Patent Publication Number: US-7915981-B2

Title: Coaxial-to-microstrip transitions

Description:
BACKGROUND 
     Coaxial-to-microstrip transitions find application in microwave and high-frequency systems. Generally, coaxial-to-microstrip transitions are structures that provide a transition between a coaxial line and a microstrip line. Transitions between coaxial lines and microstrip lines can be “inline” or angled. Inline transitions occur along a common axis, and angled transitions occur along disparate axes, such as at a bend or a right-angle turn. 
     Angled portions of high-frequency transmission lines, such as angled transitions, can be a source of impedance discontinuity that degrades signal transmission. Impedance discontinuities degrade signal transmission by causing energy to reflect back toward the energy source and radiate away from the transmission line, which reduces the input energy reaching the intended destination. Parasitic inductance is a cause of impedance discontinuity in angled portions of transmission lines. Parasitic inductance generally includes both signal conduction path inductance and ground path inductance. 
     The following U.S. patents provide examples of devices and methods relevant to coaxial-to-microstrip transitions, and they are expressly incorporated herein by reference for all purposes: 
     U.S. Pat. Nos. 2,983,884, 5,557,074, 4,611,186, 4,837,529, 4,951,011, 4,994,771, 5,123,863, 5,175,522, 5,308,250, 5,402,088, 5,418,505, 5,517,747, and 5,552,753. 
     A further example of devices and methods relevant to coaxial-to-microstrip transitions is found in Morgan and Weinreb “A millimeter-wave perpendicular coax-to-microstrip transition,”  Microwave Symposium Digest,  2002  IEEE MTT - S International , Vol. 2, pp. 817-820, June 2002, which is expressly incorporated herein by reference for all purposes. 
     SUMMARY 
     Coaxial-to-microstrip transitions may include a microstrip line and a coaxial-line assembly. The microstrip line may include a first substrate dielectric, a conductive strip on one face of the dielectric, and a ground plane disposed on a second face of the dielectric opposite the first face. The coaxial-line assembly, extending transverse to the microstrip ground plane, may include an outer conductor and an inner conductor. In some examples, the ground plane contacts an end of the outer conductor and extends between the outer conductor and the inner conductor on a side of the coaxial-line assembly proximate the conductive strip. In some examples, the inner conductor extends through an aperture in the ground plane. The aperture may extend beyond the outer conductor on a second side of the coaxial-line assembly opposite the first side. In some examples, the ground plane has a non-circular aperture. In some examples, a cross-sectional area bound by the outer conductor is less than a corresponding cross-sectional area of the aperture. In some examples, the cross-sectional area bound by the outer conductor has a width that is less than a first-aperture width. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a coaxial-to-microstrip transition including a microstrip line and a coaxial-line assembly. 
         FIG. 2  is a top view of the coaxial-to-microstrip transition of  FIG. 1 . 
         FIG. 3  is a side cross-sectional view of the coaxial-to-microstrip transition of  FIG. 1  taken along the line  3 - 3  in  FIG. 2 . 
         FIG. 4  is a side view of the coaxial-to-microstrip transition of  FIG. 1  taken from a side of the coaxial-line assembly opposite the microstrip. 
         FIG. 5  is a cross-sectional view of a coaxial-to-microstrip transition including an aperture in a dielectric plated with a conductive material to form a via. 
         FIG. 6  is a top view of a coaxial-to-microstrip transition including a ground plane having a straight interface edge. 
         FIG. 7  is a top view of a coaxial-to-microstrip transition including a ground plane having an edge facing the inner conductor that forms a convex curve relative to the inner conductor. 
         FIG. 8  is a flow chart of a method of manufacturing a coaxial-to-microstrip transition. 
         FIG. 9  is a structural illustration of positioning a microstrip line according to the method of  FIG. 8 . 
         FIG. 10  is a structural illustration of moving a microstrip line according to the method of  FIG. 8 . 
         FIG. 11  is a structural illustration of a dielectric substrate of a microstrip line abutting a center conductor of a coaxial-line assembly according to the method of  FIG. 8 . 
         FIG. 12  is a structural illustration of electrically connecting a conductive strip with a center conductor according to the method of  FIG. 8 . 
