# Патент USA US2111483

код для вставкиM 15, 1938. c, E, TRUBE _ 211L483 ELECTRIC COUPLING SYSTEM _ Original Filed July 2, 1926 2 Sheets-Sheet 1 sg @rE O FREQUENCY @w I RESPOoNE FREQUENCY @9164 RESPON FREQUENCY . 359.65%, RESPON. \ ' ° FREQUENCY INVENTOR ACOT/ E. Trube - M’ QM’ BY ATTORNEYS I C. E T R U B E - 2,111,183 ELECTRIC COUPLING SYSTEM Original Filed July 2, 1926 ' 2 Sheets-Sheet 2 0 _ FREQUENCY INVENTOR Ca-r/ ETrube - ’ BY ' ATTORNEYS Mensa ‘Mn. 15,1938 ' 2,111,483 """ED STATES PATENT OFFICE " snsc'mrc COUPLING SYSTEM Carl E. Trube, Maplewood, N. J., assignor to ‘ Hazeltine Corporation, Jersey City, N. L, a cor- ‘ _ 1 poration of Delaware ‘Application July 2, 1926, Serial No.12o,o45 Renewed June 18. 1930 ' (Cl. 179—171) the best compromise design, considering sensitivi-' 'This'lnvention relates to electric coupling sys ty and selectivity and‘ this ratio also generally tems particularly adapted for use with radio-fre 38. Claims. varies rapidly with frequency. ‘This invention provides means for securing substantially the 5 effectively over a relatively wide range infre- ' most desirable ratio at all frequencies in order to procure the most desirable frequency-response quency. This application is a continuation-in part of my copending application Serial No. 101,- q and. selectivity characteristics without having any adjustable element except the tuning adjustment. 906, ?led April 14, 1926. In United StatesLet . Stated in another way, the present invention ters Patent No. 1,762,431, granted June 10, 1930, provides a new and improved means for procuring 10 10 are shown electric coupling systems arranged to give effective operation over a range in frequency an effective coupling between the input and out by providing a single manual device to adjust si put circuits of the coupling system that varies multaneously the tuning and the voltage ratio. with frequency in a preselected manner under the control of the designer. By the term “e?ective The present invention constitutes an improve ment over that of the above-mentioned Patent coupling” is meant the ratio of the effect coupled 1:, No. 1,762,431 in that the coupling system is so into‘ the secondary or output circuit-which may arranged as to give a voltage ratio that varies be a current or a voltage, to the input or primary quency vacuum tube ampli?ers and more particu larly to circuit arrangements which operate most automatically with the frequency‘ thus leaving effect, which may also be either a current or a only the single adjustment of tuning for different voltage. When the effective-coupling is meas frequencies. This simpli?es the construction ured as the ratio of the voltage coupled into the 20 and increases the reliability of the system. This invention is applicable both to coupling systems interposed between consecutive vacuum tubes of an ampli?er, and to the coupling system‘ interposed between an antenna and a vacuum 2 tube.‘ Furthermore, this invention is applicable to vacuum-tube ampli?ers that are stabilized by the use of a high step-up voltage ratio in the cou pling system, as described in my prior patent above referred to, to ampli?ers that are stabilized 3O by partial neutralization or by other means, and. - to amplifiers wherein complete neutralization of capacity coupling is attained and wherein regen~ erationis eliminated. 3,. - ‘ The degree of responsiveness or ampli?cation of an inter-tube coupling system is dependent, among other factors, on the voltage ratio of the system and the nature and magnitude of the in put impedance of the system, which comprises 43 the plate circuit load impedance of the preceding vacuum tube. Ordinarily, the-finput impedance of such a system> varies substantially over the tuning range of the system, following generally the impedance variations of the secondary tuned , circuit, increasing with frequency when the sec ondary circuit is tuned bymeans of a variable condenser and decreasing with frequency when the secondary circuit is tuned by means of a vari ometer. As a result of- this impedance variation, 50 at each frequency there is a particular ratio of output voltage to input voltage that will give the best compromise design. This ratio generally varies rapidly with the frequency, being relatively high at high frequencies. Similarly, in the an “ tenna circuit, there is a voltage ratio that gives output circuit to the input current, as’is the case 20 in an inter-tube coupling system, this ratio may be termed the “e?ective mutual reactance” of the coupling system. , , A feature of the invention is the maintenance, , during tuning, of the effective reactance appear- 2” ing at the output of the vacuum tube within such ‘limits that the reaction upon the input circuit through the inherent interelectrode capacityv of the tube is held within predetermined limits and in any event is insufficient to produce oscillations. Referring to the drawings: Fig. 1 illustrates a vacuum tube and an electric coupling system of the conventional type, in which the voltage ratio does not vary with the frequency. - Fig. 1A is the response-frequency curve corre sponding to Fig. 1. ~ Fig. 2 illustrates a modi?cation of Fig. 1 and also is a conventional type.’ Fig. 2A gives re spouse-frequency curves corresponding to Fig. 2 or to Fig. 6. _ , Fig. 3 illustrates an electric coupling system in which the voltage ratio varies with the frequency in accordance with this invention, but in which the variation with frequency is more rapid than 45 is usually desired. Fig. 3A. is the corresponding response-frequency curve. Fig. 4 illustrates a preferred form of this in vention which combines Figs. 1 and 3 to ‘give a voltage ratio which varies with the'frequency 50‘ Fig. 4A is the response frequency curve corresponding to Fig. 4 or to 1 in a desired manner. Fig. .5. . Fig. 5 is the combination of Figs. 2 and 3 and ‘gives results similar to those of Fig. 4. 