US2318237A - Antenna feed system - Google Patents

Description

Patented May 4, 1943 Nils E. Lindenblad', Rocky Point, N'. to Radio Corporation of America,

of Delaware Y., assignor a corporation Application June 8, 1940, Serial No. 339,468

' Claims.

This invention relates to electrical transmission systems and, more particularly, to a system for feeding a load, such as an antenna system, simultaneously with energy from a plurality of transmitters operating at different frequencies.

One of the objects of the present invention is to enable a plurality of sources of oscillations operating at different frequencies to feed the same load system simultaneously over different branch circuits in such a manner that there is no reaction between the sources over a wide range of frequencies.

A further object of the invention is to provide an arrangement for coupling a pair of independent single-sided transmission lines to a single transmission line carrying the energy from both of said independent lines without interaction between the independent lines.

' Still a further object of the present invention is to enable four transmitters operating at different frequencies to feed a turnstile' antenna without interaction between the transmitters.

In accordance with a feature of the invention there is employed between One transmitter and an intermediate loop circuit a transformer for energizing the intermediate circuit in a balanced or .push-pull relationship. The intermediate loop circuit may comprise a pair of balanced transmission lines each having a line conductor surrounded by a grounded shield. Across the intermediate circuit is connected a half wave loop c rcuit with the second transmitter connected to its midpoint. Energy from the second transmitter is thus introduced into the balanced or intermediate circuit in a push-push or in-phase relationship. I

An output transmission line is then connected to the intermediate circuit at such point that the lengths of line from the output line to the points of introduction of energy from the two transmitters differ by an amount which is an odd, multiple of half waves for the first transmitter and an even and adjacent multiple of half waves for the second transmtter. In this way the push-pull voltages feeding into the differential length lines, when these differ in length by an Odd multiple of half waves, add up correctly for feeding into the s ngle line utilization circuit.

The push-pull voltages also add up equally correct at a frequency at which the differential length lines differ in length by an even multiple of half waves.

he present invention further contemplates utilizing a phase quadrature type of utilization circuit or load in the way disclosed in my 00- pending application No. 338,177, filed May 31, 1940, in combination with the circuits described above to feed the power from four transmitters into'a single load. In accordance with this aspect of my invention, a tumstile antenna'of the type shown in my copending application, SerialNo.

208,573, -filed May 18, 1939, now Patent No.

2,239,724, issued April 29, 1941, may be simultaneously energized with power from four independent transmitters.

Further objects, features and'advantage of the present invention will appear from the following detailed description which is accompanied by a drawing in which Figure 1 shows an embodiment of the invention, while Figure 2 shows a modification and further development of the form shown in Figure 1.

Referring, now, to Figure 1, there is shown a single-sided concentric cable or transmission line composed of an outer sheath 5 and an inner conductor and energized from transmitter A. I have also shown a pair of lines constituting an intermediate coupling circuit and adapted to be energized in a push-pull relationship from transmitter A, one of said line's being composed of an outer sheath 25 and an inner conductor 26 and the other being composed of an outer sheath 35 l and an inner conductor 36. The outer sheaths 5, 25 and 35 may be grounded if desired. The inner conductor 26 is directly connected to inner conductor 6 and is therefore energized in the same relationship as the inner conductor 6. The I other inner conductor 36 is directly connected to the end of the sheath 5 of the single-sided line from transmitter A and is therefore energized in phase opposition to the inner conductor 26. In order to completely uncouple the last quarter wave section of the single transmission line 5,

6 from the remainder of the same so that one side of the balanced circuit is not shorted, I have provided an outer shell 7 surrounding the end of sheath 5. The'shell I has a length equal to a quarter of the mean operating wavelength and is connected to sheath 5 of the single transmission line at its end remote from the end of sheath 5. The length of the conducting path of the outer surface of sheath 5 is of such length that the point of connection of 36 at the free end of sheath 5 is electrically freed from the outer conductor of the transmission line 5,6 as far as radio frequency potentials are concerned. This eii'ect is due to the fact that the length, of the conducting path including the outer surface of sheath 5 is substantially equal to a quarter wavelength at the operating frequency of transmitter mission line from A and, pedance conductor 36. take place from the current flowing along the outer surface of sheath since any current .flowing along the inside of the outer shell I is equal and of opposite direction. Thus it will be seen that at the frequency for which the junction is designed the balanced line will not be subject to any unbalancing effects from the connection to the single line. This condition is, however, true only when the surrounding section approximates a quarter of the length of the operating wave. If the frequency is changed or if the operating frequencyis widely modulated some current will lealr' over the edge of the single transmission line, sheath 5 and the push-pull output circuit will be unbalanced. In order to overcome this effect and maintain perfect balance over a wide frequency band, I employ a second quarter wave shell section arranged in an end-on relationship with the outer shell 1; Within the second shell section I is an inner conductor i5 having the same diameter as the outer diameter of sheath 5 of the single transmission line. Though I have referred to shells l and i1 separately forconvenience in description, it should be understood that in practice it may be found more convenient to form them in one continuous piece. Theinner therefore, presents a distinctly high im-- conductor i5 is connected at its inner end to the center conductor 5 of the single line and, also, to the center conductor 26 of one of the balanced lines. The other end is electrically connected to the end of shell II. The points of connection, and