         FIG. 13  is a top view of a further embodiment of a coaxial-to-microstrip transition. 
     
    
    
     DETAILED DESCRIPTION 
     Coaxial-to-microstrip transitions and manufacturing methods disclosed in the present disclosure will become better understood through review of the following detailed description in conjunction with the drawings and the claims. The detailed description, drawings, and claims provide merely examples of the various inventions described herein. Those skilled in the art will understand that the disclosed examples may be varied, modified, and altered without departing from the scope of the inventions as defined in the claims, and all equivalents to which they are entitled. Many variations are contemplated for different applications and design considerations; however, for the sake of brevity, each and every contemplated variation is not individually described in the following detailed description. 
     As shown in  FIGS. 1-7 , a coaxial-to-microstrip transition  10  may include a microstrip line  20  and a coaxial-line assembly  60 . Coaxial-to-microstrip transition  10  may function to transition radio frequency (RF) signals, such as microwave or millimeter wave signals, between coaxial-line assembly  60  and microstrip line  20 . 
     Microstrip line  20  may be oriented in various positions relative to coaxial-line assembly  60 . For example, as shown in  FIGS. 1-7 , coaxial-to-microstrip transition  10  may have a central or inner conductor  66  of coaxial-line assembly  60  that is oriented at a transverse angle relative to a plane P of microstrip line  20  (shown in  FIGS. 1 and 2 ). In other examples, coaxial-to-microstrip transition  10  may generally be coplanar, having a coaxial inner conductor that is oriented generally inline with microstrip line  20 . The following examples have transverse angled transitions, and more particularly transitions forming a 90-degree angle. 
     As shown in  FIGS. 1-4 , microstrip line  20  may include a dielectric substrate, referred to as a first dielectric  22  interposed between a conductive signal strip  34  and a return-signal ground plane  36 . Any material, gas, composition, or element known in the art to be suitable as a dielectric may be used. For example, semiconductors, plastics, porcelains, ceramics, glasses, or gasses, such as air, nitrogen, or sulfur hexafluoride may be suitable for use as first dielectric  22  in certain applications. 
     In the examples shown in  FIGS. 1-7 , first dielectric  22  is a substrate having a first primary face  24  and a second primary face  26  opposite first primary face  24 . Additionally or alternatively, first dielectric  22  may include a leading-edge face  28  extending between first and second primary faces  24 ,  26  that is proximate coaxial-line assembly  60 .  FIGS. 1 ,  2 , and  13  show leading-edge face  28  being curved and concave relative to coaxial-line assembly  60 . A leading-edge face  28 D that is curved and convex relative to coaxial-line assembly  60  is shown in  FIG. 7 . A leading edge face  28 E that is planar and parallel to line LD is shown in  FIG. 6 . As will be seen in some examples, a trailing-edge face  30  is disposed opposite leading-edge face  28 , as is shown in  FIGS. 3 ,  4  and  5 . 
     Conductive strip  34  may be disposed on, supported by, secured to, or printed on first primary face  24  of first dielectric  22 . In the example shown in  FIGS. 1-4 , conductive strip  34  is formed from a relatively thin conductive material and secured to first primary face  24 . As is known in the art, conductive strip  34  generally functions to propagate a signal along its length. The signal may follow an inner conduction path  67  illustrated in  FIG. 3 . In the examples shown in  FIGS. 1-7 , a bond wire  48  electrically connects conductive strip  34  with an end of inner conductor  66  of coaxial-line assembly  60 . A relatively short bond wire may provide reduced parasitics for transition  10 . As is known in the art, conductive strip  34  may vary in width to provide impedance transformation at the transition and to facilitate construction. 
     In the example shown in  FIGS. 1 ,  3 ,  4 , and  5 , ground plane  36  is a conductive layer disposed on all or a portion of second primary face  26  of first dielectric  22  opposite conductive strip  34 . Ground plane  36  provides a signal-return path. Ground plane  36  is directly or indirectly electrically connected to an outer conductor  62  of coaxial-line assembly  60 , such as by being directly connected to outer conductor  62 . Ground plane  36  may be formed of any suitable material. 
