WO1995005012A1 - High frequency antenna system - Google Patents

High frequency antenna system Download PDF

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Publication number
WO1995005012A1
WO1995005012A1 PCT/FI1993/000314 FI9300314W WO9505012A1 WO 1995005012 A1 WO1995005012 A1 WO 1995005012A1 FI 9300314 W FI9300314 W FI 9300314W WO 9505012 A1 WO9505012 A1 WO 9505012A1
Authority
WO
WIPO (PCT)
Prior art keywords
antenna
support
arrays
subarrays
antenna system
Prior art date
Application number
PCT/FI1993/000314
Other languages
French (fr)
Inventor
Simo Lehto
Original Assignee
Rautio, Aune
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rautio, Aune filed Critical Rautio, Aune
Priority to AU47105/93A priority Critical patent/AU4710593A/en
Priority to PCT/FI1993/000314 priority patent/WO1995005012A1/en
Publication of WO1995005012A1 publication Critical patent/WO1995005012A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/02—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical movement of antenna or antenna system as a whole
    • H01Q3/04—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical movement of antenna or antenna system as a whole for varying one co-ordinate of the orientation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
    • H01Q21/061—Two dimensional planar arrays
    • H01Q21/062—Two dimensional planar arrays using dipole aerials

Definitions

  • the present invention is related to antenna systems for high frequency (HF) uses.
  • High frequency (HF) broadcasting and other HF services operate in the 3-30 MHz frequency range.
  • the HF broad ⁇ casting stations require economical high performance antenna systems which are rotatable in azimuth for providing high effective power gain for the present and future target areas in varying ionospheric condi- tions.
  • the invention is also related to other HF services (maritime, aeronautical, defence etc.) re ⁇ quiring high performance transmitting and receiving antenna systems.
  • HF broadcasting utilizing s ywave propagation on frequencies between 5.85 - 26.1 MHz for international broadcasting differs from other broadcasting services (e.g. VHF/UHF broadcasting) in several ways.
  • HF broad ⁇ casting takes place through one or more reflections from the ionosphere (generally 100-400 km above the the surface of the Earth) , which acts as a natural satellite of the Earth. Therefore, it requires trans- mitting antennas with high performance.
  • HF broadcasting transmis ⁇ sions are generally directed to separate target areas determined by language, political reasons, listening times, and propagation conditions.
  • An HF broadcasting station is usually designed to transmit programs to a number of target areas within a country or interna ⁇ tionally. During a 24 hour period an HF broadcasting station successively covers a relatively large number of target areas. In most cases the target areas change during the lifetime of a station.
  • the geometry of the propagation and the properties of the propaga ⁇ ting channel also change with time.
  • the variations of the ionosphere can be taken into account by using prediction methods based on the periodicity and/or the measured (near) real-time properties of the ionosphe ⁇ re. In statistical HF propagation prediction methods the changes are treated as disturbancies to deter- ministic propagation.
  • the present HF broadcasting antennas utilized at these stations have the following deficiencies:
  • a dipole curtain antenna of the present state of the art consists of a number of simple horizontal dipole radiators which typically are approx. .5 or 1 wave ⁇ lengths long on the center operating frequency of the antenna.
  • the gain of a single radiator is low.
  • the dipole radiators are arranged into a 2-dimensional planar group. They are placed vertically one above the other (stacked) or placed side-by-side (as bays) to form a regular mat- rix-like configuration.
  • a 4*4 dipole array is de ⁇ fined as a 4-bay, 4-stack array. All the dipoles of the array are fed by means of a feed system consisting of feedlines and matching components.
  • the radiators and the feed system are broadband. Unidirectional operation is achieved by using a parasitically excited wideband screen reflector behind the radiator plane.
  • the fixed dipole curtains have limited controllability in the horizontal plane.
  • the electrical slewing of the main beam is limited to a maximum of ⁇ 30°, which leads to the inherent requirement for a large number of antennas for full coverage of present and future target areas.
  • 4-5 fixed antennas per trans- mitter are needed.
  • the azimuth control of the main beam of fixed curtain antennas requires at least 2 bays (parallel vertical stacks) of dipoles.
  • the planar configuration makes the antenna system wide in the direction perpendicular to the main beam requiring two supporting towers. If employed, the vertical control interacts with the horizontal slewing resulting in a large total number of control switches.
  • the present rotatable log-periodic antennas lack the high power gain needed for high quality HF broadcast- ing.
  • the present rotatable dipole curtain antennas are in fact fixed dipole curtains which have been made rotatable by rotating the whole fixed structure on a bearing or a circular rail. They offer high gain but require very large self supporting structures with high cost. The high cost results from the inherent wide configuration of the dipole curtain arrays which makes it impossible to use guywires for supporting the rotating structure.
  • Rotatable dipole curtains covering the 6 MHz band require a self standing (nonguyed) support typically 80 m high.
  • Higher structures needed for obtaining lower take-off-angles down to 2° or for obtaining effective vertical control on the lower frequency bands require self standing supports 120-140 m high.
  • the large moment of inertia limits the time for 360° rotation of the rotating dipole curtains to approx. five minutes.
  • the problems related to the known state of technology in the field have lead to the present invention, in which a high performance antenna system is described.
  • the antenna system meets the requirements of modern HF broadcasting and other HF services together with economical advantages over present antenna construct- ions.
  • the availability of effective CAD programs for subarray and array design has made the invention practical.
  • the present invention introduces a high frequency HF antenna system comprising a combination of an HF antenna and a support system, wherein the HF antenna comprises two or more arrays, each array comprising two or more subarrays, each subarray comprising two or more radiators, each radiator electrically covering two or more frequency bands, feeding system for brin ⁇ ging the transmitter power to the arrays, and suppor ⁇ ting means for supporting the radiators of the subar ⁇ rays and the subarrays on the vertical support and wherein the support system comprises a single vertical support which is supported at the base, means for supporting the vertical support in the vertical posi ⁇ tion, and means for rotating at least part of the HF antenna.
