EP-4740265-A1 - POWER AMPLIFIER

EP4740265A1EP 4740265 A1EP4740265 A1EP 4740265A1EP-4740265-A1

Abstract

The invention relates to a power amplifier comprising a power divider (2), a plurality of amplifying channels (3) and a power combiner (1), the power combiner comprising a first subcombiner (4), a second subcombiner (5), a plurality of input couplers (6) and an output coupler (7), the first subcombiner (4) comprising a first cylindrical cavity (8) along an axis of symmetry (Z) and a first plurality of waveguides (9) extending radially from the first cylindrical cavity (8), the second subcombiner (5) comprising a second cylindrical cavity (10) along the same axis of symmetry (Z) and a second plurality of waveguides (11) extending radially from the second cylindrical cavity (10), each input coupler (6) being configured to receive an amplified elementary signal from an amplifying channel (3) and to divide it into a first signal transmitted through a waveguide (9) and a second signal transmitted through a waveguide (11).

Inventors

HOARI, Mouayd
BOUSBIA, Hind
MARTIN, Audrey
BLONDY, PIERRE

Assignees

Safran Data Systems
Université de Limoges
Centre National de la Recherche Scientifique (CNRS)

Dates

Publication Date: 20260513
Application Date: 20240703

Claims (11)

1. Power amplifier comprising: - a power divider (2) configured to receive an initial input electromagnetic signal and divide it into a plurality of elementary signals, the power of the initial input electromagnetic signal being distributed over the elementary signals, - an amplifier comprising a plurality of amplifier channels (3), each amplifier channel (3) being configured to amplify an elementary signal of the plurality of elementary signals, - a power combiner (1) configured to recombine the plurality of amplified elementary signals into an amplified initial electromagnetic signal, the power combiner (1) comprising a first sub-combiner (4), a second sub-combiner (5), a plurality of input couplers (6) and an output coupler (7), the first sub-combiner (4) comprising: - a first cylindrical cavity (8) along an axis of symmetry (Z) forming a first radial waveguide, the first cylindrical cavity (8) comprising a first plurality of inputs arranged in a plane (P) perpendicular to the axis of symmetry (Z), - and a first plurality of rectangular waveguides (9), each waveguide (9) of the first plurality of waveguides extending radially with respect to the axis of symmetry (Z) from an input of the first plurality of inputs, the second sub-combiner (5) comprising: - a second cylindrical cavity (10) along the same axis of symmetry (Z) forming a second radial waveguide, the second cylindrical cavity (10) comprising a second plurality of inputs arranged in a plane (P') perpendicular to the axis of symmetry (Z), the second plurality of inputs being superimposed with the first plurality of inputs, - and a second plurality of rectangular waveguides (11), each waveguide (11) of the second plurality of waveguides extending radially relative to the axis of symmetry (Z) from an input of the second plurality of inputs, each input coupler (6) being configured to receive an amplified elementary signal from an amplifying path (3) and to divide said amplified elementary signal into a first signal intended to be transmitted in a waveguide (9) of the first plurality of waveguides and into a second signal intended to be transmitted in a waveguide (11) of the second plurality of waveguides, the first signal being in phase with the amplified elementary signal and the second signal being phase-shifted by a quarter of a wavelength relative to the amplified elementary signal, the first sub-combiner (4) being configured to combine the first signals transmitted in each waveguide (9) of the first plurality of waveguides into a first combined signal and the second sub-combiner (5) being configured to combine the second signals transmitted in each waveguide (11) of the second plurality of waveguides into a second combined signal, the output coupler (7) being configured to combine the first combined signal and the second combined signal into an output electromagnetic signal by inducing a phase shift of the first combined signal by a quarter wavelength, such that the output electromagnetic signal has an amplified power relative to the initial input electromagnetic signal.
2. Power amplifier according to the preceding claim, in which each input coupler (6) and the output coupler (7) are “branch-line” type couplers.
3. Power amplifier according to one of the preceding claims, wherein at least one input coupler (6) is a rectangular waveguide coupler extending, radially with respect to the axis of symmetry (Z), from a waveguide (9) of the first plurality of waveguides and a waveguide (11) of the second plurality of waveguides.
4. Power amplifier according to one of the preceding claims, further comprising at least one first transition (13) between an input coupler (6) of the plurality of input couplers and the waveguide (9) of the first plurality of waveguides, the first transition (13) preferably comprising a rectangular waveguide impedance transformer of variable section, and/or further comprising at least one second transition (14) between an input coupler (6) of the plurality of input couplers and the waveguide (11) of the second plurality of waveguides, the second transition (14) preferably comprising a rectangular waveguide impedance transformer of variable section.
5. Power amplifier according to one of the preceding claims, wherein the first combined signal is emitted by a first output (15) of the first sub-combiner (4), and the second combined signal is emitted by a second output (16) of the second sub-combiner (5), the power amplifier further comprising a third transition (18) between the first output (15) and the output coupler (7) and/or a fourth transition (19) between the output coupler (7) and the second output (16).
6. Power amplifier according to one of the preceding claims, in which each waveguide (9,11) of the first plurality of waveguides and of the second plurality of waveguides is a rectangular waveguide comprising a capacitive element (12) positioned inside the waveguide (9,11) so as to form staircase steps. of a depth measured in the radial direction in which the waveguide (9,11) extends equal to a quarter of the wavelength of the initial input electromagnetic signal.
7. Power amplifier according to one of the preceding claims, in which the number of input couplers (6), the number of waveguides (9) of the first plurality of waveguides and the number of waveguides (11) of the second plurality of waveguides are equal.
8. Power amplifier according to one of the preceding claims, in which each amplifier channel (3) comprises a phase shifter of the elementary signal comprising a microstrip line of variable length.
9. Power amplifier according to the preceding claim, wherein the variable length microstrip line is formed by a first microstrip line (51) on a first printed circuit (52) and by a second microstrip line (53) and a third microstrip line (54) on a second printed circuit (55), the third microstrip line (54) being parallel to the second microstrip line (52), a first end (56) of the first microstrip line (51) being in contact with the second microstrip line (53) and a second end (57) of the first microstrip line (51) being in contact with the third microstrip line (54), the first printed circuit (52) being movable relative to the second printed circuit (55).
10. Power amplifier according to one of the preceding claims, the power divider (2) comprising: - a third cylindrical cavity (34) along the same axis of symmetry (Z), the third cylindrical cavity (34) comprising an input (35) of the initial electromagnetic input signal on the axis of symmetry (Z) and a plurality of outputs (36) of the third cylindrical cavity (34) on the same plane (P”) perpendicular to the axis of symmetry (Z), - a plurality of air-suspended strip lines (37), each air-suspended strip line (37) extending radially with respect to the axis of symmetry (Z) in the plane (P”) from inside the third cylindrical cavity (34) through an outlet (36) of the plurality of outlets of the third cylindrical cavity, each air-suspended strip line (37) being configured to pick up an elementary signal of the plurality of elementary signals.
11. Power amplifier according to claim 9, comprising a coaxial input (48) extending axially along the axis of symmetry (Z) and opening into the third cylindrical cavity (34) via the input (35) of said third cylindrical cavity (34), the coaxial input (48) comprising a conductive core (49) which extends inside the third cylindrical cavity (34) up to the plane (P”).

