US2341408A

US2341408A - Antenna feed system

Info

Publication number: US2341408A
Application number: US338177A
Authority: US
Inventors: Nils E Lindenblad
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1940-05-31
Filing date: 1940-05-31
Publication date: 1944-02-08
Anticipated expiration: 1961-02-08

Description

Feb. 8, 1944.

N. E. LINDENBLAD ANTENNA FEED SYS TEM Filed May 31, 1940 7'0 LOAD I I W TRA NSM/ TTERS INVENTOR. A/Ilj. L/NDENBLAD BY M5 ATTORNEY.

Patented Fgba 8,

ANTENNA FEED SYSTEM Nils n. Lindenblad, Rocky Point, N. 1%., assignor to Radio Corporation of America, a corporation of Delaware Application May 31, 1940, Serial No. 338,177

12 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 two transmitters operating at different frequencies.

One of the objects of the present invention is to enable two transmitters 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 transmitters 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 pair of transmission lines delivering the energy from both of said independent lines in a phase quadrature relationship at the load terminals.

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

In accordance with a feature of the invention there is employed between one transmitter and the load circuit a transformer for converting from a single-sided circuit to a circuit balanced with respect to ground. Across the balanced circuit is connected a half wave loop circuit with the second transmitter connected to its midpoint. Energy from the second transmitter is thus introduced into the balanced or push-pul circuit in a push-push relationship. Then, in order to obtain a phase quadrature relationship at the outactive components introduced into the lines due to the heretofore mentioned connection between the single-sided and push-pull circuits..

Further objects, features and advantages 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 of the form shown in Figure 1.

Referring, now, to Figure 1, there is shown a single-sidedtransmisslon line in the. form of a concentric cable having an outer sheath 5 and an inner conductor 6, and energized from transmitter A. I have also mown a pairof lines adapt- 44) is equal and of opposite direction.

be seen that at the frequency for which the iunc tionship as the inner conductor 6. The 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 25. In order '15 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 I surrounding the end of sheath 5.

The shell I is a quarter of the length of the operating wave long and is connected to sheath 5 of the single transmission line at its end remote from the open end of sheath 5.' The length of the conducting path within the outer shell I and including the outer surface of sheath 5 is of such length that the point of connection of con- 1 ductor 36 is electrically freed from the outer conductor of the transmission line 6, 6 as far as radio frequency potentials are concerned. This eflect is due to the fact that the length of' the conducting path including the outer surface of sheath 5 and the inner surface of shell 1 is substantially equal. to a half wavelength of the operating frequencyof transmitter A and therefore presents a distinctly high impedance thereto at the point of connection of conductor 38. Furthermore, no radiation can take place from the current flowing along the outer surface of sheath 5 since the current flowing along the inside of the outer shell 5 Thus it will tion is designed the balanced line will not be subiect to any unbalancing effects from the connection to the single line. This condition is, howit ever, 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 frequency is widely modulated some current will leak over the edge of sheath 5 of the single transmission line,cand 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 l1 arranged in as an end-on relationship with and having'the same diameter as the outer shell I. Within the second shell section I! is an inner conductor I! having the same diameter as the outer diameter of sheath 5 of the single transmission line 5. Though I have referred to shells I and I1 separately for convenience in description, it should be understood that in practice it may be found more convenient to form them in one continuous piece. The inner conductor [5 is connected at its inner end to the center conductor 6 of the single line and, also, to the center conductor 26 of one of the balanced lines. The other end of inner conductor I5 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 'l, I 1. With this construction it will be seen that looking from the push-pull line toward the junction along either conductor 26 or conductor 36, an exactly esimilar set of conditions is encountered. Therefore, for a-wide frequency band, or for frequencies varying widely from the frequency for which the Junction is designed, the reactive drain on conductor 36 due to an improper length of shell I is duplicated by an equal drain on conductor 28 by shell portion I1.

