PATENT DOCUMENT

Publication Number: US-10637590-B2
Application Number: US-201715429511-A
Country: US
Kind Code: B2

Title: Millimeter wave test systems

Abstract:
An electronic device may be provided with wireless circuitry that handles millimeter wave communications. The wireless circuitry may be tested using a test system that includes a fixture, computing equipment, and a substrate placed in the fixture. The fixture may hold an array of antennas on the substrate at a selected distance from an array of antennas on the wireless circuitry under test. The array on the substrate may receive millimeter wave test signals from the wireless circuitry under test. A transmission line may convey the millimeter wave test signals to a signal analyzer without down-converting the signals. The analyzer and computing equipment may identify performance metric data based on the test signals and may determine whether the wireless circuitry has satisfactory performance based on the performance metric data. The test system may be calibrated using settings that are specific to the design of the wireless circuitry under test.

Claims:
What is claimed is: 
     
       1. A test system for performing wireless testing operations on communications circuitry, the test system comprising:
 a substrate; 
 an array of antennas on the substrate, wherein the array of antennas wirelessly receives test signals from the communications circuitry at a millimeter wave frequency; 
 a signal analyzer; 
 a transmission line coupled between the substrate and the signal analyzer, wherein the transmission line conveys the test signals received by the array of antennas to the signal analyzer, and the signal analyzer receives the test signals at the millimeter wave frequency, wherein the signal analyzer is configured to gather information from the received test signals; and 
 computing equipment, wherein the computing equipment is configured to identify radio-frequency performance metric data based on the information gathered by the signal analyzer, and the computing equipment is further configured to determine whether the communications circuitry has satisfactory performance based on the identified radio-frequency performance metric data. 
 
     
     
       2. The test system defined in  claim 1 , further comprising:
 phase-shifting circuitry on the substrate, wherein the phase-shifting circuitry conveys the test signals from the array of antennas to the transmission line. 
 
     
     
       3. The test system defined in  claim 2 , further comprising:
 conductive traces on the substrate, wherein the conductive traces are coupled between the phase-shifting circuitry and the transmission line. 
 
     
     
       4. The test system defined in  claim 3 , further comprising:
 switching circuitry interposed on the conductive traces; and 
 control circuitry on the substrate, wherein the control circuitry is configured to control the switching circuitry to couple a single antenna in the array of antennas to the transmission line at a given time. 
 
     
     
       5. The test system defined in  claim 4 , wherein the control circuitry is configured to provide a control signal to the phase-shifting circuitry that controls the phase shifting circuitry to provide a selected phase shift to the test signals received by the array of antennas. 
     
     
       6. The test system defined in  claim 1 , wherein the array of antennas wirelessly receives the test signals from the communications circuitry via near field electromagnetic coupling. 
     
     
       7. The test system defined in  claim 1 , further comprising:
 a test fixture, wherein the test fixture is configured to hold the array of antennas at a selected distance from an additional array of antennas in the communications circuitry. 
 
     
     
       8. The test system defined in  claim 7 , wherein the selected distance is greater than zero mm and less than a wavelength of the test signals. 
     
     
       9. The test system defined in  claim 1 , wherein the information gathered by the signal analyzer comprises a magnitude and a phase of the test signals received at the signal analyzer. 
     
     
       10. The test system defined in  claim 9 , wherein the radio-frequency performance metric data comprises attenuation information and phase discontinuity information that is generated by the computing equipment based on the magnitude and phase of the received test signals. 
     
     
       11. The test system defined in  claim 1 , further comprising:
 alignment structures on the substrate, wherein the alignment structures align each antenna in the array of antennas with a corresponding antenna in an additional array of antennas in the communications circuitry. 
 
     
     
       12. The test system defined in  claim 11 , wherein the alignment structures comprise a magnet that surrounds the array of antennas on the substrate. 
     
     
       13. The test system defined in  claim 1 , wherein the test signals are not down-converted to a frequency that is lower than the millimeter wave frequency prior to being received at the signal analyzer. 
     
     
       14. The test system defined in  claim 1 , wherein the millimeter wave frequency is greater than 27 GHz. 
     
     
       15. A method of operating a millimeter wave test system, the method comprising:
 with a first reference circuit formed on a first substrate, wirelessly transmitting millimeter wave test signals to a second reference circuit formed on a second substrate; 
 with the second reference circuit, conveying the millimeter wave test signals to a signal analyzer that is external to the first and second substrates; 
 with the signal analyzer, gathering measurement data from the millimeter wave test signals received from the second reference circuit; 
 with computing equipment, generating calibration settings for the millimeter wave test system based on the measurement data gathered by the signal analyzer, wherein the millimeter wave test system further comprises a signal generator and a transmission line that are external to the first and second substrates; 
 with the signal generator, generating the millimeter wave test signals; and 
 with the transmission line, conveying the millimeter wave test signals from the signal generator to the first reference circuit. 
 
     
     
       16. The method defined in  claim 15 , further comprising:
 loading the first and second reference circuits into a test fixture; and 
 with the test fixture, adjusting a distance between the first and second reference circuits, wherein the first reference circuit wirelessly transmits the millimeter wave test signals to the second reference circuit both before and after adjusting the distance between the first and second reference circuits. 
 
     
     
       17. The method defined in  claim 15 , wherein generating the calibration settings comprises generating a setting that identifies a phase shift, and the first reference circuit comprises phase shifting circuitry that applies the phase shift to the millimeter wave test signals prior to transmitting the millimeter wave test signals to the second reference circuit. 
     
     
       18. The method defined in  claim 15 , wherein the first reference circuit comprises an array of antennas and control circuitry formed on the first substrate, the method further comprising:
 with the control circuitry, selecting an antenna in the array of antennas; and 
 with the selected antenna, transmitting the millimeter wave test signals to the second reference circuit. 
 
     
     
       19. The method defined in  claim 18  further comprising:
 with the control circuitry, selecting an additional antenna in the array of antennas; and 
 with the selected additional antenna, transmitting the millimeter wave test signals to the second reference circuit. 
 
     
     
       20. The method defined in  claim 15 , wherein generating the millimeter wave test signals comprises generating the millimeter wave test signals at a frequency between 27 and 29 GHz, and gathering the measurement data comprises gathering the measurement data from the millimeter wave test signals at the frequency between 27 and 29 GHz. 
     
     
       21. The method defined in  claim 15 , wherein gathering the measurement data from the millimeter wave test signals comprises measuring an amplitude and a phase of the millimeter wave test signals. 
     
     
       22. The method defined in  claim 15 , wherein the second reference circuit comprises control circuitry and phase shifting circuitry formed on the second substrate, the method further comprising:
 with the control circuitry, adjusting a phase shift provided by the phase shifting circuitry to the millimeter wave test signals, wherein the first reference circuit wirelessly transmits the millimeter wave test signals to the second reference circuit before and after adjusting the phase shift provided by the phase shifting circuitry. 
 
     
     
       23. A test system, comprising:
 a first printed circuit board having a first array of antennas; 
 a second printed circuit board having a second array of antennas; 
 a test fixture configured to hold the first printed circuit board at a selected distance from the second printed circuit board, wherein the test fixture has alignment structures configured to align each antenna in the first array with a different respective antenna in the second array; 
 a signal generator coupled to the first printed circuit board by a first transmission line; and 
 a signal analyzer coupled to the second printed circuit board by a second transmission line, wherein the signal analyzer is configured to generate millimeter wave test signals that are conveyed to the first printed circuit board over the first transmission line, the first array of antennas is configured to wirelessly transmit the millimeter wave test signals to the second array of antennas, and the second transmission line is configured to convey the millimeter wave test signals from the second array of antennas to the signal analyzer. 
 
     
     
       24. The test system defined in  claim 23 , wherein the selected distance is greater than zero mm and less than 1.0 mm. 
     
     
       25. The test system defined in  claim 23 , further comprising:
 a first set of phase shifter circuits formed on the first printed circuit board and coupled between the first array of antennas and the first transmission line; and 
 a second set of phase shifter circuits formed on the second printed circuit board and coupled between the second array of antennas and the second transmission line. 
 
     
     
       26. The test system defined in  claim 25 , wherein the signal generator and the signal analyzer are formed external to the first and second printed circuit boards. 
     
