Power amplifier device with reduced bulk

An amplification device with reduced bulk including at least one plate parallel to a plane XY and at least two amplifier modules mounted on the plate, each amplifier module including an amplifier element, an input connection waveguide, and an output connection waveguide oriented in one and the same direction X corresponding to a direction of longitudinal propagation, the amplifier element having an input and output axis oriented in a direction Y perpendicular to the direction of propagation X, wherein the input connection waveguides of the amplifier modules are distinct, have different lengths and are mounted in parallel to one another, the output connection waveguides of the amplifier modules are distinct, have different lengths and are mounted in parallel to one another, and the sum of the lengths of the input and output guides of one and the same amplifier module is identical for each amplifier module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International patent application PCT/EP2010/055300, filed on Apr. 21, 2010, which claims priority to foreign French patent application No. FR 09 02006, filed on Apr. 24, 2009, the disclosures of each of which are incorporated by reference in their entireties.

FIELD OF THE DISCLOSE SUBJECT MATTER

The present invention relates to a power amplification device having reduced bulk. It applies to the field of microwave semiconductor-based amplifiers and more particularly to power combining systems and notably to active antennas.

BACKGROUND

Decreases in the output power of semi-conductor elements together with increases in the operating frequency of amplification devices are leading to the need to combine several elementary semi-conductor amplifiers so as to achieve the output powers required by certain applications in the microwave field. In particular, for an active Ku-band antenna and to obtain a sufficient power level, it is often necessary to combine several amplifier modules in an antenna grid cell whose dimensions are of the order of a few centimeters.

Contemporary power combining systems based on corporate or radial architectures using lines or waveguides do not make it possible to efficiently combine elementary amplifiers in a confined environment with a rectangular-waveguide output interface able to cooperate with the downstream devices.

In a corporate structure combining several amplifiers, the amplifiers are disposed in parallel to one another and aligned along one and the same axis. The input and output waveguides of the amplifiers, the divider and the combiner are also aligned along this same axis. In the Ku-band and in rectangular guide technology, the width of such an amplification device is mainly constrained by the considerable size of the rectangular guides of the combiner. Thus, by taking into account only the value of the interior dimension according to a cross-section of a standardized Ku-band rectangular guide, equal to 1.9 cm, the width of an amplification device comprising for example eight amplifiers is at the minimum eight times as large, i.e. greater than 15 cm. This width being much greater than the dimensional constraints of an application relating to an active Ku-band antenna, this technique is therefore not suited to this type of application. For applications to higher frequencies, the size of the rectangular guides decreases and the width of the amplification device is no longer imposed by the combiner but by the width of the elementary amplifiers, decoupling capacitors and polarizing ports of these amplifiers. This width is therefore also too considerable with respect to the grid cell of an active antenna.

The spatial combining technique such as developed in U.S. Pat. No. 5,736,908 comprises several amplifier modules disposed on plates, overlaid in a rectangular waveguide. The input signal generated by a single source is apportioned among the amplifier modules by virtue of the spatial distribution of the energy of the signal and is recombined at the output once it has been amplified in accordance with the same principle. This solution makes it possible to perform in a single step on the one hand the combining of the signals and on the other hand the transitions between the planar-technology lines and the rectangular-waveguide output interface. By virtue of these characteristics, it makes it possible to minimize the combining losses and the bulkiness of the structure. However, this combining technique, such as described in the prior art, exhibits drawbacks and limitations.

Indeed, the number of plates stacked in a rectangular waveguide and the number of associated amplifiers on one and the same plate decrease with the reduction in the size of the rectangular waveguides which is imposed by the increase in operating frequency.

For applications to high frequencies such as for example in the Ka-band, the standardized size of the rectangular guides is much smaller than the size of the amplifier modules, thereby making it necessary to have long transmission lines for linking the amplifier modules to the transitions of the spatial divider excited by a single source and to the transitions of the spatial combiner. These transmission lines are very penalizing in terms of losses and the dividing and combining efficiency is degraded. A structure with four plates would be the best adapted in terms of compactness for combining eight elementary amplifiers in the case of an active Ku-band antenna. However, in this configuration, this type of architecture exhibits unfavorable thermal management in respect of the plates located at the center of the structure and a lack of isolation between the combined amplifiers possibly giving rise in certain cases to an instability of the amplification device.

