WO2012131126A1

WO2012131126A1 - Daisy antenna for the emission and reception of linearly and circularly polarized electromagnetic waves

Info

Publication number: WO2012131126A1
Application number: PCT/ES2012/070123
Authority: WO
Inventors: Juan LLABRES FOYO; Juan Vassal'lo Sanz; Jorge Caravantes Tortajada; Ángel MEDIAVILLA SÁNCHEZ; Antonio TAZÓN PUENTE
Original assignee: Consejo Superior De Investigaciones Científicas (Csic); Universidad De Cantabria; Universidad Complutense De Madrid
Priority date: 2011-03-29
Filing date: 2012-02-28
Publication date: 2012-10-04
Also published as: ES2395429A1; ES2395429B1

Abstract

The invention relates to an antenna formed by the coplanar grouping of an even number of radiating wires which together form a shape similar to the petal distribution of a daisy (see figure 1). The radiating wires or petals of the daisy antenna work by resonance and have a flat geometry, as well as all having the same structure and being in the same plane, referred to as the antenna plane. The only difference between the petals is in the relative distribution of the current flow directions, which determines the form of the radiation diagram and characterizes the behavior of the antenna, in order to allow users a wide range of applications.

Description

MARGARITE ANTENNA FOR EMISSION AND RECEPTION OF LINEAR AND CIRCULARLY POLARIZED ELECTROMAGNETIC WAVES FIELD OF THE INVENTION

The present invention belongs to the sector of transmitting and / or receiving antennas, of electromagnetic signals, and more precisely it is related to the following sub-sectors of antenna technology: broadband antennas, electric and magnetic dipoles, radiating transmission systems and reception, antennas for communication systems, antennas for television signal receivers, antennas of low cost and visual impact, antennas for observation and surveillance systems, and antennas for frequency inhibiting systems.

STATE OF THE TECHNIQUE An antenna is an element or system designed and manufactured to receive or emit electromagnetic waves (EM). From an elementary point of view, the emission consists of transforming an electric potential difference, variable in time, applied to the metallic structure of the system in an EM wave train so that they propagate through the free space around. The opposite is the reception of EM waves. There are various forms and appearances of antennas, the simplest and best known is the dipole to capture the terrestrial television broadcast, the most complicated can be any of the extensive paraboloids used in radio astronomy to capture very weak signals coming from the confines of the universe. The various designs, and therefore their technical characteristics, depend on the specific application to which they will be reserved. The form and concept that the technician faces are decisive in the operating results of the antenna. In basic excess terms, everything lies in comparing the geometric dimensions of the emitting or receiving element and the wavelength to be emitted or captured. On the one hand, the demand made by the markets for new techniques both for broadcasting in the domain of radio waves and, also, on TV, as well as in the security sector, has long been demanding new increasingly complex designs of antennas to cover a number of new applications.

The basic ideas to be developed are presented in the book "Antennas: Theory and Practice", by Schelkunoff SA and Friis HT, published by Bell Telephone Laboratories, Inc., LCCCN 52-5083, 1952, and in the article "Ultrahigh-frequency loop antennas", by Andrew Alford and Arming G. Kandoian, published in AIEE Trans., 59, 1940, pp 843-848. In the first one, the models of the classic wire antennas are described in detail, such as dipoles, simple and folded (folded dipols), as well as antenna systems that generate an omni-directional beam in a plane, with the electric field polarized in said plane. In the second it is worth mentioning the references to the "Alford loops" or Alford circles, as the first example of complex systems. A manual with more general descriptions about wire antennas and clusters in general, would be the book by Stutzman WL and Thiele GA "Antenna Theory and Design", published by John Wiley & Sons, ISBN 0-471-0448-X, 1981.

In the design of these elements or devices, the parameter to be taken into account is the radiation diagram, that is, the representation on a graph, depending on the direction, of the intensity of the EM field. Other parameters to consider are: bandwidth, which is the frequency range in which certain characteristics on directivity or gain are met. Likewise, the width of the radiation beam and the polarization of the emitted or captured signal are to be considered (PH Smith, "Cloverleaf Antenna for FM broadcasting", IRE Proc. 35, December 1947, 1556-1563, although the latter is illustrated and explained in Schelkunoff's book, on page 504 and following). In this reference, there is a flat antenna formed by 4 turns that generate an omnidirectional beam with the linearly polarized electric field in the plane of the antenna, specifically designed for a specific application that was novel because of the advantages offered at the end of the 40s. In this article it is mentioned that the "Cloverleaf Antenna" (Clover Antenna) can resolve in a fast and natural way the perverse influence of the environment, especially snow and frost.

In the book of FH. Jasik, "Antenna Engineering Handbook", Me Graw HUI, I edition of 1961 (rather than later), speaks of "tripole radiator" consists of a flat array of three dipoles which also has an omni-directional beam similar to of the "Cloverleaf Antenna". In the communication by J. Vassal'lo, "Low profile radiator with horizontal polarization on the horizon", presented at the X National Symposium USSR 95, Valladolid 1995, pp 743-746, the same 3-dipole radiator is presented in circular made by photogravure techniques. In these references, different technologies on circular groupings of 3 electric dipoles are mentioned, as well as 4 turns to achieve the same objective: an omni-directional diagram with the linearly polarized electric field and contained in the antenna plane. In none of these references is anything cited that another flat distribution of currents could generate other types of diagrams, both in the case of dipoles and in turns.