From the foregoing description it will be seen that transmitter A feeds transmission lines 25,

35 in a push-pull relationship through a singlesided line 5.

transmitter B and having a central conductor 6' and an outer sheath 5'. It will be seen that there is in eflect a half wave loop connected across the adjacent ends of conductors 28 and I6. Such a half wave loop will, of course, not adversely afiect the operation of the circuit as far as transmitter A is concerned. The energy from transmitter B is fed to conductors 26 and 36 through exactly equivalent lengths of line and is therefore in an in-phase or "push-push" relationship.- Since it is desired to feed the energy from both transmitters to the load in a phase quadrature relationship, a loop 3l'is placed in one of the transmission lines. This loop has a length such that one output transmission line is a quarter of the mean operating wavelength, or an odd multiple thereof, longer than the other.

Figure 2 shows a more complicated arrangement required to eliminate the still existing but balanced reactance of the coupling arrangement at frequencies remote from the mean operating frequency. The construction of each of the portions within the dotted box III is the same as shown in box III in Figure -1. a In Figure 2 each of the input and output lines to boxes III are connected together through lines which differ in length by an odd multiple, including unity, of a quarter of the mean operating wavelength. Since all physical dimensions in each coupling unit are the same the reactance and resistance of'both sections is exactly the same and due to the quarter wave spacing each compensates for the other on each side of themean operating frequency. The theory upon which this depends is disclosed in more detail inapatent to E. C. Cork, et al.. #2,165,96l, granted July 11; 1939. p

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

I claim: 7

1. Means for supplying energy to a high frequency load simultaneously at two different frequencies, a first and a second source of oscillations, each of said sources being adapted to supply one of said diii'erent frequencies, a pair of transmission lines coupled to said load, means for applying energy from the first of said sources to said pair of transmission lines in a push-pull relationship, means for applying energy from the second of said sources in an in-phase relationship, one of said lines having a length from said 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 said sheath at a distance equal to a quarter of the mean operating wavelength from the end of said single line, and a balancing circuit including an inner conductor connected to the inner conductor of said single line and having a diameter equal to the diameter of the outer sheath 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 the end of said single transmission line, a second single transmission line having an outer sheath and an inner conductor, 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, one of said pair of lines being a quarter of the mean operating wavelength longer than the other.

3. In combination, a first single transmission line having an outer sheath and an inner conductor and a pair of transmission lines, a connecsingleline, said shell being connected to said sheath at a distance equal to a quarter of the mean operating wavelength from the end of said single line, and a balancing circuit-including an inner conductor connected to the inner conductor of said single line and an outer shell connected to said first outer shell, the inner con-, ductor and outer shell of said balancing circuit being connected together at a distance equal to,

a quarter of the mean operating'wavelength from said last connections, a second single transmission line having an outer sheath andan inner conductor, a separate'connection from its inner conductor to each of said pair of lines, said separate connections each having a length equal to a quarter of the length of the mean operating wavelength, one of. said pair of lines being aquarter of the mean operating wavelength longer than the other. Y

