ES2384951A1 - Double coplanar lemniscate antenna - Google Patents

Abstract

The invention relates to an antenna formed by the coplanar grouping of two lemniscate antennas of different sizes, such that one of said antennas is located inside the other with a shared power supply point being maintained. This novel antenna design is advantageous in that it provides a larger bandwidth than that of the singe lemniscate antenna and in that it prevents inclination of the radiated beam as occurs with double asymmetric ring antennas. The invention is suitable for use in communication and observation systems that require the radiation characteristics of the antenna to be maintained in broad band.

Description

COPLANAR DOUBLE LEMNISCATA ANTENNA

FIELD OF THE INVENTION

The present invention belongs to the sector of the transmitting and / or receiving antennas, of electromagnetic signals, and more precisely it is related to the following sub-sectors of the antenna technology: broadband antennas, magnetic dipoles, radiating systems of

10 transmission and reception, antennas for communications systems, antennas for television signal receivers, antennas of low cost and visual impact, and antennas for observation and surveillance systems.

15 STATE OF THE TECHNIQUE

It is well known that resonant electric dipoles are classic radiant elements, well known both in their design and in their manufacturing process, and used as the base element of numerous antenna groupings in

20 different communication systems, for simultaneous reception and transmission of signals, or in reception-only systems such as the antennas for the reception of terrestrial television channels in the VHF and UHF bands.

25 The fact that the electric and magnetic fields are associated in all electromagnetic radiation, allows that when designing an antenna you can work thinking only of any of them, knowing that the other will respond accordingly. The simplicity of the design when working thinking about the electric field, means that many designs have been made

30 on electric dipoles, and instead there are few developments made on the so-called magnetic dipoles, which are turns of conductive material whose circumference length is resonant at the working frequency of the dipole.

However, both electric and magnetic dipoles are

5 sufficiently referenced in any textbook relating to antennas. Examples of these textbooks are for example "Antenna theory, analysis and design" by C.A. Balanis, edited by John Wiley & Sons, chapter 9, second edition of 1997; "Antenas", by J.D. Graus, edited by McGraw-Hill, chapter 15, second edition of 1988; "Antenna Engineering Handbook", by R.A.

10 Jonson, edited by McGraw-Hill, chapters 14 and 26, third edition of 1993; "Antenna Theory and Design" by W.L. Stutzman and G.A. Thiele, edited by John Wiley & Sons, chapter 6, second edition of 1998; or "Frequency independent antennas", by V.H. Rumsey, edited by Academia Press in 1966. As cited in these references both circular geometry and

Any other polygonal are valid for use in the case of magnetic dipoles.

There are also numerous articles in magazines, which deal with the grouping of electric dipoles with the aim of obtaining greater gain and width of 20 bands. As examples of these references the following can be cited: "Log-periodic dipole Arrays", by D.E. Isbell, IRE Transactions on Antennas and Propagations, vol 8, n 3, May 1960; and A note on the calculation of the gain of log-periodic dipole antennas ", by P.C. Butson and G.T. Thompson, IEEE Transactions on Antennas and Propagation, vol 24, n1, pages 105 to 106,

January 25, 1976.

On groups of magnetic dipoles, US Patent 6,255,998 B1, dated July 3, 2001 and entitled "Lemniscate Antenna Element", defines a double spiral geometry that adopts the geometric shape that is called lemniscate, and in which the Spiral diameters have the same size. This document also describes the grouping of radiating elements with this double spiral geometry to form a simple antenna

speech therapy, with a radiant device with a wide operating bandwidth.

The problem of grouping several lemniscatas to form a single

5 radiant element that can also be grouped together to form a logoperiodic antenna, is analyzed in US Patent 6,469,674 B1, dated October 22, 2002 and entitled "Double-Lemniscate Antenna Element". In this patent the authors also define an antenna configuration in which the turns that make up the lemniscata adopt other types of geometry to

10 generate it; In addition to circular use configurations with triangular geometry, and combinations of circular with triangular.

