Abstract:
A differential pin to RF adaptor includes a center conductor contact with an RF connector on one end and a signal contact on the other end. An insulating sleeve surrounds the central contact. A reference contact surrounds the insulating sleeve. The signal pin of the differential pair interfaces with the center conductor contact of the RF connector. The adaptor is structured to slide down over a pair of pins/leads so that the reference contact abuts a circuit board attached to the pins. The pins/leads are shielded all the way to the circuit board, which shields/isolates the pins from common mode and other types of interference. The adaptor maintains the shape of the signal pin and the reference pin during testing. The adaptor maintains a fixed impedance of the pins, which reduces or eliminates uncontrolled impedance and hence preserves system frequency response and reduces/eliminates erroneous ripple currents.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application claims benefit to U.S. Provisional Patent Application Ser. No. 62/310,159, filed Mar. 18, 2016, and entitled “Square Pin to RF Adaptor For Probing Applications,” which is incorporated herein by reference as if reproduced in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This disclosure is directed to a mechanism for signal probing, and, more particularly, to an adaptor for interfacing from square or round pins/leads into a coaxial Radio Frequency (RF) connector for testing by a test and measurement system. 
       BACKGROUND 
       [0003]    Various systems have been developed to measure differential signals from a device under test (DUT). There are a variety of ways to connect the test system to the DUT. These may include a soldered connection, RF connector, pressure contacts, wires/leads, pins, adapters, interposers, clip-ons etc. A common interface to connect the test system to the DUT is accomplished by using a pair of pins/short wires that are soldered to the differential test points, which are then connected to the test system. The problem with such systems is that ambient electric fields may interact with the exposed leads/pins, which lack shielding, injecting interference into the signals being measured. Interference injected into both leads/pins is referred to as common mode interference. The exposed leads/pins may experience both common mode interference and interference affecting the individual leads/pins. There is no mechanism to isolate the differential signal from these interferences at the exposed leads/pins, resulting in added signal noise that is measured by the testing system but is not present in the actual DUT&#39;s differential signal. Further, maintaining a uniform controlled impedance of these differential leads/pins supports repeatable measurements without degradation in the frequency response. However, real exposed leads/pins may bend and change position significantly during the testing process. Bending the exposed leads changes the corresponding impedances of the differential pair. Such uncontrolled impedances alter the frequency response of the signal at the testing system, leading to bandwidth loss and ripple currents. As such, the exposed leads reduce the accuracy of test measurements taken by a testing system, particularly when measuring a differential signal with higher frequency content. 
         [0004]    Embodiments of the invention address these and other issues in the prior art. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    Embodiments of the disclosed subject matter include a differential pin to RF adaptor. The adaptor contains a central contact with an RF connector on one end and a signal contact on the other end. An insulating sleeve surrounds the central contact. A reference contact surrounds the insulating sleeve. Securing elements, such as leaf springs, are employed to engage the reference pin of a differential pair to the reference/shield contact. The signal pin of the differential pair interfaces with the central contact. A protective layer surrounds the securing elements and the reference contact. The adaptor is structured to slide down over the differential pair so that the outer reference/shield contact abuts a circuit board attached to the pins. In this way, the differential pins (e.g. leads) are completely shielded all the way down to the circuit board&#39;s surface, which shields/isolates the pins from common mode and other types of interference. Further, the adaptor&#39;s contact spacing is selected to match the pin spacing. As such, the adaptor maintains the shape of the signal pin and the reference pin during testing. Accordingly, the adaptor maintains a fixed/controlled impedance of the differential pair, which reduces or eliminates impedance variations and hence preserves system frequency response and reduces/eliminates erroneous ripple currents. The RF connector may be any type of RF connector desired to connect to a corresponding probe. In some embodiments, an attenuator is positioned between the RF connector and the signal contact. The attenuator reduces the gain associated with the differential signal to increase the input signal range of the test system. The attenuator in the adaptor allows for a broader range of RF connectors to be employed (e.g. RF connectors without pre-conditioning circuits). 
