EP1532713A1

EP1532713A1 - Hectometric wave transmission antenna

Info

Publication number: EP1532713A1
Application number: EP03763918A
Authority: EP
Inventors: Philippe Piole
Original assignee: Telediffusion de France ets Public de Diffusion
Current assignee: Telediffusion de France ets Public de Diffusion
Priority date: 2002-07-08
Filing date: 2003-06-16
Publication date: 2005-05-25
Anticipated expiration: 2023-06-16
Also published as: FR2842024B1; ES2701002T3; EP1532713B1; US20050253771A1; US7109946B2; WO2004008572A1; FR2842024A1; AU2003258808A1; PT1532713T

Abstract

The invention concerns an antenna for eliminating the need to search for a new location for very high hectometric wave antennae, comprising an existing vertical structure (1) having a height of some ten meters containing at least one electrically conductive element (3) connected to the ground (T), and an excitation conductor wire (4a) extending at least partly outside and along the structure and connected to a transmitter (E) so that the structure radiates substantially hectometric waves. The existing structure may be a broadcasting tower, a water tower, a chimney, a lighthouse or an illuminating mast, wherein the excitation wire merges visually. The wire can be replaced by a conductive loop a few meters long, magnetically coupled to the structure.

Description

MF emission antenna

The present invention relates to a transmitting antenna in particular hectometric waves, that is to say in a medium frequency band of approximately between 300 kHz and 3 MHz. More particularly, it relates to a broadcasting antenna for radio program broadcasting in the medium wave band between 500 kHz and 1600 kHz in the context of the development of the worldwide digital broadcasting standardization DRM (Digital Radio Mondiale).

Currently, to emit signals in the MF band, insulated radiant towers of very great height of the order of 20 to 200 meters are generally installed far from the cities and diffuse relatively high powers. If it is desired to install such a pylon near an agglomeration or in the city, an important location, particularly for security purposes, must be available to erect the radiating pylon and install the network of earth associated with the pylon and comprising several wires placed on the ground. soil or shallow depth in the soil. Therefore, to install a pylon type antenna, it is necessary to obtain land for its location as well as administrative permissions, and approval from immediate neighbors. In addition, the pylon-type antenna does not multiplex high power several transmission signals with different frequencies; for example, it is impossible to multiplex transmission signals whose power differences are for example, one at 300 k and the other at 1 kW.

The objective of the invention is to overcome the disadvantages of known MF antennas, so as to avoid any search for a new location for such an antenna and to propose more economical and more discreet solutions in the landscape especially in the periphery agglomeration.

To achieve this objective, a transmitting antenna in substantially hectometric waves is, according to the invention, characterized in that it comprises an existing vertical structure having a height of at least ten meters containing at least one electrically conductive element. connected to the earth and a wired electromagnetic excitation means essentially electrically conductive disposed at least partly near and outside the structure and connected to a transmitter so that the work radiates waves substantially hectometric.

The invention thus makes use of existing vertical structures, especially reinforced concrete or metal structures, such as broadcasting antenna towers, lighthouses, chimneys, water towers or lighting masts, which are often present near city to install antennas of high height according to the invention. No search for available land is necessary, and the complement provided by the wired means of excitation is discreet and blends visually with the existing structure. The main element radiating in the antenna according to the invention is constituted by the existing structure which radiates for a wide frequency band of a few tens of kilohertz effectively day and night in a coverage of between about 3 km and about 15 km at the soil surface.

According to a first embodiment, the excitation means is electrically coupled to the structure and comprises an excitation conductor wire extending substantially at least partially outside and along the structure. The lead wire has a first end connected to the emitter through an impedance matching means located substantially in front of the base of the work and a second end attached to the work.

In a second embodiment, the excitation means is magnetically coupled to the structure and comprises a conductive loop located outside and close to the structure, above the earth.

These two achievements can be combined. The electromagnetic excitation means then comprises several excitation conductor wires for different frequency bands according to the invention and / or several conductive loops for different frequency bands in accordance with the invention.

