EP0320404B1 - Helix-type antenna and its manufacturing process - Google Patents

Abstract

The antenna comprises at least one radiating wire (11, 12, 13, 14) wound into a helix following a body of revolution (1). The antenna comprises a supply circuit (2) for the radiating wire(s) which consists of a transmission line of the strip line type (20), which ensures both the function of distribution of supply and of matching of the radiating wires of the antenna. <??>Application to the construction of circularly polarised radiating antennas for satellite telecommunications, radiolocation. <IMAGE>

Description

The invention relates to a helix-type antenna and its manufacturing method.

The propeller type antennas have the advantage of radiating an electromagnetic wave in good quality circular polarization over a wide coverage and with an emission lobe possibly formed.

These characteristics make them interesting in many fields of use, and in particular, in the case of ground / satellite links with scrolling or mobiles / geostationary relays.

. rd et chaque brin est alimenté à partir d'un signal présentant un déphasage angulaire successif relatif égal à $\frac{\text{π}}{\text{2}}$

. Pour un brin rayonnant 1 alimenté avec un signal de phase relative nulle, notée 0° sur la figure 1a, les brins rayonnants notés successivement 2, 3, 4 sont alimentés avec des signaux de même amplitude A mais de phase successive relative à -90°, - 180°, - 270°.However, this type of antenna generally comprises four radiating strands which it is necessary to supply according to laws of adequate amplitude and phase. As shown in FIG. 1a, the four radiating strands are wound on a circular sleeve with a pitch p, along a guideline of the sleeve, corresponding to an angular offset of $\frac{\text{<figure-callout id="2" label="π" filenames="imgf0003.png" state="{{state}}">π</figure-callout>}}{\text{2}}$

. rd and each strand is supplied from a signal having a relative successive angular phase shift equal to $\frac{\text{<figure-callout id="2" label="π" filenames="imgf0003.png" state="{{state}}">π</figure-callout>}}{\text{2}}$

. For a radiating strand 1 supplied with a zero relative phase signal, denoted 0 ° in FIG. 1a, the radiating strands noted successively 2, 3, 4 are supplied with signals of the same amplitude A but of successive phase relative to -90 ° , - 180 °, - 270 °.

In order to supply these antennas, various solutions have been proposed to date.

According to a first solution, as represented in FIG. 1b, the excitation is done firstly through a hybrid coupler which separates the energy into two equal-amplitude channels and phase shifted relative to each other by 90 ° . A double balun, housed in the axis of the antenna, makes it possible to pass, for each of the two channels, from the coaxial line to the diametrically opposite strands. The latter are therefore supplied by equal amplitudes and in phase opposition. Using a compensated balun allows the operating frequency range of the antenna to be adjusted.

According to a second solution, as shown in FIG. 1c, as in the case of FIG. 1b, a hybrid coupler makes it possible to separate the energy into two equal-amplitude channels and in phase quadrature.

The energy is then conveyed to the supply point by two of the radiating strands which are, in fact, made up of coaxial cables then it is distributed at equal amplitudes and in phase opposition between the diametrically opposite strands, some connected to the cores of the coaxial, the others formed by the external part of the shielding of the coaxials themselves.

This solution has, compared to the previous one, according to FIG. 1b, the advantage of eliminating the central balun, on the other hand its frequency characteristic is narrower due to the absence of any adjustment.

According to a third solution, as shown in FIG. 1d, the coaxial supply line is split at its end to constitute a balun. The distribution of the energy in quadrature between the two bi-helices is carried out by adjusting the length, therefore the reactance, of the radiating strands.

This solution advantageously makes it possible to eliminate the hybrid coupler, but it requires a delicate adjustment of the length of the strands. In addition, these being of different lengths, the geometry of the antenna no longer exhibits symmetry of revolution and the production of the antenna is more complex.

According to a fourth solution, as shown in FIG. 1e, the simplest solution from a theoretical point of view, the four radiating strands are supplied from a distributor.

These distribution circuits are made up of discrete elements which it is necessary to connect to the antenna by four connections and it is sometimes difficult to adapt this solution to the geometry of the antenna.

