US2043624A - Method and means for direction finding - Google Patents

Description

June 9, 1936. A. LEIB 2,043,624

METHOD AND MEANS FOR DIRECTION FINDING Filed Jan. 27, 1952 s Sheets-Sheet 1 m y i /60" A 0' MOMW 3 90 270 0 yaa" INVENTOR AUGUST LEIB ATTORNEY June 9, 1936. A. LEIB 2,043,624

METHOD AND MEANS FOR DIRECTION FINDING Filed Jan. 27, 1952 s sheets-sheet 2 INVENTOR AUGUST LEIB 2 BY V rv ATTORNEY 9, 1936. 5 LElB 2,043,624-

METHOD AND MEANS FOR DIRECTION FINDING Filed Jan. 27, 1932 3 Sheets-Sheet 3 k [M g A]! 2 U? l i I Full" INVENTOR AUGUST LEIB ATTORNEY Patented June 9, 1936 KJNE'EED STATES PATENT OFFICE METHOD AND MEANS FOR DIRECTION FINDING Application January 27, 1932, Serial No. 589,100 In Germany June 15, 1926 7 Claims. (Cl. 250-11) The present invention, which is a continuation in part of United States application #198,926, filed June 15, 1927, relates to an arrangement for directional signalling and in particular for direction finding work in wireless telegraphy. This invention is universally useful, but is illustrated as being particularly for use on vessels, automobiles, ships, or aircraft.

It is well known that for direction finding work loop or coil antennae, or other antennae having directional characteristics, are employed, and that the intensity of the signal currents set up in the aerial system by absorbed signal energy vary in accordance with the particular position of such directional. antenna relative to the position of the source of signals. In using such devices, it has been found that an absolute zero, that is, a complete absence of current, in the absorption circuits can not be obtained no matter how the directional antenna is positioned with respect to the distant transmitter. Such lack of sharpness of minimum response of the absorption structure to incoming current intensity may be the result of various causes. These causes may reside either in the directional absorption structures themselves or else in efiects external to the latter. Particularly on ships there is one special source of disturbance, namely reradiations from adjacent metallic structures or wires or other conducting elements or structures mounted on the ships. This re-radiation from adjacent conducting elements to the directional aerial system results in the introduction in the circuits of currents not in phase with the current therein representative of directly absorbed signal energy. These disturbing currents result in masking the null point on the energy curve representative of the absorption characteristics of the receiver and result in a reading which does not give the true direction of the source of signals. This re-radiated energy may be of any frequency, and may be of a frequency above or below the signal frequency but is in general in its worst form thought to be of a frequency higher than the signal frequency. This effect of re-radiation of energy from adjacent conducting elements to the directional absorption system is known as mast effect. It must be kept in mind that the result of this out-of-phase energy in the loop circuit is to dull or mask the null point of the loops signal absorption characteristic rather than to shift it, and the object of the present invention is to provide means to clear up or make more definite the null point of the characteristic curve rather than to shift it.

Briefly and broadly the above difficulties are obviated in accordance with the present invention by introducing into the loop circuit energy to oppose and compensate the energy induced therein from the adjacent masts or other conducting elements.

More in detail, the null point of the characteristic curve of the absorption system is made more sharp (i. e., energy reaches zero) by the introduction into the absorption circuit or circuits associated therewith of energy opposite in phase and equal in amplitude to the disturbing energy. This may be accomplished in any manner. Applicant uses a vertical aerial coupled to the loop circuit to introduce the compensating energy. It will be understood however, that directional or non-directional auxiliary antennae may be used which occasion an additional action on the receiving apparatus so that the disturbing actions are compensated and the null point rendered more definite.

One form of the invention is shown in the accompanying drawings in which:

Figure 1 shows diagrammatically the circuit arrangement of a loop and compensating antenna arrangement and their connection with a receiver;

Figures 2 and 2a show, for purposes of illustration, the direction finder of Figure 1 as installed on a ship;

Figure 2b shows in detail a modification of a part of the device of Figures 2 and 2a;

Figure 3 is a curve showing the relation between loop positions and absorption characteristics of the loop;

Figure 4 shows the relative positions between the antennae and an inductance associated therewith; while,

Figures 5 and 6 illustrate modifications of the arrangements of Figures 1 and 2.

