Patent Publication Number: US-10790915-B2

Title: Over-the-air test fixture using antenna array

Description:
PRIORITY CLAIM 
     This application claims priority to U.S. provisional patent application Ser. No. 62/674,455, entitled “Over-the-Air Testing of Millimeter Wave Integrated Circuits with Integrated Antennas,” filed May 21, 2018, which is hereby incorporated by reference in its entirety as though fully and completely set forth herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of radio frequency (RF) transmitter and RF receiver testing, and more specifically, to testing of devices that incorporate an antenna. 
     DESCRIPTION OF THE RELATED ART 
     RF and millimeter wave (mmW) technology are rapidly growing in importance, e.g., as 5th generation (5G) wireless technology is becoming more widespread. Current methods for testing devices with integrated antennas for transmitting and/or receiving RF and mmW signals may be slow and/or expensive. Improvements in the field are desired. 
     SUMMARY OF THE INVENTION 
     Various embodiments are presented below of a system and method for testing (e.g., rapidly and cheaply) devices with integrated antennas configured for radio frequency (RF) and millimeter wave (mmW) transmission and/or reception. A device to be tested (e.g., the device under test (DUT)) may be mounted to an interface providing wired or wireless connections for input and output signals, power, control, and positioning in a measurement fixture. Exemplary devices that may be tested include: integrated circuits (ICs) with built in antennas, massive multiple-in, multiple-out (MIMO) transceivers, automotive radar, beam steering base stations, and various devices with phased antenna arrays, among various possibilities. 
     Power and data connections of the DUT may be tested over the interface. RF characteristics (e.g., including power, spectrum occupancy, and/or modulation for transmission, reception, and/or beamforming) of the DUT may be tested over-the-air using an array of antennas or probes, e.g., within the measurement fixture. Any combination of the antennas or probes of the array may be connected to RF testing equipment, possibly by one or more switches. 
     The antenna probe array may be used for production testing. The antenna probe array may be used to characterize a DUT and to determine which subset of elements of the larger array provide relevant (e.g., particularly useful) measurement results for one or more antenna patterns. The antenna probe array may later be used to production test a DUT (or plurality of DUTs) by performing measurements of the DUT using the subset of relevant elements. 
     The antenna probe array may be used to measure parameters (e.g., any or all of: power, phase, frequency, modulation quality, intermodulation, spectrum occupancy, receiver characteristics, etc.) over the air. Such measurements may be performed using a subset of relevant elements of the antenna probe array (e.g., at optimized locations). Further, signals from several elements may be combined, e.g., using a beamforming algorithm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiment is considered in conjunction with the following drawings, in which: 
         FIG. 1  illustrates a computer system configured to perform testing of an integrated circuit, according to some embodiments. 
         FIG. 2A  illustrates an instrumentation control system according to some embodiments. 
         FIG. 2B  illustrates an industrial automation system according to some embodiments. 
         FIG. 3  is an exemplary block diagram of the computer systems of  FIGS. 1, 2A , and  2 B, according to some embodiments. 
         FIGS. 4-9  illustrate exemplary integrated circuits, according to some embodiments. 
         FIGS. 10-16  illustrate aspect of testing millimeter wave integrated circuit radio frequency performance, according to some embodiments. 
         FIGS. 17-20  illustrate various testing approaches, according to some embodiments. 
         FIGS. 21-28  illustrate various aspects of methods and systems for production testing of millimeter wave devices, according to some embodiments. 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Terms 
     The following is a glossary of terms used in the present application: 
     Memory Medium—Any of various types of non-transitory computer accessible memory devices or storage devices. The term “memory medium” is intended to include an installation medium, e.g., a CD-ROM, floppy disks  104 , or tape device; a computer system memory or random access memory such as DRAM, DDR RAM, SRAM, EDO RAM, Rambus RAM, etc.; a non-volatile memory such as a Flash, magnetic media, e.g., a hard drive, or optical storage; registers, or other similar types of memory elements, etc. The memory medium may comprise other types of non-transitory memory as well or combinations thereof. In addition, the memory medium may be located in a first computer in which the programs are executed, or may be located in a second different computer which connects to the first computer over a network, such as the Internet. In the latter instance, the second computer may provide program instructions to the first computer for execution. The term “memory medium” may include two or more memory mediums which may reside in different locations, e.g., in different computers that are connected over a network. 
     Carrier Medium—a memory medium as described above, as well as a physical transmission medium, such as a bus, network, and/or other physical transmission medium that conveys signals such as electrical, electromagnetic, or digital signals. 
     Programmable Hardware Element—includes various hardware devices comprising multiple programmable function blocks connected via a programmable interconnect. Examples include FPGAs (Field Programmable Gate Arrays), PLDs (Programmable Logic Devices), FPGAs (Field Programmable Object Arrays), and CPLDs (Complex PLDs). The programmable function blocks may range from fine grained (combinatorial logic or look up tables) to coarse grained (arithmetic logic units or processor cores). A programmable hardware element may also be referred to as “reconfigurable logic.” 
     Processing Element—refers to various elements or combinations of elements that are capable of performing a function in a device, such as a user equipment or a cellular network device. Processing elements may include, for example: processors and associated memory, portions or circuits of individual processor cores, entire processor cores, processor arrays, circuits such as an ASIC (Application Specific Integrated Circuit), programmable hardware elements such as a field programmable gate array (FPGA), as well any of various combinations of the above. 
     Software Program—the term “software program” is intended to have the full breadth of its ordinary meaning, and includes any type of program instructions, code, script and/or data, or combinations thereof, that may be stored in a memory medium and executed by a processor. Exemplary software programs include programs written in text-based programming languages, such as C, C++, PASCAL, FORTRAN, COBOL, JAVA, assembly language, etc.; graphical programs (programs written in graphical programming languages); assembly language programs; programs that have been compiled to machine language; scripts; and other types of executable software. A software program may comprise two or more software programs that interoperate in some manner. Note that various embodiments described herein may be implemented by a computer or software program. A software program may be stored as program instructions on a memory medium. 
     Hardware Configuration Program—a program, e.g., a netlist or bit file, that can be used to program or configure a programmable hardware element. 
     Program—the term “program” is intended to have the full breadth of its ordinary meaning. The term “program” includes 1) a software program which may be stored in a memory and is executable by a processor or 2) a hardware configuration program useable for configuring a programmable hardware element. 
     Computer System—any of various types of computing or processing systems, including a personal computer system (PC), mainframe computer system, workstation, network appliance, Internet appliance, personal digital assistant (PDA), television system, grid computing system, or other device or combinations of devices. In general, the term “computer system” can be broadly defined to encompass any device (or combination of devices) having at least one processor that executes instructions from a memory medium. 
     Measurement Device—includes instruments, data acquisition devices, smart sensors, and any of various types of devices that are configured to acquire and/or store data. A measurement device may also optionally be further configured to analyze or process the acquired or stored data. Examples of a measurement device include an instrument, such as a traditional stand-alone “box” instrument, a computer-based instrument (instrument on a card) or external instrument, a data acquisition card, a device external to a computer that operates similarly to a data acquisition card, a smart sensor, one or more DAQ or measurement cards or modules in a chassis, an image acquisition device, such as an image acquisition (or machine vision) card (also called a video capture board) or smart camera, a motion control device, a robot having machine vision, and other similar types of devices. Exemplary “stand-alone” instruments include oscilloscopes, multimeters, signal analyzers, arbitrary waveform generators, spectroscopes, and similar measurement, test, or automation instruments. 
     A measurement device may be further configured to perform control functions, e.g., in response to analysis of the acquired or stored data. For example, the measurement device may send a control signal to an external system, such as a motion control system or to a sensor, in response to particular data. A measurement device may also be configured to perform automation functions, i.e., may receive and analyze data, and issue automation control signals in response. 
     Functional Unit (or Processing Element)—refers to various elements or combinations of elements. Processing elements include, for example, circuits such as an ASIC (Application Specific Integrated Circuit), portions or circuits of individual processor cores, entire processor cores, individual processors, programmable hardware devices such as a field programmable gate array (FPGA), and/or larger portions of systems that include multiple processors, as well as any combinations thereof. 