In no case, the authors of these patents (US 6,255,998 B 1 and US 6,469,674 B1), grant technical interest to a combination of two lemniscatas

15 of different sizes, arranged in the same plane, and in which the smaller lemniscata is contained within the larger one, keeping the feeding point in common.

It should be noted that in the case of isolated elements such as

20 electric or magnetic dipoles, or even the lemniscate shaped element defined in another patent, US 6,255,998 B 1, the operating band, by adaptation or by shape of the diagram, turns out to be insufficient to cover the entire terrestrial television broadcasting band . To cover this band it is necessary to go to groups of several elements of different sizes to form

25 a logoperiodic antenna. Normally groupings in numbers greater than 5 are used, being able to be superior to 20 elements, increasing the size of the antenna, and therefore its directivity, which forces to take care of the aiming of the antenna.

30 The advantage of broadband radiating elements is that it avoids the use of clusters with a high number of elements, as is the case of logoperiodic antennas designed to widen the band, and in this way devices would be obtained from lower volume, which would achieve a lower visual impact, in addition to providing great simplicity of aiming for its lower directivity.

5 Finally, in the communication "Antenna of double hexagonal ring", Vassal'lo J, Torres J, and Marante F.R. published in the 2010 USSR National Congress, Bilbao (Spain), a double ring antenna is defined, similar to the lemniscate curve but with asymmetric hexagonal rings, thus achieving the objective of increasing the band, although presenting the inconvenience of a

10 inclination of the maximum pointing direction in the radiation diagram, which varies with frequency, and which is a direct consequence of the asymmetric antenna geometry.

15 BRIEF DESCRIPTION OF THE INVENTION

The present invention is an antenna formed by the coplanar grouping of two lemniscata antennas of different sizes, so that one of them is contained within the other, keeping in common the feeding point

20 (see figures 1 and 2).

The advantage of this new antenna conception lies in its application possibilities, since with this grouping of two lemniscate antennas a bandwidth greater than that provided by an antenna is obtained

25 simple lemniscate, and also avoids the inclination of the radiated beam as in the case of the asymmetric double ring antenna, as mentioned at the end of the section on the state of the art.

This antenna concept is useful in signal reception systems in

30 broadband and half gain, as is the case of television, analog or digital terrestrial broadcast signals, due to its simplicity of configuration and electromagnetic response. It is also especially useful in passive observation systems in which an important and restrictive requirement is to maintain the characteristics of the radiation pattern in the operating band in the operating band, such as: the shape of the diagram, the coverage area and the signal polarization.

Detailed description of the invention

The demand of the antenna technology markets imposes on the designer,

10 for some time now, radiant elements increasingly selective and capable of being adapted to new and different communications systems, so that their manufacturing cost can be reduced. The objective then sought by the inventors in designing the present antenna was multiple:

15 a) Take advantage of the fact that structures based on the functions of Cassini's ovals, such as lemniscata, have a proven resonance with the electromagnetic signal, b) Relate the physical dimensions of the antenna to the applications sought,

20 c) Relate the distribution of current lines in the antenna, and how to achieve it, with the shape of the radiation pattern required by the applications sought,

d) Achieve a simple manufacturing with the consequent cost savings, maintaining the highest possible gain and width values of 25 operating band.

The dimensions, the geometric shape and the distribution of currents, are the most important parameters that condition the operation of the antennas based on the use of conductive turns. On these parameters depends the

30 radiation pattern shape, gain and stability of its band behavior. As each application sector demands different characteristics, then the way to achieve them is in:

•

dimension the turns of the antenna according to the requirements in bandwidth,

•

find a geometry with modal stability appropriate to the operating band of the application,

5 • distribute the currents appropriately to the requirements of the desired radiation pattern.

The coplanar double lemniscate antenna that is protected by this document is based on the constructive sum of the radiation generated by

10 two different sized lemniscatas, arranged in the same plane and so that the smaller one is contained within the larger one, both lemniscatas keeping the same feeding point (see figures 1 and 2).

