Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
2002-04-02
2004-12-21
Nguyen, Linh My (Department: 2816)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S245000
Reexamination Certificate
active
06833775
ABSTRACT:
The present invention relates to a microwave circuit and has particular, but not exclusive, application to a circuit fabricated on an RF printed circuit board (PCB).
Typically microwave circuits such as frequency converters for converting L-band to RF or RF to L-band include passive components such as filters. For convenience it is desirable if the filter could be defined as a pattern in the metal layer of the PCB. However, currently used commercial PCB patterning techniques are only able to define circuit tracks with 150 &mgr;m gaps and track widths to a precision of ±20 &mgr;m. This level of precision is too coarse to be able to define a filter having the performance required.
It is an object of the present invention to provide a microwave circuit having a desired performance on a PCB and in a cost effective manner.
According to one aspect of the present invention there is provided a microwave circuit comprising a printed circuit board consisting of a substrate having a metal backing on one surface of the substrate and at least one microstrip track on another surface thereof, and at least one sub-circuit mounted on the printed circuit board, the sub-circuit comprising a substrate having a higher dielectric constant than that of the printed circuit board substrate and having a conductive pattern thereon, the conductive pattern being coupled electrically to the at least one microstrip track.
According to another aspect of the present invention there is provided a microwave circuit comprising a printed circuit board on which is fabicated an RF stage having a frequency up-converter having an RF output coupled to a local oscillator reject filter and an image reject filter coupled to an RF input of a frequency down-converter, wherein the local oscillator reject filter and the image reject filter respectively comprise a sub-circuit comprising a substrate having a higher dielectric constant than that of the printed circuit board substrate and having a printed conductive pattern thereon, the conductive pattern being coupled electrically to the at least one microstrip track provided on the printed circuit board.
By virtue of the substrate having a higher dielectric constant than that of the printed circuit board, the sub-circuit can be physically smaller compared to a similar circuit made in PCB material. In an embodiment of the microwave circuit, the dielectric substrate comprises alumina which has a dielectric constant ∈
r
=9.9 compared to an ∈
r
=2.2 for the PCB material. The higher dielectric constant enables the sub-circuit on alumina to be half the size of that on the PCB material. The patterning technique can be done in a technology which is capable of achieving the required definition accuracy and which enables many hundreds of sub-circuits to be made simultaneously. Thus the method in accordance with the present invention enables two different technologies to be combined with a beneficial performance gain and cost effectiveness.
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patent: 5202752 (1993-04-01), Honjo
patent: 5569879 (1996-10-01), Gloton et al.
patent: 6057600 (2000-05-01), Kitazawa et al.
patent: 6060967 (2000-05-01), Asada
patent: 6525623 (2003-02-01), Sridharan et al.
patent: 2297652 (1996-01-01), None
patent: 05-259720 (1993-08-01), None
Patent Abstracts of Japan, vol. 2000, No. 03, May 3, 2000, JP11340709.
Buck Christopher M.
Williams Keith R.
Belk Michael E.
Koninklijke Philips Electronics , N.V.
Nguyen Linh My
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