1 #ifdef HAVE_STDLIB_H
2 #include <stdlib.h>
3 #endif
4 #include <stdio.h>
5 #include <memory.h>
6 #include <errno.h>
7 #include "yagi.h"
8 #include <errno.h>
9
10 #define MAX_NON_ITERATIVE 100000
11
solve_equations(double frequency,int driven,int parasitic,double ** driven_data,double ** parasitic_data,double * v,double ** z,double * pin,struct FCOMPLEX * voltage,struct FCOMPLEX * current,struct FCOMPLEX * input_impedance,struct element_data * coordinates,double ** A,double * b,int * indx)12 void solve_equations(double frequency, int driven, int parasitic, double **driven_data, double **parasitic_data, double *v, double **z, double *pin, struct FCOMPLEX *voltage, struct FCOMPLEX *current, struct FCOMPLEX *input_impedance, struct element_data *coordinates, double **A, double *b, int *indx)
13 {
14 int elements, element_number, i, j;
15 double d, **A_pre_LUdcmp, *b_copy, t1, t2;
16 elements=driven+parasitic;
17 fill_z_matrix(frequency,driven,parasitic,driven_data,parasitic_data, z);
18 /* Now we must fill the V vector, which gives the voltage at the centre of
19 each driven element. Since we know the magnitude of the voltage and phase,
20 we can calculate the real and imaginary components of voltage. NB */
21 fill_v_vector(driven, parasitic, driven_data, v);
22
23 /* We now have the voltage vector V, and the impedance matrix Z. All
24 we need to do now is solve a set of NxN equations, where N is the
25 number of elements, to get N values of current, which we can put in
26 the I matrix.
27 Unfortunately, this is not trivual, by any standards!!! It is
28 complicated by the fact the the N equations are all complex.
29 The method used us a brute-force approach mentioned by Press
30 in their 2nd Edition of the Numerical Recipes in C book. Here we
31 put the data in the form:
32
33 |Zr -Zi| |Ir| = |Vr| which we will call A.x=b
34 |Zi Zr| |Ii| |Vi|
35
36 so the Z data goes now in a 2Nx2N matrix. This is a bit wasteful of space
37 and time, but it will do here. */
38 /* Copy impedance data from 'z' to matrix A */
39 copy_complex_data_to_real_matrix(elements,z,A);
40 /* The following function prints to stantard output the z matrix of the
41 antenna. It is really only used during debugging, so it can be commented
42 out normally. */
43 /* print_z_matrix(frequency,elements,z); */
44 /* read voltage data from v into b */
45 for(i=1;i<=elements;++i)
46 {
47 b[i]= v[2*i-1]; /* real data */
48 b[i+elements]=v[2*i]; /* imaginary data */
49 voltage[i].r=v[2*i-1];
50 voltage[i].i=v[2*i];
51 }
52 /* If there are a lot of elements, its possible that rounding errors
53 will destroy the accuracy of the results. If there are more than
54 MAX_NON_ITERATIVE elements, we do the usual LU decompositioon and
55 back-substitution, then do an iterative improvement of the
56 solution */
57 if(elements > MAX_NON_ITERATIVE)
58 {
59 A_pre_LUdcmp=dmatrix(1L, 2L*(long)elements, 1L, 2L*(long) elements);
60 b_copy=dvector(1L, 2L*(long)elements);
61 /* I had troubled using memcpy to copy matrices - probably becuase
62 they are offset by 1 */
63 copy_matrix(2*elements, 2*elements, A_pre_LUdcmp, A);
64 /* copy vector b */
65 for(j=1;j<=2*elements;++j)
66 b_copy[j]=b[j];
67 }
68 /* Perform a LU decompositon of A */
69 ludcmp(A, elements*2, indx, &d);
70 /* We now have the voltages in b. After lubksb is run, we get the
71 currents in b . A contains an LU decomposed version of the original A*/
72 lubksb(A, 2*elements, indx, b); /* current's in b after lubksb has run*/
73 if(elements>MAX_NON_ITERATIVE)
74 {
75 t1=b[1];
76 mprove(A_pre_LUdcmp, A, 2*elements, indx, b_copy, v);
77 free_dmatrix(A_pre_LUdcmp,1L, 2L*(long)elements, 1L, 2L*(long) elements);
78 /* free_dvector(bcopy,1L,2L*elements); */
79 t2=b[1];
80 if(t1!=t2)
81 {
82 printf("b[1]'s differ before and after mprove: before = %.16f after =%.16f\n", t1, t2);
83 exit(1);
84 }
85 }
86 /* Put currents an FCOMPLEX matrix current[element]
87 currents are stored in b as r,r,r,r ..... i,i,i,i */
88 for(element_number=1;element_number<=elements;element_number++)
89 {
90 current[element_number].r=b[element_number];
91 current[element_number].i=b[element_number+elements];
92 }
93 z_input(voltage[1], current[1], input_impedance);
94 *pin=calculate_power_input(input_impedance->r,current[1]); /* in Watts */
95 /* Sometimes the input power goes < 0. I'm not sure why this occurs, but
96 the implication is that the antenna is a source of energy, which is silly.
97 The gain is negative then (not in dB), so taking the log to put in dB
98 would cause a numerical error. When this occurs, we print a message to
99 stderr, then write the data in a file "problem". The user may then
100 investigate what went wrong. */
101 if(*pin <= 0.0)
102 {
103 /* fprintf(stderr,"Input power less than 0! Undesirable, but non-fatal error.\n"); */
104 *pin=1e20; /* Force it to a large value */
105 /* do_since_better(0,"problem","problem",*input_impedance, \
106 rubbish,flag, "This causes Pin < 0.0 - findout why!",frequency, frequency, \
107 frequency,frequency/10.0, elements, driven, parasitic, \
108 180.0, driven_data, parasitic_data, 1.0, 0.0); */
109 }
110 for(i=1;i<=driven;++i)
111 {
112 coordinates[i].x=driven_data[i][X];
113 coordinates[i].y=driven_data[i][Y];
114 coordinates[i].length=driven_data[i][LENGTH];
115 }
116 for(i=driven+1;i<=elements;++i)
117 {
118 coordinates[i].x=parasitic_data[i-driven][X];
119 coordinates[i].y=parasitic_data[i-driven][Y];
120 coordinates[i].length=parasitic_data[i-driven][LENGTH];
121 }
122
123 #ifdef DEBUG
124 if(errno)
125 {
126 fprintf(stderr,"Errno =%d in solve.c\n", errno);
127 exit(1);
128 }
129 #endif
130 }
131