US2311467A - Radio relaying system - Google Patents

Description

Feb 16, 1943. H. o. PETERSON RADIO RELAYING SYSTEM l Filed sept. 27, 1941 INVENTO R ,Z13/0n ronm Y .Wkml

Patented F eb. 16, 1943 Zandt? 2,311,467 RADIO RELAYING SYSTEM Harold O. Peterson,

Riverhead, N. Y., assigner to Radio Corporation 'of America, a corpora'- tion of Delaware 8 Claims.

This invention relates to a radio relaying system, and particularly to such a system for use on ultra short waves.

.An object of the present inventionis to provide a unidirectional antenna or wave directive structure .which reduces to substantially zero the eifect of an undesired wave received from a direction opposite to that in which the antenna is intended to operate.

Another object of the invention is to provide a unidirectional antenna or Wave directive structure which neutralizes the effect of waves emanating therefrom but traveling in a direction opposite to that intended.

A further object of the invention is to provide A a unidirectional antenna or wave directive structure which discriminates substantially completely between the desired Wave arriving from one direction and an undesired wave arriving from an opposite direction.

A further object is to provide a signal repeater system for a radio relaying system,` having an tennas positioned in substantially opposite directions, in which there is an improved frontto-back ratio of the directive pattern of each antenna. Y

A more detailed description of the invention follows in conjunction with a drawing, wherein:

Fig. 1 illustrates diagrammatically a radio relaying system of the type to which the principles of the present invention are applicable;

Fig. 2 illustrates in detail only those elements of a repeater station necessary for an understanding of the invention and equipped in accordance with the principles hereof;

Fig. 3 illustrates an expansion of the system of Fig. 2; and

Fig. 4 illustrates one arrangement of the antennas of Fig. 3.

`Referring to Fig. 1 in more detail, there is shown a radio relaying system having terminal stations A and C, each equipped with a transmitter and a receiver, and a repeating station B located between the terminal stations for relaying or repeating the signals between station A and station C. As indicated in the drawing by the direction of the arrows, terminal station A is provided with a transmitter I arranged to transmit signals over directive antenna 2 to the intermediate station B, and station A is also provided with a receiver 8 arranged to receive signals over directive antenna 9 from intermediate station B. Similarly, terminal station C is provided with a transmitter I4 arranged to transmit signals over directive antenna I3 to intermediate station B, and a receiver l arranged to receive signals over directive antenna 6 from intermediate station B. Intermediate station B is illustrative of any one or more repeater stations whichy can be used in a relay system, and is provided with a directive antenna 3 for receiving the signals transmitted from station A and another directive antenna 5 for relaying or repeating the received signals from A toward terminal stationV C. Intermediate station B is,

also provided with another directive antenna l2 for receiving the signals transmitted from terminal station C and for relaying or repeating the signals over another directive antenna le toward the terminal station A. Apparatus 4 and Il constitute suitable equipment for conyerting the signals received respectively on antennas 3 and I2 to new frequencies which are then transmitted over antennas 5 and I0. The directive antennas shown in Fig. 1 may be any suitable wave directive structure, such as a parabolic antenna having a dipole at its focus or an electromagnetic horn. If a horn is used, it is preferred, though not necessary, that it be or' the type described in copending Katzin applications Serial No. 363,248, filed October 29, 1940, and Serial No. 381,264. filed March l, 1941.

l In a system of Fig. 1, transmitter I is arranged to transmit over directive antenna 2 a signal carrier wave at, let us say, 500 megacycles, which isreceived at station B on directive antenna 3 and converted by apparatus l to a new frequency of, .for example, 550 megacycles. The new 550 megacycle carrier wave is then transmitted over directive antenna 5 to be received at terminal station C on antenna 6. Terminal station C is arranged to transmit a signal carrier Wave of 500 megacycles over directive antenna I3, which is received at intermediate station B by directive antenna I2, then converted by apparatus II to a new frequency of 550 megacycles which is retransmitted over antenna I0 toward terminal station Aand received at station A on directive antenna 9. Apparatus ll and .Il at intermediate station B are, in effect, repeaters which amplify the received signals and convert them to a new frequency by heating with oscillations produced by a local oscillator of suitable frequency m known manner.