     Automatically—refers to an action or operation performed by a computer system (e.g., software executed by the computer system) or device (e.g., circuitry, programmable hardware elements, ASICs, etc.), without user input directly specifying or performing the action or operation. Thus the term “automatically” is in contrast to an operation being manually performed or specified by the user, where the user provides input to directly perform the operation. An automatic procedure may be initiated by input provided by the user, but the subsequent actions that are performed “automatically” are not specified by the user, i.e., are not performed “manually,” wherein the user specifies each action to perform. For example, a user filling out an electronic form by selecting each field and providing input specifying information (e.g., by typing information, selecting check boxes, radio selections, etc.) is filling out the form manually, even though the computer system must update the form in response to the user actions. The form may be automatically filled out by the computer system where the computer system (e.g., software executing on the computer system) analyzes the fields of the form and fills in the form without any user input specifying the answers to the fields. As indicated above, the user may invoke the automatic filling of the form, but is not involved in the actual filling of the form (e.g., the user is not manually specifying answers to fields but rather they are being automatically completed). The present specification provides various examples of operations being automatically performed in response to actions the user has taken. 
     Concurrent—refers to parallel execution or performance, where tasks, processes, or programs are performed in an at least partially overlapping manner. For example, concurrency may be implemented using “strong” or strict parallelism, where tasks are performed (at least partially) in parallel on respective computational elements, or using “weak parallelism,” where the tasks are performed in an interleaved manner, e.g., by time multiplexing of execution threads. 
     Wireless—refers to a communications, monitoring, or control system in which electromagnetic or acoustic waves carry a signal through space rather than along a wire. 
     Approximately—refers to a value being within some specified tolerance or acceptable margin of error or uncertainty of a target value, where the specific tolerance or margin is generally dependent on the application. Thus, for example, in various applications or embodiments, the term approximately may mean: within 0.1% of the target value, within 0.2% of the target value, within 0.5% of the target value, within 1%, 2%, 5%, or 10% of the target value, and so forth, as required by the particular application of the present techniques. 
       FIG. 1 —Computer System 
       FIG. 1  illustrates a computer system  82  configured to implement embodiments of the techniques disclosed herein. Embodiments of a method for (e.g., for production testing of integrated circuits) are described below. Note that various embodiments of the techniques disclosed herein may be implemented in a variety of different ways. For example, in some embodiments, some or all of the techniques may be implemented with textual or graphical programs that may be deployed to, or used to configure, any of various hardware devices. 
     However, while some embodiments are described in terms of one or more programs, e.g., graphical programs, executing on a computer, e.g., computer system  82 , these embodiments are exemplary only, and are not intended to limit the techniques to any particular implementation or platform. Thus, for example, in some embodiments, the techniques may be implemented on or by a functional unit (also referred to herein as a processing element), which may include, for example, circuits such as an ASIC (Application Specific Integrated Circuit), portions or circuits of individual processor cores, entire processor cores, individual processors, programmable hardware devices such as a field programmable gate array (FPGA), and/or larger portions of systems that include multiple processors, as well as any combinations thereof. 
     As shown in  FIG. 1 , the computer system  82  may include a display device configured to display a graphical program as the graphical program is created and/or executed. The display device may also be configured to display a graphical user interface or front panel of the graphical program during execution of the graphical program. The graphical user interface may comprise any type of graphical user interface, e.g., depending on the computing platform. 
     The computer system  82  may include at least one memory medium on which one or more computer programs or software components according to one embodiment of the present invention may be stored. For example, the memory medium may store one or more programs, such as graphical programs, that are executable to perform the methods described herein. The memory medium may also store operating system software, as well as other software for operation of the computer system. Various embodiments further include receiving or storing instructions and/or data implemented in accordance with the foregoing description upon a carrier medium. 
     Exemplary Systems 
     Embodiments of the present invention may be involved with performing test and/or measurement functions; controlling and/or modeling instrumentation or industrial automation hardware; modeling and simulation functions, e.g., modeling or simulating a device or product being developed or tested, etc. Exemplary test applications include hardware-in-the-loop testing and rapid control prototyping, among others. 
     However, it is noted that embodiments of the present invention can be used for a plethora of applications and is not limited to the above applications. In other words, applications discussed in the present description are exemplary only, and embodiments of the present invention may be used in any of various types of systems. Thus, embodiments of the system and method of the present invention is configured to be used in any of various types of applications, including the control of other types of devices such as multimedia devices, video devices, audio devices, telephony devices, Internet devices, etc., as well as general purpose software applications such as word processing, spreadsheets, network control, network monitoring, financial applications, games, etc. 
       FIG. 2A  illustrates an exemplary instrumentation control system  100  which may implement embodiments described herein. The system  100  comprises a host computer  82  which couples to one or more instruments. The host computer  82  may comprise a CPU, a display screen, a memory, and one or more input devices such as a mouse or keyboard as shown. The computer  82  may operate with the one or more instruments to analyze, measure or control a unit under test (UUT) or process  150 , e.g., via execution of software  104 . 
     The one or more instruments may include a GPIB instrument  112  and associated GPIB interface card  122 , a data acquisition board  114  inserted into or otherwise coupled with chassis  124  with associated signal conditioning circuitry  126 , a VXI instrument  116 , a PXI instrument  118 , a video device or camera  132  and associated image acquisition (or machine vision) card  134 , a motion control device  136  and associated motion control interface card  138 , and/or one or more computer based instrument cards  142 , among other types of devices. The computer system may couple to and operate with one or more of these instruments. The instruments may be coupled to the device under test (DUT) or process  150 , or may be coupled to receive field signals, typically generated by transducers. The system  100  may be used in a data acquisition and control application, in a test and measurement application, an image processing or machine vision application, a process control application, a man-machine interface application, a simulation application, or a hardware-in-the-loop validation application, among others. 
       FIG. 2B  illustrates an exemplary industrial automation system  200  which may implement embodiments described herein. The industrial automation system  200  is similar to the instrumentation or test and measurement system  100  shown in  FIG. 2A . Elements which are similar or identical to elements in  FIG. 2A  have the same reference numerals for convenience. The system  200  may comprise a computer  82  which couples to one or more devices or instruments. The computer  82  may comprise a CPU, a display screen, a memory, and one or more input devices such as a mouse or keyboard as shown. The computer  82  may operate with the one or more devices to perform an automation function with respect to a process or device  150 , such as HMI (Human Machine Interface), SCADA (Supervisory Control and Data Acquisition), portable or distributed data acquisition, process control, advanced analysis, or other control, among others, e.g., via execution of software  104 . 
     The one or more devices may include a data acquisition board  114  inserted into or otherwise coupled with chassis  124  with associated signal conditioning circuitry  126 , a PXI instrument  118 , a video device  132  and associated image acquisition card  134 , a motion control device  136  and associated motion control interface card  138 , a fieldbus device  270  and associated fieldbus interface card  172 , a PLC (Programmable Logic Controller)  176 , a serial instrument  182  and associated serial interface card  184 , or a distributed data acquisition system, such as Fieldpoint system  185 , available from National Instruments Corporation, among other types of devices. 
     In the embodiments of  FIGS. 2A and 2B , above, one or more of the various devices may couple to each other over a network, such as the Internet. In one embodiment, the user operates to select a target device from a plurality of possible target devices for programming or configuration. Thus the user may create a program on a computer and use (execute) the program on that computer or deploy the program to a target device (for remote execution on the target device) that is remotely located from the computer and coupled to the computer through a network. 
     Software programs that perform data acquisition, analysis and/or presentation, e.g., for measurement, instrumentation control, industrial automation, modeling, or simulation, such as in the applications shown in  FIGS. 2A and 2B , may be referred to as virtual instruments. 
       FIG. 3 —Computer System Block Diagram 
       FIG. 3  is a block diagram  12  representing one embodiment of the computer system  82  illustrated in  FIG. 1, 2A or 2B . It is noted that any type of computer system configuration or architecture can be used as desired, and  FIG. 4  illustrates a representative PC embodiment. It is also noted that the computer system may be a general purpose computer system, a computer implemented on a card installed in a chassis, or other types of embodiments. Elements of a computer not necessary to understand the present description have been omitted for simplicity. 
