This application claims priority to French Patent Application 19 10719, filed Sep. 27, 2019, the entirety of which is incorporated by reference.
This description concerns a multi-band antenna as well as a method for manufacturing such an antenna. The antenna described is particularly suitable for installation on an aircraft.
Many applications require the use of multi-band antennas, particularly data communication between an airplane and the ground infrastructure of an airport. Such a communication link can in particular enable the transmission of data from the airplane when it is located near the airport or parked at its boarding gate, to an operator of the commercial line served by the airplane or to an aircraft maintenance operator. The Gatelink system, for example, provides a high speed wireless communication protocol for such an application. However, when the antenna is attached to the airplane fuselage, it forms a barrier to the optimal flow of outside air along the airplane fuselage.
The article which is entitled “New kind of microstrip antenna: the monopolar wire-patch antenna”, by C. Delaveaud, P. Leveque and B. Jecko, Electronics Letters, Jan. 6, 1994, Vol. 30 (1), describes an antenna constituted by a metal base plate which serves as an electrical ground plane, and by a metal patch which is parallel to the metal base plate and distanced from it. The metal patch is electrically connected to a signal lead wire, and is electrically connected to the metal base plate by electrical circuit closure connections. Such an antenna, of the shorted capacitive roof type, is single-band with a single resonant frequency value which is determined by the surface area of the metal patch and the length of the electrical circuit closure connections. Its radiation pattern is monopolar, with a polarization of the far-field electrical field that is essentially linear and oriented perpendicularly to the metal base plate.
In addition, document FR 2 709 878 discloses the addition of a second metal patch to such an antenna with shorted capacitive roof, smaller than and parallel to the previous one, on a side of the first patch which is opposite to the metal base plate. The second patch is electrically connected only to the first patch, independently of the signal lead wire, the metal base plate, and the electrical circuit closure connections of the first patch. Such an antenna is then dual-band, with two different resonant frequency values. But the second patch increases the total thickness of the dual-band antenna compared to the single-band antenna with shorted capacitive roof which only has the first metal patch.
The present invention may be embodied to provide improved multi-band antennas which are thin and inexpensive, and whose geometric characteristics can be determined by digital simulations based on desired values for the resonant frequencies.
A first embodiment of the invention is a multi-band antenna which comprises: a metal base plate, which is intended to serve as an electrical ground plane; and a plurality of metal patches, which are parallel to the metal base plate and which are each arranged at a different respective distance from this metal base plate.
According to one feature of the invention, the metal patches are each electrically connected to one and same signal lead wire, which is shared by the metal patches, and each metal patch is furthermore connected to the metal base plate independently of the other metal patches, by at least one electrical circuit closure connection which is dedicated to that metal patch. Thus, all the metal patches are connected in parallel between the signal lead wire and the metal base plate.
According to another feature of the invention, the respective distances of the metal patches to the metal base plate and respective surface area values of the metal patches are such that each metal patch with said at least one electrical circuit closure connection dedicated to that metal patch constitutes a radiating element which has at least one resonant frequency value which is different from that of each other radiating element. The antenna is thus multi-band.
Such an antenna can be produced by simple and inexpensive manufacturing techniques, in particular by printed circuit board technology, or PCB. Furthermore, by selecting an appropriate size for each metal patch, the antenna can have a reduced total thickness perpendicular to the metal base plate. With such a reduced thickness, the antenna can be attached to the fuselage of an aircraft without significantly interfering with airflow along the fuselage of the aircraft.
In embodiments of the invention, the metal patches may be superimposed in a direction of superposition which is perpendicular to the metal base plate, and each metal patch may have a surface area value which is different from that of each other metal patch. This patch surface area value may increase between two different metal patches as a function of the distance of each metal patch from the metal base plate. For such a configuration, the metal patch that is farthest from the metal base plate, with its electrical circuit closure connection(s), produces the lowest resonant frequency value, and each additional patch produces an additional resonant frequency value which is increasingly higher for patches which are smaller and closer to the metal base plate.