The applications, more and more exclusive on demand from the technical markets, have moved from the simplest antenna, such as the dipole or the spire, to more complex ones. In the article "Satellite communication with moving vehicles on Herat: two prototype circular array antennas", published in the journal Micro waves and Optical Technology Letters, vol 39, ni, ppl4 - 16, 5 October 2003, the authors F. Ares, G Franceschetti, J. Mosig, S.Vaccaro, J. Vassal'lo and E. Moreno, present a flat and circular grouping of 8 microstrip radiators that generates a conical beam in circular polarization for use in communications between mobile phones via satellite. This grouping provides the possibility of pointing for elevations between 35 ° and 55 ° above the plane of the antenna.

In this case, in addition to the polarization must be circular, the required radiation pattern requires that its omni-directional character be defined according to the trace defined by the generator of a cone, so that for a mobile, located in a position of latitude determined on the earth's surface, the connection with a geostationary satellite can be ensured regardless of the orientation of the mobile. For those 35 ° and 55 ° elevation mentioned above, the connection for a mobile that moves in the southern and central part of Europe would be ensured.

The circular polarization diagram is obtained as a result of the sum of the circular polarization diagrams of each of the 8 microstrip radiators. That is, the microstrip radiators themselves, individually, work in circular polarization. Extensive information on microstrip radiators and clusters of this type of radiators can be found in the books: "Microstrip Antennas" by I. Bhal and P. Bhartia, published by Artech House in 1980, and "Microstrip Antenna Design Handbook", by R. Garg , P. Bhartia, I. Bahl and A. Ittipiboon, published by Artech House in 2001, ISBN 0-89006-513-6. Circular polarization can be obtained from radiant elements that work in linear polarization, by what is called "sequential rotation." This consists of distributing the elements sequentially (every 3607n for n elements), on a circle, rotated and offset that same amount, as can be seen in "3. Improvement of the co-cross polarization ratio" by J. Barbero and J. Vassal'lo, in the "Contribution from Spain" chapter of the "Final Report of the COST 223 - Antennas in the 1990s, Active Array Antennas Future Satellite and Terrestrial Communications", edited by the European Commission, Directorate General XIII : Telecommunications, Information Market and Exploitation of Research, Brussels, 1995. This technique for generating circular polarization is sufficiently known and valid, but is only applicable when the pointing direction coincides with the zenith of the antenna, that is, it is perpendicular to the plane defined by the circular grouping. In no case is the possibility of obtaining a conical beam in circular polarization mentioned, based on a sequential rotation of radiating elements in linear polarization.

Non-omni-directional diagrams in a plane but with a maximum radiation in a certain direction, can also be obtained with wire antennas, as is the case of the antenna defined by Podger in its US patent 6,255,998 Bl. This patent defines a radiating element called "Lemniscate Antenna Element" that provides a maximum of radiation with linear polarization, according to the direction perpendicular to the plane that contains the antenna.

This podger lemniscate antenna comes to have a configuration similar to Smith's "Cloverleaf Antenna", but with only 2 turns (Smith's has 4 turns), and with the essential difference that the current in the turns of the lemniscate circulates in the opposite direction, while the four turns of the Smith antenna have the same direction of rotation of the current. On the other hand, in the Podger patent as well as in a later one of the same inventor (US 6,469,674), the possibility of circularly grouping several lemniscate antennas, all with the same center or feeding point, to improve Some of the characteristics of the set.

As can be seen from the description of the lemniscata antenna presented by Podger in US 6,255,998 and US 6,469,674, it can be considered as the particular case of one of the daisy antennas object of the invention herein. In particular it would be the case of the daisy with only two petals, since in the invention of the daisy antenna of the present document, the number of petals only presents the restriction of being even (they can be 2, 4, 6 ...), and the petals they can have different flat geometries (not only the so-called "lemniscata curve"), they can also not be turns, but can be used as petals another type of radiating element, such as the classic dipole, microstrip radiators, or even waveguides open or finished in horn to increase its directivity. Nor in any of the two Podger patents mentioned, it is said that circular polarization can be obtained with two lemniscate antennas, placed one at 90 ° from the other, in the same plane, and with the turns λ / 4 away from the center of the pair of antennas, those of a lemniscata with respect to the turns of the other lemniscata antenna.

BRIEF DESCRIPTION OF THE INVENTION.

The present invention is an antenna constituted by the coplanar grouping of radiating wires whose assembly adopts a shape similar to the distribution of petals in a daisy (see figure 1).

The radiating wires or petals of the daisy antenna work in resonance, have flat geometry, all have the same structure and are contained in the same plane, called the antenna plane. The only difference between the petals is in the relative distribution of the current flow directions, which determines the shape of the radiation pattern and is essential in the characterization of the operating behavior of the antenna.

DETAILED DESCRIPTION OF THE INVENTION

The reason antenna of this invention patent and which we call "daisy" for simplification, is constituted by the coplanar grouping of radiant wires working in resonance, adopting a flower-like shape (see figures 1 and 2), and with a special distribution of currents by the radiating wires that determines and fully characterizes the behavior of the antenna.

