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RFbeam Microwave GmbH | Schuppisstrasse 7 | CH-9016 St. Gallen | www.rfbeam.ch | K-LD2 | data sheet

09/2018 - Revision B | Page 10/20

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

= bin ·

N

FFT

ƒ

Sample

256

ƒ

Sample

moving object

radar sensor

v =

=

44.7 Hz · cos( )

ƒ

256 44.7 Hz cos( )

bin ƒ

Sample

km/h

Figure 10: FFT bin to speed conversion