US2400641A - Radio obstacle localizing apparatus - Google Patents

Description

May 21, 1946. R. J. HARDY 2,400,543

RADIO OBSTACLE LOGALIZING APPARATUS l he INVENTOR /PfA/f' J #Afa/9V May 21, 1946. R. J. HARDY RADIO OBSTACLE LOCALIZING APPARATUS Filed March 7, 1941 2 Sheets-Sheet 2 INVENT OR.

FFA/f' Z/VARDY ATT ORNE'X Patented May2l, 1946 RADIO GBSTACLE LOCALIZING APPARATUS Ren Jean Hardy, Lyon, France, assignor to International Standard Electric Corporation, New

York, N. Y.

Application-March 7, 1941, Serial No. 382,152

(Cl. 25o-11) 7 Claims.

The present invention relates to direction nding systems and particularly to radiogoniometers and obstacle radio localizing apparatus.

An object of the invention is to provide radio direction nders giving instantaneous indications of directions without the use of any rotating element for the search of said directions.

Another object of the invention is to provide a radio obstacle direction nder giving simultaneous and instantaneous indications of the directions oi a plurality of obstacles.

Another object of the invention is to improve the accuracy and the stability in time of radio direction ilnders.

More specifically, an object of the invention is to provide a radio direction nder which is able to operate as a panoramic obstacle localizing apparatus giving instantaneous and simultaneous indications of directions.

According to some features of the invention, a radiogoniometer comprises a wave collector having crossed diagrams of reception and associated to an omnidirectional antenna adding algebraically a constant phase energy to each energy of said diagrams, two radio receivers supplied from said collector with the respective energies from said diagrams and an indicator such as an oscillograph the deection circuits of which are respectively connected to said radio receivers, means for automatically correcting` gain diilerences between said radio receivers and means for automatically checking the emciency of this gain regulating arrangement.

According to some features of the invention, an obstacle direction finder comprises a radio pulse generating and transmitting arrangement,

a wave collector having two crossed diagrams ofreception, and associated to an omnidirectional antenna adding algebraically a constant phase energy to each energy of said diagrams, two radio receivers supplied from said collector with the respective energies from said diagrams and an indicator the deflection circuits of which are respectively connected to said radio receiversl means for automatically correcting gain difierences between said radio receivers and means for automatically checking the efllciency of this gain regulating arrangement.

According to another feature of the invention, said checking means comprises an impulse generator and a transmission path for supplying periodically these short pulses to the inputs ot said radio receivers, so that a luminescent indication of the reference line will periodically appear on the screen of the indicating oscillograph.

According to another feature, the transmission path for checking the regulating action of the gains of said radio receivers comprises a spatial path from a transmitting aerial energised by a pulse transmitter and arranged in front of the wave collector, to said wave collector.

These objects and features, as well as others, will now be described in details in the following specification based upon the attached drawings. in which:

Figure l represents diagrammatically an em bodiment of a radiogoniometer or of an obstacle direction ilnder, according to certain features of the invention;

Figure 2 shows a wave train such as transmitted from the transmitting aerial of the arrangement of Figure 1;

Figure 3 shows the transmitted pulse or wave train and return pulses after reection upon obstacles in the space around the direction nder;

Figure 4 shows an example of simultaneous indications which may appear on the screen of the oscillograph in the embodiment of Figure 1;

Figures 5 and 6 show diagrammatically circuit arrangements embodying a feature of the invention used in the embodiment of Figure 1; and

Figure 7 shows a diagram relating to the indication 'obtained upon the screen of the oscillograph of Figure 8.

Referring now to Figure l of the attached drawings, a wave collector comprises two crossed elements Ci, C2, which may consist of loops, frames, antennae or any other suitable collectors having crossed diagrams of reception. The elements of said wave collector are connected respectively to two radio receivers Ri, R2. These receivers are of such structure that. connected by a well-known coupling circuit N which applies the output of the receivers to separate opposite deilecting electrodes of the deflection systems, for example the deflecting plates, of a cathode ray oscillograph, they produce a scanning of the cathodic spot controlled by the differences of the currents received in each of the collecting elements CI, C2. Thus, if, by means of a transmitting aerial placed along the axis Z', i. e. along the blsector plane oi' the wave collectors Ci, C2. a short duration high frequency pulse is transmitted, the receivers RI, R2 will .receive with equal strength said transmitted signal and the luminescent spot S on the screen of the oscillograph normally at the center O will be deflected with an equal strength by the two plates Pz, Pu or other deiiecting elements, in the direction OT. When said signal is received by the collectors tude, in order to obtain a luminescent line on the'- screen, it will be suilicient'to eii'ect a radial modulation of the cathode beam, for example by su' permipressing on the anodic voltage of the tube an alternating voltage which will eifect this radial tated around point Z, the line OT on the screen I will come at T', for example. 'I'his type of cir-v cuit provides in this way a manually rotatable goniometer enabling the finding of the direction of propagation of a radioelectric source of waves.