The radiating wires or petals of the antenna, which in their most general configuration take the form of the contour of the petals of the flower, in addition to working in resonance, have flat geometry, are contained in the same plane, called the antenna plane, and placed at the same distance from the center of the antenna, where the antenna power and the circuit that distributes the signal to the petals.

The operating frequency band of the daisy antenna is in the range of microwaves and millimeter waves.

The radiating wires can be constituted by wires or conductive tubes, or they can also be manufactured by photogravure techniques, being constituted by photogravure tapes on dielectric substrate.

Layered configuration of the daisy antenna

In addition to the antenna power circuit (1), the elements that make up the antenna and that can be seen in figures 1 to 6, are: the radiating petals or wires (2), and the distribution circuit (3), formed by adaptation or balun, the splitter, and where appropriate the transmitter lines to carry the signal from the splitter to the petals, when they are located far from the center of the antenna. These elements, together with the antenna petals, are distributed in 3 flat layers parallel to each other, as indicated in Figure 3.

This layered distribution facilitates the design of the antenna and optimizes the symmetry of the antenna, to obtain the desired emission characteristics. Figure 3 shows the layered distribution, seen according to a cross section to the antenna plane. The petals (2) are located in the intermediate layer, while the metallizations of the signal distribution circuit are located in the upper and lower layers. The power of the antenna (1) connected to the center of the antenna, is perpendicular to the plane defined by the antenna, and is done by coaxial line, similar to the stem that supports a daisy flower. The metallisations of the coaxial power cable are electrically connected to the metallizations of the distribution circuit (upper and lower layers of the antenna).

Distribution circuit

It is one of the essential elements of the emitting or receiving device, because as will be seen in the description of the operation of the antenna, it defines the directions of circulation of the current in the petals. In the central area of the antenna is the signal distribution circuit, (3) in Figures 1 and 2, which is composed of:

• an adaptation circuit,

• a splitter that distributes the signal to each of the petals,

· And bi-filar lines (see (4) in Figure 4), which are used to carry the signal from the divider to each of the petals. These lines are necessary when the number of antenna petals is high, or the geometry of the petals requires it because of their size or configuration. Figure 4 shows a daisy antenna with the same number of petals as the antenna shown in Figure 1, but located farther from the center. That implies the existence of bi-filar transmission lines to carry the signal from the divider to each petal (3). In the case of Figure 4, there are therefore as many transmission lines as petals, and all those lines are exactly the same in cross section and length, so that they do not introduce differences in the response radiated by each petal, derived from providing different amplitude or phase.

Bi-filar lines are an integral part of the distribution circuit, together with the splitter and the adaptation circuit or balun.

The adaptation circuit can be adjusted by design, varying the capacity between the metallizations of the upper and lower layers, that is: varying their surface and / or the separation between layers, as well as using separators of different dielectric constant between them.

Petals

Petals are individual radiating elements, which work in resonance and are characterized in that their structure is based on conductive wires or tapes to produce a certain distribution of currents on which the radiation they produce depends.

The simplest structure is that of the electric dipole, but it can also take other forms, such as: • turns with circular, elliptical or polygonal geometry, both regular and irregular, any geometric shape that is the result of a mixture of those mentioned being valid, provided that the total length of the loop is a multiple of the wavelength, for that meets the condition of working in resonance.

• any geometric shape given by a mathematical function defined in a plane, and whose length is a multiple of the wavelength, so that it meets the condition that it works in resonance. The petals can take different forms of geometric curves, which converted into wires or conductive tapes can channel the electric current. They must also work in resonance, so their length must be a multiple of the wavelength.

It is therefore valid, also, to use double electric dipoles (also called folded dipoles), or even the classic electric dipole, as daisy antenna petals, since they are also conductive wire antennas in which their radiation pattern is characterized by the distribution of currents in the radiating element, thus presenting the particularity that by reversing the direction of the current flowing through them, a 180 ° offset is achieved in the phase of the radiated signal.

Figure 5 shows, for comparison, three two-petal daisy antennas with different geometric shapes each: petals similar to those in the antenna of Figure 2, folded dipoles, and the classic electric dipoles. Figure 6 shows a 6-petal daisy antenna, using electric dipoles as petals.

The radiating wires that shape the petals of the daisy antenna, can be constituted by wires or conductive tubes, or they can also be manufactured using photogravure techniques, being constituted by photogravure tapes on dielectric substrate.

Cassini ovals

Petals are radiant elements that are characterized by their current distribution. As described above, a petal can be, for example, a conductive thread. With a spiral shape and a spiral in its broadest sense is what is called in mathematical terms a Jordan curve, that is, any closed curve in the plane that does not cut itself. Examples of Jordan's curves arise from the so-called Cassini ovals. These are defined as the geometric place of the plane that fulfills that the product of the distances to two fixed points (the focal points of the curve), is a constant. These curves are defined by the expression in Cartesian coordinates: Í ...,,, 2, 2 ..2, - ... 2 ..: 2 - _XJ _ ..4 ¡A

[: + y) - ¿a \ x - y.! + = or where, a = b-k

Figure 7 shows the Cassini ovals for the most representative values of k: k = 1, and k> 1. The Cassini oval generated with k = 1, is the best known and is also called the lemniscate curve.

