Test measurement systems and test methods for devices under test

Abstract

a test and measurement system including a test and measurement instrument having an input channel, a reference array of antennas connected to the input channel, and one or more processors within the test and measurement instrument, the one or more processors configured to execute a program that causes the one or more processors to receive a first signal from a phased array of antennas connected to a device under test, directed toward a first side of the reference array, and receive a second signal from the phased array of antennas connected to the device under test, directed toward a second side of the reference array, without moving the device under test, the phased array, or the reference array; a method of testing a device under test using a phased array of antennas, the method comprising: tuning the phased array to a first position on the first side of the reference array of antennas by adjusting the phase of each antenna in the phased array; receiving the first signal from the device under test at the first position; tuning the phased array to a second position on the second side of the reference array of antennas; and receiving the second signal from the device under test at the second position. The test and measurement instrument has at least two input channels, an array of at least two reference antennas each connected to one of the input channels, and one or more processors within the test and measurement instrument, the one or more processors configured to execute a program that causes the one or more processors to receive input signals from the one or more reference antennas and measure the input signals from the one or more reference antennas.

Description

Technical Field

[0001] This disclosure claims the benefit of U.S. Provisional Patent Application No. 63 / 120,689, filed Dec. 2, 2020, entitled “System and Method for Phased Array Wireless Testing Using a Multi-Channel Oscilloscope,” which is hereby incorporated by reference in its entirety.

[0002] This disclosure relates to a test apparatus using a phased array antenna, and more particularly to using a test apparatus having an array of reference antennas.

Background Art

[0003] The use of millimeter wave (mm wave) frequency signals has been increasing. Due to the large path loss of signals at these frequencies, a phased array antenna, also called a beamformer, is used to direct the EM (electromagnetic) energy from a transmitter to a specific point in the space where the signal is received. The signal may be radio frequency (RF) or optical. The process of beamforming often involves a unique method that requires testing and tuning. To avoid cable loss, integrating a mm wave phased array antenna into a beamforming network makes cable measurement impossible. Therefore, it is necessary to measure these beamformer / antenna networks wirelessly.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Typically, a beamformer IC (integrated circuit) and its integrated phased array antenna are directed towards a reference antenna connected to test measurement equipment such as a network analyzer or spectrum analyzer. Current processes involve adjusting the phase and amplitude of each antenna element in the phased array so that their signals arrive simultaneously. This requires the device under test (DUT), IC, and phased array to rotate 180 degrees so that the rotating beam pattern can be measured each time the beam direction changes. This is time-consuming and can lead to inaccuracies if the DUT is not rotated precisely.

[0006] The embodiments of the disclosed apparatus and method address the shortcomings of the prior art. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows an embodiment of a test measurement system including an array of reference antennas. [Figure 2] Figure 2 shows a flowchart of an embodiment in which the device under test is tested using a reference antenna array. [Figure 3] Figure 3 shows a flowchart of an embodiment in which the device under test is tested using a reference antenna array. [Figure 4] Figure 4 shows an example of the waveforms produced when the phased array of the device under test is directed towards a single reference antenna. [Figure 5] Figure 5 shows an example of a waveform used to determine the center point of the reference antenna array. [Figure 6] Figure 6 shows an example of a waveform resulting from orienting a phased array towards the center point of a reference antenna array. [Figure 7] Figure 7 shows a diagram used to determine the phase offset for an antenna in a phased array in one example. [Figure 8]Figure 8 shows an example of waveforms generated from a phased array of the device under test, tuned to the first reference antenna, without moving the device under test. [Figure 9] Figure 9 shows an example of waveforms generated from a phased array of the device under test, tuned to a second reference antenna, without moving the device under test. [Figure 10] Figure 10 shows an example of a waveform resulting from varying the amplitude of an antenna in a phased array of the device under test in order to determine the interference source-to-signal ratio. [Figure 11] Figure 11 shows a graph comparing the use of a current single boresight antenna with the use of a reference antenna array. [Modes for carrying out the invention]

[0008] This description uses several terms as defined in this application. The term “test and measurement apparatus” means apparatus used to test devices such as integrated circuits and circuit boards (all of which are referred to in this application as “Device Under Test (DUT)”). This apparatus may include, but is not limited to, oscilloscopes, including multi-channel and mixed-signal (MSO) oscilloscopes; apparatus including arbitrary waveform or waveform generators; analyzers, including spectrum analyzers, parameter analyzers, network analyzers, and modulation analyzers; and multimeters.

