PATENT DOCUMENT

Publication Number: US-9157954-B2
Application Number: US-201113153153-A
Country: US
Kind Code: B2

Title: Test system with temporary test structures

Abstract:
Electronic device structures such as a conductive housing member that forms part of an antenna may be tested during manufacturing. A test system may be provided that includes a test probe configured to energize the conductive housing member or other conductive structures under test and that includes temporary test structures that may be placed in the vicinity of or in direct contact with the device structures during testing to facilitate detection of manufacturing defects. Test equipment such as a network analyzer may provide radio-frequency test signals in a range of frequencies. An antenna probe may be used to gather corresponding wireless radio-frequency signal data. Forward transfer coefficient data may be computed from the transmitted and received radio-frequency signals. The forward transfer coefficient data or other test data may be compared to reference data to determine whether the device structures contain a fault.

Claims:
What is claimed is: 
     
       1. A test system for detecting manufacturing defects in conductive electronic device antenna structures under test, comprising:
 temporary test structures that are brought into contact with the conductive electronic device antenna structures under test only during testing; 
 a fixture that receives the conductive electronic device antenna structures under test and the temporary test structures, wherein the temporary test structures are configured to enhance the detection of manufacturing defects; and 
 test probe structures configured to convey radio-frequency test signals to the conductive electronic device antenna structures under test and to receive corresponding test data from the conductive electronic device antenna structures under test while the radio-frequency test signals are being conveyed to the conductive electronic device antenna structures under test. 
 
     
     
       2. The test system defined in  claim 1 , wherein the test probe structures comprise a first test probe configured to convey the radio-frequency test signals to the conductive electronic device antenna structures under test, and wherein the first test probe comprises a test probe selected from the group consisting of: a wired test probe, a wireless test probe, and a capacitive coupling test probe. 
     
     
       3. The test system defined in  claim 2 , wherein the test probe structures comprise a second test probe configured to receive the corresponding test data from the conductive electronic device antenna structures under test, and wherein the second test probe comprises a test probe selected from the group consisting of: a wired test probe, a wireless test probe, and a capacitive coupling test probe. 
     
     
       4. The test system defined in  claim 3 , wherein the temporary test structures comprise a printed circuit board on which a transmission line path is formed, and wherein the transmission line path has a first end that is coupled to a portion of the conductive electronic device antenna structures under test and a second end that is coupled to the first test probe. 
     
     
       5. The test system defined in  claim 3 , wherein the temporary test structures comprise electronic device housing structures configured to temporarily mate with the conductive electronic device antenna structures under test while the radio-frequency test signals are being conveyed to the conductive electronic device antenna structures under test. 
     
     
       6. The test system defined in  claim 3 , wherein the conductive electronic device antenna structures under test comprise a conductive peripheral housing member having at least first and second gaps, and wherein the temporary test structures comprise a conductive member having first and second ends configured to contact respective portions of the conductive peripheral housing member on opposing sides of the second gap. 
     
     
       7. The test system defined in  claim 3 , wherein the conductive electronic device antenna structures under test comprise a conductive peripheral housing member and an antenna ground member, and wherein the temporary test structures comprise a conductive member having a first end configured to contact a portion of the conductive peripheral housing member and a second end configured to contact a portion of the antenna ground member. 
     
     
       8. The test system defined in  claim 3 , wherein the temporary test structures comprise at least one conductive structure selected from the group consisting of: a flex circuit, conductive tape, metal strip, radio-frequency cables, dielectric material, resistor, capacitor, and inductor. 
     
     
       9. A method for manufacturing an electronic device using test equipment, wherein the electronic device includes input-output devices that receive inputs directly from a user, wherein the electronic device includes device housing structures under test at least a portion of which serves as a housing for the electronic device, and wherein the test equipment includes test probe structures and a test fixture, the method comprising:
 with the test fixture, receiving the device housing structures under test; 
 mating temporary test structures with the device housing structures under test; 
 with the test probe structures, performing radio-frequency measurements on the device housing structures under test while the temporary test structures are mated with the device housing structures under test to determine whether the device housing structures under test contain a manufacturing defect; and 
 removing the temporary test structures from the device housing structures under test. 
 
     
     
       10. The method defined in  claim 9 , further comprising:
 assembling the electronic device by incorporating additional structures with the device housing structures under test, wherein the temporary test structures are configured to emulate radio-frequency characteristics associated with the additional structures when the temporary test structures are mated with the device housing structures under test during radio-frequency testing. 
 
     
     
       11. The method defined in  claim 10 , wherein the test probe structures comprise a first test probe and wherein performing the radio-frequency measurements on the device housing structures under test comprises:
 transmitting radio-frequency test signals to the device housing structures under test using the first test probe, wherein the first test probe comprises a test probe selected from the group consisting of: a wired test probe, a wireless test probe, and a capacitive coupling test probe. 
 
     
     
       12. The method defined in  claim 11 , wherein the test probe structures further comprise a second test probe and wherein performing the radio-frequency measurements on the device housing structures under test further comprises:
 receiving corresponding radio-frequency test signals from the device housing structures under test using the second test probe, wherein the second test probe comprises a test probe selected from the group consisting of: a wired test probe, a wireless test probe, and a capacitive coupling test probe. 
 
     
     
       13. The method defined in  claim 12 , wherein the test equipment further includes a test unit, the method further comprising:
 with the test unit, computing a complex impedance magnitude based on the transmitted and received radio-frequency test signals. 
 
     
     
       14. The method defined in  claim 12 , wherein the temporary test structures comprise a printed circuit board on which a transmission line path is formed and wherein mating the temporary test structures with the device housing structures under test comprises:
 coupling a first end of the transmission line path to a portion of the device housing structures under test; and 
 coupling a second end of the transmission line path to the test probe structures. 
 
     
     
       15. The method defined in  claim 12 , wherein the temporary test structures comprise temporary electronic device housing structures and wherein mating the temporary test structures with the device housing structures under test comprises:
 temporarily bearing the temporary electronic device housing structures against at least a portion of the device housing structures under test. 
 
     
     
       16. The method defined in  claim 9 , wherein the input-output devices comprise a button configured to receive inputs directly from the user. 
     
     
       17. A method for detecting manufacturing defects in device structures under test using test equipment having test probe structures and a test fixture, the method comprising:
 receiving the device structures under test with the test fixture, wherein the device structures under test comprise a peripheral conductive housing member; 
 with the test probe structures, performing radio-frequency measurements on the device structures under test while the peripheral conductive housing member is placed within the test fixture; 
 enhancing the accuracy of the radio-frequency measurements gathered using the test-probe structures by physically mating temporary test structures with the device structures under test; and 
 determining whether the device structures under test contain a manufacturing defect based on results gathered from the radio-frequency measurements. 
 
