HYPERFREQUENCY SOLID BODY AMPLIFIER AND POWER COMBINATOR WITH FOUR SUCH SOLID BODY AMPLIFIERS

Description

[0001] The invention relates to a solid-state power microwave amplifier and power combiner comprising four such solid-state amplifiers.

[0002] The invention lies in the field of solid state power microwave amplifiers or SSPAs, for "Solid State Power Amplifier" in English.

[0003] It is known that amplification systems, such as SSPAs and traveling-wave tubes or TWTAs (Traveling-Wave Tube Amplifier), with spatial or classic combinations, all have major drawbacks.

[0004] Indeed, these amplification systems present problems of compactness, efficiency, repair, maintainability, assembly, assembly cost and evolution, scalability and power limitation.

[0005] This is known from tube amplifiers or traveling wave tubes (TWTAs), which use a heated filament, producing a release of electrons by thermionic emission. These electrons are then accelerated in a vacuum by a high-intensity electric field generated by a very high voltage (THT). Once accelerated, these electrons are focused into a beam that interacts with a microwave. Gradually, the direct current (DC) energy contained in the electron beam is converted into microwave energy as the electrons travel along the interaction line. This energy is then transferred out of the tube, while the residual energy is transferred to the collector and dissipated as heat.

[0006] These amplifiers are very compact and operate at high efficiency, but in an all-or-nothing fashion, and in case of failure, the products are unusable. They require very high voltage, advanced technology, are very expensive to produce, and very difficult to maintain.

[0007] Document EP 2 201 679 A1 is known to disclose a printed circuit board and waveguide interface system with an adjustment screw to adjust the dimensions of the interface cavity.

[0008] Also known is document EP 0 074 613 A1 which discloses a transition using a metallic ribbon interposed between the edge of the waveguide and the propagation line.

[0009] Also known is US document 4,458,222 A, which discloses a capacitive coupling using a dielectric film between the edge and the propagation line.

[0010] It is also known from monolithic SSPA solid-state amplifiers spatially combined via Vivaldi-type antipodal lines which will then radiate into cavities.

[0011] These cavities form the input points of a conical cavity combiner. This type of amplifier, for example described in US patent 10,340,574 B2, offers good compactness, relatively low losses, and no interstage interconnection problems. However, their radial configuration makes managing heat dissipation very complex and virtually impossible for optimal operation in pulsed mode, as the energy storage capacitors cannot be placed close to the monolithic microwave integrated circuits (MMICs).

[0012] It is also known as SSPA solid-state amplifiers in hybrid or T-junction combination, in which monolithic microwave integrated circuits (MMICs) are combined via hybrid couplers, Wilkinson or T-junctions.

[0013] Such amplifiers are relatively inexpensive, but nevertheless have relatively high losses, a lack of scalability (power limitation), and are very difficult to repair due to the chip and wire type assembly.

[0014] None of the existing solutions mentioned above are satisfactory because they all have major flaws.

[0015] Also known is document EP0074613A1, which uses a ribbon connection, as illustrated in the figure 1 in reference 28. This embodiment uses the ridge feeding function, as illustrated in the figure 1 corresponding to figure 3B of document EP0074613A1 with references 24, 25, 26 and 27. This ribbon connection has the advantage of being flexible but does not allow for simple repair because the implementation of such a ribbon requires a return to the factory and specific machines.

[0016] One aim of the invention is to overcome the problems mentioned above, and in particular to facilitate repairability, compactness and scalability.

[0017] Also, according to one aspect of the invention, a solid-state power microwave amplifier is proposed comprising an upper part of a waveguide, a linearized impedance matching waveguide ridge, a lower part of the waveguide, a propagation line, and at least one interconnection between the propagation line and the linearized impedance matching waveguide ridge, provided with a clamping device ensuring direct contact between the ridge and the propagation line, wherein the clamping device comprises at least one pressure screw and a pressure support stiffener, the pressure screw exerting a force on the propagation line via the stiffener to maintain direct contact.

[0018] Such a system improves repairability, compactness and scalability.

[0019] Thus, the stiffener system will give the pressure device an elasticity which will guarantee the absence of deformation and the flat-ended pressure screw will not pierce the material attached to the edge.

[0020] Thus, tightening this screw makes it possible to constrain the edge of the guide and to keep its end in contact with the propagation line on the printed circuit board, thus offering a flexible and easily repairable connection.

[0021] For example, the pressure screw includes a spherical end or a flat end.

[0022] According to another aspect of the invention, a power combiner is also proposed comprising four solid-state power microwave amplifiers according to one of the preceding claims, connected in H by a magic T device.

[0023] Thus, the H-shaped arrangement allows direct interconnection of the amplification modules to the combination system without the need for guided links, thereby limiting losses and improving the distribution of hot spots.