  • the antenna system of the invention uses only one vertical support instead of two supports, which makes it possible to rotate the structure economically for directing the main beam accurately towards each target area. Therefore, only a small number of antennas is required for full coverage of all target areas.
  • an HF antenna of the invention is compact with simultaneous broadband coverage of frequency bands, which can be selected to correspond to the needs of each antenna system in accordance with the basic characteristics of the invention.
  • the geometrically partitioned antenna configuration makes it possible to support the rotatable structure by one or more sets of guy wires. This makes it eco ⁇ nomical in comparison to unguyed rotatable dipole curtains. Also the electric horizontal slewing system is eliminated making vertical control much simpler. Because of the small moment of inertia the new antenna system can be rotated 360° in 1-2 minutes.
  • the invention is a combination of a number of new inventions in the fields relevant to obtaining the benefits of the antenna system.
  • the new invention possesses an inherent capability for optimizing the design to meet the specific requirements of each application.
  • Fig. 1 shows an overall schematic view of one embo ⁇ diment of the single support antenna system
  • Fig. 2 shows three possible embodiments a-c of mul ⁇ tiband radiators for the subarrays of the antenna system
  • Fig. 3 shows three possible embodiments a-c of su- barrays for the antenna system
  • Fig. 4 shows two possible embodiments a-b of the array configurations of the antenna system
  • Fig. 5 shows schematically four embodiments a-d of multisupport antenna systems of the inventi ⁇ on
  • Fig. 4 shows two possible embodiments a-b of the array configurations of the antenna system
  • Fig. 5 shows schematically four embodiments a-d of multisupport antenna systems of the inventi ⁇ on
  • Fig. 6 shows schematically two embodiments a-b of the transmitting stations using the antenna systems of the invention.
  • the antenna system comprises a vertical support, e.g. tower 1 of any kind.
  • Two or more 3-dimensional subarrays 2 are accommodated in the spaces between and above the guywires 5.
  • the tower 1 is placed on a bearing 3 which is located on the ground at the base of the tower 1.
  • the whole antenna system is rotated by means of a rotating mechanism 4 located at the base of the tower 1.
  • One or more sets of the guywires 5 (three in each set shown as an example) are attached to the tower 1 by placing a bearing or a slip ring 6 around the tower for each set, e.g. at each guying level.
  • the guywires 5 are attached at the low end of each guywire to the ground at a distance from the vertical tower 1 and at the high end of each guywire 5 to a bearing 6 on the vertical tower above the base level.
  • Fig. 2 (a-c) shows examples of embodiments of multi- band (for two or more bands) radiators 7 which are combined to obtain multiband subarrays with the re ⁇ quired electrical performance for the antenna systems.
  • radiators consists of optimally shaped radiating portions which are connected by means of optimally shaped feedlines.
  • the radiators are optimized for maximum gain and required feed proper ⁇ ties by selecting the shapes, dimensions and thick ⁇ nesses of the radiating portions and the shapes and dimensions of the feedlines.
  • the widths of the radiators are .5 - 1 wavelengths on the lowest operating frequency.
  • the heights of the radiators are .4 - .5 wavelengths on the lowest opera- ting frequency.
  • FIG. 2a An example of a broadband embodiment of the radiator is shown in Fig. 2a. This type of radiator is optimi ⁇ zed by selecting the dimensions of the horizontal radiating parts (heavy line) and the dimensions of the feedline (thin line) .
  • Fig. 2 (b) shows an example of the optimized shape of the radiating portion (heavy line) and optimized shape of the feedline (thin line) .
  • the radiator type shown electrically covers at least two broadcast frequency bands (e.g. the 6/7 MHz bands) with a free space gain of approx. 7-8 dBi depending on the exact dimensions.
  • Fig. 2c shows an example of the embodiment of a diffe ⁇ rent type of braodband radiator.
  • the radiators are constructed of metal wires, tubing or lattice structures.
  • the electric thickness of the radiating parts can be increased up to one meter or more by using e.g. cage-type structu ⁇ res or special types of folded dipole or other optimi ⁇ zed wideband structures.
  • the horizontally polarized radiators can be made vertically polarized e.g. by rotating them 90° or different types of vertically polarized radiators can be designed.
  • Fig. 3 Three embodiments of the structures of possible subar ⁇ rays are described in Fig. 3. They are directive arrays exhibiting directivity in the horizontal and vertical plane for obtaining high gain.
  • the basic design method is to use one radiator as driven ra ⁇ diator 8 and the other radiator as an reflecting radiator 9.
  • the reflecting radiator can be excited parasitically by bringing power to the undriven ra ⁇ diator by mutual coupling only or actively by using a feed line or a feed network for bringing power to the reflecting radiator.
  • the required current amplitudes and phases are ob ⁇ tained by optimizing the shapes and dimensions of the radiators and the feed networks.
  • the spacing between the radiators is typically .08 to .20 wavelengths on the lowest operating frequency.
  • the log-periodic feed is an example of the possible active feed networks for the subarrays. All types of compensation and phasing methods and components are included in the subarray design.
  • Typical free space gain of the optimized subarrays with two radiators is 10-11 dBi.
  • Subarrays with proper phasing provide front-to-back ratios of 15-25 dB.
  • the feed properties of the subarrays can be optimized to obtain VSWR below 1.5 on two or more frequency bands. More than two radiators can be added for improving the radiation properties if needed.
  • the group of two or more subarrays fed simultaneously through a common feedline is defined as an array of subarrays.
  • the simplest examples of arrays are regular arrays of identical subarrays. Two subarrays placed side-by-side at the same heigth form a 2-bay array. Two subarrays placed one above the other form a 2-stack subarray. The combination of these forms a 2-bay, 2-stack array of four subarrays.
  • the distances between the centers of the subarrays are .5 - 1 wavelengths on the lowest operating frequency of the array.
  • the invention comprises all possible 3-dimensional arrays of all types of subarrays electrically covering two or more frequency bands.
  • arrays with uneven spacings in the vertical plane are typical of the invention.
  • two or more arrays can be placed on the single vertical support. They can be identical or different in size and dimensions for different frequency bands. Some of the radiators of the subarrays of the separate arrays can be common. They can radiate to any direction.
