PATENT DOCUMENT

Publication Number: US-9000989-B2
Application Number: US-201113212108-A
Country: US
Kind Code: B2

Title: Test system with adjustable radio-frequency probe array

Abstract:
Electronic device structures may be tested using a radio-frequency test system. The radio-frequency test system may include radio-frequency test equipment and an associated test fixture. The radio-frequency test equipment may be used in generating and measuring radio-frequency signals. The test fixture may contain adjustable structures that allow the positions of radio-frequency test probes to be adjusted. The test system may be configured to position radio-frequency probes in the test fixture so that some probe contacts form electrical connections with conductive antenna structures. The radio-frequency probes may contain other contacts that are positioned to form electrical connections with conductive electronic device housing structures. During radio-frequency testing, the test equipment in the test system may apply radio-frequency test signals to the device structures under test using the test probes. Corresponding radio-frequency test signals may be measured by the test equipment.

Claims:
What is claimed is: 
     
       1. A method of testing electronic device structures that have a plurality of antenna resonating elements and an antenna ground structure, comprising:
 coupling a plurality of radio-frequency probes to the electronic device structures so that each probe has a first probe conductor directly connected to a respective one of the antenna resonating elements and each probe has a second probe conductor directly connected to the antenna ground structure; and 
 with test equipment coupled to the radio-frequency probes, performing radio-frequency tests on the electronic device structures using the radio-frequency probes. 
 
     
     
       2. The method defined in  claim 1  wherein performing the radio-frequency tests comprises:
 applying radio-frequency signals to the electronic device structures through the radio-frequency probes from the test equipment and receiving radio-frequency signals at the test equipment from the electronic device structures through the radio-frequency probes. 
 
     
     
       3. The method defined in  claim 1  wherein performing the radio-frequency tests comprises identifying faults associated with insufficient electrical coupling between the resonating elements and the ground structures. 
     
     
       4. The method defined in  claim 1  wherein the antenna resonating elements and the antenna ground structure form at least one antenna and wherein performing the radio-frequency tests comprises identifying faults in the at least one antenna. 
     
     
       5. The method defined in  claim 1  wherein coupling the plurality of radio-frequency probes to the electronic device structure comprises positioning the radio-frequency probes using adjustable probe positioning structures. 
     
     
       6. The method defined in  claim 5  wherein positioning the radio-frequency probes comprises adjusting positions of the radio-frequency probes in first, second, and third orthogonal dimensions in three dimensional space. 
     
     
       7. The method defined in  claim 1  wherein performing the radio-frequency tests further comprises:
 with the test equipment, comparing radio-frequency signal data gathered using the probes to reference data. 
 
     
     
       8. The method defined in  claim 1  wherein performing the radio-frequency tests comprises obtaining forward transfer coefficient data using a pair of the probes. 
     
     
       9. The method defined in  claim 1  wherein performing the radio-frequency tests comprises obtaining complex impedance data using at least one of the probes. 
     
     
       10. The method defined in  claim 1  further comprising:
 clamping the electronic device structures to a test stage while performing the radio-frequency tests. 
 
     
     
       11. The method defined in  claim 1  wherein clamping the electronic device structures to the test stage comprises using a clamp and opposing horizontal and vertical locking blocks to hold the electronic device structures. 
     
     
       12. The method defined in  claim 11  further comprising:
 supporting the test stage on a sliding mechanism; and 
 with an additional clamp, clamping the test stage against at least one motion limiting structure. 
 
     
     
       13. A method of testing electronic device structures that have a plurality of antenna resonating elements and an antenna ground structure, comprising:
 coupling a plurality of radio-frequency probes to the electronic device structures so that each probe has a first probe conductor coupled to a respective one of the antenna resonating elements and each probe has a second probe conductor coupled to the antenna ground structure, wherein coupling the plurality of radio-frequency probes to the electronic device structures comprises capacitively coupling the radio-frequency probes to the electronic device structures; and 
 with test equipment coupled to the radio-frequency probes, performing radio-frequency tests on the electronic device structures using the radio-frequency probes. 
 
     
     
       14. A method of identifying an optimal set of testing locations for radio-frequency probes to couple to an electronic device structure that has a plurality of antenna resonating elements that are coupled to an antenna ground structure, comprising:
 with adjustable probe positioning structures, positioning the radio-frequency probes at a plurality of different potential testing locations so that each probe is coupled to a respective one of the antenna resonating elements and the antenna ground structure; 
 with test equipment coupled to the radio-frequency probes, transmitting radio-frequency test signals and measuring responses to the radio-frequency test signals while the radio-frequency probes are located at each of the plurality of different potential testing locations; and 
 based on the measured responses, identifying an optimal set of testing locations for the radio-frequency probes to couple to the electronic device structure. 
 
     
     
       15. The method defined in  claim 14  wherein adjusting the positions of the radio-frequency probes comprises adjusting the positions of the radio-frequency probes along first, second, and third orthogonal axes in three dimensional space. 
     
     
       16. The method defined in  claim 14  further comprising:
 with the test equipment, calculating input reflection coefficients based on the measured responses to the radio-frequency test signals.

