JP2008263406A - Testing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a testing device capable of testing a MIMO (Multiple Input Multiple Output) radio apparatus. <P>SOLUTION: The testing device 1 is provided with: three input terminals 11a to 11c connected to antenna terminals of a transmitter; three output terminals 12a to 12c connected to antenna terminals of a receiver; distributors 13a to 13c connected to respective input terminals 11a to 11c to distribute signals inputted from the input terminals 11a to 11c into three signals; combiners 14a to 14c respectively connected to the output terminals 12a to 12c to combine signals inputted from the distributors 13a to 13c and input the combined signals to the output terminals; a phase shifter 15a arranged on a route between the distributor 13a and the combiner 14c, a phase shifter 15b arranged on a route between the distributer 13b and the combiner 14b; and a phase shifter 15c arranged on a route between the distributer 13c and the combiner 14c. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a test apparatus used for testing a wireless device in which a MIMO (Multiple Input Multiple Output) transmission system is implemented.

  Conventionally, performance evaluation of a wireless device has been performed for the purpose of quality control of the wireless device or confirmation of connection between wireless devices of different manufacturers. As one method of connection test of wireless devices, there is a method of performing a test by actually performing wireless communication in an anechoic chamber with reduced wall reflection. In addition, there is a method of performing a test using a wired test apparatus that creates an environment close to a real environment, instead of performing wireless communication between wireless devices.

  IEEE 802.11 has proposed a method for evaluating the performance of wireless LAN devices (Non-Patent Document 1). Here, the wired connection test described in Non-Patent Document 1 will be described with reference to the drawings.

  FIG. 14 is a diagram illustrating a configuration of a test system that performs a connection test between wireless devices assuming an antenna diversity system in which one signal sequence is received by two antennas. The wireless devices used for the connection test in Non-Patent Document 1 are a WLCP (Wireless Counterpart) 40 and a DUT (Device Under Test) 41. The DUT 41 is a test target and is a wireless device that operates mainly as a receiver. The WLCP 41 is a wireless device that is paired with the DUT 40 and mainly operates as a transmitter. In the example shown in FIG. 14, since a test of a wireless device in which the antenna diversity system is mounted is assumed, both WLCP 40 and DUT 41 have two antenna terminals.

Coaxial cables that transmit RF signals are connected to the two antenna terminals of the WLCP 40, respectively. These coaxial cables are input to a combiner 42 that combines the power of two RF signals. The output of the synthesizer 42 is input to a distributor 44 that distributes power of one RF signal via a variable attenuator 43. The two outputs of the distributor 44 are connected to the two antenna terminals of the DUT 41 via variable attenuators 45 and 46, respectively. As described above, in the configuration of the test system disclosed in Non-Patent Document 1, the transmission path between wireless devices is a single coaxial cable on the way. The two antenna terminals of the WLCP 40 and the DUT 41 are connected via a distributor.
IEEE 802.11-03 / 940r2, “IEEE P802.11 Wireless LANs, TGn Channel Models”, Jan. 9, 2004.

  In recent years, in the field of wireless LAN, a MIMO transmission system that realizes high-speed transmission has been put into practical use. In the MIMO transmission system, a plurality of signal sequences are spatially multiplexed and transmitted simultaneously, so that the transmission capacity can be increased in proportion to the number of antennas.

  In the conventional test apparatus described above, the transmission paths between the wireless devices are concentrated on a single coaxial cable on the way. That is, the test apparatus simulates a transmission line having one path. The transmission path having this one path is completely different from the transmission path having a plurality of paths assumed by the MIMO transmission scheme in which a plurality of signal sequences are spatially multiplexed and transmitted simultaneously. Therefore, it is not possible to perform a connection test of a wireless device of the MIMO transmission system using the conventional test apparatus as described above.

  Accordingly, an object of the present invention is to provide a test apparatus capable of testing a MIMO radio.

  The test apparatus of the present invention, a plurality of input terminals connected to a plurality of antenna terminals of the transmitter, a plurality of output terminals connected to a plurality of antenna terminals of the receiver, and connected to the input terminal, A distributor that distributes a signal input from the input terminal to a plurality of signals; a combiner that combines the signals distributed by the plurality of distributors; and a combiner that inputs the combined signal to the output terminal; And a device that is provided on a path from the distributor to the synthesizer and that changes the pass characteristic of the path in the test frequency band.

  In this way, by connecting a plurality of input terminals and a plurality of output terminals via a distributor and a combiner, an actual use environment of a MIMO radio in which signals transmitted from each antenna are received by a plurality of antennas It is possible to create a transmission line condition close to. In addition, by providing a device that changes the passage characteristics on the path from the distributor to the combiner, it is possible to artificially create a change in transmission path condition that can occur in the actual environment.

  In the test apparatus of the present invention, the device for changing the passage characteristic of the route may be provided in one of the plurality of routes distributed by the distributor.

