Wave transmission lines and networks – Miscellaneous – Multipactor applications
Reexamination Certificate
1998-06-03
2001-02-06
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Miscellaneous
Multipactor applications
C333S246000, C333S260000
Reexamination Certificate
active
06184757
ABSTRACT:
This invention relates to electronic modules. It particularly relates to assemblies operating at cryogenic temperatures.
BACKGROUND OF THE INVENTION
A known technique of operating electronic components at cryogenic temperatures is to mount the components on a so-called “cold finger” within an evacuated chamber. A problem can arise in making electrical connections between the exterior of the enclosure, which may be at ambient temperature, and the electronic components, which are at cryogenic temperatures, in that electrically conductive signal paths also provide thermally conductive paths. The more connecting paths, the greater the conducted heat and the heavier the loading on the cryogenic cooler. This is a particular problem with radio-frequency signal paths where conductor dimensions are determined by the need to maintain a good impedance match and may involve the provision of a conducting ground plane. The coupling paths also need to allow for the thermal expansion and contraction which may arise due to the thermally-produced movement between the components and the enclosure which occurs when the assembly is being brought to its cryogenic operating temperature or returns to ambient temperature when the apparatus is shut down.
In one known approach, each path comprises a length of coaxial cable extending between the walls of the enclosure and the cryogenic components. However this known arrangement suffers the disadvantage that, in order to minimise heat loss by conduction, the cable must be made relatively long. While this arrangement has proved satisfactory where a small number of signal paths is concerned, for large numbers of paths, the large number of parallel paths provides a correspondingly reduced thermal resistance, leading to a proportional increase in heat load. Another disadvantage is that coaxial cable will inevitably contain a certain amount of trapped gas which will progressively leak into the vacuum space over a period of time. This gas will provide another mechanism for heat transfer by convection or conduction between ambient and the cold component. The longer the cable, the greater the potential for out gassing of trapped gases. The user then has the inconveniences of having to periodically re-pump the enclosure to restore vacuum.
Another problem which can arise concerns adjustment of adjustable components such as tuning screws which may be necessary when setting up a circuit operating at cryogenic temperatures.
The present invention seeks to ameliorate the above disadvantages of the prior art.
BRIEF SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention there is provided a circuit assembly comprising a first substrate having a first stripline conductor arranged on a first surface thereof and having an end terminating at an edge of the first substrate, a second substrate having a second stripline conductor arranged on a first surface thereof and having an end terminating at an edge of the second substrate, means to align the first and second substrates with their edges spaced apart with the respective ends of the striplines aligned, respective first and second wire links extending between respective longitudinal edges of the end of the first stripline conductor and corresponding edges of the end of the second stripline conductor.
In accordance with a second aspect of the invention there is provided apparatus for adjusting a circuit operated at cryogenic temperatures comprising an evacuable housing, and means for mounting a circuit to be adjusted within the evacuable housing, the apparatus comprising a cover for the housing arranged to be hermetically sealed to the housing, the cover comprising at least one adjuster disposed in a through bore in the cover, the bore having seal means arranged to cooperate with the adjuster and provide hermetic seal therewith while allowing movement of the adjuster relative to the cover, the other end of the adjuster being arranged to cooperate with an adjustable member of the circuit whereby the circuit can be adjusted from the exterior of the housing when the interior of the housing is evacuated.
In the present specification the expression “stripline” refers to transmission lines in which at least one conductor comprises a planar conductive member arranged on a substrate. It includes but is not limited to, microstrip and stripline configurations and balanced and unbalanced configurations.
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Greed Robert Brian
Mistry Ramanlal Chhiba
Rosenthal Keith Ronald
Donald C. Casey, Esq.
GEC--Marconi Limited
Pascal Robert
Summons Barbara
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