The Response Of Electromagnetic Waves In The Uhf Band; The Effect Of Reflections And Interference; Influence Of Metals - Siemens SIMATIC RF600 System Manual

RF600 system planning

4.5 The response of electromagnetic waves in the UHF band

4.5 The response of electromagnetic waves in the UHF band
4.5.1

The effect of reflections and interference

Reflections and interference
Electromagnetic waves in the UHF band behave and propagate in a similar manner to light
waves, that is they are reflected from large objects such as ceilings, floors, walls and
windows and interfere with each other. Due to the nature of electromagnetic waves,
interference can lead to wave amplification which can produce an increased reading range.
In the worst case, interference can also result in waves being extinguished which causes
holes in reader coverage.
Reflections can also be beneficial when they cause electromagnetic waves to be routed
around objects to a certain extent (deflection). This can increase the reading probability.
Due to these electromagnetic characteristics, it is extremely difficult in the multiple-reflection
environment that is usually found in the real environment on site, to determine propagation
paths and field strengths for a particular location.
Reducing the effect of reflections/interference on tag identification
● Reducing the transmit power:
● Increasing the number of antennas to 3 or 4:
4.5.2

Influence of metals

Metal can have an effect on the electromagnetic field depending on the arrangement or
environment. The effect ranges from a hardly determinable influence through to total
blocking of communication. The term metal in this context also includes metallized materials
that are either coated with metal or shot through with metal to such an extent that UHF
radiation cannot penetrate or only to a minimal extent.
The effect of metal on the electromagnetic field can be prevented as follows:
● Do not mount tags on metal.
● Do not place metallic or conducting objects in the propagation field of the antenna and
72
To reduce interference to a minimum, we recommend that the transmitter power of the
reader is reduced until it is sufficient for an identification rate of 100%.
More antennas in a suitable antenna configuration can prevent gaps in reader coverage.
transponder.
System Manual, 05/2012, J31069-D0171-U001-A13-7618
SIMATIC RF600