the dimensions of the parts are so chosen, that the junction is perfectly symmetrical with respect to a center plane perpendicular to the axis of shells I, i1. Ordinarily, shell l1 has the same diameter as shell I and conductor i5 has the sam diameter as sheath 5. with this construction it will be seen that looking from the pushpull line toward the junction along either con ductor 26 or conductor 36, an exactly similar set of conditions is encountered. Therefore, for a wide frequency band orfor frequencies varying widely from the frequency for which the Junetion is designed, the reactive drain on conductor 38 due. to an improper length of shell 1 is duplicated by an equal drain on conductor by shell portion H.

v From the foregoing description it will be seen that transmitter A feeds conductors 25, in a push-pull relationship through a single-sided line 5.

In order to simultaneously feed the same balanced push-pull lines from a second transmitter .B, a pair of conductors i3, i5 is connected to the adjacent ends of shell 5 and conductor IS. The length of each of the conductors i6, i6 is equal to a quarter'of the mean operating wavelength of the system. These conductors are connected to the central conductor of a single-sidedtranstransmitter B composed of central conductor 6' and an outer sheath 5'. It will be seen that there is in effect a half wave loop connected across the adjacent ends of conductors 26 and 36. Such a. half wave loop will, of course, not adversely affect the operation of the circuit as far as transmitter A is concerned. The energy from transmitter B is fed to conductors 25 and 36 through exactly equivalent lengths of line and the resultant energy is therefore in an in-phase or push-push relationship.

Since it is desired to feed the energy from both transmitters to a load through a single transmisthereto at the point of connection of I Furthermore, no radiation can anced lines.

sion line 30, a loop 31 is placed in one of the balthe connections from elements 5 and iii to the inner conductor of a single transmission line 30 have a differential length which is an odd multiple of a half wavelength for the frequency of transmitter A and an even and adjacent multiple of a half wavelength for transmitter 13. Thus, the push-pull voltages on conductors 26 and 36 from transmitter A add up correctly for feeding into transmission line 30. Likewise, the pushpush voltages on conductors 25 and 36 from transmitter l3 add up in a correct relationship for feeding intotransmission line 30. Furthermore, any energy at the frequency of transmitter A reflected back from the antenna is of an incorrect wavelength to enter transmission line 5', 6 from conductors i6, I6, in an in-phase relationship and a similar situation exists with respect to energy from transmitter B in transmission line 5, 5.

Figure 2 shows a further development of the present invention which is capable of feeding the energy from four transmitters into a single turnstile antenna of the type referred to above without permitting any interaction between the separate transmitters. The construction of the elements within boxes I0 in Figure 2 is the same as that shown within box In in Figure 1 and the operation thereof may be understood by referring to the detailed disclosure in Figure 1 and the deunit similar to that described with reference to Figure 1 is provided. The energy in transmission lines 225 and 235 comprises the energy from transmitters A and B in a push-push relationship and energy from transmitters A, B in a pushpull relationship. Since, in this embodiment, it is desired to obtain a phase quadrature relationship between the energies at the utilization end of transmission lines 225 and 235, a phase shifting loop 331 having a length equal to a quarter of the mean operating wavelength is introduced in one of the transmission lines. While it is shown in transmission line 225 it is obvious that it may equally well be placed in line 235.

