EP0032332A1 - Radiofrequency power divider, and radiofrequency devices, especially solid-state devices, using the same - Google Patents

Abstract

The invention relates to a radio power distributor. The distributor is made up of several dividers D (i - I), (D (i)... Cascaded, each having a primary channel A (i - I), A (i).. Dividing into channels secondary, one of which, main, B (iI) is connected to the primary channel A (i) of the next, and the others of which, C, are terminated at the points of use; all channels C are connected to a same point a of line B of same rank i by resistive elements. This arrangement allows the absorption of the powers reflected in these lines when mismatches occur there, even when these mismatches are identical. A phase-shifter Ø is possibly placed in the primary branch Application in particular to the input and output of distributed amplifiers.

Description

The invention relates to a power distributor for radio waves. It relates in particular to the variants of such a distributor made in the solid state for application to microwave frequencies. It also relates to devices using one or more of these distributors.

Power divider and recombiner circuits are used whenever it is sought, for example, to add the powers of several independent amplifiers, in particular when a power higher than that supplied by the existing amplifiers is required.

The circuits proposed so far generally do not meet a condition considered to be fundamental, which is that of allowing proper operation, even in the presence of identical mismatches on the loads of the different branches, or channels, of the divider, of the transistors for example, in high frequency distributed amplifiers; in the case of such amplifiers, an operation is always sought in a frequency range as wide as possible, the range in which such mismatches usually manifest themselves. _-

Among these mismatches, there are two kinds: some, as has just been said, resulting from the variation of the impedance of each elementary amplifier, following the displacement of the operating frequency, others resulting, at frequency given, disparities between amplifiers in the same batch.

In the context of the invention, there will be a major interest in the first of them, the most important by far with respect to the natural dispersion of manufacturing, in the current state of the art. We will therefore deal with the case of somehow symmetrical mismatches, where all the components charging the branches are supposed to be identical at the outset, then vary in the same way according to the frequency, the variations between elements of the batch being considered as second order compared to the previous ones.

Generally, to cope with the mismatch, the excess power is absorbed, that reflected by the mismatched element, in a resistive member mounted between the branches of the distributor.

In the branches of a divider, like the one discussed above, these resistors were in the prior art mounted in parallel on each of the branches of the divider, as will be specified in the description which follows, and in some way so symmetrically with respect to these branches; so that the set, set for an initial state with zero absorption, only ensures the absorption function sought in the event of asymmetric imbalance of the branches, that is to say in particular of random mismatches of the branches, such as those arising from dissimilarities between amplifying elements.

However, such an arrangement was not adapted to the power absorption imposed by a symmetrical adjustment of the branches.

The invention relates to a power distributor capable of catching up, unlike those of the prior art, even symmetrical imbalances of its branches, in particular on the occasion of variations in impedance presented by the active elements which charge them. ci, when the frequency moves; such a distributor can a fortiori also make up for the non-symmetrical imbalances that may arise.

• - Figure 1 : la forme générale, schématisée, d'un circuit diviseur de l'art antérieur ;
• - Figure 2 : le schéma d'un circuit diviseur de l'invention ;
• - Figures 3 et 4 : des compléments au schéma de la figure précédente ;
• - Figure 5 : une vue d'une réalisation en technologie micro-bandes d'un amplificateur utilisant le répartiteur de l'invention ;
• - Figure 6 : une variante de la figure précédente ;
• - Figure 7 : une vue d'une autre réalisation dans la même technologie.
• - Figure 8 : une vue d'un exemple d'utilisation du répartiteur de l'invention dans un amplificateur à plusieurs étages ;
• - Figure 9 : une vue schématique d'une autre forme de réalisation du répartiteur de l'invention.

