US2817822A - Negative impedance converter - Google Patents

Negative impedance converter Download PDF

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Publication number
US2817822A
US2817822A US417650A US41765054A US2817822A US 2817822 A US2817822 A US 2817822A US 417650 A US417650 A US 417650A US 41765054 A US41765054 A US 41765054A US 2817822 A US2817822 A US 2817822A
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United States
Prior art keywords
terminals
impedance
resistance
negative
converter
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Expired - Lifetime
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US417650A
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English (en)
Inventor
Stanley T Meyers
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AT&T Corp
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Bell Telephone Laboratories Inc
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Filing date
Publication date
Priority to NL100386D priority Critical patent/NL100386C/xx
Priority to NL192904D priority patent/NL192904A/xx
Priority to BE536601D priority patent/BE536601A/xx
Priority to US417650A priority patent/US2817822A/en
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to FR1117757D priority patent/FR1117757A/fr
Priority to DEW15779A priority patent/DE974956C/de
Priority to GB7958/55A priority patent/GB780177A/en
Priority to CH330330D priority patent/CH330330A/fr
Application granted granted Critical
Publication of US2817822A publication Critical patent/US2817822A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H04B3/16—Control of transmission; Equalising characterised by the negative-impedance network used

Definitions

  • This invention relates generally to negative impedance circuits and more particularly to four-terminal negative impedance converters, which over a prescribed frequency range present at one pair of terminals an impedance which is substantially a negative multiple of any passive impedance connected to its other pair of terminals.
  • One object of the invention is to produce a stable negative impedance of the shunt or reversed-current type.
  • Another object is to produce a stable negative impedance of the shunt type without using transformers or inductance coils.
  • Still another object is to minimize the power requirements of a stable negative impedance of the shunt type.
  • a further object of the invention is to avoid disturbing the longitudinal balance of a transmission line across which a negative impedance of the shuut type is connected.
  • negative impedances may be classified in two categories. The first of these includes negative impedances of the series or reversed-voltage type. Such negative impedances are open-circuit stable and can be connected in series in a transmission line, without singing, to produce amplification. The second group includes negative impedances of the shunt or reversed-current type. Such negative impedances are short-circuit stable and can be connected in shunt across a transmission line, without singing, to produce amplification. One or more negative impedances of each type may be associated with each other to reduce the loss of a transmission line below the level which would be made possible through the use of negative impedances of one type alone.
  • Fig. 6 of the article and Fig, 7 of the patent illustrate a four-terminal negative impedance converter which,'when an impedance Z is connected across one pair of terminals, presents an impedance of substantially kZ at its other pair of terminals and, when an impedance Z is connected across the other pair of terminals, presents an impedance of substantially at the first pair of terminals.
  • kZ represents a negative impedance of the represents a negative impedance of the shunt type
  • k is substantially a real number over a prescribed operating frequency range.
  • the above-mentioned negative impedance converter has been found very useful in the production of negative impedances of the series type.
  • this converter In addition to the actual negative impedance produced by this converter, there is a spurious series impedance component substantially proportional to the plate resistances of the vacuum tubes forming the active elements of the converter.
  • this spurious component is of negligible importance.
  • Coupling to a low impedance line is made through a step-down transformer to bring the negative impedance down to its proper relation with respect to the line.
  • the spurious series impedance component proportional' to plate resistance is large enough to be a substantial percentage of the converted impedance. Under such conditions, variations in the magnitude of this resistance can have an adverse effect on the impedance stability of the converter.
  • the percentage level of this series resistance may be reduced by adding additional push-pull stages of amplification to the: converter, but such a solution to the difficulty tends not only to be expensive but also to increase power and space requirements and create problems of heat dissipation.
  • the present invention overcomes this difliculty by permitting a shunt type of negative impedance to be produced with a much smaller spurious impedance com,- ponent.
  • Converters embodying the invention require no transformer to achieve impedance stability and require no increase in the total number of active devices used to produce amplification.
  • the present invention takes the form of a negative impedance converter having two pair of terminals, a pair of resistances connected from a common point to respective ones of each pair of terminals, connections from another common point to the respective remaining ones of each pair of terminals, and a single-sided two-stage amplifier the input terminals of which are connected to the two common points and the output terminals of which are connected to the sides of the respective resistances remote from the common point between them.
