Power link, protected by redundancy, for microwave signals.

0001The present invention relates to a power link for microwave signals, this link being protected by redundancy, for example through the use of several power amplifiers operating in active redundancy.

0002At the level of the power transmitters equipping for example the earth stations, it is often necessary to use links which either carry out a coupling between separate channels, or tend to gather several power transmitters on only one output access, it is to say in fact on the transmit antenna. Furthermore, it is currently generally required, in order for the link to be protected against power amplifier failures, that this link uses redundant power amplifiers.

0003For this purpose, the most common transmitters use a main amplifier, normally active, and also provide another amplification channel comprising another amplifier identical to the first, this second channel being able to be switched in place of the first one. failure of this main amplifier. In general, in order to avoid an excessive loss of information in the event of switching on this backup amplifier, the latter is constantly kept under voltage, in standby state: it is then said that it operates in "hot" redundancy.

0004As is well understood, this type of conventional device has the disadvantage of being expensive, since it requires providing two identical amplification chains in parallel, one of which only works in the event of a breakdown. or disconnection of the first.

0005To remedy this drawback, we tend to focus on installations operating in "active" redundancy: these are installations which comprise two amplifiers, each at half the nominal power, which operate continuously and in parallel. In the event of a failure of one of the two, the other continues to operate, so that the connection is ensured anyway in this case, at power lower than the nominal power however, but this is not unacceptable drawback taking into account tolerance limits conventionally adopted for these power amplifiers.

0006There are commercially available connecting devices of this type, but these devices, because the coupling of the two redundant amplifiers on the transmitting antenna is carried out in waveguides and by the use of "orthomode" transducers ("Ortho-Mode-Transducers) associated with a phase shifter in a TE11 circular guide, have two drawbacks:<ul id="ul0001" list-style="none"><li>. it is thus possible to simply make only power connections using two amplifiers in active redundancy, and not four, six, eight, or more: the input on orthomode transducers in fact uses two rectangular and orthogonal guides, of so that putting more than two amplifiers in parallel would pose delicate and costly phase path compensation problems for grouping them into a "pyramid";</li><li>. this technique for orthomode transducers is a purely "waveguide" technique: it does not have its direct equivalent in coaxial technique or in microstrip technique ("microstrips"), so that these installations cannot be transposed in these two latest techniques, which would however be desirable in certain cases where one operates at low transmission power.</li></ul>

0007The invention aims to remedy these latter drawbacks. To this end, it relates to a power link for microwave signals, this link being protected by redundancy, in particular by the use of several power amplifiers operating in active redundancy, characterized in that it comprises at least:<ul id="ul0002" list-style="none"><li>. a 3dB, 0 ° coupler capable of dividing the input signal to be amplified into one or more pairs of synchronous frequency and phase signals;</li><li>. an adaptation circulator followed by a power amplifier on each of the channels corresponding to each of these signals; a phase shifter "0 or" being arranged on one of the channels of each pair before the adaptation circulator; and</li><li>. a "Variable Rank Coupler" associated with each pair of channels downstream of these two amplifiers which it comprises and comprising in cascade:<ul id="ul0003" list-style="dash"><li>an 3dB 90 ° input coupler, the two input terminals of which are respectively driven by the two signals from the respective outputs of these two amplifiers;</li><li>an adjustable phase shifter, capable of producing a phase shift ranging from 0 ° to 180 °, placed on one of the two output channels of this input coupler; and</li><li>a 3dB output coupler, 90 ° similar or identical to the input coupler and whose two input channels are respectively attacked by the output signal of this adjustable phase shifter and by the signal from the other output channel of the coupler input, and one output terminal of which is connected to a load while the other output terminal either constitutes the power output of the link, or in turn attacks one of the two input terminals of another Coupler at Rang Variable.</li></ul></li></ul>

