US2985878A - Wound antenna with conductive support - Google Patents

Description

May 23, 1961 L. o. KRAusE ETAL wouND ANTENNA WITH coNDucTIvE SUPPORT original Filed Feb. 13, 1952 v 2 Sheets-Sheet 1 Inventors: L Iogd O. Krause, j Howard G. Smith,

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ENERG/ZAT/ON May 23, 1961 o. KRAUsE ETAL WOUND ANTENNA WITH CONDUCTIVE SUPPORT Original Filed Feb` 13. 1952 2 Sheets-Sheet 2 *Figi r I /0 20 J0 40 J0 60 DSREES W/TH RESPECT 70 Z'N/TH Inv enters:

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United States Patent O WOUND ANTENNA WITH lCONDUCIIVE SUPPORT Lloyd 0. Krause, North Syracuse, and Howard G. Smith, Ithaca, N.Y., assignors to General Electric gonlxpany, New York, N.Y., a corporation of New Continuation of application Ser. No. 271,374, Feb. 13, 1952. This application May 2, 1958, Ser. No. 732,482

16 Claims. (Cl. 343-895) The present invention relates to antenna structures of the kind used for the radiation and reception of electromagnetic energy and has yfor an object to provide antenna structures having a uniform or other predetermined radiation pattern in azimuth and a narrow radiation pattern in elevation at high frequencies.

Antenna structures of this kind nd extensive application in television broadcasting where the need for structures of this character is becoming increasingly felt.

Another object of the present invention is to provide an antenna which can be energized easily and eiiieciently over a broad band of frequencies from a source of energization with a minimum of electrical connection or feed complexities.

Still another object of the present invention is to provide a new and improved high gain antenna.

An additional object of the present invention is to provide an antenna which will radiate electromagnetic energy extending over a broad band of frequencies with substantial uniformity.

A further object of the present invention is to provide an antenna which presents substantially constant impedance over a broad band of frequencies.

A still further object of the present invention is to provide an antenna which is simple to construct, easy to install, rugged, effective in operation, easily de-iced and which can be readily grounded against lightning.

In accordance with one embodiment of the invention, there is provided a conductive element (which may be a cylindrical mast) with a radiative conductor (which may be helical) developed about the conductive element and in spaced relation thereto. The spacing between the radiative conductor and the conductive element is rsuch to permit the establishment of a wave of energy on the radiative conductor and for it to be conducted between the radiative conductor and the conductive element and radiated from the radiative conductor.

Energization is applied between the radiative conductor and the conductive element to cause electromagnetic waves of energy to travel continuously around and outward along the radiative conductor and the conductive element. During the travel of electromagnetic waves between the radiative conductor and the conductive element, energy is continuously radiated from the system causing a progressive attenuation of the waves to a small magnitude at the end of the radiative conductor. The radiation in a plane perpendicular to the axis of the radiative conductor is substantially uniform and the radiation in planes including the axis is confined to a narrow beam.

In accordance with another aspect of the invention, each of the turns of the radiative conductor is an integral number of operating wavelengths. Other aspects of the invention are: the spacing between turns of the radiative conductor is substantially one-half of an operating wavelength; and a unit length of surface of the radiative conductor is less than a unit length of surface of the conductive element. The operating wavelengths are related to Patented May 23, 1961 the phase velocity of propagation along the radiative conductor.

An advantage of the invention is that antennas of the above-described character may be easily arranged in a manner so that the conductive elements of the respective antennas lie in a common axis to produce a composite antenna which radiates electromagnetic energy in a very narrow segment perpendicular to the axis of the antenna. High gain antennas of this character are highly advantageous at high frequencies where it is difficult to generate large amounts of power. The small number of points of energization required for such an array of radiating structures greatly simplifies the problem of energization of the composite antenna structure.