Referring to the drawings, and more in particular to Figures 1, 2 and 2a thereof, the loop antenna R comprises symmetrical energy absorption portions r1, r2 closed through inductances m1, m2 and a coupling inductance 1'. For reasons which will appear more in detail hereinafter, these coils may be symmetrical and equal or unsymmetrical and unequal. The loop aerial inductance may be tuned to the signal frequency by a capacity K connected across the terminals i, 3 thereof. Compensating energy is obtained from a vertical aerial A connected through a tuning capacity TC and coupling inductance a to ground G or equivalent oountercapacity. The amount of the inductance in this vertical aerial may be regulated by moving the points 8 and 9 along the inductance a. The'inductance a is coupled as shown to the inductance r. The said auxiliary antenna A serves to introduce an additional signal potential in the loop antenna circuit. 'The variable capacity TC, and inductance a insures that said energy may be maintained in the proper phase and amplitude to suppress and action from the auxiliary antenna will vary between z ero,'in-ship position I relative to the sigcompensate currents therein due to re-radia'tion from adjacent structures; 'ThelOOIIV'R has one terminal connected through a connector 3 to the grid of an electron tube e, the filament of which is connected by connector 1' to themidpoint of inductance r. The other terminalof loop R. is connected by lead 4 through a variable capacity no to the anode of thermionic tube e. The voltage set-up across the portion 12, the conductor 2,

m2, lead 6 and half of the inductance rbythe signal is impressed across the cathode control electrode impedance of e. Anode grid reactance -is controlled by the condenser connected between the anode and the-inductance m.

Now, the influence of -re-radiation of signal energy upon theloop antenna circuit differs according to the particular position of the vessel relative to the source of signalv energy so that the requisite auxiliary antenna; effect required for the compensation of the disturbing action must be varied according to the position of the ship,-with the result that the coupling between the auxiliary antenna A and the loop antenna or the receiving apparatus must be varied according to the position of the ship at any given time. To make such alterations is a rather complicated task under practical conditions of working, since in case of improper or unskilled operation and manipulation of the apparatus the compensating energy will be introduced in the wrong phase and amplitude. This will cause deviations from the true bearing'of the signalling source. Even in case a skilled direction finderoperator is in charge the changing of the-coupling relations j between A and R. involves a' by no means inconsiderable loss of time.

Now, according to the present invention, this inconvenience isobviated'thus: 'The auxiliary antenna A is coupled to the receiving antenna R.

through a 'coupling'impedance ha'vinga variable adjustment which is automatically controlled in accordance with themovementoffthe loop aerial.

It has been found'that the disturbance due to re-radiation changeswith the change of position of the vessel in accordance with a simple periodical 'law. "The manner in which thedisturbing efiect varies with rotation of the loop or .turningof the ship whilethe'ioopis pointed toward a source may be seen by an inspectionof Figure 2a in which two positions, .I .and 2,1'of theship are indicated. from these figures it will be seen that in one case the. disturbance effect on the loop is of a maximum amount, while. inthe other case no disturbance at all is present. Suppose the transmitter is'located in the, direction indicated by the arrowS. Suppose r represents the position of the receiving antenna .e. .g. the position of R of B represents a re-radiating mast or other conductor, whose ,re-radiation efiect, in

this position, acts in the same direction as the Wave coming in from the distant transmitter. In this particular position of the receiving loop R, no additional action from the auxiliary antenna A is required because the loop R has its plane at right angles to the wave from the source and the re-radiating memberB. "But the situation is different when the ship'is in the position a sinuous curve, as=shown in Figure 3. *cordance with the present invention this varymarked 2. In this case, the excitation of the loop by the waves transmitted from B will be of a maximum amount since the plane of the loop R points toward the re-radiating member B. Hence, an equally large opposite action from the auxiliary antenna A of Figures 1 and 2 will be required to introduce compensating energy into the loop circuit. Hence, it will be seen that the naling source, and a maximum, in ship position 2, or between the values present when just the opposite positions are dealt with. Consequently, the variation in disturbing effect from a re-radiating member. onA during a total turn of the vessel about 360 degrees can be represented by In acing efiect of the re-radiation on the loop is compensated by an opposing efiect which is introduced-fromA tothe loop circuit in amounts which vary directly with the variations in reradiation. In the embodiment shown thisis accomplished by varying the coupling between the auxiliary antenna and the receiving apparatus or frameaerial in the same manner as the intensity of the re-radiation varies. This --is accomplished by arranging "the coupling coi1s-so "that one thereof is rotatable with the loop, while the otherone-is'mounted stationary-on the ship -so that ithas no movement relative to B. The position of one of the coils (that is, the one-turning with the loop) remains unvaried-with respect to the loop, while its disposition-with reference to the re-radiating mast will be varied'as the loop is rotated. The second coil, however, is so disposed that its positionwith' reference to the =re-radiating mast remains unchanged, while its -position with reference to the distance trans- ;mitter is varied. In the specific embodiment shown the coil' a is fixed relative to the ship while the coil 1" is movable with the loopR.

