KR101661165B1 - Method and apparatus for detection of mimo antenna characteristics and performance - Google Patents

Abstract

A method for measuring an antenna performance for a multi-antenna system including at least one transmission antenna and at least two reception antennas includes the steps of measuring radiation patterns for the multiple antennas, The antenna performance is measured using the predicted antenna spatial correlation coefficient including the process of determining the spatial correlation coefficient between the antennas using the radiation pattern and the Angle of Arrival (AoA) profile, And can save time, effort, and cost.

Description

[0001] METHOD AND APPARATUS FOR DETECTION OF MIMO ANTENNA CHARACTERISTICS AND PERFORMANCE [0002]

The present invention relates to antenna characteristics and performance measurements, and more particularly, to a method and apparatus for detecting antenna characteristics using spatial diversity of an inter-antenna signal in a multi-antenna system.

A multi-input-multiple-output (MIMO) antenna communication method is attracting attention as a next generation communication system. Accordingly, two or more antennas are mounted on the wireless communication device. It is difficult to grasp the 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 is because it is difficult to see the characteristics of each antenna as a characteristic of the MIMO antenna because the characteristics of each are distorted by the mutual coupling between the two antennas.

Conventionally, the performance of an antenna in a communication system that performs communication with one antenna is estimated by an antenna gain. This is applicable to single-input single-output (SISO) communication characteristics in which communication performance is affected by received power. However, not only is the MIMO communication performance affected by the antenna gain, but also the coupling between the antennas changes depending on the channel environment, thereby causing inter-channel interference. For this reason, it is difficult to predict the performance of a MIMO antenna with parameters of the antenna itself.

On the other hand, the detection of antenna characteristics in the conventional anechoic chamber is based on one antenna. At the same time, it is possible to detect the characteristics of two or more antennas in the same frequency band by using feedlines as many as the number of antennas. However, even in this case, because 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 spatial correlation coefficients of multiple antennas for MIMO communication.

That is, the spatial correlation coefficient of the MIMO antenna can be measured in a reverberation chamber, which is measured in a real environment or constitutes a scattering environment similar to an actual environment, which is not 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 the detection of the spatial correlation coefficient is not explained by the conventional technique.

There is a method of calculating the correlation coefficient between antennas using the radiation characteristic of the antenna, but there is a significant difference from the spatial correlation coefficient which is the characteristic of the antenna depending on the MIMO environment.

Therefore, 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.

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

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

According to a first aspect of the present invention, there is provided a method for measuring antenna performance for a multi-antenna system including at least one transmission antenna and at least two reception antennas, And determining a spatial correlation coefficient between antennas using the measured radiation pattern and the angle of arrival (AoA) profile of the multiple antennas.

According to a second aspect of the present invention, there is provided an apparatus for measuring antenna performance for a multi-antenna system including at least one transmission antenna and at least two reception antennas, And a calculation unit for determining spatial correlation coefficients between antennas using a radiation pattern and an angle of arrival (AoA) profile for the measured multiple antennas.

As described above, by predicting the spatial correlation coefficient that can be obtained in a real environment based on the radiation pattern of the antenna, it is possible to measure the performance of multiple antennas without directly measuring the spatial correlation coefficient between antennas in a 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 the MIMO antenna design can be reduced.

FIG. 1 is a flow chart for measuring the performance of multiple antennas according to an embodiment of the present invention. FIG.
FIG. 2 is an apparatus for measuring performance of multiple antennas according to an embodiment of the present invention. FIG.
3 is a view showing a radiation pattern distortion caused by mutual coupling of a dipole antenna according to an embodiment of the present invention,
FIG. 4 shows an example of the radiation pattern of each antenna according to the antenna direction according to the embodiment of the present invention,
FIG. 5 is a graph illustrating an angular pattern according to an exemplary embodiment of the present invention,
FIG. 6 is a graph showing a comparison of spatial correlation coefficients according to the present invention and measurement in a 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, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and these may be changed according to the intention of the user, the operator, or the like. Therefore, the definition should be based on the contents throughout this specification.

Hereinafter, a method and an apparatus for measuring multi-antenna performance will be described. In particular, a spatial multiple-input-multiple-output (MIMO) antenna design and array is proposed by predicting the spatial correlation coefficients of signals between antennas without conducting actual environment testing or propagation simulation based on each antenna characteristic. And a method for determining the method and the like will be described.