     
     
       18. The method defined in  claim 17 , wherein the peripheral conductive housing member has at least first and second gaps, wherein the temporary test structures comprise a conductive bridging member having first and second ends, and wherein performing radio-frequency measurements on the device structures under test comprises:
 gathering radio-frequency test measurements on the device structures under test while the first and second ends of the conductive bridging member is placed in contact with respective portions of the peripheral conductive housing member on opposing sides of the second gap. 
 
     
     
       19. The method defined in  claim 17 , wherein the device structures under test further comprises an antenna ground member, wherein the temporary test structures comprises a conductive shorting member, and wherein performing radio-frequency measurements on the device structures under test comprises:
 gathering radio-frequency test measurements on the device structures under test while the conductive shorting member is coupled between a portion of the peripheral conductive housing member and a portion of the antenna ground member. 
 
     
     
       20. The method defined in  claim 17 , wherein the temporary test structures comprise conductive structures selected from the group consisting of: a flex circuit, conductive tape, metal strip, radio-frequency cables, dielectric material, resistor, capacitor, and inductor. 
     
     
       21. The method defined in  claim 17 , wherein the test equipment further comprises a test unit and wherein performing radio-frequency measurements on the device structures under test comprises:
 with the test unit, transmitting radio-frequency test signals to the device structures under test; 
 with the test unit, receiving corresponding radio-frequency test signals from the device structures under test; 
 with the test unit, computing a complex impedance magnitude from the transmitted and received radio-frequency test signals; and 
 comparing the complex impedance data to reference data to determine whether the device structures under test is faulty.