From the foregoing, it will be apparent that directive antennas 3 and I2 both receive signals on the same carrier frequency, but from approximately opposite directions. The amount of energy received on antenna 3 from antenna I3 will obviously be less than the amount of energy received by antenna 3 from antenna 2, by a factor which corresponds to the front-to-back ratio of the directive pattern of antenna 3. Likewise, the amount of energy received on antenna I2 from antenna 2 is less than the amount or" energy received by antenna I2 from antenna I3, by a factor which corresponds to the front-toback ratio of the directive pattern of antenna I2.

Since it is desired to increase the factor of discrimination between the desired and undesired carrier wave received on the antennas 3 and I2, it is proposed to polarize either vertically or horizontally the electromagnetic wave emanating from antenna 2 and to polarize at a 90 relation to the first polarization, i. e., either horizontally or vertically the wave emanating from antenna I3, and to arrange the antennas 3 and Cil i2 to respectively receive these polarized waves f from antennas 2 and I3. Obviously, the arrangements for polarizing the antennas 2, 3, I2 and I3 are not limited solely to vertical and horizontal directions, since other angles such as a 45 angle can be used, provided the aforementioned 90 relation is maintained between transmitting antennas 2 and I3 and between receiving antennas 3 and I2.

We have a similar problem in the case of the transmitting antenna 5. Here again it is desired to radiate a signal from antenna 5 to be received by antenna 6. The undesired radiation from antenna 5 in the back-end or reverse direction will reach antenna 9 along with the desired signal from antenna I0 and may produce interference. This interference can be reduced by polarizing the waves radiated by antennas 5 and I0 perpendicular to each other, and arranging the antennas 6 and 9 to be responsive, respectively, solely to the polarized waves radiated by 5 andl.

Fig. 2 shows an improved system for increasing the factor of discrimination between the desired and undesired waves arriving from opposite directions. This system is primarily intended for use at the repeater station B, although it may also find other applications.

In Fig. 2 the antenna elements I5 and I6 replace the single antenna element 3 of station B of Fig. l, While the antenna elements I8 and I9 replace the single antenna 5 of station B of Fig. 1. These antenna elements I5 and I5, it should be noted, are an even number of units which are displaced along the direction of propagation by a distance 2I of approximately one-quarter wavelength at the operating frequency or an odd multiple thereof. Antenna units I5 and I6 are connected respectively by lines 22 and 23 to a common point J from which the energy is passed through line 21 to repeater amplifier I'I. Repeater II may or may not be a frequency converter, as desired. Line 22 is made suiliciently longer than line 23 so that the desired received energies from antenna units I5 and I6 reach the junction point J in phase. If the velocity of the wave along the lines 22 and 23 approximates the velocity of the wave in free space, then line 22 should be longer than line 23 by a quarter wavelength or an odd multiple thereof at the operating frequency. If, however, the velocity of the wave traveling along the lines 22 and 23 do not approximate the velocity of the wave in free space,l then the dierence in lengths between lines 22 and 23 should be such that a wave traveling over line 22 will' take longer to reach junction point J by 90 than a wave traveling over line 23 to reach the same point. With this condition fullled, it will be noted that waves arriving at units I5 and I5 from the desired direction indicated by the arrows, will reach junction point J in phase, due to the fact that the signal arriving at I5 is a quarter wavelength earlier than the signal arriving at I6, but will take longer to arrive at junction point S. As for a signal wave arriving from the opposite direction, such a wave would reach antenna I6 ninety degrees earlier in phase than the same wave reaches antenna I5, in view of which the energy from antenna I6 would reach junction point J another ninety degrees earlier than the energy from antenna I5, thus making the energy arriving from antenna i6 one hundred and eighty degrees earlier in phase than the energy from antenna I5. In other words, the undesired signal from the reverse direction is substantially neutralized by this balance between the undesired energies from antenna units I5 and I6.