In addition to the classic geometry of the lemniscate curve, as a case

In particular, of Cassini's ovals, for the sake of manufacturing, essentially, in the coplanar double lemniscata antenna, the turns of the lemniscatas can take on any other geometric shape, such as being circular, or polygonal.

20 In the coplanar double lemniscata antenna, and also for the sake of manufacturing convenience, both lemniscatas can also have in common the section of the turns of different sizes that are located near the feeding point. This is clearly seen in the example described in this document, and as shown in Figure 3.

The circular turns, polygonal or with the geometry based on the Cassini ovals, which form each of the two lemniscatas, work in their fundamental resonant mode, so that their length coincides with the value of the wavelength at two values of frequency within the operating band of the double lemniscate antenna. These resonance frequency values are close to the center of the operating band of the

antenna, so that overlapping increases their effective antenna bandwidth.

Both turns can be made with wire or conductive tape (figure 1), whose

5 cross section depends on the impedance of the power line of the antenna. In the case shown in this figure, each turn is a brass tape of length according to the desired resonance frequency, and the line of Food is bi-filar.

10 In order for the sum of the radiated field to be constructive in the direction perpendicular to the plane containing the coplanar double lemniscata antenna, the turns of the turns in each lemniscata must turn counterclockwise relative to each other, and in the same direction in the case of the turns of different lemniscata when one contains the other. Electrical contacts

15 of the turns of both lemniscatas are made at the antenna feed point as indicated in Figure 1, or they may have in common a spiral section as indicated in Figure 3.

In addition to with wire or conductive tape as shown in Figure 1, other methods

20 manufacturing and other alternative power lines can be used to construct a double-planar coplanar lemniscate antenna; but any of them must contain two pairs of turns of different sizes, contained in the same plane, with the small turns inside the larger ones, and all connected to the transmission line that is used as the line of

25 antenna power.

In addition to the bi-filar line of the case of Figure 1, a coaxial line can be used as a feed line, photograding the turns of the asymmetric lemniscatas on the metallic face of a substrate.

The directivity of the coplanar double lemniscata antenna can be increased by a maximum of 3 dB, by placing a mass plane parallel to the plane defined by

the antenna, at a distance equal to a quarter of the wavelength at the frequency half of the resonance frequencies of the turns of different sizes that form the antenna.

The present invention could also be considered, from another point of view, as the grouping of two asymmetric double ring antennas, in which one of the antennas is placed inverted with respect to the other, so that the turns of larger size of each of those asymmetric antennas, shape the larger lemniscata, while the smaller turns

10 of each of those asymmetric antennas, shape the other lemniscata. This results in an electromagnetic response in radiation that corrects the inclination that characterizes the asymmetric double ring antenna, since the geometry of the coplanar double lemniscata antenna, considered as the inverted grouping of two asymmetric double ring antennas, lacks

15 asymmetries with respect to the center of the antenna.

EXAMPLE OF APPLICATION OF THE INVENTION.

In order to demonstrate the application of the invention, a double planar lemniscata antenna was designed using photogravure techniques, and whose turns have polygonal geometry. The antenna consists of photogravures made in 3 flat layers separated by substrates of low permittivity and thickness of 15 mm each.

25 Figure 3 shows the photogravure metallization in the central layer of the 3 layers that make up the coplanar double lemniscata antenna. The turns of one of the largest lemniscata have a hexagonal shape (1), while those of the smaller lemniscata have a pentagonal shape (2). He

30 width of the photogravure line of the turns, both hexagonal and pentagonal, is 5 mm. The hexagon side is 70 mm.

Four of the sides of the pentagon correspond to the sides of the larger lemniscata hexagon, to which they are ascribed. The fifth side of the pentagon coincides with one of the diagonals of the hexagon (see figure 3).

5 For convenience of frequency adjustment of the resonance of the turns at Perform the antenna design, the vertex of the hexagon, not common to the pentagon and located in the position opposite to the feeding point, it has been replaced by a 30 mm line section (see figure 1).