  • the use of subarrays covering two or more frequency bands with broadband radiators allows arrays covering all the required frequency ranges (e.g. ten international broadcasting bands) to be placed on a single guyed support.
  • Fig. 1 illustrates the invention by showing an antenna system which consist of a 1-bay, 2-stack array of subarrays of two optimized radiators for the lower frequency bands (shown on the left of the vertical support) and a 1-bay, 4-stack array of subarrays of two optimized radiators for the higher bands (shown on the right of the vertical support) .
  • the arrays radiate into the common direction shown in the drawing.
  • CAD-methods the interaction of the arrays is minimized.
  • Fig. 4 illustrates two embodiments of array configura ⁇ tions for the international broadcasting bands.
  • Fig. 4a shows a 4-band antenna system consisting of two 2- band arrays.
  • Fig. 4b shows a 10-band antenna system consisting of two 5/6-band arrays.
  • the 4-band antenna system is obtained by placing a 1-bay, 3-stack array of 6/7 MHz subarrays of Fig. 3b on the tower and a 2- bay, 3-stack array of 9/11 MHz subarrays of Fig. 3b in front of it. Both arrays radiate in the same directi- on.
  • the 10-band antenna system is obtained by placing a 2-bay, 2-stack array of 6/7/9/11 MHz subarrays on the tower and a 2-bay, 2-stack array of 13/15/17/19/- 21/26 MHz subarrays of Fig. 3a behind it. The arrays radiate 180 degrees apart.
  • the reflecting radiators of the side-by-side subarrays (of the type shown in Fig. 3a) have been mechanically integrated to form single wide radiating structures.
  • Typical array choices for the invention are 1-, 2-, or 3-stack arrays.
  • a rotating 3-stack anten ⁇ na system on a 130-140 m guyed tower with optimized subarrays makes it possible to obtain approx. 20 dBi gain on the 6 MHz broadcast band.
  • the feeding systems for bringing the transmitter power to the feed points of the subarrays are similar to the ones employed in dipole curtain antenna systems.
  • the feedlines (open wire lines, coaxial lines) , the mat ⁇ ching components, and the control switches are placed on the outside of the tower or inside the tower.
  • a rotating joint, flexible cables or other means are used for transfering the transmitter power to the antenna system.
  • the arrays are attached to the tower by means of 3-dimensional support structures.
  • the support structures of all the subarrays in the space available between or above the guy wire levels are integrated into 3-dimensional structures.
  • the invention places the rotating system on the ground for high reliability and easy maintainance. Standard components and subsys ⁇ tems from different fields of mechanical engineering can be used.
  • the two or more arrays fed simultaneously or at diffe- rent times form an antenna.
  • the combination of the antennas and the mechanical support results in the antenna systems invented.
  • the invention also includes a multisupport antenna system consisting of two or more single support anten ⁇ na systems operated collinearly for obtaining addi ⁇ tional gain for a horizontal angle sector.
  • a multisupport antenna system consisting of two or more single support anten ⁇ na systems operated collinearly for obtaining addi ⁇ tional gain for a horizontal angle sector.
  • Fig. 5 shows four embodiments of possible configurations.
  • Fig. 5 shows a line (a), arc (b) , triangle (c) and square (d) configuration.
  • the configurations of the multisupport antenna systems are selected and optimized to suit the radiation properties needed.
  • the rotation capability of the single support antenna systems increases the sector available in comparison to the collinear operation of fixed dipole curtains. It is also possible to obtain very high performance by feeding a multisupport antenna system with two or more transmitters for difficult target areas and/or propagation conditions.
  • Feedback control methods for the horizontal and vertical beam control based on (near) real-time data from the target areas can be added to the antenna systems.
  • a modern HF station can be built by using 1-2 antenna systems per transmitter depending on the frequency coverage.
  • Typical examples of stations with two and four transmitters are shown in Fig. 6.
  • Fig. 6a shows a two transmitter station with two antennas.
  • Fig. 6b shows a four transmitter station with five antennas. Virtually complete 360° coverage on ten frequency bands can be obtained.
  • Each single support antenna system or multisupport antenna system can be replaced by two (or more) antenna systems with cover less frequency bands.
  • Two antenna systems covering 4 and 6 bands respectively, are an example. They can be separately designed and optimized for the bands they cover. This flexibility allows all the antenna systems to be designed for optimizing the total performance and performance/cost- ratio of the station.
  • the benefits of the invention result from the inherent flexibility of the design approach which is based on separating an HF antenna system into a hierarchical structure consisting of the radiator, subarray, array, single support antenna system, and multisupport antenna system levels. This intellectual achievement forms the underlying idea of the invention.
  • the invention makes it possible to build an HF broadcasting station in several stages by starting with a small number of antenna systems.
  • the station can be expanded easily by adding new transmitters and optimally designed antenna systems.
  • the antenna systems are also well suited to the refurbishing and upgrading of existing HF stations.
  • the invention is not limited to HF broadcasting. It can be used in other HF services (maritime, aeronautical, defence, etc.) for transmitting and receiving purposes. In total, the invention provides a modern cost-effective antenna solution for most high performance, high-tech HF applications.
  • radiators there is large number of possible radiators, subarrays, and array configurations. This gives the invention an inherent flexibility for optimizing the design. Importantly, different types of radiators and subarrays can be combined. Subarrays with vertical polarization may be used in special applications. CAD methods allow antenna systems with optimized radiators, optimized subarrays and optimized arrays to be designed in practice for different applications.
  • All possible methods switching, broadbanding methods, compensation methods, remote or local mechanical control etc.
  • All possible methods for obtaining the broadband coverage needed for the radiators and subarrays are included.
  • All types of feeding systems for the subarrays are included in the invention.
  • All types of feeding, phasing and control systems for the arrays are also included.
  • All types of support structures e.g. telescoping towers, pivoted towers, mobile towers etc., and all hoisting and rotating methods can be used in connection with the invention.
  • the antenna systems made mobile for special purposes are also included.