4. In combination, a first single concentric line having an outer sheath and an inner conductor, a pair of concentric transmission lines each having an outer sheath and an inner conductor, a connection from the inner conductor of said single line to an inner conductor of one oi said pair 'of lines, a connection from the end of the sheath oisaid single line to the inner conductor of the other of said pair of lines, an outer shell surrounding the end of said single lines 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 operating wavelength from the end of said sheath, and a balancing circuit, including an inner conductor having 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 a diameter equal to the diameter of said first outer shell and forming an extension thereof, 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 the end adjacent the end of said single line, a second single transmission line having an outer sheath and 'an inner conductor, a pair of connections from its inner conductor to said pair of lines, said pair of connections each having a length equal to a quarter of the length of the mean operating wavelength, one of said pair of lines being a the operating wave longer than the other of said branches, a connection from one of said pair of lines to each of the inner conductors of said branches, a connection from the inner conductor of the other of said pair of lines to the end of the outer sheath of each of said branches, said connections differing in length by an odd multiple, including unity, of a quarter of the operating wavelength, an outer shell surrounding the end ing connected to the outer sheath of said length of the operating wave from the end of each branch, said outer shell extending beyond the ends of said branches, and an inner conduc- -tor within the extending portion of said shells and connected to the inner conductors of said t branches, each of-said outer shells and said last mentioned innerconductors being connected together a distance-equal to a quarter of the length "of the operating wave beyondvthe point of connection to said inner conductors, a second single concentric transmission line having an outer sheath and an inner conductor, a half wavelength loop connected across the end of each of said first single line branches, connections from a midpoint on each of said loops to said second single line, said last connections difiering in length .by an odd multiple, including unity, of a quarter wavelength; one of said pair of lines being aquarter wavelength longer than the other whereby phase quadrature output is obtained.

6; In combination, a pair of transmission lines adapted to supply energy to a load in a phase quadrature relationship, means for energizing said transmission lines in a push-pull relationship entirely irom afirst source of oscillations of one frequency, and means for simultaneously energizing said lines in an in-phase relationship entirely from a second source. of oscillations of a different frequency, one of said pair of lines being a quarter of the mean operating wavelength longer than the other.

'7. In combination, a first and a second transmission line and a pair of concentric trsion lines, each of said lines having an inner conductor and an outer shell, each of said first and second transmission lines being connected to a source of oscillations of difierent frequencies, a-

coupling circuit for energizing the inner conductors of said pair of lines in a push-pull relationship from only the source connected to said first transmission line,- connections from the inner conductors of said pair of lines to the inner conductor of said second line for simultaneously energizing said pair of lines in. an in-phase relationship from only the source connected to said second line.

8. In combination, a pair of transmission lines adapted to supply energy to a load in a phase quadrature relationship, means for energizing said transmission lines in a push-pull relationship entirely from a first source of oscillations, and means for simultaneously energizing said lines in an in-phase relationship entirely from a second source of oscillations, one of said pair of lines being a quarter of the operating wavelength longer than the other, and means connected to one of said pair of lines for neutralizing the undesired unbalance on said pairs due to the reactance of said first means.

9. In combination, a pair of transmission lines and a first and a second single transmissionline, each connected to a source of high frequency energy, a coupling circuit for energizing said pair of lines in a push-pull relationship from one of said single lines, connections from said pair-of lines to the other of said single lines for simultaneously energizing said pair of lines in an inphase relationship, said coupling circuit including means for maintaining saidpair of transmission lines balanced, .a second coupling circuit conof each branch of said single line, said shells bebranches at a distance equal to a quarter of the nected to said one single line and said-pair of lines, a second set-of connections from said pair of linesto said other single line, the connections of said second coupling circuit and said second set of connections diflering inlength from said first mentioned connections by an odd multiple, including unity, of a quarter of the mean operating wavelength.

10. An arrangement as set forth in claim 7 in which a second set of coupling circuits and con"- nectio'ns connecting said 'singlelines and said equal to an odd. multiple, including unity. of one quarter or the mean operating wavelength.

11. In combination, a pair of sources of alternating current energy. a first and a second transdlicer means, connections from each or said sources of energy to each of said transducer nections from said transducers to said load, the

connections from said second transducer to said load being one quarter oi. the operating wavelength longer than the corresponding connections 15 from said first transducer means to said load.

12. In combination, a source of alternating current ener y. a first and a second transducer means, connectionsirom said source or ener y to each or said transducer means, the connection from saidfirst transducer means to said source being one quarter of the operating wavelength-longer than the connection from said second transducer means to said source, aload, and

connections from said transducers to said load,

the connection from said second transducer means being one quarter of the operating wavelength longer than the connection from said first transducermeans to. saidload.

mns E. insomnia.-