[0024] In one embodiment, the elements of the combiner are mounted flat.

[0025] This allows for easy management of the thermal environment and maintenance, as well as stacking multiple functions.

[0026] According to one embodiment, the magic tee device is monobloc (in the sense that the line-to-guide transitions, the two-to-one elementary magic tees of the magic tee device, the impedance transformation sections and the bi-directional coupler are fused).

[0027] This allows the different elements to be assembled by simply screwing them together without waste, and reduces costs and bulk.

[0028] For example, the one-piece magic tee device includes an S-flange, a bidirectional coupler, three elementary two-to-one magic tees, line-to-guide transitions, and guide-to-coaxial transitions.

[0029] The invention will be better understood upon examination of some embodiments described by way of non-limiting examples and illustrated by the attached drawing in which: [ Fig.1 ] schematically illustrates a solid-state microwave power amplifier, according to the state of the art; [ Fig.2 ] schematically illustrates a solid-state microwave power amplifier, according to one aspect of the invention; [ Fig.3 ] schematically illustrates a solid-state microwave power amplifier, according to one aspect of the invention; [ Fig.4 ] schematically illustrates a solid-state microwave power amplifier, according to another aspect of the invention; [ Fig.5 ] schematically illustrates a solid-state microwave power amplifier, according to another aspect of the invention; [ Fig.6 ] schematically illustrates a solid-state microwave power amplifier, according to another aspect of the invention; [ Fig.7 ] schematically illustrates a power combiner, according to another aspect of the invention.

[0030] Across all figures, elements with identical references are similar.

[0031] On the figure 2 is illustrated, according to one aspect of the invention, a solid-state microwave power amplifier.

[0032] Contrary to the transition principle between a track acting as a propagation line and the edge of the waveguide described in the state of the art of the figure 1 , achieved by a micro-strip connection between the edge of the guide and the microtrack, the present invention achieves this transition by a direct contact between the edge and the propagation line ensured by a clamping device, comprising for example at least one pressure screw.

[0033] The solid-state microwave power amplifier includes an upper part 0 of a waveguide, a linearized impedance transformation edge 1, and a lower part 2 of the waveguide, which may, in some cases, also have a linearized impedance transformation edge.

[0034] The solid-state amplifier comprises a printed circuit board 3 with a propagation line or microtrack 6, at least one pressure screw 4, and a pressure support stiffener 5. The amplifier also includes a support base 7 and a waveguide cavity 8. The figures show only a device with one pressure screw 4, but this is not a limitation.

[0035] State-of-the-art solid-state amplifiers all use wired (ribbon link), connectorized (coaxial link) or radiated (antenna) interconnections.

[0036] THE figures 3 et 4 represent cross-sectional views of a solid-state amplifier according to one aspect of the invention, respectively in front and side view.

[0037] The objective of the solid state amplifier of the invention is to transmit an electromagnetic signal from a propagation line or microtrack 6 to a guide section or section of the guide cavity 8.

[0038] This transmission can be achieved in narrowband using a single edge 1, or "ridge" in English. To extend the bandwidth to 6-18 GHz, a linearized double-edge impedance transformation system 3, 6 is required, as illustrated. figures 3 et 4 For this transmission to be effective, electrical contact must be guaranteed between edge 1 and microtrack 6.

[0039] However, due to the manufacturing and assembly tolerances of the mechanical parts and the printed circuit board 3 mounted on its printed circuit board base 7 (we therefore have a printed circuit board 3 mounted on a metallic base), there remains a thin residual space separating the two transmission lines or edges (edge ​​1 and microtrack 6) which it is necessary to fill.

[0040] In order to ensure electrical contact over the entire temperature range (due to the consideration of expansion effects) and during any intended use (constraints of resistance to vibration and shock), at least one pressure screw 4 is anchored in a pressure support stiffener 5 and deforms the cavity 8 by pressing on the edge 1 while remaining in the elastic domain.

[0041] Pressing on edge 1 allows contact to be made between its lower end and the propagation line or microtrack 6.

[0042] The proper functioning of the amplifier depends on: The pressure on edge 1 must be controlled and the deformation limited so as not to significantly alter the dimensions of cavity 8 (impact on propagation quality); the printed circuit board on which edge 1 makes contact must be hard and must have a line or microtrack width compatible with the width of the edge at its end; the type of printed circuit board must be able to pass the expected power (50W CW) over the entire temperature range, from -40° to +85°C; the operating time of the solid-state amplifier must not cause degradation of the printed circuit board, so that it remains within the elastic range; the connection must be able to be mounted and dismounted without altering performance by simply screwing and unscrewing.

[0043] Preferably, the substrate resists deformation under a minimum pressure of 500 MPa, and is made of Al 2 O 3 or duroid (registered trademark) of type RO4350 or RO4003, and the tightening torque of the screw must not cause irreversible deformation while remaining within the limit of the elastic range.

