US2172923A - Antenna coupler - Google Patents

Description

Sept. 12, 1939. M, Y Y 2,172,923

ANTENNA COUPLER Filed June 15, 1937 2 Sheets-Sheet 1 INVENTOR. MUEZE'A r 641A)" BY K YL/Vk ATTORNEYS.

M. G. CLAY ANTENNA COUPLER Sept. 12, 1939.

Filed June 15, 193'? 2 Sheets-Sheet INVENTOR. Ml/E'E'A) 6. CLA Y I val/4% ATTORNEYS Patented Sept. 12, 1939 UNITED STATES PATENT OFFICE ANTENNA COUPLER Application June 15, 1937, Serial No. 148,309

9 Claims.

This invention relates to improvements in antenna circuits, and more particularly to an improved noise reducing antenna circuit and coupler therefor.

In antenna couplers, the object is to obtain the greatest transfer of signal energy caused by interception of desirable signals from the antenna to the receiver, with a minimum transfer of undesirable disturbances caused by various 1 electrical apparatus. These forms of energy are picked up by both the antenna proper and also the lead-in from the antenna.

It has been found, however, that the lead-in wires from the antenna are often more prone to pick up the undesirable electrical impulses because they actually come closer to the originating points of such impulses. Many attempts have been made to eliminate the disturbances picked up by the lead-in, one such being the use so of two lead-in wires in either a transposed relation or as a twisted pair, the object being to have both wires so exposed to the undesirable electrical impulses that each has an equivalent pickup with the impulses in each wire in phase with 2 those of the other. The signals in one wire are then supposed to oppose or cancel those in the other wire. In antennas and their lead-ins of the type under consideration, two sets of currents arise due to the interception of electrostatic and magnetic waves. Signals which arise in the horizontal or flat top portions of antennas provide currents which are known as out of phase or transverse currents, while those picked up in the double lead-ins of the twisted pair type and Which may be considered as traveling downward or upward in each wire simultaneously, are known as in phase or longitudinal currents.

Inasmuch as the currents produced by lead-in pick-up are undesirable, it is proposed to dispose of these currents and to use with the utmost efficiency the currents generated in the flat top portion of the antenna.

Although certain systems have heretofore been designed which have to some extent attempted to accomplish the foregoing, and with some measure of success, there have been certain undesirable features in the previous antenna circuit arrangements. Not least of these are the current losses before the signal is amplified. The antenna coupler itself, having in most instances been a separate unit, an appreciable loss of signal strength has been apparent, particularly since it has previously been difficult to secure a high degree of efficiency in that unit. Heretofore built-in couplers that gave an increase in efliciency in signal transfer have resulted in a sacrifice of the noise reducing ability.

Still other disadvantages present in separate couplers included the necessity of added controls not conveniently operable with the regular set controls.

By my present invention I have provided an antenna coupler which has avoided the shortcomin s of the prior devices. To this end, the separate coupler has been eliminated and the eiiiciency as a result has been materially improved, making the circuit capable of receiving weaker stations, and the ratio of the. desired signal, to noise picked up by the lead-in, is increased over the best previous systems by a very large factor.

The foregoing is accomplished as will hereinafter more clearly appear by providing a complete elimination of capacitive coupling between the antenna system and the first tuned circuit; by obtaining a substantially exact magnetic balance hence avoiding undesirable transfer of magnetic energy due to longitudinal currents; by providing an exact impedance match of the primary coil to antenna lead-in for developing maximum transfer of the magnetic field due to transverse currents; by providing maximum energy transfer from antenna to grid of first tube on each wave band; and by complete elimination of intermediate transformers at the receiver end of the transmission line and their unavoidable loss of efficiency and narrow band coverage.

All of the foregoing and still other advantages of the invention, as well as the invention itself, will become more apparent from the following description which, together with the accompanying drawings, illustrates an embodiment of my invention.

In the drawings:

Fig. 1 is a perspective view of a coupler and lead wires constructed according to my invention;

Fig. 2 is a. diagrammatic view of one form of an antenna system employing my improved coupler;

Fig. 3 is a fragmentary section, somewhat enlarged, taken on the line 3-3 of Fig. 1;

Fig. 4 is a perspective view illustrating the manner of winding the primary coil;

Fig. 5 is an enlarged fragmentary perspective illustrating a portion of the primary winding; 50 and Fig. 6 is a similar view of a portion of the winding taken from between the points 66 of Fig. 4.