10 Figure 4 shows the photogravure metallization in the upper layer of the antenna, while Figure 5 shows the photogravure metallization in the lower layer of the antenna. The metallizations of these two layers are connected by means of short circuit paths (6), to the metallization of the central layer where the turns are photographed. In this way two things are achieved:

15 • use the separation between the photo-recorded layers as an impedance adapter element to the coaxial line (3), which serves as the antenna power supply,

• facilitate the proper distribution of currents in the turns, maintaining the geometry of the antenna

20 The central part of the metallization in the lower and upper layers is rectangular in shape, and has a size of 20 x 30 mm on the side.

The central part (3) of the rectangle in the metallization of the upper layer (figure

25 4), corresponds to the point at which it is connected to the central core of the supply coaxial, while the central part (3) of the rectangle in the metallization of the lower layer (Figure 5), is connected to the external metallic mass or coating of the coaxial.

30 Figure 6 shows the three photo-etched layers of the antenna, superimposed.

The results obtained are shown in Figures 7, 8, 9 and 10 Specifically, Figure 7 shows the module of the reflection coefficient at the antenna input, seen from a 50 Ohm coaxial of characteristic impedance to which the antenna. Figure 8 shows the flat section H of the diagram of

5 radiation, in its two linear components of electric field ES and ElIJ, as well as the gain value in said plane H.

The plane H of the radiation pattern of the coplanar double lemniscata antenna is the plane that contains the line that passes through the centers of the 10 turns and is perpendicular to the plane defined by the antenna.

Figure 9 shows the flat section E of the radiation diagram, in its two linear electric field components ES and ElIJ, as well as the gain value in said plane E.

The plane E of the radiation pattern of the coplanar double lemniscata antenna is the plane that is perpendicular to the plane H and the plane defined by the antenna.

20 Figure 10 shows the directivity, as a function of frequency, of the double coplanar lemniscata antenna (continuous curve), compared to the response obtained with the hexagonal spiral turnstile antenna (dot curve). Figure 10 serves to demonstrate the increase in the operating band provided by the coplanar double lemniscata antenna.

DESCRIPTION OF THE FIGURES

Figure 1 30 Antenna of double coplanar lemniscate made with circular turns of conductive tape, perspective view, and fed by bi-filar line

1 -Pair of circular turns of equal diameter, which give shape to the larger lemniscata of the double coplanar lemniscata antenna 2 -Par of circular turns of the same diameter, which give shape to the smaller lemniscata of the double antenna coplanar lemniscata

5 3 -Connection point to the bi-wire line of the coplanar double lemniscata antenna power supply

Figure 2 Top view of the coplanar double lemniscata antenna that allows to distinguish

10 the two lemniscata antennas that compose it, by continuous line and of 1-Par lines of circular turns of equal diameter, that give shape to the larger lemniscata of the antenna of double coplanar lemniscata 2 -Par of circular turns of equal diameter , which shape the smaller lemniscata of the coplanar double lemniscata antenna

Figure 3 Photogravure metallization in the intermediate layer of a coplanar double lemniscata antenna, performed by photogravure techniques 1-Hexagonal shaped turns of the larger lemniscata antenna, of

20 the two lemniscatas that make up the coplanar double lemniscata antenna 2 -Pentagonal shaped turns of the smaller lemniscata antenna, of the two lemniscatas that make up the coplanar double lemniscata antenna

Figure 4

25 Photogravure metallization in the upper layer of a double coplanar lemniscata antenna, performed by photogravure techniques 3 -Connection point of the coaxial power line of the coplanar double lemniscata antenna 6 -Short circuits between the upper and intermediate layers of the antenna of

30 double coplanar lemniscata, necessary to close the current lines of the

turns Figure 5

Metallized photogravure in the lower layer of a coplanar double lemniscata antenna, performed by photogravure techniques 3 - Connection point of the coaxial power line of the double antenna

5 coplanar lemniscate 6 - Short circuit paths between the lower and intermediate layers of the double coplanar lemniscate antenna, necessary to close the turns of the turns