Description:
BACKGROUND 
     This relates generally to test fixtures and more particularly, to test fixtures that are used to test electronic devices. 
     Wireless electronic devices typically include transceiver circuitry, antenna circuitry, and other radio-frequency circuitry that provide wireless communications capabilities. During testing, wireless electronic devices under test (DUTs) can each exhibit different performance levels. For example, each wireless DUT can exhibit its own output power level, gain, frequency response, efficiency, linearity, dynamic range, and other performance characteristics. 
     It can be challenging to make satisfactory measurements on electronic device structures, particularly in manufacturing environments in which low cost, low complexity, high manufacturing volumes, and high test accuracy are desired. 
     It would therefore be desirable to be able to provide improved techniques and systems for testing electronic device structures such as antenna structures and other structures associated with electronic devices. 
     SUMMARY 
     Electronic device structures such as structures associated with wireless electronic devices may be tested using a radio-frequency test system. The radio-frequency test system may include radio-frequency test equipment and an associated test fixture. The radio-frequency test equipment may be used in generating and measuring radio-frequency signals. 
     The test fixture may contain adjustable structures that allow the positions of radio-frequency test probes to be adjusted. The test fixture may allow radio-frequency test probes to be positioned in three dimensions (e.g., along first, second, and third orthogonal axes or dimensions in three dimensional space). The test fixture may include an adjustable test stage that provides support for device structures under test. The device structures under test may be all or part of the structures associated with an electronic device such as a wireless electronic device. As an example, the device structures under test may include antenna resonating element structures and conductive housing structures such as portions of a portable computer housing or housing structures for other electronic devices. The conductive housing structures and antenna resonating element structures may be used in forming an array of antennas in a completed electronic device. 
     To test device structures such as device structures that contain antenna structures, the test system may be configured to position radio-frequency probes in the test fixture so that some probe contacts in the probes form electrical connections with conductive antenna structures. The conductive antenna structures may, for example, be conductive antenna traces mounted on a substrate such as a plastic carrier. The radio-frequency probes may contain other contacts that are positioned to form electrical connections with conductive electronic device housing structures. 
     During radio-frequency testing, the test equipment in the test system may apply radio-frequency test signals to the device structures under test using the test probes. Corresponding radio-frequency test signals may be measured by the test equipment. As an example, radio-frequency tests may be performed to gather complex impedance measurements and complex forward transfer coefficient measurements. These measurements and other gathered test data may be compared to previously obtained baseline measurements on properly assembled structures to determine whether the electronic device structures under test contain a fault. For example, radio-frequency test measurements may be used to determine whether conductive antenna traces have been properly grounded to portions of a conductive device housing structure. 
     Further features of the present invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustrative diagram of a test system that may include a test fixture and test equipment for testing a radio-frequency device in accordance with an embodiment of the present invention. 
         FIG. 2  is an illustrative diagram of adjustable probe structures that may be coupled to a device under test in accordance with an embodiment of the present invention. 
         FIG. 3  is an illustrative diagram of a test stage that may hold a device under test in accordance with an embodiment of the present invention. 
         FIG. 4  shows an illustrative close-up view of adjustable probe structures with probes that may be coupled to a device under test in accordance with an embodiment of the present invention. 
         FIG. 5  shows an illustrative close-up view of adjustable probe structures with probes in accordance with an embodiment of the present invention. 
         FIG. 6  shows an illustrative view of probes that may be configured to couple to a device under test at desired test points in accordance with an embodiment of the present invention. 
         FIG. 7  is an illustrative diagram of a probe pad that may provide capacitive coupling between a probe and a test point in accordance with an embodiment of the present invention. 
         FIG. 8  is an illustrative diagram of an absorber block that may absorbs radio-frequency signals in accordance with an embodiment of the present invention. 
         FIG. 9  shows a perspective view of a radio-frequency antenna that is electrically coupled to conductive ground structures via conductive braces. 
         FIG. 10  shows a cross-sectional side view of the radio-frequency antenna of  FIG. 9 . 
         FIG. 11  shows a cross-sectional side view of a radio-frequency antenna that located on top of a display driver. 
         FIG. 12  shows a cross-sectional side view of the radio-frequency antenna of  FIG. 11  that is coupled to a conductive laptop housing structure via conductive braces and conductive screws. 
         FIG. 13  is an illustrative diagram of a test stage operable to hold a device under test with a radio-frequency antenna and adjustable probe structures operable to couple to the device under test at desired test points in accordance with an embodiment of the present invention. 
         FIG. 14  shows an illustrative close-up view of adjustable probe structures with probes that may be configured to couple to test points on a device structure under test in accordance with an embodiment of the present invention. 
         FIG. 15  shows an illustrative close-up view of a first set of test points from  FIG. 14  in accordance with an embodiment of the present invention. 
         FIG. 16  shows an illustrative close-up view of a second set of test points from  FIG. 14  in accordance with an embodiment of the present invention. 
         FIG. 17  shows an illustrative perspective view of a support structure that may be used to support an adjustable test stage in accordance with an embodiment of the present invention. 
         FIG. 18  shows an illustrative perspective view of a support structure that may be used to hold a test stage in accordance with an embodiment of the present invention. 
         FIG. 19  shows an illustrative perspective view of a support structure with a test stage that may be used to hold a device under test in accordance with an embodiment of the present invention. 
         FIG. 20  is a flowchart showing illustrative steps that may be performed to identify structural faults using a test system with a test fixture in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     This relates to test systems for testing electronic device structures. Electronic device structures may be tested to reveal the presence of faults during manufacturing. If a fault is detected, the device structures under test may be reworked or scrapped before additional manufacturing operations are performed. 