[0009] The term "phased array" refers to a phased array of antennas connected to the DUT, and this DUT is sometimes referred to as the device under test "having" a phased array. The terms "reference array" and "reference antenna" refer to antennas connected to a test measurement device that receives signals from the phased array on the DUT. The phased array may transmit RF signals or light.

[0010] Currently, millimeter-wave technology testing is performed by using a phased array to direct the beam formed by a beamformer DUT (Digital Output Unit) towards a single reference antenna, then rotating the DUT 180 degrees and measuring the beam pattern. Since the DUT needs to be rotated 180 degrees each time the beam direction being tested is changed, it is necessary to be able to tune and measure the beam as the direction changes.

[0011] In contrast, embodiments of the present invention use multiple reference antennas patterned at equal intervals around the DUT. Instead of rotating the DUT, the system tunes the beam and measures the beam as its direction changes. Typically, the tuning process is performed once to the right and once to the left of the array's center point, and the location where the beamformer phased array is tuned depends on the arrangement of the reference antennas. The location where tuning is performed also depends on whether or not a boresight antenna is present.

[0012] If a boresight antenna is present, the position where the beamformer phased array is tuned is midway between the boresight antenna and the first antennas on either side. For example, if the antennas on either side are offset at a 20-degree angle from the boresight antenna, the position will be 10 degrees from the boresight. In this example configuration, there may be three antennas in the array, one at the boresight and one on each side for symmetry. Any number of antennas can be placed on either side, limited only by the number of channels in the test measurement device. For example, in an 8-channel device, the antenna array may have 3, 5, or 7 antennas, provided that symmetry on either side of the boresight is maintained. More than 8 input channels can be provided using multiple test measurement devices, thus supporting more than 8 reference antennas. Multiple test measurement devices may be synchronized to provide time alignment of the measurement signals.

[0013] For arrays without boresight antennas, such as those with 2, 4, 6, or 8 antennas, the phased array tunes to the antennas on either side closest to the center point between the two central antennas. In all cases, the beamformer is tuned slightly to each side of the array. This is sometimes referred to as "partial tuning" in this application. Over-tuning would cause a large change in the pattern, and the process would not function. This allows the beamforming process to be realized by the beamforming DUT being tested and tuned.

[0014] Figure 1 shows an embodiment of a test measurement system for testing a beamforming algorithm generated by a beamformer DUT. The DUT 10 has a phased array 12 consisting of multiple antennas and may be connected to one or more test measurement devices that can interact with the DUT and array as needed. The test measurement device 14 may include a computer and, although not shown, should be noted that the test measurement device 14 typically consists of a device having the same or similar components as the test measurement device 20. The test measurement device 14 may be able to test a DUT having both a transmitter and a receiver, and therefore the test measurement device 14 is optional.

[0015] The test measurement device 20 has an array consisting of multiple reference antennas, such as antenna 16 connected to input channel 22. The illustrated embodiment has eight reference antennas, each connected to its respective channel on the test measurement device 20. Other numbers of antennas may be used in the reference array, and Figure 1 is merely an example. Since each reference antenna is typically connected to one input channel of the test measurement device, the number of reference antennas is limited only by the number of available channels.

[0016] In addition to channel 22, test measurement device 20 generally includes one or more processors 24 configured to execute code (programs) that cause the processor to perform specific tasks, and a memory 26 that stores code and data resulting from the operation of the antenna array. Device 20 includes at least one user interface 28, which may include a touch screen, a display, and user operating devices such as knobs and buttons.

[0017] In the following description, experiments performed using a reference antenna array consisting of two horn antennas are described, on the condition that the methods described in the present application are applied to any number of reference antennas that can be connected to different input channels of a test measurement device such as an oscilloscope. A general embodiment for testing a beamformer DUT is described together with the experimental results. FIG. 2 shows an embodiment of a method for testing a beamformer DUT. Note that in this system and procedure, the DUT performs part of the process. The DUT may be composed of a beamformer IC or a beamformer system on a board and may be configured to supply various signals described below before this procedure, or may be placed under the control of another device during this test. As shown in FIG. 1, the DUT may receive environmental setting, programming, and control using a test measurement device connected to the DUT as part of the system.

