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WO1996018220A1 - Antenne helicoidale - Google Patents

Antenne helicoidale Download PDF

Info

Publication number
WO1996018220A1
WO1996018220A1 PCT/NZ1995/000128 NZ9500128W WO9618220A1 WO 1996018220 A1 WO1996018220 A1 WO 1996018220A1 NZ 9500128 W NZ9500128 W NZ 9500128W WO 9618220 A1 WO9618220 A1 WO 9618220A1
Authority
WO
WIPO (PCT)
Prior art keywords
antenna
wires
fed
voltage maxima
helical
Prior art date
Application number
PCT/NZ1995/000128
Other languages
English (en)
Inventor
Cornelis Frederik Du Toit
Original Assignee
Deltec New Zealand Limited
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 Deltec New Zealand Limited filed Critical Deltec New Zealand Limited
Priority to NZ296605A priority Critical patent/NZ296605A/en
Priority to AU41252/96A priority patent/AU693616B2/en
Publication of WO1996018220A1 publication Critical patent/WO1996018220A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q11/00—Electrically-long antennas having dimensions more than twice the shortest operating wavelength and consisting of conductive active radiating elements
    • H01Q11/02—Non-resonant antennas, e.g. travelling-wave antenna
    • H01Q11/08—Helical antennas

Definitions

  • the present invention relates to a helical antenna. More particularly, but not exclusively, the present invention relates to a multifilar helical antenna operating in the "back-fire scanning mode" suitable for satellite communications over a frequency range between 500MHz to 5GHz.
  • a helical antenna may be used to generate substantially circularly polarised electromagnetic radiation.
  • the radius of a multifilar helix is much smaller than the pitch length (about half a wavelength) radiation is directed along the helical axis, opposite to the propagating direction of the wave giving rise to the radiation.
  • a helix antenna operating in this mode is called a "back-fire helix antenna" .
  • radiation is directed away from the helical axis at an angle, forming a conically shaped beam. The angle of the conical beam increases with increasing frequency. Since a multifilar, back-fire helical antenna can be designed with beam angles suitable for direct communication with satellites, it is well suited for land mobile satellite communications, or even GPS applications.
  • a helical antenna configured to operate in a resonant mode at a desired operating frequency having one or more wire of the antenna fed at or near a point of voltage maxima along each wire at resonance.
  • the wires of the antenna are preferably fed at centrally positioned voltage maxima.
  • the length of the antenna preferably either short circuited or open circuited at both ends, is preferably an integer multiple of half the wavelength at which the antenna operates in a resonant mode.
  • the multiple is an odd number for short circuited ends, or an even number for open circuited ends.
  • the antenna comprises three or more wires.
  • Figure 1 shows an end-fed quadrifilar helical antenna.
  • the pitch length p is defined as the linear length of one turn of the helix, and r is the radius of the cylinder encompassing the helixes.
  • Figure la shows the elevation pattern of a bottom- fed quadrifilar helix, 4.5 wavelengths long, excited at 0.969 times the resonant frequency.
  • Figure lb shows the elevation pattern of a bottom- fed quadrifilar helix, 4.5 wavelengths long, excited at 1.032 times the resonant frequency.
  • Figure 2 shows the phase distribution along the length of a multifilar helical antenna, excited at its resonance frequency, for a non-radiating wave.
  • Figure 3 shows the phase distribution along the length of a multifilar helical antenna, excited at its resonance frequency, for a radiating wave.
  • Figure 4 shows a typical voltage standing wave pattern along the length of the multifilar helical antenna.
  • Figure 5 shows the phase distribution of a radiating wave along the length of a resonant centre-fed multifilar helix, excited at a frequency slightly lower than its resonance frequency.
  • Figure 6 shows the elevation pattern of a centre- fed quadrifilar helix excited at a frequency of 0.969 times the resonant frequency.
  • Figure 7 shows the elevation pattern of a centre- fed quadrifilar helix excited at a frequency of 1.032 times the resonant frequency.
  • Figure 8 shows a quadrifilar helical antenna using an infinite balun according to a first aspect of the invention.
  • Figure 9 shows a quadrifilar helical antenna using half-wave baluns and a hybrid power splitter according to a third aspect of the invention.
  • Figure 10 shows a trifilar helical antenna using a three-way power splitter and electrical delay lines according to a further aspect of the invention.
  • the quadrifilar helix shown in figure 1 can be viewed as two pairs of parallel wire transmission lines, each pair being twisted into bifilar helixes. Since the bifilar pairs are positioned on each others zero potential surface, they act as balanced, independent or isolated transmission lines.
  • each lengthwise incremental section of the multifilar helix acts as a small circularly polarised antenna element.