The manner-inwhich the loop, the balancing coils and the coupling inductances may be 'mounted on the ship willbe' understood byr'efer ring to 'Figure 2 of the drawings. In Figure 2 the coil 1 representative'of the loop position is "fixed in the 'plane of 'the-loopR, while the coil a representative of 'theve'rtical aerial efiect coupling is fixed to the ship. The coilr is mounted on a sleeve p'clamped at q to the shaft cwhich supports the loop-R. The loop-R and coil 1' may be rotated by means of hand wheel I) fastened to shaftc. The vertical aerial coupling coila is stationarily'secured, asindicated by members g to support (1 which'may in turn be fastened to the ship. "The coil 11 is stationary with respect to r, c, and-R. The direction finder scale 1 is fastened-to d and cooperates with a; pointer secured-to d to indicate the, pointing position of the'loop R. It'will be seen that as the loop is rotatedfthe coupling between r and a-will vary fromminimum, as indicated, in position I of 2a,

where no compensating energy is induced in the loop or receiver circuit, to maximum coupling at whichamaximum amount of energy is induced from-a to thereceiver circuit or the loop. ,The latter position is indicated in position 2'of 2a..

For convenience of illustration the coils are shown in position of maximum coupling in Figure 2.

The mutual position of coils r and a, in case of turning of the ship; can be seen from Fig. 4,

' where four positions are indicated corresponding to the turning "of' the'vessel, through zero, 90, 1

180, and 2'70 degrees. The case here cited is particularly simple because the assumption has been made that both the transmitter as well as the disturbing source and the loop antenna are located upon a straight line. Whenever this condition is not fulfilled, the zero point of the correction curve will shift, and then a coupling would have to exist also in position I, in other words, the position of the two coupler coils with reference to each other must be turned a certain angle.

In actual practice it may be found that in addition to the re-radiating structure B considered above, compensated as indicated above, there may be other re-radiating structures which may very well cause a constant disturbance independent of the turning movements of the ship. The present invention obviates thisby the use of a fixed coupling between the auxiliary antenna circuits and the receiving circuits or loop circuit in addition to the variable coupling described above. The fixed coupling compensates the constant source of disturbance. In the present invention this fixed coupling is obtained by means of coils m1 and mz in series with the loop circuit, as indicated in Figures 1 and 2. m1 is carried on a support hr fastened at 1'1. This coil may be adjusted to the desired position with respect to a and fixed in said position by means of said screw i1. m2 which is also in series with loop R, is mounted adjacent a on a support hz. m2 is movable with respect to a as indicated. The position of me with respect to a is indicated by pointer i2 cooperating with a scale 1'. The position of 1m may be varied by handle iz.

If the disturbing actions bear a more complicated relationship to the position or turning of the vessel, compensating of the disturbing actions can be insured by altering the mutual positions of the coupling coils according to a law different than the one hereinbefore described, that is to say, in a way other than according to a sine law. This could be accomplished, for example, by the aid of a cam, as illustrated in Figure 2b.

The non-sinuous or irregular movement of the coupling coil 1' with respect to the coil a. may be accomplished by fixing a cam ID to the sleeve p bolted at q to the shaft e so that said cam rotates with said shaft when the loop R is rotated. The surface of the cam IU of varying radius acts through roller I2 on a lever l3 which oscillates a rack l5 about a point 14. The rack I5 cooperates with a pinion 16 torotate shaft I1 to which pinion I6 is fixed. The coupling coil 1' is fixed to shaft [1 for rotation therewith. The roller [2 is maintained in contact with the periphery of cam l by spring l8 fixed at I9. The center of cam It! may be given any shape, and is given a shape such that the coupling between a. and 1' is varied directly as the intensity of the re-radiated energy from the one or more adjacent structures varies.

In order to realize variation of the potentials induced by the auxiliary antenna in relation to the potentials of the loop circuit, another scheme would be to vary the electrical resistance of one or both antennae in dependence upon the turn of the vessel, instead of by variation of the coupling between the antennae and the receiving apparatus.

An understanding of the last mentioned modification will be had by referring to Figures and 6 of the drawings. The arrangement shown in Figures 5 and 6 is quite similar to the arrangements shown in Figures 1 and 2. In Figure 5, however, the coupling inductances m1, 1112 are omitted and the terminals of a are connected through leads I and 2 to the loop R. Here the center'point of a is grounded, and the signal voltage across T2 is impressed between the grid and cathode of tube R as in Figures 1 and 2. The potential introduced from the vertical aerial A through coupling coil a to the loop or receiver circuit may be determined by adjusting point 20 along a resistance W in series with a. The manner in which the position of 2!) along W is determined by the position of the loop is illustrated in Figure 6. In Figure 5 the sleeve carries a pinion 2| cooperating with a second pinion 22 which drives the contact member connected to A and bearing on resistance W. When the shaft 0 is rotated to rotate the loop, the pointer 20 is rotated, thereby varying the amount of resistance in the vertical aerial circuit and consequently determining the amplitude ofthe vertical aerial component introduced in the loop through coupling a, r. The resistance turns of the rheostat W may be disposed on their support in non-uniform manner corresponding to the regularity or irregularity of the desired compensating action.