     
       27. The test system defined in  claim 23 , wherein the signal analyzer is configured to measure a magnitude of the millimeter wave test signals, the system further comprising:
 computing equipment, wherein the computing equipment is configured to identify an attenuation of the millimeter wave test signals between the first and second arrays of antennas based on the magnitude of the millimeter wave test signals measured by the signal analyzer. 
 
     
     
       28. The test system defined in  claim 23 , wherein the second array of antennas includes the same number of antennas as the first array of antennas.

Description:
This application claims the benefit of provisional patent application No. 62/374,436, filed Aug. 12, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with wireless communications circuitry. 
     Electronic devices often include wireless communications circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications. 
     It may be desirable to support wireless communications in millimeter wave communications bands. Millimeter wave communications, which are sometimes referred to as extremely high frequency (EHF) communications, involve communications at frequencies of about 10-400 GHz. Operation at these frequencies may support high bandwidths, but may raise significant challenges in ensuring satisfactory radio-frequency performance. 
     Wireless communications circuitry such as millimeter wave circuitry is tested in a test system to ensure adequate radio-frequency performance. In conventional test systems, radio-frequency testing is performed on the communications circuitry after the communications circuitry has been disposed within a fully-assembled electronic device. The millimeter wave communications circuitry is tested by transmitting millimeter wave signals from the fully-assembled electronic device to radio-frequency test equipment in the far field domain (i.e., several meters away from the device). 
     When performing testing in this manner using conventional test systems, it is difficult to pinpoint whether test failures are attributable to the millimeter wave circuitry or to other components in the electronic device. In addition, the electronic device needs to be disassembled to replace the millimeter wave communications circuitry when a test failure is detected, regardless of whether or not the millimeter wave communications circuitry actually caused the test failure. Disassembling electronic devices in this way can be difficult, time consuming, and cost prohibitive. 
     It would therefore be desirable to be able provide improved systems and methods for testing millimeter wave communications circuitry. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry. The wireless circuitry may include one or more antennas. The antennas may include phased antenna arrays each of which includes multiple antenna elements. The phased antenna arrays may be used to handle millimeter wave wireless communications and may perform beam steering operations. 
     Performance of wireless communications circuitry for handling millimeter wave communications may be tested and verified using a test system prior to assembling the wireless communications circuitry into a completed device. The test system may include a test fixture, a signal analyzer, computing equipment, and a substrate placed in the test fixture. An array of antennas may be formed on the substrate. The test fixture may hold the array of antennas at a predetermined distance (e.g., less than 1 mm) from an array of antennas on wireless communications circuitry under test. The array of antennas on the substrate may wirelessly receive millimeter wave test signals (e.g., signals at a millimeter wave frequency of greater than 27 GHz) from the array of antennas on the wireless communications circuitry under test. A signal analyzer may be coupled to the substrate by a transmission line. The transmission line may convey the millimeter wave test signals received by the array of antennas on the substrate to the signal analyzer (e.g., the signal analyzer may receive the test signals at the millimeter wave frequency). 
     The signal analyzer may gather measurement data such as phase and magnitude information from the received millimeter wave test signals. The computing equipment may identify performance metric data such as attenuation and phase discontinuity data based on the gathered measurement data. The computing equipment may determine whether the wireless communications circuitry under test has satisfactory performance based on the performance metric data. If the communications circuitry under test has unsatisfactory performance, the communications circuitry may be discarded or reworked. If the communications circuitry under test has satisfactory performance, the communications circuitry may be further assembled into the electronic device. In order to perform accurate and reliable testing on the wireless communications circuitry under test, the test system may be calibrated using calibration settings that are specific to the particular design of the wireless communications circuitry under test. 
     The test system may generate the calibration data by loading first and second reference circuits into the test fixture. The first and second reference circuits may be formed on separate substrates (e.g., printed circuit boards). A signal generator in the test system may generate the millimeter wave test signals and may convey the test signals to the first reference circuit. An array of antennas on the first reference circuit may wirelessly transmit the test signals to the second reference circuit. An array of antennas on the second reference circuit may wirelessly receive the test signals from the first reference circuit and may convey the test signals to the signal analyzer. 
     The signal analyzer and the computing equipment may generate a performance model of the first reference circuit by processing the received test signals. The test system may generate the performance model based on test signals that are transmitted using different combinations of transmit phase shifts (e.g., provided by phase shifters on the first reference circuit), receive phase shifts (e.g., provided by phase shifters on the second reference circuit), frequencies, test signal amplitudes, and/or distances between the antenna arrays on the first and second reference circuits. The calibrated settings may identify a range of phase shift settings for use by the wireless communications circuitry under test and/or by phase shifter circuitry on the substrate during testing. The calibrated settings may identify an optimal distance between the array of antennas on the substrate and the array of antennas on the wireless communications circuitry for use during testing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is schematic diagram of an illustrative electronic device having millimeter wave communications circuitry in accordance with an embodiment. 
         FIG. 2  is a circuit diagram of illustrative millimeter wave communications circuitry for transmitting millimeter wave signals using a phased antenna array in accordance with an embodiment. 
         FIG. 3  is a diagram showing how an illustrative test system may be calibrated using a millimeter wave reference circuit in accordance with an embodiment. 
         FIG. 4  is a flow chart of illustrative steps that may be performed to test and assemble an electronic device having millimeter wave circuitry in accordance with an embodiment. 
         FIG. 5  is a flow chart of illustrative steps that may be performed to calibrate a test system using a millimeter wave reference circuit in accordance with an embodiment. 
         FIG. 6  is a diagram showing how an illustrative calibrated test system may perform testing operations to ensure satisfactory performance of millimeter wave communications circuitry in accordance with an embodiment. 
         FIG. 7  is a flow chart of illustrative steps that may be processed by a calibrated test system to perform testing operations on millimeter wave communications circuitry in accordance with an embodiment. 
         FIG. 8  is a front view of an illustrative test head for calibrating a millimeter wave test system and for performing test operations on millimeter wave communications circuitry in accordance with an embodiment. 
         FIG. 9  is a diagram of an illustrative manufacturing and testing system for testing millimeter wave communications circuitry prior to assembly of the millimeter wave communications circuitry within an electronic device in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A schematic diagram showing illustrative components that may be used in an electronic device such as electronic device  10  is shown in  FIG. 1 . Electronic devices such as electronic device  10  may contain wireless circuitry. The wireless circuitry may include one or more antennas. The antennas may include phased antenna arrays that are used for handling millimeter wave communications. Millimeter wave communications, which are sometimes referred to as extremely high frequency (EHF) communications, involve signals at 60 GHz, 28 GHz, or other frequencies between about 10 GHz and 400 GHz. If desired, device  10  may also contain wireless communications circuitry for handling satellite navigation system signals, cellular telephone signals, local wireless area network signals, near-field communications, light-based wireless communications, or other wireless communications. 
     Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     As shown in  FIG. 1 , device  10  may include a housing such as housing  12 . Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). Antennas may be mounted along the peripheral edges of housing  12 , on a rear of housing  12 , under a dielectric window in a conductive portion of housing  12 , or at any other desired location in device  10 . 
     Device  10  may include control circuitry such as storage and processing circuitry  14 . Storage and processing circuitry  14  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  14  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processor integrated circuits, application specific integrated circuits, etc. 
     Storage and processing circuitry  14  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, storage and processing circuitry  14  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  14  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, MIMO protocols, antenna diversity protocols, satellite navigation system protocols, etc. 