Document WO 2006096771 describes another spatial combining technique in which the axes of the amplifiers are disposed along a direction perpendicular to the input and output waveguides, but for applications to high frequencies, in the Ka-band for example, the long input transmission lines are penalizing in terms of division losses.

SUMMARY

The aim of the invention is to produce an amplification device with reduced bulk not comprising the drawbacks of the existing devices and making it possible to combine notably a large number of amplifiers in the grid cell of an active Ku-band antenna of dimensions of the order of a few centimeters with a high combining efficiency and little division loss.

Accordingly, the invention relates to an amplification device with reduced bulk comprising at least one plate parallel to a plane XY and at least two amplifier modules mounted on the plate, each amplifier module comprising an amplifier element, an input connection waveguide and an output connection waveguide oriented in one and the same direction X corresponding to a direction of longitudinal propagation, the amplifier element having an input and output axis oriented in a direction Y perpendicular to the direction of propagation X, characterized in that the input connection guides of the two amplifier modules are distinct, have different lengths and are mounted in parallel to one another, the output connection guides of the two amplifier modules are distinct, have different lengths and are mounted in parallel to one another, and in that the sum of the lengths of the input and output guides of one and the same amplifier module is identical for each amplifier module, the amplifier modules being mounted in parallel in at least one row, the input waveguides of the amplifier elements of the row being preceded by a power divider and the output waveguides of the amplifier elements of the row being linked to an output power combiner, so that the signals transmitted by the output connection waveguides (13a,13b) to the power combiner (16) are in phase.

Advantageously, the input waveguides, respectively the output waveguides, of the amplifier elements of the row adjoin one another and the amplifier elements of the row are offset with respect to one another in the two perpendicular directions X and Y.

Advantageously, the input divider and/or the output combiner can comprise a resistive septum which extends walls separating the connection waveguides.

Advantageously, the amplification device furthermore comprises an input transition disposed between each input connection guide and the corresponding amplifier element and an output transition disposed between each output connection guide and the corresponding amplifier element.

According to one embodiment, the amplification device comprises two distinct amplification rows, each amplification row comprising the same number of amplifier modules, the amplifier modules of the first row being mounted symmetrically with respect to the amplifier modules of the second row on either side of an axis of symmetry parallel to the direction of propagation.

Advantageously, each amplifier module of the first row comprises an amplifier element having an input and output axis oriented along the direction Y and aligned respectively with an input and output axis of an amplifier element of an amplifier module of the second row.

Advantageously, the output connection waveguides of the amplifier elements of all the amplifier modules of the two rows are distinct, adjoining one another and linked to an output power combiner, common to all the output connection waveguides.

Advantageously, the amplification device furthermore comprises a first input power divider having two outputs linked respectively to the two amplification rows across two transitions and each amplification row comprises a second power divider having outputs linked respectively to each input connection waveguide of the corresponding amplifier modules. The first input power divider can comprise an input of microstrip type.

According to one embodiment, the amplification device comprises at least two amplifier modules overlaid one above the other, the two amplifier modules being disposed on at least two distinct plates overlaid one above the other and comprising one and the same number of amplifier modules and the two overlaid amplifier modules have an input guide and an output guide in common.

Advantageously, the transition elements are chosen from among fin lines, or plungers comprising a metallization line placed on a substrate, or mechanical plungers using a glass bead.

Preferably, the input and output connection waveguides are metallic waveguides with rectangular cross-section. Furthermore, the power divider and the power combiner can also be metallic waveguides with rectangular cross-section.

Preferably, each input connection waveguide is equipped with a phase adjustment element.

Advantageously, the amplification device comprises an opto-electronic feed device connected at the input of the amplification device by way of an optical fiber and of a transition.

DETAILED DESCRIPTION

The amplifier module represented inFIG. 1comprises an amplifier element11, an input connection waveguide12, an output connection waveguide13, an input transition14ensuring the transition between the input guide and the amplifier module, an output transition15ensuring the transition between the output guide and the amplifier module. The input and output waveguides12,13are oriented in one and the same direction X corresponding to a longitudinal direction of propagation and have a cross-section which may for example be rectangular. The amplifier element11has an input and output axis18oriented in a direction Y perpendicular to the direction of longitudinal propagation. The input transition14and output transition15are perpendicular to the direction of longitudinal propagation X and ensure the electrical matching between the amplifier element11and the rectangular input waveguide12and output waveguide13.

