvalues, where each value is

Assume that And

Is

Consists of columns of eigenvalues corresponding to the respective eigenvalues of

Matrix, which represents the noise subspace. When the subspace of the jammer is represented in the above manner, the noise subspace may be obtained through an orthogonal projection matrix of the jammer subspace represented by Equation 11 below.

은 역행렬을 나타낸다. 따라서

의 열은 노이즈 부분 공간(subspace)을 나타낸다. 수신된 신호

을 아래와 같이

에 투영(projection) 시킴으로써, 하기 <수학식 12>와 같이 GPS 성분과 노이즈 성분으로만 구성된

신호를 얻을 수 있다.At this time,

Represents an inverse matrix. therefore

The column of denotes the noise subspace. Received signal

As below

By projecting onto the Equation 12, only the GPS component and the noise component are formed as shown in Equation 12.

You can get a signal.

As described above, in order to project the jamming signal, the direction component of the jamming signal component may be obtained through singular value decomposition (SVD) of the received signal. This is because the spatial signature of the jamming signal represents the subspace of the jamming signal, and it is difficult to find the spatial signature of the jamming signal from the actual received signal. Start with the assumption that the direction of signal reception is unknown. In the case of the multipath interference signal, it is reflected from various terrains and enters in a direction horizontal to the horizon, whereas the satellite signal enters in a direction perpendicular to the horizon.

,

로 나타내고 이 방향성분은 어떤 임의의 각

를 나타내는 것으로 정의한다.

를 각 방향의 공간 표지(spatial signature)로 구성된

행렬로 나타내면 이 때,

라고 가정하며, 각각의 공간 표지(spatial signature)는 선형적으로 독립이며, 다중경로 간섭신호의 범위로서 설정되는 것이다.

을 다중경로신호에 직교(orthogonal)한 부분 공간에 투영시키기 전에

는 이미 이전의 부분 공간 투영(subspace projection)을 통해 전파방해신호의 수신 방향이 제거된 신호임을 고려해야 한다.Therefore, the direction of the incoming signal near the horizon

,

This aromatic component represents any arbitrary angle

It is defined as representing.

Consists of a spatial signature in each direction

In matrix, at this time,

Each spatial signature is linearly independent and is set as a range of multipath interference signals.

Before projecting into a subspace orthogonal to the multipath signal

Consider that the signal reception direction of the jamming signal has already been removed through the previous subspace projection.

In the antenna array of the receiver, all incoming signals are composed of the same direction component. Therefore, the orthogonal projection matrix of the multipath interference signal in which the component of the interference signal remains again cannot be directly applied to the signal from which the direction component of the interference signal is removed.

과 동일한 공간 성분을 갖는 다중경로 간섭신호의 직교 투영 매트릭스(orthogonal projection matrix)를 얻기 위해 하기 <수학식 13>과 같이

를 전파방해신호의 직교 투영 매트릭스(orthogonal projection matrix)

에 먼저 투영(projection) 시킬 필요가 있다.Therefore, as shown in the projection of the spatial marker matrix for the multipath interference signal shown in FIG.

In order to obtain an orthogonal projection matrix of a multipath interference signal having the same spatial component as

Is an orthogonal projection matrix of jamming signals

Needs to be projected first.

은

과 동일한 방향성분으로 구성되고

는

행렬의 계수(rank)이며

은 특이값 분해(SVD)를 통해 아래와 같은 식으로 분리 할 수 있다.Through this process

silver

Consists of the same aromatic components as

Is

Rank of the matrix

Can be separated by singular value decomposition (SVD)

와

는 각 각

와

의 크기를 갖는 단일(unitary) 행렬이며, 하기 <수학식15>는

의 고유값들(eigenvalues)로 각각의 고유값들(eigenvalues)의 크기는

와 같다.At this time,

Wow

Is each

Wow

It is a unitary matrix having a size of and Equation 15 is

The eigenvalues of are the magnitude of each eigenvalues

Same as

를

의 처음

개만큼의 열로 구성된 행렬이라 하면,

는 전파방해신호가 존재하지 않는 공간에서의 다중경로 간섭신호의 부분 공간(subspace)을 나타낸다. 다중경로 간섭신호가 제거된 공간은 다음의 <수학식 6>과 같은 다중경로 간섭신호의 직교 투영 매트릭스(orthogonal projection matrix)를 통하여 구할 수 있다.

To

Beginning of

A matrix of as many columns as

Denotes a subspace of a multipath interference signal in a space where no radio interference signal exists. The space from which the multipath interference signal is removed can be obtained through an orthogonal projection matrix of the multipath interference signal as shown in Equation 6 below.