         [0006]    Accordingly, in at least some embodiments a differential pin to RF adaptor includes a central contact with a proximate end and a distal end, the proximate end including an RF connector and the distal end including a signal contact structured to interface with a signal pin of a differential pair. The adaptor also includes an insulating sleeve surrounding the central contact. Further, the adaptor includes a reference/shield contact separated from the central contact by the insulating sleeve and structured to interface with a reference pin of the differential pair. 
         [0007]    In another aspect, in at least some embodiments a differential pin to RF adaptor includes a central contact structured to communicate a signal portion of a differential signal from a distal end to a RF connector at a proximate end. The adaptor also includes a reference contact structured to communicate a reference portion of the differential signal from the distal end to the RF connector at a proximate end. Further, the adaptor includes an insulating sleeve structured to isolate the reference portion of the differential signal from the signal portion of the differential signal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic diagram of an embodiment of a test and measurement system. 
           [0009]      FIG. 2  is a cross sectional view of an embodiment of a differential pin to RF adaptor. 
           [0010]      FIG. 3  is a cross sectional view of an embodiment of a differential pin to RF adaptor with a resistor network. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    As described herein, the embodiments of the disclosure are directed to a differential pin to RF adaptor. The adaptor may be configured to attach to square or round pins, or short wire leads and interface from this differential pair to a testing system via a probe. The adaptor employs a center conductor contact structured to communicate a signal from a distal end to a RF connector at a proximate end. The adaptor also employs a reference contact structured to communicate a reference signal corresponding to the signal. Accordingly, the center conductor contact and the reference contact communicate the differential signal to the RF connector. The adaptor also employs an insulating sleeve structured to isolate the reference signal from the signal traversing the center conductor contact. The reference/shield contact is structured to shield the signal from common mode interference or other interference received between a circuit board of a DUT and the RF connector. The adaptor is also structured to maintain a constant coaxial connection between the RF connector, the reference connection, and the center contact pin to maintain a controlled impedance between the pins. In some embodiments the central contact further includes an attenuator structured to reduce a gain of the differential signal prior to communicating the differential signal to the RF connector at the proximate end in order to match the gain of the differential signal to an expected gain across an RF probe and/or electrically isolate the DUT from the test system. Securing elements are employed to maintain connection with the pins and a protective layer protects the adaptor, and the interfaced pins, from damage during use. 
         [0012]      FIG. 1  is a schematic diagram of an embodiment of a test and measurement system  100 . System  100  includes a DUT  110  with a pair of differential pins  111 . Differential signals  161  from the differential pins  111  are sent to the host  150  for testing. The differential signals  161  encode information as the difference between a signal traversing the signal pin  111   a  and a reference signal traversing the reference pin  111   b . The host  150  is configured to receive differential signals  161 , so an adaptor  120  conducts signals traversing the two pins/leads into a coaxial connection to be sent to the host  150 . The differential signals  161  are sent to the host  150  via a probe  130  and, in some embodiments, an accessory  140  that acts a controller and/or pre-processor for the host  150 . 
         [0013]    A DUT  110  is any device structured to generate differential signals  161  for testing. For example, a DUT  110  may include a circuit board with any differential signals. These differential signals may be for transmission of data, controlling or biasing power supplies, high voltage signaling, or employed in other transmission systems etc. One of ordinary skill in the art will appreciate that a DUT  110  employing differential signaling encompasses a wide range for devices and the examples provided herein are included for purposes of explanation and should not be considered limiting. The DUT  110  includes differential pair  111  which are a pair of output pins that can be used to tap into the differential signal in the DUT  110  for testing purposes. The differential pair  111  include a signal pin  111   a  and a reference pin  111   b . The differential signal  161  is a signal encoded as the difference between the signal traversing the signal pin  111   a  and the reference signal traversing the reference pin  111   b.    
