US 2256619 A
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Description (OCR text may contain errors)
Sept. 23, 1941. Q G, Q LUCK 2,256,619
DIRECTIONAL ANTENNA Filed June l, 1940 HG. Z.
VERT/CHL L 00P REVERS/NG W/ 'ra H VER Tlc/7L D/POLE l Snventor David G. C. Lucl Gttorneg 'ponent's Y a directional antenna so schematic -tical loop antennaA along Awhich the loop rotates.
1so that the centers of the loops coincide. '.zontal dipole D is arranged symmetrically in the planes of both loops.
lThe vertical loop A is ldipole D which includes a phasing resistor I. The 'horizontal dipole DA is connected to either the horizontal loopv B' or Patented Sept. 23, 1941 UNITED sTATss oFF-ics DIREGTIONAL ANTENNA David G. C. Luck, Haddon Heights, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application June 1, 1940, Serial No. 338,326 16 Claims. (Cl. 25u- 11) This Vinvention relates to directional antennas 'and especially to a radio compass antenna in which the deleterious eiects ofv Heaviside layer vkreflections are eliminated or minimized.
It is well known that aradio compass antenna is'n'ot only responsive tothe ground waves from 4a radio transmitter but'the antenna is Valso re- 'sponsive' to unwantediwaves. waves are established by components of the transmitted waves which are reflected from the Heaviside layer.
These unwanted The radio compass errors caused by theseand like reflections are called "night errors.
It is an object of this invention to minimize nighterrors in a radio compass by providing means'- for balancing out -the unwantedvcom- Another object is to provide means in that itv will be responsive to ground waves but not to sky waves. Another f object is to provide means for connecting a plurality of directional antennas so that the result- `ant -directive pattern will lie vonly in a desired plane. "in a directional antennasystem whereby the systern may be used selectively for direction finding j of either vertically or horizontally polarized waves. I Y Y An additional object is'to provide means yThe invention will be described byv referring to the accompanying drawing in which Figure vl is a schematic perspective view of the directive antenna array ofthe invention; and Figure 2 is a circuit diagram of the radio compass ofthe invention, Similar reference numerals will be'applied'to similar elements of the drawing. Referring to Fig. 1 a vertically disposed dipole C is arranged symmetrically in the plane of a verthe vertical axis about A horizontal loop antenna Bis positioned normal to the vertical loop A hori- VTo avoid unnecessary confusion, the connections from the loops and dipoles :have noti'been shown in the perspective view. v"It should be'understood that the several antennas 'arefb'alanced-with' respect to VVground and are symmetrically -farrangedf'to provide no mutual coupling, which condition might otherwise be vobtained byelectrical methods. :"The 'schematic circuit diagram,vFig..2, shows the'connections of the several directive antennas. connected to the horizontal Vthe vertical dipole C. The
`dipole Czo'r loop` B, whichever not connected to the horizontal dipole, may be used as a sense antenna and is connected to the input of a radio receiver 3 by a reversing switch 5.V yThe'output `of the radio receiver is connected'through a reversing switch 'I to a left right indicator 9. lThe reversing switches 5, 1 are operated in synchronism by a motor ll. U
" The connections which connected the sense antenna, i. e. either the -horizontal dipole'Dorthe vertical loop B, to the receiver 3.and loop B' or dipole C '(as the case may be) tothe vertical loop A and horizontal dipole D, respcctiv'elmmaybe made by means Aof a two position multipole switch i3. When the switch I3 is in the upper position, the directive antenna array includes the loop A, the dipole D, and the loop B; and the vertical dipole C serves as the sense antenna. When the switch I3 is'in the lower position, the directive antenna array includes theA loop 4A,the dipole D, and the dipole C; and the horizontal loop B serves as the sense antenna. The former connection is used for vertically polarized waves; the latter for horizontally polarized waves.-
Inasrnuch` as.y thev operation of a left-.righ
radio compass indicator is well known to those skilled in the art, the present description will be limited to the operation of the directional array. In general, the night errors in a radio compass employing a loop antenna are the result ofthe sensitivity of the loop to waves which. are relected from the Heaviside layerand are therefore obliquely incident. In general, a wave 0bliquely incident on' the receiving antennamay be resolved' into four plane polarized components: (a) a horizontally incident wave having its electrical vector vertical, (b) a horizontally incident wave having its electrical vector horizontal (perpendicular to the plane of incidence), (c) a ver- "tically incident wave having its electricalvector in the plane of incidence, and (d) a.V vertically incident wave having its electrical vector perpendicular to the plane of incidence. While the foregoing resolution is not absolutely rigorousfitis sufciently exact for the purposes ofthe present invention. For our purposes. component (d) may be regarded together with component (c), simplyl as an unwanted vertically incident wave.