     Device  10  may include input-output circuitry  16 . Input-output circuitry  16  may include input-output devices  18 . Input-output devices  18  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  18  may include user interface devices, data port devices, and other input-output components. For example, input-output devices may include touch screens, displays without touch sensor capabilities, buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, accelerometers or other components that can detect motion and device orientation relative to the Earth, capacitance sensors, proximity sensors (e.g., a capacitive proximity sensor and/or an infrared proximity sensor), magnetic sensors, a connector port sensor or other sensor that determines whether device  10  is mounted in a dock, and other sensors and input-output components. 
     Input-output circuitry  16  may include wireless communications circuitry  20  for communicating wirelessly with external equipment. Wireless communications circuitry  20  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas  30 , transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless communications circuitry  20  may include radio-frequency transceiver circuitry  23  for handling various radio-frequency communications bands. For example, circuitry  20  may include transceiver circuitry  22 ,  24 ,  26 , and  28 . 
     Transceiver circuitry  24  may be wireless local area network transceiver circuitry that may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and that may handle the 2.4 GHz Bluetooth® communications band. 
     Circuitry  20  may use cellular telephone transceiver circuitry  26  for handling wireless communications in frequency ranges such as a low communications band from 700 to 960 MHz, a midband from 1710 to 2170 MHz, and a high band from 2300 to 2700 MHz or other communications bands between 700 MHz and 2700 MHz or other suitable frequencies (as examples). Circuitry  26  may handle voice data and non-voice data. 
     Millimeter wave transceiver circuitry  28  may support communications at extremely high frequencies (e.g., millimeter wave frequencies from 10 GHz to 400 GHz or other millimeter wave frequencies). 
     Wireless communications circuitry  20  may include satellite navigation system circuitry such as Global Positioning System (GPS) receiver circuitry  22  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data (e.g., GLONASS signals at 1609 MHz). Satellite navigation system signals for receiver  22  are received from a constellation of satellites orbiting the earth. 
     In satellite navigation system links, cellular telephone links, and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. Extremely high frequency (EHF) wireless transceiver circuitry  28  may convey signals over these over these short distances that travel between transmitter and receiver over a line-of-sight path. To enhance signal reception for millimeter wave communications, phased antenna arrays and beam steering techniques may be used. Antenna diversity schemes may also be used to ensure that the antennas that have become blocked or that are otherwise degraded due to the operating environment of device  10  can be switched out of use and higher-performing antennas used in their place if desired. 
     Wireless communications circuitry  20  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  20  may include circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc. 
     Antennas  30  in wireless communications circuitry  20  may be formed using any suitable antenna types. For example, antennas  30  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, hybrids of these designs, etc. If desired, one or more of antennas  30  may be cavity-backed antennas. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. Dedicated antennas may be used for receiving satellite navigation system signals or, if desired, antennas  30  can be configured to receive both satellite navigation system signals and signals for other communications bands (e.g., wireless local area network signals and/or cellular telephone signals). Antennas  30  can include phased antenna arrays for handling millimeter wave communications. 
     Transmission line paths may be used to route antenna signals within device  10 . For example, transmission line paths may be used to couple antenna structures  30  to transceiver circuitry  23 . Transmission lines in device  10  may include coaxial cable paths, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, transmission lines formed from combinations of transmission lines of these types, etc. Filter circuitry, switching circuitry, impedance matching circuitry, and other circuitry may be interposed within the transmission lines, if desired. 
     In some configurations, antennas  30  may include antenna arrays (e.g., phased antenna arrays to implement beam steering functions). For example, the antennas that are used in handling millimeter wave signals for extremely high frequency wireless transceiver circuits  28  may be implemented as phased antenna arrays. The radiating elements in a phased antenna array for supporting millimeter wave communications may be patch antennas, dipole antennas, or other suitable antenna elements. Transceiver circuitry can be integrated with the phased antenna arrays to form integrated phased antenna array and transceiver circuit modules. 
       FIG. 2  is a diagram of illustrative millimeter wave communications circuitry  28  in device  10  that may perform wireless communications using a phased array of antennas  30 . As shown in  FIG. 2 , millimeter wave communications circuitry  28  may include baseband circuitry such as baseband processor  32 , intermediate frequency circuitry such as circuitry  34 , and extremely high frequency (EHF) circuitry such as millimeter wave circuitry  44 . Millimeter wave circuitry  44  may be coupled to phased array  56  of antennas  30 . Array  56  may include a number N of antennas  30  (e.g., a first antenna  30 - 1 , a second antenna  30 - 2 , a third antenna  30 - 3 , etc.). Antennas  30  may be arranged in any desired pattern (e.g., an array having a desired number of rows and columns or in any other desired shape). 
     Baseband processor  32  may generate baseband data signals (e.g., data signals at a baseband frequency). The data signals may be conveyed to intermediate frequency circuitry  34  over path  36 . The data signals may be, for example, in-phase quadrature-phase (I/Q) baseband data. 
     Intermediate frequency circuitry  34  may up-convert the baseband signals received over line  36  to a corresponding intermediate frequency (IF). For example, mixer circuit  38  may up-convert data received over line  36  to generate intermediate frequency signals at the intermediate frequency. The intermediate frequency may be, for example, between 5 GHz and 10 GHz, between 1 GHz and 5 GHz, or less than 1 GHz. IF circuitry  34  may sometimes be referred to herein as IF transceiver circuitry  34 . IF circuitry  34  may include other components (e.g., switching components, filtering components, matching components, transmission line structures, or other components) that operate on the intermediate frequency signals. IF circuitry  34  may convey the intermediate frequency signals to EHF circuitry  44  over line  42 . 
     EHF circuitry  44  may up-convert the intermediate frequency signals received over line  42  to a corresponding millimeter wave frequency (extremely high frequency). For example, mixer  46  may up-convert data received over line  42  to generate EHF (millimeter wave) signals at the millimeter wave frequency. The millimeter wave frequency may be, for example, 28 GHz, 60 GHz, 40 GHz, between 28 GHz and 85 GHz, greater than 85 GHz, greater than 27 GHz, between 27 and 29 GHz, or any other desired millimeter wave frequency. Mixer circuit  46  may pass the EHF signals to phase antennas  30  in array  56  via phase controller circuits  52  and path  50 . If desired, circuitry  44  may include other components (e.g., switching components, filtering components, matching components, transmission line structures, or other components) that operate on the EHF signals. 
     The use of multiple antennas in array  56  allows beam steering arrangements to be implemented by controlling the relative phases of the signals for the antennas. Each antenna  30  in array  56  may be coupled to a corresponding phase controller  52 . For example, phase controller  52 - 1  may be coupled between antenna  30 - 1  and path  50 , phase controller  52 - 2  may be coupled between antenna  30 - 2  and path  50 , phase controller  52 - 3  may be coupled between antenna  30 - 3  and path  50 , etc. 
     Control circuitry  14  may provide control signals  54  to each phase controller to adjust the phase of the EHF signals transmitted by each antenna (e.g., first controller  52 - 1  may receive control signal  54 - 1 , second controller  52 - 2  may receive control signal  54 - 2 , third controller  52 - 3  may receive control signal  54 - 3 , etc.). In this way, phase controllers  52  may serve as phase shifting circuits that shift or adjust the phase of the signals transmitted over path  50 . Control circuitry  14  may use phase controllers  52  or any other suitable phase control circuitry to adjust the relative phases of the transmitted EHF signals that are provided to each of the antennas in the antenna array. If, for example, control circuitry  14  adjusts phase shifters  52  to produce a first set of phases on the transmitted EHF signals, the signals transmitted from antennas  30  will form a radio-frequency beam such as beam  60  that is oriented in the direction of point B. If, however, control circuitry  14  adjusts phase controllers  52  to produce a second set of phases on the transmitted EHF signals, the signals transmitted from antennas  30  will form a radio-frequency beam such as beam  62  that is oriented in the direction of point A. 
