PATENT DOCUMENT

Publication Number: US-8610439-B2
Application Number: US-201113086670-A
Country: US
Kind Code: B2

Title: Radio-frequency test probes with integrated matching circuitry for testing transceiver circuitry

Abstract:
Wireless electronic devices include wireless communications circuitry such as transceiver circuitry coupled to an antenna resonating element. The transceiver circuitry and the antenna element may be formed on first and second substrates, respectively. In compact wireless devices, transceiver and antenna matching circuits may be formed on the first substrate. During production testing, a radio-frequency test probe with integrated matching circuitry may be used to mate with a corresponding contact point on the first substrate. The integrated matching circuitry may include resistors, capacitors, and inductors soldered in desired series-parallel configurations within the test probe. When the test probe is mated to the contact point on the first substrate, a test unit connected to the test probe may be used to perform radio-frequency measurements to determine whether the transceiver circuitry satisfies design criteria.

Claims:
What is claimed is: 
     
       1. A method of testing device structures under test with test equipment that includes a test probe, wherein the device structures under test include a transmission line path, transceiver circuitry coupled to a first end of the transmission line path with a transceiver impedance matching circuit, an antenna resonating element removably coupled to a second end of the transmission line path through a coupling member, and an antenna impedance matching circuit in the transmission line path between the coupling member and the transceiver impedance matching circuit, the method comprising:
 removing the antenna resonating element from the coupling member; and 
 with a radio-frequency test probe, gathering radio-frequency test measurements through the coupling member while the antenna resonating element is removed from the coupling member. 
 
     
     
       2. The method defined in  claim 1 , wherein the test probe includes a test probe impedance matching circuit that compensates for the impedance of the antenna impedance matching circuit when gathering the radio-frequency test measurements through the coupling member. 
     
     
       3. The method defined in  claim 1 , wherein the test probe has positive and ground lines and at least one electrical component bridging the positive and ground lines. 
     
     
       4. The method defined in  claim 3 , wherein the test probe further comprises at least one additional electrical component connected in series along the positive line. 
     
     
       5. The method defined in  claim 4 , wherein the at least one electrical component and the at least one additional electrical component each comprise at least one component selected from the group consisting of: an inductor, a capacitor, and a resistor. 
     
     
       6. The method defined in  claim 1 , wherein the test equipment further comprises a test unit, and wherein gathering the radio-frequency test measurements comprises:
 with the test unit, transmitting radio-frequency test signals to the test probe via a radio-frequency cable; and 
 with the test unit, receiving corresponding reflected test signals via the radio-frequency cable. 
 
     
     
       7. The method defined in  claim 6 , wherein the test equipment further comprises a radio-frequency adapter that couples the radio-frequency cable to the coupling member, and wherein the radio-frequency adapter includes an adapter impedance matching circuit that compensates for the impedance of the antenna impedance matching circuit when gathering the radio-frequency test measurements through the coupling member. 
     
     
       8. The method defined in  claim 7 , wherein the test equipment further comprises a radio-frequency adapter that couples the radio-frequency cable to the coupling member, wherein the radio-frequency adapter has positive and ground conductors and at least one electrical component bridging the positive and ground conductors, and wherein the at least one electrical component comprises at least one component selected from the group consisting of: an inductor, a capacitor, and a resistor. 
     
     
       9. The method defined in  claim 1 , wherein coupling member comprises a conductive member selected from the group consisting of: a radio-frequency connector, a spring, and a screw. 
     
     
       10. The method defined in  claim 1 , wherein the device structures under test form part of a portable electronic device, and wherein the transceiver circuitry comprises a transceiver selected from the group consisting of: a cellular telephone transceiver, a wireless local area network transceiver, and a satellite navigation system receiver.