In all the aforementioned cases, the other end of the strands, relative to the end constituting the feed point, is either in open circuit with then a length of strands equal to an odd whole number of quarter wavelengths, or a short circuit with a length of strands equal to an integer number of half-wavelengths. In practice, a true open circuit is impossible to achieve, unlike a good short circuit. This is why the four strands are generally short-circuited together at the end opposite to the supply point, this short-circuit being produced in the form of a cross as shown in FIG. 1f.

The object of the present invention is to remedy the aforementioned drawbacks by using a particularly simple helical antenna structure.

Another object of the present invention is the implementation of a helix type antenna of particularly reduced weight and size.

Another object of the present invention is the implementation of a helix type antenna with very high reproducibility of radiation pattern characteristics.

Another object of the present invention is finally the implementation of a method of manufacturing a helix type antenna, particularly simple and very easily adaptable on an industrial scale with very high reproducibility and automation qualities.

The antenna of the helix type, object of the invention, comprises at least two radiating strands wound in a helix according to a form of revolution. It is remarkable in that it comprises a supply circuit, of said radiating strands, constituted by a transmission line of the ribbon line type ensuring both the power distribution function and the adaptation of the radiating strands of the 'antenna.

The method of manufacturing a helix-type antenna in accordance with the subject of the invention is remarkable in that it consists in cutting a flexible double-sided printed circuit sheet with the corresponding dimensions of a sleeve of revolution, on said printed circuit, to delimit a first zone intended to contain said ribbon line and a second zone intended to contain said radiating strands, on a first face of the printed circuit, to remove metallization at said second zone, said metallization being maintained over the whole of the first zone to constitute said reference propagation plane, on the second face of said printed circuit, to be formed by removal of material, at the level of the second zone, on the one hand , from said metallization in defined zones, said radiating strands and said annular conductive zone, and at the level of the first zone on the other hand, a conductive zone forming with said reference propagation plane said strip line, for winding the sheet of printed circuit, side of the reference propagation plane or strand side on the sleeve, the radiating strands being suitably oriented.

The invention finds application in the manufacture and realization of antennas of the propeller type used in ground / satellite telecommunication links with scrolling or mobiles / geostationary relays, and in radiolocation.

• la figure 2a représente, en développé, une antenne de type hélice conforme à l'objet de la présente invention,
• la figure 2b représente une vue de face d'une antenne conformément à l'objet de l'invention,
• la figure 2c représente une coupe selon le plan de coupe AA de la figure 2a,
• la figure 2d représente un détail de réalisation de la figure 2a,
• la figure 3 représente en a), b), c), d), les différentes étapes d'un procédé de fabrication d'une antenne conformément à l'objet de l'invention,
• la figure 4 représente un mode opératoire avantageux de mise en oeuvre du procédé de la figure 3,
• la figure 5a représente un circuit imprimé développé à plat permettant la mise en oeuvre d'une antenne de type hélice de forme conique,
• la figure 5b représente une antenne de type hélice de forme conique obtenue à l'aide du circuit imprimé de la figure 5a.

It will be better understood on reading the description and on observing the drawings below in which, in addition to FIGS. 1a to 1f relating to the prior art,

• FIG. 2a represents, in the developed, a helix type antenna in accordance with the object of the present invention,
• FIG. 2b represents a front view of an antenna in accordance with the object of the invention,
• FIG. 2c represents a section along the section plane AA of FIG. 2a,
• FIG. 2d represents a detail of embodiment of FIG. 2a,
• FIG. 3 represents in a), b), c), d), the different stages of a method of manufacturing an antenna in accordance with the subject of the invention,
• FIG. 4 represents an advantageous operating mode for implementing the method of FIG. 3,
• FIG. 5a represents a printed circuit developed flat allowing the use of a conical-shaped helix-type antenna,
• FIG. 5b represents an antenna of the helical type of conical shape obtained using the printed circuit of FIG. 5a.

The antenna object of the invention is a helix type antenna comprising at least two radiating strands wound in a helix according to a form of revolution.

It will first be described in connection with Figures 2a, 2b and 2c, the shape of revolution being cylindrical.

According to the aforementioned figures, the helix type antenna according to the invention comprises at least two radiating strands denoted 11, 12, 13 or 14 wound in a helix in a circular shape around a sleeve 1 for example. In FIG. 2a, which shows the antenna in developed form according to a particular embodiment of the invention, there is shown in dotted lines the sleeve 1 on which the antenna is normally wound to constitute the antenna actually obtained as shown in Figure 2b.