  With this configuration, it is possible to perform a test under various conditions without providing a device that changes the passage characteristics in all paths distributed by the distributor. By reducing the number of devices that change the pass characteristics, the manufacturing cost of the test apparatus can be reduced.

  In the test apparatus of the present invention, the device that changes the passage characteristic of the path may be a phase shifter or a variable attenuator.

  Thus, by using a phase shifter or a variable attenuator as a device that changes the passage characteristics of the path, the characteristics of the transmission path can be appropriately changed.

  In the test apparatus of the present invention, the distributor distributes the signal input from the input terminal into the same number of signals as the combiner, and inputs the distributed signal to each of the plurality of combiners. May combine the same number of signals as the distributor.

  In this way, the distributor distributes the same number of signals as the combiner, and the combiner combines the signals transmitted from all the distributors so that the signals output from all the antenna terminals are received by all the antenna terminals. As a result, transmission path conditions close to the actual environment can be created in a simulated manner.

  A test apparatus according to another aspect of the present invention includes three input terminals connected to an antenna terminal of a transmitter, three output terminals connected to an antenna terminal of a receiver, and each of the input terminals. The first distributor, the second distributor, and the third distributor for distributing the signal input from the input terminal into three signals, and the first distributor, respectively. A first combiner, a second combiner, and a third combiner that combine signals input from the second distributor and the third distributor and input the combined signal to the output terminal; , A first phase shifter provided on the path between the first distributor and the first combiner, and a first phase shifter provided on the path between the second distributor and the second combiner. 2 phase shifters, and a third phase shifter provided on the path between the third distributor and the third combiner, Provided.

  With this configuration, a 3 × 3 signal series transmission path can be simulated. In this test apparatus, the minimum eigenvalue that affects the MIMO transmission characteristics changes continuously in the range of the phase shift amount 0 to 2π / 3. Therefore, the test can be performed when the MIMO transmission characteristics change by moving the phase shift amount. The Moreover, since the phase shifters are not provided in all nine paths connecting the input terminals and the output terminals, but the apparatus is configured using three phase shifters, the manufacturing cost can be reduced.

  A test apparatus according to another aspect of the present invention includes three input terminals connected to an antenna terminal of a transmitter, three output terminals connected to an antenna terminal of a receiver, and each of the input terminals. The first distributor, the second distributor, and the third distributor for distributing the signal input from the input terminal into three signals, and the first distributor, respectively. A first combiner, a second combiner, and a third combiner that combine signals input from the second distributor and the third distributor and input the combined signal to the output terminal; , A first variable attenuator provided on the path between the first distributor and the first combiner, and a second provided on the path between the second distributor and the second combiner. Provided on the path of the variable attenuator, the third distributor and the third combiner And a third variable attenuator that.

  With this configuration, a 3 × 3 signal series transmission path can be simulated. In this test apparatus, since the minimum eigenvalue that affects the MIMO transmission characteristics changes continuously in the range of −6 to −∞ (dB), it is possible to perform a test when the MIMO transmission characteristics change by moving the attenuation amount. . Moreover, since the variable attenuator is not provided in all nine paths connecting the input terminal and the output terminal, but the apparatus is configured using three variable attenuators, the manufacturing cost can be suppressed.

  A test apparatus according to another aspect of the present invention includes three input terminals connected to an antenna terminal of a transmitter, three output terminals connected to an antenna terminal of a receiver, and each of the input terminals. A first distributor for distributing a signal input from the input terminal into two signals, a second distributor and a third distributor, and a first combiner connected to each of the output terminals, A second combiner and a third combiner, wherein the first distributor is connected to the second combiner and the third combiner, and the second distributor is connected to the second combiner. The third combiner is connected to the first combiner and the third combiner, and the third distributor is connected to the first combiner and the second combiner.

  By using a distributor that distributes to two paths in this way, the cost of the test apparatus can be reduced.

  The test apparatus of the present invention may be configured by cascading the above-described test apparatuses in a plurality of stages.

  In this way, the characteristics of the transmission path can be adjusted by cascading the above-described test apparatuses in a plurality of stages.

  According to the present invention, by providing a device for changing the pass characteristic on the path of the combiner connected to the output terminal from the distributor connected to the input terminal, it is possible to simulate a change in the transmission path condition that may occur in an actual environment. It has the effect that can be created.

ここで、行列Ｘは複数の送信信号系列からなる送信ベクトルを示し、行列Ｙは複数の受信信号系列からなる受信ベクトルを示す。行列Ｈは、チャネルの応答行列を示す。送信信号数をＮ、受信信号数をＭとすると、行列ＨはＭ行Ｎ列で表される。 First, the theory of a MIMO transmission line that is a test target of the MIMO test apparatus according to the present embodiment will be described. In general, a MIMO transmission path is expressed by the following equation (1) using a transmission path matrix H.

Here, matrix X represents a transmission vector composed of a plurality of transmission signal sequences, and matrix Y represents a reception vector composed of a plurality of reception signal sequences. Matrix H represents the response matrix of the channel. When the number of transmission signals is N and the number of reception signals is M, the matrix H is represented by M rows and N columns.