Description:
BACKGROUND 
     This relates to testing and, more particularly, to testing of electronic device structures. 
     Electronic devices such as computers, cellular telephones, music players, and other electronic equipment are often provided with wireless communications circuitry. In a typical configuration, the wireless communications circuitry includes a radio-frequency transceiver, a transceiver matching circuit, an antenna matching circuit, a switch connector, and an antenna connector each of which is mounted on a printed circuit board. The wireless communications circuitry also includes an antenna. The antenna includes an antenna resonating element that is coupled to the transceiver through the antenna connector or other coupling mechanism (i.e., via a screw or a spring). 
     The switch connector is connected between the transceiver and the antenna resonating element. During normal device operation, the switch connector serves to electrically connect the transceiver to the antenna resonating element so that radio-frequency signals can be conveyed between the transceiver and the antenna. During production testing, a radio-frequency test probe is mated with the switch connector to decouple the antenna from the transceiver during conducted test of the transceiver. The antenna resonating element is typically decoupled from the printed circuit board during conducted test. The test probe is connected to a test box such as a vector network analyzer through a coaxial cable. Radio-frequency test signals can be conveyed between the vector network analyzer and the transceiver when performing desired radio-frequency testing and calibration operations. 
     To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications components using compact structures. As device size continues to decrease, there may be insufficient space for the placement of the switch connector on the printed circuit board. To test the transceiver in the absence of the switch connector, the transceiver may be accessed via the antenna connector (with the antenna disconnected from the printed circuit board). If, however, the antenna resonating element is decoupled from the antenna connector and the antenna matching circuit is connected in series between the transceiver and the antenna connector on the printed circuit board, the test probe connected to the antenna connector will not see a 50 ohm impedance looking toward the transceiver. 
     In view of these considerations, it would be desirable to provide improved ways for testing wireless transceiver circuitry. 
     SUMMARY 
     Electronic devices may include wireless transceiver circuitry and antenna circuitry. The wireless transceiver circuitry may include cellular telephone transceiver circuitry, wireless local area network transceiver circuitry, satellite navigation systems transceiver circuitry, and other wireless communications circuitry. The antenna circuitry may include at least one antenna resonating element associated with a loop antenna, inverted-F antenna, strip antenna, planar inverted-F antenna, slot antenna, hybrid antenna that includes antenna structures of more than one type, or other suitable antennas. 
     The transceiver circuitry may be mounted on a substrate (e.g., a printed circuit board), whereas the antenna resonating element may be formed as a separate conductive element. The printed circuit board on which the transceiver circuitry is formed may sometimes be referred to as a main logic board. The transceiver circuit and the antenna resonating element may be connected at opposing ends of a transmission line path. The antenna resonating element may be coupled to the transceiver circuitry through first and second antenna connectors. The first antenna connector may be formed on the printed circuit board, whereas the second antenna connector may be formed on the antenna resonating element. During normal operation, the first and second antenna connectors are mated to allow radio-frequency signals to be conveyed between the transceiver circuitry and the antenna circuitry. The antenna resonating element need not be coupled to the printed circuit board through a radio-frequency connector. If desired, the antenna resonating element may be coupled to the printed transceiver circuitry via a spring, a screw, a shorting conductor, or other coupling mechanisms. 
     Transceiver matching circuitry may be formed on the printed circuit board to provide desired termination impedance for the transceiver circuitry. Antenna matching circuitry may also be formed on the printed circuit board in series between the transceiver circuitry and the first antenna connector to provided desired matching for the antenna resonating element (e.g., so that the antenna resonating element is matched with the transceiver circuitry during normal wireless transmission). 