     The computer may include at least one central processing unit or CPU (processor)  160  which is coupled to a processor or host bus  162 . The CPU  160  may be any of various types, including any type of processor (or multiple processors), as well as other features. A memory medium, typically comprising RAM and referred to as main memory,  166  is coupled to the host bus  162  by means of memory controller  164 . The main memory  166  may store a program (e.g., a graphical program) configured to implement embodiments of the present techniques. The main memory may also store operating system software, as well as other software for operation of the computer system. 
     The host bus  162  may be coupled to an expansion or input/output bus  170  by means of a bus controller  168  or bus bridge logic. The expansion bus  170  may be the PCI (Peripheral Component Interconnect) expansion bus, although other bus types can be used. The expansion bus  170  includes slots for various devices such as described above. The computer  82  further comprises a video display subsystem  180  and hard drive  182  coupled to the expansion bus  170 . The computer  82  may also comprise a GPIB card  122  coupled to a GPIB bus  112 , and/or an MXI device  186  coupled to a VXI chassis  116 . 
     As shown, a device  190  may also be connected to the computer. The device  190  may include a processor and memory which may execute a real time operating system. The device  190  may also or instead comprise a programmable hardware element. The computer system may be configured to deploy a program to the device  190  for execution of the program on the device  190 . The deployed program may take the form of graphical program instructions or data structures that directly represents the graphical program. Alternatively, the deployed program may take the form of text code (e.g., C code) generated from the program. As another example, the deployed program may take the form of compiled code generated from either the program or from text code that in turn was generated from the program. 
       FIGS. 4-9 —Integrated Circuit (IC) with Antennas 
     Integrated circuits (IC) with integrated antennas are increasingly common. Such ICs are included in many devices and may be configured to perform various functions including wireless communication (e.g., including transmission and/or reception) and radar. In particular, 5G wireless communication standards (or other standards) may provide for the use of millimeter wave (mmW) band wireless signals and beamforming (e.g., directional transmission/reception). ICs or application specific ICs (ASICs) may be an important element of many wireless devices configured to communicate using such standards. For example, an IC with an integrated array of antennas (e.g., a phased array) may be a common means of including such 5G wireless capabilities. Further, some ICs may include multiple arrays of antennas. 
       FIG. 4  illustrates a phased array of antennas which may be incorporated into an IC such as a complementary metal-oxide-semiconductor (CMOS) Monolithic Microwave Integrated Circuit (MMIC). As illustrated the IC may be approximately 1 cm by 1 cm, among various possibilities. 
       FIG. 5  illustrates an exemplary IC, including an integrated antenna array ( 502 ). Such an IC may be approximately 2.5 cm wide, among various possibilities. The IC may include wired and/or wireless connections ( 504 ) for data, control, and power. 
       FIG. 6  illustrates an exemplary array of 256 antennas on a chip. The array may be approximately 4 cm wide, among various possibilities. It should be noted that other numbers or configurations of antennas are possible, as well as other sizes of chips. Further, the antennas may be on-chip, on-package, or even located on a separate physical structure, according to some embodiments. 
       FIG. 7  illustrates an exemplary IC. As shown, the IC includes multiple (e.g., any desired number) of antenna patches ( 702 ) mounted to a chip ( 704 ) (e.g., a printed circuit board (PCB), glass wafer, silicon wafer, etc.). The antenna patches may transmit signals to and from an integrated RF chip (or chips) ( 706 ). Note that the RF chip ( 706 ) may be included in the chip ( 704 ), but may not reach the full thickness of the chip ( 704 ). In the illustrated example, the RF chip ( 706 ) reaches height h 1 , which is less than the full height of the chip ( 704 ), h 2 . The RF chip ( 706 ) may be connected to other elements of the IC, e.g., via wired connections. 
       FIG. 8  illustrates different types of antenna connections of exemplary ICs. In a first configuration ( 802 ), antennas may be embedded in a printed circuit board (PCB), to which RF chips and a heat sink are mounted. Such a configuration may be useful for relatively low frequencies, e.g., approximately 75 GHz, according to some embodiments. In a second configuration ( 804 ), antenna patches may be embedded in package tiles, which are in turn mounted to RF chips and a (e.g., 2 nd  level) PCB. The RF chips may be connected (thru the PCB) to a heat sink. Such a configuration may be useful for medium frequencies, e.g. 94 GHz, among various possibilities. A third configuration ( 806 ) may include antenna patches embedded in a glass substrate and stacked on RF chips, e.g., above a package, 2 nd  level PCB, and heat sink. In a variation, the glass wafer may be mounted on a silicon wafer instead of a package. Such configurations may be useful for higher frequencies, e.g., 110 GHz and above, among various possibilities. 
       FIG. 9  illustrates an exemplary mmW IC ( 902 ) with an integrated antenna array ( 904 ). As shown, each antenna element (e.g., patch) ( 906 ) may have dedicated (e.g., per element) circuitry ( 908 ). Note that the specific antenna element circuitry shown is exemplary only, and that other circuit configurations may be used. 
       FIGS. 10-16 —Testing of mmW IC RF Performance 
     As demand for ICs with integrated antenna arrays grows, improvements in the cost of producing and testing such ICs are desired. Testing of mmW ICs, e.g., according to conventional techniques, may be challenging for various reasons. There may be no physical (e.g., wired) connections such as coax, waveguide or pins with which to connect the antennas to test equipment. However, power and control connections may be made using conventional, e.g., wired methods. Therefore, the radio frequency (RF) performance (e.g., mmW transmission and reception) must be tested over-the-air. Anechoic chambers may be a common technique to avoid interference, e.g., due to reflected signals and multipath effects that can complicate test measurements. However, in order to avoid RF coupling (e.g., interference of the testing equipment with the performance of the antenna array), the testing equipment may require significant space. Further, beamforming requirements may lead to many antennas on a package or on a chip and it may be desired to test the beamforming directional capabilities of the antenna array/IC. Testing of the beamforming capabilities may be expensive, time-consuming, or difficult, e.g., to take measurements from a potentially large number of positions, e.g., because the RF performance may vary spatially. In other words, in order to test the spatial RF performance, measurements must be taken in many positions (e.g., in 3 dimensions, e.g., as a function of x, y, and z position). Such detailed spatial testing may require complex calibration. Still further, a relatively large distance (e.g., away from the antenna array) may be needed to measure a fully formed beam, and small anechoic chambers may not allow measurement in the far field of the array (e.g., where the beam may be fully formed). 
       FIG. 10  illustrates certain aspects of over-the-air testing of RF performance, according to some embodiments. An entire array may be tested, e.g., using an antenna ( 1002   a  and  1002   b ), e.g., a horn antenna as illustrated or other type of antenna (e.g., patch, dipole, loop, directional array, etc.). In order to test the beamforming capability of the array, the antenna (or antennas) may be positioned at a sufficiently large measurement distance ( 1004 ) that the beam is fully formed. Further, measurements may be taken from a variety of different positions in order to test the performance of the beam in different directions. An entire array test ( 1006   a ) may involve relatively high power signals, e.g., +40 dB (e.g., Equivalent Isotropically Radiated Power (EIRP)), as shown, among various possibilities. The array of antennas may have a power gain (e.g., array gain) relative to a single antenna. Alternatively, single element tests ( 1006   b ) may be performed. A test may require that the horn antenna be far enough away from the antenna element(s) to be tested to avoid RF coupling. This distance may be smaller for a single element test than the distance for beam formation, e.g., for an entire array test. A single element test may not test the beamforming performance of the array. Single element tests may involve relatively low power signals, e.g., −10 dB, as shown, among various possibilities. 
       FIG. 11  illustrates fields generated by a short dipole antenna, specifically the wave impedance as a function of distance from the antenna. A “short” dipole may be one where its length is (e.g., much) shorter than ½ wavelength. For the far field, where the distance is greater than the wavelength, the following relations may hold: 
     E/H=377, for r/λ&gt;1, where E is electric field, H is magnetic field, r is radius, and A is wavelength; 
     E and H reduce as 1/r; and 
     Power drops as 1/r{circumflex over ( )}2. 
     For the near field, either the magnetic field or the electric field may dominate. A conductor placed in the near field reactive region may couple electrically or magnetically (e.g., Reactive coupling) and load down the source driving the antenna. For example, test equipment placed in the near field region may interfere with the operation of the antenna, due to reactive coupling. 
       FIG. 12  illustrates fields generated by a short dipole antenna, with further detail of different regions, e.g., as a function of distance from the antenna. In the near-field radiative and transition regions, E and H may reduce as 1/r{circumflex over ( )}n, where n varies from 1 to 6. 
       FIG. 13  illustrates radiation zones for antennas larger than half a wavelength, e.g., in contrast to a short dipole antenna. In some embodiments, the length of an individual antenna patch ( 1302 ), e.g., as incorporated in an mmW IC, may be approximately equal to half a wavelength. However, an array of such antennas may be (e.g., much) larger than half a wavelength. Therefore, such an antenna array may exhibit characteristics similar to a single antenna larger than half a wavelength, e.g., as illustrated. The near field (e.g., reactive) region ( 1304 ) may be defined as: 
               r   ≤     0.62   ⁢         D   3     λ           ,         
where D is the length of the antenna. Conductors in this region may load down the antenna and significantly change the radiation pattern.
 
