US1789419A - Radio receiving system - Google Patents

Description

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RADIO RECEIVING SYSTEM Filed May '7, 1925 6 Sheets-Sheet 6 AAAAAAA AA INVENTOR (19km Jzfmze J'zone f ATTORNEY Patented Jan. 29, 1931 wane JOHN STONE STONE, OF SAN DIEGO, CALIFORNIA, ASSIG-NOR T0 AMERIGAN TELEPHONE AND TELEGRAPH COMPANY, A COR PO BAIION OF NEW YORK RADIO RECEIVING SYSTEM Application filed May 7, 1925. Serial No. 28,633.

An object of my invention is to provide a new and improved system of selective radio receiving. Another object of my invention is to provide a radio receiving system that shall receive with relatively high intensity in a certain direction and with relatively low intensity in materially different directions. Another object of my invention is to combine loop receivers in a directionally selective array. Still another object is to make this array extend over only a moderate distance in its greatest extent. Another object of my invention is to provide apparatus that shall rectify and detect a certain alternating cur rent in accordance with its phase range, and another object is to utilize such apparatus in increasing the directional selectivity of my receiving system. These and other objects of my invention will become apparent on consideration of a limited number of examples of embodiments of the invention, which I have chosen to illustrate in the accompanying drawings, and which 1 will now proceed to describe in the following specification. It will be understood that the invention is de* lined in the appended claims and that the following description relates to the particular embodiments of the invention chosen to illustrate it.

deferring to the drawings, Figure 1 is an elevation of a receivin array comprising two loop antennae; Fig. la is a plan diagram of the same; Fig. 2 is an elevation of a receiving array comprising four loop antennae; Fig. 3 is an elevation of a receiving array comprising eight ioop antennae; l is a polar diagram showing the relative intensity of reception in various horizontal directions for a single loop receiving antenna and for the antenna arrays of Figs. 1. 2 and 3; is a diagram in Cartesian co-ordinates corresi irinding to the polar diagram of Fig. i; Fig. 6 is diagram corresponding to Fig. l but showing an alternative coupling arrangement between the loop antennae and the common circuit; Fig. 7 is an elevation of a loop antenna and an ordinary vertical antenna comdirectionally selective receiving; 0 a h oiar diagram in a horizontal glane ensity oi reception with the systemoi Fig. 7 and .the systems obtained by combining units like Fig. 7 according to the principles involved in Figs. 1, 2 and 3; 9 is the diagram in Cartesian co-ordinates corresponding to the polar diagram of Fig. 8; Figs. 10 and 11 show alternative arrange ments by which arrays may be built up of loop antennae; Figs. 12, 12a and 1526 are diagrams that will be referred to in explaining the principle involved in the modification shown in Fig. 17; Fig. 13 is a polar diagram for the modification of Fig. 17 and other modifications with other numbers of component loop antennae combined according to the same principle; Fig. 14 is a diagram in Cartesian oo-ordinates corresponding to the polar diagram of Fig. 13; Figs. 15 and 16 are diagrams of rectifiers which discriminate according to phase; and Fig. 17 is an elevation of a receiving array like Fig. 2 with the addition of a vertical receiving antenna and a device such as in Fig. 15 or 16, by which the directional selectivity is enhanced.

Referring to Fig. 1, a and a are two equal multiple turn loop antennae in the same vertical plane, the circuits of which are tuned to the same frequency w/Qw. hey are loosely coup-led through like transformers M and M with the common receiver circuit 6 which is also tuned to the frequency (0/21; and contains the receiving indicator R. The transformers M and M are wound in phase opposition, so that equal currents in the same phase in the antennae a, and a will produce a null effect in the receiver R.

Referring to the plan diagram of Fig. 1a, the sides of one coil a are represented in section at 1 and 1, and the sides of the other coil a are shown in section at 2 and 2. The arrow h at angle 6 with the plane of the loops indicates the direction of incidence of the received waves on the receiving system. Let A be the wave length corresponding to the frequency (0/277. Then the current wave in the coil a is of the form B sin (wt+b) where b is a phase angle the value of which is determined by when the time is taken as zero and the position from which distances are measured. If a is the phase of g the incoming wave when the time t is zero :he resultant eflect-in at the vertical central axis of the system shown by of Fig. la and if cl s the distance from O to the vertical central axis of the loop al or a then urther, it is evident that the amplitude of the coil-o due to the eiectromotive force induced in the two verb acos 6.

tica sides of the coil, depends upon th di- 13' A cos 6. Thus the current in the coil may be expressed as and likewise the current in the coil a will be expressed as A cos 6 sin me cos 0) 7 1) A cos 6 sin (wi-l-oz r gl cos 6) (2) provided the width of the coils is a small fraction of the wave length.