The invention both as to its organization and method of operation together with further objects, features and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

Figure l is a front view of a portion of an antenna structure embodying the invention and illustrative of some of the principles thereof;

Figure 2 is a side view of the central part of the antenna structure of Figure 1 to show certain details thereof;

Figure 3 is an enlarged sectional view of the central part of the antenna struct-ure of Figure 1 to show certain constructional details thereof;

Figure 4 is a view in partial section of an antenna structure constructed in accordance with one embodiment of the invention showing the manner in which units or sections ofthe kind shown in Figure 1 may be axially aligned or stacked and energized from a common source of energization;

Figure 5 is an antenna pattern showing the radiation characteristics of a single section of the antenna structure shown in Figure 1; and

Figure 6 is an antenna pattern showing the radiation characteristics of the antenna shown in Figure 4. In Figure 1 is shown a single section 1 of an antenna structure embodying the invention comprising the hollow cylindrical conductor or mast 2, on which, and concentrically about which, the helical conductors 3 and 4 are mounted. The hollow cylindrical conductor 2 and the helical conductors 3 and 4 forming the antenna may be supported from a horizontal platform 5 on the top of a structural tower, for example, which is preferably llocated at the center of an area desired to be serviced by the radiations from the antenna.

The hollow cylindrical conductor 2, which preferably is made of steel or any suitable metal having similar structural properties, is suitably fastened to the plate 5 as shown. The helical conductor 3 surrounds one portion of the hollow cylindrical conductor 2 and the helical conductor 4 surrounds another portion of the hollow cylindrical conductor 2. The helical conductors 3 and 4 are wound about the hollow cylindrical conductor 2 with opposite winding sense; they extend in the same transverse direction about the cylindrical conductor but in opposite axial directions. The helical conductors 3 and 4 are maintained in insulated relationship with the hollow cylindrical conductor 2 by insulator assemblies 6. Y

The helical conductors 3 and 4 and the hollow cylindrical conductor 2 together form sections of a radiating transmission line. Electromagnetic energization applied between adjacent ends of the helical conductors 3 and 4 and the hollow cylindrical conductor 2 cause electromagnetic waves to travel along the transmission line sections away from the point of energization. As the electromagnetic waves travel along the transmission line sections they gradually decay in amplitude due to radiation of electromagnetic energy from the helical conductors 3 .v and 4. By making the helical conductors 3 and 4 0fy sucient length, reflections of electromagnetic waves from the remote ends of the transmission line sections can be made substantially insignificant in effect.

A radiative transmission line of the type in which reection effects are minimized by making the transmission line sufficiently long possesses the advantage of presenting a substantially constant impedance to the source of energization independent of frequency. The magnitude of this impedance is the characteristic impedance of the transmission line section. Another advantage in making the transmission line sufiiciently long is that no problem arises in properly terminating the tranmsission line to minimize reflections.

The radial spacing of the helical conductors 3 and 4 from the hollow cylindrical conductor 2 determines in large part the characteristic impedance of the transmission line sections; that is, the greater the spacing the higher the characteristic impedance and vice versa.

The radial spacing of the helical conductors 3 and 4 from the hollow cylindrical conductor 2 also determines in large part how long the helical conductors should be made in order to cause substantial radiation from the helical conductors with inappreciable reflection from the remote ends of these helical conductors.

In order to provide substantially uniform radiation in a plane transverse to the axis of the helical conductors 3 and 4, and concentration of energy in a narrow beam in the planes passing through the axis, it is essential that the conductor length of a single turn be substantially an integral number of operating wavelengths long, preferably two or greater. If a single turn is not equal to an integral number of operating wavelengths, a radiation pattern which is non-uniform in a plane transverse to the axis of the helical conductors 3 and 4 results.

It should be noted that if a large number of turns are used, the 4portions of the helical conductor in a particular transverse plane progressively farther from the end to which energization is applied are excited by currents of progressively different phase when the frequency of energization departs appreciably from a predetermined center frequency. Accordingly, in order to maintain the radiation characteristics of the antenna uniform for a broad band of frequencies, it is desirable to keep the number of turns to a reasonable value.

The concentration of radiation into a narrow beam in planes including the axis of the antenna is determined by the number of axially aligned turns in the helical conductors, by the axial distribution of these turns and by the distribution of current on the helical conductors.

In order further to confine the radiation in the axial planes, it has been found desirable to make the axial length of a single turn of the helical conductors equal to substantially one-half the operating wavelength of the antenna system.