0008In any case, the invention will be well understood, and its advantages and other characteristics will emerge during the following description of a nonlimiting example of embodiment of this redundant link, with reference to the appended schematic drawing in which:<ul id="ul0004" list-style="dash"><li>Figure 1 recalls the constitution of a variable rank coupler of the known art;</li><li>Figure 2 is a cross section of one of the couplers "RIBBLET" usable in a variable row coupler according to Figure 1;</li><li>Figure 3 is a median cross section of the coupler according to Figure 2, showing the shape of the waves generated in this section when using this coupler in accordance with the invention;</li><li>Figure 4 is a block diagram of the power installation according to the invention, with only one pair of amplifiers in active redundancy; and</li><li>Figure 5 shows the extension of the diagram according to Figure 4 to an installation comprising several pairs of amplifiers in active redundancy.</li></ul>

0009In Figure 1 is shown a known component, called "Variable Row Coupler", or "CRV", which is the basic component for the implementation of the present invention.

0010This CRV is a quadrupole which comprises two upstream access terminals 1, 2, which can be considered as the input terminals and two downstream terminals 3, 4 which can be considered as the output terminals of the quadrupole. In current use of this CRV component, terminals 2 and 3 are connected to ground by the respective load resistors 5 and 6, so that the microwave input signal is applied at 1, while the output signal is taken in 4.

0011Terminals 1 and 2 are the two upstream terminals of a "3dB-90 °" coupler, referenced 7, which is conventionally a RIBBLET coupler (Figure 2). This RIBBLET coupler is such that the signal applied at 1 gives, at outputs 8 and 9 of this coupler 7, two signals respectively phase shifted by 0 ° and 90 °, and of amplitude half of this input signal.

0012The signal at 8 is applied to the input 10 of a second RIBBLET coupler 13 identical to the coupler 7, the other input 11 of the latter not being charged to ground, but being connected to the output 9 of the coupler 7 by means of an adjustable microwave phase shifter 12. The above-mentioned terminals 3 and 4 are also the two downstream terminals of this coupler 13.

0013In its most conventional use, the CRV of FIG. 1 is a loss circuit able for example to select a frequency F₁ from two input frequencies F₁, F₂.

0014The invention is based on the use of a particular property of a "3dB-90 °" coupler, such as the RIBBLET coupler 7 of FIG. 2, a property which will be set out and demonstrated as follows, with reference to the figures 2 and 3:    This coupler 7 has, adjacent to the accesses 1 and 2, two first identical sections 14, 15 in rectangular guide, which open into a median section 16 in rectangular guide of width a (long side of the guide), and of length 1, this section 16 leading to two other sections 17 and 18 identical to the sections 14 and 15 and exiting at 8 and 9. The dimension a differs very little from the sum of the widths of the guides 14 and 15 (or 17 and 18)

0015In conventional use of this coupler 7, a wave is applied to one of the ports 1 or 2, and, in plane A (FIG. 2), two modes of propagation of equal amplitudes exist, with phase velocities however different. It's about :<ul id="ul0005" list-style="none"><li>. a symmetrical TEO1 mode of guided wavelength:<maths id="math0001" num=""><img file="EP0443484A1_D0001.tif" /></maths> where λ is the wavelength of the order applied in 1 or 2; and</li><li>. a TEO2 asymmetric mode of guided wavelength:</li></ul><maths id="math0002" num=""><img file="EP0443484A1_D0002.tif" /></maths>

0016In plane B, after traveling the length L (Figure 2), the relative phase shift of these two waves is:<maths id="math0003" num=""><img file="EP0443484A1_D0003.tif" /></maths> which gives rise to two quadrature waves if L is chosen so that this relative phase shift is equal to π / 2.

0017Thus, when a wave attacks access 1, there will be found in 8 a wave of half amplitude and not phase shifted, and in 9 a wave of amplitude half and phase shifted by 90 °.

0018If now two waves in phase attack accesses 1 and 2, we will find in a junction plane 16 (plane A for example), the composition of four waves (Figure 3), including:<ul id="ul0006" list-style="none"><li>. two antisymmetric waves 19 and 20, in TEO2 mode, which destroy themselves by phase opposition; and</li><li>. two symmetrical waves 21 and 22, in TEO1 mode, which sum up in phase.</li></ul>

0019It follows that this coupler 7 behaves, for two synchronous frequency and phase input waves, like two parallel guides.

0020We will now refer to FIG. 4, which shows an amplification chain, according to the invention, in active redundancy of order 2.