In various embodiments of the invention, at least one of the following additional features may optionally be reproduced, alone or in combination:
each metal plate may have any shape. For example, at least one metal plate may have a disk shape, or square, or any other appropriate shape;
each electrical circuit closure connection may be a conductive wire, a metal contact stud, or a conductive tab;
each metal patch may be connected to the signal lead wire at a central point of that metal patch;
several electrical circuit closure connections may be dedicated to a same one of the metal patches, and these electrical circuit closure connections dedicated to a same metal patch may be in an arrangement which is symmetrical relative to a connection point of that metal patch to the signal lead wire;
each electrical circuit closure connection dedicated to one of the metal patches may be connected to a peripheral edge of this metal patch;
each metal patch may be connected to the metal base plate by any number of electrical circuit closure connections, such as less than or equal to twelve, for example by two or four electrical circuit closure connections;
the metal patches may be superimposed in a direction of superposition which is perpendicular to the metal base plate, and a separation gap between two successive metal patches in this direction of superposition is a gap of air or of solid electrically insulating material; and
separation gaps between pairs of successive metal patches in the direction of superposition may be of thicknesses that are identical between different pairs and identical to the thickness of a separation gap which exists between the metal base plate and the metal patch which is closest to the metal base plate.
A second aspect of the invention proposes an aircraft, for example an airplane, which comprises a multi-band antenna according to the first aspect, attached to a fuselage of the aircraft.
Finally, a third aspect of the invention relates to a method for manufacturing a multi-band antenna in accordance with the first aspect, this method comprising the sequence of the following steps (1) to (4):
(1) for the one of the metal patches which is farthest from the metal base plate, referred to as the first metal patch, determining a surface area value of this first metal patch and a spacing distance value between this first metal patch and the metal base plate such that a first elementary antenna, of shorted capacitive roof type, which is formed by the first metal patch with the at least one electrical circuit closure connection dedicated to this first metal patch, and with the metal base plate and the signal lead wire, has a first resonant frequency target value and a first spectral width of resonance;
(2) for a second of the metal patches, which comes after the first metal patch in the direction of superposition moving towards the metal base plate, setting a spacing distance between the second metal patch and the metal base plate to a value which is less than that of the spacing distance between the first metal patch and the metal base plate, then determining a surface area value of the second metal patch such that a second elementary antenna, of shorted capacitive roof type, which is formed by the second metal patch with the at least one electrical circuit closure connection dedicated to this second metal patch, and with the metal base plate and the signal lead wire, has a second resonant frequency target value and a second spectral width of resonance;
(3) adjusting the value of the spacing distance between the second metal patch and the metal base plate, and the surface area value of the second metal patch, so that a quotient of the first and second resonant frequency values which are effective when the first and second metal patches are associated together with the metal base plate by the signal lead wire shared by the first and second metal patches, and with the respective electrical circuit closure connections of the first and second metal patches, matches a quotient target value which is equal to a quotient of the second resonant frequency target value over the first resonant frequency target value; and
(4) applying a common scale factor to the respective spacing distance values of the first and second metal patches relative to the metal base plate, and to the dimensions of the first and second metal patches which produce their respective surface area values, so that the first resonant frequency value which is effective when the first and second metal patches are associated together with the metal base plate by the signal lead wire shared by the first and second metal patches, and by the respective electrical circuit closure connections of the first and second metal patches, matches the first resonant frequency target value.
The sequence of steps (1) to (4) is then repeated for each pair of neighboring metal patches in the multi-band antenna, shifting by one metal patch in the direction of the metal base plate between two repetitions of the sequence of steps, if the multi-band antenna comprises more than two metal patches.
The method further comprises a step (5) of manufacturing the multi-band antenna in accordance with the values obtained for the spacing distance of each metal patch from the metal base plate, and for the surface area of each metal patch.
An advantage of the method lies in the progressive determination of the respective geometric parameters of the metal patches, given that significant interactions primarily only occur between patches which are neighbors along the direction of superposition. Optionally, the sequence of steps (1) to (4) may be repeated several times for each pair of neighboring metal patches. Also optionally, all the executions of the sequence of steps /1/ to /4/ in order to obtain the values relating to all the patches, may be repeated to achieve a general refinement of the spacing distances and surface area values of the patches.
The first resonant frequency target value may be chosen to be less than the second resonant frequency target value. In this manner, the metal patches can have decreasing surface area values when they are closer to the metal base plate.
For first embodiments of the multi-band antenna, each metal patch may be formed in step (5) in a metallized surface of a respective printed circuit board substrate. Then, segments of the electrical circuit closure connections may be formed through at least some of the printed circuit board substrates. Then the printed circuit board substrates are stacked on the metal base plate so as to establish electrical contact between all segments of a same electrical circuit closure connection, separately for each of the electrical circuit closure connections.
