US2191315A - Electric translation circuit - Google Patents

Description

Feb. 20, 1940. G. GUANELLA 2,191,315

ELECTRIC TRANSLATION CIRCUIT Filed Nov. 1, 1938 2SheetsSheet l a of J Z I 0c EIT IMPEDANCE T Z K 15 T (MPEDANCE T 2 INVENTOR. qusi'awfluanella ATTORNEY.

Patented Feb. 20, 1940 UNITED STATES ELECTRIC TRANSLATION CIRCUIT Gustave Guanella, Zurich, Switzerland, assignor to Radio Patents Corporation, a corporation of New York Application November 1, 1938, Serial No. 238,127 In Switzerland November 25, 1937 11 Claims.

The present invention relates to electric circuits or networks and more particularly to arrangements for and a method of controlling the propagation factor or coupling coefllcient of such circuits or networks in dependance upon a controlling current or potential.

A further object of the invention is the provision in a translation circuit of means for and a method of controlling the phase rotation of a current or potential impressed upon such circuit in dependance upon variations of a controlling electric current or potential.

The problem of controlling the coupling effected by electrical circuits or networks in dependence upon a controlling current or potential arises in many cases in communication and high frequency engineering systems. Thus, it is often required to vary the amplitude relation between the input and output potentials of a tor of a coupling or translating circuit or net' work is suited for various purposes, more particularly if it is desired to control the amplitude relation and/or the phase rotation of alternating currents or potentials rapidly or slowly in accordance with variations of a controlling potential.

It is well known to adjust the transmitting characteristics of a network or circuit purely electrically by the employment of electron tubes as coupling elements having a curved operating characteristic and by varying the average grid bias potential or potential of a special auxiliary grid or other control electrode.

it has furthermore been proposed to effect a coupling variation purely electrically by the employment of iron cored induction coils as coupling elements provided with a special magnetizing control winding energized by the controlling current.

According to the present invention, it is proposed to employ devices in a translation circuit having mechanically fixed electrodes which electrodes in conjunction with a suitable intermediate layer disposed therebetween form a condenser the capacity of which can be varied by a potential impressed upon the electrodes in such a manner that a certain variation of the applied biasing potential causes a corresponding variation of the coupling or propagation factor of the circuit'or network without essentially affecting the frequency or tuning characteristics of the circuit.

Such condensers which are also described in my copending U. S. application, Serial, No. 201,945, filed April 14, 1938, include a very thin blocking layer embedded between suitable electrodes in such a manner that the capacity for the frequencies to be dealt with is dependent upon an applied biasing potential and the loss angle of the condenser does not exceed about 45". Since this thin blocking layer of low electrical conductivity which in general does not have a thickness greater than 10- cm. constitutes an essential element of variable potential controlled condensers of this type and in many respects resembles the construction and arrangement of the known blocking layer or dry rectifiers, potential controlled or biased condensers of this type will be referred to as blocking layer condensers for the purpose of this specification.

As pointed out in the above copending application, no fully satisfactory physical explanation has been found for the behavior and characteristics of these blocking layer condensers. However, extensive practical experiments made by applicant have shown that by using a sulficiently thin intermediate or blocking layer embedded between the electrodes of suitable composition and characteristics substantial capacity variations can be realized. This phenomenon for instance may be demonstrated with most of the known dry rectifiers such as selenium rectifiers, cuprous oxide rectiflers, by applying the controlling potential in the current blocking direction of the rectifier. A capacity variation has also been found to be present in the less common rectifier combinations such as uranium dioxide rectifiers, zinc dioxide rectifiers, and others. The blocking layer between the electrodes may consist of a suitable insulating material applied or formed in any suitable manner upon the electrodes such as a suiilciently thin layer of organic lacquers applied to a conducting or semi-conducting electrode. It was found furthermore that the capacity variations are dependent upon the nature or composition of the adjoining electrodes, the kind of contact and the transition or boundary zone between the blocking layer proper and the adjoining electrodes.

. The above phenomenon has also been observed in dry or electrolytic condensers. Substantial capacity variations have been obtained with arrangements containing tungsten, niobium, or tantalum as anode material and placed in a suitable electrolyte. The blocking layer in such electrolytic devices is produced by electrolytic formation between the electrolyte and the metal. In addition to the capacity variations in devices of the latter type, there is in most cases present a very slow action of the biasing potential resulting in a variable formation depending on the magnitude of the control potential.

