Data Sheet

©
RFbeam Microwave GmbH | Schuppisstrasse 7 | CH-9016 St. Gallen | www.rfbeam.ch | K-LD 2 | data sheet 02 / 2020 – Revision C | Page 11 / 25
Stand-alone Operation
With the factory settings the sensor starts up and
scans the beam for potential movements with a
sampling rate of 2560Hz (app. 0.3 to 29.1 km/h). Itfil-
ters out interferences and looks for movements with
a magnitude that is higher than the threshold level set
with the sensitivity.
If there is a valid movement the detection output
(Pin 2) goes high and the direction is latched to the
miscellaneous output (Pin 8) for the length of the set
hold time.
The hold time (Pin 6) and the sensitivity (Pin 7) can
be set using analogue inputs (for example with exter-
nal potentiometers) in the following ranges:
– Hold time from 0.2 to 160s
– Sensitivity from 0 to 34dB (app. 2 to 20 m for wal-
king humans)
With the factory settings the reaction time of the sen-
sor is approximately 800ms.
Host driven Operation
With a connection of the serial interface to a host (for
example MCU or PC) it is possible to read-out advan-
ced detection data including speed and magnitude of
a valid detection or to use some advanced features of
the K-LD2 which are described in the next chapters.
The detection output can be used to trigger a seri-
al read-out command over an interrupt. If there is no
interrupt input, it is possible to poll the detection state
register and then trigger the additional read-out com-
mands.
The command set features different parameters to
read-out additional detection data.
The K-LD2 can also be factory configured
with your settings. Contact RFbeam for
more information.
APPLICATION INFORMATION
K-LD2 Host
Detect out
Misc. out
Input or INT
Input or INT
RX
TX
TX
RX
optional
Figure 9: MCU or PC connection example
Parameter Description Note
R00 Get detection state register Includes detection, direction, speed range and micro detection information
R01 Get detection speed in bin Only valid when the detection bit in the detection state register is high.
R02 Get detection magnitude in dB Only valid when the detection bit in the detection state register is high.
C00 Get detection string Complete set of data of the parameters R00 to R02
Table 3: Useful commands to read-out advanced detection data
Speed measurement
The speed of a detected object is returned in bin and
can be easily converted into the doppler frequency
with the sampling rate and the FFT width. The sample
rate is adjustable over the command S04 and the FFT
width is fixed to 256.
The measured doppler frequency is proportional to the
speed of the object when it is measured frontal to the
sensor. An angle between the object and the sensor
reduces the doppler frequency. The speed in km/h is
easily computable with the equation below based on
the doppler effect.
ƒ
Doppler
= bin · = bin ·
N
FFT
ƒ
Sample
256
ƒ
Sample
α
moving object
radar sensor
v
= =
44.7 Hz · cos(
α
)
ƒ
Doppler
· km/h
256 ∙ 44.7 Hz ∙ cos(
α
)
bin ∙ ƒ
Sample
∙ km/h
Figure 10: FFT bin to speed conversion