Abstract

An HF antenna system consisting of two or more arrays of multiband subarrays consisting of multiband radiators attached mechanically to a single vertical support. The antenna system is rotated by placing it on a bearing at the base of the vertical support and supported in vertical position by attaching one or more sets of guy wires to one or more bearings on the vertical support. The invention includes a multisupport antenna system consisting of two or more single support antenna systems located less than one wavelength apart in an optimized configuration, rotated and fed collinearly from one or more transmitters for obtaining very high performance. It also includes an HF transmitting station using 1-2 single support and/or multisupport antenna systems per transmitter with the inherent design flexibility for optimizing the cost/performance ratio of the station.

Description

HIGH FREQUENCY ANTENNA SYSTEM
The present invention is related to antenna systems for high frequency (HF) uses.
TECHNICAL FIELD
High frequency (HF) broadcasting and other HF services operate in the 3-30 MHz frequency range. The HF broad¬ casting stations require economical high performance antenna systems which are rotatable in azimuth for providing high effective power gain for the present and future target areas in varying ionospheric condi- tions. The invention is also related to other HF services (maritime, aeronautical, defence etc.) re¬ quiring high performance transmitting and receiving antenna systems.
BACKGROUND OF THE INVENTION
HF broadcasting utilizing s ywave propagation on frequencies between 5.85 - 26.1 MHz for international broadcasting differs from other broadcasting services (e.g. VHF/UHF broadcasting) in several ways. HF broad¬ casting takes place through one or more reflections from the ionosphere (generally 100-400 km above the the surface of the Earth) , which acts as a natural satellite of the Earth. Therefore, it requires trans- mitting antennas with high performance.
To obtain the best signal strength (or the best signal quality) for the listeners HF broadcasting transmis¬ sions are generally directed to separate target areas determined by language, political reasons, listening times, and propagation conditions. An HF broadcasting station is usually designed to transmit programs to a number of target areas within a country or interna¬ tionally. During a 24 hour period an HF broadcasting station successively covers a relatively large number of target areas. In most cases the target areas change during the lifetime of a station.
Because the ionosphere changes with time, the geometry of the propagation and the properties of the propaga¬ ting channel also change with time. The variations of the ionosphere can be taken into account by using prediction methods based on the periodicity and/or the measured (near) real-time properties of the ionosphe¬ re. In statistical HF propagation prediction methods the changes are treated as disturbancies to deter- ministic propagation.
This approach can be seen in the structure of classi¬ cal HF broadcasting stations. They consist of a rela¬ tively large number of antennas with static properties directed to predetermined target areas. The stations require a large area with associated high acquisition and operating costs.
The present HF broadcasting antennas utilized at these stations have the following deficiencies:
Fixed (nonrotatable) HF broadcasting antennas:
The fixed dipole curtain antennas have been available since the 1930*s. The present state of the art of the dipole curtain antenna systems is presented in the IEEE Transactions on Broadcasting, June, 1988.
A dipole curtain antenna of the present state of the art consists of a number of simple horizontal dipole radiators which typically are approx. .5 or 1 wave¬ lengths long on the center operating frequency of the antenna. The gain of a single radiator is low. For obtaining the high gain required the dipole radiators are arranged into a 2-dimensional planar group. They are placed vertically one above the other (stacked) or placed side-by-side (as bays) to form a regular mat- rix-like configuration. In the standard terminology of the dipole curtain arrays a 4*4 dipole array is de¬ fined as a 4-bay, 4-stack array. All the dipoles of the array are fed by means of a feed system consisting of feedlines and matching components. The radiators and the feed system are broadband. Unidirectional operation is achieved by using a parasitically excited wideband screen reflector behind the radiator plane.
The fixed dipole curtains have limited controllability in the horizontal plane. The electrical slewing of the main beam is limited to a maximum of ± 30°, which leads to the inherent requirement for a large number of antennas for full coverage of present and future target areas. Typically, 4-5 fixed antennas per trans- mitter are needed.
The azimuth control of the main beam of fixed curtain antennas requires at least 2 bays (parallel vertical stacks) of dipoles. The planar configuration makes the antenna system wide in the direction perpendicular to the main beam requiring two supporting towers. If employed, the vertical control interacts with the horizontal slewing resulting in a large total number of control switches.
Rotatable HF broadcasting antennas:
The present rotatable log-periodic antennas lack the high power gain needed for high quality HF broadcast- ing. The present rotatable dipole curtain antennas are in fact fixed dipole curtains which have been made rotatable by rotating the whole fixed structure on a bearing or a circular rail. They offer high gain but require very large self supporting structures with high cost. The high cost results from the inherent wide configuration of the dipole curtain arrays which makes it impossible to use guywires for supporting the rotating structure.
