NEC2++

https://tmolteno.github.io/necpp/
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NEC2++ is an open-source electromagnetic simulation software and library compatible with NEC-2, used...
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### Main function calling all nec2++ examples

Source: https://tmolteno.github.io/necpp/test_nec_8c-example.html

Calls the three example functions in order: simple_example, example3, and seven_wire_antenna.

```C
int main() {
simple_example();
example3();
seven_wire_antenna();
return 0;
}
```

--------------------------------

### reset_processing_to_excitation_setup

Source: https://tmolteno.github.io/necpp/classnec__context.html

Resets the processing state to excitation setup.

```APIDOC
## reset_processing_to_excitation_setup

### Description
Resets the processing state to excitation setup.

### Method
reset_processing_to_excitation_setup

### Signature
void reset_processing_to_excitation_setup()

### Parameters
None

### Returns
void
```

--------------------------------

### nec_ground::setup_cliff()

Source: https://tmolteno.github.io/necpp/classnec__ground.html

Sets up the cliff geometry with given parameters.

```APIDOC
## nec_ground::setup_cliff(nec_float in_eprs2, nec_float in_sig2, nec_float clt, nec_float cht)

### Description
Sets up the cliff geometry with given parameters.

### Parameters
- in_eprs2 (nec_float) - Relative dielectric constant of medium 2.
- in_sig2 (nec_float) - Conductivity of medium 2.
- clt (nec_float) - Cliff edge distance.
- cht (nec_float) - Cliff height.

### Method
Member function
```

--------------------------------

### get_xpr2

Source: https://tmolteno.github.io/necpp/classnec__context.html

Gets the xpr2 parameter.

```APIDOC
## get_xpr2

### Description
Gets the xpr2 parameter.

### Method
get_xpr2

### Signature
nec_float get_xpr2() n
### Parameters
None

### Returns
nec_float - The xpr2 value.
```

--------------------------------

### Setup cliff ground

Source: https://tmolteno.github.io/necpp/nec__ground_8h_source.html

Sets up a cliff (two medium ground) with the given second medium parameters and cliff dimensions.

```cpp
void setup_cliff(nec_float in_eprs2,
nec_float in_sig2,
nec_float clt, nec_float cht);
```

--------------------------------

### get_xpr1

Source: https://tmolteno.github.io/necpp/classnec__context.html

Gets the xpr1 parameter.

```APIDOC
## get_xpr1

### Description
Gets the xpr1 parameter.

### Method
get_xpr1

### Signature
nec_float get_xpr1() n
### Parameters
None

### Returns
nec_float - The xpr1 value.
```

--------------------------------

### get_inc

Source: https://tmolteno.github.io/necpp/classnec__context.html

Gets the inc parameter.

```APIDOC
## get_inc

### Description
Gets the inc parameter.

### Method
get_inc

### Signature
int get_inc() n
### Parameters
None

### Returns
int - The inc value.
```

--------------------------------

### C++ example using nec_context, c_geometry, and nec_radiation_pattern

Source: https://tmolteno.github.io/necpp/test_cpp_8cpp-example.html

Complete C++ program that builds a NEC2++ geometry, sets ground and loading cards, excites a linear antenna, and prints the radiation pattern. Requires the nec2++ headers and the test_cpp makefile target to compile. The program catches nec_exception and prints its message on failure.

```cpp
#include <iostream>
using namespace std;
/*
An example of how to use nec2++ from within a C++ program.
See the makefile target 'test_cpp' for how to compile this
(as well as the nec2++) source code.
Copyright (C) 2005,2015 Timothy C.A. Molteno (tim@molteno.net)
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "c_geometry.h"
#include "nec_context.h"
#include "nec_exception.h"
#include "nec_radiation_pattern.h"
int main(int argc, char **argv) {
try {
cout << "Nec2++ C++ example. Running (takes a few minutes...)" << endl;
nec_context nec;
nec.initialize();
c_geometry* geo = nec.get_geometry();
geo->wire(0, 70, -0.048, 0.021, -0.005, 0.035, 0.043, 0.014, 0.001, 1.0, 1.0);
geo->wire(0, 66, 0.017, -0.015, 0.014, -0.027, 0.04, -0.031, 0.001, 1.0, 1.0);
geo->wire(0, 47, 0.046, -0.01, 0.028, -0.013, -0.005, 0.031, 0.001, 1.0, 1.0);
geo->wire(0, 77, -0.048, -0.038, -0.04, 0.049, -0.045, -0.04, 0.001, 1.0, 1.0);
nec.geometry_complete(0);
nec.gn_card(-1,0,0.0, 0.0, 0.0,0.0, 0.0, 0.0);
nec.ld_card(5,0,0,0,3.72e7,0.0,0.0);
nec.pt_card(-1, 0, 0, 0);
nec.ex_card(EXCITATION_LINEAR, 1, 1, 0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
nec.fr_card(0, 2, 2400.0, 100.0);
nec.rp_card(0, 10, 10, 0,5,0,0, 0.0, 0.0, 9.0, 9.0, 0.0, 0.0);
// now get the radiation pattern data. The result index is 0 since
// this is the first (and only) radiation pattern.
nec_radiation_pattern* rp = nec.get_radiation_pattern(0);
int nth = rp->get_ntheta();
int nph = rp->get_nphi();
cout << endl << "Theta \tPhi \tHorizontal \tVertical \tTotal" << endl;
for (int j=0; j<nph; j++) {
for (int i=0; i<nth; i++) {
cout
<< rp->get_theta(i) << " \t"
<< rp->get_phi(j) << " \t"
<< rp->get_power_gain_horiz(i,j) << " \t"
<< rp->get_power_gain_vert(i,j) << " \t"
<< rp->get_power_gain(i,j) << " \t"
<< rp->get_etheta_magnitude(i,j) << " \t"
<< rp->get_etheta_phase(i,j) << " \t"
<< rp->get_ephi_magnitude(i,j) << " \t"
<< rp->get_ephi_phase(i,j)
<< endl;
}
}
}
catch (const nec_exception& e) {
cout << e.get_message() << endl;
}
return 0;
}
```