  The communication capacity in the MIMO transmission path can be estimated using a value obtained by squaring a singular value obtained by singular decomposition of the matrix H (hereinafter referred to as “eigenvalue” of the transmission path matrix H). That is, the characteristic of the MIMO transmission path is expressed by the eigenvalues of the matrix H.

  The transmission path matrix H has a plurality of eigenvalues. It is known that the transmission quality of a MIMO transmission line is governed by the smallest eigenvalue among a plurality of eigenvalues (RW Heath, Jr. and AJ Paulraj, “Switching Between Diversity and Multiplexing in MIMO Systems”, IEEE trans on Communications, Vol. 53, No. 6, June 2005.). For example, when a MIMO transmission path is represented by a matrix H of 3 rows and 3 columns, the transmission path matrix H has three eigenvalues. The three eigenvalues are defined as a first eigenvalue, a second eigenvalue, and a third eigenvalue in descending order. If the transmission line matrix H is regarded as a MIMO transmission line in which three signal sequences are spatially multiplexed, the transmission quality is governed by the third eigenvalue, that is, the smallest eigenvalue. Further, according to the above-mentioned document by R. W. Heath, Jr., etc., it is shown that the error performance of the MIMO transmission path can be estimated based on the minimum eigenvalue of the transmission path matrix H.

  It is preferable that the test apparatus can simulate MIMO transmission lines having various characteristics. From the above, it is possible to determine whether or not the test apparatus can simulate transmission lines having different characteristics by looking at the minimum eigenvalue.

(First embodiment)
Hereinafter, a MIMO test apparatus according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of a MIMO test apparatus 1 according to the first embodiment, and FIG. 2 is a diagram illustrating a test environment when a connection test of a wireless LAN device is performed using the MIMO test apparatus 1. is there. First, the test environment will be described with reference to FIG.

  In the test environment shown in FIG. 2, the test targets are AP (Access Point) 20 and STA (Station) 24. The STA 20 is a card-shaped MIMO receiver that mainly operates as a MIMO receiver. The AP 20 is a MIMO transmitter that transmits data to the STA 24. In the actual environment, data is transmitted from the AP 20 to the STA 24 by radio. In the test environment, instead of performing wireless communication, the AP 20 and the STA 24 are connected by wire, and the MIMO test apparatus 1 is provided on the connection path.

  In the example shown in FIG. 2, both the AP 20 and the STA 24 have three antennas. In the test environment, the antenna is removed and the antenna terminal and the MIMO test apparatus 1 are connected. The MIMO test apparatus 1 has three input terminals 11a to 11c and three output terminals 12a to 12c. The three antenna terminals 23a to 23c of the AP 20 and the MIMO input terminals 11a to 11c are connected by a coaxial cable. The three antenna terminals 25a to 25c of the STA 24 and the three output terminals 12a to 12c of the MIMO test apparatus 1 are connected by a coaxial cable. The coaxial cable has a function of transmitting an RF signal.

  In addition, variable attenuators 12 a to 12 c are arranged between the output terminals 12 a to 12 c of the MIMO test apparatus 1 and the antenna terminals 25 a to 25 c of the STA 24. The variable attenuators 28a to 28c simulate power attenuation in the MIMO transmission path. Here, when the variable attenuators 28a to 28c are all adjusted to the same attenuation α, the transmission path shown in FIG. 2 is expressed as (α1 / 2) F (φ) using a scalar coefficient α of 1 or less. . That is, the attenuation amount α gives an average attenuation amount of power in the MIMO transmission line.

  The AP 20 is connected to a PC (Personal Computer) 23 via Ethernet (registered trademark). The STA 24 is inserted into the card slot of the PC 26. The AP 20 is disposed in the shield case 22, and the STA 24 is disposed in the shield case 27 together with the PC 26. Thereby, in the AP 20 and the STA 24, spatial electromagnetic coupling is suppressed.

  Next, the configuration of the MIMO test apparatus 1 will be described with reference to FIG. The MIMO test apparatus 1 is configured by an RF circuit. The MIMO test apparatus 1 has an external housing 10 that protects an RF circuit from electromagnetic radiation and interference.

  The MIMO test apparatus 1 includes three input terminals 11a to 11c connected to the antenna terminals 21a to 21c of the AP 20 on the transmission side and three output terminals 12a to 12c connected to the antenna terminals 25a to 25c of the STA 24 on the reception side. Have The input terminals 11a to 11c of the MIMO test apparatus 1 are connected to the three distributors 13a to 13c, respectively. The three distributors 13a to 13c have a function of distributing power from one RF signal to three signals. The output terminals 12a to 12c of the MIMO test apparatus 1 are connected to the three synthesizers 14a to 14c, respectively. The three synthesizers 14a to 14c have a function of combining the power of three RF signals into one signal. The three distributors 13a to 13c and the three combiners 14a to 14c are the same device, and their input / outputs are interchanged.

