# Cascade connection of coaxial cables

Cascade Connection of Coaxial Cables When coaxial cables of the same characteristic impedance but of different sizes (different diameter), are connected in series, do electromagnetic waves have reflection at the connecting point? Or, is it right to think of no reflection?

coaxial cable 1    coaxial cable 2
o------------------o-----------------o
Z0                 Z0
o------------------o-----------------o
^
Connecting Point
Of course, the connecting point must be structured with the best effort,
because a bad connection naturally causes big reflection.  It is assured
in textbooks on "Transmission Theory" that, when a line of
characteristic impedance, Z0, is connected to a line of characteristic
impedance, Z, in series, the voltage reflection constant at the
connecting point is as follows:

r = (Z/Z0 - 1)/(Z/Z0 + 1)

where, r = Voltage reflection coefficient
Z0 = Characteristic impedance of Line 2 (Ohm)
Z = Characteristic impedance of Line 1  (Ohm)
This well-known relation implies that reflection of electromagnetic waves is determined only by the characteristic impedance of the lines and, therefore, there seems to be no reflection in the above circuit as a matter of course. If so, we may not need even to take the matter into consideration. However ..