         [0014]    Adaptor  120  is a differential pin to RF adaptor and is hence a device structured to interface between the pins/leads from the DUT&#39;s test points and a controlled impedance coaxial connection. Adaptor  120  is structured to interface with the pins/leads of differential pair  111  and transmit the differential signal  161  to probe  130 . Specifically, adaptor  120  includes a pair of contacts that connect to an RF connector. The RF connector is selected to interface with the probe  130 . The central contact of the adapter  120 , which connects to the signal pin  111   a , is connected to the center pin contact of the RF connector. Further, the adaptor  120  includes a reference contact, which connects to the reference pin  111   b , and is connected to the outer shield contact of the RF connector. The adaptor  120  is further structured to abut the DUT  110  when interfacing with the differential pair  111  in order to shield/isolate the differential signals  161  from common mode or other ambient electrical interference occurring between the DUT  110  and the RF connector. The adaptor  120  is further structured to provide physical support for the differential pair  111 . Specifically, the adaptor  120  maintains the differential pair  111  in a controlled position relative to each other and relative to RF connector and a corresponding coaxial connection, causing the entire connection to maintain a controlled impedance. The adaptor  120  may also include securing elements structured to secure reference pin  111   b  to the reference contact and/or to secure the signal pin  111   a  to the central contact. The adaptor  120  also includes a protective layer structured to protect the adaptor  120  and the coupled differential pair  111  during use. The adaptor  120  may or may not be soldered to the differential pair  111 . The differential pair  111  may employ round or square pins or short wire leads, and the adaptor  120  is structured accordingly to engage with the pins/leads as needed. In some embodiments, the adaptor  120  includes an attenuator between the central and/or reference contacts and the RF connector to adjust the gain of the differential signals  161  to increase the acceptable input signal range and to better electrically isolate the DUT  110  system from the host  150 . 
         [0015]    Probe  130  is device structured to couple to adaptor  120  at the RF connector and communicate the differential signals  161  toward accessory  140 . Probe  130  includes a coaxial cable with a probe RF connector to mate with the adaptor&#39;s RF connector. Specifically, probe  130  contains a coaxial cable with a center conductor and an outer shield. Probe  130  may also be constructed using a twisted pair and may be shielded. In some embodiments, the probe  130  includes an attenuator (e.g. if adaptor does not employ an attenuator). Further, the probe  130  includes a plurality of magnetic elements (e.g. ferrites) surrounding the coaxial cable and spaced along the length of the cable. The ferrites reject common mode interference. The magnetic elements are separated by gaps, which are filled with elastomeric elements. The elastomeric elements are compressible, which allows the probe to bend and prevent adjacent magnetic elements from pressing together (e.g. reducing wear and preventing stress fractures). The probe  130  is structured to couple to, and propagate the differential signals  161  to accessory  140 . In some embodiments, the probe  130  also includes an Electrically Erasable Programmable Read Only Memory (EEPROM) containing probe  130  specifications, for example the resistance in the probe tip, tip attenuation, frequency response, and/or other parameters specific to probe  130 . 
         [0016]    Accessory  140  is any device structured to sense and/or precondition the differential signals  161  for host  150 . The accessory  140  may include a sensor head for sensing the differential signals  161 , a controller for preconditioning the differential signals  161 , or combinations thereof. For example, the accessory  140  may obtain information from the EEPROM to adjust the gain of the signals  161  to compensate for power loss naturally occurring when the differential signals  161  traverse the probe  130 . Accessory  140  is designed to deliver the differential signals  161  to the host  150  while maintaining substantially the same electrical properties as the differential signals  161 . Specifically, the accessory  140  is designed to minimize noise injected into the signals  161  while traversing the differential pair  111 , adaptor  120 , and probe  130 . 
