Crosstalk Between Coaxial Conductors in Cable

In spite of the geometrical and electrical symmetry of the coaxial circuit and the excellent shielding properties of the outer conductor, a part of the electromagnetic energy escapes from the circuit through the outer conductor and sets up an electromagnetic field in the space around it. Any circuit, be it even another coaxial placed in this field will absorb a part of the energy stored in the field and deliver it to the terminals of the circuit in the form of an unwanted or interfering current--the crosstalk current. The magnitude of this crosstalk current depends on a variety of factors, such as the physical characteristics of the conductors and of the intervening space, the frequency and the length of the circuit. Expressions for two important cases of crosstalk between two coaxial circuits in free space, namely, the so-called "direct" crosstalk with the outer conductors in continuous contact and the "indirect" crosstalk with the outer conductors insulated from each other, were determined 358