IWR1642: Analog peak power dissipation

Hello,

The power calculator, does not have detailed chirp and frame parameters.  The suggested approach is to actually measure on an EVM either the 5v input current, or with careful modification to the PMIC inductors ( Inductor and series loop wire for current sensor) individual rail currents.   Please consider programming the device, than having a method to turn off 3.3v board.  (replace R159 with 1K resistor, have a method to jumper R158 to GND to turn off 3.3v Brd XDS110)

a) enter your use case into the power calculator

b) as close as practical program the use case with the EVM

c) compare the power draw on the 5v input to the total current (with R158 jumpered across)

d) there are 3 methods to reduce the mmwave sensor power.

    d1) follow swra577 (~10% power savings) - replace U8 with LP87524J, remove the LDO regulators U4, U5, remove resistors 81,82, 121, 122, 131, 132

    d2)  using the Sensing Estimator, reanalyze your use case, to make sure that the number or ADC samples, DFE output rate, the idle time, adc start time, ramp            end time, along with the number of chirps per frame.  The RF chirping consumes the highest power.

    d3)  Tx power backoff can lower the Tx output power, selection of MIMO Tx instead of beam formed Tx can reduced RF power

measuring the EVM with the Power Estimation spreadsheet, you can estimate the nominal (EVM) then add margin to the strong process at 85C 

Regards,

Joe Quintal

Hi Joe,

Thanks for detailed steps, but I found an issue at step a).
I got below requirements from customer.

- maximum range : 15m
- Range resolution : 7.5cm
- Maximum velocity : 4km/hr
- velocity resolution : Don’t care

Then I got below Chirp configuration by mmWave Sensing Estimator.
(please change *.txt to *.json)

{
    "platform": "xWR1642",
    "num_rx": 4,
    "num_tx": 2,
    "tx_gain": 9,
    "rx_gain": 9,
    "frequency_range": "77 - 81",
    "maximum_bandwidth": 4000,
    "tx_power": 12,
    "ambient_temperature_degC": 20,
    "maximum_detectable_range": 15,
    "range_resolution": 7.5,
    "maximum_velocity_kmph": 4,
    "velocity_resolution_kmph": 4,
    "measurement_rate": 10,
    "typical_detected_object": "Adult",
    "detection_loss": 1,
    "system_loss": 1,
    "implementation_margin": 2,
    "detection_SNR": 12,
    "maximum_radar_cube_size": 768,
    "maximum_RF_bandwidth": 5,
    "maximum_sampling_frequency": 6.25,
    "sensor_maximum_bandwidth": 4000,
    "maximum_allowed_bandwidth": 4000,
    "starting_frequency": 77,
    "maximum_velocity": 1.1111111111111112,
    "velocity_resolution": 1.1111111111111112,
    "valid_sweep_bandwidth": 2000,
    "idle_time": 7,
    "adc_valid_start_time": 6.4,
    "excess_ramping_time": 1,
    "periodicity": 100,
    "ambient_temperature": 293.15,
    "noise_figure": 16,
    "num_virtual_rx": 8,
    "non_coherent_combining_loss": 3,
    "rcs_value": 1,
    "combined_factor_in_dB": -5,
    "combined_factor_linear": 0.31622776601683794,
    "inter_chirp_time": 14.4,
    "aux_comp_coeff_a": 78000000000,
    "aux_comp_coeff_b": -32614000,
    "chirp_time": 418.12820512820514,
    "ramp_slope_init": 4.783221929232845,
    "ramp_slope_parameter": 99,
    "ramp_slope": 4.779696464538574,
    "aux_comp_T1": 1,
    "maximum_beat_frequency": 0.4779696464538574,
    "sampling_frequency": 3,
    "number_of_samples_per_chirp": 1255,
    "total_sweep_bandwidth": 2034.8761081695554,
    "idle_time_minimum": 6,
    "ramp_end_time": 425.7333333333333,
    "carrier_frequency": 77.03059153130039,
    "aux_comp_T2": 5.4,
    "adc_valid_start_time_2": 6.4,
    "lambda": 3.894556617523817,
    "max_chirp_repetition_period": 876,
    "chirp_repetition_period": 865,
    "num_range_fft_bins": 2048,
    "min_num_of_chirp_loops": 3,
    "max_range_for_typical_detectable_object": 50.79815097084035,
    "min_rcs_detectable_at_max_range": 0.007602797415471368,
    "num_doppler_fft_bins": 4,
    "active_frame_time": 2.595,
    "range_inter_bin_resolution": 4.595947265625,
    "velocity_inter_bin_resolution": 0.8333333333333334,
    "radar_cube_size": 192
}

Hello,

The power calculator has a limited set of accepted conditions.  I modified your Sensing Estimator design, and modified the power input parameters.   The Sensing Estimator indicates that >=19 chirps per frame, are OK for these conditions.   Usually a smaller number of ADC samples per chirp are used, if there are velocity requirements.   In this case if your radar programming had 32 chirps per frame.  The power calculator would be providing a 64 chirp per frame power number.  

