US3626314A - Resonant transfer employing negative resistance amplifiers - Google Patents

Resonant transfer employing negative resistance amplifiers Download PDF

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US3626314A
US3626314A US14768A US1476870A US3626314A US 3626314 A US3626314 A US 3626314A US 14768 A US14768 A US 14768A US 1476870 A US1476870 A US 1476870A US 3626314 A US3626314 A US 3626314A
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resistance
negative resistance
negative
circuit
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Joseph Antonius Broux
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Alcatel Lucent NV
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International Standard Electric Corp
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Assigned to ALCATEL N.V., DE LAIRESSESTRAAT 153, 1075 HK AMSTERDAM, THE NETHERLANDS, A CORP OF THE NETHERLANDS reassignment ALCATEL N.V., DE LAIRESSESTRAAT 153, 1075 HK AMSTERDAM, THE NETHERLANDS, A CORP OF THE NETHERLANDS ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: INTERNATIONAL STANDARD ELECTRIC CORPORATION, A CORP OF DE
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/20—Time-division multiplex systems using resonant transfer

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  • the invention relates to negative resistance amplifiers including a reactive storage device, a negative resistance and switching means to couple said storage device and negative resistance during a predetermined time interval during which time the energy originally stored in the storage device is amplified by a predetermined amount.
  • Such a negative resistance amplifier has been disclosed in the U.S. Pat. No. 3,187,100.
  • An arrangement of this kind may be advantageously used in time division multiplex systems using the resonant transfer principle and more particularly the principle of intermediate storage as disclosed in the British Pat. No. 822,297 (E.P.G. Wright-W. Bezdel 192-1).
  • energy may be transferred, i.e., by a resonant transfer operation to an intermediate storage capacitor, and, before being retransferred therefrom, to a load, i.e., to another capacitance and again by resonant transfer operation, the sample on the intermediate storage capacitor may be amplified by connecting the latter during a predetermined time between the two resonant transfer operations, to a negative resistance.
  • An amplification system of this kind may be of particular interest in relation to so called time division hybrid circuits disclosed in the French patent of addition No. 75,359 to H. Adelaar corresponding to U.S. Pat. No.
  • 3,267,218 which enable the interconnection of four-wire and two-wire circuits on a time division multiplex basis by using the resonant transfer principle.
  • three intermediate storage capacitances may preferably be used and between transfers into and from such capacitances, they may be temporarily connected to negative resistances in order to amplify the samples stored before forwarding them to other circuits.
  • amplification in this manner may be carried out on a time division multiplex basis.
  • a first object of the invention is to provide conditions under which such negative resistance amplifiers may operate satisfactorily.
  • said storage device and negative resistance when coupled by said switching means constitute a capacitance shunted by a short circuit stable negative resistance or a dual circuit thereof.
  • said switching means include a switch which in the unoperated position couples said negative resistance to a positive resistance of such a value that the combined resistance is positive.
  • said switching means include a second switch which in the operated position couples said negative resistance to said storage device and to a second positive resistance of such a value that the combined resistance is negative.
  • the time during which said second switch is operated encompasses the time during which said first switch is operated.
  • a short circuit stable negative impedance converter may be coupled across a capacitance without creating an unstable condition.
  • this capacitance must be able to receive an initial charge and then be able to deliver an amplified charge to a load, at such moments it must not be short-circuited whereas in rest condition, a short circuit is essential for the short circuit stable negative impedance converter.
  • by the use of two switches it becomes however possible to avoid any undesired transient condition during which the short circuit stable negative impedance converter would be left open-circuited.
  • the invention also relates to negative resistance amplifiers including a resonant transfer network with a reactive storage device, a negative resistance and switching means to couple said resonant transfer network and negative resistance during a predetermined time interval whereafter the energy originally stored in said storage device is amplified by a predetermined amount.
  • Such negative resistance amplifiers are also disclosed in the U.S. Pat. No. 3,187,100 to H. Adelaar and due to the resonant transfer operation they offer the advantage that the currents when switching the negative resistance in or out of the circuit across the storage capacitance are zero.
  • a second object of the invention is to provide conditions under which such amplification by resonant transfer operation may adequately be secured.
  • said resonant transfer network and negative resistance when coupled by said switching means constitute a capacitance, an inductance and an open-circuit stable negative resistance all in series or a dual circuit thereof.
  • negative resistance amplifiers including a resonant transfer network between two reactive storage devices, negative resistances and switching means to couple said storage devices via said resonant transfer network during a predetermined time interval, said network being so designed that with a given energy in any one of said storage devices and none in the other at the beginning of an effective interconnecting time, after said time, amplified energy is now stored in said other device while there is substantially none in said one device.
  • Yet a third object of the invention is to provide a condition under which suitable bidirectional amplification may be secured in a resonant transfer circuit using the so called second harmonic principle.