     In one suitable test arrangement, a jumper (sometimes referred to as a removable coupling circuit) may be interposed in the signal path between the transceiver circuitry and the antenna. The jumper may be removed to decouple the antenna from the transceiver circuitry so that test equipment will see a desired 50 ohm impedance looking into the transceiver circuitry (as an example). Signal and ground test pads may be formed on the printed circuit board between the transceiver circuitry and the jumper. The signal test pad may tap into the signal path of the transceiver circuitry, whereas the ground test pad is shorted to ground. A pogo pin test probe may make contact with the test pads. A test unit to which the pogo pin test probe is connected may be used to make desired radio-frequency measurements on the transceiver circuitry during production testing (e.g., the pogo pin test probe will see 50 ohms looking into the transceiver circuitry). 
     In another suitable test arrangement, a coaxial test probe may be mated with the first antenna connector during transceiver testing/calibration. In this embodiment, jumpers and test pads need not be present on the printed circuit board. The coaxial test probe may include integrated matching circuitry. For example, the coaxial test probe may include an inner signal conductor and a surrounding shielding ground conductor. The integrated matching circuitry may include passive surface mount components such as capacitors, inductors, and resistors soldered in parallel between the signal and ground conductors and soldered in series along the signal conductor. The integrated test probe matching circuitry allows the test unit to be properly matched to the device structures under test even if the antenna matching circuitry is present in the transmission line path between the first antenna connector (or other coupling mechanism) and the transceiver circuitry. Test probes with integrated matching circuitry need not be used if the antenna matching circuitry can be decoupled from the transceiver circuitry during wireless testing. 
     In another suitable test arrangement, a pogo pin test probe with integrated matching circuitry may make contact with signal and ground test pads formed on the printed circuit board. Jumpers need not be used with test probes having integrated matching circuitry. For example, the pogo pin test probe may include an inner signal conductor and a surrounding tubular ground conductor. The integrated matching circuitry may include passive surface mount components such as capacitors, inductors, and resistors soldered in parallel between the signal and ground conductors and soldered in series along the signal conductor. If desired, test probes with integrated matching circuitry may be used to testing any number of antennas on a wireless electronic device. 
     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 a diagram of an illustrative electronic device containing wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram of a conventional test setup for testing device structures. 
         FIG. 3  is a diagram of illustrative device structures under test that include radio-frequency transceiver circuitry, an antenna resonating element, and a jumper circuit coupled between the transceiver circuitry and the antenna resonating element in accordance with an embodiment of the present invention. 
         FIGS. 4 and 5  are diagrams of illustrative test stations each having a radio-frequency test probe with integrated matching circuitry in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram showing integrated matching components within the test probe of  FIG. 4  in accordance with an embodiment of the present invention. 
         FIG. 7  is a diagram showing integrated matching components within the test probe of  FIG. 5  in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagram showing a coaxial adapter containing integrated matching components in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Wireless electronic devices include antenna and transceiver circuitry that support wireless communications. Examples of wireless electronic devices include desktop computers, computer monitors, computer monitors containing embedded computers, wireless computer cards, wireless adapters, televisions, set-top boxes, gaming consoles, routers, and other electronic equipment. Examples of portable wireless electronic devices include laptop computers, tablet computers, handheld computers, cellular telephones, media players, and small devices such as wrist-watch devices, pendant devices, headphone and earpiece devices, and other miniature devices. 
     Devices such as these are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry such as cellular telephone circuitry to communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz (e.g., the main Global System for Mobile Communications or GSM cellular telephone bands). Long-range wireless communications circuitry may also handle the 2100 MHz band. 
     Electronic devices may use short-range wireless communications links to handle communications with nearby equipment. For example, electronic devices may communicate using the WiFi® (IEEE 802.11) bands at 2.4 GHz and 5 GHz and the Bluetooth® band at 2.4 GHz. It is sometimes desirable to receive satellite navigation system signals such as signals from the Global Positioning System (e.g., to receive GPS signals at 1575 MHz). 