In the case of a wave initially plane polarized, y all four components are in phase in time.. In the limiting case of a circularly polarized original Y wave, the two components polarized in theplane of incidence are in time phase but are in phase,
quadrature with the other two components. yThe two horizontally incident components arev of use for direction finding. A In the case of a 'loop' antenna with a vertical axis of rotation only the vertically polarized of these two components is effective. In the case of a horizontal dipole, only the horizontally polarized component can act. With either type f antenna a vertically incident component may cause errors. The vertical component displaoes the signal null as the antenna is rotated.
A horizontal dipole in the plane of the turns of a vertical loop has, proportionally, exactly the same strength of response to the vertically incident waves as the loop for all rotational positions of the pair about a vertical axis. However, the voltages induced in the horizontal dipole will be in time quadrature with the voltages induced in the loop. If the horizontal dipole is short with respect to the wave length, so that it approximates a pure capacitance, and includes a suitable phasing resistance, this quadrature is removed and the dipole may be connected in series with the loop so that the vertically incident response of the two antennas may be made to neutralize for all frequencies for which. the antennas are small in comparison to va wave length. This combination of loop and dipole will exhibit pairs of opposite null points 90 apart for waves horizontally incident and, respectively, vertically and horizontally polarized. If a horizontal loop is also serially connected with the vertical loop and horizontal dipole, its response to horizontally incident, horizontally polarized radiation will cause suppression of one null of the horizontal dipole and coincidence of the other null with a vertical loop null to give a usable directive system. While this system will have two null points spaced 180 for vertically polarized horizontally incident waves, a tilt of the polarization will cause the reciprocal null to shift toward the true null, being 90 from the true null for 45 plane polarization and coincident with it for horizontal polarization.
Horizzntally Horiznntally V t u inci ent inci ent er ica y Antenna vertically horizontally incident c polarized a polarized b Aa Ab Ac Vertical loop A Sensitive Insensitive Sensitive.
Ba Bb Bc Horizontal loop B Insensitive Sensitive Insensitive.
Ca Cb Cc Vertical dipole C Sensi1t)ive.. Insensijtive. Insensitive.
a D c Horizontal dipole D Inscnsitive. Sensitive..- Sensitive.
Instead of connecting a horizontal loop to the serially connected vertical loop and horizontal dipole, a vertical dipole may be connected so that the directive array may be used to suppress one null of the vertical loop and shift the other to coincide with one of the nulls of the horizontal dipole. Thus connected, the system is useful for horizontally polarized waves while the former system is used for vertically polarized waves.
While no type oi' incident wave will shift the true null in either system, the choice of the true null is simplied by a phase comparison in which a non-directive antenna may be used to obtain the reference phase. This arrangement corresponds to the well known use of a sense antenna. In the first described system, a vertical dipole is Used to determine sense. In the second described system, which is responsive to horizontally polarized waves, a horizontal loop is used for sense determination. In the arrangement shown in Figs. 1 and 2 all four types of antennas are available, so that the switch places the two combinations at the disposal of the operator.
As an aid in understanding the invention reference is made to the accompanying table which indicates the sensitivity of the various types of antennas to the various types of waves. For the reception of vertically polarized waves the un- Wanted components are minimized or neutralized by serially connecting the antennas A, B and D. Thus connected, the vertical loop A is sensitive to horizontally incident, vertically polarized waves a and to verticalyl incident waves c. The vertically incidence response Ac is neutralized by the vertical incidence response Dc of the horizontal dipole D. However, the horizontal dipole D is sensitive to horizontally incident, horizontally polarized waves b. These waves are neutralized by the horizontal loop B which is only sensitive to the horizontally incident, horizontal polarized waves b and is insensitive to the other components.
In a similar manner, for horizontally polarized waves, the antennas A, C and D are serially connected. The horizontal dipole D is sensitive to the horizontally incident horizontally polarized waves b but it is also sensitive to the vertically incident waves c. This sensitivity is neutralized by the sensitivity of the vertical loop A to the vertically incident waves c. However, the vertical loop is also sensitive to horizontally incident, vertically polarized waves a. This sensitivity of the vertical loop A is neutralized by the vertical dipole C which is only sensitive to the horizontally incident, vertically polarized waves c and insensitive to the other components.