     The Fresnel (or transition) region ( 1306 ) may be defined as: 
     
       
         
           
             r 
             ≤ 
             
               0.62 
               ⁢ 
               
                 
                   
                     D 
                     3 
                   
                   λ 
                 
               
             
             &lt; 
             r 
             ≤ 
             
               2 
               ⁢ 
               
                 
                   D 
                   2 
                 
                 λ 
               
             
           
         
       
     
     The radiation pattern may not be fully formed in this region. Conductors in this region may not significantly change the radiation pattern. 
     The radiating far field region may be defined as: 
     
       
         
           
             r 
             &gt; 
             
               2 
               ⁢ 
               
                 
                   D 
                   2 
                 
                 λ 
               
             
           
         
       
     
     The radiation pattern ( 1308 ) may be fully formed in this region. 
       FIG. 14  illustrates the radiation pattern of an exemplary array of 4 antenna elements. Note that the radiation pattern is not fully formed close to the antennas, and becomes clearer (e.g., more fully formed) at increasing distance. 
       FIGS. 15 and 16  illustrate the boundary of a near field and far field regions (e.g., respectively) for a 5 cm (e.g., square) antenna array as a function of frequency (in GHz). Receiving antennas (e.g., such as testing equipment) may significantly affect the pattern when placed in the reactive near field, e.g., due to RF coupling, e.g., reactive (capacitive or magnetic) coupling. Receiving antennas may not significantly affect the pattern when placed in far field, e.g., because power in the far field is radiated into space. The pattern may not be fully formed in between the near field boundary and the far field boundary (e.g., in the transition zone or Fresnel region, e.g., at distances greater than the near field boundary of  FIG. 15  but less than the far field boundary of  FIG. 16 ), but it may not be significantly affected by a receiving antenna. The transition zone may be the far field for each element. However, the (e.g., combined) beam may not be fully formed in this range, e.g., the beam pattern may be different from near field or far field beam patterns. 
     For example, consider a 30 GHz transmission, e.g., which may be common in a 5G communication system. As shown in  FIG. 15 , the near field region may end at approximately 7 cm away from the antenna array. The far field region may begin at approximately 50 cm away from the antenna array. Therefore, for the exemplary case of a 30 GHz transmission associated with a 5 cm array, the transition zone may be the zone between 7 and 50 cm from the antenna array. It is noted that other array sizes and frequencies are possible, that the techniques and systems disclosed herein may be applied to other sizes and frequencies as desired, and that the zone boundaries may vary, e.g., based on size and frequency. 
       FIGS. 17-19 —Testing in the Fresnel Region 
     In a first group of embodiments, a mmW array of antennas may be tested using a 3-D positioner. Such a 3-D positioner may operate in an anechoic chamber, e.g., sized for 18-87 GHz frequencies, among various possibilities. A 3-D positioning arm may perform spiral scanning, e.g., to take measurements at any number of locations, e.g., using a horn antenna. A low reflection antenna (e.g., a small radar cross section) may be used for testing, e.g., in order to minimize effects on the fields. The measurements may be taken in the near field (e.g., in the Fresnel zone of the near field). Tests may be performed to measure magnitude and phase of the signal/field at any number of locations. The far field pattern may be computed based on the near field measurements. The conversion of near-field to far-field may be accomplished using any appropriate calculation approach. Such calculations may be relatively straight forward if the antenna pattern/configuration is known, or more complex for an arbitrary pattern. Plots of the far field pattern may be generated. Such a 3-D positioning system may be useful for design and characterization tests, however the equipment may be relatively expensive and the tests may be time consuming. First, the testing process itself may take significant time, e.g., because of the need to move the 3-D positioning arm through a large number of positions to test each DUT. Second, the anechoic chamber may need to be large enough to allow for measurements to be taken in enough positions (e.g., in 3-D space) to compute the far field pattern. In some embodiments, the anechoic chamber may be large enough so that measurements may be taken in the radiating far field. 
       FIG. 17  is a block diagram illustrating a 3-D positioner ( 1702 ) in an anechoic chamber ( 1704 ), according to some embodiments. As shown, the array (e.g., DUT  1706 ) may be mounted in the chamber, and may be configured to transmit a signal in a beamforming pattern (e.g., in a tested beam form) ( 1708 ). The 3-D positioning arm may move a horn antenna in various positions in the chamber for measurements. 
       FIG. 18  is an exemplary depiction of a 3-D positioning arm inside an anechoic chamber. 
       FIG. 19  is an example plot of a field generated by the DUT. Such a plot may be generated based on the tests performed. 
       FIGS. 20 —Testing in the Near Field Region 
     In a second group of embodiments, rather than performing testing in the Fresnel region of the near field as in the first group of embodiments, testing may be performed in the reactive near field (e.g., in near field  1304  as depicted in  FIG. 13 ). For example, each antenna may be measured separately, e.g., by matching the DUT antenna elements to an array of antenna elements in the test fixtures. 
       FIG. 20  illustrates such an exemplary testing approach. As shown, the chip with an array of antennas may be positioned close to (e.g., in the reactive near field, e.g., potentially touching) a matching array of test fixtures. This approach may allow each antenna to be measured individually, e.g., the antenna drive (e.g., magnitude and phase of driving signal) may be determined. Relative to the embodiment discussed above, this embodiment may not require bulky testing equipment, e.g., a large anechoic chamber nor testing among a wide variety of spatial positions with such a large anechoic chamber. However, the reactive coupling in the near field may change the loading of each antenna as well as the magnitude and phase of the response of each antenna. Further, the array of test fixtures, may be specifically created to match each different DUT (e.g., or type of DUT), and may therefore result in a costly and time-consuming test process. 
       FIGS. 21-28 —Antenna Array Production Testing 
     In a third group of embodiments, an array of testing antennas (e.g., antenna probe array) may be positioned in a measurement fixture. In some embodiments, the measurement fixture may be or include a compact anechoic chamber. In some embodiments, the measurement fixture may be or include a socket. The measurement fixture may provide an interface that includes connections (e.g., wireless and/or wired connections which may be easily attached/detached) for power, control, and data (e.g., input/output signals) to a device under test (DUT). Exemplary devices that may be tested include: integrated circuits (ICs) with built in antennas, phased antenna arrays, massive multiple-in, multiple-out (MIMO) transceivers, automotive radar, and beam steering base stations, among various possibilities. 
     The interface may also position the DUT in three dimensional space relative to the testing antennas, e.g., in order to perform over-the-air testing of the wireless capabilities/performance of the DUT. The testing antennas may be positioned at various distances from the device under test, e.g., in the Fresnel region of the near field, the reactive near field, or the far field, among various possibilities. 
     In some embodiments, each antenna of the array of testing antennas may be connected to a diode power detector, and the voltages of each antenna may be measured. 
     In some embodiments, each antenna of the array of testing antennas may be connected to Rx/Tx test equipment. The Rx/Tx test equipment may measure one or more of: power, phase, frequency, modulation quality (e.g., as measured by error vector magnitude (EVM), cumulative distribution function (CCDF), etc.), intermodulation (e.g., a third-order intercept point (IP3)), spectrum occupancy (e.g., as measured by adjacent channel power (ACP), etc.; note that the spectrum occupancy measurements may include detection and measurement of harmonics, e.g., as may be necessary to ensure that a DUT complies with regulatory and/or other requirements to limit/avoid transmissions in some frequency ranges), and/or receiver measurements (e.g., sensitivity, selectivity, image rejection, spurious responses, blocking, etc.). 
     In some one or more pieces of Rx/Tx test equipment (e.g., instruments) may be connected via one or more switches (e.g., a switch matrix) to any combination of the antennas of the array of testing antennas. Such a switch may be configured to connect the test equipment to one (or more) antennas of the array of testing antennas at a time. Thus, any combination of the antennas may be used to perform measurements (e.g., while connected via the switch(es) to the Rx/Tx test equipment) in a sequence, e.g., a first antenna may be connected, then the switch may disconnect the first antenna and connect a second antenna, etc. Any number of switches and/or pieces of test equipment may be included. For example, a first instrument may be connected to a first switch, which may connect the first instrument to any one (or more) of a first subset of the antennas of the array of testing antennas. Similarly, a second instrument may be connected to a second switch, which may connect the second instrument to any one (or more) of a second subset of the antennas of the array of testing antennas, etc. A single switch may be configured to connect any number of instruments to any number of antennas. 
     In various embodiments, the spatial arrangement of the antennas of the array of testing antennas may be configured as desired. For example, the array of testing antennas may be flat, mounted to a spherical surface (e.g., in a hemisphere), mounted to a parabolic surface, or in any other prescribed shape. 
     In various embodiments, the array of testing antennas may be located at various distances relative to the DUT. For example, the array of testing antennas may be located in the near field, the Fresnel zone, or the far field. The distance may be fixed or adjustable. Multiple arrays may be included and may be located at the same or different distances. 
