Abstract:
A versatile quick connect/disconnect coaxial 3.5 mm male connector which can be used to mate with unmodified standard SMA, 2.92 mm, and 3.5 mm female connectors with or without the use of a threaded nut. The connector employs simple construction and achieves excellent electrical performance. The connector allows the user the option of a push to engage and pull to disengage operating feature, plus the additional option to connect using a threaded nut with reduced thread engagement, which can be hand tightened or torqued to a specific value. The threaded nut is retractable and is held clear of the mating area for push/pull operation, and due to the minimum number of threads, the nut can be coupled and uncoupled in one third to one fourth the time needed to thread a conventional nut.

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention generally relates to microwave connectors and more specifically, to quick connect/disconnect coaxial connectors. 
     BACKGROUND OF THE INVENTION 
     In testing microwave devices, it is desirable to provide a connection which can be made quickly while providing low VSWR (Voltage Standing Wave Ratio), high isolation, and most importantly, repeatable measurements, ideally exhibiting repeatability greater than 40 dB. It is also desirable that the connection be stable and not require any external fixturing to insure repeatability, but may require support when used on a cable or test device which would normally require support during test. 
     Various quick disconnect coaxial connectors are described in U.S. Pat. Nos. 4,846,714; 4,891,015; 4,941,846; and 5,401,175. All of the above employ relatively complex and expensive methods for achieving a quick connect/disconnect feature for coaxial connectors. 
     SUMMARY OF THE INVENTION 
     A male slotted connector is described according to an aspect of the invention, which incorporates a compression ring that provides additional support to slotted and spread fingers of the outer conductor resulting in electrically repeatable couplings. The male connector can be mated to a female connector and connected and disconnected using a simple push on/pull off motion without the need for other action. 
     The connector may be used with an optional integral coupling nut to provide the option of a threaded coupling when performing calibration, or when verification of the measurement is desired. When used, the coupling nut provides engagement of one-half to one and one-half threads in one embodiment, providing the ability to quickly thread or unthread the mating connectors, or allowing a torqueable mating using industry standard torque wrenches. 
     This multi-function connector can be used to measure devices that utilize various types or sizes of female connectors, e.g.,SMA (Sub-Miniature Series A), 2.92 mm, or 3.5 mm female connectors. The female connector of these series connectors conventionally mate with a male connector that is screwed on and typically requires five to six revolutions of the coupling nut to mate. 
     The simplicity and ease of use of this invention, plus the low cost to manufacture, provides the user a low cost alternative to the more complex and costly methods currently available today. 
     Similar connectors can be provided using this coupling technique in connector types such as type N, TNC (Threaded Neille Concelman), 2.4 mm, 1.85 mm, 1.0 mm, and other sexed connectors with similar construction. 
     Another embodiment of the male connector employs a solid outer conductor structure with the compression ring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     These and other features and advantages of the present invention will become more apparent from the following detailed description of an exemplary embodiment thereof, as illustrated in the accompanying drawings, in which: 
     FIG. 1 is a partially broken-away, cross sectional view of a connector type embodying aspects of this invention, showing the configuration of the outside diameter of the outer conductor, and the placement of the compression ring, the nut, and retaining ring. 
     FIG. 2 is a view similar to FIG. 1, without the nut and retaining ring. 
     FIG. 3 is an end view showing the slotted outer conductor. 
     FIG. 4 is a partially broken-away, cross sectional view showing the connector of FIG. 1 mated with a female connector, showing the nut in the retracted position. 
     FIG. 5 is a partially broken-away, cross sectional view similar to FIG. 4, but showing the connector mated with a female connector showing the nut in a forward threaded position. 
     FIG. 6 is a cross sectional view similar to FIG. 5, less the nut and retaining ring. 
     FIG. 7 is a cross-sectional view depicting the connector structure in a downwardly oriented position, showing the retention of the outer nut by a ring retainer. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A male slotted connector  10  is illustrated in FIGS. 1-6, which incorporates a slotted outer conductor having spread fingers and a compression ring that provides additional support to the fingers, resulting in electrically repeatable couplings. This embodiment yields a quick disconnect configuration that provides excellent electrical specifications, and with the use of heat treated beryllium copper material also provides long life and reliable test characteristics. Conventional 3.5 mm connectors, 2.4 mm, 1.85 mm, and 1.0 mm connectors are only available with unslotted outer conductors. 
