Wave transmission lines and networks – Coupling networks – With impedance matching
Reexamination Certificate
1999-05-12
2001-05-22
Bettendorf, Justin P. (Department: 2817)
Wave transmission lines and networks
Coupling networks
With impedance matching
C333S260000
Reexamination Certificate
active
06236287
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to RF devices, and more particularly to a shielded coaxial to microstrip orthogonal launcher with multiple matching junctions for wideband microwave frequency operation with improved shielding and flexible routing of RF signals along the transmission line.
BACKGROUND OF THE INVENTION
There is a need in many RF systems to provide an orthogonal transition from a microstrip transmission line to a coaxial transmission line. A known technique of accomplishing this is to end launch a right angle coax connector onto microstrip along the substrate edge. Disadvantages of this approach include the relatively large space and volume requirements, and the requirement that the transition be made at the edge of the substrate.
It would therefore be an advantage to provide a transition technique which required less space, and offered the flexibility to vertically launch anywhere along the microstrip circuit board.
Another problem not addressed by known transition techniques between coaxial and microstrip transmission lines involves the issue of complete ground shielding the coaxial launcher as it contacts the microstrip center conductor vertically from an air dielectric side. In known techniques, the coaxial outer ground shield is partially removed to prevent that shield from short circuiting the microstrip center conductor. Exposing the coaxial section to air will result in RF leakage and the generation of the higher order waveguide modes, and thus degrades the RF performance when used at higher frequencies. Commercially available coaxial launchers are thus limited at the high frequency end to about 7 Ghz. Launchers for channelized microstrip transmission line described in U.S. Pat. No. 5,416,453 are limited at the high frequency end to about 14 Ghz.
SUMMARY OF THE INVENTION
A coaxial-to-microstrip vertical transition in accordance with this invention can operate at higher frequencies with better RF performance than what has been accomplished in the past. A coaxial-to-microstrip transition in accordance with an aspect of this invention is completely shielded with little possibility of leakage or generation of higher order waveguide modes at higher frequency. The transition incorporates matching junctions for improved performance, and a compressible center conductor to allow for blind mate connections.
In an exemplary embodiment, the coaxial-to-microstrip vertical transition includes a dielectric substrate having formed on a first surface thereof a primary microstrip conductor trace, and on a second surface a secondary microstrip conductor trace. A first conductive via extends through the dielectric substrate and electrically connects the primary conductor trace to the secondary conductor trace. A second conductive via is spaced from the first conductive via and extends through the dielectric substrate to electrically connect the secondary conductor trace to the coaxial center conductor. A bottom microstrip ground plane layer is defined on the second substrate surface. A conductive base plate structure has a cavity formed therein, the substrate positioned relative to the base plate structure such that the base plate structure is in contact with the bottom ground plane layer, and the secondary conductor trace is positioned over the cavity so that the secondary conductor is not in electrical contact with the base plate structure. A conductive cover structure is disposed such that the substrate is positioned between the cover structure and the base plate structure, the cover structure disposed in spaced relation with respect to the first surface of the substrate. The transition further includes a coaxial transmission line structure having an outer shield, a coaxial center conductor structure disposed within the outer conductor and transverse to the substrate, the center conductor passed through an opening in the cover structure to contact the second via. A conductive plate has an opening formed therein, and is positioned between the cover structure and the substrate, the plate providing shielding surrounding the center conductor in a space between the cover and the substrate.
REFERENCES:
patent: 5872550 (1999-02-01), Quan et al.
patent: 5886590 (1999-03-01), Quan et al.
Hashimoto Mark Y.
Jorgenson Rosie M.
Quan Clifton
Roberts David E.
Robertson Edward L.
Alkov Leonard A.
Bettendorf Justin P.
Lenzen, Jr. Glenn H.
Raytheon Company
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