System and method for testing multi-user MIMO communication systems

Abstract

A method for testing a test object, the method comprising the following steps: Generating a plurality of independent signals; applying first decay channel characteristics to the independent signals to generate a plurality of first decayed test signals; Delivering the plurality of first decayed test signals to one or more signal input interfaces of the device under test (DUT); Applying second decay channel characteristics to a plurality of output signals of the DUT to generate a plurality of second decayed test signals, wherein the second decay channel characteristics are derived from the first decay channel characteristics; and Measuring, with one or more test instruments, at least one performance characteristic of the DUT from the plurality of second decayed test signals.

Description

BACKGROUND

[0001] The demands of communications, and especially wireless communications, continue to grow. Next-generation wireless communications systems, commonly referred to as "5G communications systems," are currently being developed to meet these demands. A key technology adopted by 5G communications systems involves the use of base stations with a large number of inputs and outputs (sometimes referred to as a massive MIMO communications system) to serve a large number of communications users. Massive MIMO represents a significant departure from previous approaches by utilizing a large surplus of antennas and time-division duplex operation to serve multiple active terminals (users).Additional antennas focus energy into ever-smaller regions of space to achieve enormous improvements in throughput and radiated energy efficiency. Such systems can have hundreds of transmit (Tx) and receive (Rx) channels.

[0002] In general, communication systems and devices, like other electronic systems, require testing and, in some cases, calibration. However, testing and calibration can be challenging in the case of a multi-user massive MIMO communication system or terminal device with a large number of inputs and outputs. For example, evaluating system performance (system behavior) depends on the wireless channel characteristics between the massive MIMO communication system and the terminal devices (users) with which it communicates, which can vary for different users and different inputs and outputs simultaneously. Therefore, appropriate solutions for testing the performance of multi-user massive MIMO communication systems are needed.

[0003] US 2013 / 0 303 089 A1 discloses a system for testing wireless devices that includes a reverberation chamber and antennas placed within the chamber. The system uses downlink channel emulators and uplink channel emulators to evaluate the behavior of a wireless device.

[0004] Thus, it would be desirable to provide a more convenient and reliable method and system for testing and calibrating the performance of a multi-user communication system or a multi-user communication device having multiple inputs and outputs. SUMMARY

[0005] In one aspect, a method is provided for testing a device under test (DUT), which may be a massive MIMO communication system or terminal. The method comprises the steps of: generating a plurality of independent signals; applying first fading channel characteristics to the independent signals to generate a plurality of first fading test signals; providing the plurality of first fading test signals to one or more signal input interfaces of the device under test (DUT); applying second fading channel characteristics to a plurality of output signals of the DUT to generate a plurality of second fading test signals, the second fading channel characteristics being derived from the first fading channel characteristics; and measuring, with one or more test instruments, at least one performance characteristic (orpower curve) of the DUT based on the majority of second decayed test signals.

[0006] In some embodiments, measuring at least one performance characteristic comprises measuring a signal-to-interference-and-noise ratio (SINR) of a plurality of channels of the DUT.

[0007] In some embodiments, the method further comprises the steps of: varying at least one of the first decay channel characteristics and / or the second decay channel characteristics; and measuring the SINR of the plurality of channels of the DUT with the varied at least one of the first decay channel characteristics and / or the second decay channel characteristics.

[0008] In some embodiments, providing the plurality of first decayed test signals to one or more signal input interfaces of the DUT comprises providing the plurality of first decayed test signals to one or more signal input interfaces of the DUT via an optical baseband input of the DUT.

[0009] In some embodiments, the method further comprises providing one or more baseband output signals of the DUT to one of the test instruments and measuring at least one performance characteristic of a baseband processing module of the DUT in response to the plurality of first decayed test signals.

[0010] In some embodiments, applying the first decay channel characteristics to each of the independent signals to generate the plurality of first decayed test signals comprises the steps of: applying the first decay channel characteristics to each of the independent signals to generate a plurality of decayed baseband uplink signals; and applying the plurality of decayed baseband uplink signals to one or more RF signal generators to generate the plurality of first decayed test signals as RF signals.

[0011] In some embodiments, applying the plurality of decayed baseband uplink signals to one or more RF signal generators to generate the plurality of first decayed test signals comprises providing each of the independent signals to a corresponding one of the RF signal generators, each RF signal generator generating a corresponding one of the first decayed test signals as a corresponding RF signal.