  • Negative impedance converters embodying the inven tion resemble the prior art converter disclosed in the Merrill article and patent in that an impedance Z connected across one pair of terminals causes an impedance of substantially kZ to be presented at its other pair of terminals, and an impedance connected across the other pair of terminals causes an impedance of substantially to be presented at the first pair of terminals. They differ from the prior art converter in, among other things, their circuit configuration, the lower spurious impedance component they produce, and their lack of transformers and inductance coils. They tend, therefore, in their shunt type negative impedance applications to be much more suitable than prior art converters for connection in shunt across a transmission line to reduce loss, either alone or in association with series type negative impedances connected in series with the line.
  • An important feature of the invention permits a negative impedance of the shunt type to be connected across a balanced two-wire transmission line without disturbing the longitudinal balance of the line.
  • the D.-C. power supply for the two-stage amplifier is effectively connected between the line terminals of the negative impedance converter.
  • the anode and cathode potentials of the amplifier tubes are thereby permitted to rise and fall together with signal variations on the balanced transmission line and a substantially constant D.-C. potential is maintained between them.
  • Fig. 1 is a block diagram of a four-terminal negative impedance converter embodying the invention
  • Fig. 2 is a block diagram like that of Fig. 1, redrawn to illustrate further the general nature of circuits embodying the invention
  • Figs. 3 and 4 are block diagrams which are used in the explanation of the mode of operation of negative impedance converters embodying the present invention.
  • FIG. 5 is an equivalent circuit of .the embodiments of the invention shown in ,Figs. ,1 and 2;
  • Fig. '6 is a schematic diagram of a specific negative impedance converter embodying the invention.
  • the embodiment of the invention illustrated in Fig. 1 includes ,a first pair of terminals 11 and 12, a second pair of terminals 13 and 14, an amplifier 15, and a pair of resistances a and c. Resistances a and c are connected between a common point '16 and terminals 11 and :13, respectively, while terminals 12 and 14 are both connected :to a common point 17.
  • the input terminals of amplifier 15, which has substantially no phase shift over a prescribed operating frequency range, are connected to 100111111011 points .16 and 17, respectively, while the output terminals are connected to terminals 13 and .11,.respectively.
  • n p d nce substantially equal to is presented at terminals 13 and 14 while if an impedance Z is connected across terminals 13 and 14, an impedance substantially equal to -kZ is presented at terminals 11 and "1 2.
  • the first of these impedances presented by the converter is a negative impedance of the :s'huntor reversed current type, and the second is a negative impedance of the series .or reversed-voltage y
  • k' is substantially a real numher (i. e., has no phase angle) over the frequency range of interest.
  • terminals 11 and 12. have been labelled network and terminals 13 and 14 line to indicate the proper converter orientation for the production of a shunt negative impedance to be bridged across a transmission line.
  • a negative impedance of the shunt yp r at to the net or mped nc y e peda transformation ratio of the converter appears at the line terminals 13 and 14.
  • spurious negative impedance which the present invention reduces almost to the vanishing point.
  • the invention is not limited to the production of negative impedances of the shunt type and that the converter orientation may be reversed to provide a nega: ive imped nce of the r es ty Sin e the prcs h n ention as app oached fr m t stan poi t of s unt ne a ve mpedances, h e er s bs u n n se o t mode o oper t on of the c n rter w l b de ted largely to the production of negative impedances of that WP?- Broadly, both the line and the network connected to the respective terminals of the embodiment of the invention illustrated in Fig.
  • the converter presents to one terminating circuit an impedance which is substantially a negative multiple of the impedance presented to the converter by the other terminating circuit. Conversion in one direction yields a negative impedance of the shunt type and conversion in the other a negative impedance of the series type.
  • Fig. 2 the embodiment of the invention shown in Fig. 1 is rearranged to demonstrate more clearly certain aspects of the circuit configuration
  • resistances a and c actually constitute two adjacent arms of a four-terminal bridge circuit, the other WO arms of which are formed by"networ k terminals 11 and 1 2 and line terminals 13 and 14.
  • the input and output terminals of amplifier 15 are connected to conjugate terminals of the bridge circuit.
  • Fig pr se t th embodimen of t e e on it lustrated in Fig. 1 connected to produce a negative impedan o the h nt typ and with t pu nd Qwpu mpeda ce o amp fier 15 ho s ance 4 t e input resistance of amplifier 15, is shown connected across the amplifier input terminals between common Points 16 and 17, while resistance b, the amplifier output resistance, is connected across the amplifier output terminals between terminals 11 and 13.
  • Z is the network impedance presented to the converter at terminals 11 and 12, and :Z' is the impedance seen looking in at terminals 13 and ,14.
  • Fig. 3 For purposes of analysis, the circuit of Fig. 3 can be redrawn as shown in Fig. .4.
  • amplifier input resistance d is assumed .to :be infinite. In specific embodiments of the invention, d is usually of the order of a megohm :or more, making this a reasonable assumption.