The potentials induced from the auxiliary antenna, as is well known, may be brought to act directly upon the loop circuit as shown, or else upon intermediate circuits or upon direct reception indicators. These are different well-known schemes of combination of the effects of two antennae.

In all of the above arrangements the output elements of tube e may be connected with an indicating means directly, or by way of amplifiers, rectifiers, etc. The tube e may therefore be a detector or a radio frequency amplifier. ure 1 the anode electrodes of e are connected with an indicator T. -In Figure 2 the output electrode of tube e is connected through a capacity 24 and high resistance 25 to the input electrodes of a second tube 6' which may have an indicator in the output thereof as shown or be connected with further thermionic tubes. In Figure 5 the output elements of tube e are connected with an indicator while in Figure 6 they are connected with a relay 28 which in turn is connected with an indicator T.

Having described my invention, it is understood that I do not limit myself to the form shown, but what I claim is:

1. A directional receiver to be used adjacent metallic structures which tend to re-radiate signal energy comprising, a frame aerial circuit including a plurality of series inductances, the first of which inductances is rotatable and is exposed to the direct field of the signal energy, the second of said inductances being also rotatable with said first named inductance, a third one of said inductances being stationary with respect to said rotatable inductances, and a vertical aerial circuit including an inductance coupled to said second and third inductances.

2. A directional aerial system as specified in claim 1 in which cam means is provided for controlling the coupling between said inductances.

3. A receiving system for accurately determining the line of direction and sense of direction of a signaling source including, a frame aerial, said frame aerial including a pair of rotatable inductances exposed to the signaling wave, said inductances being in series with a plurality of coupling inductances, a pair of which is fixed and another of which is movable, a circuit for symmetrically grounding said loop aerial, a vertical aerial comprising a linear conductor and tuning means, a coupling inductance connecting In Figsaid: vertical aerial toraground, said, couphnainzi dnctance being coupled to said Lmovable, inductanceinsaidfrarne aerial circuit, means for simultaneously rotating said first named pair. of inductances in said frame 1 aerialiand' said movable inductanca and a thermionic translating device havingits control grid connected toa point :on saidframe aerialicircuit and .its cathode connected to ground. e

4:. In a radio direction finding system, a pair of rotatable absorptionmembers each including a plurality of turns .of conductingmaterial, a plurality of iinductances in series. connecting said absorption members inseriesto form therewith a directional antenna circuit, a connection between the electrical midpoint of the said an-= tennacircuit. and groundga'vertic'al aerial path,

an inductance in said vertical aerial. path, an adjustable coupling-between said lastnained ;in-;

ductance and one of said first named in'ductances, and a variable coupling between said inductance in said vertical aerial path and oneof'said first 2 named inductances, and cam controlled means operable: in accordance with theorientation of said-frotatable absorption members for adjusting the last said coupling; 1 I I I I 5; Adirectional antenna system comprising two rotatable inductive absorption memberaa first inductance mounted: for rotation with. said two absorption members, similar series inductances connecting the opposite ends of said-first:i nductance to adjacentends of said absorption members, a condenser connecting the remote terminals said tuned I closed circuit to be balanced with respect. to ground.

Itr az'directional,antenna-system,.a first pair of. similarsinductances adapted to be exposed to radiant energy, a secondpair of similar inductances; leads connecting. said second pair of similarinductances in seriesbetweenterminals of said: first pair of inductances, an odd inductance -symmetrically disposed in circuit between the twozinductances of thesecondpair, a tuning a capacity connected in shunt with all of said inductances to; form therewith a tunable circuit,

and: a connectionbetweena movable point on said thirdinductance'and ground to permit said tunable circuit to be balanced with respect to ground.

"I; In :a devicerfor-receiving radiant energy and forproducingcurrents characteristic of the direction and sense of direction of thesourceof said energy, a'loop aerial having 'twoportions each including a plurality of turns of conductive material exposed tothe radiant energy, an inductive circuit comDrising-aplurality of portions in series and having'a. series connection between the two portions ofssaiddoopaerial, a connection between a point of electrical symmetryon saidinductive circuit andxground, meansincludinga tuning capacitor interconnecting the free ends of the turns of each aerial portion for establishing a closedcircuit which may be tuned to the frequency-cithe radiant energy to. be received, a

vertical antenna, an inductance connected theree to and to earth'which inductance, is coupled to the first said inductivexcircuit and an electron discharge device having. an anode, a cathode and a control grid,said controlgridand said anode beingrespectively, coupled to opposite free ends of said. aerial portions and said cathode being grounded; said electron discharge device having a ivorkcircuit connected thereto for'indicating the eifects ofthe received radiant energy.

AUGUST LEIB.

Images