Radiation is confined to the desired transverse polarization by having the helical conductors 3 and 4 extend in the same transverse direction about the cylindrical conductor 2 as viewed from the feed point but in opposite axial directions at a small rate of axial progression, for example, helical conductors 3 and 4 are arranged as left and right-hand helices of small pitch as best seen from Figure 2 of the drawing. With this arrangement the axial electric field components of the radiation from each helical conductor are small, and the axial electric field components from one helical conductor tends to cancel the axial electric lield components of the other helical conductor. With this arrangement, and by making the axial length of a single turn of the helical conductors equal to substantially one-half the wavelength of the radiation at the frequency of operation of the antenna, the fraction of energy having axial electric field polarization, as distinguished from the desired transverse polarization, is reduced to a small value.

More particularly, the electric field component of an electromagnetic wave radiated from a linear conductor is parallel to the length of the linear conductor and has an amplitude and direction related to the amplitude and direction of signal current flowing in the linear conductor. As the electromagnetic field radiates from the linear conductor, the orientations are maintained. Since incremental lengths of the helical conductors 3 and 4 may be considered as small linear conductors, the electric field components associated with their radiation have a similar parallelism. Thus the electric field components are linear and make an angle with the axis of the cylindrical conductor 2 which is the same as the pitch angle of the helical conductors 3 and 4.

Electric field components are superposed on each other as vector quantities, in accordance with the rules of vector algebra. When the electric field components radiated from the helical conductors 3 and 4 have the same directions and senses, they interact to produce resultant electric field components that are horizontally polarized. The symmetry of the helical conductors 3 and 4 about a horizontal plane ensure that the electric field components have the same directions. Their sense is determined by the instantaneous polarity of the signal current flowing in the helical conductors 3 and 4. Thus, when there are similar polarities of signal currents at corresponding points on the helical conductors 3 and 4, the electric held components will have the same senses. To produce the same polarity signal currents it is necessary to feed each helical conductor with the same signal.

The connection of the helical conductors 3 and 4 at their adjacent ends has the effect of connecting their characteristic impedances in parallel, thereby facilitating the matching of their impedances to the characteristic impedance of commonly used transmission lines.

The spacing of the helical conductors 3 and 4 with respect to the hollow cylindrical conductor 2 may be different for different axial locations of the helical conduc tors. It may be desirable, for example, to change the current distribution along the helical conductors in order to produce a different radiation pattern transverse to the axis of the helices, or it may be desirable to change the impedance of the radiating transmission line.

The pitch of the helical conductors 3 and 4 also may be made different for different axial locations of the helical conductors to cause the formation of a different radiation pattern. For example, in order to cause a tilt of the axis of maximum transverse radiation, the length of the upper turns of the helical conductor 3 are made a fraction shorter than is required for a radial radiation pattern and the length of the lower turns of the helical conductor 4 are made a fraction longer than is required for a radial radiation pattern.

The length of each of the helical conductors 3 and 4 is determined principally by the radiation per unit length of the helical conductors which is, in turn, determined principally by the radial spacing of the helical conductors 3 and 4 from the cylindrical conductor 2.

While the locations of the insulator assemblies 6, which support the helical conductors 3 and 4 and insulate them from the hollow cylindrical conductor 2 are not critical when good insulators of the kind described below are used, it has been found quite satisfactory to locate the insulator assemblies 6 three quarters of an operating wavelength apart measured along the helical conductors 3 and 4.

An actual antenna of the kind described in previous paragraphs and shown in Figure l was constructed for operation at 500 megacycles. `As stated above, the axial length of a single turn of the helical conductors is taken as substantially one-half the wave length at the center frequency of operation. The length of a single turn of the helical conductors 3 and 4 was made approximately equal to two wavelengths at the center frequency of operation. The radial spacing of the helical conductors 3 and 4 from the hollow cylindrical conductor 2 was made equal to about one-eighth of a wavelength. The diameter of the helical conductors 3 and 4 was about three-eights of an inch. Each of the oppositely extending helical conductors 3 and 4 had iive turns about the hollow cylindrical conductor l2. With this configuration a substantially uniform radiation was obtained in a plane transverse to the axis of the helical conductors 3 and 4. The radiation in the planes including the axis of the helical conductors 3 and 4 was coniined substantially to a narrow segment. The impedance presented by these two radiating transmission lines in parallel to the energizing source was of the order of 9() ohms substantially pure resistance. Substantial departures in the applied frequency above and below 500 megacycles over a broad band produced inappreciable change in the radiation characteristic of the antenna structure or in the impedance presented by the antenna structure to the energizing source. The foregoing proportions of an actual antenna structure were described for the purposes of illustration and are in no way to be construed as limitations of the invention.