  • V is the voltage appearing across the input terminals of amplifier 15, and n is the amplifier gain.
  • E is a voltage across line terminals 13 and 14, and ,uV is the output voltage of amplifier 15.
  • Fig. 4 ,uV is shown as a separate generator appearing in series with amplifier output resistance 12.
  • I is the current flowing around the loop formed by E, c, a, and Z while I is the current in the loop formed by ,uV, b, a, and c.
  • the u ent and v lta e po ities are ss e to be those shown in ;Eig. 4, ,although these are arbitrary and .do not
  • the circuit equations for the are as follows:
  • the impedance presented at the line terminals 13 and 14 of the converter is, therefore, equal to a negative multiple of the network impedance Z plus a spurious negative component represented by the right-hand expression on the right side of Equation 8.
  • Fig. 5 is an equivalent circuit of the negative impedance converter analyzed in connection with Fig. 4 and'illustrates the'meaning of Equation 8.
  • the negative impedance converter embodying the present invention is electrically equivalent to an ideal converter having a conversion ratio of plus a spurious series resistance composed of a resistance converter shown in Fig. 4"
  • a negative impedance of the series type may be obtained from converters embodying the present invention by connecting the passive impedance network to the opposite set of terminals from those used to produce a negative impedance of the shunt type. It can readily be shown that the conversion ratio of the ideal converter in the equivalent circuit would then be With both ,ttfl and 5 very large in comparison with unity, the negative impedance component would be kZ where k is substantially equal to the ratio of 13 to 8
  • the equivalent circuit shown in Fig. 5 illustrates the: importance of the feature of the invention relating to the improvement of the impedance stability of the com verter.
  • the spurious series resistance component produced by the converter may be considered as being made up of three resistances All three of these resistances are reduced to a low value by the presence of the (l;r/3 term in the denominator.
  • Amplifier 15 is preferably a two-stage single-sided ampli- 7 andfier, making the 9 term very large in comparison with unity.
  • the spurious resistance component produced by the converter is, very small in comparison with the impedance of the line to which the converter is connected, and variations in its magnitude are of little consequence.
  • the output resistance of amplifier 15 may itself be reduced and stabilized through the application of negative feedback to amplifier 15.
  • FIG. 6 A full schematic diagram of a specific embodiment of the invention appears in Fig. 6.
  • terminals 1-1 through 14 resistances a and c, and common points 16, and 17 are the same as in the preceding figures, but instead of a block diagram the complete circuit details of the amplifier are shown.
  • terminals 11 and 12 are labelled the network terminals and terminals 13 and 14 the line terminals.
  • such an arrangement produces a negative impedance of the so-called shunt or reversed-current type at the, It should be remembered line terminals 13 and 14. however, that these connections may be reversed to pro Jerusalem a negative impedance of the series or reversedvoltage type at terminals 11 and '12, which would then be the line terminals.
  • n. in, fit rasi t nes'psa an c, are. conne ted in series betweenterminals 11 and 12, with a coupling condenser. 18 connected between terminal 11 and resistance a and a coupling condenser 19 connected between terminal 13 and resistance c.
  • Terminal 12 is connected directly to common point 17, while a coupling condenser. 20 is connected between there and terminal 14.
  • D.C. power is supplied to the negative impedance converter illustrated in Fig. 6 by a pair of potential sources 21' and 22;
  • Source 21 which supplies a small negative potential; has its positive terminal grounded and its negative terminal connected through a resistance 23 to common point- 17.
  • Source 22, which supplies a larger positive potential has its negative terminal grounded and its positive terminal connected through the series combination ofresistances 24 and 25 to the junction between resistance c and: condenser 19.
  • a condenser 26 is connected from the negative terminal of source 21 to the junction between resistances 24'and 25.
  • the amplifier in the negative impedance converter shown in Fig. 6 is a two-stage single-sided amplifier composed of a pair of triodes 27 and 28. If desired, these two tuhe,s.-,maybe. within assingle, envelope.
  • the grid of the first tuhe .2? 7; is connected to common point 17 through the series combination of a small protective resistance 33 and a large grid biasing resistance 29, while the cathode ofthe; same; tube, is; connected to the same point through a smallercathodezresistance 30.
  • the cathode of tube 27. isalsoreturned toground through a small balancing condenser 39; The anode.
  • tube 27 is connected to the grid; 051 the; second tube, 28 through a coupling condenser 31 and: a small. protective resistance 42.
  • a pair of resistances 32 and 33 are connected in series between common point 17 and the junction between resistance a and condenser 18.
  • the grid of the tube 28 is returned to the junction between resistances 32' and 33 through a large lidz. iasing resistance 34:, and a condenser and a resistan e-41am connected in series across resistance 32.
  • Fig.6 Resistance'a ohms 100,000 Resistance; 0; do 84,500 Condenser 18;. microfarads 0.5 Condenser. 19-. do 1 Condenser 20 do 1 Potential source 21 volts -24 Potential source 22". a do +130 Resistance 23". ohms 3010 Resistance 24;.
