US1665501A

US1665501A - Ampli

Info

Publication number: US1665501A
Authority: US
Publication date: 1928-04-10
Anticipated expiration: 1945-04-10

Description

April 10, 1928 r 1,665,501 J. S. JAMMER AMPLIFYING REPEATER Filed May 22. 1923 I l I l I l l l I l I hue/WW: I Jaca J. Jammer Patented Apr. 10, 1928.

UNITED STATES 1,665,501 P TEN OFFICE.

. JACOB s. JAMMER, on NEW YORK, N. ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INGORPDRATED, OF NEW roan, N. Y., A CORPORATION on NEW YORK.

AMPLIF ING nnrna rnni Application filed May 22,

This invention relates to an amplifying repeater such as employed in multiple); car rier current telephone and telegraphsystems wherein diflferent channel frequencies for transmission in one direction are grouped in a different frequencyrange from that employed fortransmission in the opposite direction. p 1

Among the objects of the invention are:

To produce a two-way amplifying repeater wherein the amplifiers for oppositely directed transmissions have different amplitying characteristics.

To produce a tWo-wayamplifying repeater wherein the amplifying characteristics of the amplifiers for oppositelydirected transmissions are particularly suited to the frequency range of the currents to he amplified therefier for the transmitted currents of the lower frequencies.

To produce an elficient and economical two-Way repeater.

The invention is illustrated as applied to a two-way amplifying repeater for use in a multiplex carrier current telephone and telegraph system, but itis to be understood that it may also he applied to two-way amplifying repeaters for use in other signaling systems wherein the frequencies of the Waves transmitte din one direction are in a different frequency range thanthat embracing the waves transmitted in theopposite direction.

In the drawing- "Fig.1 illustrates diagrammatically a two-- way amplifying repeater having a two-stage amplifier for the group of higher frequency wares and a single stage amplifier for the group of lower frequency waves.

Fig. Qillustrates diagrammatically a twoway amplifying repeater having a single stage amplifier for each group, the ampli" tying factor of one heinggreater than that of the other. e Fig. 3 shows curves representing the ant plifying"characteristics of the amplifiers of Figures" land 2. e Fig. lrepresents the gains ofthe respective amplifiers of the two-way repeaters shown in Figs. 1 and 2. p

The two-way repeater of Fig. l, compris- 1923. seriarNo. 640, 43.

ing two one-way repeating channels RE and RVV, is adapted to couple two transmission line sections E and 7.

The currents incoming to the repeater station from line section E are amplified in the repeating channel RE and the amplified currents are delivered to line section V. Likewise, the. currents incoming from line section W are amplified in the repeating channel RVV and the amplified currents are delivered to line section E. e

The currents incoming from the line section W are of higher frequencies than those incoming from line section E, and, as will more fully hereinafter appear, the respective repeating channels are provided with frequency discriminating filters which direct the incoming currents to the proper channel.

It is Well known that the characteristics of a line are such that theattenuation of the currents traversing it increaseswith an in crease of frequency. The attenuation per unit length of line will, therefore, be greater for the currents incoming from line section V, than for those incoming from line section E.

Since the repeater is for the purpose of amplifying the attenuated currents and it is desirablethat the outgoing transmissions of all frequencies from the repeater be at substantially the same energy level the attenuated currents of the higher frequencies.

. means having amplifying factors selected in accordance with the frequencies of the currents to he amplified are Reduction in number and cost of amplifiers. e Reduction incest of directional filters employed in the repeating channels.

The repeating channel RE includes input.-

and output filters, EIF and EOF, an amplifier EA and an attenuation equalizer The input and output filters EIF and 357 granted April 18, 1922.

EOF may be low pass filters of the type disclosed in the patei'it to ltaibonrn, No. 1,t13,-

They are designed to pass currents of the frequencies to be amplified inthe repeater channel RE and to suppress currents of higher frequencies.

The amplifier EA. may be of any well known type, but, as illustrated, is of the balanced type somewhat similar to that disclosed in Fig. l of U. patentto' Colpitts, No. 1,128,292 granted February 16, 1915, but it must be adapted to handle the wide range of frequencies encountered in a multiple-X carrier current system.v

The input current to the amplifier EA may be regulated by a potentiometer 1.

The attenuationequalizer EAE, comprising an inductance 2 shunted by a capacity 3 connected in series with resistances at and 5, serves to so terminate the input filter Ell? as to equalize the differences in line attenuations at the different frequencies of the currents to be amplified by amplifier EA. -Thus the outputs from the amplifier are of substatially equal value for the different frequencies.

The repeating channel It? includes input and output filters VVIF and VVOF, two amplifielj's WA and IVA connected in tandem by an inter-stage filter ISF, and an attenuation equalizer \VAE. The input and output filters .VIF and 0F may be high pass filters of the type disclosed in the Raibourn patent, supra. They are designated to pass currents of the frequencies to be amplified in the repeating channel Riv and to suppress currents of lower frequencies. The interstage filter ISF is of the same type as the high pass filters WIE and WOF and passes only currents of the frequencies passed by these in- I put and output filters.

A two-stage amplifier. wherein the twoamplifying structures are connected by a directional filter is disclosed and claimed in my copending' applicationSerial No. 616,- 243, filed February ,1, 1923.