10 Figure 6 Overall and superimposed view of the 3 layers of the coplanar double lemniscata antenna, made by photo-etching techniques 1 - Hexagonal shaped turns of the larger lemniscata antenna, of the two lemniscatas that make up the double antenna coplanar lemniscata

15 2 -Pentagonal shaped turns of the smaller lemniscata antenna, of the two lemniscatas that make up the coplanar double lemniscata antenna 3 -Connection point of the co-axial line of the coplanar double lemniscata antenna 6 -Short circuits between the lower and intermediate layers of the antenna of

20 double coplanar lemniscata, necessary to close the winding current lines

Figure 7 Graphical representation of the reflection coefficient (ordinate axis in dB), 25 as a function of frequency (abscissa axis in GHz), seen from the power point (3) of the coplanar double lemniscate antenna described in the figure

7.

Figure 8 30 Graphical representation of the plane H of the radiation pattern of the coplanar double lemniscata antenna described in Figure 7. Gain values in dBi

(rhombus curve), and in dB for the two components of the radiated electric field: ES (square curve) and ElIJ (triangle curve)

Figure 9

5 Graphical representation of plane E of the radiation pattern of the coplanar lemniscata antenna described in Figure 5. Gain values in dBi (diamond curve), and in dB for the two components of the radiated electric field: ES (square curve) and ElIJ (triangle curve)

10 Figure 10 Graphical representation of the gain (ordinate axis in dB), as a function of the frequency (abscissa axis in GHz), of the coplanar double lemniscate antenna (continuous curve), compared to the response of the lemniscate antenna of equal turns with hexagonal shape (curve of points).

Claims (6)

1. Antenna of emission and reception of electromagnetic signals characterized by being the grouping of two different sized lemniscatas, arranged 5 in the same plane (coplanar), so that the larger one contains the smaller one, keeping in common the feeding point, located in the center of the antenna. 2. Antenna for transmitting and receiving electromagnetic signals defined 10 according to claim 1, characterized in that the turns that shape the lemniscatas are circular, polygonal or derived from the Cassini ovals. 3. Antenna for transmitting and receiving electromagnetic signals defined 15 according to claims 1 and 2, and characterized in that the turns operate in their fundamental resonant mode, whereby the length of the turns coincides with the value of the wavelength at two frequency values within the operating band of the antenna.

20 4. Antenna for the emission and reception of electromagnetic signals defined according to claims 1, 2 and 3, and characterized in that the turns are made of wire or conductive tape, or by photogravure methods on a dielectric substrate.

5. Antenna for transmitting and receiving electromagnetic signals defined according to claims 1, 2, 3 and 4, and characterized in that the dimensions of the turns of the lemniscatas are chosen according to the intended application.

30 6. Antenna for transmitting and receiving electromagnetic signals defined according to claims 1, 2, 3, 4 and 5, and characterized in that the currents of the turns in each lemniscate rotate in the opposite direction a

respect

to the other, and in the same sense in he case of the turns of

different lemniscate when one contains the other.

7.

Antenna from issue Y reception from signals electromagnetic defined

5

according The claims 1, 2, 3, 4, 5 and 6, and characterized because the

antenna directivity

be may increase by a maximum of 3 dB,

placing a

mass plane parallel to the plane defined by the antenna, and a

a distance of

a quarter of the wavelength at the frequency half of

the resonance frequencies of the turns of the two lemniscatas that

10

Make up the antenna.

8.

Antenna from issue Y reception from signals electromagnetic defined

according to claims 1, 2, 3, 4, 5, 6 and 7, and characterized in that at

to be seen as a result of the inverted grouping of two antennas

fifteen

double asymmetric ring, corrects the inclination of the radiation pattern

presented by asymmetric double ring antennas.

9.

Antenna from issue Y reception from signals electromagnetic defined

according

The claims 1, 2, 3, 4, 5, 6 AND 7, AND characterized by its

twenty

application in communications systems and observation systems Y

surveillance