Other features and advantages of the present invention will emerge more clearly on reading the following description of several preferred embodiments of the invention with reference to the corresponding appended drawings in which: - Figure 1 is a schematic vertical view of a transmitting antenna according to a first embodiment of the invention with an excitation conductor wire for electrical coupling; - Figure 2 is similar to Figure 1 and relates to a variant of the first embodiment of the folded dipole type;

FIG. 3 is a schematic vertical view of an antenna according to a variant of the first embodiment of the symmetrical doublet type; FIG. 4 is another variant of the first embodiment without an impedance matching cell but with conductors displaceable at the ends of the excitation conductor wire; FIG. 5 is yet another variant of the first embodiment without an impedance matching cell and with J-driving of the excitation wire;

FIG. 6 is a variant of the first embodiment with a terminal load for the excitation conductor wire;

FIG. 7 is a schematic vertical view of a dual frequency antenna with two excitation conductor wires of the type shown in FIG. 4;

FIG. 8 is a diagrammatic vertical view of a dual frequency antenna with a plug circuit excitation conductor wire according to another variant of the first embodiment;

FIG. 9 is similar to FIG. 8 but with a capacitive termination of the two-frequency excitation conductive wire;

FIG. 10 is a schematic vertical view of a dual-frequency antenna with deployed conductor wires forming two terminal capacitors at the high ends of two excitation conductor wires; FIGS. 11 and 12 still show other antennas according to the first embodiment with a terminal capacitance of the coaxial type internal to the structure; Figure 13 shows a symmetrical doublet type antenna as shown in Figure 3, but with two coaxial terminal capacitors;

FIG. 14 is a schematic vertical view of an antenna with an excitation conductive loop for magnetic coupling according to a second embodiment of the invention;

FIG. 15 shows a radiating antenna with three frequencies according to the second embodiment;

FIG. 16 is a schematic vertical view of an electrically and magnetically coupled antenna combining an excitation conductor wire according to the first embodiment and a conductive excitation loop according to the second embodiment; and

- Figures 17 to 22 are respectively vertical schematic views of antennas according to the invention using at least partially elements of various existing vertical structures.

Reference will be made below to an existing DVRN tower for Network Video Broadcasting

National intended to support various transmit and receive antennas especially for television signals and other telecommunications signals, particularly with mobile terminals, as an existing vertical structure having a height of at least about ten meters .

For example, as shown in FIG. 1, the tower 1 is a long shaft constructed of reinforced concrete, the height of which is generally between about 10 m and more than about 100 m, and which may comprise a intermediate platform 2 for supporting various transmitting and / or receiving antennas.

The tower 1 comprises one or more electrically-connected conductive elements connected to earth T which are schematically represented by a metal column 3 extending vertically from the ground in the tower 1. In practice, the electric ground is constituted by a network or trellis of conduct son 11 buried under and / or near the tower 1. The metal column 3 is schematically representative for example of a metal staircase so as to access from the ground T to the platform 2, and / or from one or several metal conduits or sheaths of water, or one or more metal reinforcements and reinforcements generally embedded in the concrete walls of the tower.

Typically, the transmitting antenna is capable of transmitting signals at a frequency of the order of 1.5 MHz with a power of 5 kW fed by a transmitter E assumed for example connected to the antenna through a cable d AC coaxial power supply.

According to a first embodiment, the metal elements of the tower 1 radiate in response to electromagnetic excitation by coupling or electrical continuity by a wire-type excitation means of the conductive wire type extending substantially at least half to the outside and along a vertical part of the existing structure that constitutes tower 1.

The first embodiment can be divided into a first group of variants for relatively high revolutions, whose height is at least equal to λ / 4 substantially, or at least of the order of 50 m for a transmission frequency of 1, 5 MHz, and a second group of variants for relatively low turns whose height is substantially between λ / 8 = 25 m and λ / 4 = 50 m.

