KR20110112048A - Method and apparatus for detection of mimo antenna characteristics and performance - Google Patents

Abstract

A method for measuring antenna performance for a multi-antenna system including at least one transmit antenna and at least two receive antennas includes measuring a radiation pattern for the multiple antennas, and measuring the multiple antennas for the measured multiple antennas. Processor for MIMO antenna design by measuring antenna performance using predicted inter-antenna spatial correlation coefficients, including the process of determining the inter-antenna spatial correlation coefficients using a radiation pattern and an Angle of Arrival (AoA) profile. And saves time, effort and money.

Description

METHOD AND APPARATUS FOR DETECTION OF MIMO ANTENNA CHARACTERISTICS AND PERFORMANCE}

The present invention relates to antenna characteristics and performance measurement, and more particularly, to a method and apparatus for detecting antenna characteristics using spatial diversity of signals between antennas in a multi-antenna system.

As a next generation communication system, a multiple-input-multiple-output (MIMO) antenna communication method is drawing attention. Accordingly, two or more antennas are mounted in the wireless communication device. It is difficult to grasp antenna performance for predicting the performance of the MIMO antenna communication.

In other words, it is difficult to measure the performance of MIMO antenna communication in which two or more antennas are mounted in the conventional measurement method in which the performance characteristics of the antenna are limited to one antenna. This distorts the characteristics of each antenna due to the mutual interference between the two antennas, and thus it is difficult to regard the characteristics of each antenna as the characteristics of the MIMO antenna.

In the related art, the performance of an antenna in a communication scheme for performing communication with one antenna is estimated by the antenna gain. This can be applied to SISO (Single-Input Single-Output) communication characteristics whose communication performance is affected by the received power. However, MIMO communication performance is not only influenced by the antenna gain, but also the coupling between antennas varies depending on the channel environment, resulting in mutual interference between channels. For that reason, MIMO antennas are difficult to predict antenna performance with their own parameters.

On the other hand, the detection of antenna characteristics in the conventional anechoic chamber is based on one antenna. Simultaneous spatial correlation coefficient Detection of two or more antennas in the same frequency band is possible only by the number of feedlines of the antennas. However, even in this case, since spatial correlation is determined not only by the characteristics of the antenna but also by the propagation environment, it is impossible to detect the characteristics of the spatial correlation coefficient of the multi-antenna for MIMO communication.

That is, the spatial correlation coefficient of the MIMO antenna can be measured in a reverberation chamber in which a scattering environment similar to the real environment is arbitrarily measured, not in the real environment or an anechoic chamber. Therefore, it is impossible to predict the communication performance of the MIMO antenna using the data measured in the anechoic chamber. This is because detecting the spatial correlation coefficient is not explained by the prior art.

There is also a method of calculating the correlation coefficient between antennas using the radiation characteristics of the antenna, but this is quite different from the spatial correlation coefficient, which is a characteristic of the antenna depending on the MIMO environment.

Accordingly, there is a need for a method and apparatus for efficiently measuring the performance of multiple antennas.

It is an object of the present invention to provide a method and apparatus for efficiently measuring the performance of multiple antennas.

Another object of the present invention is to provide a method and apparatus for measuring performance according to an antenna array based on measurement data in an anechoic chamber.

Yet another object of the present invention is to provide a method and apparatus for determining inter-antenna interspatial correlation coefficient for measuring the performance of multiple antennas.

According to a first aspect of the present invention for achieving the above objects, a method for measuring antenna performance for a multi-antenna system comprising at least one transmit antenna and at least two receive antennas, And determining a spatial correlation coefficient between antennas by measuring a radiation pattern for each of the plurality of antennas and using the measured radiation pattern and angle of arrival (AoA) profile of the plurality of antennas.

According to a second aspect of the present invention for achieving the above objects, there is provided an apparatus for measuring antenna performance for a multiple antenna system comprising at least one transmit antenna and at least two receive antennas. And a calculation unit for measuring a radiation pattern for each antenna, and a calculation unit for determining a spatial correlation coefficient between antennas using the measured radiation pattern and angle of arrival (AoA) profile of the plurality of antennas.