A brief understanding of the functions to be 55 accomplished will materially assist in an understanding of the means for carrying out these functions. As previously stated, the energy received in the fiat top portion of the antenna furnishes transverse currents which may be thought of as arising in one end of the flat top l (as shown in Fig. 2), passing down through one of the twisted pair lead-ins 3, through the primary l and up through the other of the twisted pair and out the other section of the flat top. These impulses con ist primarily of the signal desired to be received. Obviously certain other undesirable electrical impulses are also present, but are not usually as strong as the desired signal except in the case of unusual atmospheric disturbances. These signals are indicated in the drawings by the solid line arrows and are alternating in character.

The lead-in which comprises the twisted pair (this type of lead-in being selected because it is desirable to have both wires of the lead-in affected equally by impulses picked up therein) comes down from the antenna passing through or adjacent to a zone of disturbances set up by various electrical apparatus. For instance the disturbances emitted by automobile ignition systems, oil burners, vacuum cleaners, etc. Since the lead-in passes close to these sources of disturbances, it picks them up more readily than the antenna proper. The twisted pair lead-in, which may be assumed to occupy substantially a single line in space, picks up these disturbances in each wire equally. The impulses travel along the lines indicated by the broken arrows, the currents traveling downward or upward through both wires in the same direction into the primary where they meet and substantially neutralize each other. Inasmuch as the in phase or longitudinal currents cancel each other in the primary, there is no magnetic transfer of energy to the secondaries, the only tendency being to transfer the impulses capacitively; this tendency is completely eliminated by the capacitive effect between the turns of the primary and the walls of the electrostatic shield lb.lii which is grounded.

Referring now to the drawings throughout which like parts have been designated by like reference characters, as best shown in Fig. 2, the antenna may include the top portion comprising two horizontal conductors l secured in spaced end-to-end relation to each other connected to a twisted pair of lead-ins 3 at a junction block 2. In event a single horizontal antenna wire should be used, one of the twisted pair would merely terminate at the junction block or strain insulator.

The twisted pair extend to and are secured to appropriate antenna binding posts on the receiver, not specifically illustrated. The binding posts are connected by leads t and 5 in a shield ii to: the primary '5 of the antenna coupler. At an intermediate point in the shield 6 the wires 4 and project out of the shield to form a loop 3 in one of the conductors and the other being connected to a switch, the purpose of which will hereinafter more clearly appear.

The primary and secondary are supported by a tube ll, upon which secondaries l2 and 53 are directly wound in spaced relation to each other. A substantially annular primary supporting member is concentrically supported on the tube M by arms M which extend radially from the tube, intermediate the two secondaries. Each secondary is particularly adapted to a certain band of frequencies, in the illustration secondary 52 being for higher frequencies than secondary 63.

The support for the primary is an open channel of metal being generally annular in form (Figs. 1 and 3), the cross section of which comprises a substantially V-shaped bottom I5 with outwardly extending parallel sides l6 and with the periphery open as at ill. The ends of the ring it overlap each other but are insulated from each other by a dielectric such as fiber l9 interposed between the overlapping parts, the object being to have a continuous support for the primary which acts as an electrostatic screen and yet does not provide a continuous annular conductor which would load the primary inductively.

It will be noted that the secondaries are located on opposite sides of the primary in axial alignment with each other and the primary. It is desirable to have these inductances so placed that each will be within the field of the primary and receive optimum coupling therewith but still not so close that the tuning of the secondaries will be affected by the primary.

Considering one of the secondaries, say l3, it is evident that one portion (S) of the primary 1 is more closely coupled to the secondary than the corresponding portion on the opposite side of the primary. Therefore, while corresponding portions of the primary symmetrically disposed about its electrical center may carry currents equal in magnitude and opposite in phase due to undesired longitudinal currents induced in the lead-in by interference sources, the portion of the primary having the greater coupling to the secondary in use will induce a voltage in the secondary exceeding the voltage of opposite polarity induced in the secondary by the corresponding portion of the primary having less coupling to the secondary. Thus a residual undesired voltage will appear across the secondary terminals proportional to the vector sum of all voltages appearing in all parts of the secondary through induction from all parts of the primary.

This statement applies to all noise reducing systems which depend upon the separation of transverse from longitudinal currents for their operation even Where the primary may be symmetrically disposed in relation to the secondary in all planes since in practical operation small differences in primary lead lengths, chassis currents, both conductive and induced, stray induction from primary wiring and switching, etc., cause energy transfer into the secondary circuit in the presence of undesired longitudinal primary currents.

