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Homemade 6 GHz FMCW radar

Posted on Friday, September 29th, 2017 in RF by DP

pfinished

Henrik Forstén has a nice build log on his newest version of this homemade 6 GHz FMCW radar:

Frequency Modulated Continuous Wave (FMCW) radar works by transmitting a chirp which frequency changes linearly with time. This chirp is then radiated with the antenna, reflected from the target and is received by the receiving antenna. On the reception side the received signal that was delayed and undelayed copy of the transmitted chirp are mixed (multiplied) together. The output of the mixer are two sine waves that have frequencies of sum and difference of the waveforms. The frequencies of the received signals are almost the same and the sum waveform has frequency of about two times of the original signal and is filtered out, but the difference waveform has frequency in kHz to few MHz range. The difference frequency is dependent on the delay of the received reflection signal making it possible to determine the delay of the reflected signal. The electromagnetic waves travel at speed of light which allows converting the delay to distance accurately. When there are several targets the output signal is sum of different frequencies and the distances to the targets can be recovered efficiently with Fourier transform.

See the full post on his blog. Project files are available at github.

This entry was posted on Friday, September 29th, 2017 at 9:07 pm and is filed under RF. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

One Response to “Homemade 6 GHz FMCW radar”

  1. Drone says:

    A bit of background on why the radar signal is a “chirp” would have been nice in this DP post. I’ll add a bit here:

    http://www.rfcafe.com/references/electronics-world/chirp-new-radar-technique-january-1965-electronics-world.htm

    For a LOT more on this subject of “chirps” and signal processing, do a Wikipedia search and dig through the seemingly endless layers.

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