[0044] In a preferred embodiment, the mechanical and assembly tolerances are compatible with the type of substrate used and therefore with its dielectric permittivity. ε r. Therefore, the maximum permissible dimension of the gap G1, as illustrated on the figures 5 et 6 The tolerance is 0.1 mm to ensure that the clamping device remains within its elastic range. The Tx and Tz tolerances are therefore less than 0.1 mm. The architecture illustrated on the... figure 7 This allows the printed circuit board to be brought against the lower part 2 of the guide, resulting in G2=0, a crucial element for proper microwave operation. Thus: G1, Tx, Tz and Ty < 0.1mm and G2 = 0.

[0045] As shown by figure 5 , the Z-axis alignment tolerance Tz between the lower guide 2 and the support plate 7 remains much less than the substrate thickness H with H T > 5 .

[0046] Similarly, it is important that the support area of ​​edge 1 is aligned with the microtrack as shown in the figure 6 Therefore, preferably, the x-alignment tolerance Tx between edge 1 and microtrack 6 remains much smaller than the width Wr of edge 1 at the contact area with the printed circuit board, or the width WI of microtrack 6 is larger than Wr plus the assembly tolerance of 0.1 mm. The simulations thus imply that it is necessary to have: Wr Tx < 4 ou Wl > Wr + 0 , 1 mm

[0047] Also the target value ε The r of the printed circuit board substrate is given by the following relationship: Pour W h < 1 Z 0 = 60 ε eff ln 8 h W + W 4 h Avec ε eff = ε r + 1 2 + ε r − 1 2 1 + 12 h w − 1 2 + 0 , 04 1 − W h 2

[0048] Also, preferably the substrate is low loss, i.e. it should offer the lowest possible tangent delta (tan δ) (classically <0.001) to limit heating by linear losses and offer excellent thermal conductivity.

[0049] As illustrated on the figure 7Also proposed is a power combiner comprising four solid-state microwave power amplifiers 10 as previously described, connected in an H configuration by a magic T-connector 11, known as a four-to-one H-topology, which has the particularity that one half is fused with a chassis 12, and the other half is assembled by screwing 13. The combiner includes a bidirectional coupler 14. In addition, the upper part of the combiner device covers both the lower part of the combiner fused with the chassis and the four solid-state microwave amplifier modules.

[0050] The pressure screws 4 ensure contact between the amplifiers 10 and the access points of the magic T 11.

[0051] The combiner's H-shaped configuration optimizes the footprint and distributes hot spots. The four-to-one Magic Tee is a single-piece unit (the S-flange and 14 bidirectional coupler are machined from a single piece) and incorporates microtrack-to-double-edge waveguide transitions with non-standard impedance transformation, enabling optimal compactness without transitions. Losses are therefore minimal and efficiency maximized.

[0052] The microwave power amplifiers 10, the magic T-junction 11, and the bidirectional coupler 14 are very easily assembled and disassembled by simple screwing. Maintenance and repairability are thus greatly facilitated.

[0053] The interconnections of the combiner device are not hyperstatic.

[0054] The combiner device also includes a driver module or "driver" in English 18 to pre-amplify the signal.

[0055] The "flat" mounting configuration of the combiner unit's components allows for easy thermal management. The modular design enables cost-effective scalability and easy maintenance.

[0056] The combiner device provides isolation between lanes which allows for the maintenance of performance during mild degradation.

[0057] In this example, the substrate used is an alumina with a thickness H=0.6mm and a line width WI=0.6mm, resulting in a characteristic impedance of 50 ohms. On the side of the supporting edge, the width is Wr=0.4mm and the overlap length S=0.8mm.

Claims

1. Solid state hyperfrequency power amplifier comprising an upper part (0) of a waveguide, a linearised impedance transforming waveguide ridge (1), a lower part (0) of the waveguide, a propagation line (6), and at least one interconnection, between the propagation line (6) and the linearised impedance transforming waveguide ridge (1), provided with a clamping device (4) that guarantees direct contact between the ridge (1) and the propagation line (6), wherein the clamping device comprises at least one pressure screw (4) and a pressure support stiffener (5), the pressure screw exerting a force on the propagation line (6) via the stiffener (5) to maintain direct contact.

2. Solid state hyperfrequency power amplifier according to claim 1, wherein the pressure screw (4) comprises a spherical end or a flat end.

3. Power combiner device comprising four solid state hyperfrequency power amplifiers according to any one of the preceding claims, which are connected in an H configuration by a magic T device (11).

4. Power combiner device according to claim 3, wherein the elements are mounted flat.

5. Power combiner device according to claim 3 or 4, wherein the magic T device (11) is in one piece.