According to a particularly advantageous characteristic of the antenna of the propeller type which is the subject of the invention, it comprises a supply circuit denoted 2 by the radiating strands. This circuit consists of a transmission line of the ribbon line type denoted 20. The ribbon line 20 performs both the power distribution function and the impedance matching of the radiating strands of the antenna.

In the particular embodiment represented in FIGS. 2a, 2b and 2c, the helix-type antenna object of the invention comprises four radiating strands denoted 11, 12, 13 and 14. Each radiating strand is constituted by a metallized zone in shape of strip wound in a helix on the lateral surface of the sleeve 1. Each strip constituting the radiating strands 11, 12, 13 and 14 is spaced from the next along a guideline of the sleeve 1 by a determined distance P. Thus, as shown in FIG. 2b, the radiating strands are inclined at an angle α with respect to any guideline of the sleeve 1 and are thus wound in a helix.

According to an advantageous characteristic of the supply circuit 2, the transmission line 20 constituting the latter can advantageously be constituted by a meander line denoted 200 in FIGS. 2a and 2b. Each radiating strand 11, 12 13 and 14 is at its supply point denoted 110, 120, 130, 140 or entry end, connected in electrical contact with the strip constituting the meander line 200. According to an advantageous characteristic of the antenna feed circuit object of the invention, the electrical distance on the meandering line between two entry points of two consecutive radiating strands, entry points such as 110, 120, 130 and 140 is equal at an odd multiple of quarter wavelength of the transmit-receive signal propagating in the ribbon line under consideration.

Under these conditions, and in particular in the case where the odd multiple of quarter-wavelengths is equal to 1, each feed point or entry point 110, 120, 130 and 140 of the radiating strands 11, 12, 13 and 14 is supplied by signals of equal amplitude, respectively phase-shifted by π / 2 rd, that is to say in the supply conditions as shown in FIG. 1a.

The adaptation function of the radiating strands can advantageously be achieved by the use of line sections 201, 202, 203, 204, of variable width, thus constituting the line 20, as shown in FIG. 2d, and by the sections 110 to 112 , 120 to 122, 130 to 132 and 140 to 142 of the radiating strands.

According to another advantageous characteristic of the helix-type antenna object of the invention, the end of the strands opposite the input ends 110, 120, 130, 140, end noted 111, 121, 131, 141 in FIGS. 2a and 2b is advantageously connected in short circuit to the same annular conductive zone 100. As will be easily understood, depending on the phase conditions of the supply signal at the input point 110, 120, 130, 140 of each radiating strand 11, 12, 13, 14, one end of one of the radiating strands 111, 121, 131, 141 is necessarily short-circuited, that is to say with an amplitude of field electric zero and all opposite ends 111, 121, 131, 141 by the connection to the conductive area, are thus short-circuited. The annular conductive zone 100 thus imposes a short circuit on the end of the four radiating strands 11, 12, 13 and 14.

As has also been shown in Figure 2c, in a section along the section plane AA of Figure 2a, the ribbon line 200 constituting the supply circuit 2 comprises a sheet of dielectric material 2000, of which a first face intended to be applied to the lateral surface of the sleeve 1 is entirely metallized, to constitute a reference propagation plane denoted 2001. A second face of the sheet of dielectric material 2000 opposite the first face comprises a metal strip 2002, forming with the first metallized face 2001, the ribbon line 20.

As has also been shown in FIG. 2c, and in a particularly advantageous manner, the supply circuit 2 constituted by a ribbon line 20, radiating strands 11, 12, 13 and 14 and the annular conductive zone 100 short circuits are formed on the same sheet of dielectric material.

FIG. 2b shows a front view of the antenna obtained after mounting, that is to say after winding of the sheet of dielectric material 2000, provided with its various conductive zones around the sleeve 1.

A method of producing a helix-type antenna in accordance with the object of the invention will be described in conjunction with FIGS. 3 and 4, and in particular with FIG. 3 at points a, b, c, d, of that -this.

