US1621998A - Arrangement for eliminating disturbing waves in radiofrequency circuits - Google Patents

Description

M. OSNOS ARRANGEMENT FOR ELIMINATING DISTURfSING' WAVES IN RADIOFREQUENCY CIRCUITS Filed April 30. 1923 W W 1 iMW Patented Mar. 22, 1927.

UNITED STATES PATENT QFFICE.

MENDEL OSNOS, OF BERLIN, GERMANY, ASSIGNOR TO GESELLSCHAFT FUR- DRAHTLOSE TELEGRAPHIE M. B. H. HALLESCHES UFER 12/13, OF BERLIN, GERMANY.

ARRANGEMENT FUR ELIMINATING- DISTURBIN-Gr VJ'AVES IN RADIOFREQUENCY CIRCUITS.

Application filed April 30, 1923, Serial No. 635,413, and in Germany May 8, 1922.

This invention relates to the elimination of disturbing waves, for example, harmonics, in radio frequency circuits especially in the aerial.

It is known that the disturbing harmonics in the aerial can be weakened by coupling so-called protecting circuits to the aerial but the harmonics cannot be totally destroyed by this method.

It has been determined that the reason why the above-mentioned method has not succeeded is that it is impossible by such method to bring the currents which are to act upon the aerial in order to destroy the harmonics into the right phase.

According to this invention the disturbing waves are destroyed by opposing electromotive forces of the same frequency which can be regulated, not only as to amplitude but also as to phase.

In the drawing, which illustrates the invention by way of example;

Fig. 1 is a diagrammatic representation of a circuit arrangement embodying the invention;

Figs. 2 and 8 are graphic illustrations for facilitating explanation of the invention;

Fig. 4 is a diagrammatic representation of a circuit of modified form for eliminating the disturbing waves from the aerial;

Fig. 5 is a diagrammatic representation of a circuit arrangement of modified form; and i Fig. 6 is a diagrammatic representation of a circuit arrangement in which the invention may be embodied and in which a vacuum tube is employed for producing electromot-ive forces for eliminating the dis turbing waves. 7 y

In the circuit arrangement shown in Fig. 1. A. is the aerial, L its loading coil, and I the circuit which supplies the aerial with the useful current and is coupled with it galvanirally or inductively in any suitable manner, for instance, by means of a coupling transformer K. The mode of coupling, as well as the kind of circuit I producing the useful frequency, is of no concern for the invention. The useful frequency can be provided directly by the radio frequency source such as a high frequency machine, vacuum tube etc. or the current can be raised to the necessary frequency in one or more steps by the use of frequency converters.

If the circuit I also carries besides the useful frequency other disturbing frequencies or waves, for instance, higher harmonics, these disturbing waves are also transferred to the aerial by the coupling K. In consequence a certain disturbing frequency may be observed for instance a harmonic of the circuit I which may be termed i According to the invention a special circuit II is provided for eliminating the disturbing waves. A current is generated in the circuit II of thesame frequency as that of the disturbing waves, and the field of this current acting upon the aerial circuit is regulated according to amplitude and phase so that the electrornotive force induced by this field in the aerial circuit is equal. but opposite in phase, to the electromotive force of the disturbing waves Which are transferred to the aerial by the coupling K.

The circuit II, which may hereinafter for convenience be termed the quenching circuit, is preferably provided with energy of the frequency in question by the circuit I, for instance, by means of a coupling coil K which is inductively coupled either with the primary coil L of the coupling transformer K or with a choke coil K as represented in Figure 1. The counter-electromotive force which is necessary to eliminate or quench the disturbing aerial wave is transferred to the aerial circuit for instance, by the coupling means K K The quenching circuit II is. approximately syntonized to the disturbing frequency in question, but this syntony need not be very sharp, so long as the occurrence in this circuit of currents of the useful frequency is prevented. If, for instance, the quenching circuit is supplied by the circuit I. as shown, it is desirable to make the resulting reactance of the quenching circuit a little inductive or a little capacitive in order to regulate the phase properly.

It is always possible to give the current flowing through the coupling coil K the right phase by means of suitably dimensioning and adjusting of the constants of the quenching circuit.

In Figure 1, R denotes the ohmic losses in the circuit caused by the heating of the wires, and L, signifies the leakage self-inductance of the coil K C is a tuning condenser. r is an ohmic resistance connected in parallel with one of the coils K or K,,

for ezfample, K the resistance 1" being required for the adjustment of the necessary phase in the coil Assuming that the current of the disturbing frequency in the circuit Iis termed z',, the corresponding total current in the quenching circuit II is termed i rhe branch current through the resistance r is termed 2' and the other branch current through the coil K, is termed 2' the relations of the voltages, currents and their phases may be seen from the vector diagram of Fig. 2 which holds good for any choice of the constants.

The current OF:'i,, induces in the couplingcoil'K a disturbing voltage harmonic OA, lagging by 90 which is to be neutralized by the counter voltage induced by the quenching circuit in the coil K,.