According to a first variant of the first embodiment shown in FIG. 1, the antenna comprises a thin linear excitation conductor wire 4a, for example of diameter approximately 10 mm, having a length substantially equal to λ / 4 and extending vertically. near the tower 1, for example 1 m to 5 m from the tower. The wire 4a is stretched between a first end 41a connected to the output 51d of an impedance matching cell 5 disposed on the ground T substantially in front of the base of the tower 1 and a second end 42a remote from the ground and fixed to platform 2 of tower 1 through an electrical isolator 6a. The adaptation cell 5, also called adaptation cabin, comprises for example at the output of a power amplifier connected through the coaxial cable CA to the emitter E, various inductive and capacitive variable adaptation elements in series and in parallel in order to reduce the complex impedance of the antenna substantially to the characteristic resistive impedance of the coaxial cable typically equal to 50 Ω. For example, the cell comprises two capacitors in series between the power amplifier if it exists, or the internal conductor of the AC cable, and the first end 41a of the excitation wire 4a, as well as an inductance between a common terminal to abilities and the earth. The adaptation cell thus constitutes a preferably adjustable impedance transformer, which may be supplemented by safety circuits to prevent any heating of the adaptation elements as a function of the transmission power. The insulator 6a is for example constituted by an insulating wire of synthetic material stretched between the second end 42a of the excitation conductor wire and the platform 2. In FIG. 1, the exciter wire 4a of length λ / 4 acts as a means coupling tightly with the tower to excite the conductive element 3 in the tower 1 which constitutes the main radiating element. The impedance of the antenna is relatively low and depends on the ratio of the dimensions, in particular diameters and lengths, of the wire 4a and the tower 1.

In operation of the antenna, the inductor current in the excitation wire 4a and the currents induced in the tower 1 are balanced, and a part of the induced currents is also distributed in the tower, in the upper part above the wire 4a. The invention thus exploits the entire infrastructure of the tower for the radiation of emission signals transmitted by the emitter E. The wider the tower, the wider the bandwidth of the antenna, which advantageously decreases the reactance of the antenna and increases the radiation resistance of the antenna.

The main radiating element is thus the tower according to the variants described above and the lower part of the tower is not isolated but to the ground. The lower part of the tower has a very low impedance and therefore a strong current area equivalent to a current belly. The conductor wire 4a placed at a distance of about 1 m to about 5 m from the tower excites the latter in quarter-wave in order to obtain a complex impedance adaptable in the adaptation cell 5. When the electric ground offered by the tower is correctly made, the apparent power of the antenna is substantially equal to the power of the emission transmitter E. Preferably, a ground network 11 is added to the existing network and improves the efficiency of the antenna typically by constituting a dozen son or metal conductive strips arranged in a star and having each a length of λ / 4. The ground network may be installed beneath the matching cell 5 and connected thereto.

In order to allow a relatively high transmission power and to reduce the electrical losses, the conductive wire 4a is replaced by a conductive tube or by a cage of several parallel conductive wires, which makes it possible to reach transmission powers of 5. kW while guaranteeing a relatively wide bandwidth.

Two other variants of the first embodiment shown in FIGS. 2 and 3 still relate to an electrically conductive wire type excitation means with an impedance matching cell 5.

In FIG. 2, the excitation lead 4b still has its lower end 41b connected to the impedance matching cell 5, but has its upper end 42b connected to the conductive element 3 of the tower 1. For example , the conductive wire 4b of approximately λ / 4 length extends mainly vertically close to the tower 1 under the platform 2 by means of an insulator 6b which suspends it under the platform, then is bent under the platform and closed under the conductor 3 through the end 42b which is welded to the conductive element 3 of the tower. When the excitation conductor wire 4a has a length substantially equal to λ / 4 and the length of the conductive element 3 in the tower 1 between the earth T and the weld connection point at the wire end 42b is substantially equal to λ / 4, the antenna is of the half-wave dipole type folded and provides a higher impedance to earth. This arrangement globally places the antenna, including the excitation wire 4b, galvanically to ground.