As will be understood, the biasing potential applied to blocking layer condensers of the above described type should be varied only to such an extent as to maintain the loss angle within the permissible limits to prevent undesirable distortion of the alternating current potentials to be translated due to incidental rectification and also to prevent the direct current from assuming excessive values. In devices which pass the electric current in one direction only such as dry electrolytic rectifiers, it is therefore not generally necessary to operate with biasing potential applied in the blocking direction.

According to the present invention, blocking layer condensers of the above type are connected suitably in electrical networks of both simple and cbmplex construction in such a manner that the variations of the capacity eflected by an applied controlling or biasing current isadapted to vary the propagation factor or coupling characteristics of the circuit or network in a desired manner without substantially interfering with the tuning of frequency characteristics of the.

circuit.

Further details and aspects of the invention will become more apparent from the following detailed description taken with reference to the accompanying drawings forming part of this specification, and wherein Figures 1 to 3 illustrate schematically simple networks or four-pole circuits adapted for practising the invention, a

Figure 3a is a graph illustrating the variation of the capacity and resistance of a blocking layer condenser in dependance upon the applied bias or control potential,

Figure 4 illustrates a simple potentiometer. circuit with a variable blocking layer condenser embodied therein according to the invention,

Figure 5 is a modification of Figure 4 embodying two blocking layer condensers controlled by a common biasing battery,

Figures 6 and 7 are bridge type transmission networks embodying controllable blocking layer condensers according to the invention,

Figure 8 is a network illustrating the employment of the invention for effecting a variable phase rotation between input and output potential in dependance upon a controlling or biasing electric current,

Figure 9 illustrates an embodiment of the invention for effecting a current limitation in a translating circuit,

Figure 10 is a further exemplification of an arrangement embodying potential controlled condensers for efiecting automatic expansion or contraction of the intensity range of signals or potentials to be translated,

Figures 11 and 12 illustrate substitute or limiting networks to be used in connection with the remaining figures, and

Figure 13 represents an amplifying circuit utilizing potential controlled condensers according to the invention in place of amplifying tubes.

Similar reference characters identify similar parts throughout the different views of the drawings. a Referring to Figure 1, there is illustrated a four-pole network known as a T-circuit having a pair of input terminals a, b and a pair of output terminals 0, d. A pair of impedances Z1, Z: are serially connected between the terminals a and 0 while a further impedanceZ: is connected between the junction of the impedances Z1 and Zr and the remaining input and output terminals b and 11, respectively. An input potential E1 impressed upon the terminals a, b will be translated through the circuit and an output potential E2. is derived from the terminal c, 07.

Figure 2 shows a general network or four-pole circuit known as a w-circuit wherein the impedances Z1 and Z: are connected across the input and output terminals, respectively, and the impedance Z: is arranged between the input terminal a and the output terminal c in a manner well known.

Figure 3 shows a translation network of the Wheatstone bridge type comprising four bridge arms formed by impedances Z1 to Z4 with the input terminals a, b connected to one pair of apices of the bridge and the output terminals 0, 41 connected to the remaining pair of apices of the bridge circuit.

The impedances Z are so-called two-pole circuits or networks and should not contain any resonating elements forming resonant systems likely to interfere with the control of the transmission characteristics or propagation factor in accordance with the invention. By varying one of the impedances Z it is possible in a known manner to control the ratio between the input and output potentials E1 and E2, or in other words the propagation or translation factor of the circuit or network.

According to the present invention, at least one orseveral of the impedances Z include one or more blocking layer condensers which if desired may be operatively associated with other circuit elements in such a maner that the propagation factor of the network may be varied within predetermined limits by the controlling or biasing potential.

Referring to Figure 311 there is shown a graph illustrating the variations of the capacity C and the internal resistance Rv of a blocking layer condenser in dependance upon a biasing or controlling potential e applied thereto in the current blocking direction. Such a condenser may be e. g. of the oxide type comprising a base electrode (negative electrode) coated with an oxide layer formed thereon in any suitable manner and a covering electrode (positive electrode) in contact with the oxide or blocking layer such as a plate or disc pressed against the blocking layer by a spring or the like. As is seen fromthis graph which represents the results obtained from a large number of experiments conducted by applicant, the capacity of a blocking layer condenser decreases as the biasing potential is increased while the internal resistance varies in the opposite direction.