The invention will be better understood by referring to the description which follows and to the attached figures which represent:

• - Figure 1: the general form, schematically, of a divider circuit of the prior art;
• - Figure 2: the diagram of a divider circuit of the invention;
• - Figures 3 and 4: complements to the diagram in the previous figure;
• - Figure 5: a view of an embodiment in micro-band technology of an amplifier using the distributor of the invention;
• - Figure 6: a variant of the previous figure;
• - Figure 7: a view of another embodiment in the same technology.
• - Figure 8: a view of an example of use of the distributor of the invention in a multi-stage amplifier;
• - Figure 9: a schematic view of another embodiment of the distributor of the invention.

All the dividing devices of which figure 1 gives the diagram can be regarded as deriving from the assembly of Wilkinson, on the subject of which one will refer to the article of IRE Trans. MTT3, page 116, January 1960. The diagram represents the case of the power division starting from a high frequency generator R _G debiting on N branches, each charged by the same impedance of use to the second order near, R; each line has m sections of impedances Z ₁ , Z ₂ ... Z _m , between which are mounted in parallel, as shown in the drawing, dissipative elements R ₀₁ , R ₀₂ .- ..R _Om . All these branches are voluntarily represented of identical constitution even if in reality they contain some minor differences between them. In the case of microwaves, the sections of impedances Z ₁ , Z ₂ ... Z _m are quite simply sections of coaxial lines, for example quarter wave, that is to say whose length is equal to quarter of the average wavelength of the high frequency operating wave supplied by the generator R _G.

The larger the operating frequency band of the device, all other things being equal, the greater the number m.

This being the case, a brief analysis of the behavior of the device is carried out below for equal mismatches of the loads R.

The device being provided for given initial conditions, in accordance with the above, that is to say with N branches formed of m section of lines, all identical to each other (same impedances Z ₁ ... Z _m same dissipative elements R ₀₁ , R _0m and same charges R _s ), and adjusted so that the charges R _s are perfectly adapted, no power is reflected in the branches, in which the points located at the same distance from the source, such as L ₁ , M ₁ , N ₁ , are in phase on all the lines; no energy is then dissipated in the resistive elements placed in bridge between the lines. It is no longer the same if unequal adaptations occur in the branches, because then this phase concordance is no longer preserved and a current flows between the points such as L ₁ , M ₁ , N ₁ , L ₂ , M ₂ , N ₂ , etc.

On the other hand, in the event of symmetrical mismatches of the charges R, all the lines, identical, undergo the same disturbances and the points L ₁ M ₁ N ₁ are found in phase, as well as M ₂ N ₂ P ₂ etc, as they were at the time of the initial setting. Under these conditions, the additional powers reflected by the mismatched charges cannot be absorbed by the resistors, at the terminals of which there appears no potential difference. There are various variants to the Wilkinson assembly described above on which we will not extend, all these variants, which fall under the same principle, having the same drawbacks.

We will also mention Lange, IEEE Trans MTT 17, December 69, page 1150, as prior art of these power distributors, as well as the patents of Marvin H. White and Gary H. Hoffmann granted in the United States under the respective numbers 3.593 .174 and 3.963.993.

To remedy this state of affairs, the invention provides an arrangement in which is ensured, permanently, that is to say whatever the state of the loads, a phase shift allowing the desired absorption. According to the invention, the distributor comprises several dividers arranged in cascade, each of them being connected by an output branch to the next; each of them further comprises, at its outlet, a certain number of branches on which the loads are mounted.

All these branches, as well as the one used to connect with the following divider, that those closed on the loads, will be called secondary branches, the first named being the main secondary branch. In addition, according to the invention, this branch is connected to the input branch in the next divider, called the primary branch, through a phase shifter if necessary; this divider also has, like the previous one, secondary branches, including a main one connected to the primary path of the following divider, possibly through a phase shifter, etc.