--------------------------------

### get_frequency

Source: https://tmolteno.github.io/necpp/classnec__base__result.html

Gets the frequency of the results.

```APIDOC
## get_frequency

### Description
Gets the frequency of the results.

### Method
get_frequency

### Signature
nec_float get_frequency()

### Parameters
None

### Returns
nec_float - The frequency value.
```

--------------------------------

### void initialize()

Source: https://tmolteno.github.io/necpp/nec__context_8h_source.html

Initializes everything, called after construction so that the geometry object can be told about the nec_context.

```APIDOC
## void initialize()

### Description
Initializes everything, called after construction so that the geometry object can be told about the nec_context.

### Method
initialize

### Parameters
None.

### Response
No return value.
```

--------------------------------

### Simple dipole example using nec2++ library

Source: https://tmolteno.github.io/necpp/test_nec_8c-example.html

Defines a simple dipole using nec_wire, sets up geometry, ground, frequency, excitation, and radiation pattern cards, then prints gain values. Includes a commented NEC card equivalent.

```C
void simple_example() {
/* GW 0 9 0. 0. 2. 0. 0. 7 .1
GE 1
FR 0 1 0 30.
EX 0 5 0 1.
GN 1
RP 0 90 1 0000 0 90 1 0 
*/
nec_context* nec; 
nec = nec_create();
nec_wire(nec, 0, 9, 0, 0, 2, 0, 0, 7, 0.1, 1, 1);
nec_geometry_complete(nec, 1);
nec_gn_card(nec, 1, 0, 0, 0, 0, 0, 0, 0);
nec_fr_card(nec, 0, 1, 30, 0);
nec_ex_card(nec, 0, 0, 5, 0, 1.0, 0, 0, 0, 0, 0);
nec_rp_card(nec, 0, 90, 1, 0,5,0,0, 0, 90, 1, 0, 0, 0);
printf("Gain: %f, %f +/- %f dB\n",nec_gain_max(nec,0), nec_gain_mean(nec,0), nec_gain_sd(nec,0));
printf("RHCP Gain: %f, %f +/- %f dB\n",nec_gain_rhcp_max(nec,0), nec_gain_rhcp_mean(nec,0), nec_gain_rhcp_sd(nec,0));
printf("LHCP Gain: %f, %f +/- %f dB\n",nec_gain_lhcp_max(nec,0), nec_gain_lhcp_mean(nec,0), nec_gain_lhcp_sd(nec,0));
nec_delete(nec);
}
```

--------------------------------

### safe_array segment and eigen_segment methods

Source: https://tmolteno.github.io/necpp/safe__array_8h_source.html

Creates a non-owning view of a sub-range of the array. segment takes start and end indices, while eigen_segment takes start and length. The segment method throws a string exception if end_index is -1.

```cpp
safe_array<T> segment(int64_t start_index, int64_t end_index) {
  if (int64_t(-1) == end_index)
    throw "foo";
  int64_t n = end_index - start_index + 1;
  safe_array<T> result;
  result._view_ptr = data() + start_index;
  result._len = n;
  result._rows = 0;
  result._cols = 0;
  result._own_data = false;
  return result;
}

safe_array<T> eigen_segment(int64_t start_index, int64_t n) {
  return segment(start_index, start_index + n - 1);
}
```