As described above, by predicting the spatial correlation coefficient obtained in the real environment based on the radiation pattern of the antenna, it is possible to measure the performance of the multi-antenna without measuring the spatial correlation coefficient between the antennas directly in the real environment. have. In addition, by measuring the performance of multiple antennas using the predicted inter-antenna spatial correlation coefficient, the processor, time, effort, and cost for MIMO antenna design can be reduced.

1 is a flow chart for measuring the performance of a multi-antenna according to an embodiment of the present invention;
2 is a device diagram for measuring the performance of a multi-antenna according to an embodiment of the present invention;
3 is a diagram illustrating radiation pattern distortion caused by mutual coupling of dipole antennas according to an embodiment of the present invention;
4 is an example of the radiation pattern of each antenna according to the direction of the antenna according to an embodiment of the present invention,
5 is an angular pattern according to an angular profile according to an embodiment of the present invention, and
6 is a graph comparing the spatial correlation coefficients measured by the present invention and the real environment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the following description of the present invention, detailed descriptions of related well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, the present invention will be described a method and apparatus for measuring multi-antenna performance. In particular, multiple-input-multiple-output (MIMO) antenna designs and arrays are estimated by predicting the spatial correlation coefficient of signals between antennas without performing real-world tests or propagation simulations based on the characteristics of each antenna. Techniques for determining the method will be described.

The spatial correlation coefficient is an important factor in determining communication performance in MIMO communication. The spatial correlation coefficient is determined by the channel environment as well as the antenna characteristics, and it is difficult to predict the spatial correlation coefficient. The present invention predicts a spatial correlation coefficient in an antenna design by providing information about a channel environment in measuring antenna characteristics.

The present invention detects the spatial correlation coefficient by obtaining parameters for mutual interference between antennas and defining a channel environment by a channel model in an Angle of Arrival (AoA) profile.

The performance of the MIMO communication is defined by Equation 1 below by Shannon's capacity.

Where M _T is the number of transmit antennas, M _R is the number of receive antennas, I _MR is an identity matrix of size M _R , SNR is the Signal to Noise Ratio, and H is the channel matrix (M). _R x M _T ).

The spatial correlation coefficient is expressed by Equation 2 below.

Where vec (.) Is a vectorizing operator and E (.) Is an average value.

In Equation 1, the capacity of MIMO communication having M _T and M _R is determined by SNR and HH ^H. The SNR depends on the received power and antenna gain. However, HH ^H depends on antenna characteristics and channel environment. Therefore, for the antenna design, it is necessary to predict the spatial correlation coefficient according to the channel environment as well as the communication device and antenna characteristics. In the present invention, a complex radiation pattern, which is an antenna characteristic, and a channel environment based on a channel model are introduced to predict spatial correlation coefficients through mathematical operations.

Channel capacity according to the spatial correlation coefficient in MIMO communication is defined as in Equation 3 or Equation 4 below.

는 크로네커(Kronecker) 연산을 의미한다.
Here, R _R and R _T are the correlation matrix at the receiving end and the transmitting end, respectively.

Means Kronecker operation.

에 의해 변화한다. 공간 상관 관계가 높으면 α는 작아지게 되고 채널 용량의 열화를 가져오게 된다. 그러므로 본 발명은 공간 상관 계수를 미리 판단하여 안테나 특성에 의한 MIMO 통신 성능을 예측한다.
Channel capacity due to cross-spatial correlation

To change. If the spatial correlation is high, α becomes small, resulting in deterioration of channel capacity. Therefore, the present invention predicts the MIMO communication performance by antenna characteristics by determining the spatial correlation coefficient in advance.

1 is a flowchart for measuring the performance of a multi-antenna according to an embodiment of the present invention.

Referring to FIG. 1, the antenna performance measuring apparatus sets i = 1 in step 101. Where i is the antenna index.

In operation 103, the antenna performance measuring apparatus selects an antenna based on the antenna index i, determines a complex radiation pattern for the antenna selected in step 105, and sets a database of the radiation pattern of the selected antenna in step 107. Store in Here, the antenna radiation pattern means a curve showing how strongly the radio waves are radiated in each direction in the antenna.

Thereafter, the antenna performance measuring apparatus determines whether i = N in step 109, and sets i = 1 + 1 in step 111 and proceeds to step 103 when i ≠ N. Where N is the number of antennas in the multiple antenna system.