Description:
BACKGROUND 
     This relates generally to testing, and more particularly, to testing electronic device structures for manufacturing faults. 
     Electronic devices such as portable computers and cellular telephones are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry such as cellular telephone circuitry and short-range wireless communications circuitry such as wireless local area network circuitry. 
     In some devices, conductive housing structures may form part of an electronic device antenna. The performance of this type of antenna may depend on how accurately the conductive housing structures are manufactured. Excessive variations in the size and shape of conductive electronic device housing structures or other manufacturing variations may have a negative impact on the performance of antennas formed using the structures. Variations in conductive electronic device structures of other types may also impact device performance. 
     It would be desirable to be able to provide ways to test electronic device structures such as conductive electronic device structures that form parts of antennas and other structures. 
     SUMMARY 
     Electronic devices may include conductive structures such as conductive housing structures. Conductive electronic device housing structures may form part of an antenna or other structures. 
     To ensure that conductive electronic device structures have been fabricated properly, the conductive electronic device structures may be tested during manufacturing. A test system may be provided that includes a test probe (e.g., a wireless test probe, a contact probe with pins, a capacitive coupling test probe, etc.) and an antenna test probe. 
     The test system may also include temporary test structures that may be placed in the vicinity of or in direct contact with the device structures under test and that may serve to facilitate in the detection of manufacturing defects in the device structures (e.g., the use of the temporary test structures during early stages of production may help reveal defects that would normally manifest their negative impact on device performance only during later stages of production). Upon completion of testing, the temporary test structures may be removed from the device structures. The temporary test structures may resemble components that are actually assembled within a finished product or other structures that are not normally part of the finished product. 
     Test equipment such as a network analyzer may provide radio-frequency test signals in a range of frequencies. The radio-frequency test signals may be applied to the conductive housing member or other conductive structures under test using the test probe contacts. The antenna test probe may be used to gather corresponding wireless radio-frequency data. 
     Forward transfer coefficient data may be computed from the transmitted and received radio-frequency signals. The forward transfer coefficient data or other test data may be compared to reference data to determine whether the conductive electronic device structures contain a fault. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device of the type that may include conductive housing structures that may be tested in accordance with an embodiment of the present invention. 
         FIG. 2  is a top view of an illustrative electronic device of the type shown in  FIG. 1  showing the locations of gaps in a peripheral conductive housing member and the locations of possible antennas within the electronic device in accordance with an embodiment of the present invention. 
         FIGS. 3A and 3B  are diagrams of an illustrative test system environment in which electronic device structures may be tested using temporary test structures in accordance an embodiment of the present invention. 
         FIG. 4  is a side view of an illustrative antenna probe in accordance with an embodiment of the present invention. 
         FIG. 5  is a top view of an illustrative wireless probe based on a loop antenna structure in accordance with an embodiment of the present invention. 
         FIG. 6  is a top view of an illustrative wireless probe structure having two probe antennas that are configured to test a device of the type shown in  FIG. 2  in accordance with an embodiment of the present invention. 
         FIG. 7  is a diagram of an illustrative test probe configured to make physical contact with device structures under test in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagram of an illustrative radio-frequency cable configured to convey radio-frequency test signals to device structures under test in accordance with an embodiment of the present invention. 
         FIG. 9A  is an exploded perspective view of a capacitive coupling probe and an associated probe with mating spring-loaded pins in accordance with an embodiment of the present invention. 
         FIG. 9B  is a cross-sectional top view of the capacitive coupling probe of  FIG. 9A  in accordance with an embodiment of the present invention. 
         FIG. 10  is a diagram of electronic device structures being tested with a temporary printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 11  is a diagram of electronic device structures being tested with temporary housing structures in accordance with an embodiment of the present invention. 
         FIG. 12A  is a diagram of electronic device structures of the type shown in connection with  FIG. 2  being tested with temporary gap bridging members configured to short at least one gap in the peripheral conductive housing member in accordance with an embodiment of the present invention. 
         FIG. 12B  is a perspective view of the temporary bridging structure of  FIG. 12A  in accordance with an embodiment of the present invention. 
         FIG. 13  is a diagram of electronic device structures being tested with a temporary antenna shorting conductor in accordance with an embodiment of the present invention. 
         FIG. 14  is a diagram of electronic device structures of the type shown in connection with  FIG. 2  being tested with conductive structures temporarily coupled to the peripheral conductive housing member in accordance with an embodiment of the present invention. 
         FIG. 15  is a graph of illustrative impedance magnitude data of the type that may be gathered using a test system in accordance with an embodiment of the present invention. 
         FIG. 16  is a graph of illustrative impedance phase data of the type that may be gathered using a test system in accordance with an embodiment of the present invention. 
         FIG. 17  is a graph of illustrative impedance magnitude difference data of the type that may be gathered using a test system in accordance with an embodiment of the present invention. 
         FIG. 18  is a graph of illustrative impedance phase difference data of the type that may be gathered using a test system in accordance with an embodiment of the present invention. 
         FIG. 19  is a flow chart of illustrative steps involved in testing electronic device structures using a test system of the type shown in  FIG. 3A  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with wireless communications circuitry such as antennas and associated transceiver circuits. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. The wireless communications circuitry may include one or more antennas. 
     The antennas can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive housing structures. The housing structures may include a peripheral conductive member that runs around the periphery of an electronic device. The peripheral conductive member may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, or may form other housing structures. Gaps in the peripheral conductive member may be associated with the antennas. 
     The size of the gaps and the presence or absence of manufacturing artifacts such as metal burrs or other unintended conductive structures in the gaps and other abnormalities in the peripheral conductive member that are produced during manufacturing can influence the electrical properties of the antennas that are formed using the peripheral conductive housing member. To ensure that the peripheral conductive member is manufactured properly, it may be desirable to electrically test the peripheral conductive housing member during manufacturing. The electrical test measurements may reveal undesired manufacturing variations in the gaps (as an example). Other conductive electronic device structures may also be tested in this way if desired. 
     With conventional testing arrangements, these faults may sometimes be detected after final assembly operations are complete. For example, over-the-air wireless tests on a fully assembled device may reveal that an antenna is not performing within desired limits. This type of fault may be due to variation in the size of the gaps, the presence of metal burrs in the gaps, variation in the thickness of the peripheral conductive member, splits along the peripheral conductive member, or other manufacturing defects in the peripheral conductive member. Detection of faults at late stages in the assembly process may, however, result in the need for extensive reworking. It may often be impractical to determine the nature of the fault, forcing the device to be scrapped. 