0021The microwave signal to be transmitted E is applied to the input 23 of a "3dB-0 °" coupler such as a WILKINSON coupler 24.

0022Two synchronous signals but with half amplitudes therefore appear on outputs 25 and 26 of this coupler.

0023The signal at 26 passes through a small adjustable phase shifter 27, optional, which has the role of perfecting the phase synchronism of the two waves emitted at 25 and 26, then through an adaptation circulator 28 to be finally applied to a first power amplifier 29.

0024The signal at 25 passes through a phase shifter "O or π" 30, then through another adaptation circulator 31, to be finally applied to the second power amplifier 32, identical to the amplifier 29.

0025Amplifiers 29 and 32 are the two amplifiers with active redundancy of the link according to FIG. 4.

0026The outputs of amplifiers 32 and 29 are respectively applied to inputs 1 and 2 of a CRV (7, 12, 13) identical to that of FIG. 1, but whose terminal 2 is not loaded to ground.

0027In this preferred embodiment, the phase shifter 12 of the CRV is only capable of producing a phase shift ranging from 0 ° to 180 ° (which does not pose the difficult and expensive problems of producing a phase shifter which would go from 0 ° to 360 °). The operation of the device in FIG. 4 is then as follows:    In the case where the "O ° or 180 °" phase shifter 30 is in the 0 ° phase shift position (switches having the position of FIG. 4), the two waves at 1 and 2 sum up completely in phase on terminal 4 (output S of the link), and no signal appears at 3 (load 6), provided that the phase shift due to 12 is equal to 90 °.

0028If we then increase the phase shift due to 12 between 90 ° and 180 °, the wave in 4 decreases and that in 3 increases, to reach respectively half of the initial power when this phase shift reaches 180 °.

0029If, on the other hand, this phase shift is decreased between 90 ° and 0 °, the wave in 4 decreases and that in 3 increases, so as to reach the half power at each of these two output ports when this phase shift reaches 0 ° .

0030In the position of the phase shifter 30 corresponding to a phase shift of π (position of switches of inverse 30 from that of FIG. 4), the entire signal is switched to the access 3, nothing going out in 4, provided that the phase shifter 12 provide a phase shift of 90 degrees (we would obtain the same result without phase shifter 30, but using a phase shifter 12 covering a wider range, which would be much more complex and expensive to achieve.

0031The connection in FIG. 4 therefore has infinite flexibility of use and it easily lends itself to the production of redundancies greater than 2, since the output 4 takes place in a rectangular guide able to directly attack the RIBBLET coupler of another CRV By way of illustration, FIG. 5, to which we will now refer, shows an embodiment of an active redundancy link of order 4.

0032In this FIG. 5, there are provided 4 redundant power amplifiers 34 to 37 which are similarly supplied by the input signal E through a divider by four 33, and twice two circuits such as (30, 31, 27, 28 ), not shown.

0033The amplifiers 34 and 35 attack, in the same way as in FIG. 4, a CRV 38, charged by the resistor 40 and leaving at 42, while the amplifiers 36 and 37 similarly attack a CRV 39, charged by the resistor 41 and leaving in 43.

0034The outputs at 42 and 43 are grouped together in a third CRV 44, to provide the single output S at 46, this CRV being in turn charged by the resistor 45.

0035A "pyramid" circuit such as that of FIG. 5 is very flexible, since it allows all possible combinations of amplifiers, always guaranteeing a useful signal output as 46 as at least one of the amplifiers 34 to 37 is not broken.

0036It goes without saying that the invention is not limited to the embodiment which has just been described. Thus, for example, it would be convenient, in the circuit of FIG. 4, to use a phase shifter 12 varying in steps: o °, 90 °, 180 ° only, on channel 48 between 7 and 13, and to provide, for the intermediate values ​​of the phase shift, a small phase shifter 49, with continuous variation, on the other channel 48. Instead of a RIBBLET 7 coupler produced in waveguides, it would be possible to use a similar coupler, but produced either in microstrip technique or in coaxial technique, this type of coupler being easily transposable in one or the other. other of these two techniques.