US1687253A

US1687253A - Negative impedance device

Info

Publication number: US1687253A
Application number: US675833A
Authority: US
Inventors: Latour Marius
Original assignee: LATOUR CORP
Current assignee: LATOUR Corp
Priority date: 1923-12-05
Filing date: 1923-11-20
Publication date: 1928-10-09
Anticipated expiration: 1945-10-09

Description

Oct. 9,-1928. v v 1,687,253 M. LATOUR NEGATIVE IMPEDANCE DEVICE Filed Nov. 20, 1923 Suva/.4 60:

MARI US LATOUR Patented Oct. 9, 1 928.

UNITED STATES MARIUS LATOUR, OE PARIS, FRANCE, ASSIGNOR TO LATOUR CORPORATION, OF "JERSEY 1,687,253 PATENT OFFICE.

CITY, NEW JERSEY, A CORPORATION OF DELAWARE.

NEGATIVE IMPEDANCE DEVICE.

Application filed November 20, 1928, Serial No. 675,838, and in France December 5, 1922.

This invention relates to improvements in arrangements for producing negative impedance, and has for its purpose the produc-' tion of negative impedance which may be interposed in a telephone line in order to counterbalance the impedance of the line and reduce the attenuation, but it-will be understood that this invention is not limited to the use just indicated.

Various specific features of the invention will appear from the detailed description and appended claims.

yinvention is illustrated in the accompanying drawing, in which v Fig.1 shows one form of my invention as embodied in a resistance-coupled amplifier;

Fig.2 shows an arrangement according to mydinventipn utili z'ingtransformer coupling;

F-igsa3 and 4 show arrangements of apparatus adapted to'be inserted in a telephone line to reduce attem1ationand prevent distortion. T v v In Fig. 1 there are shown two three-electrode vacuum tubes 1 and 2, each having a plate, a filament and a grid with circuits arranged to constitute a two-stage resistancecoupled amplifier. The plate circuit of vacuum tube 1 is energized by the combined

voltagesof batteries

3 and 5 through resistance 12. The voltage of battery 5 is such that it normally compensates for the resistance drop of the plate voltage in resistance 12 in such a manner that the voltage between

points

10 and 11 is normally equal to zero. In the same .way,the plate circuit of vacuum tube 2 is energized by the sum of the two voltages of "the batteries 4 and 6 through resistancelfi, the voltage of battery 6 being such that the resultant voltage between terminals 13- and 141' is'normally zero. An impedance 9 having a value a is shunted between the grid and filament of vacuum tube 1 between the

terminals

7 and 8.

From Fig. 1 it will be noted that there is a circuit including the

various terminals

7, 8, 11, 14 and 13-andif we consider that a current flows in this circuit through the impedance9 which has a value a, it will be understood that the passage of current develops a voltage 1% between the grid and filament of vacuum tube 1 and this voltage amplified successively by the two vacuum tubes 1 and 2 results, in accordance with the usual characteristicofvacuum tubes, as a negative ohmiedrop between the points 14: and 13 of the resistance 15. It, therefore, results that for a suitable value of imped- -ance 9 having a resistance, an inductive reactance, and capitance, there is obtained between terminals 7 and 13 a negative im edance depending on the characteristics 0 the clrcuits.

In order to obtain a negative impedance of a sign exactly opposite to that of the impedance 9, which is connected in shunt to the grid and filament of the first vacuum tube 1, it is necessary to place in series with the Impedance -9 a certain resistance 16 which, transformed into a negative resistance by the operation of the amplifying system, serves .to counterbalance the effect of the positive resistance'connected in the late circuit of the'second vacuum tube 2.

he resistance 16 is substantially equal to v the resistance 15.

According to this invention, we may emplo instead of direct coupling by resistance, coupling by

transformers

17 and 18 as shown in Fig. 2 in which the same reference characters indicate the same parts as in Fig. 1. In this case an even number of tubes is no longer necessary. It is sufficient to take a convenient sense of circulation of the windings of the transformers interposed in the work circuit and the number of tubes may be anything. If it is supposed that we have to do with a perfect type of transformer (magnetizing current zero, capacity of windings zero, leakage zero, losses zero), the operation will be that shown in Fig. 1. In practice it should be arranged that

transformers

17 and 18 approach the perfect type of transformer with theorder of magnitude of the frequencies considered. The

magnetizing current. may be compensated by a capacity in shunt. These transformers may be without iron in the case of very high frequencies. The input transformer, on the other hand, may be arranged with a ratio of transformation sufliciently low so as not to cause in the grid filament circuit a resultant eifect capable of disturbing the desired operation. The resistance 15 may be variable; it may be represented by the winding connected to the plate and represented even by the losses in the iron of the transformer.

Fig. 3 shows an arrangement in which the real impedance .2 is a cable or artificial line equivalent to a real cable or real line in a responds to a cable or artificial line of inverse constants, as compared with Fig. 3, (capacities in series and inductances in shunt in such a manner that the negative impe ance obtained may permit not only the reduction of the attenuation, but prevent distortion. In a general way, the real impedance 9 may be constituted by all elements appro riately selected, inductances, capacities an resistances combined in any manner to represent a suitable artificial line.

In order to satisfy symmetry, we may arrange two amplifier systems for a single line. In the first system t on the north side and the plate circuit on the south side; While in the second system the grid circuit will be on the south side and the plate circuit on the north after themanner of the well known one-way repeater. The real impedance 9 may also be, for example, the modulation circuit of a magnetic amplifier or of a frequency multiplier, the excitation circuit of a high frequency alternator and in a general way any circuit resenting a reactance which is a function 0 the frequency. The distortion suffered by telephonic current in traversing such a circuit e grid circuit may be may then be prevented by roviding on the plate side a negative impedance of a valve equivalent to that shunted about the grid side in such a way that the whole represents only a residual impedance corresponding to a pure ohmic resistance.

Having described my invention, what I claim is:

1. In apparatus for producing a negative impedance, a vacuum tube amplifier comprising an anode, a cathode and a control electrode, an impedance connected in circuit between said cathode and said control electrode, a transformer having its windings inative impedance, the combination of a vacuum tube amplifier having an anode, a cathode and a control electrode, an input circuit comprising an impedance having a resistance associated therewith, an output circuit comprising a resistance, a transformer having its primary shunting said impedance, and its secondary connected in the control circuit of said amplifier, and a second transformer having its primary winding in the anode-cathode circuit of said amplifier and its secondary winding shunting the resistance in said output circuit.

MARIUS LATOUR.