Cassini ovals are really pairs of curves (when k> l), symmetrical with respect to the center of coordinates, so they are valid for daisies antennas of even number of petals, but obviously they can also be used as isolated elements for the case of daisy antennae with odd number of petals.

Figure 8 shows a 6 petal daisy generated by Cassini ovals, using k = 1.1.

The ovals can be connected directly to the divider, or through power lines to connect them electrically to the divider, and thus move them away from the geometric center of the daisy antenna, similar to the case shown in Figure 4. Parameterizable analytical expressions of the petals

In order to automate the design process of the daisy antenna, it is useful to have analytical expressions that make it possible to explicitly determine the geometry of the petals, based on parameters of the design itself. In addition to the antenna design, the use of computer means for other and different purposes, such as the electromagnetic analysis of the antenna, the elaboration of manufacturing drawings, or even its use in the manufacturing and assembly processes.

Mathematically it is known that there are few geometries that can be expressed analytically explicitly, with respect to the following design parameters:

• the length of the curve (L)

• the central opening angle of the petal (2a)

Cassini's ovals do not admit analytical expression with respect to them, but nevertheless, some family of analytically parameterizable curves can be defined with a view to process automation. One of these families is that given by the following expressions:

being :: maíi (¾)

sienuo) and where t is a number belonging to the interval (-1, 1)

The expressions [1] explicitly give the coordinates of the petals, depending on the basic design parameters mentioned above:

· The length of the petal (L), which being the resonant petals, must be a multiple of the wavelength at the center frequency of the antenna's operating band

• the semi-angle (a) of opening of the petal, seen from its vertex The advantage of the expressions [1], is that they are compatible with any computer system of numerical calculation, and therefore are integrable in the process of analysis, design , drawing or manufacture of antennas. On the other hand, this same geometry admits a simpler form of expression in the case of α = π / 6

one

x (t, L, e): = ^ ^• L. (t ² - l) - cos (0) ^• Lt (t ² - l) -sin (e)

[2]

Y (t, L, 9): = ^ ^• L- (t ² - l) -sin (0) + Γ— -Lt- (t ² - l) -cos (Θ) where Θ is the angle that forms the axis of symmetry of each petal with the axis of abscissa.

Figure 9 shows the typical petal shape for α = π / 6 and θ = 0 ^or .

Since this particular geometry is for the case α = π / 6, it admits the classic representation of the 6-petal daisy shown in Figure 10.

Since the distribution circuit is located in the central area of the antenna, it is necessary to move the petals radially and outwardly a distance D from the center of the antenna, so that the geometry of the petals is given by the expressions: x (t, L, 0, D)

Y (t, L, e, D)

Figure 11 shows the definition of the parameters used in this new petal geometry, which is displaced from the center of the daisy by a distance D.

A simpler curve can be obtained, based on 2 lines and a circumference section, which is an approximation to that given by the expressions [3]. This new petal geometry is based on the use of the circumference that stops for three points: the outer end and the maximum and minimum points of the curve given by the expressions [3], and then draw the tangents to said circumference from the apex of the petal, located in the center of coordinates. Figure 12 shows the geometry of this new curve approximated to the petal of the expressions [3], and whose axis of symmetry is the axis of abscissa.

13-L

The circumference has a radius of value: V 15552

center is located at the abscissa point:

The tangent lines pass through the center of coordinates, and have a slope of:

Naturally, the slope of the tangents is independent of the length of the petal (value related to its operating frequency), and only depends on the central opening angle of the petal (2a), which in this case is fixed at π / 3.

Connections between layers and sense of current in the petals

The connections between the metallizations of the upper or lower layers and the petals are made by means of short-circuit paths between layers. In this way the ends of the petals are contacted with the signal distribution circuit, one end of the petal is connected to the upper layer and the other to the lower one. Depending on which of the ends is connected to one layer or another, so will the direction of the current flowing through the petal.

As stated in the definition of the daisy antenna, the relative direction of the currents flowing through the petals characterizes the operation of the antenna, and to obtain a maximum of the radiation pattern in linear polarization, in the direction perpendicular to the plane of the antenna, it is enough that:

• the antenna is made up of an even number of petals

• a line of symmetry for the currents of the petals must be defined in the antenna plane, which must be parallel to the direction of the electric field of the linear polarization sought

• the distribution of the currents in the antenna petals is done so that all the petals that are located on the same side of the line of symmetry, have the same direction of current flow, and logically, that direction is contrary to the current of those located on the other side of the line of symmetry.

Figure 13 shows the top view of the metallizations of the upper and lower layers of the 6-petal antenna of Figure 1. Said metallizations make up the distribution circuit (adaptation and divider). Figure 14 shows the distribution of currents in the petals of said antenna.

Figure 15 shows the top view of the metallizations of the upper and lower layers of the 6-petal antenna of Figure 4. Said metallizations make up the distribution circuit (adaptation, divider and bi-wire transmission lines). Figure 16 shows the distribution of currents in the petals of said antenna, distribution of currents that is identical to that shown in Figure 14. Figure 17 shows the top view of the metallizations of the upper and lower layers of the antenna 6 petals, whose petals are simple electric dipoles. Comparing this figure with figure 15, the different length of the feeding lines derived from the different size of the petals can be seen. Obviously, the line width depends on the value of the impedance of the petal.