[0018] In this experiment, a 4x phased array antenna was connected to a beamformer IC and an up-converter. As described above, the antennas used in the phased array may be more or less numerous, which is just an example. An arbitrary waveform generator (AWG) generates a 2 GHz IF (intermediate frequency) signal, which is up-converted to a 25 GHz 5G signal. The reference antennas were connected to separate channels of an oscilloscope.

[0019] In this experiment, each horn reference antenna was connected to its respective channel on an oscilloscope and down-converted back to 2 GHz. These reference antennas were located approximately 45 inches (about 114 centimeters) from the phased array, and 36 inches (about 91 centimeters) apart. First, regardless of the number of reference antennas, the beamformer DUT must be calibrated relative to the reference antennas, as shown in Figure 2, 30. After the initial calibration, additional DUTs can be tested using the same phased array, so calibration is not required each time. In the experiment, the phased array was pointed directly at one of the multiple reference antennas, and for the beamforming DUT, all antennas within that phased array were set to zero phase. Figure 4 shows the results.

[0020] The display is common to all results. The top signal 50 shows the spectral display for the first reference antenna, and the second signal 52 shows the spectral display for the second reference antenna. The third signal 54 shows the waveform display for the first reference antenna, and the fourth signal 56 shows the waveform display for the second reference antenna. This result can be used later in the process to verify the calibration by looking at the result for the first reference antenna.

[0021] Since the method of the embodiment uses multiple antennas, the next step may include a process to determine the position of the center point of the reference array, depending on the configuration of the reference array, as described above. If there is an antenna at the boresite, either the antenna or the DUT should simply be positioned to obtain the maximum amplitude during calibration. If there is an antenna at the boresite, an even number of reference antennas will be located on both sides of the boresite antenna to maintain symmetry. In the case of an 8-channel test and measurement device, there is a boresite antenna and three reference antennas on each side thereof. If all 8 channels of an 8-channel device are to be used, it is also possible to place four antennas on each side of the center point without a boresite antenna. If there is no boresite antenna, calibration is performed by equalizing the amplitude and phase of the two antennas closest to the center point, as follows.

[0022] Next, the DUT transmits a calibration signal, and the phased array is directed until the phase and amplitude of the signal are the same at each reference antenna. In the experiment, a sine wave was used until the phase and amplitude of the signals received by the two reference antennas matched, as shown in Figure 5. Figure 6 shows the signal obtained when the DUT transmits a 5G signal.

[0023] Before testing the beamformer, phase adjustment was necessary to move the beam from the center point to the reference antenna. An example is shown in Figure 7. In this particular experiment, the arrival angle of the plane wavefront relative to the array plane is approximately 18 degrees. The hypotenuse of the triangle between antenna 1 and antenna 2 is 230 mils (5.84 millimeters: half a wavelength at 25 GHz). Then, the base of the right triangle is 71 mils (1.80 millimeters), or approximately 55.6 degrees. The beamformer used in the experiment is adjustable in increments of approximately 5.6 degrees, so setting the phase to 10 results in approximately 56 degrees. Antenna 4 has the largest delay, so its phase is set to 0. The phase delay of antenna 3 is set to 10, the phase delay of antenna 2 to 20, and the phase delay of antenna 1 to 30.

[0024] In the experiment, we used the ADMV4801 beamformer IC from Analog Devices. This was programmed for the right-hand reference antenna with the phase offset described above. The left-hand reference antenna has the same value, but antennas 1 through 4 are swapped. With the phased array set in place and calibrated as described above, the beamformer was tuned to the left-hand horn antenna, and the results are shown in Figure 8. Comparing Figure 8 with the results in Figure 4, it can be seen that these results match even though the phased array is tuned but not moved from its position. Figure 9 shows the results after tuning the beamformer to the right-hand horn. Again, these results are obtained by tuning without rotating the phased array and moving it at various angles.

