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PyNEC

README.md

Python NEC2++ Module

This module wraps the C++ API for antenna simulation of nec2++. It is easier to work with, and more powerful than the C-style API wrapper. Works with Python 2.7 and 3+.

Usage

Here is an example that plots a radiation pattern.

from PyNEC import *
import numpy as np

#creation of a nec context
context=nec_context()

#get the associated geometry
geo = context.get_geometry()

#add wires to the geometry
geo.wire(0, 36, 0, 0, 0, -0.042, 0.008, 0.017, 0.001, 1.0, 1.0)
context.geometry_complete(0)

context.gn_card(-1, 0, 0, 0, 0, 0, 0, 0)

#add a "ex" card to specify an excitation
context.ex_card(1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0)

#add a "fr" card to specify the frequency 
context.fr_card(0, 2, 2400.0e6, 100.0e6)

#add a "rp" card to specify radiation pattern sampling parameters and to cause program execution
context.rp_card(0, 91, 1, 0, 5, 0, 0, 0.0, 45.0, 4.0, 2.0, 1.0, 0.0)

#get the radiation_pattern
rp = context.get_radiation_pattern(0)

# Gains are in decibels
gains_db = rp.get_gain()
gains = 10.0**(gains_db / 10.0)
thetas = rp.get_theta_angles() * 3.1415 / 180.0
phis = rp.get_phi_angles() * 3.1415 / 180.0


# Plot stuff
import matplotlib.pyplot as plt

ax = plt.subplot(111, polar=True)
ax.plot(thetas, gains[:,0], color='r', linewidth=3)
ax.grid(True)

ax.set_title("Gain at an elevation of 45 degrees", va='bottom')
plt.savefig('RadiationPattern.png')
plt.show()

Manual Build & install

Requirements

  • Pandoc
  • Swig
  • For Windows: C/C++ compilers.
  • Git bash (for running build.sh script)
  • Latest python packages: pip, setuptools, numpy, wheel, numpy. Run: $ pip install --upgrade pip setuptools wheel numpy

Note: Download and extract swigwin.zip and add the path to swig.exe to environment.

Then do following:

    $ git clone --recursive https://github.com/tmolteno/python-necpp.git
    $ cd python-necpp
    $ cd PyNEC
    $ ./build.sh
	$ python setup.py bdist_wheel (For generating wheel, requires wheel package)
    $ sudo python setup.py install

Note: 'sudo' is not required in windows.

Install from PyPI

$ sudo pip install pynec

Note: 'sudo' is not required in windows.

Testing

Requirements

  • python package: matplotlib

    $ python example/test_rp.py

The example directory contains the following additional examples (that are inspired by excercises from a course on antennas):

  • logperiodic_opt.py is an example on how to combine PyNECPP with scipy.optimize to use a genetic algorithm to optimize an antenna for multiple frequency bands at the same time (which I thin is not possible in 4nec2). The resulting gains and VSWR are plotted over the frequency range of interest. This requires scipy >= 0.15.0 due to the usage of scipy.optimize.differential_evolution.
  • monopole_realistic_ground_plane.py plots the vertical gain pattern of a monopole antenna. Its dimensions are optimized with a local search, and the path through the search space is visualized with a heat map.
  • dipole.py does a very simple optimization of a dipole, and plots the VSWR over a given frequency range for different system impedances to file.
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