Ordinarily a high degree of balance or equality of noise pickup in the lead-in conductors is easily attained by twisting or transposing them using conductors of equal length. The main problem, then, is" to get a perrect neutralizing balance to longitudinal currents within the receiver over the complete tuning ranges of one or more wave bands. The present invention relates to a practical method of attaining this result by overcoming the difficulties heretofore mentioned by shifting the effective electrical center of primary l, to compensate for unequal or unbalanced coupling and strays.

Referring to Fig. 2 for the purpose of illustration only, the loop 3 may be considered as one inch in length; the loop 2% as one and one-half inches; and the combined length of the leads 22, to the switch 2B, as one-half inch in length. When the switch arm, 29, is connected to contact, 24, the primary lead wire containing loop 8 will be one-half inch longer than the primary lead circuit through the switch thus shifting the effective electrical center of the primary to some point, say S or toward the side having the greater lead length. By adjustment of the length of loop 8, any desired accuracy of balance may be obtained. For example, in receiver set production a ratio of 10,000 to 1 in favor of out of phase compared to in-phase impressed primary voltage has been consistently exceeded.

When switches, 20 and 26, are moved to another position by movement of mechanical link 23, for operation over the frequency range of secondary I2, the loop 2| is automatically included in the switch side of the primary circuit. This loop may, for example, be one-half inch longer than loop 8, and thus shift the effective electrical center of primary 1, toward secondary l2. By proper adjustment of the length of this loop any desired degree of perfection of balance may be obtained as before, so that this system as set forth in the example, provides hitherto unattainable freedom from lead-in interference pick- Obviously this system of balance compensation may be extended to apply to any desired number of primaries by additional switching arranged to automatically and economically include the required compensating lead lengths in the primary circuits for perfect balance.

I have previously mentioned the formation of the primary and its electro-static shield. This is best shown in Figs. 1, and 3 to6 inclusive. There are several things to be accomplished in this winding, the foremost of which is effective electro-static shielding of all parts of the primary from the secondary and its associated circuits. To this end the shield has a V-shaped bottom I5 and parallel sides Hi. The lead-in wires 4 and 5 come into the shield from the binding posts, not shown, through a shield 6 which is grounded (Figs. 1 and 2). They enter between the walls 16 of the shield and extend around the shield in opposite directions, each being adjacent and parallel to a wall I6. They remain parallel to each other and the wall for substantially one complete loop after which each dips down as at 21 and 28 ((Fig. 5) to the bottom of the V I5 still traveling in opposite directions and meet at the opposite side in the bottom of the V, it being understood that there is actually only one wire, but for the purpose of description it has been considered as two wires up to the point of junction.

By this arrangement every equi-distant point in opposite direction in the primary has equal capacitive or electrostatic coupling with the shield; and hence an exact electrostatic balance can be maintained between the shield and the primary, and the coil also has a more exact magnetic balance which assists in the elimination of the longitudinal currents,

Variations in the shield l5|6 are possible and obvious, the main thing to bear in mind being that it should not form a short circuiting or inductive loop. Although certain specific structure is shown in the drawings, such showing should not be considered as limiting the invention as numerous and extensive departures may be made therefrom without departing from the principles of the invention or the scope of the appended claims.

I claim:

1. In an antenna coupler for an antenna circuit, a cylindrical form having a secondary winding thereon, a primary supporting member carried by said form and comprising an electrostatic shield spaced from the secondary, said primary being wound on said shield to provide equal electrostatic coupling between the shield and corresponding parts of the primary symmetrically disposed about its electrical or geometrical center.

2. In a device of the class described, an antenna having a portion for receiving radiant energy which provides transverse currents for a receiver, a lead connected to the antenna which upon reception of radiant energy provides longitudinal currents, a coupler for connecting the lead-in to the receiver comprising a primary connected to the lead-in and a plurality of secondaries adapted for selective energization from the primary, means in the primary circuit to control the polarity positions in the primary to provide a magnetic balance with either one of said secondaries.

3. In an antenna coupling system including a portion for intercepting desirable signals to provide transverse currents and a portion to receive undesirable signals and provide longitudinal currents, means to separate the transverse currents from the longitudinal currents by by-passing the longitudinal circuit comprising a shield and a primary winding disposed on the shield and directly connected to said antenna and being so disposed in the shield to provide an electrostatic balance therewith, a secondary disposed within the electrical field of said primary and adapted to receive inductively the transverse currents from the primary, said secondary circuit being connected to the in-put of a vacuum tube amplifier.