     In one suitable arrangement, phase controllers  52  may each include radio-frequency mixing circuitry. Mixing circuitry in phase controllers  52  may receive EHF signals from path  50  at a first input and may receive a corresponding signal weight value from control input  54  (e.g., mixer  52 - 1  may receive a first weight value, mixer  52 - 2  may receive a second weight value, etc.). The mixer circuitry may mix (e.g., multiply) the EHF signals received over path  50  by the corresponding signal weight value to produce an output signal that is transmitted on the corresponding antenna. This is merely illustrative. In general, phase shifting circuits  52  may be formed using any desired circuitry that applies a desired phase shift on the signals received over path  50  so that phase shifted signals are provided to antennas  30 . The output signals transmitted by each antenna may constructively and destructively interfere to generate a beam of radio-frequency signals in a particular direction (e.g., in a direction as shown by beam  60  or a direction as shown by beam  62 ). 
     If desired, baseband processor  32 , IF circuitry  34 , EHF circuitry  44 , and phased antenna array  56  may each be formed on different substrates (e.g., different printed circuit boards, dielectric substrates or carriers, integrated circuits, or other substrates). If desired, one or more of circuits  32 ,  34 ,  44 , and  56  may be formed on a common (shared) substrate. In one suitable arrangement, EHF circuitry  44  and phased antenna array  56  may be formed on a shared printed circuit or integrated circuit substrate, sometimes referred to herein as a millimeter wave (EHF) module, integrated circuit, or package. Antennas  30  may be formed using traces on the shared substrate or from other structures formed on the shared substrate (e.g., traces on a flexible printed circuit mounted to the shared substrate, metal structures on plastic support blocks placed on a surface of the shared substrate, etc.). If desired, EHF signals may be received by antennas  30  and conveyed to baseband processor  32  via IF circuitry  34  and EHF circuitry  44 . Phase shifters  54  may provide a non-zero phase shift or may provide no phase shift to the received signals. Circuitry  46  and  48  may down-convert the received EHF signals to baseband frequencies. 
     In order to ensure satisfactory radio-frequency performance of EHF circuitry  44  and antenna array  56 , radio-frequency test operations (sometimes referred to herein as EHF test operations or millimeter wave test operations) may be performed on EHF circuitry  44  and antenna array  56  by an EHF test system prior to assembling circuitry  44  and  56  into a finished device  10 . In practice, the performance of the EHF test systems for testing EHF circuitry  44  and antenna array  56  may be dependent upon the particular design of circuitry  44  and  56 . For example, some circuit and antenna designs may have different radiative characteristics than others and may therefore require a different test arrangement than others. If care is not taken (e.g., if the test system is not properly calibrated), EHF signals that are conveyed between the EHF test system and antennas  30  may scatter or be undesirably attenuated. If desired, EHF test systems used to test EHF circuitry  44  and antenna array  56  may be calibrated prior to performing the EHF testing to account of the requirements of the particular design to be tested. After the test system has been calibrated, the test system may be used to perform production testing on millimeter wave circuitry that will later be assembled within the completed device. 
       FIG. 3  is a diagram of an illustrative EHF test system that can be calibrated to perform EHF testing on circuitry  44  and antenna array  56 . As shown in  FIG. 3 , an EHF (millimeter wave) test system such as test system  80  may include a test fixture  82 , an EHF signal generator  84 , computing equipment such as test host  86 , and an EHF signal analyzer  88 . 
     In order to calibrate test system  80 , a prototype for EHF circuitry  44  and antennas  56  may be provided and placed within test fixture  82 . In the example of  FIG. 3 , prototype EHF circuitry  90  is placed within transmit side  92  of test fixture  82 . The prototype EHF circuitry may reflect a particular design for circuitry  44  and circuitry  56  that is intended for inclusion in finished device  10 . However, prototype  90  may be used only for calibrating system  80  and is not actually used in a finished device  10 . Prototype circuit  90  may sometimes be referred to herein as reference circuitry  90  or reference circuit  90  (e.g., because circuit  90  serves as a reference by which to calibrate test system  80 ). 
     Reference circuitry  90  may include antenna array  56  and portion of EHF circuitry  44  of transceiver  28 . For example, reference circuitry  90  may only include the portion of EHF circuitry  44  that handles EHF signals (e.g., reference circuitry  90  may include the circuitry shown in  FIG. 2  below dashed line  64 ). In other words, reference circuitry  90  may include the components of circuitry  28  prior to assembling or fabricating circuitry  32 ,  34 , and  46  within circuitry  28 . By omitting circuitry  32 ,  34 , and  46  from reference  90 , the EHF performance of antenna array  56 , phase shifters  52 , and path  50  may be characterized and verified prior to assembling circuitry  32 ,  34 , and  46  into circuitry  28 . This may help to pinpoint any flaws in the design of circuitry  28  prior to further assembly (e.g., so that unnecessary assembly and disassembly of circuitry  28  or device  10  after testing may be avoided, thereby reducing test time and cost). 
     The components of reference circuitry  90  may be mounted to a common substrate  96 . Substrate  96  may, for example, be a rigid or flexible printed circuit board, a semiconductor substrate (e.g., an integrated circuit), a dielectric substrate, or any other desired substrate. Reference circuitry  90  may sometimes be referred to as reference chip  90 , reference module  90 , or reference package  90 . 
     Antenna array  56  may be mounted to a surface of substrate  96  or otherwise formed on substrate  96 . Each antenna  30  in array  56  may be coupled to conductive path  50  via a corresponding phase shifting circuit  52 . Conductive path  50  may include, for example, conductive traces, wiring structures, and/or conductive via structures formed on or within substrate  96  (e.g., conductive traces that are configured to convey EHF signals). Phase shifting circuits  52  may be formed on a surface of substrate  96  (e.g., as surface mount components) or embedded within substrate  96 . Reference circuitry  90  may include control circuitry  102  (e.g., a microprocessor or other processing circuitry formed on or embedded within substrate  96 ). Control circuitry  102  may generate control signals  54  that control the phase of phase shifting circuits  52 . Switching circuits may be interposed between path  50  and each of phase shifters  52  for selectively activating one or more of antennas  30 . The switching circuits may be controlled by control circuitry  102 . Reference circuitry  90  may, if desired, include other circuitry (not shown) that operates on signals in the millimeter wave domain. 
     The particular design of reference circuitry  90  may be duplicated (copied) to generate duplicate reference circuitry  98 . Duplicate reference circuitry  98  may be an exact copy of reference circuitry  90 . For example, duplicate reference  98  may include conductive traces  106 , phase shifting circuits  108 , antennas  110  arranged in an array  112  that are duplicates of structures  50 ,  52 ,  30 , and  56  of reference circuitry  90 , respectively. Array  112  may, for example, have the same number N of antennas  110  as array  56  and antennas  110  may be arranged in the same pattern as antennas  30  in array  56  of circuitry  90 . Duplicate reference circuitry  98  may include control circuitry (e.g., an embedded microprocessor)  116  that provides control signals  118  that control the phase shift provided by phase shifting circuits  108 . Circuitry  116 ,  108 ,  50 , and  110  may be embedded or formed on a substrate  100  (e.g., a printed circuit board or semiconductor substrate). 
     Duplicate reference circuitry  98  may be placed within receive side  94  of test fixture  92 . Test fixture  82  may include tray structures, holder structures, clamping structures, pinning structures, jig structures, cavity structures, or any other desired structures for holding circuitry  90  and  98  in a fixed position during testing. Test fixtures  82  may hold reference circuitry  90  and duplicate circuitry  98  so that antennas  30  on reference circuit  90  and antennas  110  on duplicate reference circuit  98  are separated by a selected distance D. When placed within fixture  82 , each antenna  30  in circuitry  90  may be held distance D apart from a corresponding antenna  110  on circuitry  98  (e.g., antenna  30 - 1  may be placed distance D apart from antenna  110 - 1 , antenna  30 - 2  may be placed distance D apart from antenna  110 - 2 , etc.). Test fixture  82  may ensure that each antenna  30  is aligned with the corresponding antenna  110 . When held in this way, each antenna  30  may transmit signals by near field coupling to the corresponding antenna  110 . Forming reference circuitry  98  as a duplicate of circuitry  90  that is aligned with circuitry  90  may minimize EHF signal scattering between circuitry  98  and  90 . 
     If desired, reference circuitry  90  and/or duplicate reference circuitry  98  may include alignment structures  104 . Alignment structures  104  may further ensure that each antenna  30  on circuitry  90  is aligned with a corresponding antenna  110  on circuitry  98  when placed within fixture  82 . Alignment structures  104  may include, for example, magnetic structures, pin structures, post structures, interlocking structures, clasp structures, or any other desired alignment structures. 
     Distance D may be adjusted to tune the EHF performance of test system  80 . For example, some distances D may involve more signal attenuation or phase discontinuity (e.g., EHF signal scattering) between antennas  30  and  110  than other distances D. Calibrating test system  80  may identify an optimal distance D such that signal attenuation and phase discontinuity (e.g., EHF signal scattering) is minimized between circuitry  90  and  98 . Distance D may, in general, be any distance across which antenna  30  is near field coupled to the corresponding antenna  110 . For example, distance D may be any distance that is greater than zero mm and less than an upper limit for signals to be conveyed between antennas  30  and  110  in the near field domain (e.g., any distance greater than zero and less than the wavelength of the signals conveyed between antennas  30  and  110 ). As an example, distance D may be less than 1.0 mm. 