Figure 18 shows the distribution of currents in the dipoles or petals of the antenna, and as can be seen said distribution of currents is identical to that shown in Figures 14 and 16 for the other 6-petal antennas. Figure 19 shows the top view of the metallizations of the upper and lower layers of the 2-petal antenna, whose petals are electric dipoles. Figure 20 shows the distribution of currents in the petals of said antenna. Comparing figures 18 and 20, it can be seen that this 2-petal antenna matches the central petals of the 6-petal daisy.

Daisy antenna for maximum radiation in circular polarization, in the direction perpendicular to the antenna plane

The circular polarization is obtained by interleaving two equal daisy antennas, rotated 90 ° to each other, to generate the orthogonal linear polarizations, and adding to one of the antennas the length of a quarter of the guided wavelength in the bi-filar power lines, to introduce the required 90 ° offset between polarizations.

Thus, to obtain a maximum of the circular polarization radiation pattern, in the direction perpendicular to the plane of the antenna, it is sufficient that the antenna is formed by two equal, coplanar and with the same feeding point superimposed on the same flat, with the following particularities:

• the lines of symmetry that determine the distribution of currents of each antenna must be orthogonal so that the polarization of the field radiated by each antenna is also.

• The antenna power is unique to the two daisy antennas, as well as the adaptation and the splitter. If the daisy antennas have 2 petals each the divisor must be 1: 4; if they have 6 petals, the divider should be 1: 12.

• the bi-filar lines of the signal distribution circuit to the petals must differ by a quarter of a wavelength, to provide the 90 ° offset necessary to generate the circular polarization. That means that the petals of one of the daisies are distributed inside the petal distribution of the other daisy. Since each of the daisy antennas that generate the linear polarizations must have an even number of petals (2, 4, 6 ... n petals), the daisy antennas that generate circular polarization must be 4, 8, 12 .. . 4n petals

The simplest case is that of the four-petal antenna, which would be the grouping of 2 daisies with 2 petals each). Figure 21 shows the distribution circuit, separated in layers 2 and 3 according to the exploded view shown in Figure 3. It can be seen in said figure, the different length of the bi-wire feed lines to each of the daisies of 2 petals that make up this antenna. Figure 22 shows the distribution of petals in layer 2 of the daisy with 4 petals (electric dipoles), which generates circular polarization. In this figure, together with the distribution of currents, the lines of symmetry corresponding to each pair of petals, or what is the same, to each polarization can be seen: 5A for petals 2A, and 5B for petals 2B. Figure 23 shows the overall view of the 3 superimposed layers that shape the 4-petal daisy antenna, whose petals are electric dipoles. Figure 24 shows the distribution circuit in layers 2 and 3 of a 12-petal daisy that generates circular polarization. It would therefore be an antenna that is the sum of two 6-petal daisy antennas, with the petals of both overlapping. In this figure it can be seen that half (6) of the power lines differ in length from those of the other half, in a quarter of guided wavelength, and that the lines of one of the 6-petal daisy antennas are interspersed between those of the other. This causes one of them to be contained within the other, with the same point or power cable, and even using the same splitter, and thus both antennas have the same phase center of the radiated field. Figure 25 shows the distribution of petals in the intermediate layer, also showing the distribution of currents. This figure shows what is the set of 6 petals generated by each of the two linear orthogonal polarizations necessary for circular polarization. Figure 26 shows the overall view of the 3 layers of the 12-petal daisy antenna that generates circular polarization.

As it has been said, to have circular polarization in the direction perpendicular to the plane of the antenna, the daisy antenna is in turn the sum of 2 sub-antenna daisies, so it must have 4n petals. When looking at the cases of 4 and 12 petals, one might think that it is to add the same antenna (2 or 6 petals), but rotated 90 °. This is valid in cases where the antenna has no petal at 90 °, although more correctly it would be to say that it is one of the possibilities, since in the case of 12 petals (2 antennas of 6), the circular polarization could be obtained by rotating 30 ° , 90 ° or 150 °, and offset 30 °, 90 ° or 150 ° respectively, obviously obtaining cross polarization in other directions with different signal level.

For that reason, it is possible to obtain circular polarization with an 8-petal antenna (adding 2 antennas with 4 petals), although it may not result from a 90 ° rotation, but 45 ° or 135 °, so the distribution circuit must in this case introduce a 45 ° or 135 ° offset respectively.

Advantages of the margarita antenna

The advantage of this new antenna concept lies in its ability to adapt to different types of applications, being especially useful in:

• the reception systems of broadband and half-gain signals, as is the case of terrestrial television, analog or digital broadcast signals, in urban areas, in which the position of the transmitter is known but not visually located. Its simplicity of design and configuration provides a low manufacturing cost, as well as low visual impact and ease of pointing to the emitter,

• passive observation systems in which maintaining the characteristics of the radiation pattern in the operating band, such as the shape of the diagram, the coverage area and the polarization of the signal, are the most important and restrictive requirements of the system.