  • said storage devices and said network constitute a pair of capacitances interconnected via at least one series branch including an open-circuit stable negative resistance and shunt branch including a short circuit stable negative resistor or a dual circuit thereof.
  • FIG. I the equivalent circuit of a practical open-circuit stable, negative resistance
  • FIG. 2 the equivalent of a practical short circuit stable negative conductance
  • FIG. 7 a circuit enabling amplification by using the intermediate storage principle in conjunction with a resonant transfer circuit including the open-circuit stable negative resistance of FIG. 1;
  • FIG. 8 the dual circuit of that shown in FIG. 5;
  • FIG. 9 the dual circuit of that shown in FIG. 7;
  • FIG. 10 a bidirectional resonant transfer amplifier using two open-circuit stable negative resistances and one short circuit stable negative resistance
  • FIG. 1 part of a circuit corresponding to FIG. 10 modified in order to realize an adjustable gain.
  • the latter usually employ a sampling frequency of the order of IO kc./s. and with 25 channels using the same multiplex highways, the channel time slot is then equal to 4 microseconds out of which half is reversed as a guard time in order to reduce crosstalk between adjacent channels to an acceptable value.
  • amplitude modulated pulses of 2 microseconds duration appear at the rate of 250 kc./s. and as it can be shown that the contribution to the total waveform power by frequencies higher than the fifth harmonic of the frequency is less than 0.15 percent, for resonant transfer time division multiplex systems, there is no reason to require a larger frequency bandwidth than 1.25 Mc./s. for the negative resistances used in such systems to secure amplification. Indeed, it will be shown that the larger the required bandwidth the more the negative resistance becomes critical.
  • negative resistance converters can be of the open-circuit or of the short circuit stable type. If one assumes an open-circuit stable negative resistance converter, one may consider the conditions which the impedance Z(p) seen through that negative resistance converter should fulfill. This will permit to define the structure of the equivalent circuit of a negative resistance which will be useful to determine suitable negative resistance amplifier circuits.
  • a first condition is that the impedance Z(p) should be a rational function of p, i.e., the imaginary angular frequency.
  • Z(p) may be written as In the above expression, .4 A ...,B,,, 8,, K are constant together with the exponents a and b of the power series in the numerator and in the denominator of the expression which are identified by N(p) and D(0respectively.
  • a second condition should be that when p tends to zero, Z(p) should reduce to a purely negative resistance R, i.e. KA /B R (2)
  • a third condition is that since the circuit has been assumed to be open-circuit stable, Z(p) should have no poles in the right half of the p-plane or in other words the denominator D(p) should be a Hurwitz polynomial.
  • Z(p) should at least have one zero in the right-half p-plane which means that the numerator N(p) should not be a Hurwitz polynomial.
  • the latter may be represented by a negative conductance in parallel with a positive capacitance.
  • FIG. 1 represents this network for Z and it is seen to include a negative resistance R in series with a parallel circuit constituted by the inductance L and the resistance (positive) R,..
  • the shunt capacitance C shown in dotted lines across the impedance Z can for the moment be disregarded.
  • the impedance Z can be written as P O O wJLJR in which w represents an angular cut off frequency at which this resistive component of Z has become a certain predetermined fraction of the resistive component -R at zero frequency. This fraction is defined by the coefficient k From equation (4) an explicit relation for the angular cut off frequency w can be obtained, i.e.,
  • a factor of merit may be associated to a negative impedance by expressing the ratio of the real part to the imaginary part of the impedance, which ratio will of course decrease as the frequency increases.
  • the shunt capacitance C will now be considered. It may represent a stray capacitance inevitably associated with the input of a negative impedance converter. If this spurious capacitance reaches a certain value, the arrangement will become unstable. This can be shown by considering the admittance dipole of FIG. I and by equating this admittance expression to zero. This gives the following quadratic in p implicitly defining the resonant frequency;
  • FIG. 3 represents the open-circuit stable negative resistance of FIG. 1 but with a resistance R connected in parallel thereto.
  • This kind of connection may be desireable if one wishes to adjust the gain provided by a negative resistance.
  • a gain variation may for instance be desired in the case of time division multiplex interconnection on a resonant transfer basis as envisaged for instance in the above mentioned Belgian Pat. No. 654,515 A. FETTWEIS, corresponding to U.S. Pat. No. 2,324,247.
  • FIG. 3 involving three resistances and one inductance may of course by simplified to a two-resistance/one-inductance structure, i.e., the basic one for the open-circuit stable negative impedance. It may also be shown that the value of the critical capacitance will be increased so that there is no worsening of the stability condition. Only the figure of merit will be reduced by this increase of the negative resistance. Similar results can be secured for the short circuit stable type of negative impedance represented in FIG. 2. Again, paralleling such a negative impedance with a positive resistance of larger magnitude than the original one will result in a combined negative resistance of larger magnitude without a deterioration of the stability condition, but merely with a decreased figure of merit.