--------------------------------

### Seven-wire antenna example using nec2++ library

Source: https://tmolteno.github.io/necpp/test_nec_8c-example.html

Defines a seven-wire antenna using nec_wire calls, sets up geometry, ground, frequency, excitation, and radiation pattern cards, then prints impedance and gain values. Uses the NEC_ERROR_HANDLE macro to check for errors.

```C
#include <libnecpp.h>
#include <stdio.h>
/*
C Example using nec2++ as a library
Enter the following file into test_nec.c, and compile with
gcc -o test_nec test_nec.c -L . -lnecpp -lm
*/
#define NEC_ERROR_HANDLE(_x) { if (_x != 0) printf("Error: %s\n", nec_error_message()); }
void seven_wire_antenna() {
nec_context* nec; 
nec = nec_create();
NEC_ERROR_HANDLE(nec_wire(nec, 1, 9, 0.0, 0.0, 0.0, -0.0166, 0.0045, 0.0714, 0.001, 1.0, 1.0));
NEC_ERROR_HANDLE(nec_wire(nec, 2, 7, -0.0166, 0.0045, 0.0714, -0.0318, -0.0166, 0.017, 0.001, 1.0, 1.0));
NEC_ERROR_HANDLE(nec_wire(nec, 3, 7, -0.0318, -0.0166, 0.017, -0.0318, -0.0287, 0.0775, 0.001, 1.0, 1.0));
NEC_ERROR_HANDLE(nec_wire(nec, 4, 11, -0.0318, -0.0287, 0.0775, -0.0318, 0.0439, 0.014, 0.001, 1.0, 1.0));
/* NEC_ERROR_HANDLE(nec_wire(nec, 5, 7, -0.0318, 0.0439, 0.014, -0.0318, 0.0045, 0.0624, 0.001, 1.0, 1.0));*/
NEC_ERROR_HANDLE(nec_wire(nec, 6, 5, -0.0318, 0.0045, 0.0624, -0.0106, 0.0378, 0.0866, 0.001, 1.0, 1.0));
NEC_ERROR_HANDLE(nec_wire(nec, 7, 7, -0.0106, 0.0378, 0.0866, -0.0106, 0.0257, 0.023, 0.001, 1.0, 1.0));
NEC_ERROR_HANDLE(nec_geometry_complete(nec, 1));
NEC_ERROR_HANDLE(nec_gn_card(nec, 1, 0, 0, 0, 0, 0, 0, 0));
NEC_ERROR_HANDLE(nec_fr_card(nec, 0, 1, 1600.0, 0.0));
NEC_ERROR_HANDLE(nec_ex_card(nec, 0, 1, 1, 0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0));
NEC_ERROR_HANDLE(nec_rp_card(nec, 0, 17, 45, 0,5,0,0, 0, 0, 5, 8, 0, 0));
printf("Impedance: %f, %f\n",nec_impedance_real(nec,0), nec_impedance_imag(nec,0));
printf("Gain: %f, %f +/- %f dB\n",nec_gain_max(nec,0), nec_gain_mean(nec,0), nec_gain_sd(nec,0));
printf("RHCP Gain: %f, %f +/- %f dB\n",nec_gain_rhcp_max(nec,0), nec_gain_rhcp_mean(nec,0), nec_gain_rhcp_sd(nec,0));
printf("LHCP Gain: %f, %f +/- %f dB\n",nec_gain_lhcp_max(nec,0), nec_gain_lhcp_mean(nec,0), nec_gain_lhcp_sd(nec,0));
nec_delete(nec);
}
```

--------------------------------

### nec_radiation_pattern::get_pol_sense

Source: https://tmolteno.github.io/necpp/nec__radiation__pattern_8h_source.html

Get the polarization sense.

```APIDOC
## get_pol_sense

### Description
Get the polarization sense.

### Method
const

### Endpoint
nec_radiation_pattern::get_pol_sense

### Parameters
- **theta_index** (int) - Required - The index of the theta angle.
- **phi_index** (int) - Required - The index of the phi angle.

### Returns
- **int** - The polarization sense.
```

--------------------------------

### Vertical half-wavelength antenna over ground example using nec2++ library

Source: https://tmolteno.github.io/necpp/test_nec_8c-example.html

Defines a vertical half-wavelength antenna over ground, using extended thin wire kernel (EK), and demonstrates both perfect and imperfect ground cases. Prints impedance values for each case.

```C
void example3() {
/*
CMEXAMPLE 3. VERTICAL HALF WAVELENGTH ANTENNA OVER GROUND 
CM EXTENDED THIN WIRE KERNEL USED 
CM 1. PERFECT GROUND 
CM 2. IMPERFECT GROUND INCLUDING GROUND WAVE AND RECEIVING 
CE PATTERN CALCULATIONS 
GW 0 9 0. 0. 2. 0. 0. 7. .03 
GE 1 
EK 
FR 0 1 0 0 30. 
EX 0 0 5 0 1. 
GN 1
RP 0 10 2 1301 0. 0. 10. 90. 
GN 0 0 0 0 6. 1.000E-03 
RP 0 10 2 1301 0. 0. 10. 90. 
RP 1 10 1 0 1. 0. 2. 0. 1.000E+05 
EX 1 10 1 0 0. 0. 0. 10.
PT 2 0 5 5 
XQ 
EN
*/
nec_context* nec; 
nec = nec_create();
nec_wire(nec, 0, 9, 0., 0.0, 2.0, 0.0, 0.0, 7.0, 0.03, 1.0, 1.0);
nec_geometry_complete(nec, 1);
nec_ek_card(nec, 0);
nec_fr_card(nec, 0, 1, 30., 0 );
nec_ex_card(nec, 0, 0, 5, 0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0);
nec_gn_card(nec, 1, 0, 0, 0, 0, 0, 0, 0);
nec_rp_card(nec, 0,10,2,1,3,0,1,0.0,0.0,10.0,90.0, 0, 0);
printf("Impedance %f\n", nec_impedance_real(nec,0)); // 83.7552291016712)
nec_gn_card(nec, 0, 0, 6.0, 1.000E-03, 0.0, 0.0, 0.0, 0.0);
nec_rp_card(nec, 0,10,2,1,3,0,1, 0.0,0.0,10.0,90.0, 0, 0);
printf("Impedance 2 %f\n", nec_impedance_real(nec,0)); // 83.7552291016712)
}
```