     In various embodiments, the antennas of the array of testing antennas may be any type (or multiple types) of antennas. For example, the antennas may be dipoles, loops, patches, horns, dielectric antennas, and/or ferrite antennas, etc. 
     In various embodiments, the size and spacing of the antennas in the array of testing antennas may scale with wavelength (e.g., according to the frequency of transmissions to be tested with the DUT acting as a transmitter and/or receiver). Further, as the array size increases, the antenna gain and effective antenna cross section may increase. 
     In various embodiments, the antennas of the array of testing antennas may be arranged according to a pattern, or may be located randomly. For example, the antenna locations in the pattern can have a regular spacing. The pattern may be a grid, concentric circles, stripes, etc. 
     The array may be a sparse or full array. In a full array, there may be an antenna located at each point in an antenna pattern of the array (e.g., all points may be populated by antennas). In a sparse array, only a fraction of the locations may be populated by antennas. The locations populated in a sparse array may be determined to gather useful testing data, e.g., the antennas may be positioned at locations that are most likely to yield information useable to determine the RF performance of a DUT. 
     In some embodiments, the phase and/or amplitude (e.g., power) of the antennas of the array of testing antennas may be adjustable, e.g., for beamforming. Similarly, various combinations of antennas may be activated and/or deactivated for beamforming. In other words, any subset of antennas of the array may be activated and the relative phases/amplitudes of the active subset of antennas may be configured to transmit and/or receive directional/beamformed signals as desired. For example, a codeword (e.g., from a codebook) may be used to set relative phase and amplitude of various antennas to form a desired beam for transmission and/or reception. Each codeword may correspond to an antenna pattern, e.g., the subset of active antennas and their phases/amplitudes. The beam created by each antenna pattern may have characteristics such as direction, shape (e.g., peaks, nulls), width, focus, etc. These characteristics may vary between different codewords and/or antenna patterns. Multiple different codewords may create the same (or similar) antenna patterns or beams. 
     As explained further below, this third group of embodiments may be well suited to production testing (e.g., rapid screening) of RF capabilities of DUTs as well as full characterization testing. Production testing may include performing incomplete test of the DUTs, e.g., at a lower level of detail or thoroughness than a full characterization test. DUTs may be tested for transmission (Tx) and reception (Rx) functionality, including antenna pattern testing, e.g., beamforming. In beamforming, the relative phase of the antennas in the array may be adjusted in order to “direct” or “shape” a transmission or reception “beam” in one or more ways/directions. To test Tx, the DUT may be configured to transmit a signal (or pattern of signals) and the resulting signal(s) may be received by the array of testing antennas and measured and/or analyzed by the system. Antenna pattern testing may be a type of Tx testing where the spatial variation of a beamformed Tx signal is tested. Conversely, to test Rx, the DUT may be configured to receive a signal transmitted by one or more of the testing antennas, and the received signal may be measured and analyzed by the system. 
     This third group of embodiments may offer several advantages, e.g., relative to the first and second group. These advantages may include: 
     1) positioning an anechoic chamber (or other measurement fixture) and an array of testing antennas within a BATS, thus allowing for simultaneous testing of RF capabilities and other features (e.g., power, data connections, etc.) of the DUT; 
     2) positioning an array of testing antennas inside of a measurement fixture for means of testing a beam pattern; 
     3) the antenna array may be placed in a fixed location, e.g., to allow for rapid evaluation/screening of DUTs; 
     4) the antenna array may be mounted in/on a movable actuator (For example, the array elements may be positioned on the X-Y plane. The actuator may move the entire array in the Z-direction. This may be useful for 3-D mapping of the antenna pattern.); 
     5) diode detectors may be connected to each antenna in the test antenna array to turn the measurement of field strength into a number of DC measurements; 
     6) A field pattern signature may be used to do production testing or screening of mmW ICs or other devices; 
     7) Far-field beam patterns may be computed from measurements from the antennas, e.g., even if the array of testing antennas is located in the near field or Fresnel zone; 
     8) parameters may be measured over the air using the antenna probe array. For example, power, phase, frequency, modulation quality (e.g., as measured by error vector magnitude (EVM), cumulative distribution function (CCDF), etc.), intermodulation (e.g., a third-order intercept point (IP3)), spectrum occupancy (e.g., as measured by (ACP), etc.; note that the spectrum occupancy measurements may include detection and measurement of harmonics, e.g., as may be necessary to ensure that a DUT complies with regulatory and/or other requirements to limit/avoid transmissions in some frequency ranges), and/or receiver measurements (e.g., sensitivity, selectivity, image rejection, spurious responses, blocking, etc.). may be tested over the air. 
       FIG. 21  illustrates an exemplary system configured for testing of DUT antenna arrays, e.g., according to at least some of the third group of embodiments. It is noted that the system of  FIG. 21  is merely one example of a possible system, and that features of this disclosure may be implemented in any of various systems, as desired. In various embodiments, some of the elements shown may be configured, connected, or adjusted in a different position than shown, may be substituted for by other elements, or may be omitted. Additional elements may also be included as desired. As shown, the system may operate as follows. 
     As shown, the system may include a Built-in Antenna Test System (BATS)  2102  such as a semiconductor test system (STS)  2102 . A BATS may be a system to test any of various forms of devices that include antennas, e.g., mmW ICs. The BATS may be configured to perform over the air testing of one or more DUTs. The BATS may also be configured to perform other types of testing, e.g., of power, control, and/or data connections of the DUT, etc. 
     One or more DUTs to be tested may be mounted on a tray ( 2104 ). The tray may allow for simple, rapid installation of the DUT(s). For example, power, data, and control connections may be available, e.g., via an interface board and/or standard mating connectors (e.g., DSUB, VHDCI, etc.). The connections may be wired and/or wireless (e.g., over-the-air). For example, power may be provided wirelessly, e.g., via inductive charging, one or more antennas, a coil structure, etc. Similarly, data and/or control connections may be provided using any suitable form of wireless connection. For example, various radio access technologies (RATs) such as wireless local area network (e.g., IEEE 802.11 or Wi-Fi), Bluetooth, near-field communication (NFC), radio frequency identification (RFID), and/or cellular may be used. For example, a wireless connection to be tested (e.g., a cellular connection) may also be used to transmit/receive data and/or control signals related to the testing process. The power, data, and/or control connections may be made via conductive connections and/or via one or more antennas of the DUT. The connections may be standard, customized and/or configurable. The connections may provide for input and/or output signals. The interface may be fixed or may be adjustable, e.g., the interface may provide for fixed or configurable positioning. The tray may mount on one side (e.g., to the top of, in the illustrated example; other positions are possible, including measurement fixtures of other shapes, e.g., spherical) of a measurement fixture. In the illustrated embodiment, the measurement fixture is an anechoic chamber ( 2106 ). The tray may be configured to be loaded in a loading position ( 2108 ) (as illustrated in the diagram) and to easily fit on to (e.g., or into) the measurement fixture, e.g., the tray may be attached to a “lid” of the measurement fixture which may simply be closed, e.g., to place the DUT(s) into testing position ( 2110 ). For example, the tray may be attached via a hinge mechanism. 
     One or more other sides/regions of the measurement fixture may include an antenna array for testing (e.g., testing antennas) ( 2112 ). The array of testing antennas may be positioned at a distance (e.g., or range of distances) away from the DUT that is within the Fresnel region/transition zone, e.g., for the size of DUT antenna array and frequency or range of frequencies to be tested. The array of testing antennas may be positioned at other distances, e.g., in the near field or in the far field. In some embodiments, the array of testing antennas may be configured to be stationary at a fixed position or distance from the DUT. In other embodiments, the array of testing antennas may be moved. For example, in the illustrated example, the testing antenna array may be vertically adjusted, e.g., in order to allow measurements at different distances from the DUT. For example, the position may be adjusted within the range of the transition zone. 
     In some embodiments, multiple arrays of testing antennas may be included. For example, one or more antenna arrays may cover multiple surfaces of the measurement fixture. Similarly, antenna arrays may be positioned at different distances from the DUT. 
     In some embodiments, the power, data, and/or control connections may be made over-the-air via one or more elements of antenna array  2112 . For example, some of the antennas of antenna array  2112  may be used to transmit and/or receive data and/or control signals to/from the DUT, e.g., in addition to performing testing measurements. Further, one or more of the antennas may be overloaded to provide a power connection. Additionally, or alternatively, the connections may be made via one or more other antennas of the BATS, e.g., other than elements of an array of testing antennas  2112 . In other words, the BATS may include any number of antennas (not illustrated in  FIG. 21 ) that are configured to provide power, data, and/or control connections to the DUT via any desired RAT(s). 
     In some embodiments, the measurement fixture may include any of various other elements. For example, the measurement fixture may include any number of sensors or probes associated with any number of measurement devices, and/or may include entire measurement devices. The measurement fixture and/or the array of testing antennas  2112  may include any number of antennas of any type. For example, the fixture/array may include relatively simple antenna patches or probes and/or may include directional antennas (e.g., highly directional antennas) or other types of antennas. 
