US1543775A - Apparatus for neutralizing radiointerference on wire lines - Google Patents

Description

Patented dune 3Q, i925.

LESTER M. ILGENFRITZ, GF GRANGE, NEW JERSEY, SSIGNOR T0 IEERGN EHONE AND TELEGRAPH COMPANY, .A 'CGRPOBATXON 0F NEW' YORK.

APPARATUS FR NEUTRALIZING RADXOINTEREERENCE 0N VDB/E LNES. i

Application filed November To all whom t may concern:

Be it known that I, Lns'rnn M. ILGENFRITZ, residing atOrange, in the county of Essex and State oi New Jersey, have inventedcertain Improvements in Apparatus for Neutralizing Radiointert'crence on lVire Lines, of which. the following is a specification.

This invention relates to transmission cir cuits, and more 'particularly to a new and improved system for overcoming interference on signaling conductors due to radio transmission.

In carrier transmission systems in which carrier channels are superposed on ordinary signalingcoductors, interference is sometimes produced in one or more of the carrier channels due to radio signals transmitted at the carrier frequency assigned to the channel. In order to overcome this difficulty, it has heretofore been proposed to balance out the interfering frequency by impressing upon the channel a balancing frequency of equal amplitude and opposite phase, the balancing frequency being obtained from the disturbing source through the medium of an auxiliary circuit which is subject to the disturb ing influence.

In applying this remedy, some difficulty has been experienced in obtaining the proper balance due to the fact that adjustments of the balancing potential must be made both with respect tophase and amplitude, and instrumeutalities heretofore used. for obtaining such adjustments have been of such a character that an adjustment of either the phase or the amplitude results in a change in the other, so that it has required considerable manipulation in order to obtain a balance. It is one of the objects of the present invention to provide a systenrin which the phase and amplitude of the balancing potential may be controlled each independently of the other, so that when the phase angle has once been adjusted, changes in amplitude may thereafter be made Without changing the phase angle, or vice versa. rlhis object and other objects of the invention may be attained by means of the arrangement set forth in the following description and illustrated in the accompanying drawing, Figure l of Which discloses one form or' circuit arrangement for practicing the invention..

Referring to the drawing, EFL desigao, 1922. serial ne. 602,193.

n ates a high frequency carrier transmission line terminating at a carrier station. branch leading through a low-pass iilter ,"lf' to a low-frequency line LFL and in another branch leading through a. high-pass iilter HP to the terminal carrier equipment. The carrier equipment comprises a transmitting circuit TLand a receiving circuit EL asso# ciated with the carrier branch throu'fvh the usual high frequency balanced trans crmer 10. The transmitting' circuit TL is connected t0 midpoints of the balanced transformer', and the receivingA channel RL is sho-Wn as being connected to the third Winding of the l transformer, and a balance is obtained by l means of the usual balancing network MN.

The various carrier receiving channels7 such `1 as RLI, BLZ, etc., are associated with the receiving circuit BL through suitable lilters,

such as F1, F2, etc., adapted to select the range of frequencies assigned to each receiving channel.

lf the main line HFL is subject to interferencefrom a radio station employing a carrier frequencylying `Within the range of one or' the receiving channels, as, for er:n ample, the channel RL2, it is apparent that the interfering radio frequency will be transmitted over the line HFL to the receiving channel BLZ .in the same manner as the modulated carrier frequency transmitted to said channel in the normal operation ofthe carrier system. In order to balance out the interfering frequency, a radio antenna A may be provided for absorbing from the distant radio station the same radio signals which are impressedupon the line HFL, and this frequency may be impressed upon the channel RLS through the circuit 1l in opposite phase relation, but with the same amplitude as the interfering potentialP ln order to adjust the phase angle ci the balancing potential, a rotary field phase adjustment device is provided. This arrangement comprises two branch circuits 13 and 11i, including suitable field windings 'l5 and 1G for producing the rotary lield, ln circuit with one ot the windingsj as, fer er,- amplc, the Winding 16, is a capacity Ugand in each of the branches resistances and "19 are provided. Since the capacity l? is included in one of the branches, and not in the other one, the component of. the ire dll channel RL,. not disturb the phase angle obtained by the quency receivedv from the antenna iiowing through the Winding 16 will be 90 out of phase' with the component flowing through the winding l5.' The resistances 18 and 19 may be set, so that both components have the same amplitude. Consequently, the two components energizing the two field Windings and 16 will produce a rotary ield which rotates at the frequency of the electromotive force impressed uponv the antenna A. A third Winding is placed Within the iield of infrluence of the windings l5 and 16, and, by merely shifting the angle of the coil 20 with respect to the field of thev coils l5 and 16, any desired phase angle may be obtained for the induced electromotive forces in the lcircuit 1l. These electronictive forces will, of course, have the same frequency as the electromotive forces impressed upon the antenna A, the phase angle being dependent only upon the angle at which the point 20 cuts the rotar iield.