     The connector structure  10  includes a slotted outer conductor structure  12 , having a plurality of slots  14  (FIG. 3) formed longitudinally in the leading end  16  of the outer conductor structure. The slots  14  separate finger regions  15  in the outer conductor structure  12 . In an exemplary embodiment, the slots and the finger regions have a length of 0.100 inch. 
     The configuration of the leading end  16  of the outer conductor allows smooth entry and make excellent electrical contact with the inner diameter of the female connector  50  (FIGS.  4 - 6 ). The leading end  16  is radiussed with a smooth finish to provide a smooth wiping action on the female connector  50 . It further features a flat end surface  17  to rest against a corresponding flat end surface of the female connector, thus minimizing any discontinuity at these mating surfaces of the respective connector structures. 
     A split compression ring  20  encircles the outer conductor structure  12  at region  12 A, and is designed to exert force on the inner surface of the female connector  50  and provide mechanical stability. The ring is split to facilitate assembly onto the outer conductor structure  12 . In this exemplary embodiment, the split ring is fabricated of heat treated beryllium copper, and is spread and held during the heat treatment to yield a ring diameter that provides optimal pressure against the inner surface of the mating female connector. Further, the ring is provided with a 30 degree lead-in chamfer on the outer diameter to assist entry into the female connector. As the ring compresses, it reduces the air gap over the outer diameter of the outer conductor between the outer conductor structure  12  and the female conductor structure  50 . This in turn reduces RF leakage through the slots  14  in the outer conductor and eliminates radiation over a rated operating frequency range of the connector, which in this exemplary embodiment is from 0 to 26.5 GHz. 
     The finger regions  15  are spread to provide a compression fit with the inner circumferential surface of the female connector. The outer diameter of the outer structure  12  at the radiussed end of the outer conductor structure  12  is machined to a diameter of 0.181 inch +/− 0.0006 inch, in an exemplary embodiment, and the finger regions are then spread and heat treated with the diameter set at 0.189 inch +/− 0.0015 inch. The inner diameter of the corresponding female outer connector structure at its leading end for this embodiment is 0.1812 inch, and so the outer diameter of the outer structure at the leading end is slightly oversized with respect to the female connector structure. When engaged with the female connector structure, the inner surface of the female connector structure forces the spread finger regions  15  together and returns the inside diameter of outer conductor structure  12  at the slotted finger regions to the nominal 3.5 mm coaxial line size dimension of 0.1378 inch diameter. The radiussed leading end surfaces of the finger regions facilitate the engagement with the female connector structure. 
     A threaded coupling nut  22  with reduced thread engagement is held in place by a retaining ring  24 . The coupling nut  22  is fabricated with an inner area between shoulders  22 A,  22 B of increased diameter, forming an elongated relief area  25 . This relief area allows the coupling nut  22  to retract towards the rear of the connector  10  to ensure that the threads on the coupling nut do not contact the threads  52 A on the female connector  52  (FIG. 5) should the user desire not to thread or couple the nut. Further, the retaining ring  24  exerts pressure on the coupling nut  22  when retracted, so that, should the connector be oriented with the nut  22  facing down, the retaining ring  24  exerts sufficient pressure to overcome the weight of the nut  22  and maintain it in a retracted position, as illustrated in FIG.  7 . An exemplary material for the retaining ring is phosphor bronze. 
     The connector structure  10  further includes an inner conductor pin  26  with a leading end pin region  27  of reduced diameter with respect to that of the pin  26 . The leading end pin region  27  in this exemplary embodiment has a reduced length as compared to prior connectors, to provide unrestricted entry into a mating female contact. The leading end pin region  27  has a length of 0.070 inch in this exemplary embodiment, as compared to a typical standard length of SMA pins of 0.090 inch and 3.5 mm connectors of 0.085 inch. Thus, in this exemplary embodiment, the reduced length of pin region  27  allows the entry of the outer conductor  12  into the female connector outer conductor structure  52  (FIGS. 4-6) prior to the pin region  27  engaging the socket  54  of the female contact structure  56 . In the case of a SMA connector with a dielectric sleeve  58  about the female contact structure  56 , the outer conductor  12  provides alignment of the pin region  27  during entry and therefore reduces the risk of damaging the mating female contact  56  or dielectric  58  by misalignment during insertion. 
