Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
1999-09-17
2001-07-03
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S219100
Reexamination Certificate
active
06255919
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a electromagnetic filter that uses coupling devices to transmit an electromagnetic wave from the filter input to the filter output through a plurality of resonator cavities.
A bandpass filter passes frequencies falling within a specified band of frequencies. A microwave resonator filter is a particular type of bandpass filter that is used in communications systems on Earth and in space. Such systems include cellular, PCS, and satellite systems. Microwave resonator filters are particularly useful in spaced-based applications where the mass, volume, and electrical performance of the filter are of critical importance.
A prior art microwave resonator filter
10
is shown schematically in
FIG. 1-3
. The filter
10
includes an enclosure structure
12
which defines first and second cavities
14
and
16
. The cavities
14
and
16
contain first and second resonators
18
and
20
, respectively.
An electromagnetic (“EM”) wave is received by the filter
10
through an input device
22
which is coupled to the first resonator
18
. The EM wave is transmitted to the second resonator
20
through a coupling member
24
, and is transmitted from the filter
10
by an output device
26
, which is coupled to the second resonator
20
. The structure of the cavities
14
,
16
, the resonators
18
,
20
, and the coupling member
24
affect the frequency response of the filter
10
, as is known in this art.
The enclosure
12
includes a peripheral outer wall
28
, an inner wall
30
, a base wall
32
and a removable closure wall
34
. The inner wall
30
is shorter than the outer wall
28
such that a gap
35
(
FIG. 2
) is defined between the inner wall
30
and the closure wall
34
. As shown in
FIG. 3
, the coupling member
24
is a wire surrounded by an insulating material
36
. A holding device
38
holds the coupling member
24
beneath the closure wall
34
in a position extending longitudinally between the two cavities
14
and
16
through the gap
35
. The positioning of the coupling member
24
affects the transmission of the electromagnetic wave between the resonators
18
and
20
in the cavities
14
and
16
. Therefore, the coupling element
24
must be positioned precisely relative to the resonators
18
and
20
.
SUMMARY OF THE INVENTION
In accordance with the present invention, a cavity filter apparatus includes an enclosure defining a plurality of cavities. A pair of resonators are located in a corresponding pair of the cavities. The apparatus further includes an elongated coupling structure operatively interposed between the pair of resonators. The elongated coupling structure is spaced from each of those resonators uniformly along its length.
In a preferred embodiment of the invention, the enclosure includes an outer wall structure surrounding the cavities and an inner wall structure separating the cavities. The coupling structure comprises a rigid electrically conductive bar, such as Aluminum or Invar, projecting longitudinally from the outer wall structure. The bar is located directly above an upper edge surface of the inner wail structure between the pair of cavities in which the resonators are located.
REFERENCES:
patent: 4692723 (1987-09-01), Fiedziuszko et al.
patent: 5220300 (1993-06-01), Snyder
patent: 5495216 (1996-02-01), Jachowski
patent: 5841330 (1998-11-01), Wenzel et al.
patent: 5936490 (1999-08-01), Hershtig
patent: 6111483 (2000-08-01), Haapakoski
patent: 8700350 (1987-01-01), None
patent: 9629754 (1996-09-01), None
patent: 9731402 (1997-08-01), None
COM DEV Limited
Jones Stephen E.
Jones Day Reavis & Pogue
Pascal Robert
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