       FIG. 1  is a diagram of an exemplary wireless electronic device. As shown in  FIG. 1 , device  10  may have a device housing such as housing structure  12  that forms a case for its associated components. Housing  12  may be formed from 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 conductive elements (e.g., a conductive peripheral bezel member). 
     Device  10  may include within its housing at least one antenna having an associated antenna resonating element  18 , radio-frequency (RF) transceiver circuitry  16 , storage and processing circuitry  14 , input-output devices, and other electronic components. Transceiver circuitry  16  may be coupled to antenna element  18  through a corresponding pair of antenna connectors  24  (sometimes referred to as coupling members or coupling elements). Coupling element  24  need not be a radio-frequency connector. If desired, element  24  may be a screw, spring, or other suitable types of conductive structures. 
     Storage and processing circuitry  14 , transceiver circuitry  16 , and a first antenna connector  24  in the corresponding antenna connector pair may be mounted on a substrate such as printed circuit board (PCB)  20 . Printed circuit board  20  may be, for example, a rigid printed circuit board formed from fiberglass-filled epoxy (e.g., FR-4) or may be a flexible printed circuit (“flex circuit”) formed from a sheet of polymer such as a polyimide sheet. Printed circuit board  20  may, if desired, be mounted to housing structure  12 . 
     Storage and processing circuitry  14  may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  14  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio codec chips, application specific integrated circuits, etc. 
     Storage and processing circuitry  14  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, storage and processing circuitry  14  may be used in implementing communications protocols. Communications protocols that may be implemented using circuitry  14  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, etc. 
     Radio-frequency transceiver circuitry (sometimes referred to as radio circuitry)  16  may include satellite navigation system receiver circuitry for receiving satellite positioning signals at 1575 MHz, wireless local area network (WLAN) circuitry for handling the 2.4 GHz and 5 GHz WiFi® (IEEE 802.11) communications bands and the 2.4 GHz Bluetooth® communications band, cellular telephone circuitry for handling telephone bands such as bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz, and other suitable types of transceiver circuitry. 
     Conductive traces  22  may be used to form a transmission line (e.g., a microstrip transmission line, a stripline transmission line, an edge coupled microstrip or stripline transmission line, etc.) through which radio-frequency signals can be conveyed between transceiver  16  and antenna element  18 . The example of  FIG. 1  in which conductive traces  22  in printed circuit board  20  are used in forming a transmission line path coupled between transceiver  16  and the antenna is merely illustrative. If desired, one or more segments of coaxial cable may be incorporated within transmission line path  22 . 
     Antenna element  18  may include antenna resonating element conductive structures. Antenna element  18  may form at least a portion of a loop antenna, inverted-F antenna, strip antenna, planar inverted-F antenna, slot antenna, hybrid antenna that includes antenna structures of more than one type, or other suitable antennas. The conductive structures may, if desired, be formed from portions of housing structure  12 . The conductive structures may also include patterned metal traces formed on a substrate such as a plastic support structure, a rigid printed circuit board, or a flex circuit. The conductive structures on antenna element  18  may be coupled to a second antenna connector  24  in the corresponding antenna connector pair. First and second connectors  24  may be, for example, male and female U.FL (or W.FL) connectors, respectively. 
     The wireless communications circuitry within housing  12  may be tested and calibrated during production of device  10 . The components being tested and calibrated may sometimes be referred to as device structures under test. Device structures under test may include transceiver circuitry  16 , antenna element  18 , and other wireless communications circuitry. These device structures under test may neither be attached to one another nor completely assembled within housing  12  during production testing. 
       FIG. 2  is a diagram showing a conventional test setup for testing device structures under test  200 . Structures  200  include transceiver  202 , transceiver matching circuit  204 , and first antenna connector  222  mounted on printed circuit board  252 . Structures  200  also include antenna resonating element  206  that is disconnected from first antenna connector  222  (i.e., second antenna connector  224  on antenna element  206  is not mated with corresponding first antenna connector  222 ). Antenna matching circuit  208  is connected to antenna element  206 . 
     Ground power supply line  218  is formed in printed circuit board  252 . Transceiver  202  has a terminal that is connected to ground line  218  through via  220 . Transceiver  202  is electrically coupled to antenna connector  222  through conductive paths  210  and  213 . Transceiver matching circuit  204  is connected in parallel with transceiver  202 . 