  • the conversion bandwidth of theconverter illustrated in Fig. 6 is limited at low frequencies by the resistance-capacitance coupling provided by resistance: 29 and capacitance 36 between the bridge and the grid of tube 27 and at high frequencies by the condenser 37. connected across resistance a.
  • a two-wire transmission line which is balanced with respect to ground potential, a two-terminal terminating network of passive impedance elements, and a negative impedance converter which comprises a first pair of terminals connected to opposite sides of said transmission line, a second pair of terminals connected to opposite sides of said terminating network, first and secondresistances connected in series between: one of said first pair of terminals and one of said second pair. of terminals; the others: of said first and. second. pairs of terminals: being connecteddirectly together with respect to A.-C., firstan'd secondarnplifying devices each havingx a currenteemissive:electrode,.a current-receiving electrode,
  • receiving electrode of said second device being connected to the end of said first resistance electrically remote from said second resistance, and a D.-C. power supply for both of said amplifying devices connected across said first pair of terminals between the current-emissive electrode of said first device and the end of said first resistance electrically remote from said second resistance to avoid disturbing the longitudinal balance of said line, the impedance presented to said transmission line by said converter being related to the impedance presented to said converter by said terminating network by factor where k is substantially a real number over a predetermined operating frequency range.
  • a two-wire transmission line which is balanced with respect to ground potential
  • a two-terminal terminating network of passive impedance elements and a negative impedance converter which comprises a first pair of terminals connected to opposite sides of said transmission line, a second pair of terminals connected to opposite sides of said terminating network, first and second resistances connected in series between one of said first pair of terminals and one of said second pair of terminals, the others of said first and second pairs of terminals being connected directly together with respect to A.-C.
  • first and second amplifying devices each having an anode, a cathode, and a control grid, the control grid of said first device being connected to the junction between said first and second resistances, the cathode of said first device being connected to the junction between said other terminals, the anode of said first device being connected to the control grid of said second device with respect to A.-C.
  • the cathode of said second device being connected to both the end of said second resistance electrically remote from said first resistance and the junction between said other terminals, and the anode of said second device being connected to the end of said first resistance electrically remote from said second resistance, and a D.-C.
  • the impedance presented to said transmission line by said converter being related to the impedance presented to said converter by said terminating network by the factor 10 where k is substantially a real number over a predetermined operating frqeuency range.
  • a two-wire transmission line which is balanced with respect to ground potential
  • a two-terminal terminating network of passive impedance elcnrients and a negative impedance converter which comprises first, second, third, and fourth terminals, said first and second terminals being connected to opposite sides of said transmission line and said third and fourth terminals being con-- nected to opposite sides of said terminating network, first and second resistances connected from a first common point to said first and third terminals respectively, connections from a second common point to said second and fourth terminals respectively, first and second amplifying devices each having an anode, a cathode, and a control grid, the control grid of said first device being connected to said first common point, the cathode of said first device being connected to said second common point, the anode of said first device being connected to the control grid of said second device with respect to A.-C.
  • the cathode of said second device being connected to both the end of said second resist- 'ance electrically nearest said third terminal and said second common point and the anode of said second device being connected to the end of said first resistance electrically nearest said first terminal, and a D.-C. power supply for both of said amplifying devices connected across said first and second terminals between said second commin point and the end of said first resistance electrically nearest said first terminal to avoid disturbing the longitudinal balance of said line, the impedance presented to said transmission line by said converter being related to the impedance presented to said converter by said terminating network by the factor where k is substantially a real number over a predetermined operating frequency range.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)
  • Devices For Supply Of Signal Current (AREA)
US417650A 1954-03-22 1954-03-22 Negative impedance converter Expired - Lifetime US2817822A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
NL100386D NL100386C (de) 1954-03-22
NL192904D NL192904A (de) 1954-03-22
BE536601D BE536601A (de) 1954-03-22
US417650A US2817822A (en) 1954-03-22 1954-03-22 Negative impedance converter
FR1117757D FR1117757A (fr) 1954-03-22 1954-12-22 Convertisseur d'impédance négative
DEW15779A DE974956C (de) 1954-03-22 1955-01-20 Negativer Impedanzwandler
GB7958/55A GB780177A (en) 1954-03-22 1955-03-18 Improvements in or relating to negative impedance converters
CH330330D CH330330A (fr) 1954-03-22 1955-03-22 Convertisseur d'impédance négative