In order to produce on an industrial scale an antenna of the helix type in accordance with the object of the invention, the production method may consist, as shown in point a) of FIG. 3, of cutting a sheet 10 of printed circuit flexible, double-sided, the double-sided being denoted 101, 102 and provided with a metallization, with the corresponding dimensions for a cylindrical sleeve 1 of given dimension. Of course, the printed circuit sheet may be constituted by a sheet of high quality, of which the sheet of dielectric material 2000 consists for example of a sheet of plastic material such as kapton or polytetrafluoroethylene reinforced with glass.

As also represented in point a) of FIG. 3, the method can then consist in delimiting on the printed circuit sheet 10 a first zone denoted I intended to contain said ribbon line and a second zone denoted II intended to contain the radiant strands.

As shown in FIG. 3 in point b) thereof, the embodiment then consists in removing on a first face of the printed circuit 10, in particular at the level of the second zone denoted II, the metallization 101 for example, this same metallization 101 being maintained over the entire first zone of the same face to constitute the reference propagation plane noted 2001.

As has also been shown in point c) of FIG. 3, the embodiment then consists in forming by removing material on the second face of the printed circuit 10 at the level of the second zone on the one hand, of the metallization 102, according to determined zones, the radiating strands 11, 12, 13 and 14 and the annular conductive zone 100. In the same way, at the level of the first zone on the other hand, a conductive zone is then formed constituting with the reference propagation plane 2001, the ribbon line 20. The aforementioned conductive zone can then be constituted by a conductive zone denoted 200 constituting the meandering line.

As shown in point d) of FIG. 3, the sheet thus obtained in FIG. 3c, provided with its various conductive zones, is then wound on the sleeve 1, the side of the reference propagation plane 2001 or the strand side being pressed against the lateral surface of the sleeve 1. The sleeve can then be withdrawn or not. Of course, the radiating strands 11, 12, 13 and 14 are suitably oriented.

The different steps shown in Figure 3 at points a, b, c,) thereof, are conventionally advantageous, carried out by masking, exposure and chemical attack. Of course, the step shown in point c of Figure 3 can advantageously be achieved by means of a single mask.

Advantageously, the step consisting in cutting the flexible printed circuit sheet 10 double-sided with the corresponding dimensions of the cylindrical sleeve 1, can advantageously be carried out by stamping from an appropriate cutting tool.

As has also been shown in FIG. 4, advantageously, the cutting of the double-sided printed circuit sheet 10, with the dimensions corresponding to those of the sleeve 1 may consist, for example, of cutting the aforementioned sheet along a contour whose shape corresponds to that of a rectangle whose length L corresponds to the perimeter of the section of the sleeve 1, and whose width 1 has a determined value. In addition, this shape includes a parallelogram superimposed on the aforementioned rectangle. This parallelogram includes a small side noted a, which corresponds to the length L of the aforementioned rectangle, and whose height h is such that the width 1 of the rectangle increased by the height h of the parallelogram is equal to the height H of the sleeve 1, thus that it has been represented in FIG. 4, the sleeve 1 of substantially corresponding dimension being represented in line with the cut out printed circuit sheet. Of course, the angle of the parallelogram corresponds to the helical winding angle of the radiating strands on the sleeve 1, the radiating strands 11, 12, 13 and 14, then being formed, as described above, parallel to the corresponding sides of the above parallelogram.

After winding the antenna, it is necessary to ensure the electrical contact of the ends 101, 102 of the annular zone 100 by welding or riveting or bonding with a conductive adhesive. A suitable connector 30 can then be put in place at the end 25 of the line 20 by a conventional technique, such as screwing, clamping, welding or gluing.

The propeller type antenna object of the invention may also, as shown in Figures 5a and 5b, include at least one strand radiating 11, 12, 13, 14 wound in a helix according to a form of conical revolution.

In Figure 5a, there is shown the flat developed form of the printed circuit, which corresponds to the conical sleeve used.

The process which is the subject of the invention in its various stages of etching the supply circuit 200, the radiating strands 11, 12, 13, 14 and the possible final short circuit 100 can, of course, be applied to any antenna of developable shape and, in particular, with conical helix antennas.

Compared to cylindrical antennas, the latter have lower circular polarization of better quality and lower radiation on the connector side. On the other hand, their bulk is greater, at equal frequency, and the developed circuit has a more complex shape, as indicated in FIG. 5a.

The production method differs from that of cylindrical helix antennas only in the particular shape of the developed circuit, and in the shape in which it is wound.