Rotatable dipole curtains covering the 6 MHz band require a self standing (nonguyed) support typically 80 m high. Higher structures needed for obtaining lower take-off-angles down to 2° or for obtaining effective vertical control on the lower frequency bands require self standing supports 120-140 m high. The large moment of inertia limits the time for 360° rotation of the rotating dipole curtains to approx. five minutes.
As to the present needs for development in the field of HF broadcasting, the requirement for vertical control has become more widespread among the HF broad- casters for suiting different target areas and propa¬ gation conditions during the station operation, parti¬ cularly for rotatable antennas.
International efforts through the International Tele- communication Union are directed towards decreasing the pollution on the HF bands. This objective can be partly realized by using transmitting antenna systems with improved effective directivity.
As the same time the advances of technology during the past decades (PC:s, CAD-design methods, control meth¬ ods, satellite communications, data communications, new materials) have improved the technological possi¬ bilities to design modern high performance HF broad- casting antennas and stations. SUMMARY OF THE INVENTION
The problems related to the known state of technology in the field have lead to the present invention, in which a high performance antenna system is described. The antenna system meets the requirements of modern HF broadcasting and other HF services together with economical advantages over present antenna construct- ions. The availability of effective CAD programs for subarray and array design has made the invention practical.
The present invention introduces a high frequency HF antenna system comprising a combination of an HF antenna and a support system, wherein the HF antenna comprises two or more arrays, each array comprising two or more subarrays, each subarray comprising two or more radiators, each radiator electrically covering two or more frequency bands, feeding system for brin¬ ging the transmitter power to the arrays, and suppor¬ ting means for supporting the radiators of the subar¬ rays and the subarrays on the vertical support and wherein the support system comprises a single vertical support which is supported at the base, means for supporting the vertical support in the vertical posi¬ tion, and means for rotating at least part of the HF antenna.
The antenna system of the invention uses only one vertical support instead of two supports, which makes it possible to rotate the structure economically for directing the main beam accurately towards each target area. Therefore, only a small number of antennas is required for full coverage of all target areas.
Further, an HF antenna of the invention is compact with simultaneous broadband coverage of frequency bands, which can be selected to correspond to the needs of each antenna system in accordance with the basic characteristics of the invention.
The geometrically partitioned antenna configuration makes it possible to support the rotatable structure by one or more sets of guy wires. This makes it eco¬ nomical in comparison to unguyed rotatable dipole curtains. Also the electric horizontal slewing system is eliminated making vertical control much simpler. Because of the small moment of inertia the new antenna system can be rotated 360° in 1-2 minutes.
The invention is a combination of a number of new inventions in the fields relevant to obtaining the benefits of the antenna system. The new invention possesses an inherent capability for optimizing the design to meet the specific requirements of each application.
DESCRIPTION OF THE DRAWINGS
The invention is more closely described in the follo¬ wing detailed description together with references to the accompanying drawings, in which
Fig. 1 shows an overall schematic view of one embo¬ diment of the single support antenna system,
Fig. 2 shows three possible embodiments a-c of mul¬ tiband radiators for the subarrays of the antenna system,
Fig. 3 shows three possible embodiments a-c of su- barrays for the antenna system,
Fig. 4 shows two possible embodiments a-b of the array configurations of the antenna system, Fig. 5 shows schematically four embodiments a-d of multisupport antenna systems of the inventi¬ on, and
Fig. 6 shows schematically two embodiments a-b of the transmitting stations using the antenna systems of the invention.
DETAILED DESCRIPTION OF THE INVENTION
According to Fig. 1, the antenna system comprises a vertical support, e.g. tower 1 of any kind. Two or more 3-dimensional subarrays 2 are accommodated in the spaces between and above the guywires 5. The tower 1 is placed on a bearing 3 which is located on the ground at the base of the tower 1. The whole antenna system is rotated by means of a rotating mechanism 4 located at the base of the tower 1. One or more sets of the guywires 5 (three in each set shown as an example) are attached to the tower 1 by placing a bearing or a slip ring 6 around the tower for each set, e.g. at each guying level. The guywires 5 are attached at the low end of each guywire to the ground at a distance from the vertical tower 1 and at the high end of each guywire 5 to a bearing 6 on the vertical tower above the base level.
Fig. 2 (a-c) shows examples of embodiments of multi- band (for two or more bands) radiators 7 which are combined to obtain multiband subarrays with the re¬ quired electrical performance for the antenna systems.
One embodiment of the radiators consists of optimally shaped radiating portions which are connected by means of optimally shaped feedlines. The radiators are optimized for maximum gain and required feed proper¬ ties by selecting the shapes, dimensions and thick¬ nesses of the radiating portions and the shapes and dimensions of the feedlines. Typically the widths of the radiators are .5 - 1 wavelengths on the lowest operating frequency. Typically the heights of the radiators are .4 - .5 wavelengths on the lowest opera- ting frequency.