A concept that is useful for defining the just described dimensional interrelations, is the ratio of the eiiective diameter of the helical conductors 3 and 4 to the effective diameter of the hollow cylindrical conductor 2. This ratio is of the order of 0.6 for the preferred embodiment just described on the basis of the following calculations.

The effective diameter -D of the helical conductors 3 and 4 is the diameter of the circle formed by projecting the helix on a plane perpendicular to the axis of the helix. The circumference of this circle, the axial length of a single helical turn, and the length of a single helical turn are interrelated by the Pythagorean theorem:

The turn length and axial length were 2 wavelengths and V2 wavelength respectively. Thus, in terms of operating wavelengths,

(frD)2= (2)2-(1/2)2, and D==0.62

The radial spacing of the helical conductors 3 and 4 and the hollow cylindrical conductor 2 was Ms wavelength, as stated above. Hence the effective diameter of the hollow cylindrical conductor in terms of operating wavelengths is and the ratio of the effective diameter of the hollow cylindrical conductors and the effective diameter of the helical conductors is The simplicity inthe means used to supply energization to the antenna structure is very important in any practical antenna structure. To this end a conductive member 7 is mounted inside of and concentrically with the hollow cylindrical conductor 2 by means of insulating spacers 8 and 9 to form a first internal transmission line 7 with the inside surface of cylindrical conductor 2. Connection is made from this transmission line 7 to a source of electromagnetic waves by a matching assembly 10.

The matching assembly 10 comprises a hollow cylindrical outer conductor 11 having the same inner diameter as the hollow cylindrical conductor 2 and an inner conductor member 12 having the same diameter as the conductive mem-ber 7. One end of the outer conductor 1'1 and one end of the inner conductor member 12 of the matching assembly are conductively fastened to the corresponding portions of the transmission line 7', to form in effect an extension of the internal transmission line. The conductive -member 7 is fastened to inner conductor member 12 by means of a conventional bayonet connection 13 as shown. The other end of the matchi-ng assembly 10 is covered with a conductive plate -11', shortcircuting the inner conductor member 12 to the outer conductor 11. The inner conductor 14 and outer conductor 15 of a second internal transmission line 1 6 are 6 connected at a point one quarter of a wavelength from conductive plate 11 along the inner conductor member 12. The other end of transmission line 16 is connected to a generator of electromagnetic oscillations or waves.

A capacitive tuning probe 17 conductively engages the outer conductor 11 and is located one quarter of a wavelength of the operating frequency from the-shorting plate 11. A similar capacitive tuning probe 18 is located at a distance three-eighths of a wavelength beyond* the iirst capacitive tuning probe 17 in a direction away from the shorting plate 11. These probes function to match the impedance of the transmission line 7' to the impedance of a transmission line 16 connected to the generator of electromagnetic waves.

A second radiating -unit or section 19, a part of which is shown in Figure 1, substantially similar to the section 1 previously described, may be connected to section 1 as shown to increase the directivity of the composite structure.

The helical conductor 22 of section 19 corresponds to helical conductor 4 of section 1 and each of these conductors extend in the same axial and transversedirections from corresponding reference points. The hollow cylindrical conductor 20 is fastened to the hollow cylindrical conductor 2 or these conductors may comprise a single integral member. The inner conductor 21 is connected through a suitable connection, for example, a bayonet type connection to the conductive member 7.

` The helical conductor 22 may be connected to helical conductor 3 by means of conductor 23 so that the helical conductors are in continuous conductive contact. The advantage in connecting the helical conductors together in this way is that these conductors may be grounded against lightning by grounding the helical conductors at a single point and also heater currents may be circulated through the helical conductors to melt ice and snow formation on the helical conductors as it will become more readily apparent below in connection with Fig. 4.

With regard to the operation of section 1 as a radiator it is immaterial whether the remote end of helical conductor 3 is open, connected to hollow cylindrical conductor 2, or connected through conductor 23 to helical conductor 22 since traveling waves existing on the helical conductors are attenuated to a small value -by the time they reach the remote ends of the helical conductors.