[0012] In some embodiments, the DUT comprises a multi-input, multi-output (MIMO) transceiver, and providing the plurality of first decayed test signals to one or more signal input interfaces of the DUT comprises providing the plurality of first decayed test signals to a plurality of RF inputs of the MIMO transceiver.

[0013] In some embodiments, the one or more test instruments comprise one or more RF test instruments, the method further comprising providing one or more RF output signals of the DUT as one or more input signals to the one or more RF test instruments, and measuring at least one performance characteristic of the DUT from the plurality of second decayed test signals comprises measuring at least one performance characteristic of an RF processing module of the DUT with the one or more RF test instruments.

[0014] In some embodiments, the one or more test instruments comprise one or more RF test instruments, and the method further comprises: providing one or more RF output signals of the DUT to the one or more RF test instruments; and applying second decay channel characteristics to a plurality of outputs of the one or more RF test instruments, wherein measuring at least one performance characteristic of the DUT in response to the plurality of decayed test signals comprises measuring at least one characteristic of the plurality of second independent decayed test signals.

[0015] In another aspect, a test system for testing a device under test (DUT) is provided. The test system includes one or more signal processors configured to generate a plurality of independent signals and apply first decay channel characteristics to each of the independent signals to generate a plurality of first decayed test signals; at least one test system interface configured to provide the plurality of first decayed test signals to one or more signal input interfaces of the device under test (DUT); and one or more test instruments. The one or more signal processors are configured to apply second decay channel characteristics to a plurality of output signals of the DUT to generate a plurality of second decayed test signals.The one or more signal processors are configured to derive the second decay channel characteristics from the first decay channel characteristics. The one or more test instruments are configured to measure at least one performance characteristic of the DUT based on the plurality of second decayed test signals.

[0016] In some embodiments, the one or more test instruments are configured to measure a signal-to-interference-and-noise ratio (SINR) of a plurality of channels of the DUT.

[0017] In some embodiments, the one or more signal processors comprise a first signal processor having a memory and a digital processor configured to execute instructions stored in the memory to cause the digital processor to generate the plurality of first decayed test signals.

[0018] In some embodiments, the digital processor is further configured to vary the first decay channel characteristics, wherein the one or more test instruments are further configured to measure the SINR of the plurality of channels of the DUT with the varied first decay channel characteristics.

[0019] In some embodiments, the one or more output signals generated by the DUT comprise one or more baseband output signals, and the one or more test instruments comprise one or more baseband test instruments configured to receive the one or more baseband output signals and measure at least one performance characteristic of the DUT based on the one or more baseband output signals.

[0020] In some embodiments, the test system further comprises one or more RF signal generators, wherein the first signal processor is configured to apply the first decay channel characteristics to each of the independent signals to generate a plurality of decayed baseband uplink signals, and wherein each of the one or more RF signal generators is configured to receive one or more of the plurality of decayed baseband uplink signals and generate therefrom the plurality of first decayed test signals as RF signals.

[0021] In some embodiments, the test system further comprises one or more RF signal generators, wherein the one or more signal processors comprise a first signal processor configured to apply the first decay channel characteristics to each of the independent signals to generate a plurality of decayed baseband uplink signals, and wherein each of the RF signal generators is configured to receive one of the plurality of decayed baseband uplink signals and generate therefrom a corresponding one of the decayed test signals as a corresponding RF signal.

[0022] In some embodiments, the DUT comprises a multi-input, multi-output (MIMO) transceiver, and the RF signal generators are configured to provide the plurality of first decayed test signals to a plurality of RF inputs of the MIMO transceiver.

[0023] In some embodiments, the one or more test instruments comprise one or more RF test instruments, the RF test instruments configured to receive one or more RF output signals of the DUT as one or more input signals to the one or more RF test instruments and to measure at least one performance characteristic of an RF processing module of the DUT. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The exemplary embodiments are best understood from the following detailed description when considered in conjunction with the accompanying drawing figures. Indeed, dimensions may be arbitrarily exaggerated or reduced for clarity of discussion. Where applicable and practical, like reference numerals refer to like elements. Fig. 1 illustrates an exemplary embodiment of a test system for testing a multi-user, multi-input, multi-output communication system or a multi-user, multi-input, multi-output test object (DUT). Fig. 2 illustrates an exemplary embodiment of signal processing operations of a signal processor used in the test system of Fig. 1 may be included. Fig. 3 illustrates another exemplary embodiment of signal processing operations of a signal processor used in the test system of Fig. 1 may be included. Fig. 4 is a flowchart of an exemplary embodiment of a method for testing a DUT, for example a MIMO communication system. DETAILED DESCRIPTION

[0025] In the following detailed description, for purposes of illustration and not limitation, exemplary embodiments disclosing specific details are set forth in order to provide a thorough understanding of an embodiment in accordance with the present teachings. However, it will be apparent to those of ordinary skill in the art having the benefit of the present disclosure that other embodiments in accordance with the present teachings that depart from the specific details disclosed herein remain within the scope of the appended claims. Moreover, descriptions of well-known devices and methods may be omitted so as not to obscure the description of the exemplary embodiments. Such methods and devices are clearly within the scope of the present teachings.

