US2248778A - Antenna network - Google Patents

Description

July 1941. G. E. M. PERRoux 2,248,778

ANTENNA NETWORK Filed D60. 17, 1957 Fig. 1. Fig. 2;

Patented July 8, 1941 ANTENNA NETWORK Georges Edme Marcel Perroux, Paris, France, assigner to International Standard Electric Corporation, New York, N. Y.

Application December 17, 1937, Serial N o. 180,3l4 In France December 31, 1936 (Cl. Z50-l1) 4 Claims.

The present invention relates to antenna systems particularly applicable to directional insta1- lations for the transmission or reception of radio electric waves. The invention provides, in particular, an antenna system for use in systems for guiding vehicles by radio and means for eliminating certain disturbances in the transmission of the waves employed.

In known arrangements such as those employed in installations for blind landing of aircraft a directional beam is radiated and deflected, usually by means of an antenna system comprising an energising antenna, one or more reflectors and one or more directors. An arrangement of this kind may generally be considered to comprise a longitudinal alignment giving a directional diagram and a transverse alignment giving another directional diagram, these two diagrams being combined to give a resultant direc-` tional diagram having desired characteristics.

An automatic manipulator modifies the characteristics of the transverse diagram according to a predetermined law by means of appropriate devices. Consequently the resultant diagram is deflected to the right or to the left of the datum line, direction or axis. In accordance with known methods the modification of the transverse diagram may be obtained by the operation of relays which control the action of reflectors.

In accordance with the same known methods, any increase of the longitudinal directivity, for a given transverse directivity, reduces the inclination of the resultant diagram with respect to the datum direction or in other words the datum vdirection or axis is not so well donned.

One of the objects of the present invention is to provide means to increase the definition of the datum axis ordirection.

Another object of the invention is to provide means for increasingk the longitudinal directivity of the antennae whilst maintaining a good definition of the datum axis or direction.

Another object of the invention is to provide means for eliminating the clicking or cracking disturbances due to. the operation of the manipulator referred to above without, however, reducing the definition of the datum axis or direction.

In accordance with one of the features of the present invention, each of the conductors of the transverse alignment is continuously traversed by a current; each conductor is adapted to operate alternately as a reflector, or as a director, the frequency ofr alternation depending upon the frequency of operation of the manipulator and consequently its action is never interrupted.

In accordance with another feature of the invention, means is provided to synchronise the lateral reflectors of an antenna system, that is to say, to eliminate harmful fiel-ds during a part of the period of operation of the maniuplator,

In accordance with another feature of the invention, means are provided for rendering the gain and the front to back ratio of a directional diagram independent of the reflector elements of the system.

These and other characteristic features will appear in'more detail in the following description given by way of example and based on the accompanying drawing in which:

Fig. 1 shows by way of example a directional antenna system in which means is provided to ensure a satisfactory definition of the datum axis;

Fig. 2 shows a dipole adapted to operate as director during one lpart and a reflector during another part of the operation period of the manipulator;

Figs. 3 and 4 represent directional longitudinal and transverse diagrams of the antenna system shown in Fig. 1, and

Fig. 7 shows the resultant directional diagram;

Figs. 5 and 6 show vertical diagrams for the purpose of explanation in relation to the transverse directional diagram of Fig. 4; and

Fig. 8 represents an arrangement of reflectors embodying features of the invention, by which the clicking or cracking noises due to the operation of the manipulator are eliminated.

It will bee-understood that the following explanation describes only one possible combination of energising antennae directors and reflectors by way of example and that other combinations may be used whilst embodying the features of the present invention.

Referring to the drawing, Fig. 1 shows an antenna system particularly adapted to be used in blind landing systems or systems for the radio guiding ofvehicles, and comprises an energising antenna A, a reflector Rl and two directors DI and D2, which form the longitudinal alignment of the directing station, and dipoles R2 and D3, which function alternately as reflector and diirector during the operation of the manipulator, and which form, with the energising antenna A, a transverse alignment,

Experience has shown that during the operation of the manipulator, on account of retardation of the relays, the two lateral conductors operate simultaneously either as reflectors or as directors. During these periods of simultaneous operation the eld on the datum axis undergoes a sudden change of value which is translated in a receiver by the so-called clicking or cracking noises due to the operation of the manipulator. The presence of such cracking noises is a cause of disturbance for the auditory observation of the true signals, and falsies the indications of a visual apparatus.