Since the turnstile antenna 350 requires two sets of push-pull voltages mutually in phase quadrature with each other and each of transmission lines 225 and 235 are each single-sided lines carrying energy in phase quadrature, it is only necessary to terminate each line in a coupling circuit for transforming each of these transmission lines into push- pull lines 325, 326, 335, 336. The end of transmission line 225 is surrounded by a sleeve 3 having a length equal to a half the length of the mean operating frequency. In an end-on relationship with the transmission line 225 and within sleeve 3" is a conductor 3i5 connected to the inner conductor of transmission line 225. Lines 325 and 326 are connected to the adjacent ends of conductor 3i5 and 305 and are thereby energized in phase opposition. The operation of the coupling circuit whereby any inactive unbalance is compensated is the same as described with referenceto the structure within box in in Figure 1 wherein trans- The loop 31 has such length that 2,818,287 mission line 5, 6 is connected to transmission lines 25, 25 and 35, 36. A more complete analysis may be obtained by reference to my copending application, Serial No. 276,193, filed May 27, 1939, now

1 Patent No. 2,231,839, issued Feb; 11, 1941.

A similar coupling circuit is connected to the end of transmission line 235 and supplies pushpull energy to conductors 335 and 336. The turnstile antenna 350 is indicated merely by a pair of crossed dipoles. Opposite ends of-one dipole are fed from transmission lines 326 and 325 while opposite ends of the other dipole are fed from lines 335 and 336. Since the energy inthe'two dipoles is in a phase quadrature relationship a rotating field will be radiated.

While I have shown four transmitters feeding a single tiered turnstile antenna, it should be clearly understood that the turnstile antenna can be of the multiple type to obtain increased vertical directivity. Furthermore, additional transmitters can be coupled to the antenna in the same way as outlined for transmitters A, A and B, B.

While I have shown and particularly described several embodiments of my invention, it is to be distinctly understood that my invention is not limited thereto but that further modifications within the scope of my invention may be made.

I claim:

1. In combination, a first single transmission line having an outer sheath and an inner 'conductor, and having a first source of oscillations connected thereto, a pair of transmission lines. a connection from the inner conductor of said single line to a conductor of one of said pair of i lines, a connection from the sheath of sa d single line to a conductor of the other of said pair of lines, an outer shell surrounding the end portion of said single line, said shell being connected to of the mean operating wavelength from the end of said single line, and a balancing circuit including an inner conductor connected to the inner conductorof said single line and having a diameter equal to the of said single line and an outer shell having a diameter equal to the diameter of the first outer shell and connected thereto, the inner conductor and outer shell of said balancing circuit being connected together at a distance equal to a quarter of the mean operating wavelength from said connections, a second single transmission line having an outer sheath and an inner conductor, and having a second source of oscillations connected thereto, a connection from its inner conductor to each of said pair of lines, said connections each having a length equal to a quarter of the length of the mean operating wavelength, a single output circuit connected to the end of said pair of lines, said pair of lines having a differentiallength which is an even multiple of a half wavelength of said first source and an odd and adjacent multiple of said second source.

2. In combination, a pair of sources of oscillations of difierent wavelengths, a firstconcentric line coupled to a first one of said sources and having an outer sheath and an inner conductor, a balanced pair of concentric transmission l'nes, each having an outer sheath and an inner conductor, a connection from the inner conductor of said first line to an inner conductor of one of said pair of lines, a connection from the end of the sheath of said first line to the inner conductor of the other of said' pair of lines, an outer shell surrounding the end of said single line and said sheath at a distance equal to a quarter diameter of the outer sheath line coupled to a having an outer sheath and an inner conductor,

second line, said its junction with said vpair of lines, said shell being connected to the outer sheath of said single line at a distance equal to a quarter of the mean wavelength from the end of said sheath, a second concentric line coupled to the second of said sources, connections from each of the inner conductors of said pair of 'said lines to said second line, said last connections each having a length equal to a quarter or the mean operating wavelength, said pair of lines having difierent lengths and being connected together at their other end, the wavelengths of said pair of sources being so related that the difierential length of said pair of lines is an even multiple of a half wavelength of said first source and an adjacent and odd multiple of a half wavelength of said second source.

