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Frank-W
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Hello,

I recently upgraded RDK verison to 3.5.1 with FW 2.6.0 (from a pretty old one). In the release note, it states that 

- `ifx_Fmcw_Frame_t` includes an array of cubes containing raw ADC data.
- Raw data is normalized to the range [-1, +1].

which make me wonder

  • what did we get from the older interface? an array of pre-processed ADC data as opposed to raw ADC? if so, could you clarify what had been preprocessed before?
  • the output data is now normalized to the range [-1 , +1]. In the previous RDK, I suppose it was in the range of [0, 1]. What has driven you to change the normalization range?

In addition,

There are two configurable cutoff frequencies available now in the waveform configuration. Are they referred to as the cutoff frequencies of baseband filters (see the attached baseband filter.png)?

Best regards,

/Frank

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Pugitha_N
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Hello @Frank-W,

The ifx_FMCW_Frame_t is a recently introduced API in the RDK that is designed to hold a complete frame of radar data in [-1,1] normalization. By default, the raw data app utilizes cube data that has been normalized between [0,1]. Please refer to the image below, taken from the latest RDK, which displays BGT60TR13C raw data normalized between [0,1].

Pugitha_N_0-1702981446261.png

Yes, the two cutoff frequencies, hp_cutoff_Hz and aaf_cutoff_HZ, they respectively indicate the Cutoff frequency for the high pass filter and the Cutoff frequency for the anti-aliasing filter.

Best Regards,

Pugitha

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Pugitha_N
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Hello @Frank-W,

The ifx_FMCW_Frame_t is a recently introduced API in the RDK that is designed to hold a complete frame of radar data in [-1,1] normalization. By default, the raw data app utilizes cube data that has been normalized between [0,1]. Please refer to the image below, taken from the latest RDK, which displays BGT60TR13C raw data normalized between [0,1].

Pugitha_N_0-1702981446261.png

Yes, the two cutoff frequencies, hp_cutoff_Hz and aaf_cutoff_HZ, they respectively indicate the Cutoff frequency for the high pass filter and the Cutoff frequency for the anti-aliasing filter.

Best Regards,

Pugitha

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Hello Pugitha,

Thank you for your reply.

What do you mean by default? In the latest SDK, if we call get_next_frame from radar sdk python wrapper, it will return radar data in [-1,1] normalization by "ifx_avian_get_next_frame". I thought this was the default behavior in the latest SDK. 

So, Is the difference between the newly introduced API and the legacy one merely at the normalization range ([-1 1] vs [0 1])? no other functional changes under the hood, right?

Best regards,

/Frank

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Pugitha_N
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Hello @Frank-W,

As you see from below get_next_frame holds ifx_FMCW_Frame_t which has complete frame of radar data in [-1,1] normalization and is used by python application where as ifx_avian_get_next_frame holds ifx_Cube_R_t which has frame data in [0,1] normalization and is used by c application in default. 

Pugitha_N_0-1703067651295.png

Pugitha_N_1-1703067790764.png

If the raw data has a range that includes negative values, then normalizing to [-1,1] can be useful to preserve the sign of the data. For example, if the radar data represents the relative velocity of a target, then negative values of raw data could be used to indicate that the target is moving away from the radar.

For further information about all the changes and new features, please refer to the release notes.

Best Regards,

Pugitha

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Hello Pugitha,

The negative/positive sign of range rate is given by doppler fft. What I am asking about is the time domain ADC data. Normalization to [0, 1] in ADC can also lead to the correct relative velcoity of a target in doppler fft stage.

Best regards,

/Frank 

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Pugitha_N
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Hello @Frank-W,

Simply normalizing the radar data is not enough to accurately determine the relative velocity. Additional processing steps are required, which will vary based on the specific radar system being used.

One common method to estimate relative velocity involves utilizing the Doppler effect. While normalization can certainly help to improve the accuracy of the Doppler estimation, it is not sufficient on its own.

It should be noted that normalizing data to the range [0,1] may not be appropriate in situations where relative velocities are high, as it can cause the dynamic range of the data to become compressed. Conversely, normalizing to the range [-1,1] can be particularly useful in scenarios where target velocities are relatively high, as it helps preserve the dynamic range of the data.

Best Regards,

Pugitha

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Hello Pugitha,

Thank you for your clarification. Your argument seems very compelling but I just don't have deep insights on normalization to grasp the whole idea (of [-1 1] more advantageous over [0 1] in this context). Any literature or web page for me to read it myself? I tried to google it but didn't find anything relevant.

Best regards,

/Frank

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Pugitha_N
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Hello @Frank-W,

There are many online resources available that can help you learn about radar raw data normalization. Here are some of the top resources to consider:

  1. IEEE Xplore: This digital library is an excellent source for finding research papers on radar signal processing and data normalization.

  2. Radar Basics: This website provides a comprehensive introduction to radar systems, including signal processing and data normalization.

  3. Books: There are several books available on radar signal processing and data normalization.

Best Regards,

Pugitha

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