The electromotive force induced in the common circuit Z) may then be expressed as (wt+oc+ A cos 6 [cos (wt+(x cos 6) cos cos 6)] This expression reduces to 2A cos 6 sin andwith the assumption that cos a) sin (n w 4 sin 2L cos 6= cos 6 The expression (4:) reduces to K A @05 0 cos (wH-a) V (6) The foregoing condition is approximate- It will be seen that, according to curve 2 of Fig. 4c, the array of two loop antenna of Fig. 1 has greater directional selectivity than a single loop. 7 Fig. 2 shows an extension of the system rection from which the wave comes so thatas given by the to comprise four lops in the array. The

assembly will be readily understood fronr the diagram with the explanation that the transforn ers M. and M must be coupled in opposition; likewise M and M}; and

likewise M and M The pair of loops a and a have the di rectional factor cos 6 as given by the foregoing expression Hence the ampliy tude of the electrom'otive force or current in the circuit 0 of Fig. 2' is given by the absolute value of the expression i I Where A i'lrd and this absolute value may be Written in the form f 3 A cos 6 (8) provided that according to a line of reasoning similar to that givenabove in connection with Equation (5).

The polardiagram for Fig. 2 is given by tae curve 3 of Fig. t which corresponds to the foregoing expression (8) when A =A.

Fig. 3 illustrates a system of eight receiving loops. The manner in which they are combined will be apparent from the draw ing, with the explanation that the transformers M lvi li i M M M and M are so poled that their electromotive forces'oppose those of transformers M lv 'M M g, M M1 and .M respectively. The

electromotive force or the current in circuit?! of Fig. 3 may be expressed as (A cos 6 cos (wt+a) (10) provided that The corresponding polar diagram for Fig.

3 is shown by curve 4 in Fig. 4 when A =A.

Fig. '5 corresponds to Fig. 4t except that Cartesian co-ordinates are employed instead of polar co-ordinates, that is, the angles of Fig. a are laid off as abscissee along the line AD of ig. 5. and the radius vectors of Fig. 4 are erected as ordinates for Fig. 5. The

area of the entirerectangle ABCD of Fig. 5

compared with the area under each curve gives a measure of the directional selectivity of the corresponding system. This ratio may be called the figure of merit of the system, so far as it relates to minimizing static and general interference. The figures of merit for the systems corresponding to curves 1, 2, 3 and 4 are as follows:

Curve (1) 1.57 Curve (2) 2.00 Curve (3) 2.36 Curve (4) 2.67

With the successively enhanced directive and interference exclusive properties of the systems shown in Figs. 1, 2 and 3, there goes a sacrifice of intensity. In Fig. 1 an amplification of at least twofold would be required to make the intensity the'same as for a single loop; similarly Fig. 2 would require four-fold amplification; and Fig. 3 would require eight-fold amplification.

The necessary loose coupling between the several loops and the circuits common thereto is obtained in Figs. 1, 2 and 3 by means of transformers M. An alternative loose coupling is indicated in Fig. 6 by means of the condensers V and V each of capacity large compared to the condensers G and C In accordance as the loop antennae, such as a and a of Fig. 1, differ in size, compensation may be made by correspondingly adjusting the looseness of coupling in the transformers M and M but it will usually be advantageous to make the loops equal and have a like degree of coupling in the transformers.

In Fig. 7 a loop receiving antenna in a vertical plane is shown and combined therewith a vertical antenna lying in the vertical axis of the loop. This is a combination that secures a degree of directional selectivity as shown by the curve 1 in the polar diagram of Fig. 8.

