Move octave scripts to Octave dir.

Erik de Castro Lopo committed 19 years ago

Commit 497f1c61 parent ad6e0fd3 files · +0 −231Browse files

Unified · Split

3 files

generate_filter.m +0 −35
make_src_filter.m +0 −126
measure_filter.m +0 −70

@@ -1,35 +0,0 @@
1	function f = generate_filter (cycles, fudge_factor, increment, atten)
2
3	if nargin != 4,
4	error ("Need four args.") ;
5	endif
6
7	# Calclate N and make sure it is odd.
8	N = fix (4 * cycles * fudge_factor * increment) ;
9
10	if rem (N, 2) != 1,
11	N = N - 1 ;
12	endif
13
14	# Generate the Sinc function.
15
16	m = -((N-1)/2):((N-1)/2) ;
17	f = sinc (m / fudge_factor / increment) ;
18
19	# Genertate the window function and apply it.
20
21	w = kaiser (N, (atten + 0.5) / 10) ;
22	w = w' ;
23
24	f = f .* w ;
25
26	f = f / sum (f) ;
27
28	endfunction
29
30	# Do not edit or modify anything in this comment block.
31	# The arch-tag line is a file identity tag for the GNU Arch
32	# revision control system.
33	#
34	# arch-tag: 7e57a3cb-3f5c-4346-bfcd-4da1e758e2a7
35

make_src_filter.m+0−126

@@ -1,126 +0,0 @@
1	function f = make_src_filter (cycles, increment, atten, filename)
2
3	# This works :
4	#
5	# f = make_filter (67, 128, 100.3) ;
6	# f = make_filter (13, 128, 100.5) ;
7	# f = make_filter (185, 4, 157.0) ;
8
9
10	#=======================================================================
11
12	if nargin < 3,
13	error ('Try make_filter (12, 32, 88, "output.txt")') ;
14	endif
15
16	if nargin < 4,
17	filename = 0 ;
18	elseif (isstr (filename) == 0),
19	error ("Fourth parameter must be a file name.") ;
20	endif
21
22	fudge_factor1 = 1.0 ;
23	f1 = generate_filter (cycles, fudge_factor1, increment, atten) ;
24	[stop_atten stop_band_start1 minus_3db] = measure_filter (f1, atten) ;
25	printf (" fudge_factor : %15.13f stop_band_start : %15.13f 1\n", fudge_factor1, stop_band_start1) ;
26
27	fudge_factor2 = 1.25 ;
28	f2 = generate_filter (cycles, fudge_factor2, increment, atten) ;
29	[stop_atten stop_band_start2 minus_3db] = measure_filter (f2, atten) ;
30	printf (" fudge_factor : %15.13f stop_band_start : %15.13f 2\n", fudge_factor2, stop_band_start2) ;
31
32	f = f1 ;
33	fudge_factor = fudge_factor1 ;
34	stop_band_start = stop_band_start1 ;
35
36	while ((stop_band_start1 - stop_band_start2) > 0.00000001)
37	if (stop_band_start1 < stop_band_start2)
38	printf ("stop_band_start1 < stop_band_start2\n") ;
39	break ;
40	endif
41
42	fudge_factor = fudge_factor1 + (fudge_factor2 - fudge_factor1) / 2 ;
43	f = generate_filter (cycles, fudge_factor, increment, atten) ;
44	[stop_atten stop_band_start minus_3db] = measure_filter (f, atten) ;
45
46	if (stop_band_start > 1.0)
47	printf ("A %10.8f %10.8f %10.8f\n", fudge_factor1, fudge_factor, fudge_factor2) ;
48	continue ;
49	endif
50
51	if (stop_band_start < 0.5 / increment)
52	f2 = f ;
53	stop_band_start2 = stop_band_start ;
54	fudge_factor2 = fudge_factor ;
55	choice = 2 ;
56	else
57	f1 = f ;
58	stop_band_start1 = stop_band_start ;
59	fudge_factor1 = fudge_factor ;
60	choice = 1 ;
61	endif
62
63	printf (" fudge_factor : %15.13f stop_band_start : %15.13f %d\n", fudge_factor, stop_band_start, choice) ;
64	endwhile
65
66	printf ("\n") ;
67
68	#-------------------------------------------------------------------------------
69	# Grab only half the coefficients.
70
71	N = length (f) ;
72
73	f = increment * f' ;
74
75	if rem (length (f), 2) == 1,
76	index = find (f == max (f)) ;
77	half_f = f (index:length (f)) ;
78	else
79	error ("Length should be odd.") ;
80	half_f = f ((length(f)/2):length(f)) ;
81	endif
82
83	#-------------------------------------------------------------------------------
84	# Print analysis.
85
86	printf ("# f = make_filter (%d, %d, %4.1f) ;\n", cycles, increment, atten) ;
87	printf ("# Coeff. count : %d\n", N) ;
88	printf ("# Fudge factor : %9.7f\n", fudge_factor) ;
89	printf ("# Pass band width : %12.10f (should be %12.10f)\n", stop_band_start, 0.5 / increment) ;
90	printf ("# Stop band atten. : %5.2f dB\n", abs (stop_atten)) ;
91	printf ("# -3dB band Width : %5.3f\n", 0.5 / increment / minus_3db) ;
92	printf ("# half length : %d\n", length (half_f)) ;
93	printf ("# increment : %d\n", increment) ;
94
95	if filename,
96	file = fopen (filename, "w") ;
97	if file == 0,
98	str = sprintf ("Error, not able to open '%s'", filename)
99	error (str) ;
100	endif
101
102	fprintf (file, "/*\n") ;
103	fprintf (file, "** f = make_filter (%d, %d, %4.1f) ;\n", cycles, increment, atten) ;
104	fprintf (file, "** Pass band width : %9.7f (should be %9.7f)\n", stop_band_start, 0.5 / increment) ;
105	fprintf (file, "** Stop band atten. : %5.2f dB\n", abs (stop_atten)) ;
106	fprintf (file, "** -3dB band width : %5.3f\n", 0.5 / increment / minus_3db) ;
107	fprintf (file, "** half length : %d\n", length (half_f)) ;
108	fprintf (file, "** increment : %d\n", increment) ;
109	fprintf (file, "*/\n\n") ;
110
111	for val = half_f,
112	fprintf (file, "% 24.20e,\n", val) ;
113	endfor
114
115	fprintf (file, " 0\t\t\t/* Need a final zero coefficient */\n\n") ;
116	fclose (file) ;
117	endif
118
119	endfunction
120
121	# Do not edit or modify anything in this comment block.
122	# The arch-tag line is a file identity tag for the GNU Arch
123	# revision control system.
124	#
125	# arch-tag: 2f1ff4fa-ea6a-4e54-a5f8-dad55def9834
126