  • the phase of these incremental elements changes along the helical length due to two factors. Firstly, the phase of the wave exciting the elements changes as a function of position along the helical axis. Secondly, the geometrical rotation of each element around the helical axis changes the phase of the elemental circular polarisation as a function of position along the helical axis.
  • phase gradient along the helical length will tend to cancel for a wave propagating in one direction, but will add up for a wave propagating in the opposite direction.
  • the result is a steep phase gradient associated with the wave propagating in one direction along the helix, and a small phase gradient associated with the wave travelling in the opposite direction.
  • phase gradient For a steep phase gradient (see figure 2) the electromagnetic fields emanating from different parts of the helix will cancel some distance away from the antenna, and no radiation will occur. For a small phase gradient (see figure 3) , radiation will occur in a direction depending on the phase gradient.
  • the transmission line will be resonant (i.e: when excited a standing wave pattern will be produced along the line, as shown in figure 4) .
  • Resonance can also be achieved when the line is open circuited at one end while short circuited at the other end, if the total length is equal to an odd number of quarter wavelengths.
  • the phase gradient changes, and the beam direction will change for an end-fed helix, as illustrated by figures la and lb.
  • a step occurs in the phase distribution at the feed point (see figure 5) .
  • This phase step causes the average phase gradient of the radiating wave over the total length of the helix to be less dependent on the frequency.
  • frequency scanning will be reduced.
  • the technique is most effective when the feed point is near the centre of the helix (in the longitudinal direction of the antenna) . It is therefore preferred that the multifilar helix, when short circuited/open circuited at both ends, is an odd/even number of half wavelengths long in order to provide a voltage maxima at the centre of the antenna, where the feed point can be placed.
  • the reduction in frequency scanning can be illustrated by way of an example of a resonant centre-fed quadrifilar helix antenna, short circuited at both ends. If the total length is chosen to be 4.5 internal wavelengths long, and a pitch length of 0.553 free space wavelengths is combined with a radius of 0.031 free space wavelengths, the beam will be directed at an angle of about 45° from the helical axis.
  • the elevation radiation patterns for the configuration are shown in figures 6 and 7 for frequencies below and above resonance respectively.
  • the beam direction for frequencies above and below the resonant frequency fo can be inferred from figures 6 and 7 as follows:
  • Figures la and lb show that when the same antenna is fed at one end, while short circuited at the other end, the beam direction changes by over 8.6° over the same frequency range. Beam scanning is thus reduced to about 1° over a 6.3% band width using the centre- fed antenna of the invention. This reduction in scanning has been confirmed by practical experimentation.
  • the technique of the invention may be implemented in a variety of ways. It is preferred that the helical . antenna comprise three or more wires. Although monofilar and bifilar topologies exhibit one or more grating lobes in elevation, these grating lobes may be compensated by the use of reflectors etc. Thus although it is preferred that the antenna comprise three or more helical wires there may be applications where monofilar or bifilar topologies may be used if suitable compensation is provided.
  • FIG 8 there is shown a quadrifilar helical antenna according to a first aspect of the invention.
  • a radio frequency source signal is applied via a coaxial line 1 to a -3dB hybrid coupler 2.
  • the hybrid coupler 2 provides an equal two way power split over a relatively wide frequency band, with a first output supplying a signal to coaxial line 3 that is 90° phase delayed with respect to the signal supplied to coaxial line 3a.
  • a 50 ohm load 2a is connected to the isolation port .
  • Power is delivered from the hybrid coupler 2 to the antenna via the two thin semi-rigid coaxial cables 3 and 3a, which also act as two adjacent helical wires of the helix.
  • the other wires of the helix may consist of copper wires 4 and 5 with the same diameter as the coaxial cables 3 and 3a.
  • the centre conductors 6, 7 of coaxial cables 3, 3a are connected tc respective helical wires 4,5 diagonally across the cylindrical space defined by the helixes tc form an infinite bandwidth balun.
  • the antenna is an odd integer multiple of ⁇ (half the wavelength at which the antenna is resonant) long to ensure that a voltage maxima is present at the centre of the antenna.
  • the copper wires 4 and 5 are both fed at the central voltage maxima at resonance.
  • the wires are shorted at each end by conductive discs 8 and 9.
  • the antenna operates in a resonant mode.