Regarding the assembly of Fig. 7 as a unit, let such units be combined in the same way that the simple coil antennae of Figs. 1, 2 and 8 were combined. The polar diagrams of receptivity for these combinations will be represented by the respective curves 2, 8 and 4 of Fig. 8 and the corresponding diagrams using the angle 6 and intensity as Cartesian co-ordinates are given in Fig. 9. The figures of merit for these combinations are as follows:

Curve (1) 2.00 Curve (2) 3.14 Curve (3) 4.00 Curve (4) 4.71

. rays of Fig. 8 are unidirectional, whereas those of Fig. 4 are bidirectional. Comparison of Fig. 9 with Fig. shows greater efliciency for the arrays of Fig. 9 in excluding static and strays from miscellaneous directions.

If it were attempted to build up a directionally selective array of eight loop antennae in accordance withthe space relationships which have been found to be most advantageous for open aerials, the arrangements would be arrived at which are shown in either Fig. 10 or Fig. 11, the former corresponding to bidirectional reception and the latter to unidirectional reception. It will be seen that in these cases the extreme dimensions of the a dimension is not greater than 7 A axa or about Thus, in the case of a wave length corresponding to a frequency of a million cycles per second, the arrangement shown in Fig. 10 or Fig. 11 would require a linear dimension of something like 450 meters, whereas the arrangement of Fig. 8 would be confined within a range of about 42 meters.

I will now disclose how the addition of a single vertical type antenna to any such syste m as that of Figs. 1, 2 or 3, may be made to convert the system from bidirectional to unidirectional and thus virtually double its selectivity in respect to interference from random directions. Fig. 17 shows a four-unit array of loop antennae with the addition of asingle vertical type antenna. The principles involved will be appreciated on consideration of an explanation that will now be given in connection with Figs. 12 to 16.

The phase of the received oscillations in a bidirectional receiver passes abruptly through 180 when the angle 6 passes through and 27 0- -Thus, if 1 and 2 in Fig. 12 are the horizontal sections of the sides of a loop antenna and if the waves are incident in the direction of the arrow h, then the electromotive force inducedin the loop antenna, provided its width d is a small fraction of a wave length, may be expressed as cos 6 SII1 T t+ a) where T is the period corresponding to wave length A and a is the phase of the waves at the time t=6.

To illustrate, suppose the angle 6 increases uniformly with a period T greater than T; then the electromotive force inducedby the incident waves will be substantially as shown in the diagram of Fig. 12a. Here it will be the electrom'otivc. "force of noticed thatthe phase of the electroinotive force is reversed at 6' SO -and at 6 270.

Proceeding with the illustration,- let it be assumed that the circuit efthe coil of Fig. 12

has device introduced which periodically opens and closes it with period 1 then assume 111g that this device is suitably chased, the re- 1 .l 1 1 L 1 I1 suiting c" rrent will no as snown oy tne diagram of Fi g. 12?). It Will be seen-that the 011'- cuit controller of period T rectifies the current first one way and-then the other. The system has been rendered discriminating between values or" 6 correspondingto opposite directions. it a galvanometer could be used as a detector it would give a positive defiec- Before describing the s to etlcct the results indicated ng discursion let attention he (.urected to the polar diagram of Fig. 13 which is obtained by cutting of? all reception from the direction opposite to that desired. It i 'll be seen that the diagram of 13 isobtaned from Fig. 4 by suppressing one of the two of loops of Fig. l. l

The corresponding diagram in Cartesian co-or z'linates is shown in Fig. The curves have the sameshape and dimensions as those of Fig. but the rectangle with which con1 parison is to he made to get the figure of merit is t rice as large and the corresponding figures of merit are Curve (1),. i 31 i Curve (2);"- 4.00 Curve (3) e 4.71 Curve (4) 5.33

It will be seen that these figures are respectively obtained by doubling those given earlier in the specification tor 5 I In Fig. 15, r P and 1 5 are rectifying valves. B is a receiving indicator,G and (l -are two alternating current generators of the same frequency, and the impedances z, s, 2 and 2' are proportioned to make the circuits of Pt and G conjugate to one another; Let the frequency of the generators G and correspond to the period "l of Fig. l2a and let G be relatively to G It G were not erating. it is readily apparent that some of vthe current from G would get through to the rectifier W and the receiver R, and th the receiver 3 would get the rectified cur t. Consider two cases for operation of generator G in the same hase relation indicated b the arrows 1 and int-he opposite p'hase relatiom as indi-, cated by the arrows (2). In either case the generatorG has no effect on receiver R, be-

cause of the conjugate relation. But-when G and G in the same phase of arrows (1), the current from V is superposed and gets "oogh to receiver the same as if G were opcr Qn the other hand, when G 7 the opposite phase of arrows electronic ive force is built up at and so that no current from l 1 L128- geneiat newer :51.