Referring to Figure 4, there is shown a simple potentiometer circuit for translating an input potential E1 comprising an impedance Z and a blocking layer condenser K in series and connected across the input terminals 0., b. In the for instance if a constant input and output reexample shown the output potential Es is derived from the voltage drop developed across the im pedance Z connected to the output terminal c, d. In a simple potentiometer circuit oi this type the voltage ratio 5 E1 with no load connected to the output is equal to whereby Zx represents the impedance of the blocking layer condenser K. By varying the capacity 0! the latter according to an impressed controlling potential it is seen that the voltage transmitting ratio of the circuit can be varied in a desired manner. This transmitting ratio in general is or a complex nature; that is, it includes a phase rotation of the output potential E1 relative to the input potential E1. The phase rotation may be avoided in practice if Z constitutes a capacity having a loss angle corresponding to the average loss angle of the blocking layer condenser K. i This can be realized by the provision of a resistance in series with the blocking layer condenser as shown in Figure 12. The blocking layer condenser K and impedance Z may be mutually exchanged without essentially aflecting the operation of the circuit, as is understood.

In place of the impedance Z in Figure 4, it is possible to provide a further blocking layer condenser such as shown in the embodiment according to Figure 5. In the latter, two blocking layer condensers K1 and K: are connected in series in the same sense as regards their current passing directions and placed across the input terminals a, 17 through a coupling or blocking condenser 01., while the output potential is derived from the potential drop developed across the condenser K: through a further coupling or blocking condenser C2. The bias or control potential is supplied by a battery B connected across both condensers in series with an induction or choke coil I1. In this arrangement both condensers K1 and K2 are controlled diiferentially by the connection from the common junction point thereof to a variable tap t of the battery B, said connection including a further choke coil Is. In the representation of the blocking layer condenser in the drawing, the thin line represents the negative electrode, the thick line represents the positive electrode, while the dashed line represents the blocking layer embedded between the electrodes.

It is thus seen that in Figure 5 both condensers are biased in the blocking direction and that the bias may be controlled differentially by adjusting the tap t or any equivalent potential supply means such as a potentiometer resistance as will be understood by those skilled in the art. The condensers C1 and C: serve to block the biasing potential from the input and output circuits while the choke coils I1 and I: are provided to prevent a short circuit of the alternating current potentials through the direct current control cir cuits. As pointed out, by varying the tap t of the battery B the capacities of the blocking layer condensers K1 and K2 vary in opposite directions, thereby effecting a variation of the amplitude of the output potential E2 in relation to a given amplitude of the input potential E1.

Potentiometer circuits according to Figures 4 and 5 derived from Figure 1 by omission of the impedance Z2 in many cases are unsuited to fully comply with the practical requirements. Thus sistance is required the network: should comprise at least three two-pole elements such as shown in Figures 1 to 8.

On the other hand, arrangements based on a Wheatstone bridge according to Figure 3 are to be preferred in cases when coupling variations are desired down to a complete decoupling between the input and output circuits.

An arrangement adapted for this latter purpose is shown in Figure 6. The latter represents a 'Wheatstone bridge comprising two arms formed 'by impedances Z1 and Z: and a pair of further arms formed by blocking layer condensers K1 and K: each in series with a biasing battery B1 and B1,

respectively. The batteries B1 and B2 provide a steady or constant biasing potential in the blocking direction (e0 according to Figure 3a). The controlling potential e which may be derived from any suitable source such as a battery with associate potentiometer, a microphone or any other varying potential source is impressed through terminals r, 3 across the input terminals a, b or upper and lower apices of the bridge circuit in series with a pair of choke cells 11 and In. The impedances Z1 and Z: may consist of induction coils, resistors, condenser, or a combination of these elements. If condensers are used they should be shunted by an impedance passing direct current such as a resistance to provide a conductive current path for the control potential e to the blocking layer condensers K1 and K2, respectively. The steady bias potentials provided by the bat--- teries B1 and B2 are such as to normally produce a balance of the bridge circuit. The blocking layer condensers K1 and K: are then controlled differentially by the variable or alternating control potential e applied to terminals 7', 3, thereby upsetting the balance of the bridge circuit. Thus, if the amplitude of the input potential E1 is kept constant it is possible in this manner to vary the amplitude of the output potential E: between zero (balance condition) and a limit value. In place of the two impedances Z1 and Z; in Figure 6, it is possible to provide in certain cases an induction coil with a center tap the inductance of which is suificiently high to avoid resonance effects in conjunction with the condensers K1 and K2.

As pointed out hereinbeiore, the potential controlled condensers K1 and K2 in general require, although not necessarily, a definite zero or bias potential acting in the blocking direction, specially in the case of devices of the type constructed in accordance with the known dry rectiflers. For this purpose the batteries B1 and B2 are provided to produce a fixed bias or operating point so as seen from Figure 3a. In place of separate batteries it is also possible to provide a voltagesource in series with an alternating current blocking impedance such as an inductance connected across the output terminals 0, oi.

