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Modelling of EPR of elementary objects

The example considers the modelling of the reflected signal from elementary radar objects (cylinder and cone). The peculiarity of these objects is that
they have an analytical expression for the calculation of the effective scattering surface (ESR).

In [ ]: 
# Подключение вспомагательного файла, в котором 
# реализованы аналитические выражения для расчета ЭПР
include("$(@__DIR__)/helperTargetRCS.jl")
plotlyjs();

1. object - cylinder

Let's set the dimensions of the cylinder: height - 10 m, radius - 1 m. The carrier frequency of the radar is 850 MHz.

In [ ]: 
c = physconst("LightSpeed") # скорость распространения сигнала, м/с
fc = 850e6 # несущая частота, Гц
R1 = 1; # Радиус нижней части цилиндра, м
R2 = 1 # Радиус верхней части цилиндра, м
H = 10; # высота, м

Using the function rcscylinder, we calculate the inverse of the cylinder. The function helperTargetRCSPatternPlot allows us visualise the 3D model of the EPR.

In [ ]: 
cylrcs,az,el = rcscylinder(R1,R2,H,c,fc);
helperTargetRCSPatternPlot(az,el,cylrcs)
Out[0]:

To simulate a radar object (cylinder) with previously calculated EPR - cylrcs, we will use the built-in system object EngeePhased.BackscatterRadarTarget

In [ ]: 
tgt_rcs = EngeePhased.BackscatterRadarTarget(
    PropagationSpeed=c, # скорость распространения сигнала
    OperatingFrequency=fc, # несущая частота
    AzimuthAngles=az, # сетка по азимутальному углу
    ElevationAngles=el, # сетка по углу места
    RCSPattern=cylrcs # ЭПР объекта
);

Let's simulate a scenario of rotational motion of the target based on the harmonic law:

In [ ]: 
N = 1000 # количество импульсов
num_turn = 4 # количество колебаний объекта

# модель вращения тела
mod_az = (0 .+ LinRange(0,40,N))' .+ ((LinRange(20,90,N)) .* sin.(LinRange(0,num_turn*2π,N)))' # азимутальный угол, град          
mod_el = (0 .+ LinRange(0,45,N))' .+ ((LinRange(20,45,N)) .*sin.(LinRange(0,num_turn*2π,N)))' # угол места, град

# Отображение модели
plot([mod_az[:] mod_el[:]],lab=["азимутальный угол" "угол места"],legend_position = :topleft)
xlabel!("Отсчеты")
ylabel!("Угол, град")
title!("Модель вращения тела")
Out[0]:

Next, we calculate the reflected signal for N single pulses at different sighting angles using the function calc_resp_sig

In [ ]: 
in_sig = ones(N) # входной сигнал - последовательность одиночных импульсов 
out_sig_cyl = calc_resp_sig(tgt_rcs,in_sig,[mod_az;mod_el]); # расчет выходного сигнала

# Отображение результата
plotting_sig(out_sig_cyl,[mod_az[:] mod_el[:]];title = "Отраженный сигнал от цилиндра")
Out[0]:

The graph shows that the amplitude of the reflected signal decreases with increasing target deviation amplitude of the reflected signal decreases due to EPR decreases when approaching the boundary angles

2- The object is a cone

The next object of the study is a cone. To calculate the EPR of the object we use rcstruncone, which forms a truncated cone. To obtain a normal cone, it is necessary to zero the upper radius of R1

In [ ]: 
R1 = 0; # Радиус верхней части конуса, м
R2 = 1 # Радиус нижней части конуса, м
H = 1; # высота конуса, м

cone_rcs,az,el = rcstruncone(R1,R2,H,c,fc);
helperTargetRCSPatternPlot(az,el,cone_rcs)
Out[0]:

Let's reuse the system object tgt_rcs for modelling the EPR of the cone.Let's use the method release! to update field RCSPattern - EPR matrix.

In [ ]: 
release!(tgt_rcs)
tgt_rcs.RCSPattern = cone_rcs;

Then, by analogy with the previous point, calculate and display the reflected signal

In [ ]: 
in_sig = ones(N) # входной сигнал - последовательность одиночных импульсов 
out_sig_cone = calc_resp_sig(tgt_rcs,in_sig,[mod_az;mod_el]); # расчет выходного сигнала

# Отображение результата
plotting_sig(out_sig_cone,[mod_az[:] mod_el[:]];title = "Отраженный сигнал от конуса")
Out[0]:

Compared to the cylinder, the graph of the reflected signal from the cone has a smoother character when the angle of place changes.

Conclusion

In the example we have considered modelling of EPR for elementary objects - a cylinder and a cone. objects - a cylinder and a cone. By changing the direction of arrival of the probe signal was simulated rotational motion of the target. of the target. As a result, the reflected signal was calculated.