The antenna elements I8 and I9 are shown coupled to the repeater amplifier I'I through transmission lines 24, 25 and 26. Lines 24 and 25 differ in length by a desired amount and are joined at junction point S to the line 26. An-

tenna element I8 is displaced along the direction of propagation from antenna element I9 by approximately one quarter oi a wavelength at the operating frequency. Likewise, transmission line section 24 is suiciently longer than transmission line 25 so that the energies radiated by the two elements I8 and I9 are practically in phase with respect to the propagation in the desired direction. Here again, if the velocity of the wave along the lines 24 and 25 approximates the velocity of the wave in free space, then line 24 should be longer than line 25 by one-quarter of a wavelength at the operating frequency. With this condition fulfilled, it will be noted that the energy from the output of repeater II will be in phase with respect to the propagation in the desired direction indicated by the arrows, due to the fact that the signal arriving at I8 arrives there one-quarter of a wavelength or ninety degrees later in phase than the signal arriving at I9. Because of the quarter wavelength space displacement of antenna elements IB and I9, the waves add in space in the desired direction. However, as for the energies radiated by elements I8 and I9 in the back-end direction, that is in the reverse direction toward amplifier II, such radiated energies are undesired and are caused to cancel. This cancellationoccurs by virtue of the fact that the energy radiated in the back-end direction by I9 is substantially one hundred eighty degrees out of phase with respect to the energy radiated by I8 in the backend direction, thus causing neutralization.

Obviously, it is contemplated to provide means where desired, to enable a mechanical adjustment of the relative displacement of the antennas I5, IB, I8 and I9, and also an adjustment of the relative lengths of the transmission lines 22, 23, 24 and 25. It is preferred that the mechanical adjustment for the antennas I5 and I6 be unicontrolled with respect to the adjustment of the relative lengths of line sections 22 and 23. This should also be the case for antenna elements I8 and I9 and for lines 24 and 25.

Fig. 3 is an expansion of the ideas described above in connection with Fig. 2. In Fig. 3, there are employed two pairs of antennas 3|, 32 and 33, 34 arranged side by side, but with one pair displacing 90 relative to the other pair along the direction of polarization. The outputs are combined in proper phaseerelationship by means of'the interconnected transmission line sections. The arrow represents the direction or propagation. Units 3|, 32, 33 and 34 represent antennas which, in this case, are horn antennas. Considering the aperture of the antenna as the front, I have shown antenna 32 as being approximately one-quarter wave length behind antenna 3| along the direction of propagation and antenna 34 is similarly approximately onequarter wavelength behind antenna 33. The apertures of antennas 32 and 33 are approximately in the same plane.v The differences in orientation of antennas along the direction in propagation is made up in the transmission line system by differences in length of the connections. Thus, the electrical length of transmission line section 35, 36 is approximately one-quarter wavelength longer than that of transmission line section 36, 3l. A similar relationship exists between the electrical length of transmission line sections 38, 39 and 39, 46 and between sections 3S, 4| and 4|, 39. By virtue of this relationship, the effects of all four antennas add substantially in phase for the desired direction, While in the opposite direction the eiects of antennas 3| and 32 tend to be 180 degrees out of phase and the effects of antennas 33 and 34 likewise tend to be one hundred eighty degrees out of phase, and the resultant residual component from antennas 3| and 32 tends to be one hundred eighty degrees out of phase with the residual component from antennas 33 and 38. Putting it in other words, the four antennas operate in phase for signals in the desir-ed direction and the effects in the reverse direction are doubly balanced.

The relative positions of the four antennas as viewed from a point at a distance along the direction of propagation need not be that suggested in Fig. 3, but it may be such as shown in Fig. 4, or still other arrangements at the discretion of the designer.

Obviously, an arrangement similar to Fig. 3 can be used to radiate waves as well as to receive waves.

Although the invention has been described in connection with relay systems employing different frequencies between terminal stations, it should be understood that the principles of the invention are equally applicable to relay systems where the incoming and outgoing energies are relayed at a single carrier frequency for a given channel.