     A typical test setup used to detect such types of manufacturing defects involves passive antenna testing. During passive antenna testing, the antenna is energized using a radio-frequency input signal, the reflection of which is measured to obtain a reflection coefficient (S 11 ). Simply monitoring S 11  may not sufficiently characterize the antenna because no radiated signal from the antenna is measured. Certain defects may cause a drop in antenna efficiency without a corresponding or measureable change to antenna input impedance (i.e., certain defects cannot be detected by simply monitoring S 11 ). In these cases, only a radiated test is capable of detecting such variations. This requires an antenna test probe that samples signals radiated from the antenna under test. 
     An illustrative electronic device of the type that may be provided with conductive electronic device structures such as a peripheral conductive housing member that forms part of one or more antennas is shown in  FIG. 1 . Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a cellular telephone, a media player, etc. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material. In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may, for example, be a touch screen that incorporates capacitive touch electrodes. Display  14  may include image pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electronic ink elements, liquid crystal display (LCD) components, or other suitable image pixel structures. A cover glass layer may cover the surface of display  14 . Buttons such as button  19  may pass through openings in the cover glass. 
     Housing  12  may include structures such as housing member  16 . Member  16  may run around the rectangular periphery of device  10  and display  14 . Member  16  or part of member  16  may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or helps hold display  14  to device  10 ). Member  16  may also, if desired, form sidewall structures for device  10 . 
     Member  16  may be formed of a conductive material and may therefore sometimes be referred to as a peripheral conductive housing member or conductive housing structures. Member  16  may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, or more than two separate structures may be used in forming member  16 . 
     It is not necessary for member  16  to have a uniform cross-section. For example, the top portion of member  16  may, if desired, have an inwardly protruding lip that helps hold display  14  in place. If desired, the bottom portion of member  16  may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ). In the example of  FIG. 1 , member  16  has substantially straight vertical sidewalls. This is merely illustrative. The sidewalls of member  16  may be curved or may have any other suitable shape. In some configurations (e.g., when member  16  serves as a bezel for display  14 ), member  16  may run around the lip of housing  12  (i.e., member  16  may cover only the edge of housing  12  that surrounds display  14  and not the rear edge of the sidewalls of housing  12 ). 
     Display  14  may include conductive structures such as an array of capacitive electrodes, conductive lines for addressing pixel elements, driver circuits, etc. Housing  12  may include internal structures such as metal frame members, a planar housing member (sometimes referred to as a midplate) that spans the walls of housing  12  (i.e., a sheet metal structure that is welded or otherwise connected between the opposing right and left sides of member  16 ), printed circuit boards, and other internal conductive structures. These conductive structures may be located in center of housing  12  (as an example). 
     In regions  20  and  22 , openings may be formed between the conductive housing structures and conductive electrical components that make up device  10 . These openings may be filled with air, plastic, and other dielectrics. Conductive housing structures and other conductive structures in device  10  may serve as a ground plane for the antennas in device  10 . The openings in regions  20  and  22  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, or may otherwise serve as part of antenna structures formed in regions  20  and  22 . 
     Portions of member  16  may be provided with gap structures  18 . Gaps  18  may be filled with dielectric such as polymer, ceramic, glass, etc. Gaps  18  may divide member  16  into one or more peripheral conductive member segments. There may be, for example, two segments of member  16  (e.g., in an arrangement with two gaps), three segments of member  16  (e.g., in an arrangement with three gaps), four segments of member  16  (e.g., in an arrangement with four gaps, etc.). The segments of peripheral conductive member  16  that are formed in this way may form parts of antennas in device  10  and may therefore sometimes be referred to as conductive antenna structures. 
     A top view of an interior portion of device  10  is shown in  FIG. 2 . If desired, device  10  may have upper and lower antennas (as an example). An upper antenna such as antenna  40 U may, for example, be formed at the upper end of device  10  in region  22 . A lower antenna such as antenna  40 L may, for example, be formed at the lower end of device  10  in region  20 . The antennas may be used separately to cover separate communications bands of interest or may be used together to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme. 
     Antenna  40 L may be formed from the portions of midplate  58  and peripheral conductive housing member  16  that surround dielectric-filled opening  56 . Antenna  40 L may be fed by transmission line  50 , which is coupled to positive feed terminal  54  and ground feed terminal  52 . Other feed arrangements may be used if desired. The arrangement of  FIG. 2  is merely illustrative. 
     Antenna  40 U may be formed from the portions of midplate  58  and peripheral conductive housing member  16  that surround dielectric-filled opening  60 . Member  16  may have a low-band segment LBA that terminates at one of gaps  18  and a high-band segment HBA that terminates at another one of gaps  18 . Antenna  40 U may be fed using transmission line  62 . Transmission line  62  may be coupled to positive antenna feed terminal  66  and ground antenna feed terminal  64  (as an example). Conductive member  68  may span opening  60  to form an inverted-F antenna short-circuit path. Segments LBA and HBA may form low-band and high-band cellular telephone inverted-F antennas (as an example). 
     Gaps  18  separate respective portions of peripheral conductive housing member  16 . Due to manufacturing variations, the structures associated with antennas  40 U and  40 L may not always be perfect. For example, during machining operations, small conductive filaments (metal burrs) may be produced within gap  18 . These burrs may adversely affect antenna operation (e.g., by giving rise to inductances or other parasitic electrical characteristics that detune the antenna and/or reduce antenna efficiency at desired frequencies of operation). 
     As discussed previously, wireless over-the-air communications testing on completed devices such as device  10  may reveal the presence of wireless performance problems, but may not reveal whether or not these problems are due to burrs or other manufacturing defects and may not detect these problems at a sufficiently early stage in the manufacturing process. Manufacturing defects that degrade antenna performance are typically not be easily detected via visual inspection. 
     A test system of the type that may be used in testing electronic device structures such as peripheral conductive housing member  16  at a potentially earlier stage in the assembly process is shown in  FIG. 3A . The electronic device structures being tested/calibrated may sometimes be referred to as device structures under test. The device structures under test may or may not resemble a partially assembled electronic device. In test system  98 , test unit  100  may be used to perform radio-frequency tests on device structures under test  10 ′. Device structures under test  10 ′ may include portions of a functional electronic device such as conductive housing structures, electronic components such as microphones, speakers, connectors, switches, printed circuit boards, antennas, parts of antennas such as antenna resonating elements and antenna ground structures, metal parts that are coupled to each other using welds, assemblies formed from two or more of these structures, or other suitable electronic device structures. These test structures may be associated with any suitable type of electronic device such as a cellular telephone, a portable computer, a music player, a tablet computer, a desktop computer, a display, a display that includes a built-in computer, a television, a set-top box, or other electronic equipment. 
     Test unit  100  may be coupled to one or more test probes such as test probe  104 . Test probe  104  may be used to transmit radio-frequency signals  112  to device structures  10 ′ and may be used to receive corresponding radio-frequency signals  113  reflected from device structures  10 ′. 
     Test probe  104  may be a wireless test probe (e.g., a non-contact antenna test probe), a wired test probe (e.g., a test probe having contact points configured to make physical contact with the device structures under test), a capacitive coupling test probe, or any suitable type of test probe that can be used to energize conductive antenna structures in device structures  10 ′. 