  • FIG. 4 shows the short circuit stable negative impedance of FIG. 2, normally short-circuited by the closed break contacts S applied across a capacitance C. It can be shown that with a certain amount of energy stored in the capacitance C, by the parallel connection of such a short circuit stable negative impedance, amplification of the stored energy can be secured. Considering the admittanceof the dipole shown in FIG. 4, when the break contact S is open, this can be equated to zero in order to find the roots of the network. This produces the equation which is a quadratic in p having always two real roots, as can readily be verified.
  • FIG. 5 shows how such an amplification may be achieved.
  • the capacitance C has one of its plates grounded, while the other may be connected either to a source of energy (not shown) through the normally open make contact 8,, or alternatively, to a load (not shown) through the normally open break contact S4.
  • One side of the negative resistance circuit of the type shown in FIGS. 2 and 4 is grounded, while its other terminal may be connected to the upper plate of C through a normally open make contact S2 in series with resistance R,,.
  • the open-circuit stable negative impedance is normally short-circuited through closed break contact 81 in series with resistance R
  • FIG. 6 identifies the sequence of operation when transferring a sample of energy into C in order to withdraw thereafter an amplified sample.
  • the pulse S3 indicates the closure of the corresponding contact so that an energy sample is stored, e.g., by resonant transfer operation (not shown), into C. Thereafter, $3 being again open, S2 is closed so that the energy stored in C is allowed to be partially discharged through resistance R in series with resistance R, shunted by the negative resistance. Thereafter S2 being still closed, S1 is now opened whereby capacitance C is now coupled to a resultant negative resistance equal to the difference between the magshown).
  • the total gain in Nepers may be expressed by A possible drawback of the circuit of FIG. is that the switches SI and S2 must be able to pass sufficiently high currents as the operating times of closure.
  • FIG. 7 shows that this may be remedied by resonant transfer operation for the amplification, but provided an opencircuit stable type of negative impedance is used in conjunction with capacitance C.
  • Switch SI is no longer necessary and the negative resistance of FIGS. l and 3 has one of its terminals connected to the grounded plate of C while its other terminal may be coupled to the other plate of C through make contact S2 in series with the resonant transfer inductance L.
  • n,,, n and w may be found from the cocfficicnts of equation (10) and from the term independent of p one will in particular obtain giving the product of the spurious real root n, by the sum of the squares of the real and imaginary parts of the complex conjugate roots.
  • the possibilty of there being a parasitic oscillatory mode which prevents adequate operation of the air rangemcnt of FIG. 7 will be investigated by considering what happens when the spurious inductance L tends towards zero.
  • circuits of FIGS. 5 and 7 use capacitances as the energy storage element, this could also be achieved by way of an inductive element.
  • FIG. 3 shows the dual circuit of FIG. 5.
  • L is the energy storage element and instead of being isolated from the other circuits as in FIG. 5 with the help of the normally open switches S2, S3, 54, it is now normally short-circuited with the help of the normally closed break contacts 8'2, 8'3 and S'4.
  • Normally open make contact S'I corresponds to the normally closed break contact SI
  • conductances G and G correspond to the resistances R and R while an open-circuit stable negative impedance involving the element -R, R and L now corresponds to the short circuit stable negative impedance of FIG.
  • the circuit of FIG. 8 will operate in a dual manner to that of FIG. 5.
  • FIG. i represents another variant, again obtained by the normal duality rules.
  • Circuit of FIG. 9 is dual of that of FIG. 7 and as in FIG. 8, the energy stored in L can be kept therein due to the break contact 8'2, 8'3 and S'4 being normally closed.
  • Capacitance C normally short-circuited by S'2 corresponds to inductance L while the short circuit stable negative impedance also short-circuited by S and involving the elements G, G, and C, corresponds to the open-circuit stable negative impedance of FIG. 7.
  • the circuit of FIG. 9 of course operates in a dual manner to that of FIG. 7.
  • FIG. l0 shows the arrangement represented in FIG. 3 of the above mentioned Belgian patent.
  • the storage capacitance C I may be coupled to the other storage capacitance C2 when the normally open make contacts S3 and S4 are closed and when simultaneously, the normally closed break contact S] is opened.
  • the resonant transfer network is essentially a T-circuit which as disclosed in the above mentioned Belgian patent has symmetrical series branches including the inductance LI and L2 associated with their respective resistance RI, R, and R lR'
  • the shunt branch includes the capacitance 2c/k-l in parallel with resistance R /Z.
  • Such dipoles as L,, R,, R', may be considered as equivalent dipoles corresponding to the original transfer inductance with its associated series and shunt resistances corresponding to the losses inevitably associated with physical inductances, in series with the resistance of the electronic transistorized gates symbolized by the switch such as S3 and also in series with a negative resistance which will be responsible for the negative value of R, in the resultant dipole shown in FIG. 10.
  • dipole L,, R,, R is in series with an additional dipole comprising the inductance L in shunt with the resistance R a like dipole being also shown in the other series branch going towards the capacitance C,.
  • Such dipoles as L R obviously correspond to the dipole L,, R, represented in FIG. I as inevitably associated with practical negative impedances which can never by purely resistive.
  • FIG. 10 also shows a branch in shunt with R,l2 and comprising resistance R /2 in series with capacitance 2C, which corresponds to the spurious elements shown in FIG. 2 as inevitably associated with a short circuit stable negative impedance, i.e., the conductance G and the capacitance C,.
  • the resonant transfer amplification circuit of FIG. 10 is seen to include in its series branches, negative impedances of the open-circuit stable type while it has a short circuit stable negative impedance in its shunt branch.