Figure 3 illustrates the central portion of the structure of Figure 1 in greater detail. The helical conductors 3 and 4 are energized from the lirst internal transmission line 7' through conductive probe 24. Probe 24 extending through an opening in hollow cylindrical conductor 2 has one end in spaced relation to conductive member 7 forming an adjustable capacitance therewith .and has the other end in threaded engagement with conductive plate 25 which connects the adjacent ends of -helical conductors 3 and 4. Insulator 26, located between hollow cylindrical conductor 2 and conductive plate 2S, main tains the helical conductors 3 and 4 in the proper spaced relationship to hollow cylindrical conductor 2. At the same point along the axial direction of the hollow cylindrical conductor 2 at which the probe 24 is located, a second radially adjustable capacitive element 27 is located in threaded engagement with the hollow cylindrical conductor 2 to form with the conductive member 7 a second adjustable capacitance.

In operation the capacitance associated with the inductance due to the finite length of the pro-be 24 may form a series resonant circuit, or a series circuit which is in ductive. The capacitance of the capacitive element 27 is in shunt with the series combination of the impedance of the radiating structure and the series circuit associated with thte probe 24. The aforedescribed series combination shunted by the capacitance associated with the capacitive element 27 can be converted to an equivalent impedance of resistance, inductance and capacitance allV 7 of the equivalent impedance are different. By adjusting the probe 24 and capacitive element 27 to particular values, this equivalent impedance can be made a pure resistance, different of course from the resistance of the original combination. The magnitude of this latter resistance with respect to the impedance presented at this same point of the transmission line 7' by radiating sections connected' beyond this point determines the percentage of the electromagnetic energy absorbed in this section. Thus, by adjusting the probe 24 and the capacitive element 27, the amount of energy absorbed by this radiating section can be controlled for reasons which will be mor efully apparent after consideration of Figure 4.

Since the first internal transmission line 7' is shunted by an impedance corresponding to the transformed impedance of the antenna, a means shown as a cylindrical conductive sleeve 2S is provided to match the impedance at the shunt point to the characteristic impedance of the transmission line to minimize standing waves on the line. Cylindrical conductive sleeve 28 has an axial length substantially equal to a quarter of a wavelength at the operating frequency and an outer radius greater than the radius of conductive member 7 but less than the inner radius of the hollow cylindrical conductor 2. The cylindrical conductive sleeve 28 concentrically surrounds and is in conductive engagement with conductive member 7 to form with the hollowV cylindrical conductor 2, a section of transmission line one quarter of a wavelength long whose impedance differs from the characteristic impedance of the transmission line 7'. One end of cylindrical conductive sleeve 28 is located adjacent the aforementioned shunted point and its outer radius is arranged so that the impedance of the shunted point is matched to the characteristic impedance of 7 in a manner well known to the art.

Figure 3 illustrates the manner in which conductive member 7 is maintained in spaced relation to hollow cylindrical conductor 2 by means of insulator 9. Insulator 9 may have a variety of shapes and may be pinned to hollow cylindrical conductor 2 by pins 29.

The insulator assemblies 6 may comprise an insulating rod 30 having one end pinned to the hollow cylindrical conductor 2 and the other end fastened to the helical conductor by a hook bolt as shown. The insulating rod 30 may be made from a number of materials. A polymer of triuorochloroethylene commonly referred to as Kel-F has been found quite suitable for this purpose because of its good electrical, mechanical, chemical, and thermal properties.

The simplicity of energization of an antenna structure made according to our invention will be further apparent from a consideration of the antenna structure of Figure 4 which is made up of four sections of units 1, 19, 31 and 32 substantially identical to the section shown in detail in Figure l, arranged in end to end or in stacked relationship in order to obtain a narrower radiation pattern in axial planes. One end of the coaxial transmission line 7' contained within the hollow cylindrical conductor 2 thereof is connected through a matching assembly 10 to a source of energization. The lower ends of the transmission lines 7 formed within the hollow conductive member portions 2 of sections 19, 3-1 and 32 are conductively connected to the upper ends of the corresponding conductors of the sections 1, 19 and 31, respectively. Thus, a continuous coaxial transmission line 7' is provided with energization for the individual radiating sections being tapped off at discrete points along the length of the coaxial transmission line. Preferably, the latter points are separated by an integral number of wavelengths from one another to facilitate the matching of impedances of the various sections under conditions of desired phase energization of each section.

