FR2570546A1 - Helicoid multiwire antenna for simultaneous transmission of a plurality of VHF/UHF transmission and reception signals - Google Patents

Abstract

The invention relates to the field of antennas used in space communication and in particular antennas mounted on manmade telecommunication satellites. The problem solved consists in making such an antenna which operates in multiplex mode and is of minimum bulk, for transmitting and/or receiving signals with frequencies close to each other. According to the invention, the antenna is a helicoid multiwire antenna, constituted by independent radiation cords which are wound in a helix around the same core and are angularly offset in a regular manner from each other, at least two of these cords each being connected to a separate transmitter or receiver apparatus. Preferential application as a diplex system of a source element of a reflector antenna.

Description

1! 2570546

  "Helical multi-wire antenna for simultaneous transmission

  of several VHF / UHF transmit and receive signals.

  The invention relates to the field of antennas used

  sées in space communications and in particular the antennas mounted on artificial telecommunications satellites. The technology of these antennas is subject to two essential types of constraints;

  - the constraints linked to the transmission of si-

  radio signals: these include the limitation of transmission frequency registers in specific windows, directivity and interference problems between the many nearby artificial emissions, or

  interference from thermal noise from antennas

  celestial noises and noises: - the constraints linked to the launching techniques into space of communication satellites: these are, in particular, weight and volume limitations, the

  reliability of the operation of satellite equipment, and

  core of the ability to undergo significant accelerations.

  This second type of constraint led to the development

  satellite transmitting and receiving devices, susceptible

  bles to suit several different uses, in order to reduce the number of these devices, and therefore their weight and volume.

  Thus, transmission techniques tend to be

  blir as much as possible, radio-electric links in diplex

  (simultaneous transmission of two independent signals on the same

  me channel), or in multiplex (simultaneous transmission of several

signals on the same channel).

  Thanks to this type of link, a single antenna element can be shared between several transmitting and receiving devices, which makes it possible to significantly reduce the volume.

  and the weight of the satellite, with equal service.

  The present invention relates to such a device for the simultaneous transmission of radioelectric transmission signals.

2. 2570546

  and reception, of very close frequencies, on a common antenna, the device being usable for

continuous communications.

  Technical solutions are already known which make it possible to carry out simultaneous transmission by diplexing or multiple-

  xing, radio-transmitting and receiving signals,

  very close quences, on a common antenna. Such a solution

  known is shown in Figure 1.

  This known device consists of pass filters

  bands 11, 12, 13 respectively connected at the output of the transmitters El, E2, E3, and connected downstream to a mixer14 whose single output routes the resulting signal to the single antenna 30. A receiver R is also connected to the same antenna 30 , through a circulator 31, the purpose of which is to isolate all of the channels

  transmission of all reception channels. The reception

  In addition, R is fitted with a bandpass filter 20. The circu-

  reader 31 can be replaced by a polarization duplexer, or

  still deleted for certain uses Its role is to improve

  rer the adaptation of the receiver with the antenna 30, and ensure a

  additional insulation to that provided by the pass filters

  bands, between transmit and receive frequencies. For their part, the bandpass filters ensure the rejection of signals whose frequency is not located inside the passband of

each of them.

  This device has the disadvantage of being volumi-

  neux when used for low frequencies of the VHF / UHF ganges. The size and weight of the filters and mixers which are then used are relatively large and constitute an obvious handicap to orbiting; these bulky elements also constitute a potential source of passive intermodulation. Depending on the number of sections, losses in the chain

  multiplexing / diplexing can vary between Q, 5 dB and 1 dB.

  The object of the invention is therefore to provide a multiplex transmission device on a common antenna making it possible to eliminate the use of a mixer, and even in certain cases, the use of bandpass filters 3. According to the invention, the device for the simultaneous reception and transmission of several radio signals of close or identical frequencies, in particular for space communications in the VHF / UHF ranges, is of the type comprising at least one transmitting device and at least one receiving apparatus, said transmitting and receiving apparatus being connected to a single common antenna; this device is characterized in that the common antenna is a helical multi-wire antenna, made up of strands of

  independent radiation, wound in a helix around the same no-

  yau, said strands being angularly offset in a regular manner

  in relation to each other, and in that at least two strands of radiation from said antenna are each connected in

  continuous to a separate transmitting or receiving device.

  This unique common antenna design allows multiple signals to be transmitted and / or received, including frequencies

  carriers are relatively close to each other but diff-

  ferent, with a minimum number of elements, since there is no longer a need for a mixer or even bandpass filters separating the different channels, insofar as the coupling between the different strands of the antenna is sufficiently weak. The result

  dnc a gain in weight and volume for the satellite equipment.