I current for half of one cle or values of 6, that isR gets waves of current on one side of axis shown in Fig. 12?), pro- "reversed in phase every half ows aniodificationas compared Fin. 15. Here two equal generators are provided in series and the circuit for generator G is connected at a point between G and G The half waves from G will reach R eflectively when G is in the same phase with G and G and they will not'reach R ehfectively when in the opposite phase.

The arrangement of Fig. 15 has been incorporated in Fi l7, where it will be seen that the generator G is rellaced by the transformer X whose primary receives amplified current from'the vcrti Also, the generator G o 15 has been replaced by the secondary windings of the transformers M and BL of Fig. 2. The result that the system of 1? operates according to the curves 3 oli Figs. 13 and let in-.

2. In combination, a plurality of loop receiving antennae in a horizontal row in a'common vertical plane. and all connected through loose couplings with a common receiving in dicator the entire length of said row being small relatively to a wave length ofthe waves to be received and the combination being highly selective in the direction of said row e ach way non-selective to different directions, and means connecting the said vertical antenna withthesaid combination to make it selective in one or the two directions along the the row ofloop' H type antenna V.

along the row, a. vertical antenna row of loop antennae and against the opposite direction.

3. In combination, a plurality of loop receiving antennae in a horizontal row in a common vertical plane, and all connected through loose couplings with a common receiving indicator, the combination being highly selective in the direction of the said.

crease their selectivity, and means connect ing the said loop antennae and the vertical type antenna to make the combination selective in a narrow angular range in one general direction only.

5. In combination, a receiving antenna system comprising a plurality of loop antennae all lying in one common plane and selective in two opposite directions in said plane, a commonreceiving circuit, a rectifier therein, an auxiliary antenna adapted to receive in all directions, and means actuated thereby to block the currents to the said rectifier when received in one of the said two different directions and to pass them when received in the other said direction, whereby the receiver becomes further selective as between the said two directions.

6. In combination, a receiving antenna system selective in two different directions, a vertical type antenna and a receiving circuit having independent conjugate connections with said antenna system and said vertical type antenna to make it selective as between the said two directions.

7 Apparatus for receiving from a source waves in one phase and excluding waves in another phase, consisting of a receiver in circuit with said source, an auxiliary source in conjugate relation with said receiver, and a rectifier in combination with the other elements, said auxiliary source agreeing in phase with one only of the said two phases,'whereby the currents reach the receiver in that phase and not in the other phase.

8. Apparatus for selectively receiving currents from a source in only one of two opposite phases, consisting of a receiver and a generator in conjugate relation, a rectifier, said generator agreeing in frequency with said source and being in one of the said two phases whereby the rectifier passes the currents of that phase and blocks the currents of the opposite phase.

9. Incombination, a receiver, two sources ofthe same frequency, one of them of a certain phase and the other alternatively of the same or opposite phase, the said one source and the receiver being connected in conjugate relation, and a rectifier, whereby currents from said other source reach the receiver only when in one phase and not in the other phase. 10. The method of discriminating between received currents according to their phase, which consists in superposing an alternating current electromotive force in a certain part of the circuit of said received currents and always in .thephase to be selected and rectifying the composite currents in said certain part of the circuit, whereby only the received currents in that phase are rectified and passed.

11. The method of selecting between two alternating currents in two opposite phases which consists in locally superposing an alternating electromotive force in one of those phases and. rectifying the resultant current at the place of such superposition, whereby only those currents of the desired phase are passed and rectified.

'12. A circuit comprising a rectifier and a source of alternating current and a receiver, and a local source of alternating electromotive force associated with said rectifier to make it selective of currents to the receiver from the first mentioned source according as they are .r

April 1925.

JOHN STONE STONE.

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