4. An antenna coupler in combination with a balanced transmission line, comprising a plurality of secondaries adapted for selective inclusion in a receiver circuit, a primary disposed in inductive relation to said secondaries and connected to said transmission line, means interposed in the primary circuit to provide equal and opposite magnetic coupling of said primary with any selected one of said secondaries in the presence of in-phase primary currents.

5. In a device of the class described in combination with an antenna for providing out of phase currents and a balanced transmission line for providing in-phase currents, means to eliminate said in-phase currents from the receiver circuit and to transmit said out of phase currents comprising an antenna coupler having a plurality of secondaries disposed on a cylindrical form and a primary supported by said form and having an electrostatic shield shielding said primary from the secondary. said primary having shielded leads connecting the same to said transmission line and means in said primary leads to shift the magnetic balance of the primary without disturbing the electrostatic coupling, to provide equal and opposite magnetic coupling of said primary with one of said secondaries in the presence of inphase currents.

6. In an antenna coupler for coupling an antenna having a balanced transmission line to a receiver. comprising a cylindrical support having one or more secondaries disposed therein, a primary support including radial arms carried by the secondary support and carrying at their extremities a form comprising a circular metallic trough having a V-shaped bottom and outwardly extending parallel sides formed to provide a split ring with overlapping ends insulated from each other to provide a substantially annular support for the primary, said primary comprising a pair of conductors extending around the support in opposite directions for one turn adjacent opposite parallel walls and each wire dipping downward into the V-shaped bottom adjacent the point of entrance and extending around the form at the bottom and meeting each other opposite to the point of entrance to provide symmetrical electrostatic coupling of corresponding parts of the primary with said support, shielded conductors extending from said primary to said transmission line, means to change the coupling balance of the transmission line with said primary comprising conductors inserted in said primary leads to change the effective length of the leads, one of said conductors being of a length suificient to change the magnetic balance of the primary to cause said primary when energized with longitudinal currents to have equal and opposing magnetic coupling with one secondary, and the other of said conductors being of sufficient length to overcome the effect of said first conductor and change the magnetic balance of said primary when energized with longitudinal currents so that all parts of said primary have an equal and opposing magnetic coupling with the other secondary, switch means to shift either of the secondaries into said receiver circuit and switch means to change said second conductor into and out of said primary leads and a single control 30'- for said switches.

'7. In a device of the class described having a plurality of primary and secondary circuits; means including a switching system for automatically incorporating in each primary lead circuit suitable lead lengths to shift the eiiective electrical center of the primary to provide substan-- tially neutralized magnetic fields in the vicinity of any secondary in operation when the primary is energized with iii-phase currents. 40

8. In an antenna. coupler for coupling an antenna, having a balanced transmission line, to a receiver, comprising a support having one or more secondaries disposed thereon, a primary support comprising a metallic trough formed to provide a split ring with overlapping ends insulated from each other to provide a substantially annular supporting member, said primary comprising a pair of conductors extending around the support in opposite directions to provide equal electrostatic coupling of all parts of the primary with said support, leads extending from said primary to said transmission line and means to change the coupling balance of the transmission line with said primary comprising conductors insertable in said primary leads to change the effective length of the leads.

9. In an antenna coupling device of the class described, including a support having one or more secondaries disposed thereon, a primary support carried by the secondary support and comprising a metallic shield having a V-shaped bottom and outwardly extending side walls formed to provide a split ring with overlapping insulated ends, said primary comprising a pair of conductors wound around the support and so disposed as to provide equal electrostatic coupling of all parts of the primary with said supports, shielded leads extending from said primary for connection to a transmission line, means to change the cou pling balance of the transmission line with said primary comprising conductors inserted in said leads to change the eifective length thereof, one of said conductors being of a length sufficient to change the magnetic balance of the primary to cause said primary to have all points thereof in equal magnetic coupling with any one point of one secondary, and the other of said conductors being of suiiicient length to overcome the effect of said first conductor and change the magnetic balance of said primary so that all parts of said primary have an equal magnetic coupling with any one point on the other secondary, and switch means having a common control to shift either one of the secondaries into said receiver circuit and to change said second conductor into and out of said primary leads.

MURRAY G. CLAY.

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