  The three outputs from which power is distributed by the three distributors 13a are input to the three combiners 14a to 14c, respectively. Similarly, the three outputs power-distributed by the three distributors 13b are input to the three combiners 14a to 14c, respectively, and the three outputs power-distributed by the three distributors 13c are the respective three combiners 14a to 14c. Is input. In a real environment, radio waves output from each antenna on the transmission side are received by any antenna on the reception side. By connecting all nine paths between the input terminals 11a to 11c and the output terminals 12a to 12c using the distributors 13a to 13c and the combiners 14a to 14c, an environment close to an actual MIMO transmission path is simulated. Producing. In addition, if the connection used for the circuit structure of the MIMO test apparatus 1 can transmit RF signal, the material and shape will not be limited. For example, a semi-rigid cable can be used.

  In addition, the MIMO test apparatus 1 includes a phase shifter 15a on a path connecting the three distributor 13a and the three combiner 14a. Similarly, a phase shifter 15b is provided on a path connecting the 3 distributor 13b and the 3 combiner 14b, and a phase shifter 15c is provided on a path connecting the 3 distributor 13c and the 3 combiner 14c.

試験行列Ｆ（φ）は、３行３列の複素正方行列である。９つの行列要素の振幅値がすべて等しく、且つ、３つの対角要素がφ［ｒａｄ］だけ移相している。 A test matrix F (φ) of the MIMO transmission path simulated by the above-described MIMO test apparatus 1 is expressed by the following equation (2).

The test matrix F (φ) is a 3 × 3 complex square matrix. The amplitude values of the nine matrix elements are all equal, and the three diagonal elements are phase-shifted by φ [rad].

  FIG. 3 is a graph showing changes in the three eigenvalues of the test matrix F (φ). The graph shown in FIG. 3 shows the eigenvalue (vertical axis) with respect to the phase shift amount φ [rad] (horizontal axis) of the phase shifters 15a to 15c. Here, the same phase shift amount φ is given to the phase shifters 15a to 15c. In FIG. 3, the solid line indicates the characteristic of the first eigenvalue, the dotted line indicates the characteristic of the second eigenvalue, and the alternate long and short dash line indicates the characteristic of the third eigenvalue.

  From the graph shown in FIG. 3, it can be seen that the test matrix F (φ) has the following eigenvalue characteristics. That is, (i) in the region where the phase shift amount φ is 0 to 2π / 3, the second eigenvalue and the third eigenvalue are the same value and become the minimum eigenvalue, and the value is in the range of −∞ to −4.8 (dB). It changes continuously. (Ii) When the phase shift amount φ is 2π / 3, the eigenvalues are all the same value. (Iii) In the region where the phase shift amount φ is 2π / 3 to π, the third eigenvalue is the minimum eigenvalue, and the value continuously changes in the range of −4.8 to −9.5 (dB).

  Since the test matrix F (φ) of the MIMO test apparatus 1 of the present embodiment has the above characteristics, the minimum eigenvalue of the MIMO transmission line is desired by adjusting the phase shift amount φ given to the phase shifters 15a to 15c. Can be set to As described above, when the test matrix F (φ) is regarded as a MIMO transmission path in which a plurality of signal sequences are spatially multiplexed, the transmission quality is governed by the minimum eigenvalue. Error performance can be estimated. Therefore, by adjusting the phase shift amount φ, a 3 × 3 MIMO transmission line having various characteristics can be simulated.

  In the region where the phase shift amount φ is 0 to 2π / 3, the second eigenvalue and the third eigenvalue of the test matrix F (φ) coincide with each other, so that the number of spatially multiplexed signal sequences is either 2 or 3 However, the minimum eigenvalue of the transmission line can be set by the phase shift amount φ.

  FIG. 4A is a block diagram functionally showing the test environment (see FIG. 2) described in the above embodiment. That is, the test environment described in the present embodiment includes a MIMO transmission unit 30 having N antenna terminals (three antenna terminals in FIG. 2) and a test matrix calculation unit simulating an M × N MIMO transmission path. 31, an attenuation coefficient calculation unit 32 that gives an average attenuation on the transmission line, and a MIMO reception unit 33 having an M antenna terminal (three antenna terminals in FIG. 2) are connected in order. In FIG. 4A, the test matrix calculator 31 functionally shows the MIMO test apparatus 1, and the attenuation coefficient calculator 32 functionally shows the variable attenuators 28a to 28c.

  FIG. 4B shows a test environment having a configuration in which the test matrix calculation unit 31 and the attenuation coefficient calculation unit 32 are replaced in the configuration shown in FIG. As the MIMO transmission path, the transmission path shown in FIG. 4 (a) and the transmission path shown in FIG. 4 (b) are equivalent, and the MIMO test apparatus 1 of the present embodiment has the test environment shown in FIG. 4 (b). It can also be applied to.