In fact, if the wave collectors CI C2 are fixed and if the distant transmitter lies in a direction diiferent from Z, Z', an effect similar to that described for line OTzwill be obtained and the luof said transmitter.

The operation of the portion of Figure 1 al- 1 ready described will be better understood with reference to Figures 5 to 'I which will now be described.

In Figure 5, is schematically shown an example of embodiment of one of the paths from the collector, let it be Cl, constituted by two windings LI, L2 through the receiver RI and the coupling circuit N to a pair of deilecting plates Pz, Px' of the oscillograph I.

The windings LI, L2 are the two halves of a frame collector placed into the field of a distant radiotransmitter E the direction of propagation of which makes an angle a with .the plane of said frame, said windings LI, L2 having their outputs respectively connected to the grids of amplifying valves Vi, V2, the output circuits of which are then connected through transformers Ti, T2 to detectors DI, D2. 'I'he D. C. voltages at the outputs of DI, D2 would be identical if, according to a feature of the invention, the current from an omni-directional or. vertical antenna A2 were not applied by an inductive coupling L upon the two windings LI, L2, in opposite directions. Said antenna current has a phase in definite relation with the high frequency current received by the windings LI, L2. The phase of the incoming current will be additive to the phase of the current in one winding, LI for example, and subtractive in the other L2. At DI and D2, there will be then different voltages and, as these voltages are applied on the control grids of the double triode valve V3 (in the N circuit of Figure 1) the output voltages of which control the deilection of the cathodic spot S, this spot will come to a position, S' for example, diiferent from the center of the screen, which will depend on the angle of the radiotransmitter with the plane of the frame LI, L2, and the direction of this variation on the screen will then be from Pz to-Pz' and vice versa.

If, now, as shown-in Figure 8, a second frame` C2, having two'windings Il, IA is Dcrpcndicularly associated to the frame CI, each frame will be used for supplying deiiecting voltages to one pair of perpendicular plates, or other denecting elements,ofanoscillographIthroughradiore-V ceivers Ri, R2 which may each comprise the'circuits shown in Figure 5. 'Ihe circuit of Figure 6, which, it may be seen. corresponds to a portion of the circuit shown in Figure 1 comprising the wave collector CI, C2, the two radio receivers RI.

R2, the coupling or distributing circuit N (valve' Vl of Figure 5) and the oscillograpl indicated by the plates Pz, Pv. operates as a phase indicator giving the angle between the direction of the radiotransmitt'er E, Figure 5, and a determined direction of reference. The cathodic spot S will be on a circle M and, according to the direction of the radiotransmitter or to the orientation of.

the wave collector structure, CI, C2, -Figure 1, or LI, L2, Ll, L4, Figure 6, the angle of the radius upon which rests the cathodic spot will change.

In Figure Lvthere is shown the screenof the cathode ray oscillograph I, von which line OP corresponds to the axis of the horizontal deflecting plates and line OQ to the axis of the vertical deilecting platen. 'I'he cathodic spot will always be on a radius OA, the angle a of which with line OQ will depend upon the orientation of the radio transmitter with respect .to these axes, and, ac cording to the strength of the detected signal, the spot S will be at a point of line OA such as a, having coordinates q and p.

As mentioned above, according to a feature of the invention, in such direction finding arrangements, the constant phase current from antenna A2 is permanently superimposed on the currents of the windings LI to L4 of the frames. This markedly increases the highfrequency voltage entering into the radio receivers Ri, R2 and moreover all this high frequency of constant phase, which enables the complete scanning of the spot along two rectangular diameters and consequently along a whole circumference, does not effectively appear on the cathode ray indicator since the difference only of the high frequency voltages collected on the frames Ci, C2 is used for deflecting the cathodic spot.

