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Original question:

IWR1443: IWR1443 RF questions

IWR1443: IWR1443 : bandwidth of thermal noise power, kTB in radar equation.

user5243633
Intellectual 360 points
Part Number: IWR1443

I have a quation about bandwidth, B in the thermal noise power, kTB in radar equation.

In FMCW, according to hforsten.com/third-version-of-homemade-6-ghz-fmcw-radar.html ,
"Noise bandwidth is clearly smaller than the sweep bandwidth
since the IF filter filters most of the RF noise out.",
(skip)
"Bandwidth of one FFT bin depends only of the lenght of the FFT.
With FMCW radar FFT length equals length of one sweep, ts
and bandwidth of one FFT bin is 1/ts."

So, in TI dev IWR1443, do the same way
B = 1/Tr
where Tr is Chirp Time (= sweep time).

Is this right?

Also, P.15 in TI document training.ti.com/.../Mmwave_webinar_Dec2017.pdf
SNR = Rx signal level * noise level
Rx signal level = Pt Gt (RCS) Gr lambda^2/ (4 PI)^3/R^4
noise level = Tf/{ kT (NF) }

Tf -> integration time

To be more exact,
SNR = Rx signal level * noise level
Rx signal level = Pt Gt (RCS) Gr lambda^2/ (4 PI)^3 /R^4 *N ( as integration effects)
noise level = 1 /{ kT (1/Tr) (NF) }

N -> Number of chirps

Is this understanding correct?

  • 0
    TI__Mastermind 37500 points
    Hello,
    if you download the mmwave SDK, under the docs folder, Section 3 discusses our terminology in programming the mmwave sensor.
    We can have RF profiles - specific mmwave sensor RF parameters, and DFE output rate; Chirp - selected active Tx, selected RF profile; Frame


    the Sythesizer sweeps during the ADC Start Time, ADC sampling time, and Excess Ramp time (sum (RampEndTime))
    the collected Radar Rx samples see a reduced time and reduced sampled sweep frequency
    sampled sweep frequency = (Synthesizer slope * numADC samples/chirp) / DFE sample rate

    the num ADC samples/ chirp is padded to the next size up power of 2.
    Depending on the sampling mode real, complex1x, complex 2x (we will discuss complex 1x)
    Frequency / bin = DFE sample rate / padded_numadc_samples-chirp

    the DFE digital IF filters have a passband of 80%.

    The Integration time is the numADC_samples_chirp / DFE output rate

    The Radar Equation - is normally evaluated, along with the above mmwave sensor configuration using the mmwave Sensing Estimator.
    " training.ti.com/mmwave-sensing-estimator-overview "

    Another reference is " www.radartutorial.eu/.../Book1.pdf "

    Regards,
    Joe quintal
  • 0 in reply to Radio-Joe
    Intellectual 360 points
    Thank you for the detailed infomation of sampled sweep frequency
    and bandwidth of one bin.
    It is useful to understand a link budget in FMCW radar.

    Please confirm some words in your answer.
    1.
    Do DFE output rate and DFE sample rate have the same meaning in your answer?
    Or you used intentionally?

    2.
    what does "Chirp - selected active Tx" mean in your answer?

    There is "number of loops" of frameCfg
    in TI mmwave SDK, under the docs folder, Section 3 discusses your terminology in programming the mmwave sensor.

    Do "Chirp" and "number of loops" of frameCfg have the same meaning?
    ( Maybe generally thinking it's related to the number of chirps
    in FFT processing, like an angle estimation )

    3.
    About numADC_samples_chirp in your answer
    "The Integration time is the numADC_samples_chirp / DFE output rate".

    numADC_samples_chirp = numADC_samples/chirp ???
  • 0 in reply to user5243633
    TI__Mastermind 37500 points

    Hello

    1) DFE output rate - the ADC sample rate is much higher than the DFE output rate.   The DFE block has filtering, decimation, and mixing components.

    The DFE sample rate DFE output rate are the same.

    2) the Chirp configuration portion of the RF profile, chirp, and frame - see mmwave SDK User Guide, contains an active Transmit Tx selection.

    This feature is used for Tx time division multiplexed MIMO (see MIMO radar application note)

    3) the integration time is numADC_samples per chirp / DFE output rate * numloops in a frame.

    yes

    Regards,

    Joe Quintal

  • 0 in reply to Radio-Joe
    Intellectual 360 points
    Thank you so much.