|
When
“impedance” is mentioned in reference
to coaxial cables, the “characteristic
impedance” is normally implied. Characteristic
impedance (Z0)
is the ratio of voltage to current in a
traveling wave. In low loss coaxial cable,
the impedance is directly related to the
logarithm of the ratio of the inner and
outer diameters, and inversely related to
the square root of dielectric constant of
the core material. In a low loss coaxial
cable, the impedance is always a positive
real number. Maximum power transfer results
only when the characteristic impedance of
the transmitter, RF line, and the receiver
(or antenna) are equal to each other or the complex conjugate. If
the match is exact, losses are only due
to the attenuation of the transmission line.
If there is a mismatch, reflection
losses will result.
d
= Center conductor diameter in inches.
D = Dielectric core diameter in
inches.
Engineering
Home | Back
| Next
|
