RF lightning protector principles

Overvoltage protection in the field of RF engineering must meet special requirements in comparison with general, low-frequency signal transmission and power supply applications. In particular, coupling capacitances towards ground must be minimized in order to prevent any significant loss of the transmitted RF signals. This essentially rules out the wide-band application of varistors and semiconductor diodes.

There are three principal designs for coaxial lightning protection components in RF applications:

• Gas capsule (spark gap) – the well-known principle in electronics since many years

and, in addition, two principles which
make use of the limited frequency range
of the LEMP and the NEMP (refer to Fig.
«Comparison of the frequency spectra
of a genuine lightning current surge and
a test current surge 10/350 µs" in section
electrical specification). They allow to
transmit only RF signals within a
certain specified range:

High-pass – a principle which has certain disadvantages due to the necessary inductance which increases the residual pulse level. Therefore, it is not applied by HUBER+SUHNER.

Bandpass – a very effective principle which HUBER+SUHNER employs with their quarter-wave protectors featuring the lowest possible inductance. The operation frequency band can be properly adjusted to any application.