--------------------------------

### nec_impedance_real

Source: https://tmolteno.github.io/necpp/libnecpp_8h_source.html

Gets the real part of the impedance.

```APIDOC
## nec_impedance_real

### Description
Gets the real part of the impedance.

### Function Signature
double nec_impedance_real(nec_context *in_context, int freq_index)

### Parameters
- **in_context** (nec_context*) - Required - Pointer to the NEC context.
- **freq_index** (int) - Required - Frequency index.

### Returns
- **double** - Real part of impedance.

```

--------------------------------

### nec_gain

Source: https://tmolteno.github.io/necpp/libnecpp_8h_source.html

Get the gain from a radiation pattern.

```APIDOC
## nec_gain


### Description
Get the gain from a radiation pattern.

### Syntax
```c
double nec_gain(nec_context *in_context, int freq_index, int theta_index, int phi_index)
``` n
### Parameters
- **in_context** (nec_context*) - Pointer to the NEC context.
- **freq_index** (int) - Frequency index.
- **theta_index** (int) - Theta index.
- **phi_index** (int) - Phi index.

### Returns
- **double** - Gain value.
```

--------------------------------

### c_ggrid class definition with initialization and interpolation methods

Source: https://tmolteno.github.io/necpp/c__ggrid_8h_source.html

Defines the c_ggrid class with static grid parameters, complex arrays, and an evlcom member. The initialize() method resizes arrays and sets interpolation cache defaults. The interpolate() method performs bivariate cubic interpolation, and sommerfeld() computes Sommerfeld attenuation.

```cpp
class c_ggrid
{
public:
 static int m_nxa[3], m_nya[3];
 static nec_float m_dxa[3], m_dya[3];
 static nec_float m_xsa[3], m_ysa[3];

 nec_complex m_epscf;
 complex_array m_ar1, m_ar2, m_ar3;

 c_evlcom m_evlcom;

 void initialize() {
 m_ar1.resize(11*10*4);
 m_ar2.resize(17*5*4);
 m_ar3.resize(9*8*4);

 // initialize interpolation cache
 m_ip_ixs = -10;
 m_ip_iys = -10;
 m_ip_igrs = -10;
 m_ip_ixeg = 0;
 m_ip_iyeg = 0;
 m_ip_dx = 1.0;
 m_ip_dy = 1.0;
 m_ip_xs = 0.0;
 m_ip_ys = 0.0;
 }

 void interpolate( nec_float x, nec_float y, 
 nec_complex *f1, nec_complex *f2,
 nec_complex *f3, nec_complex *f4 );

 void sommerfeld( nec_float epr, nec_float sig, nec_float wavelength );

private:
 // interpolation cache (per-instance, thread-safe)
 int m_ip_ix, m_ip_iy, m_ip_ixs, m_ip_iys, m_ip_igrs, m_ip_ixeg, m_ip_iyeg;
 int m_ip_nxm2, m_ip_nym2, m_ip_nxms, m_ip_nyms, m_ip_nd, m_ip_ndp;
 nec_float m_ip_dx, m_ip_dy, m_ip_xs, m_ip_ys, m_ip_xz, m_ip_yz;
 nec_complex m_ip_a[4][4], m_ip_b[4][4], m_ip_c[4][4], m_ip_d[4][4];
};
```

--------------------------------

### nec_structure_currents::get_frequency

Source: https://tmolteno.github.io/necpp/classnec__structure__currents.html

Gets the frequency for the results.

```APIDOC
## nec_structure_currents::get_frequency

### Description
Gets the frequency for the results.

### Method
Member function

### Signature
nec_float get_frequency()

### Parameters
None.

### Returns
- **nec_float** - The frequency value.
```

--------------------------------

### nec_gn_card

Source: https://tmolteno.github.io/necpp/libnecpp_8h_source.html

Sets up ground parameters.

```APIDOC
## nec_gn_card

### Description
Sets up ground parameters.

### Function Signature
long nec_gn_card(nec_context *in_context, int iperf, int nradl, double epse, double sig, double tmp3, double tmp4, double tmp5, double tmp6)

### Parameters
- **in_context** (nec_context*) - Required - Pointer to the NEC context.
- **iperf** (int) - Required - Iperf parameter.
- **nradl** (int) - Required - Nradl parameter.
- **epse** (double) - Required - Epse parameter.
- **sig** (double) - Required - Sig parameter.
- **tmp3** (double) - Required - Temporary parameter.
- **tmp4** (double) - Required - Temporary parameter.
- **tmp5** (double) - Required - Temporary parameter.
- **tmp6** (double) - Required - Temporary parameter.

### Returns
- **long** - Status code.