(Second Embodiment)
FIG. 5 is a diagram illustrating a configuration of the MIMO test apparatus 2 according to the second embodiment. The basic configuration of the MIMO test apparatus 2 of the second embodiment is the same as that of the MIMO test apparatus 1 of the first embodiment. In the MIMO test apparatus 2 of the second embodiment, variable attenuators 16a to 16c are used instead of the phase shifters 15a to 15c. The MIMO test apparatus 2 of the second embodiment simulates a change in the characteristics of the MIMO transmission path by adjusting the variable attenuators 16a to 16c so as to give the same attenuation.

試験行列Ｆ（β）は、３×３の実正方行列である。βは１以下のスカラ係数である。３つの対角要素がスカラ係数βの平方根として与えられ、且つ非対角要素の振幅値はすべて等しく一定となる。 The test matrix F (β) of the MIMO transmission path of the MIMO test apparatus 2 of the second embodiment is expressed by the following equation (3).

The test matrix F (β) is a 3 × 3 real square matrix. β is a scalar coefficient of 1 or less. Three diagonal elements are given as the square root of the scalar coefficient β, and the amplitude values of the non-diagonal elements are all equally constant.

  FIG. 6 is a graph showing changes in the three eigenvalues of the test matrix. The graph shown in FIG. 6 shows the eigenvalue (vertical axis) with respect to the scalar coefficient β (horizontal axis). From this graph, it can be seen that the test matrix F (β) has the following eigenvalue characteristics. That is, (i) regardless of the value of the scalar coefficient β, the second eigenvalue and the third eigenvalue are always the same value and become the minimum eigenvalue, and the value continuously changes in the range of −6 to −∞ (dB). (Ii) When the scalar coefficient β is 0, the minimum eigenvalue is the maximum and the value is −6 (dB).

  Since the test matrix F (β) of the MIMO test apparatus 2 according to the second embodiment has the above-described properties, by adjusting the variable attenuators 16a to 16c to give the same attenuation β, the MIMO transmission line The minimum eigenvalue can be set to a desired condition. Therefore, by adjusting the scalar coefficient β, a 3 × 3 MIMO transmission line having various characteristics can be simulated.

  In the MIMO test apparatus 2 of the second embodiment, since the second eigenvalue and the third eigenvalue of the test matrix F (β) match regardless of the value of the scalar coefficient β, the number of spatially multiplexed signal sequences is 2. In either case, the minimum eigenvalue of the transmission line can be set by the same scalar coefficient β.

  Since the MIMO test apparatus 2 of the second embodiment can be configured without using the phase shifters 15a to 15c, it is possible to easily perform a wide band that does not require phase calibration with respect to the used frequency. This is because the dividers 13a to 13c and the variable attenuators 16a to 16c are easier to smooth the frequency characteristics than the phase shifters 15a to 15c.

(Third embodiment)
FIG. 7 is a diagram illustrating a configuration of the MIMO test apparatus 3 according to the third embodiment. The MIMO test apparatus 3 of the third embodiment is a MIMO test apparatus 3 having an RF circuit equivalent to a circuit in which the scalar coefficient β is 0 in the MIMO test apparatus 2 of the second embodiment described above. A circuit in which the scalar coefficient β is 0 is a case where the attenuation of the variable attenuators 16a to 16c is set to a value that can be regarded as −∞. The circuit shown in FIG. 7 in which the path (connection) in which the variable attenuators 16a to 16c are provided does not exist is equivalent to a circuit in which the scalar coefficient β is 0 in the MIMO test apparatus 2 of the second embodiment.

  The MIMO test apparatus 3 according to the third embodiment includes an external housing 10 in order to protect an internal RF circuit and avoid unnecessary electromagnetic radiation and interference. Input terminals 11a to 11c of the MIMO test apparatus 3 are respectively connected to two distributors 17a to 17c that distribute power from one RF signal to two signals. The output of the 2 distributor 17a is connected to the 2 combiners 18b and 18c. Similarly, the output of the 2 distributor 17b is connected to the 2 combiners 18a and 18c, and the output of the 2 distributor 17c is connected to the 2 combiners 18a and 18b. The outputs of the two synthesizers 18a to 18c are connected to the output terminals 12a to 12c of the MIMO test apparatus, respectively. The two distributors 17a to 17c and the two combiners 18a to 18c are the same device, and are used by switching input / output.

試験行列Ｇの固有値は、第１固有値が０（ｄＢ）となり、第２固有値と第３固有値がいずれも−６（ｄＢ）となる。つまり、式（４）の試験行列Ｇで模擬されるＭＩＭＯ伝送路は、最小固有値が最大固有値に対して−６（ｄＢ）となるように条件設定される。この条件の試験を行なう場合には、可変アッテネータを用いないでＭＩＭＯ試験装置を構成できる。 The test matrix G of the MIMO transmission path of the MIMO test apparatus 3 of the third embodiment is expressed by the following equation (4).

As for the eigenvalues of the test matrix G, the first eigenvalue is 0 (dB), and the second eigenvalue and the third eigenvalue are both -6 (dB). In other words, the MIMO transmission line simulated by the test matrix G in Equation (4) is set so that the minimum eigenvalue is −6 (dB) with respect to the maximum eigenvalue. When a test under this condition is performed, a MIMO test apparatus can be configured without using a variable attenuator.