An example of a broadband embodiment of the radiator is shown in Fig. 2a. This type of radiator is optimi¬ zed by selecting the dimensions of the horizontal radiating parts (heavy line) and the dimensions of the feedline (thin line) .
Fig. 2 (b) shows an example of the optimized shape of the radiating portion (heavy line) and optimized shape of the feedline (thin line) . The radiator type shown electrically covers at least two broadcast frequency bands (e.g. the 6/7 MHz bands) with a free space gain of approx. 7-8 dBi depending on the exact dimensions.
Fig. 2c shows an example of the embodiment of a diffe¬ rent type of braodband radiator.
Typically the radiators are constructed of metal wires, tubing or lattice structures. The electric thickness of the radiating parts can be increased up to one meter or more by using e.g. cage-type structu¬ res or special types of folded dipole or other optimi¬ zed wideband structures.
The horizontally polarized radiators can be made vertically polarized e.g. by rotating them 90° or different types of vertically polarized radiators can be designed.
Three embodiments of the structures of possible subar¬ rays are described in Fig. 3. They are directive arrays exhibiting directivity in the horizontal and vertical plane for obtaining high gain. The basic design method is to use one radiator as driven ra¬ diator 8 and the other radiator as an reflecting radiator 9. The reflecting radiator can be excited parasitically by bringing power to the undriven ra¬ diator by mutual coupling only or actively by using a feed line or a feed network for bringing power to the reflecting radiator.
The required current amplitudes and phases are ob¬ tained by optimizing the shapes and dimensions of the radiators and the feed networks. The spacing between the radiators is typically .08 to .20 wavelengths on the lowest operating frequency. The log-periodic feed is an example of the possible active feed networks for the subarrays. All types of compensation and phasing methods and components are included in the subarray design.
Typical free space gain of the optimized subarrays with two radiators is 10-11 dBi. Subarrays with proper phasing provide front-to-back ratios of 15-25 dB.
By utilizing CAD-design methods for the radiators and subarrays and applying broadbanding and matching techniques and components the feed properties of the subarrays can be optimized to obtain VSWR below 1.5 on two or more frequency bands. More than two radiators can be added for improving the radiation properties if needed.
Combining the subarrays into 3-dimensional groups of two or more subarrays allows high gain and the re¬ quired radiation properties to be obtained on the bands covered electrically by the subarrays. The group of two or more subarrays fed simultaneously through a common feedline is defined as an array of subarrays. The simplest examples of arrays are regular arrays of identical subarrays. Two subarrays placed side-by-side at the same heigth form a 2-bay array. Two subarrays placed one above the other form a 2-stack subarray. The combination of these forms a 2-bay, 2-stack array of four subarrays. Typically, the distances between the centers of the subarrays are .5 - 1 wavelengths on the lowest operating frequency of the array.
The invention comprises all possible 3-dimensional arrays of all types of subarrays electrically covering two or more frequency bands. For example, arrays with uneven spacings in the vertical plane are typical of the invention.
By effectively using the space around the tower two or more arrays can be placed on the single vertical support. They can be identical or different in size and dimensions for different frequency bands. Some of the radiators of the subarrays of the separate arrays can be common. They can radiate to any direction. The use of subarrays covering two or more frequency bands with broadband radiators allows arrays covering all the required frequency ranges (e.g. ten international broadcasting bands) to be placed on a single guyed support.
Fig. 1 illustrates the invention by showing an antenna system which consist of a 1-bay, 2-stack array of subarrays of two optimized radiators for the lower frequency bands (shown on the left of the vertical support) and a 1-bay, 4-stack array of subarrays of two optimized radiators for the higher bands (shown on the right of the vertical support) . In this case the arrays radiate into the common direction shown in the drawing. By using CAD-methods the interaction of the arrays is minimized. Fig. 4 illustrates two embodiments of array configura¬ tions for the international broadcasting bands. Fig. 4a shows a 4-band antenna system consisting of two 2- band arrays. Fig. 4b shows a 10-band antenna system consisting of two 5/6-band arrays. The 4-band antenna system is obtained by placing a 1-bay, 3-stack array of 6/7 MHz subarrays of Fig. 3b on the tower and a 2- bay, 3-stack array of 9/11 MHz subarrays of Fig. 3b in front of it. Both arrays radiate in the same directi- on. The 10-band antenna system is obtained by placing a 2-bay, 2-stack array of 6/7/9/11 MHz subarrays on the tower and a 2-bay, 2-stack array of 13/15/17/19/- 21/26 MHz subarrays of Fig. 3a behind it. The arrays radiate 180 degrees apart. In both 2-bay arrays, the reflecting radiators of the side-by-side subarrays (of the type shown in Fig. 3a) have been mechanically integrated to form single wide radiating structures.
Typical array choices for the invention are 1-, 2-, or 3-stack arrays. For example, a rotating 3-stack anten¬ na system on a 130-140 m guyed tower with optimized subarrays makes it possible to obtain approx. 20 dBi gain on the 6 MHz broadcast band.
The feeding systems for bringing the transmitter power to the feed points of the subarrays are similar to the ones employed in dipole curtain antenna systems. The feedlines (open wire lines, coaxial lines) , the mat¬ ching components, and the control switches are placed on the outside of the tower or inside the tower. A rotating joint, flexible cables or other means are used for transfering the transmitter power to the antenna system.