In the variant shown in FIG. 3, the excitation wire has a symmetrical doublet structure and is composed of two excitation conductor wires 4c aligned vertically along the tower 1 and each having a length substantially equal to λ / 4 . The tower is then very high, more than 100 m approximately. The ends close to the two conductive wires 4c are connected by an insulator 61 and are powered by the transmitter through the matching cell 5 and a power balancer 52 which equi-distributes the power of the transmission signal between the two wires. drivers 4c. The upper end 41c of the upper conductor wire 4c is suspended under the platform 2 of the tower 1 by an insulator 6c, and the lower end 51c of the lower conductor wire 4c is located above the ground T and can be connected to this one also by an insulator. The antenna according to this third variant of the half-wave half-wave type with symmetrical power supply has a higher gain and a lower dependence on the earth since a belly current is present in the center of the tower at the insulator central 61.

Two other variants of the first embodiment of the invention are shown in FIGS. 4 and 5 and differ from the first three variants in the absence of the impedance matching cell 5, which makes them makes it more economical. The adaptation cell is replaced, as parts of the adaptation means, by a movable conductor at the top of the excitation wire and / or a length adjustable conductor at the bottom of the excitation wire.

The antenna, according to FIG. 4, comprises, as in the first variant shown in FIG. 1, an excitation conductor wire 4d which is stretched substantially vertically along the tower 1 between an insulator 6d suspended under the platform 2 and the vicinity of the earth T. The impedance of the antenna is adapted to the impedance of the AC power supply coaxial cable connected to the emitter E by adjustable matching means at the ends of the excitation conductor wire 4d. The upper end 42d of the excitation wire 4d is connected to the tower 1 through a short-circuit conducting wire 44d which extends substantially perpendicularly to the tower and slides via a metal slider on the wire 4d along the tower 1, and / or the lower end 41d of the excitation wire 4d is connected to the transmitter through a telescopic conductor 43d whose one end adjacent to the ground T is fixed and connected to the conductor internal of the AC power coaxial cable and whose other end slides along the wire 4d. Three positions of the conductor 43d are shown schematically in FIG. 4. The conductor 44d movable along the upper portion of the excitation wire and the height adjustment with respect to the ground of the active portion of the excitation wire 4d by the Conductor 43d minimizes the antenna reactance in order to reduce the impedance of the antenna to a resistive value substantially equal to the characteristic impedance of the AC power cable at 50 Ω. The fifth variant of the first embodiment shown in FIG. 5 concerns an antenna with a J-point of attack in which the lower 41e and upper ends 42e of the excitation wire 4e are respectively connected to the inner conductor of the coaxial power supply cable. CA located at the ground T and the conductive element 3 internal to the tower 1. The excitation wire 4e then extends obliquely relative to the vertical axis of the tower. The advantage of this variant is to adjust the height of the connection point 42e of the excitation wire 4e to the conductive element 3 in the tower in order to adapt the impedance of the antenna thus formed to the characteristic impedance AC power cable. The height of the end 42e, the inclination of the conductive wire 4e and the distance of the attachment point 41e of the wire 4e relative to the ground T and the tower 1 contributes to the impedance matching.

By eliminating the impedance matching cell 5, the cost of the two variants according to FIGS. 4 and 5 is less than that of the three variants according to FIGS. 1, 2 and 3.

The antenna shown in FIG. 6 is a combination of those shown in FIGS. 2 and 4. It comprises an excitation conductor wire 4f extending substantially parallel to the tower 1. The upper end 42f of the wire 4f is not not connected directly to the conductive element 3 of the tower 1, but is connected through a load 44f to the conductive element 3. The lower end 41f of the excitation wire 4f is connected to the inner conductor of the coaxial cable. supply CAf through a conductor of adjustable length 44f similar to the conductor 43d shown in Figure 4, which allows to adjust the active height of the excitation wire 4f with respect to the earth T. The load 44f may be a terminal capacitance at a loss or preferably the characteristic impedance of the coaxial supply cable CAf so that the conductive element 4f the seat of a progressive wave. These arrangements allow a change in frequency without using the adaptation cell and place such an antenna on towers of low height, less than λ / 4, while expanding the bandwidth.

The antennas described above, according to the first embodiment of the invention, relate to mono-frequency antennas, that is to say for a length of the excitation conductor wire substantially equal to λ / 4, where λ is the length wave corresponding to the center frequency of the band in which signals are to be transmitted by the antenna.