Note: the idle time limit may need to be extended per your end of chirp processing.   I have attached the revised Sensing estimator and power design, to get a better estimate, use a DC current probe on 5v current input, in your compiled example, toggle GPIO_1 at the beginning of radar programming, and after the data collection - frame processing, by measuring the software time, you can measure the frame radar, calculate power.  

Regards,

JoeQuintal

TI_Radar_power_calculator_v0p7_050718.xlsx

{
    "platform": "xWR1642",
    "num_rx": 4,
    "num_tx": 2,
    "tx_gain": 9,
    "rx_gain": 9,
    "frequency_range": "77 - 81",
    "maximum_bandwidth": 4000,
    "tx_power": 12,
    "ambient_temperature_degC": 20,
    "maximum_detectable_range": 20,
    "range_resolution": 7,
    "maximum_velocity_kmph": 4,
    "velocity_resolution_kmph": 0.45,
    "measurement_rate": 10,
    "typical_detected_object": "Child",
    "detection_loss": 1,
    "system_loss": 1,
    "implementation_margin": 2,
    "detection_SNR": 12,
    "maximum_radar_cube_size": 640,
    "maximum_RF_bandwidth": 5,
    "maximum_sampling_frequency": 6.25,
    "sensor_maximum_bandwidth": 4000,
    "maximum_allowed_bandwidth": 4000,
    "starting_frequency": 77,
    "maximum_velocity": 1.1111111111111112,
    "velocity_resolution": 0.125,
    "valid_sweep_bandwidth": 2142.8571428571427,
    "idle_time": 7,
    "adc_valid_start_time": 12.2,
    "excess_ramping_time": 1,
    "periodicity": 100,
    "ambient_temperature": 293.15,
    "noise_figure": 16,
    "num_virtual_rx": 8,
    "non_coherent_combining_loss": 3,
    "rcs_value": 0.5,
    "combined_factor_in_dB": -5,
    "combined_factor_linear": 0.31622776601683794,
    "inter_chirp_time": 20.2,
    "aux_comp_coeff_a": 78071428571.42856,
    "aux_comp_coeff_b": -32146814.285714287,
    "chirp_time": 411.7615736505033,
    "ramp_slope_init": 5.2041212196162,
    "ramp_slope_parameter": 108,
    "ramp_slope": 5.214214324951172,
    "aux_comp_T1": 1,
    "maximum_beat_frequency": 0.6952285766601562,
    "sampling_frequency": 2,
    "number_of_samples_per_chirp": 824,
    "total_sweep_bandwidth": 2217.0839309692383,
    "idle_time_minimum": 6,
    "ramp_end_time": 425.2,
    "carrier_frequency": 77.06361438372019,
    "aux_comp_T2": 9.7,
    "adc_valid_start_time_2": 10.7,
    "lambda": 3.892887744743198,
    "max_chirp_repetition_period": 875.9,
    "chirp_repetition_period": 864.4,
    "num_range_fft_bins": 1024,
    "min_num_of_chirp_loops": 19,
    "max_range_for_typical_detectable_object": 67.49001259481163,
    "min_rcs_detectable_at_max_range": 0.0038559549405853184,
    "num_doppler_fft_bins": 32,
    "active_frame_time": 27.6608,
    "range_inter_bin_resolution": 5.6328125,
    "velocity_inter_bin_resolution": 0.07421875,
    "radar_cube_size": 608
}

Hi,

I tried to load your config(design_51718.json) to Sensing Estimator, but it generates an error.
Is this correct file?

Error 1: The radar cube size is larger than the available memory on the device

Tips: Increase the "Range Resolution"/"Velocity Resolution", decrease the "Maximum Range"/"Maximum Velocity", and/or reduce the "# of Rx Antennas"/"# of Tx Antennas"

And I am not sure I understood below comments correctly.

Usually a smaller number of ADC samples per chirp are used, if there are velocity requirements.    

As customer does not have specific velocity requirements. Still they can use a smaller number of ADC samples like 64 (your calculator sheet uses 1024)?
This reduce total power consumption from 3.49W to 1.34W.

In this case if your radar programming had 32 chirps per frame.  The power calculator would be providing a 64 chirp per frame power number.

With 32 Chirps per frame configuration, customer can expect the power consumption will be reduced roughly a half?

Thanks and regards,
KoT

Hello

Using the Sensing Estimator 1.01, the  design_51718.json, does not generate an error for my software.  This used a 1642 example.  If you are trying to fit these constraints into a IWR1443, select this at the top, and increase the max velocity, decrease the velocity resolution to lower the number of ADC samples per chirp.

Reducing the number of Tx or Rx antennas - lowers the Radar Cube size.

Lowering the number of ADC samples per chirp - lowers the Radar cube size.

The power calculator has a minimum of 64 chirps per frame, you would lower the meausrement power, the boot power would be the same.,   This is why I suggested that eventually you have to measure the example on the EVM.

Example - if you selected xWR1443 as the mmwave sensor, then change max velocity to 10 km/h, and velocity resolution to 1.5 km/h  - we fir within the xWR1443 radar cube size.

Regards,

Joe Quintal

Hi Joe,

My tools generates an error like this;

Where can I get version 1.01? The latest one is 1.00.00 and I used this version.



Thanks and regards,
KoT