의 열은 다중경로 간섭신호가 제거된 부분 공간(subspace)을 나타내고,

을 아래와 같이

에 투영(projection) 시킴으로써 GPS 신호와 노이즈로만 구성된 신호

를 얻을 수 있다.therefore

Column represents the subspace from which the multipath interference signal has been removed,

As below

A signal consisting only of GPS signals and noise by projecting onto

Can be obtained.

를

크기의 필터 가중치 벡터(weight vector)라고 하면 필터의 출력

은 아래와 같은 <수학식 18>로 나타낼 수 있다.Even after the removal of the jamming signal and the multipath interference signal by the subspace projection, the GPS signal is still smaller than the noise. Therefore, it is necessary to obtain the maximum signal-to-noise ratio in order to accurately acquire the satellite signal in the receiver. Thus, by configuring a filter having the maximum signal-to-noise ratio, the signal-to-noise ratio of the GPS signal is increased.

To

Speaking of the filter weight vector of magnitude, the output of the filter

Can be represented by Equation 18 as shown below.

는 다음과 같이 결정된다.Filter weight vector

Is determined as follows.

를 알아야 한다는 것을 보여준다. 하지만 GPS 수신기에서 GPS 신호의 상관 행렬을 알기는 어려운 일이며, GPS 수신기에서 GPS 신호에 대한 상관 행렬을 알 수 없다면, 가중치 벡터를 구하기 위해 최대 신호 대 잡음비에 대해 다른 방법으로 접근이 필요하다. 한 편, <수학식 17>에서

가 GPS 신호 성분과 노이즈 성분만으로 구성되어 있음을 알 수 있다. GPS 신호가 노이즈 성분에 비해 상대적으로 약하기 때문에 GPS 수신기에서 2번의 투영(projection) 후 출력되는 신호는 거의 대부분 노이즈 성분으로 구성된 신호이다. 이에 <수학식 19>에

을 적용하면 아래와 같은 <수학식 20>이 산출된다.Equation (19) is a correlation matrix of GPS signals at the receiver to obtain a weight vector for the maximum signal-to-noise ratio.

Show that you need to know However, it is difficult to know the correlation matrix of the GPS signal at the GPS receiver, and if the correlation matrix of the GPS signal is not known at the GPS receiver, another approach to the maximum signal-to-noise ratio is required to obtain the weight vector. On the other hand, in <Equation 17>

It can be seen that is composed of GPS signal component and noise component only. Since the GPS signal is relatively weak compared to the noise component, the signal output after the two projections from the GPS receiver is mostly composed of the noise component. In Equation 19

Applying Eq. (20) yields:

을 적용한 후의 최대 신호 대 잡음비 식이 처음 최대의 비율을 얻기 원했던 아래 <수학식 21>과 동일한 결과를 가져온다는 것을 확인 할 수 있다.Equation 20 is

It can be seen that the maximum signal-to-noise ratio equation after applying the results is the same as in Equation 21 below.

를 구하는 것은 하기 <수학식 22>에서 최대 신호 대 잡음비를 위한

를 구하는 것과 동일하다.Therefore, the weight vector that maximizes Equation 21

To obtain the maximum signal-to-noise ratio in Equation 22 below.

Is equivalent to finding.

를 구할 수 있다.Through this method, the maximum signal-to-noise ratio

Can be obtained.

는 하기 <수학식 24>와 같은 일반적인 고유값 문제(eigenvalue problem)로 얻을 수 있다.In Equation 23,

Can be obtained as a general eigenvalue problem as shown in Equation (24).

는 최대의 신호 대 잡음비를 얻기 위한 고유값(eigenvalue)이다.At this time,

Is an eigenvalue to obtain the maximum signal-to-noise ratio.

On the other hand, Figures 3 to 7 show the simulation results by the proposed technique according to an embodiment of the present invention. For the simulation, it is assumed that each antenna mounted in the GPS receiver is a linear array antenna composed of seven antennas separated by 1/2 of the wavelength. In this first simulation, the jamming signal was removed. It is assumed that two jamming signals enter SIR = -30 dB in the directions of 30 ° and 60 °, respectively, and the noise is removed with SNR = -20 dB. .

In the second simulation, multipath interference signals were removed in the presence of jamming signals. Assuming that the GPS signal is coming in the direction of 10 °, one multipath interference signal is coming in the direction of 320 °, and two jamming signals are introduced in the direction of 30 ° and 60 ° respectively. It was carried out under the same conditions as the first step.