The conductor BB', shown in Fig. 2, which may be employed for the alternate reflector RZ-director D3 system, comprises a self-inductance coil L to the terminals of which is connected a contact device of the usual manipulation relay R. This self-inductance coil L is of such a value that it de-tunes the reflector unit through excess of self-inductance, when the contact device is open. At this moment the current has a value I and a phase angle 41. The conductor BB' acts against the radiation of the energising antenna, that is, it functions as a reflector. At the next operation of the manipulator the relay R operates to close the contact device and short-circuits the self-inductance L, thus reducing the electrical length of the conductor BB', and is such that the value of the current remains I, but the phase thereof becomes minus qb. I'he conductor BB thus acts to reinforce the radiation of the antenna A, that is, as a director. 'Ihe relays associated with the reflector R2 and the director D3 operate inversely with respect to each other, and these relays will at any moment, perform inverse functions with respect to each other, that is, that at one operation of the manipulator, R2 will be the reflector and D3 the director and that at the next operation R2 will be the director and D3 the reflector. Since these members R2 and D3 are situated one on either side of the energising antenna A, it is obvious that their actions at a distance will be added and produce effects more intense than those obtained with a single active conductor acting, for example, as a reflector in accordance with the known methods.

These intense effects, while preserving a suffcient denition of axis, permit of the use of longitudinal alignments with high directivity having a diagram such as that shown in Fig. 3. This directional diagram is that of the longitudinal alignment of the system comprising the energising antenna, reector RI and directors DI and D2. The form of this diagram is of little importance in itself, but it should possess an advantageous ratio of the front radiations OM to the rear radiations ON, as shown.

The transverse alignment comprising the energising antenna A, and the reector RZ-director D3 unit with reversible functioning gives a directional diagram shown in Fig. 4. An analysis of this diagram is facilitated by an examination of Figs. 5 and 6.

In Fig. 5, AEo represents the free electric field created by the antenna A at the point A at a moment under consideration. The vector BE represents the field of antenna A at point B at the same moment. Assuming clockwise rotation of the vectors BE is retarded by 1r/2 with respect to A if the distance AB is made equal to a quarter of a wavelength. A conductor of the type shown in Fig. 2 is located at B. Let us assume that this conductor is intended to act as reflector at the moment under consideration. The vector BEi then represents the field of this conductor. It is retarded by an angle 1 with respect to the normal to BE at B. The resultant eld. in the direction AB is the component in that direction of the resultant of BE and of BE1, and is thus weak with respect to the inductor field BE, the conductor thus acting as a reflector.

If on the other hand the self-inductance of the conductor is short circuited, the phase of the current changes, the radiated eld becomes BEz in advance of the normal to BE by an angle dz: The resultant field of BE and BE2 is greater than BE; in this case the conductor acts as a director.

In order to simplify the drawing it is assumed that the angles 1 and p2 are equal to a value approaching the optimum value which is 1r/4.

On this hypothesis, Fig. 6 represents at AEo the field of the energising antenna, at BEz the eld of a director element located at a quarter of a Wavelength from the antenna, and at CE1 the eld of a reflector element located at a quarter of a wavelength from the antenna.

The fields BEz and CE1 may be split up into their longitudinal components Bez and Ce1 (in phase) and transverse components Bez and Ce1 (in phase opposition).

Fig, 4 represents at OABC and ODEF, the diagram of the components in phase opposition and at OGI-II and OJKL the diagram of the components in phase.

If, as shown in Fig. 6, the longitudinal and transverse components exist at the same time the two elementary diagrams of Fig. 4 co-exist and the total effect of the transverse alignment is the resultant of these two elementary diagrams. When they are combined with the longitudinal radiation (diagram of Fig. 3), it is easy to see that only the diagram OABCODEF of the components in phase opposition contributes to the deflection of the beam from the axis, that is, to the denition of the datum axis.

Itis clear that the diagrams of the components in phase opposition produce a zero field in the direction of the longitudinal axis; these components have thus no action on the intensity of the field on the datum axis. The gain and the ratio of the front to the back radiations of the system are consequently independent of the presence of these components of the reflector and director systems. Therefore if these components disappear during the intervals of operation of the manipulator there will be no variations of field on the axis and thus no cracking noises due to these components.

The components which are in phase, and which alternately are added to or subtracted from the longitudinal field during the operation of the manipulator, will produce considerable cracking noises. In particular during the transitory periods of manipulation mentioned above, the two lateral conductors tend to function simultaneously (as reflectors or directors). In this case only the components in phase exist in accordance with the diagram OGI-II-OJKL (Fig. 4) and have the effect of modifying the eld value along the datum direction. This variation of field is the cause of the cracking noises of manipulation observed.

In accordance with certain features of the invention conductors such as BB' and CC can be synchronised at their electrical centres by means of a transmission line XY having a length equal to half a wavelength. Such an arrangement is shown schematically in Fig. 8. In this figure the conductor BB' is shown operating as director with its relay R short-circuiting the self-inductance L, L' and the conductor CC is shown operating as a reflector with the contacts of its relay R' afa-4eme open and its self-inductance coils effective in series with the conductors C, C'.