     The test systems may use radio-frequency test equipment to generate and measure radio-frequency signals. The test equipment may, for example, generate radio-frequency signals in a range of about 0-6 GHz (as an example). The radio-frequency signals may be applied to device structures under test using one or more radio-frequency test probes. During testing, the radio-frequency test equipment may gather corresponding radio-frequency test data (e.g., test data for computing complex impedance values and/or complex forward transfer coefficient values). The test data that is gathered in this way may be used in determining whether the tested structures are satisfactory or contain faults. 
     In other words, radio-frequency testing may be performed on electronic device structures (e.g., electronic device structures that have many antenna resonating elements and an antenna ground structure) by applying radio-frequency signals to the electronic device structures through radio-frequency probes from test equipment and receiving radio-frequency signals at the test equipment from the electronic device structures through the radio-frequency probes. 
     The radio-frequency test probe equipment that is used in applying radio-frequency test signals to the device structures under test and that is used in gathering corresponding radio-frequency test measurements may be mounted in a test fixture. 
     Any suitable electronic device structures that are sensitive to radio-frequency testing may be tested using the test system. For example, electronic devices such as wireless electronic devices may be tested after some or all components within the devices have been assembled. Partially formed devices may also be tested. For example, portions of a device housing and/or other structures such as antenna structures may be tested. These structures and devices are sometimes referred to as devices under test and/or device structures under test. 
     Examples of device structures under test that may be tested using the test system include structures associated with electronic devices such as desktop computers, computer monitors, computer monitors containing embedded computers, wireless computer cards, wireless adapters, televisions, set-top boxes, gaming consoles, routers, or other electronic equipment. Examples of portable wireless electronic device structures that may be tested include structures associated with cellular telephones, laptop computers, tablet computers, handheld computers, media players, and small devices such as wrist-watch devices, pendant devices, headphone and earpiece devices, and other miniature devices. Examples of test units (sometimes referred to as test boxes or test equipment) that may be used in the test system include network analyzers (e.g., vector network analyzers), spectrum analyzers, oscilloscopes, and other radio-frequency testers. 
     Test system  2  in  FIG. 1  shows an illustrative system that may be used to test a device under test  8 . Test system  2  may include test equipment  12  and a test fixture  10  that may hold a device under test  8 . During manufacturing testing, device under test  8  (e.g., device structures under test that are associated with an electronic device such as a wireless device) may be tested in test fixture  10  as shown in  FIG. 1 . Test fixture  10  may be coupled to test equipment  12  via cables  18 . Cables  18  may be cables such as coaxial cables that are suitable for transmitting radio-frequency (RF) signals. Test fixture  10  may be used by test equipment  12  to test electronic device  8 . Test fixture  10  may include probe structures  14 , a test stage  16 , a support structure  17 , an adjusting mechanism  20  for physically adjusting test stage  16  and an adjusting mechanism  21  for physically adjusting probe structures  14 . 
     Test system  2  may be used to detect faults in conductive housing structures, faults associated with welds or solder joints between conductive structures, antenna structure faults, faults in connector structures such as connector structures coupled to cables and printed circuit boards or other conductive structures that form electrical connections, faults in conductive traces, faults in conductive surfaces, faults in dielectric structures adjacent to conductive structures, faults in structures that include components that are electrically connected using springs or other contacts, or faults in other device structures under test  8 . Any fault that affects the electromagnetic properties of device structures under test  8  and therefore affects radio-frequency test data that is gathered using test equipment  12  may potentially be detected using test system  2 . For example, radio-frequency testing may identify faults associated with insufficient electrical coupling between antenna resonating elements and ground structures. 
     Test equipment (tester)  12  may be a radio communications tester of the type that is sometimes referred to as a test box or a universal radio communications tester. Testers of this type may perform radio-frequency signaling tests for a variety of different radio-frequency communications bands and channels. Test equipment  12  may include signal generator equipment that generates radio-frequency signals over a range of frequencies. Test equipment  12  may also include radio-frequency transceiver circuitry that is able to transmit the radio-frequency signals and able to gather information on the magnitude and phase of corresponding received signals from device structures under test  8  and may include one or more displays for displaying the gathered information. Test equipment  12  may include processing circuitry that can process the gathered information (e.g., by comparing the gathered information to reference information). Using the transmitted and received signals, the magnitude and phase of the complex impedance and/or complex forward transfer coefficient of the device structures under test may be determined. With one suitable arrangement, test equipment  12  may be a vector network analyzer (VNA) or other network analyzer and a computer that is coupled to the vector network analyzer for gathering and processing test results. This is, however, merely illustrative. Test equipment  12  may include any suitable equipment for generating radio-frequency test signals of desired frequencies while measuring and processing corresponding received signals. 
     For example, test equipment  12  may perform S-parameter tests such as input reflection coefficient tests (S 11  tests) that measure input reflection coefficients at desired test points (e.g., locations) on the device structure under test. If desired, any type of radio-frequency tester may be used to test device  8 . 
     Test equipment  12  may be coupled to probe structures  14  via radio-frequency (RF) paths  18 . RF paths  18  may be formed from cables such as coaxial cables that are suitable for transmitting RF signals to probe structures  14 . Probe structures  14  may be coupled to a device under test via coupling paths  25  and  26 . Coupling path  25  may couple probe structures  14  and an antenna resonating element  22  of device under test  8 . Coupling path  26  may couple probe structures  14  to conductive ground structures  24  of device under test  8 . Probe structures  14  may be physically adjustable via adjusting mechanism  21 . Adjusting mechanism  21  may adjust probe structures  14  to contact device under test  8  (e.g., coupling paths  25  and  26  may be provided by adjusting probe structures  14  to physically contact DUT  8 ). If desired, adjusting mechanism  21  may be formed as part of probe structures  14 . Adjusting mechanism  21  may sometimes be referred to as adjustable probe positioning structures (e.g., adjustable structures that position radio-frequency probes to contact DUT  8 ). 
