US2131193A - Transformer coupling for television amplifiers - Google Patents

Description

Sept. 27, 1938. K. SCHLESINGER 13 TRANSFORMER COUPLING FOR TELEVISION AMPLIFIERS Filed June 4, 1935 Patented Sept. 27, 1938 TRANSFORMER COUPLING FORTT ELEVI- SION AMPLIFIERS Kurt Schlesinger, Berlin, Germany, assignor to Radioaktiengesellschaft D. S. Loewe, Berlin- Steglitz, Germany Application June 4, 1935, Serial No. 24,901

In Germany June 5, 1934 1 8 Claims.

The use of choke coils for coupling amplifier stages, more particularly in the case of carrier frequency amplification, is already known for television purposes. The selection of the natural frequency of the oscillator choke may be in resonance with the unmodulated carrier wave, whereby the ratio between the free oscillations and the forced Oscillations requires to be made sufficiently small by means of a relatively strong parallel damping. The natural frequency, however, as set forthin my previous application Ser. No. 749,511, of October'23rd, 1934 may also be detuned as compared with the unmodulated carrier frequency, whereby, generally speaking, a small parallel damping of the coil is then permissible. Y

The subject matter of the present invention concerns certain features of design in respect of a transformer coupling in television high frequency amplifiers.

In the drawing:

l is an amplifier stage, the anode circuit of which is coupled by a primary coil 2 with a secondary 'coil 3, the carrier frequency being transmitted to the grid of the next stage 4. Two resistances 5 and 6 on the primary and secondary side produce damping, and the parallel capacities 1 and 8 furnish the two circuits with a defined natural frequency (up and ws.

The applicant has found experimentally and theoretically that a pair of coils of this nature are equivalent to a coupling choke with the following inductance Lx:

DJ 1 K s) 1 5 In this Zps is the geometric means of the two oscillation resistances of the primary and secondary side, and mp5 is the geometric mean of the two natural frequencies. to is the frequency transmitted by the coupling device, K is the coupling factor of the two coils. In considering this equation in the case of different coupling factors it will be found that, generally speaking, there are two coupling, frequenoies at which resonance occurs situated to the right and left of ms, of which the long-wave coupling frequency for the extreme case of a coupling amounts'to- 70% of the secondary natural frequency.

As compared with a simple choke with equal windings and capacity conditions, a tightly coupled transformer with two coils equivalent to the choke accordingly proves to be a structure, the transmission resonance of which islocated at a longer natural wave, viz., a naturalflwave which is longer to theextent of This shows that in the case ofa television plifier with fixed carrier frequency.

more windings can be wound onthe twotran'sformer coils than onan equivalent choke. In this case, however, the. transmission resistance will be twice as great as inthe case of a chokecoupling, and there is accordingly received in the extreme case a translation of potential which is twice as good as in the case of a simple oscillation choke coupling.

Practical experiments-in conjunction with cor} responding amplifiers have also shown that television images of equal quality were obtained with the following data: i

Y Amplifica- Turns on Gamer Oou hn Damping tion at p g Wmdmgs Wave S=5nia/volt Choke; 15o "spoon m. 25 Transformerur 200 10,000 S2 p. 150 m. 50

Conditional for the'accomplishment of this inf;

provement are v l. A coupling as tight as possible. a v i 2. The avoiding of all detrimental capacities in parallel withthecoils and reducing of the capacities to the unavoidable line and design ca pacities, i. e., avoiding particular tuning conis effected solely by correct selection-of the num:

ber of their turns for the purpose of obtaining an os'cillation'resistance g L I as large as possible, because the mean va'nieibr Zp and 25 occurred as factors in the equation cited 1 ,45

. 4 .5 densers in concentrated form. Tuning of thecoils of the two coils differ. thisa'ccordingto the jequa.v

tion merely becomes apparent in that instead ofan actual coupling factor K a modifled effective coupling factor. K" .K--..-. 1.1; f

enters into effect." It is accordingly in the interests of a coupling as tight as possible to select the natural oscillation of the secondary coil not lower but higher than that of the primary coil if there is any compulsion at all to accept different 1' "sioned with their inherent capacities in such natural oscillations. Beyond this there applies according to the inventionthe dimensional equation: Natural frequency equals 1/ of the unmodulated carrier frequency.