The coaxial transmission line 7' thus formed is terminated by a plate 33 in the fourth section located at a point substantially one-quarter of a wavelength beyond 8 the point of energization of the helical conductor 2 of section 32 and which conductively short circuits the hollow cylindrical conductor 2 to the conductive member 7. Thus, in effect the transmission line is terminated by the impedance of the helical conductors of section 32.

This latter irnpedauce is made equal to the impedance of the transmission line 7'. A quarterwave matching section 34 of the kind described in Fig. 3 is provided in the vicinity of the energization point for the helical conductors of section 31 to provide the required impedance matching. Likewise, corresponding matching sections are provided in the second and first sections to minimize standing waves within the hollow cylindrical conductor 2. The capacitive probes 27, 35, 36 and 37 in the vicinity of the point of energization of respective sections 1, 19, 31 and 32 are adjusted in a manner explained in connection with Fig. 3 so that equal amounts of energy, or amounts in predetermined ratios, are supplied to each of the sections 1, 19, 31 and 32, respectively.

The wave transmission characteristics of the transmission line 7 of Fig. 4 in an actual structure constructed for operation at 500 megacycles were inappreciably affected over a broad band of frequencies above and below the center frequency of operation.

The axis of maximum radiation in the transverse direction may be tilted or changed by changing the phase of excitation of one or more of the sections. This may be done by mechanically rotating about the axis of the antenna one or more of the sections with respect to the others, thereby causing the elements of the helical conductors lying in a given transverse direction to be excited effectively in different phases. This action has the effect of tilting the radiation pattern of the antenna with respect to the axes of the helical conductors 3 and 4.

When the above referred to rotation is 180 mechanical degrees for an antenna in which the length of a turn is twice the wavelength of applied waves, or mechanical degrees for an antenna in which the length of a turn is three times the wavelength of the applied wave and so on, the elements of the helical conductors lying in a given transverse direction are excited in the same phase. Rotation of sections in this way may be used to compensate for the small variations in transverse radiation with transverse direction so that the corresponding variation for a composite antenna made up of several sections is less than the aforementioned variation for a single section.

lIn order to provide protection from lightning, the ends of the helical conductors of the four sections may be grounded separately to the respective sections of the hollow cylindrical conductor 2, or the helical conductors of the sections may be connected together by conductors 23 as shown in Figure l and only the helical conductor of section 32 (Fig. 4) grounded at point 38` as shown. When the latter ground connection is provided and adjacent ends of the helical conductors are connected together by conductors 23 as shown in Figure l, a source of power 39 may be connected between the open end of the helical hollow cylindrical conductor of the `first section and the conductor 2 to supply heater current to these conductors to melt formations of ice and snow thereon. The power source 39 may be of the direct current type as shown, or may be a 60 cycle source.

Beacon light 42 may be energized by connecting one electrode thereof to the hollow cylindrical conductor 2 and connecting the other electrode thereof to wire 40 which passes through conductive member 7. The other end of wire 40 is connected to one terminal of a source of power 41, the other terminal of which is connected to hollow cylindrical conductor 2.

Referring now to Figure 5, there is shown a graph 42 of the vertical pattern of the single structure of Figure l operated at 500 megacycles. The ordinates of this graph represent relative radiated power. The abscissa represents angular displacement measured with respect to zenith.

In Figure 6 is shown a graph 43 of the vertical radiation pattern for the antenna structure of Figure 4 operated at 500 megacycles. In this graph the ordinates represent relative radiated power and the abscissa represent displacement of the radiation with respect to zenith. It is readily apparent that the beam characteristics of the antenna system of Figure 4 can be changed by varying the number of sections utilized; that is, the greater the number of sections, the narrower will be the beam in the planes including the axis of the antenna.

It is readily apparent that the various sections of the composite antenna structure of Figure 4 may be energized if desired from different transmisison lines all connected to a common source.