     The scenario of  FIG. 1  showing probe structures  14  coupled to antenna resonating element  22  and conductive ground structures  24  is merely illustrative. Probe structures  14  may be coupled to any desired locations of device structures under test  8  that may contain structural faults. 
     Device under test (DUT)  8  may be located on a test stage  16  that provides structural support during testing. Test stage  16  may be adjusted via adjusting mechanism  20  to more precisely control contacts between probe structures  14  and test points on DUT  8 . For example, adjusting mechanism  20  may allow a device under test to be moved closer to or further from probe structures  14 . 
       FIG. 2  shows an illustrative device structure under test  8  that may be coupled to probe structures  14 . As shown in  FIG. 2 , DUT  8  may include a housing unit  27  (e.g., a non-conductive plastic housing unit) with antenna resonating elements  22 . Antenna resonating elements  22  may be partially enclosed by housing unit  27 . Housing unit  27  may be located on a conductive grounding plate  28  that is electrically coupled to a conductive support structure  29  (e.g., a metal laptop housing structure). Conductive grounding plate  28  may be coupled to conductive support structure  29  using conductive flaps that clasp support structure  29 . Conductive grounding plate  28  and conductive support structure  29  may form a conductive grounding structure that couples to antenna resonating elements  22 . 
     Probe structures  14  may include probes  36 . Probe contacts  38  (sometimes referred to herein as probe conductors) may be inserted into probes  36  and probe structure  14  may be configured so that the probes contact desired test points on antenna resonating elements  22  and conductive support structure  29 . For example, to perform reflection coefficient testing, probe structure  14  may be adjusted to position a first probe contact  38  to contact a first desired test point on resonating elements  22  and position a second test probe contact  38  to contact a second desired test point on conductive support structure  29 . Test procedures may be performed using probes  36  (and probe contacts  38 ) that have been positioned at desired locations to test the integrity of the electrical coupling between conductive support structure  29  and antenna resonating elements  22  (e.g., by performing reflection coefficient testing). 
     During testing, probes  36  may be used to communicate with each other. For example, test signals may be transmitted from a first probe  36  that contacts support structure  29  at a first location and received at a second probe that contacts support structure  29  at a second location. In this scenario, conductive support structure  29  and conductive grounding plate  28  may form an electrical signal path for the test signals (e.g., for forward impedance test signals transmitted by a first probe coupled to antenna resonating element  22  and conductive support structure  29  and received by a second probe coupled to antenna resonating element  22  at a different location and conductive support structure  29 ). 
       FIG. 3  shows an illustrative DUT  8  located on a test stage  16  (sometimes referred to herein as a testing platform). Test stage  16  may provide support for DUT  8  during test procedures (e.g., by holding DUT  8  at a desired location). Probe structures  14  may be used for testing DUT  8 . For example, probe structures  14  may include test probes, probe contacts and adjustable mechanisms for positioning the test probes at desired locations for testing DUT  8 . 
       FIG. 4  shows an illustrative close-up view of probe structures  14  that may be electrically coupled to DUT  8 . As shown in  FIG. 4 , probe structures  14  may include probes  36  with probe contacts  38  and adjustable structures  32  (e.g., plastic sliding brackets or metal sliding brackets). Adjustable structures  32  may allow the locations of probes  36  to be adjusted to contact desired test points on DUT  8 . For example, adjustable structures  32  may allow probes  36  to be adjusted along a horizontal axis  39  or a vertical axis  40  (e.g., adjusted left or right along a horizontal axis of adjustable structures  32  or adjusted up and down along a vertical axis of adjustable structures  32 ). The positions of probes  36  may be adjusted vertically and horizontally by adjustable structures  32  to contact desired test points on DUT  8 . If desired, the positions of probes  36  may be adjusted towards and away from DUT  8 . Adjustable structures  32  may be formed as part of adjusting mechanisms such as adjusting mechanism  21  of  FIG. 1 . 
       FIG. 5  shows an illustrative close-up view of probe structures  14  that may be used to provide test probes with adjustable positioning. As shown in  FIG. 5 , probe structures  14  may include adjustable structures  32 , probe mounts  34 , probes  36 , and removable probe contacts  38 . Probe mount  34  may be formed from a non-conductive material (e.g., plastic) to help prevent electrical coupling between adjustable structures  32  and probes  36 . For example, a non-conductive probe mount  34  may help prevent test signals that are conveyed or received through probes  36  from being shorted to adjustable structures  32 . 
     The position of probe mounts  34  may be adjustable along the length of probe mount  34  (e.g., in a horizontal direction along horizontal axis  39 ). The position of probe mount  34  may be adjustable along the height of adjustable structures  14  (e.g., in a vertical direction along vertical axis  40 ). Probe contacts  38  may be inserted or removed from probes  36  as desired for testing. The number of probes  36  and corresponding probe contacts  38  may be selected based on the tests that are performed with probes  36 . 
     For example, it may be desirable to form probe structures  14  with multiple probes  36  and corresponding probe contacts  38  to test the structural integrity of a device under test at many test points. In this scenario, a number of probe contacts  38  equal to the number of test points may be inserted into corresponding probes  36  and each of the probe mounts  34  may be positioned so that probe contacts  38  contact the device under test at the desired test points. 
       FIG. 6  shows an illustrative view of probe contacts  38  that may be inserted into a probe  36  to contact a device structure under test (e.g., a DUT  8 ) at desired test locations. A first probe contact  38  may contact the device structure under test at a first test point  102 A and second probe contact  38  may contact device  8  a second test point  102 B. Probes  36  may be configured to measure test values at the test points. For example, test point  102 A may correspond to a location on antenna resonating element  22  and test point  102 B may correspond to a location on grounding structure  24  that is electrically coupled to the antenna resonating element. In this scenario, probe  36  may be used to test the integrity of the electrical coupling between grounding structure  24  and antenna resonating element  22  by transmitting test signals to the device under test and measuring the responses to the test signals. 