A helix type antenna and its embodiment on an industrial scale have thus been described, which is particularly advantageous. Indeed, due to its design, the antenna object of the invention has a very high degree of reproducibility in its mechanical and electromagnetic characteristics. In addition, due to the design of the propeller-type antenna that is the subject of the invention, an implementation and production method has been defined, which allows production of this type of antenna on an industrial scale with very high reliability criteria.

Claims (12)

1. A helical type antenna comprising at least two radiating cords (11,12,13,14), helically wound in a rotational shape (1), wherein said antenna has a circuit (2) to supply said radiating cords, formed by a strip line type of transmission line (20), performing both the power distribution function and the function of matching the radiating cords of the antenna.
2. A helical type antenna according to claim 1, wherein said rotational shape (1) is cylindrical or conical.
3. A helical type antenna according to claim 2, comprising four radiating cords (11,12,13,14) each formed by a metallized zone in the form of a strip, helically wound on the lateral surface of the sleeve, said strip being distant from the next strip, along a directrix of said sleeve, by a defined distance p, said transmission line (20), forming a supply circuit being formed by a meandering line (200).
4. A helical type antenna according to claim 3, wherein each radiating cord (11,12,13,14) is, at its supply point (110,120,130,140) or incoming end, in electrical contact with the strip (200) forming the meandering line, the electrical distance on the line between the two incoming points of two consecutive radiating cords (110,120,130,140) being equal to an odd-numbered multiple of quarter wavelengths of the transmission/reception signal.
5. A helical type antenna according to any one of claims 1 to 3, wherein the end (111,121,131,141) of each cord opposite to the corresponding incoming end (110,120,130,140) is connected in a short circuit to one and the same ring-shaped conducting zone (100).
6. A helical type antenna according to any one of the preceding claims, wherein said strip line (200) forming the supply circuit has a sheet of dielectrical material, of which a first face designed to be applied to the lateral surface of the sleeve, is entirely metallized to form a reference propagation plane (2001) and of which a second face, opposite to the first face, has a metallic strip (2002) forming said strip line with the first metallized face.
7. A helical type antenna according to any one of the preceding claims, wherein said supply circuit formed by a strip line (20) of said radiating cords (11,12,13,14) and the ring-shaped conducting zone (100) in short circuit are formed by one and the same sheet of dielectrical material.
8. A method of manufacturing a helical type antenna according to any one of claims 1 to 7, consisting in :

   a) stamping a double-sided (10), flexible printed circuit sheet (101,102) with dimensions corresponding to a sleeve of a rotational shape, on said printed circuit;

   b) demarcating, on said printed circuit, a first zone (I) designed to contain said strip line and a second zone (II) designed to contain said radiating cords;

   c) removing said metallization at the level of said second zone on a first face of said printed circuit, said metallization being kept on the entire first zone to form said reference propagation plane (2001);

   d) forming, on the second face of said printed circuit, by the removal of material, firstly, at the second zone of said metallization in defined zones, of said radiating cords and of said ring-shaped conducting zone and, secondly, at the first zone, of a conducting zone, forming said strip line with said propagation reference plane (2001);

   e) winding the printed circuit sheet on the reference propagation plane side or on the side of the cords on the sleeve, these radiating cords being suitably oriented.
9. A method according to claim 8, wherein the steps (b) and (c) are accomplished by masking, insolation and chemical attack process.
10. A method according to any one of claim 8 or 9, wherein the step (c) is achieved by means of one and the same mask.
11. A method according to claim 8 wherein, said sleeve (1) being cylindrical, the stamping of the two-sided printed circuit sheet to the dimensions corresponding to that of the sleeve (1) consists in stamping said sheet along a contour, the shape of which corresponds to that of a rectangle with a length (L) corresponding to the perimeter of the section of the sleeve (1), and with a width (1) of a defined value, a rectangle on which there is superimposed a parallelogram, the small side of which, marked a, corresponds to the length (L) of the above-mentioned rectangle and the height (h) of which is such that the width (2) of the rectangle plus the height (h) of the parallelogram is equal to the height (H) of the sleeve, the angle (α) of the parallelogram corresponding to the angle (α) of the helical winding of the radiating cords.
12. A method according to any one of claims 8 to 10, wherein said sleeve (1) is conical.

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