Microwave switch with grooves for isolation of the passages

Details Microwave switch with grooves for isolation of the passages Microwave switch with grooves for isolation of the passages

1999-04-14

2001-04-17

Bettendorf, Justin P. (Department: 2817)

Wave transmission lines and networks

Plural channel systems

Having branched circuits

C333S108000

Reexamination Certificate

active

06218912

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to microwave switches.
Microwave switches are known, for example from Japanese patent application 58-141003A which was published on Aug. 22, 1983. The microwave switch disclosed in this reference has a circular cylindrical rotor having a ring-shaped outer surface provided with longitudinal and transverse slots or grooves. Due to their deep pass action, they deviate as as little high frequency energy as possible through a gap between the rotor and the housing.
A microwave switch is also disclosed in U.S. Pat. No. 4,806,887. As particularly shown in FIG.
8
and defined in claim
18
, it has grooves or so-called chokes which extend parallel to the axis of the rotor on the ring-shaped outer surface, and in particular each between two high frequency passages of the rotor. Finally, U.S. Pat. No. 4,761,622 discloses a microswitch with circumferential grooves provided on the ring-shaped outer surface of the rotor as shown in
FIGS. 8
,
13
,
14
. They serve for compensating the asymmetry of the rotor.
So-called R switches for microwaves are used in the satellite technology as redundant switches. As shown in the cross-section of FIG.
3
, they have a housing I and a rotor
2
. Four hollow conductor terminals (gates)
11
-
14
of the housing
1
are connected with one another in a different manner depending on the position of the rotor. In the rotor position shown in
FIG. 3
, the gate
11
is connected for example with the gate
14
, and the gate
12
is connected with the gate
13
. When the rotor
2
is turned by 45° in clockwise direction, the gate
11
is connected with the gate
13
. For this purpose, the rotor
2
has two passages, namely a straight passage
7
and two bent passages
8
,
9
.
Conventionally, a very high mutual isolation of the gates which are not connected with one another is required. When for example as shown in
FIG. 3
, the gate
11
is connected with the gate
14
and the gate
11
is supplied with the microwave signal, then a smallest possible signal portion must exit through the gate
12
and the gate
13
. In the case when the gate
11
is connected with the gate
13
, the gate
12
and the gate
14
must be isolated. Moreover, the gate
12
must be insulated from the gate
14
. The isolation is determined by the ratio P
ISO
/P
EIN
of the power P
ISO
occurring at the insulated gate to a power P
EIN
supplied into a gate. For redundance circuit networks in satellites, generally a value of −60dB is required. These very high requirements for the isolation can be provided only as special features:
by the longitudinal grooves
4
which are formed in the side wall of the straight passage in the rotor and which extended longitudinally parallel to the axis of the rotor;
by the longitudinal grooves
5
which are formed in the housing
1
;
by a very narrow gap
3
between the rotor and the housing.
With an operational frequency of 10 GHz (Ku-band), a gap of 50 &mgr;m is required for this. With higher operational frequencies, correspondingly narrower gaps are needed. With a doubling of the operational frequency to 20 GHz, the gap width must be halved to 25 &mgr;m to provide the same isolation as the isolation provided with 10 GHz. Narrower gaps are not possible for reliability reasons. Moreover, then the required accuracy can not be achieved with conventional production methods such as milling or turning.
Since the longitudinal grooves in the rotor shown in
FIG. 3
must have very narrow tolerances due to the very thin wall thickness and the housing grooves are provided by an expensive eroding method, the microwave switch of the prior art has a high production cost. Since the eroding generally is performed by special firms, the production time increases significantly.
SUMMARY OF THE INVENTION
Accordingly, it is an object of present invention to provide a microwave switch which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a microswitch with a housing and a rotor having passages with longitudinal directions extending transversely to an axis of the rotor as well as grooves in the ring-shaped outer surface of the rotor for improving the insulation between the passages, wherein in accordance with the inventive feature the grooves open into the passages.
When the microwave switch is designed in accordance with the present invention, it is possible without forming the longitudinal grooves in the side walls of the straight passages of the rotor (
4
in
FIG. 3
) and without the longitudinal grooves formed in the housing (
5
in FIG.
3
), to provide the same good or even improved electrical properties, in particular in an R switch. Moreover, in accordance with the present invention, it is possible to provide a substantially wider gap than used the rotor and the housing, or with the same gap width to provide a high operational frequency. By avoiding the previously existing longitudinal grooves in the housing, a substantial reduction of the production cost is obtained.
Since in the microwave switch in accordance with the present invention only short grooves must be milled in the lower and upper limiting plates of the passages of the rotor, these grooves allow greater tolerances.
The exact shape and position of the grooves in accordance with the present invention must be optimized for a corresponding application (waveguide band, operational frequency), for example by corresponding research.
The novel features which are considered as characteristic of the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.


REFERENCES:
patent: 3155923 (1964-11-01), Persson
patent: 4761622 (1988-08-01), Cracknell et al.
patent: 4806887 (1989-02-01), Au-Yeung
patent: 2250140 (1992-05-01), None
patent: 58-141003 (1983-08-01), None
patent: 53-70647 (1992-05-01), None

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