     Test procedures such as those used during radio-frequency testing may be performed using probes  36 . For example, it may be desirable to perform radio-frequency testing to identify structural faults or faulty coupling between elements of a device under test. In the example of  FIG. 6 , it may be desirable to determine whether an electrical coupling between test point  102 A (e.g., an antenna resonating element) and test point  102 B (e.g., a test point on a nearby grounding structure) is faulty. To perform radio-frequency testing, probes  36  may be positioned (e.g., using associated adjustable structures  32 ) to contact test points  102 A and  102 B and test signals may conveyed through some of probes  36 . The response of the device structure under test to the test signals may be measured to identify the existence of structural faults, faulty coupling, or other manufacturing defects that affect the response of the device under test to the test signals. 
     In one embodiment, a radio-frequency test signal may be transmitted from probes  36  to an antenna resonating element via test point  102 A (e.g., transmitted via a corresponding probe contact  38 ). An input reflection coefficient (e.g., a complex impedance coefficient or S 11  measurement) may be obtained by using the probes to measure how much of the transmitted radio-frequency test signal is reflected. The input reflection coefficient may be compared to a reference input reflection coefficient. The reference input reflection coefficient may correspond to how much of a radio-frequency test signal is reflected by a device under test that does not contain manufacturing faults or defects. Test procedures that measure input reflection coefficients may sometimes be referred to as S 11  parameter measurements or complex impedance measurements. 
     In another embodiment, S 21  parameter measurements (sometimes referred to as complex forward transfer measurements) may be made by measuring how much of a radio-frequency test signal transmitted by a first test probe  36  positioned at a first location reaches a second test probe positioned at a second location. For example, a first test probe  36  coupled to test point  102 A and  102 B may be used to measure how much of a radio-frequency test signal transmitted by a second test probe  36  at a second location reaches the first test probe. In this scenario, a measured transmittance value (e.g., a value corresponding to how much of the radio-frequency test signal reaches test point  102 B and  102 A) may be compared to a reference transmittance value (e.g., a reference value obtained by performing S 21  parameter measurements on a device known to have been manufactured properly) to identify whether or not manufacturing defects exist. 
     In situations in which device structures under test  8  are fault free, S 11  and S 21  measurements will have values that are relatively close to baseline measurements on fault-free structures (sometimes referred to as reference structures or “gold” units). In situations in which device structures under test  8  contain a fault (e.g., a structural fault) that affects the electromagnetic properties of device structures under test  8 , the S 11  and S 21  measurements will exceed normal tolerances. When test equipment  12  determines that the S 11  and/or S 21  measurements have deviated from normal S 11  and S 21  measurements by more than predetermined tolerance values, test equipment  12  can alert an operator that device structures under test  8  likely contain a fault and/or other appropriate action can be taken. 
     For example, an alert message may be displayed on a display associated with test equipment  12 . The faulty device structures under test  8  may then be reworked to correct the fault or may be scrapped. With one suitable arrangement, an operator of test equipment  12  may be alerted that device structures under test  8  have passed testing by displaying an alert message such as a green screen and/or the message “pass” on a display. The operator may be alerted that device structures under test  8  have failed testing by displaying an alert message such as a red screen and/or the message “fail” on display  200  (as examples). If desired, S 11  and/or S 21  data can be gathered over limited frequency ranges that are known to be sensitive to the presence or absence of faults (e.g., coupling faults between components of device structures under test  8 ). This may allow data to be gathered rapidly (e.g., so that the operator may be provided with a “pass” or “fail” message within less than 30 seconds, as an example). 
     Device structures under test may include a cosmetic portion  37 . It may be desirable when testing to avoid physical contact between probe contacts  38  and cosmetic portion  37 . For example, cosmetic portion  37  may be formed of materials such as aluminum, magnesium, plastic, or anodized surfaces that can be easily scratched by probe contacts  38 . This example is merely illustrative. Cosmetic portion  37  may be formed from an oxidization layer, anodization layer, metals, plastics, or other easily damaged materials. Cosmetic portion  37  may be formed as part of a housing structure, grounding structure, antenna element, or other device structures that may be easily damaged by contact with probe contacts  38 . 
     To minimize damage to cosmetic portion  37 , an insulating material may be interposed between probe contacts  38  and cosmetic portion  37 . In this scenario, the insulating material may be formed from a material that minimizes damage to cosmetic portion  37  (e.g., insulating foam material). The insulating material may prevent probe contacts  38  from contacting cosmetic portion  37  and thereby prevent the probes from physically damaging cosmetic portion  37 . The insulating material may help prevent test signals that are being conveyed via probe contacts  38  from shorting to cosmetic portion  37 . 
     It may be desirable to test some portions of a device under test without direct physical contact between probe contacts  38  and desired test points. For example, it may be desirable to test cosmetic portion  37  without damaging a surface of cosmetic portion  37 . Capacitive testing may be used to test device structures  8  with an insulating material interposed between probe contacts  38  and desired test points. 
       FIG. 7  shows an illustrative scenario in which a probe  36  may be electrically coupled to a conductive structure  102  at a test location  104  without damaging conductive structure  102 . As shown in  FIG. 7 , probe contact  38  may be electrically coupled to probe pad  108  (e.g., by physically contacting probe pad  108 ). A dielectric material  110  (e.g. a dielectric material) may be interposed between probe pad  108  and conductive structure  102 . Dielectric material  110  may be, for example, a sheet of polymer such as a polyimide sheet in a flexible printed circuit (“flex circuit”). Probe pad  108  may be formed from a metal trace in the flex circuit. When placed against conductive structure  102 , conductive probe pad  108  and a surface of conductive structure  102  may form a parallel plate capacitor. Because probe  36  is not used to directly probe conductive structure  102 , the surface of conductive structure  102  will generally not be scratched (e.g., by probe contact  38 ) during testing, which may be helpful when conductive structure  102  has a cosmetic surface that should not be damaged during testing. 
