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## PathSim Example for Simple FMCW Radar System

##

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# IMPORTS ===============================================================================

import matplotlib.pyplot as plt

import numpy as np

#the core functionalities can now be imported directly

from pathsim import Simulation, Connection

#the standard blocks are imported like this

from pathsim.blocks import (

Multiplier,

Scope,

Adder,

Spectrum,

Delay,

RealtimeScope,

ChirpPhaseNoiseSource,

ButterworthLowpassFilter

)

# FMCW RADAR SYSTEM =====================================================================

#natural constants

c0 = 3e8

#chirp parameters

B = 4e9

T = 5e-7

f_min = 1e9

#simulation timestep

dt = 1e-11

#delay for target emulation

tau = 2e-9

#target distances

R = c0 * tau / 2

#frequencies for targets

f_trg = 4 * R * B / (T * c0)

#initialize blocks

Src = ChirpPhaseNoiseSource(f0=f_min, BW=B, T=T)

Add = Adder()

Dly = Delay(tau)

Mul = Multiplier()

Lpf = ButterworthLowpassFilter(f_trg*3, 2)

Spc = Spectrum(

freq=np.logspace(6, 10.5, 500),

labels=["chirp", "delay", "mixer", "lpf"]

)

Sco = Scope(

labels=["chirp", "delay", "mixer", "lpf"]

)

blocks = [Src, Add, Dly, Mul, Lpf, Spc, Sco]

#initialize connections

connections = [

Connection(Src, Add[0]),

Connection(Add, Dly, Mul, Sco, Spc),

Connection(Dly, Mul[1], Sco[1], Spc[1]),

Connection(Mul, Lpf, Sco[2], Spc[2]),

Connection(Lpf, Sco[3], Spc[3])

]

#initialize simulation

Sim = Simulation(blocks, connections, dt=dt, log=True)

# Run Example ===========================================================================

if __name__ == "__main__":

#run simulation for one chirp period

Sim.run(T)

#plot the recording of the scope

Sco.plot()

#plot the spectrum

Spc.plot()

Spc.ax.set_xscale("log")

Spc.ax.set_yscale("log")

Spc.ax.axvline(f_trg, ls="--", c="k")

plt.show()