     Once reference circuit  90  and duplicate reference circuit  98  have been placed within fixture  82 , EHF signal generator  84  may be coupled to circuit  90  via radio-frequency transmission line  130  and radio-frequency connector  132 . EHF signal analyzer  88  may be coupled to duplicate circuit  98  via radio-frequency transmission line  134  and radio-frequency connector  136 . Transmission lines  130  and  134  may be, for example, coaxial cables or other transmission line structures. Transmission lines  130  and  132 , signal generator  84 , and signal analyzer  88  may formed separate from (e.g., external to) substrates  96  and  100 . 
     EHF signal generator  84  may be coupled to computing equipment such as test host  86  via communications path  138 . EHF signal analyzer  88  may be coupled to test host  86  over communications path  140 . Communications paths  138  and  140  may include wired and/or wireless communications paths. Test host  86  may include computing equipment such as a personal computer, laptop computer, handheld or portable computer, or any other desired computing equipment. Test host  86  may be formed separate from (e.g., external to) signal generator  84  and signal analyzer  88 . In another suitable arrangement, test host  86 , signal generator  84 , and/or signal analyzer  88  may be combined into a single testing device. Transmission lines  130  and  134 , connectors  132  and  136 , test fixture  82 , signal generator  84 , signal analyzer  88 , test host  86 , and communications paths  138  and  140  may sometimes be referred to herein collectively as a test station, an EHF test station, test equipment, or EHF test equipment. 
     A user (e.g., a test operator, manufacturer, or designer of circuitry  28 ) may control test system  80  using a user input/output interface of test system  80 . For example, a user may press buttons in a control panel on generator  84  and analyzer  88  while viewing information that is displayed on a display in test system  80 . In computer controlled configurations, test host  86  (e.g., software running autonomously or semi-autonomously on test host  86 ) may communicate with signal generator  84  and analyzer  88  by sending and receiving control signals and data over paths  138  and  140 . Test host  86  may provide control signals such as test commands to signal generator  84  and/or may receive test data from signal analyzer  88  over path  140 . 
     Test host  86  may send test commands to signal generator  84  that instruct signal generator  84  to generate test signals (e.g., EHF test signals having a known phase, frequency, and amplitude). EHF signal generator  84  may generate the EHF test signals (e.g., test signals at a millimeter wave frequency such as 28 GHz, 40 GHz, etc.) based on the test commands and may transmit the EHF test signals to conductor  50  on reference circuitry  90  over transmission line  130  and connector  132 . The EHF test signals may then be phase shifted by circuitry  52  and conveyed to a corresponding antenna  30  on reference circuitry  90 . Antennas  30  may transmit the EHF test signals to a corresponding antenna  110  on duplicate reference circuitry  98  (e.g., antenna  110 - 1  may receive EHF test signals transmitted by antenna  30 - 1 , antenna  110 - 2  may receive EHF test signals transmitted by antenna  30 - 2 , etc.). The received test signals may, if desired, be phase shifted by shifters  108  on duplicate circuitry  98  and conveyed to EHF signal analyzer  88  via path  106 , connector  136 , and transmission line  134 . If desired, connectors  132  and  136  may include radio-frequency coupler circuitry. The radio-frequency coupler circuitry may, for example, be used to measure a phase of the signals transmitted by generator  84  prior to transmission over antennas  30  and a phase of the signals after they are received by antennas  110  and prior to conveying those signals to analyzer  88 . This phase information may, for example, be used by analyzer  88  and/or test host  86  to identify a phase difference (e.g., a phase delta) between antennas  30  and  110  that may be used to characterize the performance of system  80  and structures  90 . If desired, the coupler circuitry may be interposed at any other desired locations between antennas  30  and signal generator  84  and at any other desired locations between antennas  110  and signal analyzer  88 . 
     The EHF test signals may be conveyed to external signal analyzer  88  without down-converting the signals to a lower frequency (e.g., the test signals may be at millimeter wave frequencies when analyzed by equipment  88 ). Signal analyzer  88  may analyze the received EHF test signals to extract information about the performance of reference circuitry  98  and  90 . For example, analyzer  88  may identify phase and magnitude (amplitude) information from the EHF test signals received from circuitry  98 . If desired, analyzer  88  may identify the frequency of the received EHF test signals or any other desired information about the received EHF test signals. Analyzer  88  may convey this information to test host  86  for storage. This information may be processed by test host  86  to generate a model of the EHF performance of reference  90 . The model may be used to generate calibration settings for test system  80 . The calibration settings may, for example, include a range of phases to be provided by phase shifting circuitry  52 , an optimal distance D, and any other desired calibration settings to be used during subsequent EHF testing. For example, the calibration settings may be used by test system  80  in performing EHF testing on production circuitry that is later assembled into completed electronic devices  10 . 
       FIG. 4  is a flow chart of illustrative steps that may be performed by EHF test system  80  and other manufacturing equipment for verifying satisfactory performance of EHF circuitry  28  prior to assembly of a completed device  10 . 
     At step  170 , test system  80  may be calibrated based on reference circuitry  90 . Reference circuitry  90  may, for example, incorporate a particular circuitry and antenna design for implementation within device  10 . Calibrating test system  80  initializes or sets up test system  80  to perform satisfactory EHF testing on that particular circuitry and antenna design. Test system  80  may generate calibration settings for test system  80  using reference  90  ( FIG. 3 ). The calibration settings may include, for example, phase shift ranges for phase shifting circuitry  52 , amplitude settings, frequency settings, and/or an optimal distance D to use for testing circuits having that particular reference design. 
     At step  172 , test system  80  may be set up based on the generated calibration settings. For example, reference circuitry  90  may be removed from fixture  82  and signal generator  84  may be decoupled from test fixture  82 . Production circuitry may be assembled that incorporates the particular design of the reference circuitry  90  that was used in processing step  170  and that incorporates the generated calibration settings. For example, the production circuitry may be configured to supply a range of possible phase shifts as identified by the calibration settings. Similarly, phase shifters  108  on duplicate circuitry  98  may be configured to supply the range of possible phase shifts as identified by the calibration settings (e.g., circuitry  98  may duplicate the EHF portion of the production circuitry that is to be tested). The production circuitry may be assembled to include other components in circuitry  28  such as baseband processor  32 , IF circuitry  34 , and mixer  46 . Test fixture  82  may be configured such that, when the production circuitry is placed in fixture  82 , the antennas of the production circuitry are located at an optimal distance D (e.g., as specified by the calibration settings) from antennas  110  on duplicate circuitry  98 . Each production circuit to be tested in test system  80  may sometimes be referred to herein as a circuit under test (CUT). 
     At step  174 , test system  80  may perform EHF test operations on the assembled CUTs. For example, the CUTs may be placed within test fixture  82  at the optimal distance with respect to antennas  110  on circuitry  98 . The CUTs may be controlled to generate EHF test signals that are transmitted to circuitry  98 . Circuitry  98  may convey the EHF test signals to signal analyzer  88  without converting the test signals to a lower frequency. Signal analyzer  88  and/or test host  86  may generate performance metric data based on the received EHF test signals. Test host  86  may characterize the performance of the CUTs based on the generated performance metric data. For example, test host  86  may determine whether each CUT has satisfactory EHF performance based on the generated performance metric data. If a particular CUT has unsatisfactory EHF data, that CUT may be reworked, scrapped, re-built, or flagged for review. If a particular CUT has satisfactory EHF performance, another CUT may be loaded for testing. 
     At step  176 , CUTs that were determined to have satisfactory EHF performance (e.g., while processing step  174 ), may be further assembled within device  10 . For example the CUT may be mounted to a common printed circuit board as other transceiver circuits  23  of device  10  and/or may be placed within a housing or form factor of device  10 . After a satisfactory CUT has been assembled within the device, additional testing may optionally be performed on the device to ensure that the device has satisfactory performance. Device  10  that is additionally tested after incorporation of the satisfactory CUT may sometimes be referred to herein as a device under test (DUT). 