     A variety of ground plane  36  configurations are contemplated. For example, an interface edge  37  of ground plane  36  proximate coaxial-line assembly  60  may embody a variety of geometries. Examples of different interface edges  37 A-H are shown in  FIGS. 1 ,  2 ,  6 ,  7 , and  13  and described more particularly below. The geometry of interface edge  37  may have attendant electrical effects on the transition between the microstrip line and the coaxial line. Indeed, geometries of interface edge  37  may affect series inductances and shunt capacitances existing within coaxial-to-microstrip transition  10 . 
     As shown in  FIG. 1 , the interface edge  37 A may be curved. Different degrees of curvature are contemplated. Optional curved interface edges are shown as interface edge  37 A in  FIG. 1  and  FIG. 2 , interface edge  37 B in  FIG. 2 , interface edge  37 C in  FIG. 6 , interface edge  37 D in  FIG. 7 , and interface edge  37 G in  FIG. 13 . The curved interface edges  37 A,  37 B,  37 C, and  37 G shown in  FIGS. 1 ,  2 ,  6 , and  13  are concave relative to coaxial-line assembly  60 . In contrast, the curved interface edge  37 D shown in  FIG. 7  is convex relative to coaxial-line assembly  60 . 
     In some examples, interface edge  37  of ground plane  36  is straight or a series of straight edges forming angles. For example, in  FIG. 6 , the interface edge  37 E is straight, and interface edge  37 F is a series of straight edges forming an angle. In the example shown in  FIG. 6 , angular interface edge  37 F is concave relative to the coaxial-line assembly  60 . However, in other examples, angular interface edges are convex relative to coaxial-line assembly  60 . 
     Interface edge  37  of ground plane  36  may define a portion of a peripheral edge  44  of a first aperture  40  extending through ground plane  36 . As shown in  FIGS. 1-3 ,  5 - 7 , and  9 - 12 , aperture  40  may receive at least a portion of coaxial-line assembly  60 , such as an extension portion  70  of an inner conductor  66 . As shown in  FIGS. 6 and 7 , however, in some examples coaxial-to-microstrip transitions  10  do not include apertures through ground plane  36 . Rather, interface edge  37  facing the inner conductor is an outer edge of the ground plane. 
       FIG. 2  shows a top view of transition  10 , and  FIG. 3  shows a cross section taken along line  3 - 3  in  FIG. 2 . It is seen in these figures that inner conductor  66  extends through aperture  40  along an axis LA. As further shown in  FIG. 2 , when viewing ground plane  36  from a plane spaced along axis LA, aperture  40  may have an aperture area AA in the ground plane. With further reference to  FIG. 2 , aperture area AA may have a width WA. Aperture-area width WA is the widest dimension of the first aperture along a line parallel to line LD. Line LD is a line orthogonal to a line LC extending between the end of inner conductor  66  and the point where bond wire  48  is attached to the microstrip conductor  34 . 
     Those skilled in the art will appreciate that different geometries of aperture  40  may produce different electrical field distributions.  FIGS. 1 ,  6 ,  7 , and  13  depict a sampling of the variety of shapes that aperture  40  may have. For example, in  FIG. 2 , apertures  40 A and  40 B have oval shapes. In  FIG. 6 , first aperture  40 C has a circular shape, aperture  40 E has a rectangular shape, and aperture  40 F has a diamond shape. In  FIG. 7 , aperture  40 D has an irregular shape with straight and curved edge portions. In  FIG. 13 , aperture  40 G has an oval shape. 
     In some examples, such as those shown in  FIGS. 1-7  and  13 , first dielectric  22  includes a second aperture  46  extending at least partially through its thickness. Second aperture  46  may at least partially conform to and align with first aperture  40 . For example, they may have substantially the same shape and be co-incident when viewed in the view of  FIG. 2 . However, in alternative examples second aperture  46  does not conform to first aperture  40 . First aperture  40  and second aperture  46  may separately or collectively define an unobstructed region  42 . Unobstructed region  42  may receive components of coaxial-to-microstrip transition  10 . For example, as shown in  FIGS. 1 ,  3 ,  4 , and  5 , portions of coaxial-line assembly  60 , such as inner conductor  66 , may extend into unobstructed region  42 . 
