US2223513A

US2223513A - Radio direction finder

Info

Publication number: US2223513A
Application number: US176155A
Authority: US
Inventors: Fransson Frans
Original assignee: AGA Baltic Radio AB
Current assignee: AGA Baltic Radio AB
Priority date: 1936-11-26
Filing date: 1937-11-24
Publication date: 1940-12-03
Anticipated expiration: 1957-12-03
Also published as: FR828241A; GB503428A

Description

D88. 3, 1940. F FRANSSQN 2,223,513

RADIO DIRECTION FINDER Filed Nov. 24, 1937 JPfE'D con r904 macaw INVENTOR.

/MWF1I ATT'ORNEY.

Patented Dec. 3, 1940 I it.. gUNlT-El) STATES "PATENTg OFFlCE Frans Fransson,

Aga-Baltic Radio Akti bola Stockholm, Sweden, assignor to.

Stockholm,

In Sweden November 26, 1936 Application November24, 1937, Serial No. 176,155 a 6 Claims.

I My invention relates to oscillating radio direction finders, and 'more particularly to phase shifting means for use in Connection therewith.

oscillating directional radio transmitter generally includes two antenna systems, for instanceone directed and one undirected system, and arrangements for repeated shifting of the phase conditioner the field "of one of the antenna systems-in relation to the phase condition of the field'ofithe' other antenna system. The phase shifting causes the field characteristic f the antenna systems to oscillate between two difierent positions the direction of, the so-called beam emitted by the transmitter being determined by the intersections between the field characteristics in one position and the field characteristics in the 'cther'position. It is usual to send different si nals in ,difierent positions cf'the resultant field cha'racteristics, so thatior instance a long signal is sent in one position of the field characteristics alternatin with ashort signal in the other position. 'In the direction of the ,beam the sound is then'heard as one uninterrupted signal of constant'intensity. In any directions not coinciding with the"beam,on' the other hand, a short or a long'signalof greater intensity is received alternating with long 'or short signal, respectively, of lesser intensity. I v, i

' The function-of an oscillating directional radio receiver is analogous to the function of an OS cillating direction'al'radio transmitter. Like the oscillating directional radio transmitter, the oscillating' directional radio receiver contains two difierent'fantenna systems; for instance one directedand'one undirected antenna system. Duringfrepeated shifting of the phase condition of the-current turning of the resultant field characteristics of the antenna systems, the signal from a directional radio transmitter is received. The direction of the" beam 'is recognized by the fact that the signal isreceived with constant intensity, independently of the phase shift-ings.

f The arrangements ior'theabove mentioned phase'shi'fting are connected" to the input terminals to "one of the antenna systems of the-transmitter or receiver, respectively, for instance the undirected'syst'emL. It'is of great importance that? such 'a pliaseshifting arrangement should function with very 'great speed at the moment of phase shifting, so that'the current changes its phase'without'being. interrupted for any appreciable time. 'Repeat'ed interruptions of appreciabledurat'ion of the antenna currentcause interruptionsin the signal even in the direction of from the two antenna systems and I the beam, whereby the determinings of the di rection are made'more diff cult. In addition, the phase shifting arrangements should not result in noticeable interfering sounds occurring upon phase shifting, such as audible clicking or the ll like. 'Phase shifting arrangements of the above mentioned kind are known, which consist of four fixed condenser plates shaped as sectors of a I circle and one additional plate, arranged to move ina circular path in one direction and at'a constant speed along the fixed plates, one of the antenna systems or the direction finding apparatus being connected to the movable plate, and the nected in pairs of two points in the transmitter, having voltages of opposite phase. Phase shifting occurs every time the movable plate passes the space or gap between adjacentfixed plates. '1 In order to obtain signals of different length in 20 different phase positions, the fixed plates'have surfaces of diiferent size. v I H In view of the fact that in the known'ph'ase shifting arrangement the movable plate moves one direction at a constant speed, and as this 25 speed must be considerable in order to 'obtain the quickest possible phase shifting; it is necessary that the surfaces of the fixed plates be very large in order to obtain the desired-durationof signals of difierent phases, which involvescer- 30 tain disadvantages. Fixed condenser plates of different sizeentails, further, an undesirable capacitive unbalance in those circuits of the transmitter to which the phase shifting arrangement is connected. a

