US2482767A

US2482767A - Broad band antenna

Info

Publication number: US2482767A
Application number: US501370A
Authority: US
Inventors: William W Hansen
Original assignee: Sperry Corp
Current assignee: Sperry Corp
Priority date: 1943-09-06
Filing date: 1943-09-06
Publication date: 1949-09-27
Anticipated expiration: 1966-09-27
Also published as: GB650041A

Description

Sept. 27, 1949. w. w. HANSEN BROAD BAND ANTENNA Filed Sept. 6, 1945 ATTORN EY Patented Sept. 27, 1949 BROAD BAND ANTENNA William W..Hansen, Garden City, N. Y. assignor to The Sperry Corporation, a corporation :of

Delaware Application September 6, 1943, Serial No. 501,370

12 Claims. (C1. 250-3351) My invention relates to antennae or radiators for radio communication and signaling systems, and concerns particularly radiators suitable for use in high frequency radio systems such as may be used in connection with object detection.

An object of my invention-is toprovide an antenna having a pattern like an end-fire array of dipoles, but having a broader frequency band.

A further object of my invention is to provide a balanced double-endedantenna which is useful in pulse systems and in which sparking is prevented.

A further object of my invention is to provide an antennagiving circularzpolarization of radiation-and reception.

Other and further objects and advantages will become apparent as the *descriptionproceeds.

In carrying'out my'invention in its preferred form, I utilize a-rod or wire of-suitableconducting material which is electrically continuous from one input'terminal tothe other, which is bent into helical form andhas a diameter and pitch of the helix of such a value in relation to the desired wave-length that radiation from all elements of the antenna is in phase.

A better understanding of the invention will be afiorded by the following detailed description considered in connection with the accompanying drawing, in which Fig. 1 is a diagram representing a fragmentary end view of one embodiment of my invention, and

Fig. 2 is a perspective diagram of the embodiment of my invention represented in Fig. 1.

Like reference characters are utilizedthroughout the drawing to designate like parts.

The antenna illustrated in the drawing comprises a unitary length of wire H which is bent in the form of a helix. In order that running waves instead of a standing wave may be produced, and in order that a suitable termination may be conveniently connected to the antenna I prefer to provide a pair of helices l2 and i 3 each formed of a length of wire represented by the separate symbols H and H.

For supplying input energy to the antenna at input terminals I4 and I5, a suitable transmission line, such as concentric line [6, may be provided comprising an inner rod conductor I! connected to the antenna terminal I 4 and an outer cylindrical conductor I 8 connected tothe antenna terminal I 5.

The helices l2 and I3 may have end terminals 2| and 22, respectively, between which a suitable terminating impedance 23 is'connected. Preferably the impedance 23 comprises a'highfrequency propagation.

resistor having a resistance such as to suppress any reflected current waves. In other words, the unit'2-3 has an impedance matched-to-the antenna or equalling'the characteristic impedance thereof.

.Although the value of this resistanceimay be determined bycalculation, Iconsider it preferable to determine the best valueof terminating impedance by trial and error.

Theform. of: antenna. illustratedis. advantageous when double-ended inputisrequiredand is .useful for producing circular polarization. The direction of propagation of the radiated energy is along the arrow 24. In order .that the phase relationship between the radiation and successive ele- -ments will be in the samephase, the dimensions of the antenna should be so chosen that variation in phase due to the lead or pitch of the helix compensates for the Variation :in phase due to the difference in position of said elements along the wire in any turn or portion of a turnof the wire forming the antenna. Thus, the effect ofchange in direction of the wire caused 'by bending it around an axis is-overcomaby also warping it toa pitch 'or :advance along the direction sof wave It Will be understood that an antenna of this type is particularly useful for 'high frequency radiation or radiation at frequencies such that the wavelength :is comparable with the physical dimensions of the antenna. Consequently, -the length of the wireis of the order of magnitude of a number of wavelengths, and the currents in the successive portions of the Wire produce "radiation at successively later periods of time. Consequently therradiationfrom successive elements .of the wire'would tend to vary progressively in phase relationship if "the turns of wire -all lay in-the same plane.

Since'the'direction of propagation is along a line parallel to the helix axes; the change in phase due to progress of the phase along the wire in any one'turn'is'compensatedby the pitch'ofthe Wire causing successive portions "of the wire-to have different positions with respect'to the direction'of propagation. The radiation pattern resembles that of -"an-'en'd--f1re array of dipoles.

The preferred-dimensions of'the antenna are therefore determined from the phase relationships of the radiation from various elements of the antenna. It may'hexshnwn that the phase of the radiation from any element is expressed by the equation p the phase depending on the advance of the helix. The phase of waves running down the wires depends on km for the distance along the wire and on kP/21r for the advance of the helix. When 0=1r, the direction or the wire has reversed. Ihe waves will add in front if In order to make the radiation from all elements of the same phase, dimensions should be chosen to satisfy the equation B r 27r 21r where x is the electrical wavelength of the desired radiation. Suitable dimensions, for example, are

for the pitch P and the radius A in r 81r 811' It will be apparent that the required phase relationships may be obtained by using a single helix, such as the helix IE or l3 provided, however that the waves on the wire are running waves. To insure this, some form of termination is needed and the simplest way of providing for making connections to a termination is to employ a plurality of helices, in an even number, such as 2 or a multiple thereof.

