US2272312A - Radio relaying - Google Patents

Description

Feb. 10, 1942. H, Tumck 2,272,312

RADIO RELAYING Filed May 20, 1939 4 Shets-Sheet 1 INV EN TOR.

yaw TUNICK 776? W A TTORN E Y.

Feb. 10,, 1942. T K 2,272,312

RADIO RELAYING Filed May 20, 1939 4 Sheets-Sheet 2 METAL W 3 REFLECTOR R 5 F] METAL 50X CONTAIN/N6 5;; V /'$H/ELDED AMPLIFIER RSA rRANsM/rr/ 6\ ANTENNA p5p y5 A TRANSMITTING 0R RECEIVING ANTENNA maNsMlr- \jITRANSM/T METAL $UPPORT RECEIVE REFLECTOR METAL REFLECTOR METAL METAL SUPPORT SHIELD FOR REFLECTOR INVENTOR. H 12/2) TUN/CK BY ATTORNEY.

' Feb, 10, 1942. H. TUINICK 2,272,312

RADIO REIQAYING Filed May 20, 1939 4 Sheets-Sheet s INVENTOR. :ZRRY TU/v/CK A TTORN E Y Patented Feb. 10, 1942 RADIO Harry Tunick, Rye, N. Y.,. ass'ignor to RadioCorporation of America, a cor'pbration of Delaware Application May 20, 1939. Serial N6. 274,744

3 Claims. (Cl. 250-15) My present invention relates to radio relaying. For some types of service and also in order to conserve channel frequencies, it is desirable when relaying radio signals from one point to another to retransmit on the same frequency as that received. At radio relaying stations, because of the close proximity of the receiving and transmitting antennas, some of the energy radiated from the transmitting antenna leaks back into the receiving antenna, thereby setting up sustained oscillations at the relaying point. To overcome this difiiculty is the principal object of'my present invention.

Turning to the accompanying drawings, which illustrates various ways in which the main object of my present invention may be effected:

Figure 1 illustrates a radio relaying system in which a conductive screen is employed to prevent interaction between the receiving and transmit-,

ting antennas;

Figure 2 is a modification of Figure I;

Figure 3 illustrates a modification in which undesirable interaction is avoided by using antennas of different polarization at the relaying station;

Figure 3A is a structural modification of Figure 3 Figure 4 is a modification of Figure 3;

Figure 4A is a modification of Figure 4 in which terminated rhombic antennas arranged in difierent planes of polarization are employed at the relaying station;

Figure 5 is a still further modification in which the feedback of the aerial path is neutralized;

Figure 6 illustrates a form of my invention in which the tendency towards oscillation generation is reduced by virtue of an adjustable transmission line;

Figure 7 illustrates still another modification of my invention;

Figure 7a illustrates one form of intensity and phase adjustor which may be used in the organization shown in Figure 7, while Figure 7b shows a further modification of a portion of Figure 7.

Turning to Figure 1, waves received upon a receiving antenna RA at a relay station are amplified in a relay station amplifier RSA and retransmitted at .the same frequency over a transmitting antenna TA. The entire system is preferably mounted upon a high support, such as a pole or a tower P or tall building. Preferably in my system, ultra short waves are employed of the order of magnitude of less than ten meters down to a fraction of a meter. The

antennas RA and TA are of the type such as described by P. S. Carter in U. S. Patent No. 1,974,387 or by N. E. Lindenblad in U. S. Patent 'No. 1,927,522, or they may be of the types described by Carter, Lindenblad and Hansell in the Proceedings-of the Institute of Radio Engineers for October 1931. It is to beunderstood that the receiving and transmitting antennas may be of these types in any of Figures 1 to 7 or a combination of these types, or they may be of the type described by Bruce; Beck andLowry in the Proceedings of the Institute of Radio Engineers for January 1935.

Because of the close proximity of the'transmitting antenna TA to the receiving antenna RA, especially when retransmitting at the same frequency as the frequency of the waves received upon receiving antenna RA,'it will be found that there is a tendency for oscillation generation. This is due to the fact that some of the energy radiated from the transmitting antenna TAjleaks back into the input circuit of the amplifier RSA through the receiving antenna RA. To avoid this diificulty I interpose between the transmittingYantenna and receiving antenna a large metallic shield MS which may be made in the form of a metallic billboard suitably perforated so that various leads in the amplifier RSA may pass therethrough. The shield MS is grounded by direct connection to the metallic tower P. As an alternative, a heavy connection in the form of an adjustable transmission line may be employed so that the shield MS by virtue of adjusting the trombone slide TS is maintained at ground radio frequency potential.

A variable capacitive reactance 26 may be con- ;nected to the tower P and shielding screen MS so that the tower itself series resonates with the screen MS at the operating carrier frequency, in-

suring complete grounding of the screen MS in spite of the unavoidable impedance to the operating frequencies presented by the tower P.