The amplifiers A and VVA which are similar to amplifier EA, form atwo-stage amplifier which has an amplifying factor greater than that of the single stage amplifier EA.

The input current to the amplifier We. 1 maybe regulated by a potentiometer 6.

The attenuation equalizer VVAE is similar to the equalizer EAE and serves the same general purpose.

Of course should occasion require it, additional stages of amplification maybe introduced into each repeating channel.

The repeater of Fig. 2v is similar tothat of Fig. 1, differing therefrom principally in that but a .single stageamplifier is employed in'each repeating channel. These amplifiers, however, are so construct cd that inherently the amplifying factor of the west amplifier A is greater than that of the east amplifier E A.

ll hether an electronic valve amplifier has a high or low amplifying factor depends upon the construction of the control electrodeor grid and the spacing of the grid with respect to the cathode.

Thus an electronic amplifier having a grid of fine mesh spaced relatively close to the cathode has a high amplifying factor. lf the grid is of coarse mesh and spaced farther from the cathode, the amplifying factor will be lower.

Fig. 3 shows curves illustratiin the diftierence in anngilifying clniractcris east and west amplifiers employed. in the repeaters shown in F l and 2.

These curves are obtained by plotting the input voltage E as abscissze against the out put current L as ordinates.

Curve A represents the an'iplifying characteristic or factor of the west amplifier which amplifies the higher frequency cur rents, and curve B the amplifying characteristic or factor of the east amplifier which amplifies the lower frequency currents.

In Fig. the line CD represents the attenuation characteristic of a transmission line section of approximately 250 miles of open wire No. 8 Bil G line for frequencies from (5.7 to kilocyclcs. This line Cl) also represents the necessary net gain of the two-way repeater to compensate for the line attenuation.

Where the transmissions in omiositc directions in a carrier telephone system are grouped, the channel frequencies for one direction may lie within the frequency range of 6.7 to 19 kilocycles and the channel frequencies for the opposite direction may lie within the frequency range of 21 to tit-3.3 kilocycles.

, Inspection of Fig. 4 shows that currents of frequencies within the upper group of 21 to kilocycles are attenuated more more than currents having frequencies within the lower group. conscrpiently, a lower net gain is required of the repeating channel handling the lower frequency group than is required of the repeating channel handling the upper ilrequency group.

The gross amplification of each. repeating channel must be such as to con'ipcnsatc for the attenuation of the highest frequency currents handled thereby. V

Thus, the amplifier of the repeating channel Bil provides a gross gain represented by the area DEFG. The attenuation equalizer XVAE introduces a loss represented by the area DEH thereby leaving the net gain ofv the west repeating channel equivalent to the area DHFG.

The amplifier or the repeating channel RE provides a gross gain represented by the area JKLM. The attenuation equalizer EAE introduces a loss represented by the area CJK. Consequently, the net gain is sible singing of the repeater. This loss is caused principally by attenuationwhich (the filters produce in currents outside their transmission range.

According to the usual practice, two-way repeaters are constructed so that the gross gain of each repeatingchannel is the same. Since the net gain for the two repeating channels is not the same, it is necessary, according to present practice, to introduce a loss in the channel of which the lower net gain is required, which means ordinarily that this required additional loss must be introduced by the filters or other means, thereby increasing materially and unnecessarily the cost ofthe repeater.

According to the present invention, each repeating channel provides only the gross galn necessary tocompensate for the attenuation of the highest frequency currents within the group handled thereby. Consequently,the loop gain is lower than in repeaters as previously employed. While the loop loss must exceed the loop gain to prevent sin in less loss is re uired b the repeater embodying the present invention. This loop loss is introduced by the filters "which may be less expensive as less energy is to be dissipated.

The invention set forth herein is, of course, susceptible of various other embodiments and adaptations.

The invention claimed is:

l. The combination of a transmission line for transmitting in opposite directions a plurality of carrier currents comprised in re spective frequency ranges, said line having greater attenuation for Waves of higher frequency transmitted in one direction than for Waves of lower frequency transmitted in the opposite direction, and a two-way repeater comprising oppositely directed transmission paths, each path including means to select a group of carrier currents, an a1nplifying means and an equalizer for compensating for the unequal attenuation produced by the line in the waves of the different frequencies comprised in the respective frequency ranges, the amplifying means in the path transi'nitting the waves of the higher frequencies having a greater amplifying factor than that in the path transmitting thewaves of the lower frequencies, each amplifying means having an' amplifying factor such that the net gain over the loss introduced by the entire circuit including the line and respective equalizer is substantially the same for each frequency transmitted over the system. i

2. A two-way repeater for coupling two transmission lines over which the currents transmitted in. one direction are of higher frequencies than those transmitted. in the opposite direction, comprising two asymmetric repeating channels, input and output filters in each of said channels, an amplifier connected between the input and output filters in each of said channels, and equalizers in the respective channels for equalizing the differences in line attenuation in the different frequencies tobe amplified by each repeater, the amplifying factor of the amplifier in the higher frequency channel being greater than that of the other channel to effect the same net amplification in the higher frequency repeater channel and the line therefor and in the lower frequency repeater channel and the line therefor.

In witness whereof, I hereunto subscribe my name this 18th day of May A. D., 1923.

JACOB S. JAMlMER.