Siemens SIMATIC RF600 System Manual page 64

RF600 system planning
4.3 Antenna configurations
Voltage standing wave ratio VSWR
The power sent by the transmitter cannot flow unhindered to the antenna and be radiated as
a result of the mismatching described by the VSWR. Part of the power is reflected at the
antenna and returns to the transmitter. The powers in the forward and reverse directions
produce a standing wave which has a voltage maximum and a voltage minimum. The ratio
between these two values is the VSWR (voltage standing wave ratio).
Return loss
The return loss parameter is based on the reflection factor which describes the voltage ratio
between the forward and reverse waves.
Specifications
So that the smallest possible transmitted and received powers are reflected by the antenna
under ideal conditions, you should observe the following data for the VSWR and the return
loss |S
● VSWR < 1.24:1 or
● |S
Power rating
Definition
The power rating is understood as the maximum power defined by the vendor with which the
device may be operated.
Specifications
Third-party antennas must be dimensioned for an effective power applied to the antenna
connection of at least 4 Watt.
Polarization
Definition
The polarization parameter describes how the electromagnetic wave is radiated by the
antenna. A distinction is made between linear and circular polarization. With linear
polarization, a further distinction is made between vertical and horizontal polarization.
Specifications
UHF transponders usually have a receive characteristic similar to that of a dipole antenna
which is linearly polarized. Horizontal or vertical polarization is then present depending on
the transponder mounting.
62
|/ dB in the respective frequency band (865-870 MHz or 902-928 MHz):
11
|/ dB ≥ 20 dB
11
System Manual, 05/2012, J31069-D0171-U001-A13-7618
SIMATIC RF600