         [0017]    Host  150  is structured to couple to accessory  140  and receive the signals  161  for testing and/or measurement. For example, host  150  is an oscilloscope or other test system. Host  150  receives the differential signals  161  from the accessory  140  and may display them on a graticule for a user. Host  150  may also capture characteristics from the differential signals  161  in memory for further calculation and use by the user. Accordingly, the adaptor  120 , probe  130 , and accessory  140  are employed to allow the user to measure differential signals  161  that are substantially identical to the differential signals  161  obtained from the DUT  110 . 
         [0018]      FIG. 2  is a cross sectional view of an embodiment of a differential pin to RF adaptor  200 , which is substantially similar to adaptor  120 . Adaptor  200  includes a center conductor contact  209  with an RF center contact  209   a  and a signal contact  209   b . For clarity of discussion, the portion of the adaptor  200  depicted at the top of  FIG. 2  is referred to herein as the proximate end  220 , while the portion of the adaptor  200  depicted at the bottom of  FIG. 2  is referred to as the distal end  222 . It should be noted that the terms proximate and distal are relative labels employed for the purpose of discussing component position and should not be considered limiting. Accordingly, the proximate end  220  of the center conductor contact  209  includes the RF center contact  209   a  and the distal end  222  of the center conductor contact  209  includes the pin/lead signal contact  209   b . The RF connector on end  220  may be any type of RF connector desired to couple to a corresponding RF probe, such as probe  130 . For example, the RF connector on the end of  220  may be a Sub-Miniature Push-On (SMP) connector, a Sub-Miniature version A (SMA) connector, an Micro-Miniature Coaxial (MMCX) connector, or any other coaxial connector. The signal contact  209   b  is structured to receive and interface with a signal pin, such as signal pin  111   a . Specifically, the signal contact  209   b  includes an opening  212  that receives and engages the signal pin/lead. The center conductor contact  209  may be made of any material capable of conducting electrical signals from the distal end  222  to the proximate end  220  and vice versa, for example copper, copper plated steel, brass, gold, gold plated brass, etc. The center conductor contact  209  is therefore a device that is structured to communicate a signal portion of a differential signal from the signal pin engaged at signal contact  209   b  at the distal end  222  to the RF center contact  209   a  at a proximate end  220 . 
         [0019]    The center conductor contact  209  is surrounded by an insulating sleeve  207 . The insulating sleeve  207  is as an insulator/dielectric that keeps the center conductor contact  209  from shorting to the outer conductive shield acting as the reference contact  205 . The insulating sleeve  207  may be made of any insulating material that provides the sufficient electrical insulation for the desired task, such as polyethylene, Polytetrafluoroethylene (PTFE) (e.g. Teflon), etc. 
         [0020]    The center conductor contact  209  and the insulating sleeve  207  are surrounded by a layer of conductor acting as the reference contact  205 . The reference contact  205  may be made of any conductive material, such as copper, copper plated steel, brass, gold, gold plated brass, etc. The reference contact  205  is separated and electrically isolated from the center conductor contact  209  by the insulating sleeve  207  and is structured to interface with the reference pin of the pins lead, such as reference pin  111   b , at the distal end  222 . Specifically, the adaptor  200  includes at least one opening  214  at the distal end to receive the reference pin in a manner that abuts the reference contact  205 . While only one opening  214  is required to interface with the reference pin, multiple openings may be employed for ease of use. In a particular embodiment, four openings  214  are evenly spaced around the circumference of the adaptor  200 , allowing the signal pin to engage with the signal contact  209   b  and the reference pin to be inserted into any of the openings  214 . The spacing between openings  214  and  212  is selected based on the spacing of the differential pins the adaptor  200  is designed to interface with. The reference contact  205  is structured to abut the DUT at the distal end  222  of the adaptor  200 . When abutting the DUT, the reference contact  205  physically contacts the DUT along an edge. By abutting the DUT, the reference contact  205  can shield the signal pin and the signal contact  209   b , and hence the signal portion of the differential signal, from common mode or other interference received between the DUT and the RF connector  209   a.    