I claim:

1. A high-frequency coupling transformer for carrier frequency amplifiers more particularly in television arrangements having a primary and a secondary winding-which are damped by damping resistances, both of said windings are dimensioned with their inherent capacities in such. manner that both said Winding-coils have the same natural frequency, said natural frequency being smaller than the carrier frequency to be transmitted, said winding-coils being coupled with each other as tightly aspossible and said inherent capacities being made as small as possible.

'2. A high-frequency coupling transformerfor carrier frequency amplifiers more particularly in television arrangements having a primary and a secondary winding, which are damped by damping resistances; bothof' said windings are dimensionedwith their inherent-capacities in such mannerthat both said winding-coils have the same natural frequency, said natural frequency being smaller than the carrier frequency to be transmitted, and having a value amounting to nearly 70% of the carrier frequency to be transmitted said winding-coils being coupled with each other as tightly as possible and said inherent capacities being made as smallas possible.

3. A highfrequency coupling transformer for carrier frequency'amplifiers more particularly in television arrangements having a primary and a secondary windihg, which are damped by damping resistances, both of saidwindings are dimensioned with their inherent capacities in such manner that both said winding-coilshave the same natural frequency, said natural frequency being smaller than the carrier frequency to be transmitted, said winding-coils being coupled with each otheras tightly as-possible and said inherent capacities being made assmall as pos' sible, said damping resistances being connected in parallel to said winding-coiflsanddimensioned such asto provide at least an' aperiodical damping of said coupling transformer arrangement.

4. A high-frequency coupling transformer for carrier frequency amplifiers more particularly in television arrangements having a primary and a secondary winding, both of sa idwindings' ar'edimensioned with their inherent capacitiesin such manner that both saidwinding-coils have the samenaturalfrequency, said natural frequency being smaller than the carrierv frequency to be transmitted, and having a value "amounting to nearly 70% of the carrier frequency to be transmitted said winding-coils being coupled with each other as tightly as possible and said inherent capacities being made as small as possible saidWinding-coils being damped at 'least aperiodically by resistance reaction of. the one Winding-circuitdamping on the otherWin'ding-circult.

5. A high-frequencyicoupling transformer for manner that bothsaid winding-coils have the 7 same natural frequency, said natural frequency being smaller than the carrier frequency to be transmitted, said winding-coils being coupled with each other as tightly as possible and said inherent capacities being made as small as pos sible, said damping resistances being connected in parallel to said winding-coils and dimensioned such as to provide an overdamping i. e. the logarithmic decrement of said circuit arrangement is larger than 211-.

-'6. A high-frequency coupling transformer for carrier frequency amplifiers more particularly in television arrangements having a primary and a secondary winding, both of said windings are dimensioned with their inherent capacities in such manner that both said Winding-coils have the same natural frequency, said natural frequency being smaller than the carrier frequency to be transmitted and having a value amounting to nearly 70% of the carrier frequency to be transmitted said winding-coils being coupled with each other as tightly as possible and said inherent capacities being made as small as possible, said Winding-coils being damped by resistance-reaction of theone winding-circuit-damping on the other winding circuit-such as to provide an overdamping i. e. the logarithmic decrement of said circuit arrangement is larger than 21r.

7. A high-frequency coupling transformer for carrier frequency amplifiers more particularly in television arrangements having a primary and a secondary winding, which are damped by damping resistances, both of said windings are dimensioned with their inherent capacities in such manner that both said Winding-coils have the same natural-frequency, said natural frequency being smaller than the carrier frequency to be transmitted, and having a value amounting to nearly 70% of the carrier frequency to be transmitted, said winding-coils being coupled with each other as tightly as possible and said inherent capacities being made as small as possible, said damping resistances being connected in series to said winding-coils .as to provide at least an aperiodicaldamping. of said coupling transformer arrangement.

8. A high-frequency coupling transformer for carrier frequency amplifiers more particularly in television arrangements having a' primary .and'a secondary winding, which are damped by damping resistances, both of said windings are dimensioned with their inherent capacities in such manner that both said winding-coils have the same :natural frequency, said natural frequency being smaller than the carrier frequency to be transmitted, said winding-coils being coupled with 'each other as tightly as possible and said inherent capacities being made as small as possible, saiddamping resistances being connected in parallel to said winding-coils, each of both said damping 'resistanceshaving at the most a value equal to the value

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