However, an antenna according to the invention can radiate signals in two or more frequency bands. Thus around the tower 1, several wire excitation means 4a, 4b, 4c, 4d, 4e, 4f of the same type or of different types are arranged around the tower 1 so as to transmit signals respectively in frequency bands. different. Each excitation wire is associated with a supply means comprising a respective emitter and a respective coaxial cable, where appropriate with a respective matching cell. Such an arrangement of excitation means decoupled from each other makes it possible to add or subtract an excitation means independently of the others and thus to multiplex emissions in different frequency bands as a function of requirements. For example, as shown in FIG. 7, a dual frequency antenna comprises two excitation conductor wires 4g and 4h that are diametrically opposite with respect to tower 1 and similar to the excitation wires 4d shown in FIG. 4. Each wire 4g, 4h has an upper end suspended by an insulator 6g, 6h under the platform 2 of the tower 1 and terminated by a short wire 44g vertically displaceable and in contact with the tower 1, and a lower end terminated by a conductor of adjustable length 43g, 43h connected to the inner conductor of a power cable CAg, CAh.

According to another variant of a dual frequency antenna, the excitation means is still monofilar, as in FIGS. 1 to 6 and comprises, with reference to FIG. 8, two wires 4i and 4j which are suspended between the platform 2 of the turn 1 via an insulator 6j and earth T by a conductor of adjustable length 43i and which are arranged vertically in the extension of one another. The upper end 42i of the lower wire 4i and the lower end 41j of the upper wire 4j are separated by a plug-type bandpass filter which traps the excitation frequency Fi of the lower wire 4i and which passes the frequency of Fj excitation of the upper wire 4j.

According to the embodiment illustrated in FIG. 8, the lower end of the lower wire 4i is connected, analogously to that of the wire 4d shown in FIG. 4, to an adjustable length conductor 43i itself directly connected to the cable of FIG. CAi power supply to adapt the impedance of the dual frequency antenna to the characteristic impedance of the power cable. The upper end 42j the upper wire 4j is suspended under the platform 2 by an insulator 6j, as the excitation wire 4a in Figure 1. The excitation son 4i and 4j have a length substantially equal to λi / 4 and λj / 4 corresponding to transmission frequencies Fi and Fj respectively. This variant is rather intended for a tower 1 having a relatively high height of at least about 100 m.

According to another variant shown in FIG. 9 of the type of that shown in FIG. 8, the upper conductive wire 4j is of the type of that 4f shown in FIG. 6, that is to say having a second end connected to a terminal capacitive load 44j. The capacitive load 44j is constituted by a conductive winding of a few turns of wire around the tower 1 and fixed thereto, having an end connected to the upper end 42j of the excitation wire 4j. This variant is rather intended for a tower 1 of average height of the order of 50 m for at least one of the excitation elements 4i or 4j with a length corresponding to λi / 8 or λj / 8. In this variant, the total wire 4i-4j has the lower end 41i which is a current belly for the excitation frequency Fi of the lower excitation wire 4i and is the seat of a progressive wave for the frequency of excitation Fj of the upper excitation wire 4j.

FIGS. 10, 11 and 12 show variants of the first embodiment with excitation wire for low-rise towers, for example between λ / 8 and λ / 4.

In FIG. 10, the antenna of the invention comprises two excitation conductor wires 4k and 41 whose lower ends are adjustable by to the ground through conductors of adjustable length 43k and 431, as in the dual frequency antenna shown in Figure 7. However, in the variant of Figure 10, the tower is significantly smaller than that shown in Figure 7 and the conducting wires 4k and 41 extend substantially vertically along the tower at lengths substantially equal to λk / 8 and λl / 8 respectively corresponding to emission frequencies Fk and FI produced by respective emitters Ek and El. to compensate for the insufficient electrical height of the tower 1, the upper end 42k, 421 of the excitation wire 4k, 41 is fixed by a respective insulator 6k, 61 to the platform 2 of the tower and supports one or preferably several leads respectively 45k, 451 each having a length equal to λk / 8, λl / 8. The wires 45k, 451 are deployed in a star substantially in a horizontal plane and / or obliquely to the tower and provide a terminal capacitance of the excitation wire 4k, 41 which fictitiously increases the electrical length of the excitation wire. The contribution of the excitation conductor wire 4k, 41 to the radiated electromagnetic field is greater since the tower of smaller height is less effective.