  On the other hand, one can also use several strands of 1'Ann-

  diplex valve to transmit (or receive) frequency signals, with phase shift between each wire, according to the conventional use presented

further.

  Other characteristics and advantages of the invention appear

  will read the following description of a preferred embodiment-

  rentiel, and attached drawings in which:

  - Fig. 1 represents a device of the known art for the

  sion-reception in diplex on a common antenna,

  - Fig. 2 represents the characteristics of the inter-coupling

  coming between the different strands of the antenna according to the invention, in function

  tion of the frequency, - Fig. 3 represents the following helical quadrifilar antenna

1 invention.

  The invention in fact constitutes a new development in the technology of helical antennas. The resolution of the problem posed, namely the design and feasibility of 4. VHF / UHF transmission devices operating in multiplex, first of all led to exploring the different types of VHF / UHF antennas (waves whose frequency is greater than 30 M1z). It appeared that a helical multi-wire antenna has decisive advantages for a satellite application.

  This discovery led to adapt this type of anti-

  ne to multiplex transmission devices, whereas it was previously studied with a single excitation source, under the sole angle of an extension of the single-wire helical antennas. Tests have

  allowed the applicant, finally, to verify that the invention has a real effect

  efficiency, combined with the advantages required for orbiting.

  The antennas used most often in communication

  spatial. are the reflector antennas, of the front source type

  tale or Cassegrain for example. This type of antenna is used in

  the microwave domain (waves> 1 GHz).

  For VHF / UHF bands there are several types of an-

  tennes, quite different from each other. We commonly use

  dipole antennas in the form of superimposed elements, and in particular

  the half-wave jacketed dipoles in vertical overlap.

  These antennas, of omni-directional type have a high gain.

  and are frequently used in ground stations. In the

  point-to-point applications, rather networks of an-

  wide apertures, dihedral antennas, or antennas

  Yagi. We also know 'LPA antennas (periodic log).

  In the field of space-saving antennas, whip antennas have a great advantage of simplicity and

  reliability but correspond to uses in frequency bands

  narrow quences. On the other hand, in this field antennas with-

  reduced space, the helical antenna appears entirely favorable for satellite uses. Where most of the previously mentioned antennas have a linear or surface obstruction, and often require an operation of deployment in space, the helical antenna seduces by its robustness and its reduced size. In return for these advantages, the helical antenna generally operates in a narrow band, in: 5. the extent to which its low radiation resistance must be compensated

  by a sufficient length of the strands to allow resonance.

  However, studies have been carried out on the possibility of making helical antennas in the form of several strands wound around the same core, and whose loops are inter-

  wedged together. So in an article called "the an-

  tenne helico! dale quadrifilaire published in March 1974 in the review "IEE TRANSACTION ON ANTENNAS AND PROPAGATION, Volume AP-22 n II"

  (pp. 173-178), A. Adams and AL. describe the experimental results

  rates obtained with antennas of this type. In the conventional use of these quadrifilar helical antennas, the strands are supplied normally with a phase shift of 90, with respect to each other, from a single excitation source. Such an antenna has a radiation pattern

  unidirectional, along its longitudinal axis, for certain dimensions

  sions (when the circumference of the propeller is between 0.4 and 2.0 times the working wavelength). A. Adams highlights two decisive advantages of the quadrifilar helical antenna compared to the single-wire antenna, namely: - an increase in bandwidth, and, - the lowering of the frequency necessary to obtain

operation in axial mode.

  From these observations, the author established the radiation diagrams corresponding to different modes of

  realization of quadrifilar antennas, in particular for angles of inclination

  origin of windings, diameters and lengths of variable antennas. These advantages of the quadrifilar antenna make it a

  antenna which is particularly suitable for a satellite application.

  The main disadvantage of this technology is the greater complexity of the power system, but this disadvantage

  remains entirely relative to the advantages obtained.

  It was then that we discovered that it is possible to exci-

  ter the different strands of a quadrifilar antenna or more general

  multi-wire by different power sources and not 6.

  more by a common power source. Although this new

  such an application may seem hazardous at first sight, tests; have shown that, in the case where the frequencies in question are sufficiently close to one another, the coupling between the different signals remains limited, and the antenna

presents good efficiency.

  A model for calculating the electromagnetic field produced

  along the longitudinal axis Z of a helical antenna is

  reported by S. Sensiper in the journal Proc. IRE (February 1955 PP. 149-161) under the title "propagation of electromagnetic waves

  in helical structures. "This model, called the helix-ru-

  ban, as opposed in particular to the model of the propeller-tube in the form of a continuous tube, starts from the assumption that the propeller is formed of a wire supposed to be a perfect conductor, having a zero radial thickness but a thickness axial of finite value. Insofar as the propeller is

  thus considered as a periodic structure, the ma-

  are multiplied by a complex constant which is a

  depending on the winding parameters of the propeller and its length

  cheer z. Magnetic fields along the Z axis can be expressed as follows: -'Paz. j (2 "3 z E (z) = Em e J Z. emNp = Eme-J zo Pm = Po + M. a- 2 'o with m = whole number corresponding to the wave mode (m = 1 is the axial radiation mode) N = number of separate helices or strands wound on the common core

p = no propeller.