The impedance of the conductor CC seen from the end Y of the transmission line offers a reactance having the characteristic of an inductance, which seen from the other end X of the line has changed sign and has become a reactance having a capacity characteristic. That is, it is of suitable sign for the conductor BB functioning as director with its inductances in short-circuit whose impedance matches this capacity. No current passes in the line and consequently the latter does not modify the normal operation of the reflectors with conjugate reactances. Similar effects occur upon energization of relays R and R' reversing the contacts in B, B and C, C by operation of the keying device.

During the reversal of operation of the relays, the two conductors BB' and CC tend to operate as reflectors. The terminal reactances no longer being conjugate, a synchronisation current is produced in the line XY and tends to cancel these reactances and thus to eliminate the effect of the conductors BB and CC. The transverse field then no longer exists and the diagram of the system is like that shown in Fig. 3. The cracking noises due to the operation of the manipulator are thus eliminated.

It is clear that the embodiment shown is only given by way of example and that other devices employing features of the invention may be made without departing from its scope.

In the detailed description given above this longitudinal radiation has been maintained fixed and the phase of the transverse radiation has I been reversed symmetrically in order to produce the distortions of the resultant diagram. It is also possible to maintain fixed the phase of the transverse radiation by feeding the lateral conductors through suitable transmission lines. In this case manipulation on the phase of the longitudinal field is effected by providing the central antenna A or other conductors of the longitudinal alignment with means such as shown in Fig. 2. The central antenna, or the other conductors manipulated may moreover be fed by the same source as the transverse conductors, the dephasing then being made symmetrically with respect to the common high frequency feed voltage.

It is obvious that the devices described by way of example find a eld of application in all cases where it is desired to modify as required the radiation characteristics of a radiating system without mechanically displacing one or more elements thereof.

In particular when a transmitting station serves several stations situated in different geographical azimuths, it is possible to rotate the directional diagram of transmission or of reception at a suitable angle without thereby affecting its qualities or producing the appearance of sheets of undesirable radiation. This among other things permits the number of directed antennae normally necessary to be reduced. It is clear that directional receiving antennae can also employ the same methods. It is also possible to rotate the directional diagram in time in order to obtain for example successive guidings of different direction by means of a single set of antennae. In the case in which the number of directions to be served is high, obviously it is possible to arrange several lateral systems permitting of the desirable combinations of transverse fields to be effected without requiring the subsequent modification of the adjustments of the conductors themselves and to obtain different slopes and directivities by means of a system of mechanically xed elements.

Vhat is claimed is:

1. A directional antenna system comprising an antenna, a plurality of conductor assemblies arranged abcut said antenna and spaced therefrom, at least two of said assemblies being spaced substantially one-half a wavelength apart on opposite sides of said antenna, means for rendering said two conductor assemblies operative alter-V nately as directors and reflectors at a desired frequency of alternation, said two conductor assemblies each comprising two parts in alignment each said part being connected to one end of an individual coil of large inductance the coils of each conductor assembly being adjacent one another, a transmission line connecting the other ends of the coils of one of said two conductor assemblies to the corresponding ends of the coils of the other conductor assembly.

2. A directional antenna system comprising an antenna, a plurality of conductor assemblies arranged in spaced cooperative relation about said antenna, control means for making two of said conductor assemblies on opposite sides of said antenna operative and inoperative alternately as reiiectors at a desired frequency, inductive elements in circuit with each of said two conductor assemblies, and a transmission line interconnecting said inductive elements to maintain current continuously flowing in said conductor assemblies to avoid noises due to the operation of said control means.

3. A directional antenna system comprising an antenna, a plurality of conductor assemblies arranged in a cross with the said antenna at the centre thereof, means for rendering one of said conductor assemblies in one alignment and on one side of the antenna inoperative as a reflector but operative as a director whilst the conductor assembly on the opposite side of the antenna and in the same alignment is rendered operative as a reflector but inoperative as a director, a manipulator to reverse the functions of the said two conductor assemblies at a desired frequency, and means comprising inductive elements connected in said two conductor assemblies and transmission lines interconnecting said two aligned conductor assemblies to maintain a current continuously flowing in said two assemblies.

4. A directional antenna system comprising an antenna, a plurality of conductor assemblies arranged in a cross formation with the said antenna at the centre thereof, means for causing some of said conductor assemblies to function as reflectors and others as directors and a manipulator to reverse the functions of two of said conductor assemblies arranged in alignment on opposite sides of said antenna alternately at a desired frequency of alternation, a plurality of inductive devices, one connected to each of said two conductor assemblies to retard the current flow in the conductor during the transition period when the conductor is changing over from one function to the other and transmission lines interconnecting alternately operated conductor assemblies through said inductive devices.

GEORGES EDME MARCEL PERROUX.

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