EP1460710B1 - Microwave element used for dissipation or attenuation of energy - Google Patents

Description

The present invention relates to a microwave device for the dissipation or attenuation of power.

The present invention relates in particular to a resistive load device of medium to high power, that is to say of the order of a few watts to 200 Watts, in particular for use in base stations of cellular radio or local networks wireless type WLAN.

Such a device, used in a microwave system, serves in particular to dissipate, in the event of a malfunction, in the form of heat, the non-active energy of the system, in particular the energy transported in a microwave line.

Such a microwave line may be constituted by a dielectric substrate, one side carries a conductive strip and the other side a metal ground area, the conductive strip being connected to a resistive layer deposited on the substrate.

This embodiment is generally referred to as "microstrip".

The impedance of such a microwave line is generally 50 Ohms.

The resistive load device may be housed in a housing connected to the system by a cable, which allows the device to be in contact with a cooling radiator. This device is commonly called remote load.

Alternatively, the device can be attached directly to a system equipment, for example on a circuit thereof.

The patent EP 0 092 137 discloses a resistive load device having an insulating substrate on which adjacent resistive layers in the form of circular sectors are deposited. The outer arc of a resistive layer constitutes the input of the device and the inner arc the output. This device aims to allow a uniform and greater dissipation of the caloric power.

The patent application FR 2,486,720 describes a device for terminating a microwave transmission line, comprising a dielectric substrate with, on one side, a resistive layer constituting a termination charge. The resistive layer may have a trapezoid shape whose large base constitutes the input for the microwave line and whose small base is connected to a mass metallization. A conductive, transverse strip may be deposited on the resistive layer, in contact with the conductive strip and connecting two metallizations for forming with a ground plane two capacitors.

The patent US 6,326,862 discloses an electrical termination system having a housing in which is disposed a dielectric substrate carrying a termination circuit element. The housing has a relatively high first cavity, above the junction of the inner conductor of the coaxial cable on the dielectric substrate. This first cavity opens into a second cavity of lower height. This double cavity aims to correct the impedance defects.

The patent US 4,267,531 discloses a device comprising a resistive film sandwiched between two dielectrics, on which sheets are arranged.

The patent US 4,965,538 discloses an attenuator with a resistive region of rectangular shape to which two electrodes are connected.

The present invention aims in particular to provide a new microwave device, including a resistive charging device, type "microstrip", to substantially reduce impedance defects, and this for a wide frequency range.

The invention thus relates to a microwave device, in particular a resistive load device or an attenuator, intended for power dissipation or attenuation, as defined in claims 1 or 13.

The first region may have a dimension transverse to the axis of the resistive layer, lower than that of the second region.

Thanks to the invention, since the first region is narrower than the second region, the capacitive fault at the input of the resistive layer is reduced.

Preferably, the or each first region of the resistive layer has a shape converging towards the conductive strip, this first region may for example be substantially trapezoidal, the conductive strip or strips connecting to the resistive layer by the small base of the trapezoid.

For the production of a resistive load, the entire resistive layer may have a substantially trapezoidal shape, in which case the ground area is connected to this layer by the large base of the trapezium.

In a variant, the second region is substantially rectangular and the mass zone is connected to this region by one side of the rectangle.

For producing an attenuator comprising two conductive strips, the resistive layer comprises two first regions each connected to a conductive strip and to a second rectangular central region connected to the ground zone.

As a variant or in combination with the abovementioned forms of the resistive layer, the invention makes it possible to reduce the impedance defects by covering the resistive layer, at least partially, by a ground plane connected to the mass zone and isolated from the ground. resistive layer by an insulating layer.

Thanks to the invention, by combining the aforementioned forms of the resistive layer and the presence of the ground plane above the resistive layer, a reduction of the capacitance and induction defects is obtained, thus a better microwave adaptation, for frequencies up to about 8 GHz.

In addition, the device according to the invention may have a relatively low cost.

Preferably, the ground plane does not completely cover the input region, being set back from the junction between the or a conductive strip and the resistive layer or layers.

The ground plane can completely cover the second region of the resistive layer or layers.

Advantageously, the ground plane extends transversely over the entire width of the resistive layer or layers.

In the case where the mass zone is formed directly on the substrate, being adjacent to the second region, the above ground plane advantageously comes into electrical contact with the ground zone, at the rear of the resistive layer.

Advantageously, the abovementioned ground plane connects to lateral zones of mass extending on slices of the substrate, in particular those which are parallel to the axis of the resistive layer.