Description

Power amplifier TECHNICAL AREA The invention relates to a power amplifier, in particular a multi-channel semiconductor type power amplifier (known as “SSPA”) suitable in particular for communication between a satellite and the ground. STATE OF THE ART Power amplification systems allow an output signal to be delivered from an initial input signal that is amplified relative to the initial input signal. These systems use, for example, semiconductor power amplifiers, known to those skilled in the art by the acronym SSPA for “Solid State Power Amplifier”. However, the output power achievable by such SSPA amplifiers is limited by a saturation effect when the power of the input signal is too high. In addition, the maximum output power achievable decreases with increasing frequency of the input signal. Consequently, with existing SSPA amplifiers, a single amplification path may not be sufficient to achieve the output powers required by certain applications, for example in ground-to-satellite communication. Power amplification systems therefore generally comprise a divider for dividing the input signal into different amplifier channels, at least one elementary power amplifier per amplifier channel for amplifying the signal transmitted in the amplifier channel and a combiner for recombining the amplified signals leaving the amplifier channels so as to form the amplified output signal. A combiner can be evaluated by its combination efficiency: P s T = — — x 100 PE Where P s is the output power of the amplified output signal from the combiner and P E is the total power of the amplified signals in each amplifier channel at the combiner input. Power losses between the combiner input and output, otherwise known as combination losses, have multiple causes and are evaluated by the general formula, in dB: For example, a combination loss of 1 dB corresponds to a combination efficiency of 80%. There are three main combiner technologies: radial combiners, tree combiners and spatial combiners. Tree combiners generally include several stages of binary adders allowing the different amplified signals coming out of the amplifier channels to be recombined two by two. Tree amplifiers allow a small number of channels to be combined efficiently. However, the combination losses increase rapidly with the number of combined channels and the length of the combination lines. The combination efficiency T of an n-channel tree power combiner with stage losses a dB , the value of a dB being fixed by the length of the lines and the ohmic losses due to the presence of resistors, is given by the following relation: T = 100 X 10“ ln * a dB/ As an example, a Wilkinson type power combiner has stage losses at dB around 0.7 dB in Ka band, which means that the combining efficiency of such a combiner cannot exceed 62% when it includes 8 combining channels. Spatial amplifiers typically comprise several elementary amplifiers placed in parallel on a panel perpendicular to the direction of propagation of the input signal, or placed on several plates parallel to the direction of propagation of the input signal. The propagation of the input signal before and after the elementary amplifiers can be done via waveguides or beams generated by antennas. At the input of each elementary amplifier, transitions allow switching from these guided or beam propagation modes to planar propagation. After each elementary amplifier, a new transition allows switching back to a guided or beam propagation mode. The combination efficiency of spatial amplifiers is independent of the number of combined channels. However, the level of power admitted in these amplifiers is limited because of the difficulty of evacuating the heat generated by the elementary amplifiers. Furthermore, the losses by combination of spatial amplifiers are generally significant because of the phase and amplitude dispersion of the signals circulating in the different amplifying channels before their recombination. As an example, the relationship between the combination losses due to P unbalance (which is one of the causes of combination losses) and the phase 0 and amplitude A unbalances of an isolated combiner with two combination channels is given by the following formula: [ cos 6 P = 10 x log(0.5 + 1 + ) Thus, if the signals propagated in the two channels are 180° out of phase, no power is delivered to the combiner output. Radial amplifiers generally include a plurality of combining and/or dividing paths extending radially from an axis in a plane perpendicular to said axis. Due to this radial geometry, the signals circulating in the different combination and/or division paths have the same phase and the same amplitude, so that the unbalance losses P are very low. In addition, the combination efficiency T is advantageously independent of the number of paths so that it is possible to combine a large number of paths from a large number of amplifiers and thus achieve very high powers. A major problem with these