     First aperture  40  and/or second aperture  46  may or may not be lined with a conductive material  52  to form a conductive via  50 . As is known in the art, a via may be an aperture plated or otherwise lined with a conductive material, such as a metal or alloy, to facilitate conduction of electrical currents between conductors on the respective primary faces of the substrate dielectric. Inner conductor  66  may extend through via  50  in spaced relationship from inner liner material  52 . In the example shown in  FIGS. 1-4 , second aperture  46  is not lined with conductive material  52 . In the example shown in  FIG. 5 , inner conductor  66  is asymmetrically received within via  50 . As discussed further below, asymmetrical positioning of inner conductor  66  within via  50  may cause an electric field to concentrate in a particular manner based on the proximity of conductive material  52  to inner conductor  66 . Optionally, second aperture  46  for any of the examples in  FIGS. 1-7  may be lined with conductive material  52 . 
     In some examples, a second dielectric  32  is provided within first aperture  40 . Additionally or alternatively, second dielectric  32 , or another dielectric, may be disposed within second aperture  46 . Second dielectric  32  may be the same or different from first dielectric  22 . As with first dielectric  22 , second dielectric  32  may be any material, gas, composition, or element known in the art to be suitable for use as a dielectric. For example, plastics, porcelains, glasses, semiconductors, resins, or gasses, such as air, nitrogen, or sulfur hexafluoride may be suitable for use as second dielectric  32  in certain applications. In some examples, first dielectric  22  may be a solid substrate made of one type of dielectric and second dielectric  32  may be air or may be a solid substrate made of another type of dielectric. 
     Coaxial-line assembly  60  may include outer conductor  62  shielding at least a portion of inner conductor  66  and extending along common axis LA with inner conductor  66 . A third dielectric (or insulator)  68  may separate outer conductor  62  from inner conductor  66 . As indicated in  FIG. 2 , coaxial-line assembly  60  may be described as having two sides on either side of a dividing line LD. A first side  72  shown in  FIG. 2 , may be defined as being proximate (on the same side of line LD as) conductive strip  34 . A second side  74 , shown in  FIG. 2 , may be defined as being distal (on the opposite side of line LD as) conductive strip  34 . 
     A variety of configurations of coaxial-line assembly  60  are contemplated. In some examples, such as those shown in  FIGS. 1-7  and  13 , coaxial-line assembly  60  includes a coaxial cable configuration in which inner conductor  66  is radially surrounded by third dielectric  68  and outer conductor  62 . In a coaxial cable configuration, outer conductor  62  typically forms a concentric sheath around inner conductor  66 . In some examples, coaxial-line assembly  60  may include a coaxial cable portion and a connector portion physically and electrically coupled to the cable portion. Many connector portions suitable for use with coaxial cables are known in the art, including K flange launchers, threaded “sparkplug” launchers, C (Councelman) connectors, GR (general radio) connectors, N (Neill) connectors, glass beads, and the like. 
     In a variety of ways and with a variety of components, connector portions generally provide an inner conduction path separated by a dielectric from a surrounding coaxial outer conduction path. Inner conductor  66  thus may be a single component or collection of connected components that collectively forms the inner conduction path. Similarly, outer conductor  62  may be a single component or collection of components that collectively provides the outer conduction path. 
     Outer conductor  62  may be electrically connected to ground plane  36  to provide a signal return path continuing between coaxial-line assembly  60  and microstrip line  20 . In some examples, such as those shown in  FIGS. 1-7  and  13  at least a portion  64  (shown in dashed lines in  FIG. 2 ) of outer conductor  62  is in physical contact with ground plane  36 . Additionally or alternatively, an electrical connection device, such as solder, connector, conductors, or other circuit components, may electrically connect outer conductor  62  with ground plane  36 . 
     As shown in  FIG. 2 , when viewing the transition end of coaxial-line assembly  60  from a plane parallel to and spaced from ground plane  36  along axis LA, it can be seen that outer conductor  62  may surround an enclosed area AE. Enclosed area AE is the area enclosed by outer conductor  62  when viewed in a plane parallel to ground plane  36  where outer conductor  62  contacts at least a portion of ground plane  36 . With further reference to  FIG. 2 , enclosed area AE may have a width WE. Enclosed-area width WE may be defined to be the length along line LD. WE also corresponds to the diameter of an outer conductor having a circular cross section. 