For other embodiments of the multi-band antenna, each metal patch may be formed in step /5/ as a separate metal plate portion, then each separate metal plate portion forming one of the patches can be assembled with the metal base plate using spacers. In this case, the electrical circuit closure connections may possibly form the spacers.
The features and advantages of the invention will appear more clearly in the following detailed description of some non-limiting embodiments, with reference to the appended figures in which:
For clarity sake, the dimensions of the elements which are shown in [
According to [
For example, each of the patches 1-3 may be made in the form of a portion of metallization layer which is carried by a dielectric substrate, for example by a printed circuit board (PCB). In [
According to another possible embodiment for the antenna 100, each of the patches 1-3 may be a respective metal plate portion, and these portions forming the patches of the antenna may be retained above the base plate 10 by suitable spacers, in accordance with the values desired for the distances h1-h3. All the plate portions can thus be separated by air gaps. For such an embodiment, each electrical connection which connects one of the patches 1-3 to the base plate 10 may be composed of a segment of electrical wire, or a conductive column, which is connected by one of its ends to the patch concerned and by the other of its ends to the base plate 10.
[
[
Reference 11 designates a power cable for the antenna 100, for example a coaxial cable whose sheath 11M is connected to the base plate 10, for example in a central region of the plate. Reference M10 designates the annular electrical connection of the sheath 11M to the plate 10, around an orifice in the plate 10 through which passes a core wire 11A of the coaxial power cable 11. The core wire 11A of the coaxial cable, referred to as the signal lead wire in the general part of this description, is not directly in electrical contact with the base plate 10. The base plate 10 thus acts as an electrical ground plane during operation of the antenna 100, in emission or reception. The power cable 11 may arrive at the base plate 10 on the side facing away from the patches 1-3.
Each patch i, i being equal to 1, 2, or 3 in the example of [
Each patch i forms, with its additional electrical connections Ci, the base plate 10, and the signal lead wire 11A, an elementary antenna with shorted capacitive roof which has its own resonant frequency value. However, due to the proximity between all the patches i and also, to a lesser extent, due to the proximity between some of the additional electrical connections Ci which are dedicated to different patches i, the resonant frequency values are modified compared to those which would be effective if the elementary antennas with shorted capacitive roof were spatially distant from each other, for identical geometric characteristics of the patches i and of the additional electrical connections Ci.
During operation of the antenna 100, the signal to be emitted is brought to the antenna 100 by the core wire 11A, in the form of an electrical signal. It is therefore transmitted simultaneously to all the patches i, and each elementary antenna with shorted capacitive roof emits radiation whose frequency corresponds to its resonant frequency value that is in effect within the antenna 100. This radiation also corresponds to the amplitude of the frequency component of the electrical supply signal for the same frequency value. The antenna 100 is thus multi-band, with simultaneous emissions in all its bands.
We now describe a method for manufacturing such an antenna 100, which for clarity has only two patches. These patches are denoted 1 and 2. h1 (respectively h2) designates again the spacing distance between patch 1 (resp. 2) and the base plate 10, and a1 (resp. a2) designates the diameter of patch 1 (resp. 2), the two patches here each being disc-shaped. It is assumed again that each of the patches 1, 2 is provided with four additional electrical connections C1, C2, located at the edge of each patch and on two perpendicular diameters thereof. The desired transmission bands for antenna 100 are the S and C bands of the Gatelink system. In other words, the desired resonant frequency values are within the 2400 MHz (megahertz)-2483.5 MHz range for one, corresponding to the S band, and within the 5150 MHz-5300 MHz range for the other, corresponding to the C band. The first resonant frequency value, in the S band, corresponds to the largest patch, i.e. patch 1, and the second resonant frequency value, in the C band, corresponds to the smallest patch, i.e. patch 2.
A first step of the method consists in determining the geometric parameters h1 and a1 of patch 1, such that an antenna with shorted capacitive roof which would be formed by patch 1, the base plate 10, the four electrical circuit closure connections C1, and the coaxial power cable 11, in the absence of patch 2 and connections C2, has a desired resonant frequency value f1 in the S band, called the first resonant frequency target value in the general part of the present description. For this purpose, a starting value for the spacing distance h1 can be chosen, for example equal to one-twentieth of the desired resonance wavelength, i.e. h1=C/(20·f1), where C is the speed of light. The coefficient of one-twentieth is arbitrary and can be changed. Next, the diameter or width al can be calculated as being substantially equal to 8.749·h1, where the coefficient 8.749 has been determined empirically such that the antenna with shorted capacitive roof has a reflection coefficient value |S11| which is less than −20 dB (decibel), such as less than −30 dB, for the first resonant frequency target value. This is a criterion of resonance sharpness, which is equivalent to a desired value of resonance spectral width. The value of h1 can then be refined by a simulation calculation, for example a “full-wave” type of calculation known to those skilled in the art, while keeping the value of a1 constant, to obtain the first resonant frequency target value f1. Such a simulation calculation indicates that the resonant frequency varies as a decreasing function of the spacing distance h1. Finally, the value of a1 can be recalculated with the equation a1=8.749·h1, using the refined value of h1.