[0025] Returning to Figure 2, the tuning process at 32, the receiving process at 34, and then the measuring process at 36 are repeated until, at 38, the beamformer is tuned to both sides of the reference antenna array. Figure 3 is essentially the reverse of this process to test reception at the DUT. In this process, at 40, phase adjustment is applied to tune the reference antenna, and then at 42, the reference antenna transmits a signal to the phased array / DUT. In 44, This may include measuring the signal received by the beamformer to test the DUT's receiving capability.

[0026] The Error Vector Magnitude (EVM), a measure of how accurately a wireless system transmits symbols within its constellation, was approximately 1.8% for this phased array antenna in this experiment.

[0027] Another aspect of MIMO (Multiple-In Multiple Out), besides beamforming, is its ability to create nulls in the direction of interfering signals by adjusting the amplitude of the channels. In this experiment, the reference antenna on the right was treated as the interferer. The transmit amplitudes of antennas 1 and 4 were reduced. The resulting signal, shown in Figure 10, decreases from the reference trace to the trace of channel 4, appearing to decrease by approximately 6 dB. This is the signal-to-interferor ratio. The bottom trace, 60, is the saved reference trace. As the amplitude on the antenna decreases, trace 62 changes from trace 60 to 62 in the figure. Trace 64 is connected to the reference antenna. In this process, it is undesirable to change the amplitude of trace 64 too much. However, a small loss of amplitude in 64 in the main lobe results in a much larger reduction in the side lobes. This allows us to determine when trace 62 reached the amplitude of the signal-to-interferor ratio.

[0028] In this way, a DUT operating in the millimeter-wave frequency range can be tested without moving the DUT for each beam. This tuning allows the DUT to remain in the same location and the phased array to be tuned relative to each reference antenna.

[0029] Figure 11 shows a comparison of tuning the DUT to a single antenna (curve 70) and partial tuning to multiple antennas (curve 72). Curve 74 shows the results when the DUT is rotated. This is because, Compared to curve 70, curve 72 is a curve with a shape very similar to curve 74. This demonstrates that the technique of using multiple reference antennas without moving the DUT works very well.

[0030] Embodiments of the disclosed technology can operate on a specially programmed general-purpose computer, including specially created hardware, firmware, digital signal processors, or processors that operate according to programmed instructions. The terms “controller” or “processor” in this application mean microprocessors, microcomputers, ASICs, and dedicated hardware controllers, etc. Embodiments of the disclosed technology can be implemented by one or more computers (including monitoring modules) or other devices, using computer-readable data such as program modules and computer-executable instructions. Generally, program modules include routines, programs, objects, components, data structures, etc., which, when executed by a processor in a computer or other device, perform specific tasks or implement specific abstract data formats. Computer-executable instructions may be stored on computer-readable storage media such as hard disks, optical disks, removable storage media, solid-state memory, RAM, etc. As will be understood by those skilled in the art, the functions of the program modules may be combined or distributed as needed in various embodiments. Furthermore, these functions can be embodied in whole or in part in firmware or hardware equivalents such as integrated circuits or field-programmable gate arrays (FPGAs). One or more aspects of the disclosed technology can be more effectively implemented using specific data structures, such data structures are considered to be within the scope of computer-executable instructions and computer-usable data described herein.

[0031] The disclosed embodiments may, in some cases, be implemented in hardware, firmware, software, or any combination thereof. The disclosed embodiments may also be implemented as instructions carried or stored in one or more computer-readable media that can be read and executed by one or more processors. Such instructions may be referred to as computer program products. The computer-readable media described herein means any medium accessible by a computing device. For example, but not limited to, computer-readable media may include computer storage media and communication media.

[0032] Computer storage media means any medium that can be used to store computer-readable information. Examples of computer storage media include, but are not limited to, random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory and other memory technologies, compact disc read-only memory (CD-ROM), DVD (Digital Video Disc) and other optical disc storage devices, magnetic cassettes, magnetic tapes, magnetic disk storage devices and other magnetic storage devices, and any other volatile or non-volatile removable or non-removable media implemented by any technology. Computer storage media exclude signals themselves and temporary forms of signal transmission.

[0033] A communication medium means any medium that can be used for the communication of computer-readable information. Examples of communication mediums, though not limited to them, include coaxial cables, fiber optic cables, air, or any other medium suitable for the communication of electrical, optical, radio frequency (RF), infrared, sound, or other forms of signals.

