The reasons and parameters of mutual influence between TL

     The reasons and parameters of mutual influence between TL

     Quality of signaling of communication on chains of cable lines in many respects depends on size of hindrances in these chains.Hindrances name extraneous currents and pressure in a chain which frequency spectrum coincides with a spectrum of useful signals transferred on a chain. The hindrances resulting electromagnetic influence of parallel chains, name linear. In case of transfer on parallel chains of telephone conversation linear hindrances name transitive conversation.

     If in a chain subject to influence, it is listened and the sense of the conversation transferred on the influencing chain such transitive conversation name distinct can be understood. If listened in a chain subject to influence, sounds have character of speech, but it is impossible to distinguish its sense, such sort of influence name muffled transitive conversation and it carry to noise which can arise in a chain and as a result influences of other reasons, for example transitions from other channels of the given system of transfer owing to nonlinear elements in a chain. To noise carry also currents and the pressure caused by influence of external electromagnetic fields from a line of a strong current, radio stations, power supplies sources, the thermal phenomena in lamps, resistance etc.

     Availability of noise in channels at telephone conversation lowers legibility of speech, and by transfer of other kinds of signals leads to distortion of signals transferred on the channel or in general does impossible signaling with necessary fidelity. At telephone conversation on a communication channel occurrence of distinct transitive conversation as it distracts attention is especially inadmissible and breaks privacy of telephone transfer. It is necessary to notice that an ear of the person especially sensitively to distinct transitive conversation, therefore admissible size of influence from parallel chains in a cable establish proceeding from admissible size of level of distinct transitive conversation.

     On each such elementary site of length of a line in a chain II the currents caused by electric communication With and and magnetic communication М12 are created. Thus the current/2h „, going to the beginning of a line from this elementary site, is equal to the sum of currents from electric (72с) and magnetic (/2m) influences: 
 

Fig. 3.21.The equivalent scheme of influence between chains on unit of length of a line

(3.34)

the current going by the end of a line/2hk, is equal to a difference of these currents:

(3.35)

     The combined value of a current of hindrances in the beginning and the end of the chain subject to influence, is determined by the sum of the currents which have come from all elementary sites accordingly to the beginning and the end of this chain. At summation of currents consider change of size of an influencing current at its distribution from the beginning of a chain to each elementary site, size of electric and magnetic communication on each elementary site, and also current change in a chain subject to influence on ways from an elementary site at its distribution on this chain to its beginning and the end. Change of currents in the chains influencing and subject influence, depends on coefficients of transfer of these chains, i.e. from coefficients of attenuation and and coefficients of a phase of these chains, and length of a way of currents. Schematically ways of transition of currents on all length of parallel run of chains are represented on fig. 3.22.

     Parameters of mutual influence characterize degree of easing of currents of the influence passing from one chain another owing to electromagnetic communication between them.

     In a general view noise immunity of chains from mutual influences is estimated by the relation of capacity of useful signal Р \, transferred in an influencing chain 1, to capacity of a stirring signal (hindrance) Р2, passed in a chain 2 subject to influence (fig.3.23).

Fig. 3.22.

The influence scheme between chains on separate elementary sites of a line  

Fig. 3.23. To the explanatory of concepts of transitive attenuations between chains

     Differentiate two concepts of noise immunity – transitive attenuation (A) and security А3. The first is determined by the relation of capacity of a signal in the beginning of an influencing chain to capacity of a hindrance in any point of the chain subject to influence and second - the relation of capacity of a signal in an influencing chain to capacity of a hindrance in a chain subject to influence in any point, general for both chains  

     In practice for the purpose of unification it is normalized three parameters of mutual influence, transitive attenuation on the near and far end and security on the distant end.

     Between chains it is accepted to express influence in size of transitive attenuation in decibels (dB). The size of transitive attenuation on the near end (fig. 3.23) is equal to 10 decimal logarithms of the module of the relation of capacity of a transferred signal in the beginning of an influencing chain to capacity of hindrances and in the beginning of the chain subject to influence. The size of transitive attenuation on the distant end is equal to 10 decimal logarithms of the module of the relation of capacity of a signal in the beginning of an influencing chain to capacity noises at the distant end of the chain subject to influence.

     If entrance resistance of the generator and receivers are equal to sizes of wave resistance of chains in which they are included mathematical expressions of sizes А0 and And / can be presented in a following kind:

     

If chains between which influence is considered, are identical, i.e. Zwj = Zw2,

Security between chains on the distant end is determined by expression

     Distinction between transitive attenuation and security on the distant end consists that in the first parameter capacity of a transferred signal appears in the beginning, and in the second – in the end of an influencing chain. 
 

     Both parameters are connected among themselves by a following ratio: coefficient of attenuation of an influencing chain length lines (km).

     All parameters are specified for sinusoidal signals.

     Formulas (3.36) and (3.37) give the chance to specify sizes of transitive attenuation between chains if sizes of capacities, pressure and currents in the beginning of an influencing chain and accordingly in the beginning and the end of the chain subject to influence are known. On a line or in separate building lengths the specified sizes can be measured.

     Admissible extent of parallel run of chains and communication quality at parallel chains basically depend on size of mutual influence between chains. Its reduction to admissible limits is one of the primary goals in technics of linear constructions of communication.

     Mutual influences between chains are caused by availability electric and magnetic water round chain wires by transfer on it electromagnetic energy.

     In technics of communication apply two-wire chains. The influence scheme between two-wire chains can be clear by consideration fig. 3.20 on which the cross-section of wires of two parallel chains is presented. Wires of an influencing chain are designated by figures 1 and 2, and wires of the chain subject to influence, - 3 and 4. Firm lines designate power lines of a magnetic field, and dotted – electric field lines. Intensity electric and magnetic water in points of an arrangement of wires 3 and 4 неодинакова. Hence, in these wires there will be electric charges different in size and electromotive forces.