55 a,111,4sa Fig. 6 illustrates an alternative arrangement Cs a very low‘ impedance; the former acting - in vmich some of the advantages of this inven- . substantially as an open cirhuit and the latter tion may be secured. ~ ’ Fig. 7 also illustrates a modi?cation of this invention in which some of the advantages may be secured. Fig. "7A is the corresponding re _ sponse-frequency curve. Fig. 8 is a further modi?cation, in which the primary circuit is isolated from the secondary 10 and main resonant circuit. Fig. 9 illustrates the application of this inven tion to a complete uni-control radio-frequency ampli?er, including the coupling between the antenna and a vacuum tube. 15 20 , For convenience, the voltage E: measured at the output terminals of the coupling system may be called the "output voltage”, and the voltage E1 measured at the input terminals of the cou- pling system may be called the "accompanying alternating voltage” or “input alternating volt age”. It may here be pointed out that the out put voltage will in certain modi?cations of this invention be identicallwith the "resonant volt 1. e., the voltage across the adjustable .main '25 age”, resonant circuit, as in Figs. 3 and 6; while, in other modi?cations the output voltage will not necessarily be the same as the resonant voltage, as in Fig. 5. 30 _ In the coupling system of Fig. 1, the ratio of the output voltage E2 built up across the resonant circuit Ca, La to the accompanying alternating input voltage E1 across the coil L1 is substan tially equal to the ratio of the self-inductance 35 L2 to the mutual inductance M, and is therefore independent of the frequency. The rate at which the reactances and the resistances vary with the frequency, however, is such that the input im pedance at resonance as measured between the 40 terminals of L1‘ is relatively low at low fre quencies. Therefore, both the effective coupling and the response or ampli?cation are corre spondingly low. For reasons of selectivity and stability, it is ordinarily the-practice to make the voltage ratio (Ea/E1) higher than that giv ing maximum ampli?cation at the highest fre quency. This is especially necessary in an un neutralized ampli?er, where stability is particu larly di?lcult to attain at high frequencies. The 50 result is that both the effective coupling and the amplification fall off markedly .at ‘the lower frequencies, as illustrated by the full-line curve in Fig. 1A, which indicates qualitatively the rela tive response of a complete ampli?er as /a func 55 tion of frequency. In a neutralized ampli?er it is possible to lower the voltage ratio, by em-_ ploying larger values of self-inductance L1 and thus of mutual inductance M, resulting in a re sponse curve such as the dotted line in Fig. 1A; but still the ampli?cation falls off at the lower end of the frequency range, and ‘furthermore the selectivity is impaired at the higher fre quencies. - q ' In place of the series-feed arrangement of 65 Fig. 1, in which direct current is supplied by the battery 13 connected in series with the primary coil L1, it is sometimes the practice to employ a parallel-feed system as illustrated in Fig. 2, where the direct plate‘ current is supplied through 70 the choke coil L: which is e?ectively in parallel with the input circuit of the coupling system, including condenser C5 and coil L1. It is the practice to design the choke coil 'L: and the blocking condenser Cs so that L3 offers a very 75 high impedance to radio-frequency current, and as a short circuit. Under'these conditions, the system of Fig. 2 is electrically equivalent to that of Fig. l, and has therefore the same disadvan tages, giving the same response-frequency curve, as represented‘by the full-line curve in Fig. 2A. In the arrangements of the-,wprior art, of which Fig. 1 is typical, the coupling transformer gen erally has an effective step-up ratio greater than the optimum value; in other words, the primary or input impedance of>the coupling ‘system is less than the internal plate resistance of the tube. By virtue of the use of the greater than optimum value instead of the optimum value,v the selectivity is greatly improved, while the am pli?cation is decreased by only a small amount.‘ In this region of operation, an increase in the e?'ective step-up ratio causes a further departure from the optimum value and results in decreas 20 ing the ampli?cation, and vice versa. In Fig. 3, there is provided a system essentially the same as that illustrated in Fig. 1 of my pat ent above referred to, but the condenser 0: now has a ?xed capacity, and the condenser C4 alone is the adjustable tuning element. This circuit, like Fig. 2, embodies a parallel feed; and it will also be understood thatv the choke coil La has it ~ very high impedance. The resonant circuit then includes the two ‘condensers Ca and C4 and the inductance coil L2. As the impedance of La varies directly with the frequency, and the impedance of Ca varies inversely with the frequency, the ratio Ez/Ei of the resonant output voltage across L: to the accompanying alternating input voltage across Cs varies as the square of the frequency. Such a variation is in the right sense to result in an improvement over the constant ratio given by the arrangements of Figs. 1 and 2, and under some conditions may be satisfactory, particu larly when stability is the most serious‘ limita tion and where the high-frequency losses in the coupling system are especially low, but ordinarily such a variation is too rapid in rate, resulting in a rapid falling off of both the effective coupling and the response at the higher frequencies, as shown in Fig. 3A. In general, therefore, an effective combination of Fig. l or 2 with Fig. 3 will give the most desir able variation with frequency of the voltage ratio 60 E2/E1 and of