     During testing, a second test probe such as antenna probe  116  may be placed in the vicinity of device structures under test  10 ′ for receiving radio-frequency signals radiated from device structures under test  10 ′. For example, antenna probe  116  may be placed within 10 cm or less of device structures under test  10 ′, within 2 cm or less of device structures under test  10 ′, or within 1 cm or less of device structures under test  10 ′ (as examples). These distances may be sufficiently small to place antenna probe  116  within the “near field” of device structures under test  10 ′ (i.e., a location at which signals are received by an antenna that is located within about one or two wavelengths from device structures under test  10 ′ or less). 
     Device structures under test (DUT)  10 ′ may be mounted in a test fixture such as test fixture  110  during testing. Test fixture  110  may contain a cavity that receives some or all of device structures under test  10 ′. Test fixture  110  may, if desired, be formed from dielectric materials such as plastic to avoid interference with radio-frequency test measurements. The relative position between test probe  104 , antenna probe  116 , and device structures under test  10 ′ may be controlled manually by an operator of test system  98  or may be adjusted using computer-controlled or manually controlled positioners such as positioners  114 ,  118 , and  114 . Positioners  114 ,  108 , and  118  may include actuators for controlling lateral and/or rotational movement of device structures under test  10 ′, test probe  104 , and/or antenna probe  116 , respectively. 
     As shown in  FIG. 3A , device structures under test  10 ′ may be placed in an optional test chamber during test operations. Test chamber  122  may have radio-opaque walls (e.g., metal walls) to reduce electromagnetic interference. 
     Test unit  100  may include signal generator equipment that generates radio-frequency signals over a range of frequencies. These generated signals may be provided to test probe  104  over path  106  and may be transmitted towards device structures under test  10 ′ as transmitted radio-frequency (RF) test signals  112 . Path  106  may include, for example, a coaxial cable or, when multiple test probes are being used, may include multiple coaxial cables. Test unit  100  may also include radio-frequency receiver circuitry that is able to gather information on the magnitude and phase of corresponding received signals from device structures under test  10 ′ (i.e., radio-frequency signals  113  that are reflected from device structures under test  10 ′ and that are received using test probe  104 ). 
     With one suitable arrangement, test unit  100  may include a vector network analyzer (VNA), a spectrum analyzer, or other radio-frequency analyzer and a computer that is coupled to the vector network analyzer for gathering and processing test results. This is, however, merely illustrative. Test unit  100  may include any suitable computing equipment for generating radio-frequency test signals of desired frequencies while measuring and processing corresponding received signals. 
     By analyzing the transmitted and reflected signals, test unit  100  may obtain measurements such as S-parameter measurements that reveal information about whether the device structures under test are faulty. Test unit  100  may, for example, obtain an S 11  (complex impedance) measurement and/or an S 21  (complex forward transfer coefficient) measurement. The values of S 11  and S 21  (phase and magnitude) may be measured as a function of signal frequency. 
     Complex impedance measurements (S 11  phase an magnitude data) on device structures  10 ′ may be made by transmitting radio-frequency signals with test probe  104  and receiving corresponding reflected radio-frequency signals from device structures  10 ′ using the same test probe  104 . Complex forward transfer coefficient measurements (S 21  phase and magnitude data) on device structures  10 ′ may be made by transmitting radio-frequency signals with test probe  104  and receiving corresponding radio-frequency signals radiated from device structures under test  10 ′ using a separate antenna test probe  116  (e.g., receiving the corresponding radiated radio-frequency signals via radio-frequency cable  120 ). 
     In situations in which device structures under test  10 ′ 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 a “gold” unit). In situations in which device structures under test  10 ′ contain a fault that affects the electromagnetic properties of device structures under test  10 ′, the S 11  and S 21  measurements will exceed normal tolerances. When test unit  100  determines that the S 11  and/or S 21  measurements have deviated from normal S 11  and S 21  measurements by more than predetermined limits, test unit  100  can alert an operator that device structures under test  10 ′ likely contain a fault and/or other appropriate action can be taken. For example, an alert message may be displayed on display  102  of test unit  100 . The faulty device structures under test  10 ′ may then be repaired to correct the fault or may be scrapped. 
     With one suitable arrangement, an operator of system  98  may be alerted that device structures under test  10 ′ have passed testing by displaying an alert message such as a green screen and/or the message “pass” on display  102 . The operator may be alerted that device structures under test  10 ′ have failed testing by displaying an alert message such as a green screen and/or the message “fail” on display  102  (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. 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). 
     Test system  98  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 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  10 ′. Any fault that affects the electromagnetic properties of device structures under test  10 ′ and therefore affects the measured S 11  and/or S 21  data that is gathered using test unit  20  may potentially be detected using test system  98 . 
     Measuring S 11  and/or S 21  on partially assembled device structures under test  10 ′ may sometimes fail in detecting certain types of manufacturing defects that manifest their negative impact on antenna performance in fully assembled devices (i.e., certain types faults are more detectable at later stages of production). 
     One way to enable detection of such types of manufacturing defects is to couple temporary test structures  112  (formed as part of test fixture  110 ) to device structures under test  10 ′ during testing. The addition of temporary test structures  112  to device structures under test  10 ′ may serve to make device structures  10 ′ more sensitive to manufacturing defects so that the discrepancy between gathered test data for faulty device structures and satisfactory device structures are more pronounced (i.e., so that manufacturing defects can be more easily detected during early stages of production). Temporary test structures  112  may include structures that resemble device components that are normally part of an assembled device  10  (e.g., temporary test structures  112  may include structures that are configured to emulate radio-frequency characteristics associated with actual electronic device components that will be incorporated within assembled device  10  at later stages of production) and/or structures that are not normally part of assembled device  10 . Test structures  112  may be temporarily attached to device structures under test  10 ′ during radio-frequency testing/calibration and may be removed from device structures under test  10 ′ upon completion of testing/calibration. 
     Test structures  112  that are used for magnifying antenna-related faults to allow for easier detection may include antenna subcomponents and auxiliary antenna components such as shorting pins, conductive elements attached to antenna member  16 , or dielectric material (e.g., a dielectric member having any desired shape/dimension that serves no mechanical purpose in supporting device structures  10 ′ in test fixture  110 ) in the near-field or far-field that influence the behavior of the antenna. 
     In general, test equipment  101  may include test unit  100  coupled to any number of launching test probe  104 ′, receiving test probe  116 ′, and/or unitary test probe  105  (see, e.g.,  FIG. 3B ). Test probe  104 ′,  116 ′, and  105  may sometimes be referred to as test probe structures. Test probe  104 ′ may be any type of test probe (e.g., a wired, wireless, or capacitive coupling test probe) configured to convey radio-frequency test signals to device structures under test  10 ′, whereas test probe  116 ′ may be any type of test probe configured to gather radio-frequency test data from device structures under test  10 ′. Unitary test probe  105  configured to transmit and receive radio-frequency test signals to and from device structures  10 ′ may also be used, if desired. 
       FIG. 4  is a cross-sectional side view of an illustrative antenna probe of the type that may be used in test system  98  of the type shown in  FIG. 3A . As shown in  FIG. 4 , antenna probe  116  (and optionally probe  104 ) may include a substrate such as substrate  140 . Substrate  140  may be formed from a dielectric such as plastic, may be formed from a rigid printed circuit board substrate such as fiberglass-filled epoxy, may be formed from a flexible printed circuit (“flex circuit”) substrate such as a sheet of polyimide, or may be formed from other dielectric substrate materials. Conductive antenna structures may be formed on substrate  140  to form one or more antennas. In the example of  FIG. 4 , antenna probe  116  includes conductive traces  142  and  144  formed on the surface of substrate  140 . Traces  142  and  144  may be separated by a gap such as gap  148  and may form a dipole patch antenna. Conductive traces  146  supported by substrate  140  (e.g., one or more surface traces and/or buried metal traces) may be used in electrically coupling a connector such as coaxial cable connector  150  to traces  142  and  144 . Connector  150  may receive a mating connector such as coaxial cable connector  152  on the end of coaxial cable  106 , thereby coupling antenna probe  116  to test unit  100  ( FIG. 3A ). 
