US2267945A - Long wire antenna - Google Patents

Description

Dec. 30, 1941.

LONG WIRE 'ANTENNA Filed Dec. 30', 1939 4 Sheets-Sheet l INVENTOR W/LHELM PETERS BY m N ATTORNEY w. PETERS 2,267,945

Deg. 30, 1941. w. PETERS 2,267,945 I LONG WIRE ANTENNA- F'iled Dec. 30, 1939 4 Sheets-Sheet 2 Z1 Z2 Z3 9' /s v Z I f) INVENTOR w/ HELY ATTORNEY Dec. 30, 1941. w. PETERS LONG WIRE ANTENNA Filed Dec. 30, 1959 4 Shets-Sheet ,3

DISTANCE ALONG ANTENNA DISTANCE ALONG ANTENNA \7 j INVENTOR W/LHE'LM PETERS ATTORNEY Dec. 30, 1941. w. PETERS 2,267,945

- LONG WIRE ANTENNA Filed Dec. 30, 1939 4 Sheets-Sheet 4 INVENTOR W/LHELM ErsRs" ATTORNEY Patented Dec. 30, 1941 LONG WIRE ANTENNA Wilhelm Peters, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic in. b. H., Berlin, Germany, a corporation of Germany Application December 30, 1939, Serial No. 311,862

In Germany October 21, 1938 11 Claims.

In communication with short waves, transmitter antennas and receiver antennas are required which, owing to the variation of the optimum transmission wave from time to time, must cover a rather wide short wave range, for instance, a range from about 16 to 60 meters. Furthermore, such antennas are required to have a favorable directional effect and favorable degree of efliciency as regards this effect. Therefore, antennas with tuned dipoles must be excluded for this type of service since for a variation of the operating'wave the length of the dipoles of such antennas as well as the relative spacing and the length and phase of the reflectors thereof would have to be changed within wide limits. But the above stated requirements are favorably complied with by means of long wire antennas whose length is several wavelengths and which are fed with travelling waves. In fact, on these antennas the waves can appear and propagate in accordance with the length thereof. The greater the number of travelling dipoles presented along the length of the wire the more the direction of the main radiation approaches the direction of the axis of the wire. Within a certain range the radiation angle formed with the main axis remains unchanged and hence, it is not sensitive as regards frequency. Such an outstretched long wire whose length is equal to several wave-lengths therefore produces a conical radiation diagram whose opening angle changes but slightly with the frequency. Figure 1c shows such a diagram; it is formed from the known diagram of a wire fed with a standing wave as shown in Figure 1a, wherein the radiation towards the front and rear is symmetrical, in that the latter is converted into a travelling wave by adding a wave of same length which is displaced in space and as regards time at 90, whereby each current loop dipole of the latter acts as reflector of the former wave, and thus the radiation diagram of Figure la is to be multiplied with the reflector group characteristic of the cardioid of Figure 1b in order to obtain the Figure 1c. This presentation reveals that in the case of travelling waves the eifective reflector may be considered as always moving along at the proper distance and phase with variations of the wavelengths. In this way there is always realized a favorable shielding towards the rear. A further advantage of a travelling wave antenna resides in the fact that the transmitter always remains under effective load. The effective resistance is equal to the wave resistance for all frequencies. Since also the radiation angle is almost constant, the result is that the radiated field strength remains. practically constant within a wide frequency range. Now, in

order to obtain from the radiation cone a single resultant pointed ray, two such long wire antennas may be placed with respect to each other in V-form and with opposite polarity and at such an angle that the radiation will be doubled in the direction of the bisector of the angle of the cone. Since the radiation for other directions and larger azimuth angles is extinguished by interference between the radiation from the two wires. From the two ray cones of the individual wires only the common mutually covered part in the direction of the bisector of the angle remains and is thereby doubled. Now, it is possible to combine two or a greater number of such V-antennas in the form of a rhombus which thus radiates a field intensity which is four times that of a single wire. The radiation power is thus concentrated into a muchsharper cone.

Such long-wire antennas'or antenna systems entail in their known mode of construction serious disadvantages, among other things, a

poor effectiveness and incomplete shielding towards the rear, the first mentioned disadvantage reducing the effectiveness of such antennas as transmitter antennas while the second disadvantage greatly decreases the efiectiveness of said antennas for receiving. For the production of travelling waves the end of the antenna facing away from the transmitter and receiver has hitherto been terminated by an ohmic resistance whose value is equal to the wave resistance of the line since it was sought to realize the condition for travelling waves on the basis of the theory of the telegraph line equation. The wave resistance depends on the proportion between the wire spacing s and diameter d and is calculated in accordance with the following formulai The said wave resistance is about 400 to 600 ohms in general. For a radiation resistance of about 300 .ohms about one-half of the high frequency energy would be lost in the terminal resistance. A further disadvantage is the appearance of a back radiation which will be much more appreciable than in the diagram shown in Figure 10.

