US1690228A - High-frequency transformer - Google Patents

Description

NOV. 6, 1928. 1,690,228

R. A. HEISING HIGH FREQUENCY TRANSFORMER Original Filed Dec. :51, 1925 Fig.2. /0 /L[Ew l /2 9 ifiw ffiw 2/ if E? WI w -a 'l-l-l +l lnvenTor: Raymond A.Heism7 Patented Nov. 6, 1928 UNITED STATES PATENT "OFF-ICE.

RAYMOND A. HEISING, OF MILLBURN, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIC'GOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

HIGH-FREQUENCY TRANSFORMER.

Original application flied December 81, 1928, Serial No. 683,629. Divided and this application filed August 20, 1925.

This invention relates to radio signaling systems and more particularly to a transformer for coupling high frequency circuits.

This application is a division of an appli- 6 cation of R. A. Heising, Serial No. 683,629, filed December 31, 1923.

In radio receiving circuits employing high frequency amplification it is desirable to intercouple the amplifying devices by means of 10 circuits tuned to the incoming signal waves.

Thus the coupled circuit between the ampl fiers and between the high frequency amplifiers and the detector should be selectlve of the frequency of the signal waves received by the antenna. The input and output circuits of the amplifiers being both tuned to the same frequency, considerable difficulty has been encountered due to the production of undesired oscillations or singing in the amplifier circuits. This singing is largely due to a coupling effect between the input and output circuits of the amplifier.

The usual method for preventing singing in amplifier circuits is to include a resistance at some point in the coupled circuits or else to construct the primary winding of the transformersof resistance wire. In accordance with this invention a transformer, prov1ded with adjustable means for controlhng the electrical characteristics ofits primary and secondary circuits, is used to intercouple the high frequency amplifiers andto couple the amplifiers to a detector.

It is an object of this invention to provide for intercoupling high frequency circuits in such manner that singing 1s prevented.

A feature of the invention is an adjustable high frequency transformer.

The above object and others, which will be 40 apparent as the nature of the invention is disclosed, are accomplished by employing ar. air core transformer having primary and secondary windings. Effective resistance is 1ntroduced by the hysteresis effect of a. magnetic ribbon adjustably associated with the primary winding. The effective inductance of the secondary winding is varied by means of a conductive core adj ustably associated therewith. V

I0 Althou h the novel features which are believed to e characteristic of this invention will be pointed out with particularity in the Serial No. 51,305.

claims appended hereto, the invention itself, its ob ects and advantages, the manner of itspart thereof in which Fig. 1 shows an adjustable high frequency transformer constructed in accordance with this invention, and Fig. 2 shows a circuit arrangement in which this transformer may be used.

The coupling transformer shown in detail in Fig. 1 comprises an air core transformer having primary and secondary windings l and 2, respectively wound on an insulating core 3 secured to a supporting frame 4. The supporting frame is shown as of insulating material and may be of any material and-of any form. Arms 5 of frame 4 are adapted to support elements 6 and 7 axially of the core 3. Windings 1 and 2, when used with discharge devices as herein described, are each wound to cooperate with the internal capacity of the associated discharge device to constitute a tuned circuit. When used with other forms of high impedance amplifiers and detectors, such windings should be designed to have the necessary inductance and distributed capacity to determine its tuning. The element 6 consists of the spirally Wound laminated strip or ribbon with its convolutions spaced apart. This element is carried by a threaded shank engaging a screw threaded opening in one of the arms 5 and is associated with the primary winding 1.

A conductive element 7, which may be a copper or brass rod, is provided with a screw thread to engage a screw threaded opening in the other arm 5. The area of the rod 7 should be as large as possible. and preferably its diameter should be only slightly less than the internal diameter of the secondary winding 2. The transformer should preferably be mounted so that the only coupling between the windings 1 and 2 is that due to their mutual inductance. In other words, the supporting means for the windings should in troduce substantially no coupling effect between the primary and secondary circuits of the transformer.