The same current 2', induces in the coil K a voltage OA also lagging by 90. This voltage produces in the quenching circuit 11 a total current 21,200. one of the component branches of which, i ":OD. flows through the coil K and the other, z' 'zDO, through the ohmic resistance r.

The voltage ezOA consists of three parts, one of which,

voltage component is in phase with 2' The second voltage component is the inductive voltage drop caused by the current 2' L, denoting the aggregate reactance of the coil K., including its leakage,

. the current in.

and the capacity C This voltage component is perpendicular to the current 2', and consequently also to the vector OB. The third voltage component is the voltage across the terminals of the resistancer; consequently it is in phase with If the constants are not suitably chosen, the current 2'," is generally not perpendicular to the voltage OA and the voltage induced in the coil K by this current. The

, induced voltage, lagging the current by 90,

for that reason cannot quencher balance out the voltage OA.

In order to arrive at this balance the current '2', must be perpendicular to the voltage OA, and consequently the current i, which is perpendicular to i, must be in phase with OA, and the ohmic voltage drop 7 PA also. so that the point- P must fall on the vector OA. This relation of the voltage necessary in order to attain the desired quenching effect is represented in S.

The condition for. the accomplishment of 'this relation may be expressed in the following, Figure 3. shows that the rectangular triangles OBP and ODO are similar to one another and consequently the proportion is:

OD DCzPB BO in," Z i :mL Z K722110111: I R

As the two branch currents are inversely proportional to their reslstances (0L, and r, it follows that:

If the resistance 1- is regulated according to this condition, the desired phase of the current '5 can be obtained.

Of course, one must try to keep the losses which occur by using ohmic resistance 'r in the quenching'circuit as small as possible. In order to diminish these losses. it is advisable to connect a suitable condenser O in series with the coil K as is shown in Fig. 4. This can be explained by the following:

Let L be the self-inductance of the coil K and L the aggregate reactance of this branch including capacity. Then dis smaller than 1, as long as the self-inductance L remains larger than If the terminal voltage across the resistance 1' is E the losses in this resistance are:

On the other hand, E is also the terminal voltage of the branch O, Then, if L denotes the self-inductance of the coil K E g am, 4

Substituting the expression (4) for E and the expression (1) for r in the equation one gets V aR (5) of the coil K,. On the other hand, the selfinductance L, is' proportional to the square of the number of windings. Therefore the field is proportional to the product If the field is given, the product is constant and the other Zi 1] also.

If L, is given and R little variable, the expression for the energy losses V in the first line depends on the value of on, the ratio of the resulting self-inductance L to the self-inductance L see equation (2), and can be considerably diminished by a suitable choice of the condenser C. This is the advantage of the condenser C.

Furthermore, it mustbe taken into consideration, that 1 must be positive in the can pression (1). Both values L and L must therefore have the same signs. If L is positive, that is, if the resulting reactance L is inductive, the resulting reactance L, must also be inductive; but if L is negative, that is, if the reaetance L has a capacitive character, L, must also be capacitive.

So it follows that the quenching circuit II must be appropriately syntonized in such a way that its resulting impedance has either a capacitive or an inductive character.

Allof the above derivations were based upon the supposition that the current always produces in the coil L as well as in the coils K and K a field which is in phase with it, and therefore induces in the corresponding secondary coils a voltage lagging it by exactly 90.

Under some conditions, this supposition is not exactly correct. If the conductors are solid enough, eddy currents occur in them which, just as the secondary short-circuit currents in ordinary transformers, make the field lag slightly in comparison with the primary current. These eddy currents have the same effect as an ohmic resistance con nected in parallel would have. Therefore, the ohmic resistance r is in some cases superfluous, namely, when the eddy current-losses in the coil K are large enough to cause the necessary retardation of the field of the coil K and consequently the voltage induced in the coil K This leads to a simplified connection of the quenching circuit as shown in Fig. 5.

Here, for instance, a transmitting apparatus is shown in which the current of the generator is led into an iron core choke coil D which principally produces harmonics of the useful frequency, but also produces disturbing harmonics owing to the conditions of its saturation when the transmitter is syntonized by means of the condensers C and C and the variometer L These harmonies are transferred to the aerial across the coupling coil K, as in the former example. The right phase of the field, transferred from K, to K can for instance be attained by the suitable regulation of the distance between K and K because not only the magnetic field transferred to K but also the eddy current losses caused by this field in K,, depend on the distance between K and K,.

The regulation of the distance between K and K is therefore equivalent to the regulation of the parallel resistance of Fig. 1.

Here the quenching circuit II is simplified by leaving out a particular ohmic resistance connected in parallel. Of course, the coil K; as well as the secondary coil K can be combined with the lengthening coil L of the aerial. On the other hand, K can be com-. bined with L,.

i The coupling of the quenching circuit with its source of energy and with the aerial can be inductive on both sides, as drawn, but it can also be galvanical on one side and inductive on the other.