These lateral zones of mass may consist of metallizations carried out on these slices.

The insulating layer may be a layer of glass deposited for example by screen printing on the resistive layer.

The mass zone on the substrate may be connected to a mass range on the other side of the substrate, in particular by one or more metallizations on a wafer of the substrate or, alternatively, by metallized bores made in the thickness of the substrate.

In a variant, the device comprises an insert comprising a conductive wall that is applied to the insulating layer and defines the ground plane.

In an exemplary implementation of the invention, the insert comprises at least one lateral conductive arm connected to the ground plane and adapted to be applied on a wafer of the substrate and optionally, if necessary, on one side. aforementioned lateral conductive tracks.

When the device is a remote load, the insert may comprise at least one elastically deformable and conductive tab adapted to be applied on a wall of the housing, thereby providing the electrical connection between the ground plane of the device and the wall of the housing .

The insert may also be arranged to retain the substrate on the bottom of the housing. In other words, it is not necessary to perform a metallurgical bond, for example brazing, the substrate on the bottom of the housing, its maintenance in the housing being of a mechanical nature. The substrate can then be devoid of metallization on its face opposite to that carrying the resistive layer, the ground plane being connected to the body of the housing.

In particular in the case where the device is directly attached to a system equipment, the insert may for example comprise at least one fixing portion for fixing it, in particular by brazing on a support.

The invention may comprise at least one elastically deformable and conductive tab adapted to be applied on a wall of a housing.

The insert may comprise at least one fixing part for fixing it, in particular by brazing, to a support.

Advantageously, the first region has a dimension transverse to the longitudinal axis of the resistive layer, lower than that of the second region.

The device may comprise two conductive strips and the resistive layer comprise two first trapezoidal regions each connected to a conductive strip and a second central rectangular region connected to the ground area.

• la figure 1 représente, schématiquement et partiellement, en vue de dessus, un dispositif formant charge résistive,
• les figures 2 et 3 représentent, schématiquement et partiellement, respectivement en perspective et en vue de dessus, une mise en oeuvre de dispositif formant charge résistive selon l'invention,
• la figure 4 représente, schématiquement et partiellement, en vue éclatée, un dispositif formant charge résistive conforme à l'invention, logé dans un boîtier,
• la figure 5 représente, schématiquement et partiellement, en perspective, un dispositif formant charge résistive conforme à une variante de mise en oeuvre de l'invention, et
• la figure 6 représente, schématiquement et partiellement, en perspective, un mode de réalisation d'atténuateur selon l'invention.

The invention will be better understood on reading the detailed description which follows, non-limiting examples of implementation, and on examining the appended drawing, in which:

• the figure 1 represents, schematically and partially, in plan view, a resistive load device,
• the Figures 2 and 3 represent, schematically and partially, respectively in perspective and in view from above, an implementation of a resistive load device according to the invention,
• the figure 4 represents schematically and partially, in exploded view, a resistive charging device according to the invention, housed in a housing,
• the figure 5 represents, schematically and partially, in perspective, a resistive charging device according to an alternative embodiment of the invention, and
• the figure 6 represents, schematically and partially, in perspective, an attenuator embodiment according to the invention.

We have shown on the figure 1 a device 1 forming a microwave resistive load intended for power dissipation, comprising a resistive layer 2 deposited on a face 4 of an insulating substrate 3, the resistive layer 2 being connected, on the one hand, to a conductive strip 5 and, on the other hand, to a mass zone 6 also deposited on the face 4 of the insulating substrate 3.

The device 1 is intended to be used in a microwave system.

The substrate 3 may be made of ceramic, in particular alumina or aluminum nitride (A1N).

The substrate 3 forms with the conductive strip 5 and a mass range 8 located on a face 7 opposite the face 4 a microwave line.

The mass range 8 can be brewed on a support, not shown.

The ground area 6 can be connected to the ground area 8 by one or more metallizations made on a wafer 3a of the substrate 3 or by metallized bores made in the thickness of the substrate 3.

The resistive layer 2 may be deposited on the substrate 3 by screen printing or in a thin layer, for example.

In the example considered, the resistive layer 2 comprises an input region 2a having a substantially isosceles trapezoidal shape, the conductive strip 5 being connected to this region 2a by the small base 10 of the trapezium.

The region 2a extends, on the opposite side to the small base 10, by a rectangular region 2b whose long side coincides with the large base of the trapezium.

