Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
2002-04-16
2004-05-11
Ham, Seungsook (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S206000, C333S229000, C333S234000, C333S235000
Reexamination Certificate
active
06734766
ABSTRACT:
BACKGROUND
1. Field of the Invention
This invention relates generally to the field of electronic filters. More particularly, the present invention provides a microwave filter having a temperature compensating element.
2. Description of the Related Art
Microwave filters are known in this art. A microwave filter is an electromagnetic circuit that can be tuned to pass energy at a specified resonant frequency. The filter is used in communications applications to filter a signal by removing frequencies that are outside a bandpass frequency range. This type of filter typically includes a housing with an input port and an output port. Internally, a typical microwave filter includes an array of interconnected filter cavities. In many microwave filters, the resonant frequency of the filter may be adjusted with tuning screws that typically protrude through the housing and into each filter cavity. One such filter type is a coaxial microwave filter.
FIG. 1
is a cross-sectional view of a known coaxial microwave filter
10
. The coaxial filter
10
includes a housing wall structure
12
that defines a plurality of interconnected filter cavities
13
, and a filter lid
14
that is fixedly mounted to the housing wall structure
12
to cover the cavities
13
. Each filter cavity
13
includes a resonator rod
16
projecting upward from a bottom wall of the housing wall structure
12
, typically at the center of the cavity
13
, and a tuning screw
18
mounted through the filter lid
14
opposite the resonator rod
16
. The tuning screw
18
may be adjusted to extend into a bore
19
in the center of the resonator rod
16
. It should be understood, however, that although only one cavity
13
is shown in
FIG. 1
, the filter
10
typically includes an array of cavities
13
that are interconnected through openings, such as irises, in the cavity walls. It should also be understood that a three dimensional view of the cavity
13
would show the resonator rod
16
and tuning screw
18
in the center of an open cavity
13
, i.e., there is open space within the cavity
13
on all sides of the resonator rod
16
.
The electrical resonance of each cavity
13
in the filter
10
is determined by the combination of the length of the resonator rod
16
, the size of the cavity
13
, the size of the gap
20
between the resonator rod
16
and the filter lid
14
, and the insertion depth of the tuning screw
18
into the resonator rod
16
. The insertion depth of the tuning screw
18
into the resonator rod
16
can, therefore, be adjusted to change the resonant frequency of the filter
10
.
The resonant frequency of the filter
10
may be undesirably altered, however, by minute changes in the size of the cavity
13
resulting from thermal expansion or contraction of the housing material and the resonator rod
16
during a change in ambient temperature. This drift in frequency with temperature may be reduced by using different materials for the resonator rod
16
and the housing
12
. For example, the filter lid
14
and housing wall structure
12
may be manufactured from aluminum, while the resonator rod
16
is made from some other type of metal or possibly a ceramic material. Even with such a design, however, some amount of temperature-dependant frequency drift typically remains.
SUMMARY
A microwave filter having a temperature compensating element includes a housing wall structure, a filter lid, a resonator rod, a tuning screw and the temperature compensating element. The housing wall structure defines a cavity. The filter lid closes the cavity. The resonator rod is within the cavity. The tuning screw is adjustably mounted through the filter lid and has a portion that protrudes into the cavity and is coaxial with the resonator rod. The temperature compensating element is joined to the filter lid or the housing and forms a bimetallic composite with the filter lid or housing that deforms with a change in ambient temperature.
REFERENCES:
patent: 2795764 (1957-06-01), Mittelman et al.
patent: 4389624 (1983-06-01), Aihara et al.
patent: 4890078 (1989-12-01), Radcliffe
patent: 5039966 (1991-08-01), Schmid et al.
patent: 5208567 (1993-05-01), Bell et al.
patent: 5216388 (1993-06-01), Dipoala
patent: 5233319 (1993-08-01), Mizan et al.
patent: 5304968 (1994-04-01), Ohtonen et al.
patent: 5309129 (1994-05-01), Arnold et al.
patent: 5905419 (1999-05-01), Lukkarila
patent: 6057748 (2000-05-01), Hsing et al.
patent: 6172880 (2001-01-01), Petitpierre et al.
patent: 6362708 (2002-03-01), Woods
patent: 6407651 (2002-06-01), Wulff et al.
patent: 4029410 (1992-03-01), None
patent: 05259719 (1993-10-01), None
Harish Ayyangar R.
Howcroft Gerrard V.
Lye David J.
COM DEV Ltd.
Glenn Kimberly E
Ham Seungsook
Jones Day
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