Thus, it is seen that in accordance with the invention an antenna structure has been provided which has highly desirable radiation characteristics, which is easy to energi'ze and which will operate over a broad band of frequencies. The antenna structure is simple to install and easy to construct. The antenna structure is readily grounded against lightning strikes and is easily de-iced. lIn the antenna structure, the supporting mast is itself integral with the antenna structure. The antenna structure has a minimum resistance in high winds. These and other highly desirable advantages of the antenna structure are readily apparent to one skilled in the art.

This application is a continuation of copending application Serial No. 271,374 filed February 13, 1952, now abandoned.

While particular embodiments of the invention have been shown, it will of course be understood that the invention is not limited thereto, since many modifications, both in circuit arrangement and in the instrumentalities employed may be made. Therefore, it is contemplated by the appended claims to cover any such modifications as fall within the true spirit and scope of the invention,

What we claim as new and desire to secure by Letters Patent of the United States is:

l. An antenna comprising a linear conductor, a pair of conductors extending from a common point adjacent said linear conductor in the same direction about said linear conductor and in opposite directions along the length of said conductor, and a pair of energization terminals, one of said terminals being connected to said common point and the other of said terminals being connected to a point on said linear conductor.

2. An antenna comprising a first conductor extending along the axis of said antenna, a radiative conductor extending in axially progressive turns about said first conductor and in spaced relationship thereto, the spacing of said radiative conductor from said first conductor being substantially less than the spacing between corresponding points on adjacent turns of said radiative conductor, the ratio of the effective diameters of said first conductor to said axially progressive turns being greater than one-half, and circuit means connected between adjacent ends of said conductors.

3. An antenna comprising a first conductor extending along the axis of said antenna, another conductor extending in axially progressive turns about said conductor and in spaced relationship thereto, means to apply oscillations between one end of said other conductor and said first conductor, each of said turns being spaced substantially closer to said first conductor than to adjacent turns, the ratio of the effective diameters of said one conductor to said axially progressive turns being greater than one-half, whereby waves travel from said end along said other conductor and about said one conductor, said other conductor being spaced with respect to said one conductor in a manner that said waves are progressively radiated in said travel, and said other conductor having a length such that said Wave is attenuated by said radiation along the length of said other conductor to a small value at the opposite end from its value at said end.

4. An antenna comprising a first conductor extending along the axis of said antenna, a radiative conductor extending in axially progressive turns about said first conductor and in spaced relationship thereto, the spacing of said radiative conductor from said first conductor being substantially less than the spacing between corresponding points on adjacent turns of said radiative conductor, the ratio of the effective diameters of said first conductor to said axially progressive turns being greater than one-half, and circuit means connected between said conductors, the length of a turn of said radiative conductor being equal to an integral number of wave lengths at the frequency of operation of said antenna.

5. An antenna comprising a first conductor extending along the axis of said antenna, a radiative conductor extending in axially progressive turns about said first conductor and spaced therefrom, the radial spacing of said radiative conductor from said yfirst conductor being substantially less than the spacing between corresponding points on adjacent turns of said radiative conductor, the ratio of the effective diameters of said first conductor to said axially progressive turns being greater than one-half, and circuit means connected between said conductors, the length of a turn of said radiative conductor being equal to twice the wave length at the frequency of operation of said antenna.

6. An antenna comprising a tirst conductor extending along the axis of said antenna, a pair of generally helical radiative conductors extending in axially progressive turns in the same transverse direction but in opposite axial directions about said first conductor from a common point, and spaced from said first conductor, the spacing of said radiative conductor from said rst conductor being substantially less than the spacing between corresponding points on adjacent turns of said radiative conductor, and circuit means connected between said first conductor and said common point.

7. The antenna of claim 6 wherein the ratio of the effective diameters of said first conductor and said axially progressive turns is greater than one-half.

8. An antenna comprising a first conductor extending along the axis of said antenna, a pair of generally helical radiative conductors extending in axially progressive turns in the same transverse direction but in oppositeaxial direction about said first conductor from a common point, and spaced from said first conductor, the spacing of each of said radiative conductors from said first conductor being substantially less than the spacing between corresponding points on adjacent turns of each of said radiative conductors, circuit means connected between each of said conductors, the length of a turn of said radiative helical conductors being equal to an integral multiple of wave lengths at the frequency of operation of said antenna, and each of said radiative helical conductors having a length such that waves applied to said circuit means are substantially attenuated by radiation along the lengths thereof.