[0034] In addition, the description of this application refers to certain features. It should be understood that the disclosures herein include all possible combinations of these particular features. Where a particular feature is disclosed in relation to a particular aspect or example, that feature may, to the extent possible, also be used in relation to other aspects and examples.

[0035] Furthermore, when this application refers to a method having two or more defined steps or processes, these defined steps or processes may be performed in any order or simultaneously, as long as the circumstances do not rule out such possibilities. Examples

[0036] The following examples are provided that are useful for understanding the technology disclosed herein. These embodiments may include one or more of the examples described below, or any combination thereof.

[0037] Embodiment 1 is a test measurement system comprising a test measurement device having an input channel, a reference array of antennas connected to the input channel, and one or more processors within the test measurement device, wherein the one or more processors are configured to execute a program that causes the one or more processors to perform the following processes: receiving a first signal directed from a phased array of antennas connected to the device under test towards the first side of the reference array, and receiving a second signal directed from a phased array of antennas connected to the device under test towards the second side of the reference array, without moving the device under test, the phased array, or the reference array.

[0038] Example 2 is the test measurement system of Example 1, wherein the test measurement device receives calibration signals from the phased array on the first side and the second side of the reference array until the received signals on each side match those on the other side.

[0039] Example 3 is a test measurement system according to either Example 1 or 2, wherein the test measurement device receives the calibration signal with a boresite antenna in the reference array until the amplitude of the calibration signal is maximized.

[0040] Example 4 is a test measurement system according to any of Examples 1 to 3, wherein the reference array does not have a boresight antenna, and the device under test is configured to set each of the antennas in the phased array to zero phase, determine the center point of the reference array, and orient the phased array toward the center point of the reference antenna array.

[0041] Example 5 is a test measurement system of any of Examples 1 to 4, wherein the device under test is further configured to reduce the amplitude of the signal for one or more of the phased array antennas until the main beam begins to decrease, and to set the signal-to-interference ratio to be equal to the amount by which the amplitude has been reduced.

[0042] Example 6 is a test and measurement system according to Examples 1 to 5, the test and measurement system further comprising a second test and measurement device connected to the device under test.

[0043] Example 7 is the test measurement system of Example 6, wherein the second test measurement device has an arbitrary waveform generator.

[0044] Example 8 is a test measurement system according to any of Examples 1 to 8, wherein the phased array transmits an EM signal, which is either a 5G RF signal or an optical signal.

[0045] Embodiment 9 is a method for testing a device under test using a phased array consisting of multiple antennas, comprising: a process of tuning the phased array to a first position on the first side of a reference array consisting of multiple antennas by adjusting the phase of each of the antennas in the phased array; a process of receiving a first signal from the device under test at the first position; a process of tuning the phased array to a second position on the second side of the reference array consisting of multiple antennas; and a process of receiving a second signal from the device under test at the second position.

[0046] Example 10 is the method of Example 9, wherein the reference array does not have a boresight antenna, the first position includes the position of the first antenna on the reference array closest to the center point of the reference array, and the second position includes the position of the second antenna on the reference array closest to the center point.

[0047] Example 11 is the method of either Example 9 or Example 10, wherein the first position includes a position midway between the boresite antenna and the antenna closest to the boresite antenna on the first side of the reference array, and the second position includes a position midway between the boresite antenna and the antenna closest to the boresite antenna on the second side of the reference array.

[0048] Example 12 is a method of any of Examples 9 to 11, further comprising the process of tuning each of the antennas in the reference array using phase adjustment, the process of transmitting a signal from the reference array to the phased array, and the process of measuring the signal received by the DUT.

[0049] Example 13 is a method of any of Examples 9 to 12, further comprising the steps of: setting each of the antennas in the phased array to zero phase; determining the center point of the reference array which does not have a boresight antenna; and oriented the phased array toward the center point of the reference array, thereby calibrating the phased array.

[0050] Example 14 is the method of Example 13, wherein the process for determining the center point of the reference antenna array includes the process of setting each of the antennas in the phased array to zero phase, and the process of adjusting the position of the phased array until the phase and amplitude of the sinusoidal signal are the same at the antenna in the reference array that is closest to the center points on each side of the reference array.