That is, through steps 101 to 111, in the antenna array composed of a plurality of antennas, the radiation pattern is determined for each antenna. In general, antenna radiation patterns are measured in an anechoic chamber. If there are N receive antennas, the radiation pattern is measured according to each antenna. In this case, the selected antenna obtains a radiation pattern coupled by the remaining antennas (see FIG. 3 below).

In operation 113, the antenna performance measuring apparatus performs a coupled radiation pattern of N antennas, and then reads each profile obtained from the channel model from a database. Each of the profile (angular profile ) means beam pattern information according to channel environment .

In operation 115, the antenna performance measuring apparatus uses the antenna radiation pattern and the respective profile to angular the pattern. pattern). That is, each pattern (angular) pattern) is defined as the product of the beam pattern of each profile and the antenna radiation pattern.

In operation 117, the antenna performance measurement apparatus determines each pattern correlation coefficient. Here, each pattern correlation coefficient is a spatial correlation coefficient for determining MIMO antenna performance.

The spatial correlation coefficient can be calculated only when the channel matrix H is measured as shown in Equation 2. Therefore, in the present invention, the matrix for the spatial correlation coefficient is predicted by using the antenna radiation pattern and the radio wave intensity (AoA profile) or the antenna radiation pattern according to the direction in which the radio wave transmitted from the transmitter is received.

In general, a pattern correlation between antennas of a MIMO antenna is calculated as shown in Equation 5 by a radiation pattern.

Where m and n are antenna indices and E _m is two orthogonal electric fields. Equation 5 is an example of calculating a correlation coefficient between antenna 1 and antenna 2.

In Equation 5, when the spatial correlation coefficient influenced by the channel environment is applied, Equation 6 is expressed.

)는 상기 각 프로파일(angular profile)을 가중치 함수(weighting function)으로 정의하여 하기 <수학식 6>과 같이 정의하여 계산한다.That is, the spatial correlation coefficient (

) Is calculated by defining each of the profiles (angular profile) as a weighting function (Equation 6).

는 무반사실에서 측정된 안테나 방사 패턴과 각 프로파일(angular profile)에 의해 예측된다. 제안된

를 각 패턴 상관계수(angular pattern correlation)으로 칭한다.
Where w (φ) is a weight and is an angular profile. Referring to Equation 6, the spatial correlation coefficient of the present invention

Is predicted by the antenna radiation pattern and the angular profile measured in the anechoic chamber. Proposed

Is referred to as angular pattern correlation.

2 illustrates an apparatus for measuring the performance of multiple antennas according to an embodiment of the present invention.

Referring to FIG. 2, the antenna performance measuring apparatus includes a transceiver 200, a measurement unit 205, a controller 210, a calculator 215, and a channel storage 220.

The transceiver 200 transmits an RF signal through a switched antenna under the control of the controller 210, receives the transmitted RF signal through a reception antenna, and provides the received RF signal to the measurement unit 205.

The measurement unit 205 measures a radiation pattern of the corresponding antenna based on the signal from the transceiver 200.

The controller 210 controls the transceiver 200, the measurement unit 205, and the calculator 215 to perform overall control of the measurement device.

For example, the controller 210 controls a switching operation so that the corresponding antenna and the transceiver 200 are connected, and controls the measurement unit 205 to configure antenna radiation pattern information. In addition, the operation unit 215 controls to calculate the spatial correlation coefficient in Equation (6).

The calculation unit 215 applies a spatial correlation coefficient by applying the radiation pattern information of the corresponding antenna determined from the measurement unit 205 and the angular profile from the channel storage unit 220 to the equation (6). Determine.

The channel storage unit 220 stores / manages each profile according to a channel environment, and provides each profile information to the calculation unit 215 when necessary.

3 is a diagram illustrating radiation pattern distortion due to mutual coupling of dipole antennas.

Referring to FIG. 3, an antenna radiation pattern measured when two dipole antennas are separated by 0.3 wavelength is illustrated.

(a) is the radiation pattern of the antenna when there is no inter-antenna coupling, (b) is the radiation pattern when the first antenna is coupled with the second antenna, and (c) is the second antenna 1 Radiation pattern when coupled with an antenna.