High frequency current flowing through primary winding 1 will produce a magiietic field in the space surrounding it. With the element 6 lying in this magnetic field losses will be introduced into the primary circuit due to edd currents traversing the ribbon winding an the hysteresis of the iron. These losses appear as an effective resistance load in the primary circuit. Because of the high frequencies involved the item does not function to decrease the reluctance of the magnetic circuit. Hence the reactance of the rimary circuit and the mutual inductance etween the transformer windings remain winding 2 and element 7 the magnetic field.

due to the flow of eddy currents in the element 7 will be opposed tothe magnetic field resulting from current flow in the winding 2, and consequently the effective inductance of the winding 2 will be decreased by adjusting the element 7 relatively to the winding. 2. The coupling therebe-tween can be varied to control the amplitude of the eddy currents and hence the value of the inductance introduced into the secondary circuit. In this manner the tuning of the circuit including the winding 2 may be accurately adjusted.

Fig. 2 shows a circuit arrangement particularly adapted for point-to-point radio communication in which the above described transformer may be advantageously employed as a coupling means. This particular system is given by way of illustration onl and notas a limitation upon the uses to whic the transformer may be applied. Obviously, the transformer is of general application in circuits involving the use of a high frequency coupling means.

The radio receiver shown in Fig. 2 is adapted to operate on the basis of the well-known successive detection system in which the incoming signal waves are combined with other oscillations to produce an auxiliary inter'-.

' mediate frequency signal modulated wave,

which is then detected to yield the signal current. The receiver includes a rotatable loop antenna 8 adapted to be sharply tuned to the incoming signal Wave'by an adjustable con-' denser 9. The received high frequency'wave's are amplified bythe amplifiers 10 and 11 and impressed upon the input circuit of the'deteotor 12. The devices 10, 11 and 12are intercoupled by transformers 13, the construc- Heterodyne oscillations are impressed upon the input circuit of detector 12 from source 14 coupled to the input circuit of the detector by transformer 15. The output circuit of the detector 12 includes a coupling inductance 16 shunted by an anti-resonantcircuit 17 which is of high impedance for the auxiliary intermediate frequency, but provides a low impedance path for other frequencies.

The resultant intermediate frequency wave is amplified by the amplifiers 18 and 19, transmitted through the selective means 20, and detected by the device 21. The selective means 20 may be either a tuned circuit resonant to the intermediate frequency or a filter ada ted to freely pass a frequency band inclu ing the intermediate'frequency wave while suppressing frequencies outside this band. The low frequency currents resulting from the second stage of detection are supplied to the indicating device 22 which may be of any well-known design but is herein shown as a telephone receiver.

A system embodying certain apparatus and certain specific details has been described for the purpose of completely and clearly disclosing the principles of the invention. However, it is to be understood that this invention is not limited to the arrangement or specific features disclosed but only by the scope of the attached claims.

What is claimed is:

1. A couplin means for high frequency apparatus whic comprises inductively associated coils, a resistance control element and an inductance control element respectively included in the magnetic fields of said coils.

2. A coupling means for high frequency apparatus which comprises inductively asso ciated coils, an ad'ustable resistance control element and an adjustable inductance control element respectively included in the magnetic fields of said coils.

3. A transformer for coupling high frequency apparatus which includes a resistance control element in the magnetic field of one of said windings and an inductance control element in the magnetic field of the other of said windings. 4 4. A transformer for coupling high frequency apparatus which includes an adjustable resistance control element in the magnetic field of one of said windings and an adjustable inductance control element in the magnetic field of the other of said windings.

5. A coupling means for high frequency apparatus comprising inductively coupled coils and a variable resistance control element imizlluded in the magnetic field of one of said co s. V

6. A coupling. means for high frequency amplifiers comprising inductively coupled coils and a control element comprising a spirally wound ribbon of high resistance material included in the magnetic field of one of said coils. p

7. A coupling means for high frequency amplifiers comprising inductively coupled coils and a spirally wound iron ribbon included in the magnetic field of one of said coils.

8. A coupling means for high frequency amplifiers comprising inductively coupled coils and a control element comprising a spirally wound ribbon of high resistance material included in the magnetic field of one of said coils, and means for adjusting said control element relatively to said coil.

9. A tuned coupling means for high frequency apparatus comprising inductively coupled coils, and a conductive element included in the magnetic field of only one of 20 secondary, and to a negligible extent in that 2 of the primary.

11. A transformer including inductively coupled coils one of which is included in a circuit tuned to a wave of definite frequency, and means for varying the tuning of said circuit comprising an adwstable'conductive element in the magnetic field of the coil included in said circuit, and to a negligible extent in the field of the other coil.

In witness whereof, I hereunto subscribe ll my name this 17th day of August A. D., 1925.

RAYMOND A. HEISING.

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