• satellite mobile communication systems, in which the signal is circularly polarized, thus avoiding ignorance of the position or attitude of the satellite with respect to the mobile, and having to turn the mobile antenna to match it with the satellite, as it would be the case that the communication was carried out using a linearly polarized signal.

Increased directivity incorporating a mass plane

The directivity of the daisy antenna that generates a maximum of radiation in the direction perpendicular to the plane of the antenna, both in linear and circular polarization, can be increased by a maximum of 3 dB, by placing a mass plane parallel to the plane of the antenna, at a distance equal to a quarter of the wavelength of the operating frequency of the antenna, thus being able to add in phase, in the desired direction, the signal reflected in the ground plane. Application of this concept to radiating elements other than wires

Since the essential characteristic of the daisy antenna is in the distribution of the direction of flow of the current through the petals, and this only has two possibilities: to come or go, which means that in the petals it occurs, in addition to a change of petal position relative to the daisy antenna assembly, a binary phase change of the radiated signal for each petal, that is: 0 ^or 180 °, depending on the direction of the current flowing through it.

This allows the concept defined for radiating wires, can also be applied to other types of radiating elements that admit by construction a binary change of the radiated phase from 0 ^or 180 °. This would be, for example, the case of microstrip radiators or waveguides open or terminated in horns, where changing only the position of the power supply achieves this change from 0 ^or 180 ° in the phase of the signal radiated by each element, and maintaining the direction of the linear polarization they generate.

The antenna would have a configuration that increases in complexity depending on the volume of the radiating element considered, but in essence it would have an electromagnetic operation similar to that of the previously defined daisy antenna and based on the use of wires. Figure 27 shows the sketch of a 6-petal daisy antenna with a maximum of radiation in the direction perpendicular to the plane of the antenna (performance similar to those described in example 1), where the petals are small speakers in a rectangular guide.

EXAMPLES OF APPLICATION OF THE INVENTION.

EXAMPLE 1 - Margarita antenna for maximum radiation in linear polarization, in the direction perpendicular to the antenna plane

Figure 28 shows the geometry of the upper and lower layers that make up the distribution circuit and indicates the distribution of currents, of a 4-petal daisy antenna that generates a maximum in linear polarization in the direction perpendicular to the plane of the antenna. The base of the distribution circuit is a metal square 30 mm side. The distance between layers is 5 mm, so the separation between the upper and lower layers is 10 mm.

Figure 29 shows the geometry of the central layer containing the 4 petals that are generated by photogravure methods on a dielectric substrate of low effective permittivity. The width of the metal tape is 10 mm, and the length of the petal is 432 mm. Figures 30 and 31 show the two linear electric field components ΕΘ and ΕΦ, as well as the gain value, in planes E and H respectively, of the radiation pattern of the four-petal antenna of Figures 28 and 29, a the frequency of 800 MHz.

EXAMPLE 2 - Margarita antenna to obtain maximum radiation in circular polarization, in the direction perpendicular to the antenna plane

Figure 21 shows the geometry of the upper and lower layers that make up the distribution circuit and indicates the distribution of currents, of a 4-petal daisy antenna, which generates a maximum in circular polarization in the direction perpendicular to the plane of the antenna. The base of the distribution circuit is a metal square 40 mm side, and the power lines have a width of 20 mm. The difference in length between the lines that feed the dipoles is 50 mm. The distance between layers is 5 mm, so the separation between the upper and lower layers is 10 mm.

Figure 22 shows the geometry of the central layer containing the 4 petals, which in this case are 220 mm long electric dipoles. The width of the metal tape is 10 mm, and the length of the petal is 432 mm. All layers are generated by photogravure methods on dielectric substrate of low effective permittivity. Figure 23 shows the 3 layers superimposed to give an idea of the set.

Figures 32, 33, 34 and 35 show the two orthogonal components in circular polarization to the right and left of the RHCP and LHCP electric field, as well as the gain value, in the meridian cuts for Φ = 0 ^or , 30 °, 60 ° , and 90 ° respectively, of the radiation pattern of the four-petal antenna of Figure 23 at the frequency of 730 MHz. Figure 36 shows the axial ratio in dB as a function of the frequency expressed in GHz. DESCRIPTION OF INDICATORS IN FIGURES

(1) - antenna power

(2) - antenna petals

(2 A) - petals that generate horizontal linear polarization

(2 B) - petals that generate vertical linear polarization (3) - distribution circuit

(4) - petal divider feed lines

(5) - short circuit paths between layers

(6) - line of symmetry of the distribution of currents in the petals

(6 A) - line of symmetry of the petals that generate the horizontal linear polarization (6 B) - line of symmetry of the petals that generate the vertical linear polarization

(7) - springs of power lines

(8) - sinks of power lines DESCRIPTION OF THE FIGURES

Figure 1 shows a 6 petal daisy antenna.