If it is desired to maintain the input and output potential symmetrical with respect to a predetermined reference or zero potential such as ground, arrangements of the type shown in Figure 7 may be employed. In the latter, the input terminals a, b are shunted by an impedance passing direct current such as an inductance or a resistance R1 provided in the example shown, choke coils i1 and is being arranged in the connecting leads from the terminals a, b for the purpose pointed out hereafter. Similarly the output terminals 0, d are shunted by a resistance R2. The upper ends of the resistances R1 and R2 are connected through a blocking layer condenser K1 in series with a biasing battery R1, and similarly the lower ends of the resistances R1 and R: are connected through a blocking layer condenser 1Q in series with a biasing battery Ba. There are provided a further pair of blocking layer condensers K: and K4 in series with biasing sources B2 and B4, respectively, and connected between the lower end of resistance R1 and the upper end or resistance R2 on the one hand, and the upper end of resistance R1 and the lower end of resistance R: on the other hand. The input or control terminals r, s are connected to the center tap points of the resistances R1 and R2. If for a certain control potential such as zero control potential the capacities of all four blocking layer condensers are equal to each other, the output potential E: for any given amplitude oi the input I potential E2 will also be zero. With increasing control potential the balance of the bridge will be disturbed and the amplitude of the output potential increased accordingly.

According to a modification of Figure 7, the control potential e may be impressed across the output terminals 0, d and the output potential E2 derived from the terminals 1', s without ailecting the operation or the system as is obvious in view of the symmetry of the circuit arrangement.

It will be obvious from the above that the blocking layer condensers in Figure 7 in addition to the controlling potential should in general be biased in the blocking direction by a certain steady potential (eo according to Figure 3a) in order s to prevent the direct potential through the condensers from exceeding a permissible limit. The steady biasing potentials are provided in Figure 7 by the batteries B1 to B4. In special cases the steady biasing potential may be applied in a different manner. According to a simple arrangement the steady biasing potential may be supplied together with the control potential superimposed thereon such as by replacing the condensers m andK4 or the condensers K1 and K: by fixed condensers having a capacity and loss angle corresponding to the respective average values of K1 and K! or K: and K4,

v respectively, if necessary by the provision of additional substitute elements as shown in Figures 11 and 12. In this case the controlling-potential e varies within such limits as to act always in the blocking direction of the two remaining blocking layer condensers K1 and K1 or K: and K4, respectively, thereby dispensing with additional current sources.

Many of the circuits for eflecting coupling variations by the aid of blocking layer condensers resemble the known circuit arrangement for mutually modulating alternating currents. Thus, for instance the circuit according to Figure 7 may be converted into a known ring modulating circuit by substituting rectifiers for the blocking layer condensers and by omititng the special steady bias potentials. 0n the other hand, it is possible to convert the known modulating circuits into arrangements for coupling controlby substituting blocking layer condensers for the non-linear resistances or rectifiers used in the former. The basic difference however in all cases is the fact that in the known modulating circuits circuit elements such as dry or vacuum tube rectifiers are employed whose alternating current resistance is dependent upon a. biasing potential according to a nonlinear relationship, while in the case of arrangements according to the invention for coupling control there are employed condensers having a loss angle not exceeding 45' and being capable of control by a variable potential impressed thereon. In this manner it is possible to eflect a variable coupling without appreciable electric losses in the circuit.

The employment of blocking layer condensers in many cases may result in a substantial capacitive load imposed upon the associate circuits. Thus in the case of an arrangement according to Figure 7 the internal apparent impedance at the input terminals a, b is equal to the average capacity of a single blocking layer condenser. The controlling potential e does not materially eflect this input impedance. If it is desired to transmit a definite frequency or a small band of frequencies the internal capacity may be compensated by a properly designed inductance thereby leaving only a resistance caused by ohmic losses. This inductance is preferably connected in parallel to the input terminals a, b and designed in such a manner as to become resonant to the frequency of the input potential together with the average capacity of one of the blocking condensers. It is further possible for this purpose to provide an inductance having a center tap in place of a resistance R1 designed in such a manner as to result in the desired compensation of the internal capacity of the circuit.

