Explanation Of Cw Radar Function - Bosch FR5CUEC Quick Start Manual

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FR5CUEC User Manual ITA

2 Explanation of CW Radar function

Continuous-wave radar is a type of
continuous-wave radio
Continuous-wave (CW) radar uses Doppler, which renders the radar immune to interference
from large stationary objects and slow moving clutter.
Maximum distance in a continuous-wave radar is determined by the overall bandwidth and
transmitter power. This bandwidth is determined by two factors.
•
Transmit energy density (watts per Hertz)
•
Receiver filter size (bandwidth divided by the total number of filters)
Frequency-modulated continuous-wave radar (FM-CW) – also called continuous-wave
frequency-modulated (CWFM) radar – is a short-range measuring radar set capable of
determining distance. This increases reliability by providing distance measurement along with
speed measurement, which is essential when there is more than one source of reflection arriving
at the radar antenna. This kind of radar is often used as "radar altimeter" to measure the exact
height during the landing procedure of aircraft. It is also used as early-warning radar, wave radar,
and proximity sensors. Doppler shift is not always required for detection when FM is used.
In this system the transmitted signal of a known stable frequency continuous wave varies up
and down in frequency over a fixed period of time by a modulating signal. Frequency difference
between the receive signal and the transmit signal increases with delay, and hence with
distance. This smears out, or blurs, the Doppler signal. Echoes from a target are then mixed
with the transmitted signal to produce a beat signal which will give the distance of the target after
demodulation.
A variety of modulations is possible, the transmitter frequency can slew up and down as follows :
•
Sine wave, like air raid siren
•
Sawtooth wave, like the chirp from a bird
•
Triangle wave, like police siren in the United States
•
Square wave, like police siren in the United Kingdom
Range demodulation is limited to 1/4 wavelength of the transmit modulation. Instrumented range
for 100 Hz FM would be 500 km. That limit depends upon the type of modulation and
demodulation.
Document
radar
energy is transmitted and then received from any reflecting objects.
Dept.
XC-DA/ESR1
system where a known stable frequency
Leonberg
20 December 2021
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