     During testing, a vector network analyzer (VNA)  250  is used to perform radio-frequency testing on transceiver  202 . Vector network analyzer  250  is coupled to a coaxial test probe  240  through coaxial cable  248 . In particular, coaxial cable  248  has a first end that is mated to a corresponding input-output port in vector network analyzer  250  and a second end that is connected to test probe  240 . Test probe  240  is a female U.FL connector. 
     Test probe  240  includes an inner signal conductor  242  surrounded by an outer tubular ground conductor  244 . Signal conductor  242  and ground conductor  244  share the same geometric axis and are separated by a tubular dielectric layer. When test probe  240  is mated with antenna connector  222 , signal conductor  244  is electrically connected to conductive path  213 , whereas ground conductor  244  is electrically connected to ground line  218  through via  247 . 
     Connected in this arrangement, radio-frequency test signals can be conveyed back and forth between vector network analyzer  250  and transceiver  202 . Based on radio-frequency test measurements gathered using vector network analyzer  250 , transceiver  202  is marked as satisfying performance criteria or as failing performance criteria. 
     Transceiver matching circuit  204  serves to provide a 50 ohm impedance for test probe  240  during transceiver testing (i.e., test probe  240  “sees” 50 ohms looking into antenna connector  222 ). Antenna matching circuit  208  serves to provide matching for antenna element  206 . In the conventional device configuration of  FIG. 2 , antenna matching circuit  208  is formed as a part of antenna element  206  and may therefore be decoupled from the wireless circuitry on board  252  during transceiver testing (i.e., by disconnecting antenna element  206  from PCB  252 ). 
     As manufacturers push towards more compact antenna designs, it may be necessary to form the antenna matching circuit on the printed circuit board. In the circuit shown in  FIG. 2 , if antenna matching circuit  208  is formed on printed circuit board  252 , test probe  240  will no longer be properly matched when test probed  240  is mated with antenna connector  222  (i.e., antenna matching circuit  208  will alter the 50 ohm impedance previously provided by transceiver matching circuit  204 ). It may therefore be desirable to provide an improved arrangement for testing wireless communications circuitry for antenna designs in which the antenna matching network cannot be decoupled from the radio-frequency transceiver during testing. 
       FIG. 3  is a diagram showing one exemplary arrangement for performing transceiver testing and calibration. As shown in  FIG. 3 , device structures under test  302  may include RF transceiver circuitry (or radio transceiver circuitry)  16 , transceiver matching circuit  306 , antenna matching circuit  310 , antenna connector  336 , and other wireless communications circuitry formed on substrate (e.g., a printed circuit board, a flex circuit, a rigid-flex, or other suitable substrates). 
     Structures  302  may also include antenna resonating element  18  and ground plane structure  344 . Antenna element  18  may have an associated antenna connector  338  that can be used to mate with corresponding antenna connector  336  (e.g., antenna element  18  may be removably coupled to the second end of the transmission line path). Ground structure  344  may be formed from portions of housing structure  12  or other conductive components within housing  12 . Ground structure  344  may be coupled to antenna element  18  through conductive path  346 . Ground structure  244  may be coupled to ground path  314  in printed circuit board (PCB)  20  through conductor  348 . Conductors  346  and  348  may include shorting inductors, springs, screws, metal traces, coaxial cabling, or other conductive parts and may therefore sometimes be referred to as coupling members. 
     Transceiver circuitry  16  may have a ground terminal coupled to ground path  314  through via  316  (e.g., a conductive through-hole in PCB  20 ). Transceiver circuitry  16  may be coupled to antenna connector  336  through a transmission line path that includes at least conductive paths  318 ,  320 ,  322 , and  324 . The transmission line path may, for example, include one or more conductive traces formed in at least one signal routing layer in PCB  20 , one or more coaxial cable segments, or other suitable radio-frequency signal conduits. 
     Antennas in device  10  may have antenna feed terminals. For example, antenna element  18  may have a first antenna feed terminal such as positive antenna feed terminal  340  and a second antenna feed terminal such as ground antenna feed terminal  342 . Ground antenna feed terminal  342  may be shorted to ground path  314  through via  372 . Transmission line  324  may be used to feed antenna resonating element  18  at positive and negative antenna feed terminals  340  and  342 , respectively. Antenna resonating element  18  need not be coupled to printed circuit board  20  through antenna connectors. If desired, positive and negative antenna feeds  340  and  342  may be electrically coupled to antenna element  18  through springs, screws, conductive pads formed on flex circuits, or other conductive means. 