  The MIMO test apparatus 3 of the third embodiment does not use a phase shifter and a variable attenuator, and the condition that the scalar coefficient β of the variable attenuators 16a to 16c is 0 in the MIMO test apparatus 2 of the second embodiment. MIMO transmission path can be realized.

(Fourth embodiment)
Next, a MIMO test apparatus according to the fourth embodiment will be described. The MIMO test apparatus according to the fourth embodiment is configured by cascading a plurality of MIMO test apparatuses 3 according to the third embodiment.

式（５）に示すＧ^２の固有値は、第１固有値が０（ｄＢ）であり、第２固有値と第３固有値がいずれも−１２（ｄＢ）となる。つまり、式（５）の試験行列Ｇ^２で模擬されるＭＩＭＯ伝送路は、最小固有値が最大固有値に対して−１２（ｄＢ）となる条件に設定されている。前述したように、Ｋが１の場合、Ｇの固有値は、第１固有値が０（ｄＢ）、第２固有値と第３固有値がいずれも−６（ｄＢ）となる。つまり、Ｇの２回乗算を行なうと、ＭＩＭＯ伝送路の最大固有値は０（ｄＢ）で不変だが、最小固有値が−６（ｄＢ）から−１２（ｄＢ）へと変更される。 8 and 9 are diagrams illustrating the configuration of the MIMO test apparatus 4 according to the fourth embodiment. In the example shown in FIG. 8, the MIMO test apparatus 3 of the third embodiment is connected in two stages in cascade, and the example shown in FIG. 9 shows an example in which three stages are connected in cascade. Test matrix ^{G 2} of the MIMO testing device 4 shown in FIG. 8 is represented by the following formula (5), the test matrix ^{G 3} for MIMO testing device 4 shown in FIG. 9 can be expressed by the following equation (6).

Eigenvalue of ^{G 2} shown in Equation (5), the first eigenvalue is 0 (dB), both the second eigenvalue and the third eigenvalue becomes -12 (dB). That, MIMO transmission line is simulated by the test matrix ^{G 2} of formula (5), the minimum eigenvalue is set in the condition to be -12 (dB) relative to the maximum eigenvalue. As described above, when K is 1, the first eigenvalue is 0 (dB), and the second eigenvalue and the third eigenvalue are both -6 (dB). That is, when G is multiplied twice, the maximum eigenvalue of the MIMO transmission line is 0 (dB) and is unchanged, but the minimum eigenvalue is changed from −6 (dB) to −12 (dB).

Eigenvalues of ^{G 3} shown in equation (6), the first eigenvalue is 0 (dB), both the second eigenvalue and the third eigenvalue becomes -18 (dB). That, MIMO transmission line is simulated by the test matrix ^{G 3} of formula (6), the minimum eigenvalue is the condition set to be -18 (dB) relative to the maximum eigenvalue.

From the above, it can be seen that G ^k obtained by multiplying the test matrix G K times has a first eigenvalue of 0 (dB) and a second eigenvalue and a third eigenvalue of -6 × K (dB). If the number of cascade connections is increased by one step, the minimum eigenvalue can be lowered by 6 (dB). Therefore, the minimum eigenvalue can be adjusted in 6 (dB) steps by changing the number of cascade connections.

  Since the MIMO test apparatus 4 according to the fourth embodiment can be realized without using a phase shifter or a variable attenuator, it is low-cost and can easily be widened, and by changing the number of cascade connection stages. The eigenvalue of the MIMO transmission line can be adjusted in −6 (dB) steps.

Next, the cascade connection structure of the MIMO test apparatus 4 will be described.
FIG. 10 is a diagram illustrating an example in which a MIMO test apparatus serving as one unit of cascade connection is realized by an RF circuit having a planar structure. Input terminals 11 a to 11 c and output terminals 12 a to 12 c are arranged on each side of the hexagonal housing 10. The input terminal 11a and the output terminal 12a, the input terminal 11b and the output terminal 12b, and the input terminal 11c and the output terminal 12c are disposed on the opposing surfaces. Further, the input terminals 11a to 11c and the output terminals 12a to 12c are alternately arranged. The outputs of the distributors 13a to 13c connected to the input terminals 11a to 11c are input to the combiners 14a to 14c connected to the adjacent output terminals 12a to 12c. The circuit shown in FIG. 10 is equivalent to the one MIMO test apparatus shown in FIGS.

