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IWR6843AOPEVM: Duty Cycle with multiple TX antennas

Morten Nissov
Intellectual 380 points
Part Number: IWR6843AOPEVM

Suppose I launched the ros driver on my radar for a config which returns the following information:

List of parameters
==============================
Number of range samples: 64
Number of chirps: 128
f_s: 9.142 MHz
f_c: 61.050 GHz
Bandwidth: 700.066 MHz
PRI: 130.000 us
Frame time: 100.000 ms
Max range: 13.704 m
Range resolution: 0.214 m
Max Doppler: +-3.148 m/s
Doppler resolution: 0.049 m/s
==============================

I want to calculate the duty cycle for this, the frame time is 100ms so that's simple enough, now we just need to know the "on" time. For one frame that should, approximately, be PRI * NUMBER_OF_CHIRPS, in this case resulting in 16.64ms.

One doubt I've had, since this radar has 3 TX channels, if I'm using all three and assuming they're each transmitting separately (i.e. the bpmCfg option is disabled) shouldn't the actual "on" time be 16.64ms * 3? Meaning this is the difference between a 16% on time and a 50% on time?

  • 0
    TI__Mastermind 19620 points

    Hello.

    If bpmCfg is disabled, then you are correct; the on time would be triple as each Tx is transmitting individually.  However, if you do have bpmCfg enabled, then you could reduce the on time as you can have 2 chirps transmitted at the same time and then the third will be transmitted individually.

    Sincerely,

    Santosh

  • 0 in reply to Santosh Krishnan
    Intellectual 380 points

    Great, one other question. In my mind duty cycle has been a metric to ensure I avoid over-taxing the sensor, I think the manual say duty cycle above 50% is a bad idea and from experience, duty cycles near 50% cause problems as well.

    2 Questions:

    • Does running two tx simultaneously provide any savings from this perspective? Because while yes the duty cycle reduces by 33%, two tx are sending simultaneously, which should generate twice the heat I suppose? So in conclusion, does bpmCfg enable more resource-consuming chirp configs to run smoother than without bpmCfg.
    • is bpmCfg supported with iwr6843AOPEMV in SDK 3.6? Thought I had had some problems with this before.
  • 0 in reply to Morten Nissov
    TI__Mastermind 19620 points

    Hello.

    According to the sdk user guide, you should be able to use the bpmCfg to enable this mode.  This mode provides a higher SNR, but is likely to have greater power consumption for running 2 Tx simultaneously.

    It should be supported, but you can refer to the SDK user guide as to the format of the parameters for this command.

    Sincerely,

    Santosh

  • 0 in reply to Santosh Krishnan
    Intellectual 380 points

    Is it supported in the out of the box demo binary?

    When trying to use a config file with bpmCfg enabled in the demo visualizer, it returns "Error: invalid configuration. bpmCfg command is not supported."

  • 0 in reply to Morten Nissov
    TI__Mastermind 19620 points

    Hello.

    It should be supported and there is a configuration for out of box demo using bpmCfg in the sdk itself.  I would use that for reference but I will also double check to see if that works.

    Sincerely,

    Santosh

  • 0 in reply to Santosh Krishnan
    TI__Mastermind 19620 points

    Hello.

    The bpmCfg command should work.  Please refer to the sdk for an example chirp configuration using the bpmCfg.

    Sincerely,

    Santosh