In order to obtain correct indications of direction, it is necessary to have a great stability of operation and gain of the two radio receivers Ri, R2, the circuits of which are provided as identical as practically possible. If the receivers Rl, R2 were not identical, when the received signal arrives along the axis Z, Z', Figure 1, this signal would not be amplified the same in the two receivers and the indication obtained would no longer be the line OT but another line, such as OT for example, and all further indications of direction will be erroneous, since this line OT is taken as a direction of reference or zero angle.

Consequently, according to a feature of the invention, a device such as indicated at V is provided. This device automatically corrects the gains of the two receiversand may, for example, consist of a well-known automatic volume control circuit, suitably provided to correct the gain of each receiver according to the gain of the other, as indicated by the cross-connections F. l

According to another feature of the invention, means are provided for obtaining a visual check of this gain regulation. Thus, for example, from time .to time, the high frequency circuits of the frames CI, C2 are disabled, and, at repeated intervals, a sht pulse is sent with equal strength into the high frequency inputs of the two receivers. These'short pulses may be created from an impulse generator D, of any well-known type. creating pulses from the output of a sinusoidal generator G. and brought to the inputs oi the receivers by the connection or line K. Automatical- 1y, upon the screen of the oscillograph I, will appear a luminescent line which is to be coincident with line OT if the gains of the receivers are o! the suitable value. as in the case of the reception of a signal along the line ZZ'. I! the gains are not correct, a line such OT' will appear. It will thus be easy to observe the operation of the automatic volume control circuit V. This injection of short pulses into the inputs of the receivers A axis ZZ near the wave collector CI, C2, and to energize said antenna by means oi' a pulse transmitter E controlled by a pulse generating circuit D in order to transmit from time to time a pulse which is passed to the receivers by the collectors CI, C2 and acts as above described for giving an indication of the oscillograph screen.

An arrangement such as shown in Figures 1, 5 and 6, may be used, as described, for the purpose of iinding the direction of radio sources, broadcast transmitters or others. It may be used equally as an obstacle direction nder, and in this case, will be able to give simultaneous indications of a number of obstacles on the screen of the oscillograph.

For such an operation, the pulse transmitter E is provided of the necessary power to transmit by its antenna AI regularly spaced impulses to a distance. Figure 2 shows, as an example, a short duration pulse such as transmitted by antenna Al. This pulse te consists of a series of high frequency oscillations having an envelope curve which increases progressively from zero to a maximum value then back to zero. This wave train te is immediately applied to the wave collector CI, C2'since antenna AI is placed in close proximity of said wave collector, and along the axis ZZ'. The receivers RI, R2 will then amplify the received energy and on the screen of the oscillograph will give the luminescent line OT. It should be noted that the coincidence of said line OT with a marked direction on the screen will give the desired visual checking of the operation of the automatic volume control circuit V. However, as the diierence between the energy of this transmitted pulse and those of the pulses which eventually come back after reflection upon obstacles is very great, as shown for example in Figure 3, by the difference of surfaces between the pulse to and the successively reflected pulses t1, t2, t3, there is need to reduce the sensitivity of the receivers RI, R2 at times when each pulse is transmitted by antenna AI, in order to receive the pulse to with a suitable apparent strength. For this purpose, the pulse generator D, which controls in the pulse transmitter E by controlling the and ensures the visual check ot the gain regulating arrangement V, instead oi' being completely eliminated by the usual blocking 'of the receiver as in ordinary obstacle direction ilnding equipments. This synchronous supply for controlling attenuation networks may be made either through the connection K. or through aseparate connection K' coupled inductively at L to the mid point of the wave collector or directly from the signal transmitted from antenna AI to the wave collector CI. C2 or a combination of both as shown in the drawing. i

A further connection J is also indicated from the puise generator D to the automatic volume control circuit V in order to provide a control of an attenuation network, which maybe a grid bias network, in this circuit for adjusting the sensitivity of the gain of the receiver.