  FIGS. 11A and 11B are diagrams showing an example in which the MIMO test apparatus shown in FIG. 10 is cascade-connected in three stages. FIG. 11A and FIG. 11B are views of the MIMO test apparatus 4 connected in cascade as seen from different directions. As shown in FIG. 11, the first-stage MIMO test apparatus from the top and the third-stage MIMO test apparatus are arranged such that the positions of the input terminals 11a to 11c and the output terminals 12a to 12c are the same. ing. The second-stage MIMO test apparatus is arranged by rotating 60 degrees with respect to the first-stage and third-stage MIMO test apparatuses, and is arranged so that the positions of the input terminals 11a to 11c and the output terminals 12a to 12c coincide. Has been. The output terminals 12a to 12c of the first stage MIMO test apparatus are connected to the second stage input terminals 11a to 11c, and the second stage output terminals 12a to 12c are connected to the third stage input terminals 11a to 11c. The

  As described above, the input terminals 11a to 11c and the output terminals 12a to 12c of the MIMO test apparatus are alternately provided on the side surfaces of the hexagonal casing 10, so that the input terminals 11a to 11c and the output terminals 12a are provided inside and outside the casing 10. The length of the coaxial cable connecting ˜12c can be shortened, and the RF signal attenuation and phase deviation can be suppressed.

(Fifth embodiment)
FIG. 12 is a diagram illustrating the configuration of the MIMO test apparatus according to the fifth embodiment. The MIMO test apparatus 5 of the fifth embodiment includes a phase shifter 19 on the path between the two distributors 17a and the two combiners 18b in the MIMO test apparatus 3 of the third embodiment. . By adjusting the phase shift amount φ of the phase shifter 19, the MIMO test apparatus 5 can be regarded as a transmission line that reproduces the eigenvalue characteristics of the test matrix G (φ).

試験行列Ｇ（φ）は、３×３の複素正方行列である。３つの対角要素が零で、且つ非対角要素の一つがφ［ｒａｄ］だけ移相している。 A test matrix G (φ) of the MIMO transmission path of the MIMO test apparatus according to the fifth embodiment is expressed by the following equation (7).

The test matrix G (φ) is a 3 × 3 complex square matrix. Three diagonal elements are zero, and one of the non-diagonal elements is phase-shifted by φ [rad].

  FIG. 13 shows the eigenvalue (vertical axis) of G (φ) when the phase shifter 17 has the phase shift amount φ (horizontal axis). From FIG. 13, it can be seen that G (φ) has the following eigenvalue characteristics. That is, (i) In the region where the phase shift amount φ is 0 to π, the third eigenvalue which is the smallest eigenvalue continuously changes in the range of −6 to −∞ (dB). (Ii) When the phase shift amount φ is 0, the second eigenvalue and the third eigenvalue are both −6 (dB) and become the minimum eigenvalue, and the first eigenvalue is 0 (dB). (Iii) When the phase shift amount φ is π, the first eigenvalue and the second eigenvalue are both 0 (dB), and the third eigenvalue that is the minimum eigenvalue is −∞.

  Therefore, the MIMO test apparatus 5 of the fifth embodiment can set the minimum eigenvalue to a specific condition by changing the value of the phase shift amount φ. Therefore, by adjusting the phase shift amount φ, a 3 × 3 MIMO transmission line having various characteristics can be simulated.

  Further, in the region where the phase shift amount φ is 0 to 2π / 3, the second eigenvalue and the third eigenvalue of F (φ) coincide with each other. Therefore, even when the number of spatially multiplexed signal sequences is 2 or 3, The minimum eigenvalue of the transmission line can be set with the same value of φ.

  Further, the MIMO test apparatus 5 of the fifth embodiment is composed of two distributors 17a to 17c and two combiners 18a to 18c, which are cheaper than three distributors and three combiners, and a single phase shifter 19. Therefore, the manufacturing cost of the test apparatus can be reduced.

  Note that the phase shifter 17 is not necessarily used when the phase shift amount φ is adjusted to a specific value such as π / 2 or π. For example, when the phase shift amount φ is adjusted to π / 2, as described in K. Chang, “Microwave Ring Circuits and Antenna”, Wiley Inter-Science, 1996. The distributors 13a to 13c may be realized by a 90 ° Branch-Line circuit. Similarly, when adjusting the phase shift amount φ to π, the distributors 13 a to 13 c may be realized by 180 ° Rat-Race circuits instead of the phase shifter 19.

  The test apparatus of the present invention has been described in detail with reference to the embodiment, but the present invention is not limited to the above-described embodiment.

  The present invention can also be a test apparatus provided in a circuit other than the circuit configurations described in the first to fifth embodiments as long as the minimum eigenvalue of the MIMO transmission path test matrix can be changed. is there.

  In the above-described embodiment, a test apparatus that simulates a 3 × 3 MIMO transmission path has been described, but the number of signal sequences to be tested is not limited to 3 × 3. The present invention can be applied to a test of a MIMO transmission line of an N × M signal sequence.

  According to the present invention, there is an effect that it is possible to artificially create a change in the environment that can occur in an actual environment, and it is useful for application to a connection test of a wireless device in which the MIMO transmission method is implemented. In particular, the test apparatus of the present invention is used to evaluate the performance of a mobile communication system such as a mobile phone or a wireless LAN, and the performance of a mobile communication system that implements the antenna diversity method or a television broadcast receiver. Is suitable.