I claim:

1. In a radio relay system, a repeater station having a unidirectional wave directive structure composed of a pair of horn antenna elements positioned for effective operation in the same direction, said horn elements being spaced one from another along the line of said direction a distance equal to an odd multiple including unity of a quarter of the operating wavelength, connections differing by an electrical length of an odd multiple including unity of a quarter of the operating wavelength extending from said elements to the input of an amplifier system to produce a cophasal relationship for waves arriving from said direction, and a similar unidirectional wave directive structure coupled by connections arranged similarly to said rst connections to the output of said amplier system and positioned for effective operation in a substantially opposite direction than said rst structure.

2. In a radio relay system, a transmitting station radiatinga carrier wave of one frequency, a

receiving station forreceiving 'a carrier wave of another frequency, and a repeater station located intermediate said stations and having thereat` a unidirectional antenna systempositioned to receive the wave from said transmitting station, another vunidirectional antenna positioned to transmit a carrier Wave to said receiving station and a frequency converter for converting the frequency of the received wave from the transmitting station to a frequency to which thereceiving station is responsive, at least one of said unidirectional antennas at said repeater station comprising a pair of elements positioned for effective operation in the same direction, said elements being spaced one from another along the line of said direction a distance equal to an odd multiple including unity of a quarter of the operating wavelength, means connecting said elements in parallel to the input of an amplifier system in a mutual in-phase relationship for Waves arriving from said direction.

3. In a radio relay system, a pair of terminal stations both having transmitters for radiating a carrier of frequency f1 and receivers for receiving a carrier wave of frequency f2, a repeater station located intermediate said stations and having a first unidirective antenna positioned to receive the wave f1 radiated from one terminal station, a second unidirective antenna positioned to transmit a Wave f2 to the other terminal station, a third unidirective antenna positioned to receive the wave f1 radiated from said last terminal station, and a fourth unidirective antenna positioned to transmit a wave f2 to said one terminal station, repeater apparatus coupled =be tween said first and second unidirective antennas and between said third and fourth unidirective antennas, one pair of said unidirective antennas which are coupled to the same repeater each comprising two wave directive elements positioned for eiective operation in the same direction and spaced from one another along the line of said direction a distance equal to an odd multiple including unity of a quarter of the operating wavelength, lines coupling said wave directive elements to a common junction, said lines differing in length by an amount sufficient to compensate for the phase shift produced by the spacing between said directive elements for Waves traveling in a predetermined direction.

4. A system in accordance with claim 1, characterized in this that said elements comprise electromagnetic horns.

5. A system in accordance with claim 2, characterized in this that said transmitting station has an antenna polarized in a particular direction and the antenna at said repeater station which is positioned to receive the wave radiated from said transmitting station is also polarized in the same direction.

6. A system in accordance with claim 2, characterized in this, that said transmitting antenna at said repeater station is polarized in a particular direction and said receiving station has an antenna which is positioned to receive the wave radiated from said repeater station and .also polarized in the same direction.

7. In a radio relay system, a repeater station having a unidirectional Wave directive structure composed of a pair of elements positioned for effective operation in the same direction, said elements being spaced one fro-m another along the line of said direction a distance equal to an odd multiple including unity of a quarter of the operating wavelength, means connecting said elements in parallel to the input of an amplifier system in a mutual in-phase relationship for waves arriving from said direction, and a similar unidirectional Wave structure also coupled to the input of said amplifier system but displaced in space along the direction of propagation from said first wave structure, said two wave structures being positioned for effective operation in the same direction.

8. In a radio relay system, a repeater station having a unidirectional wave directive structure composed of a pair of elements positioned for effective operation in the same direction, said elements being spaced one from another along the line of said direction a distance equal to an odd multiple including unity of a quarter of the operating Wavelength, means connecting said elements in parallel to the output of an ampliier system in a mutual in-phase relationship for waves toy be transmitted by said structure in said direction, and a similar unidirectional wave structure, also coupled to the output of said amplifier system but displaced in space along the direction of propagation from said first Wave structure, said two wave structures being positioned for effective operation in the same direction.

HAROLD O. PETERSON.

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