[0026] Unless otherwise stated, an indication that a first device is connected to a second device also includes cases where one or more intermediate devices may be used to connect the two devices. However, a statement that a first device is directly connected to a second device only includes cases where the two devices are connected without any intervening or intermediate devices. Likewise, an indication that a signal is coupled to a device also includes cases where one or more intermediate devices may be used to couple the signal to the device.However, when it is stated that a signal is directly coupled to a device, this only includes cases where the signal is directly coupled to the device without any intervening or intermediate devices.

[0027] Fig. 1 illustrates an exemplary embodiment of a test system 100 for testing a device under test (DUT) 10. Here, the DUT 10 comprises a multi-user, multi-input, multi-output (multi-user MIMO) communication system including a MIMO transceiver, in particular a MIMO wireless RF transceiver. In some embodiments, the DUT 10 may comprise a base station or repeater for a wireless communication system, such as a cellular phone system.

[0028] The DUT 10 includes a MIMO baseband module 12 that communicates with baseband interfaces 11, 13, and 15 of the DUT 10, and a MIMO RF module 18 that communicates with RF inputs 17 and RF outputs 19 of the DUT 10. It is assumed here that, in operation, the RF inputs 17 and the RF outputs 19 may be connected to a corresponding plurality of antennas for wireless communication, wherein the antennas may be omitted from the test system 100 for testing purposes. In exemplary embodiments, the baseband interfaces 11, 13, and 15 may each include a baseband interface for communicating one or more baseband data sequences and / or may include an optical interface in which the baseband data sequence(s) is / are provided on one or more optical signal carriers. In some embodiments, the baseband interfaces 11, 13 and 15 may be implemented as a single baseband interface.

[0029] In some embodiments, the DUT 10 comprises a massive MIMO system having a large number of RF inputs 17 and RF outputs 19 configured to be operatively connected to a large number of antennas. In some embodiments, the DUT 10 may have at least N=64 RF inputs 17 and RF outputs 19. In some embodiments, the DUT 10 may have N=400 or more RF inputs 17 and RF outputs 19.

[0030] The test system 100 includes: a first signal processor 110; a test mode baseband interface 122; a plurality of RF signal generators 124; a second signal processor 130; a plurality of test instruments including one or more baseband test instruments 142, one or more RF test instruments 144, and (optionally) one or more baseband test instruments 146; and a control and analysis subsystem 150.

[0031] The first signal processor 110 may further include one or more digital microprocessors and memory, which may include volatile and / or non-volatile memory, including random access memory (RAM), read-only memory—for example, electrically erasable programmable read-only memory (EEPROM), FLASH memory, etc. In some embodiments, the memory may store instructions to be executed by the digital microprocessor(s) to cause the digital microprocessor(s) to perform one or more algorithms for generating a plurality of decayed baseband uplink signals to be provided to the DUT 10, as discussed in more detail below.The first signal processor 110 may also include firmware, one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), programmable gate arrays, etc.

[0032] In some embodiments, the first signal processor 110 and the second signal processor 130 may be combined into a single signal processor and / or may share some elements or components, such as one or more shared digital microprocessors, shared memory, shared firmware elements, etc.

[0033] As in Fig. 1, the first signal processor 110 is configured to generate a plurality of independent signals 112. In the illustrated embodiment, each of the independent signals 112 is a baseband signal and represents one of a plurality of user uplink signals for the DUT 10, which may be communicated wirelessly to the DUT 10 over one or more RF channels during operation from corresponding user terminals (e.g., cellular telephones and other wireless communication devices). Since user uplink signals are generated independently of one another during operation, particularly in a test mode test system 100, the first signal processor 110 generates independent signals 112 intended to have characteristics (e.g., data sequences) that are generally independent of one another. For example, in some embodiments, independent signals 112 may comprise a plurality of different pseudorandom bit streams.In some embodiments, each of the independent signals 112 may be structured as a series of data packets that conform to a communication protocol used by the DUT 10. In this case, each of the independent signals may include management data (overhead data) and payload data. Management data may include packet headers, whose formats may be defined by a standard for a communication protocol used by the DUT 10. In this case, the header format may be the same for all independent signals 112. Payload data may include a pseudorandom bit stream, as mentioned above.

