US2268664A - All-wave antenna system - Google Patents

Description

Jan. 6, 1942. v.0. LANDON 2,

ALL-WAVE ANTENNA SYSTEM Original Fil ed Sept. 29, 1934 LONG flND SHORT WE'VE mum RECEIVER ZSnnentor a don (Ittorneg I Patented Jan. 6, 1942 ALL-WAVE ANTENNA SYSTEM Vernon D. Landon, Haddonfi'eld, N. -J., assignor to Radio Corporation of America, a corporation of Delaware Original application September 29, 1934, Serial No. 746,081, now Patent No. 2,147,168, dated February 14, 1939. Divided and this application October 31,1936, Serial No. 108,507

19 Claims.

' My invention relates to antenna systems and more particularly to a transmission line coupling system between a radio receiver and a remote source of long and short waves.

This application is a divisional of application Serial No. 746,081, filed September 29, 1934, assigned to the same assignee.

It is an object of my invention to provide an antenna system that is highly efllcient for reception of radio waves of frequencies extending over a considerable range.

Another object of my invention is to provide an all-wave antenna system in combination with suitable filter and coupling networks whereby radio waves of any desired frequency band may be efiiciently transferred to a radio receiver with minimum pickup of stray interference waves or certain forms of static while receiving short wave signals.

It is a further object of my invention to provide, at the receiver end of a two-wire transmission line that'is connected at the other end to a source of long and short wave signals, a coupling network including a path that will select opposed phase short wave currentsand a path that will, simultaneously or alternately, select inphase long wave currents from said line, and which will prevent line in-phase stray currents from traversing said paths.

It is another object of my invention to provide a simplified and inexpensive all-wave antenna and transmission line coupling system wherein a dipole type antenna is adapted to function automatically as a dipole for receiving short waves, and as a capacity type antenna for receiving long waves, without the usual transformer or other coupling networks at the antenna, and without a switch at the receiver end of the line for selecting dipole or capacity antenna operation.

A further object of my invention is to provide a transmission line coupling system, between a source of long and short wave signals and a receiver, that is balanced for short wave signal transmission, but, although unbalanced for long wave signal transmission, the receiver is protected from high frequency stray pickup on the line while receiving short wave signals.

A still further object of my invention is to provide, in combination with a source of long and short waves and a transmission line connected thereto, an electrical coupling network from the line to a receiver whereby long and/or short waves may be automatically selected by the receiver.

Further objects and advantages of my invention will be apparent upon reading the following detailed description in connection with the accompanying drawing which the figure is an electrical circuit diagram illustrating my invention and showing a dipole type antenna remotely connected to a radio receiver through a transmission line coupling system.

Referring to the figure, I have shown a signal energy selecting device comprising two dipoles, the arms of which'are designated at l0, l3, l2 and II, respectively. The antenna, per se, and its connection to the transmission line is disclosed and claimed in a copending application Serial No. 722,842, filed April 28, 1934, by Landon and Reid, as joint inventors, assigned to the same assignee. The arms l0 and I3 are preferably of equal length. The arms II and 12 are also of equal length but this length is different from that of the arms ID and I3 in order that different resonant points may be had at somewhat widely separated portions of the frequency'spe'ctrum to be received. Arms 12 and Il constitute a dipole that is responsive to a certain frequency range and arms I!) and i3 constitute a dipole responsive to another and higher frequency range. In accordance with the teachings of said application Serial No. 722,842, adjacent arms I0 and I2 and adjacent arms [-3 and H are connected, respectively, to opposite sides of a transmission line 22 for the reason that the fields of the adjacent arms will not counteract each other, in other words, will be additive over'a wide frequency range. For high frequency reception, the antenna will operate in such manner that the dipole arms I0, l2 and I3, H are in phase opposition, dipole fashion, whereas for low frequency reception all arms operate in parallel or in phase, in other words, as a capacity antenna.

In the preferred embodiment of my invention, inthe parent application, a plurality of transformers are employed adjacent the antenna for transferring high and low frequency energy from the antenna to the transmission line, as circulating currents for both long and short waves, the transmission line being balanced for .both conditions. While such an arrangement gives a condition wherein the line is balanced against interference pickup, for both long and short wave reception, it isa more expensive and complicated arrangement. In the present modification of my invention, I utilize a double dipole antenna,as in Fig. l of the parent application, but the transformers adjacent the center of symmetry of the dipole antenna are'omitt'ed and the lead-in conductors are connected directly to the dipoles at the points [5.