The accurate adjustment of the necessary effect is here preferably produced by regulating the coefiicient ofcoupling at one or both transformers K K and K K,. A further regulation of the desired counter-effect can also be made by a slight alteration of the syntonization of the quenching circuit towards the inductive or capacitive side.

A further example, according to Fig. 6, differs from the former only in so far as the aerial is here provided with the useful frequency in a known manner by a cathode tube F with anode a, incandescent cathode b, grid (Z and battery E.

If there are several disturbing harmonics, a separate quenching circuit can be provided for each of them, or a common quenching circuit can be constructed in the known manner and tuned to all disturbing frequencies at the-same time, accurately or approximately. Finally, several quenching circuits can be used as multi-wave circuits in order to generate special frequency groups, for instance, one for the even harmonics and one for the odd harmonics.

For all examp es as above described. the quenching circuits are supplied by the circuit which also produces the useful frequency, but this is not the only possibility, for the quenching circuit can also be supplied with the necessary quenching frequencies by any special source Working synchronously with the arrangement. This source can, for example, be a small auxiliary frequency changer connected in parallel tothe chief frequency changer or to the high frequency generator or to any other part of the arrangement. In this case, it is advisable to choose the auxiliary frequency changer in such a way that it generates the quenching frequencies, but not the useful frequencies.

In order to produce the necessary quench- Ill ing frequencies in the quenching circuits, one or more special cathode valves can be used. In order to cause these valves to pernumeutly work synchronously with the arrangement, they are preferably connected in such a way that their grids arc-excited by the transi'nitting arrangement directly or in directly.

However, the method of supplying the quenching circuits, as shown in Figures 1, and (3, has the advantage that the same current a, which produces the disturbing harmonic in the aerial, is also used for supplying the quenching circuit, and therefore also for quenching the respective aerial harmonic, so that the quenching effect once adjusted is always automatically sustained, even when the current i, a'rters in frequency.

Having described my invention, what I claim is: g V

1. A means for eliminating disturbing waves in radio frequency circuits. comprising, an antenna circuit, an energy circuit adapted to supply energy to said antenna, a coupling means between said energy circuit and said antenna circuit, a quenching circuit coupled to said energy circuit and also to said antenna circuit, said quenching: circuit adapted to be tuned to an undesired harmonic in said antenna, and means for shifting the phase of the harmonic oscillation in said quenching circuit so that the harmonic in the said antenna circuit may be neutralized, said phase shifting being accomplished by varying the degree of coupling between the said energy and quenching circuits.

2. A means for eliminating disturbing waves in radio frequency transmission circuits comprising, an antenna circuit, a circuit adapted to supply energy oscillations to said antenna circuit, a quenching circuit, variable couplings adapted to couple each of said energy circuits and quenching cir cuits to said antenna circuit, said energy circuit comprising a high frequency oscillation source and a frequency-changer connected in series therewith and adapted to supply ergy circuit adapted to supply energy oscil-- lationsto said antenna, a frequency changer in said oscillation circuit, a coupling means between said oscillation circuit and said antenna circuit, a. quenching circuit coupled with each of said antenna circuit and oscillation circuit, said quenching circuit being adapted to be tuned to an undesired oscillation frequency of said oscillation supply in said antenna, and means to adjust the amplitude and phase of the oscillation in said quenching circuit so as to neutralize the harmonic in the said antenna circuit.

A means for eliminating disturbing waves in radio frequency transmitting circults comprising, a non-directional antenna circuit, an energy circuit adapted to supply energy oscillations to said antenna, said energy circuit being variably coupled with said antenna so that the said antenna may he tuned'to any desired frequency, a source of high frequency oscillations in said energy circuit and a frequency changer in series therewith, a quenching circuit coupled with said energy circuit and with said antenna, said quenching circuit being adapted to be tuned to the undesired harmonic in said antenna. and means for shifting the phase of the harmonic oscillation in said quenching circuit so that the harmonic in the antenna may be neutralized, said phase shifting being accomplished by varying the degree of coupling between said energy circuit and said quenching circuit;

5. means for eliminating disturbing waves in radio frequency transmitting cir- .cuits comprising, a non-directional antenna,

an energy circuit adapted to supply oscillations to said antenna. a source of energy consisting of a thermionic tube in said energy circuit, a frequency changer in series therewith, and a coupling between said energy circuit and said antenna, said coupling serving as a means to tune said antenna to any desired frequency, a quenching circuit coupled with said energy circuit and adapted to receive energy therefrom, a coupling between said quenching circuit and said antenna. means for tuning said quenching circuit to any desired oscillation frequency of said oscillation supply, and means for shifting the phase of said oscillation in said quenching circuit so that the corresponding undesired'oscillation in the said antenna may be neutralized, said phase shifting being accomplished by varying the impedance of said quenching circuit.

M. OSNOS.v

Images