Since rotational symmetr exists with respect to the helix axes parallel to the direction of propagation 24, the radiated wave is circularly polarized.

In accordance with the provisions of the patent statutes I have described the principle of operation of my invention, together with the appara tus which I now believe to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown and described is only illustrative and that my invention may be carried out by other arrangements.

What is claimed is:

1. An antenna composed of a length of conductor material curved to form successive elements with progressively different directions and. in difierent planes with successive elements bent along a circle with a radius r and successive elements also warped into difierent planes with a pitch P satisfying the equation where x is the electrical wave length of oscillations to be transmitted or received by the antenna.

2. An antenna comprising a length of conductor material bent to a radius equal to and warped to give a pitch or advance equal to where x is the electrical wave length of oscillations to be transmitted or received by the antenna.

3. An antenna comprising a length of wire in the :form of a helix having a radius T and having a helix pitch P satisfying the equation P 21r 2 1 r where x is the electrical wavelength of oscillations to be transmitted or received by the antenna.

4. An antenna comprising a length of conductor material bent into the form of a helix having a radius equal to and a helix advance or pitch equal to where A is the electrical wavelength of oscillations to be transmitted or received by the antenna.

5. An antenna system for use with ultra short waves, comprising a length of conductor in the form of a helix having a diameterof the same order of magnitude as the length of said waves, and means supplying radio frequency energy to said helix, said helix having a pitch in relation to the diameter of said helix as to cause the same variation in phase due to the pitch of said helix as is due to the length of the conductor, whereby a unidirectional radiation pattern having a maximum directivity in the axis of the helix is formed.

6. An antenna system for producing circularly polarized ultra short waves, comprising a pair of conductors bent in the form of a pair of helices each helix having an input terminal and an end terminal connected to the other end terminal .of said other helix of said pair of helices by a terminating matched impedance placed therebetween, and each of said helices further comprising a plurality of successive loops having diami eters of the same order of magnitude as the length of said. waves at the operating frequency, said loops of said helices being spaced from each other by a distance sufficient for radiation from each of said loops to arrive in phase at the next successive loop, whereby a radiation pattern having a maximum directivity along the axes of the helices is formed.

7. An antenna system for use with ultra short waves, comprising an even number .of helices connected in series, a pair of input terminals each connected at one end of one of the helices, a

terminating impedance connected in series with said helices and being matched thereto, and each of said helices further comprising a plurality of successive loops having diameters of the same order of magnitude as the length of said Waves at the operating frequency, said loops of said helices being spaced from each other by a distance suiiicient for radiation from each of said loops to arrive in phase at the next successive loop, whereby a unidirectional radiation pattern having a maximum directivity along the axes of the helices is formed.

8. An ultra high frequency antenna system for use with ultra short waves comprising a plurality of radiating loops, means connecting each of said loops in electrical series with respect to one another, each of said loops being pitched from each other at a distance of the same order of magnitude as the length .of said waves and having a suitable diameter so that the difference between the electrical phase displacement due to the length of conductor and the space phase displacement due to pitch is substantially a half-wavelength whereby radiation from each of said loops arrives in phase reinforcement at the next successive loop to form a radiation pattern having a maximum directivity in a plane perpendicular to the plane of said loops.

9. An antenna system for use with ultra short waves comprising a plurality of parallel displaced helices connected in series, each of said helices having a plurality of loops pitched in the same direction from each other by a distance in the same order of magnitude as said waves, a plurality of input terminals connected at one end .of said helices and a terminating matched impedance connected in series with each of said helices so as to define a maximum radiation directivity characteristic for said waves along the axes of said helices.

10. In an antenna system for use with ultra short waves means for producing circular polarization comprising a pair of parallel displaced helices connected in series, each of said helices having a plurality of loops pitched in the same direction from each other by a distance in the same order of magnitude as said waves, a pair of input terminals connected at one end of said helices and a matched terminating impedance connected in series between said helices so as to define a maximum radiation characteristic for said waves along the axes of said helices.

11. A circularly polarized antenna system for use with ultra short waves comprising a pair of conductors having the shape of parallel displaced helices connected in series, each of said helices having a plurality of loops pitched in the same direction from each other by a distance in the same order of magnitude as said waves, and a terminating matched impedance connected between said conductors so as to define a maximum radiation directivity characteristic for said waves along the axis of said helices.

12. An ultra high frequency antenna system for use with ultra short waves comprising a pair of adjacent helices each having a plurality of radiating loops, said loops being connected in electrical series with respect to one another, each of said loops having a diameter .of the same order of magnitude as the length of said waves, a terminating impedance interconnecting said adjacent helices for cancelling standing waves in said loops, said loops further being pitched from each other by a distance such that radiation from each of said loops will arrive in phase reinforcement at the next successive loop so as to form a radiation pattern of circular polarization having a maximum directivity parallel to the axes of said helices.

WILLIAM W. HANSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain Oct. 30, 1923 Number Number