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stjischl
Level 1
Level 1
5 questions asked 5 replies posted 10 sign-ins

Hi,

I am using a DEMO BGT60TR13C with #MCU7 Baseboard and the Python3 ifxAvian package and am trying to understand the raw data coming from the sensor after acquiring a frame: 

from ifxAvian import Avian

with Avian.Device() as device:

config = Avian.DeviceConfig(

sample_rate_Hz=1_000_000,
rx_mask=1,
tx_mask=1,
if_gain_dB=33,
tx_power_level=31,
start_frequency_Hz=60e9,
end_frequency_Hz=61.5e9,
num_chirps_per_frame=128,
num_samples_per_chirp=64,
chirp_repetition_time_s=0.0005,
frame_repetition_time_s=0.25,
mimo_mode="off",

)
device.set_config(config)

f = device.get_next_frame()
print(f.shape)
print(f)

# (1, 128, 64)
# [[[0.45470086 0.41855922 0.4058608 ... 0.4859585 0.4893773 0.46984127]
# [0.45274726 0.41807082 0.4068376 ... 0.4869353 0.4893773 0.46984127]
# [0.45177045 0.41807082 0.4063492 ... 0.4859585 0.4888889 0.46886447]
# ...
# [0.45347986 0.41855922 0.4056166 ... 0.4888889 0.4903541 0.46837607]
# [0.45250306 0.41807082 0.4043956 ... 0.4884005 0.4908425 0.46837607]
# [0.45372406 0.41855922 0.4058608 ... 0.4884005 0.4901099 0.46788767]]]

I understand that the shape of the array is determined by (rx_antenna_count, num_chirps_per_frame, num_samples_per_chirp).
However I don't understand the individual cell values.
What do the numbers represent? Do they have a unit?

Thanks,

Jannik

 

 

1 Solution
Siddharth_H
Moderator
Moderator
Moderator
100 solutions authored 50 likes received First question asked

Hello @stjischl ,

The data cube of shape num_rx_antennas x num_chirps_per_frame x num_samples_per_chirp contains the normalised ADC samples of the received signal.

Thank you,

Siddharth.

View solution in original post

3 Replies
Siddharth_H
Moderator
Moderator
Moderator
100 solutions authored 50 likes received First question asked

Hello @stjischl ,

The data cube of shape num_rx_antennas x num_chirps_per_frame x num_samples_per_chirp contains the normalised ADC samples of the received signal.

Thank you,

Siddharth.

stjischl
Level 1
Level 1
5 questions asked 5 replies posted 10 sign-ins

If I understand correctly, then each row in the matrix is the Intermediate Frequency of that chirp. In this case 64 amplitude samples. The total chirp length is 500µs as determined by chirp_repetition_time_s=0.0005, so the sample interval is 500µs / 64 samples = 7.8125µs.
Is that correct?

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Siddharth_H
Moderator
Moderator
Moderator
100 solutions authored 50 likes received First question asked

Hello @stjischl ,

No, Chirp repetition time is the time interval between two consecutive tchirp_start i.e. chirp execution starts and not the chirp length. You should be looking out for sampling frequency instead.

Total chirp time can be calculated from the diagram below, you can also consider the sampling

 

Siddharth_2-1695294032736.png

 

T_adc=N_samples/f_adc

where f_adc is sampling frequency which also defines sample interval.

Thank you,

Siddharth

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