the response of the system. The combination of Fig. l with Fig. 3 is illustrated in Fig. 4, in which the main resonant circuit com prises the two condensers Ca and C4 and the in ductance coil In. If, as before. L: is a choke-coil of very high impedance, then between the input terminals of the coupling system there are two coupling elements across which are developed two components of voltage: that across the electro magnetic or inductive coupling element L1 which is constant relative to the resonant output voltage E2; and that across the electrostatic or capacitive coupling element 03 which varies‘ inversely as the, square of the frequency-relative to E2. Thus, so there is obtained a resultant voltage ratio which 65 increases with frequency but at a rate which is somewhat less than proportional to the square of the frequency, a variation of this sort being desir able ,for certain types of receivers. By properly choosing the magnitudes of the capacity C: and -70 the mutual inductance M, it is thus possible to obtain any desired law of variation of both the voltage ratio. Ea/Ei- and the effective coupling of the system intermediate between that of Fig. 1 II 3 9,111,498 and that of m. a That a‘ to say. auce of the tunable absorbing circuit is not re input voltage relative to the output voltage will fall oi! ' ilected into the-said input circuit to a su?lcient . asthe frequencyincreases, but the. rate of falling extent to cause the output impedance connected ,istic of the coupling system, isunder the control ' plate capacity of the saidiampli?er tube and co- - oil. and thus the frequency-response character-~ to the ampli?er to act'throughthe internal grid _. of the designer and the voltage ratio and response can begiven preselected values at any two speci fled frequencies. Ordinarily, it is preferable to have the voltage across C3 considerably exceed 10 that across L1 at the lower ‘radio frequencies, while at the higher radio frequencies the voltage across L1 may be the greater. More specifically. elements Ca and L1 cause theratio of the output alternating voltage to the input voltage (Ea/E1) tofall off automatically when the tuning element 0 is adjusted for higher frequencies, but at a'rate which is less rapid than the inverse square of the frequency. Under this condition, the response curve has a form such as illustrated in Fig. 4A. In the coupling system of Fig. 4. coil L1 is ordi narily woundwith only a few turns, while coil L: I is wound with many times that number. Capacity C3 is much larger than capacity C4. The actual operate with the currents in the ampli?er input to a su?ioient extent to produce ‘oscillation. The tendency toward oscillations in ampli?er coupling circuits is particularly pronounced when the in put circuit of theampliiler tube is tunable in con 10 sonance with the tunable circuit associated with the coupling system inthe output of the amplifier tube; such tunable circuits are shown, for ex ample, in Fig. 9. ' The objects of this invention may be attained by a great number of circuits, of more or less complexity. [For example, one of the simpler em bodiments of the invention may comprise a modi fication of the circuit arrangement of Fig. 2 as by replacing the choke-coll In by a radio-frequency 20 self-inductance and the blocking condenser C5 by a radio-frequency condenser, the two being de signed to be resonant together at a frequency inductance and. capacity values may be of the somewhat lower than the lowest frequency of the signals to be ampli?ed. Under these conditions, same order of magnitude as the values given here inafter for the identically numbered elements of the voltage ratio Ez/E1 is no longer substantially , independent of the frequency, but falls off at the the circuit of Fig. 5. Fig. 5 illustrates the combination of Fig. 2 with lower radio frequencies due to the approach to. . ‘that of Fig. 3, the coupling system, per se, being resonance of La and C5 in parallel, the increase in 30 identical with that of Fig. 4 of my previously input impedance thus compensating at least in 30 mentioned copending application, Serial ' vNo. part for the variation in the coupling reactance 101,906. The operation is essentially the same as provided by the coil L1. This arrangement, how ever, is not so desirable as that of Fig. 4 or Fig. 5; that just described for Fig. 4 and gives a response frequency curve as in Fig. 4A. The main resonant for the voltage ratio will be relatively too high at 35‘ circuit in this instance comprises the two con— intermediate frequencies, with the result that the densers Ca and C4 and the inductance coll L2. response curve tends to have a dip in the central There is an advantage in the circuit arrangement portion, as illustrated by the dotted curve in ' of Figure 5 over the ‘preceding circuits in that in Fig. 2A. 7 In Fig. 6, which illustrates a coupling system the circuit of this ?gure the outputvoltage is the 40 40 sum of the resonant voltage; (i. e., the voltage in many respects similar to that system illus~ trated in Fig. 2 of my Patent No. 1,762,431 above developed across the adjustable main resonant referred to, the voltage ratio E2/E1 will be sub circuit C4, C3. L2) and the voltage across in ductance L1. Ordinarily L3 is a choke-coil of very stantially constant if the coil L3 is a choke coil of high impedance. This voltage ratio is ob high impedance and C5 is a large capacity intro 4.5 duced to reinforce C3 and C4 in insulating for tained from a double step-up, ?rst between C3 direct current; if L3 and C5 are made somewhat and the combination of Ca and C5, and then be smaller they will have a qualitative effect in the tween L1 and L2; but both of these step-up ratios radio-frequency system, but will not change the are constant under the‘ condition just stated. The essential operation. The circuit of Fig. 5 was the response-frequency curve is then given by the 50 basis of certain models of a successful commercial receiver known as the “Thermiodyne”. In order that one skilled in the art may im mediately practice this invention, the following constants for the system of Fig. 5 are given: 55 L1+L2=one tapped solenoid coil of 390 micro henries inductance, tapped so that L1=12 micro henries. - C5==lto 10 milli-microfarads. 