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IWR1443BOOST: FMCW radar working.

Rahul Sharma
Expert 2725 points
Part Number: IWR1443BOOST
Other Parts Discussed in Thread: IWR1443

Hi all,

While reading the documents and training materials for FMCW radar, i have a small doubt regarding the working of the CHIRP signal (EM wave).

As it is mentioned that the CHIRP signal is generated by the synthesizer and transmitted through the TX and the object gets detected when it receives the reflected back CHIRP signal and thus passes through the mixer.

Now the doubt is -  Is the principle of working is same like Ultrasonic sonar? How does it sweeps the full azimuth as well as elevation area to determine the multiple objects at one time?

Please elaborate.

Thanks.

  • 0
    TI__Mastermind 30405 points

    Hi Rahul,

    As explained in the mmWave Training Series module on Range Estimation, FMCW Radar transmits a continuous ramping frequency called a chirp. The difference between the instantaneous TX frequency and the instantaneous RX frequency (the delay being proportional to the distance of the object) forms the IF signal and the frequency peaks in the IF signal correspond to the distance to the objects from the sensor. Velocity and Angle are computed by measuring the phase variation in the reflected signal. The phase variation of the signal in time gives the velocity and the phase variation in space, i.e. across the different RX antennas, gives angle of arrival.

    The sensor FOV (Field of View) in Azimuth and Elevation depends upon Antenna Design. If by sweep in Azimuth and Elevation (not to be confused with the frequency sweep of the chirp signal) you meant that if there is a beam e.g. in a LIDAR system, that scans the azimuth and/or elevation, that's not the case here. The sensor gets reflection from the complete FOV (both Azimuth and Elevation) with every chirp and by performing the FFTs in sequence (Range, Doppler, and Angle) computes the 3D point Cloud returning the range, velocity and angle associated with each point.

    For the IWR1443BOOST EVM, the Azimuth FOV is about 120 degrees (i.e. +/- 60 degrees) and the Elevation FOV is about 30 degrees (i.e. +/- 15 degrees). The FOV can be made narrower or wider using a different antenna design based on application requirements.

    Regards

    -Nitin

  • 0 in reply to Nitin Sakhuja
    Expert 2725 points
    Ok, well discibed thanks for that.
    I have an another doubt regarding heart rate measurement in vital sign measurement lab.
    How does it count that? On the basis of small chest displacement its ok to get the breathing rate but if there is no any chest displacement and breathing rate is 0, then how its measurng the heart rate?
    Will appreciate your elaboration on that.
  • 0 in reply to Rahul Sharma
    Expert 2725 points

    Hi,

    Any update?

    Thanks.

  • 0 in reply to Rahul Sharma
    TI__Mastermind 30405 points

    Rahul,

    As described in the Vital signs lab user's guide, the chest displacement consists of two components, one due to breathing and the other due to the heart beat. The demo uses the programmable core on the IWR1443 chip to filter these two frequencies from the chest displacement and displays them separately. You can hold your breath for a few seconds to remove the movement due to breathing but the chest displacement due to heart beat still remains present which the sensor is able to detect. This is described in the demo user's guide.

    Regards

    -Nitin