     As shown in  FIGS. 1-4 , extension portion  70  of inner conductor  66  may extend along axis LA beyond outer conductor  62 . Extension portion  70  may be positioned proximate to microstrip line  20 , for example, proximate to conductive strip  34  and/or ground plane  36 . Extension portion  70  is electrically connected to conductive strip  34  either directly or indirectly, such as via bond wire  48 , solder, or other connector. In the examples shown in  FIGS. 1-5 , extension portion  70  extends into first aperture  40  of ground plane  36  and into second aperture  46  of first dielectric  22 . 
     During use of transition  10 , an electrical field may exist between extension portion  70  and ground plane  36  in examples where extension portion  70  is adjacent to ground plane  36  or extends into first aperture  40  of ground plane  36 . Of relevance, the electrical field may tend to concentrate towards portions of ground plane  36  in relatively close proximity to extension portion  70 . In some examples, such as those shown in  FIGS. 1 ,  2 ,  3 ,  5 ,  6 , and  7 , interface edge  37  of the ground plane is in relatively close proximity to extension portion  70 . In some applications, concentrating the electric field in certain positions may provide certain utility, such as affecting ground-path series inductances and shunt capacitances that may be present. 
     In the examples shown in  FIGS. 1-7  and  13 , extension portion  70  and interface edge  37  or conducting material  52  of via  50  are placed in relatively close proximity to conductive strip  34  on first side  72  of the coaxial line. The proximity of extension portion  70  relative to interface edge  37  may be selected to produce desired electrical properties, such as series inductance along and shunt capacitance between the signal and signal-return conductors. In the examples shown in  FIGS. 1-7  and  13 , the electrical field tends to concentrate toward the conductive strip side of coaxial-to-microstrip transition  10 . Concentrating the electrical field toward the conductive strip side of coaxial-to-microstrip transition  10  may reduce the inductance occurring in the transition. 
     One source of ground-path inductance can be due to a portion of the electrical field occurring between inner conductor  66  and a second side  74  of coaxial-line assembly  60  opposite conductive strip  34 . In general, a portion of the electrical field may extend between extension portion  70  and portions of either ground plane  36  or outer conductor  62  on second side  74 . This field produces return currents that travel through long ground paths to reach the microstrip ground. The portion of the electrical field occurring on second side  74  is reduced when the electrical field is concentrated on first side  72 , thereby reducing ground-path inductance. 
     As is seen in the figures, coaxial-to-microstrip transitions  10  may have a variety of configurations. Different orientations, geometries, and proximities of components in coaxial-to-microstrip transitions  10  may produce different electrical properties in the transitions, and may have different costs to produce. 
     In the example shown in  FIGS. 1-4 , ground plane  36  extends between outer conductor  62  and inner conductor  66  on first side  72  of coaxial-line assembly  60 . In this context, ground plane  36  may be referred to as overlapping a portion of enclosed area AE. The portion of enclosed area AE overlapped by ground plane  36  may be referred to as an overlap area or portion AO, which is shown in  FIGS. 2 and 13 . 
     As can be seen in the example shown in  FIG. 2 , overlap portion AO is located substantially on first side  72  of dividing line LD. In other examples, a small fraction of overlap portion AO may be located on second side  74  of dividing line LD. For example, a small fraction of overlap portion AO may be located on second side  74  in first aperture  40 B in  FIG. 2  and first aperture  40 C in  FIG. 6 . Most of overlap portion AO—for example, over 75%—may be located on first side  72 . For example, having over 85% of the overlap on first side  72  provides increased concentration of electric fields between the ground plane and the inner conductor on first side  72 . In some examples, overlap portion AO may be located entirely on first side  72 , thereby attracting essentially all of the electric field on side  72  of the inner conductor. As further shown in  FIG. 2 , enclosed area AE may be less than aperture area AA and enclosed-area width WE may be less than aperture width WA, as shown. 