60 C3=2 to 10 milli-microfarads. C4=variab1e condenser having a range of from 15 to 220 micro-mlcrofarads. - La=a choke coil of not less than 500 micro henries inductance. ‘ It will be observed that when values ofthe order of those given‘ above as applicable to the system of Fig. 5 are assigned to the elements, the mutual reactance of the input and output circuits of the coupling system is fairly low. This result follows from the fact that the inductance of L1 is small in comparison with that of L2, and that the capacity of C3 is large in comparison with that of C4. Since the mutual reactance between the input circuit and the variably tunable absorbing 75 circuit" of the coupling system is small. the react full-line curve of Fig. 2A. However, if L3 is made a lower radio-frequency selfeinductance, so as to be resonant with the combination of C3 and C5 at a somewhat lower frequency than that of any signal to be ampli?ed, then a variable voltage will 55 be obtained which will automatically vary with the frequency in the same manner as for Fig. 2 when modi?ed as described in the preceding para graph. The response-frequency curve is then given by the dotted curve in Fig. 2A. The circuit 8.0 of Fig. 6, when adjusted in this manner, was em ployed in some of the earlier models of the men tioned “'I'hermiodyne" receiver. . Fig. 7 shows a modi?cation of Fig. 6, which ob tains a voltage ratio which varies automatically 65 with the frequency by the insertion of a small self-inductance L6 in series with C3. L6 is given such a value that its reactance is lower than that of condenser C3 at all ‘frequencies to which the system is to respond. At relatively high fre 70 quencies it will subtract a relatively large portion of the reactance of C3, thus giving a relatively low voltage E1 between the plate and the ?lament. This makes the step-up ratio Ez/E1 increase as the frequency rises, which is the result desired.v 4 v8,111,688 However, this effect does not become important vacuum tubes of s‘sid apparatus, said ?xed reac except near the high-frequency‘ end of the range. The result is that the voltage ratio is relatively tive elements being so arranged that between two trated in Fig. 7A. The system is therefore in alone is adjusted for higher frequencies. ' ~ . points, thereof there is developed an alternating too low at intermediate frequencies, and the re- ' voltage which automatically falls all relative to sponse curve is correspondingly too high, as illus said output voltage when said tuning element i‘erior to that of I"igs'.'_4 and 5. . Fig. 8 shows a system embodying my inven tion in which the primary circuit Cs, L1, In is The 10 isolated from the secondary circuit 0:, Le. proportions‘ of Co, Li and In and thecoupling's be tween “L1, In and'Ic may be adjusted to give a desirable variation with frequency of the voltage ratio Es/Ei. This modi?cation of my invention 15 is more fully described in my United States Iet ters Patent No. 1,763,380, granted June 10, 1930, which is a continuation-in-part of the present application. 1 Fig. 9 shows the application of the arrangement of Fig. 5 to a.._gcomplete uni-control radio-fre quency ampli?er, both as coupling between the . antenna and the grid of the ?rst vacuum tube and as coupling between consecutive vacuum tubes. The advantages of vapplying such a com pound coupling system to an antenna circuit are: ?rst, to permit of attaining at all frequencies the most suitable compromise between sensitive ity and selectivity; and second, to make the elec trical constants of the tuned antenna system and the subsequent coupling systems substantially identical at all frequencies, so as to permit them to be tuned alike, particularly when it is desired to employ a single control for tuning all circuits, as has been done in the "'I'hermiodyne" receiver. It is to be understood that by the'terms “an tenna” and "antenna and ground", as employed in this speci?cation and the appended claims, is meant any suitable system for collecting radio frequency energy to- which the input terminals of 40 an ampli?er would customarily be connected. I claim: 1. An electric coupling system adapted to be interposed between elements of a radio signaling apparatus, including terminals across which an 45 alternating voltage is developed, a main resonant circuit across which an output voltage is devel _ oped, and means for adjusting said circuit over a certain frequency range, an input path through said coupling system, and means including said 50 path for causing the ratio of the output voltage to the accompanying alternating voltage in said input path of the coupling system to rise as the frequency of said resonant circuit is increased, whereby high degrees of sensitivity, selectivity and stability are maintained. 2. A tuned radio-frequency coupling system interposed between elements of a vacuum tube radio-frequency ampli?er, including terminals across which an alternating voltage is developed, 60 an adjustable main resonant circuit across'which an output voltage is developed, an input path through said coupling system, and means includ ing capacity and inductance in said input path for causing the ratio of the output voltage to the accompanying alternating voltage in said path to rise as the frequency is increased, whereby '70 high degrees of sensitivity, selectivity and sta bility are maintained. 