The present invention relates to an improvement in the known phase shifting arrangements and consists in the movable plate being given an oscillating movement back and 'forth over two adjacent fixed plates, or movement in one di- 40 rection at a varying speed. For movement of the plate in one direction the speed should be higher during the passage over the space between the fixed plates than during the passage over one, at least, of the fixed plates. With the oscillating movement, as well as. with the movement in the same direction at a varying speed, the same speed, or even a higher speed of phaseshifting. can, be obtained than in thephase "shifting arrangement previously known, and inaddition the fixed plates may be made considerably smaller. Also, all the fixed-plates may be of the same size and alternating long and short signal signs may beobtained with movement in the same direction by causing movable condenser 10 fixed plates beingfcon- 1 5 the movable plate to of an apparatus suitable move at a lower speed when passing, for instance, every other fixed plate than when passing the other plates or the movement of the plate may be caused to take place in steps and to remain sta tionary during intervals of difierent lengths before difierent fixed plates. If the plate has an oscillating movement the same result may be obtained by causing the plate to move through arcs of different amplitude over the fixed plates.

The arrangement according to the invention may be modified in such a way that the plate described in the above as being movable is arranged as a fixed plate, whereas the other plates are arranged to be movable. All plates may be arranged to be movable in such a way that the same relative movement desired between the plates is obtained.

Furthermore, the invention is not limited to purely capacitive phase shifting arrangements but ma also be applied to inductive phase shifting arrangements, or to commutator phase shifting devices and is not limited to any particular number of fixed or movable plates.

The invention will be described further in the following with reference to the attached drawing that shows one embodiment of the invention.

Fig. 1 is a wiring diagram of an oscillating directional radio transmitter including a phase shifting device according to the present invention;

Fig. 2 is a more or less diagrammatic View of the phase shifting device shown in Fig. 1;

Fig. 3 is a cross-sectional view taken on the line 33 of Fig. 2;

Fig. 4 is a diagram showing certain field characteristics;

Fig. 5 is a diagram showing certain other field characteristics;

Fig. 6 is a diagrammatic View of an example for operating the phase shifting device; and

Fig. 7 is a diagrammatic View of a modification of the apparatus shown in Fig. 6.

In Fig. 1 reference character I indicates an oscillating circuit included in an oscillating directional radio transmitter, in which circuit the signal oscillations of high frequency occur. To the oscillating circuit I, a directed antenna system consisting of two similar directional antennae 2 and 3' is connected through a goniometer 4 and a coil 5 inductively connected to the oscillating circuit.

The oscillating circuit I is grounded at the middle point of the coil 6 and the ends of the coil are connected to an undirected antenna system consisting of an open antenna 1 through a phase shifting arrangement in accordance with the present invention. The phase shifting arrangement which in this case is shown as a capacitance includes four fixed condenser plates 8, 9, I0 and II, and two movable plates I2 and I3; the latter being connected to each other and to the antenna 7. The fixed plates are all of the same size and are connected in pairs to the opposite ends of the coil 6.

The construction of the phase shifting arrangement is seen more clearly from Figs. 2 and 3 which show two sections taken at right angles to each other. The movable plates are secured to a rotatable shaft I4'of a driving device I5 which is arranged to oscillate the shaft I4 and plates I2 and I 3 through an angle 21 of The antenna 1 is connected to the movable plates through a capacitive collector, consisting of condenser plates I6 secured to the shaft I4 and of fixed plates I! connected with the antenna. Shaft I4 serves as a conductor for connecting plates I2 and I3 to plates IS.

The two ends of the coil 6 carry voltages of opposite phase. The oscillations of the movable plates cause the antenna tobe connected alternately to either of these ends, whereby the desired phase shifting of the antenna current is obtained. These phase shiftings cause the resultant field characteristic of the antenna systems to oscillate between two different positions, as is shown graphically in Figs. 4 and 5.

In Fig. 4, I8 represents the field characteristic for the undirected antenna system I at a certain value of the current through it. Reference character I 9 represents the field characteristic for the directed

antenna systems

2, 3. The last mentioned field characteristic is of so called figure-8 form. At the phase condition of the fields indicated by the signs and a resultant cardioidic field characteristic 2!] isobtained.

