Several targets in phased.TwoRayChannel

Hello,

I wanted to investigate several targets in one simulation. Assuming the 'MeanRCS' property of the phased.RadarTarget consists of [RCS1, RCS2, ... RCSM] 1xM elements, the phased.TwoRayChannel models Nx2M channels, where N denotes the number of samples of the signal and 2M because it is a two ray channel model. Hence, every radar target scatters back in two channels. Running the simulation, I get the following error:

Error using coder.internal.errorIf (line 8) MeanRCS must be a scalar or a vector with the same number of columns as the input 'X'.

Now the questions:

- Do I have to change the MeanRCS property to [RCS1, RCS1, RCS2, RCS2, ... RCSM, RCSM] with size 1x2M elements?

- For the GroundReflectionCoefficient property of the phased.TwoRayChannel object do I have to give 1xM elements or 1x2M elements?

Thank you in advance!

Best regards, Dominic

Answer 1

[Honglei Chen]

From the surface, I would say MeanRCS needs to be made to a 1x2M vector as you outlined, but GroundReflectionCoefficient property probably just need a 1xM element. If you encounter any issue, it would be helpful to provide how you call the channel and the dimension of each input and I'd be more than happy to look into it.

HTH

[Dominic Ruh]

Setting up the objects:

channelForward = phased.TwoRayChannel('PropagationSpeed',c, 'OperatingFrequency',fc, 'SampleRate', fs, SpecifyAtmosphere', false, Temperature', 20, 'DryAirPressure', 101.325e3, 'WaterVapourDensity', 7.5, 'LiquidWaterDensity', 0.0, 'RainRate', 0.0, 'GroundReflectionCoefficient', 0.0, 'CombinedRaysOutput', false); 

channelBackward = clone(channelForward);
obj_rcs_sm = [RCS1, RCS1, RCS2, RCS2, RCS3, RCS3] % Case of 3 objects    
obj = phased.RadarTarget('MeanRCS', obj_rcs_sm, 'PropagationSpeed',c, 'OperatingFrequency',fc);

Call throughout the simulation i.e. the loop (m = 1:nChirpsPerFrame*Nt) for every chirp:

[obj_dist2Ray, tgt_ang] = rangeangle(tgt_pos,radar_pos,'two-ray');
Gamma_v = epsilon_r_medium2 * sind(tgt_ang(2,2:2:end)) - sqrt(epsilon_r_medium2 - cosd(tgt_ang(2,2:2:end)).^2)./ ...
            (epsilon_r_medium2 * sind(tgt_ang(2,2:2:end))+ sqrt(epsilon_r_medium2 - cosd(tgt_ang(2,2:2:end)).^2));

release(channelForward);      
channelForward.GroundReflectionCoefficient = Gamma_v;
channelBackward = clone(channelForward);

propagateToTarget = channelForward(sigRadiated, radar_pos, tgt_pos, radar_vel, tgt_vel);

reflectOfTarget = obj(propagateToTarget);

[Honglei Chen]

Thanks for the code, do you encounter any issue with this code? if so, what is it? Thanks.

[Dominic Ruh]

Actually, I hope you can tell me if this is the way Mathworks wanted to implement multi target simulations using phased.TwoRayChannel?

[Honglei Chen]

It looks reasonable to me. I notice one thing is you want to change reflection coefficient from run to run. We currently don't have good support for this and I'll look into this and see how we can make this easier for you in the future.

[Dominic Ruh]

But it is correct, that the reflection coefficient has to change from run to run in case of a moving target since the angle of incidence changes?

[Honglei Chen]

Yes, I agree. I'm simply saying that we didn't consider your use case. In polarized case, this is automatically done but you want to do it manually and we should make it easier for you by not having to call release().

HTH