3. In a radio-frequency signaling apparatus in‘ cluding vacuum tubes, an electric coupling sys tem including the combination of ?xed reactive elements and a resonant circuit across which an output voltage is developed, said resonant circuit having a single adjustable tuning element, said coupling system being interposed between two 4. In a radio-frequency vacuum tube ampli? er, an electric coupling ‘system including a com- . bination of ?xed reactive elements and a resonant circuit across which an output voltage is devel oped, said resonant circuit having a single ad Justable tuning element, said coupling system being interposed between two vacuum tubes oi.’ said ampli?er, each tube having a grid, a- plate and a ?lament, said output voltage being im pressed across the grid and the ?lament of one of said vacuum tubes, said ?xed reactive elements being so related to each other and to said vacuum tubes that between the plate and the ?lament of the other of said tubes there is developed an alternating voltage which automatically falls of! 20 relative‘ to said output voltage when said tuning element alone is adjusted for higher frequencies. 5. In a radio ampli?er stage, including a vac uum tube having a ?lament, a grid and a plate, 25 an electric coupling system comprising a main resonant circuit in which a resonant voltage is built up, a path through said coupling system be tween said plate and said ?lament, a ?xed con denser in series both with said path and with said main resonant circuit, and reactive means so associated with said path and with said main resonant circuit that there is developed in said path a voltage whose ratio to said resonant volt age falls rapidly as the frequency is‘ increased. ,A 6. A system of ampli?cation of radiant energy comprising an electronic device, a transformer, a tuning capacity, a capacity connected in series between the primary and secondary of the trans former, said capacity being also in series with the tuning capacity, and both capacities being con nected in shunt across the secondary of the trans former, and the electrical values of the said in ductances 'of the transformer and of the said capacities being relatively such that the system is essentially nonregenerative. - _ 7. A system of ampli?cation of radiant energy as set forth in claim 6 which provides capacities to form an electrostatic‘ path of energy transfer whose value' is de?nitely variable, and induct ances comprising a transformer to form an elec tromagnetic path whose value is naturally vari able with changes of frequency; the electrical re lationship of these two paths and their values being such'that a maximum transfer of energy is obtained without regeneration or any ?ow of undesirable disturbing currents at_any desired frequency. a 8. A system of ampli?cation of radiant energy as set forth in claim 6 which comprises an elec tromagnetic and an electrostatic path of energy‘ transfer whose values are variable, automatically, by the act of tuning, said values being so related to each other as to produce a zero di?'erence of potential in respect to all undesired currents be tween‘ the grid and plate‘ of the electronic device when the set is tuned to any given frequency. ' - 9. A system of ampli?cation of radiant energy comprising an electronic device, a transformer, a tuning capacity, a capacity connected in series 70 between the primary and secondary of said transformer, said capacity being also in series with the tuning capacity and both capacities be ing connected in shunt across the secondary of the transformer, and the electrical values of said 5 2,111,483 coupled to said‘ tuned circuit, and at least two so related to each other as to- simultaneously of said elements having di?erent reactance vari ations with change of frequency, whereby the maintain a condition of complete non-regenera tion and a condition ‘of energy transfer main¢ total effective coupling can be made any desired function of the frequency to which said circuit tained constant at its maximum value at any de inductancesand capacities being‘. so selected and sired frequency. 10. A system of amplification of radiant energy : comprising an electronic device having an output is tuned. ’ 16. A tuned radio-frequency coupling system comprising two pairs of terminals, a tunable cir circuit which comprises a transformer, a variable cuit connected with one ofsaid pairs of terminals, and a network including ?xed reactance elements 10 10 condenser, and a series condenser, said variable ' , connected with the other of said pairs of termi and series cor'idensers being connected in series with each other and the two being connected in nals, at least one of said elements being coupled shunt across the secondary of said transformer to said tunable circuit, and at least two of said and one end of the primary of said .transformer elements having different reactance variations with change of frequency, the values of said two 15 being connected into the series connection be tween the two said condensers and their values elements being so proportioned and said elements being selected so as to prevent the production of being so related to said tunable circuit that the undesired disturbing oscillations in the electronic total effective coupling is a preselected-function of the frequency to which said circuit is tuned. device. 17. A tuned radio-frequency coupling system 20 11. In a system of ampli?cation of radiant en 20 comprising two pairs of terminals, a tunable cir ergy comprising an electronic device, a trans former, a tuning capacity, a capacity connected cuit connected with one of said pairs of termi in series between the primary and secondary of said transformer, said'capacity being also in se '25 ries with the tuning capacity, and‘ both capacities being connected in shunt across the secondary of the transformer, the process'of simultaneously maintaining a condition of complete non-regen eration and a condition of energy transfer main ‘so tained constant at its maximum value over any desired range of frequency by the selection and. relation of the electrical values of said induct ances and capacities. 