Near the receiver I employ a short wave transformer 23 having a primary 10, a secondary l2, and a grounded electrostatic shield 32 interposed therebetween. The shield comprises a fabric having metallic strands as illustrated in the aforementioned copending application, Serial No. 722,- 842, and as shown and claimed in patent to Shapiro 1,942,575. The secondary coil 12 is connected in series with a low-pass filter comprising an inductance coil 13 and two capacitors 14 and 15 arranged as shown. This filter and the secondary 12 are series connected between a mid-tap ll of the primary and anantenna terminal post of a long and short waveradio receiver 3|. One side of each of the condensers l4 and 15' is connected to ground as shown.

An embodiment of the system shown, which was made and tested, had substantially the following electrical characteristics: The filter inductance 13 was about 125 microhenries, and the capacitors l4 and 15 were each about 125 micromicrofarads. Such a filter readily passed the long waves of the usual broadcast band (540 to 1500 kilocycles) while considerably attenuating waves corresponding in frequencies to those of the short wave bands. The number of turns of wire in the primary and secondary of transformer 23- were of the order of ten each and about microhenries each. The embodiment described provided high efiiciency particularly over the two frequency bands for which it was designed, namely, from 540 to 1500 kilocycles, and from 6000 to 18,000 kilocycles. Reception at frequencies from 1500 to 6000 kilocycles was also fair, although it was not to be expected that it would be as favorable as in the aforementioned bands.

The short wave signals are effectively transferred by electromagnetic induction between the primary l0 and the secondary 12 of the high frequency transformer to the input of the radio receiver 3|,ibecause of the voltage difference across the primary l0. Interfering pick-up energy collected on the lead-in wires 22 does not produce a voltage difference across the primary l0, and is drained to ground by the static shield 32 that is connected to the ground terminal of the receiver. The low pass filter operates efficiently to bypass signals of the lower frequency broadcast band around the high frequency transformer.

In other words, short wave signal energy is fed into the transmission lines from the long and short pairs of dipole arms of the all-wave antenna, and is carried by the line in balanced relation as circulating high frequency currents, the line being balanced to ground by means of the .connection through capacitor 14 to the mid-tap II, or electrical point of symmetry, of the transformer primary. The high frequency transformer 23 operates to transfer these signal currents to the receiver. Any stray interference picked up by the transmission line produces currents in the same direction in the line wires, and is balanced out electromagnetically by reason of the differential action of current flow in the two halves'of the coil in respect to the connection at H to ground. Secondly, capacity transfer of the static component of the strays through the transformer is prevented by the electrostatic shield, directly connected to the ground terminal, or chassis ground, of the receiver. Thirdly, the stray currents are prevented from going through the long wave path around the transformer by means ofthelowpass filter that offers high attenuation to the passage of high frequency currents. In the reception of long waves the dipole arms act as a capacity antenna and in-phase signal currents flow through the transmission line, as though it were a single conductor, to point ll, through coil I3 and thence through coil 12 to the antenna binding terminal, coils 10, I3, and 12 offering negligible impedance to the flow of long wave signal energy.

Although I have illustrated my invention in connection with one form of antenna, it will be obvious to those skilled in the art that other forms of antennae or sources of high frequency and low frequency waves may be employed without departing from the spirit of my invention. It should also be obvious to those skilled in the art that the load circuit, instead of being a receiver of the multi-band, or long and short wave type, may be divided between a plurality of receivers adapted to receive simultaneously a plurality of different carrier waves, each of which will be picked up by the antenna operation best adapted to receive the same, and transmitted to the receiver, or receivers, which are suitably tuned in.

I claim as my invention:

1. In combination, a multi-dipole antenna system, a radio receiver, a two-wire lead-in connection from said system to said receiver, separate wires of said connection being adapted to receive energy from symmetrical halves respectively of said system, a transformer adjacent said receiver having a primary winding connected across the two wires of said lead-in connection, a low-pass filter the input side of which is connected to a mid-tap on said primary winding and the output side of which is connected in series with the secondary of said transformer, a grounded shield between the primary and secondary of said transformer, and means including suitable connections between said secondary and said receiver, also between said filter and ground whereby signals of relatively high and low frequencies are transferred to said radio receiver, while stray interference waves impressed uniphasally on said lead-in connection are drained toground.