     In the example of  FIG. 5 , conductive traces  130  on substrate  140  have been used to form a loop antenna. Coaxial cable  106  (or other transmission line) may have a positive conductor coupled to positive antenna feed terminal  136  and a ground conductor coupled to ground antenna feed terminal  138 . Positive antenna feed terminal  136  is coupled to upper conductive trace  130 . Via  134  couples upper trace  130  to lower trace  132  (e.g., a trace on an opposing surface of a printed circuit board substrate or in a different layer of substrate  140 ). After looping around the periphery of substrate  140 , lower trace  132  may be connected to ground feed terminal  138  by a via structure. The illustrative loop antenna of  FIG. 5  uses two loops (upper and lower), but additional loops (e.g., three or more loops) or fewer loops (e.g., a single loop) may be used in antenna probe  116  if desired. 
     In general, antenna probes  116  (sometimes referred to as a wireless probe or a non-contact probe) may include any suitable type of antenna (e.g., a patch antenna, a loop antenna, a monopole antenna, a dipole antenna, an inverted-F antenna, an open or closed slot antenna, a planar inverted-F antenna, open-ended waveguides, horn antennas, coil antennas, etc.). 
     When testing device structures under test such as device structures  10 ′ having more than one antenna, it may be desirable to provide antenna probe  116  with multiple antennas each of which corresponds to a respective one of the antennas ( 40 U,  40 L) or other structures to be tested. An illustrative antenna probe that includes two antennas  105 A and  105 BB for testing structures  40 U and  40 L in device structures under test  10 ′ is shown in  FIG. 6 . As shown in  FIG. 6 , antenna probe  116  may include first probe antenna  105 A (e.g., a first dipole patch antenna of the type shown in  FIG. 4 , a first loop antenna of the type shown in  FIG. 5 , or an antenna of another suitable type) and second probe antenna  105 B (e.g., a second dipole patch antenna of the type shown in  FIG. 4 , a second loop antenna of the type shown in  FIG. 5 , or an antenna of another suitable type). Test unit  100  may be coupled to antennas using transmission line paths  106 A and  106 B. If desired, paths  106 A and  106 B may be coupled to a single vector network analyzer port using a signal combiner, paths  106 A and  106 B may be coupled to separate ports in one or more vector network analyzers or other suitable test equipment, and one or more radio-frequency switches may be used in conjunction with combiners or other radio-frequency components to interconnect one or more vector network analyzer ports to one or more different paths such as paths  106 A and  106 B. 
     During testing of device structures under test  10 ′, antenna probe  116  may be placed in the vicinity of device structures under test  10 ′ so that probe antenna  105 A is aligned with antenna  40 U and so that probe antenna  105 B is aligned with antenna  40 L. If desired, probe antenna  116  may be provided with additional antennas. For example, if there are three or more antennas or other structures to be wirelessly tested in device structures under test  10 ′, antenna probe  116  may be provided with three or more corresponding test antennas. 
     Test probe  104  may be implemented as an antenna probe as described in connection with  FIGS. 4-6 . In another suitable arrangement, test probe  104  may be implemented as a wired test probe configured to make physical contact with device structures under test  10 ′.  FIG. 7  shows an exemplary wired test probe  104  that includes a conductive signal pin  160  and a conductive ground pin  162 . At least one of pins  160  and  162  may be spring-loaded to provided improved mate-ability for test probe  104  during testing. 
     As shown in  FIG. 7 , radio-frequency cable  106  may be a coaxial cable having an inner signal conductor  164  surrounded by a ground shielding layer  166 . Dielectric material  168  may be interposed between inner signal conductor  164  and ground shielding layer  166 . Signal conductor  164  may be electrically connected to signal pin  160 , whereas ground shielding layer  166  may be electrically connected to ground pin  162 . During testing, signal pin  160  may be placed into contact with a portion of peripheral conductive member  16 , whereas ground pin  162  may be placed into contact with a portion of midplate  58  (as an example). If desired, contact probe  104  of  FIG. 7  may be used to make contact with any desired region on device structures under test  10 ′. If desired, contact probe  104  may be an RF connector (e.g., a SubMiniature version A connector, a mini U.FL connector, etc.). 
     In another suitable arrangement, a stripped portion of coaxial cable  106  may be used a wired test probe  104  (see, e.g.,  FIG. 8 ). As shown in  FIG. 8 , an exposed portion of ground shielding layer  166 ′ may not be covered with rubber coating  170 . Moreover, a protruding portion of inner signal conductor  164 ′ may not be covered with insulating material  168 . During testing, protruding signal conductor  164 ′ may make electrical contact with a portion of peripheral conductive member  16  (via a spring, screw, or other suitable types of conductive coupling mechanism), whereas exposed ground shielding layer portion  166 ′ may be shorted to a portion of midplate  58  (via conductive foam material, conductive adhesive, or other suitable conductive materials). If desired, contact probe  104  of  FIG. 8  may be used to feed radio-frequency test signals to any part of device structures under test  10 ′. 
     In another suitable arrangement, test probe  104  may include a capacitive coupling probe  182  and wired probe  180  ( FIG. 7 ). As shown in the exploded perspective view of  FIG. 9A , probe  180  may include contacts such as signal and ground pins  184  and  186 . Probe  182  may have a dielectric substrate such as a flex circuit substrate  181 . Openings such as openings  190  may be used to expose contact pads in probe  182  (i.e., contact pads that allow gold-plated tips  188  of pins  184  and  186  to electrically connect with respective pads in probe  182 ). During testing, probe  182  may be placed against the outer surface of member  16  to capacitively couple probe  182  to member  16 . 
       FIG. 9B  contains a cross-sectional top view of probe  182 . As shown in  FIG. 9B , the dielectric substrate of probe  182  may include one or more layers such as layers  181 - 1 ,  181 - 2 , and  181 - 3 . Layers  181 - 1 ,  181 - 2 , and  181 - 3  may be polymer layers (sub-layers) such as layers of polyimide in a flex circuit layer. Layer  181 - 3  may have a thickness of about 20-30 microns (as an example). Layers  181 - 2  and  181 - 1  may have thicknesses of about 20-70 microns (as an example). One or more metal layers such as metal layers  192  may be patterned to form pads for probe  182 . In configurations with multiple metal layers, intervening vias such as metal vias  194  may be used to short the metal layers together to form unitary pad structures. Opening  190  in outermost polymer layer  181 - 1  may be used to allow contact with pins  184  and  186  when pins  184  and  186  are moved in direction  202  by biasing structures  108 . 
     Test measurement accuracy may be enhanced by ensuring that probe  100  is placed in firm contact with the outer surface of member  16 . This helps ensure that the distance between metal  192  and member  16  is uniform and is dictated by the known thickness of dielectric layer  181 - 3 . With one suitable biasing arrangement, which may be helpful when biasing probe  182  against a curved portion of member  16 , a compressible elastomeric substance such as polymer foam  198  may be interposed between the wall of test fixture  110  and probe  182  (e.g., capacitive coupling test probes  182  may be attached to the inner walls of the test cavity in which device structures under test  10 ′ are inserted during testing). When device structures under test  10 ′ are placed within test fixture  110 , foam  198  will be compressed and will bias probe  181  in direction  202  towards the outer surface of member  16 . If desired, other biasing structures may be used between probe  182  and the inner surface of test fixture  110  (e.g., springs, spring-based and actuator-based pushing mechanisms, levers, etc.). The biasing structures may be formed from plastic, metal, other materials, combination of these materials, etc. The use of a foam biasing member is merely illustrative. 
     As described in connection with  FIGS. 4-9 , test probe  104  can be any suitable test equipment configured to energize device structures under test  10 ′ (i.e., any suitable type of radio-frequency conduit through which radio-frequency test signals may be fed to device structures under test  10 ′). The exemplary test probes of  FIGS. 4-9  are merely illustrate and are not intended to limit the scope of the present invention. 