The mass zone 6 is connected to the resistive layer 2 along a long side 11 of the rectangle.

The resistive layer 2 has a longitudinal axis X which is, in this example, parallel to the conductive strip 5.

This particular form of the resistive layer 2 notably makes it possible to reduce the capacitive defects at the input of the resistive layer.

To further improve the microwave adaptation of the device 1, it is possible, as illustrated in FIGS. Figures 2 and 3 to extend the mass zone 4 by a ground plane 12 partially covering the resistive layer 2.

For this purpose, the resistive layer 2 is entirely covered with an insulating layer 13, which is constituted for example by a layer of glass deposited by screen printing.

The ground plane 12 has a rectangular shape of length substantially equal to the width of the substrate.

The ground plane 12 covers the ground area 6 and is set back from the small base 10 of the trapezium.

In other words, the ground plane 12 completely covers the region 2b of the resistive layer 2 and leaves clear the junction portion between the conductive strip 5 and the resistive layer 2.

In the example considered, the ground plane 12 is made from a conductive paste deposited on the insulating layer 13.

As can be seen on the Figures 2 and 3 , the ground area 6 can be connected to two lateral conductive tracks 14, 15, parallel to the axis X.

The ground plane 12 comes to cover these tracks 14, 15, being in contact with them.

The presence of these tracks 14, 15 connected to the ground plane 12 makes it possible to further improve the microwave adaptation.

The slices 3a of the substrate 3 parallel to the X axis may be metallized and be electrically connected to the ground plane 12.

We have shown on the figure 4 a device 1 'forming a remote resistive load according to an alternative embodiment of the invention.

The device 1 'is housed in a housing 20, which may be remote from the microwave system to be brought into contact with a cooling radiator in particular.

The device 1 'differs from the device 1 previously described in that the ground plane does not consist of a layer of a conductive material deposited on the substrate, but is defined by a central wall 23 of a metal insert 22 being applied to the substrate 3.

The conductive strip 5 is intended to be connected to the central conductor of a coaxial cable 21 mounted at one end on the housing 20.

The insert 22 comprises on either side of the central wall 23 two lateral arms 24 intended to be applied on two parallel edges of the substrate 3 and on the conductive tracks 14, 15. These arms 24 each comprise a portion 24a vertical application on a wafer of the substrate 3.

The insert 22 has on its upper face an elastically deformable and conductive tab 25 adapted to be applied on a conductive cover 26 of the housing 20. According to the invention, it is possible to provide a plurality of conductive tabs 25.

In the example considered, the resistive layer 2 is obtained by depositing a conductive paste on the substrate 3.

The insert 22, in the example considered, keeps the substrate 3 on the bottom of the housing 20, the maintenance being of a mechanical nature.

The lug or tabs 25 also make it possible to make an electrical contact between the ground zone 6 and the housing 20.

In the case where the resistive load device is attached directly to a system equipment, without being housed in a specific housing, the insert 22 'may be free of an elastically deformable tab 25 and its lateral arms 24' may have extensions 31 allowing brazing the insert 22 on a support 30.

This support 30 may be constituted by a circuit or a metal flange fixed on the equipment of the system, for example.

Of course, the invention is not limited to the implementation examples which have just been described.

It is also possible to provide, directly on the face of the insert coming opposite the resistive layer 2, an insulating layer which replaces an insulating layer 13 deposited on the substrate.

The microwave device according to the invention can be further arranged as an attenuator. An embodiment of an attenuator device is illustrated in FIG. figure 6 .

The resistive layer 2 'has a symmetrical configuration comprising two trapezoidal regions 2'a connected by their large bases to the long sides of a rectangular central region 2'b whose short sides are connected to the ground. The trapezoidal regions 2'b are connected by their small bases to conductive strips 5.

As for the previous embodiments, there is provided a ground plane, not shown, not entirely covering the resistive layer 2 '.