     The transmission line path coupling transceiver circuitry  16  to antenna connector  336  may have first and second ends. Transceiver circuitry  16  may be connected to the first end of the transmission line path with transceiver matching circuit  306  (e.g., circuit  306  may be coupled in parallel with transceiver circuitry  16 ) and may serve to provide a 50 ohm impedance matching for circuitry  16 . Antenna connector  336  may be connected to the second end of the transmission line path with antenna matching circuit  310  (e.g., circuit  310  may be coupled in series between transceiver circuitry  16  and antenna connector  336 ) and may serve to provide proper matching for antenna element  18  during normal operation of device  10  (e.g., to ensure that the antenna is properly matched with transceiver circuitry  16 ). Matching circuits  306  and  310  may be coupled to ground, as indicated by shorting paths  345  and  347 . Matching circuits  306  and  310  may sometimes be referred to as impedance matching networks and may provide termination impedance values other than 50 ohms, if desired. Matching circuits  306  and  310  may include any number of electrical components (e.g., discrete and/or integrated capacitors, inductors, and resistors) coupled in any suitable series-parallel configuration in the transmission line path between circuitry  16  and connector  336 . 
     A removable coupling circuit such as a jumper circuit  326  may be interposed in the signal path between transceiver circuitry  16  and antenna element  18 . Jumper circuit  326  may include first jumper pin  328  and second jumper pin  330 . First jumper pin  328  may be coupled to transceiver circuitry  16 , whereas second jumper pin  330  may be coupled to antenna element  18 . A conductive sleeve (sometimes referred to as a jumper shunt)  332  may be mated with jumper pins  328  and  330 . For example, jumper shunt  332  may include a plastic block having two pin holes corresponding to jumper pins  328  and  330 . Jumper  332  may also include shorting conductor  334  that electrically connects pins  328  and  330  when jumper  332  is in the mated state. 
     Jumper  332  is placed in the mated state during normal device operation, whereas jumper  332  may be removed during transceiver testing. In the absence of a switch connector, jumper circuit  336  provides one way of decoupling the antenna from transceiver circuitry  16 . 
     As shown in  FIG. 3 , test station  300  may include a test unit such as test unit  303  that can be used to perform desired radio-frequency performance measurements on device structures under test  302 . Test unit  303  may include signal generator equipment that generates radio-frequency signals over a range of frequencies. These generated signals may be provided to test probe  360  over radio-frequency cable  370  (e.g., a coaxial cable). 
     Test unit  303  may also include radio-frequency receiver circuitry that is able to gather wireless performance information for incoming signals (i.e., radio-frequency signals that are received through test probe  360 ). With one suitable arrangement, test unit  303  may be a vector network analyzer and a computer that is coupled to the vector network analyzer for gathering and processing test results. Tester  303  may, for example, be the CMU300 Universal Radio Communication Tester available from Rohde &amp; Schwarz. This is, however, merely illustrative. Test unit  303  may be a radio communications tester of the type that is used to perform radio-frequency signaling tests for a variety of different radio-frequency communications bands and channels (e.g., test unit  303  may be a spectrum analyzer, a power meter, a wireless protocol tester, etc.). 
     Test unit  303  may include a transmitter and a receiver that can be used to transmit and receive radio-frequency signals to and from device structures  302 . The transmitted and received signals may be processed to compute complex impedance data (sometimes referred to as S11 parameter data), complex forward transfer coefficient data (sometimes referred to as S21 data), or other suitable data for determining whether device structures  302  satisfy design criteria. 
     Test probe  360  may include a tubular ground conductor  364  that forms a bore through which an inner signal conductor is concentrically located. Test probe  360  may also include pin support member  366 . Pin support member  366  (sometimes referred to as a front plunger) may serve to hold signal pin  369  and ground pin  368  in a way such that the distance between pins  369  and  368  is fixed at a desired distance. Signal pin  369  may be connected to signal conductor  362 , whereas ground pin  368  may be connected to ground conductor  364 . At least one of pins  368  and  369  may be a spring-loaded pin. Test probe  360  of this type may sometimes be referred to as a pogo pin test probe. 
