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AWR1243: Reception frequency range?

Canan Aydogdu
Prodigy 30 points
Part Number: AWR1243
Other Parts Discussed in Thread: AWR1642

Hi!

AWR1243 sends frequency chirps and the receiver listens to the chirps. At any time instant when a transmitter transmits frequency f, what is the range of frequencies that the receiver is tuned for listening? Does it listen to [f, f + (maximum IF frequency)] ? 

How well are the filters at the transmitter? When the transmitted chirp at any time has frequency f, what exact frequency spectrum does it have? It should have a peak at f but how much power does leak to other frequencies? What is the frequency difference (deltaF) where the signal power level f +/- deltaF  can be considered to fall by 3dB, 10 dB, for example?

Best regards,

Canan

  • 0
    TI__Expert 4720 points

    Hi Canan

    Answers are provided inline.

    AWR1243 sends frequency chirps and the receiver listens to the chirps. At any time instant when a transmitter transmits frequency f, what is the range of frequencies that the receiver is tuned for listening? Does it listen to [f, f + (maximum IF frequency)] ? 

    Yes, it listens to [f, f + (maximum IF frequency)]. If you are new to FMCW radar signal processing, please go through the training videos @ . 

    How well are the filters at the transmitter? When the transmitted chirp at any time has frequency f, what exact frequency spectrum does it have? It should have a peak at f but how much power does leak to other frequencies? What is the frequency difference (deltaF) where the signal power level f +/- deltaF  can be considered to fall by 3dB, 10 dB, for example?

    The signal transmitted is a chirp - which is essentially a ramping frequency. It is not possible to consider the instantaneous spectrum at any time t, and it is necessary to charaterize the chirp as a whole. The data sheet of XWR1XXX provides chirp linearity, and tx output spur characterization. Please go through the data sheet for these numbers. 

    Regards

    Anil

  • 0 in reply to Anil Mani
    Prodigy 30 points
    Thanks for the reply.
    Regarding question 1: I already have watched the videos, there is no information on which band the receiver locks to. However, if the receiver listens to [f, f + (maximum IF frequency)] then it would not capture Doppler shift variation of an object close to the range limit. I would be pleased to learn the implementation.

    Regarding question 2: For my algorithm the instanteneous spectrum at any time for a chirp is important. When I search the datasheet of AWR1243 for "tx output spur", there is nothing related there...

    So, my question remains "how well are the filters at the transmitter? When the transmitted chirp at any time has frequency f, what exact frequency spectrum does it have? It should have a peak at f but how much power does leak to other frequencies? What is the frequency difference (deltaF) where the signal power level f +/- deltaF can be considered to fall by 3dB, 10 dB, for example?"

    Best regards.
  • 0 in reply to Canan Aydogdu
    TI__Expert 4720 points

    Hi Canan,

    AWR1642 only guarantees that the spectrum up to 90 % of the max IF frequency is  available. As per our experiments, doppler of objects at 90 % of the IF frequency can be correctly estimated.  Beyond this limit, the low pass filters (LPF) of the digital front end (DFE) attenuate the signal heavily.  Note that the IF frequency is programmable.

    The notion of an 'instantaneous spectrum' doesn't make sense to me. In order to construct a spectrum (using say an FFT) you need multiple samples over time. As for the 'leakage' specification, there are two numbers that should interest you, the first is 'amplitude noise', and the second is 'phase noise'. Both these numbers are given in the screengrab below.  

    Regards

    Anil