SELF

36

S.B. Karavashkin and O.N. Karavashkina

The second factor considerably affecting the variation of EM wave velocity in the near field is non-ideality of measuring dipole. Actually, in all investigations presented in this paper we did not take into account the influence of the very measuring dipole. However in the near field this influence has to and will take place. Namely due to this influence, between the radiating and measuring dipoles we observe the standing waves, which considerably change the total delay phase of the wave process and increase the virtual velocity of wave propagation. Virtual - because in reality this will be the superposition of progressive and standing waves, but all calculations show the growing velocity. This is one more example, how experimental methods can affect the results. If we do not take into account this factor, the measurement will show the abruptly growing velocity in the immediate near from the centre of radiating dipole. But if we note the growing coefficient of standing wave caused by the fields inter-affection, the velocity growth will go much slower, which will most fully account the real physical processes in the studied system.

At the same time, the influence of finite size of measuring dipole will be confined to the numerical characteristics, which is easy to show. Actually, to determine the wave velocity variation in the near field with the finite size of measuring dipole, we have to use the diagram shown in Fig. 23.

Fig. 23. Construction to determine the EM wave velocity variation in the near field for a half-wave dipole and with the size of measuring dipole matched with the radiating dipole

In Fig. 23, the measuring dipole is shown in two positions, in which the phase of wave process is shifted exactly by a wave period. In accordance with (22) and (26), the potential at the point P₁ will be determined as follows:

where

In (49) we immediately sought the real part of complex function of scalar potential, as we are interesting just in the phase determined by (51).

Similarly, the scalar potential at the point P₂   will be determined as follows:

where

The regularity of our interest c() will be determined by the implicit function

The plot of  c() is shown in Fig. 24.

Fig. 24. Variation of wave velocity in the near field calculated with the account of finite size of measuring dipole

Comparing the plot in Fig. 24 with that in Fig. 22, we see that the asymptotic pattern of this regularity has fully remained, only the size of near field changed. When we did not take into account in our calculation the size of measuring dipole, we could evaluate this size as (5 6), and when taking that, this size lessens to .

The conducted analysis showed the increase of wave propagation velocity in the near field is the objective regularity, caused by the affecting here size of radiating system onto the parameters of wave propagation in space.