```

--------------------------------

### nec_structure_currents::get_patch_number

Source: https://tmolteno.github.io/necpp/classnec__structure__currents.html

Gets the patch numbers.

```APIDOC
## nec_structure_currents::get_patch_number

### Description
Gets the patch numbers.

### Method
Member function

### Signature
vector<int> get_patch_number() n
### Parameters
None.

### Returns
- **vector<int>** - Vector of patch numbers.
```

--------------------------------

### simulate

Source: https://tmolteno.github.io/necpp/classnec__context.html

Starts a simulation. Optionally computes far fields if the flag is set.

```APIDOC
## simulate

### Description
Starts a simulation. Optionally computes far fields if the flag is set.

### Method
void

### Signature
void simulate(bool far_field_flag=false)

### Parameters
- far_field_flag (bool) - Optional - If true, compute far fields (default false)
```

--------------------------------

### void nec_context::gn_card(int _ground_type_, int _rad_wire_count_, nec_float _tmp1_, nec_float _tmp2_, nec_float _tmp3_, nec_float _tmp4_, nec_float _tmp5_, nec_float _tmp6_)

Source: https://tmolteno.github.io/necpp/classnec__context.html

Sets ground parameters under the antenna. Specifies the relative dielectric constant and conductivity of ground, and optionally models a radial wire ground screen or a second medium.

```APIDOC
## void nec_context::gn_card(int _ground_type_, int _rad_wire_count_, nec_float _tmp1_, nec_float _tmp2_, nec_float _tmp3_, nec_float _tmp4_, nec_float _tmp5_, nec_float _tmp6_)

### Description
Sets ground parameters under the antenna. Specifies the relative dielectric constant and conductivity of ground in the vicinity of the antenna. A second set of ground parameters for a second medium can be specified, or a radial wire ground screen can be modeled using a reflection coefficient approximation.

### Method
C++ method

### Parameters
- **_ground_type_** (int) - Required - Ground-type flag. Options: -1 (nullifies ground parameters, free-space condition), 0 (finite ground, reflection-coefficient approximation), 1 (perfectly conducting ground), 2 (finite ground, Sommerfeld/Norton method).
- **_rad_wire_count_** (int) - Required - Number of radial wires in the ground screen approximation; set to zero implies no ground screen.
- **_tmp1_** (nec_float) - Required - Relative dielectric constant for ground (EPSE). Set to zero for perfect ground.
- **_tmp2_** (nec_float) - Required - Conductivity in mhos/meter of ground (SIG). Set to zero for perfect ground. If negative, complex dielectric constant is set to EPSR - |SIG|.
- **_tmp3_** (nec_float) - Required - For radial wire ground screen: radius of screen in meters. For second medium: relative dielectric constant of medium 2.
- **_tmp4_** (nec_float) - Required - For radial wire ground screen: radius of wires in meters. For second medium: conductivity of medium 2 in mhos/meter.
- **_tmp5_** (nec_float) - Required - For second medium: distance in meters from origin to join between medium 1 and 2.
- **_tmp6_** (nec_float) - Required - For second medium: distance in meters (positive or zero) by which surface of medium 2 is below medium 1.

### Remarks
Options for remaining floating point fields (F3-F6):
- For infinite ground plane, F3 through F6 are blank.
- Radial wire ground screen approximation (NRADL nonzero): screen centered at origin, lies in XY plane. F3 is radius of screen, F4 is radius of wires, F5 and F6 blank.
- Second medium parameters (NRADL = 0) for medium outside the first medium (cliff problem). These alter far field patterns but not antenna impedance or current distribution. F3 is relative dielectric constant of medium 2, F4 is conductivity of medium 2, F5 is distance to join, F6 is height difference.

### Examples
Referenced by benchmark(), and nec_gn_card().
```

--------------------------------

### nec_structure_currents::get_m

Source: https://tmolteno.github.io/necpp/classnec__structure__currents.html

Gets the number of patches.

```APIDOC
## nec_structure_currents::get_m

### Description
Gets the number of patches.

### Method
Member function

### Signature
int get_m() n
### Parameters
None.

### Returns
- **int** - The number of patches.
```

--------------------------------

### nec_structure_currents::get_n

Source: https://tmolteno.github.io/necpp/classnec__structure__currents.html

Gets the number of segments.

```APIDOC
## nec_structure_currents::get_n

### Description
Gets the number of segments.

### Method
Member function

### Signature
int get_n() n
### Parameters
None.

### Returns
- **int** - The number of segments.
```

--------------------------------

### Build geometry programmatically with c_geometry methods

Source: https://tmolteno.github.io/necpp/c__geometry_8h.html

Builds geometry programmatically by calling wire(), arc(), and other geometry methods, then finalizes with geometry_complete(). Use this when constructing the antenna from primitives rather than reading a file.

```cpp
c_geometry g = new c_geometry();
g.wire(xxxxxxx);
g.arc();
...
g.geometry_complete();
```