[0034] The first signal processor 110 is further configured to apply first decay channel characteristics 114 to independent signals 112 to generate a plurality of decayed baseband uplink signals 116 that, when combined, represent a decayed multi-user uplink signal. In some embodiments, first decay channel characteristics 114 may be determined or selected by a control and analysis subsystem 150 (i.e., a user of a control and analysis subsystem 150 via a user interface) and provided therefrom to a first signal processor 110. First decay channel characteristics 114 may represent data determined through experimentation or computer modeling to represent typical decay characteristics experienced by user data when communicated wirelessly from a user terminal (e.g., a cellular phone) to a DUT 10.For example, in some embodiments, some or all of the first decay channel characteristics 114 may reflect a Rayleigh decay model for a communication channel between a transmit antenna of a user terminal (e.g., a cellular phone or other wireless communication device) and a receive antenna of the DUT 10. In some embodiments, a plurality of different possible decay channel characteristics may be stored in a memory in the first signal processor 110, and a first signal processor may select the first decay channel characteristics 114 from those stored in the memory. In some embodiments, the first signal processor may receive selected first decay channel characteristics 114 from the control and analysis subsystem 150.

[0035] In some embodiments, the first signal processor 110 may generate independent signals 112 using a digital microprocessor executing a software algorithm. In this case, the software algorithm may include a routine for generating a plurality of pseudorandom bitstreams as payload data, and may include another routine for encapsulating the payload data in a predefined packet format recognized and used by the DUT 10. The first signal processor 110 may also have the plurality of first decay channel characteristics 114 in its associated memory and may execute a software algorithm to apply each of the plurality of first decay channel characteristics 114 to a corresponding one of the independent signals 112 to generate the plurality of decayed baseband uplink signals 116.

[0036] In some embodiments, one or all of the characteristics of independent signals 112 may be designed by the control and analysis subsystem 150 and communicated therefrom to the first signal processor 110. In some embodiments, the control and analysis subsystem 150 may include a general-purpose computer including one or more digital microprocessors, memory (including volatile and / or non-volatile memory), data storage (e.g., a hard disk or a flash memory drive), one or more interfaces (e.g., an Ethernet port, a wireless network interface, etc.) for communicating with the first signal processor 110, the second signal processor 130, and the baseband test instruments 142, the RF test instruments 144, and the baseband test instruments 146.The control and analysis subsystem 150 may further include a user interface, which may include one or more of a display, a keyboard, a keypad, a touchscreen, a mouse, a trackball, a microphone, etc. In some embodiments, a user may execute one or more software algorithms stored in a memory and / or data storage of the control and analysis subsystem 150 to design or adjust parameters for the independent signals 112 and / or the first decay channel characteristics 114, and may communicate this data to the first signal processor 110 via a communication interface.

[0037] In some embodiments, the control and analysis subsystem 150 may communicate any or all of the data and parameters necessary for operation of the first signal processor 110, as needed. In some embodiments, all of the data and parameters necessary for operation of the first signal processor 110 may be stored in non-volatile memory within the first signal processor 110.

[0038] As in Fig. 1, the test system 100, and in particular the first signal processor 110, may, in one or more test modes, output the plurality of decayed baseband uplink signals 116 via the test mode baseband interface 122 as a plurality of first decayed test signals 118a that are input to the DUT 10 via the baseband interface 11.

[0039] As also in Fig. 1, the test system 100, and in particular the first signal processor 110, may output the plurality of decayed baseband uplink signals 116 to a plurality of RF signal generators 124 in one or more test modes. The RF signal generators 124 may use the plurality of decayed baseband uplink signals 116 to generate a plurality of first decayed test signals 118b, which are RF signals and are input to the DUT 10 via the RF inputs 17.

[0040] Fig. 2 illustrates an exemplary embodiment of signal processing operations of a signal processor 200 used in the test system of Fig. 1 for generating a plurality of decayed baseband uplink signals. Here, it is assumed that the DUT 10 includes a plurality of RF inputs 17, each of which corresponds to an antenna port of the DUT 10, and a plurality of decayed uplink signals are to be provided to each RF input 17 for each antenna port.