The pulse to being transmitted into free space, will be reflected by the obstacles surrounding the equipment, for example, by planes moving around a landing neld, and at times t1, t: and ta, for example. as shown in Figure 3, echoes will arrive onto the wave collector CI, C2 from dierent directions. Indications such as shown in Figure 4 at OA, OB and OC, will then simultaneously appear on the screen of the oscillograph, the angles of which with the line OT giving instantaneously the orientations of said obstacles'with respect to the axis ZZ. The values OP and OQ for example in the case of the obstacle along the direction OA correspond to the respective currents in the collectors CI and C2. If the transmission of pulses by antenna AI is continuous, the lines OA, OB, OC will move in accordance with the respective motions of the diilerent obstacles to which they correspond.

Such a system of observation of obstacles is obviously based on the fact that the various obstacles are located at different distances. When two obstacles are at the same distance, their reected pulses will arrive at the same time on the wave collector and will give a mean indication on the oscillograph, consequently an erroneous indication of their direction. However, as generally these obstacles will be of small dimensions with respect to the distances to the equipments, and also, as in the case of planes, are of speedy displacements, there is no practical confusion in the indications obtained.

It is clear that in the preceding description, no details have been given on the known elements used.

It is also clear that the invention is not restricted in the specic embodiments described, but is meant to cover all embodiments making use separately or in combination of the arrangements disclosed in the following claims.

What is claimed is:

1. Obstacle radio direction nder comprising a radio pulse generating and transmitting arrangement, a directive wave collector means having crossed diagrams of reception and an associated omnidirectional antenna coupled to said directive collector means for supplying a constant phase energy added algebraically to the received energy representing each energy of said diagrams, two radio receivers supplied from said collector with the respective energies from said diagrams and said antenna and an oscillograph indicator having the deiiection circuits which are respectively connected to said radio receivers, means for correcting gain dierences between said radio receivers and means for automatically checking the operation of this gain regulating arrangement.

2. Direction iinding equipment as claimed in claim i, said gain correcting means comprising an automatic volume control circuit arranged to correct the gain of each receiver according to the gain oi' the other.

3. obstacle radio direction under as claim in claim l, wherein said transmitting arrangementcomprises an antenna arranged along the reference axis oi said wave collector, a space transmission path between said antenna and said wave collector, and means responsive to application of said impulses to-said receivers for lowermission path between said antenna and said wave collector, and means for controlling the sensitivity and gain of said receivers in response to transmitted impulses comprising a conductive -transmission path from said generator` to said receiversto reduce the sensitivity of said receivers under control of said impulses, and a conductive transmission path from said generator to said gain correcting means to reduce the gain of said receiver under control of said impulses.

5. A radio direction finder comprising a directive collection means having crossed diagrams of reception and an associated omni-directional antenna coupled to said directive collector means for supplying a constant phase energy added algebraically to the received energy representing each of said diagrams, two radio receivers supplied ix'om said collector with the respective energies from said diagrams and said antenna and an oscillograph indicator having deflection circuits, said deiiection circuits being respectively connected to said receivers, means for correcting the gain dierences between said radio receivers y applying the generated pulses into the two radio receivers in a direction .of reference, so that indications created by'these pulses appear on the oscillographic indicator of the system.

6. Aradiodlrectionilndercomprisinga directive collection means having crossed diagrams of reception and an associated omni-directional antennacoupledtosaiddirecnvecollectormeans for supplying a constant phase energy added algebraic'ally to the received energy representing each of said diagrams, two radio receivers supplied i'rom said collector with the respective energies from said diagrams and said antenna and an osciilograph indicator having denection circuits, said 'deection circuits being respectively connected to said receivers, means for correcting the gain differences between said radio receivers and means for automatically checking the operation oi' this gain regulating arrangement, said means for checking the operation of said gain regulating arrangement comprising an electrical impulse generator and a wire transmission path from said generator to the inputs of saidv receivers.

7. A radio direction ilnder comprising a directive collection means having crossed diagrams oi reception and an associated omni-directional antenna coupled to said directive collector means for supplying a constant phase energyv added algebraically to the received energy representing each of said diagrams, two radio receivers supplied from said collector with the respective energies from said diagrams and said antenna and an oscillograph indicator having deiiection circuits, said deection circuits being respectively connected to said receivers, means for correcting the gain differences between said radio receiversl and means for automatically checking the operation of this gain regulating arrangement, said means for checking the operation of said given regulating arrangement comprising an electrical impulse generator, an antenna connected thereto and `arranged along the reference axis of saidA wave collector and a space transmission path from said antenna to said wave collector.

REN JEAN HARDY.

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