ELECTROMAGNETIC PROTECTION DEVICE ABLE TO PROTECT A
MICROWAVE CONNECTION BETWEEN A CONNECTOR AND A
MICROWAVE ELEMENT
The present invention relates to the field of wideband microwave
circuits placed in a housing. The present invention relates more specifically to
an electromagnetic protection device able to protect a microwave connection
between a connector and a microwave element placed in a housing.
5 The present invention is used in wideband microwave circuit housings
ranging from a few megahertz to several tens of gigahertz.
In the microwave field, and more specifically with high frequencies,
such as frequencies on the gigahertz scale, unprotected electric connections
10 behave similarly to antennas and are able to receive different parasitic
elements present within the housing. These parasitic elements are then
transmitted to the circuits and disturb the correct operation of these
microwave circuits.
So as to standardize and protect a microwave connection between a
15 connector and a circuit element arranged on a dielectric substrate, it is known
to produce a cylinder, or bushing, by mass-production machining of the
housing around a microwave connector. A disadvantage of this device is the
rigidity thereof. As a result, the mechanical and electric contacts are
dependent on the application of a number of tightening sequences at
20 tightening torques above the standard and on the use of specialized tools. In
addition, a matching of the structure comprising the bushing(s) and the cover
thereof is necessary.
In addition, this hyperstatic assembly is not suitable for use in harsh
environmental conditions, such as for an airborne application.
25
One object of the invention in particular is to correct the
aforementioned disadvantages. This object is achieved by an
electromagnetic protection device able to protect a microwave connection
between a microwave connector placed on a housing and at least one
30 microwave circuit element contained in said housing, the device being
formed by a separate part made of a resilient electrically conductive material
and ensuring ground continuity between the electric ground of the microwave
circuit and the mechanical ground of the housing and of the cover.
In accordance with a particular feature of the invention, the device is
formed by a pipe made of an annealed copper alloy.
5 In accordance with a further particular feature, the device is made of
beryllium copper CuBe2.
A gold-plating treatment is advantageously performed on the outer
surface of the device.
In an embodiment, the characteristic impedance of the device is equal
10 to that of the connector and that of the microwave circuit element.
In accordance with a variant, the characteristic impedance of the
device is standardized to 50 ohms.
In another embodiment, the inner diameter of the device is equal to
1.73 millimeters, and the outer diameter thereof is 1.93 millimeters.
15 Another object of the invention is to propose a method for producing
the device according to the invention. This object is achieved by a method
comprising:
- a step of machining a through-hole in the wall of the housing to be
traversed, the section of the hole being substantially equal to the
20 section of the protection device,
- a step of passing the device through the wall of the housing,
- a step of fixing the connector on the wall of the housing,
- and a step of passing the connection into the electromagnetic
protection device.
25
The main advantages of the invention described above compared with
the systems used conventionally are:
- to simplify the current process by compensating for manufacturing
and assembly tolerance deviations of the mechanical parts (structure, cover)
30 and by making it less dependent notably on the tolerance ranges of the
printed circuit board, mechanical tolerance ranges and tolerance ranges of
the cover,
- to make it possible to obtain mechanical and electrical contact
facilitated by the resilient properties of the new device, thus significantly
simplifying the process of tightening the cover on the structure by means of a
standard tightening of screws, without use of special tools,
5 - to prevent successive dismantling operations of the microwave cover
during control and test phases from altering the electrical performance,
- to avoid the matching of the microwave cover with the structure,
- to reduce the cost price of the function.
10 Further features and advantages of the present invention will become
clearer upon reading the following description, which is given by way of nonlimiting
example with reference to the accompanying drawings, in which:
- figure 1 shows an exemplary embodiment of the protection device
15 prior to the invention.
- figure 2 shows an exemplary embodiment of the protection device
according to the invention.
With reference to figure 2, the protection device 20 according to the
20 invention is formed by a pipe made of a resilient conductive metal, such as a
copper alloy. So as to increase the resilience of the material, the copper alloy
is preferably annealed. In accordance with an embodiment, the pipe is
substantially cylindrical. In accordance with a specific embodiment, the
protection device 20 is made of beryllium copper.
25 The resilience of the material advantageously makes it possible to
compensate for the manufacturing and assembly tolerance deviations of the
different mechanical parts, such as the housing, the cover thereof and those
of the printed circuit board.
30 One purpose of this device 20 is to ensure electromagnetic protection
around the connection 21 between a microwave connector and the
microwave circuit. It also makes it possible to ensure, in combination with the
cover, transmission continuity with high immunity. This connection 21, for
example, may be the central core of the connector. It should be noted that
35 the device according to the invention is a separate part independent of the
microwave connector. The device can be likened to an armored bushing
within the housing. The insulation is ensured by connecting the device to
ground. This connection to ground is ensured by tightening the cover of the
housing against the protection device according to the invention as the
housing is closed. The resilience of the material used to produce the
separate resilient bushing advantageously makes it possible to reduce the
tightening forces of the fixing screws and to thus use standard tools. In
addition, the standard tightening of the screws makes it possible to avoid the
breakage thereof.