Claims (16)

1. A microwave device (1; 1') for at least one of dissipating and attenuating power, the device comprising:

   - an insulating substrate (3);

   - at least one conductive strip (5) of a microwave transmission line on a face (4) of the substrate (3);

   - at least one ground zone (6); and

   - at least one resistive layer (2; 2') placed on said face (4) of the substrate, the resistive layer (2; 2') having at least a first region (2a; 2'a) to which said conductive strip (5) is connected and a second region (2b; 2'b) connected to the ground zone (6), the resistive layer (2) presenting a longitudinal axis (X);

   in which device:

   - the resistive layer (2; 2') is covered at least in part by a ground plane (12) connected to the ground zone (6) and insulated from the resistive layer (2; 2') by an insulating layer (13);

   - the ground plane (12) comprises a conductive material silkscreen printed on the insulating layer (13),

   characterized in that the substrate (3) carries two lateral conductive tracks (14, 15), on either side of the resistive layer (2; 2'), and connected to said ground zone (6), the ground plane (12) covering said tracks (14, 15).
2. A device according to claim 1, characterized by the fact that the first region (2a; 2'a) of the resistive layer (2; 2') presents a shape that converges towards the conductive strip (5).
3. A device according to claim 2, characterized by the fact that the or each first region (2a; 2'a) presents a substantially trapezoidal shape, the conductive strip(s) (5) being connected to the resistive layer via the minor base (10) of the trapezoid.
4. A device according to claim 3, forming a resistive load, characterized by the fact that the entire resistive layer (2) is substantially trapezoidal in shape, the ground zone (6) being connected to said resistive layer (2) via the major base of the trapezoid.
5. A device according to anyone claims 1 to 3, forming a resistive load, characterized by the fact that the second region (2b) is substantially rectangular, and the ground zone (6) connects to said region via one side of the rectangle.
6. A device according to any one claims 1 to 3, forming an attenuator, characterized by the fact that the device comprises two conductive strips (5) and wherein the resistive layer (2') comprises two trapezoidal first regions (2'a) each connected to a conductive strip (5), and a central rectangular second region (2'b) connected to the ground zone (6).
7. A device according to any one preceding claims, characterized by the fact that the ground plane (12) does not completely cover the first region (2a;, 2'a), being set back from the junction between the conductive strip (5) and the resistive layer (2; 2').
8. A device according to any one preceding claims, characterized by the fact that the ground plane (12) covers the second region (2b; 2'b) completely.
9. A device according to any one preceding claims, characterized by the fact that the ground plane (12) extends transversely over the entire width of the resistive layer (2; 2').
10. A device according to any one preceding claims, the ground zone (6) is formed on the substrate, being adjacent to the second region (2b; 2'b), characterized by the fact that the ground plane (12) comes into electrical contact with said ground zone behind the resistive layer.
11. A device according to any one preceding claims, characterized by the fact that the ground plane (12) is connected to lateral ground zones extending along the edge faces of the substrate (3).
12. A device according to any one preceding claims, characterized by the fact that the first region (2a; 2'a) presents a dimension extending transversely to the longitudinal axis (X) of the resistive layer, that is less than that of the second region (2b; 2'b).
13. A microwave device (1; 1') for at least one of dissipating and attenuating power, notably a device forming a resistive load or an attenuator, comprising:

    - an insulating substrate (3),

    - at least one conductive strip (5) of a microwave transmission line on one face (4) of the substrate (3),

    - at least one ground zone (6),

    - at least one resistive layer (2; 2') deposited on the above-specified face (4) of the substrate, the resistive layer (2; 2') including at least a first region (2a; 2'a) to which said conductive strip (5) is connected, and a second region (2b; 2'b) connected to the ground zone (6), the resistive layer (2) presenting a longitudinal axis (X),

    in which device:

    - the resistive layer (2; 2') is covered at least in part by a ground plane (12) connected to the ground zone (6) and insulated from the resistive layer (2; 2') by an insulating layer (13);

    characterized bu the fact that the device includes an insert (22) comprising a conductive wall (23) pressed against the insulating layer (13) and defining the ground plane (12), and two lateral arms (24) on either side of the central wall (23), and by the fact that the insert (22) is arranged to hold the substrate (3) on the bottom of a package (20) in which the device is housed
    and by the fact that, the substrate (3) carries two lateral conductive tracks (14, 15) connected to said ground zone (6), the ground plane (12) covering said tracks (14, 15), the two lateral arms of the insert being intended for pressing against the conductive tracks (14, 15).
14. A device according to claim 13, characterized by the fact that the insert includes at least one conductive and elastically deformable tab (25) suitable for pressing against a wall of a package (20).
15. A device according to claim 13 or claim 14, characterized by the fact that the insert includes at least one fastener portion (31) enabling it to be fastened, notably soldered, on a support (30).
16. A device according to any one claims 13 to 15, characterized by the fact that the first region (2a; 2'a) presents a dimension extending transversely to the longitudinal axis (X) of the resistive layer that is less than that of the second region (2b; 2'b).

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