It should be understood that the foregoing response characteristics of the several types of antennas is based upon the antenna being so disposed with respect to the wave front that it will have a nite response. As the antenna array is rotated with respect to the Wave front, responses of the several sensitive elements will be reduced occasionally to zero in accordance with the well known characteristic figure-of-eight. However, as the response of one of the neutralizing antennas, for example, the horizontal dipole D, falls off, the response of the antenna to be neutralized, say the vertical loop A, will also fall off so that there is no change in neutralization as the antennas are rotated about the common axis.
Thus the invention has been described as a directional antenna in which the undesired vertically incident wave components are minimized or eliminated. The elimination is effected by neutralizing the undesired response by connecting, in proper phase, an element equally responsive to the undesired component. Since the added element also has an additional undesired response, this second undesired response is in turn neutralized by connecting, in proper phase, an element equally responsive to the second undesired component but to no other undesired wave or component. The array maybe used to indicate the direction of either vertically or horizontally polarized waves. Furthermore, a sense antenna may be added. The array may be used for transmission or reception, and may be arranged for uni-directional or bi-directional operation.
I claim as my invention:
l. A directive antenna array including a directional antenna having a desired response to horizontally incident waves and an undesired response to vertically incident waves, means connected to said antenna to minimize Vsaid undesired response, said minimizing means being responsive to both vertically incident waves and to waves polarized at substantially right angles to said neutralizing means said horizontally incident Waves, and means connected to said rst mentioned minimizing means for minimizing said response' to said waves polarized at substantially right angles.
2. A directive antenna array of the character yof claim 1 including a sense antenna non-directively responsive to said desired horizontally incident Waves.
3. A directive antenna array including in cornbination a vertical loop, connecting said loops in series, a horizontal ,dipole, phasing means connected to said dipole and means connecting said dipole in series with said loops.
4. A directive antenna including a loop antenna responsive to horizontally incident vertically polarized vvaves and to vertically incident Waves, means serially connected to said loop antenna for neutralizing its response to said vertically incident Waves, said neutralizing means being responsive to horizontally incident horizontally polarized Waves, and means for neutralizing the response of said rst mentioned neutralizing means to said horizontally incident horizontally polarized Waves.
5. A directive antenna array including a horizontal dipole, said horizontal dipole including phasing means, a vertical dipole, said vertical dipole including phasing means, means serially connecting said dipoles, a vertical loop and means serially connecting said loop and said f dipoles. y
6. A directive antenna including a horizontal dipole responsive to horizontally incident horizontally polarized Waves and to vertically incident Waves, neutralizing means serially connected to said dipole antenna for neutralizing its response to said vertically incident Waves,
being responsive to horizontally incident vertically polarized Waves, and means for neutralizing the response of said first mentioned neutralizing means to said horizontally incident vertically polarized waves'.
7. vA directive antenna array including in combination a vertical loop, a horizontal loop, said loops having a common center, means connecting said loops in series, a horizontal dipole, arranged symmetrically in the planes of said vertical loops, phasing means connected to said dipole, and
means connecting said dipole in series with said loops.
8. A directive antenna including a loop antenna responsive to horizontally incident vertically polarized Waves and to vertically incident Waves, means serially connected to said loop antenna for neutralizing its response to said vertically incidentV Waves, said neutralizing means a horizontal loop, means being responsive to horizontally incident horizon- V tally polarized Waves, and means for neutralizing the response of said rst mentioned neutralof said neutralizing means being arranged with a common center.
9. A directive antenna array 1ncluding a horil zontal dipole, said horizontal dipole including phasing means, a vertical dipole, said dipoles' having a common center, said horizontal dipole including phasing means, means serially connecting said dipoles, a vertical loop having its center coincident with said common center, and means serially connecting said loop and said dipoles.
10. A directive antenna including a horizontal dipole responsive to horizontally incident horizontally polarized Waves and to vertically incident Waves, neutralizing means serially connected to said dipole antenna for neutralizing its response to said vertically incident Waves said neutralizing means being responsive to horizontally incident vertically polarized Waves, and means for neutralizing the response of said first mentioned neutralizing means to saidhorizontally incident vertically polarized Waves, said dipole and each of said neutralizing means being arranged about a common center. 11. An antenna of the character of claim 3 including a sense antenna non-directionally recharacter of claim 5 which said horizontal dipole, said vertical dipole,
and said vertical loop are arranged to provide a minimum of mutual coupling.
16. A directive antenna array of the character of claim 1, including a sense antenna non-directionally responsive to said desired incident Waves and in which said directional and said vnondirectional antennas and said rst and second minimizing means are arranged to provide a minimum of mutual coupling.
DAVID G. C. LUcK.
non-directionally re-` v