In many cases it is furthermore desirable to provide the compensating inductance in series with the input terminals in place of a parallel inductance mentioned, whereby the input current passes through the compensating inductance. For matters of symmetry in an arrangement of the type as shown in Figure 7 it is advantageous to provide the series inductance in the form of two windings i1 and is each connected in series with one of the input leads. In an analagous manner a substantially constant input capacity may be compensated by one or more series or parallel inductances in the remaining circuits shown. 1

In the foregoing circuit arrangements have been shown and described embodying blocking layer condensers and enabling a control 01' the amplitude ratio or propagation factor purely electrically in accordance with a variable control potential. In many cases it is required to effect a variable phase rotation of the transmitted alternating potential in accordance with a controlling potential. This object can be realized according to the present invention by the aid of special circuits, an exempliflcation of which is shown in Figure 8. The phase shifting circuit as shown in the latter is of the Wheatstone bridge type comprising two impedances such as resistances R1 and R2 shown in the example illustrated and forming two opposite arms 01' the bridge circuit and a pair of blocking layer condensers K1 and K2 forming the remaining bridge arms. The input terminals a, b are connected to one pair of apices of the bridge and the output terminals 0, d are connected to the remaining pair of apices of the bridge while the controlling potential e is impressed in the example shown across the input in series with choke coils .I1 and Is in a manner substantially similar to Figure 4. The apparent reactive impedances of the blocking condensers K1 and K: for a certain bias potential are designed to be equal to the ohmic resistances R1 and R2. In this case the output potential E2 is phase rotated relative to the input potential E1 by not considering any additional incidental phase shift due to the loss resistances of K1 and K: and the load connected to the output terminals 0, d. This phase rotation may be increased or decreased by a corresponding variation of the capacities of the blocking layer condensers; that is, in accordance with the controlling potential e causing an unbalance of the bridge circuit. As is understood the blocking layer condensers K1 and K: may be properly biased in the blocking condensers by batteries or in any othersuitable manner as described hereinbefore.

From the foregoing it will be obvious that any other known type of phase shifting circuit employing condensers in conjunction with resistors or other impedances may have embodied therein one or more variable blocking layer condensers with means for electrically controlling the same to eifect a variable phase shift in accordance with the invention. It is understood that the circuit according to Figure 8 may serve for controlling the propagation factor or input-output amplitude ratio by replacing the resistances R1 and-R1 by corresponding condensers bridged by resistors to complete the direct current control circuit.

In the preceding embodiments the control potential is derived from a separate source and impressed from the outside upon the network whose transmission characteristics are to be controlled. According to a further embodiment of the invention the control potential may be generated within the circuit or network in dependence upon the amplitude, frequency, phase, or any'other characteristic of the energy being transmitted for obtaining special effects and results as will be further understood from the following.

Referring to Figure 9, there is illustrated an embodiment for limiting the ampltude of an alternatng current to a predetermined value. An

.ductance I is connected across the input termore connected to the output terminal through a fixed condenser C while a blocking layer condenser K is connected between the lower end of the inductance I and the right hand terminal of the condenser C or the output terminal 0. The condenser C is so designed as to have a capacity corresponding to a predetermined limit capacity of the blocking layer condenser K when a maximum control potential is applied to the latter. Preferably the condenser C has connected therewith a resistance corresponding to the loss resistance of the condenser K such as a shunt resistance R as shown in Figure 11 or by providing both shunt and series resistances R1 and R2 or R1" and R2", respectively, as shown by the substitute networks according to Figures 12a and 12b. In this case the bridge will be balanced or in other words the output circuit will be completely decoupled from the input circuit in such a manner that the output potential E2 will be zero independently of the magnitude of the input potential E1. There is further provided a rectifier G connected across the output terminals 0, d shunted by an impedance W1 in series with a fixed condenser C. The rectifier G will charge the condenser C through the resistance W1 to a potential depending upon the amplitude of the output alternating potential E2. Thus, the rectified potential the magnitude of which is proportional to the output potential E2 is impressed upon the blocking layer condenser K through the lower half of the inductance I. If the amplitude of the output potential E1 is low,

the rectified control potential is small; that is, the capacity of K will deviate substantially from the capacity of C resulting in a". tight coupling of the output circuit with the input circuit. If the amplitude of the output potential increases the two capacities C and K will become more and more alike; that is, the coupling will decrease in such a manner as tocounteract the increase of the amplitude of E2 beyond a predetermined limit. Thus, if the amplitude of the input potential E1 is subject to substantial variations it is possible in this manner to maintain the amplitude of the output potential E2 at a predetermined substantially constant value.

In the arrangement according to Figure 9 the control is retroactive; that is, the rectified potential controlling the blocking condenser is derived from the output of the circuit, or the propagation factor or coupling is governed by the output of the circuit. As is understood it is also possible to employ a forward control in which case the regulation is effected in dependance upon the input such as amplitude, phase, etc., of the input potential. Aitematively, the arrangement may be designed and adjusted so as to automatically prevent excessive amplitude differences in which case an increasing control potential applied to the condenser K will cause a gradually increasing unbalance oi the bridge system.