9. An antenna comprising a cylindrical conductor, a wire-like conductor extending in axially progressive turns from a point adjacent said cylindrical conductor about and along the length thereof, and spaced therefrom, circuit means connected between said conductors, the external conductive surface of a unit length of said wirelike conductor being substantially less than the external conductive surface of a corresponding unit length of said cylindrical conductor, the spacing of said wire-like conductor from said cylindrical conductor being substantially less than the spacing between corresponding points vof adjacent turns of said wire-like conductor and the ratio of the effective diameters of said cylindrical conductor to said axially progressive turns being greater than one-half, whereby the coupling between a portion of said wire-like conductor and an adjacent portion of said cylindrical conductor is substantially lgreater than 11 the coupling between said portion of said wire-like conductor and a corresponding portion of an adjacent turn of said wire-like conductor.

10. An antenna comprising a rst conductor, another conductor extending about and along the length of said first conductor, and spaced therefrom, the spacing of said other conductor from said first conductor being substantially less than the spacing between corresponding points on adjacent turns of said other conductor, whereby the coupling between adjacent turns of said other conductor is substantially less than the coupling between adjacent portions of said conductors thereby forming a transmission line from said conductors in which waves applied thereto travel about said first conductor, the ratio of the effective diameters of said first conductor to said other conductor about said rst conductor being greater than one-half so that appreciable radiation is had from said other conductor, the length of a turn of said other conductor being equal to an integral number of wave lengths at the frequency of operation of said antenna.

1l. An antenna comprising a first conductor, another conductor extending about and along the length of said rst conductor, and spaced therefrom, the spacing of said other conductor from said first conductor being substantially less than the spacing between corresponding points on adjacent turns of said other conductor, whereby the coupling between adjacent turns of said other conductor is substantially less than the coupling between adjacent portions of said conductors thereby forming a transmission line from said conductors in which waves applied thereto travel about said linear conductor, the ratio of ythe effective diameters of said first conductor to said other conductor about said rst conductor being greater than one-half, whereby appreciable radiation is had from said other conductor, the length of a turn of said other conductor being equal to an integral number of wave lengths at the frequency of operation of said antenna, said other conductor having a length such that substantially all of the wave energy applied to one end thereof is radiated before it reaches the other end.

12. An antenna comprising a hollow conductor extending along the axis of said antenna and having an aperture on the surface thereof, said aperture having a relatively small extension in the direction of the axis of said hollow conductor, a radiative conductor extending in axially progressive turns about said hollow conductor, and spaced therefrom, and having an end adjacent said aperture, the ratio of the effective diameters of said hollow conductor to said axially progressive turns being greater than one-half, and an electrical connection from said end of said radiative conductor through said aperture to the interior of said hollow conductor, means to apply oscillations between the interior surface of said hollow conductor and said electrical connection, the length of a turn of said radiative conductor being equal to an integral multiple of wave lengths at the frequency of said oscillations whereby energy is radiated uniformly in directions transverse to the axis of said antenna, said radiative conductor having a length such that said energy is substantially radiated from said radiative conductor before said energy reaches the other end thereof.

' 13. An antenna comprising a conductive element, a radiative conductor developed about said conductive element in turns and in spaced relationship thereto, the ratio of the effective diameters of said conductive element to said turns being greater than one-half, and feeding means adapted to feed energy between said radiative conductor and said conductive element.

14. The antenna of claim 13, said radiative conductor having a length such that the energy is attenuated by radiation along its length to a small value at one end of said radiative conductor.

15. The antenna of claim 13 wherein the length of each of said turns is substantially equal to an integral number of operating wavelengths.

16. The antenna of claim 13 wherein said radiative conductor is developed about said conductive element as a plurality of turns each having a length equal to an integral number of operating wavelengths, the length of said radiative conductor being such that the energy is attenuated by radiation to a small value at one of its ends.

References Cited in the le of this patent UNITED STATES PATENTS 1,684,009 Brown Sept. 11, 1928 2,354,332 Polydoroif July 25, 1944 2,405,123 Fyler Aug. 6, 1946 2,511,611 Wheeler June 13, 1950 OTHER REFERENCES Antennas by J. D. Kraus, copyright 1950 by McGraw- Hill Book Co., pp. 179 and 214.

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