FIG. 2 gives the general diagram of the distributor of the invention, limited to two dividers, D (i - 1) and D (i), diagram on which we find the main secondary channels in B (i - 1) and B ( i), the other secondary routes in C. (i - 1) ... C _m (i - 1) and C (i) ... C _m (i), the primary routes A (i - 1) and A (i) and the phase shifters 0 (i -1) and Ø (i), designated by the same letter as the phase shift that they introduce on the primary branch on which they are mounted. A network of resistive elements, represented as such and left without reference for clarity, is used, in addition, as in the prior art as described with reference to FIG. 1. These elements connect the secondary pathways to the secondary pathway main, star in the case of the example, any other arrangement being possible within the framework of the invention. Finally each of the dividers introduces itself a phase shift which will be called Ø _D with the index of rank i as for the rest of the elements above.

The loads are mounted, as we have said, at the ends of the secondary branches, according to the distribution deemed best in relation to the use for which the distributor is intended. In the example of FIG. 2, these loads are distributed in a number equal to the output of the dividers; but any other distribution could be envisaged where the index m would not have the same value for all the divisors.

In operation, the device is first adjusted, including the phase shifters Ø (i), so that, for practically zero reflections in the secondary branches, the absorption is negligible in the resistive elements. When the charges on which are closed the secondary branches C are mismatched, and substantially all of the same quantity, the phase differences introduced between the outputs of the successive dividers cause the waves reflected in the main secondary channel B (i) and in the various secondary channels C (i ) are not in phase; a potential difference then appears between point a on the one hand and points b, c, d on the other hand, and an absorption of the power reflected in the resistive elements is made possible. Identical variations in load in the branches of the distributor are thus possible without interfering with operation, contrary to what takes place in devices of the same kind of the prior art.

, entre A et la voie secondaire principale B du dernier diviseur, les autres branches secondaires étant toutes reliées à d'autres charges ; ou bien toutes les branches secondaires du dernier diviseur, y compris la voie secondaire principale, sont reliées directement à des charges : voir figures 3 et 4 où toutes les autres voies secondaires sont désignées de façon indistincte par C.The structure is completed (i = n) by connecting the main track to a load. Two assemblies are possible: either we introduce a phase shifter Ø ≠ 0, preferably as in the above

, between A and the main secondary path B of the last divider, the other secondary branches all being connected to other loads; or all the secondary branches of the last divider, including the main secondary channel, are directly connected to loads: see Figures 3 and 4 where all the other secondary channels are indistinctly designated by C.

The distributor of the invention appears as a progressive structure composed of a succession of phase dividers offset from one another.

We spoke of phase in what precedes; it should of course be specified that, so that in the absence of reflections in the lines, no current flows in the resistive elements, there must also be an amplitude relationship between the voltages appearing at the insertion points a, b, c, and d; this relation is P _o R ₀ = P _(i) R _(i) (1) if R _(i) and R _a denote the characteristic impedances of the main secondary line and that of all the other secondary lines, and P _(i) and P _o the high frequency powers in these lines.

We now come back to the phase shift. The total phase shift between a secondary branch C (i) and a secondary branch C (i - 1) is 0 (i) + Ø _D (i) with the previous notations.

.The phase shift will obviously only be effective if this sum differs from k ', which is always easily achieved. We can take in particular

.

The reflected power is, in this case, absorbed in the resistive elements, and one can make so that a collective mismatch of the charges has no influence on the reflection coefficient at the input, on the left of the figure 2, which is that of using the distributor as a divider, for a source whose power arrives in the direction of the arrow.

This characteristic is particularly advantageous in the case where the payloads are transistors used for amplification over a wide bandwidth. We know, in fact, that the gain of a transistor decreases by about 6 dB per octave depending on the frequency. At the lowest frequencies in the range, there is therefore a gain gain and the input power should be reduced accordingly. This is achieved either by introducing selective losses into the input circuit, or by voluntarily mismatching at the bottom of the band. The latter solution is the simplest, but it is necessary to absorb the power thus reflected. The structure according to the invention makes it possible to obtain this result in a particularly simple manner even in the case of a large number of transistors and over a wide bandwidth. Individual mismatches are also absorbed in the same way as in a phase divider.