Moreover, it is possible in special cases for automatic amplitude control to dispense with a special rectifier. An arrangement of this type is shown in Figure 10. In the latter, two blocking layer condensers K1 and K2 arranged serially in opposition are connected across the input terminals a, b in potentiometer fashion in series with an impedance Z and are furthermore shunted by serially connected inductances I1, I11 with condensers C and C inserted in the opposite connecting leads for the inductances I1 and I1. The junction point of the condensers K1 and K2 is connected to the common preferably variable point of the inductances I1 and I2 forming a variable voltage divider. In an arrangement of this type an increase of the amplitude of the output potential, E2 will cause a charging of the condensers K1 and K: on the one hand and of the comparatively large fixed condensers C and C, on the other hand. This charging potential is equal to one half of the peak value of the output potential E2. As a result the series capacity of the blocking layer condensers K1 and K1 will be decreased in such a manner that the voltage drop through the impedance Z will be decreased. In this manner the amplitude ratio increases with increasing output potential resulting in an increase or expansion of the intensity range of the potentials or signals translated by the system.- In special cases the condensers C and C and the ohmic or inductive impedances I1 and I: may be dispensed with in view of the fact that the average charge of the condensers K1 and K11 may be sufficient to effect the necessary capacity variation. As is understood the reverse eifect; that is, a compression of the intensity range may be realized in an analogous manner by a circuit as shown.

When dealing with alternating potentials of high amplitude, an incidental rectifying efl'ect of the blocking layer condensers may result in an undesired charge of these condensers interfering with the variations of the capacity by an impressed or internally generated controlling potential. Furthermore, non-linear distortions may occur in addition to other drawbacks and defects. According to a further feature of the invention means are provided to prevent the alternating potentials impressed upon the blocking layer condensers from exceeding a prede: termined limit amplitude. This object can be obtained for instance by connecting several blocking layer condensers in'series or byproviding a fixed condenser of sufficiently small capacity in series with a blocking layer condenser, which fixed condenser if desiredmay be shunted by a parallel resistance to form a path for the direct control potential for the blocking layer condensers. A two-pole substitute network of this type is shown in Figure 11 wherein a fixed condenser C shunted by a resistance R is connected in series with a blocking layer condenser K. Such a two-pole network may take the place of the blocking layer condensers in any one of the circuits shown.

In many cases it may be desirable that the additional fixed condensers should have similar characteristics as regards their apparent impedance, loss angle, etc., in dependence upon frequency corresponding to the respective characteristics of the blocking layer condenser for a definite or average controlling or biasing potential. The head of the impedance vector of a blockinglayer condenser for different frequencies travels approximately along a circle.

In Figures 12a and 1217 there are shown substitute networks of this type adapted for obtaining a predetermined relation between capacity and loss angle over a desired frequency range. The use of such substitute networks is especially advisable if the transmission characteristics or propagation factor of the network is to be substantially independent of frequency. Thus, the substitute networks according to Figures 12a and 12b may be provided in place of the impedance Z in Figures 4 and 10 or as a substitute for the condensers K1 and m in Figure '7, in place of the condenser C of Figure 9, or in numerous other circuit arrangements.

In the foregoing it has been shown that the coupling or propagation factor of a network may be varied by the provision of one or more blocking layer condensers as coupling or transmitting elements controlled by a potential impressed thereon either from the outside or generated within the circuit, such as in the form of a vari able series capacitance (Figure 4), a parallel circuit (Figure 10), a combination of both (Figure 5), or by the varying the balance of' a bridge circuit (Figures 6, 7, 8, 9). It has further been shown that both the amplitude relation between input and output potential and the mutual phase rotation between the potentials may be controlled in this manner purely electrically without the use of any mechanically moving parts or devices.