     At optional step  178 , test system  80  and/or other test equipment may be used to perform additional testing on the assembled DUTs. For example, additional radio-frequency testing or any other desired testing operations may be performed. DUTs that have unsatisfactory performance at this stage (e.g., that fail testing) may be reworked, scrapped, or rebuilt. Because the DUTs have already incorporated satisfactory millimeter wave circuitry  28  at this stage, any test failure of the DUT may be indicative of unsatisfactory performance by components of device  10  other than millimeter wave circuitry  28 . Reworking of millimeter wave circuitry  28  (and antenna array  56 ) may therefore be omitted at this stage, thus reducing the overall time and cost of testing and manufacturing satisfactory devices  10 . DUTs that pass the additional testing may, for example, be provided to an end user or customer for normal operation. 
       FIG. 5  is a flow chart of illustrative steps that may be performed by EHF test system  80  ( FIG. 3 ) to calibrate test system  80  (e.g., to generate calibration settings for system  80  that are used to perform EHF testing on production CUTs). The steps of  FIG. 5  may, for example, be performed while processing step  170  of  FIG. 4 . 
     At step  180 , test system  80  may obtain reference EHF circuitry  90 . Reference circuitry  90  may incorporate a particular design for antenna array  56  and components  50  and  52 . Calibrating test system  80  may account for the particular design of antenna array  56  (e.g., the particular number, type, and arrangement of antennas  30 ), as well as components  50  and  52  (e.g., so that subsequent EHF testing performed on production circuitry that incorporates the design of reference  90  can be considered reliable). If desired, reference circuitry  90  may be provided by manufacturing equipment (e.g., assembly or fabrication equipment that fabricates circuitry  90 ). Reference circuitry  90  may, for example, include the EHF portion of millimeter wave transceiver circuitry  28  as shown in  FIG. 2  (e.g., the portion of  FIG. 2  below dashed line  64 ). 
     At step  182 , reference circuit  90  may be placed within transmit portion  92  of test fixture  80 . EHF signal generator  84  may be connected to reference circuit  90  using transmission line  130  and connector  132  (e.g., connector  132  may be coupled to trace  50  on reference circuit  90 ). 
     At step  184 , a duplicate  98  of reference circuitry  90  may be obtained. Duplicate circuitry  98  may be provided by manufacturing equipment if desired (e.g., the same fabrication equipment used to produce reference circuit  90 ). Duplicate reference circuit  98  may be placed within receive portion  94  of test fixture  82 . EHF signal analyzer  88  may be connected to duplicate reference circuit  98  using transmission line  134  and connector  136  (e.g., connector  136  may be coupled to trace  106  on duplicate circuit  98 ). 
     At step  186 , test fixture  82  may be set so that transmit antennas  30  are located at a distance D away from receive antennas  110  (e.g., and so that each transmit antenna  30  is aligned with a corresponding antenna  110  on duplicate circuit  98 ). If desired, alignment structures  104  may help to ensure proper alignment between the antennas of circuits  90  and  98 . Signal generator  84  may generate EHF signals having a selected frequency, amplitude (magnitude), and phase. For example, test host  86  may instruct generator  84  to generate the test signals at the selected frequency, amplitude, and phase. 
     At step  188 , control circuitry  102  on reference circuit  90  and control circuitry  116  on duplicate reference circuit  98  may select a desired antenna in arrays  56  and  112 , respectively. The antenna selected in array  56  may be aligned with the antenna selected in array  112 . For example, control circuitry  102  may select antenna  30 - 1  for transmission whereas control circuitry  116  selects antenna  110 - 1  for reception. Control circuitry  102  may select the transmit antenna by, for example, closing (activating) a switch coupled between path  50  and phase shifter  52 - 1  and opening (deactivating) switches coupled between path  50  and the other phase shifters in reference circuit  90 . Similarly, control circuitry  116  may select the receive antenna by, for example, closing a switch coupled between path  106  and phase shifter  108 - 1  and opening switches coupled between path  106  and the other phase shifters in duplicate reference circuit  98 . Control circuitry  102  and  116  may select the antennas based on stored test instructions or based on test commands received from test host  86  over wired or wireless control paths (not shown). The phase shifter circuits of the selected antennas may be set (e.g., using control signals  54  or  108 ) to provide a selected phase shift to the transmitted and received EHF test signals. 
     At step  190 , the EHF test signals generated by EHF signal generator  84  may be conveyed to reference circuit  90  over path  130 ,  132 , and  50 . The phase shifter coupled to the selected antenna may provide the selected phase shift to the EHF test signals transmitted by signal generator  84 . That phase shifter may convey the phase shifted EHF test signals to the corresponding antenna  30  in array  56 . For example, when antenna  30 - 1  is selected, phase shifter  52 - 1  may apply a selected phase shift to the EHF test signals and may convey the phase-shifted EHF test signals to antenna  30 - 1 . Antenna  30 - 1  may transmit the phase shifted EHF test signals to antenna  110 - 1  on duplicated reference circuit  98  via near field electromagnetic radiation (e.g., as shown by arrow  111 ). 
     At step  192 , signal analyzer  88  may receive the transmitted EHF test signals via the selected antenna  110 , the corresponding phase shifter  108 , path  106 , connector  136 , and transmission line  134 . For example, when antenna  110 - 1  is selected, antenna  110 - 1  may receive the phase shifted EHF test signals transmitted by antenna  30 - 1  and may convey the test signals to phase shifter  108 - 1 . Phase shifter  108 - 1  may perform a selected phase shift on the received signals and may convey the phase-shifted signals to analyzer  88  over path  106 ,  136 , and  134 . 
     Signal analyzer  88  may analyze the EHF test signals received from duplicate circuit  98 . For example, signal analyzer  88  may identify a phase and magnitude of the EHF test signals. Signal analyzer  88  may pass the phase and magnitude data to test host  86 . Test host  86  may store the phase and magnitude data for subsequent analysis. Test host  86  may, if desired, determine performance metric data such as an attenuation value of the EHF test signals for the selected antenna and the selected settings. The attenuation value may be calculated by, for example, identifying a difference between the magnitude of the EHF test signals transmitted by generator  84  and the magnitude of those EHF test signals after being received at signal analyzer  88 . Similarly, test host  86  may identify phase discontinuities associated with the EHF test signals for the selected antenna and the selected settings. Test host  86  may identify the phase discontinuities by, for example, computing a difference between the expected phase of the signals transmitted by antennas  30  (e.g., based on the known phase of the signal transmitted at generator  84  and the known phase shift provided by phase shifter  52 ) and the received phase measured at analyzer  88 . If desired, analyzer  88  and test host  86  may identify other information such as frequency discontinuities between the transmitted and received EHF test signals. 
     At step  194 , controllers  102  and  116  may determine whether antennas remain in arrays  56  and  112  for processing. If antennas remain, processing may loop back to step  188  as shown by path  196  to select a different antenna for transmitting the EHF test signals. If no antennas remain, processing may proceed to step  200  as shown by path  198 . By conveying EHF test signals over a single antenna at a time, accurate phase and magnitude information may be recorded for each antenna in the arrays without a risk of interference between multiple antennas on each array. Conveying EHF test signals over a single antenna at a time may also allow test system  80  to pinpoint any individual antennas having unsatisfactory EHF performance. 
     At step  200 , test host  86  may determine whether distance, phase, or amplitude settings remain for processing. If distance, phase, or amplitude settings remain, processing may loop back to step  186  as shown by path  202 . EHF test signals may then be re-transmitted using additional phase shifts applied by phase shifting circuits  52  and/or  108 , using additional amplitudes, and/or using different distances D. For example, test fixture  82  may be adjusted to reduce or increase distance D to gather additional phase and magnitude data from the transmitted EHF test signals. In this way, test system  80  may gather phase and magnitude information for EHF test signals transmitted and received using any desired (e.g., every possible) combination of phase shifts provided by transmit phase shifters  52  and/or receive phase shifters  108 , distances D, and EHF test signal amplitudes. This data may be stored at test host  86  for subsequent processing. If no combinations of phase shifter settings, amplitude settings, and distance settings remain, processing may proceed to step  206  as shown by path  204 . 
     At step  206 , test host  86  may process the stored phase and magnitude measurements generated by analyzer  88  from the transmitted EHF test signals. For example, test host  86  may generate a performance model for the particular design of reference circuit  90  based on the measured phase and amplitude data. The model may, for example, model the EHF performance of that particular design of circuitry  90 . 
     At step  208 , test host  86  may analyze the generated model (e.g., as generated by processing step  206 ) to generate calibration settings for test system  80 . For example, test host  86  may analyze the generated model to identify a range of acceptable phase shift settings for phase shifting circuitry  52  and/or  108  (e.g., when incorporated into the design reflected by reference  90 ). In addition, test host  86  may analyze the generated model to identify an optimal distance D. 