       FIG. 22  illustrates further detail of the system of  FIG. 21 . As shown, the DUT ( 2202 ) may be mounted opposite an array of testing antennas ( 2204 ), e.g., inside of the measurement fixture (not shown). The testing antennas may be mounted on an RF absorbing material ( 2206 ). The testing antennas in the array may be in a constant position relative to each other, e.g., the testing antennas may not move relative to each other. For example, the testing antennas may be arrayed in any pattern, such as a grid or radial pattern, among various possibilities. Any combination of types of antennas may be included in the testing array  2204 . 
     In some embodiments, each of the testing antennas may be paired with a diode power detector, e.g., which may translate a wireless signal ( 2208 ) transmitted by the DUT and received by the respective testing antenna into a direct current (DC) voltage, e.g., in order to test the Tx functionality of the DUT under test. The DC voltages may be measured, e.g., by a multi-channel source measure unit (SMU), e.g., connected via one or more cables to the diodes. For example, an array of N×N testing antennas may produce N{circumflex over ( )}2 DC voltage signals. The system may interpret the voltages in order to determine the strength of the RF signal at the location of each of the testing antennas. The system may calculate the far field RF pattern based on the voltages and may store or display the results, e.g., for analysis or characterization of the DUT. 
     In some embodiments, some or all of the test antennas in the test antenna array may be relatively simple and cheap antenna patches (e.g., antenna patch  2210 ). However, one or more other antennas (e.g., horn, dipole, loop, or a directional array antennas) may be included in the array of testing antennas ( 2212 ). For example, horn antenna(s) (and/or antennas of other types) may be used for Rx or Tx measurements, e.g., including parametric measurements requiring a vector signal analyzer (VSA), a vector signal generator (VSG), or a vector signal transceiver (VST), or other test equipment. For example, a horn antenna may be used to transmit a test signal(s), e.g., using a VST, to the DUT under test, and the ability of the DUT to receive the test signal may be tested (e.g., using a data connection of the BATS). The results may be stored and/or displayed for characterization of the DUT. Additionally, or alternatively, the actual received signal may be compared to an expected signal/result (e.g., using one or more thresholds) and a determination may be made to reject (or not) the DUT based on the comparison. Further, in some embodiments, the other antennas (e.g., patch antennas) may also be used for Rx measurements, e.g., to transmit signals for the DUT to receive. 
     In some embodiments, the system may include more than one measurement fixture, e.g., allowing for testing of one or more DUTs in a first fixture while other DUTs are being exchanged for a testing in a different fixture. For example, a DUT may be tested through a plurality of fixtures, e.g. in series, and/or multiple DUTs may be tested concurrently, e.g., in multiple fixtures operating in parallel. Additionally, each fixture may be used at the same time for respective DUTs, e.g., allowing for testing through the chambers in a pipelined and/or automated fashion. 
     In some embodiments, additional equipment may be included in the system. For example, fan cooling may be provided, additional instruments may be included (e.g., to test other features of the DUT), etc. 
       FIG. 23  illustrates a DUT  2302  attached via a socket  2304 . As shown, the socket  2304  may position the DUT at a measurement distance (e.g., in the near field, Fresnel zone, or far field, among various possibilities.) from a measurement antenna array  2306  (multiple arrays may be included). The distance between the DUT and the measurement antenna array (e.g., array of testing antennas) may be fixed or may be adjustable. Further, the relative positions may be adjusted in other ways, e.g., changing angles or alignment between the DUT and antenna array. For example, the DUT may be offset laterally relative to one or more measurement arrays. 
     The socket may serve as an interface to provide power, data, and control connection to the DUT. The socket may also shield the DUT and/or measurement antenna array from interference (e.g., the socket may be RF shielded). The socket may further include RF absorbing materials or otherwise be configured to reduce RF reflections of transmissions between the DUT and the measurement antenna array. 
     The measurement antenna array may be connected through an RF test head  2308  to one or more RF instruments, e.g., RF measurement equipment  2310 . The RF test head and the measurement equipment may perform various measurements of signals received by the measurement antenna array. For example, the RF test head and the measurement equipment may perform DC voltage measurements. Further, the RF test head and the measurement equipment may (additionally or alternatively) perform any combination of phase, modulation, power, frequency, and/or spectrum measurements. 
       FIG. 24  illustrates an exemplary test system including multiple test Rx/Tx instruments. A DUT  2402  may be positioned at a measurement distance from a testing antenna array  2412 . As illustrated, the DUT may include an array of antennas (e.g., configured for beamforming and or MIMO) ( 2402   a ) and a (potentially physically separated) Tx/Rx device  2402   b  (e.g., a processor or controller) for controlling the antennas  2402   a . The DUT antennas  2402   a  (and possibly the Tx/Rx device  2402   b ) may be positioned in a measurement fixture. The antennas (e.g., antenna  2410   a ) may be mounted on RF absorbing material ( 2206 ). The antennas may be arrayed in any pattern and may be any type(s) of antennas. 
     Each antenna of the array of antennas may be connected to one or more Rx and/or Tx test instrument ( 2420   a  and  2420   b ). The test instruments  2420  may be configured to measure power, spectrum (frequency), and/or modulation (e.g., waveform, EVM). Thus, in order to test the Tx capability/performance of the DUT, the signal received by each antenna  2410  of the testing antenna array  2412  may be measured, e.g., while the DUT is transmitting. Similarly, to test the Rx capability of the DUT, signals may be transmitted from one, some, or all antennas  2410  of the array  2412  and the signals received by the DUT (e.g., before or after processing by the Tx/Rx device  2402   b ) may be evaluated by the system (e.g., for power, spectrum, modulation, etc.). 
       FIG. 25  illustrates an exemplary test system including one or more test Rx/Tx instruments switched to test a single element at a time. A DUT  2402  may be positioned at a measurement distance from a testing antenna array  2412 . As illustrated, the DUT may include an array of antennas (e.g., configured for beamforming and or MIMO) ( 2402   a ) and a (potentially physically separated) Tx/Rx device  2402   b  (e.g., a processor or controller) for controlling the antennas  2402   a . The DUT antennas  2402   a  (and possibly the Tx/Rx device  2402   b ) may be positioned in a measurement fixture. The antennas (e.g., antenna  2410   a ) may be mounted on RF absorbing material ( 2206 ). The antennas may be arrayed in any pattern and may be any type(s) of antennas. 
     Each antenna of the array of antennas may be connected by a switch  2530  to one or more Rx and/or Tx test instrument ( 2420 ). Any number of switches  2530  and/or instruments  2420  may be included. The switches  2530  may be used to control which antennas  2410  are active (e.g., to transmit and/or receive) at any given time. Tests of Tx and/or Rx capability of the DUT may be performed as above, e.g., using the active antennas. Tests may be performed with any sequence of active antennas. For example, antennas may be used for testing one at a time, two at a time, 30 at a time, etc., as controlled by the switches  2530 , e.g., a first set of antennas may be used while the switch is in a first position, a second set in a second position, etc. Further, combinations of testing antennas  2410  may be matched to specific functions (e.g., beamforming patterns) of the DUT. Thus, different combinations of testing antennas may be used to test different beamforming patterns or other capabilities. In other words, the Tx or Rx beam of the DUT may steered through several (e.g., known) patterns, and the switches  2530  may switch which antenna(s) is connected to the instrument  2420  and used to test the performance of the DUT for each pattern. The antenna(s) used to test each pattern may be selected in order to best determine the performance of the DUT in that pattern. 
       FIGS. 26 and 27  illustrate alternative shapes of the testing antenna array  2412 . As illustrated in  FIG. 26 , the testing antenna array  2412  may be shaped as a portion of a sphere (e.g., hemispherical, as shown). As illustrated in  FIG. 27 , the testing antenna array  2412  may be parabolic. It will be appreciated that the testing antenna array  2412  may be any shape, including flat/planar (e.g., as illustrated in  FIGS. 21-25 ), cylindrical, diagonal, convex, concave, or any custom shape as desired. 
     Method for Performing Production Testing 
     Over-the-air (OTA) testing of a DUT or DUTs may include performing measurements with an array of testing antennas. In some embodiments, an expected signature or fingerprint of a DUT may be developed, and the expected signature or fingerprint may be used to expedite and/or simplify the testing process. Further, such a signature may allow the size and/or cost of testing equipment to be reduced. During production testing (e.g., during automated production testing (APT)) one or more DUTs may be installed in a testing position and the performance of the DUT(s) may be tested. The performance of a DUT may be compared to the expected signature. Based on the comparison, the APT may determine whether the DUT meets a desired quality standard. Thus, in contrast to performing a complete test/characterization for each pattern/beam, the production testing may simply and quickly test certain measurements that are pre-selected (e.g., in the signature) based on the effectiveness of the measurements for determining the performance of the DUT. 