The terminal capacitance constituted by each set of deployed conductor wires 45k, 451 may be replaced by a roll-type capacity around the tower, such as that shown in FIG. 9.

According to another variant shown in FIG. 11, the end load is replaced by a coaxial section inside the tower. The antenna comprises a first bent portion 4ml excitation lead wire, similar to the wire 4b shown in Figure 2, extending outside the tower 1 substantially vertically along the latter and suspended by an insulator 6m, and a second portion of excitation conductor wire 4m2 extending substantially vertically in a conductive sheath 44m. The sheath 44m is fixed in the tower 1 and connected to the earth T via the conductive element 3. The part 4m2 and the sheath 44m constitute a coaxial termination. The length of the first and second portions of 4m2 excitation lead wire is substantially equal to λ / 8. For example, the lower end 41m of the first 4ml excitation lead portion is connected to an impedance matching cell 5. The active portion 4ml is thus lengthened fictitiously by the non-radiating coaxial extension 4m2-44m constituting a coaxial terminal capacitance whose role is similar to a set of deployed wires 45k, 451 or wound coils 44j. If the height of the tower 1 is not sufficient, the coaxial termination 4m2-44m may be wound for example helically inside the tower instead of extending straight. For a relatively low tower, the upper end common to the 4ml and 4m2 excitation lead portions may be located at the top of the tower, as shown in FIG. 12, so that the tower has a height substantially equal to λ / 8.

The fictitious extension of an excitation conductor wire according to the variants shown in FIGS. 10 to 12 may also be applied to each of the excitation lead wires 4c of a doublet type antenna shown in FIG. 3. As shown in FIG. 13, each excitation lead of the doublet comprises a first outer portion 4c1 and a second portion 4c2 extending in a sheath conductor 44c located inside the tower 1. The parts 4c1 and 4c2 also each have a length substantially equal to λ / 8.

According to a second embodiment of the antenna of the invention, a magnetic excitation electromagnetic excitation wired means comprises a conductive excitation loop 7a located outside and close to the tower 1 above the earth T , as shown in Figure 14.

The excitation loop 7a is for example located substantially at the base of the earth 1 and constituted by a square frame of a thin conductive wire, or a conductive tube, or a cylindrical cage of parallel conductive wires . The frame has a perimeter of several meters. Two vertical sides of the loop 7a are substantially parallel to the tower 1 and typically between about 2 m and 3 m long. The loop 7a extends in a substantially vertical plane, diametrical to the tower, at an isolation distance of 1 to 2 m from the earth T. From the ends of the mouth 7a for example located at a vertex close to the earth T and remote from the tower 1 are connected to a transmitter E through an impedance matching cell 5 and a coaxial AC power cable. The nearest side of the tower is located a few tens of centimeters in order to magnetically couple the loop and the tower. For a tower of low height substantially between λ / 8 and λ / 4, the excitation loop 7a is located substantially at a current belly to excite the conductive element 3 in the tower so that it radiates to the tuning frequency F of the loop 7a corresponding to the wavelength λ. Instead of the impedance matching cell 5 and the excitation loop 7a being fixed on the ground, these can be removable and for example installed in a reporting truck which can transmit broadcasting signals through the turn 1 when he is stopped almost against the tower.

As shown in Figure 15, several loops 7a, 7b and 7c having different dimensions and tuned to respective frequencies Fa, Fb and Fc are magnetically coupled to the tower 1 so that they radiate signals in three different frequency bands. For example, the loops 7a and 7b are located near the base of the tower 1 to emit signals whose wavelengths λa and λb are respectively substantially equal to four times the tower height and twice the height of the tower. the tower, and the third excitation loop 7c is situated substantially halfway up the tower in correspondence with a current belly in order to excite an emission whose half-wavelength λc / 2 is substantially less than height of the tower.