         [0021]    The adaptor  200  further includes one or more securing elements  203  structured to secure the reference pin of the differential pair to the reference contact  205  when the reference pin is inserted in the opening  214 . For example, one securing element  203  is employed per opening  214 . The securing element  203  may be any device that can releasably secure the reference pin in place. In the embodiment shown, a leaf spring is employed as the securing element  203 . At the proximate end  220 , the reference contact  205  forms an opening  216  that receives a probe RF connector that mates with RF center contact  209   a . The opening  216  acts as part of the RF center contact  209   a , allowing the signal portion of the differential signal to pass to a center of the probe RF connector from the center conductor contact  209  and the reference portion to pass to an outer portion of the probe RF connector. Accordingly, the reference contact  205  is a device that is structured to receive a reference pin and communicate the reference portion of the differential signal from the distal end  222  to the RF connector at the proximate end  220 . Further, as discussed above, the insulating sleeve  207  can abut the DUT. By abutting the DUT with the insulating sleeve  207 , and by securing the reference pin in opening  214  at a predetermine spacing relative to the signal pin, the adaptor  200  can maintain the signal pin in a parallel position relative to the reference pin to maintain a fixed impedance between the differential pair. 
         [0022]    The adaptor  200  may further include a protective layer  201  surrounding the securing elements  203  and the reference contact  205 , and hence also surrounding the insulating sleeve  207  and the center conductor contact  209 . The protective layer  201  is an insulating jacket that protects the reference contact  205  from shorting to adjacent contacts or components on the DUT&#39;s surface. The protective layer  201  may be made of many materials suitable for such a purpose, for example polyvinyl chloride (PVC) or other plastics, rubber, etc. 
         [0023]      FIG. 3  is a cross sectional view of an embodiment of a differential pin to RF adaptor  300  with an attenuator  320 . Adaptor  300  is substantially similar to adaptor  200 , and hence only components interacting directly with the attenuator  320  are labeled in  FIG. 3 . Compared to adaptor  200 , the central contact  309  is extended to insert the attenuator  320  between the signal contact  309   b  and the RF center contact  309   a . The attenuator  320  is any resistive network structured to reduce a gain of a signal and/or match an impedance of a signal source to minimize power transfer between the source from the test network that is unrelated to the differential signal (e.g. minimize signal reflection from the test network, etc.) By employing an attenuator  320  in the central contact  309 , a probe RF connector inserted into opening  316  need not include an attenuator for attenuation/isolation, allowing the probe to be constructed more cheaply and employ a wide variety of probe RF connectors. Functionally, the signal pin from the DUT is inserted into the signal contact  309   b  via opening  312  and the probe RF connector is inserted into RF center contact  309   a  via opening  316 . The signal portion of the differential signal is communicated from the signal contact  309   b  to the RF center contact  309   a  via the attenuator  320 . The attenuator employs a network of resistors that electrically reduce the gain of the differential signal received from the distal end of the adaptor  300  prior to communicating the differential signal to the RF center contact  309   a  at the proximate end in order to match the gain of the differential signal to an expected gain at the RF probe and electrically prevent erroneous power transfers between the DUT from the testing system (e.g. host  150 ) as discussed above. 
         [0024]    The previously described versions of the disclosed subject matter have many advantages that were either described or would be apparent to a person of ordinary skill. Even so, all of these advantages or features are not required in all versions of the disclosed apparatus, systems, or methods. 
         [0025]    Additionally, this written description makes reference to particular features. It is to be understood that the disclosure in this specification includes all possible combinations of those particular features. For example, where a particular feature is disclosed in the context of a particular aspect or embodiment, that feature can also be used, to the extent possible, in the context of other aspects and embodiments. 
         [0026]    Also, when reference is made in this application to a method having two or more defined steps or operations, the defined steps or operations can be carried out in any order or simultaneously, unless the context excludes those possibilities. 
         [0027]    Although specific embodiments of the invention have been illustrated and described for purposes of illustration, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention should not be limited except as by the appended claims.