The dipole antenna is isotropic to θ and forms a radiation pattern (a), but each antenna is distorted by another antenna ((b), (c)). The antenna radiation pattern is calculated according to Equation 5 above.

4 shows an example of a radiation pattern of each antenna according to the antenna direction.

Referring to FIG. 4, it is shown whether the coupling between antennas calculated according to the direction of the antenna changes at 0.3 wavelength and 0.6 wavelength. That is, it can be seen that the antenna radiation patterns for directions 1, 2, and 3 are different. In addition, it can be seen that not only the direction of the antenna but also depends on the separation distance (0.3λ, 0.6λ) between the two antennas.

However, the spatial correlation coefficient value according to Equation 5 has the same value even if the radiation pattern is different. However, MIMO antennas have different cross-correlation values due to different directions of receiving antennas. Therefore, not only the correlation coefficient according to the radiation pattern but also the correlation coefficient according to the direction should be considered.

FIG. 5 illustrates an angular pattern according to a channel characteristic (angular profile) according to an embodiment of the present invention.

Referring to FIG. 5, an angular pattern is shown according to a beam direction of a transmitting antenna.

Here, each of the patterns (angular pattern) is represented by the product of each profile (angular profile) representing the beam pattern information and the AoA profile (f (θ)).

By applying the determined patterns to Equation (6), a cross correlation coefficient can be obtained to predict the spatial correlation coefficient even if not measured in a real environment.

By predicting the spatial correlation coefficient, it is possible to predict the performance in the real environment according to the antenna arrangement.

6 is a comparison graph of the spatial correlation coefficients measured by the present invention and the real environment.

Referring to FIG. 6, spatial correlation coefficients obtained in a real environment, cross-correlation coefficients between antennas, and angular pattern correlations proposed by the present invention are described. It is shown together. The existing pattern correlation depends only on the separation distance of the antenna, but this proposal can predict the spatial correlation coefficient according to the channel environment.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

Measuring unit: 205, Computing unit: 215, Control unit: 210, Channel storage unit: 220

Claims (12)

A method for measuring antenna performance for a multiple antenna system comprising at least one transmit antenna and at least two receive antennas, the method comprising:
Measuring a radiation pattern for each of the plurality of antennas;
And determining a spatial correlation coefficient between antennas using the measured radiation pattern and angle of arrival (AoA) profile for the plurality of antennas.
The method of claim 1,
Wherein the spatial correlation coefficient is determined by the product of the measured radiation pattern for the multiple antennas and the Angle of Arrival (AoA) profile.
The method of claim 1,
The spatial correlation coefficient is characterized by the following equation.

here,

Is the spatial correlation coefficient, m, n is the antenna index, E _m is the two orthogonal electric fields, w (φ) is the weight and is the angular profile,

Is cross-polarization discrimination (XPD).
The method of claim 1,
And the radiation pattern of the antenna is measured and determined in the anechoic chamber.
The method of claim 1,
Wherein the spatial correlation is predictable without a channel matrix.
The method of claim 1,
The measured radiation pattern of the antenna is distorted by other antennas.
An apparatus for measuring antenna performance for a multiple antenna system comprising at least one transmit antenna and at least two receive antennas,
A measurement unit for measuring radiation patterns for the plurality of antennas, respectively;
And a calculation unit for determining a spatial correlation coefficient between antennas using the measured radiation pattern and angle of arrival (AoA) profile for the plurality of antennas.
The method of claim 7, wherein
Wherein the spatial correlation coefficient is determined by the product of the measured radiation pattern for the multiple antennas and the Angle of Arrival (AoA) profile.
The method of claim 7, wherein
Wherein the spatial correlation coefficient is determined by the following equation.

here,

Is the spatial correlation coefficient, m, n is the antenna index, E _m is the two orthogonal electric fields, w (φ) is the weight and is the angular profile,

Is cross-polarization discrimination (XPD).
The method of claim 7, wherein
And the radiation pattern of the antenna is measured and determined in the anechoic chamber.
The method of claim 7, wherein
Wherein the spatial correlation is predictable without a channel matrix.
The method of claim 7, wherein
And wherein the measured radiation pattern of the antenna is distorted by other antennas.

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