3. In combination, a pair of sources of oscillations of diiferent wavelengths, a first concentric line coupled to a first one of said sources and having an outer sheath and an inner conductor, a balanced pair of concentric transmission lines, each having an outer sheath and an inner conductor, a connection of said first line to an inner conductor of one of said pair of lines, a connection from the end of the sheath of said first line to the inner conduc tor of the other of said pair of lines, an outer shell surrounding the end of said single line and its junction with said pair of lines, said shell being connected to the outer sheath of said single line at a distance equal to a quarter of the length of said first source from the end of said sheath, a second concentric line coupled to the second of said sources, connections from each of the inner conductors of said pair of said lines to said last connections each having a a quarter of the wavelength of said first source, said pair of lines having different lengths and being connected together at their other end, the wavelengths of said pair of sources being so related that the difierential length of said pair of lines is an even multiple of a half wavelength of said first source and an adjacent and odd multiple of a half wavelength of said second source. 1

4. In combination, a pair of sources of oscillalions of difierent wavelengths, a first concentric first one of said sources and a balanced pair of concentric transmission lines, each having an outer sheath and an inner conductor, a connection from the inner conductor of said first line to an inner conductor of one of said pair of lines, a connection from the end of the sheath of said first line to the inner conductor of the other of said pair of lines, an outer shell surrounding the end of said single line and ferential length of I multiple of a'half wavelength of said first source and an adjacent and odd multiple of a half wavelength of said second source.

5. In combination, a pair of sources of oscillations of different wavelengths, a first concentric li-ne coupled to a first one of said'sources and from the inner conductor each having an outer .length from having an outer sheath and an inner conductor, a balanced pair of concentric transmission lines,

sheath and an inner conductor, a connection from the inner conductor of said first line to an inner conductor of one of said pair of lines, a connection from the end of the sheath of said first line to the inner conductor of the other of said pair or lines, an outer shell surrounding the end of said single line and its junction with said pair of lines, said shell being connected to the outer sheath of said single line at a distance equal to a quarter of the length of said first source from the end of said sheath, a pair of connections of a length equal to a quarter of the length of said first source from ach of said connections to the second of said source, said pair of lines having different lengths and being connected together at their other end, the wavelengths of said pair of sources being so related that the differential length of said pair of lines is an even multiple of a half wavelength of said first source and an adjacent and odd multiple of a half wavelength of said second source.

6. In combination, a, pair of sources of oscillations of different wavelengths, a first concentric line coupled to a first one of said sources'and having an outer sheath and an inner conductor, a balanced pair of concentric transmission lines, each having an outer sheath and an inner conductor, a connection from the inner conductor of said first line to an inner conductor of one of said pair of lines, a connection from the end of the sheath of said first line to the inner conductor of the other of said pair of lines, an outer shell surrounding the end of said single line and its junction with said pair of lines, said shell being connected to the-outer sheath of said single line at a distance equal to a quarter of the mean wavethe end of said sheath, and a balancing circuit including an inner conductorhaving a diameter equal to the diameter of the outer sheath of said single line connected to the inner conductor 'of said single line and an outer shell having adiameter equal to the diameter of said first outer shell and connected thereto, the inner conductor and outer shell of said balancing cirv cult being connected together at a distanc equal to a, quarter of the mean operating wavelength from the end of said first line, said pair of lines having different lengths and being connected together at their other end, the wavelengths of said pair of sources being so related that the differential length of saidpair of lines is an even multiple of a half wavelength of said first source and 'an adjacent and odd multiple of a halt wavelength of said second source.

7. In combination, a pair of sources of oscillationsoi different wavelengths, a first concentric line coupled to a first one or said sources and having an outer sheath and an inner conductor,

a balanced pair of concentric transmission lines,

each having an outer sheath and an inner conductor, a connection from the inner conductor of-said first line to an inner conductor of one of said pair of lines, a connection from the end or the sheath of said first line to the inner conductor of th other of said pair of lines, an outer shell surrounding the end or said single line and its junction with said pair of lines, said shell being connected to the outer sheath of said single line at a. distance equal to a quarter of the length of said first source from the end or said sheath, and a balancing circuit including an innerconductor having a diameter equal to the diameter or the inner conductor of said single line andgan outer shell having a diameter equal to the diameter of said first outer shell and connected thereto, the inner conductor and outer shell of said balancing circuit being connected together at a distance equal to a quarter of the length of said first source from the end of said first line, said pair of lines having different lengths and being connected together at their other end, the wavelengths of said pair of sources being so related that the difierential length of said pair of lines is an even multiple of a half wavelength of said first source and an adjacent and odd multiple of a half wavelength of said second source.