       FIG. 10  shows one illustrative arrangement in which device structures under test  10 ′ are tested using temporary test structures  112 . As shown in  FIG. 10 , device structures under test  10 ′ may include at least peripheral conductive housing member  16  and midplate  58 , representing a substantially unassembled electronic device in an early stage of production. 
     Temporary test structures  112  may include a printed circuit board (PCB) for test  210 , a radio-frequency connector  214  mounted on PCB  210 , a transmission line path  213  formed in PCB  210 , and an impedance matching circuit  212  formed on PCG  210 . Transmission line path  213  may have a first end that is connected to radio-frequency connector  214  and a second end that is coupled to a portion of antenna structure  16  via coupling member  218  (e.g., via a spring, screw, conductive foam material, or other suitable coupling mechanism). Impedance matching circuit  212  may be interposed in transmission line path  213  between the first and second end of path  213 . 
     PCB  210  and its associated circuitry (i.e., radio-frequency connector  214 , transmission line path  213 , impedance matching circuit  212 , coupling member  218 , etc.) may resemble components that are actually assembled as part of device  10  during later stages of production. As examples, PCB  210  may have the same shape and properties as the main logic board (MLB) that will later be mounted within device  10 , transmission line path  213  may have the same length and properties as the actual transmission line path formed on the actual MLB, connector  213  may be mounted at a location on PCB  210  that corresponds to the same location that a switch connector is to be mounted on the MLB, etc. If desired, temporary test structures  112  may also include transceiver circuitry  220 , storage and processing circuitry  222  (e.g., transceiver circuitry and/or storage and processing circuitry that are identical, similar, or substantially different versions of the wireless and processing circuitry that will be mounted within device  10  during later stages of production), surface-mount resistors, capacitors, inductors, and/or other electrical components mounted on PCB  210  so that temporary test structures  112  emulate the electromagnetic properties of the wireless circuitry on the actual MLB as closely as possible during testing or so that temporary test structures  112  help accentuate differences in test results gathered from faulty and satisfactory devices  10 ′. 
     In the exemplary test setup of  FIG. 10 , test probe  104  (e.g., a radio-frequency connector) may be mated to connector  214  so that radio-frequency test signals may be transmitted from test unit  100  to member  16  via transmission line path  213 . Reflected signal received through test probe  104  can be used to obtain S 11  parameters, whereas radiated signals received using antenna probe  116  may be used to obtain S 21  parameters (as an example). Upon completion of testing, temporary test structures  112  may be removed from device structures under test  10 ′ and may be used to test other device structures in the production line. PCB  210  that is used for testing and that includes replica wireless circuitry may sometimes be referred to as a dummy test MLB. 
     In another suitable arrangement of the present invention, test structures  112  may include first cover glass layer  230  and second cover glass layer  232  each of which is temporarily fitted to device structures under test  10 ′ during testing. As shown in  FIG. 11 , device structures under test  10 ′ may be secured to test fixture  110  while positioners  114  fit cover glass layers  230  and  232  within the inner surface of peripheral conductive housing member  16  (e.g., cover glass layers  230  and  232  may be temporarily placed against at least a portion of member  16 ). Cover glass layers  230  and  232  may resemble actual cover glass material that is secured to midplate  58  during final stages of production (e.g., cover glass layers  230  and  232  may have the same dimension and properties as the actual cover glass material that is assembled as the outer housing of device  10  at later stages of production). Cover glass layers  230  and  232  need not be firmly secured (e.g., screwed or glued) to device structures under test  10 ′ during testing. In general, temporary test structures  112  that configured device structures under test  10 ′ to temporarily resemble more complete electronic devices may include other electrical components such as conductive housing structures, electronic components such as microphones, speakers, connectors, switches, printed circuit boards, antennas, parts of antennas such as antenna resonating elements and antenna ground structures, metal parts that are coupled to each other using welds, assemblies formed from two or more of these structures, or other suitable electronic device structures. 
     In the exemplary test setup of  FIG. 11 , test probe  104  may be used to energize the antenna structures (e.g., through means of wireless transmission, direct contact, capacitive coupling, etc.) so that radio-frequency test signals  112  may be transmitted from test unit  100  to member  16 . Reflected signals  113  received through test probe  104  can be used to obtain S 11  parameters, whereas corresponding radiated signals received using antenna probe  116  may be used to obtain S 21  parameters. Upon completion of testing, temporary test structures  112  may be removed from device structures under test  10 ′ (e.g., positioners  114  may detach cover glass material  230  and  232  from device structures under test  10 ′) and may be used to test other device structures in the production line. 
     The examples of  FIGS. 10 and 11  are merely illustrative and are not intended to limit the scope of the present invention. If desired, other test structures that resemble any conductive or nonconductive component in the finished product may be temporarily placed in contact with or in the vicinity of device structures under test  10 ′ during test operations. 
     Temporary test structures that are not normally part of device  10  may also be used during testing to increase the sensitivity of device structures under test  10 ′ to manufacturing defects. As shown in  FIG. 12A , the temporary test structures may include conductive gap bridging members such as gap bridging members  240 . For example, capacitive test probe  182  may be used to measure the capacitance of a selected one of gaps  18  while the other gaps  18  are shorted out using members  240 . Capacitive coupling probe  182  may also be used to feed radio-frequency test signals to peripheral conductive member  16 . 
     Members  240  may be conductive structures that serve to short the opposing ends of gaps  18  (see, e.g.,  FIG. 12B ). When device structures under test  10 ′ are placed into test fixture  110 , members  240  may be moved in the direction of arrow  242  so that members  240  are firmly placed in contact with the inner surface of peripheral conductive housing member  16 . Members  240  may be formed using aluminum, stainless steel, or any other suitable conductive material. Shorting gaps  18  in this way may effectively increase the accuracy of the measured capacitance using capacitive probe  182  or increase the chance of detecting a manufacturing defect within gap  18  (e.g., metal burs in gap  18 ). If desired, member  16  may also be energized using a wireless probe ( FIGS. 4-6 ) or a wired probe ( FIGS. 7 and 8 ). 
     Reflected signals received through test probe  180  can be used to obtain S 11  parameters, whereas radiated signals received using antenna probe  116  may be used to obtain S 21  parameters. Upon completion of testing, the temporary test structures may be removed from device structures under test  10 ′ (e.g., members  240  are decoupled from gaps  18 ) and other device structures in the production line may be placed in test fixture  110  for testing the presence of defects. 
       FIG. 13  shows another suitable test arrangement in which the temporary test structures include a shorting conductor  256  that is configured to short midplate  58  with a corresponding portion of conductive housing member  16 . As shown in  FIG. 13 , device structures under test  10 ′ may include peripheral conductive member  16 , grounding midplate  58  secured within member  16 , and short-circuit member  68  coupled between midplate  58  and corresponding point  255  on member  16  (see, e.g.,  FIG. 2 ). Short-circuit member  68  may be part of a finished device  10 . 
     Temporary shorting conductor  256  may be placed at any desired location along midplate  58  as long as conductor  256  is coupled in parallel with shorting member  68 . Positioner  114  may be configured to place conductor  256  at a location along midplate  58  that maximizes the difference between the antenna performance of a fault-free device and the antenna performance of a faulty device. 
     A wired test probe of the type described in connection with  FIG. 8  may be used to energize antenna structure  16 . In the example of  FIG. 13 , a coupling member such as coupling member  250  may be connected to the tip of signal conductor  164 ′ so that member  250  may be placed in contact with member  16  during testing. Grounding portion  166 ′ of conducted test probe  104  may be shorted to midplate via conductive foam material  252  (as an example). If desired, antenna structure  16  may be energized using wireless or capacitive coupling test probes. 