Upon phase shifting of the current through the undirected antenna system and consequent phase shifting of the field of this system, the resultant field characteristic changes its position. The shape of the field characteristic, however, remains unchanged provided that the current is not changed. In Fig. 5, the curve 20 indicates the position of the resultant field characteristic after the phase shifting with unaltered current. In the same figure the previous position of the field characteristic is indicated by curve 20.

The directions of the beam are determined by the intersections of the resultant field characteristics 20 and 20'. As seen from Fig. 5, the directions indicated by the lines 0-1: and 0-11 are displaced by in relation to each other in the case where the current in the undirected antenna system is constant, independently of the phase shifting.

For the purpose of obtaining signals of different duration in difi'erent positions of the resultant field characteristic, the driving arrangement I5 for the movable plates of the phase shifting arrangement may be made in such a way that the movable plates will remain in one of their extreme positions for a longer time than in the other extreme position. As a rule, however, it is more desirable to have the movable plates oscillate without any other retarding of the movement in the two extreme positions than that caused by the inertia, etc., of the movable masses, and to make the duration of the signals in the two phase positions unequal by displacing the central points of the fixed plates in relation to the extreme positions of the movable plates, so that the movable plates will move over surfaces of different area on the difi'erent fixed plates. In the arrangement shown in Fig. 2 the central points of the fixed plates are displaced in relation to the extreme positions of the movable plates in such a way that the arcs indicated by a have a greater amplitude than the arcs indicated by b. The relation between the duration of the signals in the two phase positions is then determined by the relation between the are a to the are I), which relation is adjustable.

In the arrangement described above a very quick phase shifting is obtained, the speed of the movable plates being very high when these plates pass the spaces or gaps between fixed plates. This is because the mass of the movable plates is comparatively small and the driving arrangement I5 is made in such a way that the acceleration of the plates after the reversal of movement 'in 'the two extreme preciable lengthof time before the other ag-na .1'

positions is comparar ti ely' rap d. V I J I: I 7

An example of a suitable driving arrangement I is'shown more or less diagrammatically in Fig.

- 6. Reierence"character 25 designates a rotating disc mounted on a shaft 26 which is driven by a.

] slip rings 3| and 32, respectively, and are contherewith.

motor 2'|. The speed of motor 21 may be regulated in any suitable manner, such as by the rheostat 44 included in its circuit. Disc 25'includestwo sections 23' and 290i conducting material-separated by insulating material 30." Also mounted on shaft 26 are slip rings 3| and .32 which are electrically connected to

sections

28 and 29,respectively.'

"A brush 33 is arranged to bear against the outer of disc,25 and is connected to'one tera battery 34 or other source, of electriis connected to oppositely

disposed electromagnets

35 and 36.

Brushes

31 and 38 bearagainst nected to electro-magnets 3'5 and 36, respectively.

I A rack 39 is slidably mounted in suitable'supports 40 and is provided with anarmature element 4| of magnetic material which is disposed so as to be attracted by either of the

electromagnets

35 or 36 when the latter are energized' The rack 39 is provided with teeth 42 which mesh with a pinion 43 mounted on the shaft |4 shown, for instance, in Fig. 3.

The above described dev ce operates as follows: As vdisc 25 rotates brush 33 is in contact first with section 28 and then with section 23 thereof. When the brush is in contact, for instance, with section 28, as shown in Fig. 6, the circuit is completed from one terminal of the battery 34 through brush 33, section 28, slip ring 3| and brush 31 to electromagnet 35 and back to the other terminal of the battery through the permanent connection of the electro-magnet The electro-magnet 35 is thereby energized and armature member 4| is attracted thereto and moves the rack 39 to the left, as

viewed in Fig. 6 to the position shown in this figure. This causes rotation of the pinion through the are 11 shown in Fig. 2. When the disc 25 has rotated suificiently so that brush 33 comes into contact with section 29, the circuit through electro-magnet 35 is interrupted and a similar circuit is established through section 29, slip ring 32 and brush 38 with electro-magnet 36.

Thiscauses magnet 36 to'be energized and armature element 4| is attracted thereto and. causes the rack 39 to move to the right, as viewed in Fig. 6, thereby rotating pinion 43 and shaft 4 back through the are c.

