User's Manual

Chassis Systems Control
Leonberg
20 December 2021
Page 4 of 15
Model
Document
Dept.
FR5CUEC
User Manual ITA
XC-DA/ESR1
Sawtooth modulation is the most used in FM-CW radars where range is desired for objects that
lack rotating parts. Range information is mixed with the Doppler velocity using this technique.
Modulation can be turned off on alternate scans to identify velocity using unmodulated carrier
frequency shift. This allows range and velocity to be found with one radar set. Triangle wave
modulation can be used to achieve the same goal.
As shown in the figure the received waveform (green) is simply a delayed replica of the
transmitted waveform (red). The transmitted frequency is used to down-convert the receive
signal to baseband, and the amount of frequency shift between the transmit signal and the
reflected signal increases with time delay (distance). The time delay is thus a measure of the
range; a small frequency spread is produced by nearby reflections, a larger frequency spread
corresponds with more time delay and a longer range.
Ranging with an FM-CW radar system: if the error caused by a possible Doppler frequency
can be ignored and the transmitter's power is linearly frequency modulated, then the time
delay is proportional to the difference of the transmitted and the received signal at any
time
References for chapter 2 of this document:
https://en.wikipedia.org/wiki/Continuous-wave_radar
This work is released under CC-BY-SA: http://creativecommons.org/licenses/by-sa/3.0/