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AWR1243: Radar range equation cascaded modules

Part Number: AWR1243

Dear TI Team

 

I need to calculate the maximum range for 4 cascaded AWR1243 and a defined rcs. Your estimator tool can’t do the job, because it supports only one module. The equation 2 in SWRA553 can’t really help either, because I don’t know the chirp time and number of chirps for a cascaded version.

 

When evaluating the equation in the java code (see below) I realised, that this differs from the range equation in SWRA553. The java code makes total sense, apart from num_virt_rx and min_num_of_chirp_loops.

 

var max_range_for_typical_detectable_object = function(rcs_value, combined_factor_linear,

        lambda, num_virtual_rx, chirp_time, min_num_of_chirp_loops, cube_4pi, kB, ambient_temperature) {

        // K8 =SQRT(SQRT((0.001*F80*F83*K26*K26*F77*K14*K30)/(0.9*F48*F47*F75*1000000*1000000)))

        return Math.sqrt(Math.sqrt((0.001*rcs_value*combined_factor_linear*Math.pow(lambda,2)*num_virtual_rx*chirp_time*min_num_of_chirp_loops)/(0.9*cube_4pi*kB*ambient_temperature*1e12)))

    };

 

 

Is the num of loops the same as the number of chirps? Or is this the number of repetitions of all chirps? (See SWRA574a, page 12, table 6 –“Number of loops” vs. SWRA553, page 7 table 1, “number of chirps”)

 

Why is the number of virtual antenna part of this equation? I guess this is related with the following question:

What if I don’t want to apply only TDM but also BPM in combination, like you do for two modules in SWRA574a, table 5? In which manner does this change the value of chirp time, number of chirp, multiplication with number of virtual antennas or non-coherent combining loss?

 

Is it possible to calculate the non-coherent combining loss, which is included in the combined_factor_linear with the following formula: log2(num_virtual_rx) ? I know from some other thread (https://e2e.ti.com/support/sensors/f/1023/t/706506), that this is empiric data and therefore don’t know whether it is possible to extrapolate for more than 12 (>50) virtual antenna.

 

 

var non_coherent_combining_loss = function(num_virtual_rx) {

                        //F78 =IF(F77=8;3;IF(F77=4;2;(IF(F77=2;1;0))))

                        // Math.log2(x)

                        if (num_virtual_rx == 8) {

                                    return 3;

                        } else if (num_virtual_rx == 4) {

                                    return 2;

                        } else if (num_virtual_rx == 2) {

                                    return 1;

                        } else {

                                    return 0;

                        }

 

Please see the following Matlab code and tell me, whether you think the value for the max range does make any sense.

 

clc

clear

 

% Input parameters

rcs_value = 1;                      % in m^2

num_of_modules = 4;

num_tx = 2*num_of_modules;

num_rx = 4*num_of_modules;

ambient_temperature = 20+273.15;    % in Kelvin

tx_power = 12;                      % in dB

tx_gain = 9;                        % in dB

rx_gain = 9;                        % in dB

detection_loss = 1;                 % in dB

system_loss = 2;                    % in dB

implementation_margin = 1;          % in dB

detection_SNR = 12;                 % in dB

noise_figure = 15;                  % in dB

min_num_of_chirp_loops = 2;

chirp_time = 30e-6;

carrier_frequency =77e9;

 

% Constants

cube_4pi = (4*pi)^3;

kB = 1.38064852e-23;

lightSpeed = 3e8;

   

num_virtual_rx = num_rx*num_tx;

non_coherent_combining_loss = log2(num_virtual_rx);

combined_factor_in_dB = tx_power+tx_gain+rx_gain-non_coherent_combining_loss-detection_loss-system_loss-implementation_margin-detection_SNR-noise_figure;

combined_factor_linear = 10^(combined_factor_in_dB/10);

 

lambda = (lightSpeed/carrier_frequency);

 

max_range_for_typical_detectable_object = nthroot((rcs_value*combined_factor_linear*(lambda^2)*num_virtual_rx*chirp_time*min_num_of_chirp_loops)/(0.9*cube_4pi*kB*ambient_temperature),4)

 

 

 

 

max_range_for_typical_detectable_object =

 

  224.8507

 

 

 

  

 

Thank you very much for answering my questions, our team really appreciates your great work and will be very happy to use AWR1243 in out applications.

 

Best, Marcel Friesch 

  • Marcel,

    The number of loops is sometimes the same as the number of chirps. The total number of chirps in a frame is defined by the end chirp number minus the start chirp number. You then multiply the difference by the number of the loops. This gives the number of chirps in a single frame. In the case where the start chirp and end chirp are the same, the number of loops does equal the number of chirps.

    The maximum range of any of TI's mmWave solutions depends on the device (single chip vs multi-chip) and the antenna pattern configuration. In some test scenarios, TI has collected results on the AWR1243 cascade solution resolving distances of 250 meters and even further.

    Refer to this video for more information: www.youtube.com/watch

    Regards,
    Kyle
  • Dear Kyle

    Thank you for the explenation regarding the chirps, I undersrand this part now.

    What about the other questions?

    I knew the video already, but for system specification, I need to know the exact range.

    I am happy to hear from you soon.

    Best, Marcel

  • The answer did not cover all my questions.
  • Marcel,

    The range of the cascade solution depends on several factors including the RCS of the target object, the physical antenna configuration, the chirp and frame configuration, and the physical mounting the radar solution. There is not a carte blanche answer that I can just post here because it would not accurately reflect the various factors affecting the maximum range of a cascade solution. The information provided in the video can be used a reference to see if a cascade solution could work for your scenario.

    Regards,
    Kyle