As shown in FIG. 16, the tower 1 serves to radiate signals at different frequencies Fa and Fh resulting from a mixed coupling on the one hand with an excitation conductor wire according to the first embodiment of the invention, such as that the wire 4h shown in Figure 7, on the other hand magnetic with an excitation loop 7a, according to the second embodiment of the invention shown in Figure 14.

The invention is not limited to an existing diffusion tower as a workpiece radiating substantially hectometric waves by excitation of a substantially vertical conductor wire or a loop excitation. Other existing structures generally including several conductive elements connected to the earth can serve as a radiating work. For example, such a structure may be an existing tower, a water tower or an elevated reservoir, a lighthouse or a beacon at sea, a street lamp or a metal mast supporting projectors in particular.

Figures 17 to 22 show schematically by way of non-limiting examples the at least partial use of existing vertical structures to achieve a transmitting antenna according to the invention.

FIG. 17 shows an existing inclined stay 4a for a tower 1. The lower end 41a of the stay is connected to an impedance matching cell 5. The upper end 42a of the stay is connected by an isolated tensioner 6, so that to constitute an excitation wire of the type of that shown in FIG.

Figure 18 shows a folded dipole antenna shown in Figure 2, using an existing wire stay 4b of a tower 1; the stay 4b has a lower end 41b connected to an impedance matching cell 5 and an upper end 42b connected to an inner conductor 3 in the tower by a small conductive element 44b. The small attached conductor 44b has ends welded to the stay 4b and the inner conductor 3.

In Figure 19, the existing structure is constituted by a lattice 1M wire lattice which comprises two existing cable stays 4n and 8 extending obliquely along the tower. The excitation of the tower 1M is carried out by mixed coupling of the type of that described with reference to FIG. 16, by means of a conductive excitation loop 7a located at the base of the tower 1M and connected to a cell impedance matching 5a, and by means of an excitation conductor wire constituted by the stay 4n whose upper end 42n is isolated and whose lower end 41n is connected to a matching cell 5n.

In this embodiment example in FIG. 19, the second existing stay cable 8 acts as a non-powered radiating parasitic source with respect to a powered radiating pilot source constituted by the first stay 4n. One end of the stay 8, for example the upper end 82, is isolated from the tower by means of an electrical isolator 84. The other end 81 of the stay 8, in this case the lower end of the it is charged by a reactor 83 connected to the earth T. Depending on whether the reactance 83 is positive and therefore inductive, or negative and therefore capacitive, the stay 8 reacts as a reflective element or as a steering element with respect to the IM tower assembly and 4n excitation wire. The additional gain conferred by the stray strut 8 can be between 1 dB and 3 dB. The antenna according to Fig. 19 has an azimuthal pattern in which the radiated field is decreased in a particular direction in front of or behind the stray strut 8 and is increased in a direction opposite to the particular direction.

FIG. 20 shows an existing structure of the water tower or elevated reservoir type RE which serves to fix a terminal-conducting excitation wire 4f 44f surrounding the tower supporting the reservoir RE, according to a combination of the variants shown in FIGS. 9, and a dual-frequency excitation conductor wire 4i-4j with an intermediate plug circuit 44i, as shown in FIG. 8. Advantageously, the tied water distribution network the water tower constitutes, when it is metallic, a network of earth that improves all the more the performance of the antenna that the height of the water tower is low. FIG. 21 shows an existing flagship or sea-beacon type structure along which a 41-4 terminal-frequency dual-frequency driver wire 44j surrounding a top portion of the lighthouse is installed, as shown in FIG. land 11 is here constituted by the sea constituting an excellent conductor and favoring an excellent propagation of the emission signals towards coastal cities.

In Figure 22, the existing structure is constituted by a luminaire such as a mast or a lamppost LA supporting several projectors. Along the mast or lamppost are arranged a first excitation lead 4f whose upper end is terminated by a load 44f connected to mast or lamppost LA and whose lower end is adjustable in height by a conductor 43f, as shown in FIG. 6, and a second excitation conductor wire 4a whose lower end 41a is connected to an impedance matching cell 5 and whose upper end 42 is connected under an upper support of projectors by an insulator 6a. Such a mast is for example already installed in a stadium, a fairground, a road or rail interchange, near a large square, etc.