Figure 2 shows 4 and 2 petal daisy antennas

Figure 3 shows a cross section of a daisy antenna

Figure 4 shows a 6-petal daisy antenna with power lines in the distribution circuit

Figure 5 shows 2-petal daisy antennas, with different petal geometry: polygonal petals, folded dipoles and electric dipoles

Figure 6 shows a 6-dipole daisy antenna

Figure 7 shows Cassini ovals for k = 1, 1.1 and 1.4

Figure 8 shows a cluster of 6 petals originated with 3 pairs of Cassini ovals with k = 1.1, at Φ = 0 ^or , 60 ° and 120 °

Figure 9 shows a geometric curve derived from the expressions [2]

Figure 10 shows a geometric composition of a 6-petal daisy from the expressions [2]

Figure 11 shows a geometric curve derived from the expressions [3]

Figure 12 shows a geometric approximation to the curve of Figure 7, by a circle and two lines defined in [4]

Figure 13 shows metallizations of the upper and lower layers of the 6-petal daisy antenna of Figure 1.

Figure 14 the metallization of the central layer of petals, indicating the distribution of current lines, of the daisy antenna shown in Figure 1

Figure 15 shows metallizations of the upper and lower layers of the 6-petal daisy antenna of Figure 4.

Figure 16 shows the metallization of the central layer of petals, indicating the distribution of current lines, of the daisy antenna shown in Figure 4. Figure 17 shows metallizations of the upper and lower layers of the 6-petal daisy antenna of Figure 6.

Figure 18 shows the metallization of the central layer of petals, indicating the distribution of current lines, of the daisy antenna shown in Figure 6.

Figure 19 shows metallizations of the upper and lower layers of the 2-petal daisy antenna of Figure 5 (electric dipoles).

Figure 20 shows the metallization of the central layer of petals, indicating the distribution of current lines, of the daisy antenna shown in Figure 5 (electric dipoles).

Figure 21 shows metallizations of the upper and lower layers of the 4-petal daisy antenna that generates circular polarization.

Figure 22 shows the metallization of the central petal layer, indicating the distribution of current lines, of the 4-petal daisy antenna that generates circular polarization.

Figure 23 shows a 4-petal daisy antenna that generates circular polarization.

Figure 24 shows metallizations of the upper and lower layers of the 12-petal daisy antenna that generates circular polarization.

Figure 25 shows a metallization of the central layer of petals, indicating the distribution of current lines, of the 12-petal daisy antenna that generates circular polarization.

Figure 26 shows a 12-petal daisy antenna that generates circular polarization.

Figure 27 shows a 6-petal daisy antenna with a maximum of radiation in the direction perpendicular to the plane of the antenna, and where the petals are horns in a rectangular guide.

Figure 28 shows metallizations of the upper and lower layers of the 4-petal daisy antenna of Example 1, for linear polarization in the direction perpendicular to the antenna plane.

Figure 29 metallization of the central layer of petals, indicating the distribution of current lines, of the 4-petal daisy antenna of Example 1, for linear polarization in the direction perpendicular to the plane of the antenna.

Figure 30 shows a flat section E of the radiation diagram, at the frequency of 800 MHz, of the 4-petal antenna of Figures 28 and 29. The gain values are expressed in dBi (diamond curve), and dB the of the two components of the radiated electric field: ΕΘ (triangle curve) and ΕΦ (square curve).

Figure 31 shows a flat section H of the radiation diagram, at the frequency of 800 MHz, of the 4-petal antenna of Figures 28 and 29. The gain values are expressed in dBi (diamond curve), and dB the of the two components of the radiated electric field: ΕΘ (triangle curve) and ΕΦ (square curve).

Figure 32 shows a meridian cut of the radiation pattern at Φ = 0 ^or , of the 4-petal daisy antenna of Figures 21, 22 and 23. The gain values are expressed in dBi (diamond curve), and in dB the of the two orthogonal components in circular polarization to the right and left of the electric field RHCP (square curve) and LHCP (triangle curve). Figure 33 shows a meridian cut of the radiation pattern at Φ = 30 °, of the 4-petal daisy antenna of Figures 21, 22 and 23. The gain values are expressed in dBi (diamond curve), and in dB the of the two orthogonal components in circular polarization to the right and left of the electric field RHCP (square curve) and LHCP (triangle curve).

Figure 34 a meridian cut of the radiation pattern at Φ = 60 °, of the 4-petal daisy antenna of Figures 21, 22 and 23. The gain values are expressed in dBi (diamond curve), and in dB those of the two orthogonal components in circular polarization to the right and left of the electric field RHCP (square curve) and LHCP (triangle curve).

Figure 35 a meridian cut of the radiation pattern at Φ = 90 °, of the 4-petal daisy antenna of Figures 21, 22 and 23. The gain values are expressed in dBi (diamond curve), and in dB those of the two orthogonal components in circular polarization to the right and left of the electric field RHCP (square curve) and LHCP (triangle curve).

Figure 36 shows a graphical representation of the axial ratio in dB, with respect to the frequency expressed in GHz, of the 4-petal daisy antenna of Figures 21, 22 and 23.

Claims

1. Margarita antenna for emission and / or reception of linearly polarized electromagnetic waves, characterized by being the circular grouping of an even number of radiating wires, whose set adopts a similar shape to the distribution of petals in a daisy flower, and in which The radiating wires or petals work in resonance, have the same structure, are contained in the same plane called the antenna plane, and the current flowing through the petals is arranged symmetrically with respect to a predefined diameter of the circular grouping, which coincides with the linear polarization direction of the radiated electric field. This distribution of the currents determines and characterizes the operation of the daisy antenna.