[0051] Example 15 is one of the methods of Examples 9 to 14, further comprising the steps of: directing the phased array directly at a designated reference antenna during calibration; measuring the signal received by the designated reference antenna as a calibration signal; and comparing the calibration signal with the signal received by the designated antenna during testing, thereby verifying the calibration.

[0052] Example 16 further comprises a method of any of Examples 9 to 14, comprising the steps of: reducing the amplitude of one or more signals of the phased array antenna until the main beam begins to decrease; and setting the signal-to-interference source ratio to an amount equal to the amount by which the amplitude has been reduced, for determining an optimal signal-to-interference source ratio for a device under test.

[0053] Embodiment 17 is a test and measurement apparatus comprising at least two input channels, an array of at least two reference antennas each connected to one of the input channels, and one or more processors within the test and measurement apparatus, wherein the one or more processors are configured to execute a program that causes the one or more processors to perform the processing of receiving input signals from one or more of the reference antennas and the processing of measuring the input signals from one or more of the reference antennas.

[0054] Example 18 is the test measurement apparatus of Example 17, further comprising a display, and the program further causes one or more processors to perform the process of displaying data from one or more of the reference antennas on the display.

[0055] Example 19 is a test and measurement apparatus according to either Example 17 or Example 18, wherein the reference antenna array has a boresite antenna and an equal number of antennas on both sides of the boresite antenna.

[0056] Example 20 is a test and measurement apparatus according to any of Examples 17 to 19, wherein the reference antenna array has an equal number of antennas on both sides of the center point of the array.

[0057] All functions disclosed in the specification, claims, abstract and drawings, and all steps in any method or process disclosed, may be combined in any combination, except where at least some of such functions or steps are mutually exclusive. Each of the functions disclosed in the specification, abstract, claims and drawings may be replaced by an alternative function that serves the same, equivalent or similar purpose, unless otherwise specified.

[0058] For the sake of explanation, specific embodiments of the present invention have been illustrated and described, but it should be understood that various modifications are possible without deviating from the gist and scope of the present invention. Therefore, the present invention should not be limited to anything other than the appended claims.

Claims

1. A test and measurement device having an input channel, A reference array consisting of multiple antennas connected to the above input channel and spaced apart from each other, One or more processors in the above-mentioned test and measurement device and Equipped with, The one or more processors A process of receiving as a first signal using the reference array a beam directed from a phased array of an antenna connected to the device under test to a first position at a first distance away in a first direction from the physical center point of the reference array, Without moving the device under test, the phased array, or the reference array, the process involves receiving as a second signal using the reference array a beam directed from the phased array of the antenna connected to the device under test to a second position located at a second distance away from the center point of the reference array in a second direction different from the first direction, in a second direction, without moving the device under test, the phased array, or the reference array. A test and measurement system configured to execute a program that causes one or more of the above-mentioned processors to perform the above task.

2. The test measurement system according to claim 1, wherein the test measurement system is calibrated by receiving a calibration signal beam from the phased array at a first antenna and a second antenna located around the center point of the reference array, and adjusting the arrangement of the reference array and the phased array until the received signal of the first antenna matches the received signal of the second antenna.

3. The above-described test measurement system is calibrated by receiving a beam, which is a calibration signal, from the phased array with the reference array, and adjusting the arrangement of the reference array and the phased array so that the amplitude of the received signal received by the boresite antenna in the reference array is maximized.

4. A method for testing a device under test using a phased array of antennas, The process involves adjusting the phase of each of the antennas in the phased array to tune the beam from the phased array toward a first position at a first distance in a first direction from the physical center point of a reference array consisting of multiple antennas spaced apart from each other, and The process involves receiving the beam from the phased array as the first signal at the first position described above, A process of tuning the beam from the phased array toward a second position located a second distance away from the center point of the reference array, which consists of the multiple antennas described above, in a second direction different from the first direction, and in a second direction, The process involves receiving the beam from the phased array as a second signal at the second position described above. A test method for a device under test that includes [a specific feature / feature].

5. The method for testing the device under test according to claim 4, wherein the first position includes a position midway between the boresite antenna and the antenna closest to the boresite antenna in the first direction from the center point of the reference array, and the second position includes a position midway between the boresite antenna and the antenna closest to the boresite antenna in the second direction from the center point of the reference array.

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