The potential for controlling the coupling or propogation factor may be a relatively slowly varying potential or of rapidly varying character such as an audio frequency potential or a potential of higher frequency. In the latter case the frequency (carrier frequency) impressed upon the input terminals is modulated in accordance with the controlling potential. The potential at the outputterminals will be amplitude modulated if the circuit is designed in a manner so as to control the amplitude ratio in proportion to the controlling potential. Alternatively, the output potential will be phase modulated if the modulating potential eflects a phase rotation between the input and output potentials. If the arrangement is adjusted and balanced in such a manner that with the absence of the control potential the output is zero, a carrier suppressed modulated output will be obtained as is readily understood. 7

In the known modulating systems utilizing rectifier-s, the modulating effect is due to the behavior of non-linear'resistance devices in dependance upon the impressed modulating or controlling potential. As is obvious a considerable current is consumed by these resistances as compared with the inventive arrangement utilizing potential controlled condensers which consume substantially! capacitative current only which may be compensated by the provision of suitable inductances in the'manner described hereinbefore. For this reason the active power absorbed in the input in contrast to the known rectifier modulating systems is only slightly higher than the active power of the modulated alternating current potential delivered at the output. Furthermore, comparatively low controlling or modulating potentials are required by the invention. If the difference between the carrier frequency and the modulating frequency is substantial, the modulated output power may be a multiple of the controlling energy. This is basically not possible in the case of the ordinary rectifier type modulating arrangements.

In view of the comparatively small controlling energy the modulation system described may be utilized toserve as an amplifier for intensifying weak currents or potentials. Such amplifiers utilizing potential controlled or blocking layer condensers may therefore be appropriately termed as capacitative amplifiers in contra-distinction to the customary vacuum tube or electron discharge amplifiers.

A two-stage amplifier construction of this type is shown in Figure 13. In the latter, an alternating potential E1 having a constant frequency substantially in excess of the frequency of the potential e1 to be amplified and applied to the input potential 1', s serves as the local power source replacing the customary anode or B-supply in the standard amplifiers. The first amplifying stage comprises a pair of blocking layer condensers K1 and K2 connected serially in like sense and across the terminals as, b of the carrier or supply potential. Similarly, the second amplifying stage comprises a pair of blocking layer condensers K3 and K4 also connected across the terminals a, b similar to the condensers K1 and K2. The capacitative current through the blocking layer condensers is neutralized or com pensated by an inductance I tuned to resonance with frequency of the supply potential E1 together with the average capacity of the blocking layer condensers. A fixed biasing potential 80 is impressed upon the condensers K1, K2 and K3, K4 by a battery B through the upper and lower halves of the inductance I. To this end the opposite poles of the battery .8 are connected to inner ends it and v of both halves into which the inductance I is divided, while the tap w of battery B is connected to the junction z of the blocking layer condensers K1 and K: through the input circuit terminal r, s, and an ohmic or inductive resistance R3. The tapped portions of the battery B are shunted by bridging condensers C3 and C4 for the alternating currents.

In this manner'a fixed biasing potential is applied to the condensers K1 and K: from the tap of the battery l3 which potential determines the ratio of the capacities of the condensers K1 and K2. The tap of the battery B may be chosen in such a manner that the capacity of K1 is slightly higher than the capacity of K: if the potential e1 to be amplified is zero. Thus, a high potential drop E1 is developed across K: or bepacity ratio may be decreased by a negative control potential e1 until the high frequency potential E2 at the point x becomes zero.

It is obvious that the conditions will not be changed materially if high frequency power is derived from the point a: such as through a coupling condenser C4, provided that the load impedance is high relative to the impedance of the condensers K1 and K2. Moreover, the controlling energy required at the terminals r, s is not appreciably increased. In the example illustrated the high frequency potential between points a and r is rectified by the aid of a rectifier comprising four rectifiers G1 to G4 arranged in a bridge circuit in a known manner whereby a low frequency potential e2 is impressed upon the primary of a transformer T corresponding exactly to the input potential e1 except for a direct current component. The secondary voltage e; of the transformer is increased to a multiple of the primary voltage e11 and is also greater than the potential e1. The potential e3 is then further intensified by the condensers K3 and K4 in a second amplification step by impressing the same upon the point at between the condensers K1 and K4 through an impedance such as a resistance R4. Condensers & and K4 are biased by the battery B by connecting the lower end of the transformer secondary T to the tap w of the biasing battery. The amplified potential is then impressed upon a further rectifying system G5-Ga through a coupling condenser C5 and the final amplified output potential e; is derived from the terminals 0, d for further amplification or utilization in a suitable output circuit. The output energy at the terminals 0, dis a substantial multiple of the controlling energy impressed upon the terminals 1', s; that is, the system functions as an amplifier. As is obvious any other rectifying arrangement in place of the bridge systems may be employed for the purpose of the invention. The input capacity at the terminals 1, s may be eliminated by providing a suitable substitute network. If the input potential comprises a mixture of frequencies of relative small band width an inductance may be used for this purpose connected in parallel to the input terminals. In place of controlling the amplitude transmission ratio as utilized in the arrangement according to Figure 13 by the aid of the condensers K1 and K2 or IQ andKi, respectively, any other suitable arrangement embodying potential controlled condensers may be employed such as arrangements shown in Figure 4, 6 or 7. Furthermore, it is understood that the repeater or transformer T serving for increasing the amplified potential may be dispensed with if the modulated high frequency potential is increased before rectification by other suitable means such as by the aid of a high frequency or resonant transformer.

