US2290371A - Antenna system - Google Patents

Description

July 21, 1942. M KA ZIN v 2,290,371

ANTENNA SYSTEM Filed April 15, 1941 Fig. I

HIGH FREQUENCY APPjIQATUS I =1 =1l=1=, 5 1: G:' 1:: o-

PHASE CHANG/N6 NETWORK INVENTOR MART/N I64 7Z//V BYMZW ATTORNEY Patented July 21, 1942 ANTENNA SYSTEM Martin Katzin, Washington, D. 0., assignor to Radio Corporation of America, a corporation of Delaware Application April 15, 1941, Serial No. 388,609

11 Claims.

The present invention relates to an improvement in directive antenna systems and, more particularly, to such of these systems as are commonly known by the term fish-bone antenna because of their physical configuration. Such a fish-bone type of antenna, upon which the present invention is an improvement, is described in a Peterson Patent No. 2,130,675, granted September 20, 1938.

An object of the present invention is to increase the effective frequency band coverageof a fish-bone antenna.

Another object of the present invention is the provision of an ultra-high frequency traveling wave antenna having a uniform response over a wide frequency range.

Still another object is the provision of a directive antenna operative Over a wide range of operating frequencies.

Still a further object is the provision of a highly directive antenna suitable for the reception and/ or transmission of television.

The foregoing objects, and others which may appear from the following detailed description, are attained in accordance with the principles of the present invention by the provision of an elongated parallel wire transmission line having lateral signal collectors coupled thereto at intervals along its length. The signal collectors may be of uniform length or their length may taper along the length of the transmission line in order to increase the effective band width of the antenna system. The signal collectors are preferably not directly connected to the transmission line but loosely coupled thereto as by series condensers or inductances so as not to load the transmission line unduly.

In order to make the antenna uni-directional the'end of the transmission line remote" from its connection to a receiver or other transducer meansa-nd which is directed toward a remote station with which communication is to-be established is closed by a terminating resistor having a resistance equal to the surge impedance of the line. At appropriate intervals along the length of the transmission line phase changing networks are inserted therein to'overcome the effects of low velocity of signal propagation along the line compared with the velocity of signal-propagation in free space. The phase changing networks are designed to change the phase of signals. traveling along the line by 180 degrees at the high frequency end of the band of signals and tochange the phase progressively less toward the low frequency end of the band. The phase changing networks are arranged to have an impedance equal to the surge impedance of the line regardless of the frequency and to have no attenuation to the wave. 7

Although the antenna is, in this specification, described especially with reference to a receiving system, it is to be clearly understood that its use is not limited thereto since it may also be used for transmitting purposes.

The present invention may be more fully understood by reference to the following detailed description which is accompanied by a drawing in which Figure 1 illustrates schematically a simple embodiment of a fish-bone antenna embodying the principles of the present invention and Figures 2 and 3 illustrate the details of phase changing networks suitable for use in the an tenna system as shown in Figure 1.

Referring to Figure 1, there is shown a fishbone antenna comprising a closely spaced twowire horizontal feeder line I' connecting high frequency apparatus 2, conventionally shown in. box form, with externally arranged antenna doublets 3, 3. These doublets are disposed along the length of the feeder line I, there being preferably at least six to each wavelength of feeder line. The doublets may beoriented at any desired angle with respect to the plane of the earth depending upon whether horizontally or vertically polarized signals are to be received. Figure 1 is terminated at its far end by its surge impedance Z of a value equaling the surge impedance of the line I as loaded by the antenna doublets 3.

As shown in Figure 1,. the antenna is divided into two sections connected end to end by the phasev changing network 5. More sections may be used if greater directivity and sensitivity is desired. The phase changing network 5 is designed to produce a change of 180 degrees of electrical phase in the feeder line for the highest frequencies to be received or transmitted and progressively less for lower frequencies. overall length of each section of the antenna projected upon a line parallel to the direction of electromagnetic wave propagation is somewhat less than one-half wavelength less than its actual length due to the fact that the energy traveling along transmission line I travels therein more slowly than the wave is propagated through the ether. In a typical case the, phase velocity of the antenna feeder line I may be or of the velocity of the propagation in free space. The energy received by the signal collectors 3 as the received wave progresses in. space over the antenna from surge impedance Z to the receiver The.

2 produces incremental voltages in feeder line I which build up into a single resultant voltage. Since these increments of voltage progress along the feeder at a velocity slower than the velocity of the propagation of the wave front in space, the resultant of the earlier components of voltage in the antenna feeder line tend to lag farther and farther behind the space of the more recently induced increments until, without the interposition of the phase changing network 5, the resultant voltage would begin to decrease rather than increase with the length of the antenna. However, the phase changing network 5 serves to turn the voltage of the higher frequencies through an angle of 180 electrical phase so I that it may once again be directly added to all the voltages developed by the electric wave front passing by the collectors nearer the high frequency apparatus Z. Therefore, an optimum building up of the various increments of voltage occurs for a wave front advancing in the desired direction at the highest frequency for which the antenna is designed. For progressively lower frequencies less phase shift is introduced by the phase changing network 5 and since there is less l difference in wave velocity in feeder l and in free space for the lower frequency waves the energy representative of the lower frequencies will also be added in an in-phase relationship throughout the length of the antenna. For the lowest frequencies for which the antenna is designed the phase changing network 5 has substantially no phase shifting effect since the difference in phase between the various increments of voltage of the wave in feeder l and in free space for the lower frequencies is correspondingly small. It is essential that the phase changing network 5 have a surge impedance equal to the surge impedance of line I for all frequencies for whichthe antenna is designed. Otherwise, reflections would be set up and the efficiency of the antenna would decrease rapidly. Also, the phase changing network 5 must impart substantially no attenuation to the wave as, otherwise, the.losses introduced by the insertion of the phase changing network would more than counteract the advantages obtained by its use. Phase changing networks which fulfill these require ments are shown in Figures 2 and 3 of the drawing.