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Application Number Priority Date Filing Date Title
US417650A US2817822A (en) 1954-03-22 1954-03-22 Negative impedance converter

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US2817822A true US2817822A (en) 1957-12-24

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US417650A Expired - Lifetime US2817822A (en) 1954-03-22 1954-03-22 Negative impedance converter

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US (1) US2817822A (de)
BE (1) BE536601A (de)
CH (1) CH330330A (de)
DE (1) DE974956C (de)
FR (1) FR1117757A (de)
GB (1) GB780177A (de)
NL (2) NL100386C (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3001156A (en) * 1958-12-01 1961-09-19 Bell Telephone Labor Inc Active impedance branch
US3045194A (en) * 1960-11-02 1962-07-17 Bell Telephone Labor Inc Active multiport networks
US3141138A (en) * 1960-10-24 1964-07-14 Kokusai Denshin Denwa Co Ltd Unidirectional amplifier consisting of concatenated bidirectional negative resistance amplifiers which are coupled by delay networks and energized sequentially
US3514711A (en) * 1969-05-05 1970-05-26 Ericsson Telefon Ab L M Amplifier circuit including a lossless transmission line
US3521181A (en) * 1964-04-15 1970-07-21 Telefunken Patent Negative impedance converter
US3546639A (en) * 1966-11-01 1970-12-08 Ass Elect Ind Gyrator network

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1937641A (en) * 1931-09-03 1933-12-05 American Telephone & Telegraph Multiway connection for signaling circuits
US1969836A (en) * 1932-10-27 1934-08-14 Mihran M Dolmage Negative impedance
US2287280A (en) * 1939-06-30 1942-06-23 Int Standard Electric Corp Detection arrangement and negative impedance for same
FR1063497A (fr) * 1952-09-19 1954-05-04 Impédances négatives comprenant un réseau en pont fait d'éléments passifs associé à des éléments actifs et sensiblement indépendantes des valeurs de ces éléments actifs

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1937641A (en) * 1931-09-03 1933-12-05 American Telephone & Telegraph Multiway connection for signaling circuits
US1969836A (en) * 1932-10-27 1934-08-14 Mihran M Dolmage Negative impedance
US2287280A (en) * 1939-06-30 1942-06-23 Int Standard Electric Corp Detection arrangement and negative impedance for same
FR1063497A (fr) * 1952-09-19 1954-05-04 Impédances négatives comprenant un réseau en pont fait d'éléments passifs associé à des éléments actifs et sensiblement indépendantes des valeurs de ces éléments actifs

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3001156A (en) * 1958-12-01 1961-09-19 Bell Telephone Labor Inc Active impedance branch
US3141138A (en) * 1960-10-24 1964-07-14 Kokusai Denshin Denwa Co Ltd Unidirectional amplifier consisting of concatenated bidirectional negative resistance amplifiers which are coupled by delay networks and energized sequentially
US3045194A (en) * 1960-11-02 1962-07-17 Bell Telephone Labor Inc Active multiport networks
US3521181A (en) * 1964-04-15 1970-07-21 Telefunken Patent Negative impedance converter
US3546639A (en) * 1966-11-01 1970-12-08 Ass Elect Ind Gyrator network
US3514711A (en) * 1969-05-05 1970-05-26 Ericsson Telefon Ab L M Amplifier circuit including a lossless transmission line

Also Published As

Publication number Publication date
GB780177A (en) 1957-07-31
NL192904A (de)
DE974956C (de) 1961-06-15
BE536601A (de)
FR1117757A (fr) 1956-05-28
CH330330A (fr) 1958-05-31
NL100386C (de)

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