     A combination of probe  36  that contacts probe pad  108  via a probe contact  38  that is surrounded by dielectric material  110  may sometimes be referred to herein as a capacitive probe (e.g., capacitive probe  112  that may be used to perform capacitive testing on a device under test). 
     Dielectric material  110  covers probe pad  108  and, when capacitive probe  112  is placed against the surface of conductive structure  102  during testing, dielectric material  110  electrically isolates (insulates) probe pad  108  from conductive structure  102 . Because electrical coupling is achieved without requiring direct metal-to-metal contact between probe pad  108  and conductive structure  102  or between probe contact  38  and conductive structure  102 , satisfactory electrical coupling can be achieved at radio frequencies even in the presence of an oxide or other coating that may give rise to a non-negligible contact resistance when probing the conductive structure with pins. 
     The capacitive electrical coupling between probe pad  108  and conductive structure  102  may be used to perform radio-frequency testing (e.g., S 11  testing, S 21  testing, or other types of radio-frequency testing). Test signals may be transmitted from probes  36  to test location  104  (e.g., a test location  104  corresponding to desired test points on a device under test) via capacitive probe  112 . 
     Test signals may be received using capacitive probe  112 . For example, an S 11  test may be performed using capacitive probe  112 . During the S 11  testing, a radio-frequency test signal may be transmitted from probe  36  to test location  104  via capacitive probe  112 . S 11  coefficients may be obtained by using capacitive probe  112  to measure how much of the radio-frequency test signal is reflected. 
     As shown in  FIG. 7 , conductive structure  102  may, if desired, be covered with a dielectric coating such as coating  106 . For example, conductive structure  102  may be formed from metal with a layer of plastic, a native oxide such as a native oxide on stainless steel or other metals having a thickness of less than 5 microns, or other dielectric films. Coating  106  may be associated with a protective coating, a logo on a housing member, a cosmetic trim, or other structures. Interior portions of conductive structures, exterior portions (i.e., cosmetic exterior portions), combinations of interior and exterior portions, or other suitable areas on conductive structure  102  may be probed with capacitive probe  112  if desired. 
       FIG. 8  shows an illustrative view of an absorber block  17  which may provide radio-frequency isolation for test fixture  10 . Absorber block  17  may be assembled via screws  53 ,  54 ,  55 , and  56 . 
     Absorber block  17  may include a horizontal structure  58  formed from a bottom plate  52 , side plates  41  and  42 , and a top plate  48 . Horizontal structure  58  may be formed underneath other components of test fixture  10  (e.g., horizontal structure  58  may be formed underneath other support structures such as test stage  16  and probe structures  14 ). Bottom plate  52 , side plates  41  and  42 , and top plate  48  may be formed from materials such as acrylics, plastics, or insulating materials. The horizontal structure may include a radio-frequency absorber  46  formed from a material that attenuates radio-frequency signals. 
     Absorber block  17  may include one or more vertical structures  59  each formed from a front plate  47 , back plate  51 , and side plates  43  and  44 . Plates  47 ,  51 ,  43 , and  44  may be formed from acrylic materials such as poly-methyl methacrylate (PMMA). The vertical structures may contain a radio-frequency absorber  46  formed from a material that attenuates radio-frequency signals. 
     Radio-frequency absorbers  46  may be formed from dielectric materials (e.g., polyurethane foam sheets that have been injected with a conductive solution), magnetic materials (e.g., iron or ferrite material), or other materials suitable for absorbing radio-frequency signals. 
     Horizontal structure  58  and vertical structure  59  may be coupled via structural boards  49  formed from a non-conductive material such as a plastic material (e.g., polyoxybenzylmethylenglycolanhydride). Horizontal structure  58  may be located underneath probe structures  14 , test stage  16 , and device under test  8 . Vertical structure  59  may form a side wall that absorbs radio-frequency signals. If desired, additional vertical structures  59  may be added to each side of horizontal structure  58  to provide an absorber block  17  with radio-frequency absorption on all sides. If desired, an additional horizontal structure  58  may be formed on top of vertical structure  59  and bottom horizontal structure  58 . In this scenario, the combined horizontal structures and vertical structures may substantially enclose test fixture  10 . 
     Absorber block  17  may be used to isolate test fixture  10  from a testing environment. Absorber block  17  may prevent radio-frequency signals originating from external sources from affecting probes such as probes  36  during test measurements. For example, absorber block  17  may help isolate test fixture  10  from radio frequency signals that originate from nearby test systems, mobile cell phones, laptop devices, or other electronic devices. Absorber block  17  may also help prevent radio-frequency test signals generated by associated test equipment  12  from leaving test system  2  (e.g., absorber block  17  in a first test system may help prevent radio-frequency test signals generated by the first test system from reaching a second test system). 
       FIG. 9  shows an illustrative view of a device structure under test  8  that may be tested. As shown in  FIG. 9 , device structure under test  8  may include a radio-frequency antenna that is electrically coupled to conductive ground structures  24  via conductive braces  62  (sometimes referred to as waterfalls). The radio-frequency antenna may include plastic housing structure  64  and antenna resonating elements  22 . 
     It may be desirable to identify whether the device under test of  FIG. 9  contains structural faults. For example, it may be desirable to test the electrical coupling between the radio-frequency antenna and conductive ground structures  24  (e.g., if conductive braces  62  do not properly contact conductive ground structures  24 , normal operation of the radio-frequency antenna may be affected). 
       FIG. 10  shows an illustrative cross-sectional side view of the radio-frequency antenna of  FIG. 9  that is electrically coupled to conductive ground structures  24  via conductive braces  62 . 
       FIG. 11  shows an illustrative cross-sectional side view of a device structure under test  8  that may be part of a wireless device (e.g., a laptop). Device under test  8  may include a radio-frequency antenna located on top of a display driver  72 . The radio-frequency antenna may be coupled to a conductive laptop housing structure  24  via conductive braces  62 . The display driver  72  may be coupled to a laptop display  73  via a flexible path  74  (e.g., a flex circuit). Display driver  72  may provide display signals to laptop display  73  via path  74 . 
       FIG. 12  shows an illustrative cross-sectional perspective view of the device structure under test  8  of  FIG. 11  that has a radio-frequency antenna coupled to a conductive laptop housing structure  24  via conductive braces  62  and conductive screws  82 . Conductive screws  82  and conductive braces  62  may provide grounding paths between the radio-frequency antenna and conductive laptop housing structure  24 . It may be desirable to test the integrity of the coupling between conductive braces  62  and housing structure  24  or the coupling between conductive screws  82  and housing structure  24  (e.g., to identify faults that may affect normal operation of the radio-frequency antenna). 