[0041] In operation, the signal processor 200 (e.g., the first signal processor 110) generates a plurality (N) of independent signals S1...SN, designated 212-1 through 212-N. Independent signals S1...SN are each applied to a corresponding fader 214-(1,j)...214-(N,j) to generate a plurality of decayed baseband uplink signals 216-(1,j)...216-(N,j) for an antenna port J. That is, each of the decay devices 214-(1,j) ... 214-(N,j) applies first decay characteristics to its corresponding independent signal S1 ... SN to generate a plurality of decayed baseband uplink signals 216-(1,j) ... 216-(N,j) for the antenna port J. The plurality of decayed baseband uplink signals 216-(1,j) ... 216-(N,j) are combined to generate a decayed multi-user uplink signal 218-j for the antenna port J.Likewise, the independent signals S1 ... SN are each applied to a corresponding decay device 214-(1,j+1) ... 214-(N,j+1) to generate a plurality of decayed baseband uplink signals 216-(1,j+1) ... 216-(N,j+1) for an antenna port J+1. That is, each of the decay devices 214-(1,j+1) ... 214-(N,j+1) applies first decay characteristics to its corresponding independent signal S1 ... SN to generate a plurality of decayed baseband uplink signals 216-(1,j+1) ... 216-(N,j+1) for the antenna port J+1. The plurality of decayed baseband uplink signals 216-(1,j+1) ... 216-(N,j+1) are combined to generate a decayed multi-user uplink signal 218-j+1 for antenna port J+1. This is repeated for all antenna ports of DUT 10.In one or more test modes, the test system 100 may output the resulting decayed multi-user uplink signals via the test mode baseband interface 122 as a plurality of first decayed test signals 118a, which are subsequently input to the DUT 10 via the baseband interface 11. Further, in one or more test modes, the test system 100 may output the resulting decayed multi-user uplink signals to a plurality of RF signal generators 124. The RF signal generators 124 may use the resulting decayed multi-user uplink signals to generate a plurality of first decayed test signals 118b, which are RF signals and are input to the DUT 10 via the RF inputs 17.

[0042] Fig. 3 illustrates another exemplary embodiment of signal processing operations of a signal processor 300 used in the test system of Fig. 1 for generating a plurality of decayed baseband uplink signals. In particular, Fig. 3 Operations in an exemplary situation where each of a plurality of decay devices operates on a signal communicated from a user terminal having two antenna ports to a DUT 10 having four antenna ports (i.e., four RF input ports 117).

[0043] In operation, a signal processor (e.g., the first signal processor 110) generates a plurality (N) of independent signals S1 ... SN, of which only two, S(i) and S(i+1), designated 312-(i) and 312-(i+1), together with the corresponding decay devices i and (i+1), designated 314-(i) and 314-(i+1), are included in Fig. 3. Here, the independent signal S(i) is modeled as having been transmitted from a user terminal having two antennas. Accordingly, each of the decay devices 314-(i) and 314-(i+1) has two inputs I1 and I2 and four outputs O1, O2, O3, and O4—one from each of the four antenna ports (i.e., RF input ports 117). In general, each of the decay devices 314-(i) and 314-(i+1) applies different decay channel characteristics to a signal as it travels from each of the two input ports (input ports) I1 and I2 to each of the four output ports (output ports) O1, O2, O3, and O4. This means that in general, a total of eight different decay channel characteristics can be applied to the input signal for each decay device 314-(i) and 314-(i+1).

[0044] As in Fig. 3, the decay device 314-(i) outputs four decayed baseband uplink signals for the four antennas or RF inputs 17 of the DUT 10: [Fi 1,1 + Fi 2,1 ](Si); [Fi 1,2 + Fi 2,2 ]((Si); [Fi 1,3 + Fi 2,3 ](Si) or [Fi 1,4 + Fi 2,4 ](Si). Here Fi 1,1 Decay channel characteristics applied to the signal Si output by the first antenna A1 of the i-th user terminal and received by the first antenna of the DUT 10. Likewise, Fi 2,1 Decay channel characteristics applied to the signal Si output by the second antenna A2 of the i-th user terminal and received by the first antenna of the DUT 10. Furthermore, Fi 1,2Decay channel characteristics applied to the signal Si output by the first antenna A1 of the i-th user terminal and received by the second antenna of the DUT 10, and so on.

[0045] The decay device 314-(i+1) also outputs four decayed baseband uplink signals for the four antennas or RF inputs 17 of the DUT 10: [F(i+1)1,1+F(i+1)2,1](Si+1); [F(i+1)1,2+F(i+1)2,2](Si+1); [F(i+1)1.3+F(i+1)2.3](Si+1); or[F(i+1)1.4+F(i+1)2.4](Si+1).

