US1855184A - Radio receiving system - Google Patents

Description

April 26, 1932.

G. R. FISHER RADIO RECEIVTNG SYSTEM Filed Dec. 5. 1928 INVENTOR By CQ/harn 6. Fisher A TTORNE Y5.

Patented Apr. 26 1932 UNITED STATES PATENT OFFICE GERHARD R. FISHER, OF PALO ALTO, CALIFORNIA, ASSIGNOR TO FEDERAL TELEGRAPH COMPANY, OF FRANCISCO, CALIFORNIA, CORPORATION OF CALIFORNIA RADIO RECEIVING SYSTEM Application filed December 5, 1928. Serial No. 824,004.

This invention relates enerallyto systems for receiving radio signa s, and particularly to systems of this kind having means for minimizing static disturbances.

It is an object of this invention to devise a radio system incorporating static eliminating means, which utilizes a mm mum of apparatus and is comparatively s1mp1e to operate.

It is a further object of this invention to devise a radio receiving system which is comparatively free from interference due to potential static.

It is a further object of this invention to devise means in conjunction with a loop an-. tenna which can be employed for eliminatlng static interference and also for imparting unidirectional characteristics to the system.

It is a further object of this invention to devise a novel method of operating a radio system utilizing a receiver coupled to a plurality of antennas.

Further objects of the invent1on W111 appear from the following description in wh ch I have set forth the preferred embodiment of my invention. It is to be understood that the appended claims are to be accorded a range of equivalents consistent with the state of the prior art.

Referring to the drawings:

Fi re 1 is a diagrammatic view illustrating t e radio antennas utilized in my system connected to receiving apparatus.

Fig. 2 is a circuit diagram illustrating one form of the system of my invention.

The system of my invention utilizes in general a plurality of separate antennas or antenna portions which are connected to common radio receiving means. Thus referrmg to Fig. 1 I have shown antennas-11 and 12 connected to common radio receiving means 13. While these antennas may be of any form which will secure the objects of the invention, I prefer that they both be of loop form as for example a plurality of-loops of wire wound upon a suitable frame as shown. The plane of each loop is generally normally positioned vertically and the frames are mounted so as to be readily rotatable about a vertical axis. In some instances it is desirable to provide for adjustment of bothloo s about a horizontal axis, as for example w enit is desired to take'in account reflected radio signal or static energy. However such adjustment or positioning of the planes of one or both of the loops at an angle to the vertical position shown is generally unnecessary exce t for energy of short wave lengths.

eferring to the circuit diagram of Fig. 2, loop antenna 11 is shown tunable by suit able means such as a variable condenser 14 and is coupled to' the radio receiver 16 by means of a suitable wave filter 17.- Wave filter or coupling means 17 preferably is constructed so that the coupling between loop 11 and the receiver 16 can be varied as desired. The filter which I have shown gives good re sults and consists of a balancing condenser 19, in this case formed by relatively stationary electrodes 21 connected to the terminals of loop 11, and a central electrode 22. The center electrode 22 is connected to one terminal of an inductance coil 18. Another re active balancing device 23 has its fixed electrodes connected to the terminals of inductance coil 18, and has its center electrode con nected to one terminal of another inductance 24:. The other terminal of coil 24 has a ground connection 26, and this inductance can be tuned as by means of variable condenser 27. For transferring energy to the receiver 16 inductance 24 is shown coupled to a secondary inductance 28. Inductance coil 18 is preferably divided into two portions by having its center tap connected to ground as indicated at 29.

Antenna 12 is also shown provided with a variable condenser 31 shunted across its terminals, altho in practice this antenna is detuned with respect to the signal energy to be received. As a convenient means for coupling antenna 12 to" the remainder of the apparatus I have shown a condenser 32 havm its one terminal connected to one termi-- 11a of loop 12, and its other terminal connected to one terminal of inductance coil 18. In series with condenser 31 I have sh own variable reactive means formed by variable condenser 32, and phase shifting means formed by an ad-" justable or variable resistance 33. The connection established by condenser 31 in efiect couples loop 12 to one portion of the mductance coil 18.