       FIG. 13  shows an illustrative test fixture with a device structure under test  8  located on a test stage  16 . DUT  8  may be tested using probe structures  14  that may be adjusted by adjustable structures  32  to electrically couple to test points on DUT  8 . For example, probe structures  14  may be adjusted in three-dimensional space to electrically couple to locations on a radio-frequency antenna and couple to locations on a conductive housing structure. 
       FIG. 14  shows an illustrative close-up view of the test points of  FIG. 13 . As shown by  FIG. 14 , probe structures  14  may include probes  36  that may be coupled to test points  92  on device  8 . Probe contacts  38  may be mounted in probes  36 . Probe structures  14  may be adjusted in three-dimensional space (e.g., along first, second and third orthogonal axes or dimensions in three-dimensional space) to reliably, precisely, and accurately couple probes  36  to various desired test points  92  located on DUT  8 . Test procedures (e.g., test procedures associated with S-parameter testing) may be performed by transmitting test signals to device under test  8  via probes  36 . 
     Device structures under test  8  may have components that vary in exact size and shape. Manufacturing tolerances may introduce slight variations in component dimensions, which may alter the optimal locations of test points  92 . By providing a test fixture with adjustable probe structures  14 , the positions of probes  36  may be adjusted in real-time (e.g., during manufacturing) to contact each device structure under test  8  at test points that are optimal for that particular device structure. 
       FIG. 15  shows an illustrative close-up view of a first set of test points from  FIG. 13 . As shown in  FIG. 14 , probe  36  may be adjusted to contact a first test point  102 C of the first set of test points (e.g., a test location on an antenna resonating element) and a second test point  102 D of the first set of test points (e.g., a test point on a conductive ground structure). Test point  102 C may correspond to an antenna resonating element. Test point  102 D may correspond to a location on a conductive ground structure near test point  102 C. The antenna resonating element and conductive ground structure may be coupled via a brace  62  that provides an electrical path between the antenna resonating element and conductive ground structure. Radio-frequency test procedures may be performed to test the integrity of the electrical path provided by brace  62  (e.g., the path between the antenna resonating element corresponding to test point  102 C and the conductive ground structure corresponding to test point  102 D). 
       FIG. 16  shows an illustrative close-up view showing a second set of test points from  FIG. 13 . As shown in  FIG. 15 , probe  36  may be adjusted to contact a first test point  102 E of the second set of test points and a second test point  102 F of the second set of test points. Test point  102 F may correspond to a location on a conductive ground structure. Test point  102 E may correspond to an antenna resonating element that is coupled to the conductive ground structure (e.g., via a metal screw  82  as shown in  FIG. 12 ). Radio-frequency testing may be performed to test the integrity of the coupling between the antenna resonating element at test point  102 E and the conductive ground structure at test point  102 F. 
       FIG. 17  shows an illustrative support structure  150  operable to hold an associated test stage and device under test in a stable configuration for testing. In one embodiment, support structure  150  may be located on or enclosed by an absorber block that isolates the support structure from a testing environment. Support structure  150  may include a support block  152 . Support structure  150  may include limit blocks  158 , clamp  156  (sometimes referred to as a toggle clamp), and adjusting mechanism  155 . 
     A test stage (and an associated device under test) may be placed on adjusting mechanisms  155 . Adjusting mechanisms  155  may allow the positioning of the test stage to be adjusted horizontally along the length of adjusting mechanisms  155  (e.g., adjusting mechanisms  155  may allow a test stage to be adjusted along axis  162 ). 
     Clamp  156  may exert a clamping force on a test stage placed on adjusting mechanisms  155 . The clamping force may be exerted along axis  162  towards limiting block  154 . Limiting block structures  154  or other suitable motion limiting structures may be provided to limit the motion of the test stage along adjusting mechanisms  155 . Limiting block structures  154  may include a limiting peg  160  (sometimes referred to herein as a limit stick). Limiting peg  160  may determine the positioning of the test stage. For example, clamp  156  may exert a clamping force on the test stage that pushes the test stage towards limiting blocks  154 . The clamping force may force the test stage against limiting pegs  160 , thereby holding the test stage in a stable position for testing. 
     Buffers  158  may help prevent damage to the test stage or limiting pegs that is caused by the clamping force exerted by clamp  156 . For example, buffers  158  may be hydraulic spring buffers that help accommodate the clamping force exerted on the test stage. In this scenario, hydraulic spring buffers  158  may help limiting pegs  160  receive and accommodate a test stage that is pushed by a clamp  156  without damaging the test stage or limiting pegs  160 . 
     A test stage  16  (e.g., test stage  20  of  FIG. 1 ) may be placed on adjusting mechanisms  155  of  FIG. 17 . As shown in  FIG. 18 , test stage  16  may include a first layer  164  and a second layer  166 . Layer  166  and a clamp  168  (sometimes referred to as a toggle clamp) may be formed on layer  164 . A test unit (e.g., a DUT  8 ) may be placed on top of the second layer for testing. During testing, clamp  168  may exert a clamping force on the device under test. The clamping force may be exerted in direction  174  (e.g., in a diagonal direction across layer  166 ). In other words, clamp  168  may clamp a DUT to the test stage with opposing horizontal and vertical locking blocks while radio-frequency tests are being performed. 
     Suction cups  176  may be formed on layer  166  to help attach the test unit to the test stage. Suction cups  176  may be formed of rubber or other desirable materials. The test unit may be attached to the test stage via air pressure (e.g., the test unit may be attached to the test stage by air pressure imbalances that are produced by the deformation of suction cups  176  when a test unit is placed on top of layer  166 ). 
     Vertical locking blocks  172  and horizontal locking blocks  170  may be formed on layer  166 . Vertical locking blocks  172  and horizontal locking blocks  170  may together provide a structure for clamp  168  to pin a test unit against (e.g., horizontal locking block  170  may accommodate a horizontal portion of a clamping force exerted by clamp  168  in diagonal direction  174  and vertical locking block  170  may accommodate a vertical portion of the clamping force exerted in diagonal direction  174 ). By clamping a device under test to layer  166  via clamp  168  and locking blocks  170  and  172 , the stability of a test unit during testing may be improved, thereby improving the consistency and reliability of test procedures that are performed. 