     During testing of transceiver circuitry  16 , test pins  369  and  368  may respectively make contact with conductive test pads  350  and  352  formed on the surface of PCB  20 . Signal test pad  350  may tap into the signal path (e.g., conductive pad  350  may be coupled to the transceiver signal path through via  354 ), whereas ground test pad  352  may be shorted to ground  314  through via  356 . 
     Removing jumper  332  allows test unit  303  to properly communicate with radio-frequency transceiver circuitry  16  through test probe  360  whether or not antenna element  18  is connected to printed circuit board  20 . Test probe  360  will see a desired 50 ohm impedance (e.g., or any other impedance provided by transceiver matching circuit  306 ) looking into circuitry  16  if jumper  332  is removed to decoupled the loading from antenna element  18  and antenna matching circuit  310  (e.g., removing coupling circuit  332  from the transmission line path isolates the test pads from the antenna impedance matching circuit  310 ). 
     There may not always be sufficient space to form jumper circuit  326  on printed circuit board  20 . In scenarios in which the jumper circuit is absent from device structures  302 , test unit  302  may interface with transceiver circuitry  16  through antenna connector  336  (see, e.g.,  FIG. 4 ). As shown in  FIG. 4 , radio-frequency test signals may be conveyed between test unit  303  and transceiver circuitry  16  by mating radio-frequency test probe  400  with antenna connector  336 . Test unit  303  and test probe  400  may be connected through coaxial cable  370  (as an example). 
     Antenna element  18  is disconnected from printed circuit board  20  (e.g., antenna element  18  is removed from connector  336 ) while test probe  400  is mated with antenna connector  336 . Test probe  400  may include an inner signal conductor  402  surrounded by a cylindrical shielding ground conductor  404 . Signal conductor  402  and ground conductor  404  may share a common geometric axis. Test probe  400  may be a type of test probe suitable for mating with a corresponding U.FL connector, W.FL connector, SubMiniature version A (SMA) connector, SubMiniature version B (SMB) connector, or other types of coaxial radio-frequency connectors. When test probe  400  is mated with antenna connector  336 , signal conductor  402  may be coupled to positive antenna feed terminal  340 , whereas ground conductor  404  may be coupled to negative antenna feed terminal  342 . 
     A conventional coaxial test probe mated to antenna connector  336  of  FIG. 4  will not see a 50 ohm impedance looking into transceiver circuitry  16  (e.g., a conventional coaxial test probe will not be properly matched to on-board components), because antenna matching circuit  310  that is coupled in series between transceiver circuitry  16  and antenna connector  336  provides loading in addition to the 50 ohm impedance provided by transceiver matching network  306 . 
     One exemplary solution is illustrated in  FIG. 4 . As shown in  FIG. 4 , test probe  400  includes matching components  406  integrated within test probe  400 . Matching components  406  may serve to compensate for the additional loading of antenna matching circuit  310  when gathering the radio-frequency test measurements through antenna connector  336 . Matching components  406  may include surface mount resistors, capacitors, inductors, integrated impedance matching circuits, and other electrical components coupled in any desired series-parallel configuration. Using a radio-frequency test probe with integrated matching circuitry may allow the test equipment to be properly matched to transceiver circuitry  16  even if antenna matching circuit  310  is coupled in series with antenna connector  336  (e.g., the test equipment will see 50 ohms looking into the radio from reference point  409 ). 
     In another suitable arrangement, signal and ground test pads  412  and  410  may be formed on the surface of printed circuit board  20  (see, e.g.,  FIG. 5 ). As shown in  FIG. 5 , signal test pad  412  may be coupled to the transceiver signal path through via  414 , whereas ground pad  410  may be coupled to ground path  314  through via  416 . An RF test probe such as test probe  360 ′ may make contact with pads  412  and  410  during transceiver testing operations. Test probe  360 ′ may be a pogo pin test probe with integrated impedance matching circuitry  407 . Matching components  407  may serve to compensate for the impedance of antenna matching circuit  310  when gathering the radio-frequency test measurements through test pads  412  and  410 . Performing radio-frequency testing in this way allows the test equipment to communicate with transceiver circuitry  16  through an access point other than antenna connector  336 . 