  • Feeding both copper conductors 4 and 5 at the central voltage maxima may pose difficulties from a constructional point of view, especially when a larger number of wires are employed. In some embodiments it may therefore be desirable to feed copper conductors 4,5 at different voltage maxima (e.g. select the length of the antenna to have an even number of voltage maxima and feed copper conductors 4 and 5 at respective ones of the two central voltage maxima) . In some applications it may also be desirable to connect the transmit and receive feeds at different positions along the wires to provide additional compensation for beam tilt due to the different transmit and receive frequencies employed, thus producing substantially aligned transmit and receive beams.
  • the antenna length can be chosen such that it will operate in different modes at these frequencies, i.e. the length at the transmit frequency being an integer number of half wavelengths longer or shorter than at the receive frequency.
  • the transmit feed may then be placed at a voltage maxima while the receive feed is at a voltage minima, and visa versa. In this way the two feeds will provide some degree of isolation between the receiver and transmitter.
  • the feed arrangement for this embodiment is relatively simple due to the infinite balun arrangement. This arrangement avoids the need to have feed lines passing along the longitudinal axis of the helix.
  • a quadrifilar helix according to a further aspect of the invention.
  • a -3dB hybrid coupler 11 provides an equal two way power split to coaxial lines 12 and 13.
  • the signal supplied to coaxial conductor 13 is phase delayed by 90° with respect to that supplied to coaxial line 12.
  • the antenna comprises four copper wires 14, 15, 16 and 17 shorted at each end by conducting discs 18 and 19.
  • the antenna is an odd multiple of half wavelengths long so that it operates in a resonant mode with a voltage maxima at the centre of each copper wire.
  • Coaxial lines 12 and 13 pass along the axis of the helical antenna to feed their respective copper wires at the centre of the antenna.
  • Copper wire 14 is fed at its central voltage maxima directly from coaxial cable 12 and has a 0° delay.
  • Copper wire 15 is fed at its central voltage maxima directly from coaxial line 13 and has a 90° delay (i.e. : the delay produced by the hybrid coupler 11) .
  • Copper wire 16 is fed at its central voltage maxima via a half wavelength loop of the balun 20 from coaxial cable 12. This half wavelength loop of the balun introduces a 180° phase shift and so the feed signal supplied to copper wire
  • Copper wire 17 is fed at its central voltage maxima via a half wavelength loop of the balun 21 from coaxial cable 13.
  • the half wavelength loop of the balun introduces a 180° phase shift on top of the 90° phase shift produced by the hybrid coupler. Accordingly, the feed signal to copper wire
  • the antenna comprises three copper wires 27, 28 and 29 shorted at each end by conducting discs 30 and 31.
  • Three way power splitter 23 divides an input signal into three equal signals supplied to coaxial cables 24, 25 and 26.
  • the length of coaxial cable 24 is selected to produce a 0° relative phase delay.
  • the length of coaxial cable 25 is selected to provide a 120° phase shift.
  • the length of coaxial cable 26 is selected to produce a 240° relative phase shift.
  • Coaxial cables 24, 25 and 26 pass along the centre of the antenna to feed the copper wires at the centre of the antenna.
  • Each coaxial cable 24, 25 and 26 is connected to the central voltage maxima of a respective copper wire 27, 28 and 29.
  • This embodiment has a relatively simple construction and may be easily adapted to an antenna having any required number of wires.
  • the ends of the antenna wires are shorted and the length of the antenna is chosen to be an integer multiple of half wavelengths long (preferably an uneven multiple) to ensure that the antenna operates in a resonant mode.
  • the antenna is operated at or near the resonant frequency of the antenna to ensure that the wires of the antenna are fed at voltage maxima. It will be appreciated that an antenna not having its ends shorted may be employed as long as the antenna is operating in a resonant mode. It is however, preferred that the ends of the antenna be shorted due to the ease of providing support to the wire ends.
  • the antenna is driven at a central voltage maxima along each copper wire it will be appreciated that the antenna may be driven at any other voltage maxima if required for constructional or operational reasons. Different wires of the antenna may be driven at different voltage maxima. Further, the wires may be fed slightly to either side of the voltage maxima. In some embodiments transmit and receive feed lines may be connected at different points along each wire to improve alignment of the transmit and receive beams, and/or to provide some isolation between the transmitter and receiver.
  • wires provided in the antenna may be selected for any particular application.
  • the wires may be formed of a variety of conductive materials such as copper, silver plated brass or steel etc.
  • the antenna of the invention may find application in telecommunications applications, such as satellite communications.