Vertical control using the switching methods of pre¬ sent dipole curtains can be used. There is a possibi¬ lity of making vertical control easier by using sub- arrays covering 2-3 bands only, because these configurations can reduce the spurious vertical lobes on the higher bands.
Mechanically, the arrays are attached to the tower by means of 3-dimensional support structures. The support structures of all the subarrays in the space available between or above the guy wire levels are integrated into 3-dimensional structures. The invention places the rotating system on the ground for high reliability and easy maintainance. Standard components and subsys¬ tems from different fields of mechanical engineering can be used.
The two or more arrays fed simultaneously or at diffe- rent times form an antenna. The combination of the antennas and the mechanical support results in the antenna systems invented.
The electrical advantages of the single support anten- na system combine with the mechanical advantages to render the invented antenna systems overall technical and economical benefits over present fixed and rotata¬ ble HF broadcasting antenna systems.
The invention also includes a multisupport antenna system consisting of two or more single support anten¬ na systems operated collinearly for obtaining addi¬ tional gain for a horizontal angle sector. The use of optimized array configurations with subarrays for 2-3 bands makes it possible to use collinear operation on most frequency bands without excessive sidelobes on the higher bands.
Two, three of four (or more) single support antenna systems can be used depending on the sector coverage needed. Fig. 5 shows four embodiments of possible configurations. Fig. 5 shows a line (a), arc (b) , triangle (c) and square (d) configuration. The configurations of the multisupport antenna systems are selected and optimized to suit the radiation properties needed.
The rotation capability of the single support antenna systems increases the sector available in comparison to the collinear operation of fixed dipole curtains. It is also possible to obtain very high performance by feeding a multisupport antenna system with two or more transmitters for difficult target areas and/or propagation conditions.
Feedback control methods for the horizontal and vertical beam control based on (near) real-time data from the target areas can be added to the antenna systems.
A modern HF station can be built by using 1-2 antenna systems per transmitter depending on the frequency coverage. Typical examples of stations with two and four transmitters are shown in Fig. 6. Fig. 6a shows a two transmitter station with two antennas. Fig. 6b shows a four transmitter station with five antennas. Virtually complete 360° coverage on ten frequency bands can be obtained.
Each single support antenna system or multisupport antenna system can be replaced by two (or more) antenna systems with cover less frequency bands. Two antenna systems covering 4 and 6 bands respectively, are an example. They can be separately designed and optimized for the bands they cover. This flexibility allows all the antenna systems to be designed for optimizing the total performance and performance/cost- ratio of the station. The benefits of the invention result from the inherent flexibility of the design approach which is based on separating an HF antenna system into a hierarchical structure consisting of the radiator, subarray, array, single support antenna system, and multisupport antenna system levels. This intellectual achievement forms the underlying idea of the invention.
The invention makes it possible to build an HF broadcasting station in several stages by starting with a small number of antenna systems. The station can be expanded easily by adding new transmitters and optimally designed antenna systems. The antenna systems are also well suited to the refurbishing and upgrading of existing HF stations.
It is important to note that the invention is not limited to HF broadcasting. It can be used in other HF services (maritime, aeronautical, defence, etc.) for transmitting and receiving purposes. In total, the invention provides a modern cost-effective antenna solution for most high performance, high-tech HF applications.
While specific embodiments and examples of the invention have been described in detail, it is to be understood that numerous modifications and variations therein may be devised by those skilled in the art without departing from the spirit and scope of the invention. ■*.
Of course, there is large number of possible radiators, subarrays, and array configurations. This gives the invention an inherent flexibility for optimizing the design. Importantly, different types of radiators and subarrays can be combined. Subarrays with vertical polarization may be used in special applications. CAD methods allow antenna systems with optimized radiators, optimized subarrays and optimized arrays to be designed in practice for different applications.
All possible methods (switching, broadbanding methods, compensation methods, remote or local mechanical control etc.) for obtaining the broadband coverage needed for the radiators and subarrays are included. All types of feeding systems for the subarrays are included in the invention. All types of feeding, phasing and control systems for the arrays are also included.
All types of support structures e.g. telescoping towers, pivoted towers, mobile towers etc., and all hoisting and rotating methods can be used in connection with the invention. The antenna systems made mobile for special purposes are also included.
All types of mechanical support structures for the subarray assemblies around the tower are included. There are possibilities for integrating the mechanical supporting structures with the radiating structures. All new materials like composites, alloys, etc., and all present or new components from the field of sea navigation and aviation etc. are included.