FIG. 2represents a diagram of a first exemplary amplification device according to the invention, comprising two amplifier modules constituting two amplifying pathways. The two amplifier modules41a,41bare mounted in parallel on one and the same plate XY and in one and the same row41in such a way that the two input waveguides12a,12b, respectively the two output waveguides13a,13b, of the two amplifier elements11a,11bare adjoining one another and that the two amplifier elements11a,11b, are not aligned on one and the same axis but offset with respect to one another in the two perpendicular directions X and Y. The amplifier elements11a,11bhave distinct input waveguides and distinct output waveguides to which they are respectively connected by way of the input transitions14a,14band output transitions15a,15b, and respectively an input and output axis18a,18boriented along a direction Y perpendicular to the direction of propagation X. The two input waveguides12a,12b, respectively the two output waveguides13a,13b, of the two amplifier elements11a,11bhave different lengths La1, La2, respectively Lb1, Lb2, along the longitudinal propagation axis X but the sum of the lengths of the input and output waveguides of one and the same amplifier module is identical for all the amplifier modules:
La1+La2=Lb1+Lb2

The two input waveguides12a,12bof the two amplifier elements11a,11bare preceded by a power divider16making it possible to divide a microwave input signal, for example in the 10.5 GHz and 14 GHz band, into two components propagating in the two input connection waveguides12a,12band the two output waveguides13a,13bof the two amplifier elements11a,11bare linked to a power combiner17making it possible to recombine the output microwave signals amplified by each amplifier element. Each amplifier element comprises a polarization circuit with decoupling capacitors10as represented for example inFIG. 3cshowing four amplifier modules combined in one and the same row and constituting four amplifying pathways.

The power divider16is embodied using metal waveguide technology and consists of an input and of two outputs in rectangular guide form. The divider may be of “septum divider” type. In this type of divider, the two output guides are generally separated at the location of the division by a thin wall constituting the “septum” (Latin term) which may be metallic or resistive. The power combiner17is also embodied using metal waveguide technology and consists of two inputs and of an output in rectangular guide form and may be of “septum combiner” type. The divider16and the combiner17of “septum divider” and “septum combiner” types make it possible to divide and combine the microwave signals within a reduced bulk with low losses. The sum of the lengths of the input waveguides12a,12band output waveguides13a,13bbeing identical for the two amplifier modules41a,41b, the signals at the input of the combiner are in phase and the recombining of the signals amplified by the two amplifying pathways is carried out in phase without the addition of a phase shifter. The number of amplifier modules combined in this way is not limited to two.

As represented in the various diagrams and sectional planes ofFIGS. 3ato3eshowing four amplifier modules combined in one and the same row and constituting four amplifying pathways, it is possible to combine a large number of amplifier modules comprising amplifier elements offset with respect to one another in the two perpendicular directions X and Y, the input waveguides, respectively output waveguides of the various amplifier elements adjoining one another and having different input and output lengths and such that the sum of the lengths of the input and output waveguides of one and the same amplifier module is identical for all the amplifier modules. Thus, on each amplification pathway, the electrical path corresponding to the input guide is different from the electrical path corresponding to the output guide but for all the pathways, the sum of the electrical paths corresponding to the input and output guides of one and the same pathway is identical, thereby making it possible, at output, to have an identical phase for all the signals and to recombine all the microwave signals in phase without the addition of a phase shifter.

The embodiment represented inFIG. 3bshows an amplification device comprising an input divider16and an output combiner17with two stages. In this embodiment, the input signal is divided in two steps. In a first step the signal is apportioned between two intermediate rectangular waveguides31,32, and then in a second step, each of the signals propagating in the two intermediate rectangular waveguides31,32are again divided into two and apportioned among the four input connection waveguides12of the four amplifier elements11. At the level of the output combiner17, the four signals amplified by the four amplification pathways are combined pairwise in phase in two steps. In a first step, the four output signals propagating in the four output connection guides13of the amplifiers11are recombined in phase in two intermediate rectangular output waveguides33,34, and then in a second step, each of the signals propagating in the two intermediate rectangular waveguides33,34are again combined in phase in the output waveguide of the combiner17.