--------------------------------

### nec_ex_card()

Source: https://tmolteno.github.io/necpp/libnecpp_8h.html

Sets up an EX card (Excitation) for the NEC simulation. The function accepts a nec_context pointer and parameters defining the excitation type and source segment. Returns 0 on success, 1 on error.

```APIDOC
## nec_ex_card()

### Description
Sets up an EX card (Excitation) for the NEC simulation. The function accepts a nec_context pointer and parameters defining the excitation type and source segment. Returns 0 on success, 1 on error.

### Function Signature
long nec_ex_card(nec_context *_in_context_, int _extype_, int _i2_, int _i3_, int _i4_, double _tmp1_, double _tmp2_, double _tmp3_, double _tmp4_, double _tmp5_, double _tmp6_)

### Parameters
- **_in_context_** (nec_context*) - Required - The nec_context created with nec_create().
- **_extype_** (int) - Required - Type of excitation. Possible values:
  - `0` - voltage source (applied-E-field source).
  - `1` - incident plane wave, linear polarization.
  - `2` - incident plane wave, right-hand (thumb along the incident k vector) elliptic polarization.
  - `3` - incident plane wave, left-hand elliptic polarization.
  - `4` - elementary current source.
  - `5` - voltage source (current-slope-discontinuity).
- **_i2_** (int) - Required - Tag number of the source segment. This tag number along with the number given in (i3) uniquely defines the source segment. If zero, the source segment is identified by the absolute segment number in (i3).
- **_i3_** (int) - Required - Specifies the mth segment of the set of segments whose tag numbers equal the number set by the previous parameter. If the previous parameter is zero, this must be the absolute segment number of the source.
- **_i4_** (int) - Required - Meaning depends on the extype parameter. See http://www.nec2.org/part_3/cards/ex.html for details.
- **_tmp1_** (double) - Required - Floating point parameter, meaning depends on the excitation type. See http://www.nec2.org/part_3/cards/ex.html for details.
- **_tmp2_** (double) - Required - Floating point parameter, meaning depends on the excitation type. See http://www.nec2.org/part_3/cards/ex.html for details.
- **_tmp3_** (double) - Required - Floating point parameter, meaning depends on the excitation type. See http://www.nec2.org/part_3/cards/ex.html for details.
- **_tmp4_** (double) - Required - Floating point parameter, meaning depends on the excitation type. See http://www.nec2.org/part_3/cards/ex.html for details.
- **_tmp5_** (double) - Required - Floating point parameter, meaning depends on the excitation type. See http://www.nec2.org/part_3/cards/ex.html for details.
- **_tmp6_** (double) - Required - Floating point parameter, meaning depends on the excitation type. See http://www.nec2.org/part_3/cards/ex.html for details.

### Return Values
- **err** (long) - `0` indicates success, `1` indicates an error occurred. Call nec_error_message() for a detailed message.

### Remarks
Simpler versions of the function are provided for common uses: nec_voltage_excitation, nec_current_excitation, and nec_planewave_excitation. The meaning of the floating point parameters depends on the excitation type. See http://www.nec2.org/part_3/cards/ex.html for more details.

### References
References nec_context::ex_card().
```

--------------------------------

### nec_radiation_pattern::get_etheta_magnitude

Source: https://tmolteno.github.io/necpp/nec__radiation__pattern_8h_source.html

Get the magnitude of E(THETA).

```APIDOC
## get_etheta_magnitude

### Description
Get the magnitude of E(THETA).

### Method
non-const

### Endpoint
nec_radiation_pattern::get_etheta_magnitude

### Parameters
- **theta_index** (int) - Required - The index of the theta angle.
- **phi_index** (int) - Required - The index of the phi angle.

### Returns
- **nec_float** - The magnitude of E(THETA).
```

--------------------------------

### void simulate(bool far_field_flag=false)

Source: https://tmolteno.github.io/necpp/nec__context_8h_source.html

Starts a simulation. The far_field_flag indicates whether to compute far-field patterns.

```APIDOC
## void simulate(bool far_field_flag=false)

### Description
Starts a simulation. The far_field_flag indicates whether to compute far-field patterns.

### Method
simulate

### Parameters
- **far_field_flag** (bool) - Optional - If true, compute far-field patterns. Default is false.

### Response
No return value.
```

--------------------------------

### nec_radiation_pattern::get_ephi_magnitude

Source: https://tmolteno.github.io/necpp/nec__radiation__pattern_8h_source.html

Get the magnitude of E(PHI).

```APIDOC
## get_ephi_magnitude

### Description
Get the magnitude of E(PHI).

### Method
non-const

### Endpoint
nec_radiation_pattern::get_ephi_magnitude

### Parameters
- **theta_index** (int) - Required - The index of the theta angle.
- **phi_index** (int) - Required - The index of the phi angle.

### Returns
- **nec_float** - The magnitude of E(PHI).
```