The figure which shows the structure of the MIMO test apparatus of 1st Embodiment. The figure which shows the example of the test environment in the case of implementing the connection test of a wireless LAN apparatus using the MIMO test apparatus of embodiment The figure which shows the eigenvalue characteristic of the test matrix which simulated the MIMO transmission line of 1st Embodiment (A) Functionally showing a test environment of the MIMO test of the first embodiment (b) Functionally showing a test environment equivalent to the test environment of the MIMO test of the first embodiment The figure which shows the structure of the MIMO test apparatus of 2nd Embodiment. The figure which shows the eigenvalue characteristic of the test matrix which simulated the MIMO transmission line of 2nd Embodiment The figure which shows the circuit structure of the MIMO test apparatus of 3rd Embodiment. The figure which shows the circuit structure of the MIMO test apparatus of 4th Embodiment. The figure which shows the circuit structure of the MIMO test apparatus of 4th Embodiment. The figure which shows the circuit structure of the MIMO test apparatus of 4th Embodiment. The figure which shows the external appearance of the MIMO test apparatus of 4th Embodiment The figure which shows the circuit structure of the MIMO test apparatus which concerns on 5th Embodiment. The figure which shows the eigenvalue characteristic of the test matrix which simulated the MIMO transmission line of 5th Embodiment Block diagram showing a conventional test method

Explanation of symbols

1-5 MIMO test apparatus 11a-11c Input terminals 12a-12c Output terminals 13a-13c 3 distributors 14a-14c 3 combiners 15a-15c Phase shifters 16a-16c Variable attenuators 17a-17c 2 distributors 18a-18c 2 combiners 19 Phase shifter 20 AP
21a-21c Antenna terminal 22 Shield case 23 PC
24 STA
25a to 25c antenna terminal 26 PC
27 Shield Cases 28a to 28c Variable Attenuator 30 MIMO Transmitting Unit 31 Test Matrix Calculation Unit 32 Attenuation Coefficient Calculation Unit 33 MIMO Reception Unit 40 WLCP
41 DUT
42 Synthesizer 43 Variable attenuator 44 Distributor 45, 46 Variable attenuator

Claims (8)

A plurality of input terminals connected to a plurality of antenna terminals of the transmitter;
A plurality of output terminals connected to a plurality of antenna terminals of the receiver;
A distributor connected to the input terminal and distributing a signal input from the input terminal into a plurality of signals;
A combiner that combines the signals distributed by the plurality of distributors and inputs the combined signal to the output terminal;
A device that is provided on a path from the distributor to the combiner and changes a passage characteristic of the path in a test frequency band;
Test equipment with   The test apparatus according to claim 1, wherein the device that changes the passage characteristic of the path is provided in one of a plurality of paths distributed by the distributor.   The test apparatus according to claim 1, wherein the device that changes the passage characteristic of the path is a phase shifter or a variable attenuator. The distributor distributes the signal input from the input terminal to the same number of signals as the combiner, and inputs the distributed signal to each of the plurality of combiners,
The test apparatus according to claim 1, wherein the combiner combines the same number of signals as the distributor. Three input terminals connected to the antenna terminal of the transmitter;
Three output terminals connected to the antenna terminal of the receiver;
A first distributor, a second distributor, and a third distributor that are connected to each of the input terminals and distribute a signal input from the input terminal into three signals;
A first signal is connected to each of the output terminals, synthesizes signals input from the first distributor, the second distributor, and the third distributor, and inputs the combined signal to the output terminal. A combiner, a second combiner and a third combiner;
A first phase shifter provided on a path between the first distributor and the first combiner;
A second phase shifter provided on a path between the second distributor and the second combiner;
A third phase shifter provided on the path between the third distributor and the third combiner;
Test equipment with Three input terminals connected to the antenna terminal of the transmitter;
Three output terminals connected to the antenna terminal of the receiver;
A first distributor, a second distributor, and a third distributor that are connected to each of the input terminals and distribute a signal input from the input terminal into three signals;
A first signal is connected to each of the output terminals, synthesizes signals input from the first distributor, the second distributor, and the third distributor, and inputs the combined signal to the output terminal. A combiner, a second combiner and a third combiner;
A first variable attenuator provided on a path between the first distributor and the first combiner;
A second variable attenuator provided on a path between the second distributor and the second combiner;
A third variable attenuator provided on a path between the third distributor and the third combiner;
Test equipment with Three input terminals connected to the antenna terminal of the transmitter;
Three output terminals connected to the antenna terminal of the receiver;
A first distributor, a second distributor, and a third distributor that are connected to each of the input terminals and distribute a signal input from the input terminal into two signals;
A first combiner, a second combiner, and a third combiner connected to each of the output terminals;
The first distributor is connected to the second synthesizer and the third synthesizer; the second distributor is connected to the first synthesizer and the third synthesizer; The third distributor is a test apparatus connected to the first combiner and the second combiner.   A test apparatus configured by cascading the test apparatus according to claim 7 in a plurality of stages.

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