     Reflected radio-frequency signals received through test probe  104  can be used to obtain S 11  parameters, whereas corresponding radiated signals received using antenna probe  116  may be used to obtain S 21  parameters. Upon completion of testing, the temporary test structures may be removed from device structures under test  10 ′ (e.g., conductor  256  and test probe  104  may be decoupled from device structures under test  10 ′). 
     In general, any number of temporary test structures may be coupled to device structures under test  10 ′ during testing to enhance the detectability of manufacturing defects during early stages of production.  FIG. 14  is a diagram showing different types of conductive structures that may be attached to peripheral conductive member  16 . For example, while device structures under test  10 ′ is placed in test fixture  110 , conductive tape  260  may be attached to test fixture  110  in close vicinity to (but not in direct contact with) member  16 , metal strip  268  may make contact with member  16  via spring member  270  (by moving strip  268  in direction  272 ), and flex circuit  264  may be attached to member  16  at location  266  (see, e.g.,  FIG. 14 ). These examples are merely illustrative. If desired, any conductive or nonconductive (dielectric) material, radio-frequency cables, surface-mount components such as resistors, capacitors, and inductors, and other electrical components that may affect the near-field and far-field antenna properties of device  10  may be temporarily placed in the vicinity of or in physical contact with device structures under test  10 ′ during test operations. 
     In the example of  FIG. 14 , antenna probe  104  is used to energize device structures under test  10 ′. If desired, device structures under test  10 ′ may be provided with radio-frequency test signals using wired test probes, capacitive coupling test probes, or any other suitable type of radio-frequency test probes. 
     Illustrative test data gathered using test system  98  is shown in  FIGS. 15 and 16 . In  FIG. 15 , the magnitude of forward transfer coefficient S 21  has been plotted as a function of test signal frequency for a frequency range of 0 to 5 GHz. In  FIG. 16 , the phase of forward transfer coefficient S 21  has been plotted as a function of test signal frequency for a frequency range of 0 to 5 GHz. 
     There are four curves in the graphs of  FIGS. 15 and 16 . Curve  300  corresponds to data for device structures under test that include one or more manufacturing defects (e.g., peripheral conductive member  16  having ill-formed gaps, non-uniform thickness, etc.); curve  302  corresponds to reference data for satisfactory device structures under test without any manufacturing defects; curve  304  corresponds to data for faulty device structures under test that is tested using temporary test structures  112  (of the type described in connection with  FIGS. 10-14 ); and curve  306  corresponds to reference data for satisfactory device structures under test that is tested with temporary test structures  112 . 
     The discrepancy in the magnitude and phase of S 21  gathered from faulty and satisfactory device structures under test that are testing without using temporary test structures  112  is plotted as curve  310  in  FIGS. 17 and 18 . The discrepancy in the magnitude and phase of S 21  gathered from faulty and satisfactory device structures under test that are testing with temporary test structures  112  is plotted as curve  312  in  FIGS. 17 and 18 . 
     As indicated by illustrative frequency ranges  311  and  313  in  FIGS. 17 and 18 , respectively, there are portions of these graphs in which the discrepancy between the faulty and fault-free versions of the test data is substantially more pronounced when DUT  10 ′ is tested in the presence of temporary test structures  112 . Other frequency ranges may be investigated if desired (e.g. a range of frequencies covering 1 to 5 GHz, a range of frequencies including frequencies between 2 and 4 GHz, etc.). Monitoring the discrepancy between the expected (reference) and measured values of the S 21  test data (or S 11  test data or other test data measured using test system  98 ) while the temporary test structures are coupled to the device structures under test may facilitate in more effectively identifying conductive electronic device structures that contain faults. 
     Illustrative steps involved in testing device structures under test  10 ′ using a test system of the type shown in  FIG. 3A  are shown in  FIG. 19 . 
     At step  320 , a test system operator may place one or more versions of electronic device structures under test  10 ′ that have known satisfactory characteristics in test fixture  110  and may gather corresponding test results while temporary test structures  112  are coupled to device structures  10 ′. For example, reflection coefficient measurements (magnitude and/or phase) and/or forward transfer coefficient measurements (magnitude and/or phase) may be obtained over a range of frequencies, as described in connection with  FIGS. 15 and 16 . The structures that are measured in this way may include substantially perfect (fault-free) structures and/or structures that exhibit acceptable manufacturing variations. For example, the structures that are measured may be members  16  that include gaps  18  that do contain manufacturing faults such as burrs. The test measurement data that is gathered during the operations of step  320  may be stored in test equipment  100  to serve as baseline data (sometimes referred to as reference data or calibration data) to which subsequent test data may be compared when testing device structures of unknown quality during manufacturing. 
     After gathering baseline data on device structures with known characteristics (e.g., device structures that are known to be fault free) during the operations of step  320 , device structures may be tested in a production environment. In particular, during the operations of steps  322  and  324 , a test system operator may repeatedly place device structures under test  10 ′ into test fixture  110  so that test probe  104  can feed radio-frequency test signals to portions of member  16  or other conductive portions of device structures under test  10 ′ and so that temporary test structures  112  are placed in the vicinity of or in direct contact with portions of member  16  or other antenna structures in device structures under test  10 ′. 
     During the operations of step  326 , test data may be gathered on those structures. When gathering test data during the operations of step  326 , test equipment  100  may transmit radio-frequency signals via probe  104 . While transmitting radio-frequency signals via probe  104 , test equipment  100  may receive reflected radio-frequency signals via cable  106  (for measuring reflection coefficient data) and may wirelessly receive radio-frequency signals using test antenna  116  (for measuring forward transfer coefficient data). The transmitted and received signals may be processed (e.g., to compute magnitude and phase S 11  and S 21  data to determine whether filaments or other manufacturing defects are present in structures  10 ′). 
     At step  328 , temporary test structures  112  may be detached from device structures under test  10 ′ and device structures under test  10 ′ may be removed from test fixture  110  to test additional device structures. 
     At step  330 , the test data that has been gathered from the device structures under test may be compared to the reference data that was collected during the calibration operations of step  320 . In particular, the test data may be evaluated to determine whether or not the test data deviates by more than an acceptable amount from the baseline data gathered during the operations of step  320 . 
     In response to a determination that the test data is within acceptable limits (i.e., if the discrepancy levels of  FIGS. 18 and 19  are less than a predetermined threshold), test equipment  100  may issue a corresponding alert to the test system operator (e.g., by displaying a “pass” message or other suitable information on a display in test equipment  100  or by issuing an audio alert) or may take other suitable actions (step  332 ). In response to a determination that the test data has varied from the reference data by more than acceptable limits (i.e., if the discrepancy levels of  FIGS. 18 and 19  exceed the predetermined threshold), test equipment  100  may issue an alert that informs the system operator that the device structures under test have failed testing (e.g., a “fail message”) or may take other suitable action (step  334 ). Structures that have passed testing may, for example, be assembled into finished products and sold to customers. Structures that have failed testing may be reworked or scrapped. 
     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. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20110603
Publication Date: 20151013
Grant Date: 20151013
Priority Date: 20110603
Inventors: NICKEL JOSHUA G.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01L2221/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01R31/3025", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L21/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L21/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R31/3025", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2924/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2221/00", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 47261188