The connection to ground is also ensured between the device and at
any contact zone between the connector and the device according to the
invention. The continuity between the mechanical ground of the device and
the electric ground of the microwave circuit is ensured by tightening the cover
on the device 20. The protection device thus ensures a perfect continuity
between the different grounds, that is to say the mechanical ground of the
housing and of the cover, the electric ground 23 of the microwave circuit, and
that of the connector.
In accordance with a specific embodiment, a gold-plating treatment
can be applied on the outer surface of the device 20. The thickness of the
gold plating is approximately 2 micrometers, for example.
Another purpose of this device is to channel the microwave signal
between the connector and the element of the microwave circuit placed at
the other end of the device. One objective of the device is to produce a
coaxial connection between these two elements.
In some embodiments the core of the connector 21 is soldered on a
microwave circuit track 22. At the microwave connector, the signal is
transmitted in coaxial mode. At the track 22 of the microwave circuit, the
signal is transmitted in a microstrip mode. At the connection, there is thus a
changeover between two different transmission modes. So as not to disturb
the transmission of the signal and thus avoid the problems of stationary
waves, the different dimensions of the separate bushing 20 can be selected
such that the characteristic impedance of the device 20 is standardized. The
standardized impedance of the device also makes it possible to overcome
problems of impedance loss in the general case of connection between a
connector and a microwave circuit element.
In accordance with an embodiment that is in no way limiting, the
device 20 is formed as a hollow cylinder with a rim of which the outer
5 diameter measures 1.93 millimeters and the inner diameter measures 1.73
millimeters. These different sizes allow the device according to the invention
to have a characteristic impedance of 50 ohms. In some embodiments the
device 20 will measure 3 millimeters long.
The device 20 according to the invention can be produced by swaging
l o or by machining, for example by bar turning.
The device according to the invention forms a standardized microwave
connection device between a connector and a microwave element, such as a
printed circuit board, with high radio electric insulation.
15 One method of producing the device 20 may lie in placing the device
in position before placing the connector on the housing. In a first step, a
through-hole is machined in the wall of the housing to be traversed, the
section of the hole being substantially equal to the section of the protection
device. Said device is then slid through the wall of the housing, for example
20 from the outside of the housing to the inside, the inner face of the wall
corresponding to the face facing the microwave element, and the outer face
corresponding to the opposed face. The device 20 can be fitted to the wall in
a clamped or adhesively bonded manner, for example with the aid of
conductive adhesive. The connector is then fixed to the wall of the housing,
25 and the connection 21, such as the central core of the connector, is then
introduced into the device 20. Of course, the implementation of the invention
is not limited to this embodiment, and any equivalent embodiment may be
appropriate.
30 The mechanical qualities of resilience and reproducibility of the
electromagnetic protection device according to the invention may
advantageously allow a use in harsh environments, such as a military
airborne use, and civilian use.
CLAIMS
1. An electromagnetic protection device 20 able to protect a microwave
connection 21 between a microwave connector placed on a housing and at
least one element of a microwave circuit contained in said housing,
characterized in that the device is formed by a separate part made of a
5 resilient electrically conductive material and in that it ensures ground
continuity between the electric ground of the microwave circuit and the
mechanical ground of the housing and of the cover.
2. The device 20 as claimed in one of the preceding claims,
characterized in that it is formed by a pipe made of an annealed copper alloy.
l o 3. The device 20 as claimed in either of the preceding claims,
characterized in that it is made of beryllium copper CuBe2.
4. The device 20 as claimed in one of the preceding claims,
characterized in that a gold-plating treatment is performed on the outer
surface thereof.
15 5. The device 20 as claimed in one of the preceding claims,
characterized in that the characteristic impedance there is equal to that of the
connector and that of the element of the microwave circuit.
6. The device 20 as claimed in one of the preceding claims,
characterized in that the characteristic impedance thereof is standardized to
20 50 ohms.
7. The device as claimed in one of the preceding claims, characterized in
that the inner diameter thereof is equal to 1.73 millimeters and the outer
diameter thereof is 1.93 millimeters.
8. A method for producing a protection device 20 as claimed in one of
25 claims 1 to 7, characterized in that it comprises:
- a step of machining a through-hole in the wall of the housing to be
traversed, the section of said hole being substantially equal to that of
the protection device 20,
- a step of passing the device through the wall of the housing,
5 - a step of fixing the connector on the wall of the housing,
- and a step of passing the connection 21 into the electromagnetic
protection device.