Reference has hitherto been made mainly to the structure of the invention in its use as a power divider. Of course, the same structure can be used as a power recombiner provided that the different power sources have suitable relative phases. This condition can be ensured, in the case of an amplifier, by means of a distribution of the input powers by a divider of the same type. Two distributors of the invention will then be used, one acting as a divider and the other as a recombiner. FIG. 5 shows an exemplary embodiment thereof in the micro-band technique. The view represented is a view in plane of the useful part of the insulating substrate 10 on which the transmission lines are made by linear conductors applied to this substrate, coated with metal on its opposite face. It is an amplifier device for microwave with four active distributed elements consisting of four transistors T ₁ , T ₂ y T ₃ and T ₄ .

These separately manufactured elements are, in the example, attached to the substrate.

The example in the figure implements two distributors of the invention as described above, designated as a whole by I and II; the first of them operates as a power divider to the four transistors T ₁ to T ₄ from a source not shown, located at the entrance to part I (arrow), and the second as a recombiner of the powers of output of these four transistors. Each of them has three phase dividers, such as D (i) of the previous diagrams, with two secondary branches each, including the main secondary branch (m (i) of the preceding diagrams is therefore here equal to 1), and a terminal line.

For the set I, these dividers carry marks D as in the above and consist of lines (1,7), (2,6) and (3,5) as shown in the drawing; the terminal line 4 is charged by the last transistor; the drawing shows the location of the resistive elements without mark. Similar benchmarks are assigned to Set II, with the changes necessary to avoid confusion. The recombined power comes out in the direction of the arrow.

par l'emploi de lignes 1, 2, 3, 4 de longueurs égales à un quart d'onde pour la fréquence centrale on à ici Ø(i) = O car pour chaque diviseur le point B(i - 1) du schéma de la figure 2 est confondu avec le point A(i) : points u, v, w sur la figure ; les impédances caractéristiques de ces lignes sont toutes de 50 ohms ; celles des lignes 5, 6 et 7 sont au contraire inégales entre elles et sont choisies respectivement de 50, 25 et 16,6 ohms pour satisfaire à la condition (1).The phase shift Ø (i) + Ø _D (i), is chosen in the example equal to

by the use of lines 1, 2, 3, 4 of lengths equal to a quarter wave for the central frequency we have here Ø (i) = O because for each divider point B (i - 1) of the diagram of Figure 2 is confused with point A (i): points u, v, w in the figure; the characteristic impedances of these lines are all 50 ohms; those of lines 5, 6 and 7 are, on the contrary, unequal to one another and are chosen respectively from 50, 25 and 16.6 ohms to satisfy condition (1).

It often happens, however, that the impedances of the active elements, such as TT ₂ T ₃ T ₄ , are very low (a few ohms) and that the adaptation to 50 ohms is difficult. Figure 6 gives a variant of the arrangement of the previous figure particularly suitable for this case, in which, in each divider, an impedance transformer is provided on the secondary branch, as shown in the drawing, where these transformers carry the marks t t2 t ₃ ; each of them has a second line 01, 02, 03 coupled to the secondary lines 1, 2 and 3.

FIG. 7 shows, also in micro-band technique, another example of application of the distributor of the invention, to the addition of the powers of several negative resistance diodes; the variant of the figure uses impedance transformers as described with reference to the previous figure.

The output power is collected in the direction of the arrow on a frequency fixed by a "locking" signal using a circulator (curved arrow), frequency of the order of 10 to 20 gigahertz for example.

In the figure the diodes bear the marks d d2 d ₃ d ₄ ; those of the other elements, without designation, are easily deduced from the preceding figures.

We have described above embodiments applied to four active elements; it goes without saying that these examples are not limiting, the number of these elements being able, within the framework of the invention, to exceed this value or to be inferior.

Another application of the distributor of the invention consists in the repeated use of dividers, recombiners, DR ₁ D ₂ ... R ₃ connected in series. FIG. 8 shows a particularly simple example, where each of the dividers and recombiners has only two branches, and where each recombiner and the divider which follows it are directly linked together. The example shows a three-stage amplifier with two transistors each; the gain in decibels is multiplied by the number of stages between input and output (arrows). An advantage of the structure shown is to reduce the minimum necessary impedance transformations.