  • the switches S3 and S4 are open while S1 is closed, a stable condition is attained.
  • amplified resonant transfer operation may take place and after a time t, amplified samples will be found on capacitance C, and C, corresponding to the original samples on capacitances C and C, respectively.
  • FIGS. 5 and 7 it will now be proved that such a particular combination of negative impedance may indeed result in a stable amplifier.
  • the circuit Since the circuit is symmetrical, as previously done for example in the case of the above mentioned Belgian patent, it may be analyzed by separately considering the difference v,- v, and the sum v, +v, of the instantaneous voltages across the storage capacitances C, and C,.
  • the voltage v,-v is determined by the series branches including the capacitances C, and C, or in order words by the dipole obtained for instance by closing S3 while keeping Sl closed.
  • the voltage v,+v will be determined by folding the network over its central branch normally shunted by S1, or in other words by interconnecting the plates of capacitors C, and C, which are not connected together.
  • the stability of the circuit will first be examined by studying v,v, and the natural frequencies are obtained by equating the corresponding dipole impedance to zero, i.e.
  • the equation in p will be a cubic instead of a quadratic and three relations between the impedance elements appearing in (21) and the'roots of the dipole, i.e., nijw the complex conjugate roots and n, the additional real root caused by the spurious elements of the negative impedance converter, can be secured. Only that corresponding to the term independent of p need by considered here, i.e.
  • the dipole equation will include the terms of (21) plus the impedance of twice the central branch shown in FIG. 10, i.e.
  • this equation in p is now of the fifth degree involving the complex conjugate roots nizjw, and the real root n, plus two additional real roots n and n,, which are due to the spurious negative impedance elements R and C of the central branch which raise the degree of the equation in p from the third to the fifth.
  • suitable equations can be established to link the parameters n, n,,, and w, with the values of the elements appearing in (24) but these relations obviously become cumbersome and since only n,., and n,., are of interest to study the stability of the network, it is not necessary to write them all out in full.
  • FIG. 11 illustrates this possible technique for adjusting the gain after the complete connection has been established, by representing the left hand side of FIG. 10 but this time with the original inductance coil 1 and the original open-circuit stable negative impedance converter such as 2 as well as the original short circuit stable negative impedance converter 3, the shunt capacitance of value 2C/k-l being indicated by 4.
  • FIG. 11 shows the additional switches S5, S6 and S7 serially associated with the resistances 5, 6 and 7 respectively.
  • switches 8'6 and S7 are used for the righthand series branch of FIG. 10.
  • the switches S5, S6 and S7 will remain in the positions shown, that is to say closed for S5 and open for S6 and S7.
  • the switches S3 and S4 will be simultaneously closed while S1 will be open thus enabling resonant transfer amplification of the energy sample arising for instance from the left hand subscriber (not shown) through the coaxial cable 8 constituting the highway serving this group.
  • switch S5 When the connection is completely established however, switch S5 may then open in unison with S1 while switches S6 and S7 will close simultaneously with S3 and S4 whereby the disconnection of resistance 5 and the connection of resistances 6 and 7 may lead to a suitable increase in the gain which may become permissible due to both ends of the connection being terminated.
  • the resonant transfer inductance l is not inserted between the coaxial cable 8 and the storage capacitance C (not shown in FIG. 11) of the subscribers line circuit so that the capacitance of the coaxial cable, plus the parasitic capacitance accumulated at the entrance of this cable where all the various subscribers line circuits are multiplied, will be put directly in shunt with the storage capacitance C, whenever the switches of the connection are closed.
  • This direct interconnection of the capacitances will of course create a loss but this can be kept reasonably small if this spurious capacitance is relatively small with regard to the storage capacitance.
  • a negative resistance amplifier comprising a short circuit stable negative resistance device, a first open-circuit stable negative resistance device and a second open-circuit stable negative resistance device; said short circuit stable negative resistance device including a reactive storage device, a negative resistance and first switching means coupled to selectively interconnect said reactive storage device and said negative resistance; said first and second open-circuit stable negative resistance devices each including a positive inductance coupled in series with second switching means to a negative resistance; and third switching means coupling said first open-circuit stable negative resistance device in series to the short circuit stable negative resistance device and fourth switching means coupling said second open-circuit stable negative resistance device to the short circuit stable negative resistance to provide bidirectional amplification.
  • a negative resistance amplifier as claimed in claim 2 including a second positive resistance and said switching means including a third switching means which in the operated position couples the negative resistance in said short circuit stable resistance to said storage device and to the second positive resistance, said second positive resistance having a value such that the resultant resistance is negative.
  • a negative resistance device as claimed in claim 4 in which the difference between said times divided by the magnitude of said resultant negative resistance is larger than the total time during which said first switch is operated while said third switch is not operated, divided by the sum of said resultant positive resistance with said second positive resistance.