       FIG. 19  is a block diagram of a device structure under test  8  and illustrative probe test locations. As shown in  FIG. 19 , DUT  8  may include antenna housing  64  and conductive ground structures  24 . Antenna housing  64  may include antenna resonating elements  22  (e.g., RE  1 , RE  2 , RE N, etc.). Each antenna resonating element  22  may be electrically coupled to conductive ground structures  24  via paths  182 . Paths  182  may correspond to metal screw  82  and conductive braces  62  of  FIG. 12  (as examples). To test the integrity of conductive paths  182 , probes such as probes  36  of  FIG. 16  may be coupled to antenna resonating elements  22  and conductive ground structures  24 . In the example of  FIG. 19 , probe contacts PA 1  and PB 1  may correspond to a first probe. Probe contacts PA 2  and PB 2  may correspond to a second probe. Probe contacts PAN and PBN may correspond to a third probe. Probe contacts PA 1 , PA 2 , and PAN may be simultaneously coupled to respective antenna resonating elements PA 1 , PA 2 , and PAN. Probe contacts PB 1 , PB 2 , and PBN may be coupled to locations on conductive ground structures  24 . Radio-frequency tests such as S 21  and S 11  tests may be performed using the probes to test the integrity of each conductive path  182 . The radio-frequency tests may be performed using pairs of probes (e.g., a pair of probes may be formed from a first probe including probes PA 1  and PB 1  and a second probe including probes PA 2  and PB 2 ). If desired, the radio-frequency tests may be performed using several pairs of probes simultaneously or in sequence. 
     The number of conductive paths  182  shown in  FIG. 19  is merely illustrative. Any number of conductive paths  182  may exist depending on the electronic device structure under test. 
       FIG. 20  shows illustrative steps that may be performed to test device structures using test system  2 . As an example, the steps of  FIG. 20  may be performed during assembly of an electronic device to identify device structures that are unsuitable for complete assembly. 
     In step  202 , a device structure under test (e.g., DUT  8 ) may be secured on a test stage and a support structure (e.g., test stage  16  and support structure  17 ). The device structure under test may be placed on the test stage manually (e.g., by an operator) or automatically (e.g., by a robotic device). The device structure under test may be secured using clamps, locking blocks, limiting blocks, or other structures desirable for holding a device under test in a stable configuration. The support structure may include an absorber block that helps absorb undesired radio-frequency signals. 
     In step  204 , probes may be adjusted to desired test locations on the device structures under test. For example, adjustable probe structures  14  and adjusting mechanisms  155  may be adjusted so that probes  36  contact many antenna resonating elements and conductive ground structures of the device structures under test. The probes may be adjusted manually (e.g., by an operator) or automatically (e.g., by automated testing machines or robots). 
     In step  206 , test signals (e.g., radio-frequency test signals) may be applied to the desired test locations. For example, test equipment that is coupled to probe structures  14  may provide radio-frequency test signals. In this scenario, the radio-frequency test signals may be transmitted to the device structures under test at the desired test locations via probes  36 . 
     In step  208 , test data may be gathered using the probes. For example, test equipment may use probes  36  to receive and measure responses to the test signals. The responses to the test signals may be received at the test probes that were used to transmit the test signals or at other test probes. For example, a first test probe coupled to an antenna resonating element and an antenna ground structure may be used to transmit a test signal. In this scenario, a response to the test signal may be measured with the first test probe or with a second test probe (e.g., a second test probe coupled to a second antenna resonating element at a location near the first probe). 
     In step  210 , the gathered test data may be analyzed. The gathered test data may be compared to reference data (e.g., baseline measurements on fault-free device structures). Device structures under test may fail testing if structural faults or other faults exist that affect the device structure&#39;s response to radio-frequency test signals. 
     If the gathered test data does not closely match the reference data (e.g., if the gathered test data differs from the reference data by more than a predetermined tolerance), the device structures under test may fail testing and the operations of step  214  may be performed. If the gathered test data closely matches the reference data (e.g., if the gathered test data lies within a tolerance range), the device structures under test may pass testing and the operations of step  212  may be performed. 
     If desired, a new optimal test location may be determined by tuning the current test locations based on the gathered test data. For example, before mass production of a new device structure, the new device structure may be tested to identify the optimal test locations for the probes. In this scenario, if the gathered test data is of poor quality (e.g., if the response to the test signals is weak), a new optimal test location may be chosen and steps  204 - 210  may be performed with the new optimal test location. 
     In step  212 , an alert may be issued or other suitable actions may be taken in response to a device structure that passes testing. For example, an alert may be displayed using test equipment  12  that informs an operator that the device structure under test is suitable for further assembly. 
     In step  214 , an alert may be issued or other suitable actions may be taken in response to a device structure that fails testing. For example, an alert may be displayed using test equipment  12  that informs an operator that the device structure under test is unsuitable for further assembly. As another example, the device structure under test may be flagged for repair or removal from assembly. 
     In other words, an optimal set of testing locations for radio-frequency probes to couple to an electronic device structure that has one or more antenna resonating elements that are coupled to an antenna ground structure may be identified by positioning radio-frequency probes at many different potential testing locations and using test equipment to perform radio-frequency tests while the probes are coupled to the potential testing locations. Each probe may be coupled to a respective antenna resonating element and an antenna ground structure. Based on responses measured with the probes, an optimal set of testing locations may be chosen from the potential testing locations. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20110817
Publication Date: 20150407
Grant Date: 20150407
Priority Date: 20110817
Inventors: NICKEL JOSHUA G.
GUTERMAN JERZY
PASCOLINI MATTIA
CHEN CHUN-LUNG
GIDDINGS JOSS NATHAN
Assignee: APPLE INC
CPC Classifications: [{"code": "G01R31/2824", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01R29/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R31/2824", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01R29/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R29/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R31/2824", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 47712288