12. An electric coupling system for coupling a pair of input terminals to a pair of output termie nals, said system comprising an inductive cou pling element which acting alone would produce a voltage across said output terminals which rises nals and a network of ?xed reactance elements connected with the other of said pairs of termi nals, at least one of said elements being induc 25 tively coupled to said tunable circuit, and at least two of said elements having opposite reactance variations with frequency, whereby the effective mutual'reactance can be made substantially in- ' dependent of the frequency to which said circuit 30 is tuned. 18. A tuned radio-frequency coupling system comprising two pairs of terminals, a tunable cir cuit including a variable condenser and a ?xed inductance connected in parallel to one of said 35 pairs of terminals and a network of ?xed re actance elements connected with the other of said pairs of terminals, at least one of said elements being coupled to said tuned circuit, and at least two of said elements having different reactance 40 variations with frequency, the values of said two elements being so proportioned and said elements being so related to said tunable circuit that the with increasing frequency, and reactance means 40 included in said system for maintaining said out— put ‘voltage fairly constant over a substantial range of frequency. 13. An electric coupling system for interposi tion between a pair of input terminals and a pair ~ total effective coupling is a preselected function 45 of output terminals, said system comprising an of the frequency to which said circuit is tuned. 45 19. A radio-frequency coupling system com exciting circuit and a tunable output circuit cou pled to said exciting circuit, said exciting circuit prising two pairs of terminals, a tunable. circuit including an element which acting alone would including a variable condenser and a ?xed in produce a voltage in said output circuit which ductance connected in parallel to one of said with increasing frequency, and reactive so rises means in said exciting ‘circuit for causing the voltage across said input terminals to decrease with increasing frequency, whereby the voltage across said output terminals remains substanti 55 ally constant. ~’ 14. An electric coupling system having a pair of input terminals and a pair of output terminals, - said system comprising an exciting circuit con nected to said input terminals and an absorbing 60 circuit connected to said output terminals and coupled to said exciting circuit, said system in cluding only one manually variable element which selects the frequencies transmitted by said sys pairs of terminals, and a network of ?xed re 50 actance elements connected with the other of said pairs of terminals, at least one of said ele ments being capacitively coupled to said tunable circuit, and at least two of said elements having opposite reactance variations with frequency, the values of said two elements being so propor tioned and said elements being so related to said tunable circuit that the total effective coupling is a preselected function of the frequency to which said circuit is tuned. . 60 20. A tuned radio-frequency coupling system comprising two pairs of terminals, a tunable nals and a network including ?xed reactance circuit connected with one of said pairs of ter minals, and a network including ?xed reactance elements connected with the other of said pairs 65 of terminals, at least one of said elements being coupled to said tunable circuit, and at least two of said elements having different reactance var iations with change of frequency, said ?xed re actance elements being of such types and having 70 such circuit relationship with each other and with said tunable circuit that the total effective coupling can be made any desired function of the elements connected with the other of saidpairs of terminals, at least one of said elements being erly proportioning the values of said elements. . tem, and said exciting circuit including elements 65 whose impedances vary with frequency in such a manner that the voltage across said input ter minals automatically decreases when the tuning frequency is increased,‘ while the output voltage remains substantially constant. 15. An electric coupling system comprising two pairs of terminals, a variable condenser-tuned circuit connected with one of said pairs of termi frequency to which said circuit is tuned by prop 6 2,111,488 21. A tuned radio-frequency coupling system comprising two pairs of terminals, a tunable cir cuit connected with one of said pairs of termi nais, and a reactance network connected to the other of said pairs of terminals and‘including ?xed reactance means coupled to said tunable circuit which acting alone produces a ratio ofv output voltage to input current which varies in a predetermined manner with the frequency to 10 which said circuit is tuned and ?xed reactance means for substantially modifying the manner of variation of the ‘voltage introduced into said tunable circuit by said input current as said cir cuitcis tuned over its range, thereby to modify " 16 said ratio of output voltage to input current in a preselected manner. ~ 22. A tuned radio-frequency coupli system comprising two pairs of terminals, a tunable cir cult connected with one of said pairs of termi nals, and a reactance network connected to the other of said pairs of terminals and including ?xed reactance means coupled to said tunable circuit which acting alone produces a ratio of output voltage to input current which increases with the frequency to which said circuit is tuned, ' and means for varying the voltage introduced into said tunable circuit by said input current in versely in accordance with said frequency to' which said circuit is tuned, thereby to compen 30 sate at least in part for the variations in said ratio. . 