       FIG. 28  is a simplified block diagram, illustrating an exemplary method for performing production testing of devices with built in antennas, e.g., mmW ICs. It is noted that the method of  FIG. 28  is merely one example of a possible method, and that features of this disclosure may be implemented in any of various methods, as desired. Aspects of the method of  FIG. 28  may be implemented by a system, such as illustrated in and described with respect to the Figures, among other systems and devices, as desired. For example, the method of  FIG. 28  may be implemented by a systems and devices such as shown in  FIGS. 21-27 , among various possibilities. In various embodiments, some of the elements of the methods shown may be performed concurrently, in a different order than shown, may be substituted for by other method elements, or may be omitted. Additional method elements may also be performed as desired. As shown, the method may operate as follows. 
     A signature (e.g., fingerprint) may be developed for a DUT or DUTs (e.g., for production testing of a number of DUTs designed to exhibit similar performance characteristics) ( 2810 ). A signature may be developed for one or more of over-the-air (OTA) Tx, Rx, and/or VST tests. The signature may be a set of expected measurements that may be used to (e.g., simply) determine whether a DUT meets a desired performance standard or standards. The signature may include an expected “field pattern signature” based on calculations of a signal/RF field pattern that would be produced or received by an ideal or perfect DUT and/or based on measurements of another DUT. The field pattern signature may be developed and used for testing at a high level of detail (e.g., including expected values for each antenna of the array of testing antennas) or a reduced level of detail (e.g., including expected values only for the subset of antennas that provide particularly relevant measurements, e.g., a sparse array). A signature may be determined through mathematical methods, empirical methods, and/or computer-generated models (e.g., using artificial intelligence (AI) and/or machine learning (ML)). 
     In some embodiments, developing the signature may include determining which locations for antenna elements of an array of testing antennas may provide (e.g., particularly) relevant measurements (e.g., nulls or peaks, etc.) for each of one or more known antenna patterns, e.g., beams. The locations or subset of antenna elements may represent a sparse array of antennas, e.g., at key locations to measure the most relevant or useful areas of the field generated by the DUT in Tx testing and/or to generate a field to transmit to a DUT for Rx testing. For example, a first subset of antennas may be used for a first antenna pattern (e.g., beamforming pattern) and a second subset of antennas may be used for a second pattern/beam. In other words, the antenna(s) may be selected based on the location in space (e.g., x, y, and z coordinates in a cartesian system) for best performance. For example, for Tx testing, optimal antennas (e.g., antenna locations) for a Tx pattern of the DUT may be selected, e.g., so that antennas at the selected locations may be used for rapid/efficient production testing of the DUT using the same transmission pattern. One or more antennas of the array of testing antennas may be selected, e.g., based on a location with the strongest (and/or the weakest) signal for a number of known patterns (e.g., transmission beams of the DUT). Optimal antenna locations may be determined for any number of transmission patterns, and the selected antennas may be used to test as many transmission patterns as desired during production testing. 
     Further, the signature may include expected measurements associated with each antenna pattern. For example, for OTA Tx testing, the signature may include expected measurement values for each antenna location in the sparse array (note that expected values for each location in a full array may also be included). For example, for OTA Rx testing, the signature may include values for output data and/or quality metrics. 
     The signature may include any number of receive pattern definitions, e.g., codewords or beamforming patterns to use with test signals during Rx testing. Each receive pattern definition may include expected measurements, output signals, and/or quality metrics that would be generated by an ideal DUT in response to a transmission using the receive pattern definition. Similarly, the signature may include any number of transmit pattern definitions, e.g., test inputs and associated codewords or beamforming patterns to use during Tx testing. Each transmit pattern definition may include expected measurements for any combination of antenna (e.g., locations) in the array of testing antennas produced in response to a transmission by an ideal DUT using the transmit pattern definition. 
     The transmit and/or receive pattern definitions may be developed in order to evaluate the presence/absence of faults (e.g., problems) in the DUT. For example, the transmit and/or receive pattern definitions may be designed to expose common faults and/or faults of particular concern. An example of a fault that may be of particular concern may be a fault that under some conditions could cause the DUT to violate on or more standards, such as requirements related to spectrum occupancy or maximum permissible exposure (MPE). For example, empirical evaluation and/or mathematical or computer modeling of one or more (e.g., faulty) DUTs that may violate such a standard may be used to determine transmit pattern definitions that are likely to expose such faults in actual DUTs during production testing. Thus, the signature may include pattern definitions that are likely to expose faults and may further include associated expected measurements. The expected measurements may represent the measurements of an ideal or high quality DUT, e.g., which would not exhibit the fault(s). Therefore, by comparing, actual measurements to expected measurements, it may be determined whether or not a DUT exhibits the fault. 
     In some embodiments, a signature may be developed based on empirical testing or characterization of one or more model, prototype, or exemplary DUTs, e.g., DUTs of a known or high quality. For example, a relatively detailed characterization of one or more DUTs may be used to select a set of antenna elements to use for (e.g., relatively rapid) production testing of subsequent DUTs. 
     In some embodiments, the signature may be based on calculations and/or modeling of an ideal or (e.g., theoretical, hypothetical) perfect DUT. For example, a signature may be developed using mathematical methods (e.g., physics and equations representing electro-magnetic behavior), and/or computer-generated models (AI and/or ML). Such AI and/or ML may be based at least in part on empirical measurements, e.g., of model DUTs. Further, models may be developed and refined using near-field, Fresnel zone, and/or far field measurements of DUTs (e.g., in production and/or during R&amp;D). 
     In some embodiments, the signature may be based on any combination of testing/characterization of prototypes, calculations, and/or modeling. For example, ML/AI may be used to improve a signature as more data is gathered. Further, computer-generated models (and associated signatures) may be developed and refined based on testing DUTs in production and/or testing prototypes in research and development 
     One or more DUTs (e.g., mmW ICs, among various possibilities) may be installed in testing position(s) ( 2820 ). At least a first DUT may be connected (e.g., via wired and/or wireless connections) for power, data and/or control. The connection(s) may be configured to drive the antennas of the DUT for Tx testing and/or to receive signals received by the DUT for Rx testing. The first DUT may be attached to a tray, which may be fit into a first measurement fixture. 
     Antennas in one or more arrays of testing antennas may be located at locations that are expected to provide relevant measurements during testing, e.g., based on the signature. 
     The test system may perform testing of the DUT(s) ( 2830 ). The testing may include over-the-air (OTA) Tx, Rx, and/or VST tests of the DUT. The testing may further include testing of one or more connections (wired and/or wireless) of the DUT. Some tests may use a combination of over-the-air and wired techniques or connections. 
     Vector signal transceiver (VST) testing may determine the directional/beamforming capability of the DUT, e.g., as a transmitter, receiver, or both. In other words, for Tx testing, an input signal may be provided to the DUT to cause the DUT to transmit a directional beam, and the array of testing antennas may be configured to measure the beam. For example, antennas in the direction of the beam may be expected to measure relatively high power signals and antennas in other directions (e.g., outside of the expected beam) may be expected to measure low or zero power. For Rx testing, the DUT may be configured by a control signal to tune at least some of its antennas to receive from a certain direction, a signal may be transmitted from the array of testing antennas from that direction, and the strength of the signal received by the DUT may be determined based on an output signal generated by the DUT. 
     OTA Rx testing may include determining whether (e.g., the extent to which) the DUT has appropriate sensitivity, selectivity or immunity to interference. A wireless test signal may be transmitted from the array of testing antennas to the DUT. The test signal may be transmitted with a receive pattern definition, e.g., a beamforming pattern associated with the signature. The DUT may receive and decode the modulation signal. The DUT may directly report the recovered data and/or the modulation signal. Additionally, or alternatively, the DUT may perform a quality evaluation of the signal and may report the quality of the recovered modulation/data. For example, the DUT may determine and report one or more of various quality metrics, e.g., bit error rate (BER), frame error rate (FER), signal noise and distortion (SINAD), etc.). The data and/or metrics may be reported over a wired connection or a wireless connection. In other words, for this test, the DUT may receive a wireless signal from (transmitted by) the antennas in the measurement fixture and convert that input signal into either a digital representation of the received signal (e.g., IQ samples) or a measurement of the quality of the signal, and may provide the signal or measurement for evaluation. A digital representation of the received signal may be output (e.g., from the DUT to the test system) at any desired level of detail. For example, data may be output for each individual antenna of the DUT, or data from the antennas of the DUT may be combined and/or summarized as desired. 
     In some embodiments, the test signal transmitted to the DUT for OTA Rx testing may include one or more impairment. In other words, a receive pattern definition may include any number of impairments. Impairments may be introduced deliberately, e.g., to test the ability of the DUT to perform Rx functions in real world circumstances where impairments may occur. Testing impairments may include, low power, interference, noise, and/or a beamforming impairment, e.g., a poorly/inaccurately formed beam. For example, a code word or antenna pattern used to transmit a beamformed signal (e.g., with a beamforming impairment) to the DUT may be modified, e.g., in order to misdirect or otherwise poorly form the transmitted beamformed signal. 
