LFMF.h

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#pragma once
 
#include <cfloat>   // for DBL_EPSILON
#include <complex>  // for std::complex
#include <string>   // for std::string
 
namespace ITS {
namespace Propagation {
namespace LFMF {
 
// Define cross-platform DLLEXPORT
// Export the DLL functions as "C" and not C++
#ifndef DOXYGEN_SHOULD_SKIP
    #ifdef _WIN32
        #define DLLEXPORT extern "C" __declspec(dllexport)
    #else
        #define DLLEXPORT extern "C"
    #endif
#endif
 
// Enums
 
enum class Polarization {
    HORIZONTAL = 0, 
    VERTICAL = 1,   
};
 
enum class SolutionMethod {
    FLAT_EARTH_CURVE, 
    RESIDUE_SERIES,   
};
 
 
// clang-format off
enum class AiryKind {
    AIRY = 1, 
    AIRYD,    
    BAIRY,    
    BAIRYD,   
    WTWO,     
    DWTWO,    
    WONE,     
    DWONE,    
};
// clang-format on
 
 
enum class AiryScaling {
    HUFFORD, 
    WAIT,    
    NONE,    
};
 
 
// clang-format off
enum ReturnCode {
    SUCCESS = 0,                        
    // Invalid Inputs
    ERROR__TX_TERMINAL_HEIGHT = 32,     
    ERROR__RX_TERMINAL_HEIGHT,          
    ERROR__FREQUENCY,                   
    ERROR__TX_POWER,                    
    ERROR__SURFACE_REFRACTIVITY,        
    ERROR__PATH_DISTANCE,               
    ERROR__EPSILON,                     
    ERROR__SIGMA,                       
    ERROR__POLARIZATION,                
};
// clang-format on
 
// Constants
// clang-format off
constexpr double PI = 3.1415926535897932384;   
constexpr double epsilon_0 = 8.854187817e-12;  
constexpr double a_0__km = 6370;               
constexpr double C = 299792458.0;              
constexpr double ETA = 119.9169832 * PI;       
// clang-format on
 
// Data Structures
 
struct Result {
        double A_btl__db;      
        double E_dBuVm;        
        double P_rx__dbm;      
        SolutionMethod method; 
};
 
// Public Functions
 
DLLEXPORT ReturnCode LFMF(
    const double h_tx__meter,
    const double h_rx__meter,
    const double f__mhz,
    const double P_tx__watt,
    const double N_s,
    const double d__km,
    const double epsilon,
    const double sigma,
    const int pol,
    Result &result
);
 
DLLEXPORT char *GetReturnStatusCharArray(const int code);
DLLEXPORT void FreeReturnStatusCharArray(char *c_msg);
 
// Private Functions
 
ReturnCode LFMF_CPP(
    const double h_tx__meter,
    const double h_rx__meter,
    const double f__mhz,
    const double P_tx__watt,
    const double N_s,
    const double d__km,
    const double epsilon,
    const double sigma,
    const Polarization pol,
    Result &result
);
std::string GetReturnStatus(const int code);
double FlatEarthCurveCorrection(
    const std::complex<double> delta,
    const std::complex<double> q,
    const double h_1__km,
    const double h_2__km,
    const double d,
    const double k,
    const double a_e__km
);
double ResidueSeries(
    const double k,
    const double h_1__km,
    const double h_2__km,
    const double nu,
    const double theta,
    const std::complex<double> q
);
std::complex<double> wofz(const std::complex<double> z);
std::complex<double> Airy(
    const std::complex<double> Z, const AiryKind kind, const AiryScaling scaling
);
std::complex<double> WiRoot(
    const int i,
    std::complex<double> &DWi,
    const std::complex<double> q,
    std::complex<double> &Wi,
    const AiryKind kind,
    const AiryScaling scaling
);
ReturnCode ValidateInput(
    const double h_tx__meter,
    const double h_rx__meter,
    const double f__mhz,
    const double P_tx__watt,
    const double N_s,
    const double d__km,
    const double epsilon,
    const double sigma
);
ReturnCode ValidatePolarization(const Polarization pol);
bool AlmostEqualRelative(
    const double A, const double B, const double maxRelDiff = DBL_EPSILON
);
 
}  // namespace LFMF
}  // namespace Propagation
}  // namespace ITS