Logo Search packages:      
Sourcecode: yagiuda version File versions  Download package

mutual.c

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#include <stdio.h>
#include <math.h>
#include <errno.h>
#include "yagi.h"


void mutual_impedance(int i, int j, double frequency, int driven, int parasitic, double **d, double **p, double **impedance)
{
      double xi, yi, xj, yj, li, lj, s, lamda, real, imag, mean_length;
      int col;
      /* first find location x,y of first element */
      if(i<=driven)                       /* i is a  driven element*/
      {
            xi=d[i][X];
            yi=d[i][Y];
            li=d[i][LENGTH];
      }
      else if (i>driven)                  /* i is a  parasitic  element */
      {
            xi=p[i-driven][X];
            yi=p[i-driven][Y];
            li=p[i-driven][LENGTH];
      }
      if(j<=driven)                       /* j is a  driven element*/
      {
            xj=d[j][X];
            yj=d[j][Y];
            lj=d[j][LENGTH];
      }
      else if (j>driven)                  /* i is a  parasitic  element */
      {
            col=j-driven;
            xj=p[col][X]; 
            yj=p[col][Y];
            lj=p[col][LENGTH];
      }
      /* compute distance from element i to element j */
      s=sqrt((xi-xj)*(xi-xj)+(yi-yj)*(yi-yj)); /* in metres */
      mean_length=(li+lj)/2.0;
      lamda=3e8/frequency; 
      z21(lamda, s , mean_length , &real, &imag);
      /* fill in Zij and Zji at the same time, as matrix is symmetric. */
      impedance[i][(2*j)-1]=real; /* real; */
      impedance[i][2*j]=imag; /* imag; */
      impedance[j][2*i-1]=real; /* real; */
      impedance[j][2*i]=imag; /* imag; */

#ifdef DEBUG
      if(errno)
      {
            fprintf(stderr,"Errno =%d in  mutual.c\n", errno);
            exit(1);
      }
#endif
}

/* To find the mutual impedance between to arbitary length, thin elements
I used the equations on Krauss, Antennas, McGraw Hill, 1988, pp426 and
427. Original work from Brown and King, 'High Frequency Models in Antenna
Investigations', Proc IRE, vol 22, pp457-480, April 1934*/
void z21(double lamda, double d, double l, double *r21, double *x21)
{

      double  b, cos_bl, sin_bl, sin_bl_over_2, cos_bl_over_2, c, s ;
      double t1, t2, t3, t4;
      double si_t1, ci_t1, si_t4, ci_t4, ci_bd, si_bd;
      double ci_t2, si_t2, ci_t3, si_t3;

      b=M_PI*2/lamda;
      t1=b*(sqrt(d*d+l*l)+l);
      t2=0.5*b*(sqrt(4*d*d+l*l)-l);
      t3=0.5*b*(sqrt(4*d*d+l*l)+l);
      t4=b*(sqrt(d*d+l*l)-l);
      /* To save findinding the same slow trigometric and ever slower
      si and ci functions, I'll just look them up once */
      cos_bl=cos(b*l);
      sin_bl=sin(b*l);
      sin_bl_over_2=sin(b*l/2);
      cos_bl_over_2=cos(b*l/2);
      s=sin_bl_over_2*sin_bl_over_2;
      c=cos_bl_over_2*cos_bl_over_2;

      cisi(t1, &ci_t1, &si_t1);
      cisi(t2,&ci_t2, &si_t2);
      cisi(t3,&ci_t3, &si_t3);
      cisi(t4, &ci_t4, &si_t4);
      cisi(b*d,&ci_bd, &si_bd);
      /* Real part of mutual impedance, computed as equation on page
      426 of Kraus */
      *r21=(30/s)*(2*(2+cos_bl)*ci_bd
      -4*c*( ci_t2 + ci_t3 )
      +cos_bl*( ci_t4 + ci_t1 )
      +sin_bl* ( si_t1 - si_t4 -2*si_t3 +2*si_t2 ) );

      /* Imaginary part of mutual impedance, computed as equation on page
      427 of Kraus */
      *x21=(30/s)*(-2*(2+cos_bl)*si_bd
      +4*c*( si_t2 + si_t3 )
      -cos_bl*( si_t4 + si_t1 )
      +sin_bl* ( ci_t1 - ci_t4 -2*ci_t3 +2*ci_t2 ) );
#ifdef DEBUG
      if(errno)
      {
            fprintf(stderr,"Errno =%d in  z21() mutual.c\n", errno);
            exit(1);
      }
#endif
}  


Generated by  Doxygen 1.6.0   Back to index