     In the example shown in  FIGS. 1-4 , ground plane  36  physically contacts outer conductor  62  along ground-plane portion  64  shown in  FIGS. 2 and 3 . As discussed above, outer conductor  62  may include more than the outer conductor of a standard coaxial cable or a coaxial cable connector. Indeed, outer conductor  62  may include a collection of components that provides an outer conduction path for a coaxial cable assembly. 
     As shown in  FIGS. 1-3 ,  5 - 7 , and  13  extension portion  70  of inner conductor  66  may be asymmetrically disposed in first aperture  40  as viewed in  FIG. 2 . In the example shown in  FIG. 3 , extension portion  70  is spaced a first distance D 1  from interface edge  37  and spaced a second distance D 2  from peripheral edge  44  opposite interface edge  37 . A variety of D 1 /D 2  ratios may be used in coaxial-to-microstrip transition  10 . For example, ratios less than one, greater than one, or equal to one may be suitable in different applications. In the example shown in  FIG. 3 , the D 1 /D 2  ratio is less than one. Generally, neither D 1  nor D 2  should equal zero as an electrical short between inner conductor  66  and ground may result. 
     Distances D 1  and D 2  may be distances between inner conductor  66  and conductive materials  52  of a via  50  in some examples. For instance, in the example shown in  FIG. 5 , extension portion  70  is spaced a first distance D 1  from conductive material  52  of via  50  on first side  72  and spaced a second distance D 2  from conductive material  52  on second side  74 . As discussed above, D 1 /D 2  ratios less than one, greater than one, or equal to one may be suitable in different applications. 
     As shown in  FIG. 13 , extension portion  70  may be disposed asymmetrically within first aperture  40 G such that extension portion  70  abuts first dielectric  22 . In one example shown in  FIG. 13 , interface edge  37 G of ground plane  36  is offset from leading-edge face  28 F of first dielectric  22  by a distance DX. As alternatively shown in  FIG. 13 , first dielectric  22  and ground plane  36  may be disposed only on one side of extension portion  70 . In the alternative example shown in  FIG. 13 , extension portion  70  abuts leading edge face  28 G, which is offset from interface edge  37 H by distance DX. The offset distance DX between the leading edge face of first dielectric  22  and the interface edge of ground plane  36  may facilitate orienting extension portion  70  into a given position relative to microstrip line  20 . 
     In the example shown in  FIGS. 1-4 , aperture area AA of first aperture  40  extends beyond outer conductor  62  on second side  74  of coaxial-line assembly  60  in a direction DA normal to axis LA. The position of the periphery of first aperture  40  beyond outer conductor  62 , as shown in this example, may cause an electrical field to concentrate on first side  72 . In other examples, first aperture  40  may extend short of or substantially to outer conductor  62  in direction DA on second side  74 . The example shown in  FIGS. 1-4  includes second aperture  46  conforming to first aperture  40 , although, conformance of the apertures is not required. Air or another dielectric material may be disposed within second aperture  46  as a second dielectric  32  (indicated in  FIG. 5 , but not in  FIG. 3 ), shown generally in  FIG. 3 . 
     As shown in  FIGS. 1 and 6 , coaxial-to-microstrip transitions  10  may include a ground plane having an aperture having a non-circular cross section. For example, each of apertures  40 A,  40 B,  40 D,  40 E,  40 F, and  40 G shown in  FIGS. 1 ,  6 , and  13  have non-circular cross sections. The shapes of the cross sections  40 A,  40 B,  40 D,  40 E,  40 F, and  40 G in  FIGS. 1 ,  6  and  13  may be described as an oval, a narrower oval, irregular, rectangular, diamond, and a wider oval, respectively. By way of comparison, the aperture  40 C shown in  FIG. 6  has a circular cross section. 
     In some examples, the second aperture  46  extending through first dielectric  22  may also be non-circular in cross section. Extension portion  70  may be disposed symmetrically (not pictured) or asymmetrically (shown in  FIGS. 1 ,  6 , and  13 ) within aperture  46 , as was discussed regarding aperture  40 . 