The speed of motor 21 may be regulated so that the sections 23 and 29, respectively, of the disc 25 pass out of contactwith the brush 33 at approximately the instant. that armature element 4| reaches the 'electro-magnet which has just been energized. With such an adjustment of the speed of the motor, rack 39 will oscillate with but a momentary stop at its extreme positions. If it is desired to have the rack stationary for an appreciable lengthof time in its extreme positions, the speed of the motor may be reduced by means of the rheostat 44 so that the armature element will reach the energized electro-magnet before the

respective sections

28 and 29 of the disc have completely passed the brush 33, whereby the armature element will be held in its extreme position against the energized magnet for an apshown'in Fig.7, maybe substituted for the disc 25 in-Fig. 6. In thedisc 25', 29 are unequal, section 28 '-being the larger, whereby-brush 33 'r'e'mains 1 in contact with the section 28' for a greater length of time than it remains incontact with section 29'. I This in' turn causes electro-magnet 35 to be energized for a greater length of time than el-ectro-magnet 36 and consequentlythe armature'element 4| remains inits left-hand position, as viewed in Fig; 6, fora longer periodth'an it remains in the opposite position. v e

s As previously mentioned, the condenser plates included in theph ase'shifting arrangement may be replaced by commutators, or by devices-known per se for inductive transmission of voltage, and the arrangements also may be modified in various other ways without deviating from the principle of the invention. In the embodiment shown,the condenser plates H), H and |3may be omitted, in which casethe phase shifting arrangement will consist of a movable condenser plate connected to the antenna 1 and of two fixed condenser plates connected to points of the circuit which carry voltages of opposite phase. The antenna need not be connected directly to the phase shifting arrangement, but may be connected to this through coupling elements of any suitable kind.

The scope of my invention is not to be limited by the above description, given by way of example only, but is to be determined by the appended claims viewed in the light of the prior art.

What is claimed:

1. In an oscillating radio direction finder, an oscillating circuit, a directed antenna coupled to said circuit, an undirected antenna coupled to said circuit, and means for shifting the phase of the voltage applied to one of said antennae with respect to the phase of the voltage applied to the other antenna, including impedance elements connected to points of opposite phase in said circuit, animpedance element connected to said the sections 28' and one of said antennae, and means for moving the last mentioned element with respect to the first connected to points of opposite phase in said circuit, said elements being spaced with a gap 'therebetween, an impedance element connected to said one of said antennae, and means for moving the last mentioned element with respect to the first mentioned elements at a speed varying so that said last mentioned element passes said gap at a higher speed than the average speed at which it passes the first mentioned elements.

3. In an oscillating radio direction finder, an oscillating circuit, a directed antenna coupled to said, circuit, an undirected antenna coupled to said circuit, and means for shifting the phase of the voltage applied to one of said antennae with respect to the phase of the voltage applied to the other antenna, including impedance elements connected to points of opposite phase in said circuit, an impedance element connected to said one of said antennae, and means for moving the last mentioned element back and forth opposite to the first mentioned elements.

4. In an oscillating radio direction finder, an oscillating circuit, a directed antenna coupled to said circuit, an undirected antenna coupled to said circuit, and means for shifting the phase of the voltage applied to one of said antennae with respect to the phase of the voltage applied to the other antenna, including impedance elements connected to points of opposite phase in said circuit, an impedance element connected to said one of said antennae, and means for moving the last mentioned element back and forth opposite the first mentioned elements through a path of movement the extent of which is greater opposite one of said first mentioned elements than opposite the other of said first mentioned elements.

5. In an oscillating radio direction finder, an

oscillating circuit, a directed antenna coupled to said circuit, an undirected antenna coupled to said circuit, and means for shifting the phase of the voltage applied to one of said antennae with respect to the phase of the voltage applied to the other antenna, including impedance elements connected to points of opposite phase in said circuit, an impedance element connected to said one of said antennae, and means. for moving the last mentioned element relative to the first mentioned element and for stopping said last mentioned element for periods of different duration opposite dififerent of said first mentioned elements.

6. Device as set forth in claim 1 including a fixed capacity condenser between said one of said antennae and the movable element, said condenser including a stationary plate connected to said one of said antennae and a movable plate connected to and movable with said movable element.

FRANS FRANSSON.