     OTA Tx testing may include determining whether (e.g., the extent to which) the DUT accurately reproduces an intended signal as an RF signal, e.g., at the correct power, frequency, beam, timing, etc. For example, EVM testing may be performed. Similarly, spectrum occupancy, power, and/or other characteristics may be measured. In other words, the testing may include causing the DUT to transmit one or more signals based on a test input(s) and measuring the wireless signals transmitted by the DUT. The wireless signals transmitted by the DUT may be measured with the array(s) of testing antennas and any instruments connected to those testing antennas. The measurements of the wireless signals may be compared to one or more expected measurements (e.g., based on the signature) and differences of the measurements in comparison to the expected measurements may be determined. Note that the expected measurements may be associated with individual antennas (or antenna locations) of the array(s) of testing antennas. Exemplary OTA Tx measurements may include: voltages measured by one or multiple testing antenna(s), e.g., and associated diodes; error vector magnitude (EVM); spectrum occupancy (e.g., what frequencies are produced by the DUT, including harmonics, etc.). Such measurements may be taken using any antenna or antennas of the array of testing antennas. 
     For example, OTA testing may include causing the DUT to transmit a beamformed signal, e.g., using a specific pattern definition. The pattern definition may be developed in such a way that a DUT with a common fault (e.g., or type of fault) may fail spectrum occupancy requirements in at least one area of a transmitted beam, e.g., based on harmonics. The testing may include measuring spectrum occupancy in that area. 
     A quality of the DUT may be determined ( 2840 ), e.g., based in part on comparison to the signature. For example, the DUT may be scored on one or more metrics (e.g., RF transmission, RF reception, beamforming, data connection, power connection, etc.). Additionally, or alternatively, the system may determine whether or not the DUT passes one or more quality criteria (e.g., based on comparison of measurements to a standard based on the signature, etc.). Such a test may be a binary (e.g., pass/no-pass) screening test, e.g., as may be useful for rapid screening of (e.g., large numbers of) DUTs. 
     For example, the DUT may be evaluated by comparing measurements, e.g., performed as part of OTA Tx, Rx, and/or VST testing, to expected measurements based on the signature. For example, the system may compare a measured pattern of measurements (e.g., quality metrics, voltages, EVM, etc.) to an expected pattern of measurements, e.g., based on the signature. The system may make a determination of the quality or performance of the DUT based on the comparison of the measured performance to the expected/ideal measurements, e.g., based on the signature. Such a determination may be a relatively quick yes/no or go/no-go comparison. In other words, if the measurements are within a tolerance band of the ideal/expected measurements, the DUT may be determined to be of sufficient quality. Conversely, a DUT associated with measurements outside of the tolerance band may be determined to not meet a quality standard, and may be rejected, repaired, or studied further. 
     Such a determination may be based on comparing one or more of the measurements to one or more thresholds. Thresholds may be applied to individual, average/mean, median, percentile, standard deviation, or other values. For example, a DUT may be rejected (e.g., fail a production test) if a single measured value (e.g., or other number of measured values) is different from the ideal value(s) by more than a certain threshold. In other words, if the measurement measured by a single antenna (e.g., of the array of testing antennas during Tx testing) differs from an expected value for that antenna measurement by more than a threshold value, the DUT may be rejected. The threshold may be specific to each antenna/point, a group of points, or may be generalized. For example, each individual point may have an associated individual threshold or all points may share a single threshold, or any number of groups of points may be associated with threshold values, etc. Similarly, if output data of a single antenna of the DUT (e.g., during Rx testing) differs from an expected value for that antenna measurement by more than a threshold value, the DUT may be rejected. 
     Additionally or alternatively, a DUT may be rejected if the average value of the measured points is different (e.g., by at least a threshold amount) from the expected average value. For example, an average value of the absolute value of the difference between multiple respective measured values and associated respective expected values may be compared to a threshold. 
     In some embodiments, a DUT may be rejected if the variance (e.g., or standard deviation, etc.) of the difference between measurements and ideal values is higher than a threshold. As another possibility, a DUT may be rejected if a threshold fraction of values (e.g., for the DUT overall, or in one or more sub-regions or sub-portions of the DUT) differ from ideal values by more than a threshold. Other comparisons are possible according to some embodiments. 
     Additional Information 
     In some embodiments, the OTA testing may be performed with the array of testing antennas in the Fresnel zone. For example, during Tx testing, the observed patterns from measurements (e.g., DC voltage measurements, among various possibilities) in the Fresnel zone may be used to compute a far field beam pattern. The computed far field pattern may be used for characterization of the DUT, among various possibilities. The observed patterns from measurements in the Fresnel zone may be compared to an (e.g., previously stored or computed) expected signature/pattern. Alternatively, or additionally, the computed far field characterization may be compared to a calculated or previously tested model DUT&#39;s far field testing results. A comparison may use any number of thresholds and/or any statistical techniques. 
     In some embodiments, the OTA testing may performed in the near and/or far field regions. 
     In some embodiments, OTA testing may include measuring transmit and/or receive parameters such as power, frequency, phase, modulation quality, spectrum occupancy, sensitivity, selectivity, image rejection, spurious responses, blocking, etc. using an array of testing antennas. Performance as a function of distance from the DUT may represented by a bathtub curve (e.g., in Tx testing, too close to the DUT, a test antenna may be overloaded; too far from the DUT, the strength of signal from the DUT may be small relative to noise/interference). The bathtub curve may also apply in Rx testing. 
     In some embodiments, during Tx testing, signals from multiple elements of the array of testing antennas may be combined, e.g., using a beamforming algorithm, and the combined signal may be tested. In some embodiments, individual signals from individual antennas may be tested individually. 
     In some embodiments, the testing may be performed automatically, e.g., in response to placement of the DUT in the system and connection to the power/control connections. 
     In some embodiments, the testing may further include testing of the power and data connections of the DUT (e.g., simultaneously or sequentially with the over-the-air testing of the RF functions). In some embodiments, power and data connections may also be tested over the air. 
     In some embodiments, multiple transmit and/or receive pattern definitions may be used during production testing of a DUT. For example, a first receive pattern definition may be used to some aspects of a DUT&#39;s performance and a second receive pattern definition may be used to test second aspects. Similarly, multiple transmit pattern definitions may be used to test various aspects of performance. 
     In some embodiments, multiple DUTs may be tested. For example, multiple DUTs may be installed in testing positions, and may be concurrently or sequentially tested. Different field pattern signatures may be used for DUTs in different testing positions. Similarly, the method may include causing multiple DUTs to be sequentially installed in testing positions and tested, e.g., automatically. 
     In some embodiments, the DUT&#39;s wireless capabilities may be tested for phase, power, spectrum, frequency, and/or modulation. Such capabilities may be tested in transmission and/or reception. 
     In some embodiments, a signature may be determined prior to and/or during testing. For example, a signature may be refined over time, e.g., as more DUTs are tested. 
     In the following, exemplary embodiments are provided. 
     In one set of embodiments, a semiconductor test system (STS) may comprise: a processing element; an anechoic chamber; a fixed conductive interface, wherein the fixed conductive interface is configured to position a device under test (DUT) inside the anechoic chamber, wherein the fixed conductive interface provides power and data connections to the DUT; and an array of antennas, wherein the array of antennas is inside the anechoic chamber, wherein the array of antennas is configured to test radio frequency (RF) characteristics of the DUT. 
     In some embodiments, the array of antennas may be in a fixed location, wherein the fixed location is within the Fresnel region. 
     In some embodiments, the location of the array of antennas may be adjustable. 
     In some embodiments, each respective antenna of the array of antennas may be connected to a respective diode detector, wherein each diode detector converts a measurement of field strength to a respective direct current (DC) voltage measurement. 
     In some embodiments, the STS may be configured to compare the DC voltage measurements to a field pattern signature, wherein the comparison is useable for production testing or screening of the DUT. 
     In some embodiments, the STS may be configured to compute a far field beam pattern, wherein the far-field beam pattern is based on the DC voltage measurements. 
     A further exemplary set of embodiments may include a non-transitory computer accessible memory medium comprising program instructions which, when executed at a device, cause the device to implement any or all parts of any of the preceding examples. 
     A still further exemplary set of embodiments may include a computer program comprising instructions for performing any or all parts of any of the preceding examples. 
     Yet another exemplary set of embodiments may include an apparatus comprising means for performing any or all of the elements of any of the preceding examples. 
     Although the embodiments above have been described in considerable detail, numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.