     Methods of manufacturing coaxial-to-microstrip transitions  10  are also contemplated. In some examples, a method  100  may start with at least partially preassembled coaxial-line assemblies and/or microstrip lines. In other examples, method  100  may start with producing coaxial-line assemblies and/or microstrip lines. For instance, a general method  100  is shown as a flow chart in  FIG. 8 , which contemplates starting with a step  101  of providing a coaxial-line assembly  60  and a microstrip line  20 , such as has been described. 
     Method  100  may include in a step  102  positioning the microstrip line in an orientation relative to the coaxial-line assembly. The orientation in which microstrip line  20  is positioned may be one in which ground plane  36  is transverse to the common axis LA of coaxial-line assembly  60 . Transverse is defined to mean any orientation other than inline or parallel. In this example, ground plane  36  is oriented at substantially 90 degrees relative to the common axis LA, as shown in  FIG. 9 . 
     With the microstrip in this orientation, dielectric substrate  22  is spaced from extension portion  70  of inner conductor  66  and inner conductor  66  is aligned with apertures  40  and  46 . In this example, ground plane  36  is proximate outer conductor  62 . 
     In examples where ground plane  36  and/or dielectric substrate  22  includes an aperture  40  or aperture  46 , step  102  of positioning the microstrip line may include positioning extension portion  70  within apertures  40  and  46 , as represented by movement of the microstrip line from a position spaced from the coaxial-line assembly, as shown in  FIG. 9 , to a position in which the inner conductor extends into apertures  40  and  46 . This step is considered equivalent to moving coaxial-line assembly  60  toward microstrip line  20 —i.e., one component moves relative to the other, regardless of which if any are moved relative to an external reference. 
     As described in  FIG. 8  and illustrated in  FIG. 10 , method  100  may include a step  104  of moving leading-edge face  28  of first dielectric  22  toward extension portion  70  until the leading-edge face  28  abuts the extension portion In some examples, such as shown in the combination of  FIGS. 10 and 11 , moving the microstrip line  104  may include moving microstrip line  20  toward extension portion  70  until the ground plane  36  contacts outer conductor  62 . Positioning step  102  and moving step  104  may be performed in reverse sequence or as a single step resulting in the positioning of the leading-edge face  28  against extension portion  70  with ground plane  36  in contact with outer conductor  62 . 
     In certain examples, method  100  may include a step of selecting the microstrip line to be positioned and moved based on a desired final spatial relationship of the microstrip line and the coaxial-line assembly. For example, a desired relationship may be between a first distance DX and a second distance DY shown in  FIG. 9 . The first distance DX may be the distance between interface edge  37  of the ground plane  36  and leading-edge face  28  of dielectric substrate  22 . In other words, in this example, interface edge  37  is recessed from leading-edge face  28  by dimension DX. The second distance DY may be the distance between inner conductor  66  and outer conductor  62  (the radial thickness of third dielectric  68 ). In some examples, the desired relationship is that first distance DX is substantially equal to second distance DY. In other examples, the desired relationship is that the first distance is less than the second distance. By contacting the inner conductor with the leading-edge face of the substrate dielectric, the distance DX between the inner conductor and the interface edge of the ground plane is established to the manufacturing tolerances of these components. This configuration reduces variations in the electrical performance of transition  10  due to varying distances DX during assembly. 
     As described in  FIG. 8  and illustrated in  FIG. 12 , method  100  may include a step  106  electrically connecting inner conductor  66  with the conductive strip  34 . The electrical connection may be accomplished with bond wire  48  or by any other device for making an electrical connection known in the art. 
     As can be seen from the above description, a coaxial-to-microstrip transition may include a microstrip line including a first dielectric having a first primary face and a second primary face opposite the first primary face, a conductive strip disposed on the first primary face of the first dielectric, and a ground plane disposed on the second primary face of the first dielectric, and a coaxial-line assembly extending along an axis transverse to the ground plane and having an end adjacent to the microstrip line, the coaxial-line assembly including an outer conductor extending along the axis to the ground plane, an end of the outer conductor being in contact with the ground plane, and an inner conductor extending along the axis past the ground plane and being electrically connected to the conductive strip, wherein the ground plane extends to a position between the outer conductor and the inner conductor on only a first side of the coaxial-line assembly proximate the conductive strip. 