     If on the ends of a chain of a wire 3 к4 are connected to the receiver (are closed among themselves on its entrance resistance) in chain wires there are leveling currents which are perceived by the receiver as hindrances on the ends of the chain subject to influence.

     The influence caused by action of a magnetic field, name magnetic influence, and the size characterizing magnetic influence, - magnetic communication between chains. 
 

     The size of magnetic communication is determined by the relation induced ЭДС in a chain subject to influence, to current U of an influencing chain with a return sign, i.e.

The influence caused by action of electric field, name electric influence, and the size characterizing this influence, - electric communication. The size of electric communication With, 2, the Ohm, is determined by the relation of the induced current/2 in a chain subject to influence, to pressure U, in an influencing chain, i.e.

In general view М12 and С12 are the complex sizes consisting of the valid and imaginary parts:

     Here r12 - an active component of magnetic communication; т – mutual inductance or inductive communication; g12 – an active component of electric communication; to – a capacitive coupling.

     The equivalent scheme of influence of a chain of I (influencing) a chain II (subject to influence) on unit of length of a line s on distance х from the line beginning can be presented the scheme fig. 3.21. …. -

     However essential interest represents determination of sizes of transitive attenuation between chains a settlement way through influence parameters, i.e. through parameters of electric and magnetic communications between chains. Settlement formulas of influence give the chance to establish interdependence between parameters of influence and cable design data. Availability of such dependences allows at creation of cables on required sizes of transitive attenuation between chains to establish requirements to sizes of electromagnetic communications.

     In turn, already proceeding from admissible sizes of electromagnetic communications, establish requirements to sizes of separate coefficients of communication in building lengths and requirements to admissions on constructive deviations of separate elements of cables (diameters of veins, thickness of the insulation layer, etc.), and also requirements to materials (uniformity of isolation, admissions on deviations of sizes dielectric-losses in isolation and conductivity of a material of cores). 

THE NATURE AND KEY PARAMETERS OF MUTUAL INFLUENCE BETWEEN TL

     At current passage on a cable or a chain (influencing), for example (fig. 1), on wires of this charges +Q1 and — Q2 also are formed. Charges create the electric field which power lines partially touch with wires 3—4 adjacent chains (subject to influence In a consequence of it between a wire 3—4 the potential difference which creates in them a current extending along a chain is formed. The induced current reaches receivers included on the chain ends, and the Influence, the caused action of electric field is in the form of stirring influence, name electric influence.

     

     Fig. 5.1. The scheme of electric influence

Along with electric influence also magnetic influence (fig. 2) simultaneously acts. At current passage on an influencing chain 1—2 circle of wires of this chain is formed a magnetic field which power lines partially influence wires 3—4. These magnetic power lines, crossing wires 3—4, direct in them ЭДС which creates i пи 3—4 current. This current, extending along a chain, reaches the receivers included on its ends and creates stirring action. The influence caused by action of a magnetic field, is called as magnetic influence.

     Fig. 5.2. The scheme of magnetic influence

     The above frequency transmits a current, the proceeds changes electric faster and magnetic water and the more size of mutual stirring influence between chains. Electric and magnetic influence between two chains is characterized according to electric (К12) and magnetic (М12) by communications. 

     Electric communication (К12) is presented in terms of conductivity — Cм, and magnetic (M12) — in terms of resistance - the Ohm. At accounting of combined action of communications it is necessary to translate them in identical units of dimension. Meaning that U1 = I1 Zw1и 12 = E2/Zw2, it is possible to express Electric communication in terms of resistance — the Ohm:

К12= (g + j*k)Zw1Zw2 (5.3)

And magnetic communication in terms of conductivity — Sm:

M12= (r +j*m)/ Zw1Zw2. (5.4)

     Sizes r, g, k and m are called as Primary parameters of influence. The size of transitive attenuation And, characterizing attenuation of currents of influence at transition from the first chain the second, is secondary parameter of influence. In communication lines is usual aspire to reduce own attenuation of a chain and and to increase transitive attenuation And.

     Transitive attenuation is the basic measure of an estimation of properties of air and cable lines on mutual influence between chains and suitability of chains for high-frequency transfer. It is expressed by a logarithm of the relation of capacity of generator R1 feeding the influencing chain, to capacity of hindrances Р2 in a chain subject to influence, and measured in decibels. By influence consideration between communication chains differentiate two kinds of transitions of energy: on near (transferring) and on distant (acceptance) the ends (fig. 5.3). The influences, shown on that end of a chain where the generator of the first chain is located, is called as transitive influence on the near (transferring) end of Aa. Influence on the opposite end of a chain is called as transitive influence on distant (acceptance) end Al.

     Along with sizes of Ao and Аl in technics of communication the parameter Ae - security from hindrances, or simply security representing a difference of levels of a useful signal р0 and hindrances рп in considered токе:А3 = rs-rp is widely used. Entering of the given parameter is caused by that for provision of a due communication quality is necessary that capacity of a useful signal surpassed capacity of hindrances on certain size. In itself capacity of a signal doesn't warrant required quality. Really, in a lownoise line it is possible to provide considerably better quality of transfer under condition of low acceptance level, than in a line with high level of hindrances at much stronger signal. 
 

     Literature:

1. http://www.tehnauk.ru/1/14
2. http://kunegin.com/ref5/ut/page5.htm
3. http://www.toroid.ru/lomuhinUL.html

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

                              Plan

1. The reasons and parameters of mutual influence between transmission lines.

 

2. The nature and key parameters of mutual influence between transmission lines.

 

3. Literature.