FIG. 3 is a graph illustrating a GPS reception signal in which a jammer signal exists according to an embodiment of the present invention, and FIG. 3 illustrates autocorrelation of a GPS reception signal in which a jammer signal is not removed. That is, in the graph of FIG. 3, it is difficult to synchronize GPS C / A-code in the GPS receiver when there is no removal of the jammer signal, so that accurate GPS information cannot be obtained.

FIG. 4 is a graph illustrating a GPS reception signal in which a radio wave interference signal has been removed according to an embodiment of the present invention, and shows an autocorrelation graph in a GPS receiver after the radio wave interference signal is removed through subspace projection. Effective subtraction of the jamming signal through subspace projection indicates that the GPS receiver is synchronized.

However, as can be seen from the graph of FIG. 4, the noise component still remains, and the GPS signal component has a relatively small size compared to the noise component, so that the beam for obtaining the maximum signal-to-noise ratio in order to obtain more accurate GPS information. Forming (beamforming) process is required.

An autocorrelation graph of the final output signal of the GPS receiver after beamforming to obtain the maximum signal to noise ratio is shown in FIG. 5. This can confirm that the jamming signal and the signal from which the noise is removed from the GPS receiver is synchronized.

6 to 7 show beam patterns with and without the multipath interference signal when the multipath interference signal enters the GPS receiver. As shown in FIG. 6, when the multipath interference signal is not removed, it may be confirmed that each beam is formed in the GPS signal direction 600 and the multipath interference signal direction 602. However, the beam pattern after the projection algorithm for the multipath interference signal is processed can be confirmed that the beam is formed with high gain only in the GPS signal direction 700, as shown in FIG. Indicates that it was removed.

In addition, in each of FIGS. 6 to 7, it can be confirmed that nulling is performed for 30 ° and 60 °, which are directions of the jamming signal, which indirectly indicates that the jamming signal is also removed from the GPS receiver.

As described above, the present invention effectively utilizes the interference signal and the multipath interference signal by using subspace projection and beamforming when using the location information related service through the satellite navigation system receiver having the multiple antennas. Remove with.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

1 is a flowchart illustrating a procedure for removing a jammer signal and a multipath interference signal according to an embodiment of the present invention;

2 is a diagram illustrating a projection diagram of a spatial marker matrix for a multipath interference signal according to an embodiment of the present invention;

3 is a graph illustrating a GPS received signal in which a radio wave interference signal is present according to an embodiment of the present invention;

4 is a graph illustrating a GPS received signal in which radio wave interference signal is removed according to an embodiment of the present invention;

FIG. 5 is a graph illustrating a GPS received signal after removing a radio interference signal and performing beamforming according to an embodiment of the present invention;

6 is a diagram illustrating a beam pattern in a situation where a multipath interference signal exists according to an embodiment of the present invention;

7 is a diagram illustrating a beam pattern when a multipath interference signal is removed in a situation where a multipath interference signal is present according to an embodiment of the present invention;

Claims (6)

Removing the jamming signal by projecting the received signal from a GNSS receiving device that receives a satellite navigation system (GNSS) signal from at least two satellites into a subspace in which no jamming signal exists; Removing the multipath interference signal by projecting the GNSS received signal from which the radio wave interference signal has been removed to a partial space in which the multipath interference signal does not exist; In the satellite navigation receiving device comprising a radio interference signal and multipath interference signal removal method. The method of claim 1, The process of removing the multipath interference signal, Setting a range of the multipath interference signal when the partial space projection is used to remove the radio wave interference signal and the multipath interference signal; A process of obtaining an orthogonal projection matrix of multipath interference signals by performing subspace projection on the set range and removing the multipath using the orthogonal projection matrix of the obtained multipath interference signals. In the satellite navigation receiving device comprising a radio interference signal and multipath interference signal removal method. 3. The method of claim 2, The process of setting the range of the multipath interference signal includes: A method for removing radio interference signals and multipath interference signals in a satellite navigation receiver, characterized in that the spatial indication of the direction of the incoming signal at a predetermined horizontal angle from the horizon. 3. The method of claim 2, The subspace projection for the set range is The method for canceling the jamming signal and the multipath interference signal in the satellite navigation apparatus, characterized in that for projecting the set range to the orthogonal projection matrix of the jamming signal. The method of claim 1, The method, Converting the received GNSS signal including the GNSS signal and noise into a positioning signal having a maximum signal-to-noise ratio by removing the multipath interference signal The method for removing radio interference signals and multipath interference signals in a satellite navigation apparatus further comprising a. The method of claim 5, The maximum signal to noise ratio is A method for canceling a radio wave signal and a multipath interference signal in a satellite navigation receiver, comprising calculating the weight vector.

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