     The range of acceptable phase shift settings and the optimal distance D may be, for example, phase shift settings and a distance setting that generated a minimum amount of attenuation for the EHF test signals and/or a minimum amount of phase discontinuity between antennas  30  and  110 . For example, a first set of phase shift settings and a first distance D may result in a greater amount of signal attenuation and phase discontinuity for the EHF test signals when received at analyzer  88  than a second set of phase shift settings and a second distance D. By minimizing attenuation and phase discontinuity, the reliability of any subsequent testing performed by test system  80  may be maximized. The second distance D may then be used as calibration settings for any subsequent testing of circuits having the design of reference circuit  90 . 
     If desired, the steps of  FIG. 5  may be repeated for different frequencies of EHF test signals (e.g., because the performance of system  80  may vary based on the frequency of operation) and for other designs of reference circuit  90 . Similar operations may also be used to identify optimal amplitudes and/or frequencies for the EHF test signals. The example of  FIG. 5  is merely illustrative. If desired, step  188  may be performed prior to step  186  (e.g., a range of different amplitude and phase settings may be attempted for each antenna before moving on to the next antenna). 
     Once calibration settings have been obtained for test system  80  (e.g., for a particular design of reference circuit  90 ), signal generator  84  may be decoupled from reference circuit  90  and reference circuit  90  may be removed from test system  80 . The design of reference circuit  90  may then be used to generate production circuits to be tested using test system  80  (e.g., additional modules incorporating the design of reference circuit  90  may be fabricated). The production circuits may include circuitry  50 ,  52 , and  56  of reference circuit  90  after being further assembled with the remainder of millimeter wave transceiver circuitry  28 . For example, the production circuits may further include circuitry  32 ,  34 , and  46  of  FIG. 2 . Each assembled production circuit may sometimes referred to herein as a circuit under test (CUT). Further radio-frequency testing may be performed on the CUTs to ensure satisfactory performance of each CUT prior to assembling the CUTs into corresponding devices  10  (e.g., while processing step  174  of  FIG. 4 ). Each CUT may potentially be used in a completed device  10  (e.g., if that CUT has satisfactory EHF performance), whereas reference circuit  90  is only used to calibrate test system  80  and is not included in any completed device  10 . 
       FIG. 6  is a diagram of test system  80  when loaded with a CUT for performing EHF testing on the CUT. As shown in  FIG. 6 , CUT  220  may be loaded into transmit side  92  of test fixture  82 . Test system  80  of  FIG. 6  may be, for example, the same test system used to generate the calibration settings or may be a different test system (e.g., located at another geographic location) that includes similar equipment. Control circuitry  102  of CUT  220  may be configured using the calibration settings generated while processing step  170  of  FIG. 4  to control phase shifting circuits  52  to provide a predetermined range of possible phase shifts. Control circuitry  116  may be configured using the calibration settings to control phase shifting circuits  108  to provide the same predetermined range of possible phase shifts as control circuitry  102 . 
     After placing CUT  220  within test fixture  82 , test fixture  82  may be closed to place antennas  30  of CUT  220  at an optimal distance D′ from antennas  110  of duplicate reference circuit  98  (e.g., as identified in the calibration settings generated at step  170  of  FIG. 4 ). If desired, the calibration settings may identify an acceptable tolerance for distance D′. Test fixture  82  may hold antennas  30  and  110  apart by the optimal distance D′ plus or minus the identified acceptable tolerance. When incorporated into calibrated test system  80 , duplicated reference circuit  98  may sometimes be referred to as a test head or probe that is used to perform EHF testing on CUT  220 . If desired, alignment structures  104  on CUT  220  and/or test head  98  may ensure that each antenna  30  is aligned with (e.g., substantially or completely aligned with) a corresponding antenna  110 . 
     As shown in  FIG. 6 , CUT  220  may include baseband circuitry  32 , intermediate circuitry  34 , and a complete EHF circuitry  44  (e.g., including mixer  46 ). Circuitry  32 ,  34 ,  44 , and  56  may be mounted to a common substrate  222 . Substrate  222  may be, for example, a printed circuit board, integrated circuit, module, or package. In one suitable arrangement, substrate  222  is a main logic board for device  10 . 
     Test host  86  may be coupled to CUT  220  via communications path  226 . Communications path  226  may be, for example, a wired or wireless communications path between test host  86  and baseband processor  32  and/or control circuitry  102 . When generating the calibration settings, signal generator  84  is used to generate the EHF test signals (e.g., no up-conversion, baseband, or intermediate circuitry is formed on reference circuit  90 ). When performing testing on CUT  220 , CUT  220  may generate the EHF test signals itself and signal generator  84  may be disconnected from fixture  82 . 
     If desired, test host  86  may load test software (instructions) onto CUT  220  over path  226  and/or may convey test commands to CUT  220  over path  226 . For example, test host  86  may instruct CUT  220  to generate EHF test signals. Baseband circuitry  32  may generate baseband test signals that are up-converted to an intermediate frequency by circuitry  34 . Mixer  46  may generate the EHF test signals by up-converting the test signals from the intermediate frequency to a millimeter wave frequency (e.g., 28 GHz). The test signals may be conveyed over antennas  30 . Phase shifters  52  may provide a desired phase shift to the EHF test signals prior to transmitting the phase-shifted test signals over antennas  30 . The phase shifts provided by shifters  52  may, for example, be within the range of phase shifts identified in the calibration settings for test system  80 . 
     Test head  98  may receive the EHF test signals transmitted antennas  30  on CUT  220 . Test head  98  may, if desired, apply a phase shift to the received test signals using shifter circuits  108  (e.g., within the range of phase shifts identified by the calibration settings). The EHF test signals may be conveyed to signal analyzer  88  over path  106 , connector  136 , and transmission line  134 . Signal analyzer  88  may measure phase, magnitude, attenuation, phase shift or discontinuity information, or any other desired information from the received EHF test signals. Test host  86  and/or signal analyzer  88  may generate performance metric data associated with the performance of CUT  220  using the measurements gathered by analyzer  88 . Test host  86  may process the generated performance metric data to determine whether or not that particular CUT  220  has satisfactory EHF performance. If CUT  220  has satisfactory EHF performance, that CUT may be further assembled within device  10 . If CUT  220  has unsatisfactory performance, that CUT may be scrapped or reworked. 
     The example of  FIG. 6  in which CUT  220  transmits the EHF test signals is merely illustrative. If desired, the receive performance of CUT  220  may be tested. In this scenario, test head  98  may be replaced by CUT  220  on receive side  94  of test fixture  82 . Signal generator  84  and reference circuit  90  may then transmit EHF test signals to CUT  220 . Processing circuitry on CUT  220  or signal analyzer  88  and test host  86  may generate performance metric information based on the received EHF test signals for determining whether CUT  220  has satisfactory EHF performance. 
       FIG. 7  is a flow chart of illustrative steps that may be processed by calibrated test system  80  (as shown in  FIG. 6 ) to perform EHF testing on CUT  220  (e.g., after CUT  220  has been loaded into test fixture  82  and held at an optimal distance D′ from antennas  110  on circuitry  98 ). The steps of  FIG. 7  may, for example, be performed while processing step  174  of  FIG. 4 . 
     At step  240 , control circuitry  102  may select an antenna in array  56 . Control circuitry  102  may close a switch between path  50  and the phase shifter  52  coupled to the selected antenna and may open switches coupled between path  50  and the remaining phase shifters  52 . Similarly, control circuitry  116  may select an antenna in array  112  that is aligned with the selected antenna  30 . Control circuitry  116  may close a switch between the phase shifter  108  corresponding to the selected antenna and may open switches coupled between path  50  and the remaining phase shifters  108 . For example, control circuitry  102  may select antenna  30 - 2  whereas control circuitry  116  selects antenna  110 - 2 . Control circuitry  102  and  116  may select the antenna based on stored test instructions (code) and/or based on test commands received from test host  86 . 
     At step  242 , CUT  220  may generate EHF test signals. For example, baseband processor  32  may generate baseband test signals, intermediate frequency circuitry  34  may up-convert the baseband test signals to intermediate frequency test signals, and mixer  46  may up-convert the intermediate frequency test signals to EHF test signals. The EHF test signals may be transmitted over the selected antenna  30  after being phase shifted by the corresponding phase shifter  52 . Baseband circuitry  32  may generate the baseband test signals based on test instructions stored on controller  102  and/or based on test commands received from test host  86 . 
     At step  244 , EHF test head  98  may receive the transmitted EHF test signals over the selected antenna  110 . The received EHF test signals may be phase shifted using the corresponding phase shifter  108  if desired. The received EHF test signals may be conveyed to analyzer  88  over path  106 , connector  136 , and transmission line  134 . EHF signal analyzer  88  may measure phase, magnitude, frequency, phase shift or discontinuity information, attenuation information, or any other desired information from the received EHF test signals (e.g., equipment  88  may perform measurements in the EHF domain). 