--------------------------------

### nec_radiation_pattern::get_pol_axial_ratio

Source: https://tmolteno.github.io/necpp/nec__radiation__pattern_8h_source.html

Get the polarization axial ratio.

```APIDOC
## get_pol_axial_ratio

### Description
Get the polarization axial ratio.

### Method
const

### Endpoint
nec_radiation_pattern::get_pol_axial_ratio

### Parameters
- **theta_index** (int) - Required - The index of the theta angle.
- **phi_index** (int) - Required - The index of the phi angle.

### Returns
- **nec_float** - The polarization axial ratio.
```

--------------------------------

### ex_card (first overload)

Source: https://tmolteno.github.io/necpp/classnec__context.html

Sets excitation parameters (ex card) with 4 integer parameters.

```APIDOC
## ex_card (first overload)

### Description
Sets excitation parameters.

### Method
ex_card

### Signature
void ex_card(enum excitation_type itmp1, int itmp2, int itmp3, int itmp4, nec_float tmp1, nec_float tmp2, nec_float tmp3, nec_float tmp4, nec_float tmp5, nec_float tmp6)

### Parameters
- **itmp1** (enum excitation_type) - Required - Excitation type.
- **itmp2** (int) - Required - Second integer parameter.
- **itmp3** (int) - Required - Third integer parameter.
- **itmp4** (int) - Required - Fourth integer parameter.
- **tmp1** (nec_float) - Required - First float parameter.
- **tmp2** (nec_float) - Required - Second float parameter.
- **tmp3** (nec_float) - Required - Third float parameter.
- **tmp4** (nec_float) - Required - Fourth float parameter.
- **tmp5** (nec_float) - Required - Fifth float parameter.
- **tmp6** (nec_float) - Required - Sixth float parameter.

### Returns
void
```

--------------------------------

### Get ground conductivity

Source: https://tmolteno.github.io/necpp/nec__ground_8h_source.html

Returns the conductivity of the ground.

```cpp
nec_float get_conductivity() const {
  return this->sig;
}
```

--------------------------------

### NEC2++ Command Line Usage

Source: https://tmolteno.github.io/necpp/index.html

Displays the available command-line arguments for the nec2++ executable.

```text
usage: nec2++ [-i<input-file-name>] [-o<output-file-name>]
       -g: print maximum gain to stdout.
       -b: Perform NEC++ Benchmark.
       -s: print results to standard output.
       -c: print results in comma-separated-value (CSV) format,
           this options is used in conjunction with (-s) above.
       -h: print this usage information and exit.
       -v: print nec2++ version number and exit.
```

--------------------------------

### nec_gain_max

Source: https://tmolteno.github.io/necpp/libnecpp_8h_source.html

Gets the maximum gain from a radiation pattern.

```APIDOC
## nec_gain_max

### Description
Gets the maximum gain from a radiation pattern.

### Function Signature
double nec_gain_max(nec_context *in_context, int freq_index)

### Parameters
- **in_context** (nec_context*) - Required - Pointer to the NEC context.
- **freq_index** (int) - Required - Frequency index.

### Returns
- **double** - Maximum gain value.

```

--------------------------------

### get_segment_number

Source: https://tmolteno.github.io/necpp/classc__geometry.html

Gets a segment number for a specified tag.

```APIDOC
## get_segment_number

### Description
Gets a segment number for a specified tag.

### Method
int64_t get_segment_number(int in_tag, int m)

### Parameters
- in_tag (int) - Required - Tag identifier.
- m (int) - Required - Index of the segment within the tag.

### Response
Returns the segment number as an int64_t.
```

--------------------------------

### Accessing Multi-Feed Impedance in C++

Source: https://tmolteno.github.io/necpp/index.html

Demonstrates how to retrieve real and imaginary impedance values for specific feeds in a multi-excitation simulation using nec_context.

```cpp
// Single feed — default feed_index=0 works
nec_context nec;
// ... set up geometry, excitation ...
nec.simulate();
double zr = nec.get_impedance_real(); // feed 0

// Multiple feeds — request specific feeds
nec.ex_card(EXCITATION_VOLTAGE, tag1, seg, 0, 1.0, 0.0, ...);
nec.ex_card(EXCITATION_VOLTAGE, tag2, seg, 0, 1.0, 0.0, ...);
nec.ex_card(EXCITATION_VOLTAGE, tag3, seg, 0, 1.0, 0.0, ...);
// ... simulate ...
double z0r = nec.get_impedance_real(0, 0); // first feed
double z1r = nec.get_impedance_real(0, 1); // second feed
double z2i = nec.get_impedance_imag(0, 2); // third feed, imag
```

--------------------------------

### nec_gain_min

Source: https://tmolteno.github.io/necpp/libnecpp_8h_source.html

Gets the minimum gain from a radiation pattern.

```APIDOC
## nec_gain_min

### Description
Gets the minimum gain from a radiation pattern.

### Function Signature
double nec_gain_min(nec_context *in_context, int freq_index)

### Parameters
- **in_context** (nec_context*) - Required - Pointer to the NEC context.
- **freq_index** (int) - Required - Frequency index.

### Returns
- **double** - Minimum gain value.