In the embodiments in solid state of the distributor of the invention given above, lines have been shown in the form of strips deposited on a substrate. It will be noted that these lines could, in the context of the invention, be replaced by cells with localized elements - self-inductances and capacities - band-pass, low-pass or high-pass type, as shown in the diagram of the Figure 9, where these elements have been left unmarked; on the other hand, we have reproduced on this figure the reference points necessary to enable the correspondence to be drawn between this one and the diagram of figure 2. Each of the cells is one of the divisors of this figure. The part of the figure to the left of point A is an impedance adapter, and the part to the right of point B 2 is a terminal line. All secondary lines are designated by the same letter C.

In addition, it has been recognized that in a hybrid form the active elements are diodes or transistors attached to the substrate; within the limits of the invention, these elements could be integrated into the substrate.

The invention also includes, on the contrary, the case of embodiments by conventional means, other than those of the solid state, both with regard to the active elements and the transmission elements.

Claims (8)

1. Radio power distributor, for the division of power between a channel and several other channels and the recombination of the powers of several channels, in the same channel in a given operating frequency band, characterized in that it comprises several dividers (D (i)), each comprising a single channel (A (i)) dividing into several channels called secondary channels, connected in cascade, each connected to the next by one of these secondary channels, called main secondary channel (B (i )), and in that the other secondary channels (C (i) ... C (i)) are each connected by a dissipative element at the same given point (a) of the main secondary channel, the said distributor ensuring in particular the division of a radio power applied to the single channel of a first divider into partial powers, in particular substantially equal, collected in loads connected to the ends of the non-main secondary channels, or the recombination of pu transmissions, in particular substantially equal, applied to the secondary channels, in a power collected in the single channel of the last divider. 2. Radio power distributor according to claim 1, characterized in that it comprises a phase shifter (Ø (i)) mounted in the single channel of at least one of the dividers. 3. Radioelectric device for the recombination of the powers of n generators, characterized in that it comprises a distributor according to claim 1, comprising n - 1 dividers with two secondary channels, the first divider having one of the secondary channels connected to the 'one of the generators through a phase shifter. 4. Radioelectric device for the division of a power into n partial powers, characterized in that it comprises a distributor according to claim l, comprising n - 1 dividers with two secondary channels, the last divider having one of its channels secondary connected to one of the loads through a phase shifter. 5. Radio device for power division amplifiers, and for the recombination of the output powers of these n amplifiers, characterized in that it comprises a first distributor according to claim 4, the charges of which are constituted by the inputs of the amplifiers, and in that it comprises a second distributor according to claim 3, the generators of which consist of the outputs of the amplifiers. 6. A radio power distributor according to claim 4, in particular for microwave frequencies, characterized in that, the said distributor being produced according to micro-band technology, using linear conductors placed on one of the faces of an insulating substrate coated with metal on its opposite face, the dividers consist of U-shaped conductors (1,7) (2,6) (3,5) aligned, the bottom of a U (U, V, W) being located at height from the end of the branches of the preceding U and its upper branch in the extension of the lower branch of the latter and in contact with it, these branches all having a length substantially equal to a quarter of the length of the wave corresponding to the central frequency of operation, and in that the lower branch of the last divider is extended by a terminal line of length substantially equal to a quarter of this wavelength. 7. A radio power distributor according to claim 6, characterized in that it comprises additional linear conductors (O ₁ , O ₂ , O ₃ ) arranged parallel to the upper branches of the U and of the terminal line, and in their vicinity, constituting with them impedance transformers (t _j yt ₂₁ t ₃ ), and in that the charges are connected to these additional conductors at the end of the branches of the U's and of the end of the terminal line. 8. Multistage radio amplifier, characterized in that it comprises, arranged in series, several devices according to claim 5.

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