The spatial correlation coefficient is an important factor that determines the communication performance in MIMO communication. The spatial correlation coefficient is determined not only by the antenna characteristic but also by the channel environment, and it is difficult to predict the spatial correlation coefficient. The present invention predicts the spatial correlation coefficient in the antenna design by providing information on the channel environment in the step of measuring the antenna characteristics.

The present invention detects spatial correlation coefficients 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) by Shanon'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, H is the channel matrix M _R x M _T ).

The spatial correlation coefficient is expressed by Equation (2) below.

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

The capacity of MIMO communication with M _T and M _R in Equation (1) is determined by SNR and HH ^H. The SNR depends on received power and antenna gain. However, HH ^H depends on the antenna characteristics and the channel environment. Therefore, it is necessary to predict the spatial correlation coefficient according to the channel environment as well as the characteristics of the communication device and the antenna for the antenna design. 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 a spatial correlation coefficient through a mathematical operation.

The channel capacity according to the spatial correlation coefficient in the MIMO communication is defined by Equation (3) or Equation (4).

Here, R _R and R _T are correlation matrices at the receiving end and the transmitting end, respectively,

Means a Kronecker operation.

The channel capacity due to mutual spatial correlation is

. If the spatial correlation is high,? Becomes small and the channel capacity deteriorates. Therefore, the present invention estimates the MIMO communication performance based on the antenna characteristics by predetermining the spatial correlation coefficient.

FIG. 1 shows a flow chart for measuring the performance of multiple antennas according to an embodiment of the present invention.

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

Then, the antenna performance measuring apparatus selects an antenna based on the antenna index i in step 103, determines a complex radiation pattern for the antenna selected in step 105, and determines a radiation pattern of the selected antenna in step 107, . Here, the antenna radiation pattern is a curve showing how strongly the antenna is radiated in each direction.

Then, the antenna performance measuring apparatus determines whether i = N in step 109, and sets i = 1 + 1 in step 111 when i? = N. Where N is the number of antennas in the multi-antenna system.

That is, in steps 101 through 111, a radiation pattern is determined for each antenna in an antenna array composed of a plurality of antennas. Typically, the antenna radiation pattern is measured in an anechoic chamber. If there are N receive antennas, the radiation pattern is measured according to each antenna. At this time, the radiation pattern in which the selected antenna is coupled by the remaining antennas is obtained (see FIG. 3).

Then, the antenna performance measuring apparatus reads the angular profile obtained from the channel model from the database after performing a coupled pattern of coupled antennas of N antennas in step 113. Each of the profile (angular profile indicates beam pattern information according to a channel environment .

Then, in step 115, the antenna performance measuring apparatus measures an antenna radiation pattern and angular profiles pattern. That is, the angular pattern is defined as the product of the beam pattern of each profile and the antenna radiation pattern.

In step 117, the antenna performance measuring apparatus determines each pattern correlation coefficient. Here, each of the pattern correlation coefficients is a spatial correlation coefficient for determining MIMO antenna performance.

The spatial correlation coefficient can be calculated by measuring the channel matrix H 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 antenna radiation pattern according to the direction of the received signal at the receiving end (AoA profile) or the antenna radiation pattern.

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

Here, m, n is the antenna index and, E _m is one or two perpendicular (orthogonal) electric field (electric field). Equation (5) is an example of calculating the correlation coefficient between the antenna 1 and the antenna 2.

In Equation (5), when the spatial correlation coefficient affected by the channel environment is applied, Equation (6) is expressed as Equation (6).

That is,

Is defined by defining each of the angular profiles as a weighting function, as shown in Equation (6) below.

Where w () is a weight and is an angular profile. Referring to Equation (6), the spatial correlation coefficient

Are predicted by the antenna radiation pattern and the angular profile measured in the anechoic chamber. The proposed

Is referred to as an angular pattern correlation.

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

2, the antenna performance measuring apparatus includes a transmitting / receiving unit 200, a measuring unit 205, a control unit 210, an operation unit 215, and a channel storage unit 220.

The transceiver 200 transmits an RF signal through the switched antenna under the control of the controller 210 and receives the transmitted RF signal through the receive antenna and provides the measured RF signal to the measuring unit 205.

The measuring unit 205 measures a radiation pattern of the antenna based on a signal from the transmitting / receiving unit 200.