8. In combination with means for coupling a single concentric lin having an outer sheath and an inner conductor to a balanced circuit having a pair of conductors adapted to be energized in an opposing phase relationship, said line having a first source of oscillatory energy connected thereto, a connection from-said inner conductor \to one of said pair of conductors, a connection from the end of said outer sheath to the other of said pair of conductors and an outer shell surrounding the end of said single line and its junction with said pair of lines, said shell being connected to said outer sheath at a distance from its end equal to a quarter'of the length of the mean operating wavelength of means for simultaneously energizing said pair of conductors in an in-phase relationship from a second source of oscillatory ener y, comprising a pair of connections to said pair of conductors from a said second source, said connections each having a length equal to a quarter of the mean operating wavelength, said pair of conductors being connected to a single output conductor, said pair of conductors having a difierential length which is an even multiple of a half wavelength of said first source and an odd and adjacent multiple of said second source.

9. In a transmission line circuit a pair of conductors simultaneously energized at one end from one source of energy in a push-pull relationship and from another source of energy in a push-push relationship, said conductors having a differential length which is equal'to an even multiple of a half wavelength of said first source and an odd and adjacent multiple of a halt wavelength of said second source, and means for connecting said conductors together at their other ends and to a load circuit whereby said load circuit is simultaneously energized from both of said sources.

10. In a transmission line circuit a pair of conductors simultaneously energized at one end from one source of energy in a push-pull relationship and from another source of energy in both of said sources.

11. An oscillatory system comprising two pairs of sources of energy, each pair energizing a single transmission line through a circuit as set forth in claim 9, means for combiningthe energy from said single transmission lines into a pair of lines in a phase quadrature relationship, and means for obtaining push-pull energy from each 'of said pair of lines.

1 2. An oscillatory system comprising two pairs of sources of energy, each pair energizing a single transmission line through a circuit as set forth in claim 10, means for combining the energy from said single transmission lines into a pair of lines in a phase quadrature relationship,

, length of said one frequency and an odd and adenergy from said single transmission lines into a balanced circuit in a phase quadrature relationship, said means comprising a pair of concentric and an inner conductor, a connection from the inner conductor of one of said single transmission lines to each of the inner conductors of said second pair of lines, said connections having a length equal to an odd multiple, including unity, of the mean operating wavelength, a connection from a conductor of the other of said single transmission lines to the end 01 one of said second -pair of lines, a connection from the other conductor of the other of said single transmission lines to the other of said second pair of lines, an outer shell surrounding the end of the other of said single transmission lines,-said shell being connected to the second mentioned conductor of said line at a distance equal to a quarter of the length of the operating wave from the end thereof, said outer shell extending beyond the end of said other line a-quarter of the mean operating wavelength and an inner conductor within the extending portion of said shell connected to the first mentioned inner conductor of said second pair of lines, said outer shell and said last mentioned inner conductor being connected together a distance equal to a quarter of the length of the transmission lines each having an outer sheath mean operating wavelength beyond the point of connection to said inner conductor, one of said second pair of lines being a quarter wavelength longer than the other whereby phase quadrature output is obtained.

14. In combination, a pair of conductors coupled at one end to one transducer means operative at one frequency in a push-pull relationship and to another transducer means operative at a difierent frequency in a push-push relationship, said conductors having a difi'erential length which is equal to an even multiple ot a half wavejacent multiple of a half wavelength of said different frequency, and means for connecting said conductors together at their other ends and to a third transducer means.

15. In combination, a pair of transducer means operative with oscillations of different wavelengths, afirst concentric line coupled to a first one of said transducer means and having an outer sheath and an inner conductor, a balanced pair of concentric transmission lines, each havingan outer sheath and an inner conductor, a

connection from the inner conductor of said first line to an inner conductor of one of said pair of lines, a connection from the end of the sheath of said first line to the inner conductor of the other of said pair of lines, an outer shell surrounding the end of said single line and its junction with said pair'of lines, said shell being connected to theouter sheath of said single line at a distance equal to a quarter of the wavelength of "the oscillations for said first transducer means from \the end of said sheath, a pair of connectionsof a length equal to a quarter of the wavelength of the oscillations for said first transducer means from each of said connections to the second of said transducer means, said pair of lines having different lengths and being connected together and to a third transducer means at their other end, the operating wavelengths of said pair of transducer means being so related that the difierential length of said pair of lines is an even multiple of a half wavelength of said first transducer means and an adjacent and odd multiple of a half wavelength of said second transducer means.

NILS E. LINDENBLAD.

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