Margarita antenna for emission and / or reception of linearly polarized electromagnetic waves, according to claim 1, characterized in that it is composed of the following elements, distributed in 3 layers (see figure 3): a power line (1) located in the center and connected to the upper and lower layers of the antenna, the radiating wires or elements also called petals (2) located in the central layer of the antenna, and the distribution circuit (3) in the upper and lower layers, and which at their Once it is formed by the adaptation of the antenna or balun, the splitter to distribute the signal between the petals.

Margarita antenna for emission and / or reception of linearly polarized electromagnetic waves, according to claims 1 and 2, characterized by the presence of bi-filar lines to carry the signal from the divider to the petals, or vice versa in the case of reception, presence which is necessary when, due to the size of the petals or due to design requirements, the petals are located far from the divider. These bi-filar lines are equal in number to the petals, and must all be exactly the same so that they do not introduce any difference in amplitude or phase in the signals they transmit.

Margarita antenna for emission and / or reception of linearly polarized electromagnetic waves, according to claims 1, 2 and 3, characterized by emitting or capturing signals in the direction perpendicular to the antenna plane.

5. Margarita antenna for emission and / or reception of linearly polarized electromagnetic waves, according to claims 1, 2, 3 and 4, characterized in that a maximum power in the direction perpendicular to the plane of the antenna is presented in the radiation diagram. Margarita antenna for emission and / or reception of linearly polarized electromagnetic waves, according to claims 1, 2, 3, 4, and 5, characterized in that it can be used to generate circular polarization by inserting two daisy antennas in the same plane, whose petals coincide in shape and number, rotated with each other, with the same center, and sharing the same distribution circuit, and with the only difference between both daisy antennas that the bi-signal lines mentioned in claim 3, have different lengths in each antenna with the in order to provide the necessary phase difference to compensate for the rotation between antennas, and thus generate the desired circular polarization.

Margarita antenna for emission and / or reception of linear or circularly polarized electromagnetic waves according to claims 1, 2, 3, 4, 5 and 6, characterized by emitting or capturing electromagnetic radiation in the microwave range and the millimeter band of the electromagnetic spectrum . Margarita antenna for emission and / or reception of linear or circularly polarized electromagnetic waves according to claims 1, 2, 3, 4, 5, 6 and 7, characterized in that the analytical mathematical expressions are available in order to carry out the design of the petals of their geometry, which allow them to be explicitly determined from the design parameters: their perimeter length and their opening angle having the center of the antenna as a vertex. This facilitates the use of computer means for other and different purposes, such as the analysis of the electromagnetic behavior of the antenna, the preparation of manufacturing drawings, or their use in manufacturing and assembly processes.

Margarita antenna for emission and / or reception of linear or circularly polarized electromagnetic waves according to claims 1, 2, 3, 4, 5, 6, 7 and 8, characterized in that the petals are designed using the expressions:

X (t, m, L): = - - (t ² - l) - t ² (l Om - 5-Jm ² + l) + 2-m - 3 · + 1

16

Y (t, m, L): =

being: L the perimeter length of the petal

α twice the opening angle of the petal

m the tangent of α

t a number belonging to the interval (-1, 1)

10. Margarita antenna for emission and / or reception of linear or circularly polarized electromagnetic waves according to claims 1, 2, 3, 4, 5, 6, 7, 8 and 9, characterized in that the petals are designed using the expressions for the case in which the opening angle of the petal is π / 3:

x (t, L, 0, D): = L t (t ² - l) without (e) Y (t, L, 9, D): = -Lt- (t ² - l) -cos (e)

being:

L the length of the perimeter of the petal

D the distance from the apex of the petal to the coordinate axis t a number belonging to the interval (-1, 1)

Θ the angle that forms the axis of symmetry of each petal with the axis of abscissa.

11. Margarita antenna for emission and / or reception of linear or circularly polarized electromagnetic waves according to claims 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10, characterized in that the petals are designed using a circumference and the two tangent lines drawn from the apex of the petal, being:

13- L

The radius of the circumference value: V 15552 the center is located at the point of

and the tangent lines have a slope of

12. Margarita antenna for emission and / or reception of linear or circularly polarized electromagnetic waves according to claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11, characterized in that the petals are manufactured by methods of photogravure, screen printing or electrochemical processes on dielectric substrate, or by any other method that arises in the markets due to the development or normal progress of the technology.

13. Margarita antenna for emission and / or reception of linear or circularly polarized electromagnetic waves according to claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12, characterized in that The directivity of the daisy antenna designed to obtain a maximum of radiation in the direction perpendicular to the plane of the antenna, both in linear and circular polarization, can be increased by a maximum of 3 dB, by placing a plane of mass parallel to the plane of the antenna, at a distance equal to a quarter of the wavelength of the operating frequency of the antenna, thus being able to add in phase, in the desired direction, the antenna signal with that reflected by the ground plane.

14. Margarita antenna for emission and / or reception of linear or circularly polarized electromagnetic waves according to claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13, characterized by their use in terrestrial television reception systems, communication systems between fixed or mobile systems, with link through terrestrial or satellite stations, in observation and security systems, as well as in systems dedicated to scientific and technical research.