[0046] [Fi 1,1 + Fi 2,1 ](Si) is [F(i+1) 1,1 + F(i+1) 2,1 ](Si+1) and the other signals from the output O1 for all other decay devices 314 for all independent signals S1 . . . SN are combined to generate a decayed multi-user uplink signal for the first antenna port, similar to that in Fig. 2. This is repeated for all antenna connections of the DUT 10.

[0047] In some embodiments, the acts of generating the independent signals 112 and applying first decay channel characteristics to the independent signals to generate a plurality of first decayed test signals may be performed by one or more digital microprocessors of the first signal processor 110 executing one or more software algorithms.

[0048] In one or more test modes, the test system 100 may output the decayed multi-user uplink signals via the test mode baseband interface 122 as a plurality of first decayed test signals 118a, which are subsequently input to the DUT 10 via the baseband interface 11. Also, in one or more test modes, the test system 100 may output the decayed multi-user uplink signals to a plurality of RF signal generators 124. The RF signal generators 124 may use the resulting decayed multi-user uplink signals to generate a plurality of first decayed test signals 118b, which are RF signals and are input to the DUT 10 via the RF inputs 17.

[0049] In operation, in a test mode, the test system 100 may apply the plurality of first decayed test signals 118a to the DUT 10 via the baseband interface 11 and / or may apply the plurality of first decayed test signals 118b to the DUT 10 via the RF inputs 17. The DUT 10 may then perform its normal signal processing operations on the received signals, the first decayed test signals 118a or 118b, and the test system 100 may measure at least one performance characteristic of the DUT 10, for example, a signal-to-interference-and-noise ratio (SINR) of one or more of a plurality of channels of the DUT 10.

[0050] For example, the DUT 10 may perform its precoding process based on the first decayed test signals 118a or 118b. Since the first decayed test signals 118a and 118b are generated by the first signal processor 110 using predetermined decay channel characteristics, the test system 100—and in particular the control and analysis subsystem 150—may use this information to derive precoding matrices of the MIMO baseband module 12 under various conditions. For example, in some embodiments, the baseband test instrument(s) 146 may test a precoding matrix of the MIMO baseband module 12 of the DUT 10, and one or more parameters indicative of the signal quality according to the precoding matrix may be measured or determined.

[0051] Meanwhile, the RF performance of the DUT 10 may be measured using one or more RF test instruments 144 connected to one or more RF outputs 19 of the DUT 10.

[0052] Furthermore, a "round-trip" signal performance of the DUT 10 may be measured or characterized using the second signal processor 130, which may be configured to receive one or more output signals from the DUT 10 and apply second decay channel characteristics to the output signal(s) to generate one or more second decayed test signals. Subsequently, the baseband test instrument(s) 142 may be used to measure at least one performance characteristic of the DUT 10 based on the one or more second decayed test signals, e.g., a plurality of second decayed test signals.

[0053] Here, the second signal processor 130 may receive one or more baseband output signals from the DUT 10 via the baseband interface 15, and in particular baseband output signals from the massive MIMO baseband module 12. Also, the RF test instrument(s) 144 may receive one or more RF output signals from the DUT 10 via RF outputs 19 and may process (e.g., downconvert and / or demodulate) the one or more RF output signals to generate one or more corresponding baseband output signals, which it provides to the second signal processor 130.

[0054] The second signal processor 130 may be configured (e.g., by the control and analysis subsystem 150) such that the second decay channel characteristics applied by the second signal processor 130 to the output signals of the DUT 10 (e.g., baseband output signals received directly via the baseband interface 15, or RF output signals provided via the RF outputs 19 and processed to baseband using the RF test instrument(s) 144) are derived from the first decay channel characteristics 114 applied by the first signal processor 110 to the independent signals 112. In particular, in some cases, the second decay channel characteristics applied by the second signal processor 130 to output signals of the DUT 10 may be the inverse or the inverse of the first decay channel characteristics 114.

[0055] The second signal processor 130 outputs one or more second decayed test signals to one or more baseband test instruments 142. The baseband test instrument(s) 142 may measure at least one performance characteristic of the DUT 10 based on the one or more second decayed test signals, e.g., a plurality of second decayed test signals, under the control of the control and analysis subsystem 150.

