10 'COPYRIGHT F1HDD/ON1RG GHISLAIN RUY 1992
20 'FREE FOR NON COMMERCIAL USE
30 'FILTER STRUCTURE
40 '---||------------||---NEXT // LC AND SERIAL C
50 '        |    |
55 '        |    |
56 '       ___   )
57 '       ___  (
58 '        |    )
59 '        |   (
60 '        |   |
61 '       ___ ___
62 '       /// ///
70 '
80 '
90 pi = ATN(1) * 4
100 DEF FNcoth (x) = (EXP(x) + EXP(-x)) / (EXP(x) - EXP(-x))
110 DEF FNsinh (x) = .5 * (EXP(x) - EXP(-x))
120 DEF FNcosh (x) = .5 * (EXP(x) + EXP(-x))
130 DEF FNasn (x) = ATN(x / SQR(ABS(1 - x * x)))
140 DEF FNacs (x) = ATN(SQR(ABS(1 - x * x)) / x) + pi * (1 AND (x < 0))
'PRINT FNacs(-.5) * 180 / pi
900 GOTO 5000
1000 'generates max flat elts values
1010 'n is the filter order, w'1 is specified at -3dB, g0=1
1020 DIM g(n + 1)
1030 '
1040 g(0) = 1
1050 FOR k = 1 TO n
1060 g(k) = 2 * SIN((2 * k - 1) * pi / 2 / n)
1070 NEXT k
1080 g(n + 1) = 1
1090 RETURN
1100 '
1110 'computes attenuation for max flat
1120 'w'1 is -3dB frequency of lox pass proto
1130 'wc is the frequency of interest normalized to cut off frequency
1140 la = 10 * LOG(1 + .995262315# * wc ^ (2 * n)) / LOG(10)
1150 RETURN
2000 '
2005 'generates tcheb. elts values
2010 'n is the filter order, w'1 is the equal ripple pass band
2015 'lar is the ripple value
2020 DIM g(n + 1)
2030 g(0) = 1
2040 x = lar / 17.37: beta = LOG(FNcoth(x))
2050 x = beta / 2 / n: gamma = FNsinh(x)
2060 DIM a(n), b(n)
2070 FOR k = 1 TO n
2080 a(k) = SIN((2 * k - 1) * pi / 2 / n)
2090 b(k) = gamma ^ 2 + SIN(k * pi / n) ^ 2
2100 NEXT
2110 g(1) = 2 * a(1) / gamma
2120 FOR k = 2 TO n
2130 g(k) = 4 * a(k - 1) * a(k) / b(k - 1) / g(k - 1)
2140 NEXT
2150 IF 2 * FIX(n / 2) = n THEN x = beta / 4: g(n + 1) = (FNcoth(x)) ^ 2: GOTO 2165
2160 g(n + 1) = 1
2165 x = SQR(1 / eps): x = LOG(x + SQR(x ^ 2 + 1)) / n: d = FNsinh(x)
2167 delta = 1 / g(0) / g(1)
2170 e = d - 2 * delta * SIN(pi / 2 / n)
2173 x = n * LOG(e + SQR(e ^ 2 + 1)): num = FNcosh(x)
2175 x = n * LOG(d + SQR(d ^ 2 + 1)): den = FNcosh(x)
2180 tomax = ABS(num / den)
2190 RETURN
2200 '
2210 'computes attenuation for tcheb;w1 is the ripple max frequency
2220 'wc is the frequency of interest normalised to ripple max frequency
2230 eps = 10 ^ (lar / 10) - 1: IF wc < 1 THEN 2240 ELSE 2250
2240 la = 10 * LOG(1 + eps * COS(n * FNacs(wc)) ^ 2) / LOG(10)
2245 GOTO 2260
2250 x = n * LOG(wc + SQR(wc ^ 2 - 1)): la = 10 * LOG(1 + eps * FNcosh(x) ^ 2) / LOG(10)
2260 la = FIX(10 * la + .5) / 10
2270 RETURN
'
'
'
5000 'computes values for lumped elts filter
5010 'pull required params :ripple, #poles, load impedance, center frequency and limits
CLS
5015 PRINT "INPUT LOW AND HIGH FREQUENCY OF RIPPLE PASSBAND (TCHEB) OR AT -3dB FOR MAX FLAT"
5020 INPUT "Lowest frequency of pass band  (MHz)"; f1
5030 INPUT "Highest frequency of pass band (MHz)"; f2: bp = f2 - f1
5040 INPUT "Number of poles "; n
5050 INPUT "Ripple "; lar
5060 INPUT "Input impedance  "; za: ga = 1 / za
5070 INPUT "Output impedance "; zb: gb = 1 / zb
5075 INPUT "dil"; dil
5080 '
5090 '

PRINT "print screen then press key"
WHILE INKEY$ = "": WEND

5100 '