  Figure 3 shows a preferred embodiment.

  rentiel of the invention in which the helical helix is quadrifilar, and therefore consists of four strands 41, 42, 43, 44 wound around a same core, and whose turns are interposed between each other. In this case, and using the above-mentioned equations, the value m = 1 (axial radiation) and N = 4 (quadrifilar helix), we obtain E (Z) = E1 e J z ej 2z and 1 = Po 2 p Note that according to this embodiment, the fields add up along the Z axis for individual propellers

  arranged at quarter wave intervals.

  A quadrifilar propeller was produced, and the experiments

  riences and the measurements carried out have shown that the coupling between the helical strands is periodic, and exhibits the

  characteristic waveform of a standing wave, likely-

  because of modal interference. The coupling remains weak

  with a maximum of - 20 dB and a minimum of - 50 dB (see fig. 2).

  Taking into account this relative insulation existing between the different strands of the quadrifilar antenna, and therefore between the frequency signals close to the transmitters and receivers which are there

  connected, you can choose the transmit and receive frequencies

  concept so as to be placed in the optimal conditions of i

solation.

  In the embodiment presented in FIG. 3, the an-

  quadri-wire is connected to three transmitters E l E2u E3 by three first helical strands 41 r 42r L3, and to a receiver R by its fourth and last helical strand l 44. The emission frequencies of the transmitters EV, E2, E3 are respectively f f2 'f3 and the reception frequency of the receiver R is noted fr'

  Since it has been found that there is great insulation between the

  gnals of frequency fl 'f2' f3 and of frequency fr 'we have the transmission and reception frequencies as indicated in

figure 2.

  The quadrifilar antenna acts as a diplexer, in the sense that it allows to separate the transmission and reception channels, and plays the role of a mixer and a rayuxinent device for the transmitted frequencies. It should be noted that the total gain of the antenna has the

  same value as the gain of a single heliowdal strand.

  The general configuration of the device presented in Figure 3 provides the same functions as the system shown in Figure 1. It is clear that the realization of the antenna with 4 separate strands is only an example and that the invention relates to any antenna multifilar comprising at least two distinct helical strands. In the same way, each of the strands can be connected to a transmitter as well as to a receiver, without limiting the invention to the configuration shown.

in figure 3.

  The invention finally has the following advantages over the prior art: - it eliminates the need for hybrid or Wilkinson type mixers, and therefore the power losses that these mixers cause, - the diplexer filters can be eliminated for low power applications,

  - the number of diplexer filters can be substantial

  partially reduced for high power applications, - and finally, the quadrifilar propeller can be produced by printed circuit technology with all the advantages of weight, resistance to loads linked to putting into orbit or even production possibilities of Fasse, etc ... qoue oette

technology allows.

  Finally, the invention can be used as a duplex radio system.

  yonnement in a source element of a reflector antenna. A preferred application of the invention is the use in tranYpo.eurs of

  advanced satellites and in the VHF / UHF frequency bands.

9. 2570546

Claims (5)

  1) Device for simultaneously receiving   tion and the emission of several radio signals from   close or identical frequencies, especially for communications   continuous spatial tions in the VHF / UHF wave ranges, of the type comprising at least one transmitting device and at least one receiving device, said devices being connected to a single common antenna, device characterized in that this antenna is a multi-wire antenna helical, made up of independent strands of radiation, wound in a helix around the same   core, said strands being angularly offset in a regular manner   at least two of these strands   each being connected continuously to a transmitting or receiving device, separate author.   2) Device according to claim 1, characterized in that the helical antenna is quadrifilar, three of the independent helical radiation strands (41,42,43) each being separately connected to a separate transmitter E1, E2, E3, the fourth strand (44) being connected to a receiver R.   3) Device according to any one of claims   1 and 2, characterized in that the multi-wire antenna is radius-   axially, the circumference of each of its helical strands (41,42, 43,44) being between 0.4 and 2.0 times the length of the transmitted signals.   4) Device according to any one of the claims   1 to 3, characterized in that the multi-wire antenna is   produced by printed circuit technology.    ) Device according to any one of claims 1 to 3, characterized in that the multi-wire antenna is combined with diplexer filters for high power applications.   6) Device according to any one of the claims.   tones 1 to 5, characterized in that the multi-wire antenna is   kills a diplexer system of a source element of a reflector antenna.