measure_filter.m+0−70

@@ -1,70 +0,0 @@
1	function [stop_atten stop_band_start minus_3db] = measure_filter (f, atten)
2
3
4	spec_len = 400000 ;
5
6	# Calculate the spectrum.
7
8	spec = 20 * log10 (abs (fft ([f zeros(1, spec_len - length (f))]))) ;
9
10	spec = spec (1:spec_len/2) ;
11
12	#-------------------------------------------------------------------------------
13	# Find the first null which starts off the stop band.
14
15	first_null = 0 ;
16	for k = 2:length (spec) - 1,
17	if spec (k) < -0.8 * atten && spec (k-1) > spec (k) && spec (k) < spec (k + 1),
18	first_null = k ;
19	break
20	endif
21	endfor
22
23	#-------------------------------------------------------------------------------
24	# Find the stop band minimum attenuation.
25
26	stop_atten = max (spec (first_null:length (spec))) ;
27
28	#-------------------------------------------------------------------------------
29	# Find the x position on the transition band which has the same attenuation.
30
31	atten_start = 0 ;
32	for k = 1:first_null,
33	if spec (k) > stop_atten && spec (k + 1) < stop_atten,
34	atten_start = k ;
35	break ;
36	endif
37	endfor
38
39	atten_start = atten_start - 1 ; # Arrays are 1 based so subtract 1.
40
41	stop_band_start = atten_start + (stop_atten - spec (atten_start)) / (spec (atten_start+1) - spec (atten_start)) ;
42
43
44	stop_band_start = stop_band_start / spec_len ;
45
46	#-------------------------------------------------------------------------------
47	# Find -3db point.
48
49	minus_3db = 0 ;
50	for k = 1:first_null,
51	if spec (k) > -3.0 && spec (k + 1) < -3.0,
52	minus_3db = k ;
53	break ;
54	endif
55	endfor
56
57	minus_3db = minus_3db - 1 ; # Arrays are 1 based so subtract 1.
58
59	minus_3db = minus_3db + (stop_atten - spec (minus_3db)) / (spec (minus_3db+1) - spec (minus_3db)) ;
60
61	minus_3db = minus_3db / spec_len ;
62
63	endfunction
64
65	# Do not edit or modify anything in this comment block.
66	# The arch-tag line is a file identity tag for the GNU Arch
67	# revision control system.
68	#
69	# arch-tag: cc2bc9a2-d387-4fed-aa0a-570e91f17c99
70

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