In the modification shown in Figure; 2, the grounded metallic shield is diagrammatically indicated at MS and the relaying-station amplifier is indicated by BSA. The receiving antenna in thisca'sahowever, is in the form of. a receiving dipole RD and the transmitting antenna is in the form of a transmitting dipole TD. Further shielding is provided by means of the receiving parabolic reflector RPR and the transmitting parabolic reflector TPR. The parabolic reflectors may be made of continuous smooth metallic surfaces or they may be made up'in the form of wires. Also, the metallic reflectors may be cylindrical parabolas rather than the paraboloid structures illustrated.

In Figure 3 the receiving antenna RA is shown as a dipole of the vertically polarized type and the transmitting antenna TA is arranged so as to be horizontally polarized. In this way, coupling between the two antennas is reduced. To further reduce coupling, the grounded metallic shield MS, as before, may be employed.

In connection with Figure 3 the system may be modified as shown in Figure 3a, in which case the receiving station amplifier RSA" is mounted within the metallic compartments RSA which also house the two antennas, as shown. That is, the receiving station amplifier housings RSA and RSA are made of metal and serve as a screen for the amplifyin'gapparatus within, and also as reflectors for the vertically polarized receiving antenna RA and for the horizontally polarized transmitting antenna TA.

Figure 4 is similar to Figure 3 with the exception that the transmitting and receiving antennas are of the V type such as described by Carter and Lindenblad referred to hereinabove. In either Figure 3 or 4 it should be understood, of course, that the receiving antenna may be horizontally polarized and the transmitting antenna vertically polarized, or the antennas may be of any polarization provided the electrical vectors or fields emitted and received by the antennae, respectively, are at right angles to each other. As a further modification, the receiving antenna RA of Figure 4 may be of the rhombic type, as illustrated in Figure 4A, and the transmitting antenna may also be of the rhombic type, each antenna being terminated with a surge resistance SR. As before, the planes of the antennae should be at right angles to each other to reduce cross-coupling and a grounded metallic shield receiving antenna from the relay station transmitting antenna TA is efiectively reduced by the receiving antenna surge resistance SR before it is reflected back into the relay station amplifier RSA.

In the modification shown in Figure 5 the re-:

ceiving antenna RA and transmitting antenna TA are coupled together through transmission lines TLI and 'I'LZ. Connected in the transmission lines there is a phase and intensity adjusting device PA. By adjusting the phase and intensityrgjs adjusting device PA, the energy picked up by the relay station receiving antenna from the relay station transmitting antenna may be completely balanced out. If desired, shielding may also be employed in connection with the system of Fig-=5: ure 5 in the form of the grounded metallic shield I The feedback velocity through the transmission lines TLI and TL2 and phase adjuster PAI is necessarily slower than the feedback velocity" ifications, the shield MS is relatively large with respect to the physical dimensions of the antennae employed at the relaying station.

In the system shown in Figure 6, the shield MS may be employed as before. In the arrangement of Figure 6, however, the transmission line TL leading to the transmitting antenna TA is made adjustable in length by means of trombone slides TS! and TSZ. For oscillation generation, it is essential that the feedback path maintain a degree phase relationship between the input and output circuits here represented by the transmitting antenna TA and receiving antenna RA. This relationship may be spoiled for oscillation generation by the use of the sliders TSI and TS2 which should be adjusted so that the tendency towards oscillation generation is reduced or eliminated. As before, the grounded metallic shield MS may be employed. In order to efiectively ground the metallic shield, tuning means, illustrated in the form of variable inductances L and variable capacities C, may be used. These inductors and capacitors are adjusted so as to series resonate at the frequency employed whereby the shield, connected to one extreme of the series tuned circuits, is at ground potential, since the other extreme of the series tuned circuit is connected to ground.

The two wire transmission lines, such as TL of Figure 6 for example, should be short, say a few wavelengths or within a fraction of a wavelength long in order to reduce losses. Since the receiving antenna RA carries only a very small current, the transmission line TL between the receiving antenna and the relay station amplifier RSA may be made several wavelengths long since the further apart the receiving and transmitting antennas are, the less will be the reaction between them. In this respect, the receiving antenna may be mounted some distance down on the supporting tower P and the transmitting antenna may be at the highest elevation on the tower. .Both the transmission lines leading to the receiving and transmitting antennae of any of the relay stations illustrated may be placed within grounded metallic tubes to prevent stray radiation and pick-up. If desired, the transmission line to the transmitting antenna may be of the open two wire type and the line to the receiving antenna may be of the concentric conductor type, or vice versa, or both transmission lines may be of the concentric conductor type or, as illustrated, of the two conductor open wire type. In all of the modifications illustrated, the dipole antennae for very wide frequency band radio relaying may be constructed as ellipsoids, as described in the copending application of Nils E. Lindenblad, Serial #208,573, filed May 18, 1938, now Patent #2.,239,724, granted April 29, 1941.