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  • Details Of Aerials (AREA)
  • Support Of Aerials (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)

Abstract

Antenne hélicoïdale possédant un ou plusieurs conducteurs (3, 3a, 4, 5; 14, 15, 16, 17; 27, 28, 29) alimentés en tension maximum le long de chaque conducteur à un niveau de résonance. L'antenne est, de préférence, une antenne hélicoïdale multibrin et les conducteurs (3, 3a, 4, 5; 14, 15, 16, 17; 27, 28, 29) sont alimentés en tension maximum localisée au centre. La longueur de l'antenne est, de préférence, un multiple entier de la moitié de la longueur d'onde à laquelle l'antenne fonctionne en mode résonant. Les extrémités des conducteurs (3, 3a, 4, 5; 14, 15, 16, 17; 27, 28, 29) peuvent être ouvertes ou court-circuitées.
PCT/NZ1995/000128 1994-12-06 1995-12-06 Antenne helicoidale WO1996018220A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
NZ296605A NZ296605A (en) 1994-12-06 1995-12-06 Helical antenna for resonance mode at desired frequency with wire(s) fed at or near point of voltage maxima
AU41252/96A AU693616B2 (en) 1994-12-06 1995-12-06 A helical antenna

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NZ270071 1994-12-06
NZ27007194 1994-12-06

Publications (1)

Publication Number Publication Date
WO1996018220A1 true WO1996018220A1 (fr) 1996-06-13

Family

ID=19925073

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/NZ1995/000128 WO1996018220A1 (fr) 1994-12-06 1995-12-06 Antenne helicoidale

Country Status (2)

Country Link
AU (1) AU693616B2 (fr)
WO (1) WO1996018220A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002037609A1 (fr) * 2000-11-04 2002-05-10 University Of Bradford Antenne multibande
WO2005064742A1 (fr) * 2003-12-29 2005-07-14 Amc Centurion Ab Agencement d'antenne pour dispositif de radio communication portable
US6940471B2 (en) 2001-04-23 2005-09-06 Syntonic Technologies Pty Ltd Helical antenna
CN1298079C (zh) * 1999-12-23 2007-01-31 电子部品研究院 用于移动电信单元的双频带天线
WO2011001153A1 (fr) * 2009-07-03 2011-01-06 Sarantel Limited Antenne multifilaire
WO2012050617A1 (fr) * 2010-10-14 2012-04-19 Novatel Inc. Antenne hélicoïdale quadrifilaire à usage multiple
US8456375B2 (en) 2009-05-05 2013-06-04 Sarantel Limited Multifilar antenna
WO2016064307A1 (fr) * 2014-10-20 2016-04-28 Ruag Space Ab Antenne hélicoïdale multifilaire
CN116130934A (zh) * 2022-09-08 2023-05-16 电子科技大学 圆极化高增益全向/双向可重构螺旋漏波天线