2. In a radio receiving system, an all wave antenna and a receiver selectively responsive to long and short wave bands, a transmission line connecting said antenna with said receiver, a network coupling the receiver to said line, said net-, work comprising a path selective to opposed phase short wave currents in said line and a path selective to in-phase long wave currents in said line, said long wave path including means for by-passing to ground in-phase short wave currents picked up by said line.

3. The invention as set forth in claim 2 characterized in that said short wave path includes a transformer with an electrostatic shield disposed between windings and grounded to said receiver.

4. The invention as set forth in claim 2 characterized in that said means in the long wave path is a low pass filter. 1

5. The invention as set forth in claim 2 characterized in that said antenna, operating as a dipole for short waves and as a capacity antenna for long waves, is directly connected to said line.

6. The combination including an antenna, a. transmission line and a transformer, said transmission line coupling said antenna to said transformer, saidtransformer comprising a primary winding connected across said transmission line, a low pass filter the input side of which is confor the most part' nected to a mid-tap on said primary winding and the output side of which is connected through the secondary of said transformer to an output terminal, and means grounding said low pass filter, whereby circulating currents in said transmission line induce a voltage in said secondary winding, and non-circulating currents in said transmission line pass through said low pass filter to said output terminal.

'7. The invention as set forth in claim 6 further characterized by a grounded electrostatic shield disposed between said primary and secondary windings.

8. In a radio receiving system, an antenna and a receiver selectively responsive to long and short wave bands, a transmission line connecting said antenna with said receiver, a network coupling the receiver to said line, said network comprising a path inherently selective to opposed phase short wave currents in said line and a path inherently selective to in-phase long wave currents in said line, and means for by-passing to ground in-phase short wave currents picked up by said line.

9. The combination including a dipole antenna, a receiver coupling transformer, and a transmission line coupling said antenna to said transformer, said transformer comprising a path inherently selective to in-phase long wave currents in said line, and a path inherently selective to opposed phase short wave currents in said line, said long wave path including a capacitor connected between the primary of said transformer and ground for by-passing in-phase short wave currents induced in said line.

10. The invention as set forth in claim 9 characterized in that said path inherently selective to in-phase long wave currents is a low pass filter including a series inductance, said capacitor forming a shunt arm of said filter.

11. The invention as set forth in claim 8 characterized in that said means in the long wave path is a low pass filter including a series inductance.

12. The invention as set forth in claim 8 characterized in that said short wave path includes a transformer with an electrostatic shield disposed between windings and grounded to said receiver.

13. A transformer for coupling an antenna to a receiver which has at least a first and a second band of reception comprising input means for connection to said antenna; a primary winding for signals in said first band connected across said input means; a secondary circuit including a secondary winding for signals in said first band coupled to said primary winding, output terminals for connection to the input of said receiver, means connecting one terminal of said secondary to one output terminal, and means including an impedance connecting the other terminal of said secondary to the other output terminal; and filter means for passing signals substantially only in said second band of frequencies connected between a point intermediate the ends of said primary winding and a point on said secondary circuit.

14. A device of the character described in claim 13 in which said impedance is a capacitor presenting a low impedance to signals in said first band and a relatively high impedance to signals in said second band.

15. A device of the character described in claim 13 in which said impedance is connected between said point on said secondary circuit and the output terminal connected to the grounded input terminal of said receiver.

16. A device of the character described in claim 13 in which said filter includes a series inductor having a shunt connected capacitor at each end, one of said capacitors being the impedance connecting said other terminal of said secondary to said other output terminal.

17. A noise reducing antenna system for op- I eration in distinct frequency bands comprising a dipole antenna, downlead conductors coupled to said antenna, a radio receiver having a first and a second band of reception, means for applying to said receiver currents in said first frequency band induced out of phase in said antenna and flowing out of phase through said downlead conductors, and means for also applying to the input of said receiver currents only in said second frequency band induced in phase in said antenna and said downleads and flowing in phase in said downleads, and means for grounding high frequency noise representing currents flowing in phase in said downlead conductors.

18. A noise reducing antenna system for a receiver operating in distinct high and low frequency bands comprising a high frequency dipole antenna, downlead conductors coupled to said antenna, a high frequency transformer coupling the lower end of said conductors to the input of said receiver for applying high frequency signaling currents thereto, and other means for applying to the input of the same receiver low frequency signaling currents induced in phase in said antenna and downlead conductors, said means including means for by-passing to ground high frequency noise representing currents induced in phase in said downlead conductors.

19 A device of the character described in claim 18 in which said means for applying to the input of the same receiver low frequency signaling currents comprises a low frequency band pass filter.

VERNON D. LANDON.

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