These networks have been completely described in the Bell System Technical Journal for July, 1928, pages 529 and 530, and it is believed unnecessary to describe them in detail here.

Reference may be had to the above mentioned publication for design for details of the networks whereby the desired 180"phase shift at the high frequency end of the spectrum to be received may be had.

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:

1. A directive antenna system for a broad band of short waves comprising two closely spaced substantially straight feeder conductors connected at one end to high frequency apparatus, a plurality of groups of antenna units transversely coupled to said line, a phase changing network interposed between two groups of said antenna units for producing along said feeder a reversal in phase of the highest frequency energy in said connected at one end to high frequency appa- .ratus, a plurality of groups of antenna units transversely coupled to said line, a phase changing network interposed between two groups of said antenna units for producing along said feeder a reversal in phase of the highest frequency energy in said band, said phase changing network having progressively decreasing effect with decreasing frequency and an impedance connected across the end of said line remote from said high frequency apparatus, said impedance having a value equal to the surge impedance of said line as loaded by said antenna units, said phase changing network having a constant impedance equal to the surge impedance of the line and substantially zero attenuation for all frequencies within the band.

3. A directive antenna system for a broad band of short waves comprising two closely spaced substantially straight feeder conductors connected at one end to high frequency apparatus, a plurality of groups of antenna units transversely coupled to said line, phase changing networks interposed between successive groups of said antenna units for producing along said feeder a reversal in phase of the highest frequency energy in said band, said phase changing networks having progressively decreasing effect with decreasing frequency and an impedance connected across the end of said line remote from said high frequency apparatus, said impedance having a value equal to the surge impedance of said line as loaded by said antenna units.

4. A directive antenna system for a broad band of shortwaves comprising two closely spaced substantially straight. feeder conductors connected at one end to high frequency apparatus, a plurality of groups of antenna units transversely coupled to said line, phasechanging networks interposed between successive groups of said antenna units for producing along said feeder a reversal in phase of the highest frequency energy in said band, said phase changing networks .having progressively decreasing effect with decreasing frequency and an impedance connected .across the end of said line remote from said high frequencyapparatus, said impedance having a value equal to the surge, impedance of said line as loaded .by said antenna units, said phase changing networks having a constant impedance equal to thesurge impedance of the line and substantially zero attenuation for all frequencies within the band.

5. A directive antenna system for a broad band of short waves comprising two closely spaced substantially straight feeder conductors connected at one end to high frequency apparatus, a plurality of groups of antenna units transversely coupled to said line, a phase changing network interposed between two groups of said antenna units for producing along said feeder a reversal in phase of the highest frequency energy in said band, said phase changing networks having progressively decreasing effect with decreasing frequency.

6. A directive antenna system for a broad band of short waves comprising two closely spaced substantially straight feeder conductors connected at one end to high frequency apparatus, a plurality of groups of antenna units transversely coupled to said line, phase changing networks interposed between successive groups of said antenna units for producing along said feeder a reversal in phase of the highest frequency energy in said band, said phase changing networks having progressively decreasing effect with decreas ing frequency.

7. A directive antenna system for a broad band of short waves comprising two closely spaced substantially straight feeder conductors connected at one end to high frequency apparatus, a plurality of groups of antenna units transversely coupled to said line, a phase changing network interposed between two groups of said antenna units for producing along said feeder a reversal in phase of the highest frequency energy in said band, said phase changing network having progressively decreasing effect with decreasing frequency, said network having a low and constant attenuation for all frequencies within said band.

8. A directive antenna system for a broad band of short waves comprising two closely spaced substantially straight feeder conductors connected at one end to high frequency apparatus, a plurality of groups of antenna units transversely coupled to said line, phase changing networks interposed between successive groups of said antenna units for producing along said feeder a reversal in phase of the highest frequency energy in said band, said phase changing networks having progressively decreasing effect with decreasing frequency, said networks having a low and constant attenuation for all frequencies within said band.

9. A directive antenna system for a broad band of short waves comprising an elongated signal collector connected at one end to high frequency apparatus and the other end directed toward another station with which communication is to be established, said collector being divided into separate sections, phase changing networks interposed between each two successive sections for producing therealong a reversal in phase of the highest frequency energy in said band, said phase changing networks having progressively decreasing effect with decreasing frequency.

10. A directive antenna system for a broad band of short waves comprising an elongated signal collector connected at one end to high frequency apparatus and the other end directed toward another station with which communication is to be established, said collector being divided into separate sections, phase changing networks interposed between each of two successive sections for producing therealong a reversal in phase of the highest frequency energy in said band, said phase changing networks having progressively decreasing effect with decreasing frequency and means for preventing reflection of energy at said other end, said means having a resistance equal to the surge impedance of said antenna,

11. A directive antenna system for a broad band of short waves comprising an elongated signal collector connected at one end to high frequency apparatus and the other end directed toward another station with which communication is to be established, said collector being divided into separate sections, phase changing networks interposed between each two successive sections for producing therealong a reversal in phase of the highest frequency energy in said band, said phase changing networks having progressively decreasing effect with decreasing frequency, means for preventing reflection of energy at said other end, said means having a resistance equal to the surge impedance of said antenna, said networks having a low and constant attenuation for all frequencies within said band.

MARTIN KATZIN.

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