In the modification shown in Figure 7, a correcting dipole CD mounted within a parabolic reflector PR is connected by way of a transmission line TL to the input circuit of the amplifier RSA. The correcting dipole is arranged to be polarized in the same way that the transmitting antenna TA is polarized. The receiving antenna RA may be of the same polarization, but, preferably is polarized at right angles to antennae TA and CD. By means of phase adjusting and intensity controlling device PAI, the amount of energy fed from the correcting dipole into the input side of the relay station amplifier RSA is adjusted so as to equal in amplitude and be opposite in phase to that fed by the transmitting antenna TA over leakage paths into the input side of the relay station amplifier RSA. The parabolic reflector PR associated with the correcting dipole CD insures that the correcting dipole picks up only energy radiated by the relay station transmitting antenna and that it does not pick up any of the energy coming in from the left, namely, energy which it is desired that the relay station retransmit.

One form of intensity and phase adjuster PAI of Figure '7 is illustrated in Figure 7A. By varying the coupling between the loops LP, the intensity of currents fed from the correcting dipole to the receiving amplifier RSA may be controlled. By adjusting the short circuiting straps S along the line stubs LS, the phase of energy fed from the correcting dipole into the relay station amplifier RSA may be adjusted. If desired,

the lines stubs and short circuiting straps S may be replaced by trombones such as are illustrated in Figure 6.

It should be clearly understood that various features shown in the various figures may be combined without departing from the scope of my present invention. Thus, referring to Figure 7 a grounded metallic shield, which may be grounded at several points, may be employed at a position such as indicated, namely, between the receiving antenna RA and the rear of the parabolic reflector PR of the correcting dipole CD. Naturally, th screen MS of Figure 7 is also between the receiving antenna RA and the transmitting antenna TA. Also, in Figure '7 the transmission lines leading to both the receiving antenna RA and transmitting antenna TA may be provided with adjustable trombone slides TSI and TS2 as shown in Figure 7b so that their lengths may be adjusted for optimum operation with a minimum of regeneration. The portion between dotted lines XX and YY of Figure 7 in either or both transmission lines may be substituted by the structure shown in Figure 7b.

In Figure 4A the two antennae RA and TA may have their longitudinal axes in line, but the planes of the conductors of each antenna are preferably arranged at right angles to one another. In addition, with reference to Figure 4A for example, not only may the metallic shield MS be used, but the neutralizing circuit of Figure 5, or, for that matter, the correcting antenna pick-up system of Figure 7, may be employed. In the latter event, it may be found unnecessary to employ the shield MS of Figure 4A.

Also, it should be understood that my invention as described hereinabove is not limited to a relay station where retransmission takes place on the same frequency as that received. It should be understood, therefore, that in each of the figures described hereinbefore, the receiving station amplifier may be considered as employing demodulating apparatus for the received waves and means for generating a new carrier frequency which is modulated in accordance with the received demodulated waves. The retransmission may, therefore, take place on a different frequency. Further, if desired, the received waves maybe demodulated and then used to modulate locally generated waves of the same mean or carrier frequency as the waves received.

Having thus described my invention, what I claim is:

1. In an ultra short wave relaying system, a relay station comprising a receiving antenna and transmitting antenna, amplifying means connected therebetween and a metallic shield between said antennas for preventing feedback from said transmitting antenna to said receiving antenna, said station being supported a substantial distance above ground on a conductive support, said shield being connected to said support and said support unavoidably presenting an impedance between said shield and ground, and means for maintaining said shield at zero radio frequency potentials with respect to ground comprising a tuned circuit connected between said metallic shield and ground.

2. In an ultra short wave relaying system, a relay station, comprising a receiving antenna and transmitting antenna, amplifying means connected therebetween, a metallic shield between said antennas for preventing feedback from said transmitting antenna to said receiving antenna, said station being supported a substantial'distance above ground on a conductive support, said shield being connected to said support and a capacitive reactance connected across at least a portion of said support for resonating said support to the operating frequency of said station.

3. In an ultra short wave relaying system, a relay station comprising a receiving antenna and a transmitting antenna, amplifying means connected therebetween and a metallic shield between said antennas for preventing feedback from said transmitting antenna to said receiving antenna, said station being supported a substantial distance above ground on a conductive support, said shield being connected to said support, said support presenting an impedance between said shield and ground, and means for maintaining said shield at ground potential at the operating frequency of said station comprising a variable length connection between said metallic shield and ground, said connection being adjustable to such length that both ends thereof are effectively at ground radio frequency potential.

HARRY TUNICK.

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