VEGA VEGAPULS 56K - Manual (Page 5)

VEGAPULS 56K 5
22915-EN-041227
Time transformation
Pulse sequence
Meas. distance
emission - reflection - reception
1 ns
278 ns
t t
Product description
The radar pulses are emitted by the antenna
system as pulse packets with a pulse dura-
tion of 1 ns and pulse intervals of 278 ns; this
corresponds to a pulse package frequency
of 3.6 MHz. In the pulse intervals, the antenna
system operates as a receiver. Signal run-
ning periods of less than one billionth of a
second must be processed and the echo
image evaluated in a fraction of a second.
VEGAPULS can achieve this through a spe-
cial time transformation procedure which
spreads out the more than 3.6 million echo
images per second in a slow-motion picture,
then freezes and processes them.
Hence, it is possible for the VEGAPULS 56
radar sensors to process the slow-motion
pictures of the sensor environment precisely
and in detail in cycles of 0.5 to 1 second
without using time-consuming frequency
analysis (e.g. FMCW, required by other radar
techniques).
Nearly all products can be measured
Radar signals display physical properties
similar to those of visible light. According to
the quantum theory, they propagate through
empty space. Hence, they are not depend-
ent on a conductive medium (air), and they
spread out like light at the speed of light.
Radar signals react to two basic electrical
properties:
- the electrical conductivity of a substance
- the dielectric constant of a substance.
All products which are electrically conductive
reflect radar signals very well. Even slightly
conductive products provide a sufficiently
strong reflection for a reliable measurement.
All products with a dielectric constant
ε
r
greater than 2.0 reflect radar pulses suffi-
ciently (note: air has a dielectric constant
ε
r
of
1).
Reflected radar power dependent on the dielectric
constant of the measured product
2
0
0
10
25 %
40 %
5
10
5 %
20
30
40
50
%
4 6 8 12 14 16 18
20
ε
r