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0169823A1 (fr) * 1984-07-20 1986-01-29 Telefonaktiebolaget L M Ericsson Système émetteur-récepteur d'un satellite
AU5131790A (en) * 1989-12-19 1991-06-27 Chu Associates Inc. Broad-band quadrifilar helical antenna and the like and feed network therefor
GB2243724A (en) * 1990-02-27 1991-11-06 Kokusai Denshin Denwa Co Ltd Quadrifilar helix antenna
EP0469741A1 (fr) * 1990-08-02 1992-02-05 Symmetricom, Inc. Appareil à radiofréquence
US5138331A (en) * 1990-10-17 1992-08-11 The United States Of America As Represented By The Secretary Of The Navy Broadband quadrifilar phased array helix
EP0520564A2 (fr) * 1991-06-28 1992-12-30 Magnavox Electronic Systems Company Antenne à polarisation circulaire et dispositif de déphasage aux lignes à bandes pour une telle antenne
EP0521511A2 (fr) * 1991-07-05 1993-01-07 Sharp Kabushiki Kaisha Antenne en hélice à réflecteur
US5298910A (en) * 1991-03-18 1994-03-29 Hitachi, Ltd. Antenna for radio apparatus
US5349365A (en) * 1991-10-21 1994-09-20 Ow Steven G Quadrifilar helix antenna

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0169823A1 (fr) * 1984-07-20 1986-01-29 Telefonaktiebolaget L M Ericsson Système émetteur-récepteur d'un satellite
AU5131790A (en) * 1989-12-19 1991-06-27 Chu Associates Inc. Broad-band quadrifilar helical antenna and the like and feed network therefor
GB2243724A (en) * 1990-02-27 1991-11-06 Kokusai Denshin Denwa Co Ltd Quadrifilar helix antenna
EP0469741A1 (fr) * 1990-08-02 1992-02-05 Symmetricom, Inc. Appareil à radiofréquence
US5138331A (en) * 1990-10-17 1992-08-11 The United States Of America As Represented By The Secretary Of The Navy Broadband quadrifilar phased array helix
US5298910A (en) * 1991-03-18 1994-03-29 Hitachi, Ltd. Antenna for radio apparatus
EP0520564A2 (fr) * 1991-06-28 1992-12-30 Magnavox Electronic Systems Company Antenne à polarisation circulaire et dispositif de déphasage aux lignes à bandes pour une telle antenne
EP0521511A2 (fr) * 1991-07-05 1993-01-07 Sharp Kabushiki Kaisha Antenne en hélice à réflecteur
US5349365A (en) * 1991-10-21 1994-09-20 Ow Steven G Quadrifilar helix antenna

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1298079C (zh) * 1999-12-23 2007-01-31 电子部品研究院 用于移动电信单元的双频带天线
WO2002037609A1 (fr) * 2000-11-04 2002-05-10 University Of Bradford Antenne multibande
US6940471B2 (en) 2001-04-23 2005-09-06 Syntonic Technologies Pty Ltd Helical antenna
WO2005064742A1 (fr) * 2003-12-29 2005-07-14 Amc Centurion Ab Agencement d'antenne pour dispositif de radio communication portable
US8456375B2 (en) 2009-05-05 2013-06-04 Sarantel Limited Multifilar antenna
WO2011001153A1 (fr) * 2009-07-03 2011-01-06 Sarantel Limited Antenne multifilaire
WO2012050617A1 (fr) * 2010-10-14 2012-04-19 Novatel Inc. Antenne hélicoïdale quadrifilaire à usage multiple
US9214734B2 (en) 2010-10-14 2015-12-15 Novatel Inc. Multi-quadrifilar helix antenna
WO2016064307A1 (fr) * 2014-10-20 2016-04-28 Ruag Space Ab Antenne hélicoïdale multifilaire
US10079433B2 (en) 2014-10-20 2018-09-18 Ruag Space Ab Multifilar helix antenna
CN116130934A (zh) * 2022-09-08 2023-05-16 电子科技大学 圆极化高增益全向/双向可重构螺旋漏波天线

Also Published As

Publication number Publication date
AU4125296A (en) 1996-06-26
AU693616B2 (en) 1998-07-02

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