It is the purpose of the following invention to avoid these disadvantages of the travelling wave 2 log antenna thereby improving the antenna. degree of efficiency of the radiation is:

wherein Ia is the input current, Z2. is the input wave resistance, Ie is the current at the end and Ze is the terminal resistance. From this follows that in accordance with the invention the The degree of efficiency can be considerably improved.

by choosing as low as possible the proportion radiation resistance wave resistance it is necessary to choose the wave resistance as low as possible. In accordance with the invention this is accomplished by arranging the wires in the form of a cage and by providing connections between them or arranging them twisted about one another to obtain a uniform current distribution.

Figure 2a next shows an ideal long-wire radiator which may have the Wave resistance Z and the uniformly distributed radiation resistance 1 and which may be assumed as of infinite length and its associated graphical illustration of the current distribution along the wire. The beginning of the wire is connected to a high frequency voltage source G. Owing to the withdrawal of energy through lateral radiation which may be assumed as taking place ideally in a uniform manner across the length, the travelling current wave will be damped according to an exponential law. In connection with Figure 2b, which is similar to Figure 20., except that the uniformly distributed resistance is assumed to be concentrated in certain equal distances, the above per.- formance can be so conceived, as if through the resistance diffractions would occur in the advancing wave Inn-1 whereby owing to partial reflexions also rearward moving waves are produced which results from the complex resistance. This effect will repeat itself at each joint so that wave trains appear which move forwards and backwards. As shown in Figure 1, the latter produce, however, back radiation thus jeopardizing the shielding of the main wave. If the wave resistance is more and more reduced with constant radiation resistance for obtaining a high degree of efficiency of the radiation, it can be seen from the foregoing considerations that the portion of the standing wave also increases automatically thus jeopardizing the shielding towards the rear. In accordance with the invention backward moving waves are avoided by varying the wave resistance along the length of the conductor in accordance with the variation in radiation resistance. The required relation is such that for each. element of the radiator the resistances at each joint between Znr must be the same in both directions. Since viewed from this place the resistance r lies in series with Z1i+1, it follows that wherein Zn is the wave resistance ahead of the radiation, 1' is the radiation resistance and Zn+1 is the wave resistance in back of the radiation. Then there is:

This law which is not known in the customary antennaswith standing waves, is a particularity of the antennas with travelling waves and denotes that the energy entering an antenna elementwill only in part be radiated, and the other part thereof will be transferred refiexion-free for radiation to the immediately following antenna elements. From this reasoning it is further seen that a radiation wire with a constant wave resistance also carries waves moving towards the rear when said wire radiates. The necessary condition for this radiation mechanism and transfer mechanism to operate without reflexion effects, is achieved in accordance with the present invention by decreasing the wave resistance along the line. With the assumption of the ideal condition that the radiation resistance alon the line is constant, the wave resistance would; then have to, be reduced in a linear fashion such as is shown in Figure 20. A comparison; with the current curve of FigureZb shows that now reflections no longer occur. Since the terminal resistance is always matched with the wave resistance at v the end, the result is that for reflection f-ree; operation the terminal resistance is loweraccording to the inventionso that the efliciency of the radiation will be enhanced. In fact, if Z1 is the resistance of the input waves,v Z'z the terminal resistance and R the totalradiationresistance, then the efiiciency of the radiation is For 2 :50 0 0 1 5, and R=40 0 ohms. the arrangement according to the invention has a e m n ljresist n e .2.= ;1.R= .0 ohms ndit efilciency'of the: radiation is whereas in the hitherto customary arrangement the efiiciency degree is only 40%. It is even possible in accordance with the present invention to reduce the terminal resistance practically to zero thus obtainingan efiiciency of if in accordance with Equation 3 the input resistance is chosen equal tothe radiation resistance of. the antenna, so that in accordance with, Equation 1 there will be. 22:0, which means that the antenna is simply shortl-circuited atthe end. In this ideal case the transmitter feeds energy into the. antenna, in the form of traveling waves. (I .Zi) to the. same extent that, owingito. its'electromagnetic fields, the. antenna will actually radiate (RR). In practice, a low. terminal resistance will-preferably be providedsoas to assure certain possibilities of variation. Moreover, under these circumstances the termination in, the arrangement according to the, invention need not be carried out exactly with the wave resistance, buta lower resistanceL may be used to, this end since the wave .moving' towards :the rear has hardly any radiation property'owing to the wave resistance being dependent on direction of travel of the wave. The realized-advantage in accordance with the invention resides -in the fact that the matching of the terminal resistances can be chosen with lesser accuracy.