A second step of the method consists in determining the geometric parameters h2 and a2 of patch 2, such that an antenna with shorted capacitive roof which would be formed by patch 2, the base plate 10, the four electrical circuit closing connections C2, and the coaxial power cable 11, in the absence of patch 1 and connections C1, has a desired resonant frequency value f2 in the C band, called the second resonant frequency target value in the general part of the present description. For this purpose, a starting value for the spacing distance h2 can be chosen, for example equal to half the spacing distance h1, i.e. h2=h1/2. The coefficient of one-half is arbitrary and can be changed. Next, the diameter a2 can be calculated as being substantially equal to 8.749·h2. The value of h2 can then be refined by a new simulation calculation, which may again be of the “full-wave” type, while keeping the value of a2 constant, to obtain the second resonant frequency target value f2. As before, this simulation calculation indicates that the resonant frequency varies as a decreasing function of the spacing distance h2. Finally, the value of a2 can be recalculated with the equation a2=8.749·h2, using the refined value of h2.
When these values of h1, a1, h2 and a2 are adopted for the complete antenna 100, in other words by associating the two patches 1 and 2 and their connections C1 and C2 with the base plate 10, the core 11A of the coaxial cable 11 being connected to the two patches, the interactions between all these components, in particular a capacitive interaction between the two patches 1 and 2, cause the two resonant frequency values to change. They thus respectively become f1′, different from f1, and f2′, different from f2.
The third step of the method is to adjust the values of h1, a1, h2 and a2 so that the quotient of the values f2′/f1′ becomes substantially equal to the quotient f2/f1 of the resonant frequency target values. Simulations, for example also of the “full-wave” type, show that the value of the quotient f2′/f1′ varies increasingly as a function of h2, and also increasingly as a function of a2 but with a lower rate of variation. At the same time, the value f1′ varies decreasingly as a function of h2 and also of a2, while the value f2′ varies increasingly as a function of h2 and decreasingly as a function of a2.
Finally, a fourth step of the method consists in applying a same scale factor to the four values of h1, a1, h2 and a2 as resulting from the third step, in order to return the value f1′ to the first target value f1. The scale factor to apply is the value of the quotient f1′/f1. This step in fact consists in applying a proportional transformation to the antenna 100 that resulted from the third step, to obtain the first target value f1 of resonant frequency (f1′=f1). It does not change the value of quotient f2′/f1′, so the second resonant frequency target value f2 is obtained simultaneously (f2′=f2).
Thus, to obtain f1=2441.75 MHz and f2=5225 MHz, the method just described has provided the following values to be adopted for the dual-band antenna 100: a1=54.94 mm (millimeters), h1=6.05 mm, a2=43.93 mm, and h2=3.78 mm. To this end, the cross-sectional diameter of the core 11A of the coaxial power cable 11 was taken as equal to 1.27 mm, and each electrical circuit closure connection C1, C2 was taken as being a column having a square cross-section with 0.53 mm sides. The dual-band antenna 100 thus obtained has a footprint of approximately 55 mm×55 mm×6 mm. It can therefore be easily placed on the fuselage of an airplane, without significantly modifying its airflow properties.
The diagram of [
The diagram of [
The radiation pattern of the same dual-band antenna 100 for the emission frequency value f=f1=2441.75 MHz, in the S band, is reproduced in [
[
The radiation pattern of [
[
The curves of the patterns of [
It is understood that the invention may be reproduced by modifying secondary aspects of the embodiments described in detail above, while retaining at least some of the cited advantages. In particular, the number of patches may be changed, the electrical circuit closure connections are not necessarily located on the edges of the patches, the number of electrical circuit closure connections per patch may be changed, and the patches are not necessarily square or disc-shaped. In addition, all the given numerical values were for illustration only, and may be changed according to the application considered.
While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.
Number | Date | Country | Kind |
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19 10719 | Sep 2019 | FR | national |