Claims

1. High ■frequency (HF) antenna system comprising a combination of an HF antenna and a support system, wherein the HF antenna comprises
two or more arrays, each array comprising
- two or more subarrays, each subarray comprising
two or more radiators, each radiator electrically covering two or more frequency bands,
feeding system for bringing the transmitter power to the arrays, and
- supporting means for supporting the radiators of the subarrays and the ,subarrays on the vertical support,
and wherein the support system comprises
a single vertical support which is supported at the base,
means for supporting the vertical support in the vertical position, and
- means for rotating at least part of the HF antenna.
2. High frequency antenna system of claim 1 comprising a combination of HF antenna and a support system, wherein the HF antenna comprises two or more arrays, each array comprising
two or more subarrays, each subarray comprising
two or more radiators, each radiator electrically covering two or more frequency bands, and
- feeding system for bringing the transmitter power to the arrays, and
supporting means for supporting the radiators of the subarrays and the subarrays on the vertical support,
and wherein the support system comprises
a single vertical support which is supported at the base by a bearing for accomplishing rotating motion of the vertical support around its vertical axis,
- means for supporting the vertical support in the vertical position, and
means for rotating the vertical support.
3. Antenna system of claim 1 or 2, wherein the rotating motion of the vertical support and/or at least part of the HF antenna is up to ± 360° or continuous.
4. Antenna system of claim 1 or 2, wherein the means for supporting the vertical support comprise at least one set of guywires supported at the low end of each guywire to the ground at a distance from the vertical support and at the high end of each guywire to one or more bearings attached to the vertical support above the base level, the bearings allowing the vertical support to rotate around its vertical axis.
5. An antenna system of claim 4, wherein the position of the at least one set of guywires and the positions and the dimensions the arrays are arranged so that the arrays are capable of rotating up to ± 360° or continuously.
6. Antenna system of claim 1-6, wherein the HF antenna comprises two or more arrays, which have similar structures as to the radiators and subarrays therein.
7. Antenna system of claims 1-6, wherein the arrays of the HF antenna are arranged to radiate in the same direction.
8. Antenna system of claims 1-6, wherein the arrays of the HF antenna are arranged to radiate into two or more different directions.
9. Antenna system of claim 1-6, wherein the HF antenna comprises three or more arrays, at least some of which radiate in the same direction.
10. Multisupport antenna system wherein two or more single support antenna systems of claims 1-9 are combined to form a set of single support antenna systems.
11. Multisupport antenna system wherein two or more single support antenna systems of claims 1-9 are located .5 - 1 (half to one) wavelengths apart on the lowest operating frequency.
12. Multisupport antenna system of claims 10-11 wherein the antenna systems of claims 1-9 are operated as a single unit by feeding the transmitting power from one or more transmitters to the individual single support antenna systems, by rotating the individual single support antenna systems, and by phasing the transmitting power to the individual single support antenna systems.
13. Multisupport antenna system wherein one or more single support antenna systems of claims 1-9 and/or one or more multisupport antenna systems of claims 10- 12 are located at distances more than 1 (one) wave- length apart on the lowest operating frequency.
14. Multisupport antenna system wherein one or more single support antenna systems of claims 1-9 and/or one or more multisupport antenna systems of claims 10- 12 are operated separately by feeding the transmitter power from any transmitter to one antenna system directly or to two (or more) antenna systems by means of a switch between the output of the transmitter and the antenna systems.
PCT/FI1993/000314 1993-08-06 1993-08-06 High frequency antenna system WO1995005012A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU47105/93A AU4710593A (en) 1993-08-06 1993-08-06 High frequency antenna system
PCT/FI1993/000314 WO1995005012A1 (en) 1993-08-06 1993-08-06 High frequency antenna system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/FI1993/000314 WO1995005012A1 (en) 1993-08-06 1993-08-06 High frequency antenna system

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US7868843B2 (en) 2004-08-31 2011-01-11 Fractus, S.A. Slim multi-band antenna array for cellular base stations
US8497814B2 (en) 2005-10-14 2013-07-30 Fractus, S.A. Slim triple band antenna array for cellular base stations
US8941541B2 (en) 1999-09-20 2015-01-27 Fractus, S.A. Multilevel antennae

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EP0493237A1 (en) * 1990-12-28 1992-07-01 Thomson-Csf Rotary curtain antenna with dipoles

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GB2121080A (en) * 1982-06-03 1983-12-14 British Telecomm Improvements in or relating to hollow poles for cable support
EP0493237A1 (en) * 1990-12-28 1992-07-01 Thomson-Csf Rotary curtain antenna with dipoles

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9054421B2 (en) 1999-09-20 2015-06-09 Fractus, S.A. Multilevel antennae
US9362617B2 (en) 1999-09-20 2016-06-07 Fractus, S.A. Multilevel antennae
US10056682B2 (en) 1999-09-20 2018-08-21 Fractus, S.A. Multilevel antennae
US8941541B2 (en) 1999-09-20 2015-01-27 Fractus, S.A. Multilevel antennae
US8976069B2 (en) 1999-09-20 2015-03-10 Fractus, S.A. Multilevel antennae
US9000985B2 (en) 1999-09-20 2015-04-07 Fractus, S.A. Multilevel antennae
US9240632B2 (en) 1999-09-20 2016-01-19 Fractus, S.A. Multilevel antennae
US9761934B2 (en) 1999-09-20 2017-09-12 Fractus, S.A. Multilevel antennae
US7868843B2 (en) 2004-08-31 2011-01-11 Fractus, S.A. Slim multi-band antenna array for cellular base stations
US9450305B2 (en) 2005-10-14 2016-09-20 Fractus, S.A. Slim triple band antenna array for cellular base stations
US8497814B2 (en) 2005-10-14 2013-07-30 Fractus, S.A. Slim triple band antenna array for cellular base stations
US8754824B2 (en) 2005-10-14 2014-06-17 Fractus, S.A. Slim triple band antenna array for cellular base stations
US10211519B2 (en) 2005-10-14 2019-02-19 Fractus, S.A. Slim triple band antenna array for cellular base stations
US10910699B2 (en) 2005-10-14 2021-02-02 Commscope Technologies Llc Slim triple band antenna array for cellular base stations

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