IF f2 / f1 <= 1.05 THEN
GOTO 5110: lf$ = "1"
ELSE GOTO 5150: lf$ = "0"
END IF
'approx for low fractionnal pass band

5110 fc = SQR(f2 * f1): w0 = 2 * pi * fc * 1000000!
5120 bpf = (f2 - f1) / fc
5130 DEF FNwclfb (f) = ABS(1 / bpf * (f / fc - fc / f))
5140 GOTO 5200
5150 fc = (f1 + f2 - SQR((f2 - f1) ^ 2 + f1 * f2)): w0 = 2 * pi * 1000000! * fc
5160 bpf = (fc / f1 - fc / f2)
5170 DEF FNwchfb (f) = ABS((2 - fc / f - 1 / (2 - fc / f)) / (2 - fc / f2 - 1 / (2 - fc / f2)))
5200 'draws the graph
5205 PRINT "RESPONSE GRAPH"
5206 '
5210 SCREEN 12: WINDOW (-320, 399)-(320, 0)
5215  '
5400 FOR x1 = -320 TO 320
5405 IF x1 = 0 THEN GOTO 5450
5410 xx = x1 / 640 / -.5 * bp * dil: f = fc - xx
5415 IF lf$ = "1" THEN wc = FNwclfb(f) ELSE wc = FNwchfb(f)
5420 IF lar = 0 THEN GOSUB 1100: GOTO 5440
5430 GOSUB 2200
5440 PSET (x1, la * 6)
5450 NEXT
WHILE INKEY$ = "": WEND
SCREEN 0: WIDTH 80, 50
6010 '
6030 PRINT "Frequence centrale"; fc; "MHz"
6040 INPUT "Input low and high f for freq rejection info"; fl, fh
6035 interv = (fh - fl) / 40
6070 FOR f = fl TO fh STEP interv
6075 IF lf$ = "1" THEN wc = FNwclfb(f) ELSE wc = FNwchfb(f)
6080 IF lar = 0 THEN GOSUB 1100 ELSE GOSUB 2200
6085 PRINT "F="; TAB(4); f; TAB(12); "MHz"; TAB(20); "att"; TAB(25); FIX(la * 10 + .5) / 10; TAB(32); "dB"
6090 NEXT
6095 PRINT : PRINT "print screen then press key"
WHILE INKEY$ = "": WEND
6100 'computes values
6110 '
6115 CLS
6120 PRINT "Input"; n; "guessed values for parralel caps (in pF)": DIM c(n)
6125 '
6130 FOR x = 1 TO n
6140 PRINT "C("; x; ")="; : INPUT c(x): c(x) = 1E-12 * c(x)
6150 NEXT
6155 PRINT "Inductance values"
6160 FOR x = 1 TO n
6170 PRINT "L"; x; "="; FIX((1 / c(x) / w0 ^ 2 * 1000000!) * 1000 + .5) / 1000; "æH"
6180 NEXT
6190 DIM j(n)
6200 IF lar = 0 THEN GOSUB 1000 ELSE GOSUB 2000
6210 j(0) = (ga * w0 * c(1) * bpf / g(0) / g(1)) ^ .5
6220 FOR j = 1 TO n - 1
6230 j(j) = bpf * w0 * (c(j) * c(j + 1) / g(j) / g(j + 1)) ^ .5
6235 NEXT
6240 j(n) = (gb * w0 * c(n) * bpf / g(n) / g(n + 1)) ^ .5
6250 PRINT "Coupling caps"
6255 DIM cc(n)
6260 PRINT "C 0  1 ="; : cc(0) = j(0) / w0 / SQR(1 - (j(0) / ga) ^ 2): PRINT FIX(cc(0) * 10 * 1E+12 + .5) / 10; "pF"
6270 FOR x = 1 TO n - 1
6280 PRINT "C"; x; x + 1; "="; : cc(x) = j(x) / w0: PRINT FIX(cc(x) * 10 * 1E+12 + .5) / 10; "pF"
6290 NEXT
6300 PRINT "C"; n; n + 1; "="; : cc(n) = j(n) / w0 / SQR(1 - (j(n) / gb) ^ 2): PRINT FIX(cc(n) * 10 * 1E+12 + .5) / 10; "pF"
6310 '
6320 DIM cs(n)
6330 cs(1) = c(1) - cc(1) - cc(0) / (1 + (w0 * cc(0) / ga) ^ 2)
6340 FOR x = 2 TO n - 1
6350 cs(x) = c(x) - cc(x - 1) - cc(x)
6360 NEXT
6370 cs(n) = c(n) - cc(n - 1) - cc(n) / (1 + (w0 * cc(n) / gb) ^ 2)
6375 PRINT "Parralel caps"
6380 FOR x = 1 TO n
6390 PRINT "CS("; x; ")="; FIX(cs(x) * 10 * 1E+12 + .5) / 10; "pF"
6400 NEXT
6405 PRINT "Reflection coeff in passband="; tomax; "vswr="; (1 + tomax) / (1 - tomax)