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US14768A 1966-03-25 1970-02-26 Resonant transfer employing negative resistance amplifiers Expired - Lifetime US3626314A (en)

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NL6604008A NL6604008A (enrdf_load_stackoverflow) 1966-03-25 1966-03-25

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BE (1) BE696035A (enrdf_load_stackoverflow)
CH (1) CH496374A (enrdf_load_stackoverflow)
GB (1) GB1182336A (enrdf_load_stackoverflow)
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3117185A (en) * 1956-12-13 1964-01-07 Int Standard Electric Corp Transient repeater
US3202763A (en) * 1963-08-16 1965-08-24 Bell Telephone Labor Inc Resonant transfer time division multiplex system utilizing negative impedance amplification means

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3117185A (en) * 1956-12-13 1964-01-07 Int Standard Electric Corp Transient repeater
US3187100A (en) * 1956-12-13 1965-06-01 Int Standard Electric Corp Resonant transfer time division multiplex system utilizing negative impedance amplification means
US3202763A (en) * 1963-08-16 1965-08-24 Bell Telephone Labor Inc Resonant transfer time division multiplex system utilizing negative impedance amplification means

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GB1182336A (en) 1970-02-25
BE696035A (enrdf_load_stackoverflow) 1967-09-25
NL6604008A (enrdf_load_stackoverflow) 1967-09-26
CH496374A (de) 1970-09-15

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