[0056] The control and analysis subsystem 150 may be connected to each of the baseband test instrument(s) 142, RF test instrument(s) 144, and optional baseband test instrument(s) 146, and may thereby control one or more operating parameters of these instruments in a test mode, including, for example, programming the instruments to perform a variety of operations as needed to implement one or more tests to measure one or more performance characteristics of the DUT 10. The control and analysis subsystem 150 may execute one or more software routines to cause the test system 100 to perform desired tests on the DUT 10.

[0057] Fig. 4 is a flowchart of an exemplary embodiment of a method 400 for testing the DUT 10.

[0058] In an operation 410, a test system (e.g., test system 100) generates a plurality of independent signals (e.g., independent signals 112).

[0059] In operation 420, a test system (e.g., test system 100) applies a plurality of first decay channel characteristics (e.g., first decay channel characteristics 114) to independent signals 112. For example, in some embodiments, control and analysis subsystem 150 selects a plurality of first decay channel characteristics and communicates them to first signal processor 110, for example, under user control via a user interface of control and analysis subsystem 150 or automatically under the control of a software routine executed by control and analysis subsystem 150.In other embodiments, a plurality of possible first decay channel characteristics may be stored in the memory of the first signal processor 110, and first decay channel characteristics for each of the independent signals 112 may be selected from those stored in the memory by a digital microprocessor of the first signal processor 110 executing a software algorithm.

[0060] In an operation 430, a test system (e.g., test system 100) provides the plurality of first decayed test signals to one or more signal input interfaces of DUT 10. For example, test system 100 may provide the plurality of first decayed test signals to DUT 10 as one or more baseband signals via baseband interface 11. Furthermore, test system 100 may provide the plurality of first decayed test signals to DUT 10 as RF signals via RF inputs 17.

[0061] In operation 440, a test system (e.g., test system 100) applies second decay channel characteristics to a plurality of output signals of DUT 10 to generate a plurality of second decayed test signals. Here, the second decay channel characteristics are derived from the first decay channel characteristics. In some embodiments, the second decay channel characteristics may be the inverse or reciprocal of the first decay channel characteristics 114.

[0062] In an operation 450, one or more test instruments (e.g., baseband test instrument(s) 142 and / or RF test instrument(s) 144) of a test system (e.g., test system 100) measure at least one performance characteristic of DUT 10 based on the plurality of second decayed test signals. In some embodiments, the one or more performance characteristics may include an output power level, an occupied bandwidth, a signal-to-noise ratio (SNR), a harmonic output level, a harmonic distortion, a signal-to-noise and interference ratio (SNIR), a bit error rate (BER), etc., of an output signal of DUT 10.In some embodiments, the test system 100 may derive precoding matrices of the MIMO baseband module 12 of the DUT 10 under different conditions, for example, different decay channel characteristics applied to the different independent signals 112.

[0063] In an optional operation 460, a test system (e.g., test system 100) may vary first and / or second decay channel characteristics for each of the independent signals and measure the one or more performance characteristics (a) with the varied decay channel characteristics. Thus, a test system may determine the effect that various radio channel propagation conditions may have on one or more of the performance characteristics of DUT 10.

[0064] Although exemplary embodiments are disclosed herein, it will be apparent to those of ordinary skill in the art that many variations consistent with the present teachings are possible and remain within the scope of the appended claims. Therefore, the invention is to be limited only within the scope of the appended claims.