23. An electrical system composed of an am pli?er of alternating currents, a tunable input circuit, an output circuit, an internal path in said 35 ampli?er connecting said output circuit to said input circuit, a tunable absorbing circuit as sociated with said output circuit, and nieans for limiting ampli?ed energy feedbaclg through said internal path comprising means for loosely cou pling said absorbing circuit to said output circuit and electromagnetically in phase from said output circuit in frequency consonance with the currents therein to selectively’ create absorption reaction thereon, controlling said selective absorption elec-' .trostaticaliy whereby said electromagnetic ab sorption decreases with frequency decrease, and so relating the'variation of electrostatic absorp tion to the necessary electrostatic variation for ' selectiveabsorption that said electrostatic ab; sorption increases with frequency decrease at 10' such rate that the effect of said electromagnetic absorption on the reactions of said output circuit with frequency is modi?ed in a desired way. 26. In ‘an electrical system including a source of alternating currents'of a wide range of fre quencies, the electrical conduct of said source towards currents of different frequencies depend ing upon the nature of the reactions to said vcur rents of di?erentfrequencies of a circuit con nected to the output terminals thereof, the meth od of controlling said reactions with frequency 20' as the current output of said source is changed from frequency to frequency which consists of selectively absorbing energy fromsaid output circuit by way of a coupling which transfers 25 energy increasingly with frequency increase in frequency consonance with the currents therein to selectively create absorption reaction thereon, further simultaneously selectively absorbing en ergy from‘ said output in phase with said ?rst 30 selective absorption by way of a coupling which transfers energy decreasingly with frequency in crease, and selecting the rate of change of energy transfer with frequency of one of said couplings to produce a predetermined character with fre so quency of combined absorption reaction on said output circuit whereby the conduct of said source with frequency is controlled in a desired way'. 27. In an electrical system the combination of ' a source of alternating currents of a wide range and electrical elements maintaining said coupling of frequencies, an output circuit, the electrical 40 constant while said absorbing circuit is tuned in conduct of said source towards currents of dif consonance with said input circuit. . ferent frequencies depending upon the natureof 24. An electrical amplifying system including a‘ the reactions of said output circuit to said cur three-electrode vacuum tube, an adjustable pe rents, and means for controlling the electrical riod circuit connected to the input electrodes of conduct of said source from frequency to fre 45 said tube, an output circuit, a responsive device,‘ quency through control of said reactions com and means for controlling the reaction of said output circuit and abstraction of energy there from for said responsive device over a wide range of frequencies that a predetermined effect in said - responsive device with frequency is obtained, in prising a circuit variable in period over said wide range-of frequencies coupled to said output cir cuit through a coupling which changes the ab-', sorption reaction of said variable circuit on said output circuit as varied from frequency to fre ciuding a circuit coupled to said output circuit quency, and a second coupling between said cir adapted to be adjusted in period in consonance _ cuits in phase accord with said ?rst coupling, said with said adjustable period input circuit, and across which second adjustable circuit said re sponsive device is connected, said‘ coupling in cluding a pair of coupling elements transferring energy in phase, one of which couplings increases in effect with frequency increase and the other of which couplings decreases in effect with fre-. quency increase, the relative values of said cou plings being chosen to give the said predeter mined eifect over a wide range of frequencies. 25. In an electrical system including a source of alternating currents of a wide range of fre quencies, the electrical conduct of said source towards currents of di?erent frequencies depend ing upon the nature of the reactions to said cur 70 rents of different frequencies of a circuit con nected to the output terminals thereof, the meth od of controlling said reactions with frequency as the current output of said source is changed from frequency to frequency which consists of 76 ‘selectively absorbing energy both elcctl'ostatically second coupling being adapted to change the ab sorption reaction of said variable circuit'on said output circuit from frequency to frequency in versely to the change produced by said first cou pling. > ‘ ' 28. The method of transferring electrical '00 energy throughout a range of frequencies from an exciting circuit to a tunable absorbing circuit, which consists of transferring the energy both electromagnetically and electrostatically in aid ing phase, and causing said electrostatic energy 65 transfer to decrease as said absorbing circuit is tuned in such sense as to increase the frequency of the energy so selected'for transfer in sub stantially the same degree as the electromagnetic energy transfer increases through such tuning. 