     It can also be seen from the above description that a coaxial-to-microstrip transition may include a microstrip line including a first dielectric having a first primary face and a second primary face opposite the first primary face, a ground plane disposed on the second primary face of the first dielectric, a conductive strip disposed on the first primary face of the first dielectric, a first aperture extending through the ground plane and having a non-circular cross section in a plane of the ground plane, and a coaxial-line assembly extending along an axis transverse to the ground plane and being adjacent the microstrip line, the coaxial-line assembly including an outer conductor extending along the axis to the ground plane, the outer conductor being in contact with the ground plane, and an inner conductor extending along the axis into the first aperture and being electrically connected to the conductive strip. 
     Moreover, the above description discloses that a coaxial-to-microstrip transition may include a microstrip line including a first dielectric having a first primary face and a second primary face opposite the first primary face, a conductive strip disposed on the first primary face of the first dielectric, a ground plane disposed on the second primary face of the first dielectric, and a first aperture extending through the ground plane and having a cross section defining an aperture area, and a coaxial-line assembly extending along an axis transverse to the ground plane and being adjacent the microstrip line, the coaxial-line assembly including an outer conductor in contact with the ground plane and having a cross section, in a plane parallel and proximate to the ground plane, defining an enclosed area, the ground plane overlapping a portion of the enclosed area on a first side of the coaxial-line assembly proximate the conductive strip and the first aperture extending beyond the outer conductor on a second side of the coaxial-line assembly opposite the first side, and an inner conductor extending along the axis into the first aperture and being electrically connected to the conductive strip. 
     It can be further seen from the above description that a coaxial-to-microstrip transition may include a microstrip line including a first dielectric having a first primary face and a second primary face opposite the first primary face, a conductive strip disposed on the first primary face of the first dielectric, a ground plane disposed on the second primary face of the first dielectric, and a first aperture extending through the ground plane, the first aperture having a first-aperture width, and a coaxial-line assembly extending along an axis transverse to the ground plane and having an end adjacent to the microstrip line, the coaxial-line assembly including an inner conductor extending along the axis into the first aperture and being electrically connected to the conductive strip, and an outer conductor extending along the axis to the ground plane, the outer conductor surrounding the inner conductor and having a cross section defining an enclosed area, the enclosed area having a width that is smaller than the first-aperture width, an end of the outer conductor being in contact with the ground plane. 
     As can be seen from the above description, a method of manufacturing a coaxial-to-microstrip transition between a coaxial-line assembly and a microstrip line, the coaxial-line assembly including an outer conductor spaced apart from and extending along a common axis with an inner conductor, and the microstrip line including a dielectric substrate, a conductive strip disposed along a first primary face of the dielectric substrate, and a ground plane disposed along a second primary face of the dielectric substrate opposite the first primary face, the dielectric substrate having a leading-edge face extending between the first and second primary faces, there being an unobstructed region next to the leading-edge face that is sized longer than a cross-sectional dimension of the inner conductor, the ground plane having an interface edge that is recessed along the second primary face from the leading-edge face, may include the steps of positioning the microstrip line relative to the coaxial-line assembly, with the ground plane extending transverse to the common axis and proximate the outer conductor, and moving the microstrip line toward the extension portion until the leading-edge face abuts the extension portion and the ground plane contacts the outer conductor. 
     INDUSTRIAL APPLICABILITY 
     The methods and apparatus described in the present disclosure are applicable to the telecommunications and other communication frequency signal processing industries involving the transmission of signals between circuits or circuit components. 
     It is believed that the disclosure set forth above encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in a particular form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. The subject matter of the inventions includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein, and equivalents of them. Where the disclosure or subsequently filed claims recite “a” or “a first” element or the equivalent thereof, it is within the scope of the present inventions that such disclosure or claims may be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. 
     Applicants reserve the right to submit claims directed to certain combinations and subcombinations that are directed to one of the disclosed inventions and are believed to be novel and non-obvious. Inventions embodied in other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of those claims or presentation of new claims in that or a related application. Such amended or new claims, whether they are directed to a different invention or directed to the same invention, whether different, broader, narrower or equal in scope to the original claims, are also regarded as included within the subject matter of the inventions of the present disclosure.