US2227035A - Coupling circuit arrangement for ultra-short waves - Google Patents

Description

Dec. 31, 1940. K. SCHLESINGER COUPLING CIRCUIT ARRANGEMENT FOR ULTRA-SHORT WAVES Filed July 23, 1938 Jnveniop:

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Patented Dec. 31, 1940 UNITED STATES PATENT oFF cs COUPLING CIRCUIT ARRANGEMENT FOR ULTRA-SHORT WAVES Kurt Schlesinger, Berlin, Germany, assignor, by mesne assignments, to Loewe Radio, Inc., a corporation of New York Application July 23, 1938, Serial No. 220,876 In Germany October 26, 1937 1 Claim. (Cl. 178-.44)

e p t invention relates to coupl ng cirwhich assures the transmission is accordingly efcuit arrangements for the transmission of broad fected only between the coils and 6. I The tunfrequency bands such as used in television art. ing of the grid and anode circuits to the carrier It is known that in Performing p ification by wave takes place in accordance with the inven- 5 Way of oscillatory circuits the ratio between selftion by the fact that in each of the tuning coils 5 I induction and p y 3 and l, which represent the greater part of the self-inductance of the coupling circuit, there is C provided a metallic cylinder consisting of a good must be selected to be as large as possible for obconductive e al (for example copper tube) tai i a frequency range which is as large as 3a or do. In this connection it is to be observed possible, t is also known that me efiective that the diameter of the tuning cylinder differs working resistance of a tuned anode or grid cir- 'e e as pessllele from the dlameeer of the cult cannot be greater than one-half of the im- Yvmdmg of the 0011s 3 and There m" F pedance of the capacity of the circuit in respect mgly employed merely a Very 1 linsulatlrfg' of th highest, modulating frequ (maximum layer between the two and a comparat vely thin image frequency) to be transmitted. These two Wlre for the W Wlth d}mens1mng of reasons accordingly resulted at an early date in Wlth espeet the dlameter 11:16 the so-called variometer tuning of amplifiers, in tunmg cyhneer and e t'here can obtained In which, therefore, the carrier wave was adjusted h Wholly s r 1305111011 a d no the wholly 0 by variation of the self-induction in conjunction Withdrawn l l w v ngth variations of 1 :2. with the associated capacities of the circuit sys- The dlreetlon of Wmdmg of h of eeuph'ng tem and th t b coils 5/6 is so chosen that the nfluence coupl ng The amplifiers which have become known for between the two windings asslsts e eouplmg the ultra-short carrier waves employed for teleefiect Vla the Stray capaclty In thls case the vision purposes relate throughout to single-cir- Wldth of band of the ampllficiitlon remams prac- 25 cuit couplings b t tubes The result tically constant over the entire tuning range of ing frequency curve is accordingly the usual applioxlmetely an The bandresona Curve of form with a consider self 1s adJusted by the degree of coupling between able drop in the case of higher frequencies. In 5 In the ease of eomparatwely Strong a plurality of successive amplifying stages the ceuplmgs there the known resonance 30 frequency drop is naturally additive. It must ac bulges o the coupllng waves. These mu t th cordingly be corrected later by networks, possibly be flattened P bY 1"eS1StaneeS 9 and m m the after the rectification, In the known arrange anode and grid circuits. The res1stances are prefments th t i is performed by means of small erably selected not to be greater than the resistrotating plate condensers. There is not achieved ance Value I 35 in this Way an optimum amplification, as the circuit capacity is not limited to the smallest possible value, viz., the tubeand straypacities, of the appendant capacities in the case of the but is increased by the tuning condenser. highest frequency of the picture to be trans- In accordance with the present invention a mitted. It has been found that the use of special 40 circuit arrangement for coupling broad frequency tubes with particularly small loss capacities does bands modulated upon short or ultra-short waves not provide any appreciable advantage as comis claimed which avoids the stated disadvantages pared with the use of normal radio screeningand produces the greatest degree of efficiency on grid tubes the latter, however, with very conthe basis of the two aspects referred to above. siderable slope. In the latter case the gain in 45 The drawing shows an exemplary embodiment slope compensates the capacitative losses. The of the circuit arrangement in accordance with capacities can be kept below 15 cm., and this the invention. Therein the amplifier tubes l and results upon the transmission of band widths of 2 are coupled by means of two tunable circuits the order of 2 megacycles a resistance value of producing a band-filter effect. The two circuits approximately 2,000 ohms with respect to the 50 comprise pure self-inductances 3 and i and a pair damping resistances 9 and 10. The total ampliof coupling coils 5 and 6 in series connection. fication degree of an arrangement of this kind The two self-inductances 3 and l are completely can reach 8 or more, with a carrier Wave of bebalanced out in relation to one another by a tween 30 and 60 megacycles.

sheet-metal screen I. The effective coupling In the practical embodiment of such a circuit 55 arrangement which may be called a vario-bandfilter the two tuning cylinders 4a and 3a can be coupled together and pushed in simultaneously by the same actuating means. In order correct- ]y to tune the natural Wavelength one or both of the tuning coils 3 or 4 can be furnished with a preadjustment relative to the edge of the tuning cylinder. The width of band is adjusted to the desired value by a single adjustment of the coupling coil value 5 and 6. The pair of coupling coils 5/6 must naturally be screened inductively and capacitatively against the tuning coils 3 and 4. This also applies to the two coils 3 and 4 in relation to one another The entire coupling element is finally placed in a common screen-casing.

If there are to be coupled with a vario-band filter of this kind low-resistance circuits, 1. e., aerial or transmission leads, it is possible either to couple the low-resistance input inductively With the primary coil 3 or to tap the primary coil to the extent of the optimum coupling. It has been found that the coupling windings can be applied, on the tunable coil portion, together with the short-circuit cylinder, without the coupling effect being too greatly weakened upon the wave shortening.

I claim:

An amplifier system comprising a first thermionic tube and a second thermionic tube, each of said tubes having an input and an output circuit, means for applying signals for amplification to the input circuit of the first tube, a pair of inductance elements serially connected in the output circuit of the first tube, a second pair of inductance elements serially connected and included in the input circuit of the second tube, one inductance of eachserially connected pair being coupled to supply signals from the output of the first tube to the input of the second tube, a high conductivity metallic element contained within the other inductance of each of the serially connected pairs, means for simultaneously moving each oftheconductive elements within the said inductances for tuning, means for shielding each of the tunable inductance elements one from the other to prevent coupling between said two inductance elements, and a damping resistance means connected in parallel with each: of said series combinations of inductance elements.

KURT SCI-ILESINGER.

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