According to a first variant embodiment of the invention, the amplifier modules ofFIG. 3amay be grouped together in pairs, the modules of each pair being disposed on two distinct and overlaid plates21,22as shown by the transverse sectional views on the sectional plane I-I and the sectional plane J-J ofFIGS. 4aand4b. In this case, each pair comprises two overlaid amplifier modules23,24which have an input connection waveguide and an output connection waveguide in common. One and the same input connection waveguide therefore excites two elementary amplifiers by way of two input transitions. At output, the two elementary amplifiers are respectively connected to the same output connection guide by way of two output transitions. Placing the two plates opposite one another makes it possible to remove the heat flux to the exterior. In the same manner, a greater number of amplifier modules than two can be grouped together, the modules grouped together being disposed on distinct plates overlaid one above another.

A third example represented schematically inFIG. 5ashows an amplification device comprising four amplifier modules combined on one and the same plate, according to a second variant embodiment of the invention.

The four amplifier modules are combined pairwise on two distinct amplification rows41,42parallel to the propagation axis, each amplification row comprising the same number of amplifying pathways, for example two pathways as inFIG. 5a, each amplifying pathway comprising an amplifier module. The amplification device comprises a first input power divider40, of planar type, whose access port is realized by an input of microstrip type which makes it possible to divide an input microwave signal1into two components so as to illuminate two rectangular input waveguides linked respectively to one of the two amplification rows, across two transitions43,44. Alternatively, the power divider40could be a divider septum. In each amplification row41,42, the two amplifying pathways are preceded by a second power divider16a,16bcomprising two outputs linked respectively to each input connection waveguide12of the corresponding amplifier modules41a,41b,42a,42b. The second power divider16a,16b, for example of divider septum type, makes it possible for the component of the microwave signal arising from one of the transitions43,44to be divided a second time into two new components propagating respectively in the two input connection waveguides12of the two corresponding amplifying pathways. The two amplifier modules41a,41bof the two amplifying pathways of the first row41are mounted symmetrically with respect to the two amplifier modules42a,42bof the second row42, on either side of an axis of symmetry45parallel to the direction of propagation X. Each amplifier module41a,41bof the first row41comprises an amplifier element11a,11bhaving an input and output axis18a,18boriented along the direction Y and aligned respectively with an input and output axis20a,20bof an amplifier element19a,19bof an amplifier module42a,42bof the second row42. The output connection waveguides13of all the amplifier elements of the two rows are separated and adjoining one another, allowing the recombining in phase of all the signals at the output of the output power combiner17common to all the output waveguides of the two rows41,42.

The signals propagate in the rectangular connection waveguides12from the output transitions43,44of the input divider40and after division across the second divider16a,16bof each row41,42toward input transition elements14of the amplifier modules41a,41b,42a,42b. After amplification, the signals propagate in the output connection waveguides up to the power combiner17where they are recombined in phase.

The number of amplifier modules in each row is not limited to two. As represented inFIG. 5bwhich shows a combination of four amplifier modules41i,42iper row41,42, it is possible to combine a large number of amplifier modules in each row.

In the embodiment represented inFIG. 6, the amplification device comprises portions of matching guides55placed in the input and output connection waveguides just upstream and downstream of each amplifier element. Furthermore, the input divider16and the combiner17each comprise a resistive septum extending, at input and at output, the metallic walls48separating the rectangular connection waveguides. As represented for example inFIG. 7a, each septum comprises at least one wall51furnished with a resistive surface the function of which is to ensure the insulation between the amplifier modules so as to improve the electrical stability of the amplification device and to simplify the adjustment of its phase since it makes it possible to adjust each amplifier module separately from the other modules. The resistive surface can consist of a resistive film placed in a plane of symmetry between two identical substrates46,47, for example of ceramic such as alumina or aluminum nitride. As represented inFIG. 7b, in the one-stage septum, the resistive surfaces of the walls51are all mounted at one and the same distance from the input50of the combiner or the divider.