Claims

[1] A method for testing a test object, the method comprising the following steps: Generating a plurality of independent signals; applying first decay channel characteristics to the independent signals to generate a plurality of first decayed test signals; Delivering the plurality of first decayed test signals to one or more signal input interfaces of the device under test (DUT); Applying second decay channel characteristics to a plurality of output signals of the DUT to generate a plurality of second decayed test signals, wherein the second decay channel characteristics are derived from the first decay channel characteristics; and Measuring, with one or more test instruments, at least one performance characteristic of the DUT from the plurality of second decayed test signals. [2] The method of claim 1, wherein measuring at least one performance characteristic comprises measuring a signal-to-interference-and-noise ratio (SINR) of a plurality of channels of the DUT. [3] The method according to claim 2, further comprising the steps of: Varying at least one of the first decay channel characteristics and / or the second decay channel characteristics; and Measuring the SINR of the plurality of channels of the DUT with the varied at least one of the first decay channel characteristics and / or the second decay channel characteristics. [4] The method of claim 1, wherein providing the plurality of first decayed test signals to one or more signal input interfaces of the DUT comprises providing the plurality of first decayed test signals to one or more signal input interfaces of the DUT via an optical baseband input of the DUT. [5] The method of claim 1, further comprising providing one or more baseband output signals of the DUT to one of the test instruments and measuring at least one performance characteristic of a baseband processing module of the DUT in response to the plurality of first decayed test signals. [6] The method of claim 1, wherein applying the first decay channel characteristics to each of the independent signals to generate the plurality of first decayed test signals comprises the steps of: applying the first decay channel characteristics to each of the independent signals to generate a plurality of decayed baseband uplink signals; and Applying the plurality of decayed baseband uplink signals to one or more RF signal generators to generate the plurality of first decayed test signals as RF signals. [7] The method of claim 6, wherein applying the plurality of decayed baseband uplink signals to one or more RF signal generators to generate the plurality of first decayed test signals comprises providing each of the independent signals to a corresponding one of the RF signal generators, each RF signal generator generating a corresponding one of the first decayed test signals as a corresponding RF signal. [8] The method of claim 7, wherein the DUT comprises a multi-input, multi-output (MIMO) transceiver, and wherein providing the plurality of first decayed test signals to one or more signal input interfaces of the DUT comprises providing the plurality of first decayed test signals to a plurality of RF inputs of the MIMO transceiver. [9] The method of claim 6, wherein the one or more test instruments comprise one or more RF test instruments, the method further comprising providing one or more RF output signals of the DUT as one or more input signals to the one or more RF test instruments, and wherein measuring at least one performance characteristic of the DUT from the plurality of second decayed test signals comprises measuring at least one performance characteristic of an RF processing module of the DUT with the one or more RF test instruments. [10] The method of claim 6, wherein the one or more test instruments comprise one or more RF test instruments, the method further comprising the steps of: Providing one or more RF output signals of the DUT to the one or more RF test instruments; and Measuring the at least one performance characteristic of the DUT using the one or more RF test instruments. [11] A test system for testing a test object, the test system having the following features: one or more signal processors configured to generate a plurality of independent signals and apply first decay channel characteristics to each of the independent signals to generate a plurality of first decayed test signals; at least one test system interface configured to provide the plurality of first decayed test signals to one or more signal input interfaces of the device under test (DUT); and one or more test instruments, wherein the one or more signal processors are configured to apply second decay channel characteristics to a plurality of output signals of the DUT to generate a plurality of second decayed test signals, wherein the one or more signal processors are configured to derive the second decay channel characteristics from the first decay channel characteristics, and wherein the one or more test instruments are configured to measure at least one performance characteristic of the DUT based on the plurality of second decayed test signals. [12] The test system of claim 11, wherein the one or more test instruments are configured to measure a signal-to-interference-and-noise ratio (SINR) of a plurality of channels of the DUT. [13] The test system of claim 12, wherein the one or more signal processors comprise a first signal processor having a memory and a digital processor configured to execute instructions stored in the memory to cause the digital processor to generate the plurality of first decayed test signals. [14] The test system of claim 13, wherein the digital processor is further configured to vary the first decay channel characteristics, wherein the one or more test instruments are further configured to measure the SINR of the plurality of channels of the DUT with the varied first decay channel characteristics. [15] The test system of claim 11, wherein the one or more output signals generated by the DUT comprise one or more baseband output signals, and the one or more test instruments comprise one or more baseband test instruments configured to receive the one or more baseband output signals and to measure at least one performance characteristic of the DUT based on the one or more baseband output signals. [16] The test system of claim 11, further comprising one or more RF signal generators, wherein the one or more signal processors are configured to apply the first decay channel characteristics to each of the independent signals to generate a plurality of decayed baseband uplink signals, and wherein each of the one or more RF signal generators is configured to receive one or more of the plurality of decayed baseband uplink signals and generate therefrom the plurality of first decayed test signals as RF signals. [17] The test system of claim 16, further comprising one or more RF signal generators, wherein the one or more signal processors comprise a first signal processor configured to apply the first decay channel characteristics to each of the independent signals to generate a plurality of decayed baseband uplink signals, and wherein each of the RF signal generators is configured to receive one of the plurality of decayed baseband uplink signals and generate therefrom a corresponding one of the first decayed test signals as a corresponding RF signal. [18] The test system of claim 17, wherein the DUT comprises a multi-input, multi-output (MIMO) transceiver, and wherein the RF signal generators are configured to provide the plurality of first decayed test signals to a plurality of RF inputs of the MIMO transceiver. [19] The test system of claim 16, wherein the one or more test instruments comprise one or more RF test instruments, the RF test instruments being configured to receive one or more RF output signals of the DUT as one or more input signals to the one or more RF test instruments and to measure at least one performance characteristic of an RF processing module of the DUT.

Images