The amplitude maybe adjusted by means of a separate amplitude controlling device -21 Without producing'any change in the phase angle of the' balancing current, especially if the amplitude controlling device is of ,such a nature as to be adjustable Without producing any change in the .impedance of the circuit 1l as viewed from the coil 20. In, order toaccomplish this result, the ampli.- tude changing device is made up of series and snunt res1stances as indicated, the series and shunt resistances being adjustable together, so that as the series resistance is increased the shunt resistance is decreased. and vice versa. Under these conditions the impedance of the circuit l1 viewed from the coil 20 will he substantially equal to the sum ci the shunt resistance and the two resistences included in the two Wires of the circuit. l1 below the shunt resistance. Constant impedance transmission controlling devices of the type of the device 2l are well known in the art, and the theory ci such devices need not be further elucidated.

It will be apparent from this arrangement that the phase and amplitude adjustments may be made separately in a very simple manner. For example, the phase adjustment may he made first by listening in the receiving circuit RLZ and adjusting the angle ci the coil 20 until the interference is reduced to a minimum. lvlhen the minimum setting has been found, it will he apparent at once that this corresponds to the condition in which the phase of the potential from the circuit 1l. is opposite to that ci the interfering potential transmitted to the circuit RL2 over the high frequency line HFL. Having made this adjustment, the device 21 will then be adjusted until the interfering distlubauce can. no longer be heard in. the The latter adjustment Will Aauxiliary circuit upon l. In a Wire signaling system subject to interference due to radio signaling, an aux-V iliary circuit upon which a similar disturbing electromotive force may be impressed for balancing purposes, device associated with said auxiliary circuit for adjusting the phase of the current resulting from said balaning electromotive force and a device associated with said auxiliary circuit for adjusting the amplitude of said current, said phase adjusting device and amplitude adjusting device controlling their respective functions independently of each other.

2. ln a wire signaling system subject to interference due to radio signaling, an auxiliary circuit upon which a similar disturbing clectromotive force may be impressed for balancing purposes, a device associated with said auxiliary circuit for adjusting the phase of the current resulting lfrom said balancing elcctromotive force and a device associated with said auxiliary circuit for adjusting the amplitude of said current, said amplitude controlling device being capable of adjustment for controlling the amplitude Without producing any change in the phase determined by said phase adjusting means.

3.- ln a Wire signa-ling system subject to interference due to radio signaling, an auxiliary circuit upon which a similar disturbing electromotive force may be impressed for balancing purposes, a device associated with said auxiliary circuit for adjusting the phase of the current resulting from said balancing electromotive force and and a device associated With said auxiliary circuit for adjusting the amplitude of said current, said phase controlling device comprising means for producing a rotary field, and a coil inductively related to said iield and adjustable as to its angle with respect to said iield.

4. ln a Wire signaling system subject to interference due to radio signaling, an which a similar disturbing electromotive force may be impressed for balancing purposes, a device associated with said auxiliary circuit for adjusting the phase of the current resultin from said balancing electromotive force au a device associated with said auxiliary circuit for adjusting the amplitude of said current, said phase controlling means comprising a pair of branch circuits each' havin a coil, therein, means to cause 900 phase if @mams naigmoxhou 0i said coils anfl n fhird wil ing mir of branch cfcus arr'mlgs. cut said field ai', any desnef coll tharem, mesma t@ cause n

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