Alternatively, for an amplification device comprising more than two amplifier modules in one and the same row, like the example represented inFIG. 3b, it is possible to use a septum comprising several stages, for example two stages as shown by the combiner ofFIG. 7c, comprising first walls52furnished with resistive films disposed at a predetermined distance from the input50of the combiner, and other walls53furnished with resistive films disposed in an offset manner and set back with respect to the resistive films of the first walls52. A divider comprising a septum has a similar configuration by inverting the input and the output with respect to the combiner. The two-stage septum of the divider16carries out a division of the input signal in two successive steps making it possible to obtain four components of the signal, each component being directed in one of the four input connection guides of four amplification modules: a first division of the signal into two components is carried out by virtue of a first wall52of the first septum stage, followed by a second division of each of the components into two other components by virtue of two other walls53of the second septum stage. In the output guides13, the combiner17also comprises a two-stage septum making it possible to recombine the signals in two successive steps by virtue of the walls53,52of the septum. The number of walls of the septum of the divider and of the combiner is not limited to three as represented in the exemplary embodiments but may be adapted as a function of the number of signal components desired for the various amplifying pathways of the amplification device.

The adjustment of the phase may be carried out by phase adjustment elements54mounted in each of the input connection guides12so as to control the relative phase between the signals propagating in the connection waveguides12in such a way as to ensure a recombining in phase of these signals in the output waveguide once they have been amplified by the amplifier modules. This functionality makes it possible to minimize the combining losses by eliminating the losses induced by a phase imbalance of combined signals due to manufacturing tolerances. The phase adjustment elements54may be embodied for example as dielectric elements of diverse shapes. Alternatively, the phase shift elements may be phase shifters having dielectric wafers or laminas that can be adjusted with micrometer screws. The depths to which these dielectric elements are pushed into the connection guides12then make it possible to alter the phases of the signals propagating in the connection guides12.

The input and/or output transitions may be produced for example by using a fin line60furnished with a slot61associated with a microstrip line62, as represented inFIG. 8a. The signal propagating in the input connection waveguide is picked up by a Vivaldi antenna64formed on the lower face of the substrate63. The edges of metallizations on the lower face of the substrate63are demarcated by dots. At the output of the Vivaldi antenna, an open-circuit λ/4 stub65and a metallized hole66linking the two metallized faces of the substrate makes it possible to pass from the slot mode to the microstrip mode propagating in the microstrip line62.

Alternatively, as represented inFIG. 8b, the transitions may be embodied by using a plunger70comprising a metallization line67placed on a substrate68or, as represented inFIG. 8c, by using a mechanical plunger75using a glass bead69, a cylinder71extending the core of the glass bead and a dielectric72contributing to the matching of the transition.

Alternatively, it is possible to combine, at input and at output, two types of different transitions. For example, as represented inFIG. 8d, it is possible to use an input transition comprising a fin line60and an output transition comprising a plunger70mounted on a substrate. In this figure, the input73and the output74of the amplifier element are not on the same axis.

FIG. 9shows an exemplary feed device that can be applied at the input of the power amplification device with reduced bulk. The feed device comprises an opto-electronic device80, for example such as a photodiode or photodiode with amplifier, receiving, by way of an optical fiber81, a light signal modulated by an RF signal to be amplified. After detection by the photodiode device, the RF signal is transmitted as input to the power divider by way of a transition82.

The solution proposed in the present description makes it possible to combine a large number of amplifier modules, for example eight amplifiers, in one or more rows and on one or more plates in an antenna grid cell of the order of six centimeters with:very low insertion losses of the divider and of the combiner so as not to degrade the efficiency in terms of added power of the device;a rectangular waveguide output so as to be directly compatible with the interface of the circuits placed downstream;a planar technology input allowing better compatibility with the circuits placed upstream;sufficient space around the amplifiers so as to be able to site the decoupling capacitors necessary for the electrical stability of the amplifier;very good thermal management so as to adhere to the spatial constraints on the junction temperatures of the semi-conductors;reduced bulk so as to minimize the weight of the equipment;ease of assembly making it possible to offer a low-cost solution.possible compatibility with systems for transporting RF signals by optical fiber.

Although the invention has been described in conjunction with particular embodiments, it is quite obvious that it is in no way limited thereto and that it comprises all the technical equivalents of the means described as well as their combinations if the latter come within the scope of the invention.