Specifications

60
RF SOLUTION-CITEL
RF surge protection
Protection of the radiocommunication
equipment
Radiocommunication systems, connected to antennae, are
especially exposed to lightning phenomena, the maximum risk
being a direct strike on the antenna pole.
Equipment, as GSM/UMTS or TETRA base stations, must
consider this risk in order to insure a relevant service continuity.
CITEL offers several surge protection technologies for RF lines
to comply to the different operation requirements.
RF surge protection technology
●
Gas Tube Protection P8AX series
The gas discharge tube (GDT) is the only surge protection
component usable on very high frequency transmission
(several GHz) due to its very low capacitance. In a coaxial
surge protector, the GDT is connected in parallel between the
central conductor and the external shield ; when its sparkover
voltage is reached, during an overvoltage, the line is briefly
practically shorted (arc voltage). The sparkover voltage
depends on the rise front of the overvoltage. The higher the
dV/dt of the overvoltage, the higher the sparkover voltage of
the surge protector.
When the overvoltage disappears, the gas discharge tube
returns to its original condition of high insulation and is ready
to operate again. The gas tube is removable, making
maintenance rapid in the end-of-life case.
The greater advantage of this technology is its very wide
bandwidth : form DC (so, compatible with DC voltage
injection) to several GHz.
●
DC Blocked Protection CXP-DCB series
This version is a relevant hybrid association between a filter
stage and a gas tube : a such configuration allows a addition
of the advantages of the both stages : Low frequency
disturbances reduction (DC and lightning voltages) and high
discharge current capability.
●
Quarter Wave Protection PRC series
The other way to protect antenna lines is relevant replacement
of the gas tube by a proper short-circuit chosen according to
the operating frequency band. This short-circuit is tuned to one
quarter of the wavelength, giving its name to
<<
quarter-wave
protection
>> . This tuned short-circuit between the conducting
core and the external ground acts as a band-pass filter.
The filter may be selective (narrow band) or wide-band,
according to the calculation of the various mechanical elements.
Since lightning has a low-frequency spectrum (from a few
hundred kHz to a few MHz), it will be filtered out from the
operating frequencies.