       FIG. 5  shows transceiver testing with antenna element  18  disconnected from printed circuit board  20 . If desired, antenna element may be connected to printed circuit board  20  during transceiver testing and calibration operations. The configuration of test probe matching circuitry  407  may depend on whether antenna element  18  is coupled to printed circuit board  20  during testing, because antenna element  18  presents additional loading when antenna connector  338  is mated with antenna connector  336 . For example, if antenna element  18  is coupled to board  20  during transceiver testing, test probe matching circuitry  407  will have a first configuration to provide proper impedance matching. If antenna element  18  is disconnected from board  20  during transceiver testing, test probe matching circuitry  407  will have a second configuration that is different than the first configuration to provide proper impedance matching. 
     Test stations  300  described in connection with  FIGS. 4 and 5  are merely illustrative and are not intended to limit the scope of the present invention. If desired, radio-frequency test probes with integrated matching circuitry may be used to test any number of wireless transceiver circuitry and/or antennas in device  10  during device manufacturing processes. 
       FIG. 6  shows a cross-sectional view of coaxial test probe  400  with integrated matching circuitry. As shown in  FIG. 6 , passive electrical components  504  may be soldered in parallel between inner signal conductor  402  and ground conductor  404 . The portion of signal conductor  402  between two parallel-connected components  504  constitutes a transmission line having a length that is equal to a distance L between the two parallel-connected components  504 . Distance L between components  504  may therefore be adjusted to provide desired impedance match. Passive electrical components  506  may be soldered in series along signal conductor  402 . Circuits  504  and  506  may be surface mount resistors, capacitors, inductors, and other electrical components. If desired, any number of parallel and series components may be soldered within test probe  400  to provide desired matching. Non-conductive (dielectric) material  403  may be formed surrounding signal conductor  402  to insulate signal conductor  402  from ground conductor  404 . 
       FIG. 7  shows a cross-sectional view of pogo pin test probe  360 ′ with integrated matching circuitry  407 . Signal and ground conductors  362  and  364  and spring member  500  may be encased within ground shaft  502 . Spring member  500  may be interposed in the signal path between signal conductor  362  and signal pin  369  so that signal pin  369  can be depressed when making contact with a corresponding test pad during test procedures. 
     As shown in  FIG. 6 , passive electrical components  504  may be soldered in parallel between inner signal conductor  362  and ground conductor  364 . The portion of signal conductor  362  between two parallel-connected components  504  constitutes a transmission line having a length that is equal to a distance L between the two parallel-connected components  504 . Distance L between components  504  may therefore be adjusted to provide desired impedance match. Passive electrical components  506  may be soldered in series along signal conductor  362 . Circuits  504  and  506  may be surface mount resistors, capacitors, inductors, and other electrical components. If desired, any number of parallel and series components may be soldered within test probe  360 ′ to provide desired matching. 
     Coaxial test probes of the type described in connection with  FIGS. 6 and 7  are merely illustrative and are not intended to limit the scope of the present invention. If desired, other types of radio-frequency test probes such as twin-lead cable test probes, twisted pair cable test probes, test probes having a matrix of spring-loaded (pogo) pins, or other types of transmission lines having at least two conductive paths may be used to perform conducted transceiver testing. Integrated matching components may be integrated into any of these test probes. 
     Matching components need not always be formed in the radio-frequency test probes. In another suitable embodiment, an adapter such as radio-frequency adapter  600  may be interposed between antenna connector  336  and radio-frequency test probe  401 . As shown in  FIG. 8 , adapter  600  (sometimes referred to as a coaxial barrel coupler) may include integrated impedance matching components  406 ′ that can be used to compensate for the impedance of antenna matching circuit  310  (e.g., test probe  401  need not include integrated matching circuitry  406 ). 
     Adapter  600  may have a first end that can be connected to connector  336  (as indicated by line  604 ) and a second end that can be connected to test probe  401  (as indicated by line  602 ). Adapter  600  may be a male-to-male adapter, male-to-female adapter, or a female-to-female adapter suitable for coupling any type of antenna connector  336  (e.g., a U.FL connector) to any type of test probe  401  (e.g., an SMA connector). 
     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: 20110414
Publication Date: 20131217
Grant Date: 20131217
Priority Date: 20110414
Inventors: NICKEL JOSHUA G.
SCHLUB ROBERT W.
Assignee: APPLE INC
CPC Classifications: [{"code": "G01R1/06772", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R31/2822", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R1/06772", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R31/2822", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 47005963