     At step  246 , test host  86  and/or analyzer  88  may use the measured information to generate corresponding performance metric information that characterizes the EHF performance of that CUT  220 . In some scenarios, the performance metric information may be the attenuation and/or phase shift/discontinuity information. In general, any desired performance metric for characterizing the EHF performance of CUT  220  may be used. 
     At step  248 , test host  86  may determine whether CUT  220  exhibits satisfactory EHF performance based on the generated performance metric data. The EHF performance may be considered satisfactory if, for example, the generated performance metric data falls within a range of acceptable performance metric values (e.g., the performance metric data has a magnitude that is greater than a minimum acceptable performance metric threshold and/or that is less than a maximum acceptable performance metric threshold). The performance metric thresholds may, for example, be determined by manufacturer requirements, regulatory standards, standards set by the designer of circuitry  220 , or any other desired threshold. 
     If test host  86  determines that CUT  220  has unsatisfactory EHF performance, processing may proceed to step  260  as shown by path  258 . At step  260 , test system  80  may take suitable action. For example, that CUT  220  may be labeled as “failing” testing, may be discarded, or may be reworked. As an example, in scenarios where the performance metric information includes attenuation information, high levels of attenuation of the EHF test signals (e.g., attenuation greater than a minimum acceptable attenuation threshold value) may be indicative of poor or unsatisfactory EHF performance of CUT  220 . As such, if an attenuation value is generated for CUT  220  that exceeds the minimum acceptable threshold, that CUT  220  may be labeled as failing testing and may be reworked. 
     If test host  86  determines that CUT  220  has satisfactory EHF performance, processing may proceed to step  250  as shown by path  259 . At step  259 , controllers  102  and  116  may determine whether antennas  110  and  30  remain for processing. If antennas remain, processing may loop back to step  240  as shown by path  252  to test the EHF performance of the remaining N antennas on CUT  220 . By testing each antenna  30  at a given time, interference between different antennas  30  in array  56  may be prevented and reliable performance metric data may be gathered. In addition, individual antennas  30  that fail EHF testing may be identified if desired. 
     When all N antennas  30  have been tested and satisfactory EHF performance has been verified for each antenna  30  of CUT  220 , CUT  220  may be labeled as “passing” testing and processing may proceed to step  256 . CUTs  220  that pass testing may be further assembled within completed devices  10 . At step  256 , a new CUT  220  may be loaded into fixture  82  for testing (e.g., the steps shown in  FIG. 7  may be repeated for each CUT). In this way, the EHF performance of entire batches of CUTs that incorporate the design of reference circuit  90  may be tested. If desired, multiple test stations  80  may test CUTs  220  in parallel (e.g., in a manufacturing environment), thereby increasing overall test speed. 
       FIG. 8  is a top-down view of circuitry  98  of test system  80  (e.g., in the direction of arrow  111  of  FIGS. 3 and 6 ). Test head  98  may be used to generate calibration settings for test system  90  (e.g., as shown in  FIG. 3  and while processing step  170  of  FIG. 4 ) and/or may be used to perform EHF testing on CUTs  220  (e.g., as shown in  FIG. 6  and while processing step  174  of  FIG. 4 ). 
     As shown in  FIG. 8 , array  112  of antennas  110  may be formed on a front face of substrate  100  of test head  98 . Transmission line  134  may convey EHF signals received by antennas  110  to analyzer circuitry  88 . Antennas  110  may be arranged in a grid (array) of rows and columns, or may be arranged in any other desired pattern or shape. Antennas  110  are shown in  FIG. 8  as being rectangular patch antennas but, in general, antennas  110  may each have any desired shape and may each be any desired type of antenna. Each antenna  110  may be identical or two or more of antennas  110  may be different (e.g., as long as each antenna  110  is identical to and aligns with a corresponding antenna  30  on CUT  220  or reference circuit  90  when loaded into fixture  82 ). 
     Alignment structures  104  may be formed on the front face of substrate  100 . In one suitable arrangement, alignment structures  104  are magnetic structures such as a permanent magnet that is attracted to magnetic or conductive alignment structures  104  on CUT  220  or reference circuit  90 . In the example of  FIG. 8 , alignment structure  104  is a permanent magnet that surrounds all of the antennas  110  in array  112 . This type of arrangement may, for example, provide a high degree of alignment between each antenna  110  and a corresponding antenna  30  when placed in test fixture  82 . This is merely illustrative. If desired, alignment structure  104  may surround some but not all of antennas  110  or may have any other desired shape. For example, alignment structure  104  may be formed from separate structures adjacent to the edges of substrate  100  such as at locations  105 . Alignment structure  104  may, if desired, be interspersed among antennas  110  in array  112 . CUT  220  and/or reference circuit  90  may have an arrangement similar to that shown in  FIG. 8 , or alignment structures  104  on CUT  220  and reference circuit  90  may be different from alignment structures  104  on test head  98 . In general, substrate  100  may have any desired shape. 
       FIG. 9  shows an illustrative manufacturing system that may be used to test and assemble millimeter wave circuitry  28  within completed devices  10 . As shown in  FIG. 9 , manufacturing system  268  may manufacture a number of electronic devices  10  simultaneously (e.g., many electronic devices  10  may each be assembled on a respective assembly line in parallel). Manufacturing system  268  may manufacture electronic devices  10  by assembling different components within production devices (e.g., components such as millimeter wave circuitry  28 , etc.). Manufacturing system  268  may test the performance of components for use in electronic devices  10  (e.g., by gathering performance metric data from CUTs  220 ) using one or more millimeter wave test systems  80  (sometimes referred to herein as test stations). 
     In order to test the performance of many millimeter wave CUTs  220  for use in electronic devices  10  simultaneously, manufacturing system  268  may include a number of assembly lines  270  that each convey a respective CUT  220  to test stations  80  in parallel. Test stations  80  may gather EHF performance metric data associated with CUTs  220  and may process the EHF performance metric data to characterize the EHF performance of CUTs  220  (e.g., as shown in  FIG. 6  and while processing step  174  of  FIG. 4 ). Test stations  80  may be set using calibration settings identified for the particular design of CUT  220 . The calibration settings may be generated using a single (master or reference) test station  80  that transmits EHF test signals through a reference circuit  90  that includes the same phase shifter and antenna design as the CUTs  220  (e.g., as shown in  FIG. 3  and while processing step  170  of  FIG. 4 ). 
     CUTs  220  that have sufficient EHF performance may be conveyed to assembly equipment  272  via assembly lines  270  for further assembly, whereas failing components may be discarded or reworked. CUTs  220  that have passed testing may sometimes be referred to as millimeter wave transceiver circuitry  28  (e.g., because the millimeter wave circuitry has finished testing and is no longer “under test”). Assembly equipment  272  may further assemble circuits  220  (e.g., millimeter wave transceiver  28 ) to produce DUTs  276 . Assembly equipment  272  may, for example, modify circuitry  28 , attach circuitry  28  to additional components, combine multiple, place circuitry  28  within housing  12  or the form factor of device  10 , etc. In one suitable example, DUTs  276  may be a fully assembled and completed device  10 . 
     DUTs  276  may be conveyed to additional test stations  274  for performing additional testing if desired. Test station  274  may perform additional testing (e.g., radio-frequency testing, stress testing, software testing, mechanical testing, or any other desired testing) on DUTs  276  (e.g., while processing step  178  of  FIG. 4 ). If DUTs  276  exhibit satisfactory performance during testing, the DUTs may be labeled as passing devices. If DUTs  276  exhibit unsatisfactory performance during testing, the DUTs may be labeled as failing devices and may be disassembled, reworked, discarded, scrapped. Failing devices may be reworked without reworking millimeter wave transceiver circuitry  28 , because any failure of DUTs  276  at test station  274  will be due to factors other than unsatisfactory performance of circuitry  28  (e.g., because satisfactory performance of circuitry  28  has already been verified at test stations  80 ). The passing DUTs may be provided to additional assembly equipment, additional testing equipment, or elsewhere. In the example where DUTs  276  are fully-assembled devices  10 , DUTs  276  that have passed testing at test station  274  may be provided to an end user or other customer. 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20170210
Publication Date: 20200428
Grant Date: 20200428
Priority Date: 20160812
Inventors: EL-HASSAN, WASSIM
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q3/267", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/0085", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/101", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/101", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/0085", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/267", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/101", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q3/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/0085", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q3/267", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/14", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 61159557