Actually, the distribution of the radiation along the line is not uniform. But the deliberations so far made remain substantially valid, it being only necessary that the variation of the wave resistance be matched with the distribution of the radiation resistance. Figure 4a shows next for a standing wave the distribution of the radiation resistance along the radiator. It is seen that in accordance with the lateral directional effect the radiation resistance becomes higher towards both sides while it is lowest in the center. In the case of a progressing wave with unilateral directional radiation according to Figure 10, therefore, in accordance with Figure 4b, the radiation resistance greatly increases towards the end situated in the direction of the radiation. The decrease of the wave resistance must be chosen accordingly. The Figures a and 51) show examples for the single wire Beverage antenna and for the V-antenna which are dimensioned in accordance with these requirements. In the case of the rhombus various radiation wires are connected in parallel for each conductor and spread apart at the remote end to compensate for a higher radiation resistance for the sides facing away from the transmitter or receiver. This is shown in the example of Figure 3, as well as in Figure 50. A variation of the wave resistance is herein obtained by the spreading apart of two parallel connected wires at each side. With constant wave resistance along the radiation line, in the case of an antenna situated in the open, the distance between said wires would have to increase symmetrically towards the center in accordance with a parabola. But due to the decrease of the wave resistance there results a form according to Figure 50 which will also be affected by the height above ground, since with the moving apart of the V-wires the wave resistance will be reduced by the counterinductance of the ground currents. Since, however, in order to obtain a favorable vertical diagram, the antenna is to be arranged at a rather considerable height above ground, the influence is not appreciable.

Now, owing to the particularly pronounced variation of the wave resistance the antenna is not readily reversible. It possesses a pronounced direction of radiation in the direction of the terminal transmitter and which is at the same time the most favorable direction of reception for the waves arriving in the opposite direction. In the opposite directions the antenna radiates and receives only at a reduced eifectiveness. Now this dimculty can be overcome in accordance with the invention by arranging two such antenna systems having opposite directions and of which at least one or both together can be operated with the same or with different programs. This is shown in Figure 5d wherein a pair of superposed rhombic antennas 5| and 52 are connected through double pole double throw switches SW1 and SW2 to a transmitter G and a terminating resistance R. Thus, either 5| may be connected at the proper ends to the transmitter and resistance for transmission in one direction, or 52 may be similarly connected for transmission in the other direction. The rhombics are shown as single wires for simplicity but should be constructed as shown in Figures 3 and 5c.

Figure 6 shows how a plurality of rhombics may be placed in tandem to increase the directivity without occupying too much space by arranging them to substantially overlap.v

- I claim: I

1. A radiating conductor having a length at least equal to several times theoperating wavelength, a transducer means connected thereto at one end, said conductor having a wave resistance and a radiation resistance each varying along the length of said conductor, said wave resistance decreasing in proportion to the distance from said one end, while said radiation resistance increases in proportion to the distance from said one end. I

2. A radiating conductor having a length at least equal to several times the operating wavelength, and having a wave resistance and a radiation resistance each varying along the length of said conductor, a transducer means connected thereto at one end, said wave resistance decreasing with increasing distance along the length of said conductor from said one end, said radiation resistance increasing in proportion to the decrease in wave resistance along said conductor.

3. A radiating conductor having a length at least equal to several times the operating wavelength, said conductor having a wave resistance and a radiation resistance each varying along its length, a transducer means connected thereto at one end, said wave resistance constantly decreasing with increasing distance from said one end, said radiation resistance varying inversely with respect to said wave resistance.

4. A V antenna comprising a pair of conductors as set forth in claim 2.

5. An antenna comprising a pair of conductors as set forth in claim 3, said conductors being arranged in a generally diamond-shaped plan.

6. A bi-directional antenna comprising two pairs of conductors as set forth in claim 3, each pair of said conductors being arranged in a generally diamond-shaped plan, the conductors of one pair being oppositely arranged to the other pair.

7. A bi-directional antenna comprising two pairs of conductors as set forth in claim 3, each pair of said conductors being arranged in a generally diamond-shaped plan, the conductors of one pair being oppositely arranged to the other pair. said pairs of conductors being arranged one immediately above the other.

8. A radiating conductor having a length at least equal to several times the operating wavelength, said conductor having a wave resistance and a radiation resistance each varying along its length, a transducer means connected thereto at one end, said wave resistance constantly decreasing with increasing distance from said one end, said radiation resistance varying inversely with respect to said wave resistance, the other end of said conductor being directly connected to ground atits other end.

9. A V-antenna comprising a pair of conductors as set forth in claim 2, said conductors being connected to ground at their other ends through a low resistance connection.

10. A bi-directional antenna comprising two pairs of conductors as set forth in claim 3, each pair of said conductors being arranged in a generally diamond-shaped plan, the conductors of one pair being oppositely arranged to the other said transducer, means being, equal. to the radiation-.reslstanceoi said: conductor at said one end, said; conductor having a constantly decreasing wave resistance toward its. other end where it is 5 connected: to ground.

PETERS.

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