```

--------------------------------

### math_util.h Header with Type Definitions and Math Utilities

Source: https://tmolteno.github.io/necpp/math__util_8h_source.html

This is the complete math_util.h header file. It includes common.h and safe_array.h, defines typedefs for safe arrays and matrices, Eigen 3D vectors, and provides inline functions for complex constants, exponentials, pi constants, angle conversions, polar/argument helpers, decibel conversions, and vector norms. The file is licensed under GPL.

```cpp
#pragma once

/*
 Various Useful Math Utilities for nec2++

 Copyright (C) 2004-2015 Timothy C.A. Molteno
 tim@molteno.net 

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/

#include "common.h"



#include "safe_array.h"

typedef safe_array<int32_t> int_array;
typedef safe_array<int64_t> int64_array;
typedef safe_array<nec_float> real_array;
typedef safe_array<nec_complex> complex_array;

typedef safe_matrix<int32_t> int_matrix;
typedef safe_matrix<nec_float> real_matrix;
typedef safe_matrix<nec_complex> complex_matrix;

typedef Eigen::Matrix<nec_float,3,1> nec_3vector;
typedef Eigen::Matrix<nec_complex,3,1> nec_c3vector;

inline void vector_fill(complex_array& x, int64_t start, int64_t N, const nec_complex& y) {
 x.fill(start, N, y);
}


inline nec_complex cplx_00() {
 static nec_complex _cplx00(0.0,0.0); return _cplx00;
}

inline nec_complex cplx_01() {
 static nec_complex _cplx01(0.0,1.0); return _cplx01;
}

inline nec_complex cplx_10() {
 static nec_complex _cplx10(1.0,0.0); return _cplx10;
}

inline nec_complex cplx_11() {
 static nec_complex _cplx11(1.0,1.0); return _cplx11;
}


inline nec_complex cplx_exp(const nec_float& x) {
 return nec_complex(cos(x),sin(x));
}


inline nec_float pi() {
 static nec_float _pi = 3.1415926536; return _pi;
}

inline nec_float two_pi() {
 static nec_float _tmp = 2.0 * pi(); return _tmp;
}

inline nec_float four_pi() {
 static nec_float _tmp = 4.0 * pi(); return _tmp;
}

inline nec_float pi_two() {
 static nec_float _tmp = pi() / 2.0; return _tmp;
}

inline nec_float sqrt_pi() { // was SP from common.h
 static nec_float _tmp = sqrt(pi()); return _tmp;
}


inline nec_complex two_pi_j() {
 static nec_complex _tmp(0.0,two_pi()); return _tmp;
}



inline nec_float rad_to_degrees(nec_float in_radians) {
 static nec_float _rad_to_deg = 360.0 / (2 * pi()); // 57.29577951
 return in_radians * _rad_to_deg;
}

inline nec_float degrees_to_rad(nec_float in_degrees) {
 static nec_float _deg_to_rad = (2 * pi()) / 360.0;
 return in_degrees * _deg_to_rad;
}


inline nec_complex deg_polar(nec_float r, nec_float theta) {
 return std::polar(r, degrees_to_rad(theta));
}


inline nec_float arg_degrees(nec_complex z) {
 return rad_to_degrees(std::arg(z));
}


inline nec_float atgn2( nec_float x, nec_float y) {
 if ((0.0 == y) && (0.0 == x))
 return 0.0;

 return( std::atan2(y, x) );
}


inline nec_float db10( nec_float x ) {
 if ( x < 1.0e-20 )
 return( -999.99 );

 return( 10.0 * log10(x) );
}

inline nec_float from_db10( nec_float x ) {
 if ( x < -99.9 )
 return( 0.0 );

 return( std::pow(10,x / 10.0));
}


inline nec_float db20( nec_float x ) {
 if ( x < 1.0e-20 )
 return( -999.99 );

 return( 20.0 * log10(x) );
}


inline nec_float norm(const nec_float x, const nec_float y) {
 return std::sqrt(x*x + y*y);
}

inline nec_float norm2(const nec_float x, const nec_float y, const nec_float z) {
 return (x*x + y*y + z*z);
}

inline nec_float norm(const nec_float x, const nec_float y, const nec_float z) {
 return std::sqrt(norm2(x,y,z));
}

inline nec_float normL1(const nec_float x, const nec_float y, const nec_float z) {
 return std::fabs(x) + std::fabs(y) + std::fabs(z);
}




inline nec_float norm(const nec_3vector& v) {
 return v.norm();
}

inline nec_float normL1(const nec_3vector& v) {
 return normL1(v(0), v(1), v(2));
}
```

--------------------------------

### nec_gain_min

Source: https://tmolteno.github.io/necpp/libnecpp_8h_source.html

Get the minimum gain from a radiation pattern.

```APIDOC
## nec_gain_min


### Description
Get the minimum gain from a radiation pattern.

### Syntax
```c
double nec_gain_min(nec_context *in_context, int freq_index)
``` n
### Parameters
- **in_context** (nec_context*) - Pointer to the NEC context.
- **freq_index** (int) - Frequency index.

### Returns
- **double** - Minimum gain value.
```
Tokens:
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