70 29. An electrical energy transfer system com prising means for transferring energy throughout a range of frequencies from an‘exciting circuit to a tunable absorbing circuit including a coupling between said circuits comprising in combination amass a capacitive reactance element and an‘inductive reactance element poled to transfer energy in aiding phase, the reactions of said elements being therewith, ?xed reactance coupling means'in eluding inductance for providing coupling there between; which varies with frequency in one sense adjusted to produce a resultant energy transfer as said tunable circuit-is tuned over said range, which, remains substantially constant with fre ‘ and ?xed reactance coupling means including quency variationsas said absorbing circuit is capacitance for providing coupling therebetween tuned. ‘ which varies with frequency in the opposite ' 30; An electrical energy transfer system includ- sense, said coupling means beingrelatively poled ing an exciting circuit and a tunable absorbing ' in aiding phase, whereby the coupling variation 10 circuit, an electrostatic coupling between said of one said means at least partially compensates 10 circuits, and an electromagnetic coupling be -for_ the coupling variation of the other said tween- said circuits, said couplings being so poled and‘ relatively adjusted that, for such adjust-Q 36. A tunable radio-frequency coupling sys ment, their combined energy transfer remains tem comprising a resonant circuit including in substantially constant with'frequency as said ab ductive and capacitive elements, only one of said~ 15 means. sorbing circuit is variably tuned. ' - - ~ _ - - . elements being adjustable for tuning ,said cir . 31. The method of transferring electrical en- ' cuit over a wide range of radio frequencies, an ergy ‘throughout a range of frequencies from an other circuit to be coupled therewith, ?xed re- - exciting circuit to a tunable absorbing circuit,f actance coupling means including inductance for 20 which consists of transferring the energy both providing coupling therebetween which varies 20' electromagnetically and electrostatically in aid with frequency in__one sense as said tunable cir ing phase, and causing said electrostatic transfer cuit is tuned i'over said range, and ?xed react to vary in a preselected manner as said absorbing circuit is tuned. 25 ' ance coupling means including capacitance for , providing coupling ‘therebetween’ which varies ' 32. The method of transferring electrical en with frequency in the opposite sense, said cou ergy throughout a range of frequencies from an pling means being relatively poled in aiding exciting circuit to an absorbing circuit whose‘ constants include a capacitive reactance divided into two portions, which consists of transferring energy in aiding phase both electromagnetically and, through one of said capacitive portions, ad justing'said absorbing circuit for resonance with desired current frequencies in said exciting cir cuit by varying the other of said capacitive por 35 tions, and adjusting the relative values of said capacitive portions to produce an energy trans-. fer that combines with the electromagnetic en‘ ergy transfer to produce a combined transfer that varies in a preselected manner with fre 40 quency. phase, whereby the coupling variation of one said , means at least partially compensates .for the coupling variation of the other said means. 37. A tunable radio-frequency coupling system 30 comprising a'resonant circuit including ?xed in ductance and adjustable capacitance for tuning over a wide range of radio frequencies, another circuit to be coupled therewith, ?xed reactance coupling means including inductance for provid 35 ing coupli?g therebetween which increases with increasing frequency as said tunablecircuit is tuned over said range, and ?xed reactance cou-> cluding an exciting circuit and a tunable ab pling means including capacitance for providing coupling therebetween‘ which decreases with in 40 creasing frequency, said means being relatively poled in aiding phase, whereby the coupling vari sorbing circuit, an electrostatic coupling bee tween said circuits adapted to ‘decrease inva pre pensates for the coupling variation of the other 33. An electrical energy transfer system. ‘in- 45 selec'ted manner with increase of frequency as said absorbing circuit is tuned, and an electro; magnetic coupling between said circuits so poled 50 25' ation of one said means at least partially com said means. 1' ' '38. A tunable radio-frequency coupling system as to transfer energy in phase with said electro comprising a resonant circuit including in series a ?xed inductance element, a ?xed capacitance static coupling. element and an adjustable capacitance element _, _ a, 34. An electrical energy transfer system in cluding an exciting circuit and a tunableab sorbing circuit, an electrostatic coupling between ‘ said circuits adapted to decrease in a preselected manner with vincrease of frequency ‘as said .ab 55 sorbing circuit is tuned, an electromagnetic cou pling between said circuits ‘so poled as to transfer 45 for tuning the circuit over a wide range of radio 50 frequencies, and another circuit including in series said ?xed capacitance element and an other ?xed inductance element inductively cou ~'pled with that of said resonant circuit, said in ductive coupling being poled to aid the coupling 55 of said ?xed capacitance, whereby the variation energy in phase with said electrostatic coupling, ' of coupling due to. said ?xed capacitance ele and a condenser in said exciting circuit in series with said couplings. - ' ' _ 35. A tunable radio-frequency coupling system ment at leastpartialiy compensates for the cou .pling variation due to said‘ inductive coupling as - said resonant circuit is tuned over said range. comprising a circuit tunable over a wide range of ' radio frequencies,'another circuit to be coupled OARLETR'QBE. . so

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