     FIG. 2 shows the connector  10  with the coupling nut  22  and retaining ring  24  removed. This view illustrates the basic configuration to use the connector  10  for performing quick connect/disconnects during test. The nut  22  and retaining ring  24  are typically employed should the user desire to make a threaded coupling to verify the measurement accuracy or when a network analyzer calibration is being performed and the connector is used as the calibrated test port. Also, normal pressure applied (typical 8 in/lbs) for conventional connector structures to the mating interface  32  (FIGS. 2 and 4) is not necessary to achieve excellent repeatability of greater than 40 dB from 0 Hz to 26.5 GHz frequency range, even when the connection is coupled and de-coupled repeatably through 360° rotation. The arrows  36  in FIG. 2 indicate the direction of the applied force exerted by the outer conductor  12  and compression ring  20  on the female connector structure during and after mating. 
     FIG. 3 shows an end view of the connector structure  10 , and in this exemplary embodiment, the slots  14  are disposed at 45° spacings from adjacent slots. The number of slots is not critical to the invention, and the use of the compression ring  20  with a solid (unslotted) outer conductor structure  12  also provides satisfactory results for many applications. However, the slotted version exhibits better electrical performance. The width of the slots  14  is held as small as possible to minimize RF leakage at the higher operating frequencies. For this exemplary embodiment, in which the connector structure  12  has an inner diameter of 0.1378 inch when engaged with the female connector, the slots have a typical width of 0.006 inch. 
     FIG. 4 shows the connector structure  10  mated to an SMA type connector  50  having a dielectrically loaded interface  58 . This view shows the normal retracted position of the coupling nut  22  as used during test and also shows the male connector outer conductor  12  and the female connector outer conductor  52  where they contact at the interface plane  32 . In this view, the outer surfaces of the leading end  16  of the slotted connector structure  12  are shown in the compressed condition when fully engaged with initial pressure applied to the connector body. The nut is fully retracted and is not engaged or threaded during use. This mode of operation provides the user the recommended method to conduct quick tests using the connector structure  10 . 
     The connector structure  10  in an exemplary test application is intended to be used, and will provide optimum results, where the device-under-test (DUT) is supported and where the device fixed with the connector structure  10  is also reasonably supported. FIG. 5 depicts a device  102  fixed to the connector structure  10 , and a DUT (Device Under Test)  104  connected to the female connector structure  104 . In this exemplary application, the device  102  could be a network analyzer. 
     FIG. 5 shows the coupling nut  22  with the threads  22 C fully engaged with the threads  52 C on the mating female connector  50 . By virtue of the small number of threads present on the coupling nut, with a minimum of one thread, engagement and disengagement is very rapid and can typically be executed 2-3 times faster than engaging a standard fully threaded nut having 2-4 times the thread length. In this position, the coupling nut  22  can also be torqued to the recommended torque value of 8 in/lbs using a commercially available torque wrench. The electrical repeatability of a mated pair of connectors, when hand torqued or torqued using a torque wrench, is practically identical. This allows the user the option of torquing a mated pair of connectors during calibration or test to guarantee very exacting results, or hand torque the connectors very rapidly as a test mode of operation or to verify a push/pull, engage/disengage test where results of the mating are unstable for any reason. No known quick disconnect microwave connector provides this versatility of use. 
     FIG. 6 shows a configuration of the connector structure  10 , less coupling nut  22  and retaining ring  24 , mated to the female connector structure  50 . In this configuration, the connector structure  10  can only be used in the push-to-engage, pull-to-disengage mode of operation. Here, the connector offers excellent electrical repeatability. This configuration is recommended where speed is of the essence in coupling the DUT to test devices and is ideal for manual or automated test fixtures or setups. 
     This configuration of slotted outer conductor  10 , used in conjunction with a compression ring  20 , can be applied to a variety of connector types having reasonably thick outer conductor walls which will allow a recess to be provided where the compression ring can reside, and where the normally solid outer conductor walls can be slotted and expanded to provide a spring compression fit with the mating female connector. If the conductor wall is too thin to allow a compression ring, the ring may be omitted with a slight degradation in performance. 
     Microwave connectors and test adapters employing this connector can be inexpensively produced and quickly connected and disconnected from a microwave coupling while maintaining a highly repeatable and low VSWR junction. Another aspect of this invention is a connector that can either be used in the push on/pull off mode or in the threaded mode as desired by the user. 
     It is understood that the above-described embodiments are merely illustrative of the possible specific embodiments which may represent principles of the present invention. Other arrangements may readily be devised in accordance with these principles by those skilled in the art without departing from the scope and spirit of the invention.