The control unit 210 controls the transmission / reception unit 200, the measurement unit 205, and the operation unit 215 to perform overall control of the measurement apparatus.

For example, the control unit 210 controls the switching operation so that the corresponding antenna and the transceiver 200 are connected to each other, and controls the measuring unit 205 to configure the antenna radiation pattern information. Further, the arithmetic unit 215 controls to calculate the spatial correlation coefficient in Equation (6).

The operation unit 215 applies the radiation pattern information of the antenna determined by the measurement unit 205 and the angular profile from the channel storage unit 220 to Equation (6) .

The channel storage unit 220 stores and manages angular profiles according to the channel environment and provides the profile information to the operation unit 215 when necessary.

3 is a view showing a radiation pattern distortion caused by mutual coupling of dipole antennas.

Referring to FIG. 3, an antenna radiation pattern measured at a distance of 0.3 wavelength between two dipole antennas is shown.

(b) is a radiation pattern when the first antenna is coupled to the second antenna, (c) is a radiation pattern when the first antenna is coupled to the second antenna, 1 < / RTI > antenna.

The dipole antenna is isotropic in all directions with respect to [theta] 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).

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

Referring to FIG. 4, it is shown that 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. Also, it can be seen that the distance depends on not only the direction of the antenna but also the separation distance (0.3?, 0.6?) Between the two antennas.

However, the spatial correlation coefficient value according to Equation (5) has the same value even if the radiation pattern is changed. However, in the MIMO antenna, the cross-correlation value between the antennas is changed by changing the direction of the receive antenna. Therefore, not only the correlation coefficient according to the radiation pattern but also the correlation coefficient depending on the direction should be considered.

FIG. 5 shows angular patterns according to an 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 transmission antenna.

Here, each of the angular patterns is expressed as a product of an angular profile representing beam pattern information and an AoA profile (f ([theta])).

If the cross-correlation coefficient is obtained by applying each of the determined patterns to Equation (6), the spatial correlation coefficient can be predicted even if it is not measured in a real environment.

By predicting the spatial correlation coefficient, performance in an actual environment according to the antenna array can be predicted.

FIG. 6 is a graph showing a comparison of spatial correlation coefficients by measurement in the real environment of the present invention.

Referring to FIG. 6, the spatial correlation, the existing antenna correlation, and the angular pattern correlation proposed by the present invention are measured in a real environment. 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.

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 by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

A measuring unit 205, a calculating unit 215, a controlling unit 210, a channel storing unit 220

Claims (12)

A method for measuring performance of an antenna in a multi-antenna system,
Determining a radiation pattern for each of the plurality of antennas,
Determining an angular pattern based on the determined radiation pattern and an angular profile;
And determining a spatial correlation between the plurality of antennas based on the determined pattern,
Each of the profiles represents information on a beam pattern according to a channel model,
Wherein the radiation pattern represents information on radiation intensity along a direction of a beam emitted from the antenna.
The method according to claim 1,
Wherein the spatial correlation coefficient is determined based on a product of the determined radiation pattern and the beam pattern.
The method according to claim 1,
Wherein the spatial correlation coefficient is determined by the following equation.

here,

M is an antenna index, E _m is two orthogonal electric fields, and w (

) ≪ / RTI > is a weight,

Is cross-polarization discrimination (XPD).
delete delete The method according to claim 1,
Characterized in that the determined radiation pattern is distorted by other antennas.
An apparatus for measuring performance of an antenna in a multi-antenna system,
A measurement unit for determining a radiation pattern for each of the plurality of antennas,
Determines an angular pattern based on the determined radiation pattern and an angular profile, and determines a spatial correlation between the plurality of antennas based on the determined pattern and,
Each of the profiles represents information on a beam pattern according to a channel model,
Wherein the radiation pattern represents information on radiation intensity along a direction of a beam emitted from the antenna.
8. The method of claim 7,
Wherein the spatial correlation coefficient is determined based on a product of the determined radiation pattern and the beam pattern.
8. The method of claim 7,
Wherein the spatial correlation coefficient is determined by the following equation.

here,

M is an antenna index, E _m is two orthogonal electric fields, and w (

) ≪ / RTI > is a weight,

Is cross-polarization discrimination (XPD).
delete delete 8. The method of claim 7,
Wherein the determined radiation pattern is distorted by other antennas.

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