To secure certain advanta es to be later explained, I prefer to groun the electrical center of loop 11, as by means ofa ground conductor 36 connected to the center point of loop 11. L00 antenna 12 is likewise preferably grounde in a similar manner b means of a ground conductor 37 connecte to the center point of loop 12. Phase shifting 11. It has been found that this static energy can be divided roughly into two groups, one kind originatin at a remote point and having an a preamble directional effect, and another kind which ma be termed potential static which is cause by different potentials existing at various stratas above the earth. It isapparent that static having a directional effect at right angles to the plane of loop 11, will not be absorbed by thisantenna due to its figure ei ht characteristic. However when received rom other directions such static will produce appreciable interference if not neutralized or cancelled. Loop 12 is arranged in such a positionv that it will receive such interfering directional staticzand the energy so absorbed is impressed upon the wave filter or coupling means 17 together with the energy absorbed by antenna 11. The intensity of impulses impressed upon coil 18 by loop 12 can be adjusted by varying the condenser 32, and the phase relationship can be adjusted by varying resistance 33. When the system is properly adjusted impulses due to static impressed upon coil 18 by antenna 11 are of substantially the same intensity and are substantially 180 degrees out of phase with'the corresponding impulses from antenna 12. Thus such impulses are'cancelled out or neutralized and ha e substantially no 'efiect upon the receiver 16. l

The ground connections 36 and 37 for the loop antennas 11 and 12 are desirable in that they minimize the effect of potential static upon the system. As previously explained such static is largely due to the presence of different potentials occurring at difierent strata above the earth, such potential differences causing potential discharges thru the antennas. By utilizing loops grounded at their center points such discharges are in part directly conducted to ground and the efiect upon the system is minimized.

Generally in the operation of my system reception is bi-lateral in accordance with the directional characteristics of the loop antenna 11. It is possible however to modify the system so that the directional characteristics correspond to a cardioid. It will be noted that in addition to the circulatory loop currents in antenna 12 caused by absorption of static energy, this loop also has a capacitative effect and can therefore be employed as an aperiodic capacitative antenna for absorbingsignal energy. By properly adjusting the phase relationship of such signal energy, as by cuttingin and varying resistance 38, signal energy impressed upon inductance coil 18 from loop 12 can be made substantially in phase with the signal energy impressed upon the coil from main antenna 11. When this condition exists and proper coupling is provided between loop 12 and inductance coil 18, the directional characteristics of the sys-' tem'will be substantially a cardioid, or the system will be unidirectional.

In practice I have found it desirable to have the loops 11 and 12 arranged at substantially the same height from the surface of the ground and of substantially the same size. The ground connections are also preferably made to the upper sides of the loops as shown. Best results are secured by maintaining an angular relation between the planes of loops 11 and 12, although this angular relation is generally somewhat less than 90 degrees.- The antennas can be placed any desired distance apart or can be comparatively close together.

- Iclaim:

1. In a radio receiving system, a tuned loop antenna, means for grounding the center point of said loop, a receiver, means for coupling said antenna to the receiver, said last means including a coil having its center point grounded whereby it is divided into two portions, a second loop antenna, means for grounding the center point of said second antenna, said second antenna having its plane arranged at an angle to the plane of the first antenna, phase shifting means associated with the second antenna and means for coupling said second antenna across one portion of said coil.

2. In a radio receiving m, two antennas adapted to be afiected to different degrees by desired and undesired radio waves proceeding from difierent directions, a closed oscillatory circuit comprising an inductance having a mid-point tap and a three-plate balancing condenser, one of said antennas being connected across one half of said tapped inductance, the other of said antennas bein connected across the other half of said inductance, and a receiving device connected between the mid-point tap on said inductance and the third place of vsaid balancing condenser. i

In testimony whereof, I have hereunto set my hand.

GERHARD R. FISHER.

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