Claims

1 - Antenna emission in substantially hectometric waves, characterized in that it comprises an existing vertical structure (1) having a height of at least ten meters containing at least one electrically conductive element (3) connected to the earth (T) and a substantially electrically conductive electromagnetic excitation wire means (4a, 7a) disposed at least in part near and outside the structure and connected to a transmitter (E) so that the work radiates from substantially hectic waves.

2 - Antenna according to claim 1, wherein the excitation means comprises a conductive wire (4a) extending substantially at least partially outside and along the work (1).

3 - Antenna according to claim 2, wherein the conductive wire (4a) has a first end (41a) connected to the emitter (E) through an impedance matching means (5) located substantially in front of the base of the structure (1) and a second end (42a) fixed to the structure (1).

4 - Antenna according to claim 3, comprising a ground network (11) consisting of son or conductive strips arranged in a star and connected to the adaptation means (5).

5 - Antenna according to claim 2, wherein the first end (41d) of the wire excitation circuit (4d) is connected to the transmitter (E) through a conductor (43d) of adjustable length, as an impedance matching means.

Antenna according to any one of claims 2 to 5, wherein one end (42a) of the excitation wire (4a) is fixed to the structure (1) through an electrical insulator (6).

7 Antenna according to any one of claims 2 to 5, wherein an end (42b, 42e) of the excitation wire is connected to the conductive element (3) of the structure (1).

8 - Antenna according to any one of claims 2 to 5, wherein an end (42d) of the excitation wire (4d) is connected to the structure (1) through a conductor (44d) movable along the conducting wire as an impedance matching means.

9 - Antenna according to any one of claims 2 to 5, wherein one end (42f) of the conductive wire (4f) is connected to the conductive element (3) of the structure (1) through a load ( 44f).

10 - Antenna according to any one of claims 2 to 5, wherein an end (42j) of the excitation wire (4j) is connected to a terminal capacitive load (4 j) constituted by coils of conductive wire around the book (1).

Antenna according to any one of claims 2 to 5, wherein one end (42k) of the excitation wire (4k) is fixed to the structure (1) through an insulator (6k) and supports one or more deployed conductor wires (45k).

12 - Antenna according to any one of claims 2 to 5, wherein the excitation wire comprises a first portion (4ml) extending along the structure (1) and a second portion (4m2) s' extending in a conductive sheath (44m) located in the structure (1) to constitute a coaxial terminal capacitance whose length is substantially equal to the first part (4ml) of the excitation wire.

13 - Antenna according to any one of claims 2 to 12, wherein the excitation wire is composed of two son (4i, 4j) in the extension of one another and separated by a bandpass filter (44i).

14 - Antenna according to claim 2, wherein the excitation wire is composed of two excitation conductor wires (4c) aligned along the structure (1) and having close ends connected by an insulator (61) and powered by the emitter (E) through a power balancer (52).

15 - Antenna according to any one of claims 2 to 14, wherein the excitation wire is replaced by a conductive tube or a cage of several parallel conductive son.

16 - Antenna according to claim 1, wherein the excitation means comprises a loop conductor (7a) located outside and close to the work (1), above the earth (T).

17 - Antenna according to claim 16, wherein the conductive loop (7a) extends in a substantially vertical plane and has a substantially parallel side to the structure (1).

18 - Antenna according to claim 16 or 17, wherein the excitation conductive loop

(7a, 7c) is located substantially at the base or the middle of the structure (1).

19 - Antenna according to any one of claims 16 to 18, wherein the excitation loop (7a) has a perimeter of a few meters.

Antenna according to claim 1, wherein the electromagnetic excitation means comprises a plurality of excitation conductor wires for different frequency bands according to any one of claims 2 to 15 and / or a plurality of conductive loops for different frequency bands. frequency according to any one of claims 16 to 19.

21 - Antenna according to any one of claims 1 to 20, comprising another wire means (8) unpowered, disposed substantially along the structure (1), and having an end (82) isolated from the structure and another end (81) charged by a reactor (83) connected to the earth.