It will be apparent from the above that the invention is not limited to the specific arrangements of parts and circuits shown and disclosed herein for illustration but that the underlying principle and inventive thought are susceptible of numerous variations and embodiments coming within the broader scope and spirit of the invention as defined in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than in a limiting sense.

I claim:

1. A four-pole circuit for translating oscillatory energy having an input and an output, an aperiodic impedance network connecting said input and output, said network including at least one variable capacitance element comprising fixed electrodes and a semi-conducting intermediate layer intimately united to at least one of said electrodes and adapted to block the electric current in at least one direction, and means for impressing a variable control voltage upon said electrodes in the blocking direction, thereby to vary the capacitance of said element within a range so as not to affect the aperiodic condition of said network to effect a corresponding control of the energy propagation factor between said input and said output.

2. A four-pole circuit for translating oscillatory energy having an input and an output, an aperiodic impedance network connecting said input and output, said network including at least one variable capacitance element for controlling its electric propagation factor, said capacitance element comprising a pair of fixed electrodes and a semi-conducting layer therebetween intimately united to at least one of said electrodes and adapted to block the electric current flow in at least one direction, means for applying a constant biasing potential to said electrodes in the blocking direction, and further means for super-imposing a variable potential upon said biasing potential, thereby to vary the capacitance of said element within a range so as not to affect the aperiodic condition of said network and to .efiect a corresponding control of the transmitting properties of said network.

3. A four-pole circuit for oscillatory energy having an input and an output, an aperiodic impedance network comprising ohmic and capacitative impedance elements connecting said input and output, at least one impedance element of said network being constituted by a variable capacitance element adapted to control the phase relation between energy being translated by said circuit, said capacitance element comprising a pair of fixed electrodes and a thin semi-conducting layer therebetween being intimately united with at least one of the electrodes and adapted to block the electric current in at least one direction, and means for impressing a variable control voltage upon said electrodes in the current blocking direction to vary the capacitance of said element within a range so as not to affect the aperiodic condition of said network.

4. A four-pole circuit for translating oscillatory energy having an input and an output, an aperiodic impedance network comprising ohmic and capacitative impedance elements connecting said input and output, at least one impedance element of said network being constituted by a variable capacitance element adapted to control the phase relation between the energy being translated through said network, said capacitance element comprising a pair of fixed electrodes and a thin semi-conducting layer therebetween being intimately united to at least one of the electrodes and adapted to block the electric current in at least one direction, means for impressing a steady biasing voltage upon said electrodes in the blocking direction, and further means for super-imposing a variable control voltage upon said biasing voltage to vary the electrical capacitance of said element within a range so as not to afl'ect the aperiodic condition of said network.

5. In a system as claimed in claim 1 wherein said network constitutes a potentiometer circuit with said variable capacitance element forming a part thereof.

6. In a system as claimed in claim 1 wherein said network constitutes a bridge circuit with said capacitance element adapted to control the balance of said bridge.

7. In a system as claimed in claim 1 wherein said controlling potential is supplied from a separate source and impressed from the outside of said network upon said capacitance element.

8. An electric wave translation circuit having an input and an output, a pair of capacitance elements each comprising a first electrode, a thin semi-conducting layer intimately united to said electrode and a second electrode in electrical contact with said semi-conducting layer to block the electric current flow in at least one direction between saidelectrodes, said capacitance elements being serially connected in the same 1 sense and coupled to said input, said output being coupled to one of said condensers, a direct potential source connected across said condensers, a tap connection from an intermediate point 01 said source to the junction of said elements to variably and diflerentially bias said elements in their blocking directions. means for blocking wave energy being translated from said potential source, and further means for blocking the direct potential of said source from said input and output.

9. In a circuit as claimed in claim 8, means for introducing an additional varying control voltage in the pathbetween said tap and the junction of said capacitance elements.

10. In a circuit as claimed in claim 8, a current blocking impedance permeable to direct current being arranged in the path between said tap and the junction of said capacitance elements.

11. In a circuit as claimed in claim 8 wherein the input potential is supplied by a source of substantially constant alternating current,

-means for superimposing a varying control voltage of relatively low frequency upon said biasing voltage, and rectifying means connected to said output.

GUSTAVE GUANEILA.

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